Ensuring the Quality of Self-Tapping Screws by Replacing the Thermochemical Treatment Line

Abstract

The paper compares the technical characteristics of two thermochemical treatment (TCT) lines for self-tapping screws at OJSC MMK-Metiz. Quenching on TCT line 1 is carried out in the furnace by AUTOMATION SERVICE, while quenching on TCT line 2 is carried out in the furnace by KOHNLE. The authors described quenching and tempering schedules in these two furnaces, studied the microstructure of screws at all process stages, determined technical parameters and properties of finished products after thermochemical treatment. The research showed that the best performance had TCT 2 by KOHNLE. The metallographic analysis indicated more stable parameters of the layer thickness after nitrocarburizing, core and surface hardness, which was in full compliance with regulatory documents. By introducing a better structure of a new TCT line by KOHNLE, a TCT process period became shorter, and a range of self-tapping screws might be extended entailing a higher output of finished products.