METHOD FOR MAKING COILS OF HOT ROLLED TUBE STEEL Russian patent published in 2002 - IPC

FIELD: ferrous metallurgy, namely, manufacture of coils of low-alloy hot rolled steel with especially small content of sulfur and phosphorus for making electrically welded tubes of oil and gas pipelines. SUBSTANCE: method comprises steps of melting in oxygen converter low-carbon steel containing, mas. %: carbon, no more than 0.010; silicium, 0.10-0.50; manganese, 1.0-1.8; sulfur, no more than 0.005; phosphorus, no more than 0.005; chrome, 0.1; nickel, 0.1; copper, 0.03; aluminium, 0.02-0.04; titanium, no more than 0.02; niobium, 0.04-0.08; vanadium, 0.04-0.08; nitrogen, no more than 0.007; iron and inevitable impurities, the balance; continuously casting slabs; ending hot rolling of slabs at 800-850 C and cooling steel strips until mean temperature 500-700 C before coiling to tore-like coils at differentiated cooling along length and width of strips; cooling mean portion of strips until temperature lower than that of strip edges and strip end portions by 25-40 C; setting edge width consisting 0.04-0.05 of strip width; setting length of end portions according to condition of forming along height of coil inner and outer zones of elevated temperature with depth of said zones in direction from surface of coil towards annular axis of tore-like coils, said zones are formed by means of strip edges at coiling. Length of end portion forming inner turns of coil consists 0.7-0.8 of length of end portion forming outer turns of coil. EFFECT: possibility for making coils of tube strip steel with predetermined chemical content and uniform mechanical properties along length and width of strips. 2 cl, 2 dwg, 2 tbl, 1 ex