Understanding Metal Forging Processes, Methods, and Applications
Metal forging is the process in which metals are formed and shaped using compressive forces. The forces are delivered using hammering, pressing, or rolling.
There are a number of forging processes – cold forging, warm forging, and hot forging – which are classified by the temperature of the metal being worked with.
Forging is one of the more pivotal metalworking processes in the metal manufacturing industry. It’s especially vital in the iron and steel industries and is viewed as a tremendous source of productivity.
What is The Metal Forging Process?
When choosing a type of forging, buyers have a long list of options for producing a critical metal component. It can be challenging to make the right choice, because each technique comes with varying pros and cons, revolving around costs and logistics.
However, choosing the forging method brings a plethora of unique benefits unavailable with any other choice.
With regards to price and overall quality, metal forging brings the most value. This notion rings doubly when maximum part strength, custom sizes, and critical performance specifications are needed for the application.
Here are some of the more common methods used:
- Closed die forging
- Open die forging
- Cold forging
- Roll forging
Open Die Forging, Closed Die Forging, and Roll Forging
The most common metal forging processes are open die forging, closed die forging, and roll forging.
What is Open Die Forging?
In open die forging, heated metal parts are shaped between a top die attached to a ram and a bottom die attached to a bolster, anvil, or hammer. With open die forging the metal is never completely confined or restrained in the dies.
Typically, temperatures range from anywhere between 500°F and 2400°F, the appropriate temperatures are applied when working the metal parts. Once the metal has been appropriately heated, the intricate hammering – or pressing of the workpiece – is performed to gradually shape the metal to its desired form.
Typically, the open die forging process is used to produce larger, simpler-shaped parts such as bars, rings, and hollows.
What is Closed Die Forging?
Closed die forging moves the die towards each other, covering the workpiece entirely or partially. There is heated raw material that’s nearing the shape/size of the final forged part and is placed in the bottom die.
This process works by incorporating the shape of the forging into the top or bottom die as a negative image. Once the process starts, the impact of the top die on the metal material forms it into the required forged form.
This process can be used to manufacture parts that range in size from a few ounces to 60,000 lbs.
What is Roll Forging?
Roll forging, also known as roll forming, is a forging method that uses opposing rolls to form a metal part. Even though roll forging uses rolls to produce parts and components, it is still considered a metal forging process and not a rolling process.
The process involves two cylindrical or semi-cylindrical horizontal rolls that are used to deform a round or flat bar stock. Through this action, the thickness is reduced, and the length is increased. Parts produced through roll forging have superior mechanical properties than those produced from many other processes.
After being inserted, a heated bar is passed between the two rolls. It’s progressively shaped while rolling through the machine’s shaped grooves. The precisely shaped geometry of these grooves are what forge the part to the specified dimensions.
Roll forging is often used to produce parts for the automotive industry. It is also used to produce things like knives and hand tools.
Standard Forging Equipment
There are four primary tools that are used in the metal forging process depending on the exact method being used.
The hammer, or power hammer, is a tool most commonly associated with forging. Whether a hand-held hammer or a massive power hammer, the tool is used to repeatedly hit the metal in order to deform it. As long as it possesses a 50,000 lbs driving force to deliver high-pressure impact blows, a hammer can pound metal into shape.
Presses use either mechanical or hydraulic pressure to apply continuous pressure on forging dies. This kind of equipment requires a 50,000 ton driving force to vertically squeeze metal into die cavities with controlled high pressure. Instead of hitting the metal repeatedly to deform it, the metal is slowly pressed into the dies.
Upsetter forging is similar to press forging, however, the main difference is that an upsetter is a forging press that is used horizontally. Instead of forcing the metal downward into a die, the metal is moved into the die impression in a horizontal direction.
Ring rollers are used to produce rings with diameters from just a few inches to over 300 inches. Ring rollers squeeze out a one-piece ring, which removes the need for welding. It turns a hollow round piece of metal under extreme pressure against a rotating roll.
How Does Forging Strengthen Metal?
Compared to other manufacturing methods, metal forging is known to produce some of the strongest manufactured parts available. As the metal is heated and pressed, minor cracks are sealed and empty spaces found in the metal are closed up.
In addition, the hot forging process breaks up any impurities in the metal and redistributes such material across the metalwork. This results in vastly reduced inclusions in the forged part. Inclusions are compound materials embedded inside steel throughout manufacturing, causing stress points in the product.
Even though impurities should be managed during the initial casting process, this process will further refine the metal.
Another way that forging strengthens metal is through the altering of its grain structure. This has to do with the material’s grain flow as it deforms. Like other forming processes, a favorable grain structure can be created, making the forged metal sturdier.
What Products Require Forged Metal?
The forging process is incredibly versatile and can be applied to anything from small parts measured in inches to components that weigh up to 700,000 lbs.
Forged products can be structural components in the following:
- Critical aircraft parts:
- Landing gear
- Shafts for jet engines
- Transportation equipment:
- Connecting rods
Also, forging is used to fortify hand tools (e.g., chisels, rivets, screws, and bolts).
What is the Best metal for Forging?
It’s possible to forge any kind of metal, but there are certain metals and alloys that are better suited for different applications.
Most commonly, these are the kinds of metals that get forged:
- Carbon, alloy, and stainless steel
- Exceptionally hard tool steels
- Brass and copper
- High-temperature alloys containing cobalt, nickel, or molybdenum
Out of these choices, it’s almost impossible to choose which is the “best,” as it really depends on the needs of a customer.
Economics 101 for Metal Forging
In smaller quantities, forged parts can be very expensive on a price per unit basis. This is primarily due to manufacturing forging die coming at a high upfront cost – a trait shared by other expenses associated with setting up shop.
Once everything has been set up and you’ve purchased the dies, the actual costs for operating are reasonably affordable, especially with automation playing a massive role. Taking this into consideration, this metal fabrication method is typically best for products that are being produced in more substantial quantities.
As the world continues to modernize, high-quality manufactured parts will only grow in demand. Since forging produces some of the strongest metals imaginable, it should be no surprise that the market is projected to be worth $131.32 billion by 2025.
Starting A Metal Forging Project
If you’re interested in producing custom metal parts or components and think that metal forging may be the best option for you, don’t hesitate to give The Federal Group USA a call. Our experienced support team members will go through your project requirements with you, help you determine the best course of action, and provide you with a free quote for your project. Contact us today to schedule a consultation.