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Crankshaft hardening: low distortion and very high precision

Crankshafts are key parts of engines. New requirements for lightweight vehicle construction and higher efficiency in engine technology require precise crankshaft hardening within increasingly tight tolerances.

Furthermore, crankshafts must have a combination of material properties: high-precision induction hardened surfaces for low-wear operation with long service life, together with core elasticity to absorb high torque stresses. Flat hardening improves the wear resistence. Fillet hardening offers furthermore an increase of the fatigue strength of the crankshafts that is needed for high power engines as well as for medium sized and large crankshafts. Among other applications, it is used in passenger cars or trucks and as a large crankshaft for locomotives, ship propulsion systems or for large diesel engines for generators, compressors or pumps.

SMS Elotherm GmbH is amongst the market leaders in induction heating machines for crankshafts and has unique expertise. The patented low-distorsion hardening technologies are vastly superior to conventional methods.

Specifically for induction hardening of crankshafts, SMS Elotherm has developed solutions for various application cases and crankshaft sizes, which are available to our customers worldwide. All of our hardening machines have a modular structure, allowing them to be adapted, both overall and with regard to important details, to give users the greatest possible benefit.


Key Features


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Energy-efficient hardening process

SMS Elotherm has continuously refined the hardening process to achieve extremely high energy efficiency. Induction hardening with induction machines from SMS Elotherm needs less energy than comparable systems.

A crucial factor here is that with Elotherm, the converters (power generators) and the inductors (power applicators) come from the same source and are perfectly matched to each other. Elotherm therefore achieves a trend-setting energy balance, which reduces the environmental footprint as well as unit costs.

Compared to hardening processes with traditional furnace technology, induction technology needs distinctly less energy, is considerably faster and minimises distortion effects. It also eliminates the time, cost and energy expenditure of furnace preheating or charging as with thermochemical processes in the furnace is not necessary. . When induction heating machines are not needed, they automatically switch to an economical standby mode.

Stably reproducible process results, long inductor service life, short cycle and set-up times, easy access for maintenance, optimised machine footprint, and if desired fully automatic sequences are factors for optimal customer benefits. Whether with series products or package concepts aligned to the customer’s process, we stand by our customers with all of our experience and expertise and this for decades.

Induction hardening – economical and gentle on the environment

Induction hardening is generally a clean process. The process sequence for hardening usually consists of heating, holding at hardening temperature, soaking, quenching and if necessary inductive tempering or even tempering by residual heat (auto tempering). SMS Elotherm has detailed knowledge of the interactions in this process and their impact on metallurgical characteristics. Based on this expertise, we are constantly improving the efficiency of the machine technology to reduce power consumption significantly.

Crankshaft hardening zones



For varying geometries

Surface hardening of passenger vehicle crankshafts. The machine can be designed with one or two stations. Surface hardening with one station is primarily suitable for small and medium volume production, with the focus on hardening of a variety of workpieces. With two stations, the machine is ideal for large volume production with high-throughput hardening.

SMS Elotherm has created effective conditions for flexible machine layout as well as flexible application. The machines can harden crankshafts for 1 to 6 cylinders.


Designed for versatility

Both machines can be upgraded in many ways with option packages. For example, loading and unloading in the same place is possible. Furthermore, this can be linked to a gantry loader or even equipped with a through transport system. The machine can also be equipped to adapt automatically to different workpiece lengths and different pitch dimensions via NC axes.

In response to a control command, the machine automatically configures itself for different spacings between main and pin bearings.

120 crankshafts per hour

In continuous industrial operation, the machine can achieve cycle times under 30 s for hardening of four-cylinder passenger vehicle crankshafts. That means a profitable throughput of up to 120 crankshafts per hour, with consistently high quality within exactly specified tolerances.



To meet large demands

For hardening crankshafts with lengths up to 1500mm, the SMS Elotherm system opens up a solution, for trucks and other large vehicles as well as many stationary units. Customers can choose exactly the required performance profile to avoid overcapacity and/or excess capital expenditure.

Precision for highest requirements

The system can be equipped with up to 13 independent power channels, depending on cycle time requirements. A highly productive configuration with one or more multi-channel-converters with up to six separately controllable converters each for simultaneous hardening of bearing locations with different parameters. This results in extremely short cycle times, even with large crankshafts and the patented induction hardening of split pin crankshafts are also possible.

Fully automatic and flexible crankshaft hardening machine

These crankshaft hardening machines from SMS Elotherm can harden up to 40 crankshafts per hour.

Hardening of oil seal surfaces on the flange or journal end can be integrated into the machine concept. For this it is recommended to plan in a supplementary station for hardening of oil seal surfaces at the flange or journal end or a gearwheel. Integrated inductive tempering or single-location loading/unloading by an integrated shuttle transport are also optionally available.

Other machine features include automatic pitch adjustment and manual workpiece changing. These machine type from SMS Elotherm GmbH is also characterized by modular assemblies and thus enables the integration of individual additional components into the overall concept. A post-cooling station, crankshaft cleaning before hardening or integrated workpiece drying by blowing off are additional features that can be part of the scope of supply and services of SMS Elotherm GmbH.



Large-size hardening

Hardening crankshafts with lengths up to 12000 mm and weights up to 8 tonnes even with large undercuts in the fillets – those are the breathtaking dimensions of crankshaft induction hardening machines from SMS Elotherm.

This allows enormous crankshafts to be hardened with high precision and, above all, economically. Some examples are crankshafts for marine engines or locomotives, or for the large diesel engines of generators, compressors and pumps.

Customers can choose from a basic configuration with low capital expenditure or a higher configuration level with for example distinctly shorter cycle times.

The hardening process can be set individually for each bearing location and is also performed automatically.


Brochure: Automotive

Technical report: Optimized quality control in induction hardening

Technical report: State-of-the-art induction technology for crankshaft hardening plants

Technical report: ModuLine - Minimal distortion induction hardening of crankshafts


Sascha Brill

Manager Service

+49 (0) 2191 891-571e-mail

Martina Godon

Sales Heating

+49 (0) 2191 891-552e-mail