Annealing removes stresses and strains from a metal that can occur during work processes, preventing the part from warping or cracking during its operational lifetime. Process reliability and repeatability are the two big reasons for using induction annealing to relieve tension from a metal part and remove impurities.

The Induction Annealing Process

The annealing process is composed of three stages.

  1. The Recovery Stage
  2. Recrystallization Stage
  3. Grain-growth stage

In the recovery stage, the material is heated to temperature, recovering the material’s intrinsic hardness. Next, the recrystallization stage is where the temperature is held long enough to allow the formation of new grains. Finally, the grain-growth stage is when the material is slowly chilled to give time to form new grains. The rate the material is allowed to cool determines how quickly grains grow.

Induction annealing is generally performed without a controlled atmosphere because induction heat typically requires only seconds, and annealing of a part is done before the oxide can be formed.

Use in Industry

Induction annealing can be used to control the material properties of metals in different manufacturing scenarios. The process of induction annealing allows accurate and reliable control over the material properties of metals inside a part, including hardness, stiffness, and stress inside. Unlike conventional methods, induction annealing produces heat directly within a workpiece using alternating electromagnetic fields.

You can use induction to anneal parts on a continuous moving line quickly. It can be done on single parts, like casings, or in line with the milling machine to draw wires or tubes. Removing a bottleneck caused by furnaces from the manufacturing line allows manufacturers greater flexibility in controlling their line speeds and reducing idle times at other stages in the process.

The wire and cable industry typically uses induction annealing devices to anneal wire in-between and after the annealing step to improve malleability and electrical conductivity.

It is right at home on the modern high-speed spooling and rolling lines. Tube manufacturing typically requires annealing either at the time or after forming or painting. Both seamed and seamless pipes and tubes may need annealing to ensure that the products have the desired uniform and metal properties.

Benefits of Induction Annealing

Although primarily used for annealing with softer, stress-relieving materials, induction offers excellent advantages over conventional methods.

Induction heating uses less energy than flame-based and oven-based heating techniques. Yet, it produces precisely controlled temperatures and can accurately vary heat throughout the shell’s length.

Induction heating guarantees that every instance is quality-annealed, reducing the variations and damage common to mass annealing processes.