Specifying Extension Spring — ISO / DIN (Series 143) in Grade 12.9 Steel pairs the dimensional form of Extension Spring — ISO / DIN (Series 143) (ISO / DIN) with the engineering properties of Grade 12.9 Steel. This page explains when to choose the grade, how it behaves in service, and which grades to compare it against.
Why Choose Grade 12.9 Steel for Extension Spring — ISO / DIN (Series 143)
The highest common strength class, for high-load machine assembly. For extension spring — iso / din (series 143), this matters when requires plating or black-oxide protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | class 12.9 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | up to approx. +300 °C |
| Corrosion characteristic | Requires plating or black-oxide protection |
Corrosion Behavior in Service
Carbon and alloy steel extension spring — iso / din (series 143) require a coating for corrosion protection. Zinc plating (with or without passivation) is the most common; hot-dip galvanizing is used for outdoor structural service; black-oxide is mainly a tarnish-prevention finish for tool-room use.
Galvanic & Galling Considerations
For extension spring — iso / din (series 143) in steel, the dominant compatibility issue is hydrogen embrittlement at high property classes (10.9 and above) when electroplated. Plating must be followed by an appropriate baking treatment, or a non-electroplated finish (mechanical zinc, zinc flake) should be substituted.
Sizes of Extension Spring — ISO / DIN (Series 143) Available in Grade 12.9 Steel
| Wire dia d (mm) | Outer diameter De (mm) | Free length Lo (mm) | Initial tension F0 (N) | Rate k (N/mm) | Material | Reference standard |
|---|---|---|---|---|---|---|
| 0.8 | 6 | 30 | 2 | 2.5 | Music wire | DIN 2097 / GB/T 23935 |
| 1.0 | 8 | 40 | 4 | 4.0 | Music wire | DIN 2097 / GB/T 23935 |
| 1.2 | 10 | 50 | 6 | 6.5 | Music wire | DIN 2097 / GB/T 23935 |
| 1.6 | 14 | 70 | 10 | 12.0 | Music wire | DIN 2097 / GB/T 23935 |
| 2.0 | 18 | 90 | 18 | 20.0 | Music wire | DIN 2097 / GB/T 23935 |
| 2.5 | 22 | 120 | 28 | 32.0 | Music wire | DIN 2097 / GB/T 23935 |
| 3.0 | 28 | 150 | 45 | 55.0 | Music wire | DIN 2097 / GB/T 23935 |
| 4.0 | 40 | 200 | 90 | 110.0 | Music wire | DIN 2097 / GB/T 23935 |