Induction Heating for Surface Treatment

The Targeted Precision of Induction Heating

May, 2018

Bud Clark
National Accounts Manager
American Electric Power

A 3,500-year-old technology is as tried and true as it gets.  Yet even today, metal-working industries are still using the same basic methods to treat metal surfaces as were used to make swords in the Bronze Age.  Whether using bellows and charcoal in a forge or running parts through a gas oven, for a softer metal, achieving a hard-durable surface means heating the metal cherry-red before tempering, brazing, bonding, welding, curing, annealing, forging, straightening, coating, or engraving your bronze sword or intricate steel part.  It’s a process that generates high temperature in a chamber and gradually transfers the heat to the metal piece.  It’s simple.  It’s also a very slow, inefficient, uncomfortably hot, expensive and emissions-filled process.  But after 3,500 years, why change?

Because surface treatment with electric induction heating changes the entire process.  For one thing, heat isn’t transferred to the metal via hot air; instead the metal heats itself electromagnetically (through internally circulating induced currents).  And for every manufacturing consideration – speed, throughput, quality, flexibility and, above all, cost-savings – that one big difference changes the surface treatment process for the better.

A brief overview by the Electric Power Research Institute (EPRI) provides a quick overview of induction heating, and just begins to list the technical advantages as well as the non-energy benefits.  The basic concept is easy: put a metal piece inside a coil generating electromagnetic waves. Literally, in seconds, the metal surface itself will be red hot…and within a single degree of the ideal temperature set for the treatment desired.  The principles of induction heating depend on the intensity of the electromagnetic field, the metallurgical properties of microstructure at the surface of the workpiece, and the exact temperature; but the simple concept holds true: the coil almost instantly brings the metal surface to the temperature you need for your surface treatment.  It can even heat different areas of a single piece at different temperatures simultaneously.

So what changes could you expect in your processes?  Everything: more speed, precision, targeted heat, efficiency, quality – and major cost savings.

  • The induction heating process is up to 10 times faster than with gas ovens, and requires no warm-up period thereby cutting significant standby losses
  • By heating the metal rather than an oven, it directs energy only where and when needed, for exceptional energy savings
  • Induction maintains the precise surface temperature -- within one-degree Fahrenheit for completely repeatable results on every piece in production
  • Targeting heat at different sections of the piece simultaneously eliminates production steps
  • Induction heating eliminates gas heat and its emissions, for providing higher final surface quality with virtually no deformation, scale or gas emissions contamination that requires re-work
  • Less ambient heat and zero emissions keep the workplace cooler, cleaner and more comfortable than with open gas furnaces
  • It’s versatile technology: The U.S. Department of Energy has issued a detailed report on the use of electric induction heating on a wide range of metals and surface treatment processes
  • In a production environment, induction helps achieve single-piece quality certifications and can change a batch process to a continuous process

The bottom line is the most important one: the overall annual costs of electric induction surface treatments are up to 80% lower than using gas furnaces.

That’s why, for metal working industries, the Bronze Age is over….and the Induction Age has begun.