Failure Reason and Protection Countermeasures on Liquid Metal Induced Embrittlement of 770 MPa Grade Quenched and Tempered Steel Casting

The causes of cracks in a large cross-section cast steel workpiece were analyzed using metallographic microscopy, electron scanning microscopy, and other methods. The results show that during the hot-dip galvanizing process of high-strength quenched and tempered cast steel, cracks perpendicular to the surface were generated in the matrix, with a crack length of about 3 mm, and the cracks cracked along the grain. The energy spectrum results indicated that the cracks contained a large amount of zinc, which was a typical liquid metal embrittlement phenomenon. In response to this situation, protective measures were proposed to avoid liquid metal embrittlement through hot-dip galvanizing process, welding process, forming process, coating system and other aspects.