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  • Ali-GMAW property loss high currents?

    From Richard Smith@21:1/5 to All on Thu Mar 3 06:52:04 2022
    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?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jim Wilkins@21:1/5 to All on Thu Mar 3 09:44:00 2022
    "Richard Smith" wrote in message news:ly35jzwmsr.fsf@void.com...

    ...So, yes, experience?

    ---------------------

    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.

    https://www.metals4u.co.uk/blog/6082-6082t-aluminium
    "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.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jim Wilkins@21:1/5 to All on Sat Mar 5 08:21:31 2022
    "Richard Smith" wrote in message news:ly35jzwmsr.fsf@void.com...
    ............
    I just read an article on WW2 ship construction in which welding problems
    with distortion and progressive cracking were solved by partially returning
    to riveting.

    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.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Richard Smith@21:1/5 to Jim Wilkins on Sun Mar 6 07:56:56 2022
    "Jim Wilkins" <muratlanne@gmail.com> writes:

    "Richard Smith" wrote in message news:ly35jzwmsr.fsf@void.com...

    ...So, yes, experience?

    ---------------------

    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.

    https://www.metals4u.co.uk/blog/6082-6082t-aluminium
    "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."

    ...

    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.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)