Product Overview
Stainless Steel Bolts are engineered fasteners designed to provide reliable mechanical strength coupled with excellent corrosion resistance. Manufactured from austenitic chromium-nickel alloys, they are the preferred choice for applications exposed to moisture, chemicals, atmospheric conditions, or where hygiene and aesthetic appearance are critical. Unlike plated carbon steel fasteners, their corrosion resistance is inherent to the material, offering long-term integrity without coating degradation.
Key Features & Benefits
Superior Corrosion Resistance: The passive chromium oxide layer provides inherent protection against rust and oxidation in a wide range of environments.
High Strength & Durability: Available in standardized property classes (e.g., 70, 80) offering tensile strengths suitable for most mechanical and structural applications.
Hygienic & Easy to Clean: Non-porous surface resists bacterial growth, making them ideal for food processing, pharmaceutical, and marine applications.
Temperature Resistance: Maintains mechanical properties across a wide temperature range.
Aesthetic Appeal: Provides a clean, modern, and permanent metallic finish. Non-magnetic options (A2 & A4) are available.
Material Grades & Mechanical Properties
The two most common austenitic stainless steel grades for bolts are defined by ISO and ASTM standards.
| Common Name | Material Standard | ISO Property Class | ASTM Grade Designation | Typical Composition | Minimum Tensile Strength | Key Characteristics |
|---|---|---|---|---|---|---|
| A2 / 304 | ISO 3506-1 | A2-70, A2-80 | ASTM F593, Group 1 | 18% Cr, 8% Ni | 700 MPa (A2-70) 800 MPa (A2-80) | General Purpose. Excellent all-around corrosion resistance in atmospheric and mild chemical environments. Most widely used. |
| A4 / 316 | ISO 3506-1 | A4-70, A4-80 | ASTM F593, Group 2 | 16% Cr, 10% Ni, 2% Mo | 700 MPa (A4-70) 800 MPa (A4-80) | Marine & Chemical Grade. Superior resistance to pitting and crevice corrosion, especially from chlorides (seawater, de-icing salts). |
Product Range & Specifications
Our stainless steel bolts are manufactured to meet major international dimensional and mechanical standards.
Head Styles:
Hex Head (Heavy/Standard): ASME B18.2.1, DIN 933/931, ISO 4014/4017.
Socket Head Cap Screw: ISO 4762, DIN 912, ASME B18.3.
Pan Head / Countersunk (Phillips/Slot): ISO 7045/7046, DIN 7985/965.
Thread Standards: Full range of Metric (ISO) and Imperial (UNC/UNF) threads available.
Size Range: Metric: M2 to M36. Imperial: #4 to 1-1/2″.
Standard Surface Finishes
The standard and most functional finish for stainless steel fasteners is passivation. Other finishes are available for specific needs.
| Finish Type | Process / Standard | Description & Purpose |
|---|---|---|
| Passivation (Standard) | ASTM A967 / ISO 16048 | Essential post-production process. Removes free iron particles from the surface and enhances the natural chromium oxide layer, maximizing corrosion resistance. Results in a clean, matte grey finish. |
| Bright (Mechanically Polished) | – | Aesthetic finish achieved by mechanical polishing (tumbling, buffing). Provides a shiny, reflective appearance but does not enhance corrosion resistance. Often used in architectural or decorative applications. |
| Electropolished | – | An electrochemical process that removes surface material, smoothing micro-roughness. Further improves corrosion resistance, decontamination, and provides a bright, clean appearance for ultra-hygienic applications. |
Critical Application Notes
Galvanic Corrosion: Avoid direct contact with more cathodic metals (e.g., carbon steel, copper) in a conductive environment. Use insulating washers or sleeves if necessary.
Galling (Cold Welding): A risk during installation of stainless-on-stainless threads due to material adhesion. Mitigate by:
Using bolts and nuts of different hardness grades.
Applying a specialty anti-galling lubricant (e.g., nickel- or molybdenum-disulfide based).
Ensuring proper alignment and avoiding over-torquing.
Stress Corrosion Cracking (SCC): Standard A2/A4 grades are highly resistant. For extreme environments (high temp, high chloride), consider specialty alloys like A5 (Duplex) stainless.
Quality Assurance & Traceability
Material Certification: All raw material is sourced with full Mill Test Certificates (MTCs) verifying chemical composition.
Mechanical Testing: Bolts are tested for tensile strength, proof load, and hardness per ISO 3506-1 or ASTM F593 requirements.
Passivation Verification: Salt Spray Testing per ASTM B117 is performed on sample batches to validate corrosion resistance.
Traceability: Production is managed under a certified ISO 9001:2015 quality system. Products are marked with grade (A2/A4) and property class (e.g., 80).
Manufacturing Expertise
Our stainless steel bolts are produced by Hebei Wohe Fastener Manufacturing Co., Ltd., utilizing dedicated production lines to prevent carbon steel contamination. Our process includes precision cold heading for optimal grain structure, thread rolling for strength, and controlled solution annealing for A2/A4 grades to restore corrosion properties. We understand the specific handling and quality requirements of the chemical, marine, and food-grade industries, supplying certified fasteners that meet the stringent demands of international projects.
Ordering & Technical Support:
Specification: Please specify Material Grade (A2/A4), Property Class (70/80), Standard (DIN/ISO/ASME), Size, Length, and Finish.
Special Parts: Available in non-standard lengths, special threads, and custom markings.
Packaging: Standard export packaging in cartons or boxes. Vacuum-sealed packaging is available for superior protection during long-term storage or ocean transit.
MOQ: Standard items start from 2,000 pieces per size/type. Custom orders are negotiable.
Lead Time: Standard specifications: 20-25 working days.
Disclaimer: While stainless steel offers excellent corrosion resistance, performance is highly dependent on the specific chemical environment, temperature, and mechanical stresses. Selection of the appropriate grade (A2 vs. A4) and proper installation practices are the responsibility of the design engineer or end-user. The information provided is for general guidance and is subject to change.
