Specifying Sheet-Metal Self-Tapping Screw — GB/T 845 / ISO 7049 (Series 045) in A4 Stainless Steel pairs the dimensional form of Sheet-Metal Self-Tapping Screw — GB/T 845 / ISO 7049 (Series 045) (GB/T 845 / ISO 7049) with the engineering properties of A4 Stainless Steel. This page explains when to choose the grade, how it behaves in service, and which grades to compare it against.
Why Choose A4 Stainless Steel for Sheet-Metal Self-Tapping Screw — GB/T 845 / ISO 7049 (Series 045)
Specified for marine, coastal and chemical applications. For sheet-metal self-tapping screw — gb/t 845 / iso 7049 (series 045), this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | A4-80 (316) |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C |
| Corrosion characteristic | Superior, including marine and chloride environments |
Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Sheet-Metal Self-Tapping Screw — GB/T 845 / ISO 7049 (Series 045) in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Comparable Grades
For Sheet-Metal Self-Tapping Screw — GB/T 845 / ISO 7049 (Series 045), the alternative stainless grade is A2 (304). A2 (304) suits general indoor and outdoor service; A4 (316) adds molybdenum for marine and chloride environments. Where higher strength matters more than corrosion, switch to plated alloy-steel class 8.8 or 10.9.
Sizes of Sheet-Metal Self-Tapping Screw — GB/T 845 / ISO 7049 (Series 045) Available in A4 Stainless Steel
| Size | Nominal diameter (mm) | Pitch (mm) | Length L (mm) | Head diameter dk (mm) | Head height k (mm) | Reference standard |
|---|---|---|---|---|---|---|
| ST2.2 | 2.2 | 0.8 | 9.5 | 4.2 | 1.4 | ISO 1481 / GB/T 845 |
| ST2.9 | 2.9 | 1.1 | 13 | 5.6 | 1.7 | ISO 1481 / GB/T 845 |
| ST3.5 | 3.5 | 1.3 | 16 | 6.9 | 2.1 | ISO 1481 / GB/T 845 |
| ST3.9 | 3.9 | 1.3 | 16 | 7.5 | 2.3 | ISO 1481 / GB/T 845 |
| ST4.2 | 4.2 | 1.4 | 19 | 8.2 | 2.5 | ISO 1481 / GB/T 845 |
| ST4.8 | 4.8 | 1.6 | 25 | 9.5 | 2.9 | ISO 1481 / GB/T 845 |
| ST5.5 | 5.5 | 1.8 | 32 | 10.9 | 3.3 | ISO 1481 / GB/T 845 |
| ST6.3 | 6.3 | 1.8 | 38 | 12.5 | 3.8 | ISO 1481 / GB/T 845 |