[Joejoe8455]

So tonight I was starting my 3G test and decided to run one more test plate, test plate is 1/2 in with a 3/8 gap and a 5/16 backing plate, so I strike up and everything is looking good nice tight arc, then all of the sudden my arc goes crazy and I'm blowing out the bevel and the backer, I stop thinking I got the practice plate to hot son I quench it then strike up again and boom it's going crazy. So I stop and get my instructor to take a look and he's all like your going to slow, I'm thinking to myself there is no way, anyways plate is trash so I get another one and wait about 30 mins. I strike up again and this bead looks amazing then about 3/4 of the way up same thing but it's worse and I blow a hole through the backer the, I show the instructor again and he thinks I'm an idiot. So he tacks up another plate then proceeds to tell me he will show me how to do it. So he lights up and 3/4 of the way through he almost blows throught the backer but pulls it off but undercut out the butt. He looks at me and goes "damn son the line is running hot"...... So in short has anyone ever had something similar and I'm running 1/8 Lincoln Excalibur 10718 1/8 at 115

[Joejoe8455]

And this wasn't a case of backing it down some cause then the rod started sticking

[Superiorwelding]

Joe,
At least it happened to him as well. I have never as this happen so I will be of no use on this question however, I have a question for you. Why 3/8" gap and 5/16" backer plate? I have never heard of a test like that before.
-Jonathan

[AKweldshop]

Yeah,
That backing bar would build up with heat fast,I would move across the middle and hold on the corners for a full 3 seconds.

[Joejoe8455]

Navy testing regulations, and they use the 5/16 backers on 3/4 plates as well

[Superiorwelding]

So I assume it is not the backer bar if you are implying it all the sudden blows through. Are you saying it is like a sudden increase in amperage that causes a blow out?
-Jonathan

[Joejoe8455]

Yea, the rod even starts to act funny like I was keeping a good tight arc then all the sudden it would just start sputtering and blowing out the bevel, I even quenched it and when I lit up again I was blowing holes in it

[Joejoe8455]

Also I just took my 4G with same plate and backer setup and never blew a hole in the backer and I was running 1/8 and 5/16 rods with no undercut or holes, just waiting X-ray result (fingers crossed)

[Superiorwelding]

Joe,
Good luck on your tests. I don't have a answer for you but sounds like the machine is messing up or someone is running over and turning your amperage up while welding What machine are you running?
-Jonathan

[Joejoe8455]

Lol I wish I could tell ya, but I literally have no clue, I'm moving to another booth Monday to take my test so I'm not to worried, I was just wondering if anyone has had anything like this happen to them

[Superiorwelding]

Someone will come along and help you better I'm sure. Good luck!!
-Jonathan

[DylanWelds]

I was welding a flange onto a pipe today and on my cap I had what sounds like the same thing happened. Everything was going smooth then all of a sudden my arc got out of control. One of the guys I work with said maybe a bad ground. Didn't have any problems the rest of the day though

[rake]

Take a small wire stub and see if the joint is magnetized.
I've seen joints in the shipyard (submarines) that would spew
filler metal out like a volcano due to magnetism. You could actually
fill the joint with MT powder and the shit would just hang there.

Sometimes you can run a complete pass on each side of the backer bar
to give the magnetic current somewhere else to "flow".

[Bubbster]

I think rake is on it. I was on 3G a couple of weeks ago. The first rod would go in like butter and the second rod is when the arc would get crazy on me. Teacher wasn't sure. I read up a bit and think the plate got magnetized.


Sent from my iPhone using Tapatalk

[EXP500]

If its welding nice 3/4 the way through nice that means the issue looks like the nut behind the wheel, sounds like you changed your speed or maybe you need to pick up your speed just a tad bit as you are going forward, other option is turning your heat down a few amps to see if that's the issue, this is assuming you're equipment is running correctly

[rake]

If its welding nice 3/4 the way through nice that means the issue looks like the nut behind the wheel, sounds like you changed your speed or maybe you need to pick up your speed just a tad bit as you are going forward, other option is turning your heat down a few amps to see if that's the issue, this is assuming you're equipment is running correctly

Sorry but I have personally seen joints with all the symptoms of being magnetized in only one part of the joint.

I also take issue with your loose nut behind the wheel comment. That tone is awfully condescending. The OP is here
asking for help not to be belittled. That shit may fly on WW but not here.

There are many causes of magnetism. Sometimes all it takes is a little too much grinding and polishing.

[Otto Nobedder]

I'll toss this idea in the mix...

The OP has more than enough practice in this weld (and welding in general) to recognize a "one-off" situation... You don't practice this weld well 20+ times, then suddenly, abruptly, have "operator error" while doing it the same way.

I appreciate the reasoning behind the operator error theory, but perhaps you should become friendly with someone before calling him a "loose nut" in any context?

Just two cents from one of the "peacekeepers"...

Steve S

[Joejoe8455]

Thanks for all the advice, but I think after passing several X-ray test, the op isn't to much of an issue. Also my instructor with 38 years of naval welding had the same issue so I'm sure I'm alright. Sadly I threw the plate in the scrap bum out of pure frustration but I wish I kept it around to see if it was magnetized