July 1, 2014
Q: For a recently acquired large structural job, we have had to qualify a single-pass 5/16-in. fillet using 0.045-in. E71T-9M flux-cored wire. We are having trouble passing the horizontal fillet test. When performing the weld break test on the horizontal fillet weld, there is incomplete penetration on the majority of the welds tested. Any suggestions?
A: This is not an unusual problem when welding large fillet sizes in one pass. Are you using the proper torch angle? With a FCAW electrode welding in the horizontal position, you should be using a 10- to 40-degree leading, or drag, angle. When welding thinner material, you can use a push technique as long as you can maintain sufficient travel speed to keep the electrode on the leading edge of the puddle. We suggest at least a 30-degree drag angle for your application.
What gas are you using? If you are using an argon/CO2 mix, consider changing to 100 percent CO2. Changing gas is not a must, but using a 0.045-in.-dia. FCAW electrode to pass a 5/16-in. single-pass horizontal fillet test is no easy task. The problem occurs when trying to carry a large weld puddle to achieve the desired fillet size in one pass. Your travel speed is slower, allowing the puddle to build up and insulate the electrode from achieving 100 percent root penetration.
You can try using a slight stepping technique, which is moving the electrode into the root and then stepping back into the weld bead to achieve the fillet size. Although this can be done, it can be tricky. Comparatively, when welding a vertical fillet in one pass, the root penetration usually can be accomplished much easier for two reasons: Gravity will naturally pull the weld metal and slag away from the root, and you can use a slight weave or oscillation technique to ensure better root penetration.
If the wire diameter must be 0.045 in., you can make two weld passes to produce the larger fillet. The first pass helps ensure penetration, while the second achieves the desired fillet size. If you can increase your wire size to a 0.052- or 1/16-in. dia., you may find it easier to achieve the 5/16-in. fillet. By increasing to a larger size, you increase weld volume and amperage, which enables you to handle a larger puddle without compromising penetration.
If you are using an E71T-1M or T-9M type flux-core wire, the all-position types are designed with a faster-freezing slag system. A flat and horizontal E70T-1M or T-1C (100 percent CO2 shielding) flux-cored electrode will have a more penetrating arc, more fluid slag, and a less concave weld bead compared to all-position electrodes. The arc characteristic and bead profile of E70T-1 flux-core types allow you to make a larger single-pass fillet for successful welder qualification testing.
Some shops opt out of the flat and horizontal-type FCAW electrodes in an effort to minimize inventory, but the cost of rework or retesting in this case could be very costly.
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