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针对先进高强双相钢的激光焊接问题,通过拉伸试验、显微硬度测试、扫描电镜(SEM)和光学显微镜(OM)等手段分析研究1.5mm厚DP1000钢板对接接头的性能和组织,讨论了接头强度和塑性降低的主要原因。研究发现激光焊接DP1000双相钢的焊接接头热影响区(HAZ)存在严重的软化现象,软化区集中在其回火区和不完全结晶区,该软化区造成焊接接头的抗拉强度下降了10%~15%,塑性下降了60%以上。强度下降的主要原因是回火区域出现了回火马氏体,其强度低于淬火马氏体;塑性下降的主要原因是焊接热影响区的软化使得焊接接头的不同区域在拉伸过程中出现不协调的变形,变形主要集中在热影响区的软化区,而焊缝金属区、母材区及焊接热影响区的硬化区几乎没有变形。
In order to solve the problem of laser welding of advanced high strength duplex steel, the properties and microstructure of 1.5mm thick DP1000 steel butt joint were analyzed by means of tensile test, microhardness test, scanning electron microscope (SEM) and optical microscope (OM) The main reason for the reduced strength and ductility of the joint. It is found that there is a serious softening phenomenon in the heat-affected zone (HAZ) of laser welding DP1000 dual-phase steel, the softening zone is concentrated in its tempering zone and incomplete crystallization zone, and the softening zone reduces the tensile strength of the welded joint by 10 % ~ 15%, plasticity dropped by more than 60%. The main reason for the decrease in strength is the appearance of tempering martensite in the tempering region and its strength is lower than that of quenched martensite. The main reason for the plasticity decline is that the softening of the heat affected zone causes the emergence of different regions of the welded joint during the drawing process Uncoordinated deformation and deformation are mainly concentrated in the heat affected zone softening zone, while the weld metal zone, base metal zone and HAZ of hardened zone almost no deformation.