Specifying Flat Plain Washer (GB/T 95) — GB/T 97.1 / ISO 7089 (Series 086) in Grade 8.8 Steel pairs the dimensional form of Flat Plain Washer (GB/T 95) — GB/T 97.1 / ISO 7089 (Series 086) (GB/T 97.1 / ISO 7089) with the engineering properties of Grade 8.8 Steel. This page explains when to choose the grade, how it behaves in service, and which grades to compare it against.
Why Choose Grade 8.8 Steel for Flat Plain Washer (GB/T 95) — GB/T 97.1 / ISO 7089 (Series 086)
The workhorse medium-carbon alloy grade for structural joints. For flat plain washer (gb/t 95) — gb/t 97.1 / iso 7089 (series 086), 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 flat plain washer (gb/t 95) — gb/t 97.1 / iso 7089 (series 086) 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.
Comparable Grades
For Flat Plain Washer (GB/T 95) — GB/T 97.1 / ISO 7089 (Series 086), class 10.9 or 12.9 is the comparable strength step. Move up when the joint preload approaches the proof load of the current class; move down when the joint is over-specified. For corrosion-critical service, switch to stainless A2 or A4.
Sizes of Flat Plain Washer (GB/T 95) — GB/T 97.1 / ISO 7089 (Series 086) Available in Grade 8.8 Steel
| For bolt size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness t (mm) | Reference standard |
|---|---|---|---|---|
| M3 | 3.2 | 7.0 | 0.5 | ISO 7089 / GB/T 97.1 |
| M4 | 4.3 | 9.0 | 0.8 | ISO 7089 / GB/T 97.1 |
| M5 | 5.3 | 10.0 | 1.0 | ISO 7089 / GB/T 97.1 |
| M6 | 6.4 | 12.0 | 1.6 | ISO 7089 / GB/T 97.1 |
| M8 | 8.4 | 16.0 | 1.6 | ISO 7089 / GB/T 97.1 |
| M10 | 10.5 | 20.0 | 2.0 | ISO 7089 / GB/T 97.1 |
| M12 | 13.0 | 24.0 | 2.5 | ISO 7089 / GB/T 97.1 |
| M14 | 15.0 | 28.0 | 2.5 | ISO 7089 / GB/T 97.1 |
| M16 | 17.0 | 30.0 | 3.0 | ISO 7089 / GB/T 97.1 |
| M18 | 19.0 | 34.0 | 3.0 | ISO 7089 / GB/T 97.1 |
| M20 | 21.0 | 37.0 | 3.0 | ISO 7089 / GB/T 97.1 |
| M24 | 25.0 | 44.0 | 4.0 | ISO 7089 / GB/T 97.1 |
| M30 | 31.0 | 56.0 | 4.0 | ISO 7089 / GB/T 97.1 |
| M36 | 37.0 | 66.0 | 5.0 | ISO 7089 / GB/T 97.1 |