Case hardening

Whereas conventional case hardening causes gradual wear and tear, Kanthal® AF and Kanthal® APM radiant tubes have been proven to stand the test of time. Furthermore, the electrification of the case-hardening process reduces emissions and minimizes energy losses.

Case hardening is a process typically applied to automotive parts like gearboxes, whereby the surface of a metal is carburized to withstand wear. The process requires the presence of a furnace, radiant tubes and heating elements. When used together, two products from Kanthal – Kanthal® AF radiant tubes and Tubothal® heating elements – have been proven to deliver higher power ratings than any other metallic heating system on the market today.

Kanthal’s electric Tubothal® heating elements are capable of operating at a far higher power output than conventional cartridge heating elements. With a power output up to 45 kW/m (12.2 LW/ft) length, a single Tubothal® heating element may be capable of replacing up to three heating elements of standard design, leading to major savings.

Using electric heating does not only reduce CO2 emissions – cutting them to zero if green electricity is used – it also improves overall energy efficiency since flue-gas losses are minimized. Furthermore, it makes the environment around the furnace quieter, cleaner and safer.

Used in combination with Kanthal® AF or APM radiant tubes, Tubothal® heating elements are capable of delivering an almost maintenance-free case-hardening process.

Kanthal® AF tubes

Krister Wickman, Global Product Manager High Temperature Tubes, Tubothal® and Bayonet Heating Elements at Kanthal.“Unlike traditional NiCr tubes, the aluminum-oxide film on the inner and outer surface of the radiant tube and on the heater material itself protects them from contamination by the carbon in the atmosphere, which can cause scaling on the tube surface,” explains Krister Wickman, Kanthal’s Global Product Manager High Temperature Tubes, Tubothal & Bayonet Heating Elements.

“The thicker the scaling layer gets, the harder it gets for the element to dissipate heat. Eventually the heating element overheats and has to be replaced, during which time the furnace will be out of action, leading to production losses,” he continues.

Whereas NiCr tubes tend to oxidize, corrode or bend over time – requiring regular maintenance and, thereby, slowing down production – Kanthal® AF tubes still look new after two years of use.

Thomas Lewin, Senior Design Engineer at Kanthal.“The reduced thermal mass of the Kanthal® AF tubes in combination with the low thermal mass of the Tubothal® heating elements have a positive impact on the heat treatment process,” explains Thomas Lewin, Senior Design Engineer at Kanthal.

Last but not least, Lewin explains that the higher power delivered by Kanthal® AF tubes and Tubothal® heating elements, translates directly to greater output in the case-hardening process.

“The combination allows for more carbon to be added in less time, thereby contributing to enhanced productivity,” he concludes.


Key benefits of electrified case hardening

  • Zero emissions
    Electrifying the case hardening process eliminates the CO2 emissions generated by gas burners. When green electricity is used, CO2 emissions are close to zero.
  • Enhanced thermal efficiency
    Gas burners deliver poor thermal efficiency due to high flue-gas losses. In contrast, thermal efficiency from electric heating can reach more than 90%.
  • Less maintenance
    Kanthal® AF or APM radiant tubes and Tubothal® heating elements deliver almost maintenance-free case hardening since the tubes do not oxidize, corrode or bend over time, this preventing overheating and eventual failure.

Connected products

Here you can find the Kanthal product offering

Radiant tubes

Radiant tubes (radiation tubes) in Kanthal® APM and Kanthal® APMT iron-chromium-aluminium alloys (FeCrAl alloys) available as complete ready-to-install assemblies according to almost any customer specification.

See product details

Kanthal® AF radiant tubes

Our Kanthal® AF Tubes are a unique type of radiant tube that outperform common NiCr tubes in all respects. They are also more cost effective than other equivalent products on the market.

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Tubothal® heating element

Metallic heating elements of cartridge element type designed for long life and trouble-free service. Tubothal® elements can be used inside all types of radiant tubes or as stand-alone elements.

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