固溶处理对AISI 631不锈钢薄带组织与力学性能的影响

Effects of Solution Treatment on Microstructure and Mechanical Properties of AISI 631 Stainless Steel Strip

针对0.8 mm厚冷轧AISI 631半奥氏体沉淀硬化不锈钢薄带采用原有热处理工艺硬度不足问题,在原有调整冷处理、时效热处理工艺的基础上,考察了先期固溶处理(1050℃×(1~7 min))对薄带最终热处理后微观组织与力学性能的影响。结果表明,冷轧原料因成分不均有大量残余奥氏体γ和铁素体相,经原有调整、时效处理无法将奥氏体完全转变为马氏体,因而硬度较低。而先经1050℃×(1~2) min固溶热处理后,碳化物及其它合金元素充分固溶,形成成分均匀的奥氏体,再经调整、时效处理使奥氏体几乎完全转变为细小的马氏体组织,并析出高密度细小的Ni Al强化相,使631不锈钢硬度和强度综合性能升高。而继续增加固溶时间,则马氏体形核率降低,631不锈钢的硬度、拉伸性能反而下降。

In order to solve insufficient hardness problem of 0.8mm thick cold-rolled AISI 631 semi-austenitic precipitation hardened stainless steel thin strip by the original heat treatment process, the effects of the prior solution treatment(1050℃ ×(1-7) min) on the microstructure and mechanical properties of the final heat-treated thin strip based on the original aging heat treatment process were investigated. The results show that there are considerable residual austenite γ and δ ferrite phases in the cold-rolled raw material due to inhomogeneous composition. Since austenite phase cannot be completely transformed into martensite via the original condition and aging heat treatment process, the hardness is lower. After 1050℃×(1-2) min solution heat treatment, however, the carbide and other alloy elements are fully dissolved to form uniform austenite, and then the austenite is almost completely transformed into fine martensite during conditioning together with high density of fine Ni Al strengthening phase precipitation after aging treatment, which results in the highest hardness and strength of 631 stainless steel.Nevertheless, if the solution time is further increased, the nuclear rate of martensite decreases and the hardness and tensile properties of 631 stainless steel decrease instead.