1. School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China 2. Panzhihua Iron and Steel Research Institute, Panzhihua 617000, Sichuan, China
Abstract:Effects of N content in steel on precipitation of TiN inclusions during the production of 72A tire cord steel was investigated in Panzhihua New Steel Vanadium Co. Ltd. It is found that number of TiN precipitated in steel increases along with the increase of N content in steel, and TiN size becomes bigger. The results of thermodynamics study show that TiN inclusions can only form in solid phase area in tire cord steel without considering elements segregation. However, TiN inclusions can precipitate in solid-liquid two-phase area during solidification process with regarding effects of element segregation on element enrichment in solidification front. In order to restrain precipitation of TiN during production process of tire cord steel, controlling N content as well as N segregation is more important than control of Ti content. Theoretical calculation and test results indicate that controlling N content in the range of 0.0017% to 0.002% as well as controlling Ti content in the range of 0.0003% to 0.0005% can observably reduce or even eliminate precipitation of TiN in tire cord steel. Ti and N content in tire cord steel is controlled under 0.0005% and 0.002% respectively in Pangang plant, which dramaticlly reduces the precipitation of TiN in steel and resulted in none of TiN inclusion bigger than 2μm in some heats.
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