Retaining rings
For more than 100 years we have been developing and manufacturing retaining rings for turbo generators and other high-performance machines.
Our components made from austenitic steel P900 (material no. 1.3816, X8CrMnN18-18) combine exceptional strength and toughness with high resistance to stress corrosion cracking (SCC) — a decisive advantage for safe operation in power plant installations.
Key Properties
Nonmagnetic, high yield strength, very good cold and hot formability, low thermal expansion, resistant to stress corrosion cracking.
All rings are manufactured to order, special sizes available on request.
We manufacture the following dimensions:
Materials & Alloys
| Material | Material No. | Typical Application |
|---|---|---|
| P900 | 1.3816 | Standard retaining rings for turbo generators |
| Parameter | Range |
|---|---|
| Diameter | 430 – 2 200 mm |
| Weight | 15 – 4 300 kg |
From Ingot to Precision Retaining Rings — 9 Steps at a Glance
Our manufacturing begins with Green Steel ingots, melted from nearly 100% scrap in the electric arc furnace (EAF) — a key pillar of the GMH circularity strategy.
This is followed by a multi-stage quality process in which each step is designed for reproducibility, dimensional accuracy, and traceability.
Your contact for rotor retaining rings
We manufacture all our products to customer specifications. So what are your specifications?
Please feel free to contact us. Together we will find your perfectly customized solution.
Jörg Schulze
Sales Director Retaining Rings & HNS
Electroslag Remelting (ESR) / Pressure Electroslag Remelting (PESR)
The steel is remelted in ESR units. This process minimizes inclusions and produces a homogeneous microstructure — the basis for retaining rings that withstand high loads.
Your contact for Electroslag Remelting (ESR) / Pressure Electroslag Remelting (PESR)
We manufacture all our products to customer specifications. So what are your specifications?
Please feel free to contact us. Together we will find your perfectly customized solution.
Jörg Schulze
Sales Director Retaining Rings & HNS
Open-Die Forging
The remelted ingots are forged into bars and then into rings — with geometry optimized to customer specifications for ideal downstream processing
Your contact for Open-Die Forging
We manufacture all our products to customer specifications. So what are your specifications?
Please feel free to contact us. Together we will find your perfectly customized solution.
Jörg Schulze
Sales Director Retaining Rings & HNS
Pre-Turning
The forged surface is removed, and dimensions are set for expansion.
Your contact for Pre-Turning
We manufacture all our products to customer specifications. So what are your specifications?
Please feel free to contact us. Together we will find your perfectly customized solution.
Jörg Schulze
Sales Director Retaining Rings & HNS
Heat Treatment
The microstructure is homogenized by solution annealing in preparation for subsequent cold expansion.
Your contact for Heat Treatment
We manufacture all our products to customer specifications. So what are your specifications?
Please feel free to contact us. Together we will find your perfectly customized solution.
Jörg Schulze
Sales Director Retaining Rings & HNS
Cold Expansion
The ring is cold-expanded at room temperature on an expansion press used exclusively for retaining-ring production, reaching the specified dimensions and the required strength level in a single step.
Your contact for Cold Expansion
We manufacture all our products to customer specifications. So what are your specifications?
Please feel free to contact us. Together we will find your perfectly customized solution.
Jörg Schulze
Sales Director Retaining Rings & HNS
Stress-Relief Annealing
Residual stresses introduced during cold forming are removed by stress-relief annealing.
Your contact for Stress-Relief Annealing
We manufacture all our products to customer specifications. So what are your specifications?
Please feel free to contact us. Together we will find your perfectly customized solution.
Jörg Schulze
Sales Director Retaining Rings & HNS
Finish Turning
The final dimensions and specified surface finish are achieved by finish turning.
Your contact for Finish Turning
We manufacture all our products to customer specifications. So what are your specifications?
Please feel free to contact us. Together we will find your perfectly customized solution.
Jörg Schulze
Sales Director Retaining Rings & HNS
100% Final Inspection
Every ring is tested for mechanical properties and internal defects according to the customer specification, results are documented, and the finished rings are delivered with full traceability.
Your contact for Final Inspection
We manufacture all our products to customer specifications. So what are your specifications?
Please feel free to contact us. Together we will find your perfectly customized solution.
Jörg Schulze
Sales Director Retaining Rings & HNS
Retaining Rings in Power Generation – Purpose, Advantages and Applications
- High rotational speeds up to 3,600 rpm require high-strength materials that safely absorb centrifugal forces
- Severe cyclic loading of components requires optimized designs
- Critical atmospheres inside the generator during operation increase the risk of stress corrosion cracking — targeted alloy composition safeguards operational reliability
- Precision surfaces facilitate maintenance, repair, and retrofit operations during overhauls
- Cost-effective: longer service life reduces operating costs and maintenance effort
- Product safety: best-in-class material properties for safe design and dimensioning
- Power Engineering: Securing the end windings on turbo generators and motors
What you can expect
Circular economy
We use almost 100% scrap in steel production, thereby enabling closed loops
Low CO2 production
use of 100% material from the electric arc furnace
Highly resilient steel
Highly resilient steel with high yield strength, very good cold and hot forming properties, low thermal expansion, non-magnetizability and resistance to stress corrosion cracking