X60管线钢连铸过程碳、氮化物的析出热力学研究

Thermodynamic Study on Carbide and Nitride Precipitation of X60 Pipeline Steel in Continuous Casting

连铸工艺中不同温度区间内析出的碳化物、氮化物对钢的高温力学性能有重要影响。基于规则溶液理论对X60管线钢在液相、凝固过程及奥氏体相3个阶段析出的微合金元素碳化物、氮化物进行热力学分析与计算,研究析出物的析出相阶段、析出温度及析出顺序,探讨固—液两相阶段由于溶质元素富集而导致析出物溶度积增大、增大析出可能性的因素。计算结果表明:TiN在高温固—液两相区中开始析出,析出温度为1 781 K,奥氏体相区第二相析出物为NbC,NbN,AlN,TiC。

Carbides and nitrides precipitated in different temperature ranges have significant influence on the mechanical behavior under high temperature of steel in the process of continuous casting.Based on the regular solution theory,the carbides and nitrides precipitated in liquid,solid and austenitic phases of X60 pipeline steel are thermodynamicly calculated and analyzed to study the precipitation phase stage,precipitation temperature and precipitation sequence.Factors which lead to increase of precipitation solubility due to the solute element enrichment,and increase of precipitation probability in the two-phase region of solid-liquid are discussed.Calculation results show that TiN starts to precipitate in high temperature solid-liquid two-phase region,precipitation temperature is 1 781 K,and the second-phase precipitates are NbC,NbN,AlN,TiC in austenitic phase.