Welding
Shielding gases ISO 14175
In short
Read M21 ArC 18, classes I, M, C, R, N and their use.
Reading a designation
ISO 14175M21ArC18
ISO 14175StandardM21Group and subgroup: composition rangeArCGases present: Ar argon, He helium, C CO₂, O oxygen, H hydrogen, N nitrogen18Content in % of the added gas (the rest is the base gas)
Here: argon with 18 % CO₂.
Groups
IInertArgon, helium and their mixtures. TIG, aluminium and copper MIG, weld backing.
M1Slightly oxidisingArgon + a little CO₂ or O₂. Stainless MAG, thin sheet.
M2OxidisingArgon + 5 to 25 % CO₂, M21 the commonest. Steel MAG.
M3Strongly oxidisingArgon + 25 to 50 % CO₂.
CCarbon dioxidePure CO₂ or CO₂ + O₂. Steel MAG, flux-cored.
RReducingArgon + hydrogen. TIG on austenitic stainless only.
NNitrogenNitrogen or argon + nitrogen. Duplex TIG, backing gas.
Classes and nominal composition (% vol.)
| Class | Composition |
|---|---|
| I1 | Ar 100 |
| I2 | He 100 |
| I3 | Ar + He 0.5–95 |
| M11 | Ar + CO₂ 0.5–5 + H₂ 0.5–5 |
| M12 | Ar + CO₂ 0.5–5 |
| M13 | Ar + O₂ 0.5–3 |
| M14 | Ar + CO₂ 0.5–5 + O₂ 0.5–3 |
| M20 | Ar + CO₂ 5–15 |
| M21 | Ar + CO₂ 15–25 |
| M22 | Ar + O₂ 3–10 |
| M23 | Ar + CO₂ 0.5–5 + O₂ 3–10 |
| M24 | Ar + CO₂ 5–15 + O₂ 0.5–3 |
| M25 | Ar + CO₂ 5–15 + O₂ 3–10 |
| M26 | Ar + CO₂ 15–25 + O₂ 0.5–3 |
| M27 | Ar + CO₂ 15–25 + O₂ 3–10 |
| M31 | Ar + CO₂ 25–50 |
| C1 | CO₂ 100 |
| C2 | CO₂ + O₂ 0.5–30 |
| R1 | Ar + H₂ 0.5–15 |
| R2 | Ar + H₂ 15–50 |
| N1 | N₂ 100 |
| N2 | Ar + N₂ 0.5–5 |
Argon base except C (CO₂) and N1 (nitrogen).
Common shop mixtures
| Designation | Composition |
|---|---|
| I1 – Ar | Ar 100 |
| I2 – He | He 100 |
| M20 – ArC – 8 | Ar 92 + CO₂ 8 |
| M21 – ArC – 20 | Ar 80 + CO₂ 20 |
| M21 – ArC – 18 | Ar 82 + CO₂ 18 |
| M21 – ArC – 25 | Ar 75 + CO₂ 25 |
| M24 – ArCO – 12/2 | Ar 86 + CO₂ 12 + O₂ 2 |
| M14 – ArCO – 5/2 | Ar 93 + CO₂ 5 + O₂ 2 |
| C1 – C | CO₂ 100 |
| M12 – ArC – 2.5 | Ar 97.5 + CO₂ 2.5 |
| M12 – ArHeC – 38/2 | Ar 60 + He 38 + CO₂ 2 |
| R1 – ArH – 2 | Ar 98 + H₂ 2 |
| R1 – ArH – 5 | Ar 95 + H₂ 5 |
| N2 – ArN – 2.5 | Ar 97.5 + N₂ 2.5 |
Which gas suits a metal and process: the “Shielding gas” tool.
Sources
- ISO 14175:2008 : gaz de soudage : Tableau 2, classification (link)
- EWM : gaz de protection TIG et MIG/MAG : Specialised knowledge, shielding gases (débits en L/min) (link)
- BOC / Linde : gamme de gaz de soudage : The right gas working for you (link)
- Messer : gaz de soudage MAG / TIG / MIG alu : Welding gases, tableaux par procédé (link)
Tools · Welding
Heat inputHeat input in kJ/mm (EN 1011-1) from current, voltage and travel speed.Carbon equivalent and preheatCE (IIW), CET and indicative preheat temperature (EN 1011-2, method B) with validity range check.Shielding gasRecommended gas (ISO 14175 class) and flow in L/min by process, material and wire diameter.Back purgeVolume to purge between dams, pre-purge time and gas use to shield the root side.Welding settingsCurrent, voltage, wire or electrode, gas and polarity by process, material, thickness and position; dimensioned joint preparation and passes.Weld shrinkageIndicative transverse and longitudinal shrinkage of a butt joint, with pre-setting advice.Filler metal weightJoint section (V, X, fillet), deposited weight and filler weight to order by process.Weld defect diagnosisTick what you see at the arc, in the pool and on the bead: ranked likely causes and remedies (TWI).ISO 5817 criteriaPermitted limit of an imperfection by quality level B, C or D, and verdict on the measurement (ISO 5817:2023).Weld pass layoutGroove area, number of layers and passes, numbered welding sequence sketch.Dissimilar metal weldingFiller metal to join two different metals (steel, stainless, duplex, nickel, aluminium) and precautions.