Investigation of Ti inclusions in tire cord steel

In order to improve Ti inclusions removal technology for controlling their formation and size, Ti contents in melting steel specimens of 80-grade tire cord steel, obtained from the melting process, were measured by laser ablation inductively coupled plasma mass spectrometry. It was found that the average Ti content firstly increased and then decreased during the process of EAF tapping → refining → continuous casting. Under current control conditions of 80-grade tire cord steel in Nanjing Iron and Steel United Co. Ltd. (NISUCL), the calculation results of formation thermodynamics, solidification segregation and growth kinetics of TiN particles show that TiN formation takes place only in the two-phase region where the solidification ratio is greater than 98% or the solid region. The greater the cooling rate during solidification, the smaller the size of precipitated TiN particles. The size of precipitated TiN particles is 3 to 7 μm, in agreement with that measured in the metallographic image of TiN inclusions found in wire rod specimens.