轮辋用车轮钢380CL焊后扩口开裂原因分析

Cause Analysis on Flaring and Cracking of Wheel Steel 380CL for Rim after Weld

采用光学显微镜、显微硬度计等对闪光焊接的轮辋用车轮钢380CL开裂试样进行检测分析。结果表明,车轮钢380CL中C元素含量超内控上限,闪光焊接时焊缝区域为快速高温加热,焊后冷却速度快,焊缝区淬透性提高,出现粗大的贝氏体组织;基体和热影响区显微硬度(HV0.1)为303~310,而焊缝区的显微硬度(HV0.1)为346,比基体和热影响区的硬度高12%~14%,硬度差异较大,轮辋扩口变形时各组织变形协调能力差,导致在焊缝和粗晶热影响区的交界处开裂。通过严控车轮钢380CL的化学成分,同时降低焊接热输入量,可细化焊缝组织,降低焊缝和基体、热影响区的硬度差,保证焊缝具有良好的塑性,降低轮辋成形开裂率。

The cracking sample of flash welded wheel steel 380CL for rim is detected and analyzed with optical microscope and microhardness tester.The results showed that the content of C in wheel steel 380CL exceeded the upper limit of internal control,heat with high temperature in the weld region during flash welding was fast,cooling speed was fast after weld,hardenability of weld region was improved and coarse bainite structure appeared;the microhardness of matrix and heat affected zone(HV0.1)was 303~310,while that of weld region(HV0.1)was 346,which was 12%~14%higher than that of matrix and heat affected zone,so the hardness difference was greater and ability of deformation coordination of each structure was poor when the rim flared and deformed so that they were cracked at the junction of weld seam and coarse grain heat affected zone.The weld microstructure could be refined,hardness difference of weld,matrix and heat affected zone could be reduced by strictly controlling the chemical compositions of wheel steel 380CL and reducing welding heat input so that good plasticity of weld could be ensured and cracking rate of forming for rim could be reduced.