Development of Super Austenitic Stainless Steels

Summary

The growing industrial demand drives the research and development of super austenitic stainless steel. The three development stages of super austenitic stainless steel are described in the order of research and development time. The first stage is mainly to develop stainless steel to solve the corrosion resistance of sulfuric acid medium environment; the second stage is to add about 0.2% mass fraction of N element on the basis of the steel developed in the first stage, and to increase the mass of Mo element Several super austenitic stainless steels with good corrosion resistance were developed when the fraction increased to about 6%; the third stage was to significantly increase the contents of Cr, Mo, and N on the basis of 6% Mo steel. Among them, the mass fraction of Mo element is increased to about 7%, the mass fraction of N element is controlled at about 0.5%, and an appropriate amount of Mn element is added to develop a super austenitic stainless steel with excellent corrosion resistance. Two important technologies in the research and development process of super austenitic stainless steel, namely, out-of-furnace refining and nitrogen alloying technology, are expounded, and the future development and popularization and application of super austenitic stainless steel are prospected.

Introduction

Super austenitic stainless steel is an austenitic stainless steel with high Cr, Mo, and N content and a pitting corrosion resistance index PREN (Pitting Resistance Equivalent Number, PREN=w(Cr)+3.3w(Mo)+16w(N)) not less than 40. Compared with austenitic stainless steel, super austenitic stainless steel has a higher content of Cr, Mo and N, and has excellent resistance to uniform corrosion, pitting corrosion, crevice corrosion, and stress corrosion. It has both high strength and plastic toughness and is widely used in waste gas treatment fields such as municipal waste treatment and flue gas desulfurization, chemical industry and pulp and paper making and other harsh environment fields, as well as oil and gas extraction and seawater desalination and other resource extraction fields. The development of super austenitic stainless steel is based on the increasing material demand, driven by the advancement of industrial technology, and aimed at excellent corrosion resistance, after decades of development to meet the requirements for harsh environments. However, With the development of the times and the advancement of technology, the process of industrialization has accelerated, the use of super austenitic stainless steel has become wider and wider, and the use environment has become harsher. Austenitic stainless steel has an important role and significance.

Super Austenitic Stainless Steel,HSS rolls

Conclusion

(1) Super austenitic stainless steel aims to pursue excellent performance, from No. 20 alloy and 904L developed to meet the corrosion resistance of the medium environment related to sulfuric acid, to the corrosion resistance of the chloride-containing medium environment. The developed 6Mo steel represented by 254 SMO, AL-6XN, and conifer 1925hMo, to the 7Mo steel represented by 654 SMO with excellent performance, after three stages of development, the system has gradually matured. During this period, the out-of-furnace refining technology and nitrogen alloying technology represented by AOD and VOD played an important role.

(2) With the progress of industrialization technology, the application environment of super austenitic stainless steel will become more and more severe in the future. The development of materials is still mainly based on the pursuit of excellent corrosion resistance, and it is still necessary to increase the content of Cr, Mo, and N elements to improve the corrosion resistance. To achieve this, at the same time need to take into account the phase balance and economy.

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