This specification covers the requirements for 25 Cr Duplex stainless steel seamless pipes based on NORSOK M-630 MDS D51 Rev. 6. Seamless pipes supplied to this specification shall comply with ASTM A790.
25 Cr Duplex materials are limited to a maximum of 3 psia (20 kPa) partial pressure H2S in produced fluids and a maximum temperature of 450 °F (232°C).
| 1.0 Scope | 3 |
| 2.0 Reference Specifications | 3 |
| 3.0 Manufacturing Process | 4 |
| 3.1 Chemical Requirements | 4 |
| 3.2 Heat treatment | 4 |
| 4.0 Metallurgical Properties | 5 |
| 4.1 Extent of Testing and Test Sampling | 5 |
| 4.2 Tensile and Hardness Properties | 5 |
| 4.3 Impact Testing | 5 |
| 4.4 Micrographic Examination | 6 |
| 4.4.1 Preparation and Examination of Samples | 6 |
| 4.4.2 Intermetallic Phases | 6 |
| 4.4.3 Ferrite content | 7 |
| 4.5 Corrosion Test | 7 |
| 5.0 Non-Destructive Evaluation (NDE) | 7 |
| 5.1 Personnel | 7 |
| 5.2 Ultrasonic testing | 7 |
| 6.0 Dimensional Requirements | 8 |
| 7.0 Surface conditions | 8 |
| 8.0 Marking | 8 |
| 9.0 Repairs of Defects | 8 |
| 10.0 Documentation and Certification | 8 |
| 10.1 Documents to be Submitted | 8 |
| 10.2 Documents to be Submitted With Product Delivery | 8 |
This specification covers the requirements for 25 Cr Duplex stainless steel seamless pipes. Manufacturing of parts to this specification shall be made in full compliance to ASTM A790, and all supplementary requirements provided by NORSOK M-630 MDS D51 rev. 6 except where modified by this specification.
Each supplier of pipes to this specification shall be qualified in accordance with NORSOK M-650/ISO 17782. The qualification shall be relevant for the exact product supplied, in accordance with the essential variables and limitations set within NORSOK M-650/ISO 17782. The supplier shall make the entire Qualification Test Record/ Manufacturer Procedure Conformity Records (QTR/MPCR), including supporting documentation required by the qualification standard, available for review by TechnipFMC upon request.
| Document | Description |
|---|---|
| ASTM A370 | Standard Test Methods and Definitions for Mechanical Testing of Steel Products |
| ASTM A790 | Standard Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe |
| ASTM A1058 | Standard Test Methods for Mechanical Testing of Steel Products-Metric |
| ASTM E213 | Standard Practice for Ultrasonic Testing of Metal Pipe and Tubing |
| ASTM E562 | Standard Test Method for Determining Volume Fraction by Systematic Manual Point Count |
| ASTM E1245 | Standard Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic Image Analysis |
| ASTM G48 | Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution |
| EN10204 | Metallic Products- Types of inspection Documents |
| ISO 148-1 | Metallic materials - Charpy pendulum impact test - Part 1: Test method |
| ISO 6892-1 | Metallic materials- Tensile testing - Part 1: Method of test at room temperature |
| ISO 9001 | Quality management systems - Requirements |
| ISO 9712 | Non-Destructive testing- Qualification and certification of NDE personnel |
| ISO 17781 | Petroleum, petrochemical and natural gas industries - Test methods for quality control of microstructure of ferritic/austenitic (Duplex) stainless steels |
| ISO 17782 | Petroleum, petrochemical and natural gas industries - Scheme for conformity assessment of manufacturers of special materials |
| NORSOK M-630 | Material data sheets and element data sheets for piping. |
| NORSOK M-650 | Qualification of manufacturers of special materials |
| NORSOK U-001 | Subsea Production Systems |
Manufacturers and the manufacturing process used for manufacturing of products to this MDS shall be qualified in accordance with NORSOK M-650 or ISO 17782. The qualification testing shall meet the requirements of NORSOK M-630 MDS D51 rev. 6.
The steel melt shall be refined with AOD or equivalent. The chemical analysis shall be in accordance with Table 2.
| UNS | S32750 | S32760 |
|---|---|---|
| Carbon | 0.030 | 0.030 |
| Manganese | 1.20 | 1.00 |
| Phosphorus | 0.035 | 0.030 |
| Sulfur | 0.020 | 0.010 |
| Silicon | 0.80 | 1.00 |
| Nickel | 6.0-8.0 | 6.0-8.0 |
| Chromium | 24.0-26.0 | 24.0-26.0 |
| Molybdenum | 3.0-5.0 | 3.0-4.0 |
| Copper | 0.5 | 0.5-1.00 |
| Nitrogen | 0.24-0.32 | 0.20-0.30 |
| Tungsten | - | 0.5-1.00 |
| PREN, minimum | 40.0 | 40.0 |
| PREN = (% Cr + 3.3% Mo + 16% N) | ||
The pipes shall be solution annealed followed by water quenching in accordance with ASTM A790. Furnaces shall be in compliance with NORSOK M-650/ISO 17782. Pipes shall be placed in such a way as to ensure free circulation of heating and cooling media around each pipe during the heat treatment process included accelerated cooling.
One set of impact, tensile, hardness, corrosion testing and microstructure examinations shall be carried out for each heat and heat treatment lot (Lot is defined in ASTM A790).
Test specimens sampling is outlined in Table 3.
| Test sample | Product | Product dimensions | Test method | Test Direction | Thickness location1 |
|---|---|---|---|---|---|
| Prolongation of the product | Seamless pipes | All Thicknesses | Tensile | Longitudinal or Transverse per ASTM A790 | |
| Hardness | Outer Surface | ||||
| CVN2 | Transverse | 1/2 Thickness | |||
| Corrosion, Microstructure | Full Thickness | ||||
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1. The mid-length of the test specimens shall be located one T or minimum 50 mm to any second surface. 2. Where pipe dimension does not allow taking test specimens in transverse direction specimens shall be taken in longitudinal direction. |
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Tensile testing shall be performed in accordance with ASTM A370 or ISO 6892-1. The material shall meet the tensile and maximum hardness properties of Table 4.
| Type | Requirement |
|---|---|
| Tensile Strength | 750 MPa (109 ksi) |
| Yield Strength | 550 MPa (80 ksi) |
| Elongation in 2" | 25% |
| Hardness max |
UNS S32760: 310 HBW (32 HRC) UNS S32750: 300 HBW (32 HRC) |
Charpy V-notch testing shall be performed in accordance with ASTM A370, ASTM A1058 or ISO 148-1 (striker radius of 8 mm). Testing and results shall meet the requirements of Table 5.
| Type | Requirement |
|---|---|
| Testing Temperature4 | -46°C (-51°F) |
| Transverse absorbed energy (average), min1,2 | 45 J (33 ft-lb) |
| Transverse absorbed energy (single), min1,2 | 35 J (26 ft-lb) |
| Longitudinal absorbed energy (average), min1,2,3 | 65 J (48 ft-lb) |
| Longitudinal absorbed energy (single), min1,2,3 | 50 J (37 ft-lb) |
| Reduction factor for sub-size | 7.5 mm – 5/6 5.0 mm – 2/3 |
|
1. For all products, the notch axis of CVN test specimens shall be positioned perpendicular to the closest outer surface. 2. One set (3 specimens) shall be performed for all piping with thickness > 6mm (0.25 in). 3. Only where pipe dimension does not allow taking test specimens in transverse direction. 4. Testing at a lower temperature is acceptable as long as the absorbed energy meets requirement. |
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Metallographic preparation and examination of 25 Cr Duplex stainless steels shall be in accordance with ISO 17781. The etchant to detect intermetallic phases and the ferrite balance electrolytic etching shall be performed after final polishing using the following solution:
The microstructure shall basically be free from intermetallic phases. However, discrete/standalone intermetallic phases can be tolerated provided these are located in isolated areas and not homogeneously distributed throughout the test specimen, and that the maximum dimension of each phase does not exceed 10 μm.
The presence and location of intermetallic phases shall be noted and recorded with micrographs (400x minimum) representative of the location with the highest concentration of intermetallic phases.
If intermetallic phases are not detected, a representative micrograph (400x minimum) at or near mid-wall thickness shall be recorded. Micrographs shall be reported at the actual magnification and shall include a scale bar.
In case centerline intermetallic stringers are present, this shall be reported and acceptance of the product shall be based upon CVN and corrosion test results.
In the event the CVN testing cannot be completed due to geometry or size, intermetallic phases and/or precipitates are not permitted.
The ferrite content per ASTM E 562 or by image analysis according to ASTM E 1245 shall performed in accordance with ISO 17781.
The acceptance criteria shall be:
Corrosion testing per ASTM G48 Method 'A' (50˚C, 24h) shall be performed in accordance with ISO 17781.
The acceptance criteria shall be:
Personnel performing NDE shall be qualified and certified to level II or III in accordance with ISO 9712 or equivalent. The roles and responsibilities of NDE personnel shall be as defined in ISO 9712.
The pipe base material shall pass a 100 % ultrasonic testing for longitudinal defects in accordance with ASTM E213 or ISO 10893-10. Ultrasonic testing shall be performed after all mechanical processing, heat treatments and straightening operation. Longitudinal (axial) reference notches shall be introduced on the outer and inner surfaces of the calibration (reference) standard in accordance with Figure 3 of ASTM E213 to a depth not greater than the larger of 0,3 mm or 5 % of specimen thickness (U2/C) and a length not more than 50 mm.
Acceptance criteria:
Dimensional tolerances shall be per applicable ASTM standard, unless otherwise stated in TechnipFMC's part report or drawing.
Finished pipes shall be white pickled or bright annealed.
The pipes shall be marked to ensure full traceability to melt and heat treatment lot.
Weld repairs are not acceptable.
The material manufacturer shall have an appropriate quality-assurance system, such as ISO 9001, certified by a competent body established within the EEA and having undergone a specific assessment for materials.
The following document in addition to other requirements on the part report or drawing shall be submitted to TechnipFMC for approval:
The following document in addition to other requirements on the part report or drawing shall be transmitted to TechnipFMC and traceable to the products being delivered (SIR205).
The material certificate shall be issued in accordance with EN 10204, Type 3.1, and shall include the following information required by ASTM A790 and NORSOK M-630:
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