What is the glow of steel

Technical terms for heat treatment

The most important technical terms for heat treatment are compiled and explained in this glossary.

Tempering (+ QT)

Quenching and tempering is the hardening (quenching) of materials at temperatures of 800 - 1,100 ° C with subsequent reheating (tempering) to temperatures of 540 - 680 ° C. Hardening is a heat treatment process that consists of austenitizing and rapid cooling. With the corresponding structural transformation during the cooling process, the steel becomes hard, but also brittle. The subsequent high tempering temperature results in increased yield strength and tensile strength as well as high elongation and toughness values.

Normalizing (+ N)

Normal annealing is the heating of steel slightly above the austenite temperature. After it has been completely heated, the material is cooled in still air. All changes in structure and properties due to quenching and tempering, hardening, overheating, welding, cold or hot forming are reversed, provided that they have not led to material damage. The aim is to achieve a uniform, fine ferrite-pearlite structure with the associated mechanical properties.

BF annealing (+ TH)

BF annealing is the annealing of steel to a specific hardness range. The type of material structure does not play a major role here. Depending on the steel and requirements, normal types of heat treatment are used or simple tempering at high temperatures.

BG annealing / pearlitizing (+ FP)

The old term of machining annealing is officially no longer used today. In the new standardization one speaks of pearlitizing or ferrite-pearlite annealing. This is a special annealing process in which the cooling curve is interrupted after the coarse-grain annealing and is kept in the pearlite range until a pure ferrite-pearlite structure (black and white structure) has formed. This heat treatment is carried out on case-hardening steels and improves the machinability (short-brittle chipboard).

Stress relief annealing (+ SR)

As the name suggests, stress relief annealing is used to reduce residual stresses. Tensions in the material arise, among other things, from uneven cooling, structural changes that do not occur in all areas of the material, from cold deformation and from machining. As a rule, we anneal the materials between 500 and 650 ° C and let them cool down in the furnace.

Soft annealing (+ A)

The soft annealing should give the steel the lowest possible strength and hardness. The steel is annealed just below the first transformation line (AC1 Line, approx. 680 - 700 ° C) and cooled down in the furnace after a corresponding holding time. Soft annealing is suitable for hypoeutectoid steels ( < 0,8="" %="" kohlenstoff).="" der="" stahl="" lässt="" sich="" so="" einfacher="" und="" wirtschaftlicher="" zerspanen="" und="" umformen.="" für="" eine="" spanende="" weiterverarbeitung="" werden="" allerdings="" nur="" stähle="" mit="" einem="" kohlenstoffgehalt="" über="" 0,4="" %="" weichgeglüht.="" bei="" kohlenstoffgehalten="">< 0,4="" %="" können="" weichgeglühte="" stähle="" beim="" zerspanen="" bereits="" anfangen="" zu="" schmieren.="" hier="" greift="" man="" dann="" wieder="" auf="" das="" grobkornglühen="" bzw.="" perlitisieren="">

GKZ annealing (+ AC)

A new corrected description follows.


Quality is our greatest asset and the basis of our performance for you, because in order to achieve quality and precision in the heat treatment of steel, you entrust us with your workpieces. That is why this issue has been at the center of everything we do since the company was founded.

More about quality according to DIN