Basic method of die aluminum extrusion
Basic method of die aluminum extrusion
Positive extrusion (positive extrusion)
During the extrusion process of the mold, the extrusion direction of the product is the same as the extrusion direction of the spoon. The extrusion method is also called forward extrusion, as shown in Figure 1-2a. Features such as simple operation, large production flexibility, and products with excellent surfaces have become one of the widely used methods in forming aluminum and aluminum alloy materials. Forward extrusion can be further subdivided according to other classification methods not shown in Figure 1-3, such as plane deformation extrusion, axisymmetric deformation extrusion and general three-dimensional deformation extrusion, or cold extrusion, warm extrusion, and Hot shirts waiting.
The basic feature of positive extrusion is that there is a large outer ball friction between the blank and the squeeze tube during extrusion. In most cases, this friction is harmful and it makes the metal flow velocity uneven. , Which adversely affects the quality of the extruded product, resulting in uneven tissue performance of the head of the extruded product and the Ministry, the surface layer and the center of life; the energy consumption of the extrusion is increased, and the extrusion The friction energy consumption on the Yuan surface accounts for 30% to 40% of the energy consumption of the extrusion, or even higher; due to the strong frictional heating effect, the increase in the extrusion speed of aluminum and aluminum alloys with low melting points is limited, which accelerates the extrusion Wear of the die.
During metal extrusion, the extrusion where the product flows out of the direction opposite to the direction of the extrusion axis is called compression extrusion, as shown in Figure 145. c.Reverse extrusion is mainly used in aluminum and aluminum joint ventures (there are relatively many applications of small and high strength aluminum alloys) for hot extrusion forming of pipes and profiles, and cold extrusion forming of various aluminum alloy material parts. During the reverse extrusion, the knife slides between the metal blank and the extrusion die, the required extrusion force is small, and the energy consumption of the extrusion is low. Therefore, with the same ability setting, the reverse extrusion can achieve a greater degree of deformation. Extrusion deformation, or alloys with higher resistance to extrusion deformation.
As with the forward extrusion, the metal flow is mainly concentrated in the area near the die hole during reverse extrusion, so the metal deformation is more uniform along the length of the product. However, the reverse extrusion technology and shirt manufacturing are more complicated, the gap time is longer than the positive extrusion, the surface quality of the extruded products is difficult to control, and special extrusion equipment and tools are required. The application of reverse extrusion is limited to a certain extent. However, in recent years, with the development of special reverse compression machines and the development of tooling technology, the reverse extrusion of aluminum alloys has become more and more widely used.
The compound extrusion method combines the characteristics of the forward extrusion method and the reverse extrusion method to produce double cups, cups and rods with round, square, hexagonal, toothed, petal-shaped cross-sections. Extruded parts can also be produced with asymmetrical extruded parts of equal sections. In the composite extrusion method, during the forward extrusion, a part of the ingot blank's flow direction is opposed to the movement direction of the extrusion axis, while the other part of the metal flow direction is opposite to the movement direction of the extrusion axis.