Investment Casting Process

Investment Casting Process

Investment casting is also known as the "lost-wax"process, is regarded as a precision casting process to fabricatenear-net-shaped metal parts from almost any alloy.

The process begins with preparation of the wax patterns forevery casting made. Wax is injected into an aluminum or steel die to produce apattern that is an exact replica of the part to be produced. The patternsare clustered around a sprue. The cluster is dippedinto a ceramic slurry made by suspending fine ceramicmaterials in silica-sol. The excess liquid is allowed to drain off frompatterns, and then fine zircon sands are stuccoed onthis ceramic coating. Thus a small shell is formed around the wax patterns. After drying, this process of dipping and stuccoing is repeated again andagain, using progressively coarser grades of ceramic material, until aself-supporting shell has been formed. It takes approximately 5 to10 days tomake the mould. When a shell thickness of approximately 6 to 10mm has been built, the molds are dewaxed by autoclaving (pressure and steam). Thisleaves a ceramic shell containing cavities of the casting shape desired withpassages leading to them. The hollow shells are then preheated to 900-1200℃,depending on the alloy to be poured and the molten metal cast immediately intothe hot shell.  After cooling, the ceramic is vibrated and blasted off themetal parts and discarded.  The balance of the cleaning operations (cutoff, grind, heat treat, straightening, blast) arestraight forward and quite similar to the other casting processes.

The process is showas the flow-diagram.

  美工注意：此处放图片01，下面是图片上的文字：

InvestmentCasting Process  Investment Casting Process

Toolsdesign & making  Tools design & making

Waxpatterns injection  Wax patterns injection

Trimming& Inspection  Trimming & Inspection

Assemblythe wax patterns  Assembly the wax patterns

Ceramicshell building  Ceramic shell building

Dewax in steam autoclave  Dewax in steam autoclave

Sinteringthe shells Sinteringthe shells

Melting-Analyzing- Casting Melting-Analyzing- Casting

Knockout Knockout

Cutoff  Cut off

Grindingresidual gates    Grinding residual gates

Shotblasting  Shot blasting

Finishing Finishing

Inspection Inspection