METHOD FOR HOT ROLLING OF LOW-ALLOYED STEEL Russian patent published in 2009 - IPC B21B1/26 

FIELD: technological processes, metal working.

SUBSTANCE: invention is intended for formation of specified narrow interval of mechanical properties along the whole length of hot rolled strip with thickness of 7-12 mm in roll during hot rolling of wide hot-rolled strips mostly from low-alloyed steel with microalloying by carbonitride-forming elements of strength class K52 for further manufacturing of welded pipes. Low-alloyed steel is rolled mainly with carbon content of 0.05-0.11%. Besides, in interstand gaps of finishing continuous group of mill, intensity of water supply to strip is controlled. Formation of mechanical properties is provided by control of temperature-speed parametres of rolling in stands of mill finishing group, and also by temperature mode in process of cooling at outgoing roller table prior to winding of hot strip into roll, when strip cooling speed is indentified from the following expression: V=7.9-0.6*ε, where V is strip cooling speed, degree/s, ε is single relative pressing per pass, %. After strip exits the last stand of hot rolling mill at outgoing roller table, differential cooling of its upper and lower surfaces is done. Besides, water is supplied monotonously to lower surface of strip evenly along its full length, and intensity of water supply to upper surface of strip is defined from the following expression: V_upper=13.9*e^-0.16Hs, where V_upper is speed of upper strip surface cooling, degree/s, H_s is strip thickness.

EFFECT: formation of specified narrow interval of mechanical properties along the whole length of hot rolled strip.

1 ex, 2 tbl