Practical Welding Today - July/August 2010

CONSUMABLES CORNER
Selecting the correct diameter
for flux-cored wire

I work in a large manufacturing fabrication shop where we weld sub-assemblies and then fit and weld them together to complete the machines we manufacture. Currently we use gas-shielded, flux-cored wires from 0.045 to 3⁄ 32 in. in diameter. At what point is a small-diameter wire too inefficient, warranting a change to a larger-diameter wire?

JERRY
MATHISON
and
JAY GINDER

With the cored wires available today, it’s very possible to reduce some of the wire diameters used in different applications. To select the proper diameter, you must first consider the variables that will influence this decision, such as the material thickness, welding position, weld size, and welding current (amperage), and whether you are welding single or multipass weld joints. You must also ensure that your welding power source produces enough amperage output to handle whatever wire diameter you choose.

If you currently use 0.045-, 0.052-, or 1⁄16- in.-dia. flux-core wires, they probably meet the EX1T-X classification, which means they can be used in all positions. The 0.052- in.-dia. wire can replace both the 0.045- and 1⁄16-in. wires, reducing your inventory. The 0.045-in., all-position wire commonly is used with between 160 and 250 amps. If you use a 0.052-in.-dia. wire, you can increase your travel speed at comparable current levels. This is not necessarily because of a higher deposition rate. You are using the wire diameter to make a comparable weld size at a faster travel speed when welding at the same or higher welding current. This helps control overwelding the joint and reduces heat input. On the other hand, if you’re using a 1⁄16-in.-dia. wire, the 0.052 electrode would yield a higher deposition rate. You can obtain this data (deposition rates and efficiencies) from all the manufacturers of FCAW electrodes for comparison.

Larger-diameter wires are normally clas-
sified as EX0T-X types, meaning they are
designed for flat and horizontal welding
only. You also can benefit by using a 5⁄64-in.-
dia. wire in place of a 3⁄32-in.-dia. wire,
depending on the average amperage being
used. The 5⁄64 and 3⁄ 32 deposition rates and
efficiencies are going to be close to equal at
400 to 450 amps. Anything below 400 amps
gives the advantage to the 5⁄64-in. wire on
deposition and efficiencies. Current levels
above 450 amps are usually welded with the
3⁄32-in. wires. Again, these numbers will vary
slightly depending on the wire type and
manufacturer. Actual deposition rates and
efficiencies are available from the manufac-
turers via the Internet, published literature,
or from your current filler metal supplier. ■

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