Clutch spring wires are oil tempered steel wires with diameter ranging from 1 to 8mm. An oil tempered wire acquires its mechanical properties by heat treatment after it has been drawn to its final size. Tempering and annealing guarantees more uniform mechanical properties than simple cold drawing. Unalloyed steel (Becarbo 20(H)®) is used for low strength and chromium-silicon alloyed steel (Becrosi 26®) for high strength, medium dynamic applications. A clean chromium-silicon steel is used for high dynamic applications (Becrosi 36®). Eddy current testing can be applied when requested (Becrosi 26T®/36T®). According to EN10270-2 norm (EN code SiCrTD, SiCrVD).