ASTM A178 Electric-Resistance-Welded Steel Tubes
ASTM A178/A178M Standard Specification for Electric-Resistance-Welded Carbon Steel and Carbon-Manganese Steel Boiler and Superheater Tubes
1/2″ to 24″


ASTM A178/A178M 
Standard Specification for Electric-Resistance-Welded Carbon Steel and Carbon-Manganese Steel Boiler and Superheater Tubes

Main Grade
Grade A, C, or D,

ASTM A178 Grade C and D tubes are not suitable for safe-ending for forge welding.
The tubing sizes and thicknesses usually furnished to this specification are 1 ⁄ 2 to 5 in. [12.7 to 127 mm] in outside diameter and 0.035 to 0.360 in. [0.9 to 9.1 mm], inclusive, in minimum wall thickness. Tubing having other dimensions may be furnished, provided such tubes comply with all other requirements of this specification.

The steel for Grade D shall be killed.
Tubes shall be made by electric-resistance welding.

Heat Treatment
After welding, all tubes shall be heat treated at a temperature of 1650°F [900°C] or higher and followed by cooling in air or in the cooling chamber of a controlled-atmosphere furnace. Cold-drawn tubes shall be heat treated after the final cold-draw pass at a temperature of 1200°F[650°C] or higher.

Chemical Composition
The steel shall conform to the requirements as to chemical composition prescribed in Table 1.
When a grade is ordered under this specification, supplying an alloy grade that specifically requires the addition of any element other than those listed in Table 1 is not permitted.

TABLE 1 Chemical Requirements
Element Composition, %
Grade A,Low-Carbon
Grade C, Medium-
Carbon Steel
Grade D, Carbon-Man-
ganese Steel
Carbon 0.06–0.18 0.35 max 0.27 max
Manganese 0.27–0.63 0.80 max 1.00–1.50
Phosphorus, max 0.035 0.035 0.030
Sulfur, max 0.035 0.035 0.015
Silicon …. …. 0.10 min

General Requirements
Material furnished under this specification shall conform to the applicable requirements of the current edition of SpecificationA 450/A 450M unless otherwise provided herein.

Tensile Requirements
Grade C and D tubes shall conform to the requirements as to tensile properties prescribed in Table 2.

TABLE 2 Tensile Requirements
Grade C Grade D
Tensile strength, min, ksi [MPa] 60 [415] 70 [485]
Yield strength, min, ksi [MPa] 37 [255] 40 [275]
Elongation in 2 in. or 50 mm, min, % 30 30
For longitudinal strip tests a deduction for each 1 ⁄ 32 -in. [0.8 mm] decrease in wall thickness below 5 ⁄ 16
in. [8 mm] from the basic minimum elongation of the
following percentage points shall be made.
1.50 A 1.50 A

A See Table 3 for the computed minimum values.

NOTE 3—Explanatory Note—For purposes of design the following tensile properties may be assumed for Grade A tubes:

Tensile strength, min, ksi [MPa] 47 [325]
Yield Strength, min, ksi [MPa] 26 [180]
Elongation in 2 in. or 50 mm, min, % 35

Crush Test
When required by the purchaser, crushing tests shall be made on sections of tube 2 1 ⁄ 2 in. [63 mm] in length which shall stand crushing longitudinally without cracking, splitting, or opening at the weld, as follows:

Wall Thickness of Tubes, in. [mm] Height of Crushed Section, in. [mm]
0.135 [3.43] and under 3 ⁄ 4 [19] or until outside
folds are in contact
Grade C and D Tubes
Over 0.135 [3.43] 1 1 ⁄ 4 [32] ….

Mechanical Tests Required
Flattening Test:
Flange Test:
Crush Test
Tension Test
Reverse Flattening Test
Hydrostatic or Nondestructive Electric Test

Forming Operations
When inserted in the boiler, tubes shall withstand expanding and beading without showing cracks or flaws, or opening at the weld. When properly manipulated, superheater tubes shall withstand all forging, welding, and bending operations necessary for application without developing defects.