Casting vs Forging

Casting and Forging are the two most common manufacturing methods for metal components. So what is casting or forging? What are the differences between casting and forging?

Casting

Casting is a process that forming desired shapes from liquid status by pouring. In casting, material or ingots will be first poured into prepaid molds and then getting solid for finish shapes. Therefore, there are no restrictions on the shape or the size of material that is to be used for the process of casting. As all material will be melted at the start, it makes no difference. Next, the molten material, which is in liquid form, is poured into a mould with a cavity to obtain the required shape. It is then left to cool down. Once the material is cooled, the solid can be removed out of the mould. It can either be ejected or broken free. This solid material which has been newly shaped is called the ‘casting’.

The process of casting is mainly performed on metals and other cold-setting material. These are the types of polymer material that cure together, forming cross-links in order to produce hardened material. Casting helps in setting these mixtures into solid shapes. Casting can be perfected to higher quality producing material with greater strength and wearability depending on the correct selection of alloys, and heating them to their optimum temperatures.

Types of Casting

Investment Casting: Investment casting is the most precise casting process. With investment casting process, we can make all kinds of precision castings with any metal alloy, such as cast steel, cast iron, ect. The term “investment” refers to the ceramic materials that are used to build a hollow shell into which molten metal is poured to make the castings. This term is derived from the solid mold process where a plaster-type material is poured, or invested, into a container that holds a clustered tree of small plastic patterns that are identical to the casting being produced. After the plaster has set, the disposable patterns are burned out leaving a hollow cavity into which the metal is poured. The same method is used in the investment casting process (also known as the lost wax process). Wax is injected into an aluminum die to produce a pattern that is an exact replica of the part to be produced. The method is similar to die casting, but with wax used instead of
molten metal.

Sand Casting: Sand casting is a process that utilizes non-reusable sand molds to form metal castings. It is a common production method for metal components of all sizes, from a few ounces to several tons. Sand casting isn’t only versatile in the size of its products – it can also create exceptionally complex or detailed castings, and can be used to cast nearly any metal alloy. Sand casting can be divided into precoated sand casting, resin sand casting and green sand casting. Compared with investment casting, the surface finish is not so good, and is more preferred to product
large parts. See sand casting vs investment casting here

Die Casting: Die casting is a manufacturing process in which molten metal is poured or forced into steel molds. The molds—also known as tools or dies—are created using tool steel and are specially designed for each project. This allows each component to be created with accuracy and repeatability. Aluminum, zinc, and magnesium are the most commonly used die casting alloys. Die casting can have significant advantages over other manufacturing processes, which often lead to major cost savings, not only in the part price itself but also in the overall cost of production. When you cast a part, you can create complex net shapes, including external threads and complex internal features with minimal draft angles—minimizing secondary operations. You can also combine multiple parts into a single part, eliminating assembly operations and lowering labor costs, with the added benefits of simplified stock control and greater component consistency. See die casting vs investment casting here…

Benefits of Casting

Casting has been defined as the conversion of molten metal to a pre-engineered shape or form. Since there are about a dozen different commercial casting processes, each with special benefits, the design and manufacturing engineer has many options and decisions to make.

Unlike stamping or drawn shapes, casting allows the designer to put metal where it is most needed. Parts can be streamlined and contoured for aesthetic and cosmetic appeal. Welded fabrications or weldments can be converted into casting sometimes. Wall thicknesses can be varied within reasonable limits of good casting design. Pads and bosses can be added for mounting
supplemental equipment. Special castable alloys like gray iron provide superior dampening of mechanical noise and vibration. An economical, repetitive process, casting turns out thousands of part within specific dimensional tolerances. The size of component parts is limited only by the producer’s facilities to mold, melt, and pour. Casting sizes range from fractions of an ounce to hundreds and even thousands of pounds.

With modern technologies, parts are being cast which could not be made by any other method. The practical use of casting technology has commercial cost efficiencies based on man’s ability to develop molding and die materials capable of handling the extreme heat of molten metal. Over the past decades new innovations have been made in castable alloys and techniques. Even now, the search continues for better processes and refractory materials.

Forging

forging

Forging, also called drop forging, in contrast to casting, is a method of producing differently shaped material while they are still in their solid state. This process does not involve heating till they melt and pouring into moulds for setting. The shaping of the material is done by the use of localized compressive forces. In order to deliver these forces, either industrial scale hammers or dies are used. A die is a tool which is used to cut and shape a material with the aid of the press technology. Forging is performed under various temperatures; cold, warm and hot, depending on the material in question. The process of forging is preferred where a component requires higher strength. Also, it assures uniformity of composition when compared to casting. Forged material has a firm grain structure which makes them stronger in order to handle impact better than cast material. This firm structure also excludes cavities and porosity from the composition.

The process of forging dates back to the 12th century where it was thought to be performed by smiths for various metal works. It has turned into a worldwide industry today since the industrial revolution. Kitchenware, hardware tools, weapons, jewellery are made by this method.

Types of Forging

Open Die Forging: Open die forging is one of the oldest forms of manufacturing, using traditional blacksmith methods. The billet is heated above recrystallization temperature, ranging from 1000°C to 1300°C for steel, and gradually shaped by skilful hammering or pressing of the work piece to create the desired shape. Open die forgings produce strong, durable parts in sizes that range from a few pounds to hundreds of tons. As a result, it is a favorable method to produce large and simple parts such as bars, rings, blanks, hollows, and spindles. Open die forging is also a great open for custom metal components as well.

Closed Die Forging: Closed die forging is the process where a pressing of forging stock is accurately and uniformly shaped into a die, or set of top and bottom dies, depending on the design requirements. The alloy deformation is confined within the shaped cavity of the dies to achieve the desired engineering configuration. Depending on such factors as complex multi-segmented precision wrap dies to simple two-piece conventional top-and-bottom dies. Process by which the material is placed between two dies with upper & lower impressions designed for the desired shape of the forging. Conventional forgings are produced through the use of a single pair of die or with multiple impression dies.

Advantages of Forging

  • Forged parts possess high ductility and offers great resistance to impact and fatigue loads.
  • Forging refines the structure of the metal.
  • It results in considerable saving in time, labor and material as compared to the production process of similar item by cutting from a solid workpiece and then shaping it.
  • Forging distorts the previously created unidirectional fiber as created by rolling and increases the strength by setting the direction of grains.
  • The forged parts can be welded easily.
  • Because of intense working, flaws are rarely found, so have high reliability.
  • High accuracy may be obtained in forging operation.

Casting or Forging, which is better?

In terms of casting and forging, as stated above, each process has its own advantages. Below we list out the main differences between casting and forging:

Casting Forging
Definition Casting is a metal-working process where the metal is first heated till it melts, then poured into a mould and made to cool to obtain the shape. Forging involves the use of localized compressive forces on the solid material in order to create desired shapes.
Strength Casted material is low in strength as they are poured into a cavity which lets the material take its shape freely. Forged material are stronger as they possess a definite grain structure which is pressed with force, increasing their mechanical strength.
Suitability for Hollow Shapes Casting is often preferred for the production of material containing hollows spaces or cavities. Forging excludes cavities and porosity from their compositions.
Uniformity The casted material is not always uniform. Forged material can be made to a uniform structure preserving consistency in shape.
Size Restrictions Casting doesn’t have any size or shape limitations as all material will be melted before putting them into shape. Materials weighing up to 50kgs can be forged yet higher power is required if material to be forged is heavier than 50kgs. In this case, casting would be the alternative.
Level of Complexity Casting is able to produce complex patterns and shapes. Forging is more focused in producing uniform and simple material.
Cost Casting uses relatively inexpensive equipment. Machines used for forging such as heavy duty industrial dies are more expensive.

Case study on Casting vs Forging

cast knife guards

Last month, our customer from Brazil asked for john deere knife guards, we first quoted with forging, cost is around 5 usd, but he responsed that the cost is too much high for large quantity 10000pcs. To him, low cost is more competitive for him to sell in his market. So we requoted in casting with cost 2.2usd. And finally we reached agreement on the deal and supplied high quality samples shown as above picture for approval. From this case, we can see that most of the time, our customers prefer casting more than forging for the cost benefit. Also casting can provide more design freedom, that is to say, casting can make any shape products.

Act as casting expert, CFS foundry always follow customers’ first basis, and consider everything for our customers for better service. If you have any casting product, or would like to convert your forging part into casting, pls contact us, our engineering team will provide you the best solution in the shorest time.

Leave a Reply

Your email address will not be published. Required fields are marked *