In general, if there is no unscheduled downtime, then *large production is mainly determined by the extrusion speed, while the latter is subject to four factors, three of which are fixed and the other is variable. The first factor is the extrusion force of the extruder. The large pressing force can be squeezed smoothly when the billet temperature is low. The second factor is the mold design. The friction between the metal and the mold wall during extrusion is usually The temperature of the passed aluminum alloy is raised by 35-62 ° C; the third factor is the characteristic of the extruded alloy, which is an uncontrollable factor limiting the extrusion speed. The exit temperature of the profile generally cannot exceed 540 ° C. Otherwise, the surface of the material The quality will drop, the mold marks will be significantly aggravated, and even aluminum, gravure, micro-cracks, tears, etc. will appear. * The latter factor is temperature and its degree of control.
If the extrusion force of the aluminum extrusion press is not large enough, it is difficult to squeeze smoothly or even when the plugging phenomenon occurs, the spindle temperature can be increased, but the extrusion speed should be lower to prevent the material from being exported. Temperature is too high. Each alloy has its own specific *extrusion (slab) temperature. Production practice has proved that the ingot temperature* is well maintained at around 430 °C (extrusion speed ≥ 16 mm / s). The mold release temperature of 6063 alloy profile shall not exceed 500 °C, the *5 high outlet temperature of 6005 alloy shall be 512 °C, and the *60 of alloy 601 shall not exceed 525 °C. Small changes in the temperature of the mold will also affect the yield and quality of the product.
The temperature of the extrusion cylinder is also very important. In particular, the temperature rise during the preheating phase should be noted. Excessive thermal stress should be avoided between the layers. * It is good to raise the extrusion cylinder and the liner to the working temperature at the same time. The preheating heating rate should not exceed 38 °C / h. * Good preheating specification is: increase to 235 ° C, keep warm for 8 h, continue to heat up to 430 ° C, keep warm for 4 h before putting into work. This not only ensures uniform temperature inside and outside, but also has enough time to eliminate all internal thermal stresses. Of course, heating the extrusion cylinder in the furnace is a good preheating method.
During the extrusion process, the temperature of the extrusion barrel should be 15 to 40 ° C lower than the temperature of the ingot. If the extrusion speed is too fast, so that the temperature of the extrusion cylinder rises above the temperature of the ingot, it is necessary to try to lower the temperature of the extrusion cylinder, which is not only a troublesome work, but also the output is lowered. During the increase in production speed, sometimes the heating element controlled by the galvanic couple is cut off, but the temperature of the extrusion tube is still rising. If the temperature of the extrusion tube is higher than 470 ° C, the extruded waste will rise. The ideal barrel temperature should be determined for the different alloys.
Don't think that preheating the extrusion cylinder is a waste of time and energy. In order to catch up with production tasks, a factory is heated by internal resistance elements and heated by a liquefied gas burner. In this case, the temperature cannot be measured and controlled, and huge thermal stress is generated. The temperature of the lining is high, and the expansion is faster than that of the outer casing, so that the extrusion tube is cracked and a "bursting" sound is heard.
The extrusion shaft accumulates internal stress during the working process. This stress will generate fatigue cracks to a certain extent, and will break when subjected to non-axial radial force. Therefore, after the cumulative working time of the extrusion shaft reaches 4500 h, the stress relief treatment is performed once, and the temperature is maintained at 430-480 ° C for 12 h, and then cooled to below 50 ° C with the furnace. Regrettably, few factories in our country deal with this.
When producing high-quality surface building profiles, the temperature of the extrusion pad should also be strictly controlled to reduce the amount of waste inconsistent surface tones. The quality of the fixed extrusion pad is much better than that of the activity, and it can accumulate more heat, which can reduce the temperature of the end of the ingot and reduce the entry of impurities into the profile, which helps to increase the yield. Castool uses compressed air to cool the extrusion pad and the extrusion shaft to a temperature of about 50 °C.
The mold temperature plays an important role in obtaining high yield, generally not lower than 430 ° C; 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. During the heating of the mold, the molds should be avoided and the air circulation should be hindered. * Good use of boxed furnaces, each in a separate box.
The temperature of the ingot during the extrusion process can be increased to about 40 ° C or higher, and the amount of increase is mainly determined by the mold design. In order to obtain * large output, the temperature must not be neglected, the temperature should be recorded and strictly controlled to find out the relationship between the large output of the machine and the various temperatures.
* Afterwards, employees of aluminum extrusion plants should bear in mind that precise control of temperature is critical to increasing production.