Pin holes in weld !! Please Help

Date 08-15-2007 14:23

Hello FSmalley, you need to give a little bit more information here. What I mean by that is as to type and application of welds. If there is any sort of "weldable" primer that the welders are making welds over?, this could be a contributor to the problem as many of these primers are not really weldable at all, especially with the FCAW processes. Another thing that can happen is that there might be some sawing fluid or other types of processing fluids that may be pooling inside of tubes, pipes and other such enclosed parts, this is a possibility. Just a bit more information might help with an answer. Regards,aevald

By FSmalley (**)

Date 08-15-2007 15:06

Some of your information is in my latest reply as far as the primer, no we don't use that, in fact because of the shearing operation there is nothing on the tube ends. The main cord could have some oil common to tube to prevent them from rusting while in transit.

hope this helps

By Lawrence (*****)

Date 08-15-2007 14:54

The kind of discontinuities you describe are not all that common with short circuiting Mig. It sounds like you might be welding on some thin sheet and the molten pool has expanded to the point that at the weld termination the center of the puddle (the last part to freeze) is sucking in and making those fish eyes.

Some GMAW wire feeders have a "Crater Fill" function that reduces the current while feeding wire in a controlled manner after the operator lets go of the trigger. I'm not generally a fan of this little option, however, you seem to have tried the other techniques that ought to fix this probelm, but in a thin material situation it might do the trick.

By FSmalley (**)

Date 08-15-2007 15:03

Sorry made a mistake .... It's spray transfer not short circuit. We have seen this in many applications, mostly while welding squashed tube to tube (the tube wall thickness are generally around the .120 to .156 range) the squashed part of the tube is not as much squashed as it is sheared (sheared on an ironworker type machine) this is what we call a "Strut" and we weld that to the "main cord" Our welder don't have the crater fill function ... I think we have Lincon cv300's if i remember correctly.

By aevald

Date 08-15-2007 15:20

Hello again FSmalley, I think that Lawrence might still be onto something with the overheating of the ending weld pool and the suckback. Similar to what can occur with GTAW weld pools and even OAC weld pools upon termination where there is excessive penetration, you can end up with the suckback and a contamination of the weld pool termination from the other side of the puddle. As much as you may not want to decrease the welding speed or heat that is being used currently,you may want to consider this, if nothing else you may want to reduce your wire diameter to allow a slightly reduces welding heat and less possibility of burn through. Changing from a backhand to a forehand method of travel on the welding may even help with this if they are currently backhanding the welds, also increasing the welding gun angle from a less straight-in angle could help. Just a few thoughts for consideration. Regards, aevald

By aevald

Date 08-15-2007 15:43

Hello FSmalley, consistent with Mwccwi's comment about clean, since you are using pipe, I gather, the shellack may be an issue if you aren't using bare pipe. Regards, aevald

By Mwccwi

Date 08-15-2007 15:14

the original poster said they were using GMAW-S.
with spray transfer Spray transfer- the two types of these discontinuities that I have experience with are: 1- shallow dish type "dimple". 2- throught hole "pipeing porosity.
Type 1- the solution that we've found that works is to trian the welder to filck the wrist to cause the electrode to in an opposing direction to the angle (lead or drag) used during travel - this seems ot not only encourage hesitation at the termination of the weld for filling the crater but also stops the "dimple" - this is of course after we verify that the parameters use aren't "starving" the puddle. see picture

Type 2- through hole is usually found when sealing a weldiall-around joint - theory we have is anything on the faying surfaces that can be vaporized -will be vaporized and the vapor will escape as the last liquid point of the weld - Clean seems to have minimize this in our shop

Hope I was helpfull

Attachment: NewPicture.bmp (587k)

By aevald

Date 08-15-2007 15:22

Hello Mwccwi, great stuff and great answer. Regards, aevald

By js55

Date 08-15-2007 15:26

Sounds like simple stop crators. Solidification proceeds from the joint edges to the middle. And the last middle is the final weld crator, one edge being the leading edge. Its especialy aproblem with high viscosity alloys like Monels or Nickels.
MCCWI's advice is the type of thing you are looking for. Its a technique issue. Whatever manner of resolution you use needs to make sure that the solidification pattern is 'disturbed', and additional metal is added to reinforce. My technique was always to swirl slightly at the stop, while hesitating to add additional metal, consistent with Lawrences post on crator fill. There are any number of ways to accomplish it.

By FSmalley (**)

Date 08-15-2007 16:07 Edited 08-15-2007 16:22

[deleted]

By js55

Date 08-15-2007 16:38

FSmalley,
No. A crack is a crack. A crator is a crator. You cannot fail these by using the terminology 'crack'. The danger is that they can lead to cracks. But you should have something in place to have some control over this issue. Perhaps using D1.1 Table 6.1 (3).
Sometimes they are just minor dimples, in which case they may be acceptable. Sometimes they run deep, in which case D1.1 Table 6.1 (3) could be invoked.

PS: I can't tell anything from the photo.

By FSmalley (**)

Date 08-15-2007 16:51

ahhh ha, ok so it's not a failure unless there is evidence of cracking?

By js55

Date 08-15-2007 17:11

To be honest, I cannot think of a code section (thinkin D1.1) that specifically mentions as rejectable crators. Jon may help on ASME. My memory fails. Others may help here. However, there has to be a limit. Perhaps, Section 5.24 of D1.1 (unnaccetpable profile discontinuities), if thats your code.
Undersized weld per Figure 5.4. The profile is actually quite close to what I assume is your issue.
Or perhaps, 5.26.1.2 Excessive concavity of 'Crator'. This one is stretching it a bit.
If these things are deep I'd find something. Just a personal judgement.

By aevald

Date 08-15-2007 17:27

Hello js55, if it is a piping pore(I haven't heard this discussed here yet) I believe there is a section that covers that, although I can't site the exact section off of the top of my head. My interpretation of this type of discontinuity would describe a hole that extends inward towards the root of the bead and the outer edges may indicate that the hole may increase in size as you go in towards the root of the bead. My interpretation of a crater that may or may not be an issue here(depending on size) could possibly be the type that is left when the bead is terminated and there is a spot of solidified silica that can be chipped out and thus leaves a slight depression when this is done. Just a few additional thoughts. Regard, aevald

By FSmalley (**)

Date 08-15-2007 17:54

ok, maybe i can say this a different way .... this hole at the end of the weld is not considered a crater carck unless there is cracking around the hole. Sometimes these are depressions (very small) now if this is not a crater crack (because of no evidence of cracking around the hole) then what would it be? piping porosity? the depth of these can be as much as 1/16" or so

By aevald

Date 08-15-2007 18:30

Hello again FSmalley, a clearer picture giving some visual characteristics to judge might speak volumes to whether you have a real issue here or not and whether there are other things that need correction or not. Regards, aevald

By js55

Date 08-15-2007 18:59

Smalley,
"this hole at the end of the weld is not considered a crater carck unless there is cracking around the hole."..........Yes
"Sometimes these are depressions (very small) now if this is not a crater crack (because of no evidence of cracking around the hole) then what would it be?"............A stop crator. And therein is the problem. As the thread has indicated you either have to have something available in your manuals that will allow a rejection, or you have to interpret other criteria in away that allows you to reject.

But, with very few exceptions I am not comfortable with looking for ways to reject something we think is undesirable. I have seen this abused too much by inspectors with little background in engineering, metallurgy,or welding. Its a case by case basis.

By Mwccwi

Date 08-15-2007 17:44

PS: I can't tell anything from the photo.

= Dimple in the photo =widest cross diameter of pore is greater than depth

if depth is greater than diameter we consider the definition of piping porosity (which is addressed in table 6.1 :) )
see old thread on piping porosity disscussion
http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=30025;hl=#pid30025

By Mwccwi

Date 08-15-2007 18:15

No. A crack is a crack. A crator is a crator. You cannot fail these by using the terminology 'crack'. The danger is that they can lead to cracks. But you should have something in place to have some control over this issue. Perhaps using D1.1 Table 6.1 (3).
Sometimes they are just minor dimples, in which case they may be acceptable. Sometimes they run deep, in which case D1.1 Table 6.1 (3) could be invoked.

Agreed see this picture

Attachment: NewPicture1.png (904k)

By FSmalley (**)

Date 08-15-2007 19:16

ok, I have a very clear understanding now. I want to thank you all for your input.
I appreciate it

Regards
Fred