Silica Sol Precision Casting
process video
1.Definition of Silica Sol Casting
2.Process characteristics
3.Strengths and Weaknesses
4.Process
5.Product Show
Definition of Silica Sol Casting
Silica sol casting refers to the casting method of using fusible materials (such as wax) to make a pattern, coating a number of layers of refractory materials on the pattern to make a mold shell, melting out the pattern after high temperature roasting, can be poured.
Process characteristics
• High dimensional accuracy of castings, low surface roughness, small machining allowances, and even cutting-free machining;
• Can produce more complex geometric shapes of castings;
• Casting materials include carbon steel, alloy steel, stainless steel, copper alloy, aluminum alloy, but the casting cost is twice as high as the water glass casting process;
• There are 3 kinds of wax: medium temperature wax, modified wax and low temperature wax.
The products made with medium-temperature wax have the highest accuracy and the best surface roughness, but the cost is also the highest, and low-temperature wax is the worst and the cost is the lowest.
Strengths and Weaknesses
Strengths
• High dimensional accuracy, small surface roughness value: size CT4-6, surface roughness Ra3.2-12.5 (the smaller the Ra number, the higher the roughness requirements;
• Castings with complex shapes can be cast: typical hollow blades, applied to casting lightweight technology;
• Alloy materials are not limited: all kinds of alloy materials can be used.
• High production flexibility and adaptability: Due to the flexibility of the tooling, the corresponding production is not limited by the batch.
Weaknesses
• The casting size can not be too large: the maximum weight of the casting can be 1000Kg, which is difficult to exceed the weight of the casting;
• The process is complex, long production cycle: pure casting orders are generally 25 days, and the delivery time is determined according to the difficulty of the product.
• The casting cooling rate is slow: the casting grain is coarse, and the carbon steel parts are easy to decarburize.
Product process
1. Preparation of silica sol: Silane is converted into silica sol by sol-gel method, and stable silica sol is obtained after dilution, pH adjustment and other process steps.
2. Mold preparation: Mold is made according to the shape and size of the casting, and its surface treatment is carried out to improve wettability.
3. Gluing: Apply silica sol evenly on the surface of the mold to form a uniform silica sol film.
4. Storage: After a certain period of storage, silica sol forms a dense gel layer.
5. Preheating: Put the mold into the furnace for preheating, and decompose the water and organic matter in the silica sol.
6. Drying: maintain a certain temperature and time when the mold is heated, so that the silica sol solidifies into a silica shell.
7. Casting: Casting, the casting material through high temperature chemical reaction and heating liquid pouring into the silicon shell, and maintain a certain time to solidify.
8. Unloading mold: After the casting is cooled, remove it from the mold.
flow chart
Process Introduction
Mold making
Silicone sol casting molds, also known as compression molds, contain parting surfaces, cavities, cores, top mold mechanism, locking mechanism and so on.
Wax module tree
Dewax
• Dewaxing is the process in which the wax is removed from the mold shell to form the cavity, and the mold shell exists for not less than 24h before dewaxing;
• Dewaxing method: hot water method and high pressure vapor method.
• Precautions for dewaxing: clean up the residual sand on the top of the sprue cup to prevent the floating sand from falling into the cavity.
Pouring
• Common pouring methods: gravity pouring, vacuum injection, centrifugal pouring, low pressure pouring;
• Influence of pouring process parameters on quality: Casting temperature, casting speed, mold shell temperature, casting solidification cooling speed
Heat treatment
| Technology | Purpose |
| Annealing | Reduce the hardness of the metal, easy to process |
| Normalizing | Refine the structure and improve the metal properties |
| Quenching | Increase metal hardness and wear resistance |
| Tempering | Reduce the internal stress and brittleness of the metal, metal quenching metal will exist after a great deal of stress and brittleness, such as not timely tempering will produce deformation or even cracking |
Precision casting finished product process
Product Show
