2. Select a suitable extruder for production. Before extrusion production, the size of the profile section is determined according to the complexity, wall thickness and extrusion coefficient of the profile section to determine the tonnage of the extruder.
3. Reasonable selection of ingot and heating temperature, homogenization of ingot and strict control of alloy composition of extruded ingot. The company requires ingot grain size to meet high standards to improve plasticity and reduce anisotropy. When there are gas, pores, loose structures or central cracks in the ingot, the sudden release of gas in the extrusion process is similar to "blasting", so some working areas of the die are suddenly loaded and reloaded, forming a huge local impact load. It has a great influence on the mold.
4. Optimize the extrusion process to prolong the service life of the die. In extrusion production, reasonable measures must be taken to ensure the microstructure of the die and adopt appropriate extrusion speed. In the process of extrusion, the extrusion speed should usually 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 zone. Reasonable selection of extrusion temperature. The extrusion temperature is 0, which depends on the spindle temperature and the aluminum bar temperature. If the temperature of the aluminum bar is too low, the extrusion force may increase, or the vehicle may suffocate. The die is prone to local slight elastic deformation or cracking at the stress concentration part, which leads to premature scrapping of the die. If the temperature of the aluminum bar is too high, the metal structure will soften, thus adhering to the surface of the working area of the mold, and even blocking the mold (in severe cases, the mold will collapse under high pressure). The uniform heating temperature of ingot is reasonable at 460-520℃, and the casting is uniform. The reasonable heating temperature of steel ingot is 430-480℃.
5. In the early stage of extrusion, the die must be properly nitrided. It should be noted that surface nitriding cannot be completed at one time. In the process of mold maintenance, it is necessary to carry out 3-4 times of repeated nitriding. In general, the thickness of nitride layer is about 0.15 mm. Clean the mold cavity, and do not leave alkali residue or foreign matter. In general, the number of times of die nitriding is no more than 4-5 times. It should be noted that the early nitriding can be carried out by suitable production technology, and the nitriding times should not be too frequent, otherwise the working area will be easy to delaminate. 6. The working belt on the mold must be polished and polished, and the working belt generally needs to be polished to the mirror surface. The working belt on the mold must be polished. It is usually necessary to grind the working belt until the straightness and verticality of the working belt of the mold are checked before assembly. To some extent, the nitriding quality determines the smoothness of the polishing of the working belt. The mold cavity must be cleaned with high-pressure gas and brush, and there must be no dust or foreign matter. Otherwise, it is easy to pull down the working belt in the metal flow, so that the extruded profile products have rough surface or scribing defects.
6. When extrusion production is carried out, the mold holding time is usually about 2-3 hours. When using the mold, there must be a mold bracket, a mold sleeve and a supporting pad matched with the mold to avoid the die surface caused by the oversized inner hole of the supporting pad. The contact surface of the support pad is too small to deform or break the mold.
7. Use the correct alkali washing (cooking) method. After the mold is removed, the mold temperature is 500℃. If the mold temperature drops rapidly, the mold will crack easily. The correct method is to put the mold in the air of 100- 150℃, and then immerse it in alkaline water after removing the mold. After the extrusion, the extrusion rod retreats in front of the extrusion cylinder, and the pressure in the extrusion cylinder is maintained, and then the extrusion cylinder retreats. At the same time, some residual aluminum in the shunt hole of the die is pulled out and then dealkalized. Chef.
8. The mold is used from low to high and then to low. In the middle and later period of the mold use, because the performance of the mold is basically in a stable state, the application strength can be moderately improved. At the end, the metal frame of the die began to decline, and after long-term production and service, the fatigue strength, stability and toughness began to enter the decline curve. At this time, the use intensity of the mold should be appropriately reduced until the mold is scrapped.
9. Master the use and maintenance records of molds in the extrusion production process, improve the follow-up records of each mold, and enhance the use and maintenance records of molds in the extrusion processing process, which is convenient for management.