Metal casting for application

1. Sand casting

Sand casting has a wide range of adaptability, small pieces, large pieces, simple pieces, complex pieces, single pieces, and large quantities can be used. Sand molds have higher refractoriness than metal molds, so materials with higher melting points such as copper alloys and ferrous metals also use this process.

The mold used for sand casting is generally made of wood and is commonly called wooden mold. In order to improve the high dimensional accuracy, aluminum alloy molds or resin molds with long service life are often used. Although the price has increased, it is still much cheaper than the mold for metal casting. In the production of small batches and large parts, the price advantage is particularly prominent.

2. Metal mold casting

When using metal mold casting, the following factors must be considered: long manufacturing cycle, high cost, not suitable for single piece and small batch production; not suitable for casting complex shapes (especially inner cavity), thin-walled and large castings (metal type The mold is limited by the size of the mold material and the capacity of the cavity processing equipment and the casting equipment, so the metal mold is not suitable for the production of particularly large castings) The mold cost is more expensive than the sand mold and cheaper than the die casting.

3. Gravity casting

It is widely used in the production of various non-ferrous castings, but metal mold casting also has disadvantages such as low metal utilization, difficult pouring of thin-walled complex castings, and lower structure density of castings relative to pressure casting.

4. High pressure casting

Because the molten metal fills the cavity under high pressure and high speed, the air in the cavity is inevitably entrapped inside the casting, forming subcutaneous pores, so aluminum alloy die castings are not suitable for heat treatment, and zinc alloy die castings are not suitable for surface spraying. (But can be painted). Otherwise, when the pores inside the casting are heated for the above treatment, they will expand when exposed to heat and cause the casting to be deformed or bubbling.

The machining allowance of die-casting parts should also be smaller, generally around 0.5mm, which can reduce the weight of the casting and reduce the amount of cutting to reduce the cost, and it can also avoid penetrating the dense layer of the surface and exposing the subcutaneous pores, causing the workpiece to be scrapped. .

Due to the loose interior of die-casting parts, poor plasticity and toughness, they are not suitable for manufacturing parts that bear impact loads. The wall thickness of the castings is uniform, and 3~4mm thin-walled castings are suitable, and the maximum wall thickness should be less than 6~8mm to prevent defects such as shrinkage holes. Avoid machining to prevent the internal holes from being exposed.

5. Low pressure casting

The molten metal is filled under pressure, which can improve the fluidity of the molten metal. The casting has good formability, which is conducive to the formation of castings with clear contours and smooth surfaces. It is more beneficial for the formation of large thin-walled castings; the castings crystallize under pressure It solidifies and can be fully fed, so the casting structure is dense, and the mechanical properties are high; the process yield of molten metal is improved, and the riser is generally not needed, which greatly improves the yield of molten metal. Generally up to 90%. Good working conditions, high production efficiency, and easy realization of mechanization and automation are also outstanding advantages of low-pressure casting.

Low-pressure casting has a wide application range for alloy grades, and can basically be used for various casting alloys. Not only for casting non-ferrous alloys, but also for cast iron and cast steel. Especially for non-ferrous alloys that are easy to oxidize, it shows its superior performance, that is, it can effectively prevent the molten metal from oxidizing and slagging during the pouring process. Low pressure casting has no special requirements for mold materials.