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| ชื่อแบรนด์: | YUHONG |
| เลขรุ่น: | ASTM A178 Gr.A ท่อเชื่อมเหล็กกล้าคาร์บอน |
| ขั้นต่ำ: | 1,000KGS |
| เงื่อนไขการจ่ายเงิน: | แอล/C,ที/ที |
ASTM A178 / ASME SA178 Grade A Carbon Steel Welded Tube Boiler Tube Heat Exchanger Tube
ASTM A178 Grade A Welded Tube is a carbon steel, ERW tube specifically engineered for moderate to high-temperature service in boiler and heat exchanger applications. Its key advantages are good weldability and ductility, making it a reliable and economical choice for pressurized tubing in the power and process industries. When sourcing, it is crucial to confirm the tube meets all required tests, especially the reverse flattening test for weld integrity.
Key Characteristics of Grade A
Manufacturing Process: Electric Resistance Welding (ERW). The strip is formed and the seam is welded using heat generated by electrical resistance, without adding filler metal.
Material: Carbon steel.
Condition: Typically supplied in the as-welded condition, meaning the weld seam is not heat-treated after welding. (Heat treatment, if required for specific applications, is addressed in the standard but is not the default condition).
Purpose: Designed for boiler tubes, flues, superheater tubes, and safety device enclosures in pressure applications
ASME SA178 Gr.A Carbon Steel Welded Tube Chemical Composition
| GRA. | ASME SA178 CHEMICAL COMPOSITION % | ||||
|---|---|---|---|---|---|
| C | MN | P |
S |
Si |
|
| Gr.A | 0.06-0.18 | 0.27-0.63 | 0.035 | 0.035 | - |
| Gr.C | 0.035max | 0.80max | 0.035 | 0.035 | - |
| Gr.D | 0.27max | 1.00--1.50 | 0.030 | 0.015 | 0.10min |
ASME SA178 Gr.A Carbon Steel Welded Tube Mechanical Properties
| GRADE |
Tensile Strength, min ksi [MPa] |
Yield Strength, min ksi [MPa] |
Elongation in 2 in. or 50 mm, min, % |
|---|---|---|---|
| Gr.A/C/D | 47 [325] | 26 [180] | 35 |
Comparison to Other Common Boiler Tube Standards
To understand where A178 Grade A fits, it helps to compare it to other frequent specifications:
|
Standard |
Primary Process | Key Difference from A178 Gr. A | Typical Use Case |
| ASTM A178 Grade C | ERW | Higher carbon & manganese for higher strength at temp. | Superheater sections (hotter than boiler). |
| ASTM A192 | Seamless | Seamless construction, guaranteed high pressure hydraulic test. | High-pressure boiler tubes. The default choice for critical, high-pressure sections. |
| ASTM A210 | Seamless | Medium-carbon steel, higher strength than A192. Available in Grades A-1 and C. | Superheaters and heat exchangers requiring more strength. |
| ASTM A214 | ERW | Similar to A178 but for condenser and heat exchanger service. Usually supplied annealed for corrosion resistance, not specifically for high-temp boilers. | Condensers, low-pressure heat exchangers. |
Simple Rule of Thumb:
For general water-walled boiler sections at moderate temperatures and pressures, A178 Gr. A (ERW) is a cost-effective and standard choice. When pressure and temperature increase, or for superheaters, engineers often move to A192/A210 (seamless) or A178 Gr. C.
Important Testing & Inspection Requirements (per ASTM A178)
Flattening Test: A sample of the tube is flattened to a specified distance to demonstrate the soundness of the weld and ductility of the material.
Reverse Flattening Test (Critical for ERW): A special test where a short, slotted ring is reverse-flattened. This specifically checks for the quality of the weld seam by putting maximum stress on the weld root and faces.
Hydrostatic or Nondestructive Electric Test: Each tube must be tested for leak-tightness, either by hydrostatic pressure or by a nondestructive method like eddy current testing.
Bend Test: May be required to check ductility.
Application
This material is primarily used in the heat exchange and power generation industries:
Water-Tube Boilers: The tubes where water is heated to create steam.
Superheaters: Sections that further heat steam to higher temperatures.
Economizers: Heat exchangers that pre-heat feed water using exhaust flue gases.
Heat Exchangers and Condensers (in certain low to medium-pressure services).
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