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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 austenite grain size in the continuous casting process will significantly affect the thermoplasticity of the slab. The slab surface crack defects are also often associated with the formation of coarse austenite. The effect of holding time on austenite grain size of oil casing J55 steel was studied experimentally after reheating slab to 1 350 ℃. The results show that with the increase of holding time, austenite grain size becomes larger. Comprehensive analysis shows that, for the J55 steel, at a temperature of 1 350 ℃ for at least 30 min in order to make the grain size reach the austenite grain size at the time of continuous casting. In the past, the high temperature hot tensile experiment was used to simulate the high temperature thermoplasticity of the billet. Most of the actual austenite grain size in the continuous casting process was not considered. The experimental results did not reflect the thermoplasticity of the high temperature billet.