ã€China Aluminum Network】 1.Ingot heating
For extrusion production, extrusion temperature is a more basic and critical process factor. Extrusion temperature has a great influence on product quality, production efficiency, die life, and energy consumption.
The most important issue in extrusion is the control of the metal temperature. From the beginning of the ingot heating to the quenching of the extruded profile, it must be ensured that the dissolvable phase structure does not precipitate out of the solution or present as small particles.
6063 alloy ingot heating temperature is generally set in the Mg2Si precipitation temperature range, the heating time has an important impact on the precipitation of Mg2Si, using rapid heating can greatly reduce the possible precipitation time. In general, the heating temperature of the 6063 alloy ingot can be set as: ununiformed ingot: 460-520°C; uniform ingot: 430-480°C.
The extrusion temperature varies depending on the product and unit pressure during operation. During the extrusion process, the temperature of the ingot in the deformation zone is changed. With the completion of the extrusion process, the temperature in the deformation zone gradually increases and increases with the increase of the extrusion speed. Therefore, in order to prevent the occurrence of squeezing cracks, the extrusion speed should gradually decrease as the extrusion process progresses and the temperature in the deformation zone increases.
2. Control the extrusion speed of aluminum
The extrusion speed must be carefully controlled during extrusion. The extrusion speed has an important influence on the thermal effect of deformation, the uniformity of deformation, the process of recrystallization and solution, the mechanical properties of the product and the surface quality of the product.
Extrusion speed is too fast, the product surface will appear pitting, cracking and other trends. At the same time, the extrusion speed increases the non-uniformity of metal deformation. The speed of squeezing depends on the type of alloy and the geometry, size, and surface condition of the profile.
6063 alloy profile extrusion speed (metal outflow speed) can be selected from 20-100 meters / min.
With the advancement of modern technology, the extrusion speed can achieve program control or simulation program control, as well as new technologies such as isothermal extrusion technology and CADEX. By automatically adjusting the extrusion speed to maintain the temperature of the deformation zone within a certain constant range, the purpose of rapid extrusion without cracking can be achieved.
In order to increase production efficiency, many measures can be taken in the process. When induction heating is used, there is a temperature gradient of 40-60°C (gradient heating) along the length of the ingot. During extrusion, the high temperature end faces the extrusion die and the low temperature end faces the extrusion pad to balance part of the heat of deformation; Extrusion of the water-cooled die, that is, forced cooling at the back end of the die, tests have shown that the extrusion speed can be increased by 30%-50%.
In recent years, nitrogen or liquid nitrogen has been used to cool molds (extrusion dies) in foreign countries to increase the extrusion speed, improve die life, and improve the surface quality of profiles. In the extrusion process, nitrogen is introduced to the outlet of the extrusion die to rapidly shrink the cooled product, cool the extrusion die and the metal in the deformation zone so that the heat of deformation is taken away, and at the same time, the outlet of the die is exposed to the nitrogen atmosphere. The control reduces the oxidation of aluminum and reduces the bonding and deposition of alumina. Therefore, the cooling of nitrogen improves the surface quality of the product and can greatly increase the extrusion speed. CADEX is a new extrusion process that has been developed recently. It forms a closed-loop system with the extrusion temperature, extrusion speed, and extrusion force in the extrusion process to greatly increase the extrusion speed and production efficiency. More excellent performance.
3. On-machine quenching
The quenching of 6063-T5 is to leave the Mg2Si solid solution in the matrix metal at high temperature and quickly cooled to room temperature to be retained. The cooling rate is usually proportional to the content of the strengthening phase. The 6063 alloy can be strengthened with a smaller cooling rate of 38°C/min, making it suitable for air-cooled quenching. Changing the fan and fan revolutions can change the cooling intensity so that the temperature of the product before the tension leveling is reduced to below 60°C.
4. Tension straightening
After the molding holes are ejected, they are usually pulled by tractors. When the traction machine is working, it takes a certain pulling tension on the extruding product and simultaneously moves with the unloading speed of the product. The purpose of using the tractor is to reduce the length of the multi-line extrusion and scratches, but also to prevent the profile out of the hole after the twisting, bending, tension tension to bring trouble. Tension straightening can not only eliminate the longitudinal shape of the product, but also reduce the residual stress, improve the strength properties and maintain its good surface.
5. Aluminum artificial aging
Aging treatment requires uniform temperature, temperature difference does not exceed ± 3-5 °C. 6063 alloy artificial aging temperature is generally 200 °C. Aging time is 1-2 hours. In order to improve the mechanical properties, there are 180-190 °C aging 3-4 hours, but at this time the production efficiency will be reduced.
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