FIELD: metallurgy.
SUBSTANCE: invention relates to metallurgy, particularly, to production of parts for automotive industry from martensitic stainless steel as result of sheet hot forming. Stainless steel sheet of the following composition is prepared, wt. %: 0.005 ≤ C ≤ 0.3; 0.2 ≤ Mn ≤ 2.0; trace amounts ≤ Si ≤ 1.0; trace amounts ≤ S ≤ 0.01; trace amounts ≤ P ≤ 0.04; 10.5 ≤ Cr ≤ 17.0; trace amounts ≤ Ni ≤ 4.0; trace amounts ≤ Mo ≤ 2.0; Mo + 2 × W ≤ 2.0; trace amounts ≤ Cu ≤ 3; trace amounts ≤ Ti ≤ 0.5; trace amounts ≤ Al ≤ 0.2; trace amounts ≤ O ≤ 0.04; 0.05 ≤ Nb ≤ 1.0; 0.05 ≤ Nb + Ta ≤ 1.0; 0.25 ≤ (Nb + Ta)/(C + N) ≤ 8; trace amounts ≤ V ≤ 0.3; trace amounts ≤ Co ≤ 0.5; trace amounts ≤ Cu + Ni + Co ≤ 5.0; trace amounts ≤ Sn ≤ 0.05; trace amounts ≤ B ≤ 0.1; trace amounts ≤ Zr ≤ 0.5; Ti + V + Zr ≤ 0.5; trace amounts ≤ H ≤ 5 ppm; trace amounts ≤ N ≤ 0.2; (Mn + Ni) ≥ (Cr - 10.3 - 80 × [(C + N)2]); trace amounts ≤ Ca ≤ 0.002; trace amounts ≤ rare-earth elements and/or Y ≤ 0.06; balance are iron and unavoidable impurities. Temperature of onset of martensitic transformation (Ms) of steel is ≥200 °C, temperature of martensitic transformation end (Mf) is ≥ −50°C, and microstructure of sheet is formed from ferrite and/or tempered martensite and from 0.5 to 5 vol. % of carbides, wherein size of ferritic grains of sheet is in range from 1 to 80 mcm, preferably from 5 to 40 mcm. If necessary, the sheet is subject to at least one hot and/or cold transformation. Sheet is austenitized by its holding at temperature of at least Ac1 with provision of microstructure containing not more than 0.5 vol. % of carbides and not more than 20 vol. % of residual ferrite. Several stages of sheet profiling or cutting are performed on corresponding devices. Sheet is converted to appropriate devices and profiling or cutting is carried out for a period of time at which it remains at temperature not less than Ms and preserves not more than 0.5 vol. % of carbides and not more than 20 vol. % of residual ferrite. Mixture is cooled to ambient temperature to obtain a final part having a microstructure containing not more than 0.5 vol. % of carbides and no more than 20 vol. % of residual ferrite.
EFFECT: obtaining parts of complex shape with high mechanical properties.
14 cl, 2 dwg, 2 tbl
