Patent ID: 6939418

Claim:
Process for thermomechanical treatment of steel wire for torsionally-strained spring elements, comprising the steps of: heating an initial wire material with a heating rate of at least 50 K/s to a temperature above the recrystallization temperature of the initial wire material which prevents growth of austenite grains into coarser grains; austenitizing the initial material and forming the heated initial wire material into a formed product in a manner and at a temperature producing recrystallization of the austenite, said forming being performed in at least two forming passes, each of which is performed over the same parts of the wire material at a temperature above the recrystallization temperature so as to increase strength and toughness properties in a strain direction of torsionally-strained spring elements produced with the formed product; said at least two forming passes being a number of passes which has been selected based on strength and toughness requirements, and quenching the recrystallized austenite of the formed product to below the martensite temperature to martensite and then performing tempering to achieve a final strength-toughness combination; wherein the strength and toughness properties of the initial material are incrementally increased in each of said forming passes to achieve a total increase in said strength and toughness properties.