METHOD FOR PRODUCTION OF TUBULAR ROLLED PRODUCTS OF INCREASED CORROSION RESISTANCE AT A REVERSING MILL Russian patent published in 2019 - IPC C21D8/02 C22C38/12 B21B1/34 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy. Method comprises obtaining continuously cast workpiece from steel containing the following, wt%: C 0.04–0.08; Si 0.15–0.35; Mn 0.7–1.0; Ni 0.2–0.5; Cu 0.4–0.6; Nb 0.02–0.04; Al≤0.03; Mo≤0.01; V≤0.01 %; S≤0.002; P≤0.01 %, content of chromium is set depending on content of copper Cr = k₁*Cu, where k₁=1.3…1.6 – empirical coefficient, iron and unavoidable impurities – balance, and carbon equivalent is C_eq.≤0.39, the workpiece is heated to temperature not lower than 1,200 °C, then performing roughing with deformation end temperature of not less than 960 °C at partial relative reductions in the first two passes of not more than 12 % and with increase of reductions in subsequent passes, providing thickness of intermediate rolled stock in range 4.5–5.5 of thickness of finished rolled metal, intermediate coughing for no more than 1 min, finishing rolling to final thickness at particular relative reductions in first four passes of not less than 20 % with last idle passage at deformation end temperature of not less than 850 °C, accelerated cooling to temperature not higher than 550 °C to obtain fine-grained ferritobainite structure in finished rolled metal, note here that accelerated cooling of finished rolled stock is started not earlier than 20 s after its exit from mill. After its completion, obtained sheets are cooled down to room temperature in package of at least 3 pieces.

EFFECT: raised corrosion resistance of rolled stock at maintaining high strength, ductility and impact viscosity.

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