Innershield Welding Guide (pdf) - Lincoln Electric

3. Increasing WFS also increases the maximum voltage which can
be used without porosity. Lowering the WFS requires lowering
the voltage to avoid porosity.
As the WFS is increased, the arc voltage must also be increased to
maintain proper bead shape.
Travel Speed
OPERATING GUIDE
If arc voltage, WFS and CTWD are held constant, travel speed
variations have the following major effects:
1. Too high a travel speed increases the convexity of the bead
and causes uneven edges.
2. Too slow a travel speed results in slag interference, slag
inclusions and a rough, uneven bead.
Contact Tip to Work Distance (CTWD)
If the voltage and wire feed speed setting and the travel speed are
held constant, variations in CTWD have the following major effects:
1. Increasing CTWD reduces the welding current. Decreasing
CTWD increases current.
2. Increasing CTWD reduces actual arc voltage and results in
more convex beads and reduces the tendency of porosity.
3. Momentarily increasing CTWD can be used to reduce
burn-through tendency when poor fitup is encountered.
WELDER QUALIFICATION TEST
1. Remove mill scale and other contaminants from mating
surfaces of backing and test plates.
2. Preheat to 300°F for 3/8” (10 mm) thick welder qualification test.
3. Attach backing so that it is tight (NO GAP)
4. Use the least drag angle to keep the slag back from the arc.
5. Aging at 220°F, (104°C) for 48 hrs. is permitted by AWS
A5.20-95, paragraph A8.3. A naturally aged specimen may
take months to achieve the specified properties.
Because design, fabrication, erection and welding variables
affect the results obtained in applying this type of
information, the serviceability of a product or structure is
the responsibility of the builder/user.
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