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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30μm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100μm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℃。
By means of thermodynamic calculation and extraction complex analysis, the solid solution of second phase particles in high Ti-containing Nb steel at different heating temperatures and the growth of austenite grains were studied. The results show that when the reheating temperature is lower than 1 180 ℃, the content of Nb and Ti in steel increases with the increase of temperature. The solid solution amount of Nb and Ti tended to be stable at 1 210 ℃ and 1 180 ℃, respectively. When the reheating temperature was 800 ℃ to 1 100 ℃, the small particles with size less than 30 nm and uniform distribution were mainly spherical, The grain size of the austenite is below 30 μm. At the reheating temperature of 1 180 ~ 1 210 ℃, the number of second phase particles decreased and the size ranged from 100 to 200 nm. The morphology was mostly cubic and spherical, and the grain size of austenite slightly increased. With the reheating temperature further increased, the number of precipitated particles decreased rapidly, the size of more than 200 nm square particles, the rapid growth of austenite grains to 100μm above; precipitated particles are Nb, Ti composite Carbonitride, the Nb / Ti atomic ratio decreases with increasing temperature; the grain coarsening temperature of the test steel is 1 210 ℃, and the actual heating temperature is determined to be 180 ~ 1 210 ℃.