HOT-MOLDED, AIR-HARDENED AND WELDABLE STEEL SHEET Russian patent published in 2019 - IPC C22C38/38 C22C38/26 C22C38/12 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: invention relates to sheet steel used in automotive industry. Steel contains, in wt. %: 0.04 ≤ C ≤ 0.30, 0.5 ≤ Mn ≤ 4, 0 ≤ Cr ≤ 4, 2.7 ≤ Mn+Cr ≤ 5, 0.003 ≤ Nb ≤ 0.1, 0.015 ≤ Al ≤ 0.1, 0.05 ≤ Si ≤ 1.0, the balance is iron and unavoidable impurities. Steel has a microstructure including up to 10 % of bainite area and the rest is martensite.

EFFECT: obtaining hot-deformed sheets insensitive after austenisation to cooling rate and having uniform distribution of tensile strength by part in range of 800–1400 MPa irrespective of delay time between operations and final cooling/tempering, which allows cooling in both mold and cooled medium, such as air, nitrogen, oil or water.

14 cl, 6 dwg, 2 tbl