STATO 75

Oil tempered SiCrV-alloyed spring wire

STATO 75 is especially intended for the manufacture of springs exposed to static or moderately high fatigue stresses. The material has good relaxation properties.

The wire is manufactured in sizes from Ø 2.00 mm to 7.00 mm. Other wire sizes on request.

Chemical composition

C (%) Si (%) Mn (%) P max. (%) S max. (%) Cr (%) V (%)
0.50 - 0.70 1.20 - 1.65 0.50 - 0.80 0.025 0.025 0.50 - 1.00 0.05 - 0.20

Mechanical properties

For round wire

Diameter (mm) Tolerance (± mm) Tensile Strength (N/mm²) Reduct. of area (min. %)
2.00 - 2.50 0.020 2110 - 2210 45
2.51 - 3.20 0.020 2060 - 2160 45
3.21 - 4.00 0.025 2010 - 2110 45
4.01 - 5.00 0.025 1960 - 2060 45
5.01 - 5.60 0.030 1910 - 2010 40
5.61 - 6.50 0.035 1910 - 2010 40
6.51 - 7.00 0.035 1860 - 2010 40

Yield point

The proof stress Rp0.2 is min. 0.9 x tensile strength of the wire.

Surface conditions

Surface condition

Surface condition – end sample test
The wire is end sample tested by means of etch testing and binocular inspection as well as microscopical inspection of the material structure.

Max. permissible depth of partial surface decarburization and surface defects, 1.5% x wire diameter. No complete decarburization allowed.

Physical properties

E and G modulus of elasticity

About 206 kN/mm2

E and G modulus of shear

About 79.5 kN/mm2

Recommendations

Heat treatment

As soon as possible after coiling, the springs should be stress relieved.

Hot presetting

After shot peening, the springs should be hot preset or stress relieved. In order to reach optimum fatigue and relaxation properties, the springs must be preset at an appropriate stress

Shot peening

In order to obtain optimum fatigue properties, the process time should be adjusted to get a complete treatment. Size of shots should be adapted to wire dimension, pitch and shot peening equipment. Shot peening of the inside of the spring coils is particularly critical.