fusion weld discontinuity- stainless tube automatic welder

[babak]

Hello everyone,
Recently I bought a small sized automatic stainless tube welding machine.
It produces tubes from strips by roll forming.
I managed to produce 8 tons of pipes successfully at the start, but now a strange problem has occurred, stopping the whole job; there are weld discontinuities as tiny holes repeating randomly.
I contacted with the manufacturer, they say it is due to poor edges adjustments, i.e. the edges are up down when they reach under the torch but I think it is not true, considering the fact that I have produced 8 tons before and I have been doing adjustments during these two weeks with no noticeable change.
I have checked Argon gas, changed welding machine, regrind tungsten with no success. but there is one thing I have noticed; that every time I start, for 5-10 minutes there are no problems but after some time, the tiny holes start to appear, once each 2-3 meters on average.
another thing that I have found is that the Null wire of the input power of the workshop is faulty; It has 40 volts!
any ideas about the reason?

 

[penfold]

Do you have a cross-section of the faulty pipe? The weld profile looks wrong, but it's hard to tell from the angle the pictures are taken from.

 

[HughF]

Looks like Keyholing caused by too much heat, fusing stainless is a fine balance between heat and speed.

Where in Iran are you? I spent some time in Tehran and Kish Island a few years ago, brilliant memories.

 

[Robotstar5]

I would look at the tube drive rollers and their controller, are they slipping, slowing or speeding up causing the weld problem?

 

[backpurge]

As has been said it looks like it is simply getting too hot and blowing through, could be caused by inconsistency in the travel speed, what are you backing the joint with

 

[babak]

I know that the heat/speed balance is not correct in these pictures, (Amp/speed is a little high) but I have tried different conditions and the pictures belong to one of them , anyway the results were the same!

HughF, my workshop is in Kordan, a nice village 80km west of Tehran.

Robotstar5, I have been looking into the rollers, the machine is single motor drive, I have not found anything wrong.

 

[babak]

backpurge, what do you mean by "backing the joint"?

 

[babak]

one thing that is interesting to me is that just before the hole formation, the molten metal accumulates, as if the weld pool reaches an obstacle. please see the picture.
I am not an expert at welding, so I am not sure if this is an issue or something normal.

 

[babak]

here are some photos showing the same problem although the speed/amp ratio is correct.

 

[Wozzaaah]

Are you not able to set up a small video camera behind some welding glass then watch the hole appear?

 

[wheresmejumper]

is it a transformer or inverter based welder

 

[Psychosaffa]

can you run stock through the machine through without welding?
that way you can check the joint to see if there are any irregularities that may be causing the problem.

 

[wheresmejumper]

the tiny holes start to appear, once each 2-3 meters on average.

another thing that I have found is that the Null wire of the input power of the workshop is faulty; It has 40 volts!

2-3 meters ?looks more frequent on the pics?

whats the null wire?

 

[Barney1973]

I use a machine for welding a tube to a spinning and get a similar problem if there is miss-match between the two fit ups or if the prep face is too thin.

 

[Robotstar5]

2-3 meters ?looks more frequent on the pics?

whats the null wire?

I would guess it's the neutral wire and the voltage detected could be due to running fluorescent fittings.

 

[malcolm]

I'm not an expert in these things, but how is the tungsten ground (see http://www.mig-welding.co.uk/wiki/TIG_Welding_FAQ ) and positioned? The tungsten is not visible in your last photo - is it too far from the pipe? It would normally be about 2mm or closer.

 

[AndyStobbs]

What about that chip in your roller, has it always been like that?

 

[babak]

wheresmejumper:
it is not happening regularly, it is all random and unpredictable.
Null wire = wire for neutral, it is a 3-phase machine.


Psychosaffa:
I have run it, but it seemed normal. from my observations, the holes come up where there are no irregularities, however, sometimes they dont not happen where it is most expected, like edges with more burrs.

malcolm:
the tungsten is ok. I know about the axial grinding, angles and distances. like you, I keep it within 2-3 mm distance.

AndyStobbs:
yes, it was an accident and I have been working in this condition without problem.

 

[bkt]

I will install a line voltage monitoring device (on all three phases and the neutral) to se the power supply quality... perhaps there is some kind of spike related to another equipement on your workshop, or even related to the power supply itself.

Also I will check for possible air intakes from the torch to the argon supply.

Perhaps changing the whole torch and the Tig machine will be a good way to discard where is the problem.

Good luck.

 

[babak]

I will install a line voltage monitoring device (on all three phases and the neutral) to se the power supply quality...

Good luck.

I agree. I have changed the welding machine and torch but no resolution. do you think it is voltage to be monitored or amp?