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Hoda El-Faramawy, Saeed Ghali

Influence of chromium additions and true strain rate onhardness of austenitic manganese steelThe influence of solution annealing heat treatment on the microstructure and hardness ofHadfield steel containing up to 3.16% chromium and 0.15% nitrogen was investigated.Furthermore, the effects of chromium additions on the hardness and microstructure of austeniticmanganese steels in the as-cast and heat-treated conditions have been studied. The true stress-true strain response of nitrogen alloyed austenitic manganese steel with chromium additions inthe as-cast and heat treated conditions under compression loading was also studied. Themicrostructural observations on the as-cast and heat-treated steels with chromium additionsrevealed the stability of austenite phase in the as-cast state deformation with precipitation ofcarbides and carbonitrides on the grain boundaries. These precipitates increase by increasingtrue strain and chromium content.

22 factorial design was used to investigate the contribution effect of chromium additions and truestrain on hardness of austentic manganese steel as cast and after heat treatment. Thecontribution of both chromium additions up to 3.16%, true strain rate up to 0.4, and theinteraction combination effect of them were determined of cast and heat treated austeniticmanganese steel. The regression models were built up to identify the hardness as function inchromium additions and true strain rate of both cast and heat treated austenitic manganese steel.

IntroductionHadfield’s manganese steel is still usedextensively, with minor modifications inchemical composition and heat treatment.Many variations of the original austeniticmanganese steel have been proposed byvariation of carbon and manganese with orwithout addition of some elements such as Cr,Ni, Mo, V, Ti and nitrogen. Austeniticmanganese steel is sometimes referred to asHadfield’s manganese steel. This steel is lowstrength, high toughness and ductility withhigh work-hardening capacity, capable ofdeveloping excellent wear resistance whensurface hardening by cold working.

Detailed studies [1-2] have shown that carbonin these steels has a tendency to segregate tothe grain boundaries causing a thin denudedzone, which transforms to martensite ondeformation leading to intergranularembrittlement.

Chromium represents the most commonelement, which employed in Hadfieldmanganese steel to moderately raise yieldstrength [3-4]. Also, chromium addition of 1.8to 2.2% and occasionally as high as 6%, ingeneral reduces the ductility of Hadfield steelby increasing number of embrittling carbidesin austenite particularly those containing morethan 2.5% chromium. Addition of Cr toHadfield steel results in carbides surroundingthe austenite structure have a lamellarstructure. These carbides are richer in Cr andMn than the austenite grains. After solutiontreatment, the austenite grains coarsen withdecreasing the carbide volume fraction [5].

There is a trend in simulation and modeling ofsteelmaking and ferroalloys, for example the

prediction of magnesium content inproduction of ferrosilicon magnesium fromdolomite, predicted nitrogen solubility instainless steel, calculation of activation energyin nitriding ferromanganese are illustrated byauthors [6-11]. The use of factorial design insteelmaking is relatively limited. Few authorsare used it to investigate the effect of differentparameters on the metallurgical process. 22

factorial design was used to investigate theeffect of cooling rate after rolling and coolingrate after coiling on mechanical properties of65Mn steel grade[12]. Also, the influence of gasratios H2/CO on reduction kinetics wasinvestigated [13]. The influence of the presenceof iron oxide and / or silicon oxides inmanganese ore was investigated by usingfactorial design[14].

23 factorial design was used in investigationthe influence of addition of SiO2, MnO2 andreaction temperature on reduction degree ofsynthetic iron ore[15]. 24 factorial design wasused to investigate the oxidation behavior asfunction in time, temperature, nitrogen andnickel contents[16]. Also, it was used toanalysis the reduction yield of synthetic ironoxide [17].

This study aims to study the effect ofchromium additions on the strain hardeningrate, compression strength and abrasionresistance of austenitic manganese steelcontaining 0.15% N. Furthermore, it is aimedto be seen to what extent cold working processaffects transformation through microstructureexamination. In addition, the effect of solutiontreatment on microstructure and hardness ofhigh manganese steel containing 3.16% Cr and0.15% N has been also investigated. Also, thecontribution effect of chromium content and

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true strain hardening on hardness isinvestigated for cast steel and also,after heat treatment.

ExperimentsFour grades of high manganese steelswith base composition of 0.9% C, 14.5-15% Mn, 0.15% N and different Crcontents were melted in 15 kg highfrequency induction furnace. Thechemical compositions of the rawmaterials used is given in Table 1. Theseinvestigated steels were casted into aluminamoulds with 270 mm in length and 55 mm indiameter.

Samples for different tests were machined byspark erosion machine. Preliminaryexperiments were carried out to select theoptimum heat treatment condition. Forsolution annealing of all investigated steels,the specimens were heated in slow rate andsoaked at 1080°C for 2 h and then quenchedquickly in water. Specimens for compressiontest were machined in cylindrical shape withdiameter 5 mm and length 10 mm. UniversalPüf machine (1000 KN) was employed toperform the tests at room temperature (22°C)with strain rate 8.3 x 10-3/s to checkrepeatability and consistency between results,tests were repeated 3 times. Vickers hardness(HV10) was employed to measure the hardnessof cast and quenched specimens. Also,hardness of the compressed specimens weremeasured at different deformations.Microstructure of the cast, quenched andcompressed samples were performed byoptical microscope. Wear resistance test wascarried out under abrasion condition.Specimens with dimensions 12 x 12 x 8 mm3

were prepared from the investigated steels. Ahigh stress abrasion wear was performed bypin-abrasion test. The test used 70-meshalumina abrasive, a 90 N specimen load, and30 rpm specimen rotation speed. Test durationwas 10 minutes. AISI 1020 cold-rolled steelstandard was tested with each batch ofspecimens.

The factorial design was applied on the resultsof 0%, 1.65% Cr and 3.16% Cr at truestrain rates 0% and 0.4 of cast steeland heat treated steels to investigatetheir effect on hardness. Theinfluence of chromium addition,true strain rate and interactioncombination effect on hardness wasinvestigated. Regression modelswere deduced to calculate thehardness in terms of chromiumcontent and true strain.Interpretation between the

predicted values and experimental valueswere investigated.

Result and discussionThe chemical composition of produced steelsare listed in Table 2. The stress-strain testsunder compressive loading of investigated ascast and heat treated steels are diagramed inFigures 1 and 2, respectively. They show howthe work hardenability characteristics areaffected by chromium additions.

In cast condition, addition of 1.65% Cr has noeffect on the strain hardening behavior ofinvestigated nitrogen contained Hadfield steel.The true stress-true strain curves for the twofree and 1.65% Cr containing steels are verysimilar. However, further chromium additionsof 2.26-3.16% have a significant effect on thecompression yield strength and strainhardening behavior of investigated steels. Thecompression yield strength is stronglyincreased by increasing chromium addition upto 3.16%. Furthermore, effective increase incompression strength occurs at lower strainfor steels containing higher chromiumcontents. Plastic deformation is needed for thework hardening of the austenite matrix to itsmaximum strength, but the amount of plasticdeformation for steels containing higherchromium content is lower than that what isneeded for hardening the investigated Cr-freesteel to its maximum value.

The results obtained in Figure 2 clarify thesuperior high strength high ductility of as-castN-high manganese steels containing 3.16% Cr.

Comparing the results of stress-strain curvesfor the investigated steels in the two conditions

Table 1: Chemical composition of the raw materials used in theproduction of modified austenitic manganese steel

Table 2: Chemical composition of the produced ingots

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of as-cast and heat treatment, Figures 1 and 2,illustrates the negative effect of heat treatmenton the compression strength of Cr-highmanganese steels. The compression strengthvalues of heat-treated Cr-high manganesesteels are much lower comparing with that ofas-cast steels. For all stages of compression, Cr-steels in cast form have the higher loadrequired for certain strain comparing withheat-treated steels. Furthermore, solutiontreatment and quenching process of Cr-containing Hadfield steels deteriorates theductility of these steels. The most importantfeature of the Hadfield steels is the strongwork hardening ability as a result of pressureagainst the steel surface. This grade of steelcan work harden from an initial level of about

200-220 HV to more than 500 HV. Thishardening is limited, however, into a thinsurface layer of the steel whereas the innerpart remains soft and ductile and the wholesteel shows a ductile behavior [18]. Theprerequisite for this kind of behavior is thatthe microstructure of the steel is fullyaustenite without continuous band of carbidesat the grain boundaries [18]. Examination ofthe as-cast conventional Hadfield steel,exhibited the formation of brittle mixedcarbides - mainly iron/manganese carbidesalong austenite grain boundaries and otherinterdendritic areas due to Mn and Csegregation [3-5, 19] and the hole behavior ofthe steel is brittle. Under the mechanicalstresses, the steel breaks along the brittle grainboundaries. Such an as-cast structure shouldbe solution treated to the austenitizingtemperature, at a certain holding time, fordissolving the grain boundary carbides intothe steel matrix, then water quenching toprevent the precipitation of the carbides andpreserve the full austenite structure [3-5, 18-19].

In the present study, the nitrogen combinedwith chromium additions have been used toexamine their effect on the work hardening of

Hadfield steels. Chromium has a strong affinityfor both carbon and nitrogen [20]. Suchaddition of carbide and nitride formingelements permits a large quantity of dispersedcarbides and carbonitrides to be formed in themelt what provides for production of highquality and fine grain structure with locationof the most carbides and carbonitrides insideof grains. The presence of such very hardparticles inside the grains promotes steelcapability to cold hardening [21].

Metallographic examination of investigated as-cast steels illustrates carbide or carbonitrideprecipitates on the grain boundaries asillustrated in Figure 3. Increasing thechromium content in these steels leads to the

Figure 2: Effect of chromium addition on: (a) true stress-true strain curve, (b) true strain-hardness relationship ofheat treated austenitic manganese steel

Figure 1: Effect of chromium addition on: (a) truestress-true strain curve, (b) true strain-hardness

relationship of as cast

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formation of carbides/carbonitrides insidegrains accompanied with increasing ofhardness. The microstructure of investigatedsteels after austenitization at 1080°C and waterquenching is illustrated in Figure 3. Themicrostructure observations reveal coarseaustenite and the amounts ofcarbides/carbonitrides, which were not takenin solution during austenitization, have beenincreased as Cr content increased.

For as-cast steels, cold working has beencarried out up to 0.58 true strain withoutfracture. This may be explained by theunchangeable structure as the results of coldworking as shown in Figure 4. Themicrostructure reveals austenite grains withthe presence of carbides/ carbonitrides on thegrain boundaries and inside the grains, whichincrease with increasing chromium content.

The presence of nitrogen increases the stabilityof austenite as an austenite former. Nitrogenstabilizes austenite under plasticdeformation and preserves itsplastic parameters [22]. The workhardening tendency in the as-castinvestigated steels is suggested tobe improved by using nitrogen asalloying element and introducingseparately distributed hardparticles into microstructure byalloying with nitrogen andchromium as strong carbide/nitrideformer. Nitrogen in combinationwith strong nitride formingelements form hard nitride on thegrain boundary zones and partiallytransforms the grain boundarycarbides into carbonitrides [18].

Usually, a fully austenite structure,essentially free of carbides andreasonably homogeneous withrespect to carbon and manganese,is desired in the as-quenchedcondition. This is not alwaysattainable in steels containingcarbide forming element such aschromium. In solution treatment ofsuch steels, carbide andcarbonitride precipitates formed inthe microstructure followingcasting are partially but not completelydissolved [18].

The heat treatment of investigated steelsproduced relatively fine dispersion of carbideand carbonitrides in coarse austenite matrix.The coarse austenite matrix of heat-treatedsteels comparing with that of as-cast steelscould be attributed to the grain growth duringsolution treatment and the tendency of

chromium to speed up grain growth rate [5, 23-24]. Large-grained structure with individualinclusions of carbides and carbonitrides at theboundaries of austenitic grains impairs thephysico-mechanical properties of the steels,including its liability to cold hardening [21].Furthermore, the fine dispersed particles mayact as nuclei for nucleus growth of martensitetransformation.

As indicated in Figure 4., cold working of heat-treated chromium austenitic manganese steelsresults in almost transformation to inducedmartensite in deformed austenite grains. Thistransformation is enhanced either byincreasing Cr content or by increasing thepercentage of cold reduction. However, thereare differences of opinions as to whethermartensite can be produced by cold working.The obtained results of investigated heat-treated steels, confirm the possibility ofmartensite formation by cold working, whichagree with other studies [25-27].

Wear resistance. In the present study, theeffect of alloying austenitic manganese steelcontaining 0.15% N with chromium additionson the wear resistance of this type of steels hasbeen investigated. The results of the effect ofchromium contents on the relative abrasionwear of the investigated steels are given inTable 3. The relative abrasion wear values hasbeen determined as a ratio of weight loss ofthe steel sample to weight loss of the standard

Figure 3: Optical micrograph of as cast and heat treated austenitic manganesesteel at chromium contents, a-as cast 1.65% Cr, b-as cast 2.2% Cr, c-as cast

3.16% Cr, e-heat treated 1.65% Cr, f-heat treated 2.2% Cr g-heat treated 3.16%Cr, X=500

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materials AISI 1020 cold rolled steel. The lowrelative wear ratio of the investigated steelsindicates the high wear resistance of thesesteels. For both as-cast and heat treated steels,the relative wear ratio decreases by increasingchromium addition up to 3.16%, Figure 5.

The wear resistance of metal is stronglydependent on its hardness. However, inaustenitic steels, initial hardness does notcorrelate with the abrasion resistance [28].Furthermore, the amount of abrasion wear isknown to be dependent on microstructure,alloying content and second phase particles[29]. Austenite is more resistance to abrasivewear than ferrite, pearlite or martensite. Thisis mainly due to the ductility and strainhardening capacity of austenite [29]. Inaddition, at similar hardness, steels with

greater amount of carbides orcarbonitrides of a higherhardness, will show betterresistance to wear [30]. Chromiumhas a strong affinity for bothcarbon and nitrogen, and it has astrong tendency to form hard andstable carbides [20]. Chromiumcarbides are about 65/70 HRC [31].

Increasing chromium content isaccompanied by increasing thecarbides/carbonitrides contentsfor both as-cast and heat-treatedCr-containing steels. Theseembedded carbides/carbonitridesparticles are harder than the steelmatrix around them and can helpprevent the matrix from beingworn away resulting in higherabrasion wear resistance.However, comparing with otherhigh hardness carbides particlessuch as V, Mo and W carbides, Crcarbides because of theirrelatively lower hardness areamong the least effective.Comparing with as-cast steels, theheat treatment has no clear effecton the wear resistance ofinvestigated chromium-containinghigh manganese steels. The

negative effect of large-grained structure ofheat-treated steels on wear resistance isequalized with relatively fine dispersion ofcarbides/ carbonitrides with the results ofapproximately similar abrasion wear valuesfor both as-cast and heat-treated investigatedsteels.

Two models were built to cover the range ofchromium contents. The first model cover thechromium content up to 1.65% and the secondmodel cover chromium contents start from1.65% up to 3.16%. Tables 4-5 present the

Figure 4: Optical micrograph of as cast and heat treated hadfield steelcontaining chromium at different strain reduction a-as cast 1.65% Cr at

reduction 23.64%, b- as cast 2.26% Cr at reduction 26.1%, c-as cast 3.16% Cr atreduction 41%, e-heat treated 1.65% Cr at reduction 34%, f-heat treated 2.26% Cr

at reduction 39%, g-heat treated 3.16% Cr at reduction 37%, X=500.

Table 3: Effect of Cr addition on relative abrasionfactor to high stress grinding on the as cast and

heat treated investigated steels

Figure 5: Effect of chromium contents on relativeabrasion ratio of the investigated steels

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influence of chromium contents at differenttrue strain rate on hardness of cast steel andheat treated steel.

Let we donate the high chromium content(1.65%) at low true strain rate by “A”, high truestrain rate (0.4) at 0.0% Cr is denoted by “B”,high chromium content (1.65%) at high strainrate is denoted “AB” and low chromiumcontent 0% Cr at “0.0” true strain rate isdenoted by “1”. Complete analysis ofchromium content and true strain rate onhardness was illustrated as given in Table 6 ofcast and heat treated steels.

The factorial design in 22 was applied toinvestigate the contribution effect ofchromium content and true strain rate onhardness of cast and heat treated austeniticmanganese steel. The four treatmentcombinations in the design are usuallyrepresented by lowercase letters. The highlevel of any factor in the treatmentcombination is denoted by the correspondinglowercase letter and that the low level of afactor in the treatment combination is denotedby the absence of the corresponding letter.Thus, “a” represents the treatmentcombination of A at high level and B at lowlevel, “b” represents A at low leveland B at high level, “ab” representsboth factors at the high level and (1)is used to denote both factors at lowlevel.

The average effect of any factor canbe defined as the change in responseproduced by a change in the level ofthat factor averaged over the levelsof the other factor. This is illustratedelsewhere [16-21]. The main effect ofA, B, and AB can be calculated asgiven in Equations (1-3).

(1)

(2)

(3)

Based on the 22 factorial design analysis theaverage effect of A, B, and their combinationeffect (AB) on hardness can be calculated. Theresults are tabulated in Table 6.

The calculation of factorial design of cast steelin chromium range up to 1.65% shows that thetrue strain rate has positive significant effecton hardness while chromium addition hassmall negative effect on hardness. The inter-combination effect of chromium additions andtrue strain rate is small and positive and canbe neglected. This means that as true strainhardening increases the hardness of castaustenitic manganese steel increases inchromium range up to 1.65%.

While as true strain rate increases thehardness decreases of cast austeniticmanganese steel within chromium content up1.65%. The interaction combination of truestrain rate and addition of chromium is verysmall and positive which can be neglected. Thehardness can be determined as a function intrue strain rate and chromium additions asgiven in Equation (4). Figure 6 shows thevariation between the calculated hardnessfrom regression model and the measuredhardness.

Hardness = 234.6 - 20.9696 * a + 613.75 * b +8.7878 * a * b

(4)

Where hardness is in HV, “a” is chromiumcontent in wt. %, and “b” is true strain rate.

Fig. 6 shows that there is no differencebetween the predicted hardness of cast steel(0.0 – 1.65% Cr) according to Equation (4) and

Table 4: True strain rate and chromium additioneffect on hardness.

Table 5: True strain rate and chromium addition(1.65 – 3.16%) effect on hardness.

Table 6: Contribution effect of A, B, and AB on hardness of cast andheat treated steel at different chromium ranges.

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measured hardness. Equation (4) is used topredict the hardness at different true strainrate of cast steel of 0.0% and 1.65% Cr as givenin Figures 7-8 respectively. These figures showthat there are an agreement between thepredicted and measured hardness to largeextent.

The calculation of factorial design shows (asillustrated in Table 6) that both the true strainrate and addition of chromium in range 1.65 –3.16% have positive effect on hardness of castaustenitic manganese steel. These mean both

true strain rate and addition of chromium (inrange 1.65 -3.16%) cause an increasing inhardness. Also, the interaction combinationeffect of true strain rate and chromiumadditions (in range 1.65-3.16%) has smallpositive effect on hardness. The hardness ofcast austenitic manganese steel (chromiumrange 1.65 – 3.16%) can be predicted as afunction in true strain rate and addition ofchromium by using regression model as givenin Equation (5). The variation between thepredicted and measured hardness is presentedin Figure 9.

Hardness = 225.8 - 15.6969 * a + 810 * b - 68.33* a * b

(5)


Figure 9 shows that the predicted hardness –according to Equation 5 – is identical with themeasured hardness of cast steel (1.65 – 3.16%Cr). Equation 5 is used to predict the hardnessat different true strain rate of cast steel of1.65% Cr, 2.2% Cr and 3.16% Cr and presentedin Figures 10 – 12 respectively. Figures 10-12illustrated that the predicted hardness isnearly equal the measured one at differenttrue strain rate of austenitic manganese steelcontaining 1.65% Cr, 2.2% Cr and 3.16% Crrespectively.

The chromium addition of heat treatedaustenitic manganese steel has negativeinfluence on hardness while the true strainrate has positive large influence on hardness.That is mean that the hardness increase as thetrue strain increase and as the addition ofchromium decreases in range up to 1.65%. Theinteraction combination of chromium addition(up to 1.65%) and true strain rate (up to 0.4)has negative influence on hardness as given inTable 6. The hardness can be predicted as afunction in true strain rate and chromiumadditions by using regression model as given

Fig. 6 : The variation between the predicted andmeasured hardness of cast steel (0.0 – 1.65% Cr)

Fig. 7: The variation between the predicted andmeasured hardness at different true strain rate of

cast steel free chromium


cast containing 1.65% Cr

Fig. 9: The variation between the predicted andmeasured hardness of cast steel (1.65 -3.16% Cr)

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in Equation 6. The variation between thecalculated and measured hardness isillustrated in Figure 13.

Hardness = 171.04 + 17.5497 * a + 514.881 * b +68.71 * a * b

(6)


Figure 13 shows that the predicted hardness –according to Equation 6 – is identical with themeasured hardness of heat treated steel (up to1.65% Cr). Equation 6 is used to predict the

hardness at different true strain rate of heattreated steel of 0.0% Cr and 1.65% Cr andpresented in Figures 14-15 respectively.Figures 14-15 showed that the predictedhardness is in an agreement with themeasured to certain extent of heat treatedaustenitic manganese free chromium andcontaining 1.65% Cr respectively.

The calculation of factorial design shows thatboth the chromium additions (in range 1.65-3.16%) and true strain rate have positive


cast steel containing 2.2% Cr






heat treated steel containing up to 1.65% Cr


heat treated steel containing 1.65% Cr


heat treated steel free chromium.

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influence on hardness of heat treatedaustenitic manganese steel. This means thatthe hardness increases as the true strain rateand / or chromium addition increases. Also,the interaction combination effect (AB) haslittle positive effect which can be neglected.The true strain rate contribute in increasinghardness by more than 95 times ofcontribution of chromium additions as shownin Table 6. Hardness can be predicted as afunction in both true strain rate andchromium additions (1.65-3.16%) by usingregression model as given in Equation 7.Figure 16 represents the variation between thepredicted and measured yield strength.

Hardness = 170.715 + 17.748 * a + 683.91 * b +7.781 * a * b

(7)


Fig. 21 shows that the predicted hardness –according to Equation 7 – is identical with themeasured hardness of heat treated steel (containing chromium from 1.65% to 3.16%).Equation 7 is used to predict the hardness atdifferent true strain rate of heat treated steel

of 1.65% Cr, 2.2% Cr and 3.16% Cr. Thepredicted and measured data is presented inFigures 17-19 respectively. Figures 17-19showed that the predicted hardness is in anagreement with the measured to certain extentof heat treated austenitic manganesecontaining 1.65% Cr, 2.2% Cr and 3.16% Crrespectively.

ConclusionsBased on this work carried out to investigatethe effect of single addition of chromium onhigh manganese steel containing 0.15%nitrogen, the following conclusions are drawn:

In cast-condition, addition of 1.65% Cr has noeffect on strain hardening behavior of thissteel. Further chromium additions of 2.26-3.16% have a significant effect on the yieldstrength and strain hardening behavior. Thecompression strength values of heat-treatedCr-steels are much lower comparing with thatof as-cast Cr-steels. Strain hardening of heat-treated Cr-steels is accompanied withmartensite formation, whereas as-cast Cr-steels retain their basic austenitemicrostructure even after severe cold working.For both as-cast and heat-treated steels, theabrasion wear resistance increases by


heat treated steel (1.65 -3.16% Cr)







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increasing the Cr-addition up to 3.16%.

The effects of true strain rate has positivesignificant effect over chromium range up to3.16 for cast and heat treated austeniticmanganese steel. The addition of chromium upto 1.65% has negative effect on hardness forboth cast and heat treated austeniticmanganese steel. The negative effect ofchromium additions in heat treated steel isgreater than in cast steel. The addition ofchromium from 1.65% Cr to 3.16% Cr haspositive effect on hardness for both cast andheat treated austenitic manganese steel. Thepositive effect of chromium additions in heattreated steel is smaller than in cast steel. Theinteraction combination of true strain rate andchromium additions of cast steel (0.0 -1.65%Cr) and heat treated steel (1.65 – 3.16%) arepositive and small and can be neglected. Theinteraction combination of true strain ratewith chromium additions is positive in caststeel (1.65-3.16%) and negative in heat treatedsteel (0.0 – 1.65). The hardness can bepredicted as a function in true strain rate andchromium additions for both cast and heattreated steel within two interval of chromiumcontents. It was found that the predictedvalues are very close to the measured values,which means factorial design is very usefultechnique in the field of steel and it is berecommended to be used in several processesin metallurgy.

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Author`s noteProf. Dr. Hoda El-Faramawy

Head of Steel Technology DepartmentCentral Metallurgical Research and Development Institute

(CMRDI)Cairo, EgyptAssoc. Prof. Saeed Ghali (Correspondingauthor)

Steel Technology DepartmentCentral Metallurgical Research and Development Institute

(CMRDI)Cairo, Egypt

white paper influence of chromium additions and true ... · influence of chromium additions and...

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