AISC prohibits weld nuts?

[Korichnevijgigant]

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.

Thoughts? Opinions?

 

[MotorCity]

If there is load on the nuts, they are structural regardless of whether the loads come from shipping or in-place service. Your reference to "hard points" and "anchored onto the trailer" sounds to me like they are loaded in some manner. If the nuts are not accessible after fabrication, I'd be even more inclined to reject them since you have no way of observing their performance. If you can convince the EOR that there is little or no load, he might be willing to give you a pass but other than that I see no way around it. Perhaps you could substitute a threaded plate for a nut?

 

[Korichnevijgigant]

Yes the hard points are for forklifting and then as strapping points for the trailer.

When I say accessible, I mean no way to hold them with a wrench.

Well they have to be able to meet the transport forces listed in the FMCSA regs, so that is a dead end.

I might float the plate idea, thanks

 

[sandman21]

What exactly are they not "signing" off? Why does the SEOR care about these if they are for shipping? Which side was the weld preformed on? Top threads or bottom threads? Anchor rods are tack welded to prevent spinning. AISC Bolt Installation

 

[MJCronin]

http://www.eng-tips.com/viewthread.cfm?qid=269070

MJCronin
Sr. Process Engineer

 

[Agent666]

I've also stopped a few people over the years from doing welds on high strength nuts (or bolts). Their argument is that it's only a tack weld what harm could it do... Just don't do it, you need to appreciate the changes to the metallurgy that are going on and the high likelihood of hydrogen embrittlement.

I've seen grade 8.8 bolt (UTS =830MPa, not sure on US equivalent) that was welded inadvertedly (by a contractor to prevent bolts spinning during tricky erection) fracture with a gentle hit from a sledge hammer swung with a swing similar to putting a golf ball. You would be surprised by the small amount of force required to fracture the bolts.

 

[klaus.]

DO NOT WELD NUTS !!!!
Does not matter which code
Most nuts are made out of not weldable steel
Same as (high strength) bolts

 

[Metalfixer]

Would a nut with a retainer that is welded work, no weld on the actual nut?

https://www.mcmaster.com/#90955a121/=1ar0s9v

 

[desertfox]

Hi Korichnevijgigant

I've also stopped people welding nuts for the same reason as others have stated, the heat can change the mechanical properties of the nut and make it weaker than it should be, if someone is injured or killed during transportation due to the welded nut/nuts failing who will take the blame?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein