What is the scope of AWS A5.32 / A5.32M?
AWS A5.32/A5.32M is the American Welding Society specification formally titled Welding Consumables—Gases and Gas Mixtures for Fusion Welding and Allied Processes.
This standard prescribes the classification requirements for gases and gas mixtures used to chemically shield filler material, base metal, or weld metal during fusion welding and allied processes.
It is directly equivalent to ISO 14175, and the AWS edition is designated as a modified adoption of that international standard.
The specification covers shielding gases for a broad range of processes, including gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), flux cored arc welding (FCAW), plasma arc welding (PAW), plasma arc cutting (PAC), laser beam welding (LBW), laser beam cutting (LBC), arc braze welding (ABW), and electrogas welding (EGW).
It is important to clarify that AWS A5.32 does not classify welding wire, electrodes, or filler metals.
The consumables addressed by this standard are the shielding gases themselves, supplied in gaseous or liquid form but always used in the gaseous state during welding.
The current edition is AWS A5.32M/A5.32:2021, which is the third edition and revises the 2011 edition.
The specification uses both U.S. Customary Units and the International System of Units (SI), and each system must be used independently of the other.
What is the classification system used in AWS A5.32 / A5.32M?
The AWS A5.32 classification system employs a structured alphanumeric designation that conveys the chemical composition and metallurgical behavior of the shielding gas.
The prefix “SG” stands for Shielding Gas and is used for single-component gases and simple mixtures.
For a single gas such as argon, the designation follows the format SG-A, where “A” is the chemical symbol for argon.
For a binary mixture such as argon with 25% carbon dioxide, the designation follows the format SG-AC-25, where “AC” indicates argon-carbon dioxide and “25” indicates the nominal percentage of the active component.
The standard also adopts the international main group and sub-group system used in ISO 14175, which classifies gases and mixtures into five main groups based on their chemical reactivity: Inert (I), Oxidizing (M), Highly Oxidizing (C), Reducing (R), and Nitrogen-containing (N).
Within the Oxidizing group, sub-groups such as M1, M2, and M3 further distinguish mixtures based on the type and concentration of oxidizing components, primarily oxygen and carbon dioxide.
This dual system allows welding engineers to select a shielding gas based on either the AWS-specific composition designator or the international main group classification.
Verify the complete designator rules and any additional classification criteria with the latest edition.
What is the complete list of AWS A5.32 / A5.32M classifications?
The classifications below are compiled from publicly available AWS reference tables, ISO 14175 main group designations, and standard summaries.
Because AWS standards are periodically revised, verify the complete and current list with the latest edition.
Single-component gas classifications
SG-A (Argon)
SG-He (Helium)
SG-C (Carbon Dioxide)
SG-O (Oxygen)
SG-H (Hydrogen)
SG-N (Nitrogen)
These classifications designate the individual shielding gases covered by the specification.
SG-A is argon, the most widely used inert shielding gas for GTAW and GMAW of reactive metals.
SG-He is helium, an inert gas often blended with argon for increased heat input in GTAW.
SG-C is carbon dioxide, an active gas commonly used for FCAW and GMAW of carbon steel.
SG-O is oxygen, used as a minor addition to argon for improved wetting and arc stability.
SG-H is hydrogen, added in small percentages to argon for GTAW of austenitic stainless steel to increase heat input and reduce porosity.
SG-N is nitrogen, used for certain stainless steel and duplex stainless steel applications.
Verify the complete single-gas list and purity requirements with the latest edition.
Binary and multi-component gas mixture classifications (SG series)
SG-AC-25 (Argon + 25% CO₂)
SG-AC-20 (Argon + 20% CO₂)
SG-AC-10 (Argon + 10% CO₂)
SG-AC-5 (Argon + 5% CO₂)
SG-AO-2 (Argon + 2% O₂)
SG-AO-5 (Argon + 5% O₂)
SG-AHE-25 (Argon + 25% Helium)
SG-AHE-50 (Argon + 50% Helium)
SG-AH-5 (Argon + 5% Hydrogen)
SG-AN-2 (Argon + 2% Nitrogen)
These classifications designate binary and multi-component shielding gas mixtures.
The SG-AC series designates argon-carbon dioxide mixtures, which are widely used for GMAW of carbon steel; the percentage indicates the nominal CO₂ content.
The SG-AO series designates argon-oxygen mixtures, used for improved arc stability and wetting in GMAW of stainless steel.
The SG-AHE series designates argon-helium mixtures, used for increased heat input and deeper penetration in GTAW and GMAW of thick sections.
The SG-AH series designates argon-hydrogen mixtures, used for GTAW of austenitic stainless steel.
The SG-AN series designates argon-nitrogen mixtures, used for duplex stainless steel and certain nickel alloys.
Additional mixture compositions and percentage variations may be classified; verify with the latest edition.
ISO 14175 main group designations adopted by AWS A5.32
I — Inert gases and mixtures
M1 — Oxidizing mixtures with up to 5% CO₂ or up to 3% O₂
M2 — Oxidizing mixtures with 5% to 15% CO₂ or 3% to 10% O₂
M3 — Oxidizing mixtures with more than 15% CO₂ or more than 10% O₂
C — Highly oxidizing gases and mixtures
R — Reducing gas mixtures containing hydrogen
N — Low reactive or reducing gas mixtures containing nitrogen
These main group designations are adopted from ISO 14175 and are used in AWS A5.32 to classify gases and mixtures according to their chemical reactivity.
The “I” group covers pure inert gases such as argon, helium, and their mixtures.
The “M” group covers oxidizing mixtures, with sub-groups M1, M2, and M3 distinguishing progressively higher levels of oxidizing components.
The “C” group covers highly oxidizing gases such as pure CO₂ and mixtures with high oxidizing potential.
The “R” group covers reducing mixtures containing hydrogen.
The “N” group covers mixtures containing nitrogen.
This dual designation system enables international harmonization and simplifies qualification procedures across ISO and AWS frameworks.
Verify the complete main group and sub-group composition ranges with the latest edition.
Additional sub-group designations for oxidizing mixtures
M12 — 0.5% to 5% CO₂, balance argon
M13 — 0.5% to 3% O₂, balance argon
M14 — 0.5% to 5% CO₂ plus 0.5% to 3% O₂, balance argon
M20 — 5% to 15% CO₂, balance argon
M21 — 15% to 25% CO₂, balance argon
These sub-group designations provide more granular classification within the M1 and M2 main groups.
M12, M13, and M14 are sub-groups of M1, distinguished by the specific oxidizing component: CO₂ only, O₂ only, or a combination of both.
M20 and M21 are sub-groups of M2, distinguished by the CO₂ concentration range.
The sub-group designators are referenced in AWS A5.36/A5.36M for the classification of flux cored and metal cored electrodes, enabling direct correlation between the electrode classification and the required shielding gas.
Verify the complete sub-group composition ranges and tolerances with the latest edition.
What do the purity and dew point requirements signify?
In addition to the chemical composition classification, AWS A5.32 specifies minimum purity and maximum dew point requirements for each gas component.
Purity is expressed as a minimum volume percentage of the primary gas.
For argon, the minimum purity is typically 99.997%, with a maximum dew point of –51 °C (–60 °F).
For carbon dioxide, the minimum purity is typically 99.8%, with a maximum dew point that varies depending on the grade.
For helium, the minimum purity is typically 99.995%.
These requirements ensure that the shielding gas does not introduce excessive moisture, oxygen, or other contaminants into the weld pool, which could cause porosity, oxidation, or embrittlement.
The dew point is a critical parameter because moisture in the shielding gas can dissociate in the arc and introduce hydrogen into the weld metal, leading to hydrogen-assisted cracking in susceptible steels.
The specification also includes requirements for testing, retesting, packaging, and cylinder or container labeling.
Verify the specific purity and dew point requirements for each gas with the latest edition.
What are the key selection criteria for shielding gases?
Selecting the correct shielding gas involves matching the gas or mixture to the base metal, the filler metal, the welding process, and the desired weld characteristics.
For GTAW of aluminum, magnesium, and titanium, pure argon (SG-A) or argon-helium mixtures (SG-AHE) are typically used because they provide an inert atmosphere.
For GMAW of carbon steel, argon-CO₂ mixtures (SG-AC series) are common, with higher CO₂ levels providing deeper penetration but increased spatter.
For FCAW of carbon steel, pure CO₂ (SG-C) or argon-CO₂ mixtures are used depending on the electrode classification.
For GMAW of stainless steel, argon-oxygen mixtures (SG-AO series) or argon-CO₂ mixtures with low CO₂ content are preferred to maintain corrosion resistance.
For GTAW of austenitic stainless steel, argon-hydrogen mixtures (SG-AH series) can increase heat input and reduce porosity.
The ISO 14175 main group designation provides a convenient shorthand for selecting gases based on their reactivity level.
The shielding gas must also be compatible with the electrode classification, as many flux cored and metal cored electrodes are classified with specific shielding gas requirements.
Verify specific selection guidance with the latest edition and the gas supplier’s recommendations.
AWS A5.32/A5.32M does not exist in isolation; several companion specifications provide the filler metal classifications and related product requirements that complement the shielding gas specification.
AWS A5.36/A5.36M provides a unified classification system for carbon and low-alloy steel flux cored and metal cored electrodes and directly references the shielding gas designators and composition ranges from A5.32.
AWS A5.18/A5.18M specifies carbon steel electrodes and rods for gas shielded arc welding and includes shielding gas requirements for GMAW electrodes.
AWS A5.28/A5.28M specifies low-alloy steel electrodes and rods for gas shielded arc welding and similarly references shielding gas requirements.
AWS A5.9/A5.9M specifies bare stainless steel welding electrodes and rods, many of which require specific shielding gas mixtures for optimal performance.
AWS A5.14/A5.14M specifies nickel and nickel alloy bare welding electrodes and rods, which often require argon or argon-helium shielding.
The ASME Boiler and Pressure Vessel Code, Section II, Part C, adopts AWS filler metal specifications as SFA specifications; shielding gas requirements are often referenced in the qualification of welding procedures.
Consulting these specifications together provides a comprehensive framework for welding consumable selection, qualification, and quality assurance.
The AWS filler metal classification system is organized by welding process and product form, with each specification (A5.x) addressing a distinct filler metal or consumable category.
AWS A5.32 is unique within this system in that it addresses gases and gas mixtures, which are non-metallic consumables, rather than electrodes, rods, or fluxes.
The specification is closely aligned with ISO 14175, and the AWS edition is designated as a modified adoption of that international standard, reflecting the increasing harmonization of welding consumable standards across global markets.
The “A5” series covers filler metals and related consumables for arc welding, brazing, and braze welding, and the numbering sequence roughly corresponds to the chronological development of the specifications.
The “/A5.32M” suffix indicates that the specification includes both U.S. Customary Units and SI units, a convention applied to AWS standards that have been harmonized with ISO practices.
The 2021 edition represents the third edition of the specification and revises the 2011 edition, reflecting ongoing updates to purity requirements, test procedures, and classification designators.
Users should always confirm that they are working from the most current edition of any AWS specification, as classifications and requirements may be added, revised, or withdrawn between editions.
Verify the current edition number and any superseded designations with the latest edition of AWS A5.32/A5.32M.
