直接双相区热处理工艺参数对9Ni钢组织性能的影响

Influence of direct lamellarizing-tempering process parameters on microstructure and properties of 9Ni steel

研究了直接双相区热处理工艺的保温时间和回火时间对9Ni钢组织性能的影响。结果表明:在相同回火条件下,保温时间为40 min时低温韧性最好,少于Quenching+Lamellarizing+Tempering(QLT)工艺中双相区保温所需时间;保温时间为20 min时,强度增加但低温韧性降低;保温时间过长(60 min)会导致组织粗化、低温韧性差,延长回火时间低温冲击功也基本不变。保温时间为40 min时,随着回火时间的增加,回转奥氏体增加,抗裂纹扩展能力增强,低温冲击功增加,但强度降低,这主要归因于回转奥氏体在板条束间的析出和对马氏体中C及其它有害元素的净化作用。

Influence of holding time and tempering time in the direct inter-critical quenching and tempering（DLT） process on microstructure and properties of 9Ni steel was investigated.The results show that under the same tempering conditions,the highest cryogenic toughness is obtained when holding time in inter-critical region is 40 min,which is less than the optimal holding time for QLT process.Higher strength and lower cryogenic toughness are achieved when the holding time is 20 min,and the lowest cryogenic toughness is obtained when holding time is 60 min and remained almost unchange as tempering time increased due to the coarsened microstructure obtained during the long holding time.For the specimens after holding at inter-critical region for 40 min,more reversed austensite is obtained with increasing tempering time,which could hinder the cracking propagation,increase the cryogenic toughness and decrease the strength,which is caused by the precipitation of reversed austensite between martensite blocks to scavenge carbon and other deleterious elements in matrix.