Specific Features of the Formation of Structures in 60Kh2N4GМF Precipitation-Hardening Steel

Abstract

It is shown that the precipitation of large amounts (6.45-9.55%) of dispersed carbides (mainly of the cementite type) and Me 7C3 and (V, Mo)C special carbides in the process of annealing of 60Kh2N4GМF steel within the range 350-800°С promotes an 18% increase in the hardness and a 1.5- 1.61-fold increase in the wear resistance. The maximum hardening is attained in the case of low- temperature annealing at 450°С. We establish the dependence of the coercive force on hardness capable of guaranteeing the possibility to perform quality control under the conditions of manufacturing and de- termine the most efficient technological parameters of annealing without destroying the product. The improvement of the operating characteristics of rolls proves to be one of the most important problems of materials science. Its urgency became especially pronounced during the last years of the world crisis due to the increase in the requirements imposed on the quality and accuracy of rolled sheet products and the reduction of their cost. As one of the directions used for the solution of this problem, we can mention the development and application of new materials for the production of rolls. First of all, this is true for precipitation-hardening steels whose structure and properties meet the Charpy principle (1). These steels are characterized by a rela- tively low hardness in the cast state, which reduces the cost of the main mechanical treatment, and a fairly high hardness attained after low-temperature heat treatment (2). The Charpy principle is used for the development of precipitation-hardening steels and the technology of their production with an aim of manufacturing of various products, including rolls. (3). However, the available information on the application of these steels in Japan, France, and Germany contains numerous manufacturing secrets, which restricts their use in the production of massive castings. The aim of the present work is to study the distinctive features of the formation of structure, variations of the phase composition, and the amount of carbide phase in 60Kh2N4GМF steel in the process of annealing within the temperature range 350-800°С.