STATO 70
Oil tempered SiCr-alloyed spring wire (according to EN 10270-2 ; 2011 FD SiCr)
STATO 70 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 0.50 mm to 7.00 mm. Other wire sizes on request.
| C (%) | Si (%) | Mn (%) | P max. (%) | S max. (%) | Cr (%) |
|---|---|---|---|---|---|
| 0.50 - 0.60 | 1.20 - 1.60 | 0.50 - 0.90 | 0.030 | 0.025 | 0.50 - 0.80 |
1) Other wire sizes on request.
2) Ovality, i. e. the difference between the largest and smallest dimension of a cross section, is maximum half the tolerance range.
3) Conversion from tensile strength to hardness values can be calculated in standard ISO EN 18265. The tensile strength Rm within one coil does not vary more than 70 N/mm2.
4) Min No of twists in the torsion test, Nt, are to be agreed upon.
For round wire
| Diameter (mm) | Tolerance (mm) | Tensile Strength (N/mm²) | Reduct. of area (min. %) |
|---|---|---|---|
| 0.50 - 0.60 | ±0.010 | 2100 - 2300 | |
| 0.61 - 0.80 | ±0.010 | 2100 - 2300 | |
| 0.81 - 1.00 | ±0.015 | 2100 - 2300 | |
| 1.01 - 1.30 | ±0.020 | 2070 - 2260 | 45 |
| 1.31 - 1.40 | ±0.020 | 2060 - 2250 | 45 |
| 1.41 - 1.60 | ±0.020 | 2040 - 2220 | 45 |
| 1.61 - 2.00 | ±0.025 | 2000 - 2180 | 45 |
| 2.01 - 2.50 | ±0.025 | 1970 - 2140 | 45 |
| 2.51 - 2.70 | ±0.025 | 1950 - 2120 | 45 |
| 2.71 - 3.00 | ±0.030 | 1930 - 2100 | 45 |
| 3.01 - 3.20 | ±0.030 | 1910 - 2080 | 45 |
| 3.21 - 3.50 | ±0.030 | 1900 - 2060 | 42 |
| 3.51 - 4.00 | ±0.030 | 1870 - 2030 | 42 |
| 4.01 - 4.20 | ±0.035 | 1860 - 2020 | 40 |
| 4.21 - 4.50 | ±0.035 | 1850 - 2000 | 40 |
| 4.51 - 4.70 | ±0.035 | 1840 - 1990 | 40 |
| 4.71 - 5.00 | ±0.035 | 1830 - 1980 | 40 |
| 5.01 - 5.60 | ±0.035 | 1800 - 1950 | 38 |
| 5.61 - 6.00 | ±0.040 | 1780 - 1930 | 38 |
| 6.01 - 6.50 | ±0.040 | 1760 - 1910 | 35 |
| 6.51 - 7.00 | ±0.040 | 1740 - 1890 | 35 |
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.
E and G modulus of elasticity
206 kN/mm²
E and G modulus of shear
79.5 kN/mm²
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.