In Episode 2 of No Dumb Questions, we explain the concept of annealing in wire and cable manufacturing and why heat treatment is essential for conductor flexibility.
Annealing is a thermal heat-treatment process that softens metal conductors—such as copper or aluminum—after they have been cold-worked through the wire-drawing process. As bare wire is drawn through progressively smaller dies to reduce its diameter, it becomes work-hardened (hard-drawn), which increases its tensile strength but severely reduces its ductility and flexibility.
To restore flexibility, the hard-drawn wire undergoes annealing by heating it to a specific recrystallization temperature and cooling it under controlled conditions. This process relieves internal material stresses, lowers tensile strength, and significantly increases elongation and flex life. Annealed (soft) copper provides maximum bend radius flexibility and serves as the baseline for 100% IACS (International Annealed Copper Standard) electrical conductivity, making it the standard choice for flexible, high-reliability custom cable assemblies.
Key Technical Takeaways
- Definition of Annealing: A controlled heat-treatment process that softens work-hardened metal conductors to restore ductility and flexibility.
- Hard-Drawn vs. Annealed Metal: Cold-drawing wire increases tensile strength but makes conductors stiff; annealing lowers tensile strength while increasing elongation.
- Flex-Life & Bend Performance: Annealed copper is critical for high-flex applications, robotics, and custom cables requiring tight bend radii without strand breakage.
- Electrical Standard: Pure soft-annealed copper defines the 100% IACS baseline for measuring conductor electrical conductivity.
Curious about other topics? Watch Episode 3: What is attenuation?
Welcome to No Dumb Questions
Hello and welcome to another episode of No Dumb Questions, where the only dumb question is the one you don’t ask. Today we’re going to answer a question we hear frequently from engineers: what is annealing?
What Happens During Wire Drawing
To understand annealing, we first have to look at how wire is made. When bare copper or metal conductors are drawn through dies to reduce their size down to fine wire, the cold-working process changes the mechanical properties of the metal.
As the wire is drawn down, it becomes hard-drawn, or work-hardened. This increases the metal’s tensile strength, but it also makes the wire stiff, brittle, and difficult to bend without breaking.
The Annealing Heat Treatment Process
This is where annealing comes in. Annealing is a thermal heat-treatment process where hard-drawn wire is heated to a specific temperature and allowed to cool under controlled conditions.
Heating the metal relieves the internal stresses created during drawing and allows the crystal structure to reform. This softens the metal, lowers its tensile strength, and dramatically increases its ductility and elongation—meaning how far the wire can stretch and flex before breaking.
Why Annealed Copper Matters for Cable Engineering
In custom wire and cable engineering, annealed copper—often referred to as soft copper—is the industry standard for applications requiring high flexibility, extended flex life, and easy handling during installation.
Annealed copper also serves as the benchmark for electrical conductivity, establishing the 100% IACS standard. If your cable design requires high flex life, fine stranding, or tight bend radii, annealed conductor wire is essential.
Thank you for joining us for another episode of No Dumb Questions. If you have any wire and cable questions for our engineering team, please feel free to reach out to us!