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1.Process introduction
Sand casting is a traditional casting method, refers to the sand and core sand as the molding material to create the casting, liquid metal in the gravity of filling the casting to produce castings casting method. Due to the inexpensive and easy availability of the molding materials used in sand casting, the mold is easy to manufacture, and the single-piece production, batch production and mass production of castings can be adapted to, for a long time, has been the basic process of casting production.
Sand casting starts with making a sand mold, as shown in Figure 1, then filling the mold cavity with liquid metal and cooling it, and finally knocking off the sand mold to remove the casting, as shown in Figure 2.
2. Process characteristics
The process characteristics of sand casting are shown in Table 1.
Table 1 Process characteristics of sand casting
Characteristics | Parameters |
Part Weight Range /kg | 0. 3 ~ 1000 |
Minimum Thickness /mm | 5 |
Part Shape | Complex Block |
Part Shape Complexity | High |
Part Tolerance /mm | 1~3 |
Surface Roughness Ra/um | 12-25 |
Economic batch /pc | 1-1000 |
3. Process advantages and disadvantages
The advantages of sand casting include:
1) Strong adaptability, wide application, with thousands of common metals and alloys for the manufacture of cast iron parts.
2) There is basically no restriction on the shape, size and weight of the casting; it is possible to cast blanks with very complex shapes and internal cavities, pillars, chamfers, inserts, hollow and variable section thicknesses can be realized.
3) Simple tooling and equipment, low cost, suitable for various production forms.
The disadvantages of sand casting include:
1) One sand type can only be used once, and molding is time-consuming.
2) More processes, some processes are difficult to guarantee quality, so the quality is unstable and easy to form scrap.
3) The grain of the casting is coarse, loose organization, there are often pores, slag and other defects, the mechanical properties are not as good as forgings, so for carrying large loads of important parts are generally not castings.
4) Casting accuracy and its surface roughness is poor, generally need secondary processing, mostly used in the manufacture of rust.
5) It will cause sand and dust pollution, poor labor conditions, and greater environmental pollution.
4. Materials
Steel, iron and most non-ferrous alloy castings can be obtained by sand casting.
5. Economy
The lower cost of equipment and tooling makes it attractive for the production of small batches of castings; the higher cost of automated systems enables the production of complex castings.
6. Typical applications
Sand casting is widely used in machine tool beds, automobile engine blocks, cylinder heads, gearboxes, gear rusts, crankshafts and connecting rods, etc.
A typical application of sand casting is shown in Figure 3.