I girders welding problems

[pphawk]

Hi every one,
I have been welding I girders using SAW and GMAW process. I weld ASTM A36 steel using E70xx electrodes, but the girders twist or bend after the weld. What can I do to avoid this problem? There is any book where I can find out how to solve this problem.
Thanks for your reply

 

[unclesyd]

I would get this book as a starting point for general information about control of distortion in weldments.

"The Design of Weldments" by Omer Blodgett

This is a best buy.

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

 

[UcfSE]

I would buy the books by Omer Blodgett from Lincoln Electric. They will likely have some good information. Basically you will want to make sure you weld the girders with a symmetric arrangement of your welds so that warping caused by one weld cancels warping caused by the opposite. So you would end up welding, for the example of a doubly-symmetric plate girder, the bottom left, top right, top left and finally bottom right. You may also try, say, bottom right, bottom left, top right and finally top left. The idea is to place your welds symmetrically. If you have a singly- or mono-symmetric girder, the weld process would be more complex to alleviate as much warping as possible. This information can be found in Blodgett's "Design of Welded Structures" book. He has some others, and for the price I think they are an excellent investment.

Lincoln Electric Book Store

 

[UcfSE]

I forgot to mention, Lincoln Electric also has a video titled "Prevention and Control of Distortion". I haven't seen it but it may be worth while.

 

[metengr]

Try this web site, look under "How to Weld"

http://www.lincolnelectric.com/knowledge/articles/list-top-welding.asp

 

[pphawk]

Can I weld at the same time both welds at the bottom, then the two other weld of the above side? Would it produce distortion?

 

[unclesyd]

It may help, but you have to be careful with too much heat input in a small area as you may get the metal pulling in another direction.
You may try it by having one weld slightly leading the second weld.

 

[HgTX]

Welding both sides at a time is fairly common, but you need to make sure you're not melting all the way through the web, making one big weld instead of two little ones (do a sample weld and slice it up and macroetch it to find out). If this happens, you risk having a crack forming through that weld and having the whole flange come off.

And you could still, with a thin flange, have the flange cup inwards toward the welds, which is probably what unclesyd is referring to.

Hg

Eng-Tips policies: faq731-376