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Description:
A18 is a copper coated, manganese-silicon double de-oxidised mild steel wire for use with a CO2 or Ar/CO2 gas shield. The carefully controlled wire metallurgy and surface finish ensure high-quality welds and reliable wire feed for mechanised welding systems. A18 is suitable for all general engineering and structural steels.
Practical answers on choosing, using and storing A18 copper-coated mild steel MIG wire on 5kg reels.
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.
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.
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.
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.
Wires with extra silicon and manganese deoxidisers are often described as more forgiving of light surface oxide than lower-deoxidiser wires, but the tolerance is limited and varies between wires. Maker guidance is that rust or mill scale on the base metal increases both spatter and the risk of porosity.For good results, grind or brush the joint clean first, and for structural or code work follow the preparation requirements in your welding procedure. Check the wire data sheet for what the maker says about surface condition.
Match the diameter to the metal thickness and to your welder's output range. Finer wire such as 0.6 to 0.8 mm suits thin sheet and lighter welders. Around 0.8 to 0.9 mm is a common choice for light fabrication, and heavier sections on higher-powered machines commonly use 1.0 to 1.2 mm.Guidance varies between sources, so treat these ranges as a starting point. Your welder's manual and settings chart, and the wire data sheet, give the range for each size. Fit the drive rolls, liner and contact tip to the wire diameter you choose.