SA178 Grade A / Grade D Electric Resistance Welded Boiler Tubing

SA178 Grade A and Grade D electric resistance welded boiler tubing is a minimum-wall carbon steel tube specified for boiler tubes, boiler flues, superheater flues, and safe ends. The ASTM/ASME specification officially covers only three grades—Grade A, Grade C, and Grade D—and the normal size range commonly supplied under the standard is 12.7–127 mm OD with 0.9–9.1 mm wall thickness. After welding, tubes are heat treated at not less than 900°C; if cold drawn, they are heat treated again after the final cold-draw pass at not less than 650°C.

Specifications

Main Features

1. Specification-aligned dimensional envelope: the standard commonly covers 12.7 to 127 mm OD and 0.9 to 9.1 mm wall thickness, which is exactly the dimensional band most buyers use for packaged boiler tubing and superheater sections.
2. Controlled post-weld heat treatment: all SA178 tubes are heat treated after welding at 900°C or higher, which is a core requirement for weld-zone stability and service reliability. Cold-drawn product requires a further heat treatment at 650°C or higher after the final draw pass.
3. Clearly differentiated strength classes: Grade A has a minimum tensile strength of 325 MPa and yield strength of 180 MPa, while Grade D is specified at 485 MPa tensile and 275 MPa yield, giving buyers a direct choice between economical low-carbon tubing and higher-strength carbon-manganese tubing.
4. Mandatory weld and formability verification: the specification requires tensile, flattening, flange, reverse flattening, and hydrostatic or nondestructive electric testing; this is especially important for ERW boiler tubing where weld integrity is a purchasing priority.

Our Advantages

1. Weld integrity is controlled and verifiable, not assumed
   Professional buyers of ERW boiler tubes usually focus first on weld quality. SA178 addresses that concern through flattening, reverse flattening, flange, and hydrostatic or nondestructive electric testing requirements, while established ERW boiler-tube producers also emphasize controlled forming and high-frequency welding for stable weld quality.
2. Grade selection is practical for service condition matching
   Buyers often ask whether Grade A or Grade D should be quoted. Grade A is the lower-strength low-carbon option for standard boiler service, while Grade D is a carbon-manganese grade with materially higher tensile and yield strength. This allows procurement teams to align tube grade with pressure and temperature demands rather than over-specifying all lines.
3. Inspection language can be written clearly into the PO
   Another common concern is whether ERW tubes are supplied with sufficient inspection coverage. Under SA178/A450, purchase orders can explicitly require hydrostatic or nondestructive electric testing, and, when needed, additional product analysis or crush testing. That makes the QA scope easier to lock into RFQs, MTC review, and final acceptance.

Execution Standards

• ASTM: ASTM A178/A178M — Electric-resistance-welded carbon steel and carbon-manganese steel boiler and superheater tubes.
• ASME: ASME SA178 — Boiler and pressure vessel code adoption of the A178 material specification for code applications.
• EN: EN 10216-2 / EN 10217-2 — pressure-purpose boiler and elevated-temperature tube standards often used as European reference systems for comparable applications.
• JIS: JIS G3461 — carbon steel tubes for boilers and heat exchangers.
• GB: GB/T 3087 — seamless steel tubes for low and medium pressure boilers; commonly referenced in China for application comparison.
• GOST: GOST boiler-tube systems are usually specified separately by project; equivalency should be confirmed by chemistry, strength, process route, and inspection scope rather than grade name alone.

Application

Water-tube boiler economizer coils — Grade A is commonly selected for standard economizer tube sections where cost efficiency and reliable heat-transfer service are required, while Grade D is more suitable when the design calls for a stronger carbon-manganese ERW boiler tube under higher mechanical demand.

Chemical Composition

Mechanical Properties

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A: Generally speaking,it is 10-15 days if the goods are in stock,or it is 30-40 days if the goods are not in stock,

it is according to quantity.

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