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RE: Welding to hex nuts

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Bill,

Both A194 and A563 nuts are or can be high carbon and heat treated.  The
carbon equivalence varies depending on grade.  A tack weld has a very small
heat effected zone.  That combination of carbon and a small heat effected
zone is what makes tack welds on high carbon steels very vulnerable to
fracture.  That makes welds problematic structurally in general.

But to just hold a nut in place for a blind connection should not be a
problem in that the heating should not penetrate sufficiently to effect the
thread area.  Also if you are tensioning bolts as required for A325 or A490,
if there is a problem you will know it when tensioning the bolt.

Technically, you should tack weld the head of the bolt and turn the nut for
tensioning.  I would require load indicating washers for proper tension
indication.

Regards,
Harold Sprague


> -----Original Message-----
> From:	BILL PULYER [SMTP:WPULYER(--nospam--at)steelfab-inc.com]
> Sent:	Thursday, October 12, 2000 7:11 AM
> To:	'SEAINT List'
> Subject:	Welding to hex nuts
> 
> When connecting to members in steel framing that has limited or no access
> to
> one side of the joint, it is frequently specified that the nut be tack
> welded to the member at the blind side of the joint.  I know that applying
> heat to the end of a bolt (by welding or flame cutting) is not recommended
> because it may change the material characteristics of the bolt right at
> the
> area that is most important (where the nut engages the bolt threads).  Is
> there also a similar concern when tack welding the nut??   Is there any
> difference between a A563 or a A194 nut in this regard??
> 
> All opinions greatly appreciated.
> 
> William Pulyer PE
> Charlotte, NC 
>