The forging process dates back to at least 4000 BC, it is a process that involves the re-shaping of a piece of metal into the design required.
Different types of Forging
There are various types of forging, the most common ones are known as Drop forging, Hand forging, and upset forging, all have a slightly different process but the end result will basically be the same
This type of forging is achieved by positioning a pre-heated bar so it is held in place, applying pressure to the piece of metal forcing it into a die where it will then reform into the shape of that particular mould.
The benefits of upset forging include greater strength, fewer fractures, no stress areas, and the product will be able to withstand high pressure.
This type of forging is a skilled job, usually performed by the hand of a craftsman trained in forgings. This process is the main used for bespoke forgings, usually involves heating up the metal and then manually forcing it into the desired shape.
The benefits of hand forging include bespoke shapes, low setup costs, and a superior grain flow.
This process is usually achieved by two dies holding the heated piece of metal, a heavy press will then be forcefully dropped onto the metal that needs to be reshaped.
Although forging remains a huge part of the industrial processes, technological developments have led to computers getting involved and controlling the hydraulic hammers, this is still being heavily invested in and new processes are being developed all the time to make the whole forging process more economical and improved.
Open die forging, also called free forging, is where the billet is placed within dies which do not enclose the metal entirely. The dies used for this process are usually flat in shape although some are specially shaped for more custom projects. The opposite of this process is closed die forging where the workpiece is completely enclosed.
Open die forging is usually used for shapes such as discs, hubs, shafts, blocks, plates and other custom shapes. This type of forging process strengthens the material being used by refining the grain of the metal, this in turn also reduces porosity. Cast parts are usually not as strong or have the wear resistance of similar forged parts.
Closed die forging is the process of compressing a piece of metal in an enclosed die impression. The raw material is approximately the same size as the final forged part which is placed in the bottom die. The top die impacts on the raw material to form it into the required shape. Any sized parts can be made using this process, some of the smaller parts can be forged cold.
Most metals can be forged using this process, this includes carbon steel, alloy steels, stainless steel, tool steel, aluminium, copper and sometimes certain titanium. Magnesium requires a more specialist forging process due to it being a temperature-sensitive material. Titanium is another material which requires specialist equipment and processes for forging.
The advantages of closed die forging over open die forging are the reduce machining time due to the better surface finish, this makes it cost-effective for large production runs. If the part is simple then open die forging is better for short production runs, as there is little or no tooling cost. Machining will be required to achieve the level of accuracy required.
Depending on what you require will determine which type of process you choose. If your design is simple and only a few are needed, then open die forging is for you. On the other hand, if the shape is more complex and a larger production run is needed then closed die forging should be a consideration.