DIN 912304 · 316 · 202
Stainless Steel Socket Head Cap Screw (DIN 912)
Size: M3 – M16
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Material Grades
Stainless Steel Screw Grades
Selecting the correct stainless steel screw grade is essential for ensuring corrosion resistance and performance in your application. Accurate Fastners supplies SS screws in SS 202, SS 304 and SS 316 grades. This guide provides a grade comparison to help buyers make informed material selections based on operating environment and application requirements.
For screw type selection, refer to our screw types guide. For DIN standard specifications, refer to our DIN standards guide. Grade availability varies by product type — refer to individual product pages for documented grade options.
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Grade Comparison Summary
| Grade | Composition | Corrosion Resistance | Best For |
|---|---|---|---|
| SS 304 | 18% chromium, 8% nickel | Good for general industrial use | Indoor equipment, moderate outdoor exposure |
| SS 316 | Chromium, nickel, 2-3% molybdenum | Enhanced for chloride-rich environments | Coastal, marine, chemical processing |
| SS 202 | 4% nickel, 8-10% manganese | Suitable for mild conditions | Cost-sensitive indoor applications |
SS 304 Screws
Material Characteristics
SS 304 is the most widely used stainless steel grade for screws and fasteners. It contains approximately 18% chromium and 8% nickel, providing good corrosion resistance in many non-chloride environments. This austenitic stainless steel offers a balance of corrosion resistance, mechanical properties and cost.
Corrosion Resistance
SS 304 provides resistance to atmospheric corrosion, many organic chemicals and oxidizing environments. It is suitable for indoor applications, moderate outdoor exposure and general industrial use. However, SS 304 may be susceptible to pitting and crevice corrosion in chloride-rich or marine environments.
Typical Applications
SS 304 machine screws and other fasteners are used in indoor equipment, general machinery, food processing equipment (where chloride exposure is limited), pharmaceutical equipment (non-critical areas), LED lighting and electronic enclosures. Suitable for applications requiring moderate corrosion resistance.
A2 Designation
In European standards, SS 304 is commonly referred to as A2 stainless steel. A2 indicates an austenitic stainless steel with corrosion resistance suitable for general applications. Note that A2 is a material group designation and not a guarantee of exact composition matching SS 304 specifications.
SS 316 Screws
Material Characteristics
SS 316 contains molybdenum (approximately 2-3%) in addition to chromium and nickel. The molybdenum content enhances resistance to pitting and crevice corrosion, particularly in chloride-containing environments. This makes SS 316 suitable for more demanding corrosion conditions.
Corrosion Resistance
SS 316 provides superior corrosion resistance compared to SS 304, especially in chloride-rich environments such as coastal areas, marine applications and chemical processing. It resists pitting and crevice corrosion better than SS 304 and is preferred for harsh operating conditions.
Typical Applications
SS 316 machine screws and fasteners are used in coastal installations, marine-adjacent equipment, water treatment plants, chemical processing equipment, food processing with washdown requirements, pharmaceutical machinery and applications with salt or chloride exposure. Preferred for outdoor applications in marine environments.
A4 Designation
In European standards, SS 316 is commonly referred to as A4 stainless steel. A4 indicates an austenitic stainless steel with enhanced corrosion resistance, including molybdenum content for chloride resistance. Note that A4 is a material group designation and not a guarantee of exact composition matching SS 316 specifications.
SS 202 Screws
Material Characteristics
SS 202 is a lower-nickel, higher-manganese austenitic stainless steel grade. It contains approximately 4% nickel and 8-10% manganese, compared to SS 304's 8% nickel. This composition provides corrosion resistance at a lower material cost, making it suitable for cost-sensitive applications.
Corrosion Resistance
SS 202 offers corrosion resistance suitable for many indoor and protected outdoor applications where environmental conditions are less aggressive. However, its corrosion resistance is generally lower than SS 304 and significantly lower than SS 316. Not recommended for chloride-rich or marine environments.
Typical Applications
SS 202 screws are suitable for cost-sensitive applications with moderate environmental requirements. Used in indoor equipment, general hardware, light-duty applications and situations where budget constraints are a primary consideration. Confirm environmental compatibility before use.
Grade Selection Considerations
SS 202 may be considered when budget is a constraint and operating conditions are mild. However, for applications requiring verified corrosion resistance or exposure to moisture and chemicals, SS 304 or SS 316 are recommended. Consult with engineering teams before selecting SS 202 for critical applications.
A2 and A4 Stainless Steel Designations
Understanding A2 Designation
A2 is a European standard designation for austenitic stainless steel fasteners with corrosion resistance suitable for general applications. A2 typically corresponds to materials similar to SS 304 or 18/8 stainless steel. However, A2 is a material group, not a specific alloy designation. Confirm exact composition when A2 is specified.
Understanding A4 Designation
A4 is a European standard designation for austenitic stainless steel fasteners with enhanced corrosion resistance, including molybdenum content. A4 typically corresponds to materials similar to SS 316. Like A2, A4 is a material group designation and not a guarantee of exact alloy composition. Confirm specifications when A4 is required.
Designation Mapping
While A2 and SS 304 are often used interchangeably, and A4 and SS 316 are often used interchangeably, these are not universal equivalences. Exact alloy composition may vary. Accurate Fastners supplies SS 202, SS 304 and SS 316 grades as documented in the product catalogue. Specify these grades directly for clarity.
Specification Clarity
When specifying stainless steel screws, use the actual grade designation (SS 304, SS 316, SS 202) rather than relying solely on A2 or A4 designations. This ensures accurate material selection and avoids ambiguity. Contact the Accurate Fastners sales team if specification requirements are unclear.
Grade Selection Guidance
Environmental Assessment
Assess the operating environment before selecting a screw grade. Consider exposure to moisture, chemicals, salt, temperature extremes and cleaning agents. Indoor applications with moderate conditions may use SS 304 or SS 202. Outdoor or marine applications typically require SS 316.
Budget vs. Performance
SS 202 offers cost advantages but lower corrosion resistance. SS 304 provides a balance of cost and performance for general use. SS 316 provides the highest corrosion resistance at a higher material cost. Consider total cost of ownership, including potential replacement costs, when making grade decisions.
Industry Standards
Some industries or specifications may mandate particular stainless steel grades. Food processing, pharmaceutical and marine applications often have specific grade requirements. Confirm that the selected grade complies with applicable industry standards and project specifications.
Verification Requirements
For critical applications requiring material traceability, discuss certification and test report requirements with the Accurate Fastners sales team. Material test reports may be available for verification when required by project specifications or quality systems.
Featured SS Screw Products
- DIN 7981304 · 316
Stainless Steel Pan Head Self-Tapping Screw (DIN 7981)
Size: M2.9 – M6.3 (ST sizes)
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Frequently Asked Questions About Screw Grades
What is the difference between SS 304 and SS 316 screws?+
SS 316 contains molybdenum which provides enhanced resistance to pitting and crevice corrosion in chloride-rich environments. SS 304 is suitable for general industrial use but may be less resistant in marine or chemical exposure conditions.
When should I use SS 202 instead of SS 304?+
SS 202 may be considered for cost-sensitive applications with mild environmental conditions. However, for applications requiring verified corrosion resistance or exposure to moisture and chemicals, SS 304 is recommended. Confirm environmental compatibility before selecting SS 202.
What does A2 stainless steel mean?+
A2 is a European designation for austenitic stainless steel with corrosion resistance suitable for general applications. A2 typically corresponds to materials similar to SS 304, but it is a material group designation rather than a specific alloy. Specify SS 304 directly for clarity.
What does A4 stainless steel mean?+
A4 is a European designation for austenitic stainless steel with enhanced corrosion resistance including molybdenum content. A4 typically corresponds to materials similar to SS 316. Like A2, it is a material group designation. Specify SS 316 directly for clarity.
Are A2 and SS 304 exactly the same?+
No, A2 and SS 304 are not universally equivalent. A2 is a material group designation in European standards, while SS 304 is a specific alloy composition. While they are often used interchangeably, exact composition may vary. Specify the actual grade required.
Which grade is best for coastal applications?+
SS 316 is the preferred grade for coastal and marine applications due to its molybdenum content, which provides enhanced resistance to chloride-induced pitting and crevice corrosion compared to SS 304 and SS 202.
How do I confirm grade availability for a specific screw type?+
Refer to individual product pages which document available grades for each screw type. Grade availability varies by product. Contact the sales team to confirm grade availability for your specific requirements.
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