Lubrication extrusion is usually used for aluminum alloy pipe

With the increase of impact speed of aluminum alloy pipeline, the crater morphology formed by the steel bullet / magnesium target collision pair experienced the transition from spherical crown shape to hemispherical shape → cylindrical + hemispherical shape → hemispherical shape, while the crater morphology of the aluminum bullet / magnesium target collision pair gradually transited from spherical crown shape to hemispherical shape during the impact crater formation process.

The extrudable size range of aluminum alloy pipeline varies with different extrusion methods. The large outer diameter of the aluminum alloy tube extruded by the conventional piercing needle extrusion method is 600-650mm, the small inner diameter is 5-15mm, and the small wall thickness is 2-5mm. Due to the strength and rigidity of the piercing needle, the small inner diameter and wall thickness of extruded aluminum alloy pipe are greatly limited.

Reducing the occurrence of broken pins is the key to realize the production of high-quality pipes by non lubricated extrusion. It is very important to reasonably determine the process parameters, especially the ingot length, to reduce the broken pins. However, the uniaxial tension of the axial specimen can only reflect the axial mechanical properties of the pipe, but can not reflect the circumferential properties of the pipe. In the internal high pressure forming, the aluminum pipe is mainly deformed in the circumferential direction.

Because of the friction between the circumferential specimen and the D-shaped block, the strength obtained by the test is often high. In the conventional internal high pressure forming, the normal stress is usually ignored and the tube is assumed to deform under the plane stress state. In order to obtain the stress-strain curve of the tube under the two-way stress state, scholars at home and abroad have conducted a lot of research on the hydraulic bulging of the tube.