METHOD OF MAKING STEEL PART Russian patent published in 2024 - IPC C21D1/26 C21D6/00 C21D8/02 C22C38/02 C22C38/04 C22C38/06 C22C38/12 C22C38/22 C22C38/34 C22C38/38 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to production of steel part from steel sheet. Steel sheet has a composition containing the following in wt.%: C: 0.05–0.25, Mn: 3.5–8, Si: 0.1–2, Al: 0.01–3, S ≤ 0.010, P ≤ 0.020, N ≤ 0.008, optionally Cr: 0–0.5 and/or Mo: 0–0.25, the rest is iron and unavoidable impurities. Sheet has a microstructure including, in surface fractions, 10–50% of residual austenite, 50% or more of the sum of ferrite, bainite and tempered martensite, less than 5% of fresh martensite and less than 2% of carbides. Content of carbon [C]_A in austenite is strictly more than 0.4 and strictly less than 0.7 wt.%, and the weight percentage of nitrogen %N, silicon %Si, manganese %Mn, chromium %Cr, nickel %Ni, copper %Cu, molybdenum %Mo and carbon in austenite [C]_A, such that Md30 is in range of 200–350 °C, wherein Md30 is defined as: Md30(°C) = 551 – 462*([C]_A +%N) – 9.2*%Si – 8.1*%Mn – 13.7*%Cr – 29*(%Ni+%Cu) - 18.5*(%Mo). Said steel sheet is cut to preset shape to produce steel billet. Steel billet is heated to temperature T_warm of (Md30-150 °C) to (Md30-50 °C) to obtain a heat-treated steel billet. Heat-treated steel billet is stamped or cut at the specified temperature T_warm, and the heat-treated steel billet is formed at the specified temperature T_warm to produce a steel part.

EFFECT: obtaining a part from steel with a high expansion ratio of the hole.

9 cl, 4 tbl