CO_2激光焊接600MPa DP钢接头组织与性能

采用CO2激光对抗拉强度为600MPa,厚度1.4mm的DP钢进行焊接.研究焊接速度对焊缝外观和截面成形的影响、接头的组织特点、硬度、强度和成形能力.结果表明,激光功率相同,焊接速度较低时焊缝易产生气孔,焊接速度较高时易发生飞溅;焊接速度对焊缝熔深及熔宽也有影响.焊缝区组织主要由马氏体构成,从焊缝、焊接热影响区到母材,组织中马氏体含量下降,接头的最高硬度出现在焊缝或热影响区.在平行于焊缝方向,焊接接头的抗拉强度高于母材,垂直于焊缝方向,接头的抗拉强度与母材相当.由于焊缝出现马氏体组织,接头的塑性和韧性降低,板材的冲压成形能力下降.

Microstructures and properties of CO2 laser welded 600 MPa DP steel

CO₂ laser welding of cold rolled DP steel sheet with tensile strength of 600 MPa and thickness of 1.4 mm was carried out.The effects of welding speed on bead morphologies and cross-section shape were investigated.The microstructures of welded joint were observed.The hardness distribution,tensile strength and formability of the welded joint were tested.The study showed that for the same laser power porosities occurred on weld bead at low welding speed and spatters occurred at high welding speed.In addition,welding speed also had influence on penetration and bead width.The weld metal was mainly composed of martensite due to high cooling rate of laser welding.The amount of martensite decreased rapidly approaching base metal from weld bead center.Therefore,the weld metal or heat affected zone had maximum hardness for the whole welded joint.The tensile strength of welded joint perpendicular to the weld line was equal to that of the base metal.But the tensile strength of welded joint parallel with the weld line was higher than that of the base metal.The plasticity and formability of the welded joint were impaired because of the formation of martensite in the weld metal.