超级奥氏体不锈钢发展及第二相调控研究现状

Review on development and second phase regulation of super austenitic stainless steel

超级奥氏体不锈钢作为高端装备制造业的关键材料,在海水淡化、海洋油气工程、烟气处理等领域得到广泛应用。但超级奥氏体不锈钢中Cr、Mo等合金元素的含量较高,在热轧、焊接等热加工过程中,在焊接热影响区极易发生因合金元素偏析导致的第二相(如σ相、Laves相等)析出,严重影响其耐蚀性能、力学性能。简述了超级奥氏体不锈钢自诞生以来的发展,综述了抑制超级奥氏体不锈钢凝固过程中第二相析出的方式,首先增加N含量可以有效细化钢的凝固组织,并且N含量与σ相析出量呈负相关;其次稀土微合金化也为调控钢中第二相析出提供了新的方向;最后是冷却速度的提高能有效改善结晶动力学,实现凝固组织细化,从而抑制第二相析出。对时效过程第二相析出的研究表明Mo含量越高,σ相偏析越严重,并且不同金属间相还会存在转化。因此,对目前超级奥氏体不锈钢的凝固偏析行为、时效过程中第二相析出行为以及均匀化制度进行了总结。

As the key material of the high-end equipment manufacturing industry,super austenitic stainless steel has been widely used in seawater desalination,offshore oil and gas engineering,flue gas treatment,and other fields.However,the content of Cr,Mo,and other alloy elements in super austenitic stainless steel is relatively high.In the process of hot rolling,welding,and other hot processing,the precipitation of the second phase(such asσphase and Laves equality)commonly caused by the segregation of alloy elements in the welding heat-affected zone seriously affects the corrosion resistance and mechanical properties of the steel.The development of super austenitic stainless steel since its birth was briefly described and the ways to inhibit the second phase precipitation in the solidification process of super austenitic stainless steel were reviewed.Firstly,increasing the content of N can effectively fine the solidification structure of steel,and the content of N is negatively correlated with the amount ofσprecipitation.Secondly,rare earth microalloying provides a new direction for regulating the second phase precipitation in steel.Finally,the increase in cooling rate can effectively improve the crystallization kinetics,realize solidification microstructure refinement,and inhibit the second phase precipitation.The study on the precipitation of the second phase in the aging process shows that the higher the content of Mo element is,the more serious segregation of theσphase is,and there will be a transformation between different metal phases.Therefore,the current super austenitic stainless steel solidification segregation behavior,the second phase precipitation in the process of aging behavior,and the homogenization system are summarized.