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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