Centreline crack in welding
Centreline crack in welding
(OP)
Can anyone out there further explain the term "Centreline indication"? This term has been used with reference to AUT on welded joints.
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
Centreline crack in welding
|
Centreline crack in weldingCentreline crack in welding(OP)
Can anyone out there further explain the term "Centreline indication"? This term has been used with reference to AUT on welded joints.
Red Flag SubmittedThank you for helping keep Eng-Tips Forums free from inappropriate posts. Reply To This ThreadPosting in the Eng-Tips forums is a member-only feature.Click Here to join Eng-Tips and talk with other members! |
ResourcesWhat is rapid injection molding? For engineers working with tight product design timelines, rapid injection molding can be a critical tool for prototyping and testing functional models. Download Now
The world has changed considerably since the 1980s, when CAD first started displacing drafting tables. Download Now
Prototyping has always been a critical part of product development. Download Now
As the cloud is increasingly adopted for product development, questions remain as to just how cloud software tools compare to on-premise solutions. Download Now
|
RE: Centreline crack in welding
Throat cracks may occur for a number of reasons, but they are most commonly associated with hot cracking.
RE: Centreline crack in welding
Not a problem as long as concavity is not out of spec and compensating cap / re-inforcement results in a weld being thicker than parent material.
Quadswift
RE: Centreline crack in welding
It can be used for Lack of Penetration. Lack of Fusion on one side of the butt especially on horizontal welds, either butt/groove with land. The usage is quite common with autogenous tube/pipe welds.
RE: Centreline crack in welding
RE: Centreline crack in welding
Definitely centerline
Why is all the powder hanging around the toe of the weld? I would take a 4" grinder and make a light pass and then make another pass with the powder.
That is what we used to call a Ray Charles Crack (no disrespect intended).
Very nice picture
RE: Centreline crack in welding
I did grind the weld, the crack extended toward the root about 75% through the weld.
The crack was casued by a weld metal issue coupled with very high heat input. (I can say too much about the weld metal issue but 0.25% of an alloy makes a big difference on solidification segregation.)
RE: Centreline crack in welding
Just a thought from an old welder. Flux-core,looks like the weld was "pulled". You may want to try "pushing". Maybe just alittle uphill if possible.
RE: Centreline crack in welding
The weld had unmelted flux in the center of the weld.
With this lot of filler, I can reproduce the centerline cracks by either pushing or pulling. Once the weld metal chemistry and flux composition were slightly changed (still within AWS specifications), I could not produce the crack.
RE: Centreline crack in welding
Being an older Welder and Inspector the reason for mentioning the edge is that in early times of MIG welding we had 44 C/S filer bodies fabricated using Pipe and 12" 1500 # WNF. All passed 100% RT and spot MT. After about 10 Yrs service we noticed cracking at the toe (both sides) of the Grove welds at the flange. All filter bodies in service had the same cracks. In fact all MIG welds on the filter bodies had this type cracking. The toe wasn't rolled over as much as you show but you could see where considerable grinding had been done, these areas were cracked also.
The service was 6 weeks at 600°F then 1000°F for cleaning. 2 to 3 months off then another cycle. The internal pressure at this weld was 20 psig but the hydraulic end force on the flange was 2000 psig.
We had two vessels that had never been in service, only stressed relieved, and upon planishing the weld we found a considerable amount of thumbnail cracking at the toe, but also several continuos cracks 1" or better.
RE: Centreline crack in welding
Toe dressing with a grinder is a pet peeve of mine. I have seen more damage done than would have been done it left alone. If the toes need to be dressed I perfer that they be dressed with GTAW (no filler), if possible. The welder should be trained to avoid this rework.
Having a good inspector on the shop floor when welding is occurring is the key. Budget cutting indirect labor (QC/QA/Inspectors etc.)to the minimum, very few shop have enough qualified inspectors. Looking at a weld after the fact, you do not know, current, voltages, speed , preheat teemperature, electrode angle etc. One needs to stopping the problem before it starts.
RE: Centreline crack in welding
Rich2001--If you have your welders repair the lap defect at the toes with GTAW and no filler,I would really like to see how they qualified for this.
Plate bends with no filler?
Most Codes say the defect must be removed. I would say that remelting the surface would only cover it up. The stress riser would still be there.
RE: Centreline crack in welding
http://www.nbq.ch/daniel/professional/CUED/daniel/docs/...
http://www.steelstructures.com/IIW%20files/AWS%20D1-1%2...
RE: Centreline crack in welding
ASME does allow for deletion of filler metal-However it is an Essential Variable and your procedure and welder must be qualified for it.
My concern(esp.in your example)would be a slag inclusion under the toe of the weld. Your links mention a 1/16"t remelt. I believe this toe would need to be ground away first then blended with the remelt.
How would you qualifiy your procedure and welders for this?
RE: Centreline crack in welding
You didn't read my post very closely. If you had you would have noticed in the last post I used the word planished even though I did use the word grinding also. I assumed you would have realized never to grind with the axis of the weld except on straps. One should always grind with the centerline axis of the grinder parallel to the axis of the weld if you have to grind. Or better yet don't put notches in a weldment by grinding, filing or otherwise.
The overlap still bothers me and along with all the people at this end who have looked at the picture. All here agree that if this were a real weld the overlap would require investigating.
We normally see centerline crack as you have produced where there is considerable restraint and not enough material was deposited.
As you are into structurals’ look at the Northridge Earthquake Report and check some of their observations.
We make and use a considerable number of stub shafts that require machining during manufacture and tried every type of welding available in house and outside contractors (world renown) and we still haven't been able to completely overcome the thumbnail problem with GMAW. Analysis say they aren’t bad but in service observations prove otherwise.
RE: Centreline crack in welding
The Northridge earthquake report, along the Fema 350, 351, 352 & 355A through F all contain good information.
The photo - I keep a library of photographs and samples that I use to train NDE technicians and welders. In the case of this weld I was attempting to create a centerline crack after have production problems. Porosity, undercut, overlap and lack of penetration are easy defect to create, cracks are harder, so when I stumble on a technique I take full advantage of it.
The unmelted flux in the weld is the key to solving this problem. By being unmelted we did not get the welding alloy transfer from the flux to the weld pool.
BTW the crack does not break the weld surface. There are no PT indications, weak indications with AC MT and much stronger with DC and Pulse DC MT.