保温时间对J55钢坯奥氏体晶粒尺寸的影响

Effect of holding time on austenite grain size of J55 casting slab

连铸过程中的奥氏体晶粒尺寸会显著影响铸坯的热塑性,铸坯表面裂纹缺陷也往往与粗大奥氏体的形成有关。实验研究了将铸坯重新加热至1 350℃后保温时间对石油套管J55钢奥氏体晶粒尺寸的影响。结果表明,随着保温时间的增加,奥氏体晶粒尺寸变大。综合分析表明,对于J55钢,在1 350℃时至少保温30 min才能使其晶粒尺寸达到连铸过程中当时的奥氏体晶粒级别。以往采用高温热拉伸实验模拟测量铸坯高温热塑性实验中,多未考虑连铸过程中的实际奥氏体晶粒大小,实验结果不能很好地反映高温铸坯的热塑性。

The size of austenite grain plays an important role on the hot ductility of continuous casting slab,and the abnormal large austenite grain also relate to the defects on the strand surface. The results of experimental research on the effect of holding time at 1 350 ℃ on austenite grain size of J55 are compared with related literatures. It shows that the austenite grain size of J55 gets coarser with the increase of holding time at 1 350 ℃.With reference to previous researches,to get a similar level of austenite grain size in the process of continuous casting,the sample of J55 should be held for at least 30 minutes at 1 350 ℃.The results also suggest that the way usually used for high temperature thermal tensile test simulation to test the hot ductility of specimens is probably not considering the size of austenite grains during continuous casting,the results of which may not represent the hot ductility of high temperature slab.