A critical investigation into the role of Mg on the toughness and microstructure of coarse grain heat-affected zone (CGHAZ) in low carbon steel has been investigated. In this research, the specimens (Mg-free and Mg-added) underwent weld thermal cycle with heat input of 54, 80, and 100 kJ cm−1 at 1350°C peak temperature using a thermal simulator. The typical inclusions characteristics were characterised by means of scanning electron microscopy and equilibrium calculations. The precipitates were characterised by transmission electron microscopy and energy-dispersive spectroscopy. It is revealed that the occurrence of Mg in steel mostly exists in the form of Mg-Al-O oxide inclusions, but a few in the form of solid solution state and (Nb,Ti)(C,N)+MgO precipitates when the concentration of Mg is 0.0026%. The improvement of CGHAZ toughness is obtained when the heat input is 80 and 100 kJ cm−1. The possible reasons about the effects of Mg on the toughness of CGHAZ, including Mg-Al-O inclusions, precipitates, and soluble Mg, are discussed in detail.
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References
1.
MizoguchiSTakamuraJ.Control of oxides as inoculants. Proc 6th Int Iron Steel Cong ISIJ, Nagoya; 1990. p. 598–604.
2.
TakamuraJMizoguchiS.Role of oxides in steels performance, metallurgy of oxides in steels. Proc 6th Int Iron Steel Cong ISIJ, Nagoya; 1990. p. 591–597.
3.
BabuSS.The mechanism of acicular ferrite in weld deposits. Curr Opin Solid St Mater Sci. 2004;8(3–4):267–278. doi: 10.1016/j.cossms.2004.10.001
4.
ByunJSShimJHChoYWet al.Non-metallic inclusion and intra-granular nucleation of ferrite in Ti-killed C–Mn steel. Acta Mater. 2003;51(6):1593–1606. doi: 10.1016/S1359-6454(02)00560-8
5.
WanXLWeiRWuKM.Effect of acicular ferrite formation on grain refinement in the coarse-grained region of heat-affected zone. Mater Charact. 2010;61(7):726–731. doi: 10.1016/j.matchar.2010.04.004
6.
LiXBMinYLiuCJet al.Effect of Mg addition on the characterization of γ-α phase transformation during continuous cooling in low carbon steel. Steel Res Int. 2015;86(12):1530–1540. doi: 10.1002/srin.201400517
7.
LiXBMinYLiuCJet al.Study on the formation of intragranular acicular ferrite in a Zr–Mg–Al deoxidized low carbon steel. Steel Res Int. 2016;87(5):622–632. doi: 10.1002/srin.201500167
8.
AbsonDJPargeterRJ.Factors influencing as-deposited strength, microstructure, and toughness of manual metal arc welds suitable for C–Mn steel fabrications. Int Metal Rev. 1986;31(1):141–196. doi: 10.1179/imr.1986.31.1.141
9.
FarrarRAHarrisonPL.Acicular ferrite in carbon-manganese weld metals: an overview. J Mater Sci. 1987;22(11):3812–3820. doi: 10.1007/BF01133327
10.
KosekiTThewlisG.Overview inclusion assisted microstructure control in C-Mn and low alloy steel welds. Mater Sci Technol. 2005;21(8):867–879. doi: 10.1179/174328405X51703
11.
ShimJHChoYWChungSHet al.Nucleation of intra-granular ferrite at Ti2O3 particle in low carbon steel. Acta Mater. 1999;47(9):2751–2760. doi: 10.1016/S1359-6454(99)00114-7
12.
JinHHShimJHChoYWet al.Formation of intragranular acicular ferrite grains in a Ti-containing low carbon steel. ISIJ Int. 2003;43(7):1111–1113. doi: 10.2355/isijinternational.43.1111
13.
KojimaAKiyoseAUemoriRet al.Super high HAZ toughness technology with fine microstructure imparted by fine particles. Nippon Steel Technical Report. 2004;90:2–6.
14.
ChaiFYangCFSuHet al.Effect of magnesium on inclusion formation in Ti-killed steels and micro-structural evolution in welding induced coarse-grained heat affected zone. J Iron Steel Res Int. 2009;16(1):69–74. doi: 10.1016/S1006-706X(09)60013-3
15.
ZhuKYangZG.Effect of Mg addition on the ferrite grain boundaries misorientation in HAZ of low carbon steels. J Mater Sci Technol. 2011;27(3):252–256. doi: 10.1016/S1005-0302(11)60058-3
16.
ZhuKYangJWangRZet al.Effect of Mg addition on inhibiting austenite grain growth in heat affected zones of Ti-bearing low carbon steels. J Iron Steel Res Int. 2011;18(9):60–64. doi: 10.1016/S1006-706X(12)60035-1
17.
ZhuKYangZG.Effect of magnesium on the austenite grain growth of the heat-affected zone in low-carbon high-strength steels. Metall Mater Trans A. 2011;42(8):2207–2213. doi: 10.1007/s11661-011-0647-6
18.
YangJXuLYZhuKet al.Improvement of HAZ toughness of steel plate for high heat input welding by inclusion control with Mg deoxidation. Steel Res Int. 2015;86(6):619–625. doi: 10.1002/srin.201400313
19.
SeoCWKimSHJoSKet al.Modification and minimization of spinel (Al2O3·xMgO) inclusions formed in Ti-added steel melts. Metall Mater Trans B. 2010;41:790–797. doi: 10.1007/s11663-010-9377-1
20.
YangSFWangQQZhangLFet al.Formation and modification of MgO·Al2O3-based inclusions in alloy steels. Metall Mater Trans B. 2012;43(4):731–750. doi: 10.1007/s11663-012-9663-1
21.
VermaNPistoriusPCFruehanRJet al.Calcium modification of spinel inclusions in aluminum-killed steel: reaction steps. Metall Mater Trans B. 2012;43(4):830–840. doi: 10.1007/s11663-012-9660-4
22.
KimuraSNakajimaKMizoguchiS.Behavior of alumina-magnesia complex inclusions and magnesia inclusions on the surface of molten low-carbon steels. Metall Mater Trans B. 2001;32(1):79–85. doi: 10.1007/s11663-001-0010-1
23.
OhtaHSuitoH.Characteristics of particles size distribution of deoxidation products with Mg,Zr,Al,Ca,Si/Mn and Mg/Al in Fe-10mass%Ni alloy. ISIJ Int. 2006;46(1):14–21. doi: 10.2355/isijinternational.46.14
24.
YangJYamasakiTKuwabaraM.Behavior of inclusions in deoxidation process of molten steel with in situ produced Mg vapor. ISIJ Int. 2007;47(5):699–708. doi: 10.2355/isijinternational.47.699
25.
TakataRYangJKuwabaraM.Characteristics of inclusions generated during Al–Mg complex deoxidation of molten steel. ISIJ Int. 2007;47(10):1379–1386. doi: 10.2355/isijinternational.47.1379
26.
LiXBMinYLiuCJet al.Influence of zirconium on mechanical properties and phase transformation in low carbon steel. Mater Sci Technol. 2016;32(5):454–462. doi: 10.1179/1743284715Y.0000000110
27.
KosekiTOhkitaSYuriokaN.Thermodynamic study of inclusion formation in low alloy steel weld metals. Sci Technol Weld Joining. 1997;2(2):65–69. doi: 10.1179/stw.1997.2.2.65
28.
IchikawaKKosekiTFujiM.Thermodynamic estimation of inclusion characteristics in low alloy steel weld metals. Sci Technol Weld Joining. 1997;2(5):231–235. doi: 10.1179/stw.1997.2.5.231
29.
MuWJönssonPGNakajimaK.Effect of sulfur content on inclusion and microstructure characteristics in steels with Ti2O3 and TiO2 additions. ISIJ Int. 2014;54(12):2907–2916. doi: 10.2355/isijinternational.54.2907
30.
MuWJönssonPGShibataHet al.Inclusion and microstructure characteristics in steels with TiN additions. Steel Res Int. 2016;87(3):339–348. doi: 10.1002/srin.201500061
31.
SundmanBShiPBratbergJ.TCS steels/Fe-alloys database version 7.0. Sweden: Thermo-Calc Software AB; 2012.
32.
FengYYLuoZAZhangDHet al.The application of welding heat cycle computer software. Mater Sci Forum. 2008;575–578:821–826.
33.
LiXBMinYYuZet al.Effect of Mg addition on the nucleation of intragranular acicular ferrite in Al-killed low carbon steel. J Iron Steel Res Int. 2016;23(5):415–421. doi: 10.1016/S1006-706X(16)30066-8
34.
ParkJSParkJH.Effect of Mg-Ti deoxidation on the formation behavior of equiaxed crystals during rapid solidification of iron alloys. Steel Res Int. 2014;85(8):1303–1309. doi: 10.1002/srin.201300203
35.
IsobeK.Effect of Mg addition on solidification structure of low carbon steel. ISIJ Int. 2010;50(12):1972–1980. doi: 10.2355/isijinternational.50.1972
36.
KraussGThompsonSW.Ferritic microstructure in continuously called low- and ultralow-carbon steels. ISIJ Int. 1995;35(8):937–945. doi: 10.2355/isijinternational.35.937
37.
SarmaDSKarasevAVJönssonPG.On the role of non-metallic inclusions in the nucleation of acicular ferrite in steels. ISIJ Int. 2009;49(7):1063–1074. doi: 10.2355/isijinternational.49.1063
38.
ShimJHOhYJSuhJYet al.Ferrite nucleation potency of non-metallic inclusions in medium carbon steels. Acta Mater. 2001;49(12):2115–2122. doi: 10.1016/S1359-6454(01)00134-3
39.
ShimJHChoYWShimJDet al.Effects of Si and Al on acicular ferrite formation in C-Mn steel. Metall Mater A. 2001;32(1):75–83. doi: 10.1007/s11661-001-0103-0
40.
YangZBWangFMWangSet al.Intragranular ferrite formation mechanism and mechanical properties of non-quenched-and-tempered medium carbon steels. Steel Res Int. 2008;79(5):390–395. doi: 10.1002/srin.200806143
41.
WuKMYokomizoTEnomotoM.Three-dimensional morphology and growth kinetics of intragranular ferrite idiomorphs formed in association with inclusions in an Fe-C-Mn alloy. ISIJ Int. 2002;42(10):1144–1149. doi: 10.2355/isijinternational.42.1144
42.
EnomotoMWuKMInagawaYet al.Three-dimensional observation of ferrite plate in low carbon steel weld. ISIJ Int. 2005;45(5):756–762. doi: 10.2355/isijinternational.45.756
43.
WuKM.Three-dimensional analysis of acicular ferrite in a low-carbon steel containing titanium. Scr Mater. 2006;54(4):569–574. doi: 10.1016/j.scriptamat.2005.10.054
44.
ChengLWuKM.New insights into intragranular ferrite in a low-carbon low-alloy steel. Acta Mater. 2009;57(13):3754–3762. doi: 10.1016/j.actamat.2009.04.045
45.
BakerTN.Role of zirconium in microalloyed steels a review. Mater Sci Technol. 2015;31(3):265–294. doi: 10.1179/1743284714Y.0000000549
46.
ShiMHZhangPYZhuFX.Toughness and microstructure of coarse grain heat affected zone with high heat input welding in Zr-bearing low carbon steel. ISIJ Int. 2014;54(1):188–192. doi: 10.2355/isijinternational.54.188
47.
ManoharPAFerryMChandraT.Five decades of the Zener equation. ISIJ Int. 1998;38(9):913–924. doi: 10.2355/isijinternational.38.913
48.
LiXBMinYLiuCJet al.Effect of magnesium addition in low carbon steel part 1: behavior of austenite grain growth. Ironmak Steelmak: 1–9. doi: 10.1080/03019233.2017.1368953
49.
ChenJX.Common use chart and thermodynamic data for steelmaking. Beijing: Metallurgical Industry Press; 2010.
50.
SunWSDingGRFuJet al.Effect of Mg in 35CrNi3MoV steel. Ordnance Mater Sci Eng. 1997;20(4):3–8.
51.
LiYQChenGSZhangJFet al.Effect of trace elements on the grain boundaries in some superalloys. Prog Nat Sci. 2000;10:331–341.
