There are two kinds of investment casting: silica sol and water glass. The surface finish is RA 3.2-6.3 RA 6.3-12.5, and the dimension precision is ISO8062 ct4-6 ct6-8.
The suitable investment material (such as paraffin) is selected to make the investment mold; Repeat the process of dipping refractory coating and spreading refractory sand on the investment mold, harden the shell and dry it; Then the internal investment mold is dissolved to obtain the cavity; Bake the shell to obtain sufficient strength and burn off the residual investment material.
Metal materials required for casting; Solidification cooling, shelling and sand cleaning, so as to obtain high-precision finished products. Heat treatment, cold working and surface treatment according to product requirements.
Sand casting:
In the total casting output, 60-70% of the castings are produced by sand mold, and about 70% of them are produced by clay sand mold. The main reason is that compared with other casting methods, sand casting has the advantages of low cost, simple production process and short production cycle. Therefore, castings such as engine cylinder block, cylinder head and crankshaft are all produced by clay green sand process.
When the wet mold can not meet the requirements, then consider using clay sand surface dry sand mold, dry sand mold or other sand mold. The casting weight of clay green sand casting can be from a few kilograms to dozens of kilograms, while the casting weight of clay dry mold production can reach dozens of tons.
Generally speaking, for medium and large castings, iron castings can be produced by resin self hardening sand mold, steel castings can be produced by water glass sand mold, and castings with accurate size and smooth surface can be obtained, but the cost is high.
Of course, the precision, surface finish, material density, metallographic structure and mechanical properties of sand casting are often poor, so when the requirements of these properties are higher, other casting methods should be used, such as investment casting, die casting, low pressure casting and so on.