CV vs CC in SAW?

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.
Reply to
Dr Butter
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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.
Reply to
Ipeak
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
Reply to
Dr Butter
The backing strips are really the way to go.
Did you get the little mill to regrind the used flux? It can save you quite a bit over time.
Reply to
Ernie Leimkuhler
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
Reply to
Dr Butter
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.
Reply to
Ernie Leimkuhler
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
Reply to
Dr Butter
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
Reply to
MES
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.
Reply to
Dr Butter

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