For socket head shoulder screw in Grade 8.8 Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for Grade 8.8 Steel (class 8.8) is summarized below together with every size supplied.
Why Choose Grade 8.8 Steel for Socket Head Shoulder Screw — GB/T 5281 / ISO 7379 (Series 017)
The workhorse medium-carbon alloy grade for structural joints. For socket head shoulder screw — gb/t 5281 / iso 7379 (series 017), 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 socket head shoulder screw — gb/t 5281 / iso 7379 (series 017) 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 socket head shoulder screw — gb/t 5281 / iso 7379 (series 017) 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 Socket Head Shoulder Screw — GB/T 5281 / ISO 7379 (Series 017) Available in Grade 8.8 Steel
| Shoulder dia (mm) | Thread size | Pitch (mm) | Shoulder length (mm) | Head dia dk (mm) | Head height k (mm) | Reference standard |
|---|---|---|---|---|---|---|
| 5 | M4 | 0.7 | 16 | 9.5 | 5.3 | ISO 7379 / GB/T 5281 |
| 6 | M5 | 0.8 | 20 | 11.0 | 6.5 | ISO 7379 / GB/T 5281 |
| 8 | M6 | 1.0 | 25 | 13.0 | 8.0 | ISO 7379 / GB/T 5281 |
| 10 | M8 | 1.25 | 30 | 16.0 | 10.0 | ISO 7379 / GB/T 5281 |
| 12 | M10 | 1.5 | 40 | 18.0 | 12.0 | ISO 7379 / GB/T 5281 |
| 16 | M12 | 1.75 | 50 | 24.0 | 16.0 | ISO 7379 / GB/T 5281 |
| 20 | M16 | 2.0 | 60 | 30.0 | 20.0 | ISO 7379 / GB/T 5281 |
| 25 | M20 | 2.5 | 80 | 36.0 | 25.0 | ISO 7379 / GB/T 5281 |