Two systems on one label
On a spool of solid wire for mild steel you will usually find two codes. The European one looks like this: G 42 4 M21 3Si1. The American one like this: ER70S-6. They describe the same wire, but they tell you different things about it.
EN ISO 14341 classifies a wire by the mechanical properties of the weld metal, that is by what comes out of the weld. AWS A5.18 classifies a wire above all by the chemical composition of the wire itself, adding minimum strength requirements. That is why one wire has one AWS designation and often two or three EN ISO designations, one for each shielding gas.
The second thing to remember: EN ISO 14341 covers wires for MIG/MAG, while TIG rods for the same steels are classified by EN ISO 636. Hence the letter G at the start of a MIG/MAG code and the letter W at the start of a TIG rod code.
Where the letter A after the standard number comes from
The notation 14341-A and 14341-B refers to two classification systems within one standard. Variant A is European and gives the yield strength, which is why the code looks like G 42 4 M21 3Si1. Variant B is based on the pattern used in America and Japan and gives the tensile strength, so the same wire gets a code of the kind G 49A 3 C1 S6.
Manufacturers usually quote variant A, because that is what documentation in Europe expects. If you see a code in a data sheet that starts with a two digit number of the order of 49 or 55, you are looking at variant B, and you should not compare it directly with the figure 42 or 46 from variant A.
G 42 4 M21 3Si1 character by character
G, the process and the form
The letter G stands for a solid wire for gas shielded metal arc welding with a consumable electrode, that is MIG/MAG. On TIG rods the same position carries W, on flux-cored wires T, on submerged arc wires S. If the code starts with another letter, you are looking at a different product.
42, the yield strength
The second position is the strength symbol of the weld metal. 42 means a minimum yield strength of 420 MPa. You use that figure to match the wire to the steel grade: for S355 you need weld metal of at least that yield strength, for S235 a lower one is enough.
| Symbol | Yield strength min. | Tensile strength | Elongation min. |
|---|---|---|---|
| 35 | 355 MPa | 440 to 570 MPa | 22 percent |
| 38 | 380 MPa | 470 to 600 MPa | 20 percent |
| 42 | 420 MPa | 500 to 640 MPa | 20 percent |
| 46 | 460 MPa | 530 to 680 MPa | 20 percent |
| 50 | 500 MPa | 560 to 720 MPa | 18 percent |
4, the impact toughness
The third position gives the temperature at which the weld metal reaches an impact energy of 47 J on a Charpy V notch specimen. The symbol 4 means minus 40 degrees Celsius. That single digit decides whether a wire may be used on a structure working outdoors or on a refrigerated tank.
| Symbol | Temperature for 47 J |
|---|---|
| Z | no requirement |
| A | plus 20 degrees |
| 0 | 0 degrees |
| 2 | minus 20 degrees |
| 3 | minus 30 degrees |
| 4 | minus 40 degrees |
| 5 | minus 50 degrees |
| 6 | minus 60 degrees |
M21, the shielding gas
The fourth position is the gas symbol to EN ISO 14175 under which the manufacturer obtained the stated properties. This is the most commonly confused part of the code. The same wire welded in CO2 instead of in a mixture gives different weld metal, which is why the manufacturer quotes two codes, one for each gas.
| Symbol | Composition | Where it is used |
|---|---|---|
| M21 | argon with 15 to 25 percent CO2 added | mild and low-alloy steel, MAG, the most common mixture in a workshop |
| C1 | carbon dioxide, 100 percent | mild steel, heavier sections, cheaper gas, more spatter |
| I1 | argon, an inert gas | TIG on steel and stainless, MIG on aluminium |
| M12, M13 | group M1, argon with a small addition of an oxidiser (CO2 or oxygen, of the order of a few percent) | stainless steel in MIG/MAG, where a large addition of CO2 carburises the weld |
The practical conclusion: if a wire data sheet shows only a code with M21 and you weld in pure CO2, you have no confirmation of the properties for your process. On a job to EN 1090 or with a WPS that is a real problem, not a formality.
3Si1, the composition of the wire
The last position describes the chemical composition of the wire itself. G3Si1 has roughly 0.7 to 1.0 percent silicon and 1.3 to 1.6 percent manganese. G4Si1 has more of both, roughly 0.8 to 1.2 percent silicon and 1.6 to 1.9 percent manganese. G2Si has the least.
Silicon and manganese are deoxidisers. More silicon means a more fluid weld pool, a smoother face and better wetting at the edges, but also more silicate islands on the face, which have to be removed before painting. More manganese raises the strength of the weld metal, which is why G4Si1 gives 460 MPa where G3Si1 gives 420 MPa.
ER70S-6 character by character
The AWS A5.18 code reads more simply, because it has four elements. The letters ER say that the product is suitable as a consumable electrode (E) and as a rod (R). The number 70 is the minimum tensile strength in thousands of pounds per square inch, that is 70 ksi, which comes to about 480 MPa.
The letter S stands for solid wire, as opposed to C for metal-cored wire. The final digit is the number of the chemical composition from the table in the standard. The six has the most silicon and manganese of the common variants, the three noticeably less.
The difference between ER70S-6 and ER70S-3 also shows in the impact requirement. For ER70S-6 the standard calls for 27 J at minus 29 degrees, for ER70S-3 the requirement is milder. That is why ER70S-6 is the default choice for structural work, and ER70S-3 stays where a calm root run is what matters.
Three Böhler wires and their codes
Below are the three items workshops reach for most often. All three come from the Böhler Welding range, for which we are the authorised distributor.
| Product | Form | EN ISO | AWS | Diameters |
|---|---|---|---|---|
| BÖHLER EMK 6 | solid MIG/MAG wire | 14341-A G 42 4 M21 3Si1 and G 42 4 C1 3Si1 | A5.18 ER70S-6 | 0.8 / 1.0 / 1.2 / 1.6 mm |
| BÖHLER EMK 8 | solid MIG/MAG wire | 14341-A G 46 4 M21 4Si1 and G 46 4 C1 4Si1 | A5.18 ER70S-6 | 0.8 / 1.0 / 1.2 / 1.6 mm |
| BÖHLER EML 5 | TIG rod | 636-A W 2 Si | A5.18 ER70S-3 | 1.2 / 1.6 / 2.0 / 2.4 / 3.0 mm |
EMK 6 is the basic wire for S235 and S355, copper coated, with confirmation for the mixture and for CO2. EMK 8 differs in one thing, and it is visible in the code: the symbol 46 instead of 42 and 4Si1 instead of 3Si1. It is the same type of wire with higher weld metal strength, for fine-grained steels from the upper end of S355 and above.
EML 5 is a TIG rod, so the code starts with W and comes from standard 636, not 14341. The symbol 2 Si indicates low silicon, and AWS ER70S-3 confirms the milder composition. The manufacturer recommends it for root runs, where a calm, less fluid pool holds better in the root of a pipe.
The diameter the code does not give
Diameter is not part of the classification, but it decides whether the wire you have chosen can be laid down at all. Below are indicative currents for solid steel wires in an M21 mixture. The upper limit depends on the machine and the torch, the lower one on the current at which the arc still does not break up.
| Diameter | Indicative current | Typical use |
|---|---|---|
| 0.8 mm | 60 to 180 A | sheet 1 to 3 mm, body shop work, out of position welding |
| 1.0 mm | 90 to 280 A | general purpose, structures 3 to 8 mm |
| 1.2 mm | 120 to 380 A | structures 5 to 20 mm, the highest output in a workshop |
| 1.6 mm | 200 to 500 A | heavy sections, mechanised welding |
To the diameter you match the liner, the contact tip and the feed rollers. A 1.2 mm wire in a liner meant for 1.0 mm starts to jam after a few hours, and the arc pulses for no reason. A machine with a four-roller feeder pulls 1.2 mm and 1.6 mm evenly even on a 5 m lead, which is why we look at exactly that when taking in every machine in the used MIG/MAG category.
What follows for your selection
- The strength symbol has to cover the steel grade: for S355 at least 42, for fine-grained steels higher.
- You match the impact symbol to the lowest working temperature of the structure, not to the temperature in the shop.
- The gas symbol has to agree with what you have in the cylinder, otherwise the declared properties mean nothing.
- You check the AWS number when the documentation came from the USA or when you are looking for an equivalent on the other side of the ocean.
- The EN ISO code on the label and the code in the WPS have to be identical, character by character, including the gas symbol.
The most common mistake in a workshop is choosing a wire by diameter and price, and then welding in a gas for which no code was given. The second most common is taking G3Si1 for a fine-grained steel where the WPS calls for 46. Both come out only at acceptance or when the weld is tested.
We will check the code for your job
Send us the steel grade, the thickness, the gas in your cylinder and the working temperature of the structure, and we will point to a wire with a code that covers it. The catalogue of solid wires is in the solid MIG/MAG wires category, and TIG rods in the TIG rods category. On larger orders we also match the diameter and the packaging to the feeder you have at the station.