HIGH-STRENGTH STEEL STRIP WITH HIGH IMPACT STRENGTH AND YIELD POINT OF 700 MPA AND ITS PRODUCTION METHOD

摘要

FIELD: metal processing.;SUBSTANCE: present invention relates to high-strength steel strip with high impact strength and to method of its production. Steel strip contains, wt %: C 0.03-0.06, Si≤0.30, Mn 1.0-1.5, Al 0.02-0.05, Ti 0.005-0.025, N ≤ 0.006, Ca ≤ 0.005, and several following elements: Cr ≤ 0.75, Ni ≤ 0.40, Mo ≤ 0.30, indigenous inclusion P ≤ 0.020, S ≤ 0.010, the rest - Fe. Method involves vacuum degassing of steel, continuous casting or pressure casting of molten steel, continuous casting is used for slab production and pressure casting is used for bar production. Heating of slab or bar at temperature 1,100-1,250 °C, single or multiple rolling at zone of austenite recrystallization with total reduction factor of ≥ 70 % and rolling end temperature of ≥ 860 °C to produce stell strip. Water cooling at a rate of 15-50 °C/s up to 200-300°C, further air cooling for 5-60 seconds, fast heating of cooled strip in line heating furnace at the rate of 1-10 °C/s up to temperature of 450-550 °C. Tempering is performed during 15-45 seconds following with air cooling outside the furnace.;EFFECT: technical result consists in producing steel strip with thickness of 6-25 mm with yield point of ≥ 700 MPa, elongation of steel A₅₀≥18 %, A_kv≥150 J at -60 °C.;19 cl, 3 tbl, 2 dwg