Property Class 12.9 Steel Hex Flange Bolts are supplied to ISO 1665 / DIN 6921. The grade provides requires plating or black-oxide protection and is magnetic; the practical service range is commonly limited to approx. +300 °C; confirm against the coating and the load. Property data, grade comparison and the full size table follow.
Why Choose Property Class 12.9 Steel for Hex Flange Bolts
The highest common strength class, for high-load machine assembly. For hex flange bolts, this matters when requires plating or black-oxide protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 898-1 property class 12.9 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | commonly limited to approx. +300 °C; confirm against the coating and the load |
| Corrosion characteristic | Requires plating or black-oxide protection |
Corrosion Behavior in Service
Carbon and alloy steel hex flange bolts 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 hex flange bolts 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 Hex Flange Bolts Available in Property Class 12.9 Steel
| Size | Pitch (mm) | Flange diameter dc (mm) | Head height k (mm) | Width across flats s (mm) | Reference standard |
|---|---|---|---|---|---|
| M5 | 0.8 | 11.8 | 4.7 | 8.0 | ISO 1665 / DIN 6921 |
| M6 | 1.0 | 14.2 | 5.6 | 10.0 | ISO 1665 / DIN 6921 |
| M8 | 1.25 | 17.9 | 7.2 | 13.0 | ISO 1665 / DIN 6921 |
| M10 | 1.5 | 21.8 | 8.9 | 15.0 | ISO 1665 / DIN 6921 |
| M12 | 1.75 | 26.0 | 10.7 | 18.0 | ISO 1665 / DIN 6921 |
| M14 | 2.0 | 29.9 | 12.3 | 21.0 | ISO 1665 / DIN 6921 |
| M16 | 2.0 | 34.5 | 14.1 | 24.0 | ISO 1665 / DIN 6921 |
| M20 | 2.5 | 42.8 | 17.5 | 30.0 | ISO 1665 / DIN 6921 |
| M24 | 3.0 | 51.1 | 21.0 | 36.0 | ISO 1665 / DIN 6921 |
