Analysis and development of modern concepts on the rhomboidity formation nature for continuously cast billets. Part 2

Abstract

Concepts on the rhomboidity formation nature for continuously cast billets were developed and detailed within the framework of the approach proposed earlier. At the same time, the practical orientation of the research results was a priority goal. The adduced regularities and mechanisms of the rhomboidity initiation and growth processes are based on the provisions known from technical mechanics and strength of materials. Operation and maintenance experience for billet continuous casting machines was also taken into account. The achieved level of understanding of these regularities allowed to explain the increased addiction for medium carbon steel billets to rhomboidity. Moreover, the mechanism of occurrence for the extremely undesirable so-called "autocatalytic" character of the rhomboidity formation process was explained. Based on the research results, new solutions to reduce the billet rhomboidity were also proved and proposed. A noticeable improvement in the rhomboidity billet quality was achieved during the implementation of technical, technological and organizational measures, both known and new. The average annual sorting index on the rhomboidity for medium carbon steel billets 125x125 mm was reduced from 1.79 to 0.08 % for 5 years after the start of research and measures implementation. Those measures that, due to objective reasons, were not implemented, including for operational (during casting) reduction of rhomboidity, can be transferred to interested structures.