Super Duplex 2507 Stainless Steel Round Bars

Exceptional Pitting and Crevice Corrosion Resistance: PRE ≥ 42 (typically 42–45) due to high chromium (24–26%), high molybdenum (3.0–5.0%), and nitrogen (0.24–0.32%) content.

Ultra-High Mechanical Strength: Minimum yield strength ≥ 550 MPa (approximately 3.2 times that of 316L and 1.2 times that of Duplex 2205).

Superior Chloride SCC Resistance: Excellent resistance to chloride-induced stress corrosion cracking, significantly outperforming both austenitic grades and standard duplex 2205.

NACE MR0175 / ISO 15156 Compliant: Fully qualified for extreme sour service with highest allowable H₂S partial pressures and lowest pH values.

Excellent Low-Temperature Toughness: Maintains excellent impact toughness down to -50°C with Charpy V-Notch ≥ 70J typical at -46°C.

Low Thermal Expansion: Coefficient of thermal expansion (13.0 μm/m·K) – lowest among all duplex and austenitic grades.

Good Machinability: Super Duplex 2507 can be machined with proper tooling (carbide tools, slower speeds, adequate coolant).

High Strength-to-Weight Ratio: Allows smaller diameter shafts for same load capacity, reducing weight and material cost.

Good Weldability: Requires strict procedure with low heat input, N₂ shielding gas, and ER2594 filler metal.

International Certifications: Round bars can be certified by ABS, BV, DNV, LR, GL, RINA, CCS, KR, and NK, and comply with NORSOK M-630, NACE MR0175, and ISO 13628-4 standards.

Super Duplex 2507 (S32750) contains higher chromium, molybdenum, and nitrogen compared to Duplex 2205, resulting in a PRE value of ≥42 (compared to ≤35 for 2205). PREN = %Cr + 3.3 × %Mo + 16 × %N ≥ 42 (typically 42–45).

Comparison of Strength and Corrosion Resistance:

Impact Toughness (Charpy V-Notch, typical at -46°C):

l  Longitudinal: ≥ 70 J (typical)

l  Transverse: ≥ 50 J (typical)

Heat Treatment Condition:
Super Duplex 2507 stainless steel round bars are solution annealed at 1050–1120°C followed by immediate water quenching (delay must be kept under 30 seconds). This heat treatment restores the balanced 40–60% ferrite / 40–60% austenite microstructure, dissolves unwanted intermetallic phases, and ensures maximum corrosion resistance.

Critical Note: Super Duplex 2507 requires immediate water quenching after solution annealing. Air cooling is completely unacceptable and will result in intermetallic phase precipitation, severely reducing corrosion resistance and toughness.

Delivery Condition Options:

l Black (Hot-Rolled): As-rolled with mill scale – for further processing

l Peeled/Turned: Smooth, bright surface – for precision machining

l Centerless Ground: Precision ground to tight tolerances – for high-precision shafting

Precision Ground Tolerances (Centerless Ground):

Standard Lengths:

l  Random Lengths: 3000mm – 6000mm

l  Fixed Lengths: 3000mm, 4000mm, 5000mm, 6000mm

l  Custom lengths available upon request

Straightness Tolerances:

*Formula: Weight (kg/m) = Diameter² (mm) × 0.00613 (based on density 7.80 g/cm³)*

Raw Material Selection: High-quality S32750 billets from certified premium mills (Outokumpu, Sandvik) with certified chemical composition and ferrite/austenite balance.

Heating: Billets heated to carefully controlled narrow temperature range (1150–1200°C) – lower than 2205 to prevent ferrite coarsening.

Hot Rolling: Heated billets passed through roughing and finishing stands with strict temperature control.

Cooling: Controlled cooling to prevent intermetallic phase formation.

Solution Annealing: Critical heat treatment at 1050–1120°C to restore balanced microstructure.

Water Quenching: Immediate water quenching after annealing (<30 seconds delay) – mandatory.

Pickling: Removal of oxides using specialized pickling acids for super duplex.

Ferrite Content Measurement: 35–65% ferrite documented (minimum 40% for sour service).

Microstructure Examination: No sigma or chi phases allowed.

Peeling/Turning (Optional): Removal of surface defects.

Centerless Grinding (Optional): Precision grinding for tight tolerances.

Straightening: Roller straightening.

Cutting: Cut to specified lengths.

Inspection & Testing: Dimensional check, PMI, ferrite measurement, mechanical testing.

Marking & Packing: Each bundle tagged with grade, heat number, ferrite content, NACE compliance.

Chemical Analysis: PMI verification for Cr (24-26%), Ni (6-8%), Mo (3-5%), N (0.24-0.32%).

Ferrite Content Measurement: 35–65% ferrite documented (minimum 40% for sour service).

Microstructure Examination: No sigma or chi phases – per NORSOK M-630.

Mechanical Testing: Tensile (≥800 MPa), yield (≥550 MPa), elongation (≥25%), hardness (≤310 HBW / ≤32 HRC).

Charpy Impact Testing: -46°C – ≥70J typical for longitudinal.

Pitting Corrosion Test: ASTM G48 Method A – no pitting at 40°C (or 50°C for NORSOK).

Ultrasonic Testing (UT): Per ASTM A388 for internal flaw detection (upon request).

Eddy Current Testing (ECT): For surface defect detection.

Sour Service Qualification (upon request): HIC per NACE TM0284, SSC per NACE TM0177.

Third-Party Inspection: SGS, BV, DNV, TUV, LR, ABS available.

Deepwater Subsea Components: Subsea connector shafts, manifold actuator rods, ROV component shafts, subsea fastener systems (ISO 13628-4 compliant, ABS/BV/DNV certified to 3000m).

HP/HT Sour Gas Wellhead Components: Wellhead connector shafts, Christmas tree stems, choke trim shafts, valve actuator rods (NACE MR0175 compliant, API 6A certified).

Extreme Marine Propeller Shafts: Deepwater marine propulsion shafts, rudder stocks, stern tube shafts, thrust shafts for naval vessels.

Pump Shafts (HP/HT Sour Service): High-pressure seawater injection pump shafts, HP/HT chemical pump shafts, submersible pump shafts for sour service.

High-Strength Fasteners: Stud bolts, nuts, threaded rods for HP/HT sour gas flanges (NACE MR0175 compliant, NORSOK M-650 qualified).

Hydraulic Cylinder Rods: Piston rods, cylinder rods for subsea hydraulic systems (centerless ground finish, h6 tolerance).

Valve Components: Valve stems, gate valve wedges, ball valve trunnions for HP/HT sour service.

Geothermal Energy Shafts: High-temperature brine pump shafts, reinjection well components, steam valve stems.

Offshore Crane Shafts: Heavy lift crane shafts, winch shafts, deck machinery shafts (ABS/BV/DNV/LR certified).

1. What is the difference between Super Duplex 2507 and Duplex 2205 round bars?
Super Duplex 2507 has higher chromium (24-26% vs 22-23%), higher molybdenum (3-5% vs 3-3.5%), and higher nitrogen (0.24-0.32% vs 0.14-0.20%), giving PRE ≥42 (vs ≥35) and higher strength (YS ≥550 MPa vs ≥450 MPa). For deepwater subsea, HP/HT sour gas, and extreme chloride environments, 2507 is the preferred material.

2. Can Super Duplex 2507 round bars be machined?
Yes, but requires proper tooling (carbide), slower speeds (20-30% slower than 2205), and adequate coolant. Feed rates should be reduced to prevent work hardening.

3. Are Super Duplex 2507 round bars suitable for sour service (H₂S environments)?
Yes. Super Duplex 2507 is fully NACE MR0175 / ISO 15156 compliant for sour service up to 232°C (450°F) with the highest allowable H₂S partial pressure limits. HIC and SSC test reports available upon request.

4. What is the maximum service temperature for Super Duplex 2507 round bars?
250°C (482°F) for chloride service; 300°C (572°F) for non-chloride service. Above 300°C, risk of sigma phase embrittlement increases significantly.

5. What surface finish is best for subsea hydraulic cylinder rods?
Centerless ground finish with h6 tolerance is recommended for subsea hydraulic cylinder rods. This provides precise diameter (±0.013mm for 10-30mm) and smooth surface finish (Ra 0.2-0.4μm).

6. What is the maximum diameter available for Super Duplex 2507 round bars?
Standard diameters up to 200mm. Larger diameters up to 250mm are available upon request with extended lead time.

7. Are Super Duplex 2507 round bars suitable for cryogenic service?
Yes, maintains excellent toughness down to -50°C. For lower cryogenic temperatures (-196°C), consider austenitic stainless steel grades (316L, 304L).

Highest Strength: 3.2x stronger than 316L, 1.2x stronger than 2205 – smaller diameters for same load

Deepwater Subsea Certified: ABS, BV, DNV, LR certified to 3000m

NACE MR0175 / ISO 15156 Compliant: Highest H₂S partial pressure tolerance

NORSOK M-630 Qualified: Complete offshore documentation

Ferrite Controlled: 35-65% ferrite documented (minimum 40% for sour service)

Charpy Impact Tested: -46°C documented standard

ASTM G48 Corrosion Tested: Pitting resistance verified

Full Traceability: Heat number on each bundle – traceable to raw mill certificate

Precision Tolerances: h6, h9, h11 – meet your requirements

Global Delivery: Exported to major deepwater subsea and HP/HT sour gas projects worldwide

Website: www.womicstainless.com

E-mail: info@womicstainless.com

Tel / WhatsApp / WeChat:

Victor: +86 15575100681

Jack: +86 18390957568

Womic Steel – Your reliable partner for high‑quality stainless steel products, precision machined components, and custom solutions for corrosion‑resistant applications.

Stock Examples (Super Duplex 2507 Stainless Steel Round Bars – Peeled Finish – Subsea Grade):

Stock Examples (Super Duplex 2507 Stainless Steel Round Bars – Centerless Ground – High Precision):

Stock Examples (Super Duplex 2507 Stainless Steel Round Bars – Fastener Grade – NACE MR0175):

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