METHOD FOR PRODUCTION OF HIGH-QUALITY PLATE-TYPE COARSE-GRAINED PIPELINE STEEL WITH IMPROVED IMPACT VISCOSITY AT LOW TEMPERATURE

摘要

FIELD: metallurgy.;SUBSTANCE: invention relates to metallurgy, particularly, to production of high-quality plate-type coarse-grained pipeline steel having a portion of viscous component in fracture at impact of impact loads at low temperature of not less than 85 %. Slab with thickness of 320 mm is cast from steel containing the following components, wt. %: C: 0.038–0.058; Si: 0.17–0.27; Mn: 1.65–1.75; P: ≤ 0.01; S: ≤ 0.003; Al: 0.015–0.05; Nb: 0.045–0.055; Ti: 0.006–0.02; Cr: 0.11–0.16; Mo: 0.15–0.20; Cu: 0.10–0.16; Ni: 0.25–0.30; Ca: 0.0005–0.0040; Fe and unavoidable impurities are balance, and having temperature Ar₃, which is 725.73 °C. Slab is heated to temperature of 1150–1170 °C for 10.3–13 minutes per centimeter of slab thickness and held for 45–90 minutes. Slab is rolled to produce sheet with thickness 3.5–4 times less than thickness of slab at odd number of passes. Rough rolling is carried out in two stages at temperature of 810–830 °C, and finish rolling is carried out at temperature 800–830 °C. Degree of reduction at the end of rough rolling is increased to a value of more than 25 %. Rolling involves dephosphorisation in two passes, including dephosphorisation at the first pass of rough rolling and dephosphorisation at the first pass of finish rolling. Sheet is cooled from 750–770 °C feeds low-temperature water, wherein cooling is carried out by laminar cooling using 12 water feed devices. First 4 devices have a maximum water flow rate of 300–350 m³/h, and last 8 devices have a water flow rate of 200–300 m³/h. Performing subsequent self-tempering at temperature 330–420 °C.;EFFECT: production of pipeline steel with required operating characteristics.;5 cl, 1 tbl, 3 dwg