ASTM A135 Electric-Resistance-Welded Steel Pipe for Fluid Transport

ASTM A135 electric-resistance-welded steel pipe is manufactured from flat-rolled carbon steel using high-frequency electric-resistance or electric-induction welding without adding filler metal. It is intended for conveying water, gas, vapor, compressed air, and other compatible liquids in industrial and commercial piping systems.

The ASTM A135/A135M specification contains two material grades: Grade A and Grade B. Grade A provides greater suitability for bending, coiling, and flanging operations, while Grade B provides higher minimum yield and tensile strength. Grade B weld seams must be heat treated or processed so that no untempered martensite remains in the weld area.

ASTM A135 generally covers pipe from NPS 2 through NPS 30 with nominal average wall thicknesses up to 12.70 mm. It also covers selected light-wall pipe from NPS 3/4 through NPS 5. Nonstandard dimensions may be supplied when all other specification requirements are satisfied.

Specifications

Actual size availability should be confirmed against the selected pipe schedule, manufacturing route, end finish, and project quantity.

Main Characteristics

Controlled ERW Weld Integrity

The longitudinal seam is formed by electric-resistance or electric-induction heating and pressure without the addition of filler metal. This produces a narrow, continuous weld zone and supports consistent high-volume production.

For ASTM A135 Grade B, the weld region must be heat treated or otherwise processed so that no untempered martensite remains. This requirement reduces the risk of a locally hard and brittle weld structure.

Defined Strength Levels

ASTM A135 Grade A has a minimum yield strength of 205 MPa and minimum tensile strength of 330 MPa. Grade B increases these minimum values to 240 MPa and 415 MPa respectively.

Suitability for Fabrication

Grade A is the ASTM A135 grade specifically identified as suitable for flanging and bending. Grade selection should therefore consider not only operating pressure but also the required fabrication process. Grade B should not automatically be substituted where severe bending or flange forming is required.

Pressure-Leakage Verification

Each production length can be subjected to the hydrostatic test required by the standard. For certain Schedule 10 sizes, a nondestructive electric test may be accepted as an alternative when permitted by the specification and agreed by the purchaser.

Where hydrostatic testing is replaced by an approved NDE method, the inspection route and product marking must be stated clearly in the purchase documentation.

Dimensional Compatibility

Outside diameters and scheduled wall thicknesses are normally selected according to ASME B36.10M pipe dimensions. This allows compatibility with standard fittings, couplings, grooves, supports, and valves designed for NPS piping systems.

Our Technical Advantages

1. Verified Weld-Seam Condition for Grade B

A frequent procurement concern is whether Grade B pipe has merely been supplied in the as-welded condition without adequate control of the heat-affected zone.

Our production route records the weld-seam treatment parameters by production lot. Grade B material is processed to prevent untempered martensite from remaining in the weld region. On request, supporting records can include weld-treatment settings, metallographic verification, hardness mapping, and NDE results.

2. Traceable Pressure-Test Status

Buyers often receive quotations that state “tested” without specifying whether the pipe was hydrostatically tested or examined using an alternative electrical method.

Each quotation and mill certificate can identify:

• The inspection method used

• The applicable test pressure or NDE procedure

• The test date and production lot

• Whether hydrostatic testing was replaced by an approved alternative

• Any required “NH” or equivalent test-status marking

This avoids ambiguity during document review, site inspection, and final acceptance.

3. Grade and Fabrication Review Before Production

Grade B has higher strength, but it is not automatically the correct choice for every fabricated piping assembly. ASTM A135 specifically identifies Grade A as suitable for flanging and bending.

Before production, the order can be reviewed against:

• Required operating medium

• Design pressure and temperature

• Threading, grooving, bending, or flanging requirements

• Required surface coating

• Applicable fittings and joining system

• Hydrostatic or NDE acceptance route

This review reduces the risk of purchasing a higher-strength grade that is unsuitable for the intended forming operation.

Execution Standards

Equivalent standards must not be treated as automatically interchangeable. Material grade, chemistry, strength, dimensions, testing, coating, and certification must be reviewed before substitution.

Specific Application: Fire-Sprinkler Branch Piping

One specific application is a black Schedule 10 ASTM A135 Grade B ERW pipe used as a branch line in a wet-pipe fire-sprinkler system.

In this application, the pipe distributes pressurized water from the cross main to individual sprinkler heads. Grade B provides a minimum yield strength of 240 MPa and a minimum tensile strength of 415 MPa, while the lighter Schedule 10 wall can reduce installed pipe weight compared with heavier Schedule 40 configurations.

The final system design must still comply with the applicable fire code, hydraulic calculation, listing requirements, coupling system, corrosion allowance, and local authority approval. ASTM material compliance alone does not establish system approval.

Chemical Composition

ASTM A135 itself contains only Grade A and Grade B. The additional rows below are procurement-reference grades frequently compared in international fluid-pipe projects. They must not be certified or marked as ASTM A135 unless they independently meet every ASTM A135 requirement.

Maximum values are shown unless otherwise stated.

ASTM A53 Type E Grades A and B may additionally restrict copper, nickel, chromium, molybdenum, and vanadium when these elements are intentionally added or present as residual elements.

Mechanical Properties

The following values are minimum requirements at room temperature unless a range is shown.

ASTM A135 elongation for thinner-wall strip specimens is calculated from the specified wall thickness rather than being represented by one universal percentage. Reported elongation should therefore identify the specimen orientation, specimen type, gauge length, and actual wall thickness.

Inspection and Testing

A complete ASTM A135 inspection plan may include: