Stainless Steel Fastener Manufacturer & Supplier: Bolts, Nuts and Washers in A2-70 / A4-80
YP Fasteners is a stainless steel fastener manufacturer and supplier in China, specializing in A2-70 and A4-80 stainless bolts, nuts, washers and custom machined parts for marine, chemical, food processing and infrastructure projects. Backed by dedicated stainless production lines, automated optical sorting and 100% thread inspection, we supply OEM manufacturers, distributors and EPC contractors across the Middle East, Europe, Southeast Asia and Australia, with material certificates and passivation documentation prepared before dispatch.
YP Fasteners — Stainless Steel Fasteners Quick Reference:
- Execution standards: EN ISO 3506-1 (bolts), EN ISO 3506-2 (nuts), EN ISO 4017 / 4014, DIN 933 / 931, ISO 16048
- Material grades and strength: A2-70 (304, min. 700 MPa), A4-80 (316/316L, min. 800 MPa, PREN ≥ 23)
- Surface protection: ISO 16048 nitric passivation, electropolishing, factory-applied anti-galling wax coating
- Documentation: EN 10204 3.1 inspection certificates with heat number traceability and lot test reports
How Stainless Steel Fasteners Are Specified
On an engineering drawing, a stainless steel fastener is defined by three parameters: the material grade (A2 / 304 or A4 / 316), the property class (A2-70 or A4-80), and the surface finish. Mechanical performance is governed by EN ISO 3506-1 for bolts and screws and EN ISO 3506-2 for nuts, which set the tensile, yield and hardness requirements for each class. The most common procurement mistakes are mixing A2 with A4 in corrosive service, assuming property class from the grade name, and forgetting that thread fit and galling behavior change when stainless hardware is assembled at high speed.
Product Range: Stainless Bolts, Nuts, Screws and Washers
| Product | Typical Standard | Material / Property Class | Typical Service |
|---|---|---|---|
| Hex bolts and machine screws | EN ISO 3506-1, EN ISO 4017 / 4014, DIN 933 / 931 | A2-70, A4-80 | General industrial, marine, chemical |
| Hex nuts | EN ISO 3506-2, EN ISO 4032 / 4033, DIN 934 | A2-70, A4-80 | Matching all bolt assemblies |
| Washers | EN ISO 7089 / 7090, DIN 125 / 9021 | A2, A4 | Load distribution, sealing sets |
| Socket head cap screws | EN ISO 4762, DIN 912 | A2-70, A4-80 | Precision equipment, machinery |
| Stud bolts and threaded rods | DIN 976-1, DIN 938 / 939, EN ISO 3506-1 | A2-70, A4-80 | Flange connections, pipe supports |
| Self-tapping and wood screws | DIN 7504 / 7981 | A2-50, A2-70 | Enclosures, architectural fixing |
| Anchor bolts and expansion anchors | DIN 529, EN 1090-2 (execution), EN ISO 3506-1 | A4-80 | Structural fixing, coastal installations |
| Custom machined stainless parts | Drawing-based | 303, 304, 316, 316L | OEM components, valve parts |
Material Grades: A2 vs A4, 304 vs 316
- A2 stainless (304 / 1.4301) — the standard choice for atmospheric, industrial and most outdoor environments. A2-70 is the common property class for stainless bolts.
- A4 stainless (316 / 1.4401, 316L / 1.4404) — contains molybdenum for improved resistance to chlorides and chemicals. A4-80 is specified for marine, coastal, offshore and chemical environments.
Where the project involves prolonged saltwater exposure or aggressive chemicals, A4-80 hardware manufactured from 316/316L (PREN ≥ 23) with ISO 16048 passivation is the commonly specified solution, subject to project requirements. To prevent thread galling during high-speed impact wrench installation, stainless bolts can be supplied with a factory-applied anti-galling wax coating. For food and pharmaceutical equipment, A2 or A4 stainless with documented surface finish is supplied with the required hygiene documentation.
A2 vs A4: Material Comparison for Engineering Buyers
| Grade | Common Equivalent | Chromium | Nickel | Molybdenum | Min. Tensile (Class 70/80) | Typical Service |
|---|---|---|---|---|---|---|
| A2 | 304 / 1.4301 | 17.5–19.5% | 8–10.5% | — | 700 MPa (A2-70) | Atmospheric, general industrial |
| A4 | 316 / 1.4401, 316L / 1.4404 | 16–18% | 10–14% | 2–3% | 800 MPa (A4-80) | Marine, coastal, chemical, offshore |
PREN (pitting resistance equivalent number) is roughly 19 for A2 and 23 or higher for A4; the molybdenum in A4 is what lifts chloride resistance above A2.
Manufacturing and Surface Capabilities
- Cold heading and thread rolling — in-house production for standard hex bolts, screws and studs from M3 to M24, with precision thread rolling and standard metric thread tolerance per ISO 6g unless otherwise specified by drawing or application requirements
- CNC machining — for non-standard stainless parts, socket screws, studs and drawing-based components
- Passivation — nitric acid passivation per ISO 16048, with process control and documentation aligned to project requirements
- Electropolishing — for food, pharmaceutical and architectural applications requiring bright, smooth surfaces
- Mechanical testing — tensile, proof load and hardness testing per lot on stainless fasteners per EN ISO 3506-1 / -2 requirements
- Salt spray testing — performed per ISO 9227 where specified, as a comparative corrosion evaluation method; A2 passivated hardware typically achieves 240–500+ hours and A4 passivated hardware 500+ hours without red rust, while grade selection remains based on the application environment
Documentation and Traceability
- EN 10204 3.1 inspection certificates for material, mechanical and surface requirements (3.2 with third-party witnessing where specified)
- Mill certificates with heat numbers for 304 / 316 bar stock
- Passivation and surface finish reports
- Dimensional inspection reports with thread gauging
- First-article inspection reports for drawing-based stainless parts
Documentation is compiled before dispatch, so OEM and EPC buyers receive an audit-ready package with the shipment.
Why Buyers Choose YP Fasteners for Stainless Hardware
- Stainless-specific production — dedicated lines for stainless cold heading, threading and ISO 16048 passivation, backed by automated optical sorting with target defect control to prevent carbon steel contamination
- Material integrity — heat number traceability from bar stock to finished part, with mill certificates for every lot
- Grade clarity — full specification compliance with head marking verification and class-specific material stamping to guarantee job-site compliance
- Coastal and chemical expertise — A4-80 with passivation supplied for marine, offshore and chemical service
- Custom capability — drawing-based production of non-standard stainless bolts and machined parts with first articles before mass production
- Logistics — export through major China ports with inspection coordination for third-party witnessing
Need EN ISO 3506 mechanical test data or anti-galling coating specifications? Request the stainless fastener technical package from our engineering team.
Sourcing and Lead Times
- Stock sizes of A2-70 / A4-80 hex bolts, nuts and washers are available for rapid dispatch, subject to size, quantity and finish requirements
- Production lots of 10,000–500,000 pieces typically ship in 2–4 weeks depending on grade, property class and surface finish
- Mixed-container consolidation with carbon steel fasteners reduces freight cost for distributor orders
Planning a mixed-container order? Contact our logistics team for consolidated freight estimates.
FAQ
Q: What is the difference between A2 and A4 stainless steel fasteners?
A: A2 stainless (equivalent to 304) is suitable for atmospheric and general industrial environments. A4 stainless (equivalent to 316 / 316L) contains molybdenum and provides higher resistance to chlorides, saltwater and chemicals, so A4-80 (PREN ≥ 23) is specified for marine, coastal and chemical service, typically achieving 500+ hours in neutral salt spray testing (ISO 9227) after passivation.
Q: What does A2-70 or A4-80 mean?
A: The letter denotes the stainless steel group (A2 or A4) and the number denotes the property class in MPa — 70 means a minimum tensile strength of 700 MPa, 80 means 800 MPa. So A4-80 is a high-strength A4 stainless bolt with minimum 800 MPa tensile strength.
Q: Do you provide EN 10204 3.1 certificates for stainless fasteners?
A: Yes. We provide EN 10204 3.1 inspection certificates with heat number traceability for stainless fasteners, and 3.2 certificates with third-party witnessing where the project specifies it.
Q: Can you supply stainless fasteners with passivation?
A: Yes. We offer nitric acid passivation per ISO 16048 on A2 and A4 stainless hardware, with documentation included in the certificate package.
Q: Do you manufacture custom stainless steel parts to drawings?
A: Yes. Drawing-based production is our standard workflow — we review the drawing, confirm the grade and property class, produce first articles and deliver with dimensional inspection reports.
Q: What is your typical lead time for stainless steel fasteners?
A: Stock sizes dispatch quickly; production lots typically ship in 2–4 weeks depending on grade, quantity and surface finish requirements.
Request a Quote for Your Stainless Fastener Package
Send the fastener type, size, grade (A2-70 / A4-80 or equivalent), quantity and surface finish — or the drawing. Our engineering team will confirm the material, certification scope and delivery schedule within one working day.
📄 Download the stainless fastener RFQ checklist — size, grade, property class, finish and documentation requirements.
📦 Request sample bolts and MTC examples — evaluate material quality and certificate format before ordering.
💬 WhatsApp engineering support — send the drawing or bolt specification directly to our team.