How to Handle Deformation During Cold Drawing of Galvanized Welded Pipes

Galvanized welded pipes can deform when cold drawing is performed. The deformation varies under different conditions. Below, I will provide a detailed explanation of the actual deformation scenarios of galvanized welded pipes.

When the surface area of the inner surface decreases, there must be a neutral layer between the inner and outer surfaces. If the deformation is significant, the surface area of each layer between the neutral layer and the inner surface decreases after deformation, while the inner surface area decreases substantially. This production process is more targeted. Before extrusion forming during billet production processing, extruding to form pipes with a diameter of 100mm requires minimal equipment investment and raw material consumption, making the technology relatively sophisticated. As the pipe size increases, cold extrusion requires high-load and high-power machinery, thus necessitating an upgraded automatic control system.

The planned workpiece or pre-formed blank is fixed on a rotating journal, with pulley pressure applied to the blank, and a radial wheel is used. Through one or more solutions, the entire process can produce various hollow thick-walled rotational body products. Products manufactured using high-precision processing methods exhibit excellent physical properties, a wide range of specifications, simple mold shells and tools, easy replacement, and relatively low production costs.

However, the production time is not long, the production volume is not high, the production line length is relatively limited, and the scale of the machinery and equipment is generally short. The changes in the surface area of each layer of the galvanized welded pipe during evacuation affect the asymmetry of metal deformation. One characteristic is the non-uniform pure natural widening along the wall thickness.

The pure natural widening is minimal at the outer surface and maximum at the inner surface of the galvanized welded pipe. The widening increases gradually from the outer surface to the inner and outer surfaces. The second characteristic is that due to the overall relationship, the layers of the galvanized welded pipe cannot have different widenings during the deformation process, so the layers must control each other.

Because the metal material between the outer surface and the neutral layer has a smaller natural width than the metal material between the neutral layer and the inner layer, the outer layer inevitably undergoes a controlling effect from the inner layer during deformation, which limits its practical activity range compared to pure natural widening. Simultaneously, its thickness decreases because it widens. Conversely, the widening of the inner layer is hindered by the outer layer, resulting in actual widening being less than the natural widening, while its thickness increases.