An iron-related job is referred to as forging or blacksmithing. It is achieved by heating or cooling any piece of metal, striking it with a regular hammer, or using a machine designed for this purpose. Forging involves giving the metal the appropriate shape.
Small forging tasks can be completed by striking the material with a hammer, but heavier forging tasks are only completed by machines. There are three main techniques for forging: drawing out, upsetting, and bending. The two main types of forging are hot and cold.
Metal pieces are produced through forging. Metal forging provides some of the strongest manufactured parts now on the market when compared to other manufacturing processes.
The heating and pressing process fills in minor cracks and seals any open spaces in the metal. This reading will explore what forging is, its applications, purposes, diagrams, types, operations, and how it works. We’ll also explore the advantages and disadvantages of forging.
Let’s Get Started!
Related: 11 Different Types of Forging Operations
What is Forging?
The forging manufacturing process uses concentrated compressive forces, typically from a hammer or die, to shape metals. The process involves heating, forcibly deforming, and finishing a piece of metal.
By using the force of a falling ram against an anvil or by enclosing a piece of metal in a die press and squeeze-forming the parts, forging shapes are produced.
The temperature at which forging occurs categorizes it as cold, warm, or hot. This process is known as forging. In advance knowledge, forging has been a standard method of metal fabrication. Forging uses compressive, localized forces to shape metal.
Forging has undergone major improvements since it first emerged in the fertile crescent, making it a more effective, quick, and durable technique.
This advantage is due to the fact that forging is now typically carried out using forging presses or hammering equipment that is powered by electricity, hydraulics, or compressed air.
Carbon steel, alloy steel, micro-alloy steel, stainless steel, aluminum, and titanium are a few of the frequently utilized forging materials.
History of Forging as a Mechanical Process
Forging has been a skill used by the Smiths for a very long time.
Bronze and copper were the most frequently used forging metals in the Bronze Age; later, as temperature control and the process of smelting iron were discovered, iron replaced them as the most popular forging metal.
Kitchenware, hardware, hand tools, and edged weapons are examples of traditional items.
Forging was able to develop into a more productive, mass-production process because of the Industrial Revolution. Since then, equipment, robots, electronic controls, and automation have all advanced along with forging.
Modern forging facilities produce high-quality metal parts in a broad variety of sizes, shapes, materials, and finishes, transforming forging into a global industry today.
Related: 9 Different Types of Forging Defects, Causes and Their Remedies
Applications & Purpose of Forging
Forging is a manufacturing process used to create metal pieces, such as hardware, hand tools, edged weapons, jewelry, and kitchenware. This process is versatile and requires additional processing, like machining, to produce the finished piece.
Metal forging provides some of the strongest manufactured parts on the market, as it fills minor cracks, seals open spaces, and separates metal impurities.
This process also reduces inclusions in the forged portion, which can lead to stress areas in the finished pieces. Forging also changes the metal’s grain structure, resulting in a desirable grain structure. This versatile manufacturing process is used in various industrial fields, including aerospace, automotive, agricultural equipment, military weapons, medical tools, and food machinery.
Forging is essential for producing components for aircraft and transportation equipment, as well as hand tools like chisels, rivets, screws, and bolts.
Diagram of Forging
Related: 16 Different Types of Forging Tools, Their Uses & Diagram
Types of Forging
There are various types of forging: cold forging, warm forging, and hot forging.
1. Cold Forging
We carry out cold forging at room temperature, which is lower than the metal’s recrystallization temperature. We prefer it when the metal is soft, such as aluminum. Carbon and alloy steels can also be processed using cold forging due to their softness.
The cold forging process is less expensive when compared with hot forging and its end product requires no finishing work.
Many metals, like steel with a high carbon content, simply cannot undergo cold forging. Despite this obstacle, cold forging consistently outperforms its warmer counterpart in terms of contamination, surface polish, homogeneity, and dimensional control.
Cold forgings encompass a variety of forging processes, including bending, extrusion, cold drawing, coining, and cold heading. The downside to this greater adaptability is that cold forging often necessitates the use of intermediate anneals and more powerful equipment.
Advantages
- It improves mechanical properties.
- Production rates are very high with exceptional die life.
- There is less friction between the die surface and the workpiece.
- There is no oxidation or scaling on the work.
- Lubrication is easy.
Disadvantages
- We need heavier and more powerful equipment.
- Designing and manufacturing are critical.
- Stronger tooling is required.
- Residual stress may occur.
2. Warm Forging
The forging process operates at temperatures ranging from above room temperature to below the recrystallization point.
This process has more potential advantages when compared with cold forging because it increases steel ductility, reduced tooling loads, reduced press load, eliminates the need to anneal before forging, etc.
For steel, this process heats the fire source to between 700 and 800°C. This value is below the recrystallization temperature. It also reduces the flow stress associated with the forging pressures.
Advantages
- Excellent dimensional tolerances.
- Favorable grain flow to improve strength.
- High production rate.
- The surface finish for a forged part is good.
- Greater toughness of the forged part.
- significant savings in machines and materials.
3. Hot Forging
Hot forging is the most common and useful forging type out there. It is carried out at a temperature above the recrystallization temperature of the metal.
The recrystallization temperature is the level at which the new grains are formed. The extreme hotness helps to easily deform the metal.
Heating metals to 2,300 degrees Fahrenheit may be necessary. The reduction in energy needed to form the metal properly is the main advantage of hot forging. This is due to the fact that extreme heat reduces yield strength while increasing ductility.
Chemical irregularities are also removed, which benefits hot-forged items. Some advantages and disadvantages of hot types of forging are:
Advantages
- less force is required
- High strain rates and hence the easy flow of the metal.
Related: What is the Difference Between Casting and Forging?
Types of Forging Processes
The various types of forging processes are drop forging, open-die forging process, closed-die forging process, hammer forging, press forging, upset forging, roll forging, and isothermal forging.
1. Drop Forging
The method of drop forging involves striking metal with a hammer to mold it into the die’s shape. The surface that makes contact with the metal is called the die.
Open-die and closed-die forging are the two variations of drop forging. Die shapes are normally flat, while some have surfaces that are specifically formed for certain activities.
2. Open-Die Forging Process
This is mostly used in hot forging. The workpiece is heated and hammered to the desired shape. It uses a flat die or no die for the forging. Open-die produces rough products. It is suitable for simple shapes due to its less dimensional accuracy and it requires high skill of operators. This process is simple and less expensive.
The forging procedure is known as open die forging (or smith forging) when flat dies without precut profiles are used. The metal can flow anywhere except where it hits the die because of the open design.
Correct movement of the workpiece, which should weigh more than 200,000 lbs. and be 80 feet long, is crucial for getting the best results.
It is helpful for shaping ingots before secondary shaping processes or for short-run art smithing. Open die forging decreases the possibility of inaccuracy or holes while producing products with improved fatigue resistance and strength.
It can also be used to produce grains with a finer texture than other methods.
Related: What is Powder Metallurgy? its Processes and Types
3. Closed-Die Forging Process
This type of forging is also known as impression die forging. We use a set of impressions to produce the desired shape on a workpiece. The upper and lower die halves create a cavity that fully constrains the material.
It also gives accurate shape to the parts, requires very accurate control of material volume and proper die design, and higher interface pressure is also required. This process does not depend on flash formation to achieve complete filling of the die.
Molten metal is forced into the cavities of these molds by a hammer while they are mounted to an anvil. When forging complex designs, multiple strikes and/or die cavities are frequently used.
Closed die forging is expensive for short-run operations because of high initial tooling costs, but as part production increases, the forging process becomes more affordable.
Compared to other techniques, closed-die forging also offers outstanding strength. The manufacturing of hardware tools and automotive parts are two common uses for closed die forging.
4. Hammer Forging Process
This is the most common type of forging equipment used during the process. The hammer and anvil are the most cost-effective and crucial pieces of equipment for generating load and energy during the forging process.
Hammers are primarily used for hot forging. Basically, there are two types of hammer anvils used during the forging process, such as gravity drop hammers and power drop hammers.
Gravity drop hammer: it has an upper ram connected to a belt (belt drop hammer), a chain (chain drop hammer), a board (board drop hammer), and a piston (oil-, air-, or steam-lift drop hammer).
When the ram is lifted to a certain height and dropped on the workpiece placed on the surface of the anvil. The ram is accelerated by gravity and produces some blow forces. Upstroke occurs immediately after the blows.
Power drop hammer: it is similar to that of an air-drop hammer. In the down-drop stroke, the ram is accelerated by steam, cold air, or hot air pressure. The acceleration of the ram is enhanced with air pressure applied on the top side of the ram cylinder. Learn about Forging Tools Here!
5. Press Forging Process
These types of forging do not work by a series of blows on the metal but through a single continuous squeezing of the metal. Press forging equipment usually comes in two types: mechanical and hydraulic presses.
The mechanical presses function by using cams, cranks, and toggles to produce a preset (a predetermined force at a certain location in the stroke) and reproducible stroke.
Compression is the primary forming element in press forging. The metal is allowed to rest on a stationary die while being continuously compressed by a compression die to form it into the required shape.
Compared to other forms of forging, the time the metal spends in contact with the dies is significantly longer, but the forging process has the advantage of being able to simultaneously deform the entire product rather than just a small portion.
TAnother advantage of press forging is the manufacturer’s ability to track and manage the specific compression rate. PPress forging finds numerous applications due to its ability to produce products with minimal size restrictions. Cold or hot forging can be used in press forging.
Related: Difference Between Fabrication And Manufacturing
6. Upset Forging Process
In the forging process known as upset forging, the metal is compressed to expand its diameter. In upset forging procedures, a specific type of high-speed machine is used: crank presses.
In order to increase efficiency and enable speedy metal interchange from one station to the next, crank presses are typically mounted on a horizontal plane. There are also hydraulic presses and vertical crank presses.
This technique has the advantages of being fully automated and allowing for a high production rate of up to 4500 components per hour. It almost never generates trash.
7. Roll Forging Process
Increasing the length of rods or wires involves roll forging. In order to form the metal, the maker puts heated metal bars between two cylindrical rolls with grooves that revolve and exert increasing pressure.
These grooves’ exact geometry shapes the metal component to the required shape. The absence of flashing and the good grain structure of this forging technique are advantages.
Roll forging is a metal forging method rather than a rolling technique, despite the fact that it uses rolls to create parts and components. The automotive sector regularly uses roll forging to create parts. Additionally, it is employed in the forging of hand tools and knives.
8. Isothermal Forging Process
The materials and the die are both heated to the same temperature during the isothermal forging process. The word “iso” means “equal,” hence the name.
With a lower forging temperature than other metals like steel, such as aluminum, this forging technique is frequently employed to forge aluminum.
Forging temperatures for steels and super alloys can range from 930 to 1,260 °C, whereas those for aluminum are at 430 °C. Benefits include cheaper machining costs and decreased scrap rates due to near-net forms and excellent reproducibility of the metal product.
Due to the reduced heat loss, smaller machinery can be employed to produce the forging, which is an additional benefit.
The more expensive die materials needed to manage pressures and temperatures as well as the necessary uniform heating systems are a few drawbacks. Additionally, its manufacturing rate is discrete.
Related: The Four Common Types of Metal Casting
How Does Forging Work?
The “hot forging” and “cold forging” techniques, each with several subcategories, can be used to create this metal.
The most common type of forging employ in forge work is die forging, also known as closed die forging This process depends on the form of the dies, which are effectively cast imprints of the final product, and strong presses and/or hammers.
In die forging, there are five steps: heating, preforming, finish forging, cooling and finishing.
Pre-forged metal begins with metal blocks called “ingots” that are heated to a near-molten state, retaining their shape but easily altering it with force.
To form a piece for pressing between closed dies, the heated ingot is edged and blocked with a press or hammer. This process refines the shape for finish forging. The preformed metal is then forced into an impression between two dies, taking on the general shape of the end product.
The final product’s strength is increased by coordinating the cooling of the metal, deforming and optimizing grain flow within the metal.
Impressions die forging also feature the “flash,” the excess metal that flows outside of the dies, which cools and hardens rapidly, making it stronger than the metal in the dies.
After pressing, trimming and surface treatment operations are performed to improve dimensional accuracy, corrosion resistance, and the appearance of the finished forged product.
Advantages of Forging
Below are the Benefits of forging in their various applications:
- Its products are strong.
- It is more reliable and less costly.
- Forging offers more consistent and better metallurgical properties.
- It responds better to heat treatment.
- It sometimes requires a secondary operation, making its product’s final look appealing.
- Forging is used to make a variety of shapes.
- Its design is flexible.
- It offers a broad size range of products.
Related: What is Centrifugal Casting? Its Diagram & How it Works
Disadvantages of Forging
Despite the good benefits of forging, some limitations still occur. Below are some disadvantages of the forging process:
- It is difficult to perform secondary operations in hot forging.
- Capital cost is more in forging work.
- Very high man and materials safety procedures need to be followed.
As mentioned earlier, the forging process gives quality products, but there are still some defects that may occur; they include unfilled sections, cold shut, scale pitta, die shift, flakes, and improper grain flow. Learn about forging defects here!