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Ali-GMAW property loss high currents?

Hi there. Ali Pulse GMAW...

Tried posting first on s.e.j.w. but sadly have to accept that defunct now. So here - hope this is interesting for you.

I'm trying to interpret. I tried fairly identical fillet welds on 6mm (1/4inch) extruded 6082 (Al-Mg-Si) at

230A and "+9" on trim (as hot as it will adjust) - reporting about 26V 215A and no trim (synergic recommended) 185A and no trim (synergic recommended) and broke them. The 230A weld was beautiful but broke easiest, seeming soft. The tear-out was a good part of a millimetre (about 30 thou inch) into the plate under the fillet. No difference was obvious with the breaks of the fillets at 215A and 185A both no "trim". In blows to break or appearance of the very shallow tear-out. Anyone help to interpret this? I was told to be careful of beautiful smooth Ali welds as they will be seen to be the first to break when on a boat. Quite a cold looking welds with ripples best, he said.

I never tried breaking spray-transfer welds in previous jobs, which are smooth and run best (?) with simple constant progression but the smooth judged-ideal condition was at a bit lower Amps and Volts and the weld-pool was a very shallow "slanting finger-nail" on the front of a rapidly progressing fillet bead. Able to comment about these? Was on 10m/min (394ipm) and 23V as notes of day record (web search suggests 220A at 10m/min wire feed speed)

Correction - 10m/min (395ipm) is probably more like 200A.

More comment - the 200A 23V spray would be less than pulse is reporting to do the same job. (reporting - you have to rely on the pulse machine to give you an average, without a datalogger sampling at thousands of times per second and post-processing the log to get the true average power) Direct evidence would be that I have never seen a lingering liquid "stop" weldpool in "spray" - new one on me.

So, yes, experience?

Reply to
Richard Smith
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...So, yes, experience?

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No experience, but I do have some training in chemistry and metallurgy. However a search for heat treating or alloy degradation of 6082 returned little useful. If the fracture is just beyond the weld the parent metal may be reduced to the -O condition or enhanced/depleted into a weaker state by diffusion. That may be why the colder-looking welds are stronger. Perhaps an XRF analysis comparing the bulk alloy composition to that at the break surface would be helpful.

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"Grade 6082 Aluminium alloy provides good weld ability, however the strength located at the weld zones is lowered.

If you are welding 6082 alloy to its self then it is recommended that alloy

4043 wire is used. If you want to weld 6082 to 7005 alloys, then the recommended wire should be 5356 alloy."

In certain percentage ranges otherwise flexible alloys can be very brittle. Two examples are the copper/tin alloy "speculum metal" and tin/lead solder on gold plating that wasn't molten long enough to dissolve all the gold.

Reply to
Jim Wilkins

Re datalogging, I've low-pass-filtered the voltage output of a clamp-on AC+DC current probe to reduce high frequency switching noise before sampling it.

Reply to
Jim Wilkins

You make a good point. Doing tests on 6000-series is not a good way to comprehend weld quality. Because what happens to the heat-treatment is complicating / confounding. The 5000-series Al-Mg is solution-strengthening and has essentially unchanged properties after welding. (stating commonly accepted wisdom - "simply" solution hardened alloys lose no properties on welding, as their state is unchanged by welding. Well, higher-order nuances include - if it was cold-rolled and has work-hardening, that will go - then if you use too much heat and there is grain-growth that will cause property loss) I should do these tests on 5000-series.

Reply to
Richard Smith

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