METHOD OF MAKING PARTS OUT OF STEEL WITH HIGH MECHANICAL STRENGTH AND HIGH VISCOSITY AND PARTS PRODUCED BY METHOD THEREOF Russian patent published in 2020 - IPC C22C38/14 C22C38/54 C22C38/58 C21D8/02 C23C2/06 C23C2/12 C23C2/28 C23C2/40 C21D9/46 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to rolled steel sheet used for making parts with very high mechanical strength after hardening under press. Sheet has the following chemical composition, wt. %: 0.24 ≤ C ≤ 0.43, 0.05 ≤ Mn ≤ 3, 0.10 ≤ Si ≤ 1.70, 0.015 ≤ Al ≤ 0.070, 0 ≤ Cr ≤ 2, 0.25 ≤ Ni ≤ 2, 0.015 ≤ Ti ≤ 0.10, 0 ≤ Nb ≤ 0.060, 0.0005 ≤ B ≤ 0.0040, 0.003 ≤ N ≤ 0.010, 0.0001 ≤ S ≤ 0.005, 0.0001 ≤ P ≤ 0.025, optionally one or more of 0.05 ≤ Mo ≤ 0.65, 0.001 ≤ W ≤ 0.30 and 0.0005 ≤ Ca ≤ 0.005, iron and unavoidable impurities remaining. If content 0.24 ≤ C ≤ 0.38, it has content of 0.40 ≤ Mn ≤ 3, and if content 0.38 < C ≤ 0.43 it has content of 0.05 ≤ Mn < 0.4. Density of the set of particles D_i and the density of particles D_{(>2 mcm)} referred to the surface unit of the surface and the particle density D_{(>2 mcm)} larger than 2 mcm satisfy the condition D_i + 6.75D _{(>2 mcm)} < 270 at a depth of at least 100 mcm from the surface of the sheet, where D_i and D_{(>2 mcm)} denote the number of particles per square millimetre, wherein said particles denote a combination of oxides, sulphides, nitrides in pure or mixed form, such as oxysulphides and carbonitrides present in the steel matrix.

EFFECT: sheet simultaneously has both high tensile strength Rm over 1800 MPa and high viscosity.

24 cl, 3 dwg, 7 tbl