Research on Welding Quality Optimization of Ultra-High Strength Steel Welding Joint Under Different Laser Energy Inputs

Abstract

Abstract Al-Si coating 22MnB5 steel was the ultra-high strength steel, which was widely used in the field of automobile manufacturing. As an advanced manufacturing process with high energy density laser beam as heating source, laser welding can greatly improve manufacturing accuracy and efficiency. For the laser welding process, laser energy inputs was a key factor affecting the shape and stability of the molten pool. In order to clarify the optimization mechanism of different laser energy input on the welding quality of ultra-high strength steel laser welding joints, the laser welding experiments of Al-Si coating 22MnB5 steel were carried out. The results showed that if the laser power density was constant (7 × 105W/cm2), when laser energy inputs was less than 461 J/cm, undercut appeared on the front of the weld, and the incomplete penetration phenomenon appeared on the back. The welded joint was Y-shaped welded joint. In particular, when laser energy inputs was less than 428 J/cm, Aluminum-rich intermetallic compounds (IMCs) appeared at the edge of the welded joint fusion zone (FZ). When laser energy inputs was greater than 858 J/cm, a small amount of visible pores were generated on the weld. The welded joint was X-shaped welded joint, the distribution of S ferrite and lath martensite was not uniform. When laser energy inputs was 522 J/cm-749 J/cm, the weld surface was smooth and no visible pores. The δ ferrite and lath martensite were uniformly distributed and the grain size was smaller. With the decrease of laser energy inputs, the parameters such as weld penetration, upper and lower surface weld width, upper surface depression and fusion zone area of welded joints were decreased.