The four steps of die casting

The traditional die casting process mainly consists of four steps, or is called high pressure die casting. These four steps include mold preparation, filling, injection, and sand falling, which are also the basis of various modified die-casting processes. In the preparation process, the lubricant can help control the temperature of the mold. The mold can then be closed and the molten metal injected into the mold with high pressure in a range from 10 to 175 MPa. When the molten metal is filled, the pressure remains until the casting solidifies. Then the putter will push all castings due to one There may be multiple die chambers, so multiple castings may be produced during each casting process. The process of sand falling requires the separation of residue, including mold making opening, flow channel, pouring gate and flying edge. This process is usually done by a special trimming die extrusion casting. Other sand methods include saw and grinding. If the gate is relatively fragile, you can directly throw the cast, which can save manpower. The excess mold-making opening can be reused after melting. The usual yield is approximately 67%.

High-pressure injection fills the mold very quickly, so that the molten metal can fill the entire mold before any part solidifies. In this way, even thin-walled parts that are difficult to fill can avoid surface discontinuity. But this can also cause the air to stay, as it is difficult to escape from filling the mold quickly. This problem can be reduced by placing an vents on the type line, but even a very sophisticated process will holes in the center of the casting. Most die casting can be secondary processing to complete some structures that cannot be completed by casting, such as drilling, polishing.

After the sand is finished, the defects can be checked. The most common defects include the flow retardation (pouring dissatisfaction) and the cold scar. These defects may be caused by the insufficient temperature of the mold or molten metal, mixed impurities in the metal, too little vent, and too much lubricant. Other defects include pores, shrinkage holes, thermal cracks, and flow marks. Flow marks are traces left on the surface of castings by gate defects, sharp corners or excessive lubricant.

Water-based lubricants, known as emulsions, are the most commonly used type of lubricant for health, environmental, and safety concerns. Unlike solvent-based lubricants, removing minerals in the water will not leave by-products in the casting. If the water is left untreated, the mineral in the water can cause surface defects and discontinuity. There are four kinds of water-based lubricants: water oil, oil water, semi-synthetic and synthesis. Water-mixed lubricant is best, because when the lubricant is used, water ols the surface of the mold through evaporation, which can help to release.usually, The ratio of this type of lubricant is 30 parts of water mixed with 1 portion of oil. In the extreme case, the ratio can reach 100:1.

Oils that can be used in lubricants include heavy, animal, plant and synthetic oils. Heavy residual oil is highly sticky at room temperature, but it becomes a thin film at high temperatures in the die-casting process. The addition of other substances to the lubricant controls the emulsion viscosity and thermal properties. These substances include graphite, aluminum, and mica. Other chemical additives can avoid dust and oxidation. An emulsifier can be added to the water-based lubricant, so that the oil-based lubricant can be added to the water, including soap, alcohol, and ethylene oxide.

Long-based lubricants include diesel and gasoline. They benefit casting prolapse, however small explosions occur during each die casting, which leads to the accumulation of carbon on the mold wall. Solvent-based lubricants are more uniform than a water-based lubricant.