Annealing
Annealing heats metal to a set temperature, holds it and cools it slowly to soften it, relieve stresses and improve machinability or ductility. It prepares material for further machining or forming and restores properties after cold work.
What it is
Full annealing of steel heats it above the critical range and cools it slowly in the furnace, producing a soft, uniform structure. Process (sub-critical) annealing restores ductility after cold working, and spheroidise annealing improves machinability of high-carbon steels.
Non-ferrous metals such as copper, brass and aluminium are also annealed between forming stages.
Typical applications
- Softening steel before machining
- Restoring ductility between drawing stages
- Tool steel before machining
- Copper and brass forming parts
- Wire and sheet processing
Suitable materials
- Carbon and alloy steels
- Tool steels
- Stainless steel (solution annealing)
- Copper, brass and aluminium
Points to consider
- Annealing reduces strength; do it before final hardening, not after.
- Stainless steel solution annealing uses rapid cooling, unlike steel annealing.
- Scale forms in air furnaces; use controlled atmosphere where finish matters.
- State target hardness if softening for machining.
Frequently asked questions
What does annealing do?
It softens metal, relieves internal stresses and improves ductility or machinability.
What is the difference between annealing and normalising?
Both heat steel above its critical temperature. Annealing cools slowly in the furnace for maximum softness; normalising cools in air for a finer, stronger structure.
Is stainless steel annealed?
Austenitic stainless steel is solution annealed and quickly cooled to restore corrosion resistance after welding or cold work.