During tempering, hardened components are heated in a controlled manner in order to reduce residual stresses, increase toughness and set the target hardness. This produces dimensionally stable, resilient components – with reproducible quality from sample production to series production.
Tempering – also known as annealing – is a central step in the Heat treatment. After hardening or welding, it reliably brings components into the required property window. With precisely controlled temperature-time cycles, we stabilize hardness, toughness and dimensional stability – for durable, reliable components.
During tempering, previously hardened (martensitic) or stressed components are heated below the lower transformation temperature for a defined time and then cooled down in a controlled manner.
Reduction of residual stresses to prevent cracking and warping
Adjustment of the target hardness with simultaneously higher toughness
Stabilization of dimensional accuracy for precise tolerances
Improved fatigue strength and operational safety
The result is a balanced property profile with tempered martensite or a microstructure suitable for the application – the basis for resilient components.
Less risk of cracking & warping thanks to stress relief
Hardness to specification – without unnecessary brittleness
Consistent quality through documented process control
Dimensional and dimensional stability for close-tolerance precision parts
Suitability for series production: reproducible from individual parts to large-scale production
The choice of tempering temperature controls the ratio of hardness and toughness (depending on the material and application):
Stress relief with high hardness, e.g. case-hardening steels
Transformation of retained austenite, e.g. tool steels
Maximum toughness with reduced hardness, e.g. quenched and tempered steels
Multi-stage tempering (e.g. 2-3 cycles) is common for high-alloy tool steels in order to minimize retained austenite and stabilize properties.
Tempering (typically ~150-650 °C) usually follows hardening and adjusts hardness/toughness; stress relief annealing (depending on the material ~450-650 °C) is primarily aimed at stress relief, even for non-hardened, e.g. welded, machined and formed parts.
For high-alloy tool steels, 2-3 tempering cycles are common in order to reduce residual austenite and stabilize the properties. We determine the scope and parameters on the basis of the material and target values.
Regularly: Hardness test (HRC/HV/HB). As required: microstructure analysis, dimensional/shape inspection, visual inspection. Test reports as agreed.
Tempering colors indicate temperature ranges, but are not a reliable proof of quality. Verifiable measured values and process documentation are crucial.
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t.bachmann@listemann.com
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t.bitschnau@listemann.com
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j.brelinski@listemann.com
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