Metall. Res. Technol. 113, 308 (2016)c© EDP Sciences, 2016DOI: 10.1051/metal/2016006www.metallurgical-research.org

Metallurgical Research&Technology

Effect of water flow rate, casting speed, alloyingelements and pull distance on tensile strength,elongation percentage and microstructureof continuous cast copper alloys

Ehsaan-Reza Bagherian1, Yongchang Fan1, Mervyn Cooper2, BrianFrame2 and Amin Abdolvand1

1 School of Science & Engineering, University of Dundee, DD1 4HN Dundee, Scotland, UKe-mail: E.bagherian@dundee.ac.uk

2 Rautomead Ltd, DD2 4UH Dundee, Scotland, UK

Key words:Continuous casting; copper alloyssolidification; tensile test

Received 15 October 2015Accepted 5 February 2016

Abstract – Most parameters that control the solidification of castings, and consequently,microstructure and mechanical properties, are: chemical composition, liquid metal treat-ment, cooling rate and temperature gradient. In this work, characterization of the influenceof water flow rate, casting speed, alloying element and pull distance on tensile strength,elongation percentage and microstructure of continuous cast copper alloys has been carriedout. A significant different in tensile strength, elongation percentage and grain structurehas been investigated and it was also found that these parameters could improve the phys-ical and mechanical properties of samples. As a particular example, water flow rate couldimprove the elongation of samples from 10% to 25%.

C opper alloys have been used for atleast 7000 years, mostly due to theirbeneficial characteristics such as ex-

cellent electrical and thermal conductivity,high corrosion resistance and easy process-ing. The major applications of copper alloysare for wires, electronic devices, industrialmachinery and pipes for heating systems [1].

Various copper components in the formof rod, tube, strip and sections are producedby continuous casting process [2]. Continu-ous casting is a process of melting and con-tinuous solidification and it has been usedfor more than 100 years to produce compo-nents. Now the continuous casting processproduces over 1 MT of copper in the worldeach year [3, 4].

The continuous casting process ischeaper than thermomechanical processessuch as extrusion but the metallurgical andmechanical properties of components pro-duced by continuous casting such as tensilestrength or elongation percentage are lowerthan those produced by thermo-mechanicalprocesses [5, 6].

In continuous casting process usuallyfurther downstream processes such asdrawing or rolling is commonly used to im-prove both tensile strength and elongationpercentage performance of as cast rod. How-ever, alloying elements and grain refinementhas been reported as techniques to enhancethe mechanical properties of as cast copperalloys. Grain refinement techniques, whichcan refine the matrix, improve the morphol-ogy and distribution of the second phase andenhance mechanical properties [7, 8].

The thermal method is a known grainrefinement method to produce metals withsmall grains and better ductility by control-ling the cooling rate [9].

The aim of this paper is to investigate theimpact of the alloying elements and coolingcontrol on mechanical and physical proper-ties of continuous cast copper and copperalloys.

1 Materials for research

The material preparation, set-up, castingprocedure, casting parameters and tensile

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E.-R. Bagherian et al.: Metall. Res. Technol. 113, 308 (2016)

test analysis are explained from Sections 1.1to 1.4.

1.1 Material preparation

The copper alloy were produced from dry,clean, bright, flat, un-oxidized copper cath-ode feedstock, free from electrolyte nodules.The copper cathode feedstocks were meltedin a graphite crucible using graphite heat-ing element furnace technology (RautomeadRS continuous vertical casting machine). Thechemical composition of the cast alloy wasthen tested using an AMETEK spectrometer.

1.2 Set-up

All casting trials were carried out on themodel RS080 vertically upwards-continuouscasting machine at Rautomead’s premisesin Dundee. A standard Rautomead verti-cal continuous casting parameters and with-drawal system set-up for 8–22 mm rod wasutilized, which consisted of pull distance,push distance, pull dwell, acceleration anddeceleration, casting speed and water flowrate.

1.3 Casting procedure (RautomeadRS continuous casting machine)

The Rautomead RS (commercial name) ver-tical upwards casting machine is designedfor the production of 8.0 mm diameter wirerods. This machine may also be designedto produce rod up to 22.0 mm diameterdepending on or which depend on cus-tomer requirement. The Rautomead verti-cal upwards casting machines are designedto be operated for long periods of contin-uous production of continuous cast copperwire rod, and are configured as integratedmelting, holding and casting units, featur-ing graphite crucibles, protected in an inertgas atmosphere with high intensity graphiteresistance heating. The Rautomead verticalupwards casting machines for rod/tube pro-duction have the advantages, of low energyconsumption, low maintenance cost, smallcapital investment, no scrap rate and nowaste pollution in production and so on.This will be explained in more detail below.

1.3.1 Main parts of RS machines

The main components of RS continuous cast-ing machine are as follows:

(1) The resistance furnace comprises a of fur-nace body and furnace frame, and is usedto melt copper cathode or scrap into liq-uid and keep liquid at a constant temper-ature. Rautomead furnace technology isunique because graphite is employed forcontainment (crucible and valve), casting(die and packers) and heating elements(resistance heating).

(2) Continuous casting machine which is themain part of the system and its consistsof drawing mechanism, called the with-drawal.

(3) Cooling system that is the most impor-tant part of the continuous casting.

(4) Electrical control system (control panel).(5) Cathode feed system.(6) Coilers.

Figure 1 shows the schematic of continuousrod casting machine.

1.3.2 Horizontal continuous castingwithdrawal system

The withdrawal cycle in horizontal contin-uous casting is introduced by Haissig andVoss-Spilker and Reichelt in 1984 [10, 11].

In the continuous casting process, gen-erally four different withdrawal cycles areused including [12]:

1. Non-intermittent extraction which isusually used for casting alloys withlow temperature interval of solidificationsuch as pure metals or casting at highcooling rate.

2. Intermittent extraction with a pause,which is used for casting of copper al-loys at lower cooling rates.

3. Intermittent extraction with one push-back, which is usually used for the kindof alloys having wide temperature inter-val of solidification.

4. Intermittent extraction with two push-back which is used for casting alloys con-taining constituents penetrating into thegraphite pores and causing sticking thecasting to the graphite surface.

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Fig. 1. Schematic of Continuous Rod casting machine.

1.3.3 Main casting parameters

The quality of continuous cast copper rodlargely depends on microstructure as well asmechanical properties like tensile strengthand elongation percentage. The control ofthe grain structure, which develops duringsolidification processes, is a key issue for theoptimisation of the final mechanical prop-erties. These can be improved by analyzingand optimizing the process parameters dur-ing the casting process such as:

– Cooling water flow rate.– Casting speed.– Pull distance.– Melt temperature.– Withdrawal system.– Continuous casting direction.– Super cooler size.– Casting die materials.

It is also important to select the right with-drawal cycle. Generally, the continuous cast-ing process is controlled automatically butthe quality and productivity of resultingproduct are dependent on the casting pa-rameters used during the casting process.Proper withdrawal cycle and casting param-eters selection are critical to the ultimate suc-

cess of the continuous casting process. Thispaper will discuss the effect of cooling waterflow rate, casting speed and pull distance onphysical and mechanical properties of con-tinuous cast copper alloys.

1.4 Tensile testing

A tensile test was performed to investigatethe tensile strength (MPa) of the material aswell as to find the ductility in terms of elon-gation percentage of the alloy. The test spec-imens were prepared according to ASTMstandard. The specimens were tested usinga computerised universal testing machine(Make: Instron; Model: 4204).

1.5 Metallography

Samples for microstructural observationswere cut with a clean sharp hacksaw. Sec-tioning of the test sample was performedcarefully to avoid destroying the structureof the material. After the sample is sec-tioned to a convenient size, samples werethen ground by using coarse abrasive paper(Grade No. 60) and subsequently wet & dryfine silicon carbide paper (Grit No. 2500) SiC

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Table 1. CuSnP samples tested in this research.

Sample Rod Die Pull distance Pull dwell Acceleration Deceleration Casting speed Water flowdia (mm) (mm) (s) (s) (s) (mm/min) rate (l/min)

Cast 1 8 Graphite 10 0 0.02 0.02 3500 15Cast 2 8 Graphite 10 0 0.02 0.02 3500 20Cast 3 8 Graphite 10 0 0.02 0.02 3500 30Cast 4 8 Graphite 10 0 0.02 0.02 3500 40Cast 5 8 Graphite 10 0 0.02 0.02 3500 45

Table 2. OFCu samples tested in this research.

Sample Rod Die Pull Distance Pull Dwell Acceleration Deceleration Water flow Casting speeddia (mm) (mm) (s) (s) (s) rate (l/min) (mm/min)

Cast 1 8 Graphite 0.5 0.2 0.005 0.005 45 2500Cast 2 8 Graphite 0.5 0.2 0.005 0.005 45 4500Cast 3 8 Graphite 0.5 0.2 0.005 0.005 45 6000Cast 4 8 Graphite 0.5 0.2 0.005 0.005 45 7800

papers and polished on a cloth with a dia-mond suspension and lubricating solution.The grinding and polishing were both car-ried out on a Struers machine. After polish-ing, the samples were cleaned by acetonein an ultrasonic cleaner and dried with ni-trogen gas. In the chemical etching process,nitric acid and distilled water were used.

2 Experiment

2.1 Water flow rate

The aim of this section was to understandthe efficiency of water flow rate on ten-sile strength and elongation percentage ofcontinuous cast copper alloy. The trial pro-duced a vertically upward cast 8mm diam-eter CuSnP sample. The alloy was Sn 0.65%and P 0.03% balance Cu. In this investigationseveral small batches of samples were cast atdifferent water flow rate conditions. Differ-ent water flow rates have been studied in thisresearch and then tensile strength and elon-gation percentage of continuous cast wasinvestigated by universal tensile machine.Three samples are selected and an average istake. Table 1 gives the copper samples testedin this study.

2.2 Casting speed

Previous research has shows the castingspeed is one of the major controlling param-eters of the metallurgical quality of the castproduct [13].

The aim of this section was also to obtainthe relationships between casting speed andmechanical properties of continuous castcopper alloy. Low and high casting speedcoils of OFCu continuous cast copper alloywere produced and then the elongation per-centage and tensile strength were calculatedon all investigated specimens. The represen-tative copper samples analysed in this re-search are listed in Table 2.

2.3 Alloying elements

It has been previously reported that thelevel of alloying element plays a significantrole in determining the properties of castingalloys [14].

Although the relationship between theultimate tensile strength (UTS) and the elec-trical conductivity (EC) for the drawn CuZrbinary alloy wires and other conventionalcopper alloys has been reported the effectsof increasing zirconium content on the me-chanical properties of continuous cast cop-per alloy has not been investigated previ-ously. In this paper the effects of zirconiumon the mechanical properties of continuouscast copper alloy is investigated.

Experimental works to produce 15 mmdiameter CuZr rod were performed to eval-uate the effect of alloying elements on me-chanical properties of CuZr alloys. In thisstudy several small batches of samples werecast using different alloy content. In orderto investigate the alloying effect of Zr onthe mechanical properties of CuZr alloy, a

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Table 3. CuZr samples tested in this research.

Sample Rod Die Pull Pull Dwell Acceleration Deceleration Water Casting Zirconiumdia (mm) (mm) distance (s) (ec) flow rate speed percentage

(s) (l/min) (mm/min) (%)Cast 1 12 Graphite 9 0.5 0.2 0.2 45 1400 2.67Cast 2 12 Graphite 9 0.5 0.2 0.2 45 1400 2.80Cast 3 12 Graphite 9 0.5 0.2 0.2 45 1400 3.45Cast 4 12 Graphite 9 0.5 0.2 0.2 45 1400 6.80

Table 4. CuSn samples tested in this research.

Sample Rod Die Pull Acceleration Deceleration Water flow Casting Pulldia (mm) dwell (s) (s) (s) rate (l/min) speed (mm/min) distance (mm)

Cast 1 12 Graphite 0.015 0.010 0.010 55 97 3Cast 2 12 Graphite 0.015 0.010 0.010 55 1700 4Cast 3 12 Graphite 0.015 0.010 0.010 55 2100 5Cast 4 12 Graphite 0.015 0.010 0.010 55 2700 6

tensile test at room temperature was carriedout according to ASTM standard. Alloy con-tents are summarised in Table 3. Three sam-ples are selected and an average taken andthen from the generated data the ultimatetensile strength and percentage elongationof each alloy sample was calculated.

2.4 Pull distance

In continuous casting process, the distanceof one pull in one cycle for withdrawingthe cast is called pull distance. One of thepurposes of this work was to experimentallyinvestigate the dependency of the pull dis-tance and mechanical properties of continu-ous cast copper alloys.

The cast trial was attempted using a stan-dard Rautomead upward continuous cast-ing machine setup for 8 mm rod which con-sisted of varying pull distance. The alloy was0.3% Sn balance Cu. The tensile test of theCu0.3%Sn cast alloys was conducted at roomtemperature using a universal tensile testingmachine with a gage length of 100mm andcross-head speed of 10 mm/min. For eachtest, percent elongation was calculated usingHooke’s law. The representative Cu0.3%Sncopper samples analyzed in this work arelisted in Table 4.

3 Results and discussion

3.1 Water flow rate

The objective of this section was to find theeffect of water flow rate on the mechanical

properties of continuous cast copper rod byvarying water flow rates. After cooling ex-periments the tensile strength has been ex-amined and it was found that increase in wa-ter flow rate affects the tensile strength andelongation percentage. The results of aver-age elongation percentage of copper alloysamples are presented in Figure 2.

Table 5 shows the tensile strength andaverage elongation percentage of the con-tinuous cast copper rod samples, explainedin Table 1. It can be seen that sample 1 hasthe higher elongation percentage. So the wa-ter flow rate could improve the elongationpercentage of samples from 10% to 25%. Incontinuous casting process water is used tocool the mold in the initial stages of so-lidification. So water flow rate in continu-ous casting plays a key role in transformingheat from the mold and solidifying metalduring the continuous casting of copper al-loys. It has also been previously reportedthat, water flow rate is one of the main pro-cess parameters that can change upon directchill casting. Because increasing the waterflow in the mould increases the heat- trans-fer rate and thereby decreases the mouldtemperature [15, 16].

Water-cooling affects the product qual-ity by (1) controlling the heat removal ratethat creates and cools the solid shell and(2) generating thermal stresses and strainsinside the solidified metal [17]. When thecooling rate is slow, some of the large clus-ters of atoms in the liquid develop inter-faces and become the nuclei for the solidgrains that are to form. During solidification

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egatnecrep noitagnolE htgnerts elisneT

050

100150200250300350

Tens

ile S

tren

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(MPa

)

Water flow rate (ltr/min)

05

1015202530

Ave

rage

elo

nga�

on

perc

enta

ge (%

)

Water flow rate

Fig. 2. Tensile strength and elongation percentage of CuSnP samples.

Table 5. Average elongation percentage of CuSnP samples.

Sample Rod Die Pull Pull Acceleration Deceleration Casting Water Tensile Averagedia distance dwell (s) (s) speed flow rate strength elongation

(mm) (mm) (s) (mm/min) (l/min) (MPa) Percentag (%)Cast 1 8 Graphite 10 0 0.02 0.02 3500 15 310 10Cast 2 8 Graphite 10 0 0.02 0.02 3500 20 301 12Cast 3 8 Graphite 10 0 0.02 0.02 3500 30 267 15Cast 4 8 Graphite 10 0 0.02 0.02 3500 40 262 22Cast 5 8 Graphite 10 0 0.02 0.02 3500 45 248 25

15 (ltrs/mmin) 20 (ltrs/mmin) 30 (ltrs/min) 40 (ltrs//min) 45 (ltrss/min)

Fig. 3. Comparison grain structure of CuSnP samples.

the first nuclei increase in size as more andmore atoms transfer from the liquid stateto the growing solid. Eventually all the liq-uid transforms and large grains develop.The grain boundaries represent the meet-ing points of growth from the various nu-clei initially formed. Low cooling rate resultin less homogeneous micro-structure. Whenthe cooling rate is fast, many more clustersdevelop and each grows rapidly. As a resultmore grains form and the grain size in thesolid metal is finer [9, 18].

The effect of water flow rate on the struc-ture of the continuous cast copper rod isillustrated in Figure 3. From these figures,it can be observed that fine grains can beachieved by increasing the water flow rate.Water flow rate is known to affect the struc-ture formation during solidification. This isbecause of its influence on cooling condition.

So, it was observed that, the cooling rate hasa very significant effect on the grain size ofrods. This observation is defined with fol-lowing phenomena:

1. Faster cooling will result in large valuesof growth velocity, which is a result in anincrease in the number of effective nucle-ants and a finer grain size.

2. Faster cooling will result in increase thedegree of constitutional and amount ofundercooling, which is result in finegrain structure.

As well as the above phenomena, water-cooling plays a major role in extractingheat from both the casting die and solidi-fying metal during the continuous castingprocedure.

Generally, increase in strength showsthe increase in brittleness and increase in

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Tensile strength Elongation percentage

162164166168170172174176178180

2500 (mm/min)

4500 (mm/min)

6000 (mm/min)

7800 (mm/min)

Tens

ile s

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(MPa

)

Cas�ng speed (mm/min)

05

1015202530354045

2500 (mm/min)

4500 (mm/min)

6000 (mm/min)

7800 (mm/min)

Ave

rage

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Fig. 4. Tensile strength and elongation percentage of OFCu samples.

Table 6. Tensile strength and average elongation percentage of OFCu samples.

Sample Rod Die Pull Pull Accele- Decele- Water Casting Tensile Averagedia distance dwell ration (s) ration (s) flow rate speed strength elongation

(mm) (mm) (s) (mm/min) (l/min) (MPa) Percentag (%)Cast 1 8 Graphite 0.5 0.2 0.005 0.005 45 2500 178 34Cast 2 8 Graphite 0.5 0.2 0.005 0.005 45 4500 174 35Cast 3 8 Graphite 0.5 0.2 0.005 0.005 45 6000 171 37Cast 4 8 Graphite 0.5 0.2 0.005 0.005 45 7800 168 41

elongation shows the increase in ductility ofthe material. So, if strength increases, elon-gation is decreases, which mean both ten-sile strength and elongation percentage, arecontradicting with each other. However, ho-mogenizing (and the resultant grain refine-ment) increases both strength and ductility.This similarly occurs when we increased thewater flow rate.

As a summary, all these phenomena con-firmed water flow rate has an important im-pact on physical and mechanical propertiesof continuous cast copper alloy [19, 20].

3.2 Casting speed

In continuous casting process, the castingspeed is one of the most important param-eters that influence the metallurgical prop-erties of cast metals. In the other side, thecasting speed, which is directly related tothe productivity, is one of the most impor-tant parameters for continuous casting. So itis very important to pay attention to a properdetermination of the casting speed.

The aim of this section was to investigatethe impact of the casting speed on the me-chanical properties of continuous cast OFCucopper rods.

Although casting speed can be calcu-lated as a combination of steps i.e pullingtime, dwell time, push back and accelera-tion/deceleration time. This calculation isn’timpact theoretical due to the vagaries of theservo system. For this reason, in this researchthe casting speed is calculated by physicalmeasurement of the as cast rod over the spec-ify time e.g mm/min or m/min.

To study the effect of casting speed incontinuous casting of copper alloys, investi-gation has been performed with four differ-ent casting speeds. Mechanical properties ofcopper alloy tested, ranging from low up tothe high casting speed and then the resultswith the range of low casting speed to highcasting speed were analysed as shown in Ta-ble 6, Figures 4–6. A strong correlation of thetensile strength and elongation percentagewith the casting speed was observed.

For oxygen free copper obtained underindustrial conditions, an increase in tensilestrength was observed with a decrease ofcasting speed. For the material obtained at acasting speed of 2500 mm/min., the value oftensile strength is equal to approx. 178 MPa.However, for the oxygen free copper samplecast at a higher speed of 7800 mm/min., ten-sile strength was at a lower level of 168 MPa.This is a significant difference taking into

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25000 (mm/min)) 4500 (mm/m

min) 6000 (mmm/min) 7800 (mmm/min)

Fig. 5. Comparison grain structure of OFCu samples (Cross section).

25000 (mm/min)) 4500 (mm/mmin) 6000 (mmm/min) 7800 (mmm/min)

Fig. 6. Comparison grain structure of OFCu samples (Longitudinal section).

account the change of only casting speedwith no difference in the chemical compo-sition of the material as well as the generalmethod of production. It was also found thatthe casting speed could improve the elonga-tion of samples from 34% expanding to 41%.

The reason for this huge improvement ofelongation and significant difference in ontensile strength is because the casting speedaffects the structure formation during so-lidification. This is because of influence oncooling condition, which could increase themushy zone thickness. The other reason forthis is that increasing casting speed leads toa change in the heat conduction and solidi-fication condition, which results in makingit possible to obtain a structure with finergrains. This is based on a thermal change be-cause the higher the casting speed gets the

faster the material goes from liquid to solid.The measured average elongation percent-age and tensile strength are shown in Table 6and Figures 4–6.

Figures 5 and 6 shows cross and longi-tudinal sections of continuously cast rodsafter cutting, polishing and etching solidi-fied at four different pulling speeds. Fromthese, from which it can be seen that, in thecross section, the grains are radial from thesurface to the centre and in the longitudi-nal section, there is a centre line. By com-paring the physical and mechanical proper-ties of OFCu copper rods it can be concludethat, the mechanical properties have corre-lation with grain size and high mechanicalproperties are achieved by small grain struc-ture. By observing the cross section of sam-ples, it can be clearly seen that, when casting

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Table 7. Tensile strength and elongation percentage of CuZr samples.

Sample Rod Die Pull Pull Accele- Decele- Water Casting Zirconium Tensile Averagedia distance dwell ration (s) ration (s) flow rate speed percentage strength elongation

(mm) (mm) (s) (mm/min) (l/min) (%) (MPa) Percentage (%)Cast 1 12 Graphite 9 0.5 0.2 0.2 45 1400 2.67 201 6Cast 2 12 Graphite 9 0.5 0.2 0.2 45 1400 2.80 272 4Cast 3 12 Graphite 9 0.5 0.2 0.2 45 1400 3.45 484 3Cast 4 12 Graphite 9 0.5 0.2 0.2 45 1400 6.80 645 2

speed was increased from 2500 mm/min to7800 mm/min, significant reduction of grainstructure were observed. With an increas-ing of the casting speed, the grain structuretends to become finer in structure.

Longitudinal section shows, at low cast-ing speeds, the columnar grains have a ten-dency to align along the longitudinal axisof the rod whereas, at higher casting speed,they grow more or less perpendicularlyto the rod surface. This observation is be-cause faster cooling resulted in increasingthe amount of grain boundaries. It is knownfrom the above observation on the metallog-raphy analysis of grains that the number ofcolumnar grains increases after grain refin-ing by increasing the casting speed. As iswell known, smaller grains have greater ra-tios of surface area to volume, which meansa bigger ratio of grain boundaries to disloca-tions. The more grain boundaries that occur,the higher strength [21, 22].

3.3 Alloying elements

The tensile tests were performed on vari-ous samples using Introsn machine. Table 7shows the results obtained from the tensiletest carried out on various samples of theCuZr alloy, while Figures 7–9 depicts the re-lationship of the ultimate tensile strength,percentage elongation and addition of alloy-ing element for the alloys used in this study.

It was considered that the decreasein elongation and increase in strength ofcontinuous cast copper-zirconium alloy ismainly dependent on the solid solubility ofthe particular element in copper. Additivesto pure copper increase its strength and re-duce its elongation depending upon the ele-ment and amount in solid solution. Alloyingadditions also could change the microstruc-ture of the material.

The present results show that this is themost important variable, explaining about200% of the variance on ultimate tensilestrength and elongation percentage. So, thepresent study shows that the alloying el-ement significantly affects the mechanicalproperties.

This is because the pure copper is softand malleable and small amounts of an al-loying element added to molten copper willcompletely dissolve and forms as a homoge-neous microstructure. In fact, zirconium candissolve as individual atoms when added tomolten copper and may remain dissolvedwhen the material solidified and cooleddown at the room temperature. Howeverthis is depends on the solid solubility of theparticular element in copper [23].

The maximum solubility-of zirconiummetal is about 0.15% by weight and Cu-Zr alloys with zirconium contents varyingfrom 0.01 or even less up to 0.15% can bemade possessing exceptionally good proper-ties. This solid solubility is at 972-centigradedegree, which is assessed temperature of theeutectic reaction of liquid to solid. In thehigher zirconium content alloys, some CuZr-rich areas remain at the grain boundariesproviding an objectionable second phasewhich lead to unsoundness in the metalas well as various processing complicationsand difficulties [24].

The work was continued using the met-allography procedure to examine the grainstructure of each specimen and the effectof alloying elements on the size of the sec-ondary dendrite arm spacing (SDAS), whichis defined as the distance between the pro-truding adjacent secondary arms of a den-drite was investigated using a “KEYENCE”digital optical microscope.

The result is presented in Figures 7–9and Table 8. It has been shown that alloyingelements have significant influence on the

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0

1

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100

200

300

400

500

600

700

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Pa)

Fig. 7. Tensile strength and elongation percentage of CuZr samples.

rZ %8.6 rZ %54.3

2.6% Zr 2.8%% Zr

Fig. 8. Grain structure of CuZr samples.

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Table 8. Second dendrite arm space of CuZr samples.

Zirconium percentage (%)2.6% Zr 2.8% Zr 3.45% Zr 6.8% Zr

Reading SDAS (µm) Reading SDAS (µm) Reading SDAS (µm) Reading SDAS (µm)1 4.65 1 3.89 1 2.55 1 1.542 4.79 2 3.18 2 2.98 2 1.533 4.88 3 3.82 3 2.16 3 1.144 4.65 4 3.79 4 2.55 4 1.535 4.46 5 3.06 5 2.77 5 1.716 4.37 6 3.91 6 2.98 6 1.27 4.1 7 3.45 7 2.42 7 1.58 4.29 8 3.98 8 2.37 8 1.249 4.43 9 3.35 9 2.37 9 1.62

10 4.5 10 3.61 10 2.33 10 1.96

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g 6

6.8%

Zr

read

ing

76.

8% Z

r re

adin

g 8

6.8%

Zr

read

ing

96.

8% Z

r re

adin

g 10

Seco

nd d

endr

ite a

rm s

pace

(μm

)

Sample

Fig. 9. Second dendrite arm space of CuZr samples.

refinement of the grains. It is clearly shown,the space between dendrite arms decreasedby increasing amount of alloying element(zirconium). Higher concentration of alloy-ing element will cause precipitation of finerdendritic grain. Castings having a finer mi-crostructure show better tensile strength.This improvement is related to a lower SDASvalue.

3.4 Pull distance

In this section, various pull distance (forwithdrawing the cast copper in the verticaldirection) were tried from the die. Results ofthe mechanical tests are presented in Table 9and Figures 10 and 11. The figures shows theeffect of pull distance on the elongation per-centage of continuous cast copper alloys. It

can be noticed that the increase of pull dis-tance from 3 mm to 6 mm gives a slightlyincrease in the elongation percentage from31% to 37%.

Increasing pull distance is equal to in-creasing the casting speed. According to theequation proposed by Kumar’a decreasingthe solidification time is equal to increas-ing the cooling rate. Many researchers men-tioned that the cooling rate is an importantprocessing parameter that affects the me-chanical behavior. It has been reported thatthe solidification time has a significant ef-fect on the ductility of materials [2]. Meiet al. previously reported that the faster cool-ing rate increase the ductility and elongationto failure when the microstructure becomesmore refined with faster cooling rate duringsolidification and a fine microstructure pro-vides a better set of mechanical properties

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E.-R. Bagherian et al.: Metall. Res. Technol. 113, 308 (2016)

Table 9. Tensile strength and average elongation percentage of OFCu samples.

Sample Rod Die Pull Accele- Decele- Water Casting Pull Tensile Averagedia dwell ration (s) ration(s) flow rate speed Distance strength elongation

(mm) (s) (l/min) (mm/min) (mm) (MPa) Percentag (%)Cast 1 12 Graphite 0.015 0.010 0.010 55 97 3 190 31Cast 2 12 Graphite 0.015 0.010 0.010 55 1700 4 187 35Cast 3 12 Graphite 0.015 0.010 0.010 55 2100 5 185 36Cast 4 12 Graphite 0.015 0.010 0.010 55 2700 6 183 37

Tens

ile S

tren

gth

(MPa

)

Te

178

180

182

184

186

188

190

192

3 (mm

P

ensile strengt

) 4 (mm) 5

Pull distance (

th

5 (mm) 6 (mm

mm)

m)

Elon

ga�o

n pe

rcen

tage

(%)

El

2829303132333435363738

longation per

3 (mm) 4 (m

Pull dist

centage

mm) 5 (mm)

tnace (mm)

6 (mm)

Fig. 10. Tensile strength and average elongation percentage of CuSn samples.

33mm pull dis

stance 4mmm pull distance 5mm puull distance

66mm pull disstance

Fig. 11. Grain structure of CuSn samples.

than a coarse microstructure. Hence, largerpull distance would improve the ductility ofcontinuous cast copper alloy [25, 26].

4 Conclusions and future work

The effect of water flow rate, casting speed,addition of alloying elements and pull dis-tance on the mechanical properties of con-tinuous cast copper alloys were investigatedusing tensile machine. From the above ex-perimental results, some important conclu-sions can be drawn:

1. Results showed that when cooling waterflow rate was increased, an improvementof elongation percentage was observed.

2. When casting speed increased a signif-icant improvement of physical and me-chanical properties of copper alloys wereobserved.

3. The addition of alloying elements, no-tably Zr, improved the tensile strengthof continuous cast copper alloy. How-ever, elongation percentage of the alloydecreases with an increase in the amountof alloying elements.

4. The addition of zirconium reducesslightly the size of SDAS of continuouslycast copper rod.

5. Pull distance strongly affect the physicaland mechanical properties of continuouscast copper alloys.

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E.-R. Bagherian et al.: Metall. Res. Technol. 113, 308 (2016)

6. With the increasing of the casting speed,water flow rate, pulling distance thegrain structure tends to become finer incontinuous cast copper alloys.

7. A limitation observed in this study isthat, once the casting speed, water flowrate and pull distance are increased, itcan result in lower casting quality, up tofracture. At high casting speed, low pulldistance and low water flow rate chang-ing parameters should be avoided

8. As for future work, this research can beextended by comparing the influence ofother thermal factors on the structureand mechanical properties of continuouscast copper alloys such as; melt temper-ature, cleanout cycle, continuous cast-ing direction (horizontal /vertical) andsuper-cooler size.

Acknowledgements

This research project would not have been pos-sible without the support of Rautomead Ltd en-gineers. The authors would like to thank to Mr.Colin Bell and Mr Gavin Marnie. Their guidancehelped us throughout this research. The authorswould like to thank Sir Michael Nairn, Chairmanof Rautomead, for his valuable comments andsuggestions to improve the quality of the paper.

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