ASTM A178 Electric Resistance Welded Steel Tube
Material Specification
ASTM A178 is a specification that covers electric-resistance-welded carbon steel and carbon-manganese steel boiler and superheater tubes. These tubes are primarily used in high-temperature applications, such as in boilers, superheaters, and heat exchangers. The specification ensures that the tubes meet certain mechanical and chemical properties, making them suitable for such demanding environments.
Key Features
Manufacturing Process: The tubes are produced using an electric resistance welding (ERW) process, which ensures a strong and consistent weld seam.
Versatility: Suitable for high-temperature applications, particularly in boilers and superheaters.
Corrosion Resistance: Offers good resistance to corrosion, making it ideal for use in environments where moisture and heat are present.
Cost-Effective: The ERW process is efficient and cost-effective, making ASTM A178 tubes an economical choice for many applications.
Quality Assurance: The specification includes rigorous testing requirements to ensure the tubes meet the necessary mechanical and chemical standards.
Chemical Composition
The chemical composition of ASTM A178 tubes is crucial for ensuring their performance in high-temperature environments. The table below outlines the typical chemical composition:
| Element | Composition (%) |
| Carbon (C) | 0.06 - 0.18 |
| Manganese (Mn) | 0.27 - 0.93 |
| Phosphorus (P) | ≤ 0.035 |
| Sulfur (S) | ≤ 0.035 |
Mechanical Properties
ASTM A178 tubes must meet specific mechanical properties to ensure they can withstand the pressures and temperatures of their intended applications. The table below presents these properties:
| Property | Value |
| Tensile Strength | 47,000 psi min |
| Yield Strength | 26,000 psi min |
| Elongation | 30% min |
Physical Properties
The physical properties of ASTM A178 tubes contribute to their suitability for high-temperature applications:
| Property | Value |
| Density | 7.85 g/cm³ |
| Melting Point | 1425-1540°C |
| Thermal Conductivity | 51.9 W/m·K |
Process Performance
The performance of ASTM A178 tubes during processing is critical for their application in various industries:
| Process | Performance |
| Weldability | Excellent |
| Machinability | Good |
| Formability | Good |
Steel Grade
ASTM A178 tubes are available in several grades, each designed to meet specific requirements:
Grade A: Basic grade with standard mechanical properties.
Grade C: Higher manganese content for improved strength.
Grade D: Enhanced mechanical properties for more demanding applications.
Each grade is tailored to meet the specific needs of different applications, ensuring optimal performance and reliability.
Application
ASTM A178 tubes are widely used in:
Boilers: As water tubes and fire tubes in steam boilers.
Superheaters: For transferring heat from the combustion gases to the steam.
Heat Exchangers: In various industrial processes to transfer heat between fluids.
Possible Alternative Grades
While ASTM A178 is a popular choice, there are alternative grades that may be suitable depending on the specific requirements:
ASTM A179: Seamless cold-drawn low-carbon steel heat-exchanger and condenser tubes.
ASTM A192: Seamless carbon steel boiler tubes for high-pressure service.
ASTM A210: Seamless medium-carbon steel boiler and superheater tubes.
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