ERW Tube , ASME SA178 Grade A Carbon Steel Tube , Welded Steel Boiler Tube
ASTM A178 / ASME SA178 Gr.A Carbon Steel ERW Tube Boiler Tube
ASTM A178/ASME SA178 is a standard specification for electric-resistance-welded (ERW) carbon steel tubes used primarily in boiler superheaters, heat exchangers, and condensers. These tubes are designed for moderate temperature and pressure service. The key characteristic of SA178 tubes is their welded construction, making them a cost-effective alternative to seamless tubes for many applications where the highest pressures and temperatures are not a concern.
ASME SA178 Grade A Carbon Steel ERW Tube Chemical Composition
| Element %. | ASTM A178/ ASME SA-178 | ||
| Grade A | Grade C | Grade D | |
| C | 0.06~0.18 | ≤0.35 | ≤0.27 |
| Mn | 0.27~0.63 | ≤0.80 | 1.00~1.50 |
| P | ≤0.035 | ≤0.035 | ≤0.030 |
| S | ≤0.035 | ≤0.035 | ≤0.015 |
| Si | - | - | ≥0.10 |
*Grade A is a low-carbon steel with good weldability and formability. Grade C has a higher carbon and silicon content, providing higher strength at elevated temperatures, making it more suitable for superheater applications.
ASME SA178 Grade A Carbon Steel ERW Tube Mechanical Properties
| ASTM A178 | Grade C | Grade D |
|---|---|---|
| Tensile strength ksi [MPa] | 60 [415] | 70 [485] |
| Yield strength ksi [MPa] | 37 [255] | 40 [275] |
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Eelongation in 2" min. % |
30 | 30 |
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For longitudinal strip tests a deduction for each 1 ⁄ 32 in. [0.8 mm] decrease in 1.50A 1.50A wall thickness below 5 ⁄ 16 in. [8 mm] from the basic minimum elongation of the following percentage points shall be made.
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Manufacturing Process
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ERW (Electric Resistance Welding): Sheets of steel are formed into a cylindrical shape, and edges are fused using electrical resistance. This method ensures precise dimensions and cost-effectiveness.
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Post-Weld Heat Treatment: Often applied to relieve residual stresses and enhance mechanical properties.
Applications
SA178 tubes are chosen for specific, well-defined roles in thermal systems:
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Boiler Superheaters (especially Grade C): For saturated or low-temperature superheat sections.
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Water-Tube Boilers: For generating and containing steam at moderate pressures.
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Heat Exchangers & Condensers: For transferring heat between fluids (e.g., in power plants, refineries, HVAC systems).
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General Service Pressure Tubes: Where the operating conditions fall within the limits of ERW carbon steel.
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