PRODUCTION OF SHEET OR PART FROM SUPERHARD MARTENSITE STEEL AND SHEET AND PART THUS MADE Russian patent published in 2016 - IPC C21D8/02 C21D6/02 C22C38/04 C21D1/19 

FIELD: process engineering.

SUBSTANCE: invention relates to production of sheets. To produce the steel sheet of martensite structure wherein the average staff size smaller than 1 mcm, average factor of staff elongation of 2-5, elastic limit over 1300 MPa, ultimate strength of (3220(C)+958) MPa, where C is the carbon content in wt %, the semi-finished blank is made which contains the following elements in wt %: 0.15≤C≤0.40; 1.5%≤Mn≤3%; 0.005≤Si≤2; 0.005≤Al≤0.1; 1.8≤Cr≤4; 0≤Mo≤2. Note here that 2.7≤0.5(Mn)+(Cr)+3(Mo)≤5.7; S≤0.05; P≤0.1, and not obligatorily: 0≤Nb≤0.050; 0.01≤Ti≤0.1; 0.0005≤B≤0.005; 0.0005≤Ca≤0.005, iron and unavoidable impurities making the rest. Produced semi-finished blank is heated to temperature T₁ making 1050-1250°C. Then, said product is roughed at temperature T₂ of 1000-880°C with the reduction factor ε_a over 30%. Then, the sheet is made with completely recrystallised austenite structure with the grain mean size smaller than 40 mcm, preferably, smaller than 5 mcm. The sheet is cooled to temperature T₃ of 600-400°C at the rate V_R1 exceeding 2°C/s. Then, the sheet, not completely cooled, is subjected to hot finishing at said temperature T₃ with reduction factor ε_b higher than 30% and cooled at the rate of V_R2 which exceeds the critical arte of quenching to martensite.

EFFECT: higher efficiency of the process.

13 cl, 3 dwg, 4 tbl, 2 ex