Grade 8.8 Steel Square Nut — GB/T 39 / ISO 4034 (Series 075) pairs the standard GB/T 39 / ISO 4034 with a Grade 8.8 Steel base material. The sections below cover why engineers select this grade for square nut — gb/t 39 / iso 4034 (series 075), its corrosion and temperature behavior, and the sizes available.
Why Choose Grade 8.8 Steel for Square Nut — GB/T 39 / ISO 4034 (Series 075)
The workhorse medium-carbon alloy grade for structural joints. For square nut — gb/t 39 / iso 4034 (series 075), this matters when requires plating (zinc) for corrosion protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | class 8.8 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | up to approx. +300 °C |
| Corrosion characteristic | Requires plating (zinc) for corrosion protection |
Corrosion Behavior in Service
Carbon and alloy steel square nut — gb/t 39 / iso 4034 (series 075) 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 — gb/t 39 / iso 4034 (series 075) 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 — GB/T 39 / ISO 4034 (Series 075) Available in Grade 8.8 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 |