Forming method of rectangular steel pipe

Forming method of rectangular steel pipe

The method of forming a round pipe is called bending, and the method of forming a rectangular pipe is called bending. There are two basic methods of bending: solid bending and empty bending.

1.solid bend

The solid bend, as its name implies, compacts the bend, and the inner and outer rollers and the inner and outer walls of the tube blank are compacted in a two-way manner during the real bend.

1) The advantage of solid bending is that the rebound is small, and the forming is accurate. As long as the roll shape is accurate, the R of the inner corner forming is more accurate.

2) The disadvantage of solid bending is the effect of stretching / thinning. First, the actual bending will cause stretching at the bend, and the stretching effect shortens the length of the bending line in the longitudinal direction; second, the metal at the actual bending bend will become thinner due to stretching.

2. empty bend

The empty bending is to form a bending moment through the unidirectional contact between the outer roller and the outer wall of the tube blank to bend the strip. The empty bending will compress the bending line, and the compression effect will cause the bending line to extend longitudinally. This is the compression / thickening effect of void bending.

1) The advantage of empty bending is that the side length bending can be performed when the real bending cannot be performed, such as the simultaneous bending and finishing of the top / side of a rectangular tube. The empty bend can also bend the inner angle of R <0.2t without breaking the pipe wall.

2) The disadvantage of empty bending is that when the rectangular tube is simultaneously and emptily bent on the top / side, due to the simultaneous pressure generated by the upper and lower rollers, the forming force easily exceeds the critical point, causing the instability and indentation of the edges, and it also affects Unit stable operation and molding quality. This is also a different characteristic of rectangular tube and round tube in the empty bending forming.

In practical application, these two basic methods should be configured to a reasonable process position according to the needs of the product in the rectangular tube forming. Attention should be paid to the effect of the stretch / thinning effect of solid bending and the compression / thickening effect of hollow bending on product quality, otherwise the sides of the rectangular tube will be concave when forming, and the finished tube will warp longitudinally, and it will be difficult to correct. straight.