钛和钒对高锰钢高温热延性的影响

运用Gleeble-3500热力模拟试验机对700～1200℃温度范围内高锰钢Mn13单独加入钛(质量分数0.10％)、复合添加钛(质量分数0.11％)和钒(质量分数0.20％)后的高温热延性进行测试.采用扫描电镜和X射线能谱分析仪对不同温度下拉伸断裂后试样的断口形貌以及断口处的析出粒子进行了分析.温度-断面收缩率曲线表明在高锰钢中加入0.10％钛后,其断面收缩率出现了一定程度的下降,这表明钛的加入恶化了高锰钢的热延性;在此基础上加入0.20％钒,高锰钢的热延性出现了进一步的下降,即钛和钒的复合加入严重恶化了高锰钢的热延性.利用Thermo-Calc热力学计算软件对单独含钛以及复合含钛钒的高锰钢在700～1600℃存在的平衡析出相进行了计算,计算结果表明Ti(C,N)的平衡析出温度均约为1499℃,远大于其液相线温度,这说明Ti(C,N)在高锰钢的液相中就可以开始析出.扫描电镜-能谱分析结果表明在奥氏体晶界以及三叉晶界处存在大量的Ti(C,N)和(Ti,V)C粒子,这些粒子的出现抑制了动态再结晶的发生,并且加速了晶界附近裂纹的扩展.

Influence of Ti and V on the hot ductility of high manganese austenitic steel

The influence of Ti(mass fraction 0.10％)and the joint additions of Ti(mass fraction 0.11％)and V(mass fraction 0.20％)on the hot ductility of as-cast high manganese austenitic steels were studied using a Gleeble-3500 thermo-mechanical simulator over a temperature range of 700 to 1200℃.Fracture surfaces and particles precipitated at different testing temperatures were investigated via scanning electron microscopy(SEM)and X-ray energy dispersive spectrometry(EDS).The hot ductility curves as a function of temperature of high-Mn austenitic steels showed that Ti addition leads to loss of ductility in almost the entire testing temperature range.Moreover,the joint additions of Ti and V do not exhibit any improvement in the hot ductility,resulting in relatively poor hot ductility behavior.The phase diagrams of precipitates in Ti-and Ti-V-bearing high-Mn austenitic steels in the temperature range of 700 to 1600℃ were calculated via Thermo-Calc commercial software.The calculation results show that Ti(C,N)in Ti-bearing high-Mn steel precipitates at 1499℃,which is much higher than its liquidus temperature.This illustrates that Ti(C,N)particles form in the liquid steel.SEM-EDS results show that Ti(C,N)and(Ti,V)C particles form along the austenitic grain boundaries and the triple junction.These particles retard the occurrence of dynamic recrystallization and accelerate the extension of cracks near the grain boundaries.