What is Forging?

Brief History of Forging

Forging, an age-old technique, is divided into two primary types: hot and cold. While hot forging has been practiced for centuries, cold forging only emerged during the 19th-century industrial revolution. Despite their differences, both methods achieve similar outcomes. Forging involves reshaping metal into specific forms using various tools and equipment, with the choice of process—hot, cold, or warm—based on the type of metal and the intended final shape of the product.

Hot Forging and How It Works

Hot forging takes place when a piece of metal is superheated beyond its crystallization point. The average temperature at which this happens depends on the type of metal where steel crystallizes at up to 1150° C, aluminum alloys between 360° C to 520° C, and copper alloys between 700°C to 800°C. The required temperature must be maintained above the recrystallization point or the point at which the metal begins to cool. Recrystallization can form microscopic crystals that warp when the metal is reheated causing it to "strain harden", which makes it unworkable.

Environmental factors can influence the hot forging process where contact with the atmosphere can cause oxidation. To avoid this, forging may be completed in an environmentally controlled chamber or isothermal forging, which is similar to a vacuum.

The primary benefit of hot forging is the enhanced strength it imparts to the metal. Hot-forged metals exhibit excellent ductility, allowing them to be significantly deformed and reshaped, which increases their resistance to tensile stress. The hot forging process alters the internal grain structure of the metal, resulting in improved strength and structural characteristics of the final part.

Things to Consider When Choosing Hot Forging

Hot forging is used in the production of several different components and parts since the process can produce high precision and complex shapes. It is ideal for metals that have a high formability or can easily be deformed. Metals formed in hot forging gain strength and become more durable. It is a flexible process that is capable of producing customized parts. The excellent surface finishes of hot forged parts allows the use of different forms of finishing and polishing processes.

Hot forging offers several distinct advantages, such as the efficient production of individual components and generally lower precision compared to other methods. This process can result in scale formation on the metal, and it typically involves reduced metal stress with lower work hardening temperatures. Additionally, hot forging promotes uniform grain structure, enhances ductility, and helps to eliminate chemical inconsistencies in the material.

Negative factors of hot forging:

Regardless of how productive hot forging is, it does have certain disadvantages that need to be considered. During the cooling process, there is always the possibility that the metal may warp and become brittle. There are some metals that should not be used in hot forging since it may produce less precise tolerances as well as variances in the grain structure.

Despite some limitations associated with hot forging, it is particularly effective for manufacturing aerospace components and aircraft parts. The malleability of metals achieved through this process facilitates the creation of complex shapes and detailed designs needed in these sectors.

Leading Manufacturers and Suppliers

The Benefits of Cold Forging or Forming

Cold forging refers to a metal shaping and deforming process that is performed at or slightly above room temperature where the temperature is kept at near three tenths of the recrystallization point of the metal. Squeezing, bending, shearing, and drawing are the most common cold forging methods. Soft metals such as aluminum or copper are ideal for the process.

The method of cold forging uses compressive force to shape the workpiece by hand or machine. In many cases, the metal is pushed into a die shaped in the form of the final product. It is less expensive than hot forging and produces completed products that require little, if any, finishing. With aluminum, after being cold forged, it is heat treated to strengthen the piece, a process known as "tempering".

The Unique Process of Cold Forging

The most common metals in cold forging are standard or carbon alloy steels. It is used to produce small, high volume products like fasteners such as nails, screws, rivets, and such. The lack of the need for heat makes it inexpensive and efficient. The types of cold forging methods used depends a great deal on the metal and the required shape. Below are descriptions of some common cold forging processes.

Impression die forging

Impression-die forging is a typical cold forging technique where metal is inserted into a die affixed to an anvil. The metal is then hit with a hammer, which shapes it according to the die. Multiple rapid hammer strikes may be applied depending on the specific product requirements.

Squeezing

Also called sizing, squeezing decreases the thickness of metal through pressure application, which varies based on the sizing area, metal type, and the required thickness modification. This technique is usually employed to achieve accurate dimensions in forged pieces.

Cold rolling

Cold roll forming produces more attractive finished surfaces with closer tolerances in a variety of shapes that can easily be galvanized, painted, or powder coated. Thin sheets of a metal, usually steel, are rolled into shapes such as floor and roof paneling, C, or Z shapes.

Drawing

Drawing uses tensile forces to pull or stretch a metal to a particular shape or thickness. There are two forms of drawing – sheet metal and wire, bar, or tube. Drawing can only be applied to certain types of metal or materials that have sufficient tensile strength. Though it may seem similar to cold rolling, it differs in the amount and position of the applied force.

Cold forging has other processes designed for shaping metals. The ones listed here are common but only a few of the many that are in use. It is a popular process with auto manufacturers for the production of steering and suspension parts, certain braking systems, axles, and many other automobile parts.

Leading Manufacturers of Forging Machines

Various machines are essential for modern forging, allowing for the efficient creation of robust metal parts used across industries like automotive, aerospace, construction, and manufacturing. In the following sections, we highlight several popular brands of forging machinery available in the United States and Canada.

Ajax-CECO - Model: Bulldog 200

The Bulldog 200 by Ajax-CECO is a highly adaptable forging machine, praised for its sturdy design, impressive forging capabilities, and advanced control systems. It is well-regarded for its dependability, long-lasting performance, and versatility in producing various forged parts.

National Machinery - Model: FORMAX Plus

National Machinery's FORMAX Plus series incorporates cutting-edge servo-driven technology, facilitating rapid tool changes and energy-saving operations. These machines are celebrated for their precision, high productivity, and flexibility in accommodating diverse forging applications, earning them widespread acclaim.

Erie Press Systems - Model: Electric Forging Press

Erie Press Systems is known for its electric forging presses, which deliver energy efficiency, precise control, and versatility. These presses offer high force output and customizable settings, making them suitable for forging a variety of materials and shapes. Their popularity is attributed to their sustainability, precision, and ability to meet contemporary manufacturing demands.

Wyman-Gordon - Model: Radial Forging Machines

Wyman-Gordon excels in manufacturing radial forging machines, which use radial die movement to create components with exceptional strength and integrity. These machines are highly regarded for their precision in shaping, waste reduction, and production of high-quality forged parts.

Mitsubishi Heavy Industries America - Model: MF Series Forging Press

The MF Series Forging Press from Mitsubishi Heavy Industries America stands out for its robust design and versatility. It excels in various forging tasks with its precise control systems and efficiency, making it ideal for handling multiple materials and complex processes with high reliability.

These machines are widely recognized for their robustness, precise control, and versatility, effectively addressing the needs of modern forging across various industries. However, individual models and their features may differ, so it’s recommended to consult manufacturers or industry experts for the most current information on the latest forging equipment available in the US and Canada.

Things to Consider When Choosing Cold Forging

Cold forging provides various advantages, such as operating at room temperature without the need to heat the metal, which reduces the overall cost of parts. Additionally, it eliminates the need for costly equipment like blast and industrial furnaces used in hot forging.

Cold forging enables the rapid and consistent production of parts with excellent dimensional accuracy, making it ideal for companies that need high volumes and fast delivery. Thanks to computerized processes, each component is produced with identical precision and detail. Additionally, cold forging extends the lifespan of dies, as they are not subjected to the stress and wear associated with hot metals.

Cold forging enhances precision, creating parts with tight tolerances and consistent quality. By closely following design specifications, this method minimizes defects and the need for rework, while also producing components with a refined grain structure.

An important factor, in this era of environmental concerns, is the eco-friendliness of cold forging since parts are shaped and formed under high pressure at room temperature. Unlike other processes, cold forging ensures that there will not be air bubbles or other deformities trapped in the workpiece.

Some of the other benefits of cold forging include improved material usage, lower energy costs, and little to no finishing. With the rising costs of energy and the shortage of materials, cold forging is the solution to producing parts efficiently reducing the effect of those factors.

Leading Manufacturers and Suppliers