HOT-BENT PIPE AND ITS MANUFACTURING METHOD Russian patent published in 2010 - IPC C22C38/06 B21C37/08 C21D9/08 

FIELD: metallurgy.

SUBSTANCE: welded pipe is heated up to temperature of 900 - 1100°C and its bending is performed. Bent pipe is cooled to 300°C or below with cooling rate of at least 3°C/sec and further drawing is performed within 300 - 500°C. The main pipe metal has the following composition, wt %: C 0.03 - 0.12, Si 0.05 - 0.50, Mn 1.4 - 2.2, S maximum 0.005, Al maximum 0.06, N maximum 0.007, the rest is Fe and impurities, equivalent carbon content (Ceq) is maximum 0.36 %, and crack formation parametre (Pcm) is maximum 0.22 %. Weld metal has crack formation parametre (Pcm) is maximum 0.30 % and contains B maximum 5 ppm, oxygen maximum 300 ppm.

EFFECT: providing excellent strength corresponding to class X70, low-temperature impact viscosity of weld metal, perfect yield point on lower bending side.

9 cl, 2 dwg, 5 tbl, 1 ex