Duplex Steel Round Bars
Giriraj Impex is a manufacturer, stockist, supplier and exporter of duplex round bars in duplex 2205 – UNS S31803 and S32205 – to ASTM A276 and A479. We manufacture duplex round bars in black (hot rolled or forged) and bright (peeled, turned or centreless ground) condition, solution annealed, together with hexagonal and square bars, supplied in random lengths or cut to length.
Duplex bars are used for parts that need both high strength and resistance to chloride pitting and stress corrosion cracking – pump shafts, valve stems and trim, fasteners, propeller shafts, agitator shafts and machined fittings in seawater, offshore, desalination, chemical and pulp and paper service.
Specifications
| Item | Details |
|---|---|
| Standards | ASTM A276 (general use), ASTM A479 / ASME SA479 (boilers and pressure vessels), ASTM A182 F51/F60 for forged bar |
| Grades | UNS S31803, S32205; dual certified |
| Shapes | Round, hexagonal, square |
| Condition | Solution annealed and rapidly cooled; black or bright |
| Bright finish | Peeled, turned, centreless ground or polished; tolerance such as ISO h9, h10 or h11 as ordered |
| Optional tests | Ultrasonic test, ferrite count, impact test, ASTM A923, ASTM G48 |
| Documents | Mill test certificate (MTC) with PREN; third-party inspection on request |
Composition
Duplex bar has the same composition limits as duplex pipe and plate of the same UNS number:
| UNS | Grade | C | Mn | P | S | Si | Cr | Ni | Mo | N | Other elements |
|---|---|---|---|---|---|---|---|---|---|---|---|
| S31803 | 2205 | 0.030 | 2.00 | 0.030 | 0.020 | 1.00 | 21.0–23.0 | 4.5–6.5 | 2.5–3.5 | 0.08–0.20 | – |
| S32205 | 2205 | 0.030 | 2.00 | 0.030 | 0.020 | 1.00 | 22.0–23.0 | 4.5–6.5 | 3.0–3.5 | 0.14–0.20 | – |
| S32750 | 2507 | 0.030 | 1.20 | 0.035 | 0.020 | 0.80 | 24.0–26.0 | 6.0–8.0 | 3.0–5.0 | 0.24–0.32 | Cu 0.50 |
| S32760 | Zeron 100 type | 0.030 | 1.00 | 0.030 | 0.010 | 1.00 | 24.0–26.0 | 6.0–8.0 | 3.0–4.0 | 0.20–0.30 | Cu 0.50–1.00, W 0.50–1.00 |
S32760 also requires a minimum PREN of 40. Footnotes as given in the standards.
For seawater shafts and fasteners in the most demanding service, see super duplex round bars.
Why duplex for shafts and fasteners
Shafts and fasteners are stressed parts, often wet with chloride-bearing fluids and at slightly elevated temperatures – the conditions in which 316 can suffer chloride stress corrosion cracking or crevice corrosion under washers, sleeves and seals. Duplex 2205 resists these mechanisms much better, and its higher yield strength allows smaller shaft diameters or higher bolt loads. For marine propeller and pump shafts, duplex bars give a good balance of strength, fatigue performance and seawater resistance; super duplex is used where the conditions are more severe.
Manufacturing and quality checks
Duplex bars are hot rolled or forged from billets, solution annealed and rapidly cooled, then straightened and finished – peeled, turned or ground – to the ordered tolerance. Large sizes are forged and rough turned. Because the structure of duplex can change if the bar is cooled too slowly, bars for oil and gas projects are often tested for ferrite content, impact toughness and intermetallic phases (ASTM A923), and for internal soundness by ultrasonic testing. Each bar or bundle is marked with grade, size and heat number. Bars can be supplied to NACE MR0175 / ISO 15156 on request.
Machining notes
Duplex is tougher to machine than 316 because of its higher strength and work-hardening. Rigid set-ups, sharp carbide tools, lower cutting speeds than for austenitic grades and plenty of coolant give good tool life. Bright bars to a close tolerance reduce the amount of material to be removed. If parts are to be welded or hot worked after machining, they will need solution annealing to restore the structure.
Ordering
Please give the UNS grade and standard, shape and size, tolerance, black or bright condition, length, quantity and any supplementary tests or inspection required.
Bar for forged and machined components
Many duplex components – small-bore fittings, valve bodies, flanges in small sizes and special connectors – are machined from bar rather than forged to shape. In these cases the bar is ordered to ASTM A479, and often with the same supplementary tests as the forgings it replaces, so that the machined parts meet the project specification. For large components, a forged bar or forging is preferred because the forging reduction gives a sounder internal structure; ultrasonic testing confirms the soundness of the bar before machining.
Applications and related products
Duplex round bars are used for pump and agitator shafts, valve stems, balls and trim, propeller shafts, duplex fasteners, forged and machined pipe fittings and flanges, and marine and offshore hardware. To complete a duplex project we also supply duplex pipes and tubes and duplex sheets and plates. See all bar materials on the round bars, rods and wires page and grade guidance on the duplex and super duplex steel page.
Frequently Asked Questions
ASTM A276 covers duplex and stainless bars for general use, and ASTM A479 covers bars for boilers and pressure vessels. Forged bars can also be supplied to ASTM A182 F51 or F60.
Duplex 2205 combines high strength with resistance to chloride pitting, crevice corrosion and stress corrosion cracking, which are common causes of failure in 316 shafts in seawater and brine.
Yes. Its higher strength and work-hardening mean slower cutting speeds, rigid set-ups and sharp tools are needed. Bright bars reduce the machining required.
Ultrasonic testing, ferrite measurement, Charpy impact tests and ASTM A923 testing for intermetallic phases are commonly added for oil and gas projects.
Yes. Duplex bars are supplied in round, hexagonal and square shapes, black or bright, in random or cut lengths.
PREN is calculated from the actual composition (%Cr + 3.3 × %Mo + 16 × %N). For duplex 2205 it is typically in the mid-30s; the value for each heat can be worked out from the mill test certificate.
Request a Quote for Duplex Steel Round Bars
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