What Is A105 Flange Material?

Quick Answer

ASTM A105 is the standard specification for carbon steel forgings used in piping components—flanges, fittings, and valves. It is the single most common flange material in the oil and gas industry. A105 flanges operate from -29degC (-20degF) to approximately 425degC (800degF) and belong to ASME B16.5 Material Group 1.1.

Key Properties

Property	Value
Specification	ASTM A105/A105M
Product form	Forgings (flanges, fittings, valve bodies)
Carbon content	0.35% max
Manganese	0.60-1.05%
Yield strength (min.)	250 MPa (36 ksi)
Tensile strength (min.)	485 MPa (70 ksi)
Elongation (min.)	22% (in 50 mm gauge)
Hardness	187 HBW max
ASME B16.5 group	1.1
Temperature range	-29degC to ~425degC (-20degF to ~800degF)
Heat treatment	Normalized, normalized and tempered, or quenched and tempered

Chemical Composition

Element	Range
Carbon (C)	0.35% max
Manganese (Mn)	0.60-1.05%
Phosphorus (P)	0.035% max
Sulfur (S)	0.040% max
Silicon (Si)	0.10-0.35%
Chromium (Cr)	0.30% max
Nickel (Ni)	0.40% max
Molybdenum (Mo)	0.12% max
Vanadium (V)	0.08% max
Carbon equivalent (CE)	0.47% max (if specified)

The carbon content is intentionally limited to 0.35% max to ensure weldability. This is critical because weld neck and socket weld flanges require field or shop welding to connect to piping.

Pro Tip

A105 flanges are delivered in the normalized condition (heated above the upper critical temperature, then air-cooled). For thicker sections or higher-toughness requirements, normalize-and-temper or quench-and-temper heat treatments are available. Specify the heat treatment on the PO if required by the project specification.

Where A105 Flanges Are Used

A105 is the default for all carbon steel flanged piping in:

• Refineries and petrochemical plants: Process piping up to 425degC
• Power plants: Steam and feedwater lines (within temperature limits)
• Pipeline stations: Metering, pig launchers/receivers, valve stations
• Tank farms: Product transfer and loading lines
• General industrial piping: Water, air, low-pressure steam

For temperatures below -29degC, A105 must be replaced with impact-tested materials such as A350 LF2 (down to -46degC). For temperatures above 425degC, alloy materials such as A182 F11 or F22 are required.

A105 Inspection Requirements

All A105 forgings must be accompanied by a mill test certificate (typically EN 10204 Type 3.1) documenting chemical composition, mechanical test results, and heat treatment condition. Non-destructive testing (UT, MT, or PT) may be required per the project specification or piping class.

Read the full guide to flanges