top of page

ASTM A262
Intergranular Attack on Austenitic Steel

ASTM A262 Fixture
Universal Grip ASTM A262 bend fixture for universal testing machines

ASTM A262 Bend Fixture – Universal Grip Data Sheet (PDF)

What ASTM A262 Detects

ASTM A262 covers practices for detecting susceptibility to intergranular attack in austenitic stainless steels such as 304, 304L, 316 and 316L. If the steel is sensitized (chromium carbides formed at the grain boundaries during welding or heat treatment), acid exposure eats along the grain boundaries. The practices are used to qualify mill heats, welded pipe and fabricated parts for corrosive service.

The A262 Practices

  • Practice A: oxalic acid etch; a fast screening test that classifies the microstructure as step, dual or ditch

  • Practice B: boiling ferric sulfate–sulfuric acid (Streicher); weight loss

  • Practice C: boiling 65% nitric acid (Huey); weight loss over five periods

  • Practice E: copper–copper sulfate–16% sulfuric acid (Strauss), followed by a 180° bend test; the bend is inspected for fissures

  • Practice F: copper–copper sulfate–50% sulfuric acid; weight loss, used for cast steels

This fixture is used for the bend step of Practice E, and for the bend step that some product specifications add after the other exposures.

Practice E Bend Test

  • Expose the specimen in the boiling copper–copper sulfate–sulfuric acid solution with copper shot in contact, typically for 15 hours

  • Rinse, dry and bend the specimen 180° over a mandrel with a diameter equal to the specimen thickness (or as the product spec allows)

  • Bend so the surface that was exposed is on the outside (tension side) of the bend

  • Examine the outside of the bend at 5× magnification

  • Intergranular fissures or cracks mean the steel is susceptible; cracks only at the edges, or orange-peel roughening without fissures, do not count

Confirm exposure time, mandrel size and specimen dimensions against your copy of A262 and the product specification.

Specimens

  • Strip or bar cut from plate, sheet, bar, tube or welded joints; welded specimens include the weld and heat-affected zone

  • Long enough to bend: typically about 10 times as long as it is wide, so the bend forms in the middle

  • Edges ground smooth and the surface finished with 120-grit abrasive before exposure

Bend Fixture and Equipment

  • Guided bend fixture with interchangeable mandrels that bends the specimen to about 150–170° in a universal testing machine

  • Flat compression platens that close the bend to 180°

  • Benchtop arbor press as a manual option for small specimens

  • Stereo microscope (5× or higher) for inspecting the bend

Related Standards

  • ASTM A240 and A312 – stainless plate and pipe specifications that call up A262

  • ASTM A763 – intergranular attack in ferritic stainless steels

  • ASTM G28 – intergranular attack in nickel-rich alloys

  • ASTM E290 – bend testing of metals for ductility

ASTM A262 FAQ

What is ASTM A262 Practice E?

The Strauss test: the steel is boiled in copper–copper sulfate–16% sulfuric acid, then bent 180° and inspected at 5× for intergranular fissures.

What mandrel is used for the Practice E bend?

Normally a mandrel with a diameter equal to the specimen thickness, giving a 180° bend, unless the product specification allows a larger radius.

What counts as a failure in Practice E?

Intergranular fissures or cracks on the outside of the bend seen at 5×. Cracking only at the specimen edges, or surface roughening without fissures, is not a failure.

Which A262 practice is fastest?

Practice A, the oxalic acid etch. It screens out material that is clearly not sensitized; anything that fails it is tested further with one of the exposure practices.

Literature
bottom of page