METHOD OF PRODUCTION OF ROLLED PLATES WITH STRENGTH CLASS K80, X100, L690 TO MANUFACTURE ARC WELDED PIPES OF MAIN PIPELINES Russian patent published in 2017 - IPC C21D8/02 B21B1/26 C22C38/54 

FIELD: metallurgical engineering.

SUBSTANCE: steel containing, wt % is produced: C 0.03-0.08, Si 0.10-0.35, Mn 1.75-2.10, Cr 0.01-0.50, Ni 0.01-0.60, Cu 0.01-0.40, Mo 0.01-0.50, Al 0.02-0.05, Nb 0.03-0.09, V 0.001-0.10, Ti 0.010-0.035, S 0.0005- 0.003, P 0.002-0.015, N 0.001-0.008, iron and unavoidable impurities are the rest, with the following relations: 0.15<(Mn+Cr+Cu)/20+Si/10+Ni/60+Mo/15 +V/10<0.18, 2.8%<Mn+Cr+Ni+Cu+Mo+Si<3.5%. The continuous cast ingot is subjected to austenitization at a temperature T_cci+(10-50)°C on the basis of the relation T_cci=lg([C]²⁰⁴⋅[Nb]²³²)+34[Si]-1.5[Mn]-2.7[Cr]+17|3.6-[Ti]/[N]|+1657 withhold time, is calculated by the equation t=(1205-T_a)/0.53±40 min, where t is the hold time, T_a is the selected heating temperature. The preliminary deformation is carried out in such a way that the proportion of static recrystallization during the pauses between the passes is not less than 85%, and the total degree of deformation is not less than 0.9. After this, the tack is chilled to the finish rolling onset temperature, determined from the equation T_f=Ar₃+2700/N±40°C, where N is the final thickness of the sheet, mm, and finishing rolling is carried out to the temperature Ar₃+(0-15)°C. Accelerated cooling of the rolled product is carried out to a temperature of B_f-(20-120)°C, defined by the equation B_f=595-320[C]-15[Cr+Cu+Ni]-25[Mn]-2V_c±50°C. Then the rolling is cooled in air.

EFFECT: meeting of the requirements for strength, plastic and viscous properties, characteristic for the rolled strength of K80, X100, L690.

2 cl, 3 tbl