DP500高强钢脉冲激光焊接接头的组织和性能

Research on microstructure and properties of DP500 high strength steel joints by pulsed laser welding

利用小功率Nd∶YAG固体脉冲激光器,对厚度为0.65 mm的DP500高强度双相钢进行激光焊接性试验,重点分析研究在其他脉冲激光工艺参数一定,只改变脉冲频率的不同脉冲激光功率条件下的焊接接头显微组织,并对其显微硬度分布、拉伸性能和杯突成型性能进行测定比较。试验结果表明,在较低的脉冲激光功率条件下形成的焊接接头热影响区较窄,焊缝区组织主要为板条马氏体和少量上贝氏体组织;而在较高脉冲激光功率条件下形成的焊接接头,热影响区较宽并且焊缝中出现较多的上贝氏体和少量侧板条铁素体组织。其次,随着脉冲激光功率的提高,在焊接接头的热影响区出现软化区,而且其拉伸性能和杯突成型性能相比母材有所下降。当脉冲激光功率为160 W时,焊接接头纵向拉伸的抗拉强度有所下降,经杯突试验后裂纹在焊接接头平行于焊缝的中心处产生,杯突值大大降低。

wehtahility of 0.65 mm DPS00 steel is tested systematically by the SWS00 Nd：YAG low -power pulsed laser. The microstructure characteristic of Welded joints are analysed under different laser power through only changing the pulse frequency. Moreover, the microhardness, tensile properties and cup torming properties of joints are also tested,compared and analyzed. The result shows that heat affected zome is relatively narrower in the lower laser power, and the microstructure are mainly composed of martensite and the fewer upper bainite in weld. While in the higher laser power, heat ＇affected zone is not only relatively wider,but also the more upper bain- ire and fewer intergranular fen＇ire appear in the weld. With the growth of the laser power,softened zone not only appears in heat affected zone of the weht, and its tensile properties and cup forming properties are lower than those of the parent metal. When the pulse laser power is 160 W,tensile strength of longitudinal tensile test in welded joints are decreased lightly,and the welding joint in parallelling to the center of the weld appears fracture by means of the cup drawing test, the value is reduced greatly.