微合金钢第二相粒子对HAZ区奥氏体晶粒影响

Effect of second - phase particle on austenite grain size in HAZ in microallyed steel

研究了Ti—V—Nb微合金钢及热影响区(HAZ)第二相粒子及其对HAZ区奥氏体晶粒长大的影响. 结果表明,微合金钢中存在大量弥散分布、细小粒子的Ti、Nb、V的碳氮化合物.这些具有很高的稳定性,在焊接热循环过程中,显著地阻止奥氏体晶粒长大.焊接热循环峰值温度在1200℃以下时,HAZ区中第二相粒子仅发生轻微的溶解及长大,奥氏体晶粒长大程度很小,且奥氏体晶粒尺寸基本不随t8/5及热循环峰值温度Tm的变化而变化.焊接热循环峰值温度在1250℃以上时,HAZ区中第二相粒子显著减少而尺寸显著增大,奥氏体晶粒尺寸随t8/5及Tm的增大而显著增大.

Particle in Ti - V - Nb microalloyed steel and its effect on the growth of austenite grain in HAZ were investigated. Experiment results and analysis show that large amount of small dispersed particle containing Ti, Nb and V exist in the steel. Those particles are very stable and can effectively inhibit austenite grain coarsening during welding thermal cycle. With the peak temperature of welding thermal cycle not higher than 1200℃, the particle dissolving and coarsening are very weak, thus the austenite grain coarsening rate is very slow, and the austenite grains size does not increase significantly with the increase of t8/5. With the the peak temperature of welding thermal cycle higher than 1250℃, the particle in HAZ are evidently dissolved and coarsened, the austenite grain coarsening rate is very slow, and the austenite grains coarsening rate increases, and the grain size increases significantly with the increase of t8/5.