预处理温度对Cr-Ni-Co-Mo马氏体时效不锈钢强度的影响

研究了预处理温度对Cr-Ni-Co-Mo马氏体时效不锈钢强度的影响,其内容包括预处理温度对原始锻态粗晶遗传及自发再结晶的影响,以及对最终热处理后残留+逆转变奥氏体量和力学性能的影响。结果表明:900 ℃以下预处理遗传锻态粗晶,即通过α′→γ切变机制形成高缺陷密度的奥氏体。预处理温度升高,最终750 ℃固溶、－73 ℃冷处理后的残留奥氏体量,以及500 ℃时效的残留+逆转变奥氏体量减少,因此最终的抗拉和屈服强度升高。预处理温度提高到800 ℃以上,则不再影响最终热处理后的残留+逆转变奥氏体量,因此抗拉和屈服强度趋于稳定。900 ℃以上预处理遗传的锻态粗晶自发再结晶使晶粒细化,降低形成的奥氏体内的缺陷密度,降低750 ℃固溶处理后奥氏体内累积的缺陷密度,最终的时效强化效应下降,导致晶粒细化并不能提高最终的强度。

Effect of pre-treatment temperature on strength of Cr-Ni-Co-Mo maraging stainless steel

Effect of pre-treatment temperature on strength of Cr-Ni-Co-Mo maraging stainless steel was investigated, including the effect on heritability of the original forged coarse grains and spontaneous recrystallization, as well as the effect of pre-treatment temperature on the amount of retained and reversed austenite and the mechanical properties after the final heat treatments. The results show that, the pre-treatment below 900 ℃ inherits the forging coarse grains, that is, the austenite with high defect density is formed by the α′→γ shear mechanism. The pre-treatment temperature rises, the amount of retained austenite after solid solution at 750 ℃, cryogenic treatment at －73 ℃, and the amount of retained and reversed austenite after aging at 500 ℃ decrease, so the final tensile and yield strength increase. The pre-treatment above 800 ℃ does not influence much on retained and reversed austenite amount after final heat treatment, and the tensile and yield strengths tend to stabilize. The spontaneous recrystallization of the inherited forged coarse grains via pre-treatment above 900 ℃ refines the grains and reduces the density of defects in the formed austenite, and finally reduces the density of defects accumulated in the austenite after solution treatment at 750 ℃, so the final aging strengthening effect is reduced, resulting in that the grain refinement is not enough to improve the final strength.