Low-temperature and high-speed aluminum extrusion process: low-temperature and high-speed is to use a combination of lower aluminum rod temperature and the fastest extrusion speed to carry out the aluminum extrusion process. The process temperature of this aluminum profile is inversely proportional to the speed, that is, the high temperature of the aluminum rod is slow, and the low temperature of the aluminum rod is the fast extrusion speed. Under normal circumstances, the temperature of the first rod produced by the upper die is controlled at 420°C-440°C, and the temperature of the flat die aluminum rod can be cooled and accelerated when the third rod is produced, and the temperature of the flat die aluminum rod is kept at 390~420°C is the best; It is best to keep the temperature of the aluminum rod in the split die at 410~440°C.
When the aluminum rod reaches the optimal temperature, the extrusion speed is determined according to the temperature of the outlet, and the optimal temperature of the outport is 520~560°C. In other words, it is necessary to accelerate appropriately when the temperature of the discharge port is lower than the optimal temperature, and to decelerate appropriately when the temperature is greater than the optimal temperature. At the same time, it is necessary to ensure that the quality of the blank is qualified.
When the aluminum rod reaches the optimal temperature, the extrusion speed is determined according to the temperature of the outlet, and the optimal temperature of the outport is 520~560°C. In other words, it is necessary to accelerate appropriately when the temperature of the discharge port is lower than the optimal temperature, and to decelerate appropriately when the temperature is greater than the optimal temperature. At the same time, it is necessary to ensure that the quality of the blank is qualified.
Isothermal aluminum extrusion process: As the name suggests, the so-called isothermal extrusion is a combination of temperature and extrusion speed under the premise of keeping the temperature of the discharge port consistent.
In the process of aluminum alloy profile extrusion, the temperature of the extruded material is getting higher and higher due to the friction between the ingot and the extrusion cylinder and the heat generated by the extrusion deformation, and the temperature difference between the front and rear of the aluminum extrusion is large, resulting in the uneven organizational properties of the profile along the length direction, and the surface of the aluminum profile is prone to cracks if the extrusion speed is too high in the middle and late stages of aluminum production. In order to prevent this temperature rise, an isothermal extrusion method was proposed to keep the temperature of the extruded material outlet consistent during the extrusion process. The isothermal extrusion method is particularly suitable for the production of duralumin alloys such as 2000, 7000 and some 5000 series with low critical extrusion speeds, as well as for some profiles with high surface requirements (solar frames, polished profiles, etc.).
First of all, to implement isothermal extrusion, the first is the gradient heating control system of aluminum rods, and the ladder temperature heating of ingot is to determine the heating temperature gradient of the ingot according to the temperature difference between the front and back of the extruded material during the extrusion process. The cascade temperature heating of the ingot induction furnace is usually divided into several zones along the length of the heating coil, and the heating power of each zone is different, the heating power of the front end of the ingot is high, and the heating power of the rear end is low, so as to obtain the ladder temperature heating of the front end of the ingot with high temperature and low temperature at the back end, and its temperature gradient is generally 0-15 °C/100mm. Gas heating of long ingots usually adopts the gradient cooling method after heating the ingots out of the furnace, so that the ingots also form a temperature gradient of high before and low in the longitudinal direction.
Secondly, the aluminum alloy extrusion deceleration control is to gradually reduce the extrusion speed in the middle and late stages of extrusion to reduce the temperature rise of the extruded material. This kind of deceleration control is usually used to control the extrusion speed of soft alloy materials, and the average extrusion speed of this control method is greater than that of ordinary isokinetic extrusion.
In addition, it is also possible to take zoned heating measures for the extrusion cylinder. The extrusion cylinder is also provided with a cooling channel, and a spiral groove is set on the inner side of the extrusion cylinder jacket (or middle sleeve) close to the aluminum extrusion die, and compressed air is passed through the middle and late stages of extrusion to take away the friction heat between the ingot and the extrusion cylinder, so as to control the temperature rise of the ingot.
