Wärmebehandlungen – Gewinde Ziegler AG | Gewinde Satelliten Antriebe AG

In 2014, Gewinde Ziegler AG bought up Härterei Hertig AG.

Years of combined know-how acquired together with Härterei Hertig could be secured and 2019 the company moved to the new facility in Horriwil.

The newly introduced processes, like core and inductive hardening, allow us to perform thermal treatments of shafts with up to 10 meters in length. The result is our capacity to cover the completeb production process of our products in-house. This leading to a high degree of flexibility and know-how security for our customers.

The Hardening Plant

... and its construction

Process technologies

With the construction of its new hardening plant in 2019, Gewinde Ziegler AG has fully automated the salt bath hardening process. The automation and the many years of salt bath know-how reasult in consistent hardening results. Salt melting offers various advantages in contrast to other heat treatment processes. First and foremost there is temperature uniformity. In salt bath heat treatment, the heat is not transferred by radiation and convection, as with atmospheric processes (gas and vacuum), but by heat conduction gained from the contact between liquid molten medium and component surface. As a result, heat is supplied to or extracted from the material to be treated in very short time. Heat treatment in molten salts is fast and yet comes with little distortion due to the uniform heat transfer.

Case hardening in salt (see oven procedures)
Neutral hardening in salt
Quench hardening in salt
Tempering in salt

Furnace dimensions

Height: 1,100 mm
Diameter: 700 mm

Nitrocarburising is the enrichment of the surface layer of ferrous materials with nitrogen and small amounts of carbon. Nitrocarburising produces a very wear-resistant layer of iron nitrides and nitrides of alloying elements, for example chromium nitrides, on the component surface. After cooling in an oxidising salt bath, a black, decorative surface with additional high corrosion resistance is formed.

At treatment temperatures of 480 to 580 °C, the edge area is chemically altered by the incorporation of nitrogen and possibly carbon.

Advantages of salt bath nitrocarburizing

Wear resistance
Corrosion resistance
Shrink resistance
Heat resistance
Fatigue resistance

Furnace dimensions

Height: 800 mm
Diameter 500 mm

By transforming retained austenite into martensite and precipitating fine carbides, deep-freeze treatment offers the following important advantages:

Improved hardness
Dimensional stability
Improved wear resistance
Extended durability of parts

Our modern freezing plant allows us to freeze at temperatures as low as -120°C and temper under protective gas (nitrogen) up to 300°C in the freezer.

Max. batch size

Height: 900 mm
Diameter 600 mm

Inductive heating is generated directly in the component with very high power density. The area to be hardened is rapidly brought to hardening temperature and immediately quenched afterwards. Depending on the required hardening depth and component geometry, different generators (frequencies) are used. Three types are distinguished: High, medium and dual frequency generators. Depending on the material and hardening parameters, numerous quenching media are available to optimise the hardening results. E.g. up to three different polymer concentrations on different installations.

Advantages

Narrow tolerable hardness zone
High reproducibility
Partial to complete automation
Single pieces to large series
True to contour thanks to dual-frequency technology

Application fields

Shafts and axles
Rod material
General

Component dimensions

Ø 10 to Ø 310 mm
Length up to 10,000 mm
Weight up to 6 tons
Bigger elements on request

Generators

Power 1 to 400 kW
Frequency 4 to 450 kHz

(Core) hardening in inert gas

During hardening, the component is heated and then quickly cooled (quenched). The structural transformation produces hard martensite, which is then stress-relieved in a subsequent tempering process. The achievable hardness is determined by the carbon content. This is at least 0.2 % for hardenable steels. The achievable hardening depth is influenced by the other alloying elements.

Hardening under inert gas

Unalloyed and low-alloy steels are heated in a controlled atmosphere and quenched in oil. The specific adjustment of the furnace atmosphere prevents the diffusion of carbon, which is necessary for hardening.

Case hardening

Carburisation

Enriching the surface layer of a workpiece with carbon by thermochemical treatment.

Case hardening

Carburisation followed by hardening at 850 to 950 °C. During hardening, a high hardness with improved wear resistance is achieved in the enriched surface layer.

Neutral and case hardening of small and very small parts 0.3 mm - 15 mm.

(Core) hardening in inert gas

Hardening under inert gas

Element size up to approx. Ø 15 mm
Element length up to approx. 50 mm
CQi-9 conformity
Neutral hardening of small parts (up to approx. 15 mm diameter)
Hardening of large series

We can apply the following procedures in our shaft carburising furnace with gassing equipment:

Hardening in inert gas

Hardening under inert gas

In quenching and tempering, steels with a carbon content of 0.2 - 0.6% are first hardened and then tempered in a temperature range of 450-700 °C. The tempering temperature depends on the desired properties. The tempering temperature depends on the desired properties. Usually, high toughness is sought.

Annealing treatments are carried out to adjust specific microstructural states or to relieve stresses. These usually take place in inert gas atmospheres. Cooling is controlled and usually slow.

Stress-relief annealing

During stress relief annealing (450 - 650 °C), internal stresses in the component are largely relieved without significantly affecting the other properties. Internal stresses occur both in raw material production (e.g. when straightening long bars) and in mechanical production (turning, milling, deep drawing). The stress relief causes the components to warp, which must be rectified by means of machining allowances.

This heat treatment is particularly recommended for complex and precise components as an intermediate step in production (between rough and final machining) to minimise distortion during subsequent hardening.

Soft annealing, normalising, recrystallisation annealing

These annealing treatments above 700 °C can restore the original properties of the material or eliminate undesirable structural changes. Goal: To produce the optimum microstructure for further processing. Examples: Elimination of work hardening and production of formability, homogenisation of the microstructure after welding, grain refinement for best properties, shaping of carbides for more economical machining.

Carburisation

Enriching the surface layer of a workpiece with carbon by thermochemical treatment.

Case hardening

Carburisation followed by hardening at 850 to 950 °C. During hardening, a high hardness with improved wear resistance is achieved in the enriched surface layer.
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