E7018 Electrode Exposure and Porosity
A welder is making a single-V butt weld in 3/8-inch A36 plate with 1/8-inch E7018 H4R electrodes on DCEP at 125 A. The root gap is 1/8 inch and the land is 1/16 inch. On Friday the holding oven was turned off and its door left ajar. On Monday the electrodes are still in the open tray; the shop humidity is 85% and the electrodes feel cool. The welder uses them without re-drying. The completed weld shows scattered porosity, concentrated at restart points, and slag lines that are difficult to chip. The welder plans to grind the surface and run a cover pass. The machine's ammeter reads 125 A, but the welder has been using a long arc to see the puddle.
1. What is the likely effect of the electrode storage on the weld, and what should have been done with the electrodes before use?
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E7018 H4R is a low-hydrogen electrode, but it is not immune to moisture. The holding oven was off, the door was ajar, and the electrodes sat in an open tray at 85% humidity; the H4R exposure limit is limited (commonly 4 hours for that classification), so these electrodes must not be used as-is. Moisture in the coating breaks down in the arc and puts hydrogen into the weld, producing porosity and slag that is hard to chip. The correct action is to recondition at about 500–800°F for 1–2 hours per the manufacturer/AWS, or discard them. A 250°F holding oven is for storage after opening, not for reconditioning. If no drying oven is available, use a new sealed can.
2. Evaluate the restart porosity and the proposed cover pass. What technique and repair steps are required?
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Restart porosity is a technique defect: the welder is striking in the crater or on cold metal and using a long arc, which gives poor gas protection and incomplete slag removal. Chip the slag, strike ahead of the crater, backstep into it, and fill the crater before moving on. The proposed cover pass is not acceptable-it would trap porosity and slag. The failed weld must be gouged or ground to sound metal, inspected, and re-welded. Check the ammeter and use a short arc; 125 A is reasonable for 1/8-in E7018 in the flat position, but the long arc changes the actual conditions.
3. If the shop has no re-drying oven but has a portable 250°F holding oven, can it use that to fix the electrodes? Explain.
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A portable 250°F holding oven cannot recondition E7018. It can only keep already-conditioned electrodes dry during the shift. Reconditioning requires a controlled 500–800°F oven with a recorded time and temperature, or the electrodes should be replaced. Do not use a kitchen oven or an uncalibrated heater, because temperature control and contamination matter. If the shop cannot recondition, issue new electrodes from a sealed container, keep them in the holding oven, and limit exposure at the job.