ASTM A105

USED FOR:

Governs carbon steel forgings for piping components in ambient and elevated-temperature service: flanges, fittings, valves, and other forged piping parts.

This is a forging standard, not a plate, casting, or pipe standard; it covers material produced by forging processes, not bar stock machined without forging deformation (which falls under different specs).

RELATED STANDARDS:

• Sibling specs: ASTM A350 covers the equivalent low-temperature carbon/low-alloy steel forgings (grades LF1, LF2, LF3) with mandatory impact testing, used where A105’s lack of guaranteed low-temperature toughness is unsuitable; ASTM A182 covers alloy and stainless steel forgings (F-grades) for elevated-temperature or corrosion-resistant service, where A105’s plain carbon chemistry isn’t adequate.
• Design code that invokes it: ASME B16.5 and B16.47 (flange dimensional standards) reference A105 as a listed material, and ASME B31.3/B31.1 use A105 allowable stresses from ASME Section II Part D for pressure-temperature rating of forged components.
• Dimensional standard that pairs with it: ASME B16.5 (flanges NPS 1/2–24) and B16.47 (large-diameter flanges NPS 26–60) define bolt circles, facing, and thickness; ASME B16.11 defines dimensions for forged socket-weld and threaded fittings, A105 itself contains no dimensional data.

GRADE / TYPE RANGE:
A105 is essentially a single-grade specification (no letter/number grade suffixes like A182’s F-grades), covering carbon steel forgings with moderate carbon content and manganese as the primary strengthening element, normalized or as-forged depending on section thickness and supplementary requirements.

Mechanical properties sit in the same general strength range as A234 WPB and A106 Grade B pipe, which is intentional, the standard is designed to strength-match the common carbon steel pipe and fitting grades used alongside it in the same piping class.

Because it’s a single grade, the “selection” decision is less about choosing among options within A105 and more about deciding whether A105 (ambient/moderate temperature, no guaranteed toughness) is appropriate versus stepping up to A350 LF2 (impact-tested) or A182 F-grades (alloy/stainless) based on service temperature and corrosion requirements.

DESCRIPTION:
A105 covers carbon steel forgings for flanges, forged fittings, valves, and similar pressure-containing parts used in piping systems, produced by forging (hammer, press, or upset forging) rather than casting or plate fabrication.

The standard specifies chemical composition limits, mechanical property requirements (tensile, yield, elongation, reduction of area), and heat treatment requirements, normalizing is required for forgings above a certain thickness threshold to ensure adequate grain refinement and mechanical uniformity through the section.

It sets out mandatory tension testing frequency per lot, and where specified, additional testing such as Brinell hardness checks. Marking requirements call for grade, manufacturer identification, and heat traceability to be stamped on the forging in a location that doesn’t compromise the part’s structural integrity. In practice, A105 is the default “carbon steel forged” callout on flange and fitting line lists unless a specific service condition pushes the spec toward A350 or A182.

TYPICAL INDUSTRY USE:
Widely sused across oil & gas, petrochemical, power, and general industrial piping for carbon steel flanges, forged fittings, and valve bodies in ambient-to-moderate elevated-temperature, non-cryogenic, non-sour-critical service,  the single most commonly ordered forging spec in conventional plant piping.

IMPORTANT NOTES:

• We very frequently see A105 mistakenly carried onto low-temperature piping classes where A350 LF2 is actually required, this is one of the most common procurement/QA findings on projects with mixed ambient and low-temperature systems, since A105 has no mandatory impact testing and can exhibit brittle behavior at low temperature.

• Additionally requirement S1 (in current editions) adds Brinell hardness testing, generally invoked for sour service or when hardness limits are contractually specified. We recommend explicitly calling this out on the PO rather than assuming it’s automatically applied, since it isn’t part of the base standard testing.

• Not inherently NACE MR0175/ISO 15156 compliant; if sour service applies, we make sure hardness testing (typically capped around 22 HRC) and any required chemistry restrictions are explicitly specified as supplementary/additional requirements, since base A105 doesn’t guarantee sour compliance on its own.

• A105 forgings are technically not recommended for prolonged service much above roughly 800°F (per Section II Part D notes on graphitization risk in carbon steel), so we mention this to designers on high-temperature process lines where an alloy forging (A182 F-grade) may be the more appropriate long-term choice even if A105 technically appears in the allowable stress tables at that temperature.