SHAPED TRIANGULAR TUBE Russian patent published in 2007 - IPC B21C37/08 

FIELD: shaped tube production.

SUBSTANCE: tube has predetermined size of its cross section and rounding zones between joined flat portions. Less consumption of metal and improved strength characteristics of tube are achieved due forming tube cross section in the form of equilateral triangle with inner radiuses of rounding portions r = (0.9 - 1.5) S for tube made of steel with temporary resistance against rupture a_B < 450 MPa and r = (1.6 - 2.0)S if a_B > 450 Mpa where S- thickness of tube and value of relation of tube thickness S to its width B is in range 0.04 - 0.09.

EFFECT: possibility of rational usage of metal at making tube.

2 cl, 1 ex