Welding forming method of square pipe

Real Bend

Bend is compacted solid bent real-bend tube outer wall and the inner and outer roller compacted bidirectional.

1) The real advantage is that the rebound of small curved, forming an accurate, precise and long roll, inside corner molding R more accurate.

2) There is a drawback of real curved stretch / thinning effects. First, the real cause bends bend tensile stretching effect of the longitudinal length of the bend lines shortened; second, the real turning point curved metal thinning due to stretching.

Empty bend

Empty bend is curved to form a moment outside through a one-way roller contact with the outer wall of the tube so that the strip is bent, air bend bending line will produce compression, longitudinal elongation effect causes the bending line, bending occurs at the metal accumulation thickens this is compressed air bend / thickening effect.

1) The advantage is that you can bend the empty side of the bend in real time can not be bent, such as square tube and rectangular tube on top / side of sync bending and finishing. Empty bend can also bend R <0.2t inside corners without wall fracture.

2) Disadvantages is in the upper air bend / air bend when synchronous side, since the upper and lower rollers while producing pressure forming force easily beyond the critical point, resulting in instability of the concave edge portion, and can also affect the stable operation of units and forming quality. This is also the moment when the tube and the tube side air bend forming different characteristics.