Do you know why the die casting will foam? Wo Chi mold to help you analyze and analyze! When the die casting has water marks, cold lines and hot cracks, the solution will penetrate into the crack during plating, and will be converted into steam during the barbecue, and the pressure of the atmosphere will cause the plating layer to foam. (1) Thermal crack: A. When the thickness of the casting is uneven, the stress is generated during the condensation process. B. Premature ejection of metal strength is not enough. C, the top force is uneven. D, too high mold temperature makes the intergranular thick. E. Harmful impurities are present. (2) Water grain, cold grain: During the filling process, the molten metal contact wall that entered first is prematurely condensed, and then the molten metal can not be melted into the condensed metal layer, forming a fold on the surface of the casting, revealing the strip. Lack of shape. The water pattern is usually in the shallow layer of the casting; the cold grain may penetrate into the casting.
The traditional die casting process consists of four steps, or high pressure die casting. These four steps include mold preparation, filling, injection, and falling sand, which are also the basis for various improved die casting processes. During the preparation process, it is necessary to spray a lubricant into the cavity. In addition to helping to control the temperature of the mold, the lubricant can also help the mold to be demolded. The mold can then be closed and the molten metal injected into the mold with high pressure, which is in the range of about 10 to 175 MPa. When the molten metal is filled, the pressure is maintained until the casting solidifies. Then the push rod will push out all the castings. Since there may be multiple cavities in one mold, multiple castings may be produced during each casting process. The doffing process requires separation of debris, including mold openings, runners, gates, and flash. This process is usually done by extruding the casting through a special dressing die. Other doffing methods include sawing and sanding. If the gate is relatively fragile, you can directly drop the casting, which saves manpower. Excess mold openings can be reused after melting. The usual yield is about 67%. High pressure injection results in a very fast filling of the mold so that the molten metal can fill the entire mold before any part solidifies. In this way, surface discontinuities can be avoided even in thin-walled sections that are difficult to fill. However, this also causes air to stay because the air is hard to escape when filling the mold quickly. This problem can be reduced by placing a vent on the parting line, but even a very precise process will leave a hole in the center of the casting. Most die-casting can be done by secondary machining to complete structures that cannot be finished by casting, such as drilling and polishing. Automotive die-casting is a kind of pressure-casting part. It is a pressure-casting mechanical die-casting machine with a casting mold. The metal such as copper, zinc, aluminum or aluminum alloy heated to liquid is poured into the inlet of the die-casting machine. Machine die-casting, casting copper, zinc, aluminum parts or aluminum alloy parts of the shape and size of the mold, such parts are often called die castings.