Method, Technology and Equipment for in Depth Surface Hardening

Abstract

The present work deals with a new method, technology and equipment developed for “in depth surface hardening” of large rotary details and tools, made of constructional, carbon, alloyed or low-alloyed tool steels. According to the technical requirements the details and tools have to possess hardened layer with specific shape, depth in the range 20-35mm and surface hardness of 35-62 HRC. The “in-depth hardening” was performed by quenching and self-tempering. Preliminary volume heating and depth regulated local surface adjustable gas-flame heating were used. The gasflame heating was realized by gas-flame burners (CH4+O2) located near the details’ periphery, depending on the shape and depth of the hardened layer. The burners’ power and heating time were adjustable. The cooling was performed by showers located near the details’ periphery also depending on the shape of the hardened layer. Water or polymer water solution was used as cooling media and its capacity was adjusted in the beginning. Due to the heat accumulated during the preliminary heating and the heating up to the quenching temperature of the surface layer, after stopping the cooling, subsequent self-tempering was applied. All of the equipment for realizing the whole hardening cycle, temperature and time control and parameters of heating and cooling was developed. Series of different details were hardened: traversing wheels and gears, forming rolls, rolling disks etc., made of construction and tool steels. The hardened layers obtained were with specific shape, surface hardness in the range of 35-60HRC and depth of the hardened layer of 15- 25mm.