Thermal treatment

• During batch annealing, the wire is heated for several hours at temperatures as high as 700°C, under a protective atmosphere like nitrogen or hydrogen to avoid oxidation or decarburization. This recrystallisation treatment renders the wire homogeneously softer.
• During patenting the wire is continuously heated to about 1000°C, rapidly quenched and held for some seconds at about 550°C to allow for a full isothermal transformation into sorbite.
  Patenting transforms the steel structure into a homogenous fine perlitic structure, known as sorbite. This is the optimal structure to create the highest mechanical properties for further cold deformation.
• During hardening and tempering, the wire is continuously heated to about 950°C, then quenched to room temperature to create a martensitic structure, and subsequently re-heated to about 450°C to add ductility. Hardening and tempering create high mechanical properties and superior fatigue behavior in highly dynamic applications.

These three treatments are used to create specific characteristics for specific applications.