Guaranteed safety, drive for innovation

Products & services

We develop and produce nitrogen-alloyed steels such as CRONIDUR® 30. Our steels are the driving force behind a variety of markets, from warehousing technology to aerospace and medical technology. For over 100 years, we have been the global specialist for retaining rings in the field of energy-based mechanical engineering – a wealth of experience that has made us an international market leader. On top of this, Energietechnik Essen is also a leading guarantor of safety for turbo generators.
Energietechnik Essen GmbH specialises in the production of retaining rings for safety applications and nitrogen-alloyed steels with optimised properties. Our experience in manufacturing retaining rings dates back more than 100 years. Our expertise in developing our own special alloys can be seen in innovations such as our versatile CRONIDUR® 30 steel which is used, for example, in the aerospace industry as well as in medical applications.

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Retaining ring


Today, electrical energy is almost exclusively produced in rotating dynamos - so-called generators. Most of this energy by far is produced in turbo generators which run at 3,000 revolutions per minute. The rotating magnetic field is generated by windings with alternating polarity, which are caused by DC. The windings protrude from the longitudinal grooves of the rotor at the ball ends and form the winding head that must be secured against the centrifugal force. Retaining rings take over this function. They are the component bearing the greatest load in a turbo generator. In most cases, the retaining rings are shrunk overhung onto  the ball ends of the rotor bodies and secured against rotary  and axial movements. They are secured against rotary and axial movements by a type of bayonet fastening. On the side facing away from the clenches, a supporting ring shrunken into the retaining ring, der die which absorbs the longidtudinal force of the winding heads.

Our retaining rings endure the enormous centrifugal force in generators - which amounts to up to 3,600 rotations per minute. Current material standard is P900 (material number/DIN-Code: 1.3816, ASTM A 289, Class C)

  • high yield strength
  • good cold and hot forming properties
  • low thermal expansion
  • non-magnetisable
  • resistance to stress corrosion cracking 

Nitrogen-alloyed steels


P900, P900N, P900N Mo and P2000 are pressure-nitrided austenic steels. The distinctive qualities include high corrosion resistance in combination with very good mechanical properties. 

Pressure-nitrided steels with outstanding properties:
  • high corrosion resistance
  • excellent mechanical properties, i.e. high strength (yield strength from 500 MPa / tensile strength from 900 MPa) whilst maintaining toughness (fracture toughness >40% depending on degree of deformation)
  • highest cold strength potential
  • biocompatible (depending on quality)
  • Hot-stamped semi-finished products and also cold-stamped semi-finished products

Cronidur® 30


CRONIDUR® 30 is a pressure-nitrided, highly corrosion-resistant martensitic cold work steel that offers excellent toughness and hardness > 58 HRC.

  • high corrosion resistance
  • excellent machinability
  • high toughness at max. hardness
  • good wear resistance
  • high tempering resistance up to approx. 450 ° C, excellent grade of purity

ESR / PESR ingot


  • Weight: 2 -26 t
  • diameter: 400 to 1,000 mm

Materials development


We focus on pressure-nitrided austenic steels or HNS qualities. HNS stands for "High Nitrogen Steels".  Our PESR process makes it possible to produce these unique steels, which have meanwhile become well established on the stainless steel market. The outstanding properties of these steels include high corrosion resistance, very high strength, very good toughness and a higher hardness. These properties make the steels produced by Energietechnik Essen GmbH ideal structural materials – with a wide range of applications. It is, of course also possible to produce alloys in strict accordance with customer specifications. In our ESU and PESR plants we are able to produce ingots weighing between 2 t and 26 t. 

Solutions for the individual requirements of our customers: 

Custom-made alloys with 

  • high corrosion resistance
  • extremely high strengths
  • extremely good toughness properties and 
  • special harness