Die Casting

SARGAM METALS P.LTD

RedesigningAluminium Foundry Alloys

forMaterial Cost Reduction

Sargam Metals Pvt. Ltd.

- 2 -

A Compilation of the Papers presented atthe Workshop organised by

Sargam Metals Pvt. Ltdon the 21 st of November 2001

at Chennai.

‘FOR PRIVATE CIRCULATION ONLY’© All rights reserved. No reproduction in full or in part without the explicit consent ofM/s Sargam Metals Pvt. Ltd., 2, Ramavaram Road, Manapakkam, Chennai 600089,India. Tel.: +91-44-249-1796; Fax: +91-44-249-1651;email: [email protected]


- 3 -

Contents

1 Foreword 4

2 Aluminium Foundry Alloys – Position in the AluminiumChain 5

3 Why Redesign? – The Impact of Alloy Specifications on Cost 12

4 Role of alloying elements and impurities 23

5 A Comparison of major international specificationsfor Aluminium Foundry Alloys 29

6 The Process of Redesigning – a suggested approach 43


- 4 -

Foreword

Though Aluminium foundry alloys have been made in India for more than five decades andare widely used today, especially in the automotive industry, the level of awareness amongthe users of the alloys about alloy specifications is very low. The effect alloying andimpurity element specifications have, not only on the properties of the alloy, but moreimportantly, on the cost of the alloy, is not clearly known, understood and appreciated.

Till the opening up of the economy in the early nineties, Aluminium foundry alloys wereessentially made in India only from primary metal, which was an anomaly in itself.Because of this historical mind set Indian users, even today, are not fully aware of the roleof recycling and the fact that the world over, Aluminium foundry alloys are the biggestconsumers of recycled material. This quite often leads users to specify unnecessarily closeimpurity tolerances even for castings that do not warrant such restrictions. This adverselyaffects the cost of the alloy.

Secondly, improvements in foundry technology, machining capabilities, processcapabilities and in product application environments are rarely reflected throughcorresponding changes in alloy specifications. Again, the main reason for this is the lack ofawareness.

To counter this, as a first step, SARGAM METALS organised a workshop on 21st November2001 at Chennai entitled “REDESIGNING ALUMINIUM FOUNDRY ALLOYS FORMATERIAL COST REDUCTION”. The purpose was to educate the user on Aluminiumfoundry alloys, its position in the recycling chain, impact of alloy specifications on alloycosts and also to provide a comparison of current major international Alloy specifications.The ultimate objective was to encourage users of Aluminium castings to examine theiralloy specifications to see if their current specifications – of alloying elements and impuritylimits – can be changed to enable higher user of Aluminium secondary material withoutaffecting the functional requirements of the casting.

The positive response to the workshop has prompted SARGAM to compile and bring outthe papers presented in the workshop in the form of this book.

Mr. A.V.Kannan, General Manager Sales at SARGAM and Mr. V.S.Rajan, Manager-Quality and R&D at SARGAM put together a lot of the material presented here.

SARGAM also gratefully acknowledges the encouragement and support given by itsesteemed customers to the workshop and to this compilation and hopes that thiscompilation will benefit them.


- 5 -

Aluminium Foundry Alloys – Position in the Aluminium Chain

IntroductionIn order to fully understand and appreciate the concepts explained in subsequent papers, itis essential to have a clear background picture of the Aluminium family, the concept ofrecycling and where Aluminium foundry alloys fit in, in the Aluminium chain. This paperattempts to give you just such a background information.

The History of AluminiumAluminium is the most abundant metal in the earth’s crust and is the third most abundantelement after Oxygen and Silicon. Unfortunately, it is an extremely reactive elementbecause of which it is not found in the free state. The most common forms in whichAluminium occurs and from which it is commercially extracted are Hydrated AluminiumOxide more commonly known as Bauxite and Cryolite, which is a mixture of SodiumFluoride and Aluminium Fluoride.

It is because of its high reactivity, and it not being available in the free state that, thoughthe existence of Aluminium was established by Sir Humphrey Davy in 1808, it was firstcommercially produced only towards the last decade of the 19th century. In 1886, twounknown young scientists, Charles Hall of the US and Paul Heroult of France workingseparately developed in parallel the electrolytic refining process. In this process, directcurrent electricity is passed from a consumable carbon anode into molten alumina oraluminium oxide splitting the oxide into molten metal and carbon dioxide. Though,continuous progress has been made in reducing the amount of electricity used, there is noviable alternative to this electrolytic process for producing Aluminium.

Aluminium is a relatively young metal – in commercial production for only about a 120years compared to Copper, which has been used for several thousand years. In spite of this,today Aluminium production is greater than all other non-ferrous metals and is in factgreater than the combined production of Copper, Lead and Tin.

Aluminium’s usage has steadily increased, especially after World War II when it wasconsidered a strategic metal, and today it finds wide applications in the automotiveindustry, to make beverage cans, packaging foil, sheets, conductor cables, building profilesetc.

Aluminium in AutomobilesThe advantageous properties of Aluminium, which I don’t intend listing here, are the keyreasons for the sustained increase in the use of Aluminium. The statue of Eros in London’sPiccadilly Circus [Picture 1] was cast from Aluminium in 1893 and is still as good as new.It may be of interest to know that Aluminium has been used in automobiles for over ahundred years.


- 6 -

Picture 1Statue of Eros at Picadilly Circus – Cast from Aluminium in 1893

It is reported that Aluminium crankcases were first used in automobiles as far back as1897. An Aluminium cylinder block was first made in 1903 and an Aluminium rear axlehousing in 1904. The Ford Model T used Aluminium in its transmission. Aluminiumpistons were tried in 1913 on racing cars. You must reflect on this for a moment to fullyappreciate the kind of impact Aluminium must have had to generate this kind of applicationdevelopment.

Today there are more than a hundred types of auto parts made of Aluminium and the list isgrowing. An average automobile in the U.S now has more than a 100 Kg of Aluminium init representing 8 to 10% of the weight of the car. Ford Motor Company is reportedlyworking on an Aluminium Intensive Vehicle – the P2000 – that will weight only 900 Kg –60% of other cars of its size – and will use some 350 Kg of Aluminium parts.

The History of Aluminium RecyclingIt is well known that the manufacture of Aluminium from bauxite is a highly energyintensive process. In fact, roughly 50% of the cost of pure Aluminium is energy cost. Onthe one hand, therefore, you have increasing uses cropping up for Aluminium and on theother you have the high cost of getting pure Aluminium. The natural solution for thisproblem is recycling.

Again, it will be of interest to know that the Aluminium recycling industry has its origins in1904 - a mere 16 years after commercial primary Aluminium production began! In theearly years, reclamation of Aluminium was relatively insignificant because the supply ofscrap was extremely limited. However, many scrap metal collectors and processors realisedeven then that Aluminium had economic values that made it very attractive for recycling.


- 7 -

Almost a hundred years later, those same desirable properties - low energy for conversion,good product performance and favourable economics – make Aluminium recycling evenmore attractive. If you pause to think for a moment, you will appreciate that recycling ofAluminium provides a continuous source of Aluminium, helping the Aluminium industrymaintain its growth. This growth of the Aluminium industry and Aluminium applicationsin turn increases the availability of aluminium scrap thus supporting the secondaryAluminium smelting industry. Bear in mind further, that recycling conserves significantenergy as well.Thus the recycling industry is and will continue to be a significant supplyfactor in the Aluminium chain.

The Aluminium recycling industry got a big boost immediately after World War II. Thewar resulted in a huge generation of aluminium scrap, especially the aero scrap.New alloysto profitably use the scrap were developed.Alloys, especially for die-casting, producedentirely from secondary aluminium came into being. The prices of these alloys were low,thus spurring the development of new die cast products. Other uses for secondaryAluminium were developed. The number of Aluminium items produced from recycledmetal grew rapidly. Aluminium’s growth in importance never looked back.

The point to be noted here is that the recycling of Aluminium is almost a paralleldevelopment. It is not a 21st century green movement fad. On the contrary, recycling ofAluminium because of its favourable economic impact is an essential part of the Aluminiumsupply chain and is undoubtedly a critical component of the Aluminium industry and itshould be understood and appreciated as such.

The Aluminium Recycling ChainRecycling of Aluminium and the development of foundry alloys are linked and relatedactivities. In order to appreciate this, you must have a clear picture of the Aluminiumrecycling chain.

The first link in the chain is the production of Primary Aluminium pigs and ingots frombauxite. As you are aware, this is a highly energy intensive process and requires the settingup of capital intensive smelters, of which there are not too many. In India for instance, wehave five primary producers – HINDALCO, NALCO, BALCO, INDAL and MALCO.

The pure Aluminium ingots produced by the primary producers go mainly into theproduction of Aluminium wrought products. The wrought products include sheets, plates,rods, bars, extrusions, wires and foil. Wrought mills producing these products can beintegrated down stream facilities established by primary producers or separate stand-aloneplants. In India, HINDALCO has good down stream capability integrated with itsRenukoot facility while units like Jindal are separate stand-alone extrusion plants.

A relatively smaller portion of the pure ingots goes into the production of Aluminium castproducts.

The first source of scrap generation is the manufacturing scrap arising during theproduction of these wrought products whether at the primary producer or at the stand-alone


- 8 -

wrought mill. This is generally known as “new” scrap. It essentially consists of solids,clippings and cuttings, sawings, residues such as dross, skimming and spillage and floorrejections. This “new” scrap, except usually for the sawings and dross, is generallyconsumed by the wrought product producer himself who will add it back to the melt.Similarly, during the production of cast products, “new” manufacturing scrap arises such asrunners and risers, rejected castings, borings and turnings from machining operations,residues such as dross, skimming and floor rejections. Again except for the borings anddross the rest are usually consumed by the foundry itself.

Whatever “new” scraps from the wrought mills or casting shops that are not consumed in-house are sold to dealers. We will track what happens to this in just a moment.

The wrought and cast products made move onto other factories where they become part ofend products. For example, extrusions may end up getting assembled as window ordoorframes; sheets may become part of a roof, or an aircraft body panel. A cast productmay end up in a motor cycle or car. Similarly, beverage cans, cooking utensils, electricaltransmission lines, household Aluminium foils are all products, which would have startedout from a wrought mill or a cast shop. This second stage manufacturing generally takesplace in several stages in different locations. For example a pressure die cast housing madein China can become a CD drive in a Seagate plant in Taiwan and then part of a PCassembled in Malaysia.

Again, while these second stage manufacturing and assembly takes place more “new” scrapcan arise. This time essentially as trimmings and clippings in the case of wrought products,turnings and borings and of course rejections. The second stage manufacturer generally,cannot consume this scrap and this scrap too finds its way to the dealer market.Finally, the finished products that get made all have a finite life. Of course the life varies –from weeks or months for beverage cans and most packaging products to a few years forelectronic and white goods to many years for automobiles or building products. At the endof life we have the post-consumption or “old” scrap. This “old” scrap invariably ends up atthe scrap dealer.

Now, depending on the product, differing amounts of retrieval efforts may be required forseparating out the aluminium content in the product. If you take a scrapped automobile, forinstance, a lot of effort is required as there are so many different types of material makingup a car, each of it having a different recycling value. On the other hand a used beveragecan or a packaging foil, is generally, fully Aluminium as it is, and requires no specialseparation efforts.

We now have several loose ends in the Aluminium chain. From the first stagemanufacturing, we have some amounts of “new” scrap especially turnings, borings anddross that require off-site processing. From subsequent stages of manufacturing andassembly, you can have more “new” scrap including line rejections and finally you havethe post-consumer “old” scrap from which the Aluminium content has been extracted.Where do these go?


- 9 -

The largest users of such dealer-collected scrap are secondary Aluminium producers. Thesecondary aluminium producer converts such scrap into specification ingots. He would tryto use the lowest grade scrap to meet the required final specification, adding higher gradesand even pure Aluminium, as may be required, only to “sweeten” the melt. The secondaryAluminium producer essentially caters to the Aluminium cast product manufacturer. Thereason for this is not very difficult to see. Wrought Aluminium alloys generally have closeimpurity limits and much smaller alloying additions. A large portion of both “old” and“new” scraps therefore, cannot be used to make wrought alloys. The cast alloys howeverhave high percentages of alloying elements and tolerate a far higher level of impurityelements thus permitting the use of a wider range of scraps in its manufacture.

We can now close the loop by moving all the scrap to the secondary aluminium producers.The entire recycling chain is depicted figuratively in FIGURE 1. These producers convertthe scrap into graded casting alloys that go to the foundries or casting shops.

FIGURE - 1

Pure Ingots Alloy Ingots

Mill Products Castings

Useful Life

THE ALUMINIUM CHAIN

Primary AluminiumProducer

SecondaryAluminium Producer

Manufacture ofwrought products by

wrought mills

Manufacture of castproducts in foundries

New Scrap New Scrap

Consumers of mill products and castings -Manufacturers of end products

End Products New Scrap

End of Life Scrap Scrap Dealer


- 10 -

Actually today the situation is slightly different. While till about 15 years ago, the castingalloy manufacturer was the main buyer of Aluminium scraps, today he has competitionfrom the wrought mill as well. The value of recycling is so high that scrap dealers nowseparate scraps into purer grades and sell these to the wrought product manufacturers.Leading wrought product manufacturers the world over now have secondary plantsrecycling selected scrap back to specification billets. In India too, Indal has a secondarymelting facility in Taloja which processes scrap into extrusion and sheet grade billets.

However, typically, secondary cast or foundry alloy producers have a greater flexibility inusing different types of scrap while secondary wrought producers only prefer higher gradesof scrap. In fact many wrought alloy billet plants are specially designed to process one typeof scrap only. For example there are specialised plants that convert used beverage can scrapinto specification billets. In a typical can recycling facility for instance, the steps involvedwould be: debaling, separation into can, tab and end stocks as each is of a differentspecification, delaquering, melting, casting and rolling.

A point to bear in mind is that effective scrap recycling is a specialised job and a processinvolving skill. The type of scrap, its nature and typical specifications will all be known tothe skilled recycler. He would also know exactly how to use the scrap and what pre-processing to do to improve yields. And of course today, the additional requirement is to doall this in an environmentally acceptable manner. Many people outside are not aware ofthis and comparing the price of raw scrap with ingots think it’s a simple business.Unfortunately, it is not!

Recycling – Facts and FiguresThe fact that recycling is an integral part of the Aluminium supply chain, especiallyoverseas, can be understood from the following interesting and eye-opening facts onrecycling.

The recycling of beverage cans, because of its short life cycle, is tightly controlled in manycountries and represents one of the success stories in recycling. Consider this: the all-Aluminium beverage can was first introduced in 1963. Recycling of such cans began in anorganised manner in 1968 in California. In 1972, Aluminium cans had a 20% market shareof all beverage cans in the US. Today, thanks to the recycling program and the resultingcost savings, steel cans are totally out in the US and Aluminium beverage cans have a100% hold on the market. Last year 100.8 billion cans were manufactured in the US out ofwhich some 62.6 billion cans were recycled representing 62.1% of the total production.

Recycling rates from building and transport applications are equally impressive. In 1998,11.6 million tons of old and new scrap was recycled fulfilling 40% of the global demandfor Aluminium. Of this some 38% came from the transport sector and some 32% from thebuilding sector.


- 11 -

In the US the transportation industry is the largest user segment for Aluminium accountingfor some 30.9% of the total Aluminium consumed. Significantly, almost 90% ofautomotive aluminium is recycled metal. Today the Aluminium industry is working withthe automobile manufacturers to enable easier dismantling of Aluminium components fromcars in order to improve their sorting and recovery. It is no surprise therefore, that, thoughAluminium represents 10% of the weight of the typical car Aluminium scrap accounts for30 to 50% of the total car’s scrap value.

In Europe in 1996, it was decided that all the individual country standards for Aluminiumalloys would be replaced by a common Euro standard. One of the reasons for this is toreduce the number of different specifications in operation in Europe which will eventuallymake recycling easier and more effective as the number of types of scrap compositions willalso reduce.

In summary it is to be clearly understood that recycling is a vitally important part of theAluminium industry and is not some clandestine operation being carried out by a shadyproducer! Though, Excise and Customs products nomenclature unfortunately classifiesscrap as “waste and scrap”, Aluminium scrap is definitely not a “waste” but is actually avital raw-material especially for the foundry alloy industry.

World over foundry alloys are designed with an eye on scrap availability. India’s protectedeconomy did not recognise this all these years but now it is time to change. To change howwe view alloy specifications, to change how we handle our scrap generation and to changehow we view Aluminium scrap. We hope that the following papers will be a step in thisdirection.


- 12 -

Paper 2

Why Redesign? – The Impact of Alloy Specification on Cost

IntroductionThe concept of recycling and the production of Aluminium foundry alloys using secondarymaterial has been covered in the previous paper. With this as a background we will now tryand see how the alloy specifications affect the type of secondary material that can be usedand the impact of this on the alloy cost. We will simultaneously examine the possibility ofredesigning the chemical composition limits to derive cost advantagewithout affectingproduct quality.

Before proceeding look at pictures 1,2 3 and 4. These are critical castings like pistons,transmission housings and cylinder heads. You would expect that they would have beencast using special alloys with low impurity limits. Actually, they are all made from 100%secondary alloys of Grades A380 and A384, alloy compositions similar to the familiar LM-24. The fact that these critical castings like pistons, transmission housings and cylinderheads are produced using secondary alloys with pretty high impurity limits, is an eye-opener to those who still think that such critical castings are to be produced only fromfoundry alloys manufactured from primary Aluminium and virgin alloying elements!

Transmission Housing-Type I

Cu-2.33%, Si-9.09%, Mg-0.05%, Mn 0.22%, Fe-1.01%, Zn-1.12%Alloy Type - A380.0

Picture 1


- 13 -

Transmission Housing - Type – II

Cu-2.48%, Si-11.37%, Mg-0.10%, Mn-0.21%, Fe-0.81%, Zn-2.4%Alloy Type-383.1

Picture 2

ENGINE CYLINDER

Cu-2.50%, Si-6.13%, Mg-0.27%, Fe-0.42%, Zn-0.22% - Alloy Type –AC2B

Picture 3


- 14 -

PISTON

Cu-3.19%, Si-8.71%, Mg-0.05%,Mn-0.18%, Fe-0.90%, Zn.1.85%Alloy Type - A-380.1

Picture 4

The History of Alloy production in IndiaLet us look at the history of Aluminium alloy production in India. Till about 1990, alloys inour country, contrary to what was happening in the rest of the world, were producedpractically only from primary Aluminium and alloying elements. Even the so-called‘secondary alloys’ like ADC-12 were converted from pure Alumimium ingots to which therequired amounts of Copper and Silicon were added. In fact at Sargam there have beenmany occasions when we have used an Iron-Aluminium master alloy to get the iron limitup in the PDC alloys! In those days the alloy buyers did not approve using scrap to makealloys. Secondly, local generation of Aluminium scrap was extremely small and import ofscrap was not possible. Thus there was practically no need to worry about impurity levels.

The year 1991 witnessed a new era of liberalization, opening out free accessibility toimported aluminium scrap in various forms. Simultaneously it became easily possible toimport sophisticated analytical instruments like Emission spectrometers facilitating meltsto be analysed within minutes. This period also witnessed multi-national companiescoming in through collaborations or direct establishment of their manufacturing units in ourcountry and Indian companies actively chasing global markets resulting in alloyspecifications taking on a wider international flavour.


- 15 -

The beneficial effect, of course, of the liberalisation is that there are now a variety ofmodels to choose from, be it a small pager or a luxury car. The flip side is thatmanufacturing units are under intense pressure to keep costs down. Cost reduction is thuspractically an on-going process, almost a necessity for survival.

The first impact of this liberalised scenario as far as Aluminium alloys are concerned wasthe acceptance that Aluminium alloys can be made from secondary material. This is in factthe way alloys have been made overseas for many decades. Immediately, there has been aneffect on cost.

Take for example, Aluminium Alloy ADC-12 ingots – a familiar specification. This alloycontains 1.5 to 3.5% Cu, 9.6 to 12.0% Si with liberal impurity limits. If this alloy is madefrom pure Aluminium to which 3% of Copper and 11% of Silicon is added, it will probablycost the user Rs.95 per Kg.

Today, it is accepted that this alloy can be comfortably made using Aluminium secondarymaterial. In fact, today no ADC12 user will pay more than Rs.78 to Rs.80 for this alloy!This clearly shows that the price difference of an alloy made from secondary is on thelower side by Rs.15 to Rs.16/- per kg, definitely 17% cheaper than the alloy cost, ifproduced from virgin inputs. Of course, there are still certain alloys, which necessarilyneed to be made from virgin inputs – for instance the alloy A356, which is used to makeautomotive wheels. But then these are the so-called ‘premium’ alloys, which are alsopriced very high.

Thus, in the last ten years or so, Indian alloy users have got used to the fact that it isbeneficial and, in fact, a must, that foundry alloys should be made from Aluminiumsecondary material. Scrap is no longer a dirty word. It is now accepted that alloys likeADC12 and LM24 are entirely secondary based alloys. Overseas, as a matter of fact,practically all alloys, with the exception of premium alloys, are made from secondarymaterial. In India, however, due to the lack of availability of purer grades of scrap in largequantities at reasonable prices, alloys like LM4, AC4B etc. are to some extent secondarybased while alloys like LM6, LM25 etc. use a much larger quantity of primary material.

While all this is well known, we will now try and see how you can squeeze some more costbenefits in all your alloys by taking an even closer look at alloy specifications.

Some Common Scrap TypesBefore we get into this let us first take a quick look at some of the important types ofAluminium secondary material that are generally available:Used Aluminium components – usually automotive components. These will typically havea composition of around 2 to 3% Copper, 7 to 8% Silicon, 0.5 % or so of Magnesium, 1 to1.5% of Iron and anywhere from 0.8 to 3% Zinc. Such components will generally offer ayield of 90% or so and will cost around 75 to 80% of pure Aluminium. Typical cost todaymay be around Rs.62 to Rs.65 per Kg.


- 16 -

Aluminium sheet scraps: These will have a typical composition of around 0.8 to 1.0% ofMagnesium and 0.8 to 1.0% of Manganese. These will also result in a yield of around 90%and will cost just a little more than component scraps. Typical costs may be around Rs.65to Rs.70 per Kg.

Aluminium extrusions and profiles: These will typically have 0.5 to 0.7 % of Magnesiumand Manganese. However the material will be clean resulting in yields of 95% yields. Thecost will be around 90% of pure Aluminium. Typical costs may be around Rs.75 to Rs.80per kg.

Clean Aluminium scrap: This includes lithographic sheets and Aluminium cable scrap.These are 99.5% pure and the yield will also be 95% +. However the price will also be 90to 95% or so of pure Aluminium. Typical costs will be Rs.80 to Rs.85 per Kg.

Aluminium Turnings & Borings: These are basically machine shops arisings and is oftenmixed with iron and other impurities like zinc, brass and copper. If carefully segregatedand smelted could yield 70 to 75%. Its cost could be 50% to 60% of pure Aluminium.

A Typical ADC12 MeltWith this as the background let us look at a typical melt for ADC12 using secondarymaterial. The melt-size, let us assume, is 1500 Kg.

Let us assume that we start the melt using 1000 kg of old and used automobile die castcomponent scrap. (This is the normal practice.) We generally take this 1st inputcomposition to be totally unknown. Thus, after melting the charge of 1000 Kg, we have inthe furnace clean liquid metal approximately of 920.0 kg (after melt losses). A sample isdrawn from this molten metal and referred to the laboratory for analysis by EmissionSpectrometer.

The analytical result of the base metal, which we will refer to as input I, is given below: -

I. Cu – 2.01, Si – 7.22, Mn – 0.50, Mg – 0.40, Ni – 0.15, Fe – 1.0%, Zn – 0.9%

We require totally 1500 kg of ADC-12 alloy out of which we now have 920 kg of basemetal inside the furnace, which works out to 61.3% of the total required. We thus need tomake up another 580 to 600 Kg of metal. The important question is what is the finalcomposition required.

The standard ADC12 as per JIS is:Cu – 1.5 to 3.5%, Si – 9.6 – 12.0%, Mn – 0.5% max, Mg – 0.3% max,Fe – 1.3% max, & Zn – 1% max

Contrary to what you may be thinking, what we are concerned about at this point of time isnot the alloying element percentages but the impurity percentages! Addition of alloyingelements like Copper and Silicon can be made up at any point of time by adding pureCopper and pure Silicon to the extent necessary. However, if there are any impurities over


- 17 -

the permissible limits, it must be understood that they cannot be eliminated but onlydiluted.

Let us examine two cases of final specification requirements:

Case Cu Si Mn Mg Fe ZnCase I 2 to 3% 11 to 12% 0.3%

max0.3% max 0.8% max 0.8% max

Case II 2 to 3% 11 to 12% 0.4%max

0.3% max 0.9% max 0.9% max

In the first case the customer requires Manganese and Magnesium to both be under 0.3%each, with Fe and Zinc each to be under 0.8%.

The existing metal representing 61.3% of the total melt will contribute to the finalcomposition as follows:

I: Cu 1.23%, Si 4.43%, Mn 0.30%, Mg 0.25%, Fe 0.61%, Zn 0.55%.

While we are OK with the Fe and Zinc limits, we have, unfortunately, already hit the limitfor Manganese and almost hit the limit for Magnesium. Thus any material we can add nowshould not have Manganese and should have very little Magnesium. It is most likely thatwe will need to use litho sheets or cables.

The melt make-up will look something like this:

Item % of melt after melt loss Cu Si Mn Mg Fe ZincI 61.3 1.23 4.43 0.3 0.25 0.61 0.55Cu 1.5 1.50Si 7.0 6.90 0.10Litho 30.2 0.09TOTAL 100.0 2.73 11.33 0.3 0.25 0.80 0.55

The cost of this melt will be at least Rs.75 per kg (excluding production costs).

The customer in Case II has a slightly more relaxed specification. This requires Manganeseat 0.4%, Magnesium at 0.3% and Iron and Zinc at 0.9% each. For meeting thisspecification, we are a little better placed. We now have the choice of adding a little moreof Type I casting scrap till we hit the Magnesium and/ or Manganese cap or we can addsome sheet scrap or extrusion scrap and make up the rest with litho or wire scrap.


- 18 -

The melt make-up will look something like this:

Item % of melt after melt loss Cu Si Mn Mg Fe ZincI 61.3 1.23 4.43 0.3 0.25 0.61 0.55I (more) 20.0 0.4 1.45 0.09 0.08 0.20 0.18Cu 1.1 1.1Silicon 5.5 5.4 0.06Litho 12.1 0.01TOTAL 100.0 2.73 11.28 0.39 0.33 0.88 0.73

The cost of this melt will be at least Rs.2 or 3 lower than the previous melt at around Rs.72per Kg. This is because we have been able to use more of the lower priced Aluminiumcasting scrap type of material and less of the expensive lithographic sheet material.

Impurity Limits affect CostWe were able to achieve this reduction by just a 0.1% relaxation in a few impurity limits.Whether the alloy is LM4 or ADC12 or AC4B, the concept is similar. Even a 0.1%difference in impurity limits can translate into a Rs.2 or 3, or sometimes even greater,difference in cost per Kg. If you use 30 MT of the alloy per month we are talking of asaving of Rs.10 lakhs or more per year just by working on the permissible impurity limits!

Let us be clear about two things here:First, we are not suggesting that all impurity limits be opened up indiscriminately. On thecontrary, It should be a carefully studied and controlled act and will depend on severalfactors. In fact in subsequent papers we will outline some suggestions on how to go aboutthis.Second, we are not making this statement of asking for a re-look at impurity limits withoutbasis. We are stating this, fully conscious of its implications.

In the next paper we will be highlighting the effects of various alloying elements andimpurities in Aluminium and will also present various international standards including thenew EN standards. This will clearly show you what is possible, what is not and what hasalready been done in different parts of the world. This will be a good guideline to youwhile considering the possibility of re-designing or re-defining your specifications, with aview to saving of cost.

A Closer Look at Impurity LimitsNow, let us ask ourselves the question what would happen if impurity limits are relaxedslightly. Let us look at three specific impurities - Iron, Zinc and Magnesium.

Iron, is actually quite OK up to a certain limit. What is the limit is the question. Earlier, thelimitation in PDC alloys for iron was mainly due to the fact that when aluminium alloyswere melted in a cast Iron crucible, Aluminium would pick up iron from the melting pot.The combination of iron, Manganese and Zinc would form sludge resulting in theaccumulation of unusable Aluminium. However, today, almost all die-casters use graphiteor silicon carbide crucibles. Hence relaxing Fe limits marginally for PDC alloys need not


- 19 -

be a cause for concern. If you take a look at the revised American specification, as well asthe revised ENAC specifications for an alloy like LM-4, Fe is relaxed up to 1% even forgravity die-casting. Hence a little relaxation of even 0.1% in Fe would help us to use atleast 5% more of lower cost secondary material. Of course, for castings that require heattreatment to achieve better mechanical properties, the relaxation should be based on carefulstudy.

What about Magnesium? The presence of Magnesium to a level of 0.8 to 1.0% will notaffect the casting characteristics of Aluminium. On the contrary, Magnesium with Siliconand Copper will enhance the hardness of the alloy due to age hardening. As you will see inthe next paper, all the BS 1490 specifications have been completely revised in the year1998 as the unified BSEN 1706-98. All alloys have been grouped based on the alloyingelements present in each grade and each alloy type is covered by at least 2, 3 or morespecifications with different impurity levels. In most of the alloys, presence of Mg has beenrelaxed, obviously, keeping in mind that presence of Mg does not in any way affect thecasting characteristics of the alloy. There is another reason for this relaxation, which wewill see in a moment. Except in the case of alloys where natural age hardening will affectsubsequent operations or where a specific range of Magnesium is required to achievespecific properties after heat treatment, minor relaxation in Magnesium content will notgenerally cause any casting problem. It should also be borne in mind that Magnesiumlevels will keep going down with every melt and with every addition of foundry returns.

Let us take the case of Zinc. Zinc has no significant benefits by being present inAluminium alloy ingots except for marginally adding to the weight of the componentproduced. This particular element is generally permitted in pressure die-casting alloysfrom 1 to 3% and in recent gravity die-casting specifications like A319 up to 1% or more.Compare this with earlier specifications of, say, LM-4, which restricted Zinc to 0.5%maximum. In some critical alloys like LM-9, LM-6 & LM-25 the presence of Zn is stillcontrolled at 0.1% and even in these alloys, if Zn % is relaxed by 0.1%, usage of secondarycan be increased comfortably by 10 to 20% and cost of the alloy can be comfortablybrought down.

These changes can be attempted in all alloys. Even alloys like LM6 or LM25. In thesealloys, for instance, the difference between the alloy cost with 0.1% max. Copper and 0.2%max. Copper will be at least Rs.3 to Rs.4.

A Strong Case for RedesigningThis is not something radical that we are proposing. In fact the BS1490 specifications,which was and still is, considered sacrosanct in the Indian foundry industry, evolvedbasedon the type of scrap availableimmediately after World War II. In other words, foundryalloy specifications are made up with a clear eye on scrap availability and theirspecifications. For instance over the last several decades use of Aluminium extrusions andsheets for building and transport applications and thin sheets for beverage cans haveincreased. This means more extrusion scrap will be generated as buildings are torn down orautomobiles scrapped and more beverage-can scrap as cans are recycled. Most of thesespecifications will have 0.5 to 1.0% Magnesium. This is precisely the reason why in latest


- 20 -

revisions of many alloy specifications, Magnesium limits (as an impurity element) havebeen increased. This is to permit the use of the kind of scrap that is now generated byindustry.

We have customers whose alloys specify stringent Magnesium control, but the componentsare not heat-treated! So why not relax the Magnesium limits?

In fact, while close control is maintained on alloy compositions, what about thecomposition of the castings that you actually get? Many of you can try this. If you arebuying castings or getting them converted it is likely that destructive chemical analysismay not be part of your QC plan. While chemical composition of alloy ingots are carefullychecked, components are checked for dimension, casting defects etc. and rarely forcomposition. Just check a few from your next lot. There may be some surprises withelements out of range. But, if you had not checked the composition, you would haveaccepted the casting as sound!

Please reflect on the fact that while casting technologies have changed, crucibles havechanged, fluxes have changed, and application technologies have changed alloyspecifications have remained static! Take the case of the automotive piston. Machiningtechnology has changed and finer finishes are possible, lubrication technologies haveimproved by leaps and bounds and the friction levels in the engine cylinders are muchlower but have we tried to see if there is any implications on piston alloy specifications atall! Internationally specifications are reviewed and updated routinely and regularly butunfortunately, here neither is there locally driven change nor is there an effort to keepabreast of changes taking place abroad!

Thus, the first thing we have to drop is the mind set that alloy specifications are written instone and are not to be touched. They can and should be examined every once in a while,just as you would periodically examine quality procedures to see if they require change.

Finally let us be absolutely clear that our idea of suggesting to re-design or re-specify thematerial composition for cost purpose does not mean that all specifications are to berelaxed. The objective should be to workout a practical composition to save the cost of thematerial without diluting the quality. Efforts should be made to critically examine eachand every grade of alloy both as regards to the alloying elements as well as impurity levelsand re-specify wherever practically possible to achieve cost control as long as theredesigned or re-specified compositions do not affect the products performances.

Suggestions on Scrap HandlingBefore closing the paper let us spend a few minutes to discuss a related issue - the value ofthe scraps you may be generating. After all, we have just highlighted how important scrapis to alloy makers. So it is extremely important that you view your own scrap arising in anew light! You may be interested to learn that you can squeeze money out of this as wellby following some simple practices.All of you are aware, day in and day out, Aluminium Foundries, OE & sparesmanufacturers turn out considerable quantities of Aluminium scrap, the value of which is


- 21 -

even today under-estimated. Do take a look at this side of your operation and ensure thatall the scraps that are generated by a foundry and machine shops are properly segregated,sorted and stored in recommended conditions to realize their value in full. Please do notleave these materials as trash or junk. Mind you, these are all your hidden treasures whichwill help you to sustain in today’s competitive market conditions.

Let us look at a few of the common types of scrap generated and ‘Best Practices’ to handlethem.

In a foundry, fettling operations will result in an accumulation of runners and risers. Theseare called foundry returns and are usually reused in the foundry itself. However, bestpractice requires that these be collected and stored as far as possible alloy wise. Thisbecomes even more important if the ratio of runner/ riser to component is high. Withcareful segregation, the runners and risers can be comfortably used with original alloyingots in ratios ranging from 30:70 to even 50:50, depending on the finer requirement ofthe component.

While many foundries do some amount of recycling of the runners and risers, most do notconsider spillage and floor sweeping as a recyclable input at all! We have observed that, asa conservative estimate, a fifty-ton-per-month foundry will lose 500 Kg or about 1% asspillage and floor sweeping. These are either swept out or disposed at low rates, while ifthey are collected carefully and stored properly, their disposal value can increaseconsiderably.

The biggest concern for any foundry is the dross generation. This is basically a mixture ofmetal and metal oxide. For every 1000 kg of Aluminium ingots melted, the average drossgenerated varies between 30 to 40 kg. Thus, a typical Aluminium casting foundry melting100 tonnes of alloy ingots or other solid Aluminium material, generates 3 to 4 MT of dross.The two important aspects here are: (a) to minimise the quantity of dross generated permelt, through the use of covering fluxes, temperature control etc. and (b) maximise therecovery of metal from the dross, which as I pointed out is a mixture of metal and metaloxide. Do remember, however, that in spite of your best efforts in sweating out entrappedmetal from hot dross using recovering fluxes at the foundry, there will still be recoverablemetal going out in the remaining dross. The secondary recovery or off-site recovery can beanything from 15 to even 30 or 40% of the cold dross. It is now a well-accepted fact that afoundry’s profits are in the dross generated!

Foundries, which are producing or melting quantities exceeding 5 MT per day, canconsider installation of a suitable hot dross compression unit. We will be happy to provideyou information and suggestions on such useful equipment.

Another very important area is the machined turnings and borings generated by themachine shops that may be in-house or external. Turnings are generally generated duringturning operations and are generally fairly thick. Borings are relatively fine and ariseduring boring operations or during finer finishing operations. The handling practice of suchmachine-shop waste is generally not up to the mark in even large companies. The first


- 22 -

mantra here is ‘SEGREGATE AND STORE’. If you can segregate alloy-wise that wouldbe the best. If not, definitely you must separate Ferrous borings from non-ferrous andwithin the non-ferrous borings separate Zinc or Copper or Brass from Aluminium. Thesecond mantra is ‘DRAIN OUT COOLANT OIL’. As you are aware, coolant oils arebasically hydro-carbons and when they get mixed with Aluminium borings (a) they add tothe weight of the material and (b) at the time of smelting, these hydro-carbons produceCarbon Monoxide and Carbon-di-oxide gases, which are major pollutants. Equallyimportant such burning of the oil while melting adds to the oxidation and reduces the yieldand hence the value of the turnings and borings! Today, thanks to the tightening ofpollution norms and the introduction of ISO14000 standards, many companies are trying toremove the oil before disposing the borings thereby, knowingly or unknowingly, increasingthe yield! Our strong suggestion would be that you must pay attention to this aspect.Coolant oil can be removed by centrifuging, storing on a slope, pressing into a briquetteetc. The third mantra is ‘STORE CAREFULLY’. In many companies, dross and machinedborings are waste products to be dumped in some remote corner of the factory yard to behurriedly disposed off every time there are some visitors! Please spend some money inorganising a covered storage area that will permit segregated storage. And finally disposepromptly without accumulating for months on end.

ConclusionAlloy specifications should be designed bearing in mind that they are to be made as far aspossible from secondary metal.Impurity limits should not be tighter than absolutely necessary to achieve productperformance.Controlled relaxation wherever possible will yield significant cost savings.Finally, handle your own scrap arising with care and understand that they are valuable!


- 23 -

Paper 3 Part 1

ROLE OF ALLOYING ELEMENTS AND IMPURITIES

IntroductionIn this paper we will look at some of the important alloying and impurity elements whichmake up most Aluminium foundry alloys. The objective is to understand the role of thealloying elements and impurity limits.

Why Alloying?Pure Aluminium has low strength and hardness. Its machinability is also poor. The foundrycharacteristics of pure Aluminium are also very poor and presents many gating and feedingproblems, which is inherent in many pure metals. Pure Aluminium therefore is mainly usedin foundries only for a few castings such as rotor castings which are pretty straightforwardand where the high ductility and electrical and thermal conductivity are importantcharacteristics required. No other engineering products can be cast out of pure Aluminium.Alloying with other elements improves the mechanical properties as well as foundrycharacteristics of Aluminium. The effect of alloying in general is to increase the fluidity ofthe molten metal and increase the strength and hardness of the casting. Machinability isalso improved on alloying.

Those characteristics of an alloy, which determines the ease, or difficulty, of producingacceptable castings are called ‘Casting Properties’ while those properties, which are ofinterest to the designer or user of castings are the ‘Engineering Properties’. Both these setsof properties are improved by alloying in Aluminium alloys.

Let us now look at some of the common alloying elements and their role individually.

CopperCopper is an important alloying element in many Aluminium alloy families. Addition ofCopper progressively increases the strength and hardness of the alloy until the Copperadditions reach approximately 12%. Further addition of copper makes the alloy too brittlefor any engineering purpose. Copper greatly improves the machinability of the alloy andalso improves the elevated temperature properties.

Under equilibrium conditions about 5.6% copper is soluble in Aluminium at the eutectictemperature of 548°C. [See Figure 1] This solubility is reduced to below 0.5% Cu at roomtemperature. This wide decrease in solid solubility from 5.6% to 0.5% on solidification isthe principle reason on which the solution annealing and precipitation hardening heattreatment processes are based. Between 2.8 to 5% of Copper is necessary to give goodresponse to heat treatment by forming CuAl2 compound, which permits ‘precipitationhardening’.


- 24 -

FIGURE – I

Copper imparts high strength and improved machinability when added to Al-Si alloys.(Alloy 3.5% Cu, Si 6.0% is a preferred general-purpose alloy for sand castings while a3.5% Cu; Si 8.5% is preferred for pressure die castings)

Copper as an impurity element has the detrimental effect of reducing corrosion resistance.For optimal corrosion resistance the Copper content should be less than 0.05%. As Coppercontent increases there is a gradual increase in corrosion attack.

SiliconSilicon is the most important alloying addition to Aluminium foundry alloys. The reasonfor this is very simple. Silicon dramatically improves fluidity and casting characteristics ofAluminium. When Silicon is added to Aluminium the strength and hardness of the alloyimproves progressively.

800

LIQUID700

660600 Cu+ li quid

548500 5.65

Al400

300

AL+ Cu COMPOUND200

100AL 1 2 3 4 5 6 7 8 9 10

CuWEIGHT % COPPER

ALUMINIUM-COPPER EQUILIBRIUM ( PHASE) DIAGRAM -Al RICH END

TEMPERATURE

O

C


- 25 -

Another interesting aspect of Silicon additions is its effect in lowering the alloy’s meltingpoint. Addition of silicon to Aluminium steadily reduces the melting point of the alloyfrom the 660°C for pure Aluminium to 577°C for a Silicon content of 11.6 %. Thistemperature of 577°C is the eutectic temperature for binary Aluminium-Silicon alloys. [SeeFigure 2]

FIGURE – 2

The optimum Silicon content for an alloy depends on the casting process adopted. Forgeneral slow cooling castings 5 to 7% Silicon is adequate. For faster cooling castings 7 to9% would be required while for pressure die casting 8 to 12% Silicon is required.

Binary Aluminium-Silicon alloys combine the advantages of high corrosion resistance,good weldability and low specific gravity. Fluidity increases and hot-cracking tendency aswell as solidification shrinkage decreases steadily till the eutectic point (11-13%). Thismakes it easier to produce castings free from shrinkage and hot-cracks. This is whyAluminium-Silicon alloys are particularly useful to produce pressure tight castings.Aluminium-Silicon alloys do not machine as well as Aluminium alloys not containingSilicon. In fact when Silicon is present in large percentages, it is advisable to use carbidetools for machining.

1500 14301400130012001100 LIQUID1000

900800700

660600 LIQUID + SILICON

577500 11.60% silicon eutectic400

300 AL+SI COMPOUND200100

AL 10 20 30 40 50 60 70 80 90 100Si

HYPOEUTECTIC HYPER EUTECTIC

WEIGHT % SILICON

ALUMINIUM-SILICON EQUILIBRIUM ( PHASE) DIAGRAM

TEMPERATURE

O

C


- 26 -

The mechanical properties of Aluminium-Silicon alloys can be further improved by a melt-treatment process called “ MODIFICATION”1. Sodium salts or metallic sodium was usedto modify the silicon structure for many years, but due to its fading effect and itsinteraction with phosphorus resulting in reduction of modifying effect it is now beingreplaced, especially in critical applications, with strontium. Strontium at a level of 0.008-0.04% modifies the Aluminium-silicon eutectic system. Higher levels might result inporosity and can also affect the degassing efficiency and the fluidity of the metal.

Aluminium-Silicon alloys with more than the eutectic level of Silicon (more than 12%Silicon) are known as hypereutectic alloys. These high silicon alloys have out standingwear resistance, a lower thermal expansion coefficient and very good castingcharacteristics. These alloys have traditionally received limited attention and use becausethe presence of the extremely hard primary silicon phase reduces tool life duringmachining. Also, these alloys require special foundry practice/technique to control themicrostructure and casting soundness. Improvements in machine-tool technology and theintroduction of polycrystalline diamond cutting tools have done much to alleviate theproblems of poor tool life when these alloys are machined. As a matter of fact, but for thepoor tool life, the alloys actually result in excellent surface finish and their chipcharacteristics are also very good. These alloys have excellent fluidity as well.

To guarantee the best machinability and mechanical properties these hypereutecticAluminium-Silicon alloys must be treated to control primary silicon size. This treatment,termed refinement is accomplished by adding phosphorus at a level of 0.015-0.03% in theform of phosphor-copper. Phosphorus from this addition in the form of AlP3 compoundnucleates the primary silicon particles during solidification. However, when hyper- eutecticalloys are high-pressure die-cast such primary Silicon refinement is not needed. This isbecause the rapid solidification inherent in a pressure die-casting process results in finestructure even when the melt is not treated with phosphorus.

MagnesiumMagnesium at small percentages is the basis for strength and hardness development inheat-treated Aluminium-Silicon alloys like the familiar LM25 alloy of the erstwhileBS1490 or the A356 wheel alloy. In these alloys during heat treatment involving solutiontreatment and precipitation hardening Mg2Si precipitates as a hardened phase enhancingphysical properties. The usual range of Magnesium for optimal Mg2Si formation is 0.4% to0.7%.In the Aluminium-Silicon-Copper alloy system, Magnesium addition in combination withCopper affords greater response to heat treatment. A typical example is the C355 alloy - Cu1-1.5%, Si 4.5-5.5%, Mg 0.45-0.6%.

There are also Aluminium-Magnesium alloy systems like A514 or LM5 of the erstwhileBS1490 where Magnesium is a major alloying element. These alloys are characterized by

1 ‘Modification’ is the process of changing the shape of the silicon particles when they solidify in a matrix ofAluminium from its normal ‘dendritic’ or tree-like structure to a well-rounded shape.


- 27 -

excellent corrosion resistance, good machinability and attractive appearance whenanodized. Controlled melting and pouring practices are needed to compensate for thegreater oxidizing tendency of these alloys when molten. One particular aspect with respectto these Aluminium-Magnesium alloys is the allowable limit of Silicon in the system.Alloys like A511 (Mg 4%, Si 0.5%) and ENAC51400 (Mg 4.5-6.5%, Si 1.5%) permit asmall amount of Silicon. The reason is these alloys are generally used for parts in which themajor requirement is corrosion resistance or decorative appearance. Hence theaddition/presence of silicon will not in any way affect the performance.

ManganeseBinary Aluminium-Manganese alloys are not used in the foundry. Manganese is normallyconsidered as an impurity in casting compositions and is controlled to low levels in mostgravity cast compositions. Manganese forms a complex compound with Aluminium andIron and alters the shape of the Iron constituent from a plate like structure to a ‘ChineseScript’ structure. This results in improving the ductility and impact resistance of the alloy.Manganese is an important alloying element in wrought compositions. To permit the useof wrought material in the manufacture of foundry alloys most specifications permitManganese as an impurity with typical maximum limits ranging from 0.3 to 0.5%.

NickelIntroduction of up to 2.5 % Nickel increases the ability of an alloy to resist the effects ofexposure to elevated temperatures. It also reduces the coefficient of thermal expansion.Thus Nickel at 1 to 2% levels are often found only in piston alloys and in componentswhich are in high temperature service.

Titanium & BoronTitanium is used to refine the grain structure of Aluminium casting alloys with or withoutthe combination of smaller amounts of Boron. Addition of Titanium for grain refinementreduces cracking tendencies in castings.

StrontiumAs mentioned earlier Strontium is used as a permanent modifier for eutectic and somehypoeutectic Aluminium-Silicon alloys. By means of modification the Aluminium-Siliconconstituent can be changed from needles and plates to a fine spherical shape withimprovements in casting characteristics and mechanical properties. Addition of strontium istypically in the range of 0.01 to 0.03%. After the strontium addition, usually in the form ofa master alloy, the melt should be left undisturbed for a short period (say 10-15 minutes) asthe degree of modification increases with holding time.

Role of impuritiesLet us now examine the role of a few important impurity elements in Aluminium alloys.

IronIron is the omnipresent impurity in Aluminium right from the Ore processing to thefinished component stage. The degree or permissible level of Iron in Aluminium alloysdepends on the casting process employed and also on the application of the product.


- 28 -

Iron increases the hot-tear resistance which is helpful, but decreases ductility. This isbecause iron combines with other elements forming insoluble embrittling constituents thatact as severe stress raisers. Thus in premium quality alloys like the Aluminium-Silicon-Magnesium A356 ‘wheel alloy’, where increased ductility is a requirement, Iron isrestricted to 0.2% or less.

Iron is generally restricted to 0.5 to 0.8% in most sand and gravity casting alloys as anotherundesirable effect of high Iron content is the coarsening of as cast grain size. However thisnegative effect on grain size can be countered by Titanium grain refining additions andcurrent specifications even allow up to 1% Iron in gravity casting specifications.In high-pressure die casting, as the Aluminium alloy is injected into the mould underpressure, because of the high affinity Aluminium has for Iron, it tends to attack anddissolve the die steel. This can cause the metal to stick to the die and component ejectionbecomes a problem. This is known as soldering to the die. This tendency is reduced if thealloy has about 0.8 to 1.0% of Iron already alloyed in it. Thus pressure die casting alloyspecifications generally permit 1 to 1.3% Iron.

ZincNo significant benefits are obtained by the addition of Zinc to Aluminium. However, Zincalso brings in room temperature aging properties. Hence in these alloys high strengths canbe achieved without heat treatment. Thus there is an alloy known as Tenz alloy with 6 to8% of Zinc along with small amounts of Copper (0.6%) and Magnesium (0.4%). This alloyis useful for making castings with shapes difficult to solution heat treat.However, in practically all other Aluminium alloys Zinc is an impurity element. Mostcommon alloy specifications permit Zinc up to 3 %, as it has no deleterious effects onproperties. This limit enables a good amount of die cast scrap to be used in the alloypreparation.

Lead, Tin and BismuthBismuth and Lead form small, insoluble globules in a casting microstructure. This acts aschip breakers that reduce the length of chips during machining facilitating increased cuttingspeeds and reduced usage of cutting fluids. Thus both Bismuth and Lead up to 0.5% levelsare used in some specifications but mostly these are impurity elements at 0.3%.Tin is also credited with improving machinability of Aluminium casting alloys but itsusage is only in alloys where its soft nature imparts bearing properties. In mostcompositions Tin is an impurity element.


- 29 -

Paper 3 Part 2

A Comparison of Major International Specifications for AluminiumFoundry Alloys

In this presentation the following six alloy families have been chosen for comparison:• 3% Copper, 6% Silicon alloy family• 3% Copper, 8 to 12% Silicon alloy family• 11% Silicon alloy family• 7% Silicon, 0.5% Magnesium alloy family• 3 to 5% Magnesium alloy family• High silicon alloy family

The following standards have been referred for comparison purposes:• EN1676:1997 Aluminium and Aluminium alloys – Alloyed ingots for Remelting –

Specifications.• EN1706:1998 Aluminium and Aluminium alloys – Castings – Chemical composition

and Mechanical Properties.• The Aluminium Association, Registration Record Series, Designations and Chemical

Composition Limits for Aluminium Alloys in the Form of Castings and Ingot –February 1999 revision.

• JIS H 5202:1999 Aluminium Alloy Castings• JIS H 5302:2000 Aluminium Alloy Die Castings

[Note: In 1996, member countries of the European Union, brought out a unified jointstandard for Aluminium foundry alloy ingots (the EN1676) and a similar standard forcastings (the EN1706) replacing the various individual country standards such as theBS1490 of UK and the DIN1725 of Germany.]

For each alloy family a selection of the specifications in each of the standards listed abovehave been compared. The main purpose of this is to make the user aware of the wide rangeof specifications that are now available for each alloy family. By studying them carefullythe user can convince himself that depending on the application, alloys with differentimpurity limits can and should be chosen thus permitting optimal use of secondary materialwith corresponding cost savings.

It should further be noted that EN specifications now clearly have two standards – one foralloy ingots and the other for castings. The U.S Aluminium Association record alsoprovides separate specifications for alloy ingots and castings. Typically the castingspecifications will provide for slightly higher impurity limits taking into account theinvariable pick up of impurity limits like Iron during casting. In the case of Magnesium,the casting limits will generally be lower than the ingot limit providing for loss ofMagnesium during melting.

While a detailed study is left to the reader, the following two examples will be of interest:


- 30 -

Case 1:LM4 was the only 3% Copper, 6% Silicon specification in the erstwhile BS1490. Itsspecification (BS1490-1988) was:Copper 2 to 4%, Silicon 4 to 6%, Manganese 0.2 to 0.6%, Iron 0.8%, Magnesium 0.2%,and Zinc 0.5%.

The revised EN specifications have 5 alloys in this family. While the alloying elementrange is by and large similar, impurity limits vary. Iron varies from 0.9% in AB45000 to0.55% in AB45400. Zinc varies from 2% in AB45000 to 0.2% in AB45400. In otherwords, AB45000 has liberal impurity limits while AB45400 has comparatively narrowerlimits. The alloy that is meant to be heat treated – AB45100 specifies a minimumMagnesium limit while the others do not. AB45200 permits Magnesium up to 0.4% whileAB45000 permits Magnesium up to 0.55%.

Similar is the case of the specifications in AA and JIS. Both specifications have alloyswith close impurity limits and ones with wide impurity limits. In alloys A319.1 and 320.1for instance, Zinc is permitted up to 3% while AC2B of JIS permits Zinc up to 1%. Themaximum Iron limits specified is 0.9% in both the ENAB series (AB45000) and the AAseries (B319.1 and 320.1) and 1% in JIS (AC2B).

This clearly shows that alloying and impurity limits should be fixed depending on theapplication and with proper foundry practice producing sound castings with 1% Iron and3% Zinc is possible.

Incidentally, the EN standard mentions that the tonnage of castings produced in eachspecification decreases down the table. In other words, maximum tonnage (all overEurope) is of AB45000 – the most liberal specification - and the least tonnage is ofAB45400 the tightest specification.

Case 2:JIS ADC12 is the most common pressure die casting specification in India. It specifies amaximum impurity limit of 1% for Zinc. In the latest edition a new specification ADC12Zhas been added which is identical to ADC12 in all aspects except it permits Zinc up to 3%.Obviously, this is to permit a greater use of secondary material and a correspondingreduction in cost.

The reader is encouraged to study the physical property data wherever given to see whichspecification changes affect mechanical properties significantly and which do not.

Important NoteThe specifications that follow are extracts from the relevant international standards and aregiven for comparison purposes only. It does not purport to be the complete standard. Thereader is advised to refer to the original standard for their actual application and use.


- 31 -

E n s e r ie s C u S i M g M n F e N i T i Z n C r P b S n A l

E n A B 4 5 0 0 0 3 .0 -5 .0 5 .0 -7 .0 0 .5 5 0 .2 -0 .6 5 0 .9 0 0 .4 5 0 .2 0 2 .0 0 0 .1 5 0 .3 0 0 .1 5 R E M

E n A B 4 5 1 0 0 2 .6 -3 .6 4 .5 -6 .0 0 .2 0 -0 .4 5 0 .5 5 0 .5 0 0 .1 0 0 .2 0 .2 0 0 .1 0 0 .0 5 R E M

E n A B 4 5 2 0 0 2 .5 -4 .0 4 .5 -6 .0 0 .4 0 0 .2 -0 .5 5 0 .7 0 0 .3 0 0 .1 5 0 .5 5 0 .2 0 0 .1 0 R E M

E n A B 4 5 3 0 0 1 .0 -1 .5 4 .5 -5 .5 0 .4 -0 .6 5 0 .2 -0 .5 5 0 .5 5 0 .2 5 0 .0 5 -0 .2 0 .1 5 0 .1 5 0 .0 5 R E M

E n A B 4 5 4 0 0 2 .6 -3 .6 4 .5 -6 .0 0 .0 5 0 .2 -0 .5 5 0 .5 5 0 .1 0 0 .2 0 .2 0 0 .1 0 0 .0 5 R E M

A A S E R I E S C u S i M g M n F e N i T i Z n C r P b S n A l

3 0 8 . 1 4 .0 -5 .0 5 .0 -6 .0 0 .1 0 .5 0 .8 0 .2 5 1 .0 R E M

3 0 8 . 2 4 .0 -5 .0 5 .0 -6 .0 0 .1 0 .3 0 .8 0 .2 0 .5 R E M

3 1 8 . 1 3 .0 -4 .0 5 .5 -6 .5 0 .1 5 -0 .6 0 0 .5 0 .8 0 0 .3 5 0 .2 5 0 .9 0 R E M

A 3 1 9 . 1 3 .0 -4 .0 5 .5 -6 .5 0 .1 0 .5 0 .8 0 0 .3 5 0 .2 5 3 .0 0 R E M

3 1 9 . 1 3 .0 -4 .0 5 .5 -6 .5 0 .1 0 .5 0 .8 0 0 .3 5 0 .2 5 1 .0 0 R E M

3 1 9 . 2 3 .0 -4 .0 5 .5 -6 .5 0 .1 0 .1 0 .6 0 0 .1 0 0 .2 0 .1 0 R E M

B 3 1 9 .1 3 .0 -4 .0 5 .5 -6 .5 0 .1 5 -0 .5 0 .8 0 .9 0 0 .5 0 0 .2 5 1 .0 0 R E M

3 2 0 . 1 2 .0 -4 .0 5 .0 -8 .0 0 .1 -0 .6 0 .8 0 .9 0 0 .3 5 0 .2 5 3 .0 0 R E M

J IS S E R IE S C u S i M g M n F e N i T i Z n C r P b S n A l

A C 2 A 3 .0 -4 .5 4 .0 -6 .0 0 .2 5 0 .5 5 0 .8 0 0 .3 0 0 .2 0 0 .5 5 0 .1 5 0 .1 5 0 .0 5 R E M

A C 2 B 2 .0 -4 .0 5 .0 -7 .0 0 .5 0 0 .5 0 1 .0 0 0 .3 5 0 .2 0 1 .0 0 0 .2 0 0 .2 0 0 .1 0 R E M

C H E M IC A L C O M P O S IT IO N O F IN G O T S

C O M P A R IS O N O F IN T E R N A T IO N A L S T A N D A R D S - A L U M IN IU M C A S T IN G A L L O Y S

A L U M IN IU M C A S T IN G A L L O Y S - 3 % C o p p e r , 6 % S i l i c o n


- 32 -

Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn Al

ALLOYEn Ac 45000 3.0-5.0 5.0-7.0 0.55 0.2-0.65 1.00 0.45 0.25 2.00 0.15 0.30 0.15 REM AS CAST 170 1 75En AC 45100 2.6-3.6 4.5-6.0 0.15-0.45 0.55 0.60 0.10 0.25 0.20 0.05 0.10 0.05 REM T 6 320 1 110En AC 45200 2.5-4.0 4.5-6.0 0.40 0.2-0.55 0.80 0.30 0.20 0.55 - 0.20 0.1 REM T 6 230 <1 90En AC 45300 1.0-1.5 4.5-5.5 0.35-0.65 0.55 0.65 0.15 0.05-0.25 0.15 - 0.15 0.05 REM T 6 230 <1 100En AC 45400 2.6-3.6 4.5-6.0 0.05 0.55 0.60 0.10 0.25 0.20 0.05 0.10 0.05 REM T 4 230 6 75

AA SERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn Al

308 4.0-5.0 5.0-6.0 0.1 0.5 1.00 0.35 0.25 1.00 - - - REM AS CAST 193 2 70A 319.0 3.0-4.0 5.5-6.5 0.1 0.5 1.00 0.35 0.25 3.00 - - - REM No Data No Data No Data No Data

319 3.0-4.0 5.5-6.5 0.1 0.5 1.00 0.35 0.25 1.00 - - - REM AS CAST 234 2.5 85318 3.0-4.0 5.5-6.5 0.1-0.6 0.5 1.00 0.35 0.25 1 - - - REM T6 276 3 95

JIS SERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn Al

AC2A 3.0-4.5 4.0-6.0 0.25 0.55 0.80 0.30 0.20 0.55 0.15 0.15 0.05 REM AS CAST 180 2 75AC2A T6 270 1 90AC2B 2.0-4.0 5.0-7.0 0.50 0.50 1.00 0.35 0.20 1.00 0.20 0.20 0.10 REM AS CAST 150 1 70AC2B T6 240 1 90

HARDNESSBHN

ALUMINIUM CASTING ALLOYS- 3% COPPER 6% SILICON

CHEMICAL COMPOSITION

COMPARISON OF INTERNATIONAL SPECIFICATIONS

EN SERIESMECHANICAL PROPERTIES

TEMPERCONDITION

TENSILEN/mm2

ELONG-ATION%

HARDNESSBHN



MECHANICAL PROPERTIES

TEMPERCONDITION

TENSILEN/mm2

ELONG-ATION%

HARDNESSBHN


TEMPERCONDITION

TENSILEN/mm2

ELONG-ATION%


- 33 -

E n s e r ie s C u S i M g M n F e N i T i Z n C r P b S n A l

E n A B 4 6 0 0 0 2 .0 -4 .0 8 .0 -1 1 .0 0 .1 5 -0 .5 5 0 .5 5 0 .6 0 - 1 .1 0 0 .5 5 0 .2 1 .2 0 0 .1 5 0 .3 5 0 .2 5 R E ME n A B 4 6 1 0 0 1 .5 -2 .5 1 0 -1 2 .0 0 .3 0 .5 5 0 .4 5 -1 .0 0 .4 5 0 .2 1 .7 0 0 .1 5 0 .2 5 0 .2 5 R E ME n A B 4 6 2 0 0 2 .0 -3 .5 7 .5 -9 .5 0 .1 5 -0 .5 5 0 .1 5 -0 .6 5 0 .7 0 0 .3 5 0 .2 1 .2 0 0 .2 5 0 .1 5 R E ME n A B 4 6 3 0 0 3 .0 -4 .0 6 .5 -8 .0 0 .3 5 -0 .6 0 0 .2 0 -0 .6 5 0 .7 0 0 .3 0 0 .2 0 .6 5 0 .1 5 0 .1 0 R E ME n A B 4 6 4 0 0 0 .8 -1 .3 8 .3 -9 .7 0 .3 0 -0 .6 5 0 .1 5 -0 .5 5 0 .7 0 0 .2 0 0 .1 0 -0 .1 8 0 .8 0 0 .1 0 0 .1 0 R E ME n A B 4 6 5 0 0 2 .0 -4 .0 8 .0 -1 1 .0 0 .1 5 -0 .5 5 0 .5 5 0 .6 - 1 .2 0 .5 5 0 .2 3 .0 0 0 .1 5 0 .3 5 0 .2 5 R E ME n A B 4 6 6 0 0 1 .5 -2 .5 6 .0 -8 .0 0 .3 5 0 .1 5 -0 .6 5 0 .7 0 0 .3 5 0 .2 1 .0 0 0 .2 5 0 .1 5 R E M

A A S E R IE S C u S i M g M n F e N i T i Z n C r P b S n A l

3 2 0 .1 2 .0 -4 .0 5 .0 -8 .0 0 .1 -0 .6 0 .8 0 .9 0 .3 5 0 .2 5 3 .0 R E M3 3 2 .1 2 .0 -4 .0 8 .5 -1 0 .5 0 .6 -1 .5 0 .5 0 .9 0 .5 0 .2 5 1 .0 R E M3 3 2 .2 2 .0 -4 .0 8 .5 -1 0 .0 0 .9 -1 .3 0 .1 0 .6 0 .1 0 .2 0 .1 R E M3 3 3 .1 3 .0 -4 .0 8 .0 -1 0 .0 0 .1 0 -0 .5 0 0 .5 0 .8 0 0 .5 0 .2 5 1 .0 0 - - R E M

A 3 3 3 .1 3 .0 -4 .0 8 .0 -1 0 .0 0 .1 0 -0 .5 0 0 .5 0 .8 0 0 .5 0 0 .2 5 3 .0 0 - - - R E MA 3 8 0 .1 3 .0 -4 .0 7 .5 -9 .5 0 .1 0 .5 1 .0 0 0 .5 0 - 2 .9 0 - - 0 .3 5 R E MA 3 8 0 .2 3 .0 -4 .0 7 .5 -9 .5 0 .1 0 .1 0 .6 0 0 .1 0 - 0 .1 0B 3 8 0 .1 3 .0 -4 .0 7 .5 -9 .5 0 .1 0 .5 1 .0 0 0 .5 0 - 0 .9 0 - - 0 .3 5 R E MC 3 8 0 .1 3 .0 -4 .0 7 .5 -9 .5 0 .1 5 -0 .3 0 0 .5 1 .0 0 0 .5 0 - 2 .9 0 - - 0 .3 5 R E MD 3 8 0 .1 3 .0 -4 .0 7 .5 -9 .5 0 .1 5 -0 .3 0 0 .5 1 .0 0 0 .5 0 - 0 .9 0 - - 0 .3 5 R E M

3 8 3 .1 2 .0 -3 .0 9 .5 -1 1 .5 0 .1 0 .5 1 .0 0 0 .3 0 - 2 .9 0 - - 0 .1 5 R E MA 3 8 3 .1 2 .0 -3 .0 9 .5 -1 1 .5 0 .1 5 -0 .3 0 0 .5 1 .0 0 0 .3 0 - 2 .9 0 - - 0 .1 5 R E M

3 8 3 .2 2 .0 -3 .0 9 .5 -1 1 .5 0 .1 0 .1 0 .6 -1 .0 0 .1 0 - 0 .1 0 - - 0 .1 R E M3 8 4 .1 3 .0 -4 .5 1 0 .5 -1 2 .0 0 .1 0 .5 1 .0 0 0 .5 0 - 2 .9 0 - 0 .3 5 R E M3 8 4 .2 3 .0 -4 .5 1 0 .5 -1 2 .0 0 .1 0 .1 0 .6 -1 .0 0 .1 0 - 0 .1 0 - 0 .1 0 R E M

A 3 8 4 .1 3 .0 -4 .5 1 0 .5 -1 2 .0 0 .1 0 .5 1 .0 0 0 .5 0 - 0 .9 0 - 0 .3 5 R E MB 3 8 4 .1 3 .0 -4 .5 1 0 .5 -1 2 .0 0 .1 5 -0 .3 0 0 .5 1 .0 0 0 .5 0 - 0 .9 0 - 0 .3 5 R E MC 3 8 4 .1 3 .0 -4 .5 1 0 .5 -1 2 .0 0 .1 5 -0 .3 0 0 .5 1 .0 0 0 .5 0 2 .9 0 0 .3 5 R E M

3 8 5 .1 2 .0 -4 .0 1 1 .0 -1 3 .0 0 .3 0 .5 1 .1 0 0 .5 0 2 .9 0 0 .3 R E M

J IS S E R IE S C u S i M g M n F e N i T i Z n C r P b S n A l

A D C - 1 0 2 .0 -4 .0 7 .5 0 -9 .5 0 0 .3 0 0 .5 1 .3 0 0 .5 0 - 1 .0 0 - - 0 .2 0 R E MA D C - 1 0 Z 2 .0 -4 .0 7 .5 0 -9 .5 0 0 .3 0 0 .5 0 1 .3 0 0 .5 0 - 3 .0 0 - - 0 .2 0 R E MA D C - 1 1 2 .5 -4 .0 7 .5 0 -9 .5 0 0 .3 0 0 .6 0 1 .3 0 0 .5 0 0 .2 1 .2 - - 0 .2 0 R E MA D C - 1 2 1 .5 0 -3 .5 0 9 .6 -1 2 .0 0 .3 0 0 .5 0 1 .3 0 .5 0 - 1 .0 - - 0 .2 0 R E M

A D C - 1 2 Z 1 .5 0 -3 .5 0 9 .6 0 -1 2 .0 0 .3 0 0 .5 0 1 .3 0 .5 0 - 3 .0 - - 0 .2 0 R E M

C H E M IC A L C O M P O S IT IO N O F IN G O T SA L U M IN IU M C A S T IN G A L L O Y S 3 % C O P P E R 8 - 1 2 % S IL IC O N

C O M P A R IS O N O F IN T E R N A T IO N A L S T A N D A R D S


- 34 -

Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn Al

En Ac 46000 2.0-4.0 8.0-11.0 0.05-0.55 0.55 1.30 0.55 0.25 1.20 0.15 0.35 0.25 REM AS CAST 240 1 80En AC 46100 1.5-2.5 10-12.0 0.3 0.55 1.10 0.45 0.25 1.70 0.15 0.25 0.25 REM AS CAST 240 1 80En AC 46200 2.0-3.5 7.5-9.5 0.05-0.55 0.15-0.65 0.80 0.35 0.25 1.20 0.05 0.25 0.15 REM AS CAST 240 1 80En AC 46300 3.0-4.0 6.5-8.0 0.30-0.60 0.2-0.65 0.80 0.30 0.25 0.65 0.15 0.10 REM AS CAST 180 1 80En AC 46400 0.8-1.3 8.3-9.7 0.25-0.65 0.55 0.8 0.2 0.10-0.2 0.8 0.10 0.10 REM AS CAST 135 1 60En AC 46600 1.5-2.5 6.0-8.0 0.35 0.15-0.65 0.8 0.35 0.25 1.0 0.25 0.15 REM ASCAST 150 1 60

AA SERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTemperCond.

TENSILEN/mm2

ELONG-ATION%

HARDNESSBHN

A380.0 3.0-4.0 7.5-9.5 0.1 0.5 1.30 0.5 - 3.00 - - 0.35 REM ASCAST 331 3 80A380.0 3.0-4.0 7.5-9.5 0.1 0.1 1.30 0.50 - 3.00 - - 0.35 REM ASCAST 324 4 75A383.0 2.0-3.0 9.5-11.5 0.10-0.30 0.5 1.30 0.30 3.00 - - 0.15 REM No Data No Data No Data No DataA 384.0 3.0-4.5 10.50-12.0 0.1 1.3 1.30 0.50 - 1.00 - - 0.35 REM ASCAST 324 1 No Data

JIS SERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTemperCond.

TENSILEN/mm2

ELONG-ATION%

HARDNESSBHN

ADC-10 2.0-4.0 7.50-9.50 0.30 0.5 1.30 0.50 - 1.00 - - 0.20 REM AS CAST 241 1.5 73.6ADC-10Z 2.0-4.0 5.0-7.0 0.50 0.50 1.30 0.50 - 3.00 - - 0.20 REM No Data No Data No Data No DataADC-11 2.5-4.0 7.50-9.50 0.30 0.60 1.30 0.50 - 1.2 - - 0.20 REM No Data No Data No Data No DataADC-12 1.50-3.50 9.6-12.0 0.30 0.50 1.3 0.50 - 1.0 - - 0.20 REM AS CAST 228 1.4 74.1

ADC-12Z 1.50-3.50 9.60-12.0 0.30 0.50 1.3 0.50 - 3.0 - - 0.20 REM No Data No Data No Data No Data

En seriesMECHANICAL PROPERTIES



COMPARISON OF INTERNATIONAL STANDARDS

ALUMINIUM CASTING ALLOYS - 3% Copper, 8 - 12% Silicon


TemperCond. TENSILE

N/mm2ELONG

-ATION%HARDNESS

BHN


- 35 -

En series Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn Al

En AB44000 0.03 10.0-11.80 0.45 0.10 0.15 - 0.15 0.07 REMEnAB 44100 0.1 10.5-13.5 0.10 0.55 0.55 0.10 0.15 0.15 0.10 0.2 REMEn AB44200 0.03 10.5-13.5 - 0.35 0.40 0.15 0.10 REMEn AB44300 0.08 10.5-13.5 - 0.55 0.45-0.9 0.15 0.15 REMEn AB44400 0.08 8-11.0 0.10 0.50 0.55 0.05 0.15 0.15 0.05 0.05 REM


413.2 0.1 11.0-13.0 0.07 0.1 0.7-1.1 0.1 0.1 0.1 REMA 413.1 1.00 11.0-13.0 0.10 0.35 1.00 0.50 - 0.40 - - 0.15 REMA 413.2 0.10 11.0-13.0 0.05 0.05 0.60 0.05 - 0.05 - - 0.05 REMB 413.1 0.10 11.0-13.0 0.05 0.35 0.40 0.05 0.25 0.10 - - - REM


AC3A 0.25 10.0-13.0 0.15 0.35 0.80 0.10 0.20 0.30 0.15 0.10 0.10 REMAC4A 0.25 8.0-10.0 0.30-0.60 0.30-0.60 0.55 0.10 0.20 0.25 0.15 0.10 0.05 REM


CHEMICAL COMPOSITION OF INGOTS

ALUMINIUM CASTING ALLOYS - ALUMINIUM 11% SILICON


- 36 -

En series Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTempercondition

TENSILEN/mm2

ELONG-ATION %

HARDNESSBHN

En Ac44000 0.05 10.0-11.80 0.45 0.10 0.19 0.15 0.07 REM AS CAST 150 6 45EnAC 44100 0.15 10.5-13.5 0.10 0.55 0.65 0.10 0.2 0.15 0.10 REM AS CAST 150 4 50En AC44200 0.05 10.5-13.5 0.35 0.55 0.15 0.10 REM AS CAST 240 1 80EnAC 44300 0.1 10.5-13.5 0.55 1.00 0.15 0.15 REM AS CAST 240 1 60EnAC 44400 0.1 8-11.0 0.1 0.5 0.65 0.05 0.15 0.15 0.05 0.05 REM AS CAST 220 2 55

AA SERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTempercondition

TENSILEN/mm2

ELONG-ATION %

HARDNESSBHN

413 1.00 11.0-13.0 0.10 0.35 2.00 0.50 - 0.50 - - 0.15 REM ASCAST 296 2.5 80A 413.0 1.00 11.0-13.0 0.10 0.35 1.30 0.50 - 0.50 - - 0.15 REM ASCAST 241 3.5 80

REM No Data No Data No Data No DataB 413.0 0.10 11.0-13.0 0.05 0.35 0.50 0.05 0.25 0.10 - - - REM No Data No Data No Data No Data

JIS SERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTempercondition

TENSILEN/mm2

ELONG-ATION %

HARDNESSBHN

AC3A 0.25 10.0-13.0 0.15 0.35 0.80 0.10 0.20 0.30 0.15 0.10 0.10 REM AS CAST 170 5 50AC4A 0.25 8.0-10.0 0.30-0.60 0.30-0.60 0.55 0.10 0.20 0.25 0.15 0.10 0.05 REM AS CAST 170 3 60AC4A T6 240 2 90



ALUMINIUM CASTING ALLOYS Al 11.0% SILICON



- 37 -

EN SERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn Al

ENAB 42000 0.15 6.5-7.5 0.25-0.65 0.35 0.45 0.15 0.05-0.20 0.15 - 0.15 0.05 REMENAB 42100 0.03 6.5-7.5 0.30-0.45 0.10 0.15 - 0.10-0.18 0.07 - - REMENAB42200 0.03 6.5-7.5 0.50-0.70 0.10 0.15 - 0.10-0.18 0.07 - - - REM


356.1 0.25 6.5-7.5 0.25-0.45 0.35 0.5 - 0.25 0.35 - - REM356.2 0.1 6.5-7.5 0.30-0.45 0.05 0.13-0.25 - 0.20 0.05 - - REM

A356.1 0.20 6.5-7.5 0.30-0.45 0.10 0.15 - 0.2 0.1 - - - REMA356.2 0.1 6.5-7.5 0.30-0.45 0.05 0.12 - 0.2 0.05 - - - REMB 356.2 0.03 6.5-7.5 0.30-0.45 0.03 0.06 - 0.04-0.20 0.03 - - - REMC 356.2 0.03 6.5-7.5 0.30-0.45 0.03 0.04 - 0.04-0.20 0.03 - - - REMF 356.2 0.1 6.5-7.5 0.17-0.25 0.05 0.12 - 0.04-0.20 0.05 - - - REM357.1 0.05 6.5-7.5 0.45-0.60 0.03 0.12 - 0.2 0.05 - - - REM

A357.2 0.1 6.5-7.5 0.45-0.70 0.05 0.12 - 0.04-0.20 0.05 - - - REMB 357.2 0.03 6.5-7.5 0.45-0.60 0.03 0.06 - 0.04-0.20 0.03 - - - REMC357.2 0.03 6.5-7.5 0.50-0.70 0.03 0.06 - 0.04-0.20 0.03 - - - REM358.2 0.1 7.6-8.6 0.45-0.60 0.1 0.2 0.12-0.20 0.1 0.05 - - REM

A444.2 0.05 6.5-7.5 0.05 0.1 0.2 - 0.2 0.1 - - - REM


AC4C 0.2 6.5-7.5 0.2-0.40 0.6 0.5 0.05 0.20 0.30 - - REMAC4CH 0.1 6.5-7.5 0.25-0.45 0.10 0.2 0.05 0.20 0.10 0.05 0.05 0.05 REM


CHEMICAL COMPOSITION OF ALLOY INGOTS

ALUMINIUM CASTING ALLOYS -7% SILICON,0.5% MAGNESIUM


- 38 -


TEMPERCONDITIO

NTENSILEN/mm2

ELONGA-TION%

HARDNESSBHN

ENAC 42000 0.2 6.5-7.5 0.2-0.65 0.35 0.55 0.15 0.05-0.25 0.15 - 0.15 0.05 REM T6 220 1 75ENAC 42000 0.2 6.5-7.5 0.2-0.65 0.35 0.55 0.15 0.05-0.25 0.15 - 0.15 0.05 REM T6 220 1 75ENAC 42100 0.05 6.5-7.5 0.25-0.45 0.10 0.19 - 0.08-0.25 0.07 - - REM T6 230 2 75ENAC42200 0.05 6.5-7.5 0.45-0.7 0.10 0.19 - 0.08-0.25 0.07 - - - REM T6 250 1 85

AA SERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTEMPER

CONDITION

TENSILEN/mm2

ELONGA-TION%

HARDNESSBHN

356 0.25 6.5-7.5 0.2-0.45 0.35 0.6 - 0.25 0.35 - - REM T6 262 5 80A 356.0 0.2 6.5-7.5 0.25-0.45 0.10 0.2 - 0.20 0.10 - - REM T6 283 10 90B 356.0 0.05 6.5-7.5 0.25-0.45 0.05 0.09 - 0.04-0.20 0.05 - - - REM No-dat a No-data No-data No-dat aA357.0 0.2 6.5-7.5 0.4-0.7 0.1 0.2 - 0.04-0.20 0.1 - - - REM T6 283 3 100B357.0 0.05 6.5-7.5 0.4-0.6 0.05 0.09 - 0.04-0.20 0.05 - - - REM No-dat a No-data No-data No-dat a

JIS SERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTEMPER

CONDITION

TENSILEN/mm2

ELONGA-TION%

HARDNESSBHN

AC4C 0.2 6.5-7.5 0.2-0.40 0.6 0.5 0.05 0.20 0.30 - - REM ASCAST 150 3 55AC4C 0.2 6.5-7.5 0.2-0.40 0.6 0.5 0.05 0.20 0.30 - - REM T6 230 2 85


CHEMICAL COMPOSITION MECHANICAL PROPERTIES

ALUMINIUM CASTING ALLOYS- 7% SILICON 0.5%MAGNESIU M


- 39 -


ENAB51000 0.08 0.45 2.7-3.5 0.45 0.45 - 0.2 0.1 - - REMENAB 51100 0.03 0.45 2.7-3.5 0.45 0.4 - 0.2 0.1 - - REMENAB51200 0.08 2.5 8.5-10.5 0.55 0.45-0.9 0.1 0.2 0.25 0.1 0.1 REMENAB51300 0.05 0.35 4.8-6.5 0.45 0.45 - 0.2 0.1 - - - REMENAB51400 0.03 1.3 4.8-6.5 0.45 0.45 - 0.2 0.1 - - - REM


511.1 0.15 0.3-0.7 3.6-4.5 0.35 0.4 - 0.25 0.15 - - REM511.2 0.1 0.3-0.7 3.6-4.5 0.1 0.3 - 0.2 0.1 - - REM512.2 0.10 1.4-2.2 3.6-4.5 0.10 0.35-0.7 - 0.2 0.1 - - REM513.2 0.1 0.3 3.6-4.5 0.1 0.3 - 0.2 1.4-2.2 - -514.2 0.1 0.3 3.6-4.5 0.1 0.3 - 0.2 0.1 - - - REM516.1 0.3 0.3-1.5 2.6-4.5 0.15-0.40 0.35-0.7 0.25-0.40 0.1-0.2 0.2 - 0.1 REM

A 535.1 0.1 0.2 6.6-7.5 0.1-0.25 0.15 - 0.25 - - - REM


AC7A 0.1 0.2 3.5-5.5 0.6 0.3 0.05 0.20 0.15 0.15 0.05 0.05 REM

COMPARISON OF INTERNATIONAL STANDARD S

CHEMICAL COMPOSITION INGOTS

ALUMINIUM CASTING ALLOYS - 3-5% MAGNESIUM


- 40 -

ENSERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTEMPERCONDITI

ON

TENSILEN/mm2

ELONG-ATION%

HARDNESSBHN

ENAC 51000 0.1 0.55 2.50-3.50 0.45 0.55 - 0.2 0.1 - - REM AS CAST 140 3 50ENAC 51100 0.05 0.55 2.50-3.50 0.45 0.55 - 0.2 0.1 - - REM AS CAST 150 5 50ENAC 51300 0.1 0.55 4.5-6.5 0.45 0.55 - 0.2 0.1 - - REM AS CAST 160 3 55ENAC51400 0.05 1.5 4.5-6.5 0.45 0.55 - 0.2 0.1 - - - REM AS CAST 160 3 60

AASERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTEMPERCONDITI

ON

TENSILEN/mm2

ELONG-ATION%

HARDNESSBHN

511 0.15 0.3-0.7 3.5-4.5 0.35 0.5 - 0.25 0.15 - - REM ASCAST 145 3 50514 0.15 0.35 3.5-4.5 0.35 0.5 - 0.25 0.15 - - REM ASCAST 172 9 50516 0.30 0.30-1.5 2.5-4.5 0.15-0.4 0.35-1.0 0.25-0.40 0.1-0.2 0.2 - - 0.1 REM T6 No-data No-data No-data

JIS SERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTEMPERCONDITI

ON

TENSILEN/mm2

ELONG-ATION%

HARDNESSBHN

AC7A 0.1 0.2 3.5-5.5 0.6 0.2 0.05 0.20 0.10 0.15 0.05 REM ASCAST 210 12 60


ALUMINIUMCASTINGALLOYS - 3-5%MAGNESIUM

MECHANICAL PROPERTIESCHEMICAL COMPOSITION


- 41 -


ENAB 48000 0.8-1.5 10.5-13.5 0.9-1.5 0.35 0.6 0.7-1.3 0.2 0.35 - - REM


A 390.1 4.0-5.0 16-18 0.50-0.65 0.1 0.4 - 0.2 0.1 - - REMB390.1 4.0-5.0 16-18 0.5-0.65 0.50 1 0.1 0.20 1.40 - - 0.3 REM392.1 0.4-0.8 18-20.0 0.9-1.2 0.2-0.6 1.1 0.5 0.2 0.4 - - 0.3 REM393.1 0.7-1.1 21.0-23.0 0.8-1.3 0.1 1 2.0-2.5 0.10-0.20 0.1 REM393.2 0.7-1.1 21-23 0.8-1.3 0.1 0.8 2-2.5 0.1-0.2 0.1 - - - REM


AC8A 0.8-1.3 11.0-13.0 0.7-1.3 0.15 0.8 0.8-1.5 0.20 0.15 0.1 0.1 0.1 REMAC8B 2.0-4.0 8.5-10.5 0.5-1.5 0.5 1.0 0.1-1.0 0.2 0.5 0.1 0.1 0.1 REMAC9A 0.5-1.5 22-24 0.5-1.5 0.5 0.8 0.5-1.5 0.2 0.2 0.1 0.1 0.1 REMAC9B 0.5-1.5 18-20 0.5-1.5 0.5 0.8 0.5-1.5 0.2 0.2 0.1 0.1 0.1 REM

ALUMINIUM CASTING ALLOYS - HIGH SILICON


CHEMICAL COMPOSITION - INGOT


- 42 -

ENSERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTEMPER

CONDITIONTENSILEN/mm2

ELONGATION%

HARDNESSBHN

ENAC48000 0.8-1.5 10.5-13.5 0.8-1.5 0.35 0.7 0.7-1.3 0.25 0.35 - - REM T5 200 <1 90ENAC48000 T6 280 <1 100

AASERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTEMPER


ELONGATION%

HARDNESSBHN

A390.0 4-5.0 16-18 0.45-0.65 0.1 0.5 0.2 0.1 - - REM ASCAST 200 <1.0 110392 0.4-0.8 18-20 0.8-1.2 0.2-0.6 1.5 0.5 0.20 0.50 - - 0.3 REM ASCAST 290 <0.5393 0.7-1.1 21-23 0.7-1.3 0.10 1.3 2-2.5 0.1-0.2 0.1 No-data No-data No-data No-data

JISSERIES Cu Si Mg Mn Fe Ni Ti Zn Cr Pb Sn AlTEMPER


ELONGATION%

HARDNESSBHN

AC8A 0.8-1.3 11.0-13.0 0.7-1.3 0.15 0.8 0.8-1.5 0.20 0.15 0.1 0.1 0.1 REM T6 270 No-data 110AC9A 0.5-1.5 22-24 0.5-1.5 0.5 0.8 0.5-1.5 0.2 0.2 0.1 0.1 0.1 REM T6 170 No-data 95AC9B 0.5-1.5 18-20 0.5-1.5 0.5 0.8 0.5-1.5 0.2 0.2 0.1 0.1 0.1 REM T6 270 No-data 120

MECHANICALPROPERTIES

COMPARISONOF INTERNATIONALSTANDARDS

ALUMINIUMCASTINGALLOYS-HIGHSILICON

CHEMICALCOMPOSITION


- 43 -

Paper 4

The Process of Redesigning – a Suggested Approach.

IntroductionIn the preceding papers we have seen how alloys are manufactured and how the alloyspecifications determine to a great extent, the input material and thus, effectively, the costof the alloy as well. We have also looked at the role of the different alloying elements, theeffect of impurity elements and also compared current versions of different InternationalAluminium Alloy standards to give you an idea of what the rest of the world is doing. Therange of specifications even within a family or Alloy group allowing a wider choice to theuser is a key point to be noted.

At this juncture, it is possible many of you would be, to some extent, at least, convincedthat there is some logic in reviewing your alloy specifications to determine whether any ofthe limits – whether of alloying elements or impurities – are over specified and requirechange. Remember, as was described in Paper 2, even seemingly minor changes can makea substantial impact on cost.

This, the last paper is an attempt to provide you with some kind of road map on how to goabout the process of redesigning your alloy specifications to obtain a reduction in yourmaterial costs.

A Few Pre-requirementsBefore, we get into the details there are a few points you need to bear in mind. First, thissuggested road map is only one possible approach. There are many of you with severalyears of industry experience in design and development who may have better methods ofgoing about the process. Also, what we propose may not be specifically applicable in tototo your component. Thus, please bear in mind that what we are going to spell out is just asuggested approach. The approach we intend spelling out is logical but cautious. It willdefinitely work but some may consider it time consuming. However, we felt that it wouldbe best to lay down an exhaustive approach from which you can leave out steps if you areso inclined. Frankly, we will be surprised if you don’t need to modify it to suit yourorganisation and product needs.

Secondly, do bear in mind that the objective of the exercise is cost saving and is meant tobenefit your company. It is not an exercise to benefit the alloy manufacturer. After all, as acustomer, you have every right to demand whatever specification you want, and, it is up tothe alloy maker to supply it. And in fact, we at Sargam take pride in producing premiumquality alloys and consistently producing alloys with tight specification limits. Thus, thepurpose is not to get you to indiscriminately open up your specifications. That would beinviting disaster! What we have been talking about, and the question you are going to beaddressing is which specification is optimal for you, from a price-performance point ofview.


- 44 -

This in fact brings me to the third point you should bear in mind. If at the end of theexercise you arrive at the conclusion that your existing specification is the most optimal,you should not consider the exercise as a waste of time! Remember, ruling out a specificoption after careful examination is definitely progress!

Fourth, this exercise cannot be done in isolation. You would need to involve the alloymanufacturer and the caster.

Finally, it needs to be stressed that you must undertake this exercise with an open mind. Ifyou get in with a prefixed idea that the whole exercise is a waste of time and that yourexisting specificationis the most optimal, it is very likely that at the slightest hint of anyhiccups in the development process you will give up. Remember a half-hearted approachwill probably do more harm than good. If you are not convinced about the potentialbenefits of the exercise, better not try it at all. At the other extreme if you go in convincedthat whichever changes you first attempt are the correct ones, you may end up brushingaside any adverse results that crop up during your trials. Thus, during the entire process ofthe study, you must be totally objective and avoid bias. It is also important that youconvince your caster also to approach the exercise with an open mind.

The Steps in RedesigningLet us now look at the typical steps involved in the exercise.The FIRST step is to make this re-specification exercise the responsibility of a specificperson or team.

The SECOND step is to identify the components for study. While you can and probably,should, investigate all components over a period of time, obviously, you must prioritize.What are the parameters based on which you prioritize, is of course a managementdecision, unique to each organisation.

Some of the parameters could be:Consumption: Greater the monthly consumption (in tons) of a component, greater will bethe potential savings. You might therefore want to take up such castings for study first.Casting intricacy: You may wish to start with castings that do not present too manycomplications in the foundry. If for instance, you have a component that your caster findsdifficult to make consistently, with acceptable levels of rejection, he is unlikely to try outchanges in specifications with an open mind.

Application area: There could be certain castings, where the nature of the application, or itsfunction, makes it not the right candidate for study, at least not till you have gainedconfidence in your and your foundry’s ability to successfully handle the redesign process.Maturity of component: If the particular casting is still under development from otherdesign or application perspectives, you might want to wait till this process is complete and


- 45 -

the use of the component stabilises for some period before attempting a reevaluationexercise. On the other hand, if the casting, or the component or product in which thecasting is fitted is, let us say, being phased out, it may make no sense to put in any kind ofefforts in it.

There could be other parameters such as the amount of time and resources you can spareetc. Any way it is best that based on certain clearly spelt out parameters you make out apriority list for the castings.

Step 3: For the identified casting, it is best to do a quick check of the earlier design files,and drawings. You will be surprised to find the wealth of information available, whichcould save you a whole lot of time. For instance, certain specifications could have beenchanged earlier for certain reasons. If those reasons still exist, you may not want to, or needto, try and reverse those changes. On the other hand, if those reasons no longer exist,reversing the specification change could be an easy first step. There could also be basicinformation regarding the standard based on which the specification was developed and theyear in which it was developed. This will give you pointers to comparing the standard thenand now and identifying change parameters to try out. I would like to reiterate that this stepis very important and even if the archival information is not very well organised, it is wellworth putting in the effort to track it down.

Step 4: the next step is to do a status check. First check supply details and inspection andquality records for the particular component over a reasonable period of time, for hints onwhich areas to pursue and which to avoid. Second, check the chemical composition ofacceptedcastings presently in use. For this, pull out random samples from accepted lots ofrecent supplies and conduct chemical analysis on them. If there are any parameters out ofthe stated specification but with the casting still meeting acceptance criteria it will give yougreater confidence and may be even a direction to proceed. Third, machine test specimensfrom accepted castings and, if possible, ask your caster to separately cast a test-bar alongwith the next supply and check both for all required mechanical properties. Please bear inmind, however, that the mechanical properties of a specimen machined from a castingwillbe inferior to the properties attained in a separately cast test-bar. Repeat the chemical andphysical property check on at least two supplies. More, if consistent values are notobtained.

Step 5: It will be a good idea to visit the caster and observe the foundry practice currentlyin place. If required this job can be carried out by a foundry specialist. Also visit and notedown heat treatment cycles and machining operations. Details of cutting speed, feed andcutting tools and equipment in use can come in handy.

Step 6: Next, summarise the gathered information to form the base line data or control data.This will list out (a) all the functional requirements of the casting (b) the physicalproperties as stated in requirements or being met by existingacceptedcastings, whicheveris lower (c) existing rejection rates after casting, after machining etc. This will be the basisfor comparison to determine whether the changes carried out subsequently were successfulor not and hence should be prepared with care.


- 46 -

Step 7: The next step is to discuss with the alloy maker, sharing the ‘historical’information, if any, and the baseline data and then deciding on the parameters to try andalter. One or more revised specifications to be tried should be listed out. It is extremelyimportant at this stage to refer to international standard specifications for similar alloyswhile carrying out this exercise. Bear in mind that this is not some arbitrary exercise but avery studied activity to be done in consultation with the alloy maker. The cost implicationsof each of the revised specifications should be understood and noted. Remember, thepurpose of the entire exercise is to reduce costs and therefore, before you get to the nextstep, you must know what the potential rewards for successfully completing the changeswill be.

Step 8: The next step is to carry out trials. The required quantity of the new specificationalloy should be obtained and given to the foundry along with a batch of the regularmaterial. Castings should be produced using both batches, if possible, simultaneously intwo crucibles or at least as close together as possible to avoid the effect of other variationsin foundry parameters from affecting the results. Test bars should also be cast from bothmelts. You should ensure that the foundry follows identical foundry practices for bothmelts. The two sets of castings and the test bars should be separately identified. If any heattreatment is required, both sets of castings and test bars should be heat treatedsimultaneously. Subsequent machining operations can then be carried out on the two sets ofcastings taking care to preserve the identification. Physical properties of the test barsshould then be compared. For the two sets of castings, quantum and percentage of stagerejections should be tabulated and studied.

Step 9: The previous set of operations should be repeated at least once more on fresh lots ofmetal. The results of both trials should then be critically compared with the base line data.If there are unacceptable or inexplicable variations between the two field trials, furthertrials shouldbe conducted till repeatability is achieved.

Step 10: The next step depends on the results of the trials. If the results are satisfactory,depending on the nature of the component, field trials or accelerated performance trials canbe carried out. The batch size can then be increased and random castings selected from thebatch and tested. Consistent satisfactory results should increase the confidence levelssufficiently to freeze the revised specifications.

At this point pleased recall the discussions on current international standards. You wouldhave noted that currently almost all international specifications specify separate limits foralloy ingots and finished castings. It is recommended that at the end of your exercise aswell, you end up with revised specifications for the alloy ingots and castings separately.This will help avoid disputes and ensure better control over all your processes.

In case the results are not satisfactory, a failure or defect analysis should be carried outinvolving the alloy supplier and the caster. This will determine whether any modificationswill help. It should be borne in mind that if required, minor modifications in foundry


- 47 -

practice – pouring temperatures, for example – or even minor modifications in the toolingmay be worth carrying out considering the future savings possible.

Another aspect to track is the pick-up in impurity limits and drop in Magnesium limits dueto the addition of runners and risers at the foundry. The key point to note is that this is anexercise in material specification engineering. Like any other engineering project, this tooshould be carried out in a controlled manner with a clear plan and a sustained effort.Without this the chances of success will be remote.

ConclusionThis then is a broad outline of a suggested approach to the design exercise. You may, as Istated earlier, wish to modify by adding or subtracting steps to suit your individual needs.Please feel free to do so. We are not the users of the castings, and you know your productsbetter than we do. However, we know Aluminium alloys and would like to statecategorically that the alloy specifications are not static to be kept in a black box never to betouched or reviewed. Nor are they uncontrollable or incomprehensible. The specificationsare just like any other engineering parameter and should change to reflect changingmaterial availability, foundry practices and product application areas. We hope that throughthis workshop we would have convinced you about this. Needless to say, Sargam with itsyears of experience, up to date information on international standards and its well-equippedlaboratory is at your service to work with you in any such design project you may take up.

48

Sargam Metals Pvt. Ltd.2, Ramavaram Road, Manapakkam,Chennai 600089, Tamil Nadu, INDIA

Tel: +91-44-249-0885, +91-44-249-1547; Fax: +91-44-2491651email: [email protected] site: www.sargammetals.com

Documents

Die Casting