Forgings can be divided according to different classification standards:
By processing temperature: cold forging, warm forging and hot forging.
By forming method: free forging and die forging. Free forging uses general tools or forging hammers for forming, while die forging is carried out in fixed dies.
Application areas of forgings
Forgings are widely used in the following fields due to their excellent mechanical properties and load-bearing capacity:
Automobile industry: used to manufacture parts that withstand impact or alternating stress, such as wheel hub bearings, transmission spindles, gear rings, connecting rods, etc.
Mechanical equipment: main load-bearing structures and secondary load-bearing structural parts, such as the main shaft and intermediate shaft of a hydro-turbine generator.
Defense industry: such as gun barrels, door bodies, breech blocks and traction rings, etc.
Advantages and disadvantages of forgings
Advantages:
Excellent mechanical properties: The grain structure of the metal is optimized during the forging process, which improves the strength, toughness and fatigue life of the material. Strong bearing capacity: Forgings can withstand greater impact and heavy loads, and are suitable for environments with high loads and severe working conditions.
Dimensional stability: After forging, the metal has a uniform structure, reasonable fiber structure, and good shape and dimensional stability.
Classification of Forgings
Forgings are one of the most common forms of metal components used in various industrial applications, from aerospace and automotive to oil and gas and construction. They are produced by heating metal above its recrystallization temperature and then shaping it by mechanical or hydraulic pressure, usually using a die or hammer. Forgings often offer superior strength, durability, and resistance to fatigue, corrosion, and wear compared to other manufacturing processes. However, not all forgings are equal in their properties, and they can be categorized based on several factors, including their production method, shape, size, material, and application. In this article, we will explore the classification of forgings in detail.
1. Production Method
Forgings can be made by a variety of methods, each with its advantages and disadvantages, depending on the desired material properties, shape, and cost. The most common forging methods include:
- Hammer forging: This is the oldest and simplest method of forging, which involves striking the metal with a heavy hammer repeatedly to shape it. Hammer forging can produce a wide range of shapes and sizes, from small bolts to large turbine blades. However, it is labor-intensive and may not offer precise control over dimensions and surface finish.
- Press forging: This method utilizes hydraulic or mechanical presses to apply force gradually and predictably to the metal. Press forging can achieve tighter tolerances and better surface finish than hammer forging, as well as reduce material waste and energy consumption. However, it requires high-pressure equipment and may not be suitable for complex shapes or large parts.
- Upset forging: This technique involves compressing and spreading the metal in a die by applying pressure in a direction perpendicular to the metal's axis. Upset forging can increase the diameter, length, or thickness of a part, as well as reduce the grain size and improve the mechanical properties. However, it may cause internal defects if not controlled properly.
- Roll forging: This method involves passing the metal between two or more rotating rollers to shape it gradually. Roll forging can produce cylindrical or tapered parts with high strength and smooth finish, as well as reduce machining requirements and production time. However, it requires specially designed equipment and may not be suitable for irregular shapes or thin sections.
- Closed-die forging: Also known as impression forging, this process entails enclosing the metal between two die halves and applying pressure to fill the cavity and shape the part. Closed-die forging can produce highly accurate and repeatable parts with minimal machining requirements and excellent surface finish. However, it requires precise die design and maintenance, as well as a high initial tooling cost.
- Open-die forging: Also known as smith forging, this method involves shaping the metal by striking it between two or more dies that do not enclose the part completely. Open-die forging can produce larger and more complex parts than closed-die forging, as well as allow for better directional properties and grain flow. However, it may require more material and energy than other methods, as well as result in residual stresses and surface imperfections.
2. Shape
Forgings can be classified based on their shape or profile, which depends on the application and the forging method used. Some of the common forging shapes include:
- Round: This shape is the most straightforward and commonly used in various industries, such as bearings, gears, and shafts. Round forgings can be produced by hammer, press, or roll forging and offer high strength and fatigue resistance.
- Square: This shape has four sides and is often used in construction applications, such as beams, columns, and connectors. Square forgings can be produced by press or closed-die forging and offer good load-bearing capacity and weldability.
- Flat: This shape has two parallel surfaces and is often used in machining or welding applications, such as plates, brackets, and flanges. Flat forgings can be produced by roll or press forging and offer good surface finish and machinability.
- Hexagonal: This shape has six sides and is often used in fastener applications, such as bolts, nuts, and screws. Hexagonal forgings can be produced by upset or closed-die forging and offer good grip and torque transmission.
- Custom: This shape can be any non-standard shape required by the application, such as hooks, blades, and gears. Custom forgings can be produced by any forging method and offer tailored properties and functionality.
3. Size
Forgings can also be classified based on their size or weight, which depends on the dimensions and limits of the forging equipment used. Some of the common forging size ranges include:
- Small forgings: These typically weigh less than 5 kg and have a maximum length of 500 mm. Small forgings can be produced by hammer, press, or upset forging and are often used in precision and high-stress applications, such as aerospace and medical.
- Medium forgings: These typically weigh between 5 and 50 kg and have a maximum length of 1000 mm. Medium forgings can be produced by any forging method and are often used in heavy-duty and industrial applications, such as mining and marine.
- Large forgings: These typically weigh more than 50 kg and have a maximum length of 3000 mm. Large forgings require specialized equipment and expertise and are often used in critical and complex applications, such as power generation and defense.
4. Material
Forgings can also be classified based on the material used, which can affect the properties, cost, and suitability for the application. Some of the common forging materials include:
- Carbon steel: This material contains primarily iron and carbon and can be forged by any method. Carbon steel forgings offer high strength, durability, and machinability, as well as moderate corrosion resistance and hardness.
- Alloy steel: This material contains additional alloying elements, such as nickel, chromium, and molybdenum, to enhance specific properties, such as strength, toughness, and heat resistance. Alloy steel forgings can be produced by any method and offer customized properties and performance.
- Stainless steel: This material contains at least 10% chromium and can resist corrosion and tarnishing in various environments. Stainless steel forgings can be produced by any method and offer excellent strength, durability, and hygiene.
- Aluminum: This material has low density, high thermal conductivity, and good formability, making it suitable for lightweight and heat-sensitive applications. Aluminum forgings can be produced by hammer or closed-die forging and offer good strength, corrosion resistance, and electrical conductivity.
- Titanium: This material has high strength-to-weight ratio, low thermal expansion, and good biocompatibility, making it suitable for aerospace, medical, and chemical applications. Titanium forgings can be produced by closed-die or open-die forging and offer high strength, toughness, and corrosion resistance.
5. Application
Forgings can also be classified based on the application they are intended for, which can determine the requirements and properties needed for the part. Some of the common forging applications include:
- Automotive: This industry uses forgings for engine, suspension, transmission, and steering components that require high strength, durability, and wear resistance. Examples include connecting rods, crankshafts, gears, and ball joints.
- Aerospace: This industry uses forgings for aircraft, spacecraft, and defense systems that require high precision, reliability, and fatigue resistance. Examples include turbine blades, landing gear, wings, and frames.
- Oil and gas: This industry uses forgings for drilling, pumping, refining, and pipeline equipment that require high toughness, corrosion resistance, and pressure resistance. Examples include drill bits, valves, flanges, and fittings.
- Construction: This industry uses forgings for buildings, bridges, and infrastructure that require high load-bearing capacity, weldability, and weather resistance. Examples include girders, beams, bolts, and brackets.
- Medical: This industry uses forgings for implants, instruments, and devices that require high biocompatibility, wear resistance, and sterilization. Examples include bone plates, screws, hinges, and tweezers.
Conclusion
Forgings are an essential and versatile manufacturing process that has been around for centuries and can create complex, highly accurate, and durable metal components for various industrial applications. The classification of forgings based on the production method, shape, size, material, and application can help designers, engineers, and manufacturers choose the right forging process and specification for their intended purpose and performance requirements. By understanding the strengths and limitations of different forging methods and materials, companies can optimize their production efficiency, quality, and cost-effectiveness, while ensuring the safety and reliability of their products.
Classification of Forgings
Forgings are one of the most common forms of metal components used in various industrial applications, from aerospace and automotive to oil and gas and construction. They are produced by heating metal above its recrystallization temperature and then shaping it by mechanical or hydraulic pressure, usually using a die or hammer. Forgings often offer superior strength, durability, and resistance to fatigue, corrosion, and wear compared to other manufacturing processes. However, not all forgings are equal in their properties, and they can be categorized based on several factors, including their production method, shape, size, material, and application. In this article, we will explore the classification of forgings in detail.
1. Production Method
Forgings can be made by a variety of methods, each with its advantages and disadvantages, depending on the desired material properties, shape, and cost. The most common forging methods include:
- Hammer forging: This is the oldest and simplest method of forging, which involves striking the metal with a heavy hammer repeatedly to shape it. Hammer forging can produce a wide range of shapes and sizes, from small bolts to large turbine blades. However, it is labor-intensive and may not offer precise control over dimensions and surface finish.
- Press forging: This method utilizes hydraulic or mechanical presses to apply force gradually and predictably to the metal. Press forging can achieve tighter tolerances and better surface finish than hammer forging, as well as reduce material waste and energy consumption. However, it requires high-pressure equipment and may not be suitable for complex shapes or large parts.
- Upset forging: This technique involves compressing and spreading the metal in a die by applying pressure in a direction perpendicular to the metal's axis. Upset forging can increase the diameter, length, or thickness of a part, as well as reduce the grain size and improve the mechanical properties. However, it may cause internal defects if not controlled properly.
- Roll forging: This method involves passing the metal between two or more rotating rollers to shape it gradually. Roll forging can produce cylindrical or tapered parts with high strength and smooth finish, as well as reduce machining requirements and production time. However, it requires specially designed equipment and may not be suitable for irregular shapes or thin sections.
- Closed-die forging: Also known as impression forging, this process entails enclosing the metal between two die halves and applying pressure to fill the cavity and shape the part. Closed-die forging can produce highly accurate and repeatable parts with minimal machining requirements and excellent surface finish. However, it requires precise die design and maintenance, as well as a high initial tooling cost.
- Open-die forging: Also known as smith forging, this method involves shaping the metal by striking it between two or more dies that do not enclose the part completely. Open-die forging can produce larger and more complex parts than closed-die forging, as well as allow for better directional properties and grain flow. However, it may require more material and energy than other methods, as well as result in residual stresses and surface imperfections.
2. Shape
Forgings can be classified based on their shape or profile, which depends on the application and the forging method used. Some of the common forging shapes include:
- Round: This shape is the most straightforward and commonly used in various industries, such as bearings, gears, and shafts. Round forgings can be produced by hammer, press, or roll forging and offer high strength and fatigue resistance.
- Square: This shape has four sides and is often used in construction applications, such as beams, columns, and connectors. Square forgings can be produced by press or closed-die forging and offer good load-bearing capacity and weldability.
- Flat: This shape has two parallel surfaces and is often used in machining or welding applications, such as plates, brackets, and flanges. Flat forgings can be produced by roll or press forging and offer good surface finish and machinability.
- Hexagonal: This shape has six sides and is often used in fastener applications, such as bolts, nuts, and screws. Hexagonal forgings can be produced by upset or closed-die forging and offer good grip and torque transmission.
- Custom: This shape can be any non-standard shape required by the application, such as hooks, blades, and gears. Custom forgings can be produced by any forging method and offer tailored properties and functionality.
3. Size
Forgings can also be classified based on their size or weight, which depends on the dimensions and limits of the forging equipment used. Some of the common forging size ranges include:
- Small forgings: These typically weigh less than 5 kg and have a maximum length of 500 mm. Small forgings can be produced by hammer, press, or upset forging and are often used in precision and high-stress applications, such as aerospace and medical.
- Medium forgings: These typically weigh between 5 and 50 kg and have a maximum length of 1000 mm. Medium forgings can be produced by any forging method and are often used in heavy-duty and industrial applications, such as mining and marine.
- Large forgings: These typically weigh more than 50 kg and have a maximum length of 3000 mm. Large forgings require specialized equipment and expertise and are often used in critical and complex applications, such as power generation and defense.
4. Material
Forgings can also be classified based on the material used, which can affect the properties, cost, and suitability for the application. Some of the common forging materials include:
- Carbon steel: This material contains primarily iron and carbon and can be forged by any method. Carbon steel forgings offer high strength, durability, and machinability, as well as moderate corrosion resistance and hardness.
- Alloy steel: This material contains additional alloying elements, such as nickel, chromium, and molybdenum, to enhance specific properties, such as strength, toughness, and heat resistance. Alloy steel forgings can be produced by any method and offer customized properties and performance.
- Stainless steel: This material contains at least 10% chromium and can resist corrosion and tarnishing in various environments. Stainless steel forgings can be produced by any method and offer excellent strength, durability, and hygiene.
- Aluminum: This material has low density, high thermal conductivity, and good formability, making it suitable for lightweight and heat-sensitive applications. Aluminum forgings can be produced by hammer or closed-die forging and offer good strength, corrosion resistance, and electrical conductivity.
- Titanium: This material has high strength-to-weight ratio, low thermal expansion, and good biocompatibility, making it suitable for aerospace, medical, and chemical applications. Titanium forgings can be produced by closed-die or open-die forging and offer high strength, toughness, and corrosion resistance.
5. Application
Forgings can also be classified based on the application they are intended for, which can determine the requirements and properties needed for the part. Some of the common forging applications include:
- Automotive: This industry uses forgings for engine, suspension, transmission, and steering components that require high strength, durability, and wear resistance. Examples include connecting rods, crankshafts, gears, and ball joints.
- Aerospace: This industry uses forgings for aircraft, spacecraft, and defense systems that require high precision, reliability, and fatigue resistance. Examples include turbine blades, landing gear, wings, and frames.
- Oil and gas: This industry uses forgings for drilling, pumping, refining, and pipeline equipment that require high toughness, corrosion resistance, and pressure resistance. Examples include drill bits, valves, flanges, and fittings.
- Construction: This industry uses forgings for buildings, bridges, and infrastructure that require high load-bearing capacity, weldability, and weather resistance. Examples include girders, beams, bolts, and brackets.
- Medical: This industry uses forgings for implants, instruments, and devices that require high biocompatibility, wear resistance, and sterilization. Examples include bone plates, screws, hinges, and tweezers.
Conclusion
Forgings are an essential and versatile manufacturing process that has been around for centuries and can create complex, highly accurate, and durable metal components for various industrial applications. The classification of forgings based on the production method, shape, size, material, and application can help designers, engineers, and manufacturers choose the right forging process and specification for their intended purpose and performance requirements. By understanding the strengths and limitations of different forging methods and materials, companies can optimize their production efficiency, quality, and cost-effectiveness, while ensuring the safety and reliability of their products.
