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通过物理化学相分析试验和热力学平衡计算,分析了Ti、N原子比大于1、等于1、小于1的3种Nb-Ti处理ULC-BH钢板的第二相析出规律。相分析和热力学计算结果表明,3种成分钢板析出相主要为(Ti,Nb)(C,N)、MnS,试验钢中未发现Ti4C2S2和TiS相;Ti、Nb元素的氮化物主要在A1温度以上析出,而碳化物主要在铁素体相区析出。在热轧板经卷取保温后,Nb、Ti元素接近完全析出形成M(C,N);短时退火后,M(C,N)相有少量回溶。当Ti、N原子比接近1时,N主要与Ti结合,C单独由Nb固定,有利于预估钢中固溶C含量。钢中增加酸溶铝含量有利于避免形成Al2O3夹杂。
Through the analysis of physical and chemical phase analysis and thermodynamic equilibrium, the precipitation regularity of the second phase of three kinds of Nb-Ti treated ULC-BH steel with Ti, N atomic ratio greater than 1, equal to 1 and less than 1 was analyzed. The results of phase analysis and thermodynamic calculation show that the precipitates of the three components are (Ti, Nb) (C, N) and MnS, and Ti4C2S2 and TiS are not found in the test steel. The nitrides of Ti and Nb are mainly at A1 The above precipitation, and carbide precipitation in the ferrite phase region. After the hot-rolled sheet is coiled and retained, the Nb and Ti elements are almost completely precipitated to form M (C, N). After the short-time annealing, the M (C, N) phase is slightly dissolved back. When Ti, N atomic ratio close to 1, N mainly combined with Ti, C alone by the Nb fixed, is conducive to the estimated content of dissolved carbon in steel. Increasing the acid-soluble aluminum content in the steel helps to avoid the formation of Al2O3 inclusions.