COLD-ROLLED MARTENSITIC STEEL AND METHOD FOR PRODUCING THE SPECIFIED STEEL Russian patent published in 2023 - IPC C21D8/02 C21D1/22 C22C38/38 C22C38/58 C22C38/28 C22C38/50 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: cold-rolled and martensitic steel sheet used in the automotive industry. ≤≤The sheet≤≤ has a composition that includes the following elements, expressed in % by weight: 0.1≤ C≤ 0.2, 1.5≤ Mn≤ 2.5, 0.1≤ Si≤ 0.25, 0.1≤ Cr≤ 1, 0.01≤ Al≤ 0.1, 0.001≤ Ti≤ 0.1, 0≤ S≤ 0.09, 0≤ P≤ 0.09, 0≤ N≤ 0.09, optionally at least one of the following: 0≤ Ni≤ 10≤ Cu≤ 10≤ Mo≤ 0.4, 0≤ Nb≤ 0.1, 0≤ V≤ 0.1, 0≤ B≤ 0.05, 0≤ sn≤ 0.1, 0≤ Pb≤ 0.1, 0≤ Sb≤ 0.1 and 0.001≤ Ca≤ 0.01, the rest of the composition is iron and unavoidable impurities, and has a hole expansion ratio of 50% or more. The microstructure of said steel includes, in area fractions, at least 95% martensite, the total amount of ferrite and bainite between 1% and 5%, optional amount of retained austenite between 0% and 2%.

EFFECT: sheet has the required strength characteristics in combination with formability.

19 cl, 4 tbl