[1] the concept of special-shaped steel tube, rectangular tube, square tube sharp corner: special shaped steel pipe, rectangular pipe, square pipe, stainless steel rectangular pipe, usually with a Turkey head roller with a few square roller to produce. The production mainly depends on the flat rolling integer, because the flat roller is two roller structure, there are four corners of the rectangular pipe roll gap ranging and corner stress state. The problem caused by rectangular pipe four angle tip range, R=1.2t, rectangular tube ruler as radius, f wall thick. Although meet the relevant enterprise standards, but can not meet the user's high quality requirements of the product. The new design uses Turkey head four roll rolling as integer, four roller structure of Turkey with the same head, the four corners of the roll gap is equal to the corner stress state, when the force is large enough, the corner to produce plastic deformation in the metal filled corner, the outer surface of the pipe is formed between the plane intersection with the arc - angle,

[2] angle shaped steel pipe, rectangular pipe, square tube deformation mechanism of cross section in Turkey and four head at the center line, rectangular tube angle and the formation mechanism of ordinary rectangular pipe by bending angle is different, it is on the rolling force of the roller, through the curved arch produce pressure to F, as shown in Fig. 2, make steel corner plastic deformation so that the special-shaped steel pipe, rectangular pipe, square tube filled with a corner. Diagonal filling pressure arch Turkey head four roll at the same cross section in a certain role in the arc strip type (1), to meet the conditions, you can through the corner metal roller pressure to produce plastic deformation, the formation of sharp corners.