合金元素对316 LN 不锈钢的力学性能和点蚀性能的影响

研究了N、Cr、Mo和Ni四种合金元素含量的变化对核电主管道用固溶态316LN不锈钢的晶粒尺寸以及常规力学性能和点蚀性能的影响.随着N含量的升高,316LN的晶粒明显细化,其在固溶处理过程中晶粒长大趋势也减小. N含量的升高可改善316LN的力学性能和耐点蚀性能,但是当N质量分数达到0.20%时,其耐点蚀性能又开始变差.晶粒细化对316LN强度的影响远小于N含量对316LN强度的影响. Cr及Ni含量对316LN的晶粒尺寸及抗拉强度、屈服强度等力学性能影响不大；Cr含量增加可轻微改善316LN的抗点蚀能力,Ni元素对316LN的耐点蚀性能影响不大,但可增大钝态的腐蚀速度从而不利于钝化膜的稳定.随Mo含量增加,316LN的晶粒尺寸略有减小,强度增大,延伸率显著降低,耐点蚀能力改善.

Effect of alloy elements on the mechanical properties and pitting corrosion resistance of 316 LN austenitic stainless steel

The effect of four alloying elements, N, Cr, Mo and Ni, on the grain size, mechanical properties and pitting corrosion resistance of 316LN austenitic stainless steel for primary coolant pipes in nuclear power plants were investigated. When the nitrogen concentration increases in the stainless steel, the grain size and growth trend dramatically decrease. Increasing the nitrogen concentra-tion can improve the mechanical properties and particularly, the pitting corrosion resistance goes up before the nitrogen concentration reaches 0. 20%. Grain refinement achieved by the addition of nitrogen is propitious to the mechanical properties of the stainless steel, but this is not the main mechanism for the increase in mechanical properties. Cr and Ni elements have no obvious impact on the grain size and mechanical properties, but Cr can improve the pitting corrosion resistance slightly while the passive film loses its stability as the Ni concentration increases. When the Mo concentration increases, the strength and pitting corrosion resistance increase, but the grain size and elongation decrease.