高强度钢QP980激光焊接头的微观组织与力学性能

Microstructure and Mechanical Properties of Laser Welded Joint of High Strength Steel QP980

为解决高强度钢QP980在汽车轻量化应用方面存在的成分偏析、淬硬脆化和氢致开裂等焊接问题,开展了QP980钢激光焊接研究,对1.2 mm厚QP980钢进行焊接试验,并利用激光共聚焦显微镜、扫描电子显微镜、万能试验机和显微硬度计等手段,研究工艺参数对QP980钢激光焊接头微观组织和力学性能的影响。在所选焊接工艺参数下均获得了全焊透及表面成形良好的接头;QP980钢激光焊接头的横截面宏观形貌呈现“沙漏型”,接头可分为焊缝区、粗晶区、细晶区、临界热影响区、亚临界热影响区和母材区;不同工艺参数下接头的焊缝及部分热影响区的硬度均高于母材,且硬度最高值出现在细晶区,在焊缝的两端都存在一个软化区,随着热输入的增加,焊缝及热影响区的宽度变大,软化区也更加远离焊缝中心;不同工艺参数下接头的抗拉强度都能达到母材的强度,屈服强度均高于母材,而接头的伸长率都低于母材,说明在所选焊接工艺参数下,均获得了性能良好的焊接接头。

In order to solve the welding problems such as component segregation,hardening embrittlement and hydrogen-induced cracking of high strength steel QP980 in automobile lightweight application,the laser welding of QP980 steel was studied,and the welding test of 1.2mm thick QP980 steel was carried out.The microstructure and mechanical properties of the welds were evaluated.It was found that the joints with full penetration and well-formed surface could be obtained under the selected welding parameters.The cross section of the laser welding joints shows hourglass shape,and the joints can be divided into the fusion zone(FZ),the coarse-grained heat affected zone(CGHAZ),the fine-grained heat affected zone(FGHAZ),the intercritical heat affected zone(ICHAZ),the subcritical heat affected zone(SCHAZ)and the BM.The hardness of the FZ and some HAZ of the joints under different welding process parameters are higher than the BM.The highest hardness is in the FGHAZ and there is a softening zone at both sides of the weld.With the increase of heat input,the width of the FZ and the HAZ becomes larger,and the softening zone is further away from the weld center.Under different welding process parameters,the tensile strength of the joints can reach the strength of the BM,the yield strength is higher than the BM,and the elongation of the joints is lower than the BM,it indicated that the joints with good performance have been obtained under the selected welding process parameters.