We use default:patented drawn spring steel wire according to quality standard DIN EN 10270-1 in models SH and DH(Formerly DIN 17223-1 C and D - material no 1.1200.)foreign names: F: AFNOR NFA 47-301-76 / UK: BSI BS 5216-75 / USA: AISI AMS 5112Chemical analysis according to type and wire size in%C 0.35 to 1.00 / Si 0.10 to 0.30 / M 0.50 to 1.20P max. 0.035 / S max. 0.035 / Cu max. 0.20Tensile strength N / mm ² 1570 - 3110 (d 6.30 to 0.20 mm) ~ (150kp Rockwell Rc 47 - > 69 / / Brinell (Hb) / Vickers (Hv) ~ 445 - > 740/850Shear modulus of 81500 N / mm ²Finish: matte gray to bluish according to age, no platingTemperatures: Temperature range: max. 80 ° C annealing temperature: 250 - 350 ° C (280 ° C)most common grade for springsmore surface forms: tin, zinc, rhodium, copper, silver plated, gold plated, chrome plated with us possible only through external galvanic surcharge.