After the
sinking drawing, the outer surface area of the
spiral steel pipe manufacturer is increased, and the surface area of the inner surface is reduced, so a neutral layer appears between the inner and outer surface layers, and the outer surface and the neutral layer and all layers between them is increased, but the outer surface is the largest increase. The inner surface and the neutral layer have the largest reduction in the inner surface.
The above-mentioned changing properties of the surface area of each layer of the spiral steel pipe manufacturers during the emptying process affect the non-uniformity of the metal deformation. One of the characteristics is that the natural extension of each layer along the pipe wall is inconsistent. The outer surface layer of the spiral steel pipe manufacturer is the smallest, the inner surface layer of the spiral steel pipe manufacturer is the largest, and the inner layer of the inner layer is naturally extended from the outer surface. The layer to the inner surface layer is gradually increased. The second characteristic is that, due to the overall relationship, the layers of the spiral steel pipe manufacturers cannot have different extensions during the deformation, so the layers must be mutually restrained.
Since the metal of the outer layer naturally extends less than the metal of the inner layer, the outer layer is inevitably subjected to the inner layer during deformation, and the actual extension is larger than the natural extension, and is reduced by increasing the thickness of the extension. Conversely, the extension of the inner layer is hindered by the outer layer, which actually extends less than the natural extension and increases in thickness.
