GARBA 177 Premium
Precipitation hardenable stainless spring wire. Shaved and EC-tested *)
For applications demanding high fatigue properties
GARBA 177 Premium is a semi-austenitic precipitation-hardenable stainless steel with high relaxation resistance at elevated temperatures and excellent fatigue properties. This material has good formability and good form stability during the precipitation hardening heat treatment and a moderate level of corrosion resistance. The shaved surface improves the fatigue resistance as compared to GARBA 177PH.
| C (%) | Si (%) | Mn (%) | P max. (%) | S max. (%) | Cr (%) | Ni (%) | Al (%) |
|---|---|---|---|---|---|---|---|
| 0.09 | 0.70 | 1.00 | 0.040 | 0.015 | 16.00 - 18.00 | 6.50 - 7.80 | 0.70 - 1.50 |
For round wire
| Diameter (mm) | Tolerance (mm) | Tensile Strength (N/mm²) | Tensile strength after heat treatment 480C 1h (N/mm²) |
|---|---|---|---|
| 0.30 - 0.40 | ±0.005 | 1885 - 2165 | 2205 - 2525 |
| 0.41 - 0.50 | ±0.008 | 1860 - 2130 | 2180 - 2490 |
| 0.51 - 0.65 | ±0.008 | 1810 - 2070 | 2130 - 2430 |
| 0.66 - 0.80 | ±0.010 | 1810 - 2060 | 2130 - 2430 |
| 0.81 - 1.00 | ±0.010 | 1780 - 2030 | 2100 - 2390 |
| 1.01 - 1.25 | ±0.015 | 1720 - 1960 | 2040 - 2310 |
| 1.26 - 1.50 | ±0.015 | 1670 - 1910 | 1990 - 2260 |
| 1.51 - 1.75 | ±0.015 | 1610 - 1850 | 1910 - 2180 |
| 1.76 - 2.00 | ±0.015 | 1570 - 1800 | 1900 - 2160 |
| 2.01 - 2.50 | ±0.015 | 1540 - 1770 | 1860 - 2120 |
| 2.51 - 3.00 | ±0.020 | 1500 - 1710 | 1820 - 2060 |
| 3.01 - 3.50 | ±0.020 | 1400 - 1600 | 1660 - 1940 |
| 3.51 - 4.25 | ±0.020 | 1350 - 1550 | 1620 - 1920 |
| 4.26 - 5.00 | ±0.025 | 1310 - 1500 | 1580 - 1800 |
| 5.01 - 5.60 | ±0.025 | 1300 - 1490 | 1550 - 1790 |
Surface performance
AC-surface 0.30–5.60 mm Ø. The AC-coating can be removed before heat treatment by using a 10-20% nitric acid pickle at room temperature.
Surface condition
Surface condition – non-destructive testing
In the standard size range 2.00-5,60 mm the wire can be tested continuously in Eddy Current equipment to a surface level of >40 microns.
E and G modulus of elasticity
Abt. 190 kN/mm2 in drawn condition.
Abt. 200 kN/mm2 after heat treatment.
E and G modulus of shear
Abt. 73 kN/mm2 in drawn condition.
Abt. 78 kN/mm2 after heat treatment.
Density: 7.90 kg/dm3.
Heat conductivity
| Temperature oC | 20 | 100 | 300 |
| W/(m* oC) | 15.0 | 15.5 | 19.0 |
Linear expansion
| Pro oC | 30-100 | 30-200 | 30-300 |
| x10-6 | 13.0 | 13.5 | 14.0 |
Heat treatment
Normal procedure for precipitation hardening is heat treatment at 480oC (896oF) for 1 hour and then air cooling. This should be done as soon as possible after spring coiling. The tensile strength of the wire before and after this treatment is given in the table in previous page.
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.