CH. 2 - METAL MAT

CHAPTER 2METALLIC MATERIALS

SHIP MATERIALS / LGB 21203

DEPARTMENT OF APPLIED SCIENCE & ADVANCED TECHNOLOGY (ASAT)- UNIVERSITI KUALA LUMPUR : MALAYSIAN INSTITUTE OF MARINE ENGINEERING TECHNOLOGY –

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1. Introduction 1.1 Metallic materials 1.2 Ferrous and Non ferrous alloy

2. Production of iron and steel.

3. Low alloy steels, Stainless Steel and Cast Iron.

4. Aluminium alloy 4.1 Joining of aluminium and steel

5. Copper alloy, Magnesium alloy, Titanium alloy and Nickel alloy.

6. Metallic materials suited to marine environment.

CONTENT:



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INTRODUCTION: METALLIC MATERIAL These materials are composed of one or more metallic

elements and may also contain some nonmetallic elements.

Metals have a crystalline structure in which the atoms are arranged in an orderly manner.

Metals are relatively strong and ductile at room temperature and maintain good strength even at high temperature. It also good thermal and electrical conductors.



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Those with iron as prime constituent (except for high alloy steel)

Important as engineering construction material (especially steel Fe-C)

They are important because:– Abundant within the earth-crust – low cost– Easier to be produced– Good strength toughness and ductility– Versatile – wide range of mechanical and physical properties

Can be alloyed and heat treated to get desired mechanical properties– Alloying is combining or mixing other material like carbon or

other metals to iron– Heat treatment is a process of heating and cooling a metal to

achieve specific microstructure which in turns display specific mechanical properties (e.g. Quenching austenite gives martensite which can be heat treated (tampered) to produced tempered martensite which is more ductile

INTRODUCTION: FERROUS & NONFERROUS ALLOY



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METAL ALLOYS

FERROUS

STEEL CAST IRON

NON-FERROUS

Cu

Mg

Al

LOW ALLOY HIGH ALLOY

Ti



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PRODUCTION OF IRON AND STEEL

Iron extracted from iron ores in large blast furnaces

Coke (carbon) acts as a reducing agent to reduce iron oxides (Fe2O3) to produce raw pig

iron (contain 4% carbon w impurities)Fe2O3 + 3CO 2Fe + 3CO2

Pig iron from the blast furnace usually transferred in the liquid state to a steelmaking furnace. Cross-section of

Blast Furnace

Production of Pig Iron in a Blast Furnace:



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Plain carbon steel essentially alloys of iron and carbon with up to about 1.2% carbon, but majority of steels contain less than 0.5% carbon.

Steel is made by oxidizing the carbon and other impurities in the pig iron until the carbon content of the iron reduced to the required level.

Commonly process for converting pig iron into steel is the basic-oxygen process.

Steelmaking an Processing:

Cross section of basic oxygen

furnace



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Pig iron and up to 30% steel scrap are charged into a barrel-shaped refractory line converter into which an oxygen lance is inserted. Pure oxygen from the lance reacts with the liquid bath to form iron oxide. Carbon in the steel then reacts with the iron oxide to form carbon monoxide.

FeO + C Fe +CO

Before the oxygen reaction starts, slag-forming fluxes (lime) are added in controlled amounts. The carbon content of the steel can be drastically lowered with a reduction in the concentration of impurities such as sulfur and phosphorus.

The molten steel from the converter is either cast in stationary molds or continuously cast into long slabs.



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Steel are iron-carbon alloys. Mechanical properties are a function of carbon content and other alloying elements.



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LOW ALLOY STEELS, STAINLESS STEEL & CAST IRONNOMENCLATURE OF FERROUS ALLOY

Nomenclature: AISI (American Iron & Steel Institute) and SAE (Society of Automotive Engineer.

10xx – Plain carbon steels11xx – Plain carbon steels (resulfurized for machinability)15xx – Mn (10 – 20%)40xx – Mo (0.20 – 0.30%)43xx – Ni (1.65 – 2.0%), Cr (0.4 – 0.9%), Mo (0.2 – 0.3%) where xx is wt% C x 100

Example: 1060 steel – plain carbon steel with 0.60wt% C



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LOW ALLOY STEELS, STAINLESS STEEL & CAST IRON



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Alloys of low carbon steel being produced in the greatest quantity < 0.25wt %C

Consists of ferrites and pearlites hence soft and weak but can be treated to achieve high strength.

Machinable, weldable and cheaper to be produced Types: i. Plain low carbon steel - no alloying elements, variable tensile

strength (TS) (415-550MPa and Yield Strength (YS)= 275MPa Applications – crankshafts, bolts, hammers, hand tools, gears, knives ii. High strength low allow steel (HSLA) – with alloying, higher TS and YS Applications – automobiles opines, nails, wire, pipe structural and

sheet steel, railway cars

LOW ALLOY STEELS



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0.25 – 0.6 wt %C Heat treated to achieve good mechanical

properties Used in tampered condition (tampered

martensitic) Strength -ductility combination can be tailored by

heat treatment and alloying (with Ni, Cr and Mo) Applications: high strength structural components

– railway wheels, tracks, crankshafts

MEDIUM ALLOY STEELS



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0.6 – 1.4 wt %C Hardest, strongest and least ductile carbon

steel Used in harden and tempered conditions Can be alloyed with carbon and other metals to

form vary hard and wear resistance material (e.g. C, Cr, Ni, W, Mo and V)

Applications: cutting tools, drills, saws, embossing dies, cutlery, paper cutters, concrete drill, blacksmith tools

HIGH ALLOY STEELS



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Highly resistance alloy to corrosion (rusting) in a variety of environment. Mechanical integrity maintains.

Consisting of iron-carbon and chromium (> 12 wt% Cr needed)

Add nickel and molybdenum as well Example 0.08 C, 11.0 Cr, 1.Mn, 0.50 Ni, 0.75 Ti :

S40900 Examples of use of stainless-steel:

STAINLESS STEELS



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STAINLESS STEEL

Austenitic

Martensitic

Ferritic

In general there are three main types of stainless steel;

STAINLESS STEELS



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Essentially iron-chromium binary alloys containing about 12 – 30% Cr. Chromium (Cr) has the same BCC crystal structure as ferrite, extends the phase region and suppresses the phase region.

Ferritic stainless steels, since they contain more than 12% Cr, do not undergo the FCC-BCC transformation and cool from high temperatures as solid solutions of chromium in iron.

Relatively low in cost since they do not contain nickel. They are used mainly as general construction materials in which their

special corrosion and heat resistance required.

FERRITIC STAINLESS STEELS



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Microstructure in weld, HAZ and base metal of duplex stainless steel (Austenite is in white and ferrite in dark) (Source: ArcelorMittal Industry)

Duplex Microstructure with ferrite and autenite grains. (ASM Metals handbook)

FERRITIC STAINLESS STEELS



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Essentially Fe-Cr alloys containing 12 to 17% Cr with sufficient carbon (0.15 to 1.0% C) so that a martensitic structure can be produced by quenching from the austenitic phase region.

Capable to develop martensitic structure after an austenizing and quenching heat treatment.

Corrosion resistance relatively poor compared to the ferritic and austenitic type

MARTENSITIC STAINLESS STEELS



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Microstructure of martensite formed by quenching steel from the austenite region: very hard and brittle: magnification, 300x (in the book Alexander, et al)

Microstructure image of a martensitic stainless steel




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Essentially iron-chromium-nickel ternary alloys containing about 16 to 25% Cr and 7 to 20% Ni.

Structure remains austenitic (FCC, α iron type) at all normal heat treating temperatures.

Austenitic stainless steels normally have better corrosion resistance than ferritic and martensitic because the carbides can be retained in solid solution by rapid cooling from high temperature.

AUSTENITIC STAINLESS STEELS



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The image shows the microstructure of an austenitic stainless steel.




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Family of ferrous alloys with a wide range of properties. They are intended to be cast into the desired shape instead of being worked in the solid state.

Normally contain 2 to 4 % carbon and 1 to 3% silicon. Other alloying elements may also be present to control or vary certain properties.

Excellent casting since they are easily melted, very fluid in the liquid state, and do not form undesirable surface films when poured.

Relatively low impact resistance and ductility, and this limits their use for some applications.

CAST IRON



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Cast Iron

Ductile Cast Iron

Malleable Cast Iron

White Cast Iron

Gray Cast Iron

Type of cast iron

CAST IRON



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Is formed when much of the carbon in a molten cast iron forms iron carbide instead of graphite upon solidification.

To retain the carbon in the form of iron carbide in white cast irons, their carbon and silicon contents must be kept relatively low (2.5-3.0%C and 0.5-1.5% Si) and the solidification rate high.

Often used for their excellent resistance to wear and abrasion. White cast iron serves as the raw materials for malleable cast

iron.

WHITE CAST IRON



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Microstructure of White cast iron

WHITE CAST IRON



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Formed when the carbon in the alloy exceeds the amount that can dissolve in the austenite and precipitates as graphite flakes.

Unalloyed gray cast irons usually contain 2.5 to 4% C and 1 to 3% Si. Since silicon is a graphite stabilizing element in cast irons, high silicon content is used to promote the formation of graphite.

The solidification rate is also an important factor that determines the extent to which graphite forms.

Moderate and slow cooling rates favor the formation of graphite.

GRAY CAST IRON



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Gray Cast Iron - typical microstructure of gray iron is a matrix of pearlite with graphite flakes dispersed throughout.

Grey Iron Microstructure Microstructure of a grey cast iron with a carbon content of 3.2% and a silicon content of 2.2% by weight.

GRAY CAST IRON



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Sometimes called nodular or spherulitic graphite cast iron. Similar properties to those steel such as high strength, toughness,

ductility, hot workability, and hardenability. Composition of unalloyed ductile iron is similar to that of gray iron

with respect to carbon ad silicon contents. Carbon content of unalloyed ductile iron ranges from 3.0 to 4.0%C and the silicon content from 1.8 to 2.8%. The sulphur and phosphorus levels of high-quality ductile iron must be kept very low at 0.03%S and 0.1%P.

The spherical nodules in ductile cast iron are formed during the solidification of the molten iron, because the sulphur and oxygen levels in the iron are reduced to very low levels by adding magnesium to the metal just before it cast.

DUCTILE CAST IRON



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Microstructure of a ductile cast iron with a carbon content of 3.6% and a silicon content of 2.6% by weight.

DUCTILE CAST IRON



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Is a first cast as white cast irons which contain large amounts of iron carbides and no graphite.

Carbon and silicon contents of malleable irons are in the 2.0% to 2.6%C and 1.1 to 1.6% Si ranges.

Advantages: Excellent machinability Significant ductility Good shock resistance properties

Disadvantages: The major disadvantage is shrinkage. To produce a malleable iron structure, cold white iron castings are

heated in a malleablizing furnace to dissociate the iron carbide of the white iron to graphite and iron.

MALLEABLE CAST IRON



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Microstructure of a malleable cast iron

MALLEABLE CAST IRON



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Ordinary-Strength Hull Structural Steels For steel hull construction “Ordinary-strength Hull Structural

Steels” are recommended for plates and wide flats up to and including 100mm (4 ins), and for sections and bars up to and including 50mm (2 ins).

Higher – Strength Hull Structural Steels Higher-strength hull structural steels may be specified for boats

and ships larger than 30m in length, requiring construction using plates and wide flats with the following markings:

METALLIC MATERIAL SUITED TO MARINE ENVIRONMENT



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Anchor may be:

forged or cast from steel plate or bar –

fabricated steel anchors




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Chain Shackles:

~ Should be made of materials proved suitable for the type of service that will be used




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Outfitting material UseStainless steel Hardware, door handles, ship’s fittings, water holding tanks, Galley fittings,

cooking ovens, stoves, gas jets, utensils, general outfitting requirements, balastrading, steps, ladders, hatches, lift rings, door latches, pipes, stairs, fan blades, sprinklers, fire alarms, valves, springs, cogs, gears, vents, drainage pipes and grates, guard rails, louvers, fasteners, bolts, screws, rivets, eye bolts, u-bolts, miscellaneous hardware, couplings, blocks and swivels, hand and power tools, hooks and shackles, manholes, doors, sinks, food preparation counters and serving bars, storage racks, wash basins, refrigerators, racks for pots, dishes, cups, glasses, rigging hardware, overhead cabinets for general storage, bathroom and laundry services.

Copper and copper alloys

Aluminium bronze, manganese bronze, aluminium brass, gunmetal, cupro-nickel and monel are traditional shipbuilding materials that make up 2 – 3 % of deadweight of all new constructions for items such as:Pipes and piping, radiators, steam lines, cooking utensils, linings, heating elements, coils and systems, cladding, sheathing, miscellaneous fasteners and hardware, instrument casings, feed–water, fresh- water, salt – water cooling systems, pumps, evaporators, steam lines, heaters, valves, coolers, lighting, electrical cables, generators, electric motors, electrical contacts, fittings and switches, communications equipment/systems, control room equipment/systems, propellers (high tensile brass or aluminium bronze), heavy tailshafts, rudder stocks, propeller cone nuts (Admiralty gunmetal or manganese bronze), condenser tubes (cupro-nickel or aluminium brass), tube plates and baffles, deck fittings(naval brass), fasteners, screws, nails (silicon bronze).

Wood Carvel planking, hulls, frames, decking, flooring, cross-planks, topside planks, strip planking, moulds, exterior woodwork, bulkheads, shelving, berth bottoms, cabin tops, doors, interior woodwork, bench tops, cupboard doors, tables, chairs, rails, steps, stairs.




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EXERCISES;

1. Write a typical chemical reaction for the reduction of iron oxide (Fe2O3) by carbon monoxide to produce iron.

2. Explain the numbering system used by the AISI and SAE for plain carbon steels.

3. Explain how the aluminum oxide extracted from bauxite ores and aluminum extracted from pure aluminum oxide.

4. Determine how are copper alloys classified by the Copper Development Association system.

5. Explain why ferritic stainless steel considered non-heat-treatable.6. Describe why ductile cast iron in general more ductile than gray

cast iron.

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CH. 2 - METAL MAT