Forming method of square pipe
1, solid bend
Real bend, as the name implies, is compacted, inside and outside roller and tube billet inside and outside the wall bidirectional compaction.
1) The advantage of solid bending is that the rebound is small, the molding is accurate, and as long as the roller type is accurate, the R of the inner angle molding is relatively accurate.
2) The disadvantage of solid bending is the tensile / thinning effect. First, the real bending will cause the bending to produce a stretch, and the tensile effect will shorten the length of the bending line longitudinal; Second, the metal is thinned by stretching at the actual bend.
2, empty bend
The empty bend is formed by the unidirectional contact between the outer roller and the outer wall of the tube billet to make the material bend. The empty bend will cause the bending line to compress, the compression effect will make the bending line lengthen vertically, and the metal at the bend will accumulate and thicken. This is the compressive / thickening effect of the empty bend.
1) The advantage of an empty bend is that it can be bent when it is impossible to make a real bend, such as simultaneous bending and finishing of the top/side of the square moment tube. Empty bends can also bend R & lt; 0.2 T of the internal angle without fracture of the tube wall.
2) The disadvantage of the empty bend is that when the top / side is synchronized with the empty bend, due to the pressure generated by the upper roller and the lower roller at the same time, the forming force easily exceeds the critical point, resulting in the instability of the edge, and it also affects the stable operation of the unit. And molding quality. This is also a different feature of the square tube and the circular tube when they are formed.