6063 aluminium sheets is widely used in extrusion construction profiles and industrial profiles and is a very good deformation of aluminum alloy. At present, China’s aluminum alloy hot deformation extrusion process has gradually approached mature, but compared with foreign developed countries there is still a big gap.
With the material processing to high-speed, energy saving, continuous direction, many aluminium sheets extrusion manufacturers want to use low-temperature rapid extrusion of new technologies in recent years. Usually 6063 aluminium sheets solid extrusion speed between 15m / min-50m / min, hollow profiles in the 10m / min-35m / min.
If extrusion speed too fast, the surface of the product will appear pitting, cracks and other phenomena and increasing the metal heterogeneity. How to achieve rapid extrusion while ensuring product quality?
1. Excellent design of fast extrusion die
Compared to ordinary aluminium extrusion dies, porthole die requires quick large pressing, which is to ensure adequate supply of material; thin upper die, gives the material a short trip Save; short die land, i.e., the resistance of aluminium to the die is reduced; with the extrusion process is completed, the deformation zone temperature, the faster the extrusion speed, the deformation zone is also temperature rises too quickly, so the mold with the mold cooling system should be to ensure that the extrusion die temperature stability, low-temperature high, to achieve rapid extrusion also ensures mold life and profile quality. In addition, the rapid extrusion die material performance is better.
2. The quality specifications for 6063 aluminium sheets
For the rapid extrusion, aluminium sheets are required to be higher than the ordinary extrusion, aluminium sheets must be all homogeneous, aluminium sheets are not allowed to have oil, mixed. The homogeneous treatment of the alloy can increase the extrusion speed, which can reduce the pressing force by about 6% to 15% compared with the non-homogenized ingot. Mg2Si is almost completely solidified in the matrix, and excess Si will be dissolved or dispersed in fine particles.
Such ingots can be quickly extruded at lower temperatures and achieve excellent mechanical properties and surface brightness. Magnesium is generally controlled at about 0.5%, Mg2Si total control of about 0.82%. When the silicon over 0.01% of the mechanical properties of the alloy σb is about 218Mpa, has greatly exceeded the national standard performance, and excess silicon from 0.01% to 0.13%, σb can be increased to 250Mpa, that is increased by 14.6%.
To form a certain amount of Mg2Si, must first consider the Fe and Mn and other impurities caused by the loss of silicon, that is to ensure that a certain amount of excess silicon. In order to make the 6063 alloy magnesium fully match with the silicon, the actual ingredients must be consciously made of Mg: Si <1.73. The excess of magnesium not only weakens the reinforcement effect, but also increases the cost of the product.
3. Requirements for extrusion equipment
Extruder must have constant speed extrusion and isobaric squeeze control system. The progress of modern technology, extrusion speed can achieve program control or simulation program control, but also the development of isothermal extrusion process and CADEX and other new technologies.
By automatically adjusting the extrusion speed to keep the temperature of the deformation zone within a certain constant range, can achieve rapid extrusion without cracking the purpose, and with the extrusion, no isothermal extrusion control system, high-speed extrusion The actual temperature will be squeezed significantly increased, that is, there is no constant speed extrusion and isothermal extrusion control system, the product of the discharge rate is inconsistent, the surface of the extruded products will appear ripple or even crack extrusion defects, which can not To achieve rapid extrusion.
4. Rrequirements of the way out of the material
After the product is discharged from the mold discharge port, it is necessary to have a traction machine, preferably a double traction, in order to ensure that it can be advanced quickly along the longitudinal balance of the extrusion center line. There is no traction machine traction, the rapid outflow of the product surface may appear similar to the water ripple defects, or make the product partial bending, or even the material blocked.
5. Rapid extrusion of new technology
Rapid extrusion extrusion speed can generally be increased to the general extrusion speed of 2-4 times, experts through more than a year of effort, there are a few die extrusion speed has reached more than 60m / min, to achieve rapid extrusion. Compared with the general extrusion, the rapid extrusion process requires more stringent.
6. The aluminum rod, mold, extrusion cylinder heating requirements
In order to improve production efficiency, in the process can take a lot of measures. Using the induction heating, along the length of the ingot there is a temperature gradient of 40-60 ℃ (gradient heating), squeeze the high temperature side towards the extrusion die, low temperature side towards the extrusion pad to balance a part of the deformation heat.
For extrusion production, extrusion temperature is the most basic and most critical process factors. Extrusion temperature on the product quality, production efficiency, die life, energy consumption and so have a great impact. The most important problem of extrusion is the control of the metal temperature, from the beginning of the aluminium sheets to the extrusion of the quenching of the profile to ensure that the dissolved phase structure does not precipitate from the solid solution or show small particles of precipitation.
6063 alloy aluminum rod heating temperature is generally set in the temperature range of Mg2Si precipitation, the heating time on the precipitation of Mg2Si have an important impact, the use of rapid heating can greatly reduce the possible precipitation time. Aluminium sheetsheating temperature is generally set to 430-460 ℃ die, split mode set to 440-470 ℃, to achieve low temperature fast extrusion.
Mold heating furnace temperature: flat mold temperature 450-480 ℃; split mold 460-495 ℃; mold and split mold mixed heating temperature 460-495 ℃.
The heating temperature of the extruding cylinder is about 50 ℃ lower than the temperature of the aluminum bar, and gradually rises to the specified temperature when heating, so that the temperature of each part is uniform and the inside temperature of the extruder tube is controlled at 380-420 ℃. The outside temperature is higher than the inside temperature, and the temperature difference is controlled within 50 ℃.
7. Process control for rapid extrusion process
Low temperature fast extrusion refers to the extrusion temperature below 450 ℃, and the discharge rate is higher than 60m / min, that is, to ensure that the profile outlet temperature reached direct air cooling quenching temperature conditions, as far as possible to reduce the heating temperature of aluminium sheets, through Improve the extrusion speed, so that the product temperature rise to compensate, in order to achieve the purpose of low-temperature rapid extrusion, which not only improves the production efficiency, but also saves energy.
Compared with the ordinary extrusion method, the low temperature rapid extrusion method has its outstanding advantages: due to the low temperature when the extrusion, blank heating time correspondingly shortened, while the deformation speed, blank deformation time is short, both to save energy, and greatly improved the production efficiency.
