Not logged inAmerican Welding Society Forum
Forum AWS Website Help Search Login
Up Topic Welding Industry / Technical Discussions / Welded nuts
- - By Safetythird Date 12-18-2017 17:31
Having some issues with our structural engineer (EOR) not wanting to sign off on a design because we have nuts welded into the base.

The nuts are for shipping hard points and not accessible once the assembly is complete, so they need to be welded so the shipping hard points can be bolted in and anchored onto the trailer.

Anyways, the EOR is not signing off because they say that AISC and AWS prohibit welding of high strength heat treated bolts and nuts.

My argument is that these are not structural welds, and the weld only keeps the nut from spinning and in position

the other thing that makes it complicated is that there really is no room for adding a nut cage or something to hold the nut in place

Thoughts? Opinions?
Parent - By gerardo Date 12-18-2017 17:37
I'm agree with these arguments
Parent - - By WeldinFool (**) Date 12-18-2017 19:20
We have several components in our product line that involve an issue similar to what you've described. Our Engineers have approved the tack-welding of nuts for those applications where the tack-weld is only intended to hold the nut in place and keep it from spinning when a bolt is inserted and torqued, and the strength of the mechanical connection is in the bolt-nut configuration and does not rely on the tack-weld in any way. I'm pretty sure this is a common practice...
Parent - By jwright650 (*****) Date 12-19-2017 12:00
The issue is the rapid heat and cooling applied to the nut from tack welding...high strength bolts are heat treated.
Parent - - By jwright650 (*****) Date 12-19-2017 11:58
If they are not structural connections, use A307 bolting assemblies. There shouldn't be an issue with welding machine bolts. The EOR's on most of the projects that I've been involved with don't care about A307 "shipping" bolts.
Parent - By Tyrone (***) Date 12-19-2017 12:29
I agree with this solution. 

High risk of cracking when tack welding high strength steel.  Then you have no strength steel.
Parent - - By Safetythird Date 12-19-2017 14:53
I had actually floated the idea of welding A563 grade A nuts in there since they are not heat treated, but the EOR did not sign off, they just kept regurgitating the "means and methods" mantra :lol:
Parent - - By Lawrence (*****) Date 12-20-2017 12:42
Do not look to AWS (or at least D1.1) for any type of support for welding nuts.  The base metal of the nuts is irrelevant.

Here is the official code interpretation related:
Parent - By Safetythird Date 12-20-2017 19:44
thank you Lawrence, this is the hard info I was looking for
Parent - - By welderbrent (*****) Date 12-25-2017 17:18
Good Day SafetyThird,

MERRY CHRISTMAS AND A SAFE, PROSPEROUS, AND PEACEFUL NEW YEAR TO YOU AND ALL HERE.

AND, WELDCOME TO THE ORIGINAL AWS WELDING FORUM!! THE GREATEST WELDING FORUM IN THE WORLD, BAR NONE. 

So, the main objective, especially in your application, appears to be to prove that the base material is not damaged by the welding.  The normal prohibition is because the strength of the nut is compromised by welding so a structural connection is not safe and sound for the designed strength of joint required. 

As with many other issues, it is not that the codes PROHIBIT as much as it is that they 'RESTRICT' the welding of nuts.  And, it is for the integrity of the nut.  Integrity of the base material can be proven with a PQR if this is something done often enough to warrant the added expense. 

I personally have seen engineers sign off on this application using both soft, grade 2 or A307, nuts as well as structural nuts.  They are not hard enough for a tack weld to meld the properties of the two and effect the base material.  And, as we all know, the engineer may delete from, add to, or modify in any way they deem necessary the applicable code. 

Lawrence gave you the specific Official Interpretation applicable to your situation.  There may be another one but I will have to look. 

He Is In Control, Have a Great Day,  Brent
Parent - - By 803056 (*****) Date 12-26-2017 14:44
I am making the assumption the number of nut involved are few, so why not make the nuts out of A36 bar stock or use a material that is higher strength, but still prequalified? If the material selected is prequalified, so there should be no issues with welding.

If the pull out strength of the nuts is an issue, increase the length of the nut to provide the added strength needed to match the  strength of the bolt.

If there is no other solution to your quandary, the added expense of having the nuts made should not be an issue.

It is relatively easy for a local machine shop to drill and tap the number of nuts needed.

Al
Parent - By welderbrent (*****) Date 12-27-2017 15:04
Al makes a good point.  Instead of using actual nuts, use A36, A572-50 etc Flat Bar or plate cut to a reasonable size, drill, tap, and weld in place.  Done deal and no special testing or rejection by engineers.
Up Topic Welding Industry / Technical Discussions / Welded nuts

Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill