What is the deformation of seamless steel tube when it is empty?

After emptying, the surface area of the outer surface of the seamless tube increases, and the surface area of the inner surface decreases, and a neutral layer is required between the inner and outer layers. After the layer deformation between the outer surface and the neutral layer, all increase the surface area, while the outer surface layer increases relatively more. After each layer between the neutral layer and the inner surface is deformed, the surface area decreases, and the inner surface decreases even more. Divide both sides by D to get this formula.

The above-mentioned changing characteristics of the surface area of each layer of the seamless steel tube during the air-drawing process will affect the non-uniformity of metal deformation. One of its characteristics is that the natural extension of each layer along the tube wall is not uniform.

The natural extension treats the outer surface layer of the seamless steel tube as the smaller, and the inner surface layer of the seamless steel pipe as the larger. The surface layer gradually increased to the inner surface layer. Another feature is that due to the integrity, each layer of the seamless steel tube cannot have different extensions during the deformation process, therefore, each layer needs to contain each other. In fact, seamless steel pipes are mainly used for high-precision structural light-duty pipes, such as cracking pipes selected for petrochemicals, drilling pipes selected for petroleum geology, or seamless tubes used in automobiles and tractors. They all have certain high precision requirements.

Since the natural extension of the metal between the outer surface and the neutral layer (called the outer layer) is smaller than the natural extension of the metal between the neutral layer and the inner layer (called the inner layer), the outer layer needs to be Layer drag during deformation. The actual extension of the seamless tube is greater than the natural extension, and as the extension increases, its thickness decreases. In contrast, the extension of the inner layer of the seamless tube is hindered by the outer layer, which actually extends less than the natural extension and increases in thickness.