再加热温度对含Nb，Ti钢第二相粒子固溶及晶粒长大的影响

 通过热力学计算和萃取复型分析技术，对高Ti含Nb钢中第二相粒子在不同加热温度下的固溶情况和奥氏体晶粒的长大规律进行了研究。结果表明：再加热温度低于1 180 ℃时，钢中Nb、Ti含量随温度升高显著增加。Nb、Ti固溶量分别在1 210 ℃和1 180 ℃以上趋于稳定；再加热温度在800~1 100 ℃时，以尺寸小于30 nm、分布较均匀的小粒子为主，呈球形，奥氏体晶粒尺寸在30 μm以下。再加热温度在1 180~1 210 ℃时，第二相粒子数量减少，尺寸多在100~200 nm之间，形态多为立方形和球形，奥氏体晶粒尺寸略微增加。随着再加热温度的进一步升高，析出粒子数量迅速下降，尺寸多为大于200 nm的方形粒子，此时奥氏体晶粒迅速长大至100 μm以上；析出粒子组成均为Nb、Ti复合的碳氮化物，其Nb/Ti原子比随温度升高而降低；试验钢的晶粒粗化温度为1 210 ℃，确定实际加热温度为1 180~1 210 ℃。

Effect of Reheating Temperature on Solid Solution of Second Phase Particle and Grain Growth in Steel Containing Niobium and Titanium

The solid solution of the second phase particle and austenite grain coarsening in steel containing Nb and Ti were studied by using thermodynamical calculation and extraction replica technique. Results show that content of Nb and Ti obviously increases with increasing the reheating temperature, and tends to be constant at 1 210 ℃ and 1 180 ℃ respectively. The size of main particles is lower than 30 nm and these particles are spherical which are finely dispersed and the austenite grain size is below 30μm in the range of 800-1 100 ℃. The particles are mostly cubic and spherical and their is size is 100-200 nm , the amount of which is decreased and the austenite grain size slightly grows in the range of 1180-1210℃. With heating temperature further increasing the amount of particles is rapidly decreased and size of cubic particles is above about 200 nm, and the austenite grain size is sharply increased up to 100 μm. All second phase particles are complex compound Nb Ti(C,N), the atom ratio Nb/Ti of which is reduced with increasing the reheating temperature . The grain coarsening temperature of austenite grains 1 210 ℃ and the reheating temperature range of 1 180-1 210 ℃ are determined.