This is Constant Voltage Square Wave vs Constant Current Square Wave
with Lincolns controler.
I've recently started a job and am learning how to run their new SAWer.
It was recently bought and no one here knows much about it(especially
me who ain't even a welder). The Lincoln factory guy told us to run CV
but my test strips which I cut and bent showed poor penatration and a
lot of porosity. I tried CC today and it was much better. The test
piece actually bend rather than break.
So why CV over CC? What is to be gained with each?
It seems to me that CC give me a way to increase the Current and
therefore the penetration. This is what I thought I needed. With CV I
could only increase the Balance between the = and - waves and also the
amount of DC offset but can't get enought to get it right.
I'm really going mostly blind here reading the books each night and
learning as I go. My background is in maching which probably explains
why they hired me to run a welding machine.
We make tanks of 3/16 to 1/4 low carbon steel. 4 to 8 ft in diameter.
Butter,
since SAW is similar to GMAW, except the arc is submerged, this may be
of use to you, don't know the dynamics of the arc and flux, but can
tell you what I experienced with CC and CV pulsed GMAW.
I worked for an auto products company with 30 automated GMAW stations.
When I got there the previous engineer had set the machines on CC, and
explained that in his opinion it was most important to keep the current
constant, since this controls penetrations.
After maybe a year of working with the process, I came to the opinion
that I prefered CV for this application. These welds worked best with
the shortest possible arc length you could tolerate without getting
excessive spatter. If the arc length got too long, the weld would
become very irregular, not wetting and flowing evenly along the toes.
So, with CC the arc length would vary too much due to wire feed
fluctuations and contact tip wear. With CV, the arc length was
constant and current would vary some, but there was enough cushion in
the process to tolerated that.
I would run a number of CV welds at various voltages to see if maybe
this is related to your problems.
Part of the problem here was the boss was told by the salesman that
they could get 100%penatration without a root pass or backing of some
kind. SO I have been having to test with stips with gaps untill they
finally deceided to listen to everyone but the salesman(who has our
money now)
The arc length can't be any shorter than the point where the flux no
longer covers the weld and I'm shooting for this low limit. I'm having
a bit more luck with more experience and am trying different voltages,
currents, travel speed and playing with the balance and DC offset.
We are supposed to get some ceramic backing strips to try soon.
Thanks for the tips
We finally got some ceramic strips to try today. They seem to be the
answere but I got no info with them. I thought they were supposed to
have a gap between mating edges and so I took a test strip and put a
3/32 pin in one end. this gave me a tapered groove. I ran a bead from
one end to the other and found towards the 3/32 end 100% penetration.
I've been experimenting a bit since then but I'm afraid the cost is
going to be a problem.
I kept saying I thought that we could put new wider tape over the
used strips but I don't think the bosses were listening. I found on
internet tonight they sell just the tape.
Mill? Regrind flux? this is the first I've heard of it. Are you
saving the flux gets enlarged somehow? I did try a different flux today
and it improved the weld as far as less porosity
A lot of Subarc shops regrind used flux and mix it with new.
For extensive subarc production welding, like building fluid tanks, it
can save a lot of cash over time.
I hadn't seen anything in the literature we have about used flux. I
thought you just added more as it got used up. I did get some magnets
and put them in the path of the returned flux. I've got a lot to learn
thanks agin
Rosco
I have seen CC used extensively when there is a potential for arc blow or
when multiple arcs are used . As for recycling flux, it is very common but
be careful of: 1 If using stainless it can be easily contaminated.
2If using an alloying flux dont recycle
3 Make sure to rebake fully.
I hope this info helps
I have seen CC used extensively when there is a potential for arc blow
or
when multiple arcs are used . As for recycling flux, it is very common
but
be careful of:
1 If using stainless it can be easily contaminated.
2 If using an alloying flux dont recycle
3 Make sure to rebake fully.
I hope this info helps
Were only welding low carbon steel. Also were have the Lincoln
controller that is AC square wave so I don't think arc bloc is a
consideration. All these tips are helpful. I'm not a welder and after
two weeks I am the "expert" at this place. The boss should have held on
to some of the money till the people who sold this trained someone.
Apparently they installed it and ran to cash the check.
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