热处理温度对热轧态汽车用热成形钢激光焊接接头组织和性能的影响

Effects of Heat Treatment Temperature on Microstructure and Properties of Laser Welding Joints of Hot Forming Steel for Automobile in Hot Rolling State

以2 mm厚、热轧态的1500 MPa热成形钢激光焊接接头为研究对象,采用箱式电阻炉对焊接接头进行了不同温度的焊后热处理,采用杯突试验机、金相显微镜、显微硬度计等设备对接头性能和组织进行了检验。结果表明,激光焊接头在焊态下杯突值较低,成形性能较差,焊缝及热影响区明显淬硬,组织为马氏体;随着热处理温度的提高,接头成形性能逐渐改善,焊缝和热影响区的硬度值降低;当温度提高到650、800℃时,焊缝及热影响区显微组织分别为回火索氏体、贝氏体+珠光体,接头的成形性能大幅提高。

Taking the laser welding joint of 1500 MPa hot forming steel in hot rolling state with thickness of 2 mm as the object, the post weld heat treatment experiments of the welded joint with different temperatures were carried out by using box-type resistance furnace. The performance and microstructure of the joints were tested by means of Erichsen tester, metallographic microscope and micro-hardness tester. The results show that the Erichsen value of laser welding joint in welded state is relatively low, and the forming performance is poor. The weld and heat affected zones are obviously quenched, and the microstructure is martensite. With the increase of heat treatment temperature, the forming performance gradually improves, the hardness of the weld and heat affected zone decreases. When the temperature reaches 650, 800 ℃ respectively, the microstructure transforms into tempered sorbite, bainite ＋ pearlite respectively and the forming performance of the welded joint obviously improves.