Annealing With Induction

What is Annealing?

Annealing is a process used to release stresses and tensions in metals that may be present after various working procedures. This prevents warping or cracking of the part during its service life or in subsequent working operations. Annealing consists of three stages. The first is known as the Recovery Stage, where the material is heated to a temperature where the internal stresses of the material are relieved. Next is the Recrystallization Stage. At this stage, the material is held at a temperature known as the Recrystallization Temperature for a long enough time for new grains to begin forming. The stage may be absent in certain metals such as steel. Lastly, the Grain Groth stage is where the material is slowly cooled down to allow time for the new grains to form. The rate at which the material is allowed to cool determines the rate of grain growth.

Advantages of Annealing With Induction

Annealing, when done in a traditional furnace, involves holding the parts in the heat for enough time to bring them up to temperature, holding them at that temperature, and then allowing them to cool at a controlled rate. For most processes, this could mean transferring the parts between multiple furnacces for heating, holding, and cooling.

Here is where induction heating technology has the ability to turn the annealing process on its head. Induction can be used to anneal parts in a continuously moving line at high speed. This can be done with individual parts such as bullet casings, or inline with a mill for wire or tube drawing. Removing the bottleneck caused by furnaces from the production line allows manufacturers more freedom to control their line speed, and decreases idle time in other stages of the process.

Induction heating can be done very rapidly. This allows induction coils for annealing to be very short compared to furnaces or infrared tunnels. This is particularly pertinent in continuous annealing operations where induction heating may facilitate plant layouts that save considerable floor space.

Localized Induction Annealing

Induction technology also makes localized annealing possible. Localized annealing is when only a portion of the part is annealed while the others retain hardness. This is useful to manufacturers because they can anneal areas that require more ductility without losing the previous work hardening of the other portions. This technique is commonly used for the manufacture of ammunition and tools.

Induction Annealing in a Controlled Atmosphere

Induction annealing is often accomplished without a controlled atmosphere. This is possible since induction heating typically requires only seconds and anneals the part before oxides are able to form. Even so, some processes may still require a controlled atmosphere. This is another area where induction technology shines. Induction creates heat in a part by inducting a current using a magnetic field. This magnetic field can permeate through materials such as quartz, glass, various plastics, and more. This makes heating in a controlled atmosphere incredibly easy because the inductor coil can be located outside of the atmosphere chamber. Induction technology also allows controlled atmosphere annealing to be done on a continuously moving line.

Munitions/Ammunition Systems

Quality induction processing equipment for annealing brass cartridges and other firearms and ammunition manufacturing applications.

FlexScan 12

FlexScan Pop-up Scanners

The technology of choice for accuracy and rapid heating

Bright Annealing Wire Line whole system overview

Bright Annealing Wire Line

Radyne’s Bright Annealing Wire Line fits directly in line with today’s high-speed drawing and rolling lines, making them the preferred choice for lean, agile manufacturing.

Tube Dull Annealing Line

The Radyne Tube Dull Annealing Line is designed for ease of use, easy maintenance, and speed. 

Continuous Induction Annealing

Bright Annealing Tube Line

Radyne’s Tube Bright Annealing Line fits directly in line with today’s high-speed drawing and welding lines.