W Lucas
Originally published in Welding & Metal Fabrication, 2001, Vol. 69, No. 4, May, pp 16-18 by DMG World Media UK Ltd, - www.dmgworldmedia.com/
Lucas, DSc, PhD, CEng, FIM, FWeldI, is Consultant & Technology Manager, Arcs at TWI in the Metallurgy, Corrosion, Arc & Surfacing Group. He is also visiting Professor at Liverpool University.
In recent years, there have been substantial changes in the range of shielding gases available for arc welding and cutting. Equally significant has been the re-branding of gases by some of the major gas supply companies. The range of shielding gases currently available in the UK are listed in Table 1together with their designation in accordance with the requirements of BS EN 439: 1994, Welding consumables - Shielding gases for arc welding and cutting.
Classification of shielding gases
BS EN 439 classifies shielding gases into six main groups according to their chemical properties and reaction behaviour. The groups and the prefix letter are as follow:
The groups, apart from Group S, are then sub-divided with an Identification Number which specifies the components and the compositional ranges. The Identification Number and the components in percent volume are as follows:
| R | reducing gas mixtures - those mixtures containing hydrogen |
| I | inert gases and mixtures - argon, helium and their mixtures |
| M | mixed gases - argon based gases with additions of oxygen or carbon dioxide or both |
| C | carbon dioxide rich mixtures |
| F | unreactive or reducing gases and mixtures - nitrogen and nitrogen based mixtures |
| S | specials - any gas or mixture not covered in the other groups |
Table 2. Classification of shielding gases for arc welding and cutting
The shielding gases in Groups R and M containing helium have a suffix identifying the amount of helium in the mixture:
| Symbol | Components in percent volume |
| Group | Identification No. | Oxidising | Inert | Reducing | Unreactive |
| CO 2 | O 2 | Ar | He | H 2 | N 2 |
| R | 1 | | | Balance | | > 0 to 15 | |
| 2 | | | Balance | | > 15 to 35 | |
| I | 1 | | | 100 | | | |
| 2 | | | | 100 | | |
| 3 | | | Balance | > 0 to 95 | | |
| M1 | 1 | > 0 to 5 | | Balance | | > 0 to 5 | |
| 2 | > 0 to 5 | | Balance | | | |
| 3 | | > 0 to 3 | Balance | | | |
| 4 | > 0 to 5 | > 0 to 3 | Balance | | | |
| M2 | 1 | > 5 to 25 | | Balance | | | |
| 2 | | > 3 to 10 | Balance | | | |
| 3 | > 0 to 5 | > 3 to 10 | Balance | | | |
| 4 | > 5 to 25 | > 0 to 8 | Balance | | | |
| M3 | 1 | > 25 to 50 | | Balance | | | |
| 2 | | > 10 to 15 | Balance | | | |
| 3 | > 5 to 50 | > 8 to 15 | Balance | | | |
| C | 1 | 100 | | | | | |
| 2 | Balance | > 0 to 30 | | | | |
| F | 1 | | | | | | 100 |
| 2 | | | | | > 0 to 50 | Balance |
(1) contains >0 to 33% helium
(2) contains >33 to 66% helium
(3) contains >66 to 95% helium
Applying the classification
The reaction behaviour of the shielding gas will determine its suitability for arc welding and cutting processes. For example, an oxidising gas is normally required to stabilise the arc in MIG/MAG welding but an inert or reducing gas is required for TIG and plasma processes.
Typical applications of the shielding gases are given in Table 3. The Classification Code can be used to differentiate between, for example, slightly oxidising (Group M1), intermediate (Group M2) and more pronounced oxidising gases (Group M3).
Table 3. Typical applications of shielding gases for arc welding and cutting
The Classification Code can be used to identify the shielding gas on the Welding Procedure Approval Record (BS EN 288) but the range of approval is normally restricted to the type of gas (nominal composition) used in the welding procedure test. In approval testing of welders to BS EN 287, the Classification Code is shown on the Manufacturer's Welding Procedure Specification (WPS) but the test will confer approval on the welder to use any similar shielding gas.
| Group | Identification No. | Remarks | Typical applications |
| R | 1 | Reducing | TIG plasma arc welding, plasma arc cutting, back shielding |
| 2 |
| I | 1 | Inert | MIG, TIG, plasma arc welding, back shielding |
| 2 |
| 3 |
| M1 | 1 | slightly oxidizing
↓
More pronounced oxidation | MAG |
| 2 |
| 3 |
| 4 |
| M2 | 1 |
| 2 |
| 3 |
| 4 |
| M3 | 1 |
| 2 |
| 3 |
| C | 1 |
| 2 |
| F | 1 | Unreactive | Plasma arc cutting, back shielding |
| 2 | Reducing |
Acknowledgements
The author would like to acknowledge the information provided for the table by:
| A Williams | Air Products Plc |
| D Yates | BOC |
| R Eden | Linde Gas |
| G Bruton | Messer UK Ltd |
Table 1. Shielding gases available in the UK
EN 439
Class | Composition (Volume %) | Reaction
behaviour | Air Products | BOC | Messer | Linde | Process |
| Ar | He | CO 2 | O 2 | H 2 | N 2 |
| Pure gases |
| I1 | >99.998 | - | - | - | - | - | Inert | Argon HP | Pureshield Argon | Argon 4.8 | Argon | TIG, MIG |
| I2 | - | >99.9 | - | - | - | - | Inert | Helium | Helium | Helium | Helium | TIG, MIG |
| C1 | - | - | >99.9 | - | - | - | Pronounced oxidising | CO 2 | CO 2 | CO 2 | CO 2 | MAG |
| Argon-Helium |
| 13 | 70 | 30 | - | - | - | - | Inert | Alumaxx Plus | Alushield Light | Stellar 30 | Heliweld 7 | TIG, MIG |
| 13 | 50 | 50 | - | - | - | - | Inert | Astec 50 | Alushield Universal | Stellar 50 | Heliweld 5 | TIG, MIG |
| 13 | 30 | 70 | - | - | - | - | Inert | - | | | Heliweld 2 | TIG, MIG |
| 13 | 25 | 75 | - | - | - | - | Inert | Astec 75 (25) | Alushield Heavy | Stellar 75 | - | TIG, MIG |
| Argon-Hydrogen |
| R1 | 99 | - | - | - | 1 | - | Reducing | | | | Hygon 1 | TIG |
| R1 | 98.5 | - | - | - | 1.5 | - | Reducing | | Stainshield TIG | | | TIG |
| R1 | 98 | - | - | - | 2 | - | Reducing | Inomaxx TIG | | Hylar 2 | Hygon 2 | TIG |
| R1 | 95 | - | - | - | 5 | - | Reducing | Hytec 5 | Specshield 5%
H 2 | Hylar 5 | Hygon 5 | TIG |
| R1 | 85 | 11 | - | - | 4 | - | Reducing | | Specshield 11%He, 4%H 2 | | | TIG |
| R1 | 65 | - | - | - | 35 | - | Reducing | | Specshield 35% H 2 | | Hygon 35 | TIG, Plasma Cutting |
| Argon-Helium-Hydrogen |
| R1(1) | 71.9 | 25 | - | - | 3.1 | - | Inert | | | | Corgon He 25S | TIG, MIG |
| Argon-Oxygen |
| M13 | 99 | - | - | 1 | - | - | Slightly oxidising | | | | Argon S1 | MAG |
| M13 | 98 | - | - | 2 | - | - | Slightly oxidising | Prodarc 2 | Specshield 2% O 2 | Exellar 2 | Argon S2 | MAG |
| M22 | 95 | - | - | 5 | - | - | Slightly oxidising | | | Exellar 5 | | MAG |
| M22 | 92 | - | - | 8 | - | - | Slightly oxidising | | | | Argon S8 | MAG |
| Argon-CO 2 |
| M12 | 98 | - | 2 | - | - | - | Slightly oxidising | Inomaxx 2 | | | | MAG |
| M12 | 97.5 | - | 2.5 | - | - | - | Slightly oxidising | | Specshield 2.5% CO 2 | Krysal 3 | Cronigon 2 | MAG |
| M12 | 96.5 | - | 3.5 | - | - | - | Slightly oxidising | | | | Cronigon 3 | MAG |
| M21 | 92 | - | 8 | - | - | - | More oxidising | | Specshield 8% CO 2 | Krysal 8 | | MAG |
| M21 | 90 | - | 10 | - | - | - | More oxidising | | Specshield 10% CO 2 | | | MAG |
| M21 | 86 | - | 14 | - | - | - | | | | Krysal 14 | | MAG |
| M21 | 86 | - | 20 | - | - | - | More oxidising | | Specshield 20% CO 2 | Krysal 210 | Corgon 18 | MAG |
| M21 | 75 | - | 25 | - | - | - | More oxidising | | Specshield 25% CO 2 | | | MAG |
| Argon-Helium-CO 2 |
| M12(1) | 79.5 | 20 | 0.5 | - | - | - | Slightly oxidising | | | | Heliweld DB1 | MAG |
| M21(1) | 68 | 20 | 12 | - | - | - | Oxidising | Ferromax Plus | | | | MAG |
| M12(2) | 63 | 35 | 2 | - | - | - | | | | Stellar 6 | | MAG |
| M12 (2) | 60 | 38 | 2 | - | - | - | Slightly oxidising | Inomaxx Plus | Stainshield Heavy | | Heliweld 3 | MAG |
| M21(1) | 50 | 25 | 25 | - | - | - | Oxidising | | | | Cronigon He 25C | MAG |
| M12(2) | 49.95 | 50 | 0.1 | - | - | - | Slightly oxidising | | | | Cronigon He 50S | MAG |
| M12 (2) | 43 | 55 | 2 | - | - | - | Slightly oxidising | Astec S4 | Stainshield Universal | | Heliweld 6 | MAG |
| M12 (3) | 25 | 73 | 2 | - | - | - | Slightly oxidising | | | | Heliweld 1 | MAG |
| M12 (3) | 23.5 | 75 | 1.5 | - | - | - | Slightly oxidising | Astec S5 (15) | | | | MAG |
| M14 (3) | 13.5 | 85 | 1.5 | - | - | - | Slightly oxidising | | Stainshield Light | | | MAG |
| M12 (3) | 13 | 85 | 2 | - | - | - | Slightly oxidising | | | Stellar 1 | | MAG |
| Argon-Helium-O 2 |
| M13(1) | 69.97 | 30 | - | 0.03 | - | - | Slightly oxidising | | | | Varigon He 30S | MIG/TIG |
| M13(2) | 49.97 | 50 | - | 0.03 | - | - | Slightly oxidising | | | | Varigon He 50S | MIG/TIG |
| M13(2) | 49 | 50 | - | 1 | - | - | Slightly oxidising | | | | Brazematic | MAG |
| Argon-CO 2-O 2 |
| M14 | 93 | - | 5 | 2 | - | - | More oxidising | Coogar 5 | Argoshield Light | Krysal 5 | Corgon 5 | MAG |
| M24 | | - | 7 | 2.5 | - | - | More oxidising | Ferromax 7 | | | | MAG |
| M24 | 86 | - | 12 | 2 | - | - | More oxidising | | Argoshield Universal | | Corgon 12 | MAG |
| M24 | 85 | - | 13.5 | 1.5 | - | - | | | | Krysal SM | | MAG |
| M24 | 83 | - | 15 | 2 | - | - | More oxidising | Coogar SG | | | | MAG |
| M24 | 82.5 | - | 15 | 2.5 | - | - | More oxidising | Ferromax 15 | | | | MAG |
| M24 | 78 | - | 20 | 2 | - | - | More oxidising | Coogar 20 | Argoshield Heavy | Krysal 20 | Corgon 20 | MAG |
| Argon-Helium-CO 2-H 2 |
| M11(1) | 67.95 | 30 | 0.1 | | 2 | | Reducing | | | | Cronigon He 30S | MIG |
| Argon-Helium-CO 2-O 2 |
| M14(3) | 25 | 71 | 2 | 2 | | | More oxidising | | | | Heliweld 4 | MAG |
| Argon-N 2 |
| SI1 | 97.5 | | | | | 2.5 | Inert | | Specshield 2.5% N 2 | | Argon DNI | TIG |
| Argon-Helium-N 2 |
| S13 | 79 | 20 | | | | 1 | Inert | Duplex 1 | | | | TIG |
| S13 | 77.75 | 20 | | | | 2.25 | Inert | Duplex 2 | | | | TIG |
| S13 | 67.5 | 30 | | | | 2.5 | Inert | | | | Heliweld DN1 | TIG, MIG |
Notes
Identification numbers for gases in Groups R and M containing Helium
(1) Contains >0 to 33% Helium
(2) Contains >33 to 66% Helium
(3) Contains >66 to 95% Helium
