ã€China Aluminum Network】 Due to the variety of aluminum profiles and the complex material flow conditions in the extrusion process, the extrusion die is subjected to severe load conditions, making the development of aluminum extrusion products and the design of the molds a difficult task. The traditional production model that relies on experience design and trial repair can no longer meet the needs of modern economic development. In the market economy environment where efficiency is life and quality is the key, aluminum extrusion production enterprises are more concerned with improving the success rate of mold design and processing and extrusion output and yield. In the production of semi-finished products of aluminum and aluminum alloys, extrusion is one of the main forming processes. The quality of extrusion products and the output of aluminum and aluminum alloy extrusion production enterprises have a direct impact on the quality of the extrusion die and the speed of extrusion.
In this situation, how to increase the productivity of the extruder has become a top priority. There are many measures to increase productivity. Increasing the installed capacity, improving the quality of workers, and improving the management level are all effective measures.
First, the main factors affecting product output and quality 1. The importance of the quality of aluminum rods For aluminum profiles with high quality requirements, the quality of aluminum rods directly affects the quality and yield of products, alloying, graining, refinement A homogenized, high-quality ingot can reduce mold losses, increase effective production time, and increase extrusion speeds to achieve greater throughput.
2. Advanced Equipment and High-Quality Workers are the Prerequisites for Increasing Outputs To improve the output of extruded products, advanced equipment, high-quality workers, and modern scientific management play a crucial role.
3, the importance of the mold reasonable mold design, timely nitriding to improve the hardness and smoothness of the mold work belt, reduce the number of mold change, reduce non-labor time, improve product quality and reduce waste rate, to achieve greater production is very important .
4. Significant relationship between temperature control and increased production Generally, if there is no unplanned downtime, the larger output is mainly determined by the extrusion speed, while the latter is subject to four factors, three of which are fixed. The latter factor is that the temperature and its degree of control are 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 aluminum alloy passed is increased by 35-62°C. The third factor is the characteristics of the extruded alloy, which is an uncontrollable factor limiting the extrusion speed. The exit temperature of the profile cannot exceed 540°C in general, otherwise, the material surface The quality will decrease, 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 extruder is not enough, it is difficult to smoothly squeeze or even appear plug phenomenon and can increase the billet temperature, but the extrusion speed should be lower to prevent the outlet temperature of the material 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 die temperature of 6063 alloy profile shall not exceed 500°C, and the die temperature of 6061 alloy profile should not exceed 525°C. The slight change in die temperature will also affect the product's output and quality.
It is also very 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 raise the barrel and bushing to the working temperature at the same time. 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 element controlled by the electric couple will be cut off, but the temperature of the extrusion cylinder 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.
When producing high-quality surface profiles, the extrusion pad temperature should also be strictly controlled to reduce the amount of surface inconsistent 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.
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 during the extrusion process can be up to about 40°C or more, and the increase is mainly determined by the mold design. In order to obtain larger production, the temperature must not be ignored, and each temperature should be recorded and strictly controlled to find out the relationship between the larger output of the machine and the temperature.
Later, the employees of the extrusion plant should bear in mind that the precise control of the temperature is crucial to increase production.
Second, improve the product yield and quality of the main ways because the product output and quality mainly depends on raw materials, equipment and molds, appropriate process parameters set, the quality of workers. The specific ways to increase the output and quality of products and reduce the amount of waste products are as follows:
Select alloyed, grained, refined and homogenized high quality ingots;
Optimize the mold design, timely nitriding to improve the hardness and smoothness of the mold working belt, reduce the number of mold changing, and reduce the non-work efficiency;
Lengthening billet, reducing the amount of excess pressure;
The use of heat shear increases the metal yield;
Saw off at the weld of the profile, select the appropriate length of the ingot and the length of the extrusion;
Reduce the temperature of the ingot and increase the extrusion speed to ensure the outlet temperature.
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