Precision casting is one of the methods of casting. Precision casting is a special casting method compared to traditional casting techniques. It can achieve relatively accurate shape and high casting accuracy. A common practice is to first design and manufacture molds according to product requirements (with very little or no margin left), and cast wax using casting methods to obtain the original wax mold; Repeat the coating and sanding process on the wax mold, harden the shell and dry it; Dissolve the internal wax mold again to remove wax and obtain the mold cavity; Baking the shell to obtain sufficient strength and breathability; Metal materials required for pouring; After shelling, clear the sand to obtain high-precision finished products. According to product requirements or undergo heat treatment and cold processing.

1、 What is precision casting of stainless steel

When producing stainless steel products, some products have strange shapes and cannot be produced using processes such as bending pipes. In order to produce products with irregular shapes (hollow or solid inside), a process using wax mold → sand mold → liquid material filling and forming is adopted.

Advantages: It is possible to create products with diverse styles based on different wax molds.

Disadvantages: The precision of the formed billet is not high, and the surface roughness is relatively large.

2、 Precision casting process flow

1. Make molds for products of different shapes. The mold is divided into upper and lower concave molds, which are completed through comprehensive processes such as turning, planing, milling, etching, and electrical discharge. The shape and size of the pit are consistent with half of the product. Because wax molds are mainly used for industrial wax pressing, aluminum alloy materials with low melting point, low hardness, lower requirements, cheaper prices, and lighter weight are selected as molds.

2. Produce a large number of industrial wax solid core models using aluminum alloy molds. Under normal circumstances, an industrial wax solid core model can only correspond to one blank product.

3. Refine the margin around the wax mold, remove burrs, and then stick multiple single wax molds onto the pre prepared mold head (also known as the assembly tree). This mold head is also an industrial wax solid core model produced from wax molds. (It looks like a tree in appearance)

4. Apply industrial glue to multiple wax molds that have been fixed on the mold head and evenly spray the first layer of fine sand (a type of refractory sand, high temperature resistant, usually silicon sand). This sand particle is very small and fine, which can ensure that the final rough surface is as smooth as possible.

5. Let the wax mold sprayed with the first layer of fine sand air dry naturally at the set room temperature (or constant temperature), but it should not affect the shape change of the internal wax mold. The time for natural air drying depends on the complexity of the product itself. Generally, the first air drying time for precision castings is about 5-8 hours.

6. After the first sand spraying and natural air drying, continue to apply industrial glue (silica slurry) on the surface of the wax mold, and spray a second layer of sand. The particle size of the second layer of sand should be larger and coarser than that of the previous first layer of sand. After spraying the second layer of sand, let the wax mold air dry naturally at the set constant temperature.

7. After the second sandblasting is completed and naturally air dried, the third sandblasting, fourth sandblasting, fifth sandblasting and other processes are carried out in sequence. Requirement: - Adjust the sandblasting frequency according to the surface requirements, volume size, self weight, etc. of the product. Generally, the number of sandblasting cycles is 3-7- The size of the sand particles used in each sandblasting process is different. Usually, the sand particles in the subsequent process are coarser than those in the previous process, and the drying time is also different. The production cycle for a complete wax mold with sand is generally around 3-4 days.

8. Before the baking process, evenly apply a layer of white industrial latex (silicone slurry) to the completed sandblasting wax mold to bond and solidify the sand mold, as well as seal the wax mold, in preparation for the subsequent baking process. At the same time, after the baking process, it can also improve the brittleness of the sand mold, making it easier to break the sand layer and remove the blank.

9. The baking process places the wax molds fixed on the mold head and completed the sandblasting and air drying process into a specialized metal sealed oven for heating (commonly used as a steam furnace for burning kerosene). Due to the low melting point of industrial wax, the temperature is about 150 degrees Celsius. The wax mold dissolves under heat, forming wax water flowing out along the gate, which is called dewaxing. The wax model that has been dewaxed is just an empty sand shell. The key to precision casting is to use this empty sand shell. (Generally, this type of wax can be reused multiple times, but it must be re filtered, otherwise the unclean wax will affect the surface quality of the blank, such as sand holes and pitting on the surface, and also affect the shrinkage rate of precision cast products.).

10. To make the dewaxed sand shell stronger and more stable, it is necessary to bake the sand shell before pouring stainless steel water, usually in a high temperature (about 1000 degrees Celsius) furnace.

11. Pour the stainless steel water that has been dissolved into liquid at high temperature into the sand shell that has been dewaxed, and the liquid stainless steel water will fill the space previously formed by the wax mold until it is completely filled, including the middle mold head.

12. Due to the mixing of different components of materials in boilers that dissolve stainless steel, the factory must test the material percentage. Then adjust the interpretation according to the required proportion, such as adding elements of those aspects to achieve the desired effect.

13. After liquid stainless steel is cooled and solidified by water, the outermost sand shell is broken by mechanical tools or manual labor, revealing the solid shape of the stainless steel product as the original wax mold shape, which is the final required blank. Then cut and separate them one by one, and rough grind them to form a single blank piece

14. Inspection of raw materials: Raw materials with sand holes and pores on the surface must be repaired by argon arc welding. In severe cases, they should be returned to the furnace after being cleaned.

15. Clean the blank: The blank that has passed the inspection must go through the cleaning process.

16. Perform other processing steps until the finished product is produced.