车用TRIP590钢光纤激光焊接接头组织与性能研究

Microstructure and Properties of Fiber Laser Welded Joints of TRIP590 Steel Used for Automobile

为了促进先进高强钢激光焊接技术的发展,采用光纤激光器对1.5mm厚的TRIP590钢板进行焊接,对焊接接头的微观组织、硬度以及拉伸性能进行了研究,分析了焊接速度对组织、性能的影响。结果表明：焊缝组织主要为板条状马氏体,热影响区可分为完全淬火区和不完全淬火区。焊接接头硬度分布不均匀,在热影响区或焊缝处硬度最高。随着焊接速度提高,热影响区马氏体含量增多,贝氏体含量减少,热影响区和焊缝组织变得细小。焊接速度为3～5m/min时,拉伸试样均断裂在母材,断后延伸率均超过30%,随着焊接速度提高,断后延伸率也有所提高,强塑积（PSE）均在20000MPa%以上,拉伸变形过程中相变诱发效应显著,大部分残余奥氏体转变为马氏体,在提高材料塑性的同时也提高了强度,实现了高强度和高塑性的统一。

To accelerate the development of the laser welding technology of advanced high strength steel,TRIP590 steel with a thick of 1.5 mm was welded by using a fiber laser.The microstructure,hardness and tensile properties of the welded joints were studied.The influence of welding speed on the microstructure and properties were analyzed.The results showed that the microstructure of the welding zone mainly contained lathy martensite.Heat affected zone（HAZ）could be divided into two parts：incomplete quenched zone and quenched zone.The hardness distribution of weld joints was nonuniform,and the HAZ or welding zone had the highest hardness.With the increase of welding speed,martensite content increased and bainite content reduced in the HAZ,the microstructure of HAZ and welding zone became finer.The samples for tensile test which were welded at the speed from 3to 5m/min all fractured in base metal.The elongation was more than 30%,and the elongation rose with the increase of the welding speed.The product of strength and elongation（PSE）was more than 20000 MPa%.The induced effect of phase transformation was notable,resulting in the transformation of most of the residual austenite into martensite.The plasticity and strength of TRIP590 increased at the same time,which achieved a unity of high strength and high plasticity.