Precision casting is one of the casting methods. Precision casting is a special casting method compared with the traditional casting process. It can obtain relatively accurate shape and high casting accuracy. The more common method is: first, according to the product requirements, design and manufacture the mold (with very small or no allowance) and cast the wax by casting to obtain the original wax mold; Repeat the coating and sanding process on the wax mold, harden the shell and dry it; Then melt the internal wax mold to dewaxing and obtain the cavity; Baking shell to obtain sufficient strength and air permeability; Metal materials required for pouring; Remove the sand after shelling, so as to obtain high-precision finished products. Heat treatment and cold working shall be carried out according to the needs of the product.
1、 What is precision casting of stainless steel
In the production of stainless steel products, when some products have strange shapes and cannot be produced by elbow and other processes, in order to produce such products with irregular shapes (hollow or solid inside), a process of wax mold → sand mold → filling and forming with liquid materials is adopted.
Advantages: products with various styles can be made according to different wax molds.
Disadvantages: the precision of forming blank is not high and the surface roughness is large.
2、 Process flow of precision casting
1. Make molds according to products of different shapes. The molds are divided into upper and lower concave molds, which are completed through comprehensive processes such as turning, planing, milling, etching, electric spark and so on. The shape and size of the pit are consistent with the half of the product. Because wax molds are mainly used for industrial wax molding, aluminum alloy materials with low melting point, low hardness, low requirements, low price and light weight are selected as molds.
2. A large number of industrial wax solid core models are produced by using aluminum alloy molds. Under normal circumstances, an industrial wax solid core model can only correspond to one blank product.
3. The margin around the wax mold shall be refined. After deburring, multiple single wax molds shall be pasted on the pre prepared die head (also known as group tree). This die head is also an industrial wax solid core model produced by wax mold. (looks like a tree)
4. Apply industrial glue to multiple wax molds fixed on the die head and spray the first layer of fine sand (a kind of fire-resistant sand and high temperature resistant, usually silicon sand). The sand particles are very small and fine, which can ensure that the final blank surface is as smooth as possible.
5. The wax mold sprayed with the first layer of fine sand is allowed to air dry naturally at the set room temperature (or constant temperature), but the shape change of the internal wax mold cannot be affected. The time of natural air drying depends on the internal complexity of the product itself. Generally, the first air drying time of precision castings is about 5-8 hours.
6. After the first sand spraying and natural air drying, continue to apply industrial glue (silicon solution slurry) on the surface of the wax mold and spray the second layer of sand. The particle size of the second layer of sand is larger and coarser than that of the previous first layer of sand. After spraying the second layer of sand, let the wax mold dry naturally under the set constant temperature.
7. After the second sand blasting and natural air drying, the third sand blasting, the fourth sand blasting, the fifth sand blasting and other processes shall be carried out by analogy. Requirements: – adjust the number of sand blasting according to the surface requirements, volume and self weight of the product. Generally, the number of sand blasting is 3-7 times- The sand size of each sand blasting is different. Generally, the sand in the later process is thicker than that in the previous process, and the air drying time is also different. Generally, the production cycle of sand on a complete wax mold is about 3 ~ 4 days.
8. Before the baking process, the wax mold that has completed the sand blasting process shall be evenly coated with a layer of white industrial emulsion (silicon slurry) to bond and solidify the sand mold and seal the wax mold, so as to prepare for the subsequent baking process. At the same time, after the baking process, the brittleness of the sand mold can be improved, which is convenient to break the sand layer and take out the blank.
9. In the baking process, the wax mold fixed on the mold head and completed the sand blasting and air drying process is put into a metal closed special oven for heating (usually a steam furnace burning kerosene). Because the melting point of industrial wax is not high, the temperature is about 150 ゜ and the wax mold is heated and melted to form wax. The water flows out along the gate. This process is called dewaxing. The wax mold after wax removal is just an empty sand shell. The key to precision casting is to use this empty sand shell. (generally, this kind of wax can be used repeatedly, but these waxes must be re filtered, otherwise the unclean wax will affect the surface quality of the blank, such as surface sand holes and pits, and also affect the shrinkage of precision casting products).
10. Baking sand shell in order to make the dewaxed sand shell more firm and stable, the sand shell must be baked before pouring stainless steel water. It is usually baked in a furnace with high temperature (about 1000 ゜).
11. Pour the stainless steel water that has been dissolved into liquid at high temperature into the dewaxed sand shell, and the liquid stainless steel water fills the space of the wax mold until it is completely filled, including the mold head in the middle.
12. Since there will be mixed materials of different components in the boiler dissolved in stainless steel, the factory must detect the percentage of materials. Then adjust and interpret according to the required proportion, such as adding those elements to achieve the desired effect.
13. After the liquid stainless steel is cooled and solidified, the outermost sand shell is broken with the help of mechanical tools or manpower to expose the solid stainless steel product, which is the shape of the original wax mold, that is, the blank needed in the end. Then it will be cut and separated one by one, and then rough ground to become a single blank
14. Inspection blank: the blank with sand holes and pores on the surface must be repaired by argon arc welding. If it is serious, it shall be returned to the furnace after cleaning.
15. Cleaning blank: the qualified blank must go through the cleaning process.
16. Carry out other processes until the finished product.
Hebei Junya Precision Machinery Co., Ltd., founded in 2017, is a high-tech enterprise integrating product design, mold development, casting, processing, surface treatment, testing and inspection and sales services. The factory covers an area of 5000 square meters and is located in Huanghua economic and Technological Development Zone, Hebei Province. The company has superior geographical location and convenient transportation. After years of development, the company has introduced advanced production equipment and management experience in various industries, and trained dozens of excellent professional R & D and technical talents.
At present, the company has more than 100 employees and more than 20 technical and R & D personnel. The company’s main products are stainless steel cast pipe fittings, quick connectors, ball valves, check valves, precision accessories, marine hardware, cast auto parts, etc. The product material is mainly 304 304L 316 316L CF8M WCB 1.4408, etc. The company officially passed ISO9000 certification in 2020 and is actively preparing for TS16949 quality system certification. With its good product quality and reputation, the company has become more and more prominent in the international market, with partners all over the world.
In 2019, the export volume accounted for more than 60% of the total sales, and has established long-term and stable cooperative relations with many enterprises in Europe, the United States and Japan. The company always adheres to the business philosophy of heart, innovation and ingenuity. Based on the principle of seeking development from R & D, meeting opportunities in development, building trust in opportunities and consolidating contacts in trust, we look forward to cooperating with you. For details, please contact 18902146189.
Post time: Apr-29-2022
