Precision casting silica sol shell (medium temperature wax) shell making process

Precision casting silica sol shell (medium temperature wax) shell making process

This is the internationally recognized precision casting production process, which has the highest casting quality and the lowest repair rate. It is particularly suitable for small and medium-sized parts (2-1000g) with high surface roughness requirements (Ra0.8-3.2) and high dimensional accuracy (CT3-CT5 level). However, due to equipment and cost limitations, it is less commonly used for medium to large items (5-100kg). Today, precision casting manufacturer Tianyao Metal will give you a detailed introduction to the medium temperature wax shell making process.

1、 Existing problems

1. The cost is high, and the production cost of its shell is 8 times that of water glass shell. Compared to low-temperature wax silica sol shell, it is also 25% higher. The main reason is that the cost of shell and wax mold materials is high, and the equipment consumes much more electricity, resulting in a large investment in equipment.

2. The production cycle is the same as that of low-temperature wax silica sol shell, but much longer than that of water glass and composite shell (Table 1).

3. The production of 5-50kg medium and large parts often requires the use of medium temperature liquid wax (65-70 ℃) and high pressure (4.0-7.0MPa) wax injection. Thick walled wax molds are prone to shrinkage, and the dimensional accuracy of castings is not too high. Medium and large parts do not have as high requirements for dimensional accuracy and surface roughness as small parts, so silica sol (medium temperature wax) shells are less commonly used for medium and large parts.

2、 Improvement direction

1. In order to reduce cost and ensure quality, after solving the problem of poor wettability of quartz to medium temperature wax, it is undoubtedly a direction to replace zircon with quartz or fused silica. The thermal expansion coefficient of fused silica is only 5 × 10-7/℃, and its price is only 1/6 of that of zircon. In foreign countries, fused silica has gradually expanded its application range.

2. The use of quick drying silica sol to shorten the shell making cycle is a joint effort of domestic and foreign peers (see above).

Precision machining