In a variety of industries, casting and forging are popular methods of creating components and parts. In spite of this, the processes are very different from one another, and the products produced by each have different characteristics. As a leading industrial manufacturing and engineering company specialising in metal forming and fabrication, we are here to clarify casting from forging and help you decide which is best for your project.
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The process of casting involves pouring molten metal into a mould and then letting it cool and harden before removing it from the mould. This process is ideal for mass-producing parts and creating identical products using the same mould.
The casting comes in various forms. When liquid metal is forced into a die instead of a mould and kept there by pressure until it hardens, this is called die-casting. The process is known for its support for high-speed applications. Mould casting on permanent moulds is the process of pouring molten metal into a metal mould, either using gravity or a vacuum. Permanent mould castings can produce stronger castings than die casting, but they can be hard to remove from the final product. Thus, semi-permanent mould castings are also available. With these moulds, the cores can be expended, making the removal process less difficult and more affordable.
Last but not least, sand casting is a method of casting that involves pressing a pattern into a fine mixture of sand. Moulds are formed for the molten metal to be poured into. Despite its slow speed, this process is more economical than other methods of casting. For large-scale metal fabrications and intricate designs, this is a good choice.
What is forging?
In forging, metal is shaped by compressive force. Hammers or dies are used to shape metal until the desired shape is achieved. Through the process of forging, the metal becomes deformed and shaped, which results in a continuous grain flow that allows it to remain strong. Furthermore, the removal of defects, inclusions and porosity from the product is an ancillary benefit of this unique grain flow.
In addition to its low cost, forging is also beneficial for medium and long production runs. By careful design of forging tools, it is possible to manufacture products at relatively high speeds with minimal downtime.
When forging takes place at room temperature, it is referred to as cold forging. The forging process can also be undertaken with the metal heated above room temperature to temperatures below that of recrystallization, which is called warm forging. In the hot forging process, metals are heated to their recrystallization temperature, which differs for each material. With blacksmiths using forging centuries ago, forging is amongst the oldest types of fabrication.
Castings produce metal products with relatively low strength, while forgings create metal products with higher strength and hardness. Forged metals have a lower likelihood of shattering when they come into contact with different objects.
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During forging, a change of shape is forced into the metal, either by pressing or hammering. Consequently, the metal gains strength. Contrary to other fabrication methods, the forging process stretches the metal grain, aligning it in one direction rather than causing it to be randomly oriented. However, forging can only be done within size limitations.
Forging entails a greater degree of difficulty because the metal is kept in a solid state, unlike casting. Metal sizes and thickness are restricted by forging because it is more difficult to change the shape of the metal. The larger the metal section, the more difficult it is to forge.
On the other hand, casting allows more complex shapes to be produced because molten metal flows into a mould or die cavity. It is possible to cast products of up to 200 tons of weight out of almost any material. Casting is usually much cheaper than forging. Each casting method has its own advantages and disadvantages, so the most suitable method will depend on the application.
1. Size & weight of the Finished Product
2. Design of the Component
When it comes to designing a part for either casting or forging, some characteristics to evaluate include:
3. Alloy Selection
A key consideration when it comes to castings vs forgings is the availability of alloys to use. In forging, the components are made from billets produced at a steel mill. These mills generally only manufacture a specific number of grades and alloys.
In comparison, castings are melted and poured at the foundry making special alloy costs more manageable.
4. Internal Strength of the Component
Deciding between the two processes depends upon the; forgings will typically be stronger in a particular direction, but castings are stronger uniformly throughout.
When the application involves frequent impacts, a forging will retain its shape longer. If a uniformly strong component is needed for the application, a casting will perform better.
5. Cost of Castings vs. Forgings
The price of castings vs. forgings is dependent upon multiple variables. Each of the processes is less expensive in some cases and more expensive in others. Various factors that play into the price of a part are:
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In this guide, we focus on the fundamental differences between casting and forging.
When it comes to metal components, there is no such thing as a size fits all approach. The best choice for you may depend on the specific metal component, its purpose, and its overall needs. If you need particular metals, either casting or forging may be the best. Consultation with manufacturers is the best way to determine which process is right for you.
Get in touch with us or send a quote request if you think metal casting may be the right solution for your application.
While metal casting might be the best process to manufacture a wide range of components, depending on your needs, the forging process could be the best option. Or vice-versa. This is why it helps to know the key differences between forging and casting. So here are 5 things to consider when deciding if a casting or forging is right for your component, application, and overall needs.
One of the more notable differences between metal castings and forgings is the maximum size of a finished product. The process of forging moves metal while it is still in a solid-state. This requires a tremendous amount of force to modify the original shape of the metal and the force needed drastically increases as the size of the section gets larger. Since castings start out as liquid molten metal, it can flow into nearly any shape or size if there is a mold that matches.
Another consideration pertains to the weight of the parts. If there are two identical parts, one made by casting and one by forging, the casting will usually be lighter than the forging. As a result, conversions from forgings to castings typically result in a weight reduction.
When it comes to designing a part for either a casting or forging, some characteristics to evaluate include:
When assessing the complexity of a part, forgings can be limited. Small details and internal cavities are sometimes difficult, if not impossible, to shape in the forging process.
Alternatively, the beginning liquid nature of a casting creates a distinct advantage for complex shapes in that it can easily flow into small, detailed areas. Part of this benefit also comes from the reduced machining required after casting because of the details that are present in the original casting.
In the design and prototype phase of a program, castings are more cost and time-efficient. Changing a small detail in the casting pattern of a component is much easier than a forging die.
A prominent difference when it comes to castings vs forgings is the availability of alloys to use. In forging, the components are made from billets produced at a steel mill. These mills generally only manufacture a specific number of grades and alloys.
In comparison, castings are melted and poured at the foundry making special alloy costs more manageable. When choosing alloys and a manufacturing process, an important consideration is the desired ferrite content. Ferrite, in controlled amounts, has characteristics that make it more corrosion resistant than a similar forging.
I
nternal Strength of the ComponentAnother characteristic to consider relates to the internal structure and strength of the component. The forging process alters the grain structure and can “aim” or “point” it in a particular direction creating a directionally strong component. Forged parts are anisotropic (contains different property-measurement values in different directions) while castings are isotropic (contains similar property-measurement values in all directions).
Deciding between the two processes depends on the application it will be used for; forgings will typically be stronger in a particular direction, but castings are stronger uniformly throughout.
When the application involves frequent impacts, a forging will retain its shape longer, if a uniformly strong component is needed for the application, a casting will perform better.
The price of castings vs. forgings depends on multiple variables, each of the processes are less expensive in some cases and more expensive in others. Various factors that play into the price of a part are:
Forgings are most cost effective for medium to large lot sizes. Castings can be effectively purchased in small, medium, and large lot sizes.
Raw material costs for castings are generally lower than forging since the initial process of casting ingots and processing them into billets is eliminated.
Tooling for most centrifugal castings and open die forgings (ODF) is not required. For closed die forgings (CDF) tooling can be expensive. For high volume applications, purchasing dedicated tooling is a good idea for all processes as it will reduce the per-piece cost.
It is a good idea to buy castings machined since the foundry can cost effectively recycle machining chips through re-melting. Since that benefit doesn’t exist for forgings, it’s best to buy them in the as-forged condition. Machining rates for castings are comparable to forging for most alloys. However, due to finer grains in forgings, some nickel-based alloys and stainless steels have better machinability.
Since the cost comparison of metal castings vs. forgings depends on many variables, you should have discussions with leading companies in the casting and forging industry to discuss your specific project and obtain quotes for both processes.
In the world of manufacturing metal components, there is no “one size fits all”. Depending on your specific metal component, its application, and your overall needs, either a casting or forging could be the best fit. You may have some metal requirements for which casting is the best fit but forging for others. Ultimately, the best way to determine which process is best for your specific requirements is to consult with the manufacturers.
If you think metal casting might be a fit for your application, give us a call or submit a request for quote.
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