MANUFACTURING METHOD OF HOT-ROLLED TUBE STEEL COILS Russian patent published in 2009 - IPC B21B1/26 

FIELD: metallurgy industry.

SUBSTANCE: invention is meant for ensuring mechanical properties which correspond to X52 strength class for hot-rolled steel 4.5-10 mm thick, which is made from steel of tube gauge, which has decreased content of carbon and micro-alloyed niobium, mechanical properties corresponding to strength class. Method involves heating of slab to be hot-rolled, its rolling in roughing and finishing train of wide-strip rolling mill with final rolling temperature of 780-840°C, differentiated cooling of strip surface with water with spraying device at outgoing roller table with delay of water to be supplied to strip and further roll winding. There performed is hot rolling of strip 4.5-10 mm thick made from steel containing 0.04-0.07% C; 0.15-0.25% Si; 0.45-0.60% Mn, micro-alloyed Nb with cooling of its surface with water in inter-stand spaces and on outgoing roller table; at that, rolling in finishing train of wide-strip rolling mill is performed with total relative crimping of not less than 85%; strip cooling on outgoing roller table is performed with delay of water to be supplied to strip surface of not more than 2 seconds, and temperature of strip winding is set within 530-570°C.

EFFECT: eliminating decrease of plasticity and decreasing crack formation during further tube manufacture.

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