GARBA 177 Supreme
Precipitation hardenable stainless spring wire. Shaved and EC-tested*. For applications demanding superior fatigue properties
GARBA 177 Supreme® is a semi-austenitic precipitation-hardenable stain¬less steel, processed by ESR (Electro Slag Refining), which reduces the risk of harmful inclusions. The ESR process together with a 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 |
Cleanliness in steel
The presence of non-metallic inclusions in the wire rod is
inspected for every heat in accordance with the Suzuki
Garphyttan method by the steel supplier.
For wire rod samples: Inclusion size max. 15 µm down to 1 mm below surface. Inspection area: 350 mm2.
| Inclusion size, surface | 5–10 | > 10–15 | >15 µm |
| Max. number of inclusions | Max grade D3 acc. to JK scale* |
20 | 0 |
* Method for assessment of the content of non-metallic inclusions. Swedish Standard SS 111116 – Microscopic methods – Jernkontoret’s inclusion chart II for the assessment of non-metallic inclusions.
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 |
Resistivity
| Temperature ºC | 20 | 100 | 200 | 300 |
| nΩm | 900 | 950 | 1000 | 1050 |
Linear expansion
| Pro oC | 30-100 | 30-200 | 30-300 |
| x10-6 | 13.0 | 13.5 | 14.0 |
Specific heat capactity
| Temperature oC | 100 | 200 |
| J/(kg* oC) | 480 | 520 |
Electro slag refining (ESR) process
For applications demanding superior fatigue properties
Electro Slag Refining (ESR) process
ESR process, see figure 1.
The ESR process gives a material with lower level of inclusions compared to a material not processed with ESR and in addition also a better segregation level.
Material properties achieved by ESR in combination with shaved wire surface and precipitation hardening result in superior fatigue resistance.
Shaved and Eddy Current tested
Suzuki Garphyttan uses the most advanced Eddy Current testing equip¬ment available on the market. Experience from many years of surface testing in efficient continuous testing lines is a guarantee for high quality spring wire.
Eddy Current testing is carried out on material with high demands on surface quality. EC-testing is performed with both rotating (R) and stationary (D) probe test equipment.
| Steel grade | Dimension, mm | ESR | Shaved | Unshaved | RD40 |
| GARBA 177 Supreme® | 0.30 – 1.99 | x | x | - | - |
| GARBA 177 Supreme® | 2.00 – 5.60 | x | x | - | x |
Steel grade Dimension, mm ESR Shaved Unshaved RD40
GARBA 177 Supreme® 0.30 – 1.99 X X – –
GARBA 177 Supreme® 2.00 – 5.60 X X – X
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.
Relaxation And Fatigue Properties
In diagram 1 the fatigue properties of GARBA 177 Supreme® is illustrated in a Goodman-diagram, based on a special test spring design.
Diagram 2-3 show the relaxation properties (loss of load) of springs made from GARBA 177 Supreme® subjected to three different stress levels at different temperatures.