氮含量对无镍含钼奥氏体不锈钢相变的影响

Effect of nitrogen content on phase transformation of nickel-free austenitic stainless steel containing Mo

以Cr_(18)Mn_(14)Mo_(3)无镍含钼不锈钢为基本成分,设计并冶炼了电渣重熔锭实测氮含量为0.008%~0.770%的4炉高氮Cr MnMo奥氏体不锈钢(氮含量设计范围为0.004%~0.850%),对各试验钢的平衡相转变进行了热力学计算,对试验钢的显微组织形貌进行了观察。结果表明:试验钢的氮含量在0.40%到0.85%区间内时,在900~1200℃内存在较宽的单相奥氏体区。通过计算获得了不同氮含量钢的平衡相转变图,试验钢中δ铁素体的最大析出量随着氮含量的升高而降低,当N含量在0.77%时,δ铁素体最大析出量约为30%;获得了试验钢加热时δ铁素体析出温度与氮含量的关系式为T_(δ)=876+433w(N);随着氮含量的升高,试验钢在冷却时Cr2N的析出温度逐渐升高,其定量关系式为T_(Cr2N)=711+350_(w)(N)。

Based on Cr_(18)Mn_(14)Mo_(3)steel,four high-nitrogen austenitic stainless steels with 0.004%-0.850%N were designed,and smelted into electroslag remelting ingots with measured nitrogen content of 0.008%-0.770%N.The thermodynamic calculation of equilibrium phase transformations of the steels was carried out,and the microstructure morphologies were observed.The results show that for 0.40%-0.85%N steels,there is a wide single-phase austenite region in 900-1200℃.The four calculated equilibrium phase transformation diagrams for the tested steels show that,the maximum precipitation amount ofδ-ferrite is decreased with the increase of nitrogen content.When the nitrogen content is 0.77%,the maximum precipitation amount ofδ-ferrite is about 30%,the relationship between the precipitation temperature T_(δ)ofδ-ferrite and the nitrogen content(N)during the heating process is obtained as T_(δ)=876+433 w(N).With the increase of nitrogen content,the precipitation temperature of Cr2 N increases gradually in cooling of the tested steels,and its quantitative relationship is obtained asT_(Cr2N)=711+350_(w)(N)