METHOD FOR PRODUCTION OF COLD-ROLLED PIPES OF LARGE AND MEDIUM DIAMETRES OF HARDLY-DEFORMED GRADES OF STEELS AND ALLOYS WITH HIGH ACCURACY BY WALL Russian patent published in 2010 - IPC B21B23/00 B21B3/00 B21C37/08 

FIELD: technological processes.

SUBSTANCE: invention relates to pipe-rolling production, namely to method for production of cold-rolled pipes of large and medium diametres from hardly-deformed grades of steel and alloys from welded straight-line-seam conversion tubular billets, and may be used in production of cold-rolled pipes of large and medium diametres of high accuracy by wall in HPT 250 and HPT 450 mills. Method includes forming of sheet billet in rolls into tubular conversion billet for rolling of commercial or conversion pipes of large diametre, welding of longitudinal edges by a consumable electrode under a layer of flux, thermal treatment of conversion straight-line-seam tubular billet and rolling in mandrel in gauges with alternating radius, at the same time conversion tubular billet is rolled into commercial cold-rolled pipe of maximum diametre with drawing of 1.4-1.7 and pressing along wall of at least 25 %, high values of drawing and wall pressing are accepted for steels with high total content of chrome and nickel, in process of further rolling the drawing is gradually increased by 0.05-0.10 up to 1.7-2.0, and conversion tubular billet is rolled into commercial or conversion cold-rolled pipe of maximum diametre with ratio of diametre to thickness of pipe wall D/S=40-50, which in process of further rolling is rolled into pipes of smaller diametre with increase of D/S ratio from 2 to 10, and the last rolling is carried out with D/S=50-75.

EFFECT: invention provides for production of pipes having large and medium diametre from hardly-deformed grades of steel and alloys with high accuracy by wall from welded conversion tubular billets instead of seamless ones, reduction of metal consumption ratio and considerable reduction of cost of cold-rolled pipes.

2 cl, 1 tbl