Increase the output of extruded aluminum profile by temperature control
If the extrusion pressure of the aluminum profile extrusion press machine plant line is not large enough, it is difficult to smooth extrusion or even the phenomenon of plug die and squeeze, the temperature of the ingot can be increased, but the extrusion speed should be lower to prevent the material's exit temperature from being too high. Each alloy has a specific optimum extrusion (ingot) temperature. Production practice has proved that the temperature of ingot billet is better kept at about 430℃ (extrusion speed ≥16mm/s). The die temperature of 6063 alloy profile must not exceed 500℃, the higher outlet temperature of 6005 alloy is 512℃, the better of 6061 alloy is not greater than 525℃. The output and quality of the product will also be affected by the little change of the die temperature.
The temperature of the extrusion tube is also very important. Special attention should be paid to the temperature rise in the preheating stage to avoid excessive thermal stress between the layers. It is better to make the extrusion tube and the bushing rise to the working temperature at the same time. The heating rate of preheating shall not be greater than 38℃/h. The better preheating specification is: increase to 235℃, hold the heat for 8h, continue to rise to 430℃, hold the heat for 4h, then put into work. This will not only ensure uniform internal and external temperatures, but also allow enough time to remove any internal thermal stress. Of course, heating the extrusion tube in the furnace is the best way to preheat.
During the extrusion process, the temperature of the extrusion tube should be 15 ~ 40℃ lower than that of the billet. If the extrusion speed is too fast, so that the temperature of the extrusion barrel rises to higher than the billet temperature, it is necessary to try to make the temperature of the extrusion barrel drop, which is not only a troublesome work, but also the output will decrease. In the process of increasing the production rate, sometimes the heating element controlled by the galvanic couple will be cut off, but the temperature of the extrusion cylinder continues to rise. If the temperature of the extrusion cylinder is higher than 470℃, the extrusion waste will rise. The ideal extrusion tube temperature should be determined according to the different alloys.
Do not think that preheating the extrusion cylinder is a waste of time and energy. In order to meet the production task, a factory is heated by internal resistance elements on the one hand and liquefied gas burner on the other hand. In this case, the temperature can not be measured and controlled, will produce huge thermal stress, lining temperature is high, expansion faster than the coat, so that the extrusion cylinder split, and hear the sound of "bursting".
The extrusion shaft accumulates internal stress in the process of work, and this stress will produce fatigue cracks to a certain extent. Once subjected to non-axial radial force, it will fracture. Therefore, after the cumulative working time of the extrusion shaft reaches 4500h, it is better to remove the stress once, hold the heat at 430 ~ 480℃ for 12h, and then cool down to below 50℃ with the furnace. Unfortunately, there are very few factories in China to deal with this.
When producing high-grade and high-quality surface building profiles, the extrusion pad temperature should also be strictly controlled to reduce the amount of waste products with inconsistent surface tone. The quality of the fixed extrusion pad is much better than that of the active one, which can accumulate more heat, so it can reduce the end temperature of the ingot, reduce impurities into the profile, and help to improve the output. Castool uses compressed air to cool the extrusion pad and shaft to about 50 ° C.
Mold temperature plays an important role in obtaining high yield, generally not less than 430℃; On the other hand, it should not be too high, otherwise, not only the hardness may decrease, but also oxidation, mainly in the working belt. In the process of mold heating, should avoid mold close to each other, hinder air circulation. It is better to use the box type heating furnace with grid, each mold is placed in a separate box.
The temperature of ingot billet in the extrusion process can be up to 40℃ or higher, the amount of increase mainly depends on the mold design. In ORDER to OBTAIN a larger output, the temperature must not be ignored, should be recorded and strictly controlled, in order to find out the larger output of the machine and the relationship between the temperature.