In our life, there are many alloy materials used that are difficult to machine, and the shapes of the parts are so complex that they cannot or are difficult to manufacture by other methods, especially in aerospace and other fields. Stainless steel precision casting, also known as investment precision casting or silica sol process, is a casting process with little or no cutting. It is an excellent process technology in the foundry industry. It is widely used, not only suitable for various types , Casting of various alloys, and the dimensional accuracy and surface quality of the produced castings are higher than other casting methods, and even complex, high temperature resistant and difficult to process castings that are difficult to cast by other casting methods can be cast by investment casting. cast. So how does the stainless steel precision casting process work? The following is an introduction to the stainless steel precision casting process.
1. Make molds according to different shapes of products. The mold is divided into upper and lower concave molds, and is completed through comprehensive processes such as turning, planing, milling, etching, and EDM. The shape and size of the pit are the same as the half of the product. Because wax molds are mainly used for industrial wax pressing, aluminum alloy materials with low melting point, low hardness, low requirements, low price and light weight are used as molds;
2. Use aluminum alloy molds to produce a large number of industrial wax solid core models. Under normal circumstances, an industrial wax solid core model can only correspond to one rough product;
3. Refine the margin around the wax mold. After deburring, stick a plurality of single wax molds on the pre-prepared mold head (also known as group tree). This mold head is also an industrial wax solid produced by wax mold. core model.
4. Coat the multiple wax molds fixed on the die with industrial glue and spray the first layer of fine sand (a kind of refractory sand, high temperature resistance, usually silica sand) evenly. The grains of this sand are small and fine, which ensures that the surface of the final blank 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 cannot affect the shape change of the internal wax mold. The natural air drying time depends on the complexity of the product itself. The first air-drying time of the casting is about 5-8 hours.
6. After the first sand blasting and air drying, continue to apply industrial glue (silica soluble 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 than that of the first layer of sand. Come big, come thick. After spraying the second layer of sand, let the wax mold air dry naturally at the set constant temperature.
7. After the second sandblasting and natural air drying, the third sandblasting, the fourth sandblasting, and the fifth sandblasting are carried out by analogy. Requirements: – Adjust the number of sandblasting according to the product surface requirements, volume size, self-weight, etc. Under normal circumstances, the number of sandblasting is 3-7 times. – The size of the sand in each blasting is different. Usually, the sand in the subsequent process is thicker than the sand in the previous process, and the air-drying time is also different. Generally, the production cycle of sanding a complete wax mold is about 3 to 4 days.
8. Before the baking process, the wax mold that has completed the sandblasting process is evenly coated with a layer of white industrial latex (silicon soluble slurry) to bond and solidify the sand mold and seal the wax mold. Prepare for the baking process. At the same time, after the baking process, the brittleness of the sand mold can be improved, which is convenient for breaking the sand layer and taking out the blank.
9. Baking process: Put the wax mold fixed on the die head and complete the sandblasting and air-drying process into a metal-closed special oven for heating (usually a kerosene-burning steam furnace). Because the melting point of industrial wax is not high, the temperature is about 150゜, the wax mold is heated and melted to form wax water flowing out along the gate, this process is 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 wax can be used many times, but these waxes must be re-filtered, otherwise the unclean wax will affect the surface quality of the blank, such as surface sand holes, pitting, and also affect the shrinkage of the precision casting product).
10. Baking the sand shell In order to make the dewaxed sand shell more firm and stable, the sand shell must be baked before pouring the stainless steel water, usually in a high temperature (about 1000゜) furnace. .
11. Pour the stainless steel water that has been dissolved into a liquid state at high temperature into the dewaxed sand shell, and the liquid stainless steel water will fill the space where the wax mold was formed before until it is completely filled, including the middle part of the die.
12. The factory must detect the percentage of materials because different components of materials will be mixed in the boiler of molten stainless steel. Then adjust the release according to the required ratio, such as adding those aspects to achieve the desired effect.
13. After the liquid stainless steel water is cooled and solidified, the outermost sand shell is smashed with the help of mechanical tools or manpower, and the exposed solid stainless steel product is the shape of the original wax mold, that is, the final required blank. Then it will be cut one by one, separated and rough ground to become a single blank
14. Inspection of blanks: blanks with blisters and pores on the surface must be repaired by argon arc welding, and in serious cases, the waste products should be cleaned and returned to the furnace.
15. Cleaning the blanks: The blanks that have passed the inspection must go through the cleaning process.
16. Carry out other processes until the finished product.
The above is the process flow of stainless steel precision casting, I hope to provide you with reference and help. In addition, although the stainless steel precision casting process can make a variety of products, the precision of the forming blank is not high, and the surface roughness is large, which requires subsequent processing in other processes until the finished product.
Post time: Aug-18-2022