低碳视野下无镀层热成形钢的激光拼焊研究  

Research on Laser Welding of Coating-free Thermoformed Steel with Low Carbon Vision

作　　者：王舟 李昭 庞佳琛 陈震 王建锋 Wang Zhou;Li Zhao;Pang Jiachen;Chen Zhen;Wang Jianfeng(General Motors China Science Lab,Shanghai 201206)

机构地区：[1]通用汽车中国科学研究院,上海201206

出　　处：《汽车工艺与材料》2024年第6期36-43,共8页Automobile Technology & Material

摘　　要：研究了低碳足迹的无镀层热成形钢激光拼焊及其与铝硅镀层热成形钢之间的激光拼焊,结果表明:无镀层热成形钢可在没有预剥离或填丝的条件下与自身或铝硅镀层热成形钢焊接获得高质量的激光拼焊焊缝,在单向拉伸试验中,拉伸断裂均发生在远离焊缝位置;在缺口冲击试验中,无镀层钢与铝硅镀层钢之间的焊缝冲击功维持在基材冲击功的86%。无镀层钢与铝硅镀层钢之间焊缝的微观组织主要为马氏体和少量因铝硅熔入焊缝形成的铁素体。焊缝硬度与铝硅镀层钢基材相当,未发现软区。最后,结合热力学及相转变动力学计算,分析了无镀层钢与铝硅镀层钢之间获得高质量激光拼焊焊缝的机理:无镀层热成形钢稀释了熔入焊缝中铝硅的浓度,避免因高温形成大量富铝硅的脆性铁素体;无镀层钢中添加的合金元素Cr可以提高焊缝的淬透性,在热冲压冷却过程中获得全马氏体微观组织,保证焊缝强度。This article studied laser welding of the coating-free press hardened steels(CFPHS)with low carbon footprint and laser welding of aluminum-silicon coating press hardened steels(CFPHS).The study shows that both CFPHS-to-CFPHS and CFPHS-to-AlSi-coated PHS do not require filler wire and laser ablation.Both weldments demonstrate good tensile ductility,with fracture occurring away from the weld seam.Besides,CFPHS-to-AlSi-coated PHS shows high Charpy V-notch impact toughness of 86%of bulk metal.Furthermore,microstructure analysis was conducted on CFPHS-to-AlSi-coated PHS:Microstructure of weld zone is mainly martensite with very small amount of ferrite,consistent with the hardness being as high as bulk metal.Finally,thermodynamics and phase transformation kinetics were used to study the weld seam between CFPHS and AlSi-coated PHS:(1)CFPHS reduces the Al and Si content from coating contamination during weld fusion,avoiding or reducing the formation of brittle AlSi-rich ferrite at high temperatures;(2)Cr alloying improves the hardenability of the weld seam,thus full martensitic microstructure can be obtained during die quenching of hot forming,which guarantees the high hardness of the weld seam.

关 键 词：热成形钢 汽车用高强钢 激光拼焊 微观组织 

分 类 号：U466[机械工程—车辆工程]