Two systems on one label
On a spool of solid wire for non alloy steel you 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 say different things about it.
EN ISO 14341 classifies the wire by the mechanical properties of the weld metal, that is by what comes out of the weld. AWS A5.18 classifies the 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 examples in this article rest on the edition EN ISO 14341:2020 and on the current product data sheets of voestalpine Böhler Welding. The tables below are a summary for the workshop, not an extract from the standard: what binds is the text of the standard and the data sheet of the specific product.
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 the MIG/MAG code and the letter W at the start of the code for TIG rods.
One rule of selection that we come back to in every section
Whether you may use a given wire is decided by the full classification together with a qualified welding procedure. The full classification is four things at once: the strength symbol, the impact symbol, the gas symbol and the composition symbol. None of them alone is enough, and the composition of the wire itself does not settle the strength class.
On top of that comes a second layer: the WPS. The code from the label has to stay within the limits qualified in the welding procedure specification for your joint, grade, thickness and position. If the WPS points to a specific wire, that is the answer, not a table from a guide.
G 42 4 M21 3Si1 sign by sign
G, that is the process and the form
The letter G means a solid wire for arc welding with a consumable electrode under gas shielding, that is MIG/MAG. In TIG rods the same place holds W, in flux cored wires T, in wires for submerged arc S. If the code starts with another letter, you are looking at another product.
42, that is the strength symbol of the weld metal
The second position is the strength symbol of the weld metal. 42 means a minimum yield strength of 420 MPa, measured on the weld metal in the gas given further on in the code. That is a value for the weld metal, not for the wire and not for the joint.
You match the symbol to the strength required from the joint in the documentation and to what the WPS qualifies. There is no shortcut of the kind: for this steel grade always this symbol. The same grade is welded with different weld metals, depending on the type of joint, the thickness, the heat treatment and the accepted quality level. For every symbol the standard also gives the range of tensile strength and the minimum elongation; check them in the text of the standard if you design a joint.
| Strength symbol | Yield strength min. |
|---|---|
| 35 | 355 MPa |
| 38 | 380 MPa |
| 42 | 420 MPa |
| 46 | 460 MPa |
| 50 | 500 MPa |
4, that is the impact symbol
The third position gives the temperature at which the weld metal reached an impact energy of 47 J in the test of the manufacturer, on a Charpy V specimen. The symbol 4 means minus 40 degrees Celsius. This digit says what came out of the impact test, and on its own it does not settle the admission of the wire to a structure; that is settled by the full classification together with the WPS. You refer the impact symbol to the lowest working temperature of the structure from the documentation, not to the temperature in the hall.
| 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 |
This is a summary, not the full table of the standard. The standard has intermediate positions as well, and the manufacturer gives typical and minimum required values in the data sheet.
M21, that is the shielding gas
The fourth position is the gas symbol to EN ISO 14175, with which the manufacturer obtained the stated properties. This is the most often confused part of the code. The same wire welded in CO2 instead of in a mixture gives a different weld metal, which is why the manufacturer gives two codes, one for each gas.
| Symbol | Composition | Where it is used |
|---|---|---|
| M21 | argon with an addition of 15 to 25 percent CO2 | non alloy and low alloy steel, MAG, the most common mixture in the workshop |
| C1 | carbon dioxide, 100 percent | black steel, thicker sections, cheaper gas, more spatter |
| I1 | argon, inert gas | TIG for steel and stainless steel, MIG for aluminium |
| M12, M13 | group M1, argon with a small addition of an oxidiser (CO2 or oxygen, roughly up to a few percent) | stainless steel MIG/MAG, where a large addition of CO2 carburises the weld |
The practical conclusion: if the wire data sheet shows only the 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 this is a real problem, not a formality.
3Si1, that is the composition symbol 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 pool, a smoother weld face and better wetting of the edges, but also more silicates on the face, which have to be removed before painting. Manganese usually raises the strength of the weld metal, yet the strength symbol does not follow from the composition of the wire alone. The manufacturer tests the weld metal in a specific gas, and only the result of that test gives the number in the code.
An example straight from the product data sheets: the TIG rod BÖHLER EMK 6 has typically 0.9 percent silicon and a yield strength of the weld metal of 450 MPa against a required minimum of 420, that is the symbol 42. The rod BÖHLER EML 5 has typically 0.6 percent silicon, so less, and a yield strength of 520 MPa against a minimum of 460, that is the symbol 46. Less silicon, a higher strength symbol. So read the whole code, not the composition part alone.
ER70S-6 sign by sign
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 gives about 480 MPa.
The letter S means a solid wire, as opposed to C for a metal cored wire. The last digit is the number of the chemical composition from the table of the standard. The six has the most silicon and manganese of the popular variants, the three clearly less.
The AWS number says something about the composition and about the minimum strength, but it does not replace the European classification: it holds no gas symbol, and the impact requirements are covered differently. If the documentation came from the USA and acceptance goes to EN 1090, you need both codes and the data sheet of the manufacturer.
Where the letter A after the number of the standard comes from
The forms 14341-A and 14341-B are two systems of classification 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 rests 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 give variant A, because that is what documentation in Europe expects. You recognise the variant by the full form of the standard and of the code in the data sheet, not by the number alone: in variant B the strength symbol gives the tensile strength (for example 49), in variant A the yield strength (for example 42), so do not compare those numbers directly.
Four Böhler products and their codes
Below are four items that workshops reach for most often. All four come from the Böhler Welding line, for which we are an authorised distributor.
| Product | Form | EN ISO | AWS | Diameters |
|---|---|---|---|---|
| BÖHLER EMK 6 | solid wire MIG/MAG | 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 wire MIG/MAG | 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 EMK 6 | TIG rod | 636-A W 3Si1, full form W 42 5 W3Si1 | A5.18 ER70S-6 | 1.2 / 1.6 / 2.0 / 2.4 / 3.0 / 3.2 / 4.0 mm |
| BÖHLER EML 5 | TIG rod | 636-A W 2 Si, full form W 46 5 2Si | A5.18 ER70S-3 | 1.2 / 1.6 / 2.0 / 2.4 / 3.0 mm |
EMK 6 is the basic wire for structures of non alloy steel, copper coated, with confirmation for the mixture and for CO2. EMK 8 differs in two parts of the code: the symbol 46 instead of 42 and 4Si1 instead of 3Si1. It is the same type of wire with a higher strength symbol of the weld metal. Which of them goes on your joint follows from the requirements of the documentation and from the WPS, not from the name of the steel grade in itself.
TIG rods carry a code from the standard 636, not 14341, which is why it starts with W. Compare the last two rows once more: EML 5 has less silicon than the rod EMK 6, and yet the data sheet shows a higher strength symbol. The manufacturer gives EML 5 for root runs, where a calmer, less fluid pool holds better in the root of a pipe, and declares for it impact toughness tested at minus 50 degrees.
The codes, compositions and strength values come from the product data sheets of voestalpine Böhler Welding: the rod EML 5 edition 12/2021, the rod EMK 6 edition 07/2024, the solid wires EMK 6 and EMK 8 from the catalogue of the manufacturer. Before ordering check the current data sheet on the product page, because the manufacturer updates approvals and the range of diameters.
The diameter that the code does not give
The diameter does not belong to the classification, but it decides whether the chosen wire can be laid at all. Below are indicative currents for solid wires for steel in the mixture M21. The upper limit depends on the machine and the torch, the lower one on the current at which the arc still does not break.
| Diameter | Current, indicative | Typical use |
|---|---|---|
| 0.8 mm | 60 to 180 A | sheet 1 to 3 mm, sheet metal workshop, constrained positions |
| 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 the workshop |
| 1.6 mm | 200 to 500 A | thick sections, mechanised welding |
To the diameter you match the liner, the contact tip and the feed rolls. Wire of 1.2 mm in a liner for 1.0 mm starts to jam after a few hours, and the arc pulses for no reason. A machine with a four roll feeder pulls 1.2 mm and 1.6 mm evenly also on a cable of 5 m, which is why with thicker wires we look at this when we take in every machine in the category used MIG/MAG.
What follows for the selection
- You refer the strength symbol to the strength required from the joint in the documentation, not to the name of the steel grade. The final selection is given by the WPS.
- You refer the impact symbol to the lowest working temperature of the structure, not to the temperature in the hall.
- The gas symbol has to agree with what you have in the cylinder, otherwise the declared properties mean nothing.
- The composition symbol (3Si1, 4Si1, 2Si) says something about the wire, not about the strength class of the weld metal. Do not infer an approval from it.
- You check the AWS number when the documentation came from the USA or when you look for a replacement on the other side of the ocean.
- The whole EN ISO code from the label has to stay within the limits qualified in the WPS, together with the gas symbol; confirm every difference with the person who supervises the welding.
The most common mistake in the workshop is choosing the wire by diameter and price, and then welding in a gas for which the code was not given. The second most common one is reading a single part of the code instead of the whole: the wire is accepted or rejected by the composition symbol, although the strength and the impact toughness of the weld metal are stated by two completely different parts. Both come out only at acceptance or at the testing of the weld.
We will check the code for your job
Send us the steel grade, the thickness, the gas from the cylinder, the working temperature of the structure and the WPS if you have one, and we will point to a wire whose full classification covers it. The catalogue of solid wires is in the category solid MIG/MAG wires, and the rods for TIG in the category TIG rods. With larger orders we also match the diameter and the packaging to the feeder you have at the station.