Austempering Forging Heat Treatment

Austempering is a process for steel forgings which yields a bainitic microstructure. Compared to a standard quench and temper process, the austempering forging heat treatment is superior in terms of ductility and distortion.


Small batch, large batch or automated salt-to-salt system we have the capabilities to meet any needs you may have.

The maximum size of ThermTech’s austempering capacities is 50” x 50” x 48”.


Austempering is a two-step process which yields a tough & strong bainitic microstructure.

The first step in the process is to heat the steel component to a temperature at which it's in the fully austenitic phase and soaking at this temperature for a period of time. This ensures temperature uniformity throughout the entire section.

The parts are then quenched in a molten salt bath in the temperature range of 400F to 750F. During this part of the process the austenite isothermally transforms to bainite. Bainite is tougher than martensite at the same strength levels.

Because the parts are quenched in a molten salt bath the difference in temperature between the work piece and the quench bath is lower as compared to oil quenching.  This difference yields far less distortion due to stresses caused by quenching.

Also, because the transformation is isothermal and takes place over a longer period of time as compared to martensitic transformation, this component of distortion caused by quenching is lower.

The sum total of these facts leads to a real advantage in regard to distortion of the final product when austempering is compared to a traditional quench and temper process.

If you have a steel component that has been problematic with respect to distortion in heat treating, austempering may be an option to eliminate this problem!


Long slender parts or forgings that are thin in cross section are an excellent candidate for austempering.

Another excellent application for the austempering process are parts that are sensitive to quench cracking due to material or design. 

Typical steels that are austempered include:

AISI 4140
AISI 4340
AISI 1045 - 1095

Sumbit My Order for Austempering.