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Up Topic Welding Industry / Technical Discussions / Welding shrinkage tolerances
- - By uandme72 Date 07-30-2008 04:21
Are there any standards available for indicating welding shrinkage tolerances on stainless steel? If so, kindly provide us with the same so that we may not have to do calculations while providing welding allowances in the drawings of stainless steel assemblies.

Regards
Parent - - By MDG Custom Weld (***) Date 07-30-2008 12:37
You have not provided enough information. 

This has so many variables, process, type of stainless, thickness, and so on.
Parent - - By Stephan (***) Date 07-30-2008 12:57 Edited 07-30-2008 13:05
Mark,

please allow to agree entirely with you!

I'd venture to say moreover, that even the one who were able to prepare some reasonable and easy suitable standards on this (by simplifying the infinite number of variables), would become fairly rich.

At least however, he or she would have deserved to receive the Nobel Prize in Physics...

To keep it serious. All the numerical simulations on weld distortion(s), strains and tensions, ..., which I have heard or read of, were just small tessellae and always to be considered as being partially valid for even the specific part geometry, welding process, material's composition, etc.

An "in general" valid procedure making it feasible to "... not have to do calculations ..." is truly unknown to me.

Best regards,
Stephan
Parent - - By MDG Custom Weld (***) Date 07-30-2008 14:52
Now Stephan, why did you have to go back and keep it serious  :)

For the most part, regardless of material type, when you weld it, it will move....Duhhhhh..right.

Now each one of the infinite variables will affect how much.  To actually calculate how much is a very tall order.  Just a minor change in the material properties (well within any standard) will affect how much.  Now, I know from your great post in the past that you have a firm grip on mathematic equations, but I don't think anybody could calculate with great accuracy how much it will move.  Sure we all have a good idea how much things might move, and we make adjustments in our fabrications accordingly, sometimes we are right on, and sometimes we're a bit off.   This just comes with doing the work and being familiar with the materials we work with.

By the way, is that a plasma column in your picture?  It looks just like some of the MagicWave plasma columns that we run :)
Parent - By Stephan (***) Date 07-30-2008 15:06
Mark,

thanks a lot!

May I say? Your post is most excellent and it couldn't be said even better!

In particular: "... but I don't think anybody could calculate with great accuracy how much it will move. Sure we all have a good idea how much things might move, and we make adjustments in our fabrications accordingly, sometimes we are right on, and sometimes we're a bit off. This just comes with doing the work and being familiar with the materials we work with."

That hits the nail right on the head - at least in my humble opinion!

Ahhh, yes... you are absolutely right! It is a GTAW plasma column calculated numerically (but not by me!! :-)) and I like the comparison with the Magic Wave :-)

Best to you,
Stephan
Parent - - By G.S.Crisi (****) Date 08-04-2008 23:39
To answer uandme's question, I don't remember having seen shrinkage tolerances after welding on any standard issued by institutions nor welding specifications issued by engineering companies.
Has anyone seen them?
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - By HgTX (***) Date 08-06-2008 16:53
Wouldn't this normally be covered by ordinary geometry tolerances in the finished part?

Hg
Parent - By Stephan (***) Date 08-07-2008 19:45
Giovanni,

I hope you're doing quite well!

As always a pleasure to talk to you and to humble answer your question:

"Has anyone seen them?"

No! At least not me.

I guess it was excellently described by HgTX when he asked:

"Wouldn't this normally be covered by ordinary geometry tolerances in the finished part?"

Best regards to Sao Paulo!
Stephan
Parent - - By OBEWAN (***) Date 08-06-2008 18:36
For the work we do on aircraft igniter tube welds, it seems the DOE method is the only thing that works.

We have some shrinkage numbers established by welding and then measuring .035" dia stainless and Inconel tubes.
The same process will generate a bell curve even with a computerized system that can control amps within +/- .1 amps.
I think one huge variable might be small localized differences in chemistry that change melting.

In our case, we found shrinkage to vary from .008 to .012 inches!
Parent - - By Stephan (***) Date 08-07-2008 19:55
OBEWAN,

"In our case, we found shrinkage to vary from .008 to .012 inches!"

Wow, very interesting!

May I ask if the shrinkage numbers you have found out were for longitudinal contraction only or have you conducted experiments as well for other distortion phenomena? 

Thanks and best regards,
Stephan
Parent - - By OBEWAN (***) Date 08-07-2008 20:06
The shrinkage was longitudinal for a square edge butt weld.
Parent - By Stephan (***) Date 08-07-2008 21:19
I see...

Thanks Steve!

Best regards,
Stephan
Up Topic Welding Industry / Technical Discussions / Welding shrinkage tolerances

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