The segregation control of coating element for pulse fiber laser welding of Al-Si coated 22MnB5 steel

摘要

In this study, pulsed wave (PW) fiber laser welding of 1.4-mm-thick Al-Si coated 22MnB5 steel sheets was adopted to investigate the effect of pulse modulation on reducing the segregation of coating element in fusion zone (FZ) and improving mechanical properties of welded joints. It was found that the segregation of Al element in FZ was reduced greatly due to the introduction of pulse oscillation, which weakened the formation of delta-ferrite in FZ. The experiment results indicated that nearly full martensite microstructure of FZ was obtained at appropriate pulse parameters. The average microhardness of FZ in hot-stamped condition could reach to 523 HV under the condition of optimized pulse parameters, which was comparable to the BM. Meanwhile, the tensile strength and total elongation increased up to 1600 MPa and 3.7 %, respectively. In addition, lots of small dimples on the fracture surface also suggested ductile tendency. However, the failure still occurred in FZ and the crack initiated from the soft fine alpha-ferrite phase near fusion line, which could be improved in further study.