稀土处理钢中晶内铁素体的形成及其对性能的影响
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摘要
测定了稀土脱氧和铝稀土复合脱氧钢焊接热影响区(HAZ)的连续冷却转变曲线,分析了2种钢中的夹杂物种类及其HAZ的显微组织和常温冲击韧性。得到如下结论:稀土脱氧使钢中主要夹杂物从Mn S转变为RE2O2S+Mn S,而铝稀土复合脱氧钢中夹杂物主要是Ce Al O3+Ce2S3+Mn S。稀土脱氧钢HAZ中能获得晶内铁素体的冷速较宽,约为0.5~7.5℃/s。铝稀土复合脱氧钢HAZ获得晶内铁素体组织较稀土脱氧钢要困难一些,适合晶内铁素体形成的冷速变窄为1~3℃/s,HAZ中晶内铁素体的含量明显低于稀土处理钢,Al脱氧弱化了稀土处理对钢HAZ组织的改善作用。焊接热输入线能量为100 k J/cm时,稀土脱氧能够明显改善钢HAZ的室温冲击韧性。
In this paper,the continuous cooling transformation curves of the welding heat affected zones( HAZ) were measured in steels deoxidized by rare earth( RE) and composite aluminum + RE,respectively. The composition of inclusions and impact toughness of HAZ at room temperature were analyzed in the above-mentioned two steels. The obtained results were as follows: the main inclusions in the steel changed from Mn S to RE2O2 S + Mn S after rare earth treatment,the composite aluminum + RE deoxidation changed the inclusions into Ce Al O3+ Ce2S3+ Mn S in C-Mn steel. The profitable cooling rate range for intragranular ferrite formation was wide during continuous cooling,about 0.5-7.5 ℃/s,in the HAZ of rare earth treated C-Mn steel. While in the aluminum + RE deoxidized steel,the profitable cooling rate ranged for HAZ to obtain intragranular ferrite was narrow,only about 1-3 ℃/s,meaning it was difficult for intragranular ferrite formation. The content of intragranular ferrite in the HAZ of RE killed steel was more than that in the HAZ of aluminum + RE deoxidized steel,demonstrating that Al deoxidation weaken the effect of RE deoxidization on the microstructure improvement of HAZ in steel. When welding heat input line energy was 100 k J/cm,rare earth treatment in the steel could improve HAZ impact toughness at room temperature obviously.
In this paper,the continuous cooling transformation curves of the welding heat affected zones( HAZ) were measured in steels deoxidized by rare earth( RE) and composite aluminum + RE,respectively. The composition of inclusions and impact toughness of HAZ at room temperature were analyzed in the above-mentioned two steels. The obtained results were as follows: the main inclusions in the steel changed from Mn S to RE2O2 S + Mn S after rare earth treatment,the composite aluminum + RE deoxidation changed the inclusions into Ce Al O3+ Ce2S3+ Mn S in C-Mn steel. The profitable cooling rate range for intragranular ferrite formation was wide during continuous cooling,about 0.5-7.5 ℃/s,in the HAZ of rare earth treated C-Mn steel. While in the aluminum + RE deoxidized steel,the profitable cooling rate ranged for HAZ to obtain intragranular ferrite was narrow,only about 1-3 ℃/s,meaning it was difficult for intragranular ferrite formation. The content of intragranular ferrite in the HAZ of RE killed steel was more than that in the HAZ of aluminum + RE deoxidized steel,demonstrating that Al deoxidation weaken the effect of RE deoxidization on the microstructure improvement of HAZ in steel. When welding heat input line energy was 100 k J/cm,rare earth treatment in the steel could improve HAZ impact toughness at room temperature obviously.
引文
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[2]TAKAMURA J I,MIZOGUCHI S.Roles of oxides in steel performance[C]//Proceedings of the 6th International Iron and Steel Congress,Nagoya:ISIJ,1990:591-597.
[3]COSTIN W L,LAVIGNE O,KOTOUSOV A.A study on the relationship between microstructure and mechanical properties of acicular ferrite and upper bainite[J].Materials Science and Engineering A,2016,663:193-203.
[4]侯阳,杨佳林,贺磊,等.微量Ce元素对0.23C-0.36Si-0.56Mn钢显微组织和力学性能的影响[J].材料科学与工艺,2015,23(1):38-44.
[5]SHI M,ZHANG P,WANG C,et al.Effect of high heat input on toughness and microstructure of coarse grain heat affected zone in zr bearing low carbon steel[J].ISIJ International,2014,54(4):932-937.
[6]CHAI F,SU H,YANG C,et al.Nucleation behavior analysis of intragranular acicular ferrite in a Ti-killed C-Mn steel[J].Journal of Iron and Steel Research International,2014,21(3):369-374.
[7]LIU C,SHI L,LIU Y,et al.Acicular ferrite formation during isothermal holding in HSLA steel[J].Journal of Materials Science,2016,51(7):3555-3563.
[8]SHI Z,YANG C,WANG R,et al.Effect of nitrogen on the microstructures and mechanical properties in simulated CGHAZ of vanadium microalloyed steel varied with different heat inputs[J].Materials Science and Engineering A,2016,649:270-281.
[9]史美伦,段贵生.氧化物冶金技术应用及进展[J].河南冶金,2010(5):1-4.
[10]ZHANG L,PITTNER A,MICHAEL T,et al.Effect of cooling rate on microstructure and properties of microalloyed HSLA steel weld metals[J].Science and Technology of Welding and Joining,2015,20(5):371-377.
[11]HUANG Q,WANG X,JIANG M,et al.Effects of Ti-Al complex deoxidization inclusions on nucleation of intragranular acicular ferrite in C-Mn steel[J].Steel Research International,2015,DOI:10.1002/srin.201500088.
[12]ZHENG W,WU Z,LI G,et al.Effect of Al content on the characteristics of inclusions in Al-Ti complex deoxidized steel with calcium treatment[J].ISIJ International,2014,54(8):1755-1764.
[13]SONG M M,SONG B,ZHANG S H,et al.Role of lanthanum addition on acicular ferrite transformation in C–Mn steel[J].ISIJ International,2017,57(7):1261-1267.
[14]SONG M M,SONG B,XIN W B,et al.Effects of rare earth addition on microstructure of C-Mn steel[J].Ironmaking and Steelmaking,2015,42(8):594-599.