[China Aluminum Industry Network] low-temperature high-speed aluminum extrusion process: low-temperature high-speed is the use of a lower aluminum rod temperature, faster extrusion speed process combination aluminum village extrusion process. The process temperature and speed of the aluminum profile are inversely proportional to each other, that is, the temperature of the aluminum bar is high, the extrusion speed is slow, the temperature of the aluminum bar is low, and the extrusion speed is fast. Under normal circumstances, the temperature of the upper mold is controlled at 420°C-440°C by the temperature of the front rod, and the cooling rate can be accelerated by the third rod. The temperature of the flat rod is maintained at 390-420°C; the aluminum is split. The rod temperature is preferably maintained at 410 to 440°C.
When the aluminum rod reaches a good temperature, the extrusion speed is determined according to the temperature of the discharge port, and the discharge port temperature is preferably 520-560°C. That is, the outlet port temperature should be properly accelerated when the temperature is lower than the preferred temperature, and it should be appropriately decelerated when the outlet port temperature is greater than the preferred temperature. At the same time, it must be ensured that the quality of the billet is acceptable.
There are two problems in the process of low-temperature high-speed extrusion. First, whether the quenching device satisfies the quenching process requirements. Qualified companies can install on-line quenching equipment, and perform quenching, air-cooling, spraying, and water-spraying processes in zones and grades. In order to achieve the basic mechanical properties required for the profile. The second is high-speed extrusion process, especially the tail section, often because the rod temperature increases rapidly with the extrusion process, the metal will have overheating, burning, cracks on the surface of the profile or even pull the phenomenon, resulting in waste many. The current general method to solve this problem is basically to use liquid nitrogen cooling mold technology to reduce the temperature of the deformation zone to solve the problem of deterioration of the surface quality of the blank during rapid extrusion, thereby increasing the yield and ensuring the implementation of low-temperature high-speed extrusion process.
Isothermal aluminum extrusion process: As the name suggests, the so-called isothermal extrusion is a combination of temperature, extrusion speed, under the premise of maintaining the same temperature at the discharge port.
During the extrusion process of aluminum alloy extrusions, the heat generated by the friction and extrusion deformation of the ingot and the extrusion tube causes the temperature of the extrusion material to become higher and higher, and the temperature difference between the aluminum extrusion material and the front and back aluminum is relatively large, leading to the profile along the length direction. If the performance is not uniform, the surface of the aluminum profile will crack easily if the extrusion speed is too high in the later stage of aluminum production. In order to prevent this kind of temperature rise, an isothermal extrusion method is proposed to keep the temperature of the exit of the extrusion material consistent during the extrusion of the aluminum alloy. The isothermal extrusion method is particularly suitable for the production of hard aluminum alloys such as 2000, 7000, and some 5000 series with low critical extrusion speeds, and the profiles (solar frame, polished profile, etc.) with high surface requirements.
First of all, to implement isothermal extrusion is firstly a gradient heating control system for aluminum rods. Ingot temperature heating is to determine the heating temperature gradient of the ingot according to the temperature difference between the front and back of the extruded material in the extrusion process. Ingot heating of the ingot induction furnace is usually divided into several zones along the length of the heating coil. The heating power of each zone is different, the front end of the ingot heating power is high, and the rear end heating power is low, so that the front temperature of the ingot is high and the back end temperature is high. Low ladder temperature heating, the temperature gradient is generally 0-15 °C / 100mm. Long-ingot gas heating usually adopts a gradient cooling method after heating the ingot to make the ingot to form a high temperature gradient before and after the longitudinal direction.
Secondly, aluminum alloy extrusion deceleration control is to gradually reduce the extrusion speed in the middle and later stages of extrusion to reduce the temperature rise of the extrusion material. This deceleration control is generally used for the control of the extrusion speed of soft alloys. The average extrusion speed of this control method is greater than that of ordinary isostatic extrusion.
In addition, it is also possible to adopt zoned heating measures for the squeeze tube. The extrusion tube is also provided with a cooling passage, a spiral groove is arranged near the aluminum extrusion die part on the inside of the extrusion tube outer sleeve (or middle sleeve), and the compressed air is pressed in the middle and later stages to remove the frictional heat between the ingot and the extrusion tube. To control the temperature rise of the ingot.
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