What is Metal Casting?

Metal casting is a process of smelting metal into a liquid that meets certain requirements and pouring it into a mold. After cooling and solidifying and finishing, a casting with a predetermined shape, size and performance is obtained. Because the casting blank is almost formed, the purpose of avoiding machining or small amount of machining reduces the cost and time to a certain extent. Casting is one of the basic processes of modern machinery manufacturing industry.

Metal casting sand casting

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

Sand casting molds, generally made of wood, are commonly known as wooden molds. In order to improve the dimensional accuracy, aluminum alloy molds or resin molds with longer service life are also often used. Although the price has increased, it is still much cheaper than molds for metal mold casting. In small batches and large pieces, the price advantage is particularly prominent.

Metal casting

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

Metal casting gravity casting

It is widely used in the production of various non-ferrous castings. However, metal casting also has the disadvantages of low metal utilization, difficult casting of thin-walled complex castings, and low density of castings compared to pressure casting.

High pressure casting

Because metal liquid fills the cavity under high pressure and high speed, the air in the cavity is inevitably wrapped inside the casting to form subcutaneous pores. Therefore, aluminum alloy die castings should not be heat treated, and zinc alloy die castings should not be spray-coated on the surface. (But paintable). Otherwise, the internal pores in the casting will expand when exposed to heat and cause deformation or bubbling of the casting.

The mechanical cutting machining allowance of die castings should also be made smaller, generally around 0.5mm, which can reduce the weight of the casting and reduce the amount of cutting machining to reduce costs. It can also avoid penetrating the dense layer of the surface and exposing subcutaneous air holes, which will cause the workpiece to be scrapped. .

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

Metal casting

The filling of the molten metal under pressure can improve the fluidity of the molten metal, and the casting has good formability, which is conducive to the formation of clear contour and smooth surface castings, and it is more favorable for the formation of large thin-walled castings; the castings crystallize under the effect of pressure It solidifies and can be fully replenished, so the casting structure is dense and the mechanical properties are high; the process yield of the molten metal is improved, and generally no riser is required, so that the yield of the molten metal is greatly improved, and the yield Generally up to 90%. Good working conditions, high production efficiency, easy realization of mechanization and automation are also the 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 nonferrous 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 metal liquid from oxidizing slag during the pouring process. Low pressure casting has no special requirements for the mold material. ^[3]