By Ragnar Metals & Tubes Engineering Team • October 14, 2026 • 7 min read
Duplex stainless steel round bars are the starting material for machined valve bodies, pump shafts, subsea connectors, and high-strength fasteners. Choosing between Grade 2205 and Grade 2507 affects not just material cost but corrosion performance, machinability, and compliance with project specifications. This guide gives you the numbers to decide.
Unlike pipe (ASTM A790) or fittings (ASTM A815), duplex round bars fall under two main standards depending on end use:
| Property | ASTM A276 S32205 Min. |
|---|---|
| Yield strength (0.2% proof) | 450 MPa (65 ksi) |
| Tensile strength | 655 MPa (95 ksi) |
| Elongation | 25% min. |
| Hardness (max) | 293 HB |
| PREN | > 34 (typically 36-38) |
| Ferrite content | 40-60% (ASTM E562) |
| Size range (typical stock) | 10mm to 250mm diameter |
| Property | ASTM A276 S32750 Min. |
|---|---|
| Yield strength (0.2% proof) | 550 MPa (80 ksi) |
| Tensile strength | 795 MPa (115 ksi) |
| Elongation | 15% min. |
| Hardness (max) | 310 HB |
| PREN | > 41 (typically 42-45) |
| Ferrite content | 40-60% |
| Size range (typical stock) | 10mm to 200mm diameter |
| Element | Grade 2205 (S32205) | Grade 2507 (S32750) |
|---|---|---|
| Chromium (Cr) | 22.0-23.0% | 24.0-26.0% |
| Nickel (Ni) | 4.5-6.5% | 6.0-8.0% |
| Molybdenum (Mo) | 3.0-3.5% | 3.0-5.0% |
| Nitrogen (N) | 0.14-0.20% | 0.24-0.32% |
| Carbon (C max) | 0.030% | 0.030% |
The higher nitrogen in 2507 (0.24-0.32% vs. 0.14-0.20%) is what drives its superior strength and pitting resistance — nitrogen is a strong austenite-stabiliser and strengthener in duplex grades.
| Application | Grade | Standard / Grade Ref |
|---|---|---|
| Valve bodies — process plant, moderate Cl- | 2205 | ASTM A182 F51 |
| Valve bodies — seawater, offshore | 2507 | ASTM A182 F53 or F55 |
| Pump shafts — chemical plant | 2205 | ASTM A276 S32205 |
| Pump shafts — seawater lift, desalination | 2507 | ASTM A276 S32750 |
| Subsea connector bodies | 2507 | ASTM A182 F55, NORSOK M-630 |
| Machined flange blanks | 2205 or 2507 | ASTM A182 F51 / F53 |
| High-strength bolts / studs | 2507 or 6Mo | ASTM A276 / NACE MR0175 |
| Structural brackets — marine | 2205 | ASTM A276 S32205 |
Both grades machine harder than 316L: their high nitrogen and work-hardening rate mean slower cutting speeds and sharp tooling are required. 2507 is marginally harder to machine than 2205 due to higher nitrogen. For CNC turning, typical surface speeds are 80-100 m/min for 2205 and 70-90 m/min for 2507 using carbide inserts with flood coolant. Note that duplex bars should not be cold drawn to improve machinability — cold work disrupts the ferrite/austenite balance and can reduce corrosion resistance.
All duplex bars must be supplied in the solution-annealed and quenched condition. Solution anneal temperature: 1020-1100°C (2205) or 1080-1130°C (2507), followed by rapid water quench. This dissolves any sigma phase or secondary phases that form during hot working and ensures the correct ferrite/austenite balance.
Ragnar Metals supplies duplex 2205 and super duplex 2507 round bars in ASTM A276, A182, and A479 to EN 10204 3.1 MTC. Sizes from 10mm to 250mm diameter with 3rd-party inspection, PMI reports, and short lead times from Mumbai.
WhatsApp Send EnquiryRelated pages: Round Bars & Hex Bars • Duplex vs Super Duplex Guide • Duplex Flanges
Ragnar Metals & Tubes is a leading Stainless Steel Pipes, Tubes, Flanges, Fittings, Fasteners & Alloy Steel Products manufacturer and exporter from Mumbai, India supplying to Saudi Arabia, UAE, USA, UK and global markets.
ISO Certified | Global Exporter | 15+ Years Experience
Request a Quote© 2026 Ragnar Metals & Tubes. All Rights Reserved.
Stainless Steel Manufacturer & Global Exporter from Mumbai, India.