MARTENSITIC STEEL RESISTANT TO DELAYED FRACTURE AND METHOD OF MANUFACTURE Russian patent published in 2017 - IPC C22C38/54 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: steel contains, wt %: 0.30≤C≤0.5, 0.2≤Mn≤1.5, 0.5≤Si≤3.0, 0.02≤Ti≤0.05, 0.001≤N≤0.008, 0.0010≤AT≤0.0030, 0.01≤Nb≤0.1, 0.2≤Cr≤2.0, P≤0.02, S≤0.005, Al≤1, Mo≤1, Ni≤0.5, the rest is iron and unavoidable impurities formed when melting. The microstructure of sheet is 100% of martensite with size of preceding austenite grain below 20 mcm, and the delayed fracture resistance is at least 24 hours in the U-bend test by immersion in acid.

EFFECT: manufactured sheets have high strength, mouldability and delayed fracture resistance.

23 cl, 2 dwg, 5 tbl