Products Description

Our Duplex Stainless Steel Bolts deliver double the strength of 316 SS while resisting chloride attacks. With 22% chromium, 5% nickel, and 3% molybdenum (per ASTM A276), they achieve PREN values >35 - proven to withstand 100,000+ ppm chlorides in ASTM G48 testing.

Cold-forged heads provide 750 MPa tensile strength (exceeding ASME SA320 L43 requirements), perfect for offshore platforms where salt spray kills standard bolts. Third-party reports show <0.01mm/year pitting in seawater at 30°C. You'll get 2x the lifespan of 316 fasteners in chemical processing plants while saving 25% versus super duplex options.

Factory Processing

We offer two finishes: passivated (per ASTM A967) to boost corrosion resistance, creating a 7-9μm oxide layer, and sandblasted (Ra 25-50μm) for better paint adhesion in outdoor projects. The passivation process removes free iron, making them 35% more resistant to chloride corrosion than untreated bolts.

Production Strength

As a Chinese manufacturer with 10 years supplying EU offshore and chemical industries, we run 5 duplex-specific cold heading lines and 7 thread rollers, producing 3,800 tons annually. Our raw material undergoes a special annealing process to maintain the 50-50 ferrite/austenite balance, checked via our in-house magnetic tester (accuracy ±1%).

We keep 220-350 tons in stock at our Qingdao warehouse, covering sizes from ¼" to 2" and lengths 1" to 20". Inventory updates in real time on our website, and FOB Qingdao shipments for in-stock bolts leave within 5 days-handy when your customers need to keep projects on schedule.

Factory Commitment

Orders over 45 tons get a 5.5% discount, plus free passivation and 15% of sea freight.

Here's our guarantee: If any Duplex Stainless Steel Bolts fail to meet ASTM A193 mechanical standards or show pitting corrosion within 8 years, we'll replace them within 6 days and refund all shipping costs. We also offer a 35-day price lock on confirmed orders, with a 2% repeat order discount for clients who reorder within 3 months.

Material Properties

Property	Details
Material	Super Duplex Stainless Steel S31803 (UNS S31803; equivalent to 2205, DIN 1.4462)
Chemical Composition	Cr: 21.0-23.0%, Ni: 4.5-6.5%, Mo: 2.5-3.5%, N: 0.08-0.20%, C: ≤0.03%, Mn: ≤2.0%, Si: ≤1.0%, P: ≤0.03%, S: ≤0.02%
Mechanical Properties	Tensile Strength: ≥690 MPa Yield Strength: ≥450 MPa Hardness: ≤290 HB (Brinell); ≤31 HRC (Rockwell) Elongation: ≥25%
Corrosion Resistance	Excellent resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC) in chloride-rich environments (e.g., seawater, brines). Superior to 316/316Ti in harsh chemicals.
Temperature Range	Continuous service: -50°C to 250°C (limited by ductility at high temperatures); ideal for subsea and offshore environments.
Magnetic Property	Magnetic (due to duplex microstructure: austenite + ferrite)

Dimensional Specifications (Metric & Imperial)

Metric Size (M)	Thread Pitch (mm)	Hex Head Width (mm)	Hex Head Height (mm)	Length Range (mm)	Imperial Equivalent	Thread Type (Imperial)
M6	1.0	10.0	5.2	12-200	3/16"	UNC (3/16"-24), UNF (3/16"-32)
M8	1.25	13.0	6.8	16-300	5/16"	UNC (5/16"-18), UNF (5/16"-24)
M10	1.5	16.0	8.4	20-400	3/8"	UNC (3/8"-16), UNF (3/8"-24)
M12	1.75	18.0	10.8	25-500	1/2"	UNC (1/2"-13), UNF (1/2"-20)
M16	2.0	24.0	14.8	30-600	5/8"	UNC (5/8"-11), UNF (5/8"-18)

Standards & Applications

Standard Compliance	Key Applications
ASTM A193 B8S, ISO 4017, DIN 933	Offshore oil and gas platforms (subsea pipelines, wellheads) Desalination plants (reverse osmosis systems) Chemical processing (acids, chlorides, and corrosive slurries) Marine engineering (ship hulls, propeller shafts) Pulp and paper industry (bleaching systems with chlorine compounds)

Key Advantages Over Other Grades

Feature	S31803 (2205)	316Ti	304
Strength	High (yield strength 2× that of 316Ti)	Moderate	Lower
Chloride Resistance	Excellent (resists seawater/SCC)	Good (but limited in high chloride levels)	Poor
Weldability	Good (requires controlled heat input to avoid ferrite/austenite imbalance)	Excellent	Good
Cost	Higher (premium for duplex microstructure)	Moderate	Lower