Heat treatment

We change properties

The hidden talents of forged steel are only revealed through professional heat treatment. This is because it makes it possible to achieve a special surface hardness for wear resistance, good machinability for subsequent processing steps or particularly high toughness values in the low temperature range.

Only the correct heat treatment gives the forging the necessary mechanical properties required for its future application. In furnaces with state-of-the-art burner technology, we carry out all common heat treatments in a cost-effective and environmentally friendly manner. We work according to generally applicable standards or according to your specific requirements.

We have created an integrated system specifically for the forging, rolling and heat treatment of rings. This enables the workpiece to be produced directly from an upsetting and piercing press via the ring rolling mill to the continuous tempering line. Thanks to targeted heat transfers in the combination of production steps, the composite is also very energy-efficient and therefore environmentally friendly and reduces our carbon footprint.

At a glance

  • All common heat treatments
  • State-of-the-art and energy-efficient burner technology
  • More than 20 hood, bogie hearth and chamber furnaces and 5 quenching basins
  • Composite system for series production

Overview of the usual heat treatments for stainless steel

The aim of tempering is to achieve an optimum combination of hardness and yield/tensile strength. The process is a combination of hardening (quenching) and subsequent reheating (tempering). For hardening, the component is austenitized and cooled quickly after an appropriate holding time.

During quenching, the steel becomes hard but also brittle. Subsequent tempering increases the yield strength and tensile strength and resolves the high elongation and toughness values.

The aim of normalizing is to achieve a fine-grained, uniform microstructure with optimum strength and formability properties. All structural irregularities and changes in properties caused by other processes are thus eliminated.

To do this, the steel is heated above the austenitic temperature and cooled in still air after complete heating.

Solution annealing is used to improve the corrosion resistance of stainless steels by evenly distributing the alloying elements. Depending on the material, it takes place in a temperature range between 1020 °C and 1200 °C.

This annealing process is also used after shaping processes instead of recrystallization annealing.

The aim of soft annealing is to improve machinability and formability. Soft annealing is used to achieve the lowest possible hardness. To do this, select a temperature just below AC1 (approx. 680 °C – 700 °C).

After the appropriate holding time, the workpiece is cooled down in the oven. This process is used for hypoeutectoid steels (< 0.8 % carbon).

GKZ annealing (annealing on spherical cementite) is comparable to soft annealing. The aim is to achieve the highest possible degree of molding of the cementite. It is used for hypereutectoid steels (carbon content > 0.8 %).

For this purpose, the temperature is oscillated around the conversion line (AC1). After the corresponding holding time, the workpiece is also cooled down in the oven.

Ferrite-pearlite annealing is used to improve the machinability of case-hardening steels. This process used to be called machining annealing. According to the new standardization, this is now officially referred to as pearlizing or ferrite-pearlite annealing. In this annealing process, the cooling curve is interrupted after the coarse-grain annealing and kept in the pearlite range until the ferrite-pearlite structure has formed.

The aim of stress relief annealing is to reduce residual stresses in the material. Such stresses are caused, for example, by structural transformations, cold forming and machining. Not only the right temperature is important for a good result, but also careful cooling. This is the only way to avoid renewed stress formation. Typically, stress relief annealing takes place at temperatures around 600 °C (but 30-50 °C below the last tempering temperature for previously tempered components).

Insights into our heat treatment