Types of Forging operation | Theory, application, advantage and disadvantage

Types of Forging operation

Forging is a manufacturing process in which metal is shaped by applying compressive forces using a hammer, press, or other tool. There are several types of forging operations, including:

1. Open-die forging.

2. Closed-die forging.

3. Upset forging.

4. Press forging.

5. Roll forging.

6. Swaging.

7. Extrusion forging.

1. Open-die forging: 

This process involves shaping metal between two flat dies without completely enclosing the metal. It is also known as smith forging or hand forging.

Process:

The process can be broken down into the following steps:

1. Selection of material: The first step in the open die forging process is selecting the material for the workpiece. Metals such as steel, titanium, aluminum, and copper alloys are commonly used.

2. Heating: The workpiece is heated to a temperature that allows it to be shaped easily. The exact temperature depends on the type of metal being forged and the desired properties of the final product.

3. Placing the workpiece: The heated workpiece is placed on the lower die, which is usually stationary. The upper die, which is attached to a hammer or press, is then positioned above the workpiece.

4. Compression: The upper die is brought down with force to compress the workpiece between the two dies. The workpiece is deformed as it is compressed.

5. Shaping: The workpiece is rotated between compressions to shape it to the desired form. This process is repeated until the final shape is achieved.

6. Trimming and finishing: Once the workpiece has been shaped, it is trimmed and finished to remove any excess material or imperfections.

7. Cooling: The final step in the open die forging process is allowing the workpiece to cool naturally or by using a cooling medium such as water or oil. 

Advantage and disadvantage:

Advantages:

1. Flexibility: Open die forging is a versatile process that can be used to produce a wide range of shapes and sizes of forgings.

2. Cost-effective: Open die forging is often more cost-effective than other forging methods because it requires less tooling and can be used for small production runs.

3. Improved grain structure: Open die forging can produce a more uniform and fine grain structure in the material, which can result in improved mechanical properties and strength.

4. Reduced waste: Open die forging can help reduce waste and material costs by allowing for the efficient use of raw materials.

Disadvantages:

1. Limited precision: Open die forging may not be suitable for producing parts with very tight tolerances or complex shapes due to the limited precision of the process.

2. Surface finish: Open die forging can produce forgings with a rough surface finish, which may require additional finishing operations.

3. Variation in properties: Because the material is not completely enclosed during the forging process, there may be some variation in the properties of the material across different sections of the forging.

4. Required skill: Open die forging requires skilled operators to control the process and achieve the desired shape and properties of the forging.

2. Closed-die forging: 

In this process, a metal piece is placed between two dies that are shaped to the desired form, and then the dies are closed and the metal is shaped under high pressure. 

Process:

The process can be broken down into the following steps:

1. Preparation of the raw material: The raw material, which is typically a metal bar or billet, is heated to a temperature that is suitable for forging. This temperature is usually between 1,100 and 1,250 degrees Celsius, depending on the type of metal being used.

2. Placing the material between the dies: The heated material is placed between the two dies, which are usually made of steel and are pre-shaped to the desired final form of the part being produced.

3. Forging the material: The dies are then brought together under high pressure, which causes the material to flow and take the shape of the dies. The pressure applied during the forging process is typically between 1,000 and 25,000 tons, depending on the size and complexity of the part being produced.

4. Repeating the process: Depending on the complexity of the part being produced, the forging process may need to be repeated several times to achieve the final shape and dimensions of the part.

5. Trimming and finishing: Once the forging process is complete, excess material is trimmed off and the part is finished using various techniques such as grinding, machining, and polishing.

6. Final inspection: The finished part is inspected for defects and dimensional accuracy before it is shipped to the customer.

Advantage and disadvantage 

Advantages:

1. High strength and durability: Closed die forging produces parts that have high strength and durability due to the compression of the metal within the dies.

2. Excellent surface finish: The closed die forging process produces parts with a very fine surface finish, which can eliminate the need for additional machining.

3. Precise tolerances: Closed die forging allows for very precise tolerances, which is important for parts that require close dimensional accuracy.

4. Versatility: Closed die forging can be used to produce a wide variety of shapes and sizes, making it a versatile process.

Disadvantages:

1. High tooling costs: The cost of the dies used in closed die forging can be quite high, which can make it expensive for low-volume production runs.

2. Limited shape complexity: Closed die forging is limited to parts with simple to moderately complex shapes. Complex shapes may require additional machining.

3. Material limitations: Closed die forging may not be suitable for all types of materials, particularly those with poor ductility or high brittleness.

4. Process limitations: Closed die forging is not suitable for all sizes of parts, particularly those that are very large or very small.

3. Upset forging: 

This process involves compressing the metal between two dies, causing it to flow in a direction perpendicular to the applied force. It is commonly used to make bolts and other fasteners.

Process:

Here are the steps involved in the upset forging process:

1. Preparation: The workpiece is cut to the desired length and heated to a temperature that makes it malleable.

2. Positioning: The workpiece is placed in between the two dies of the forging press. The bottom die is fixed, while the top die moves vertically.

3. Forging: The top die is brought down with a great force on the workpiece, causing it to deform and fill the space between the dies.

4. Reheating: After forging, the workpiece is reheated to the optimal temperature for further forging.

5. Trimming: The excess material is trimmed off from the workpiece.

6. Finishing: The final finishing process may involve polishing, machining, or painting.

Upset forging is used to manufacture a wide variety of parts, including bolts, screws, and other fasteners. The process is particularly useful for producing components that require a high level of precision and strength

4. Press forging: 

In this process, a metal piece is shaped by applying pressure using a hydraulic or mechanical press. This is a common method used for manufacturing complex shapes such as gears and crankshafts.

Process:

The process typically involves the following steps:

1. Billet preparation: The first step in press forging is preparing the billet, which is a piece of metal that will be shaped by the press. The billet is typically heated to a temperature that makes it more malleable and easier to shape.

2. Die preparation: The next step is preparing the die, which is a tool that is used to shape the metal. The die is typically made of hardened steel and has a cavity that is the same shape as the desired final product.

3. Loading the billet: Once the billet and die are prepared, the billet is placed on the lower die and aligned with the upper die.

4. Applying pressure: The press is then activated, and pressure is applied to the billet, causing it to flow into the cavity of the die. The pressure can range from a few tons to several hundred tons, depending on the size of the part being forged.

5. Releasing pressure: Once the metal has been shaped, the press is released, and the part is removed from the die. The part may then undergo additional processing, such as heat treatment or machining, to achieve the desired final properties and dimensions.

6. Inspection: The final step in the process is inspection, where the forged part is checked for any defects or flaws that may have occurred during the forging process.

5. Roll forging: 

This process involves passing a metal piece between two or more rotating rollers to shape it. It is commonly used to make long cylindrical parts like shafts and axles.

Roll forging 

Process:

Here is a general overview of the working process of rolling forging:

1. Material selection: The first step in rolling forging is the selection of a suitable material. The material should have good ductility and should be able to withstand the compressive forces applied during the process.

2. Preparing the workpiece: The workpiece is usually preheated to improve its ductility and reduce the amount of force required to deform it. The surface of the workpiece may also be cleaned to remove any contaminants or oxidation.

3. Positioning the rolls: The rolls are positioned in a way that the workpiece can be fed through them. The rolls rotate in opposite directions and are typically powered by an electric motor.

3. Feeding the workpiece: The workpiece is fed into the rolls by a series of rollers. As the workpiece passes through the rolls, it is subjected to compressive forces that cause it to deform and take on the shape of the rolls.

4. Repeating the process: Rolling forging is a continuous process, and the workpiece is fed through the rolls multiple times until it reaches the desired size and shape.

5. Finishing: Once the workpiece has been rolled to the desired size and shape, it may be subjected to additional processes, such as heat treatment, machining, or surface finishing, to improve its properties or appearance.

Rolling forging is a highly efficient and precise process that can be used to produce high-quality metal products with excellent mechanical properties. However, it requires specialized equipment and skilled operators to ensure that the process is carried out correctly.

6. Swaging: 

Swaging is a process in which a metal piece is shaped by hammering or pressing it into a die with a tapered hole. It is used to make items such as bullets and musical instrument parts.

Swaging forging 

7. Extrusion forging: 

In this process, a metal piece is forced through a die to create a specific shape. This is commonly used for making tubing and other long, hollow parts.