Stainless steel comes in various grades, some of which are heat treatable, for enhanced mechanical and corrosion resistance properties, which is why stainless steel is commonly used for industrial and commercial investment casting products. The corrosion-resistant characteristics obtained through the stainless steel investment casting process make stainless steel castings an ideal choice for military, medical, and industrial applications.
Lost wax investment casting is the most precise casting method for manufacturing stainless steel castings, especially for those irregular-shaped or complex structured products. Therefore, stainless steel investment casting is almost equivalent to precision casting. The stainless steel investment casting process involves several steps, including mold-making, wax pattern-making, assembly, dipping and dewaxing, pouring, and more.
1. Product design and mold design: This is the first step in stainless steel investment casting. Based on the required product, we design it ourselves or obtain design drawings from our customers.
2. Wax pattern production and inspection: After the mold is prepared, wax is injected into the mold cavity. The wax pattern is then removed from the mold after cooling. The appearance defects of the wax pattern, such as grooves, wax injection nozzles, runners, etc., are inspected and repaired.
3. Assembly: After inspecting the wax pattern, the patterns are welded to the casting system one by one, forming a tree-like structure. Hence, this step is called tree assembly.
4. Shell building: Shell building is a complete silica sol process that repeats, dries, and hardens. First, the assembled tree is immersed in a good colloidal silica coating. Then, refractory sand is applied until it is dry and firm, forming a dense refractory coating surface on the wax pattern surface. This step is repeated 5 to 6 times. Finally, a silica sol shell with a certain strength and fire resistance is obtained.
5. Dewaxing: The shell is placed in a high-temperature oven. The wax inside the shell is melted and drained, leaving a cavity that can be filled with metal. This process is called dewaxing.
6. Pouring: The stainless steel ingot is melted into liquid at high temperature. Then, the liquid is poured into the shell and cooled at room temperature.
7. Cutting and grinding: The rough stainless steel casting is cut and the gating system is removed with a grinder.
8. Surface treatment: Various surface treatments, such as shot blasting, sandblasting, electro-polishing, and mirror polishing, are applied to make the surface smooth.
9. Machining: If the product needs further machining, we need to process it again.
10. Inspection: After production is completed, inspection is carried out. The inspection process for stainless steel investment casting is also an essential process before delivery. Inspection of stainless steel castings includes dimensional inspection, defect inspection, material inspection, and more. Only qualified products can be shipped to customers.