Calculate weld shrinkage? 1

[TerryR1]

Does anyone here calculate weld shrinkage?

Yes I know there are a bazillion factors. =)

There was good info here but no numbers:

http://www.eng-tips.com/viewthread.cfm?qid=142412

My specific problem:
I Have a base plate and a 1.5" thick, 18" tall vertical plate welded to it, with a bevel weld. I'm pretty sure the top will bow toward the weld somewhere between 1/8" and 1/2". I want to jig it correctly so that after the weld, the tip it is vertical +/- 1/16".

Thanks!!

 

[Mr168]

It's going to bow a heck of a lot more than that.

Do you have access to both sides of the weld? If so, use a double bevel and weld from both sides.

 

[TerryR1]

No I don't have access. More than 1/2"?? Hmm... hence the need for some sort of calculation.

 

[Mr168]

Realistically, there are too many variables to calculate. I've seen a 5/8" plate bow 3/4" and break a strongback when welded with the GTAW process, and I regularly see 1" plates with backing bowed 1/2" when welded with 1/8" SMAW electrodes. Your bevel geometry, welding process, and number of deposited weld passes will factor into your total shrinkage considerably. Most of the estimates I see tossed around are gross underestimates.

 

[unclesyd]

The Design of Weldments by Blodgett has some very good information on design and distortion control all for $15.00.

https://ssl.lincolnelectric.com/lincoln/apdirect/item.asp?prodnum=DW&PID=16

You mention using a jig which is OK but strange things happen on cooling. There is good point made here about using a jig and leaving the weldment attached and stress relieving the piece as one.

http://www.welding-advisers.com/Welding-distortion.html

 

[desertfox]

hi TerryR1

Have a look at this book reference it gives the formula:-

http://books.google.co.uk/books?id=...esnum=10&ved=0CCwQ6AEwCQ#v=onepage&q=&f=false

desertfox

 

[paddingtongreen]

Best bet is to tell the welder where you want it to end up.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[TerryR1]

Following up:

NR Mandel 21.1 worked well! I decided to adjust it for steel (different CTE), and figured a 0.32" deflection.

We jigged it to compensate; after welding the plate was right on. Thanks all for help!

And yes I am aware that the alignment of the planets was probably involved. =)