ASTM A105: Carbon Steel Forgings for Piping
ASTM A105 is the specification behind most carbon steel flanges and fittings in the world's piping systems. When a buyer asks for “A105 flanges”, they are asking for a defined chemistry, defined mechanical properties and certification proving both.
ASTM A105 is the standard specification for forged carbon steel piping components such as flanges, fittings and valve bodies. It requires carbon of 0.35% maximum, tensile strength of at least 485 MPa, yield of 250 MPa and hardness not exceeding 187 HB.
- Specification
- ASTM A105 / A105M
- Carbon
- 0.35% max
- Tensile Strength
- 485 MPa min
- Yield Strength
- 250 MPa min
- Hardness
- 187 HB max
- Typical Products
- Flanges, fittings, valve bodies
Key takeaways
- A105 is a material specification, not a dimensional one — pair it with ASME B16.5 for flange dimensions.
- The hardness ceiling of 187 HB exists to protect weldability, and exceeding it is a rejection, not a bonus.
- Carbon equivalent can fail even when individual elements pass; verify CE on the mill certificate.
- A105N means normalised, required on heavier sections and often specified for toughness.
ASTM A105: Carbon Steel Forgings for Piping at a glance
Quotable facts from Avadh Techno Forge, Gundasara, Gondal, Rajkot.
- Specification: ASTM A105 / A105M
- Carbon: 0.35% max
- Tensile Strength: 485 MPa min
- Yield Strength: 250 MPa min
- Hardness: 187 HB max
- Typical Products: Flanges, fittings, valve bodies
Chemistry and Properties
Carbon capped at 0.35%, manganese 0.60–1.05%, with limits on sulphur, phosphorus and residual elements. Mechanically it requires 485 MPa minimum tensile and 250 MPa minimum yield, with a maximum hardness of 187 HB so the material stays weldable and machinable.
- Carbon 0.35% max
- Tensile 485 MPa minimum
- Yield 250 MPa minimum
- Hardness 187 HB maximum
The Carbon Equivalent Trap
A105 caps carbon equivalent because these parts are welded into piping. A heat that passes the individual element limits can still fail the CE calculation, which is why we verify CE on the certificate rather than trusting the grade name alone.
Testing and Certification
Chemical analysis per heat, tensile testing per lot, hardness verification and marking with the heat number. Supplied with EN 10204 3.1 certification, and third-party inspection where the project specification requires it.
Topics covered on this page
- ASTM A105 specification
- A105 flange material
- ASTM A105 chemical composition
- A105 forging standard
Based on work carried out at our own forging plant at Gundasara, Gondal, Rajkot — operating since 2008.
Questions Answered
What is ASTM A105 material?
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A carbon steel specification for forged piping components — flanges, fittings and valve parts — defining chemistry, mechanical properties, hardness limits and certification.
Why is hardness capped at 187 HB?
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So the component stays weldable and machinable in the field. Excess hardness signals incorrect heat treatment and risks weld cracking.
Is A105 the same as A105N?
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A105N denotes the normalised condition. Normalising is required for certain sizes and is often specified for better toughness and uniformity.
Do you supply A105 with 3.1 certificates?
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Yes, every A105 consignment carries EN 10204 3.1 certification with heat number traceability.