Applications of metal casting

Sand casting

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

 

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

 

Metal mold casting

When using metal mold casting, the following factors must be comprehensively considered: long manufacturing cycle and high cost, not suitable for single-piece and small batch production; not suitable for casting with complex shapes (especially inner cavities), thin-walled and large castings (metal molds) The mold is limited by the size of the mold material and the capacity of the cavity processing equipment and 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.

 

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 rate, difficulty in pouring thin-walled complex castings, and lower structural density of castings than pressure casting.

 

High pressure casting

Because the molten metal fills the cavity under high pressure and high speed, the air in the cavity is inevitably trapped inside the casting to form subcutaneous pores, so aluminum alloy die castings should not be heat treated, and zinc alloy die castings should not be sprayed on the surface. (but can be painted). Otherwise, the internal pores of the casting will expand due to thermal expansion and cause the casting to deform or bubble when the above-mentioned treatment is performed.

 

The mechanical cutting allowance of die castings should also be smaller, generally around 0.5mm, which can not only reduce the weight of castings, reduce the amount of cutting to reduce costs, but also avoid penetrating the dense layer of the surface, exposing subcutaneous pores, and causing the workpiece to be scrapped .

 

Due to the internal looseness of die castings, poor plasticity and toughness, it is not suitable for the manufacture of impact load parts. The wall thickness of the castings is uniform, metal casting applications 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 exposed internal holes.

 

Low pressure casting

The molten metal is filled under pressure, which can improve the fluidity of the molten metal, and the casting has good formability, which is conducive to the formation of castings with clear outlines and smooth surfaces, which is more favorable for the forming of large thin-walled castings; the castings crystallize under the action of pressure It is solidified and can be fully fed, so the structure of the casting is dense and the mechanical properties are high; the process yield of the molten metal is improved. Generally, no riser is required, so that the yield of the molten metal is greatly improved. Generally up to 90%. Good labor conditions, high production efficiency, and easy mechanization and automation are also outstanding advantages of low-pressure casting.

 

Low pressure casting has a wide range of 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 easily oxidized non-ferrous alloys, it shows its superior performance, that is, it can effectively prevent the molten metal from producing oxidative slag inclusions during the pouring process. Low pressure casting has no special requirements for casting materials.