Inert gas procedure


 

We carry out the following heat treatments within our range of inert gas processes:

In a bell-type furnace:

  • Stress relieving (Info)
  • The BG specialised annealing process (Info)
  • The BF specialised annealing process (Info)
  • Soft annealing (Info)
  • Recrystallisation (Info)
  • Solution annealing (Info)

In a bell-type furnace with salt bath quenching, also in a multi-purpose batch furnace with an oil quench:

  • Hardening (Info)
  • Quenching and tempering (Info)
  • Carburization (Info)
  • Case hardening (Info)
  • Carbon nitriding (Info)

Special heat treatment in a bell-type furnace:

  • Precipitation hardening

Special treatment:

  • Subsequent oxidising after gas nitriding to increase corrosion resistance.
  • Artificial ageing through subzero cooling (Info)

The advantages of the inert gas process in the bell-type furnace are:

  • Vertical and suspended batches up to 1000 mm in length.
  • Accurate carbon adjustment controls.
  • Reduction of oxidation on the edges.

This is supported by a heat treatment which is individually adjusted to suit the contours of the component.

All our equipment is computer-controlled.
All processes are reproducible and consistently documented.

Hardening

The hardening serves to achieve a high hardness in the component, preferably by martensite accumulation. The process consists of the following two stages: hyper-quenching and cooling at a suitable speed.

(to top)

Quenching and tempering

Hardening with subsequent tempering, mostly above 550°C, to achieve a desired combination of mechanical properties. In particular to increase the toughness compared to the hardened condition (prior to tempering).

(to top)

Carburization

A thermo-chemical treatment of a component in an austenised condition; the carbon content of the surface layer is increased. The carbon content, when austenised, is in a solid solution.

(to top)

Carbon nitriding

A thermo-chemical treatment of a component in an austenised condition; the carbon and nitrogen content of the surface layer is increased. The carbon and nitrogen content, when austenised, is in a solid solution.

(to top)

Case hardening

Case hardening consists of carburisation, or carbo-nitriding with subsequent hardening - either directly afterwards or after an interim cooling and re-heating to achieve an adequate hardening temperature. Before hardening, the outer layer is enriched with carbon (carburization) or with carbon and nitrogen (carbon-nitriding). Compared to carburization, the additional nitrogen accumulation results in a higher hardenability by changing the conversion behaviour of the outer layer, and thus also resulting in a higher tempering stability. Depending on the required characteristics or the requirements of the following process (i.e. grinding), after the hardening process the component is tempered or deep-frozen and then tempered. Case-hardening the outer layer of components and steel tools (C contents < 0.2 %) achieves a significant increase in the harness of the outer layer and an enhancement of mechanical properties.

(to top)

Precipitation hardening

Process to increase stability by accumulation caused by precipitation. It consists of the sub-processes solution treatment and precipitation heat treatment.

(to top)

Stress relieving

In stress-relief annealing, the annealing takes place at temperatures below the Ac 1 transition temperature; it is followed by slow cooling to reduce the inner tension (residual stress).

(to top)

Soft annealing

In a soft annealing process, heat treatment takes place to achieve the lowest possible hardness with high malleability at the same time. By heating and maintaining the temperature directly below the AC1 transition temperature for several hours, hardening structure constituents and strain hardening are eliminated and the cementite fins of the pearlite take on a spheroidal form (people talk of annealing to achieve spheroidal carbide).
In most cases the soft annealed condition is the most suitable form for cutting and cold forming as well as hardening. Exceptions are steels with lower C contents which tend to "smear" when being turned or milled.

(to top)

Recrystallisation

Recrystallisation is an annealing process with temperatures above the recrystallisation temperature of the work piece to eliminate the strain hardening caused by a previous cold forming process and to restore the plastic malleability. The recrystallisation temperature depends on the degree of deformation and the alloy composition of the steel; it normally ranges from 550 to 700 °C.

(to top)

Solution annealing

Solution annealing is a heat treatment for the conversion of precipitations of the mixed crystals into a solid solution and to maintain this condition through fast cooling. (fehlt noch ein Satz).

(to top)

The BG specialised annealing process

An annealing process for creating a particular treatment condition in order to achieve specific characteristics. In this case, B G stands for a particular structure (ferrite-pearlite structure). For steels with low C content, the pearlite proportion is increased and thus the steel is better suited for chipping.

(to top)

The BF specialised annealing process

An annealing process for creating a particular treatment condition in order to achieve specific characteristics. In this case, B F stands for a particular stability. The purpose is to create certain minimum degrees of hardness which must be achieved in order to ensure that the steel is suited for chipping.

(to top)

Artificial ageing through subzero cooling

A process to achieve dimensional stability by means of subzero cooling directly following the heat treatment. Its purpose is the conversion of the remaining austenite and the creation of a stable structure.

(to top)

  • Bell furnace plant
  • Bell furnace plant
  • Bell furnace plant layout
  • Gas nitriding plant
  • Multi-purpose batch furnace
  • Loading large components
  • Suspended charge
  •     Gas nitriding charge
  • Cavity plates
  • Rescue cutter
  • Stamping die
  • Shafts
  • Rings
  • Laboratory work-place
  • Metallography

We update and optimise precision machine tools and high-grade components.