Glossary
Heat Treatment & Industrial Furnace Glossary
Key terms of industrial heat treatment and furnace technology – defined precisely and clearly. This glossary brings together the most important processes, standards and technical terms around industrial furnaces.
Industrial heat treatment encompasses a wide range of processes, standards and technical terms. This glossary explains the central concepts around industrial furnaces, heat treatment processes and the associated quality assurance – concise and practical.
- Tempering
- Tempering is the reheating of a previously hardened workpiece to a temperature below the transformation point (typically 150–700 °C) to reduce brittleness and residual stress and to set the desired toughness. It is the second step after hardening.
- Hardening
- Hardening is the heating of steel to austenitising temperature followed by rapid quenching to form a hard martensitic structure. The goal is increased hardness and wear resistance.
- Annealing
- Annealing is a heat treatment used to obtain a soft, low-stress material condition. Depending on the objective, variants include soft annealing, normalising, stress-relief annealing and recrystallisation annealing.
- Sintering
- Sintering is the compaction and bonding of pressed powder compacts (metal or ceramic) at temperatures below the melting point. Diffusion processes create a solid, load-bearing material bond.
- Carburising
- Carburising enriches the surface layer of a steel component with carbon at 880–1000 °C in a carbon-donating atmosphere. After quenching, this produces a hard, wear-resistant surface with a tough core.
- Quenching
- Quenching is the rapid cooling of a heated workpiece in air, oil, water or polymer solution to freeze in a hard structure. The quenching medium determines the cooling rate and distortion.
- Drying
- Drying is the thermal removal of moisture or solvents from a material through controlled heat input and air circulation, usually in the low-temperature range up to about 300 °C.
- Preheating
- Preheating is the deliberate warming of components before a downstream process (e.g. welding, forming or coating) to avoid thermal stress and cracking.
- Temperature Uniformity Survey (TUS)
- The Temperature Uniformity Survey (TUS) is the standardised measurement of the temperature distribution within a furnace's working zone. It proves that the actual temperature at all measuring points lies within the permitted tolerance.
- System Accuracy Test (SAT)
- The System Accuracy Test (SAT) compares the reading of the in-service temperature measurement and control system against a traceable reference system. It is part of pyrometry standards such as AMS2750 and CQI-9.
- CQI-9
- CQI-9 is the standard issued by AIAG for assessing heat treatment processes in the automotive supply chain. It defines requirements for process control, pyrometry (TUS/SAT) and documentation.
- AMS2750
- AMS2750 is the pyrometry standard prevailing in aerospace. It governs temperature measurement, calibration, test equipment, and TUS and SAT for heat treatment equipment.
- DGUV-3 Inspection
- The DGUV Regulation 3 inspection (formerly BGV A3) is the recurring inspection of fixed electrical installations and equipment required in Germany under DIN VDE 0100-600, generally on an annual basis.
- Protective Gas Atmosphere
- A protective or inert gas atmosphere (e.g. nitrogen, argon, hydrogen or forming gas) prevents oxidation and decarburisation of the workpiece surface during heat treatment.
- Vacuum Furnace
- A vacuum furnace carries out heat treatment under reduced pressure. The vacuum prevents oxidation, enables bright surfaces and is suitable for reactive materials and high-temperature processes.
Frequently Asked Questions
What is the difference between hardening and tempering?
Hardening creates a hard but brittle structure through heating and rapid quenching. Tempering is the subsequent second step: reheating below the transformation temperature to reduce brittleness and set the desired toughness.
What do TUS and SAT mean in heat treatment?
The TUS (Temperature Uniformity Survey) measures the temperature distribution in the furnace working zone; the SAT (System Accuracy Test) checks the accuracy of the measurement and control system. Both are mandatory parts of pyrometry standards such as AMS2750 and CQI-9.