When the metal is extruded, the non-uniformity of the metal flow will increase with the increase of temperature. During the whole extrusion process, the temperature of the ingot in the deformation zone also gradually increased, and the faster the extrusion speed, the higher the temperature, and the temperature rise can reach about 100C. When the metal temperature in the deformation zone exceeds the maximum permissible critical deformation temperature, the metal will enter the hot brittle state and form an extrusion crack. Therefore, when the ingot temperature is very high, the extrusion speed must be gradually reduced during the extrusion process. 6063 aluminum alloy ingot is generally preheated to 480~520C, extrusion cylinder preheated to 400~450C.

1.3: Profile shape

The influence of size and shape The shape and geometry of the concave profile have an obvious effect on the metal outflow rate of the extruded product. The general rule is: the geometric shape of the product is simple, the symmetry is good, and the product with a small width and thickness ratio can be relatively high; On the contrary, the geometric size of the product is complex, the width and thickness ratio of the large wall thickness difference, and the symmetry of the product should be relatively slow. Under the same conditions, the thinner the wall thickness of the product, the more uniform the deformation of the product along the section, the smaller the tendency of extrusion crack. Therefore, the extrusion speed can be faster.

1.4: Influence of deformation degree

The greater the degree of deformation of the product, the greater the extrusion pressure required, and the greater the heat of metal deformation, so the product flow rate is slower; On the contrary, the degree of deformation is small, the metal flow is uniform, and the extrusion speed can be faster.

1.5: Influence of mold structure

When aluminum alloy profiles are extruded, which type of die core is used is determined by the characteristics of the profiles. Generally, the solid profile uses a flat die, and the hollow profile uses a tongue type or shunt combination die. For 6063 alloy, the flat die has less resistance than the tongue die or the shunt combined die, so the extrusion speed can be higher. For the core of the same structure, the wider the working band of the core, the greater the surface friction between the alloy and the working band, the greater the attached stress on the surface of the product, and the higher the extrusion crack tendency on the surface of the product, so the extrusion speed should be reduced accordingly. Secondly, from the point of view of the surface friction between the metal and the die core working belt, the harder and smoother the die core working belt, the faster the extrusion speed should be.

2: A new process to increase the extrusion speed

The development of modern technology has emerged a new process to improve the extrusion speed, the development of isothermal extrusion, isobaric extrusion, isobaric extrusion, high temperature extrusion, low temperature extrusion and nitrogen cold extrusion and other new extrusion processes.

2.1: isothermal extrusion process

Isothermal extrusion is to automatically adjust the extrusion speed, so that the temperature in the deformation zone is maintained in a constant range, in order to achieve the purpose of rapid extrusion, especially some equipment is also equipped with a microcomputer device to achieve the purpose of automatic control of the extrusion speed.

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