合金元素及凝固模式对含氮不锈钢氮含量的影响

Influences of alloying elements and solidification modes on the nitrogen content of nitrogenous stainless steel

通过冶炼实验研究Mn、Cr和Ni对不锈钢凝固模式及铸锭氮含量的影响,探讨影响氮含量的关键因素,并分析合金元素对钢液与铸锭中氮含量影响的相互作用系数的区别.实验结果表明,影响氮含量的因素主要为钢液中氮的溶解度和不锈钢的凝固模式.增加钢液中氮的溶解度、改变凝固模式由F→FA→AF→A时,不锈钢的溶氮能力提高,氮气的溢出量减少,氮含量增加.随Mn含量增加,铸锭中氮含量线性增加,而随Cr和Ni含量增加,氮含量的变化均存在三个特征阶段.分析认为:Mn含量变化不改变凝固模式(FA),相互作用系数EMnN为-0.0286,与钢液中相近;而随Cr和Ni含量增加,凝固模式分别依次经历F→FA→AF→A和FA→AF→A模式,相互作用系数ECrN和ENiN非定值,分别为ECrN=-0.046和-0.011,ENiN=-0.011和0.033.

The effects of Mn,Cr and Ni on the solidification mode and nitrogen content of as-cast stainless steel were studied by smelting experiments. The key influencing factors on nitrogen content were explored. The coefficients of interaction between alloying elements and nitrogen were analyzed in molten steel and solidified steel. The results show that the nitrogen content is determined by both the solubility of nitrogen in molten steel and the solidification mode. When the solubility of nitrogen increases and the solidification mode changes according to the sequence of F→FA→AF→A,the solid solubility of nitrogen in the primary crystal enhances and the emission of nitrogen gas lessens during solidification. With the increase of Mn content,the nitrogen content increases monotonically.However,the nitrogen content varies with the Cr and Ni content in the above processes non-monotonically. The content of Mn does not change the solidification mode which is always FA,and the interaction coefficient is-0. 0286,similar to that in molten steel; whereas the increase of Cr and Ni changes the solidification mode according to the routine of F→FA→AF→A and FA→AF→A,respectively,the interaction coefficients between alloying elements and nitrogen in the steel are not a fixed value,ECrN=-0. 046 and-0. 011,ENiN=-0. 011 and 0. 033,respectively.