Cold Heading (Cold Forging, Cold Forming)

The following links provide introductions to the processing methods used in manufacturing terminals and pins out of wire.

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Cold heading

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Pure copper

Pure copper does not contain any additional alloying element, thus demonstrating the high electrical conductivity specific to Cu, although it is inferior to other copper alloys in strength.
The pure copper varieties used in heading processes includes electrolytic tough-pitch copper (C1100), which retains 0.02-0.05% oxygen content to detoxify any impurities which could interfere with conductivity, and oxygen-free copper (C1020), refined to remove as much oxygen contamination as possible to avoid hydrogen embrittlement, a disadvantage of electrolytic tough-pitch copper.

Brass

Brass is an alloy of copper (Cu) and zinc (Zn). As the Zn content increases, it becomes harder but also more brittle. It offers good processability for a variety of heading process needs with adjustment to the alloying agent ratios. Consequently, brass is used not only for electrical parts but also large-sized auto parts and headed parts for building construction.
Primarily C2600 (70% Cu and 30% Zn) and C2700 (65% Cu and 35% Zn) are put into wide use.

Phosphor bronze

This alloy of copper (Cu), tin (Sn) and small amounts of phosphorus (P) constitutes a type of bronze. It features high mechanical strength and spring characteristics. It is also excellent in wear resistance and is non-magnetic, thus finding wide application in springs, switches, gears and other headed parts for various types of electronic equipment.

Other Cu alloys

Other alloys like Corson are also attracting attention due to their springiness and higher electrical conductivity.

Ferrous metals

Stainless steel

Stainless steel is a steel alloy with a minimum of 10.5% chromium content by mass added to the principal component Fe to ensure that it does not readily corrode. The chromium content binds with oxygen in the air, creating a protective passivation layer on the surface and thus ensuring higher corrosion resistance.

Other metals

Aluminum

Aluminum is lightweight, approximately 35% less relative density than iron, and excellent in thermal conductivity, electrical conductivity, and ease of processing. It creates a protective film of oxide in the air and as a result provides higher resistance to corrosion. Pure aluminum offers low strength and so aluminum is often used in the form of aluminum alloys. Aluminum sees widespread use in rivets and other headed parts.

Precious metals

Precious metals like gold (Au) or silver (Ag) are often used as brazing material.

Methods for processing headed parts

In the cold heading process, headed parts are manufactured with a combination of "punches" to cause deformation by applying force directly to the material in question and "dies" to hold the material.
Punches and dies are available in various designs for different forms of materials and final intended shapes. They are combined to accommodate a wide variety of heading work, as listed below.

Upsetting

Upsetting refers to a heading process of hitting a material held in dies with a punch in the longitudinal direction to reduce the length of the material while increasing the diameter correspondingly.
It is used in processing the head section of rivets, bolts and other headed parts.

Forward extrusion

Material is placed on a die that is narrower than the material’s original diameter, and is then hit with a punch to drive it through the die and reduce its diameter while correspondingly increasing the material’s length.

Backward extrusion

A material held in dies is hit with a punch having a smaller diameter than the dies and material. The material flows into the space between the dies and punch, forming a cup-like shape.
This is used in the making of blind-rivet shanks, for example.

Cold roll forming is a manufacturing process used to shape metal materials into complex profiles with consistent cross-sections. Like any production method, cold roll forming has its own set of advantages and disadvantages.

Pros of Cold Roll Forming:

1. Cost-Efficient: Cold roll forming can be more cost-effective than other metal forming methods, such as hot rolling or extrusion, due to its lower energy consumption and reduced material waste.
2. High Production Rates: The continuous nature of cold roll forming allows for high production rates, making it suitable for large-scale manufacturing.
3. In-Line Processes: With cold roll forming it is possible to integrate processes in-line. A few examples are: in-line hole punching, bending, laser welding, swaging, foiling and customer specific assembly’s.
4. Long Part Lengths: Cold roll forming can be used to produce parts as long at 16m in length.
5. Consistent Dimensions: Cold roll forming produces profiles with precise and consistent dimensions, ensuring high levels of uniformity across the entire production batch.
6. Design Flexibility: It enables the creation of complex cross-sectional shapes and custom profiles to meet specific design requirements, in a wide variety of formable metals
7. Material Savings: Cold roll forming often requires thinner materials compared to other forming methods, leading to material savings and reduced overall weight of the final product.
8. Improved Material Properties: The cold forming process can enhance the mechanical properties of the metal, making it stronger and more durable.
9. Reduced Residual Stress: Cold roll forming generates less residual stress in the metal compared to hot rolling, which can be beneficial for certain applications.
10. Minimal Surface Imperfections: The controlled forming process reduces surface imperfections and defects, resulting in a smooth finish.

Cons of Cold Roll Forming:

1. Initial Tooling Costs: The setup costs for creating custom roll forming tooling can be relatively high, making it less economical for small production runs.
2. Lead Times: custom profiles may require dedicated tooling to be designed and manufactured, which can add to the lead time of new product introduction.

In summary, cold roll forming offers numerous benefits, including cost-efficiency, high production rates, and consistent dimensions. However, it may have some limitations related to tooling costs, and profile complexity. The decision to use cold roll forming should consider the specific requirements of the project and the material properties needed for the final product.

At Hadley, we have a team of over 50 in-house engineers to work with you on your profile and tooling needs. Having this function internally helps us reduce lead times, as we design, make and test the tooling in our own dedicated bay. Find out more with this short video  on our capabilities.

If you would like to discuss your project or have a tour of our engineering and testing facility, please drop us an email and we can find out if cold roll forming suits your project.

If you want to learn more, please visit our website Cold Heading Process.