INDUCTION HEAT TREATING STEEL: A Guide to the Heat Treating Process

Some of our customers send their products to outside heat-treaters for induction heat treating (hardening and tempering). The heat treater then sends back the heat-treated parts and the manufacturing cycle continues. But some customers have brought their heat treating back in-house, while others are seriously considering it. Why?

  • The manufacturer wants to have tighter control over their intellectual property and trade secrets. Often a manufacturer will be reluctant to allow the recipe for their “secret sauce” leaving their plant and their immediate control.
  • The manufacturer wants to have tighter quality control. Sometimes they have experienced parts getting damaged during shipment to/from the heat treater.
  • The manufacturer wants to control costs. Often outsourcers increase prices year after year, as well as shipping costs ever increasing.
  • The manufacturer wants to switch from expensive oven heat treating
    furnaces to energy-efficient, cost-effective induction heating.

Considering bringing your heat treating back in-house and considering induction but need to know more? This quick guide can help.

There are many different types of heat treating for Steel, but this guide will focus on Hardening and Tempering.

Induction Hardening

Hardening increases the strength of steel. Normally, this involves a heat treatment in which a “hard” microstructure known as martensite is produced. In a conventional hardening processes, steel is heated to a predetermined target temperature, held at that temperature for a fixed amount of time, and then rapidly quenched (cooled down with water) to room temperature or lower. Steel can also be air cooled (“normalizing”), but this method is much slower than quenching. Induction has numerous advantages over using ovens for your hardening process, including:

  • Significant energy savings
  • Consistency and repeatability
  • Clean
  • Instant power on (no warmup time required)
  • Localized and/or scan heating
  • Short-term ROI
  • Space saving
Induction Heat Treating
Induction Heat Treating, Heat & Quench

Induction Heat Treating – Tempering

While hardened steel is very strong, uneven cooling can cause microscopic stresses. Reheating the steel, known as “Tempering”, can correct these micro stresses and results in a more durable material. While the hardness of the material is reduced somewhat, the material is more durable as it is less brittle. The same induction machine and coil can be used for tempering your workpieces as for hardening – usually you can just turn the power down on the power supply to generate less heat.

Induction Heat Treating – Zone Hardening and Scanning

Zone Induction Hardening: The beauty of induction heating is that you can localize the heat by positioning the induction coil right at the part of the workpiece, or zone, that you wish to heat treat without affecting the rest of the workpiece area.

Induction Hardening The Entire Length Of A Workpiece, Commonly Known As Scanning: Depending on the length of a workpiece, you can either heat treat the entire length of the workpiece, or, if the workpiece length is too long, it is far more economical to “scan” the part. That means you heat treat the part one section at a time until the entire length is heat treated.

Induction Heat-Treating Scanning Method

In the above photo, the induction coil is used to heat only one section of the metal piece. For longer work pieces, you can either move the piece through the coil or move the coil along the workpiece (usually via automation).

For more information about heat treating workable length, please drop me an email: rayariss@inductronix.com

email: rayariss@inductronix.com

How Do I Know I’m Heating My Metal to the Right Temperature?

The most effective way is to use an Infrared temperature sensor, commonly known as IR temperature sensor. IR sensors can coordinate with and control the induction power supply, cutting power automatically when the work piece has reached the desired temperature. There are different types of IR sensors around, so please drop me an email and I will gladly steer you towards the the most reasonably priced, effective sensors that will work for you.

Induction Hardening Automation

Our high performance induction power supplies work great with automated equipment! Opportunities for automation include:

  • Feeding
  • Loading and Unloading
  • Scanning
  • Quenching
  • Any other point in the process where manual handling is necessary

As each application is different, please drop me an email so I can review your particular requirements and determine the best solution.

Induction Power Supply Selection

Not all induction power supplies are the same! Many may heat metal well, but when the metal temperature reaches above Curie point, i.e. the metal is no longer magnetic, its resistivity will change abruptly, and the power supply will begin to struggle.

With our high performance induction power supplies, the induction heater will actually adjust its output to adapt with the metal’s ever-changing Resistivity and Curie.

Please drop me an email with any questions that you might have.

About Ray Ariss and Inductronix, a West Coast-based Induction Solutions Company

Ray is so passionate about induction heating that he founded his own company back in 2011, serving his customers with high performance induction heating power supplies, coil design, consulting, infrared temperature sensors, and data logging systems.

If you have any questions about your induction heating application requirement, please call him or drop him an email at any time.

email: rayariss@inductronix.com

www.inductronix.com

LinkedIn: linkedin.com/in/raymond-t-ariss-762a1a45