CW Certified Welder common mistakes
CW Certified Welder · Understand the traps and how to avoid them.
Strikes an arc with a different electrode classification than the one printed on the WPS (e.g., picks up E6010 to root a joint that specifies E7018) because it burns in more easily.
Habit from a previous job or coupon, electrodes stored loose in the same quiver, and skimming the WPS instead of reading the electrode callout line by line.
What to do instead
Before striking the arc, read the electrode/filler classification off the WPS and compare it character by character with the rod or spool in hand; keep only the specified classification at the station and return unopened packs to stores.
Leaves E7018 (low-hydrogen) electrodes sitting in an open quiver or on the bench for hours, or uses a rod that has been wet, before welding the test coupon.
Treats low-hydrogen electrodes like rutile rods; no holding oven at the booth and no awareness that absorbed moisture drives hydrogen into the weld.
What to do instead
Take E7018 only from a holding oven at the specified temperature, keep it in a heated quiver, and discard any rod that has been exposed beyond the allowed time or has damaged/flaking coating.
Runs the machine on the wrong polarity or current range for the process and thickness (e.g., DCEN instead of DCEP for a GMAW spray/globular setting, or short-circuit transfer on thick plate).
Copies settings from the last job or from a different process, and does not verify lead connection at the machine or read the polarity line of the WPS.
What to do instead
Check the WPS polarity and current range, physically confirm which lead is in the electrode-positive and work-negative terminals, and run a test bead on scrap of the same thickness before welding the coupon.
Welds a vertical groove downhill with a wide weave when the procedure requires vertical-up progression.
Downhill feels faster and the puddle is easier to see, so the welder drifts into it under time pressure and does not check the position/progression box on the WPS.
What to do instead
Confirm the required progression (uphill vs downhill) from the WPS, set the coupon in the correct vertical orientation, and use a stringer or a weave no wider than about three electrode diameters travelling uphill.
Uses the same amperage and travel speed in the overhead position that were comfortable in flat, then watches the puddle sag and the root drop out.
Settings were dialled in on a flat coupon and the welder does not compensate for gravity, which pulls the molten puddle out of the joint.
What to do instead
Reduce current roughly 10-15% from the flat setting within the WPS range, shorten the arc, use a smaller electrode where permitted, and travel faster with a tighter, whip-free motion.
In a horizontal fillet, holds a long arc and drags the electrode at a shallow angle, gouging the upper toe and leaving undercut along the top plate.
The welder watches the puddle rather than the arc and toe, and a long arc is used to avoid sticking, so the arc force washes the vertical member.
What to do instead
Use a work angle bisecting the joint and a drag angle of about 10-15 degrees, keep a short arc, and pause briefly at the upper toe so the puddle wets both plates without gouging.
Fits the pipe coupon with a root gap and high-low that were never measured, opening the gap wide to 'see through it' or leaving the bore misaligned.
Eyeballing the gap, tacking only two points, and not having a gap gauge or Hi-Lo gauge at the bench.
What to do instead
Measure the root gap with a gap gauge at four points, check high-low with a Hi-Lo gauge or straight edge, and adjust the tacks until both are within the WPS before welding.
Welds directly over mill scale, rust, oil, or moisture on the plate coupon without grinding or cleaning the joint faces.
Assumes the process 'burns through' surface contamination, and time is spent on fit-up rather than surface prep.
What to do instead
Grind joint faces and 25 mm either side to bright metal, wipe off oil and moisture, and clean the electrode/wire before the root pass so porosity and lack-of-fusion are not built into the coupon.
Starts the next pass on top of slag left from the previous pass, only chipping the easy lumps.
Rushing between passes, poor light in the booth, and not recognising that slag trapped at the sidewall becomes an inclusion that fails inspection.
What to do instead
Chip, then wire-brush or grind each pass to sound metal, inspect the full bead for slag lines and pinholes, and only then lay the next pass.
Strikes arcs on the plate surface away from the joint to 'warm up' or restart, leaving arc strikes and spatter on the test weldment.
Uses the coupon as a scratch pad instead of a scrap plate, and does not plan restart points inside the groove.
What to do instead
Keep a scrap plate at the booth for striking and restarting, start each restart within the groove just ahead of the crater, and grind out any accidental arc strike before final inspection.