Deformation Analysis of Seamless Pipe during Empty Drawing

There will be deformation when the seamless steel pipe is drawn, and different deformations will occur in different situations, so what deformation does the seamless steel pipe have?

  After emptying, the surface area of the outer surface of the seamless steel pipe increases, while the surface area of the inner surface decreases, and there must be a neutral layer between the inner and outer surface layers. All layers between the outer surface and the neutral layer increase in surface area after deformation, with the outer surface layer increasing the most. The surface area of each layer between the neutral layer and the inner surface decreases after deformation, and the inner surface decreases the most.

The above-mentioned changing nature of the surface area of each layer of the seamless steel pipe during empty drawing affects the inhomogeneity of metal deformation. One of its characteristics is that the natural extension of the layers along the pipe wall is inconsistent. The natural extension is the smallest on the outer surface layer of the seamless steel pipe, the largest on the inner surface layer of the seamless steel pipe, and the natural extension of the middle layers gradually increases from the outer surface layer to the inner surface layer. The second feature is that due to the relationship of integrity, the layers of the seamless steel pipe cannot have different extensions during deformation, so the layers must be mutually restrained.

Since the natural extension of the metal between the outer surface and the neutral layer (called the outer layer) is smaller than that of the metal between the neutral layer and the inner layer (called the inner layer), the outer layer must be restrained by the inner layer during deformation. Its actual extension is larger than the natural extension, and its thickness is reduced due to the increased extension. Instead, the extension of the inner layer is hindered by the outer layer, whose actual extension is smaller than the natural extension, while the thickness increases.

Seamless steel pipe is a steel pipe without weld seams manufactured by hot processing methods such as piercing and hot rolling. The strength and tensile strength of the seamless steel pipe are stronger than that of the welded tube. If necessary, the hot-worked pipe can be further cold-worked to the required shape, size and performance. At present, seamless steel pipe is the most widely used pipe in petrochemical production equipment. 

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