Raw material effect the quality of investment casting

In a large extent the raw material determines the casting quality in the process of investment casting. High quality material will not necessarily increase the production cost of castings. Today we will discuss four kinds of important material that are used during lost wax casting.

1.Metal Material.

For a precision casting enterprise the main metal material comes from outsourcing in the market and wastage from production line. The purchased metal material tends to be bulk, seldom in the form of a tube, and different materials can be easily confused, such as 316 material mixed with 304 or 430 material. So we suggest the foundry to buy the metal material in form of cylindrical shape as far as possible in order to avoid the mixing up of different materials. For each batch of purchasing material it is needed to check the chemical composition by a spectrum analyzer. If possible, the foundry shall conduct a field investigation to evaluate whether the materials are labeled, protected and stored in isolation.

For the waste steel (wasted castings, pouring risers) from production line shall be treated with rust removal, oil removal, sand cleaning, cleaning and drying, and the composition of S and P shall be strictly controlled. And, the scrap of different material should be marked, protected and separately stored.

2. Mould material.

The performance index of die material mainly includes: melting temperature and solidification temperature range, heat resistance, thermal expansion rate and shrinkage rate, strength, hardness, viscosity, fluidity, coating and ash, etc. It is difficult for precision casting enterprises to test these performance indexes one by one. Therefore, when selecting the supplier, the foundry shall select some regular enterprises with relatively perfect quality management systems as far as possible and strictly evaluate the suppliers.  However, as one of the most important performance indicators of mold material -- shrinkage, it can be detected, which directly affects the size accuracy of casting and the quality of mold shell.

3. Silica sol

The physical and chemical parameters of silica sol mainly include: SiO2 content, density, Na2O content, PH value, kinematic viscosity, colloid particle diameter, etc. These physical and chemical parameters mainly affect the strength of shell, coating stability and coating powder to liquid ratio. Since it is difficult for precision casting enterprises to detect these physical and chemical parameters, on the one hand, selection, evaluation and confirmation of suppliers should be strengthened; on the other hand, silicon sols of different specifications should be selected for the surface layer and the back layer, such as s-830 silicon sols for the surface layer and s-1430 silicon sols for the back layer.

4. Surface coating

Precision foundries often choose zirconium powder as a coating. When zirconium powder contains oxide impurities, the decomposition temperature will drop, and amorphous SiO2 will be precipitated out. Chemical reaction will occur between zirconium powder and some elements in the metal, causing "pitting" and other defects on the surface of the casting and worsening the surface quality of the casting. Moreover, the particle size and distribution of zirconium powder also have a direct impact on the powder to liquid ratio. Therefore, the selection of suppliers should be strictly controlled. The application shows that the quality of Australian zirconium powder is better.

To make investment casting parts with high quality, it is necessary to control the raw materials from the origin. Sieg-Huao has done very well in this point and that is why we have achieved great success in the casting field. Welcome to send us inquiries if you have any casting demands. We shall give you best quality and best price!