Cold Forging for the Metal Parts You Need

Are you a manufacturing professional responsible for planning, acquiring, or specifying the components of your assemblies? If that’s the case, you’re undoubtedly familiar with the cost-timing-quality triangle. To keep your business alive, you must balance all three legs: low-cost, high-quality, and delivery. It only gets worse if you don’t. You’ll fall behind in the race.

“Someone is going to make your product obsolete. Make sure it’s you.” —Edwin Land.

Cold forging may provide you with the competitive advantage you need.

What is cold forging?

Cold forging is a metal forging technique to process bar stock and squeeze it into an open die. This method occurs at ambient temperature or below the metal’s recrystallization temperature to form the metal into the desired shape. 

Cold forging is an efficient and economically effective method of forming metal to manufacture large volumes of parts at low costs. The forging method is different depending on the temperature: cold or hot. It’s accomplished by machines with hammers, or by a press for shaping, pressing, and rolling steels.

This technique is comparatively less costly than hot forging as the end products require very little finishing work. Although cold forging is called cold, it happens at or close to room temperature. 

The size of the machines to accomplish cold forging varies with the material hardness and the weight of the final component to be processed.

Cold forging has a material savings of up to 70% of production costs since there is very little waste and scrap.

How does cold forging work?

The low cost of forging results from reduced labor costs and the removal of secondary  operations. Parts can be quickly and efficiently manufactured with speeds as high as 1000 pieces an hour, decreasing cost. 

Cold forging can produce near-perfect surface finishes with increased dimensional stability. Each operation enhances the strength and durability of the workpiece, making for durable components.

Forging can refer to the process of forming metal in solid form. Much forging is carried out via the upsetting process. Hammers or rams are horizontally pressed into ends to widen or change the shape of the workpiece. 

The parts usually go through station after station until they reach the final shape. Larger bolts of higher strength are traditionally cold-headed by utilizing this method. An automotive engine valve is formed through a forced forging process. In drop forging, parts are forged in dies to form finished pieces, with a large hammer attached to the machine.

Pictured above: A cold forged drive shaft.

Hot and cold forging – what’s the difference?

Forging is a typical manufacturing procedure where compressive forces can form metal parts. Forging is possible in different conditions, such as hot or cold forging. Forging uses hammers or presses that squeeze and deform materials into rigid pieces. 

The most significant difference between hot and cold forging is the temperature. Unlike cold forging, which starts at ambient temperature, the hot forging process occurs when metal gets heated above its crystallization temperature. The high temperature of hot forging helps prevent work hardening. At such temperatures, metals are plastic – albeit technically solid.

Cold forging is a vital process for shaping and strengthening metal.

In contrast, hot forging produces material with excellent yield strength, lower hardness, higher ductility, and higher strength of materials. 

You can decide between the two types based on economics, your mechanical properties requirements, and the machinery size needed to make a part of specific size and volume.

Note: Forging is entirely different from casting, where the molten material is poured into molds.

Cold forming and forging – are they the same?

Metalworking processes at room temperature can include cold forming and cold forging. They both involve the modification of metal to produce different sizes and/or forms. From iron and steel to aluminum, bronze, and more, a variety of metals and alloys are available. Even though they utilize various techniques to alter metal—forming and forging aren’t the same.

What is forming?

Deforming a metal workpiece using mechanical deformation is known as forming. By definition, the word “forming” refers to any metallurgical process that involves deforming a metal workpiece by mechanical means. The term “forming,” according to its exact meaning, refers to any metalworking operation in which a metal workpiece is deformed by physical means. Because no material is added or removed from the workpiece during forming, it does not alter its weight—only its form.

Metalworking has two types of forming: compressive and tensile. Compressive loading is used to bend metal parts via the use of compressive strain, whereas tensile stress is used to deform metal components. Rolling and extrusion are examples of compressive forming because they employ compressing force. Stretching and sinking, on the other hand, are examples of tensile forming since they subject metal products to tension stress.

What is forging?

The process of forging is a metalworking technique that uses pressurized blows to shape and manipulate the shape of a metal workpiece. All metal forging operations entail the use of powerful and pressured impacts to deform and modify a metal workpiece.

Which is best?

Metal parts can be altered in size and/or form using forming or forging. Forging entails delivering strong blows to metal pieces in order to shape them, whereas forming is achieved by using mechanical deformation. There is no waste in either approach, which makes them cost-effective if you’re working with expensive materials. To find out what procedure would be best for the geometry, volume, and mechanical requirements of your final component, you should consult an expert.

Which materials work best with the cold forging process?

When it comes to selecting a metal for a project, there are many options. Hard metals such as carbon steel, alloy steel, and stainless steel are examples of these. Aluminum, brass, copper, silicon, and magnesium are soft metals that can be utilized. The only requirement for any metal is that it has a Rockwell hardness of 44 HRC or lower.

Above: Blade Bolts manufactured via the cold forging process.

What industries use cold forging?

Automotive, aerospace, agricultural, off-road, ships, piping, and hand tools — to name a few.

Sizes range from a few ounces to thousands of pounds.

Agriculture

Cold forged hitch pins and clevises are used for connecting implements to tractors or other machinery. They are vital in agricultural operations for attaching and detaching equipment efficiently. Cold forging is also used to manufacture blades and cutters for agricultural equipment like plows, mowers, and harvesters. These components are essential for cutting, chopping, and processing crops.

Automotive

For example, suspension components like idler arm spindles and motor elements such as connecting rods and gearboxes are made using cold forging. Because of their outstanding shock resistance, cold-forged parts are used at high-stress locations. Cold-forged components include things like drive trains, gears, driveshafts, and struts or shocks.

Construction

Cold forging is used to manufacture rebar couplers, which are used to connect reinforcing bars (rebar) in construction projects to enhance structural integrity.

Hardware

Nails, screws, anchors, rivets, and different types of bolts are examples of fasteners. The tight tolerances and high dimensional accuracy make cold heading the superior option over other processes like machining. Hand tools, such as sockets, are frequently forged.

Medical

Cold forging is used to produce medical devices and components, including surgical instruments, implants, and orthopedic devices, where precision and strength are essential.

Military

Cold forging is used in the manufacture of shell casings, bullets, and other military equipment due to strict military standards. Cold forged components deliver the excellent dependability and performance that the military requires. Parts with tight tolerances and strength are ideal for military weapons.

Oil and Gas

Pipeline stems and valve bodies, which are often composed of copper alloy to enhance corrosion resistance, employ cold forging. Cold forged parts are also used in drilling equipment, pumps, and other critical components that require high strength and reliability.

Power Generation and Distribution

Cold forging is used to produce components for power generation and distribution systems, including parts for turbines, generators, and transformers.

What production volume do I need to justify cold forging processes?

For the production of high quantities of components at a low cost, cold forging is a successful and cost-effective metal deforming technique.

Cold forging is done with machines designed to deform and shape the metal.

You’ll save money on everything from materials to time. Because of the little amount of scrap generated (compared to metal removal processes), you may save up to 70% on materials. The cost per item is significantly reduced since components are manufactured at a very rapid rate.

You’ll need to think about the part’s size (and weight), as well as the material’s stiffness, and your production volumes. An expert in the field can give you some options to help you make your decision.

What type of lubricants are used in cold forging?

Lubricants play a crucial role in the cold forging process by reducing friction and wear on the tools and workpiece, enhancing surface finish, extending tool life, and improving the overall efficiency of the cold forging operation. The choice of lubricant depends on the material being forged, the specific cold forging process, and the desired outcome. Here are the main types of lubricants used in cold forging:

1. Mineral Oil-Based Lubricants: These lubricants are derived from petroleum and are commonly used in cold forging due to their excellent lubricating properties. They provide good boundary and hydrodynamic lubrication and are often used for ferrous and non-ferrous materials.
2. Vegetable Oil-Based Lubricants: Vegetable oil-based lubricants are made from renewable resources and are environmentally friendly. They offer good lubricating properties and are often used as an alternative to mineral oil-based lubricants.
3. Synthetic Lubricants: Synthetic lubricants are chemically engineered and offer excellent lubricating properties, thermal stability, and resistance to high pressures. They can be tailored to specific applications and are often used for high-speed or high-temperature cold forging processes.
4. Water-Based Lubricants: Water-based lubricants are environmentally friendly and provide effective lubrication and cooling during the cold forging process. They are often used in combination with additives to enhance performance.
5. Graphite-Based Lubricants: Graphite-based lubricants provide effective lubrication, especially in high-temperature forging operations. They can withstand extreme pressures and temperatures and are often used in warm or hot forging processes.
6. Solid Lubricants: Solid lubricants, such as molybdenum disulfide (MoS2) and boron nitride, can be used as dry lubricants or mixed with a carrier medium. They reduce friction and wear and are suitable for high-temperature and high-pressure cold forging applications.
7. Polymer-Based Lubricants: Lubricants based on polymers, such as PTFE (polytetrafluoroethylene), provide good lubrication and are often used in cold forging to reduce friction and tool wear.
8. Greases: Greases are a combination of a base oil and a thickener. They are used in cold forging to provide lubrication, reduce friction, and protect against wear and corrosion.

The selection of the appropriate lubricant depends on factors such as the material being forged, the type of forging operation (e.g., upset forging, impression die forging), the desired surface finish, and environmental considerations. It’s important to choose a lubricant that balances performance, cost-effectiveness, and environmental impact for the specific cold forging application.

FAQs

What is meant by cold forging?

Cold forging has become a popular Chip-Free Forming Process. It typically requires no other work but drilling. The most widely used definition involves making or forging a bulk material with zero heating of the workpiece.

Is cold forging good?

It has many advantages over hot forging such as tight dimensional tolerances, high-quality surface finish, and utilizing lesser cost materials.

What are the advantages of cold forging?

In cold forging, no heat is necessary. This forging method provides increased interchangeability and reproducibility. You can achieve a superior surface finish, minimal contamination issues, improved dimensional control, and greater strength as a result of enhanced grain directional qualities.

What are the disadvantages of cold forging?

Cold forging has the drawback of being unsuitable for certain materials since it may induce cracking during production, create undesirable residual stress, and forged metals are often less ductile. An expert in the field can help you choose between several alternatives.

Ready to warm up to cold forging?

Whether you’re exploring options for a new product or you have an existing one that you’d like to put into production, The Federal Group USA will give you the data and the tools you need to make an informed sourcing decision for your next product—optimized for your manufacturing operation.

We’ve also provided high-quality contract manufacturing services to a wide variety of industries for more than 41 years. Contact us today to learn more.