METHOD OF PRODUCING ROUND ROLLED BARS Russian patent published in 2003 - IPC

FIELD: ferrous metallurgy. SUBSTANCE: method involves hot rolling of steel comprising, wt%: carbon 0.6-1.0, manganese below 1.5, and silicon below 1.0; intensively cooling with water until average temperature is 770-850 C; cooling to average temperature of 750 C for at least time determined from expression: , s, where K_t is empirical coefficient equal to 2.55; D is diameter of rolled bars, mm; Mn is manganese content, wt%; providing further two-staged cooling in air: first stage involving cooling beginning from surface temperature of at least t_a=721-9.8 Mn+28.6 Si, C, where Mn and Si are manganese and silicon content, wt%, until rolled bar surface temperature t_r =(748-196C) plus and minus 10 C, where C is carbon content, wt%, for time not in the excess of 3 s, and second stage involving cooling to temperature not in the excess of t_c=715-196C, C, where C is carbon content, wt%, for time of at least 35 s. Rolled bars are directed for drawing process. EFFECT: increased efficiency, provision for obtaining homogeneous sorbite structure and uniform properties over the entire section and length of rolled product.