摘要
为了降低热成形钢连接位置的硬度,提高塑性,采用高斯激光光束快速扫描试样表面,利用高温回火原理使材料的强度、硬度降低,成功实现了局部区域的材料软化。结果表明,软区组织为回火索氏体,扫描速率越慢,软区硬度越低;温度为800℃、扫描线速率为2 mm/s时,软区硬度为230 HV,是母材硬度的47.92%,软区抗拉强度降低767 MPa,是母材的50.53%,其断后伸长率17.36%,是母材的188.08%;软化拉伸试样为韧性断裂,杯锥状断面;软化后点焊不会改变焊核的硬度,可以加宽热影响区,避免其硬度骤降骤升的情况,改善热影响区应力集中的情况,防止焊点出现界面断裂,软化后能提高焊点断裂最大位移60%,最大能量吸收功提升了10.14%。本研究证明了激光软化热成形钢具有可行性,对热冲压汽车零件局部软化有一定指导意义。
In order to reduce the hardness and improve the plasticity of the connection position of Hot formed steel,the Gaussian laser beam was used to quickly scan the surface of the sample,and the high-temperature tempering principle was used to reduce the strength and hardness of the material,thus successfully softening the material in local areas.The results show that the softening zone structure is tempered sorbite,and the slower the scanning speed,the better the softening effect.At temperature of 800℃and scanning line speed of 2 mm/s,the softening zone hardness is 230 HV,which is 47.92%of the base metal hardness.The tensile strength of the softening zone decreases by 767 MPa,which is 50.53%of the base metal.Its elongation after fracture is 17.36%,which is 188.08%of the base metal.The softened tensile specimen exhibits ductile fracture with a cup-shaped cross-section.After softening,spot welding will not change the hardness of the weld nugget.It can widen the heat-affected zone,avoid the sudden drop and rise of its hardness,improve the stress concentration in the heat-affected zone,prevent the interface fracture of the welding spot,and increase the maximum displacement of the weld spot fracture by 60%after softening.Maximum energy absorption work increased by 10.14%.This study demonstrates the feasibility of laser softening hot-formed steel and has a certain guiding significance for the local softening of hot-stamped automotive parts.
作者
刘晓龙
彭玉青
罗模芳
梁肖
王子健
LIU Xiaolong;PENG Yuqing;LUO Mofang;LIANG Xiao;WANG Zijian(Jiangxi Hot Stamping Automotive Component Co.,Ltd.,Jiujiang 332400,China;School of Iron and Steel,Sochoow University Suzhou 215031,China)
出处
《激光技术》
CAS
CSCD
北大核心
2024年第3期449-454,共6页
Laser Technology
关键词
激光技术
激光软化
力学性能
热成形钢
焊点
laser technique
laser softening
mechanical properties
hot formed steel
welding spot
