table of contents Show
MIG welding fios
In gas metal arc welding (GMAW), you will not use a coated electrode or filler rod.
Instead, all you need to deposit a solder comes from a spool of metal wire.
In this welding process, more popularly known as MIG, a gas tank (usually CO2 or argon) provides the shield while the wire is fused to the base metal.
Today, it is the most common process for structural welding and product manufacturing.
When a welder pulls the trigger on his MIG gun (shown below), a wire feed machine feeds the wire through a brass nozzle. This allows for pinpoint accuracy and an unobstructed view of what is happening inside the joint.
Welding out of position is much easier than with SMAW. And since the spool contains about a mile of cable, you don't have to stop and recharge very often. (The term MIG, by the way, means "metallic inert gas".
However, since CO2 and O2 are reactive gases, it is more correct to say MAG (active metal gas) when using these gases).
There are two consumables to consider in the GMAW process: gas and wire.
As with coated electrodes, there is a grading system for the different MIG wire options available, administered by the American Welding Society.
The American Society of Mechanical Engineers also has a code, but it is almost identical.
The AWS code for solid steel wire is known as AWS A5.18.
This is what the rating number for a common mild steel wire, ER70S-6, says:
- ES- electric rod
- 70– This two- or three-digit number represents the minimum tensile strength of the weld metal, measured in pounds per square inch (PSI) multiplied by 1000.
- S- Solid wire.
- 6– This number (sometimes with a letter added) indicates chemical additives used in the yarn that can affect the polarity setting on the machine.
The 6 in this case indicates that more deoxidizers have been added to the wire, which is useful for welding dirty or rusty steels.
The other general purpose carbon steel wire type is ER70S-3. This one has no chemicals added, so it's mostly used on new or clean steel.
The most commonly used aluminum MIG wires are ER5056, a soft wire with good ductility, and ER5356, which is harder and has high tensile strength.
The stainless steel MIG wire includes designations such as ER308, ER316 and ER308–L. TheL stands for Low Carbon, which offers greater resistance to corrosion.
Once a wire type is determined for your welding equipment, two additional pieces of information are required to purchase this consumable.
The first is the cable diameter, which is usually given in thousands of inches. The most common sizes for sheet metal welding are 0.35 and 0.45.
amount of yarn
When making a MIG wire purchase, your last decision involves the amount of wire and how it is housed.
For example, Lincoln Electric offers the ER70S-6 as a 44-pound spool or 1000-pound drum.
Obviously, the wire feed mechanism in the welder will dictate which option is chosen. (A small, non-industrial MIG machine uses a much smaller spool than what you see in the photo below.)
MIG wire can also be ordered in "TIG cut lengths". This refers to the three foot cables used in TIG welding. Diameter sizes in this case are not given in decimals but as normal TIG rod sizes such as 1/16 or 3/32.
Related:Best MIG wire
The following table is commonly found on consumables specification sheets and is worth copying for reference. It tells you how to set the equipment controls and which gas you need depending on the welding process.
related reading:MIG welding setup– How to set the correct parameters
flux cored wire
The use of "cored" wire allows a MIG welder to bypass the CO2 or argon tank andsolder without gas🇧🇷 This is because the yarn core contains ingredients that protect the melt puddle.
Like rod casings, the wire core contains a flow agent that replaces the shielding gas tank. This is particularly useful when soldering outdoors, as a strong breeze is sufficient to disperse compressed gas. The process is formally known asCast Core Arc Welding(FCAW).
see more information:Soldering flux: what does it do?
Flux cored wire also allows a welder to use higher amperage and larger diameter wires than solid wire. The process is widely used in outdoor structural welding. Although tubular wire costs significantly more than solid MIG wire, you don't have to deal with gas tanks or wait for the wind to die down before you can weld.
Despite protective additives, flux cored wire is thin enough to be fired from a MIG gun. And the dross that comes with these ingredients is a fraction of what appears in the SMAW process.
Regular flux cored wire is often referred to asAutoescudoInnershield, a brand sold by Lincoln Electric. (Therefore, when a gas tank is not used, the process is formally known as FCAW-S.)
Flux cored wire classification
Fortunately, the AWS standard for carbon steel cored wire (AWS A5.20) varies only slightly from the MIG solid wire code.
Instead of ER, anE (electrode) starts the number in the case of all flux-cored wires.
And instead of an S for solid yarn, you'll see a T for tubular or a C, indicating a "composite" yarn.
E70C-6 is an example of general purpose flux cored wire.
The number 7 in the rating refers to tensile strength, times 10,000 (instead of 1,000 for a cordless MIG wire).
0 indicates the welding position. (A zero means the wire is only good for horizontal or flat welds.)
One of the most widely used flux cored wires in construction is Lincoln Electric's Innershield 232 (also known as NR-232), which meets AWS E71T-8.
The digit 1 indicates that the handle can be used in all positions. The 8 stands for low hydrogen content, reminiscent of the common E7018 stick electrode.
NR-232 is popular because its chemical composition meets seismic requirements for seismic zones like California. On the other hand, the cable is more difficult to work with than cables that do not have the same level of seismic resistance.
The following table lists the recommended parameters for the NR-232 ("NR" spoken aloud sounds like "in", which makes it easier to memorize).
The number 0.068 in the table is the cable diameter. Note that the polarity is DCEN. The CTWD designation stands for "Contact Tip to Work Distance", which affects the amount of current moving through the junction. The "deposit fee" helps the buyer estimate how much cable will be needed for a project.
Use of shielding gas and flow: tubular wire together
When compressed gas is involved in FCAW, the welding process is known asFlux-cored welding with gas protection or double shielding, as both the flux ingredients and the compressed gas produce the shield. The formal designation isFCAW-G.
Here is a more complicated example of a flux cored wire,E71T-1CJH8, which breaks down like this:
- mi- electrode
- 7– Tensile strength measured in pounds per square inch (PSI), multiplied by 10,000; in this case 70,000 PSI.Note the difference with MIG, which uses two numbers multiplied by 1000.
- 1– Welding capability in all positions
- T- Cut Wire
- 1– This is a cable usability specification. Options range from 1 to 14). The 1 here indicates that the yarn has an arutil slag system (meaning the chemical additives are acidic). Rutile coatings provide good weldability (low spatter, good arc quality and weld puddle control), but the mechanical properties are not considered as robust as a basic slag system.
- C– This letter indicates that the cable requires CO2 shielding gas. (M would indicate an argon/CO2 shielding gas mixture).
- JH8– The last 3 are optional codes.
- j– indicates that the electrode meets the requirements for improving toughness.
- H8– designates the maximum amount of diffusible hydrogen that the cable can contain. In this example, less than 8ml of hydrogen is allowed per 100g of weld metal. The lower the number, the less hydrogen will be allowed into the wire and therefore the less chance of hydrogen-induced cracking in the final solder.
Related:best flux cored wire
As you can see, it will take a while to learn the many variables involved in choosing the right cable.
It's a good idea to focus on the most common stick classifications first and absorb the rest of the arsenal over time.
With that said though, as an entry-level welder you may need to stock up on consumables or replace empty spools on experienced, experienced MIG machines.
Therefore, exercising due diligence in the proper selection and storage of wire products is essential to avoid costly mistakes when starting a welding operation.
The American Welding Society has manuals available for purchase, but the cost can be prohibitive.
Check with your school or workplace to see if you can access a handbook and photocopy any necessary information to place in your literature folder.