A18 Mig Wire 5kg FAQs
Practical answers on choosing, using and storing A18 copper-coated mild steel MIG wire on 5kg reels.
What is A18 MIG wire and what is it used for?
A18 wire is a copper-coated solid mild steel wire for gas-shielded MIG/MAG welding of mild and general-purpose steels. Wires sold under this name are commonly classed G3Si1 or G4Si1 in the European system, and often carry an American classification such as ER70S-6, but the exact designation depends on the wire.
Wires of this type carry extra silicon and manganese as deoxidisers to help the weld pool cope with light surface oxide. Check the reel label and data sheet for the classification, diameter range and recommended gases.
Should I use CO2 or an argon/CO2 mix with A18 wire?
Wires of this class are normally run on either straight CO2 or an argon-rich mix with CO2, and the maker's data sheet lists the gases it is classified for. Straight CO2 tends to give deeper penetration but a harsher arc and more spatter. Argon-rich mixes usually give a smoother arc and a neater bead, and are generally kinder on thinner material.
The argon/CO2 ratio matters too, as different mixes give different arc behaviour and spatter levels. If you change gas, expect to adjust voltage and wire speed, and follow your welder's settings chart.
How do I avoid porosity when welding with A18 wire?
The most common cause of porosity is poor shielding of the weld pool, where gas flow is restricted, turbulent or too low. Check the flow setting, hoses and gun for leaks, that the nozzle is free of spatter, and that draughts are not blowing the gas away. Keeping the wire stick-out short also helps.
Clean oil, grease, rust, paint, mill scale and moisture off the joint, and keep the wire clean and dry. Replace any wet or contaminated gas cylinder, and do not rely on the wire's deoxidisers alone to prevent porosity.
How do I reduce spatter with A18 MIG wire?
Excess spatter is most often caused by settings out of balance, such as a voltage that is too low or too high for the wire feed speed, or a stick-out that is too long. Start from your welder's settings chart and adjust voltage and wire speed together.
Rust and mill scale add to spatter, as does a worn or wrong contact tip, poor gas coverage and a damp wire. Argon-rich gas mixes spatter less than straight CO2, so a clean joint, good tip and nozzle and the right gas all help.