Ferritic stainless steel for construction applications and method for producing same

EP4613904A1Pending Publication Date: 2025-09-10POHANG IRON & STEEL CO LTD
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Patent Information

Application Number
EP2023907285
Authority / Receiving Office
EP · EP
Patent Type
Applications
Current Assignee / Owner
Priority Date
2022-12-21
Filing Date
2023-09-04
Publication Date
2025-09-10

AI Technical Summary

Technical Problem

Existing ferritic stainless steels face challenges in maintaining structural stability and formability during square tube forming without cracking, and their strength is compromised in the event of fire, necessitating improved heat treatment methods.

Method used

A structural ferritic stainless steel composition comprising specific weight percentages of carbon, nitrogen, silicon, manganese, chromium, nickel, phosphorus, sulfur, and iron, along with a manufacturing process involving annealing, rapid cooling, and slow cooling to enhance the formation of a martensite phase, ensuring a 10% or more area fraction post-heat treatment.

Benefits of technology

The solution provides a stainless steel with enhanced strength and formability, maintaining structural integrity during square tube forming and increasing tensile strength by up to 40% after heat treatment, without cracking.

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Abstract

Disclosed herein is a ferritic stainless steel having excellent formability for square tubing and improved structural stability due to increased strength in the event of fire. The structural ferritic stainless steel according to an embodiment of the present disclosure includes, in percent by weight (wt%), 0.005 to 0.015% of carbon (C), 0.005 to 0.03% of nitrogen (N), 0.4 to 0.8% of silicon (Si), 0.7 to 1.2% of manganese (Mn), 10.5 to 14.0% of chromium (Cr), 0.2 to 1% of nickel (Ni), 0.04% or less of phosphorus (P), 0.01% or less of sulfur (S), the remainder of iron (Fe), and inevitable impurities, and wherein the steel satisfies Formula (1) below, 7≤Cr+7Si−3Mn−3Ni−50C+N≤14 (wherein Cr, Si, Mn, Ni, C, and N represent the content (wt%) of the respective elements).
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