Investment Casting | Common Questions About Vacuum ...

Investment casting is one of the most popular methods used for creating metal parts that have countless applications across a variety of industries. Also called lost-wax casting or precision casting, this expendable mold process can produce complex components with excellent surface qualities and accuracy in a broad range of materials and sizes. When intricate details, as well as undercuts, are required for a particular component, a specific type of investment casting technique called vacuum casting should be used.

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Are Vacuum Castings Similar to Investment Castings?

Vacuum investment castings are metal components that are created through the vacuum casting method, which is a type of investment casting method. Because both techniques that are being used to produce the metal components are different from each other, it&#;s safe to say that vacuum castings are not similar to the typical investment castings.

How Does the Vacuum Investment Casting Technique Work?

In case you&#;re clueless about the vacuum casting process, it starts with a two-piece mold that&#;s adequately positioned inside a vacuum chamber. The liquid metal is then drawn into the cavity through the vacuum. Once this is completed, the casting is placed inside an oven to solidify the molten metal. As soon as it hardens, the mold is removed, and the newly-produced metal component is released.

Does Your Project Require Top-Quality Vacuum Investment Castings?

Are you looking to find top-quality vacuum investment castings for your next project? Ferralloy, Inc. is ready to provide them for you. Utilizing both gravity-fed and vacuum investment casting methods, we can produce metal parts that range in weight from a few ounces up to 70 lbs. Our proven track record and our years of experience in both of these methods mean that you can expect us to supply you with the superior net shape or near-net shape components that necessitate little or no finished work. If you need more information about our products and services, get in touch with us today.

Shelling (slurry and stucco coating)

The next phase involves the building of a ceramic shell around the wax cluster, obtained by dipping the wax assembly into ceramic slurries. The achieved layer is covered with sand dropped on the wet surface of the assembly.

The operations described are at different times and between each layer there is a waiting time dedicated to drying. So, the final shell is built by several layers and their number varies until the desired shell thickness is obtained. At Deloro the use of an automated full robot shell system for the building of the ceramic mold and daily/periodical checks on the slurries guarantee repeatability and stability of the process, improving process control of the critical first ceramic shell dips and increasing productivity in the area, with both a time saving and freeing up personnel for other critical areas

Dewaxing and Pre-firing

After the building of the ceramic shell, dewaxing and pre-firing follows by removing the wax from the mold, (leaving the internal cavity empty for metal casting) and in order to increase the mechanical properties of the mold through the sintering of the refractory materials.

At Deloro there are some operations done to check and evaluate the internal quality of the ceramic shell and in order to prepare the ceramic mold for the metal casting.

Casting

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After pre-heating the ceramic mold at high temperature, the molten metal is poured inside the mold and then it is allowed to cool and solidify. Deloro Microfusione performs equiax casting, using furnaces in air and vacuum furnaces, with a pouring capability up to 160 kg. The alloys poured are stainless steel and Nickel and Cobalt based superalloys.

Shell Knock-Out and Parts Cut-Off

After cooling, the ceramic shell is removed using different processes (for example vibrations from a pneumatic hammer or knock-out with pressurized water) and the pieces are then separated from the feeding system with gate removal operation. For these final stages of cutting and gate removal, Deloro has installed an automated robotic cell used for large parts, obtaining advantages in precision of the cut and reducing handling problems. CNC grinding can be completed where complex shapes need to be restored under a gate.

Core Leaching

After cutting, any parts with a ceramic core are put in one of our 2 medium pressure vessels where, a caustic solution is able to remove the ceramic core through chemical leaching. This enables us to process the most complex of internal passage designs.

Finishing

At this point there are different finishing stages, useful for obtaining finished parts conforming to the customer's specifications from a shape and surface finish point of view, followed by heat treatments needed for obtaining the appropriate mechanical properties and hardness.

NDT (Non Destructive Testing) Inspections

Finally, the process is completed by a series of non-destructive tests i.e.:

• Fluorescent Penetrant Inspection (FPI), done for intercepting defects on the surface of parts
• X-rays, done to identify defects inside the pieces
• Dimensional check, where the conformity of the pieces from a dimensional point of view is verified
• Final visual inspection

In order to improve the quality of dimensional checks, Deloro has recently installed a 3D blue light scanning machine, which speed up the control operations and increase the precision of the check. After these tests, the full conformity of the finished parts is certified, and the castings are ready to be shipped to the customer.