铸造模具钢的焊后热处理及组织与性能研究

Study on Post Weld Heat Treatment and Microstructure & Properties of Cast Die Steel

研究了焊接电流对淬回火态铸造模具钢焊接接头成形和力学性能的影响,并对比分析了焊态和回火态焊接接头的显微组织和力学性能。结果表明,焊接电流为90～110 A时,焊接过程中不会出现断弧或者飞溅现象,焊缝中也未见明显夹渣等缺陷存在,焊缝成形性较好;500℃/2 h回火处理对焊接接头焊缝区和淬火区组织有明显改善,而对母材和回火区组织影响较小,回火态焊接接头淬火区组织为回火马氏体,焊缝区为回火马氏体+铁素体+少量残余奥氏体;焊后进行回火处理可以明显提高焊接接头的抗拉强度,但是断裂位置并不会发生改变;焊接电流为90～110 A时,焊态和回火态焊接接头的抗拉强度都要高于焊接电流为110～140 A时的焊接接头,且其回火态焊接接头的抗拉强度达到铸造模具钢母材的81.4%。

The effect of welding current on the forming and mechanical properties of quenched and tempered cast die steel welded joint was studied, microstructure and mechanical properties of welded joint of welded and tempered state were compared analyzed. The results show that when the welding current is 90~110 A, there will be no interruption or splash in the welding process, and no obvious slag inclusion in the weld, and the weld joint has good welds formability. The tempering treatment at 500 ℃ for 2 h has a significant improvement on the microstructure of the welding zone and quenching zone, but little influence on the structure of the base material and the tempering zone. The quenching zone of tempered welded joint is tempered martensite, the welding zone is tempered martensite, ferrite and a small amount of retained austenite, and the tensile strength of the welded joint can be improved obviously after welding, but the fracture position will not change;When the welding current is 90~110 A, the tensile strength of welded joint and tempered welded joint is higher than that of welding current of 110~140 A. When the welding current is 90~110 A, the tensile strength of the tempered welded joint can reach 81.4% of the cast die steel.