Developing a technological complex for restoring the properties of rolled rolls reduced in the process of grinding

Abstract

Problem. The problem of increasing the resource of equipment for rolling production is on time. Rolling mills are a piece of equipment for rolling objects made of metals and alloys. They work in difficult operating conditions: at considerable loading, friction and the raised temperatures. As a result, there is a rapid wear of their work surfaces, which leads to defects. Due to the predominantly high cost of rolled rolls, it is better to restore them than to replace with new ones. This is more profitable economically and can be realized by using different methods of influencing the structural condition of the products’ surface. The use of, for example, TFH technology [1,2] or other methods of surface strengthening is possible to solve such problems. Goal. The purpose of the work is to develop a technological complex to restore the properties of rolled rolls, which were reduced in the process of grinding. The subject of the research are the samples in the form of rolled rolls, which are made of 40X steel. To achieve this goal, heat treatment of natural samples was carried out in different modes. Metallographic analysis and measurement of hardness of natural samples after their heat treatment in different modes was made. The optimal mode was selected, which provided the necessary properties. Heat treatment of rolled rolls in need of restoration was carried out according to this mode. Methodology. Two heat treatment modes were used to restore the required hardness of the rolling rolls hardening with heating to 860ºC and cooling in water; hardening with heating to 860ºC and cooling in 10% aqueous NaCl salt solution. Results. The cooling properties of the saline solution are higher than those of water. This ensured greater completeness of the martensitic transformation and the formation of a fine-needle martensitic structure with a small amount of Cr carbides. Therefore, a technological complex for restoring the properties of rolled rolls, which were reduced during grinding, was proposed. It consists of quenching from a temperature of 860°C with cooling in 10% aqueous solution of NaCl salt. After hardening it is necessary to carry out low-temperature release at a temperature of 180ºC for 2 hours with accelerated cooling.