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NICKEL ALLOY STEEL ALLOY 20 N08020 2.4660 ASTM B729 B829 SEAMLESS PIPE ANF TUBE

Seamless Alloy 20 Pipe

Seamless Alloy 20 Pipe is a specialized nickel-iron-chromium alloy engineered for exceptional corrosion resistance in aggressive chemical environments, particularly those involving sulfuric acid. Developed as a solution to tackle acid-induced corrosion in chemical processing, this alloy combines a unique microstructure with balanced mechanical properties, making it a cornerstone material in industries requiring high durability and resistance to stress corrosion cracking (SCC).

① STANDARD: ASTM B163 ASTM B161

② OD RANGE : 6-457 MM
③ THICKNESS RANGE: 1-45 MM

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Introduction

Product Introduction

Seamless Alloy 20 Pipe is a specialized nickel-iron-chromium alloy engineered for exceptional corrosion resistance in aggressive chemical environments, particularly those involving sulfuric acid. Developed as a solution to tackle acid-induced corrosion in chemical processing, this alloy combines a unique microstructure with balanced mechanical properties, making it a cornerstone material in industries requiring high durability and resistance to stress corrosion cracking (SCC).

The alloy’s composition—32-38% nickel, 19-21% chromium, and 2-3% molybdenum—creates a protective oxide layer that withstands both reducing and oxidizing acids. Its addition of niobium (8C-1.00%) stabilizes the structure against carbide precipitation, enhancing intergranular corrosion resistance. This results in a material that not only resists general corrosion but also excels in preventing pitting and crevice corrosion in chloride-containing media.

Manufactured via seamless extrusion, N08020 pipes exhibit uniform grain structure and consistent wall thickness, ensuring reliability under high pressure and temperature fluctuations. Post-production treatments like pickling and annealing refine the surface finish and restore ductility, while optional polishing meets hygienic standards for food and pharmaceutical applications. The alloy’s unique blend of strength (tensile ≥80 ksi/550 MPa) and ductility (elongation ≥30%) enables complex forming and welding without compromising integrity, making it a versatile choice for critical infrastructure.

Key Product Parameters

Standards Compliance

ASTM B729: Specifies seamless nickel-iron-chromium-molybdenum-copper alloy pipe and tube for chemical processing.
ASTM B829: Defines general requirements for nickel and nickel alloy seamless pipe, covering testing and certification.
EN 2.4660: European standard for nickel-chromium-iron-molybdenum alloys, aligning with international corrosion resistance benchmarks.
ASME SB729/SB829: Pressure vessel and high-temperature service compliance.

Dimension Range

Outer Diameter (OD): 6 mm to 457 mm (0.24" to 18"), supporting small-bore tubing to large-diameter process pipes.
Wall Thickness: 1 mm to 45 mm (0.04" to 1.77"), available in standard schedules (e.g., SCH10 to SCH160) or custom sizes.
Length: Customizable up to 12 meters, with standard lengths of 6 meters; cut-to-length services reduce material waste.

Chemical Composition (wt.%)

Element	Range	Role in Alloy
C	≤0.07	Controls carbide formation to maintain corrosion resistance.
Mn	≤2.00	Stabilizes austenite and improves weldability.
P	≤0.045	Minimizes brittleness; controlled for formability.
S	≤0.035	Reduces hot shortness during fabrication.
Si	≤1.00	Enhances oxidation resistance at elevated temperatures.
Ni	32.00-38.00	Core component for corrosion resistance, especially in reducing acids.
Cr	19.00-21.00	Forms protective oxide layer, boosting resistance to oxidizing environments.
Mo	2.00-3.00	Improves pitting resistance in chloride-rich media.
Nb+Ta	8C-1.00	Prevents sensitization by stabilizing carbides, enhancing intergranular strength.
Fe	Balance	Provides structural strength and cost efficiency.

Note: Alloy 20’s composition yields excellent resistance to sulfuric acid across concentrations (20-80%) and temperatures up to 120°C.

Mechanical Properties

Property	Value	Significance in Applications
Tensile Strength	≥80 ksi (550 MPa)	Enables use in high-pressure systems without wall thickness overdesign.
Yield Strength	≥35 ksi (240 MPa)	Ensures dimensional stability under sustained loading.
Elongation at Break	≥30%	Facilitates cold forming, bending, and complex fabrication.
Hardness (HBW)	≤180	Balances machinability with wear resistance for installation.
Impact Toughness	≥100 J/cm² at 20°C	Maintains ductility in low-temperature applications.

Manufacturing & Quality Control

Process Flow:

Vacuum induction melting (VIM) for chemical purity
Hot-rolling of ingots into billets
Cold-drawing/extrusion for dimensional precision
Annealing at 1040-1120°C to refine grain structure
Pickling to remove scale and ensure surface cleanliness

Surface Treatments:

Pickled & Annealed (standard): Removes oxidation, ideal for general corrosion resistance.
Polished (Ra ≤0.8μm): Meets hygienic standards for food/pharmaceutical use.
Bright Annealed: Preserves surface luster via controlled atmosphere heating.

Testing Regime:

100% PMI (Positive Material Identification)
Hydrostatic pressure testing (1.5x design pressure)
Intergranular corrosion (IGC) testing per ASTM A262 Practice E
Non-destructive evaluation (UT/ET) for internal defects

Certification & Traceability

Mill Test Certificates (MTC): Compliant with EN 10204 3.1/3.2, including chemical analysis, mechanical properties, and heat treatment records.
Third-Party Inspection: Available from Lloyd’s, DNV, or customer-designated bodies.
Marking: Laser-engraved with grade, size, heat number, manufacturer logo, and ASTM/ASME standards.

Application Scenarios

Chemical Processing

Sulfuric Acid Systems: Handles 20-80% H₂SO₄ at temperatures up to 120°C in fertilizer production, metal pickling, and petrochemical refining.
Reactors & Distillation Columns: Resists corrosion from mixed acids (e.g., nitric + hydrofluoric) in pharmaceutical intermediates and dye synthesis.
Storage Tanks: Protects against stress corrosion cracking in organic acid storage (e.g., acetic, formic acid).

Petrochemical & Oil Refining

Acid Gas Treating: Used in amine regeneration units and sulfur recovery plants, resisting H₂S and CO₂ corrosion.
Heat Exchangers: Maintains efficiency in high-temperature, high-pressure services (e.g., crude oil pre-heaters).
Pipeline Systems: Suitable for transporting corrosive hydrocarbons and sour fluids.

Food & Beverage Production

Acid-Based Processing: Handles citrus juices, vinegar, and pickling solutions without contamination risk.
Brewing & Distillation: Resists chloride-induced pitting in cooling water systems and fermentation tanks.
Hygienic Pipelines: Polished surfaces meet 3-A Sanitary Standards for food-grade applications.

Pharmaceutical & Dye Industries

Acidic Reactions: Supports synthesis of active pharmaceutical ingredients (APIs) in hydrochloric acid environments.
Dye Bath Equipment: Withstands oxidative dyes and reducing agents in textile processing.
Waste Treatment: Handles acidic effluents in chemical waste neutralization systems.

Water Treatment & Desalination

Brine Handling: Resists chloride stress corrosion in seawater reverse osmosis (SWRO) plants.
Acidified Water Systems: Maintains integrity in water treatment chemicals (e.g., sulfuric acid for pH adjustment).

FAQ (Frequently Asked Questions)

Q: How does Alloy N08020 differ from 316L stainless steel in sulfuric acid?

A: While 316L fails in >50% H₂SO₄, N08020 resists corrosion up to 80% concentration due to its higher nickel and chromium content. Its PREN (Pitting Resistance Equivalent) of ~40 outperforms 316L’s PREN ~24 in acidic media.

Q: Can N08020 be used in high-temperature applications?

A: Service temperatures up to 450°C are feasible, but prolonged exposure above 500°C may cause sigma phase precipitation. For higher temperatures, consider nickel-based superalloys like Inconel 625.

Q: What welding procedures are recommended for N08020?

A: Use GTAW (TIG) with low heat input (≤1.5 kJ/mm) and ERNiCrMo-3 filler wire. Maintain interpass temperatures ≤150°C to avoid grain coarsening. Post-weld heat treatment is unnecessary if parameters are controlled.

Q: How is N08020 tested for sulfuric acid resistance?

A: Compliance with ASTM G37 (sulfuric acid corrosion test) is standard, where samples are exposed to 50% H₂SO₄ at 120°C for 100 hours, with maximum allowable corrosion rate ≤0.5 mm/year.

Q: What is the cost comparison between N08020 and other nickel alloys?

A: N08020 is more cost-effective than super duplex or nickel-chromium alloys (e.g., C-276) while offering comparable corrosion resistance in sulfuric acid. Its iron-nickel base reduces material costs without sacrificing performance.

Q: Can N08020 be used in marine environments?

A: Yes, but it is optimized for acidic rather than chloride-rich marine conditions. For offshore applications, consider super duplex steels (e.g., S32750) or nickel-copper alloys (e.g., Monel 400) for better seawater resistance.