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Introduction to ASTM A928
ASTM A928 is a standard specification established by the American Society for Testing and Materials (ASTM) , Standard Specification for Ferritic/Austenitic (Duplex) Stainless Steel Pipe Electric Fusion Welded with Addition of Filler Metal. This specification outlines the requirements for duplex stainless steel pipes intended for corrosive or high-temperature service.
Five Classes Of Pipe Are Covered As Follows:
- Class 1 -Pipe shall be double welded by processes using filler metal in all passes and shall be radiographed completely.
- Class 2 -Pipe shall be double welded by processes using filler metal in all passes. No radiograph is required.
- Class 3 -Pipe shall be single welded by processes using filler metal in all passes and shall be radiographed completely.
- Class 4 -Same as Class 3, except that the weld pass exposed to the inside pipe surface may be made without the addition of filler metal.
- Class 5 -Pipe shall be double welded by processes using filler metal in all passes and shall be spot radiographed.
Covered Grades and Chemical Composition:
- 1. ASTM A928 UNS S31803 cl.1 (Duplex 2205, 1.4462): This grade typically consists of 22% chromium, 5-6% nickel, 3% molybdenum, and 0.2-0.3% nitrogen, offering excellent corrosion resistance and high strength.
- 2. UNS S32205 (Duplex 2205, 1.4462): Similar to UNS S31803, UNS S32205 also contains 22% chromium, 5-6% nickel, 3% molybdenum, and 0.2-0.3% nitrogen, providing superior corrosion resistance and mechanical properties.
- 3. UNS S32750 (Super Duplex 2507, 1.4410): Super Duplex 2507 comprises 25% chromium, 7% nickel, 4% molybdenum, and 0.3-0.5% nitrogen, offering enhanced corrosion resistance and higher strength compared to duplex 2205.
- 4. UNS S32760 (Super Duplex 1.4501): Similar to UNS S32750, UNS S32760 exhibits excellent corrosion resistance and mechanical properties, with a slightly higher content of chromium and molybdenum.
ASTM A928 Duplex EFW Pipes Mechanical Properties:
- Tensile Strength: Typically ranging from 620 MPa to 900 MPa, depending on the grade and size of the pipe.
- Yield Strength: Generally ranging from 450 MPa to 620 MPa, with higher values for super duplex grades.
- Elongation: Typically around 25% to 30%, indicating good ductility.
Dimensions and Tolerances:
- Outside Diameter (OD): Typically ranging from 6 mm to 914 mm, depending on the grade and schedule of the pipe.
- Wall Thickness: Defined by the schedule of the pipe, with variations from SCH 5S to SCH 160.
ASTM A928 UNS S31803 EFW Pipe Production Process:
- Forming: Duplex stainless steel plates are cold or hot formed into cylindrical shapes.
- Welding: The EFW welding process employed in manufacturing ASTM A928 pipes results in strong and consistent welds, enhancing structural integrity and facilitating ease of installation.
- Heat Treatment: The welded pipes may undergo solution annealing or stress relieving heat treatment to improve their mechanical properties and corrosion resistance.
Certifications and Quality Testing:
- Mill Test Reports (MTRs): Certify that the material meets the chemical composition and mechanical property requirements of ASTM A928.
- Non-Destructive Testing (NDT): Methods such as ultrasonic testing (UT), radiographic testing (RT), and liquid penetrant testing (PT) are used to detect internal and surface defects.
- Mechanical Testing: Tensile, yield, and elongation tests are conducted to verify the mechanical properties of the pipes.
ASTM A928 Duplex EFW Pipe Applications:
- Oil and Gas: Used in offshore platforms, pipelines, and subsea equipment for their corrosion resistance in harsh environments.
- Chemical Processing: Employed in chemical reactors, heat exchangers, and storage tanks for their resistance to corrosive chemicals.
- Desalination: Utilized in seawater desalination plants for their resistance to corrosion and erosion in saline environments.
- Marine Engineering: Used in shipbuilding and marine structures for their resistance to corrosion in seawater.
Reference Standards:
- ASTM A928 references other pertinent ASTM standards and specifications, including:
- ASTM A999/A999M: Standard specification for general requirements for alloy and stainless steel pipe.
- ASTM E213: Standard practice for ultrasonic testing of metal pipe and tubing.
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