How to Tell If a Bolt Is Stainless Steel
2025-08-14
Introduction to Steel Bolt Identification
Understanding whether a steel bolt is made of stainless steel is crucial for ensuring durability, corrosion resistance, and proper application in construction, manufacturing, and industrial projects. This guide from QBH provides professional methods to identify stainless steel bolts, compares material properties, and highlights key product specifications to help you make informed decisions.
1. Visual and Physical Inspection Methods
Key Characteristics of Stainless Steel Bolts
✔ Surface Finish: Smooth, polished, or brushed appearance
✔ Magnetic Response: Most grades are slightly magnetic (except 304/316)
✔ Weight: Heavier than aluminum but lighter than carbon steel
✔ Color: Silver-white with no coating or plating
Comparison Table: Stainless Steel vs. Carbon Steel Bolts
| Feature | Stainless Steel Bolt | Carbon Steel Bolt |
|---|---|---|
| Corrosion Resistance | High (rust-resistant) | Low (requires coating) |
| Magnetism | Weak or non-magnetic | Strongly magnetic |
| Surface Finish | Uniform, no coating | Often galvanized or painted |
| Price | Higher | Lower |
2. Chemical and Professional Testing Methods
Advanced Identification Techniques
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Spark Test: Stainless steel produces short, less bright sparks
-
Nitric Acid Test: No reaction on stainless steel (bubbles on carbon steel)
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XRF Analyzer: Accurately detects alloy composition
QBH Stainless Steel Bolt Grades
| Grade | Composition | Corrosion Resistance | Tensile Strength | Common Applications |
|---|---|---|---|---|
| 304 | 18% Cr, 8% Ni | Excellent | 515 MPa | Indoor, marine |
| 316 | 16% Cr, 10% Ni, 2% Mo | Superior | 515 MPa | Chemical, coastal |
| 410 | 12% Cr | Moderate | 480 MPa | High-strength uses |
3. Common Mistakes in Bolt Identification
Misleading Factors to Avoid
✖ Assuming all shiny bolts are stainless steel (some are plated)
✖ Relying only on magnetism (some stainless grades are magnetic)
✖ Ignoring manufacturer markings (grade codes are often stamped)
How QBH Ensures Authenticity
✔ Laser-etched grade markings
✔ Material test certificates (MTC) with each batch
✔ Salt spray testing (1000+ hours for marine-grade bolts)
4. QBH Stainless Steel Bolt Product Line
Technical Specifications
| Product Code | Diameter Range | Length Range | Head Type | Finish | Standards |
|---|---|---|---|---|---|
| QBH-SS304 | M3-M24 | 10-200mm | Hex, Socket | A2-70 | DIN 933 |
| QBH-SS316 | M4-M30 | 12-250mm | Flange, Button | A4-80 | ISO 4014 |
| QBH-SS410 | M5-M20 | 15-150mm | Hex, Allen | Mechanical | ASTM A193 |
Performance Features
✔ 100% material traceability
✔ Corrosion warranty (5 years for 316 grade)
✔ Precision threading (ISO 898-1 compliant)
✔ Custom packaging (vibration-resistant)
Why Choose QBH Stainless Steel Bolts?
✔ 30+ years in fastener manufacturing
✔ BSCI-certified factory
✔ Just-in-time global delivery
✔ Technical support for material selection
Contact Our Fastener Experts Today:
📧 Email: sales@qbfastener.cn
As QBH's technical director with decades in fastener engineering, I guarantee our stainless steel bolts meet the highest industry standards. Let us help you select the perfect bolts for your project's requirements.
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