[China Aluminum] In general, if there is no unplanned downtime, then the larger output is mainly determined by the extrusion speed, while the latter is subject to four factors, of which three are fixed and the other is variable. The first factor is the extrusion force of the extruder. The extrusion force can be extruded smoothly when the temperature of the billet is low. The second factor is the design of the mold. The friction between the metal and the mold wall during extrusion can usually be achieved. The temperature of the passing aluminum alloy is increased by 35-62°C. The third factor is the characteristics of the extruded alloy, which is an uncontrollable factor that limits the extrusion speed. The exit temperature of the profile generally cannot exceed 540°C, otherwise, the material surface The quality will drop, the pattern marks will obviously increase, and even sticky aluminum, gravure, micro cracks, and tears will appear. The latter factor is the temperature and its degree of control.

If the extrusion force of the aluminum extrusion press is not large enough, it is difficult to smoothly squeeze or even cause the plug phenomenon and it can increase the temperature of the billet when it is not squeezed, but the extrusion speed should be lower to prevent the material from exiting. Temperature is too high. Each alloy has its particular preferred extrusion (got) temperature. Production practice has proved that the billet temperature is better maintained at around 430°C (when the extrusion speed is ≥16mm/s). The temperature of 6063 alloy profile should not exceed 500°C, the higher outlet temperature of 6005 alloy should be 512°C, and the better of 6061 alloy should not exceed 525°C. The slight change in die temperature will also affect the product's output and quality.

It is also important to extrude the barrel temperature. In particular, attention should be paid to the temperature rise in the preheating stage. Excessive thermal stress between the layers should be avoided. It is better to simultaneously raise the barrel and the bushing to the working temperature. The warm-up temperature should not exceed 38°C/h. The preheating specification is better: raise to 235°C, hold for 8 hours, continue to heat up to 430°C, and keep warm for 4 hours before putting it into operation. This will not only ensure uniform internal and external temperatures, but also have enough time to eliminate all internal thermal stresses. Of course, heating the barrel in the furnace is the preferred method of preheating.

During the extrusion process, the extrusion barrel temperature should be 15 to 40°C lower than the ingot temperature. If the extrusion speed is so fast that the temperature of the barrel rises above the billet temperature, it is necessary to try to lower the temperature of the barrel. This is not only a troublesome task, but also the yield is reduced. During the increase of production speed, sometimes the heating elements controlled by the electric couple are cut off, but the temperature of the barrel is still rising. If the barrel temperature is higher than 470°C, the extrusion waste will increase. The ideal barrel temperature should be determined based on the different alloys.

Do not think that preheating the barrel is a waste of time and energy. In order to catch up with the production task, a factory uses internal resistance components to heat it, on the other hand, it uses liquefied gas burners for heating. In this case, the temperature can not be measured and controlled, it will produce a huge thermal stress, the liner temperature is high, the expansion is faster than the jacket, so that the squeeze tube cracks, and hear the "broken" sound.

During the working process, the extrusion shaft will accumulate internal stress, and this kind of stress will generate fatigue cracks to a certain extent, and will break once it is subjected to a non-axial radial force. Therefore, after the accumulated working time of the extrusion shaft reaches 4500h, the stress relieving treatment is preferably performed once. The temperature is kept at 430-480°C for 12 hours, and then the furnace is cooled to below 50°C. Unfortunately, few factories in our country handle this matter.

In the production of high-quality surface construction profiles, the extrusion pad temperature should also be strictly controlled to reduce the amount of inconsistent surface waste. The mass of the fixed extrusion pad is much better than that of the activity, and it can accumulate more heat, so it can reduce the temperature of the billet end, reduce impurities into the profile, and help increase the output. Castool USA uses compressed air to cool the extrusion pad and the extrusion shaft to reduce the temperature to about 50°C.

The mold temperature plays an important role in obtaining a high yield, generally not lower than 430°C. On the other hand, it must not be too high. Otherwise, not only the hardness may decrease, but also oxidation occurs, mainly in the working belt. During the heating of the mold, close contact between the molds should be avoided to obstruct air circulation. It is better to use a grid box furnace, and each mold is placed in a separate box.

The temperature increase of the billet in the extrusion process can reach about 40°C or more, and the amount of increase is mainly determined by the mold design. In order to obtain larger output, the temperature must not be ignored, and each temperature should be recorded and controlled strictly to find out the relationship between the larger output of the machine and various temperatures.

Later, the staff of the aluminum extrusion production plant should keep in mind that: The precise control of temperature is crucial to increase production.

MONEL®