The effect of High Voltage in Welding

Date 02-19-2005 05:18

Are you talking about low-hydrogen SMAW? If so, I would tend to agree that up to 30V is not sound practice. With low-hydrogen SMAW (such as E7018), the ideal practice is to keep the arc length as short as possible witout extinguishing the arc. A good welder will keep his/her average voltage from 22-25 typically. If you are watching a meter, it will jump around quite a bit, but the average should be much less than 30. If the arc length is only sligtly too long, you might get sub-surface porosity, but if it gets even longer, it will soon become evident with porosity open to the surface. On the other hand, if you are not talking about low-hydrogen SMAW, it is a whole different ball game.

By jwright650 (*****)

Date 02-24-2005 13:00

GRoberts,
I don't want to hikack this thread, but I haven't seen any activity on it for a few days now and I'm curious about FCAW and high voltages relative to amps, and with high travel speeds. I've thought maybe these were causing worm holes with a particular welder that I would notice with his machine set up this way(ie 37-39v and 325-350a with 1/16" E71T-1 100%CO2), but don't have a firm answer in my mind about these parameters being a cause of his piping porosity. It has been talked about in other threads here on the forum, but I haven't heard any confirmation to my theory. I see this guy finish welding his end waaay ahead of his partner on the other end of the same material with approximately the same amount of weld to be placed. Of course his boss would pat him on the back for making quick work of his end, but then he would freak out when I UT and reject the joint. When gouged out, I would find 1" - 1 1/2" long tunnels approximately 1/8" in diameter running under his last pass, parallel to the joint(horz & flat positions). It looked to me that the gasses were following his puddle along as he welded and just never made it up to the surface, maybe because of his fast travel speed and the puddle cooling before allowing the gasses to escape?

I welcome any thoughts, to put this to rest in my mind. I keep talking about it like I know what I'm speaking about, but I'm only guessing, and I would like to KNOW rather than guess.
John Wright

By gsi

Date 02-24-2005 17:43

Hey John,
I have personal seen worn holes/tracks lead to piping porosity. I also have corrected the problem by adjusting volts, amps, and travel to a more optimum setting. I personally feel 37-39 volts is high? Sounds like a good boss! (I know the feeling )
Just my Thoughts
Dave

By jwright650 (*****)

Date 02-24-2005 18:00

Thanks for your thoughts Dave. I was reading some info on a few web sites that point to high voltage and or travel speed as the culprits. I also think that the E71T-1 any position wire may have been compounding the problem, freezing the puddle a little quicker than the E70T-1 wire in use on other tables. I haven't seen any of those with the E70T-1. It just plagued this one welder and he always complained it was bad wire or something. We have not had any problems with ESAB's wire, that I'm aware of. I haven't had any more trouble since he left our employment. He had a small following and several guys tried to imitate him and his speed with fitting and welding. He had talent, no doubt about it, but it really went to his head and he thought he knew it all and he wouldn't listen to anyone. He blew up one day at his boss and got himself sent up the road.
Anyway, seems my suspicions about the voltage and travel speed were somewhat on the right track, I just need some reassurance sometimes that I'm not out chasing rabbits off the beaten path too far.
John Wright

By swnorris (****)

Date 02-24-2005 18:13

Hi John,

I think you're right about the fast travel speed being a problem, because the cooling rate increases or decreases proportionately with the travel speed. If travel speeds are too fast, there is a tendency for undercut and porosity because the weld freezes faster. Also, are the parameters set forth in your welding procedure based on the manufacturers recommended procedures? If so, was this guy welding outside your WPS parameters? For 37-40 volts, he should have been running at about 480 amps, with a wire feed speed of about 600, for 1/16" diameter wire.

By jwright650 (*****)

Date 02-24-2005 18:46

Hi Scott,
I was looking over at ESAB's catalogue and the suggested voltage/amperage for that size wire is 28-34v / 250-500a w/ 3/4" - 1" ESO in the F/H position and they show an optimal setting of 32v/400a. Yes, I'm using the mfg's numbers on the WPS. I was looking them back up to make sure things haven't changed since those were written several years back. You always have a few wanting to do thier own thing as soon as you go around the corner, as you well know.
John Wright