The ASTM A178 standard is a specification for welded steel boiler tubes and superheater tubes developed by the American Society for Testing and Materials (ASTM). It covers the requirements for these pipes in terms of manufacturing, dimensions, material properties, mechanical properties, inspection and testing.
ASTM A178 pipes are mainly used in the manufacture of boilers and superheaters. They need to work in high temperature and high pressure environments, and therefore need to withstand high thermal and mechanical stress. These pipes are usually made of carbon steel and connected through a welding process.
The ASTM A178 standard specifies in detail the outer diameter, wall thickness, length, material composition, mechanical properties and other parameters of the pipe, and requires manufacturers to conduct necessary inspections and tests to ensure that the product meets the standard requirements.
Chemical Compositions (%)
| Element | Grade A, | Grade C, | Grade D |
| Low-Carbon Steel | Medium-Carbon Steel | Carbon-Manganese Steel | |
| Carbon | 0.06-0.18 | 0.35max | 0.27max |
| Manganese | 0.27-0.63 | 0.08max | 1.00-1.50 |
| Phosphorus, max | 0.035 | 0.035 | 0.03 |
| Sulfur, max | 0.035 | 0.035 | 0.015 |
| Silicon | … | … | 0.01 min |
A178 Mechanical Properties
| Grade A | Grade C | Grade D | |
| Tensile strength, min, ksi [MPa] | 47[325] | 60[415] | 70[485] |
| Yield strength, min, ksi [MPa] | 26[180] | 37[255] | 40[275] |
| Elongation in 2 in. or 50mm, min, % | 35 | 30 | 30 |
| For longitudinal strip tests a deduction for | 1.50A | 1.50A | 1.50A |
| Each1⁄32-in[0.8mm] decrease in wall thickness below 5⁄16in. [8mm] | |||
| From the basic minimum elongation of the following percentage points shall be made |
