The product uses a die-casting process to complete the blank, CNC machining and polishing treatment, suitable for auto parts.
The essence of pressure casting (referred to as die casting) is to fill the die-casting cavity with liquid or semi-liquid metal at a higher speed under high pressure, and form and solidify under pressure to obtain castings.
Due to the high precision of die-casting parts, it can be assembled and used only after a small amount of mechanical processing, and some die-casting parts can be directly assembled and used. The material utilization rate is about 60%-80%, and the blank utilization rate reaches 90%.
The dimensional accuracy of castings is high, generally equivalent to 6~7, or even up to 4; the surface finish is good, generally equivalent to 5~8; the strength and hardness are higher, and the strength is generally 25~30% higher than sand casting, but it is extended The rate is reduced by about 70%; the size is stable, and the interchangeability is good; it can die-cast thin-walled complex castings. For example, the current minimum wall thickness of zinc alloy die castings can reach 0.3 mm; aluminum alloy castings can reach 0.5 mm; the minimum casting aperture is 0.7 mm, and the minimum pitch is 0.75 mm.
Machine productivity is high. For example, the domestic JⅢ3 horizontal cold-air die casting machine can die-cast 600-700 times in eight hours on average, and the small hot-chamber die-casting machine can die-cast 3,000-7000 times in eight hours on average. The die-casting mold has a long life and one pair of die-casting molds. The die-cast clock alloy has a life span of hundreds of thousands or even millions of times; it is easy to realize mechanization and automation.
Due to the precise size of the die-casting, the surface is smooth and clean. Generally, it is not used for mechanical processing but directly used, or the processing volume is small, so it not only improves the utilization rate of metal but also reduces a large number of processing equipment and man-hours; the price of castings is easy; combination die-casting can be used with other metal or non-metal materials. It saves not only assembly man-hours but also metal.
It is easy to set a positioning mechanism on the die-casting mold to facilitate insert casting of inserts and meet the local special performance requirements of die-casting parts.
In the production, the temperature is often measured to avoid the hammerhead and the cylinder temperature from being too high to cause the hammerhead to jam; the use of materials should choose high-quality alloy materials to avoid the infiltration of impurities, and be careful not to put back the material Let the impurities mix in, so as to prevent the impurities from sticking to the hammerhead and causing the hammerhead to jam
It can be analyzed from the following points: 1. There may be problems with the material, the use of die-casting materials, try to control the proportion of waste not to exceed 30%; 2. The mold is not well opened, one is the unbalanced ejection force; the other is the cooling water Unreasonable opening leads to unbalanced mold temperature, only unreasonable filling flow. 3. Improper selection of process parameters. The main problem of process parameters is an error in retention time and ejection delay time. Mold retention time should not belong, about 3s per mm wall thickness; ejection delay cannot belong, generally 0.5-2s.
It may be silica or alumina ingots that solve the problem. But the biggest possibility comes from the release agent, spraying too much release agent or too high organic content of the release agent. Some of these organic substances are reduced to carbon at the temperature of hot melting aluminum, and some become organic macromolecular polymers. Carbon molecules and polymers are mixed, and when aluminum castings are formed, they are contained on the surface and become black spots that we see.
The clamping between the movable and fixed molds is not tight, and the gap between the two is large, or the clamping force is not enough to cause metal splashing; or the die-casting is motorized or the fixed mold is not installed in parallel; or the support plate span is large and the injection force is caused The sleeve plate is deformed, producing spray material.
At present, the spraying and injection oils are mainly distributed unevenly and gathered locally, resulting in the abnormal composition of the surface aluminum alloy or cold separation mottling, so the phenomenon of post-oxidation patterns appears; the lines of the oxidation pattern are basically the same as those on the die casting. The above is consistent.