Silica sol casting is a form of investment casting. The process is very similar except that the investment mould is made from silica sol zircon sand mixed with refractory powder.
The silica sol is usually used for shell-building during the lost wax casting process due to its high accuracy and precision. Together with the water glass casting process, silica sol plays an important role in precision investment casting foundry.
From this article you will learn:
- What is Silica Sol Investment Casting?
- Why use Silica Sol Investment Casting?
- Application of Silica Sol Casting
- Silica Sol Investment Casting Products
- Introduction to the Silica Sol Casting Process
- Advantages of Silica Sol Casting
- Basic Parameters of Silica Sol Casting
- Silica Sol Investment Casting Vs Water Glass Investment Casting
- Why Choose Besser Silica Sol Casting Services
1. What is Silica Sol Investment Casting?
Silica sol casting is the casting process that uses silica sol (silica solution) as the binder material to build the casting mold. The metal castings produced by silica sol casting have fine surfaces and high accuracy and the general dimensional tolerance grade is up to CT4 - CT6. And this process is the main investment casting process of RMC for stainless steel castings and alloy steel castings.
2. Why use Silica Sol Investment Casting?
Silica sol investment casting offers several advantages, making it a preferred choice in metal casting:
- Versatility: Suitable for casting a wide range of metals, enhancing its applicability across various industries.
- Intricate Designs: Capable of producing intricate castings with thin walls, ideal for applications requiring complex geometries.
- Smooth Surface Finishes: Provides smooth surface finishes with no parting line, reducing or eliminating the need for extensive machining and finishing.
- Precision in Un-Machinable Parts: Accurately casts complex and un-machinable parts that may be challenging with traditional methods.
- Dimensional Accuracy: Ensures excellent dimensional accuracy, meeting tight tolerances and specifications.
- Cost-Effective: Reduces post-casting machining and finishing requirements, resulting in cost-effective solutions.
3. Application of Silica Sol Casting
Silica sol is mainly used in precision casting, due to its relatively high production cost, but gives very fine precise dimensions, good surface finish, and overall very good quality.
So, when you are looking for a way to produce small parts with high precision, high surface requirements, high corrosion resistance, and don't want to waste time waiting for the quality of your castings to gradually improve, Silica Sol Investment Casting will definitely come to your list of options.
4. Silica Sol Investment Casting Products
5. Introduction to Silica Sol Casting Process
- A metal die is made, the impression being the same as required in the final mould.
- Molten wax is injected into the metal die to create a pattern, allowed to solidify and then removed. Some complex wax patterns are fabricated by joining several separate patterns together using an adhesive.
- The waxes are then assembled on a wax tree, many parts can be put on the tree depending on size, it is common for components to be in the weight range of 0.1kg up to 50kg.
- The tree is then immersed in silica sol zircon slurry to coat the wax, the slurry is exceptionally fine with low viscosity resulting in an excellent as-cast surface finish. The slurry is coated with refractory material and the process is repeated several times until a shell is created around the wax pattern.
- The drying process is critical. The shells must be allowed to dry naturally at a constant temperature to allow the silica sol-gels and refractory particles to bond, the result is a strong, high-quality shell mould. The trees of wax are put into ovens of about 200 degrees to melt out the wax.
- When all wax is removed the trees are heated up to over 1000 degrees to complete preparation for casting.
- The metal is then poured into the hot moulds, which allows the alloy to reach the thinnest sections of the mould before it solidifies.
6. Advantages of Silica Sol Casting
✔ Silica sol investment castings have better size and surface quality, but are more expensive than water glass. Usually twice the cost of water glass.
✔ The silica sol investment casting process uses silica sol zircon sand as the modeling material, and the temperature resistance can reach 2000 degrees. This molding material is very expensive.
✔ The surface quality of silica sol investment castings is very good, very smooth, with very few surface and internal defects.
7. Basic Parameters of Silica Sol Casting
| Dimension Tolerance | ±0.1mm, Ct4~6； |
| Surface Finish | Ra6.3 |
| Wall Thickness Up to | 1mm |
| Unit Weight Extent | 0.1~100kg |
| Unit Size Limit | 0.01~0.5 Meters |
| Degree of Complexity | Very Complex |
| Machining | Less or None Due to Its Accurate Dimension |
| Production Period | Long |
| Production Cost | High |
8. Silica Sol Investment Casting Vs Water Glass Investment Casting
| Aspect | Silica Sol Investment Casting | Water Glass Investment Casting |
|---|---|---|
| Material Used | Silica sol as the binder | Water glass (sodium silicate) as the binder |
| Surface Finish | Superior, smoother surface finish | Rougher surface finish compared to silica sol |
| Dimensional Accuracy | Higher dimensional accuracy and precision | Lower dimensional accuracy, suitable for less intricate parts |
| Mechanical Properties | Better mechanical properties, higher strength | Adequate mechanical properties, lower strength |
| Casting Complexity | Suitable for complex and intricate shapes | Best for simpler, less intricate shapes |
| Application | Aerospace, automotive, medical, and precision engineering | General engineering, agricultural machinery, and construction |
| Cost | Higher cost due to superior quality and precision | Lower cost, more economical for large parts |
| Mold Life | Longer mold life, reusable for more cycles | Shorter mold life, fewer reuse cycles |
| Casting Size Range | Suitable for small to medium-sized castings | Can accommodate larger castings |
| Typical Alloys Used | Stainless steel, carbon steel, alloy steel, and non-ferrous metals | Carbon steel, low alloy steel, and ductile iron |
| Heat Resistance | Higher heat resistance, suitable for high-temperature applications | Lower heat resistance, less suitable for high temperatures |
| Environmental Impact | Lower environmental impact, more environmentally friendly | Higher environmental impact due to the use of water glass |
| Post-Casting Processing | Requires less post-casting processing due to smooth finish | Often requires more machining and finishing work |
Water glass investment casting uses sodium silicate as a binder, resulting in a rougher surface finish suitable for the cost-effective production of larger, less intricate components. In contrast, silica sol investment casting employs a colloidal silica solution for a finer surface finish and higher dimensional accuracy, making it ideal for precision applications in aerospace, automotive, and medical industries.
The choice between the two methods depends on specific requirements, including surface finish, dimensional accuracy, intricacy, and cost considerations.
9. Why Choose Besser Silica Sol Casting Services
As an outstanding investment casting company in China, we have the ability to produce products that meet international quality standards for you. With a large foundry and machining plant, we can provide you with a full range of casting services. From custom pattern design to finished castings and secondary operations including CNC machining, heat treatment and surface treatment, we have it all for you.
Besser Casting works collaboratively with clients to design the pattern and molding method for each custom casting. Request a Quote to get more information on how our casting service can match your project requirements.