The flat position PA: why turning the part pays
PA is the benchmark every other position is measured against: the highest current, a pool that settles by itself, and one and a half to two times the output. Which is why the real skill here is not in the hands but in the fixturing — turning the part.
When PA, and why it is worth fighting for
PA is available whenever the part can be laid down or rolled with the weld facing up. A fillet in PA is set in the boat: the T is tilted so the corner faces up at 45°, and the pool fills it symmetrically on its own. The difference from PB is not technique but money: the same welder with the same electrode lays a 10–12 mm leg in one run in the boat against 8 mm in PB, and travels faster. A positioner, or even a pair of stands, pays for itself on the first batch.
How to run it
Hold the electrode at 70–80° to the surface with a 10–15° tilt in the direction of travel: the arc then pushes the slag behind it instead of driving it under the pool. Take the current from the top of the range — in PA the pool does not run, so the margin goes into penetration and speed. Travel steadily, without pauses: the mistake here is not letting it run but overheating it. In the boat the electrode sits on the bisector of the corner, that is at 45° to both legs.
Guide settings: PA is the base the other positions are derived from
| Thickness, mm | Electrode diameter, mm | Current, A |
|---|---|---|
| 1–2 | 1,6 | 40–60 |
| 1,5–3 | 2,0 | 50–80 |
| 2–4 | 2,5 | 70–100 |
| 3–5 | 3,0 | 80–130 |
| 3–6 | 3,2 | 90–140 |
| 6–12 | 4,0 | 130–190 |
| 10–20 | 5,0 | 180–250 |
| 16+ | 6,0 | 230–320 |
How much goes in one run
In the boat a 10–12 mm leg goes down confidently in a single run — twice what the overhead fillet allows and noticeably more than PB. That is the real gain of the position. The ceiling is set not by running but by heat input: a wide bead in one pass overheats the heat-affected zone and pulls the part. Beyond 12 mm you split it into runs not because the pool would run, but to hold the heat input down.
What to weld it with
Everything works in PA: rutile, basic, flux-cored wire, MAG in spray transfer. That is exactly why the position is chosen for critical welds — the consumable is dictated by the metal and the requirements, not by convenience. A basic electrode shows its full worth here: the best penetration and the cleanest deposit, whereas overhead it is taken out of necessity. For MAG, flat is the only position where spray transfer is available without reservations.
The usual defects and where they come from
Burn-through on thin plate: the current was taken from the top of the range without looking at the thickness — that rule works from 4 mm upwards. Slag ahead of the pool and inclusions: travel too slow, or the electrode held too upright so the slag ran under the arc. Distortion is the flip side of high output: in PA it is easy to put down more metal than needed. There are fewer pores here than in other positions, because the pool stays liquid longer and the gas has time to escape.
Designation and qualification
PA to EN ISO 6947, 1G for a butt weld and 1F for a fillet in the American system. A test in PA covers PA only — the narrowest certificate there is. That is why people usually do not sit the test flat: PF covers PA, PB and itself, and a pipe at H-L045 covers practically everything. Flat is what you take when the shop genuinely welds in nothing else.
Frequently asked questions
What is welding in the boat?
It is a fillet weld set into position PA: the T is tilted so the corner faces up at 45°. The pool fills the corner symmetrically, the leg comes out even without effort, and a single run lays 10–12 mm instead of 8 in PB. If the part can be tilted, tilt it.
What current should I use flat?
The top of the range for your electrode diameter: the pool does not run, so the margin goes into penetration. One caveat — the rule works from 4 mm thickness upwards. On thin sheet the top of the range burns through.
Why are there fewer pores in PA?
The pool stays liquid longer and the gas has time to reach the surface. Overhead and vertical the pool is kept small and freezes quickly, so with the same dirt on the edges porosity is more likely.
Is it worth taking the test in the flat position?
Only if the shop welds in nothing else. PA covers itself alone, while PF for the same test fee opens PA, PB and PF. The certificate costs the same and covers three times as much.
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