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Induction Annealing

ARC Precision uses Induction for their Brass Annealers. Let us give some basic information about induction annealing.

When a conductor is placed in an alternating magnetic field, it leads to the phenomenon of electromagnetic induction. Here’s how it works:

  1. Alternating Current (AC):
    • When you connect an AC source (such as an AC generator or power supply), the current flowing through the conductor alternates between positive and negative values.
    • The waveform of the AC current typically follows a sine wave pattern, where the current strength varies with time.
  2. Magnetic Field Generation:
    • As the alternating current flows through the conductor, it generates an alternating magnetic field around the conductor.
    • The direction of this magnetic field changes in sync with the alternating current. When the current is positive, the magnetic field has one polarity; when the current is negative, the polarity reverses.
  3. Electromagnetic Induction:
    • The changing magnetic field induces an electric current in nearby conductors (such as a wire loop or coil).
    • This phenomenon is known as electromagnetic induction.
    • The induced current flows due to the changing magnetic flux through the conductor.
  4. Faraday’s Law:
    • Faraday’s law of electromagnetic induction states that the magnitude of the induced electromotive force (EMF) is directly proportional to the rate of change of magnetic flux.
    • The induced current opposes the change in magnetic field (as described by Lenz’s law).
  5. Applications:
    • Electromagnetic induction is the basis for various devices and technologies, including:
      • Transformers: AC voltage transformation.
      • Generators: Converting mechanical energy into electrical energy.
      • Induction cooktops: Heating using alternating magnetic fields.
      • AC motors: Converting electrical energy into mechanical motion.
      • AND ARC Precision Brass Annealers!

In summary, the alternating magnetic field created by the alternating current induces an alternating current in nearby conductors, demonstrating the interconnectedness of electricity and magnetism.

Regarding annealing, let’s delve into it further:

  • Internal Resistance of Conductors:
    • All conductors exhibit some internal resistance due to their atomic structure and impurities.
    • Copper, being an excellent conductor, has very low internal resistance.
    • Brass, on the other hand, has higher resistance due to its composition (a mixture of copper and zinc).
Showing a heated brass case.

In induction annealing, the alternating magnetic field induces a current flow in the brass case.

The resistance to this current flow generates heat within the brass.

As the heat increases, so does the resistance, creating a positive feedback loop.

This controlled heating process anneals the brass, making it more malleable and suitable for reloading.

  • Gas Annealing vs. Induction Annealing:
    • Gas annealing (using a flame or torch) is cost-effective but lacks consistency.
    • Induction annealing offers precise control, faster heating, and improved consistency.
    • The choice depends on cost, convenience, and desired results.
  • Some useful links:
Next: Why Anneal?