700 MPa微合金高强钢焊接软化机理及解决方案
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摘要
700 MPa级Ti-Nb成分体系控轧控冷高强钢以其生产成本低、高强韧性以及优良的可焊性,近年来在专用车轻量化领域得到广泛应用。采用80%Ar+20%CO_2(体积分数)混合气体保护焊,对高Ti、Nb元素析出强化高强钢进行了焊接强度实验研究。结果表明,随着焊接热输入增大,焊接接头强度有降低趋势,焊接热影响区较母材硬度降低,存在软化行为,其软化机理表现在细晶强化、变形强化和析出强化效果的丧失。通过母材的B微合金化、控制焊接热输入等措施可有效缓解软化倾向,可为此种高强钢进一步推广应用提供技术参考。
Currently, Ti-Nb microalloyed high-strength steel with thermo-mechanical control process has been widely used in the field of light weight applications on special vehicles, owing to its characteristics of low production cost, high strength, high toughness, and excellent welding ability. The welding strength of Ti-Nb microalloyed high strength steel was studied by using metal active gas welding(80 vol.%Ar+20 vol.%CO_2). The results show that the strength of welded joint decreases with the increasing welding heat input. The hardness of the heat-affected zone(HAZ) is lower than that of the base metal, which indicates the existence of softening behavior in HAZ. The softening mechanism is manifested in the loss of fine grain strengthening, deformation strengthening and precipitation strengthening. Microalloying of B in the base metal and controlling welding heat input can effectively alleviate the softening tendency, and provide technical reference for the further promotion and application of this kind of high-strength steel.
Currently, Ti-Nb microalloyed high-strength steel with thermo-mechanical control process has been widely used in the field of light weight applications on special vehicles, owing to its characteristics of low production cost, high strength, high toughness, and excellent welding ability. The welding strength of Ti-Nb microalloyed high strength steel was studied by using metal active gas welding(80 vol.%Ar+20 vol.%CO_2). The results show that the strength of welded joint decreases with the increasing welding heat input. The hardness of the heat-affected zone(HAZ) is lower than that of the base metal, which indicates the existence of softening behavior in HAZ. The softening mechanism is manifested in the loss of fine grain strengthening, deformation strengthening and precipitation strengthening. Microalloying of B in the base metal and controlling welding heat input can effectively alleviate the softening tendency, and provide technical reference for the further promotion and application of this kind of high-strength steel.
引文
[1] Benedyk J.Light metals in automotive applications[J].Light Metal Age,2000,58(10):34.
[2] 陈鹰,张英建,董瀚,等.提高汽车安全性的先进高强钢高效成形技术[J].钢铁研究学报,2015,27(6):1.(Chen Y,Zhang Y J,Dong H,et al.Efficient forming technology of advanced high strength steel for car crashworthiness improvement[J].Journal of Iron and Steel Research,2015,27(6):1.)
[3] 赵少汴.抗疲劳设计手册[M].北京:机械工业出版社,2015.(Zhao S B.Anti-fatigue Design Manual [M].Beijing:Machinery Industry Press,2015)
[4] 李午申.我国合金结构钢的新发展及其焊接性[J].焊接学报,2001,22(5):83.(Li W S.The new development of alloy structure steels in China and their weldability[J].Transactions of the China Welding Institution,2011,22(5):83.)
[5] Mochizuki M,Shintomi T,Hashimoto Y,et al.Analytical study on deformation and strength in HAZ-softened weld joints of fine-grained steels[J].Welding in the World,48(9/10):2.
[6] 张楠,董现春,张熹,等.钛微合金化SQ700MCD高强钢粗晶热影响区软化的原因[J].机械工程材料,2012,36(4):88.(Zhang N,Dong X C,Zhang X,et al.Softening reasons for coarse grain heat affected zone of Ti microalloyed SQ700MCD high strength steel[J].Materials for Mechanical Engineering,2012,36(4):88.)
[7] 张楠,董现春,徐晓宁,等.Ti-Nb微合金化高强钢的焊接接头组织和性能[J].材料热处理学报,2014,35(6):115.(Zhang N,Dong X C,Xu X N,et al.Microstructure and property of welding joint with Ti-Nb microalloyed high-strength steel[J].Transactions of Materials and Heat Treatment,2014,35(6):115.)
[8] Buch A.Fatigue Strength Calculation [M].Switzerland:Trans Tech Publication,1988.
[9] Morrison M L,Buchanan R A,Liaw P K,et al.Four-point-bending-fatiguetreloy 105 bulk metallic glass[J].Materials Science and Engineering,2007,467A:190.
[10] 张楠,田志凌,张熹,等.Q690CFD高强钢焊接热影响区的断裂韧性[J].焊接学报,2018,39(1):26.(Zhang N,Tian Z L,Zhang X,et al.Fracture toughness of CGHAZ of Q690CFD high-strength steel[J].Transactions of the China Welding Institution,2018,39(1):26.)
[11] 张楠,田志凌,董现春,等.Q960E热影响粗晶区疲劳寿命与ΔKth值的关系分析[J].焊接学报,2018,39(7):106.(Zhang N,Tian Z L,Dong X C,et al.Research on relationship between ΔKth and fatigue life of heat-affected coarse grain zone in Q960E [J].Transactions of the China Welding Institution,2018,39(7):106.)
[12] Wang X M,He X L,Yang S W.Refining of intermediate transformation microstructure by relaxation processing[J].ISIJ International,2002, 42(12):1553.
[13] 雍岐龙.钢铁材料中的第二相[M].北京:冶金工业出版社,2006.(Yong Q L.The Second Phase of Steel and Iron Material[M].Beijing:Metallurgical Industry Press,2006.)
[14] 贺信莱,褚幼义,柯俊.硼钢淬透性与硼向奥氏体晶界的偏聚[J].金属学报,1983,19(6):459.(He X L,Chu Y Y,Ke J.The hardenability of boron steel and the segregation of boron[J].Acta Metallurgica Sinica,1983,19(6):459.)
[15] 贺信莱,褚幼义,柯俊.硼向奥氏体晶界的非平衡偏聚[J].金属学报,1982,18(1):1.(He X L,Chu Y Y,Ke J.The non-equilibrium segregation of boron to austenite grain boundaries[J].Acta Metallurgica Sinica,1982,18(1):1.)
[2] 陈鹰,张英建,董瀚,等.提高汽车安全性的先进高强钢高效成形技术[J].钢铁研究学报,2015,27(6):1.(Chen Y,Zhang Y J,Dong H,et al.Efficient forming technology of advanced high strength steel for car crashworthiness improvement[J].Journal of Iron and Steel Research,2015,27(6):1.)
[3] 赵少汴.抗疲劳设计手册[M].北京:机械工业出版社,2015.(Zhao S B.Anti-fatigue Design Manual [M].Beijing:Machinery Industry Press,2015)
[4] 李午申.我国合金结构钢的新发展及其焊接性[J].焊接学报,2001,22(5):83.(Li W S.The new development of alloy structure steels in China and their weldability[J].Transactions of the China Welding Institution,2011,22(5):83.)
[5] Mochizuki M,Shintomi T,Hashimoto Y,et al.Analytical study on deformation and strength in HAZ-softened weld joints of fine-grained steels[J].Welding in the World,48(9/10):2.
[6] 张楠,董现春,张熹,等.钛微合金化SQ700MCD高强钢粗晶热影响区软化的原因[J].机械工程材料,2012,36(4):88.(Zhang N,Dong X C,Zhang X,et al.Softening reasons for coarse grain heat affected zone of Ti microalloyed SQ700MCD high strength steel[J].Materials for Mechanical Engineering,2012,36(4):88.)
[7] 张楠,董现春,徐晓宁,等.Ti-Nb微合金化高强钢的焊接接头组织和性能[J].材料热处理学报,2014,35(6):115.(Zhang N,Dong X C,Xu X N,et al.Microstructure and property of welding joint with Ti-Nb microalloyed high-strength steel[J].Transactions of Materials and Heat Treatment,2014,35(6):115.)
[8] Buch A.Fatigue Strength Calculation [M].Switzerland:Trans Tech Publication,1988.
[9] Morrison M L,Buchanan R A,Liaw P K,et al.Four-point-bending-fatiguetreloy 105 bulk metallic glass[J].Materials Science and Engineering,2007,467A:190.
[10] 张楠,田志凌,张熹,等.Q690CFD高强钢焊接热影响区的断裂韧性[J].焊接学报,2018,39(1):26.(Zhang N,Tian Z L,Zhang X,et al.Fracture toughness of CGHAZ of Q690CFD high-strength steel[J].Transactions of the China Welding Institution,2018,39(1):26.)
[11] 张楠,田志凌,董现春,等.Q960E热影响粗晶区疲劳寿命与ΔKth值的关系分析[J].焊接学报,2018,39(7):106.(Zhang N,Tian Z L,Dong X C,et al.Research on relationship between ΔKth and fatigue life of heat-affected coarse grain zone in Q960E [J].Transactions of the China Welding Institution,2018,39(7):106.)
[12] Wang X M,He X L,Yang S W.Refining of intermediate transformation microstructure by relaxation processing[J].ISIJ International,2002, 42(12):1553.
[13] 雍岐龙.钢铁材料中的第二相[M].北京:冶金工业出版社,2006.(Yong Q L.The Second Phase of Steel and Iron Material[M].Beijing:Metallurgical Industry Press,2006.)
[14] 贺信莱,褚幼义,柯俊.硼钢淬透性与硼向奥氏体晶界的偏聚[J].金属学报,1983,19(6):459.(He X L,Chu Y Y,Ke J.The hardenability of boron steel and the segregation of boron[J].Acta Metallurgica Sinica,1983,19(6):459.)
[15] 贺信莱,褚幼义,柯俊.硼向奥氏体晶界的非平衡偏聚[J].金属学报,1982,18(1):1.(He X L,Chu Y Y,Ke J.The non-equilibrium segregation of boron to austenite grain boundaries[J].Acta Metallurgica Sinica,1982,18(1):1.)