Weld Sink

Date 11-21-2005 13:08

Although I have never heard the term "weld sink", it seems you might be refering to concavity. Concavity would be an inverted weld profile on groove and fillet welds. Lets say, for example, your cap of a finished weld has a rounded profile that sticks up (higher than) from base metal approximately 1/8". This would be convex(ity). Concave(ity) would be the opposite, the cap would actually be lower than the surface of the base metal.

Undercut is the melting away of the base metal at the toe (edges) of the weld that is unfilled by weld metal. On a finished weld, adjacent to the edges, there would be "pitting" of various depths.

I'm not sure of any web articles or pictures, but I'm sure there will be other replies that will help you out.

By Lawrence (*****)

Date 11-21-2005 19:53

WELD SINK

A phenomenon to be avoided in which shrinkage occurs between the weld and the parent steel.

http://208.55.2.160/definitions.html

This term is new to me and not an AWS A3.0 standard or nonstandard term.

By jwright650 (*****)

Date 11-21-2005 21:23

L,
I had to google that one too, came up with the same link that you provided.
John Wright

By cas

Date 11-22-2005 04:00

what if you WANT the weld to shrink around the article being welded into something? IE: a press fit housing for something, that has broken and you want a tight fit after weld clean-up? Something where a little "draw" is o.k. and in some cases beneficial:ie tacking the pinch holder of a round-stock "feeler" or lever arm?
Too much, if any, undercut would cause a stress-riser, where the concave weld, if a ductile filler is used, and undercut minimized, on the ID of the "clamp"; and post weld cleanup, will get a better fit/grip on the lever; Proper exterior/OD weld and clean-up to boot, that doesn't dig but just barely penetrates, or contacts this ID with out affecting it
what's to stop it from clamping a ring or tie-on,ect,if the weld is pinching it into place?
Just trying trying to learn more stuff.

By cmansonite (*)

Date 11-23-2005 02:40

Ownmind,
Weld-sink is very different from undercut. Undercut involves removing the surrounding parent or base metal around the weld into the weld pool. This can happen from feeding too little wire into the weld pool, using too much heat with the TIG torch or using a stirring motion with your torch. You are probably familiar with this since you are asking about weld-sink relative to undercut, so I won't get into it any more, except that it is really easy to see if you use a SMAW whipping motion with a lot of heat.
Weld-sink is when the base area around the weld is lower than the original surface was before being welded. This is usually only a few thousanths of an inch, if not less. I do not know of any pictures that will help you, it is hard to see. Weld-sink certainly would not matter structurally. I have only seen weld-sink matter when using a weld repair for a cosmetic part, perhaps a highly polished plastic mold like an automobile fender for a Saturn? Then the lower surrounding area will show with the high gloss surface in the sunlight, looking like a ripple. It normally extends from the weld to about 1/4" from the welded area, depending on the heat level. The best ways to avoid it are to use minimum heat levels to keep the base metal from being pulled-down, feed your filler metal as fast as possible to keep heat out of the parent metal and using the torch to heat your filler instead of the parent material.
I hope this helps. This is all just general stuff. If you have a particular problem, post some more details or just shoot an E-mail my way.
BTW: Sometimes weld-sink is called weld-suck. It sucks the surrounding metal down a few thousanths of an inch.