大型奥氏体不锈钢锻件的晶粒尺寸控制

Grain size control for large austenitic stainless steel forgings

针对大型F316H奥氏体不锈钢锻件塑性变形抗力大,锻造工艺不当易导致开裂、粗晶和混晶等难题,开展晶粒粗化实验、高温拉伸和高温压缩实验,以研究材料晶粒的长大规律、热塑性及临界变形量对动态再结晶的影响。实验结果表明:当变形温度高于1050℃时,晶粒尺寸随着保温时间的延长不断增大,变形温度越高,晶粒尺寸长大趋势越明显。随着变形温度的升高,材料的抗拉强度逐渐变小,塑性抗力逐渐减小。同一变形温度下,随着变形程度的增加,动态再结晶程度随之增大。相同变形量下,随着变形温度的升高,动态再结晶更充分,晶粒尺寸更为细小,晶粒数量大幅增加。根据实验结果制定了直径为Φ5800 mm的管板锻件的锻造工艺,经实际生产验证,取得了较好的实施效果。

For the problems of large plastic deformation resistance and cracking,coarse grains and mixed grains easily caused by improper forging process for large forgings of F316H austenitic stainless steel,the grain coarsening test,high temperature tensile and high temperature compression tests were carried out,and the influences of material grain growth law,thermoplasticity and critical deformation amount on the dynamic recrystallization were studied.The test results show that when the deformation temperature is higher than 1050℃,the grain size increases with the extending of holding time,and the higher the deformation temperature is,the more obvious the trend of grain size growth is.With the increasing of deformation temperature,the tensile strength of material gradually decreases,and the plastic resistance gradually decreases.At the same deformation temperature,the degree of dynamic recrystallization increases with the increasing of deformation degree.Under the same deformation amount,with the increasing of deformation temperature,the dynamic recrystallization is more sufficient,the grain size is smaller,and the number of grains increases significantly.According to the test results,the forging process of tube sheet forgings with a diameter ofΦ5800 mm was formulated,and a good effect was obtained by practical production verification.