Residual stresses

Date 10-28-2014 15:30 Edited 10-28-2014 18:44

I am a big fan of a well thought out application of peening.
Also preheating beyond the minimum distance. Do not allow dramatic heating and cooling cycles. Ideally, preheat the entire piece.

By Alan Viana Date 10-28-2014 16:41


The preheating control will be important entire piece.

I would like to know how can use peening in this case ( norms , literatures... ). It' s a single bevel groove.

By S J

Date 10-28-2014 18:17 Edited 10-28-2014 20:46

You are wise to seek out prior experience in the published literature. And, Superflux offers some wise counsel as well - the key being - "well thought out".

Years ago I was once advised that "peening" should be exercised with "impunity" - which most likely means that care or limited use is the suggested best practice.

George Linnert presents claims that peening can be employed to counteract weld shrinkage and/or distortion, and he goes on to note that "cold peening is more effective than hot peening". (Ref. Welding Metallurgy Vol. 2, pages 141-142.) Unfortunately, there is no data in the text (3rd edition version) to substantiate his hypothesis - but, at the same time, I have no reason do doubt his good intents.

I have not yet witnessed peening as a means of reducing weld shrinkage in a production welding process. Perhaps there have been other published reports that document the results from controlled studies, but this would be a difficult experiment due to the complex variables that contribute to weld shrinkage.

Linnert, being the practical man that he was, implies that attempts to limit distortion are a better practice than peening - he notes 5 options which when properly employed should reduce distortion on page 135.

One method is to reduce the weld heat input and/or weld size, and another method is to weld from two sides - but you may not have these options for your particular application.

He also suggests reducing the number of weld bead passes, but care is possibly required here as well due to documented evidence published elsewhere in his tomes that suggests that smaller beads and more passes yield finer grains and better impact test results - if impact testing is required by your particular code or specification.

Your final decision and best practice will possibly depend on the unique requirements that are determined by your own customer's particular specifications and needs. I also realize that the available test sample sizes and or quantities sometimes limit the precision of their comparison to real world production applications.

Aim high, and good luck!

By 46.00

Date 10-29-2014 19:02

"impunity

noun
1.
exemption from punishment.
2.
immunity from detrimental effects, as of an action."

I would think that definition would be the opposite of your suggestion that 'care or limited use is the suggested best practise'? Peening is actually suggested in AWS D1.1 as a method to prevent shrinkage and cracking/distortion control albit with certain provisos.

I have certainly used it successfully as a method to prevent cracking and limit distortion in the past, especially on cast Iron. I admit it wasn't a very scientific type of test! If I peened after welding it didn't crack, If I didn't peen after welding it did crack!

There are many and varied types of distortion control, some simple and cheap but effective, others expensive, complex and effective and some complex, expensive and not effective.

TBH, I think the OP has missed a step or two here, in that the material and thickness should not really be over prone to cracking problems given the single bevel groove weld is full penetration and whether it's an appropriate joint for that thickness? I think if the OP has cracking problems, he could well have other issues regards consumables, materials or joint configuration.

By S J

Date 10-30-2014 12:56

Sorry, I did not intend to throw the discussion off by opening up a political debate. The word has several definitions which depend on the context.

Thank you for sharing your real world experience.

By 46.00

Date 10-30-2014 17:30

Please S J, do not apologise and never to me! We are all here to debate and we all have different experiences and opinions which makes this such a rich and informative site.

I have seen too much 'Sorry *****' repeatedly on this site of late.

By welderbrent (*****)

Date 10-31-2014 01:56 Edited 10-31-2014 23:27

Both sides can be abused. Sorrow is better if it aligns with true repentance but obviously only when one has truly wronged another. Many times we can sorrow even when it has nothing to do with repentance, when someone dies for example.

To be sorry for stating opinion based upon training, experience, education, or just off the hip thoughts is nothing to be sorry for, IMHO.

But, real men can apologize when they have lashed out in passionate bursts that were uncalled for. Does not seem to be the case here though I can appreciate the desire to not offend others.

Regardless of the definitions differences between the words, I appreciated both posts. Most fabricators I have observed do not have proper training and experience to peen appropriately. Especially when it comes to roots and cap passes (which can end up being 'caulking').

But, I do find it to be suited to aid in the control of shrinkage and other issues. Mainly though, as Glyn suggests, with cast iron.

True peening is not accomplished with air tools (needle scaler, chipping gun) or slag hammers. I understand the reference Tyrone has cited but most people use the wrong shaped chisel, over use the tool in one area and many other wrong applications of air tools for the job.

As to the OP, 3.5" thickness. Pre-heat, interpass temps, welding procedures, joint configuration, are all going to be critical.

Personally, I think your joint is all wrong. If I have put this together correctly, you have 3.5" deep single bevel with a 45° bevel angle and a 1" root opening. Do you have access to the second side? What you have stated will not be a good joint for that weld regardless of the material in use. Some worse than others but none good.

EDIT: Do the math, that's a weld face 4.5" wide if you stopped exactly at the edges of the groove. More likely 4.75" (121mm). OUCH! As others have stated, even a J would be better suited for this than a pure single bevel.

This really needs to be a double V groove to distribute stresses properly and limit the amount of weld required. If this is not possible, I believe a single V would be better than a single bevel.

Next, I can't find the material used except that you said carbon steel. SO, why that electrode classification? Stronger is not always better. And the nickel content. Usually used on certain grades of structural steel for splicing WF Columns but not sure how it aids in your application.

So much for my two tin pennies. Once again the plot thickens as the posts continue.

He Is In Control, Have a Great Day, Brent

By 46.00

Date 10-31-2014 16:18 Edited 10-31-2014 16:22

I agree, something is amiss with the joint design! A picture paints a thousand words!

Also pre/post heat heat treatment! But not really enough info to comment on that issue!

By Superflux (****)

Date 10-31-2014 16:36

90mm thick with single bevel SCREAMS of "Supersize my Distortion"!
Options are many from reducing restraint of the parts, to changing to a "J" bevel, to presetting components so they may shrink into place.
Far more info is needed to figure this one out.
Pix, drawings, mail me a sample...
Where's "Mr. Shrink" when we need him now?

By S J

Date 10-31-2014 18:29

Define "Shrink".

And, it would help if we knew more about the actual product and shop equipment; however, a recent comment notes that out of position welding limitations comprise one obstacle that restricts the possibility of leveraging a process change improvement via Submerged Arc Welding.

I think I'm done with this one.

Have a nice weekend.

By Superflux (****)

Date 10-31-2014 20:36

S J,
https://www.youtube.com/watch?v=2vuGlcbDwKY

Here's "Mr Shrink".

By electrode (***)

Date 10-31-2014 19:39

S J,
interesting post(s), that is to say.
Then, forgive me my ignorance since maybe I'm simply overlooking something essential here.
Wouldn't a narrow groove joint design be an approach?
Reading through this thread; I was recalling some newer results from US's Edison Welding Institute (EWI).
Resulting from long-term investigation they could achieve some considerable output (at least to me), deploying GMAW (Tandem) for heavy wall thickness parts.
See also: http://ewi.org/the-versatility-of-tandem-gmaw-provides-higher-productivity-and-higher-performance.
But ... as I say. Maybe I haven't correctly understood the OP.

By qcrobert (***)

Date 10-28-2014 19:37

May I ask what type of bevel (V, U, Y) and process being proposed? A pix would be appreciated with dimensions.

Robert

By SCOTTN

Date 10-28-2014 20:06

Alan,

http://www.thefabricator.com/article/testingmeasuring/how-to-relieve-stress-in-welding

http://www.aws.org/wj/sept01/cullison.html

http://www.jflf.org/pdfs/papers/keyconcepts4.pdf

By jwright650 (*****)

Date 10-29-2014 11:10

Hi Alan,

On this single bevel prep, are you using a 45° bevel with a 1/4" root opening? .... something else? .....less angle and more root opening?

Either way I would like to know more about the prep of the joint because there are some rules of thumb regarding width to depth ratios that can play havoc on thicker butt joints like you have there.

Another thing, can you give us the FCAW wire designation...some of the FCAW wires(particularly the self-shielding) can have limitations on number of passes/layers that can be placed before risk of cracking due to depletion of alloying.

By Alan Viana Date 10-30-2014 14:20

Hi ,

I am using 45° but with a 1'' root opening. The wire designation is E81T1-NiC (AWS) with 1,2mm diametre.

By Tyrone

Date 10-29-2014 18:10

Alan,
Took this from Arcelor Mittal on how to weld T1 Steels...

"...air hammer peen the welds. Peening is a technique for locally redistributing welding stresses by mechanical means. Proper peening plastically deforms the weld metal so that the final shrinkage forces are greatly reduced in the joint. Peening is most effective when done while the weld metal is still hot..."

Tyrone

By ssbn727 (*****)

Date 10-30-2014 10:49 Edited 11-01-2014 02:18

First off Alan, "WELDCOME TO THE WORLD'S GREATEST WELDING FORUM of the American Welding Society!"

Okay! Now that we got that out of the way... A couple of quick questions...
1.) is this joint going to be part of a production run? Or is it going to be a one off type fabrication? I ask this question because if it's going to be a joint on more than one assembly, then you should consider what type of set up and method of stress relief to use which leads me into asking the following questions...

2.) Have you considered some form of thermal stress relief yet?
3.) Have you ever heard of VSR (Vibratory Stress Relief)?

If you're wondering which form of stress relief is better, I would say it depends on the assembly size as well as other factors also... if you're not familiar with VSR then here's a few links to help you understand how it works and some industry reports on it's use as well as a brief summary comparison of TSR (Thermal Stress Relief) and VSR:

http://www.scialert.net/fulltext/?doi=ajaps.2014.317.324&org=12

http://www.vibfem.com.au/resources/stress_relieving/Vibratory_Stress_Relieving_Part_1.pdf

http://strathprints.strath.ac.uk/41410/1/195.full.pdf

http://www.stressreliefengr.com/stressreliefvsr.html

http://www.amse.org.cn/fileup/PDF/E20070089.pdf

http://www.twi-global.com/technical-knowledge/faqs/structural-integrity-faqs/faq-is-vibratory-stress-relief-as-effective-as-thermal-stress-relief/

Over the years there has been a considerable amount of discussion and debate over the use of VSR, and I thought to include all of the threads in this forum that show VSR being mentioned in one way or another... You know, stir the pot a little. :grin:

It should be noted also that VSR has not been accepted by any of the American welding codes such as AWS and ASME so, if this job is to one of the previously mentioned codes then please disregard the alternative to TSR being VSR, unless there has been a change of heart that I'm unaware of... It should also be noted that this form of stress relief has been widely used in Europe for quite some time now and with great success... These are some of the companies below that either manufacture the VSR equipment, or perform contract VSR services for various major corporations in the US and world wide...

http://www.aws.org/cgi-bin/mwf/forum_search.pl?words=VSR&user=&board=0&field=body&min=&max=&order=desc

http://www.distortioncontrol.com/literature/Future%20of%20SR%20Booklet.pdf

http://www.vsrtechnology.net/vsr-history/

http://www.vsrtechnology.net/common-metals/

http://www.vsrtechnology.net/vsr-applications/

http://www.vsrtechnology.net/vsr-advantages/

http://www.vsrtechnology.net/vsr-limitations/

http://www.bonal.com/faq/faq.html

Note: There are Job Stories and reports in a link located in any of the last 5 url's I posted... below is a link to You Tube that shows a video on VSR and there are more video listed on the right of the video playing if you you want to see more:

https://www.youtube.com/watch?v=8Ew3NPijCVY

http://en.wikipedia.org/wiki/Vibratory_stress_relief

I think this thread in the Practical Machinist web site was interesting to say the least regarding VSR and I couldn't help but laugh at some of the responses:

http://www.practicalmachinist.com/vb/general/vibratory-stress-relief-does-work-194147/ Make sure to read both pages because they cab be hilarious indeed...

Well, that's about all I can share regarding VSR... Whichever way you decide to go with, all the best to you... Good luck.

Respectfully,
Henry

By Alan Viana Date 10-30-2014 14:47

Thank you Guy!

I am repairing a equipment and I removed all weld because I found cracks ( MPI, UT ). Now I am redoing all the welds.

Thanks for VSR / TSR information, I will analyze this possibility.

By S J

Date 10-30-2014 13:06

Did you say that your material thickness is 90mm, or was that a typo?

I apologize if my metric conversions are a little off - it has been awhile since I have gone through the drill.

Are we safe to assume that 90mm is something like 3.5 inches for your thickness??

Have you considered using a process like Submerged Arc Welding? And, an additional process improvement might be found by developing a narrow gap (small included angle) welding process.

What is your product application???

By Alan Viana Date 10-30-2014 15:03

Yes, the thickness is 90mm...3,5'' .

I can´t use Submerged Arc Welding because the groove position in the piece doesn't allow.

This product must sustain biggest weight in operation.