X70管线钢中含Nb相的析出行为

以首钢生产的某X70管线钢成分为基础,利用Thermo-Calc软件计算了不同温度下钢中析出相的组成、相的析出温度及Nb元素的析出规律,研究了钢中Nb和C含量对Nb析出规律的影响,利用热模拟和扫描电镜等手段分析了钢中Nb合金相的析出温度.结果表明,平衡态下该X70管线钢中的析出相主要为Ti、Nb的碳氮化物、合金渗碳体、Ti₄C₂S₂、MnS、AlN、M₇C₃和Mo碳化物.Nb析出相主要以Nb和C元素为主,其中固溶Ti和N元素.随Nb和C含量的增加,Nb合金相的析出温度升高,在同一温度下Nb的析出量增加.

Precipitation behaviour of Nb in X70 pipeline steel

Based on the composition of X70 pipeline steel produced in Shougang Group,the phase structure,the precipitation temperature of phases and the precipitation behaviour of Nb at different temperatures were analyzed by calculation with Thermo-Calc software.The effect rules of Nb and C contents on the precipitation behaviour of Nb were studied.The precipitation temperature of Nb in the steel was analyzed by thermal simulation and scanning electron microscopy(SEM).It is indicated that precipitation phases in the steel are the carbonitrides of Ti and Nb,alloying cementite,Ti₄C₂S₂,MnS,AlN,M₇C₃ and Mo carbides.The Nb precipitation phase mainly consists of the elements of Nb and C,and in the Nb precipitation phase,Ti and N are dissolved.With increasing Nb and C contents,the precipitation temperature of the Nb alloy phase rises and the precipitated Nb content at the same temperature increases.