Case hardening

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.

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.