Analysis of factors affecting the extrusion speed of aluminum profiles

The magnitude of extrusion speed is related to factors such as alloy type, ingot state and size, product shape, degree of deformation (or extrusion coefficient), deformation temperature, tool (mold) structure, and process conditions.

1. The influence of ingot quality

The main quality indicators of ingots are first grade grain size, low hydrogen content (below 0.1. mL/100g aluminum), small and fine slag (excluding slag particles above 0.008mm), uniform metallographic structure, no cracks, porosity, pores, and element segregation. In this way, the plasticity and deformability of the ingot are good, the extrusion pressure of the aluminum profile is reduced, and the extrusion speed is increased. Otherwise, it will result in slow extrusion speed and significant mold wear and tear.

2. The influence of extrusion temperature

When metal is extruded, the unevenness of metal fluidity increases with the increase of temperature. During the entire extrusion process, the temperature of the ingot in the deformation zone gradually increases, and the faster the extrusion speed, the higher the temperature, with a temperature rise of about 100 ° C. When the temperature of the metal in the deformation zone exceeds the maximum allowable critical deformation temperature, the metal will enter a hot brittle state and form compression cracks. Therefore, when the temperature of the ingot is very high, the extrusion speed must be gradually reduced during the extrusion process. 6063 aluminum alloy ingots are generally preheated to 480-520C, and the extrusion tube is preheated to 400-450C.

3. Profile appearance

The influence of size and shape on the external dimensions and geometric shape of concave profiles has a significant impact on the metal outflow velocity of extruded products. The general rule is that products with simple geometric shapes, good symmetry, and small aspect ratios can be relatively taller; On the contrary, products with complex geometric dimensions, large aspect ratios, significant differences in wall thickness, and poor symmetry should have relatively slower extrusion speeds. Under the same conditions, the thinner the wall thickness of the product, the more uniform the deformation along the cross-section, and the less likely it is to produce compression cracks. Therefore, the extrusion speed can be faster.

4. Influence of deformation degree

The greater the degree of deformation of the product, the greater the required extrusion force, and at the same time, the greater the heat of metal deformation, so the outflow speed of the product is slower; On the contrary, if the degree of deformation is small and the metal flows uniformly, the extrusion speed can be faster.

5. The influence of mold structure

When extruding aluminum alloy profiles, the type of mold core used is determined by the characteristics of the profile. Generally, solid profiles use flat molds, while hollow profiles use tongue shaped or split combination molds. For 6063 alloy, the flat die has lower resistance than the tongue die or split die combination die, so the extrusion speed can be higher. For mold cores with the same structure, the wider the working band of the mold core, the greater the frictional force between the alloy and the working band surface, and the greater the additional tensile stress generated on the surface of the product. As a result, the tendency for extrusion cracks to occur on the surface of the product is higher. Therefore, the extrusion speed needs to be correspondingly reduced. Secondly, from the perspective of surface friction between the metal and the core working belt, the harder and smoother the core working belt, the faster the extrusion speed should be.