Comprehensive experimental design for studying the effects of heat treatment and surface treatment on the properties of high-strength bolt steel

Aiming at the problems of low surface hardness, poor coating adhesion and easy falling off of high strength bolts in engineering applications, a comprehensive experiment was designed to study the effects of heat treatment and surface treatment on the properties of steel used for high strength bolts. The 35CrMo steel quenched at 870 ℃×25 min and then tempered at 500 ℃×1 h+550 ℃×1 h met the standards for preparing high-strength bolts of grade 12.9 and 10.9, respectively. After N infiltration treatment, the surface hardness reached 850 HV, significantly improving compared to the center. Coating the surface of 35CrMo steel with zinc aluminum solution after N infiltration significantly improves its corrosion resistance. This experiment involves material heat treatment experimental technology and material surface treatment experimental technology, as well as commonly used analytical methods for testing the microstructure and properties of metal materials. It is a typical case of research assisted teaching.