QP1180高强钢薄板激光焊接接头的组织与成形性能
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摘要
在不同焊接参数下对QP1180高强钢薄板进行激光焊接试验,对接头的显微组织、显微硬度、拉伸性能及杯突成形性能进行了分析。研究结果表明:在热影响区的回火区(软化区)形成了回火马氏体组织,导致该区存在明显的软化;提高焊接速度和降低热输入可显著降低软化程度;软化区受到两侧强体的约束而得以强化,导致拉伸后最终断裂在母材处,强度与母材相当;提高焊接速度和增加焊缝偏移可显著提高杯突值,高焊接速度下的焊板垂直于焊缝开裂,具有高杯突值,低焊接速度下的焊板沿软化区平行于焊缝开裂,具有低的杯突值;随着焊缝偏移的增大,杯突值增大,偏移至30 mm时,杯突值达到母材水平。
Laser welding experiments for QP1180 high-strength steel sheet are carried out at different welding parameters, and the microstructure, microhardness, tensile properties and bulge properties of the welding joint are investigated. The results show that tempered martensite is formed in tempered zone(soft zone) of heat affected zone, leading to the softening in this zone. Increasing welding speed and reducing heat input can significantly reduce softening degree. The soft zone is strengthened by the constraints, leading to the fracture in base metal, and the strength of the soft zone is equivalent to that of the base metal. Increasing welding speed and weld line offset can obviously improve the bulge test value of the welding sheet. The welding sheet obtained at high welding speed fractures perpendicular to the weld and has high bulge test value, and the welding sheet obtained at low welding speed fractures parallel to the weld along the soft zone and has low bulge test value. Bulge test value improves gradually as the weld line offset increases and approaches to that of the base metal when the offset reaches to 30 mm.
Laser welding experiments for QP1180 high-strength steel sheet are carried out at different welding parameters, and the microstructure, microhardness, tensile properties and bulge properties of the welding joint are investigated. The results show that tempered martensite is formed in tempered zone(soft zone) of heat affected zone, leading to the softening in this zone. Increasing welding speed and reducing heat input can significantly reduce softening degree. The soft zone is strengthened by the constraints, leading to the fracture in base metal, and the strength of the soft zone is equivalent to that of the base metal. Increasing welding speed and weld line offset can obviously improve the bulge test value of the welding sheet. The welding sheet obtained at high welding speed fractures perpendicular to the weld and has high bulge test value, and the welding sheet obtained at low welding speed fractures parallel to the weld along the soft zone and has low bulge test value. Bulge test value improves gradually as the weld line offset increases and approaches to that of the base metal when the offset reaches to 30 mm.
引文
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[15] Guo W, Li L, Dong S Y, et al. Comparison of microstructure and mechanical properties of ultra-narrow gap laser and gas-metal-arc welded S960 high strength steel[J]. Optics and Lasers in Engineering, 2017, 91: 1-15.
[2] Kang Y L, Zhu G M. Development trend of China′s automobile industry and the opportunities and challenges of steels for automobiles[J]. Iron & Steel, 2014, 49(12): 1-7. 康永林, 朱国明. 中国汽车发展趋势及汽车用钢面临的机遇与挑战[J]. 钢铁, 2014, 49(12): 1-7.
[3] Speer J G, Edmonds D V, Rizzo F C, et al. Partitioning of carbon from supersaturated plates of ferrite, with application to steel processing and fundamentals of the bainite transformation[J]. Current Opinion in Solid State and Materials Science, 2004, 8(3/4): 219-237.
[4] Kim C H, Choi J K, Kang, M J, et al. A study on the CO2 laser welding characteristics of high strength steel up to 1500 MPa for automotive application[J]. Journal of Achievements in Materials & Manufacturing Engineering, 2010, 39(1): 6-11.
[5] Wang J F, Yang L J, Sun M S, et al. Effect of energy input on the microstructure and properties of butt joints in DP1000 steel laser welding[J]. Materials & Design, 2016, 90: 642-649.
[6] Wang J F, Wang L J, Yang L J, et al. Research on microstructure and properties of laser welding DP1000 high-strength steel weld joints[J]. Chinese Journal of Lasers, 2014, 41(9): 0903003. 王金凤, 王立君, 杨立军, 等. DP1000高强钢激光焊接接头组织性能研究[J]. 中国激光, 2014, 41(9): 0903003.
[7] Xia M, Sreenivasan N, Lawson S, et al. A comparative study of formability of diode laser welds in DP980 and HSLA steels[J]. Journal of Engineering Materials and Technology, 2007, 129(3): 446-452.
[8] Panda S K, Kuntz M L, Zhou Y. Finite element analysis of effects of soft zones on formability of laser welded advanced high strength steels[J]. Science and Technology of Welding and Joining, 2009, 14(1): 52-61.
[9] Li J, Nayak S S, Biro E, et al. Effects of weld line position and geometry on the formability of laser welded high strength low alloy and dual-phase steel blanks[J]. Materials & Design, 2013, 52(24): 757-766.
[10] Guo W, Wan Z D, Peng P, et al. Microstructure and mechanical properties of fiber laser welded QP980 steel[J]. Journal of Materials Processing Technology, 2018, 256: 229-238.
[11] Li W D, Ma L X, Peng P, et al. Microstructural evolution and deformation behavior of fiber laser welded QP980 steel joint[J]. Materials Science and Engineering A, 2018, 717: 124-133.
[12] Li M, Zhang W, Hua X M, et al. Investigation of plasma and metal transfer dynamic behavior during fiber laser GMAW-P hybrid welding[J]. Chinese Journal of Lasers, 2017, 44(4): 0402008. 李敏, 张旺, 华学明, 等. 光纤激光与GMAW-P复合焊接等离子体及熔滴过渡动态特征研究[J]. 中国激光, 2017, 44(4): 0402008.
[13] Shi P F, Huang J, Tantai F L, et al. Microstructures and properties of 27SiMn high-strength steel joints by laser-MAG hybrid welding[J]. Chinese Journal of Lasers, 2017, 44(10): 1002001. 史鹏飞, 黄坚, 澹台凡亮, 等. 27SiMn高强钢激光-MAG复合焊接头组织和性能[J]. 中国激光, 2017, 44(10): 1002001.
[14] Liu Huijie. Welding metallurgy and weldability[M]. Beijing: China Machine Press, 2007. 刘会杰. 焊接冶金与焊接性[M]. 北京: 机械工业出版社, 2007.
[15] Guo W, Li L, Dong S Y, et al. Comparison of microstructure and mechanical properties of ultra-narrow gap laser and gas-metal-arc welded S960 high strength steel[J]. Optics and Lasers in Engineering, 2017, 91: 1-15.