激光功率和离焦量对2000 MPa级热成形钢激光焊接接头组织与性能影响  

Effect of Laser Power and Defocusing Amount on Microstructure and Properties of Laser Welding Joints in 2000 MPa Grade Hot-formed Steel

作　　者：周婷婷 刘岩[2] 杜安娜 张文广 ZHOU Tingting;LIU Yan;DU Anna;ZHANG Wenguang(School of Mechanical Engineering,Shenyang University,Shenyang 110044,China;Liaoning Provincial Key Laboratory of Advanced Materials&Preparation Technology,Shenyang University,Shenyang 110044,China)

机构地区：[1]沈阳大学机械工程学院,沈阳110044 [2]沈阳大学辽宁省先进材料制备技术重点实验室,沈阳110044

出　　处：《精密成形工程》2024年第5期39-47,共9页Journal of Netshape Forming Engineering

基　　金：辽宁省自然科学基金(2023-MS-320)。

摘　　要：目的研究激光功率和离焦量对PHS2000型热成形钢激光焊接接头焊缝区及热影响区显微组织、拉伸特性和硬度分布的影响。方法采用光学显微镜(OM)、扫描电子显微镜(SEM)分析焊接接头的显微结构;利用拉伸实验和显微硬度实验探究焊接接头力学性能的变化规律。结果随着激光功率从3500 W增至4700 W,焊缝区与热影响区平均晶粒尺寸总体呈上升趋势,抗拉强度先上升后下降,焊缝区平均显微硬度值在635HV~651HV内浮动,热影响区平均显微硬度值在434HV~451HV内浮动;离焦量对焊缝区的组织分布有显著影响,不同离焦量下的组织分布均较为分散,热影响区的晶粒尺寸在离焦量为−3 mm时达到最大,为10.67μm。在不同激光功率和离焦量下,焊接接头的显微硬度值存在上下浮动,焊接接头各区的显微硬度分布规律基本一致,以焊缝为中心,两侧趋于对称分布。硬度分布规律如下:焊缝区硬度>母材区硬度>热影响区硬度。结论在本实验条件下,与离焦量相比,激光功率对焊接接头显微组织及拉伸强度的影响更大。在焊接速度为150 mm/min条件下,设置激光功率为4100 W、离焦量为−2 mm,此时抗拉强度最大,为1715 MPa,达到母材抗拉强度的85%。The work aims to study the effect of laser power and defocusing amount on the microstructure,tensile properties and hardness distribution of the weld zone and the heat-affected zone of laser welding joints of PHS2000 hot-formed steel.Optical microscope(OM),scanning electron microscope(SEM)were adopted to analyze the microstructure of the welded joints;Tensile experiments and microhardness experiments were conducted to explore the change rule in mechanical properties of welded joints.With the increase of laser power from 3500 W to 4700 W,the average grain size of the weld zone and the heat-affected zone showed a general upward trend,the tensile strength firstly increased and then decreased,the average micro-hardness value of the weld zone fluctuated up and down from 635HV to 651HV,and the average microhardness value of the heat-affected zone fluctuated up and down from 434HV to 451HV;The defocusing amount had a significant effect on the tissue distribution of the weld zone,the tissue distribution in different defocusing amount were more dispersed.The grain size in the heat-affected zone grain size grew sharply due to the martensite grain.It reached a maximum of 10.67μm in the defocusing amount of−3 mm.In different laser power and focusing amount,the microhardness value of welded joints fluctuated up and down.The distribution of microhardness of welded joints of all zones of the microhardness distribution was basically the same.In a pattern with the weld as the center,the two sides tended to symmetrical distribution.The rule of hardness distribution was weld zone>base material zone>heat affected zone.Under the experimental conditions,the laser power has a greater influence on the microstructure and tensile strength of the welded joints than the defocusing amount.Under the condition of maintaining welding speed of 150 mm/min,laser power of 4100 W and defocusing amount of−2 mm,the maximum tensile strength is 1715 MPa,which reaches 85%of the tensile strength of the base material.

关 键 词：热成形钢 激光焊接 激光功率 离焦量 显微组织 力学性能 

分 类 号：TG456.7[金属学及工艺—焊接]