MUMBAI, India, Sept. 26 -- Intellectual Property India has published a patent application (202517084496 A) filed by Jfe Steel Corporation, Tokyo, on Sept. 5, for 'method of producing galvannealed steel sheet.'
Inventor(s) include Terashima Shotaro; Nakagaito Tatsuya; Yoshitomi Hiromi; Hoshino Katsuya; and Okumura Yusuke.
The application for the patent was published on Sept. 26, under issue no. 39/2025.
According to the abstract released by the Intellectual Property India: "The present invention provides a hot-dip galvannealed steel sheet that has a beautiful external appearance without defects such as bare spots, has excellent plating adhesion, and further has excellent hydrogen embrittlement resistance. This manufacturing method for such hot-dip galvannealed steel sheet comprises: heating a steel sheet having a composition containing, in mass%, Si: 0.10-2.00%, and Mn: 1.0-5.0%, to at least 600 C in an oxidizing atmosphere including 1000-30000 volumetric ppm, inclusive, of O2; holding the steel sheet after the oxidation step for at least 20 s at 700 C or higher in a reducing atmosphere having a hydrogen concentration that is greater than 8 vol% and at most 30 vol%; holding the steel sheet for 20-300 s, inclusive, at 750 C or higher in an isothermal atmosphere having a hydrogen concentration of 0.2-8 vol%, inclusive; cooling the steel sheet; immersing the steel sheet in a molten zinc galvanizing bath to obtain a hot-dip galvanized steel sheet; performing an alloying process on the hot-dip galvanized steel sheet to obtain a hot-dip galvannealed steel sheet; and, after cooling the hot-dip galvannealed steel sheet to a cooling stop temperature that is at most a Ms point, holding the steel sheet for at least 30 s at a temperature that is at least the cooling stop temperature and is 100-450 C, in a reheating atmosphere having a hydrogen concentration of at most 0.2 vol%."
The patent application was internationally filed on Apr. 28, 2023, under International application No.PCT/JP2023/016963.
Disclaimer: Curated by HT Syndication.
