line in finished weld

By pjseaman (**)

Date 10-29-2005 03:52

I'd say centerline cracking, due to different rates of cooling,
pjs

By jwright650 (*****)

Date 10-29-2005 10:07

Centerline crack most likely. Several things can cause it depending on the process used to weld it and the materials being joined. More info on the joint in question would be helpful to answer your question better.
John Wright

By NDTIII

Date 10-29-2005 10:52

What size pipe is it? If you have access to the ID you may want to perform a PT on the root or UT to try to confirm if it is a crack or not.
I have seen this "faint" line you are speaking of and it does not always turn out to be a crack. It has something to do with the root surface, whether it may be some crap on the root surface, I'm not sure.
I just think that a faint line warrants investigation before cutting it out.

By mrcleanguy (*)

Date 10-29-2005 14:37

Hi John

It is only noticed on Lap joints of flat bar. It doesn't appear to a crack

Kyle

By jerrykroll (**)

Date 10-29-2005 22:36

Sounds like simple shrinkage. the center of the liquid weld cools slowest, (impurities with lower melting temperature also migrate there), solidifies last, and as it does - contracts - pulls inward on surrounding solidified metal. a little like a pour basin in casting, piping in an ingot. When you get TOO much shrinkage TOO fast, then you get a crack.
In explaining solidification of a weld I often describe it as the same as water in an ice cube tray- the center solidifies last.

By HgTX

Date 11-22-2005 05:38

Are you asking about a crack, or that line that can be seen down the center of most sound fillet welds (at least SAW) and sometimes gets mistaken for a crack by overenthusiastic inspectors?

I used to think it was an illusion formed by the tips of the puddle "chevrons" (what's the word for them?), but I'm not so sure any more. I've also seen the weld be different colors on the two sides of the line.

Not that I'm any help either, but if the thread was astray, maybe I've steered it back.

Hg

By 56780

Date 11-22-2005 16:27

I have been welding 16 years and working as a QA/QC inspector for the last year and a half so I've seen a lot of welds.
If your weld is pretty slick it may appear to some that it may be a crack.
I have made welds with mig that have that slight line through the center of the weld. You can inspect it closer wth a magnifying lens or a sure way to tell is to check it with dye penetrant.

By rodofgod (**)

Date 11-23-2005 06:00

Hi All!

This sounds like a 'Heat' Line! Nothing to worry about!

Regards