Processo de fundição por cera perdida
15 de julho de 2024
As one of the most widely used casting methods, investment casting is also known as lost wax casting, it has been well developed and quite popular for high-quality metal casting designs. It can be used in various industries, such as Agricultural machinery, mining machinery, water treatment system, firefighting system, power system, oil and natural gas industry, food and medical industry. Investment casting adopts the method of disposable wax parts. This is suitable for producing castings with small dimensional tolerance, thin wall thickness, small draft angle and high surface finish. The castings by this method may get high dimensional accuracy and good surface quality, and can often be directly assembled and used without further machining and special treatment.
By using different binder in the slurry, there are water glass casting and silica sol casting crafts, water glass casting are more popular for carbon steel and alloy steel casting and silica sol casting are mainly for stainless steel casting, so the cost is different for each process, should be considered by particular part design.
During the production, the melten wax are injected into special designed pattern, after the wax was cool down, the wax part are formed, weld several wax parts to a wax bar then we get a wax part tree, then the wax trees with clean surface and accurate size are dipped into the slurry and covered with sand, after they are dried, the steps of dipping and covering are repeated several times. Each layer is with varies viscosity of slurry and particle size of the sand. Generally, the surface layer is fine sand, the preparation layer is coarse sand, and the last layer is only with slurry, and no sand is sticked. After the shell is fully dried, dewaxing is carried out with steam or hot water and the mold shell is produced, finally the mold shell is baked to a certain strength. Pour the molten metal into the preheated mold shell, after the casting is solidified, break the shell, trim the part, clean the sand and polish the sprue to obtain the required casting part.
Defects such as shrinkage porosity, shrinkage hold and sand hole are inevitable in investment casting. Therefore, investment casting parts are generally heat treated, so that to reduce the influence of internal defects on the performance of castings.