Hot-rolled flat steel product and method for the production thereof

US11371113B2 · kind B2 · utility

Assignee

• Evonik Operations GmbH · DE

Inventors

• Manuela Irnich · Rheinberg, DE
• Rainer Fechte-Heinen · Bottrop, DE
• Jens Horstmann · Goldkronach, DE
• Richard G. Thiessen · Malden, NL

Key dates

• Filing date: Dec 6, 2017
• Grant date: Jun 28, 2022
• Expiry date: Mar 25, 2038

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C22C38/18
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

A hot-rolled flat steel product including (in wt %) C: 0.1-0.3%, Mn: 1.5-3.0%, Si: 0.5-1.8%, Al: ≤1.5%, P: ≤0.1%, S: ≤0.03%, N: ≤0.008%, optionally one or more of Cr: 0.1-0.3%, Mo: 0.05-0.25%, Ni: 0.05-2.0%, Nb: 0.01-0.06%, Ti: 0.02-0.07%, V: 0.1-0.3%, and B: 0.0008-0.0020%, the balance being iron and unavoidable impurities. This flat steel product possesses a tensile strength of 800-1500 MPa, a yield strength of >700 MPa, an elongation at break of 7-25%, and a hole expansion of more than 20%. The structure is at least 85 area % martensite, of which at least half is tempered martensite, with the remainder being ≤15 vol % residual austenite, ≤15 area % bainite, ≤15 area % polygonal ferrite, ≤5 area % cementite and/or ≤5 area % nonpolygonal ferrite, and has a kernel average misorientation of at least 1.50°. Also, a method for producing the flat steel product, wherein the microstructure of the flat steel product is set by the heat treatment.