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LongBanShan Industrial Park

YunFeng,SuiChang, Lishui.



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LongBanShan Industrial Park

YunFeng,SuiChang, Lishui.

closed die forging

Mastering Closed Die Forging – Your Essential Guide to the Process and Benefits

What makes closed die forging a go-to for high-grade metal components? It’s the process’s unmatched precision and strength, achieved by compressing metal within customized dies to facilitate intricate shapes and exceptional durability. Contrastingly, open die forging delivers less intricate results.
This article enlightens you on its distinct process, materials used, advantages, industry applications, and more, providing a window into closed die forging without the complexity.

Key Takeaways

  • Closed die forging, known for producing precise and durable components, involves the use of custom-shaped dies and includes techniques like upsetting and flashing to manipulate metal to the desired shape and attributes, with an emphasis on the quality of grain flow and reduction of material waste.
  • Material choice in closed die forging is critical, leading to the use of a variety of metals including steel, aluminum, brass, and copper based on their unique properties and the intended application of the forged product, while heat treatment plays a pivotal role in enhancing the mechanical properties of the forged items.
  • Industries ranging from automotive to aerospace, and applications such as gears and connecting rods showcase the versatility of closed die forging. Despite its numerous benefits, challenges like die wear and size constraints exist, with advancements in technology and materials continuously evolving to improve efficiency and environmental impact.

Understanding closed die forging

Closed die forging, also known as impression die forging, is a manufacturing process that uses custom-shaped dies to create intricate, high-strength components with exceptional precision and uniformity. The magic of this process lies in the dies themselves, which play a crucial role in manipulating the metal to achieve the desired shape and characteristics. Impression die forgings are known for their remarkable quality and durability.
The forging process incorporates a variety of equipment, such as mechanical presses, gravity-drop hammers, and hydraulic presses. The choice of equipment is determined by the specific production needs, contrasting with the open die forging process, which uses simpler dies and is more suitable for larger components. In this context, understanding die forging vs open die forging is crucial for selecting the appropriate method.
The closed die forging process hinges on two main techniques: upsetting and flashing.
  • Upsetting involves plastically deforming the metal under high pressure, enabling the creation of components with varying sizes and high strength. This not only helps in attaining the desired shape of the final product, but also aligns it with the grain flow of the material, much to the benefit of the product’s strength and integrity.
  • Flashing, on the other hand, expels the excess metal from die cavities, ensuring a complete filling of the die cavity and a clean final product.

Key components of closed die forging

To comprehend closed die forging thoroughly, one must understand its key elements. The workpiece, dies, and hammers or presses work in harmony to shape the heated raw material into the desired form. The forging process involves repeated hammering or pressing, transforming the raw material into the required forged form.
The process unfolds in stages, starting with the shaping of the workpiece with generous bends and large fillets, and then forging the final shape in a finisher or final cavity. The initial stage helps distribute the raw material into the rough shape, aligning it with the raw material forms required in the cavities.

The role of heat treatment

Heat treatment is a fundamental aspect of the closed die forging process. It serves several purposes:
  1. Restoring the ductility and yield strength that may have diminished during the hot forging process.
  2. Relieving stresses and restoring the material’s original properties.
  3. Enhancing the overall strength and flexibility of the forged products.
There are various heat treatment methods employed in closed die forging, including:
  • Quenching
  • Tempering
  • Annealing
  • Normalizing
  • Precipitation hardening
These procedures, which encompass normalization, tempering & hardening, carburizing treatment, and nitridation treatment, among others, are critical to the successful execution of the heat treatment process in closed die forging.

Materials used in closed die forging

Material selection in closed die forging greatly influences both the process and the final product. Predominantly, closed die forging uses:
  • Forged steel: reduces surface porosity, offers a finer grain structure, and increases tensile strength, thereby improving fatigue life and strength and enhancing ductility compared to other steel processing techniques.
  • Forged aluminum: lightweight, corrosion-resistant, and offers excellent strength-to-weight ratio, making it ideal for applications where weight reduction is important.
  • Forged brass & copper: excellent thermal and electrical conductivity, corrosion resistance, and high ductility, making them suitable for applications in electrical and plumbing industries.
Each of these materials offers unique benefits that make them ideal for certain applications.
There are different categories of steel that are suitable for use in closed die forging, namely carbon steel, alloy steel, and stainless steel. Similarly, aluminum is used in closed die forging due to its low density, high strength-to-weight ratio, and ease of machining. The primary aluminum grades suitable for closed die forging include 6061, 6063, 6082, and 7075.

Material selection criteria

When selecting materials for closed die forging, several factors come into play.
  • For one, the use of low-alloy, pre-hardened steels with specific content of elements like carbon, chromium, nickel, molybdenum, tungsten, and vanadium is considered. The material must possess adequate strength to maintain structural integrity and withstand the high compressive forces during forging.
  • Another important factor is ductility. The material must be sufficiently pliable to undergo flow and shaping under the intense compressive forces of the forging process without experiencing fractures. This requirement underscores the significance of ductility in the selection of materials for closed die forging.

Strength and durability of closed die forged products

Closed die forging stands out for the exceptional strength and durability of the products it yields. This can be largely attributed to:
  • The positive effect of grain flow on the impact and fatigue resistance of forged components
  • Reducing the likelihood of fracture or cracking during use
  • Enhancing their strength and durability
The closed die forging process offers several advantages, including:
  • Enhanced mechanical properties, such as increased strength and precision
  • Superior surface finish
  • More compact grain structure
  • Robust and long-lasting products
These benefits make closed die forged products superior to those manufactured through other forging processes.

Grain flow and mechanical properties

Grain flow refers to the directional alignment of the metal’s internal grain structure as they undergo deformation.
In closed die forging, the metal experiences significant pressure and is compelled to flow within a closed mold, leading to the elongation of individual grains in the direction of the metal flow or plastic deformation.
Grain flow has a direct impact on the mechanical properties of the material, determining the direction in which the underlying grains push or pull when subjected to stress or fatigue. It enhances impact and fatigue resistance, reduces the likelihood of fracture or cracking during use, and increases ductility and toughness of the forged components. This improved grain flow contributes to heightened strength and toughness, vital for the functionality of forged components.

Precision and consistency in closed die forging

The accuracy and uniformity in closed die forging stems from the influence of die design on product consistency. Proper metal flow, reduction of defects, and attainment of the desired shape and dimensions of the forged part are all facilitated by efficient die design.
Achieving precision and consistency in closed die forging also involves the use of precision machined dies and maintaining high accuracy throughout the process, which ultimately minimizes the requirement for additional machining operations.
Advanced strategies like pre-testing and modifications to the forging process using simulation programs ensure that the final products meet the specified shape, stress, and strain criteria before actual production.

Die design and manufacturing

Die design in closed die forging involves the design and fabrication of dies for shaping the metal into the intended form. Factors below are all taken into account to ensure precision and uniformity.
  • Strength and weight considerations
  • Shape accuracy
  • Dimensional consistency
  • Surface finish
  • Mechanical properties
The role of computer-aided design (CAD) in refining the die design to enhance productivity in forgings is pivotal.
The production of dies for closed die forging involves a meticulous adherence to the metal molding specifications. In this regard, CNC machining plays a crucial role, offering enhanced accuracy and efficiency in die production.

Efficiency and waste reduction in closed die forging

The formation of flash notably affects efficiency in the closed die forging process. Flash increases pressure within the die cavity, leading to improved material flow and compression, ultimately benefiting the forging process.
Waste reduction in closed die forging, on the other hand, is achieved through the removal of flash. This is carried out using a punching machine post-forging, preventing excessive flash formation, facilitating complete filling of the die cavity, and decreasing the amount of metal lost to flash.
As a result, closed die forging processes typically result in an approximate material waste of 20% of the forging mass, underscoring the importance of implementing efficient waste reduction measures.

Flash formation and removal

Flash in closed die forging is the excess metal that is extruded between the die parting lines during the hot forming process. It is formed as a small amount of material flows outside the die impression, gradually thinning out until it is removed by trimming dies in a punching machine.
The formation of flash in closed die forging results in increased pressure within the die cavity, leading to improved material flow and compression.
For the removal of flash from the closed die forged parts, techniques involving the use of trimming dies in a punching machine and pressing the part through a cutting die specifically designed for flash removal are employed. This contributes to waste minimization by eliminating the excess metal squeezed out of the die cavities, thus reducing waste.
The trimmed flash cools more rapidly and is usually stronger, thereby strengthening the overall forging and making the forging process more efficient and sustainable.

Industries and applications of closed die forging

Industries requiring critical components often employ closed die forging. This includes the following sectors:
  • Railway
  • Petrochemical
  • Electrical
  • Lifting and safety systems
  • Industrial machinery
  • Agricultural machinery
In the automotive industry, for instance, closed die forging is used to manufacture high-performance engine components including:
  • Crankshafts
  • Connecting rods
  • Rocker arms
  • Camshafts
Similarly, in the aerospace industry, closed die forging is utilized to manipulate metallic components through a plastic deformation technique, creating a full enclosure around the workpiece to mold it into the intended closed shape.
The railway industry, on the other hand, uses closed die forging to produce vital components including dog spikes, eyebolts, fish plates, and various safety-critical parts.

Examples of closed die forged products

Closed die forging is used to manufacture a wide range of closed die forged components, including closed die forgings such as gears, shafts and connecting rods.
These products showcase the versatility of the forging process.
  • Gears produced through closed die forging are frequently utilized in the automotive sector and various industrial settings. They play a crucial role in the production of a wide range of components such as shafts, hammer union nuts, spike harrow teeth, tie rod ends, shackles, and hooks.
  • Shafts manufactured through the closed die forging process are utilized in various applications, functioning as essential components of larger forged products, such as forged long shafts.
  • Connecting rods made through closed die forging serve crucial functions in vehicle engines, while valve bodies forged through the closed die process offer advantages such as reduced risk of metallurgical defects, increased strength and ductility.

Challenges and limitations in closed die forging

While closed die forging offers numerous benefits, it also presents several challenges and limitations.
Die wear, for instance, significantly impacts the surface quality of the products and the lifespan of the forging dies. Size constraints in the closed die forging process can impose limitations on the size of the part that can be forged, necessitating larger forging presses for larger parts and possibly prompting the utilization of open die forging or casting for very large components.

Overcoming challenges

To overcome the challenges in closed die forging, advanced materials such as aluminum and alloy steel are utilized.
Aluminum is chosen for its advantageous blend of strength, weight, and durability, crucial for aerospace uses, while alloy steel is favored for its cost-effectiveness and malleability, making it suitable for a broader spectrum of industrial uses.
Innovative die designs are crucial in addressing challenges in closed die forging. They:
  • Ensure precise forging processes
  • Enable the creation of custom pieces with a clean surface finish
  • Maintain necessary strength levels
  • Accommodate complex designs with close tolerances, often required in high-precision applications.

The future of closed die forging

Promising industry trends and innovations are shaping the future of closed die forging.
The rising utilization of advanced technologies like robotics is contributing to a robust growth rate of approximately 5.4% in the forecast period. Moreover, these technological advancements result in heightened productivity, improved precision, enhanced quality control, and reductions in downtime, labor costs, and workplace risks.
Automation and additive manufacturing are anticipated to have a substantial impact on closed die forging, addressing the current labor shortage and enhancing operational efficiencies. Furthermore, closed die forging is implementing environmentally friendly practices, including:
  • The use of sustainable materials
  • Optimization of the forging process to minimize material waste
  • Enhancing overall environmental performance by reducing flash and waste from the head and tail of the workpiece.

Industry trends and innovations

Technological advancements in closed die forging have facilitated increased productivity, precision, and quality control, while reducing downtime, labor expenses, and workplace hazards. Innovations in press design, automation, and control systems have resulted in enhanced efficiency, accuracy, and productivity.
Moreover, the industry’s response to the growing need for lightweight and fuel-efficient components has spurred innovation. As a result, innovations in closed die forging contribute to:
  • Enhancement of product quality
  • Ensuring consistent quality of the workpiece
  • Adherence to exact specifications
  • Prevention of potential damage during the forging process
These advancements in closed die forging help to meet the demands of the industry and improve overall efficiency and performance.
Closed die forging is also incorporating more environmentally conscious methods, such as the closed die forging method, generating less waste in comparison to alternative metal forming techniques, and decreasing the overall environmental impact of production.


In the complex and fascinating world of modern manufacturing, closed die forging stands tall as a process that combines precision, strength, and consistency to create high-performance components. From its role in the automotive, aerospace, and railway industries to its use in creating a wide variety of products, closed die forging plays a critical role in our everyday lives. As we move into the future, innovations in technology and a focus on environmental sustainability will only strengthen the significance of this dynamic process.

Frequently asked questions

What is the difference between open die and closed die?

In open die forging, the metal is left open, while in closed die forging, the metal is encased in dies to achieve more precise shapes. Closed die forging allows for greater control over the final shape of the metal.

What are the disadvantages of closed die forging?

The disadvantages of closed die forging include the possibility of incomplete parts due to metal not filling all crevices, leading to wastage of time and resources.

Is closed die forging expensive?

Yes, closed die forging can be expensive initially due to high forging die costs. However, for high volume production, it is the most cost-effective method for producing metal components.

Why is flash desirable in impression die forging?

Flash is desirable in impression die forging because it helps confine the metal in the die, ensuring a more uniform product and filling the die details effectively. This contributes to the quality and precision of the forged product.