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Up Topic Welding Industry / Technical Discussions / Welding high strength bolts
- - By CHGuilford (****) Date 06-08-2007 01:49
A question came up that I'd like some help finding the answer to:

Where can it be found in writing - in codes and standards that apply to structural steel -  that high strength fasteners (nuts,bolts, washers) should not be welded?

We're involved with a project that requires all joints in the structure to be 100% seal welded; including around bolts in the erection holes.  The specs call out A307 erection bolts which get ringed with weld to seal them.  Most bolted structural joints are located outside the gas-path zones so that those don't need to be sealed but the designer goofed on a couple of joints.

Everyone involved realizes that A325 bolts and A563 nuts are not supposed to be welded, and A325 bolts are not on the D1.1 list of approved base metals, and most likely the connections will be reviewed to be welded.  However, the question came up and it deserves an answer but I haven't found a direct reference that answers it.  Just wonderfing if anyone has found a spec on the topic that does not require a logic path to explain.
Parent - - By Joseph P. Kane (****) Date 06-08-2007 12:41
Chet
Good Morning

I do not know any code book that says you can't weld HS Bolts, specifically ASTM  A325 & A490.  The AISC ASD specifically prohibited welding or even heating ASTM A449 Q&T anchor rods.   However the ASTM Specs for A325,  A490 and the ASTM A1852 look on heat treatment by anyone downstream of the manufacturer as subsequent manufacturers, who are obligated to adhere to all the manucfacturing qualification testing required of the original manufcaturer.  I would argue that welding or even subsequent heating during galvanizing, constitutes down stream manufacturing.

BTW, ASTM A307 bolts are not considered HS Bolts.  I believe that they are the metallurgical equivalent of ASTM A-36.  I arrive at this by looking at the wording under anchor rods.  So, I never heard that A307 bolts could not be welded.

Do you have the leeway to automatically weld on threaded studs instead of drilling holes and welding on bolt heads?

Joe Kane
Parent - - By js55 (*****) Date 06-08-2007 14:41
Am I wrong in thinking that you essentially back door prohibit it. In other words, for any weld to take place you have to comply with either Section 3 or Section 4 of D1.1 if that is the code of construction. Section 3 would not apply to HS bolts. And would a Section 4 PQR be able to bend without PWHT?
Parent - By CHGuilford (****) Date 06-09-2007 12:49
Yes, I believe the prohibition is from a back door approach. 
Parent - By CHGuilford (****) Date 06-09-2007 12:47
I thought that might be the case; that the prohibition comes from inferring that welding is heating and therefore would be detrimental the the fastener's properties.  It would be nice to point to a specification that outright states that, but at least no one is arguing that there is nothing to be concerned about.

I didn't intend to infer that A307 bolts were high strength.  Those were specified because the bolts must be ringed with weld to provide a seal and they are believed to be "weldable".  Once the structural joints are welded, the A307 bolts simply fill the hole.

At this point, threaded studs will not work. The plan is to weld the clips and fill the holes with A307 bolts which will be sealed.  The engineer is determining where to weld and how much weld is needed.
Parent - - By Dave Lowen1234 (*) Date 06-08-2007 19:56
I have never seen a spec that prohibits welding of A325/ A490 bolts but that does not mean they can be welded. I have seen engineers call out for bolt heads or nuts to be shop welded because they are inaccessable in the field. Our procedure was always to weld 3 of the 6 faces of the bolt head or nut.

As was stated earlier, A307 bolts are not governed by the RCSC spec.

The possibility exists that the engineer designed the structure so that the field welds will handle all the loads. This would make the bolts redundant, they could be removed and discarded. The seal welding indicates a corrosive or high humidity envionrement. If this is the case, the bolt head to structure , nut to bolt thread, nut to washer, and washer to structure would have to be welded.
Parent - By hogan (****) Date 06-08-2007 21:27
one of the state DOT's that we do work for has a standard detail requiring the welding of a F436 washer to a A449 1" dia bolt
Parent - - By CHGuilford (****) Date 06-09-2007 13:11
That is exactly right - the function of the bolts are erection aids only; field welds handle the structual loads.  A307 bolts are used wherever bolts must be seal welded  (it would be harder to fill the holes with weld if the bolts were removed).  Structural joints required to use A325 bolts are supposed to be located outside of the gas-path zone, but there was a mistake made on a couple of joints (easy to understand - this is a complex structure with many chambers and ductwork going everywhere).

We're just looking to see if any specification that normally applies to steel construction outright says "don't weld A325 bolts".  It looks like there is not.
Parent - By XPERTFAB (**) Date 06-09-2007 21:28
If you have ever performed a tension test on a A325 bolt that has been welded upon then you will quickly understand why you do not weld them.  Especially after they have been installed and fully tensioned.  when I come time for me to fix someone elses crap as i do way too regularly, I actually weld upon the head of the A325 bolts both hex and domed head (TCB style bolts) to relieve the tension on the bolt so that they can quickly be removed from the "iron" with little more then a hard tug on a spud wrench or an electric imapct of the 1/2 to 3/4 inch variety.  This saves the need for a torch to heat the bolts which takes much longer and is a bit unfriendly to the painted or primed surface.  Since I deplore looking at work that appears all burned up such as paint finishes, and I don't want to spend the time repairing finish; this method works awesome.  The bolts get loose, I correct the problem oftimes just plumb and align; new bolts go in, tension them up and I am down the road with the superintendent shaking their heads as it was completed with little effort.  Point is heat like directly welding on A325 bolts is not good.  In LA a few years back we erected some canopies made of structural steel over walkways of a mall that had direct tension connections for tension columns carrying a larger lower element below.  Columns attached to bottom flange of beams spaning walkways above.  Engineer had spec'd A325 bolts to be welded to bottom flange at bolt head for erection purposes.  Welding performed per requirements and was fully compliant with plans.  Hung the iron, tensioned the bolts and left for the day.  The next morning the whole lower element (about 6000lbs) was laying on the concrete walkway.  Must have made one hell of a noise that night when it came down.  A look at the bolt head (TCB) post to failure revealed some very interesting fracture lines.  The steel erector immediately de-erected the remaining portions of the canopy that had connections with bolts that had been welded in like fashion.  We cut off the welded bolts and erected it again with new bolts and no welding.  More hassle for sure but nobody was dead out of the deal.
Welding A307 bolts with direction of the engineer?  Sure thing.  If you have ever had to puddle weld an anchor bolt to a column baseplate then you know the drill.  Preheat to burn off galvanizing and/or zinc plating little wirebrush action and let er rip with the low-hy.  Saves the butt of the concrete guy who screwed up anchor bolt placement.  Here in western Colorado,  everything I work on has some of this action to correct anchor bolt locations.  Procedure is torch slot baseplate of column, fabricate weld washer as required with drilled/ punched hole for anchor bolt to project through (now too short owing to weld washer thickness for full engagement of nut), preheat and remove plating on anchor bolt, plug weld/fillet weld remaing stub of anchor bolt to baseplate.  Works good as long as plumb and align of building is complete prior to final welding.  Last building mess I fixed for the local hack and whack erection company who preceeded me, had 143 anchor bolts repaired just this way.  Everyone, welded A307 anchor bolts to column baseplates.

DO NOT PERFORM THIS REPAIR AS OUTLINED TO ANY ANCHOR BOLT THAT INSTALLED INTO CONCRETE WITH EITHER EPOXY OR ACRYLIC ADHESIVE AS IS COMMONLY DONE.  WELDING HEAT WILL INSTANTLY DESTROY THE INTEGRITY OF THE ADHESIVE.  SOON AFTER APPLYING HEAT TO ADHESIVE ANCHORS IN CONCRETE YOU MAY NOTICE A RAPID ACCELERATION OF THE COLUMN TOWARD EARTH IF NOT PRPOPERLY BRACED!!!!

A LITTLE OFF THE TOPIC?  SURE IS!  BUT EVERYONE HERE KNOWS HOW EASILY SPECIFIC INFORMATION PERTAINING TO A PARTICULAR SET OF CIRCUMSTANCES GETS QUICKLY DISTORTED SO THAT IT IS VIEWED AS TO SUITABLE FOR GLOBAL APPLICATION IN ALL SITUATIONS. 
XPERTFAB
Parent - By jwright650 (*****) Date 06-11-2007 20:49
Chet,
HS bolts get a quick "No" answer if you ask the mfg of the bolt about it. I asked the bolt mfg (because the higher ups wanted to know why we couldn't weld) about tacking the head of a bolt to keep it from turning and they don't like the idea of any heat being applied as all of the other replies have stated already. I even posed this question to the AISC who didn't really answer my question at all, other than to say that it was a bad idea.

If the clip angles are being welded with fillet welds to make up the designed end reactions, it seems seal welding the bolts are a mute point regardless of the grade. I don't think that enginners like to try and calculate bolts and weld in the same joint, so it is either welded or bolted, but not both.
Up Topic Welding Industry / Technical Discussions / Welding high strength bolts

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