Method for producing cold-formed steel springs

A process for producing a spring or torsion bar from a steel wire by cold forming, the process comprising:

• providing a steel wire;
• thermomechanically forming the steel wire above a minimum recrystallization temperature of the steel wire, the steel wire having an at least partly austenitic structure;
• cooling the thermomechanically-formed steel wire such that an at least partly ferritic-pearlitic structure forms in the steel wire;
• tempering the steel wire that has been cooled, wherein the tempering comprises:
• heating the steel wire at least to a hardening temperature equal to or greater than an austenite start temperature,
• quenching the heated steel wire to a first cooling temperature, the first cooling temperature being a temperature below the minimum recrystallization temperature of the steel wire, wherein an at least partly martensitic structure forms in the steel wire,
• reheating the quenched steel wire to a first annealing temperature that is less than the austenite start temperature, and
• cooling the reheated steel wire to a second cooling temperature, the second cooling temperature being less than the first annealing temperature;
• cold forming the steel wire at a cold forming temperature, the cold forming temperature being a temperature below the minimum recrystallization temperature of the steel wire;
• and
• separating the steel wire.