Views: 8 Author: Monica Publish Time: 2025-10-10 Origin: Site
ASTM B474 is the ASTM standard specification for electric fusion welded nickel and nickel alloy pipe. The latest version is ASTM B474/B474M-19 (2023). The standard classifies pipe into five types: Type 1, Type 2, Type 3, Type 4, and Type 5. It has strict manufacturing procedures, dimensional tolerances, and mechanical properties. It also requires full weld radiographic testing for Classes 1, 3, and 4, while partial testing is required for Class 5.
UNS N06022 (Hastelloy C22 or 2.4602) is a nickel alloy with a nominal chemical composition of nickel, chromium, molybdenum, tungsten, and trace amounts of iron and cobalt. This alloy exhibits excellent corrosion resistance, particularly against pitting, crevice corrosion, and stress corrosion cracking.
The manufacture and inspection of UNS N06022 electric fusion welded pipe follows a series of standards and specifications. Common product specifications include ASTM B474 (electric fusion welded pipe), ASTM B619 (welded pipe), and ASTM B626 (welded pipe).
Corrosion Resistance
UNS N06022 electric fusion welded pipe contains molybdenum, chromium, and tungsten, making it highly resistant to chloride ion attack, with tungsten enhancing overall corrosion resistance.
Hastelloy C22 offers superior corrosion resistance to alloys like C276 and C4, making it an ideal choice for handling wet chlorine gas, hypochlorites, chlorine dioxide solutions, and high-concentration chlorides.
High Strength
In terms of mechanical properties, UNS N06022 electric fusion welded pipe boasts a tensile strength of no less than 690 MPa, a yield strength of no less than 283 MPa, and an elongation exceeding 40%.
This combination of strength and toughness ensures the pipe's structural integrity under pressure while facilitating on-site installation and processing. Solution treatment of the alloy produces a uniform austenitic single-phase structure, enhancing its corrosion resistance and mechanical properties.
Excellent Weldability
UNS N06022 material inherently possesses excellent weldability. During the manufacturing process, heat input and subsequent treatments for electric fusion welded pipe are controlled to maintain consistent corrosion resistance between the weld and the base material. Welding quality must comply with relevant standards (such as ASTM B619/B626 for nickel alloy welded pipe), ensuring full penetration and conducting necessary nondestructive testing.
Thermal Stability and High-Temperature Performance
UNS N06022 electric fusion welded pipe maintains excellent structural stability and corrosion resistance even at high temperatures. Its melting point ranges from 1325°C to 1370°C. The alloy resists oxidation at high temperatures and maintains stable performance even with sustained exposure to moderate to high temperatures.
However, toughness and corrosion resistance may be compromised at temperatures between 600°C and 1100°C. Therefore, for high-temperature applications, the appropriate welded pipe condition should be selected based on the specific temperature and ambient media.
Easy to Machin and Form
UNS N06022 electric fusion welded pipe exhibits excellent cold working properties in the solution state, allowing for cold bending, expansion joints, and other forming operations. For machining, it is recommended to use carbide tools at a turning speed of 90-110 surface feet per minute. Dry or conventional coolant processing is acceptable.
The following table summarizes the main types and core characteristics according to the ASTM B474 standard for your quick understanding:
Types | Welding methods | Heat treatment requirements | Nondestructive Testing Requirements | Key Applications |
Type 1 | Double-sided welding | Usually required | 100% Full Weld Radiographic Inspection | Extremely harsh corrosive/high-pressure environments, such as nuclear fuel regeneration and critical heat exchangers |
Type 2 | Double-sided welding | Usually required | No Radiographic Inspection Required | Environments with defined corrosiveness and slightly lower pressure requirements, such as some chemical pipelines |
Type 3 | Single-sided welding | Usually required | 100% Full Weld Radiographic Inspection | Applications with limited space and single-sided welding requirements but requiring high reliability |
Type 4 | Single-sided welding (filler metal may not be added to the inner surface) | Usually required | 100% Full Weld Radiographic Inspection | Process systems with special requirements for pipe inner wall smoothness |
Type 5 | Double-sided welding | Usually required | Partial Radiographic Inspection | Non-critical auxiliary pipelines with mild corrosiveness and low pressure |
ASTM B474 standard applies to:
Nominal pipe diameter (NPS): 1/8" - 48".
Nominal outside diameter: 8" (203mm) and below.
Common wall thicknesses: Series 5S, 10S, 40S, 80S, etc.
Dimensional tolerance: ±0.5% or less
ASTM B474 electric fusion welded pipe shapes: round, square, rectangular, and special shapes.
End shapes: plain, beveled, and threaded.
Length: Customizable.
Composition | Value (%) |
Ni | Remain |
Cr | 20.0 - 22.5 |
Mo | 12.5 - 14.5 |
W | 2.5 - 3.5 |
Fe | 2.0 - 6.0 |
Co | ≤ 2.5 |
C | ≤ 0.015 |
Mn | ≤ 0.50 |
Si | ≤ 0.08 |
P | ≤ 0.02 or ≤0.025 |
S | ≤ 0.02 or ≤0.010 |
V | ≤ 0.35 |
ASTM B474 Hastelloy C22 electric fusion welded pipe prices are not a single standard. Costs are highly dependent on specific order specifications, raw materials, manufacturing standards, and market conditions. Below is a reference price list.
Factor | Typical Ranges | Price (USD) |
Material Price | Nickel Sheet | It accounts for the main part of the cost |
Pipe Outside Diameter (OD) | 1/2 inch (DN15) | 80−120 /m |
4 inch (DN100) | 300−500 /m | |
8 inch (DN200) | 800−1,400 /m | |
Pipe Wall Thickness (Schedule) | SCH 5S / 10S | 250-400/m (4-inch pipe, for example) |
SCH 40S / 80S | 450-700/m (4-inch pipe, for example) | |
ASTM B474 Types | Type 2 / Type 5 | 300-500/m (4-inch SCH10S, for example) |
Type 1 / Type 3 | 550-900/m (4-inch SCH10S, for example) | |
Purchase Quantity | <10m | 1.5-2 times the above price |
100 - 500m | Reference to the above base price | |
>5000m | Discounts can be negotiated with suppliers |
Material Preparation
Uns N06022 alloy plate or strip is prepared according to ASTM B575. The plate is then precisely slit and cut to the specific width required for the target pipe diameter. The edge quality of the slits is controlled to avoid defects such as burrs and cloaking.
Forming and Welding
The cut strip passes through a series of forming rollers, where it is gradually coiled into a round tube with an open gap. Next, welding takes place. For UNS N06022, TIG welding or plasma welding is typically used.
Welding is performed under inert gas to prevent oxidation of the weld metal at high temperatures and ensure a full-penetration weld. Welding parameters are rigorously qualified to ensure weld quality.
Weld Bead Preparation and Heat Treatment
After welding, the weld reinforcement on the outer wall of the pipe is immediately removed and ground to achieve a smooth internal and external surface. Importantly, the welded pipe undergoes solution heat treatment followed by rapid cooling. This process effectively eliminates sensitization and restores the welded pipe to its optimal corrosion resistance and mechanical properties. It is a critical step in ensuring its long-term stability in harsh corrosive environments.
Sizing and Straightening
After heat treatment, the welded pipe undergoes a slight cold deformation process using dies or rollers. This is designed to control the outer diameter and wall thickness tolerances of the finished pipe, eliminate any ovality or bend, and ensure that it meets the strict dimensional accuracy specified in ASTM B474.
Finishing and Testing
Before final shipment, the welded pipe undergoes a series of finishing and rigorous testing. Finishing includes pickling to remove the surface oxide layer and improve the appearance. Testing typically includes:
Non-destructive testing: Eddy current testing, for example, is used to quickly screen for weld defects, while radiographic testing is used to accurately assess internal weld quality.
Mechanical Testing: Samples are taken for tensile testing to verify that their strength, yield strength, and elongation meet the required specifications.
Dimensional Inspection: Precision measuring instruments are used to thoroughly inspect the pipe's diameter, wall thickness, roundness, and length. Hydrostatic Testing: A pressure test is performed on the pipe to verify its pressure-bearing capacity and sealing integrity.
Every qualified ASTM B474 UNS N06022 electric fusion welded pipe must be accompanied by detailed quality certification documentation to ensure traceability.
