Very Curious Weld Defect 1

[deco0404]

Hi Guys,

just came across a strange looking defect in a weld which I have not seen before. I would be very interested to know if anyone has seen the likes of this before, or can shed some light on to what we are looking at here.

A little background. The parent material is S355 TMCP steel, approx 500mm diameter. The area in question was where we had a weld repair. This repair was done using GTAW root and GMAW Fill & Cap. The filler material according to the supplier, is the correct type and grade for the base material, and local preheat of 120C was applied. I have had to remove some details from the photograph for confidentiality reasons, which unfortunately meant the scale has also been removed. The width of the root in the affected area is approx 10mm, so it should be reasonably easy to extrapolate the size of defects....

I have been in the welding business for 30ish years, as an NDT operator, Inspector, metallurgist & Welding Engineer, and have never seen anything like this. I have my own opinion of what this is, but for now do not want to skew anyone else's opinion

I am curious to hear what you guys think

regards

Declan

 

[metengr]

These appear to be long arc strikes leading into the weld cap region. Very poor welding technique.

 

[arunmrao]

For a long time, I have not seen such a poor weldment, surprise, how they could manage. Those streaks are long arc strikes .


"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[kingnero]

Amazing! Apart from those streaks, there appear to be lots of voids or porosities as well, which concur with long arcing.

 

[deco0404]

thanks for the opinions guys, but it cannot be arc strikes..I should have clarified a bit better. This is the root of the weld you are looking at. The welder had no internal access....

 

[ornerynorsk]

I've seen melt "stringers" like this when welding conditions were too hot. The puddle loses tension and some of it drips away. However, for this to be the case, it needs to be well off horizontal, and the attached picture would be upside-down. Furthermore, the weld appears a little too cold for this to be the case. At any rate, it's an ugly weld for GTAW.

Are these defects well adhered?

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[AndrewFinAustralia]

I was typing this reply up as ornerynorsk was replying.

It's not slag or strike, looks like run from the weld metal down the side. Strange thing is that each stringer is pretty well symmetrical. Are they brittle (heavily oxidised or porous)

My question originally was going to be:

Could you please tell us about the weld position - overhead, horizontal, vertical, ??? From the photo it looks as though it's upside down.


Former process/plant metallurgist - I've been out of the game for a while now.

AF

 

[deco0404]

Hi Ornerynorsk,

The weld is horizontal, in order for the weld to lose tension like this, it must have been white-hot, and at that point I would expect to see damage to the parent material. This is not an isolated incident. There are 3-4 other locations like this! please note that the picture has loaded onto this upside down....

 

[AndrewFinAustralia]

Horizontal, not flat - thanks

It's almost as though there's some sort of pressure buildup on the other side of the weld that's blowing the metal out of the weld pool was the only thing I could think of for the consistent size of the 'extrusions' - I've got a basic welding ticket and used to work as a senior process/plant engineer. Been out of the game for a while though - you're far more qualified to comment on the weld quality.

If it was blown out, I'd expect a porous stringer/extrusion which might be brittle due to heavy oxidation. Unsure.

Former plant engineer/metallurgist -been out of the game for a while however. Just another data point, hope it helps.

 

[deco0404]

Hi Andrew,

There is no pressure, but there could possibly be a draught. This is a 500mm diameter pipe, approx 120M high, with the weld in the middle. Obviously at this size it is not back purged. I had not really considered this, but you could very well be right...Thanks for your input

Regards

Declan

 

[AndrewFinAustralia]

Massive draft - I think from memory 10"WG at the bottom of a 60m vertical chimney, which would be the same as your case with a 60m height. I haven't got my chemical engineer's handbook handy at the moment.

Was the defect along the whole weld?

AF

 

[deco0404]

no, it was just in this location, but this is a rewelded location after a previous weld repair.....

 

[AndrewFinAustralia]

No problem - Hope you get to the bottom of it if needed.

We used to leave a chimney in a cement kiln open to give a working draft to those in the kiln during repair - similar sized chimney @ 60m

The only way we could work at the back end of the kiln was to shut the dampers completely to avoid a massive draft. Might be worth considering if you have to re-weld.

Good luck

 

[DekDee]

Declan,
Are you sure about the welding processes ?
Looks more like a cellulose (SMAW) root than a GTAW root (especially the unrepaired existing root on the left of the photo).
Why on earth would they GTAW and GMAW weld 60 metres up in the air ? (if I have read your last post correctly)

Edit: On second thoughts - has the loss of GTAW shielding gas (welded at 60 mtr high with insufficient wind protection)caused the ugly weld ? Was the weld location fully enclosed ?
I have seen the example you have posted many times before with single bevel welds in the horizontal position (square edge on bottom), usually on tanks and usually with SMAW.
Cheers,
DD

 

[deco0404]

Hi DD
I have been informed that the repair was done with GTAW. I cannot guarantee this though. The GMAW is the manufacturers standard welding mode. It is definitely not SMAW. The loss of shielding gas is a possibility, but I still perfer the idea of the draught just sucking the molten weld metal out....This to me makes most sense

 

[david339933]

It looks like the weld gap was too excessive prior to welding, which allowed the "draft" to move the molten puddle as mentioned in other posts.