When Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076) are required in Grade 12.9 Steel, the alternative grades and the trade-offs between them matter as much as the dimensions. This page covers both, plus mechanical and corrosion data.
Why Choose Grade 12.9 Steel for Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076)
The highest common strength class, for high-load machine assembly. For square nut, metric — gb/t 39 / iso 4034 (series 076), 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 square nut, metric — gb/t 39 / iso 4034 (series 076) 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 square nut, metric — gb/t 39 / iso 4034 (series 076) 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 Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076) Available in Grade 12.9 Steel
| Size | Pitch (mm) | Width across flats s (mm) | Nut height m (mm) | Reference standard |
|---|---|---|---|---|
| M3 | 0.5 | 5.5 | 1.8 | GB/T 39 / DIN 562 |
| M4 | 0.7 | 7.0 | 2.2 | GB/T 39 / DIN 562 |
| M5 | 0.8 | 8.0 | 2.7 | GB/T 39 / DIN 562 |
| M6 | 1.0 | 10.0 | 3.6 | GB/T 39 / DIN 562 |
| M8 | 1.25 | 13.0 | 4.8 | GB/T 39 / DIN 562 |
| M10 | 1.5 | 17.0 | 6.0 | GB/T 39 / DIN 562 |
| M12 | 1.75 | 19.0 | 7.0 | GB/T 39 / DIN 562 |
| M16 | 2.0 | 24.0 | 9.0 | GB/T 39 / DIN 562 |
| M20 | 2.5 | 30.0 | 12.0 | GB/T 39 / DIN 562 |
| M24 | 3.0 | 36.0 | 14.0 | GB/T 39 / DIN 562 |