Efremenko V. The development of theoretical and technological bases of production and hardening of steel grinding balls for the reason of increasing of their quality and operational durability.

The thesis is dedicated todevelopment and implementation of efficient suggestions for improvement of technologies of production and thermohardening of steel grinding balls for the reason of provision necessary structural condition and properties of the metal that will allow to obtain essential increasing of grinding balls’ quality and their working longevity. The reasons of output balls and their dominant wear mechanisms are analyzed, the influence of the structural factor on criteria of working longevity ball is explored, the principles of the choice of material for balls are offered, the optimum type and structure of the alloy for different conditions of the balls usages are determined. The mechanisms of the shaping of cavities inside the balls during their rolling are found, the recommendations for improvements macrostructural conditions of rolled grinding balls are given. With creation of mathematical models the distribution of temperature and stresses on section of ball during hardening is analytically explored, the method of the accounting determination of the depth hardening of steel ball is designed. With use of computer modeling new marks of steels with raised level of wear resistance and hardenability for balls production are designed, the technology of thermohardening of grinding balls is optimized for the reason of provision necessary hardness without hardening cracking. The main thesis’s results are implemented at “Azovstal” Steel works and at Kherson cardan shaft plant with general economic profit of 1,757 mln. grn.