I. Work Flow of Aluminum Extruder
1. Check whether the oil pressure system leaks oil and the air pressure is normal.
2. Check whether the conveyor belt, cooling bed and storage table are damaged or scratched.
3. Before stretching, ensure the length of aluminum profile. At a predetermined stretching rate, that is, the moving position of the main chuck, the stretching rate of 6063T5 is usually 0.5%- 1%, and that of 606 1T6 is 0.8%- 1.5%.
4. According to the shape of aluminum profile, determine the clamping mode. Large cross-section hollow profiles can be inserted into drawing pads, but sufficient clamping area should be ensured as far as possible.
5. When the aluminum profile is cooled to below 50 degrees, the profile can be stretched.
6. When profile colleagues have bending and distortion, they should correct the distortion first and then stretch.
7. Pull the first heel and the second heel to confirm whether the predetermined stretching rate and clamping method are appropriate. Visually check the bending and twisting, check the plane gap, flare and parallel opening of the profile, and adjust the drawing rate appropriately if it is not suitable.
8. If the normal stretching rate still can't eliminate the bending and twisting, or the geometric dimension is unqualified, the operator shall be informed to stop the extrusion.
9. The profiles on the cooling table should not rub, collide and overlap with each other to prevent scratches.
2. Matters needing attention of aluminum profile extrusion die
1. The cross section of aluminum profile itself is ever-changing, and the aluminum profile extrusion industry has developed to this day. Aluminum alloy and aluminum profile have ever-changing cross sections, which have important advantages such as clear fuselage and good strength. At present, aluminum profiles are used in many industries to replace the original materials. Because of the particularity of some profiles and the particularity of section, it brings difficulties to the design and manufacture of dies. If the conventional extrusion method is still used, it is often difficult to achieve the rated output of the die. Only by adopting special technology and strictly controlling various production process parameters can normal production be achieved.
2. Select a suitable extruder for production. Before extrusion production, the size of profile section is determined according to the complexity, wall thickness and extrusion coefficient of profile section.
3. Reasonable selection of ingot and heating temperature, homogenization of ingot and strict control of alloy composition of extruded ingot. Enterprises require ingot grain size to reach the first-class standard to enhance plasticity and reduce anisotropy. When there are gas, holes, loose structures or central cracks in the ingot, the sudden release of gas in the extrusion process is similar to "blasting", which makes the local working area of the die suddenly unload and reload, forming a local huge impact load, which has a great influence on the die.
4. Optimize the extrusion process to prolong the service life of the die. In extrusion production, reasonable measures must be taken to ensure the structure and performance of the die, and appropriate extrusion speed should be adopted. In the process of extrusion, the extrusion speed should generally be controlled below 25 mm/s. If the extrusion speed is too fast, the metal flow will be difficult to be uniform, which will accelerate the wear of the die working area. The reasonable selection of extrusion temperature depends on the heating temperature of the die, the temperature of the spindle barrel and the temperature of the aluminum bar. Too low temperature of aluminum bar is easy to cause extrusion pressure rise or truck phenomenon, and a small amount of local elastic deformation or crack is easy to appear in the stress concentration part of the die, which leads to premature scrapping of the die. The reasonable heating temperature of aluminum bar is 460-520℃, and the reasonable heating temperature of homogenized ingot is 430-480℃, which will soften the metal structure and make uneven ingot adhere to the surface of die working area or even block the die (when the die collapses under high pressure).
5. Before using the extrusion die, it is necessary to carry out a reasonable surface nitriding process for the die. It should be noted that surface nitriding can not be completed once, and it must be repeated 3-4 times during the service of the mold. Generally, it is required that the thickness of nitrided layer should reach about 0. 15 mm, and the mold cavity should be cleaned, and there should be no residue of alkali residue or foreign particles. In general, the nitriding times of the mold shall not exceed 4-5 times. It should be noted that nitriding can only be carried out after proper production technology in the early stage, and the nitriding times should not be too frequent, otherwise the working area will be easy to delaminate.
6. The working belt must be polished and polished before the mold is put on the machine. Generally, the working belt is required to be polished to a mirror surface. Before the mold is installed on the machine, the working belt must be polished and polished. The working belt is generally required to be polished into a mirror surface, and the flatness and verticality of the working belt of the mold should be checked before assembly. The quality of nitriding determines the polishing smoothness of the working zone to a certain extent. The mold cavity must be cleaned with high-pressure air and brush, and there must be no dust or impurities. Otherwise, the working area will be easily pulled by metal flow, and the extruded profile products will have defects such as rough surface or scribing.
7. During extrusion production, the heat preservation time of the die is generally about 2-3 hours. When using the mold, there should be a mold bracket, a mold sleeve and a support pad matched with the mold, so as to avoid the deformation or fracture of the mold because the inner hole of the support pad is too large and the contact surface between the mold outlet surface and the support pad is too small.
8. Adopt the correct alkali washing (mold boiling) method. The mold temperature is 500℃ after the mold is removed. If the mold temperature drops rapidly, the mold is easy to crack. The correct method is to place the mold in air at100-150 C, and then immerse it in alkaline water. After the extrusion, the extrusion rod retreats in front of the extrusion cylinder, and the residual pressure remains in the extrusion cylinder, and then the extrusion cylinder retreats, so that part of the residual aluminum in the die shunt hole is pulled out at the same time with the residual pressure, and then alkali cooking is carried out.
9. The service strength of the mold is from low to high and then to low. In the middle period of mold use, because the performance of the mold has been basically in a stable state, the use strength can be appropriately improved. In the later stage, the metal structure of the die has begun to deteriorate, and the fatigue strength, stability and toughness have begun to enter a downward curve after long-term production and service. At this time, the use intensity of the mold should be appropriately reduced until the mold is scrapped.
10. Strengthen the use and maintenance records of dies in the extrusion production process, improve the tracking records of each set of dies, and strengthen the use and maintenance records of dies in the extrusion production process to facilitate management.