TUBE ROLLING METHOD IN PLANT WITH AUTOMATIC MILL Russian patent published in 2006 - IPC B21B17/08 

FIELD: processes for producing seamless tubes in plants with automatic mills.

SUBSTANCE: method comprises steps of heating billet; piercing it to sleeve; rolling sleeve out in automatic mill; rolling it out in rolling out mill and sizing; before rolling in automatic mill, heating leading end of sleeve till temperature exceeding that of sleeve body no more than by 50°C; determining period of such heating according to formula t = (100 x S x (D -S)/a)x (T _{end ah} - T_{end bh})/(T _torch - T _{end bh}) where t - time period of heating, s; S - thickness of sleeve wall, m; D - diameter of sleeve, m; a -thermal conductivity, sq. m /h; T _{end a h} = T + (0 - 50)°C, temperature of sleeve end after heating, °C; T - temperature of sleeve body, °C; T_{end b h} - temperature of sleeve end before heating, °C; T _torch -torch temperature, °C.

EFFECT: improved strength of mandrel, elimination of flaws on inner surface of tubes.