含钛钢奥氏体中第二相析出的热力学分析和实验研究

基于含钛钢中各析出相之间的相互溶解现象，建立热力学模型，研究了低碳含钛钢中的ＴｉＮ、ＴｉＣ、ＴｉＳ、Ｔｉ４ｃ２ｓ２及ＭｎＳ等第二相在奥氏体中的平衡析出规律，对２０ＣｒＭｎＴｉ钢种成分的计算结果表明：该类含钛钢中的析出相主要为ＴｉＣｙＮ１－ｙ、Ｔｉ４Ｃ２Ｓ２及ＭｎＳ，且钛和硫含量在规格范围内的波动可导致它们析出的次序和数量发生明显的变化，对该钢种的实验研究表明，高温冷却过程中，脱溶析出的细小的沿晶Ｔｉ４Ｃ２Ｓ２等粒子是钢在奥氏体高温塑性恶化的原因之一。

THERMODYNAMIC ANALYSIS AND EXPERIMENTAL RESEARCH ON PRECIPITATION BEHAVIOR OF SECOND PHASE PARTICLES IN AUSTENITE OF Ti-BEARING STEEL

Precipitation behavior of Ti precipitates in austenite of Ti bearing steel has been studied by thermodynamic equilibrium and the calculation model is based on the hypothesis that TiC and TiN are completely soluble in each other and the solubility of MnS in Ti based sulphides is limited. From the calculation results for steel 20CrMnTi, some conclusions can be drawn as follows: most of precipitates are TiC yN 1-y ,Ti 4C 2S 2 and MnS,whose quantity and precipitation sequence depend on Ti and S content in the steel, and there is a great thermodynamic trend of reprecipitating fine Ti 4C 2S 2 particles along the grain boundaries, all calculated results are in good agreement with experimental ones. It is inferred from the calculation and experimental results that fine Ti 4C 2S 2 particles precipitated at grain boundaries deteriorate hot ductility of Ti bearing steels.