For camshafts, axles, shafts, rods and other long cylindrical parts, the main requirements can be stated succinctly:

lower weight, better vibration characteristics and higher load capacity, thereby reducing fuel consumption and increasing component lifetime.

Induction surface heating is the right technology for economical hardening of these parts in high-volume production. SMS Elotherm has comprehensive and up-to-date process expertise for this and is able to provide reliable, high-throughput hardening even with complex geometries and demanding materials.

An additional effect is tempering from residual heat, which can be integrated in the machine if required.


The fully automatic machine series achieve a throughput of up to 360 parts per hour. Accessory devices for induction annealing and tempering allows the machines to be upgraded to complete heat treatment centres with mutually compatible interfaces.


Short heat treatment times

Measurable high productivity

Very high quality assurance

No emissions


scan hardening and single-shot hardening

Single-shot induction hardening

EloShaft Singleshot is designed for single-shot hardening of axle shafts and driveshafts. EloShaft Inline enables horizontal scan and stationary hardening of parts such as camshafts, gear racks, axle shafts and driveshafts.

Induction hardening improves material properties

The main purpose of induction hardening is to improve material properties. Wear resistance and fatigue strength, as well as the associated static strength, can be improved by microstructure changes that occur during hardening. Furthermore, induction hardening is limited to the especially highly stressed areas of parts, even in gear racks. These consist of the actual teeth and, depending on the type of rack, the shank area that forms a ball screw spindle after hardening.

The areas to be heated are exposed to an alternating electromagnetic field that induces a current. The current flux heats the metal to about 900°C, after which it is hardened by quenching with a special polymer emulsion. The penetration depth of the induced current in the part depends on the frequency and the material. As a rule, a hardening depth of a few millimetres is required with gear racks, which can be achieved with working frequencies in the range of 3 to 20 kHz.

scan hardening
inductive scan hardening

Induction hardening methods: scan hardening and single-shot hardening

Two different methods have become established for the induction hardening process, known as scan hardening and single-shot hardening. With scan hardening (also called peripheral scan hardening), heating and quenching take place simultaneously. This requires continuous relative motion between a stationary inductor/spray unit and a moving part, or vice versa. With gear racks, the inductor/spray unit is usually moved along the length of the clamped gear rack. With single-shot hardening, by contrast, heating and quenching occur sequentially in one or more stations. Single-shot methods are used for relatively large hardening depths or high throughput.

Both methods have advantages and disadvantages that must be weighed against each other, depending on the hardening task and throughput requirements, to the extent that both methods are actually technically equivalent. Generally speaking, single-shot methods have distinctly shorter process times but higher power demand, while scan hardening requires less power but also has lower throughput. There are even use cases in which both methods can be applied sequentially on different parts of the workpiece.


Brochure - Automotive

Induction hardening versus case hardening – a comparison

Induction hardening of steering racks for electric power steering systems