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Forging

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Forging is a manufacturing process used to shape metal through localized compressive forces. This means the metal is shaped by being squeezed or hit with great pressure. These blows are delivered using a hammer, such as a power hammer, or a die.

Forging shop-Gesenkschmiede 1
Forging shop-Gesenkschmiede 1

Forged components vary greatly in scale. They can weigh less than one kilogram or reach hundreds of metric tons.

Alcator C-Mod superstructure forging 1
Alcator C-Mod superstructure forging 1

This process is vital for creating parts that require high strength. While forging provides the shape, many parts require further machining to reach their final, finished state.

Forging is classified by the temperature at which the work is performed. This classification depends on the metal's recrystallization temperature. If the metal is heated above this temperature, it is called hot forging. Hot forging is often faster and more precise. It also negates work hardening because the recrystallization process occurs as the metal is deformed.

Bochumer Verein-03-50142
Bochumer Verein-03-50142

Warm forging occurs when the temperature is below recrystallization but above 30% of it on an absolute scale.

Walzen Stab
Walzen Stab

Cold forging happens below 30% of the recrystallization temperature, often at room temperature. Cold forging typically results in work hardening, which makes the metal harder.

There are three main ways the metal moves during these processes. In a "drawn out" process, the length of the metal increases while its cross-section decreases. In an "upset" process, the length decreases while the cross-section increases. The third type is squeezing metal in closed compression dies, which produces multidirectional flow.

impactor flow
impactor flow

Various specific methods exist, such as roll forging, swaging, cogging, and press forging. Each method uses different tools to control how the metal flows.

Open-die forging, also called smith forging, is one common method. In this process, a hammer strikes a workpiece placed on a stationary anvil. The dies used in open-die forging do not fully enclose the metal. This allows the material to flow anywhere except where the dies make contact.

Bochumer Verein-08-50124
Bochumer Verein-08-50124

An operator must carefully position the workpiece to achieve the desired shape. This method is ideal for very large workpieces or small batches. It is often used in art smithing or to create custom shapes like shafts, cylinders, and discs. It can also be used to orient the grain of the metal to increase strength.

Impression-die forging, or closed-die forging, works differently. The metal is placed in a die that acts like a mold. When the hammer drops, the metal flows to fill the die cavities.

This process often creates "flash," which is excess metal squeezed out of the die. This flash cools faster than the rest of the part, which helps force the metal to fill the cavity completely. In commercial settings, a part might move through several cavities. It starts with an edging or fullering impression to distribute metal. It then moves to blocking cavities for a rough shape. Finally, it reaches a finisher impression for the final shape.

Some industries use a variation called flashless forging, or true closed-die forging. In this version, the die cavities are completely closed to prevent flash from forming. This method reduces metal waste, as flash can account for 20% to 45% of the starting material. However, it requires more complex die designs and better lubrication.

ForgedConrodShowingEtchedSection-s
ForgedConrodShowingEtchedSection-s

Modern impression-die forging has also improved through automation. This includes using induction heating and mechanical feeding to increase efficiency.

Forging has a long and evolving history. For millennia, smiths used a hammer and anvil to make tools, jewelry, and weapons. In the 12th century, the introduction of water power allowed for large trip hammers. This change increased the size of iron that could be forged.

Today, industrial forging uses power from compressed air, electricity, hydraulics, or steam. While some steam hammers remain, most have been replaced by more convenient power sources.

Forging is highly significant in modern engineering. Forged parts generally have a 20 percent higher strength-to-weight ratio than cast or machined parts. This makes them essential in the automotive and tool industries. The process also improves the internal quality of the metal. It provides better fatigue resistance, finer grain size, and a continuous grain flow. These factors make forged parts much more reliable under heavy use.

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🖼️ Images & Media (10)
File:Bochumer Verein-03-50142.jpg
Bochumer Verein-03-50142.jpg
File:Walzen Stab.jpg
Walzen Stab.jpg
Forging a nail. Valašské muzeum v přírodě.webm
File:ForgedConrodShowingEtchedSection-s.jpg
ForgedConrodShowingEtchedSection-s.jpg
Boat nail production.ogv
File:Bochumer Verein-08-50124.jpg
Bochumer Verein-08-50124.jpg
File:Alcator C-Mod superstructure forging 1.jpg
Alcator C-Mod superstructure forging 1.jpg
File:Industrial_furnace.jpg
Industrial_furnace.jpg
File:Forging shop-Gesenkschmiede 1.JPG
Forging shop-Gesenkschmiede 1.JPG
File:impactor flow.png
impactor flow.png
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