Hole in Weld

Date 10-13-2005 21:30

I think what the hole at the end of the weld is, is what you would see when using GTAW called a fish eye. While I never did research this, what I was told by my mentor is that when you are welding, there are gases inside the weld puddle. The little bright orange spot you see floating around in your puddle is how the gases are escaping the weld pool. When the welder stops welding, these gases are still escaping. What we taught when I was instructing at a manufacturing facility using alot of spray transfer, was as soon as the welder releases the trigger, to hit it again for a split second. This prevents the hole from appearing. Also, ensure that your welder's come back into the weld, (reverse direction) for at least 1/4th". This ensures you do not leave a crater which many times leads to crater cracks at the end of the weld. Hope this helps.

Mike

By - Date 10-13-2005 22:18

Mike,
This is good and accurate information. The hole at the end of the weld is termed as a crater crack or fish eye. Depends on the person's terminology of this discontinuity. When approaching the end of the weld, the welder can pause for just a quick moment, with the trigger pulled and depositing metal, and form a little puddle on the end of the weld. This, too, will virtually every time eliminate this little hole. This normally occurs more in GMAW than GTAW, though.

By jerrykroll (**)

Date 10-13-2005 23:17

in my experience -

"The little bright orange spot you see floating around in your puddle"

...is most likely the carbon that precipitates to the surface of the weld puddle, as it has a higher melting temp than the iron and other constituents. In OAW welding that bright incandescent spot that kind of "flitters" around is a good indicator that a neutral flame is being used.

By Shane Feder (****)

Date 10-14-2005 05:33

Chuck,
We used to do a huge amount of what we called "Dairy tube" welding in the dairy factories in New Zealand.
This was 1.6 mm (.062") WT 316 tube from 2" diameter up to 12" diameter welded square butt, single run GTAW.
If the welder pulled his Tig torch away from the molten metal too quickly when stopping it would leave a nasty little hole that quite often went right through the weld and could be seen on the inside of the pipe. As you can imagine with the hygiene standards we were working to this was a big no-no.
The way to avoid this was when the welder wanted to stop he would stop feeding wire,gradually speeding up down the centre of the prep until it was safe (cool enough) to "tail off".This was to avoid getting the "shrinkage holes / fish eyes"
Now with the new fangled machines you have slope up / down etc and when you want to stop welding you simply press the slope down button on your torch and the machine gradually reduces the amps until it has reached zero and the arc is extinguished.This removes the likelihood of getting these holes hugely.
Gee, the young fellas don't know how easy they have got it these days!!!
Regards,
Shane

By FSmalley (**)

Date 10-14-2005 10:12

Ok, as I thought. This is referred to as a crater crack and a crater crack does not need to have "cracks" propagating from the hole to be considered a "crater crack"

Thank you guys for all your help.

By jwright650 (*****)

Date 10-14-2005 13:03

Regardless of what you are trying to call this situation, it is good practice to fill the craters. I didn't notice what code you are working to but according to...

AWS D1.1:2004 Table 6.1 Visual Inspection Acceptance Criteria
(1) Crack Prohibition
says..." Any crack shall be unacceptable, regardless of size or location."
(3) Crater Cross Section
says..." All craters shall be filled to provide the specified weld size, except for the ends of intermittant fillet welds outside of their effective length."

John Wright

By QCCWI

Date 10-14-2005 13:17

John,
That is true but some welders only want to hear the leave crater at the end of intermittent but do not understand if the crater cracks it has to be fixed because cracks are unacceptable regardless of location.

By FSmalley (**)

Date 10-14-2005 15:48

We work to AWS D1.1:2004 and yes I'm failing these welds per the section stated by JWright650. So I guess i'm correct to fail these welds as this is a "hole" or "deep impression" (approx 1/32") at the end of the weld bead and is considered a "crater Crack or Fish eye". Right?

By QCCWI

Date 10-14-2005 16:02

I say you are Right as can be.I say if it looks like crap 9 times out of 10 it is crap.

By - Date 10-14-2005 12:11

Shane,
Certainly, if your machine has the capability to down slope and do those things, that is the way to go. Some of us from the "old school" had MIG torches that did not thave those things. You push the trigger and shielding gas and wire come out. You let off and everything stop.

Like you said, there are very easy ways to avoid these craters or fish eyes with TIG. I only said these discontinuities happened more often in MIG than TIG because most TIG wleders know how to avoid that. You know those TIG welders...lots of pride.. and rightfully so... ;-)

By Lawrence (*****)

Date 10-14-2005 18:19

Right on Chuck

Regardless of process, what we are discussing is a craftsmanship issue.

Fish eye, Crater Crack, Cold Shut; A defect by any other name is still rejectable!

Good GMAW advice for technique above. That little pause at the end makes a big difference. Having an overly forward push angle can also exasterbate this problem. Furthermore, High speed wire feed of 0.035 wire can be another cause of this condition with switching to 0.045 wire at a more reasonable feed rate being the solution. A little sound advice can make a big difference in production, by reducing repair, rework and rejects. Whether it's gun angle by the welder or wire selection by the weld decision maker it all comes down to craftsmanship.

I have never met a journyman GTA welder who selected the crater fill toggle on his/her power supply.

INCO 718 and Waspalloy are two examples of metals that require expert "tailing off" at the end of a weld in GTAW. If these alloys are "HIPPED" the ends of welds are even more critical.

By FSmalley (**)

Date 10-14-2005 18:33

a ton of GREAT comments !!! and Chuck, I agree with you completely.

By dasimonds (**)

Date 10-14-2005 23:14

"HIPPED"?
Dale Simonds

By Lawrence (*****)

Date 10-15-2005 07:20

Dale,

HIP= Hot Isostatic Press

A type of casting process that employs high temperature argon at high pressure to force out voids or shrink them to a size they are rendered negligable.

The alloys (in the case of the Inconel or Waspalloy) remain the same regarding constituants, but performance is increased as is sensitivity to welding. Whole Compressor cases have been cast using the HIP process in the last 20 years rather than a construction of several welded sections.

The sensitivity to welding (usually liquation cracking in the HAZ) may be dealt with using weld repair techniques that include very low relative amperage inupt and a 2.5% Hydrogen shield gas mix. The performance qualifications we did with HIP inco 718 and Waspalloy were build ups in machined scallops in 1/2 inch thick coupons. The welders considered the performance qualification more difficult to get good results than the practical repairs they faced on the job.

http://process-equipment.globalspec.com/specifications/spechelpall?name=Isostatic_Presses&comp=3101

By dasimonds (**)

Date 10-15-2005 23:36

Thanks Lawrence.

I didn't see any pictures, but the chambers must be quite something to withstand 3000 degrees F and 100,000 psi. I wonder what their made of. Niobium maybe?

Thanks for the link,
Dale Simonds