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ASTM A178 is a specification that covers electric-resistance-welded (ERW) carbon steel and carbon manganese steel boiler and superheater tubes. These tubes are intended for use in boilers, flues, and superheaters with high-pressure service. In this passage, Union Steel Industry will introduce ASTM A178 ERW steel pipe in detail.
Chemical Composition of ASTM A178 ERW Steel Pipe:
|
Element % |
ASTM A178 Gr A / SA178A |
ASTM A178 Gr C / SA178C |
ASTM A178 Gr D / SA178D |
|
Low carbon steel |
Medium Carbon Steel |
Manganess Steel |
|
|
C |
0.06-0.18 |
0.35 Max |
0.27 Max |
|
Mn |
0.27-0.63 |
0.80 Max |
1.00-1.50 |
|
P |
0.035 |
0.035 |
0.030 |
|
S |
0.035 |
0.035 |
0.015 |
|
Si |
- |
- |
0.10 Min. |
Mechanical Properties of ASTM A178 ERW Steel Pipe:
|
Item |
ASTM A178 Gr A / SA178A |
ASTM A178 Gr C / SA178C |
ASTM A178 Gr D / SA178D |
|
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 |
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 |
|
|
|
Outside Diameter and Wall Thickness Tolerance of ASTM A178 ERW Steel Pipe:
|
Outside Diameter Tol |
Wall thickness Tol |
||
|
OD < 50 |
±0.05mm |
S < 4mm |
±12.5% |
|
OD > 50 |
±1% |
4--20mm |
+15/-12.5% |
|
S≧20mm |
±12.5% |
||
Heat Treatment of ASTM A178 ERW Steel Pipe:
ASTM A178 ERW steel pipes are required to undergo the electric-resistance welding process. Subsequent to welding, all pipes must undergo a heat treatment at a temperature equal to or exceeding 1650°F [900°C], followed by either air cooling or cooling within the controlled atmosphere of a furnace. In the case of cold-drawn tubes, a heat treatment is mandated after the final cold-draw pass at a temperature of 1200°F [650°C] or higher.
Testing and Inspection of ASTM A178 ERW Steel Pipe:
- Flattening tests
- Flaring tests
- Hardness tests
- Nondestructive electric tests
Application of ASTM A178 ERW Steel Pipe:
ASTM A178 ERW steel pipes are primarily used for conveying steam, water, gas, and other fluids at high temperatures and pressures in boilers and superheaters.
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