Laser-arc hybrid welding process and joint microstructure evolution of 1 300 MPa high strength steel

Objective In order to help the further popularization and application of laser-arc hybrid welding technology of high strength steel in various fields and guide production practice. Methods Aimed at the 9 mm thick yield strength of 1300 MPa grade LG1300QT high strength steel, the study on laser-arc hybrid welding technology, the development of welding phase transformation model and the simulation of the joint microstructure evolution are carried out. Results The laser-arc hybrid welding of 9 mm thick 1 300 MPa grade high strength steel can be completed by using suitable process parameters, the weld formation is uniform, RT detection meets the working requirements, and the tensile strength of the joint can reach more than 85% of the base metal.The simulation results show that the distribution of composite welding temperature field is consistent with the weld section, and the content of martensite in coarse-grained and fine-grained regions of the joint is more than 99%, which is basically consistent with the actual results of 100% martensite. The results show that the microstructure transformation in the heat affected zone of LG1300QT steel laser-hybrid welding joint is mainly martensitic transformation. The microstructure evolution of ICHAZ in arc region is quite different from that of ICHAZ in transition region and ICHAZ in laser region, the martensite transformation degree of ICHAZ in transition region and ICHAZ in laser region is higher, the ICHAZ Austenite in arc region is not sufficient and the martensite transformation is low. Conclusion For 1 300 MPa high strength steel with yield strength, laser-arc hybrid welding can be formed by single pass welding without groove, the weld formation is beautiful and joint strength is high. The developed “thermal-metallurgical” coupling model can accurately reflect the characteristics of temperature field and microstructure field in the welding process, and can reflect the microstructure evolution law of 1 300 MPa high strength steel with laser-arc hybrid welding, which has guiding significance for practical engineering application