Precise Infrared Temperature Measurement in Induction Hardening

Solution

Short-wavelength infrared cameras measure surface temperature in real time, unaffected by electromagnetic fields. They provide continuous, wide-area monitoring of dynamic parts such as crankshafts, enabling hotspot detection and stable temperature feedback for automated power control in induction hardening systems.

Infrared Temperature Feedback for Induction Hardening

Hardening processes enhance wear resistance, surface hardness, and fatigue strength by forming a hardened outer layer while preserving the unaffected core microstructure. Induction hardening specifically improves the mechanical properties of ferrous components in selected areas subjected to high mechanical stress.

Typical applications include gears, shafts, crankshafts, cams, spindles, and stamped parts — key elements in powertrain, suspension, and engine assemblies. Suitable materials include carbon steel, alloy steel, stainless steel, cast iron, and ductile or malleable iron.

Induction heating is a non-contact process that generates heat by electromagnetic induction within the surface layer of a conductive workpiece. A copper coil produces a strong alternating magnetic field that induces eddy currents in the material. These currents generate heat through electrical resistance losses, while magnetic materials produce additional hysteresis heating below the Curie point. The current concentrates in the surface layer, with depth determined by field frequency, material properties, heating time, and part thickness.

After heating, components are quenched in water, oil, or polymer solutions, transforming the surface microstructure into a much harder phase than the base metal.
Accurate temperature control during both heating and quenching is essential — overheating can cause brittleness, while underheating results in insufficient hardness. For moving targets such as crankshafts, precise surface temperature feedback is vital for reliable process control.

Optimizing Induction Heating with Non-Contact Infrared Sensing

Non-contact infrared sensing is the preferred method for temperature measurement in induction heating. These instruments deliver fast and accurate readings even at extremely high temperatures (up to 3000 °C), without being affected by electromagnetic interference. All IR sensors are positioned outside the magnetic field, ensuring stable, undisturbed signals.

This level of accuracy is essential for consistent heat treatment results. In environments with steam, oil mist, or moving inductors, short-wavelength infrared cameras provide clear advantages. Unlike spot pyrometers, which measure a single point, infrared cameras monitor the entire field of view, allowing hotspot detection even when parts are partially obscured by inductors or vapor.

The Optris PI 1M infrared camera delivers real-time, high-resolution temperature mapping for target temperatures around 1000 °C, without interfering with the process. Depending on installation conditions, optional accessories such as an Optris cooling jacket may be used for camera protection. Temperature data can be output either as an analog signal or digitally via software.

Closed-Loop Control with Short-Wavelength Infrared Cameras

Optris short-wavelength infrared cameras are designed to deliver precise temperature data even in harsh industrial environments. They operate independently of the inductor, completely immune to electromagnetic interference. Operators receive continuous temperature feedback from one or multiple regions of interest, or full thermal images that can be stored for documentation.

While Optris also offers ratio pyrometers, infrared cameras provide a complete thermal overview, making them ideal for monitoring large-scale or moving components. Their wide field of view ensures that areas temporarily covered by inductors or steam are automatically compensated through hotspot analysis.

In this application, the PLC receives continuous temperature data from the infrared camera, enabling direct closed-loop power control for optimal hardening results. Optris also offers accessories for camera protection and cooling, ensuring reliable operation in demanding induction hardening environments.

In summary:
By integrating short-wavelength infrared cameras such as the Optris PI 1M, induction hardening processes achieve precise temperature control, improved process stability, and reduced defect rates — ensuring consistent quality and traceability across every production cycle.