The optimum study on mechanical properties of self-drilling tapping screws with carbonitriding operation

Abstract

Self-drilling tapping screws are widely used for construction works. In order to increase the strength and improve the wear resistance without affecting the soft, tough interior of the screws in self-drilling operation, a case-hardening treatment is an essential process. Carbonitriding primarily provides a needed hard, wear-resistant case of screws. In order to improve the qualities of AISI 1016 self-drilling tapping screws, a series of carbonitriding experiment is conducted in a continuous furnace. Various parameters affect the quality of carbonitriding such as quenching temperature, carbonitriding time, atmosphere composition and tempering temperature. The effects of carbonitriding parameters affected the quality characteristics, such as case hardness and core hardness of self-drilling tapping screws are analyzed by Taguchi method. It is experimentally revealed that the carbonitriding time and tempering temperature are the significant factors for both case hardness and core hardness. The optimum mean case hardness is 625.5HV, and the optimum mean core hardness is 368.7HV. With the optimum conditions, the carbonitriding treatment is capable of producing good self-drilling tapping screws. The results presented in this paper could be used as a reference for fastener manufacturers.