Investment Casting (Lost-Wax)
- Our stainless steel products are made by investment castings. It is a process that derives its name from the fact that the pattern is invested with a refractory material. Compared to other casting processes such as die casting or sand casting, it is an expensive process. However the components that can be produced can incorporate intricate contours, and in most cases the components are cast near net shape, so requiring little or no rework once cast.
- Investment casting features pattern trees and the repetition of layer-ing process. Pattern trees or clusters are mounted after wax patterns are set, cooled and carefully checked following the coating repetition.
- Investment is produced by three repeating steps: coating, stuccoing and hardening. The first step involves dipping the cluster into a slurry of fine refractory material and then letting any excess drain off. So a uniform surface (prime coating) is produced. This fine material is used first to give a smooth surface finish and reproduce fine details. In the second step, the cluster is stuccoed with a coarse ceramic particle by dipping it into a fluidized bed, placing it by applying by hand or in a rainfall sander. Finally the coating is allowed to harden. These steps are repeated till the investment thickness is achieved which is usually 5 to 15 mm.
- The investment is allowed to completely dry, which can take 16 to 48 hours. It is then turned upside-down and placed in a furnace or autoclave to melt out the wax. The mold is subjected to a burnout, which heats the mold between 870 °C and 1095 °C to remove any moisture and residual wax, and to sinter the mold. Before investment mold is placed cup-upwards into a tub filled with sand. The metal is thereafter gravity poured. In final procedures the shell is hammered to release the casting which will be cleaned up to remove signs of the casting process by grinding.
- Our stainless steel products are made from standard materials AISI #316 or casting grade CF8M, #304 / CF8 and available on request with similar German reference #1.4408, #1.4401, #1.4301 or custom Hastalloy and Monel. Material correctness is closely checked and restored in database, based on which material certificate can be retrieved upon request. As stainless steel is usually chosen for chemical aggressive applications, strict controlling methods like heat-numbered tracing system and penetrating checks are usually organized.