What is Metal Casting?
Metal casting is the pouring of molten metal into a mold with a specific shape, and then allowing that metal to cool into a solidified form. It has typically been used to create complex and large parts that would be unrealistic to make using other production methods.
Casting is generally used to produce ingots and shapes. Ingots are then set aside for further processing like forging or metal extrusion. There are multiple types, with each type able to produce specific results.
Using a mold allows the metal to fill the hollow space, and set up in the exact dimensions needed for the specific part being cast. Before finishing the product, any blemishes and excess tolerances are de-burred, and the part is then prepped to ship to the customer.
What are the Different Types in Use?
Metal casting comes in two overall groups, based on the mold design. There are expendable molds and permanent molds. These groups can be further divided into:
- Plaster molding
- Shell molding
- Ceramic mold
- Lost foam
- Investment casting
There are many factors that need to be considered before the choice of a suitable casting is given for a specific engineering design.
Sand methods generally use silica-based components. Synthetic or naturally bonded sand can both be used. Casting sand is typically finely ground grains that can be packed tightly into a smooth molding surface.
Casting with sand is beneficial because it can reduce the risk of cracking and tearing of the metal. Sand has a moderate degree of movement, letting the shape shrink during the cooling process without breaking apart. In some cases, sand can be additionally strengthened by mixing it with clay.
Engine blocks are an excellent example what can be produced with sand methods.
Sand-casting offers several advantages:
- Less expensive than other options
- Large component fabrication
- Can cast ferrous and non-ferrous metals
- Inexpensive post-cast tooling
Benefits aside, this method can deliver a lower accuracy than other methods.
This process uses wax patterns for each cast part. The wax is injected into the mold, then coated with a binding agent and refractory materials. This process requires several stages to create a thick shell. Once the shells harden, the patterns are heated in the ovens to remove any wax. Molten metal is poured into the shells, where it then cools and hardens.
Automotive, power generation and aerospace industries use this approach regularly to produce a wide range of parts.
Plaster-casting is like the sand-casting process, though gypsum, water, and a strengthening compound are used instead of sand. Once the plaster mold is used to cast the design, it generally cracks apart and needs to be replaced with a new mold. Plaster molds have several advantages:
- Cast complex shapes with thin walls.
- Smooth surface finish.
- Form large parts cheaper than other processes, like investment methods.
- Highly accurate.
Die-casting molds materials under high pressure, and is generally used on non-ferrous metals. The mold is lubricated to help regulate temperatures and make ejecting the finished part easier. Molten metal is then injected under immense pressure to fill the form. After it dries, any residual metal is ground off the part to prepare it for the client.
Permanent Mold Casting
Like die-casting, permanent mold uses reusable molds. The molds can be made from materials such as graphite or steel, and are typically used to cast metals like aluminum, zinc, lead, and magnesium. The pouring process is low pressure, and the pouring is generally done by hand. The molds are then rotated through several stations that then coat, fill, open, and empty the molds.
Get Professionally Cast Metal Parts According to Your Specifications
Here at Cliffe Metal Products, we work hard for our clients. We are capable of providing metal casting in a wide range of materials and shapes, and will assist with determining the proper methods for your needs. Contact us today with any questions you may have about centrifugal casting, open die forging, rolled ring metal forging, or to find out more about our services.