Austenitic stainless steel sheet, method for producing same, and component

EP4613897A1Pending Publication Date: 2025-09-10NIPPON STEEL CORPORATION
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Patent Information

Application Number
EP2023885868
Authority / Receiving Office
EP · EP
Patent Type
Applications
Current Assignee / Owner
Priority Date
2022-11-04
Filing Date
2023-11-02
Publication Date
2025-09-10

AI Technical Summary

Technical Problem

Austenitic stainless steels face challenges in resisting intergranular cracking and red scale formation due to nitriding and oxidation when exposed to ammonia combustion exhaust gases containing high nitrogen and water vapor at temperatures between 500 to 700°C, which existing technologies do not adequately address.

Method used

The development of an austenitic stainless steel with optimized elemental composition and a surface SiO2 coating, formulated to suppress nitriding and oxidation, achieved by controlling the nitriding trend index and forming a protective SiO2 coating through controlled internal oxidation and pickling processes.

Benefits of technology

The steel exhibits enhanced corrosion and wear resistance, reduced thermal expansion, and improved high-temperature strength, effectively preventing intergranular cracking and red scale formation in environments with high nitrogen and water vapor content.

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Abstract

The present invention has as its technical issue to suppress intergranular cracking resistance (nitriding resistance) and suppress even formation of red scale (oxidation resistance) even in a gas atmosphere containing nitrogen and water vapor such as ammonia combustion gas in a 500 to 700°C medium and high temperature region and has as its object the provision of such austenitic stainless steel. The present invention is an austenitic stainless steel sheet having a predetermined chemical composition, having a nitriding trend index of 15 or less, and having an Si oxide coating on the steel sheet surface present in an area ratio of 5% or more and is obtained by final annealing the steel sheet to form an internal oxidation layer (Si oxide layer) and removing the Cr oxide layer and Fe oxide layer of the surface layer by subsequent pickling to form an Si oxide layer on the surface layer:         Nitridation Trend Index=0.5Cr+10Al+2Mo+3Ti+0.5Cu-1.5Si
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Citation Information

Patent Citations

  • Stainless steel for ammonia-water absorption cycle heat exchanger

    JP1998280100A

  • JP3126842A