Hello All,
I need to know if welding of High Strength Bolts (say Grade 5 or A325) to Steel Plate (A36) is advisable or not. I came accross this and thought it's not good practice to do. If yes, then do we need to follow any special procedure or not.
I appreciate any response in the matter.
Regards,
PA
PA
Everything I have seen says that they are not made to weld.
A325 Structural Bolts, Steel, Heat Treated, 120/105 ksi Minimum Tensile Strength
That being read you would have to develop a procedure and have it approved by the EOR.
I have seen Engineers allow tacking nuts to plates in a blind splice connection for a HSS (Square Tube) on bridge chords.
But besides the high strength issues with your weld procedure also consider that a fastener assembly has a lubricant applied and it is essential for proper Tensioning and when you apply heat from welding it changes this also.
Good Luck
Marshall
I can save you a call to the bolt mfg. regarding this. They will answer with a big fat "No". I posed this question and they will not guarranty the fastener after you weld or impose any amount of heat on the high strength fastener.
I also called the AISC about this and they maintain that it is not recommended, but .....like Marshall stated, it has been done before in blind locations where the nut or bolt head is inaccessable and signed off by the EOR of the project.
There are not any restrictions or prohibitions on capturing the nut or bolt head with additional plates that are welded down to prevent the nut or bolt head from turning or falling out. I vote to use this method where ever possible in lieu of welding.
Hope this helps.
PA,
Marshall and John are right on as far as 'Code' applications and even 'MOST' other applications. AND, it is never the best course of action.
My question would be, are you doing this in a structural or other code application? Maybe some equipment repair? As a makeshift threaded stud on A36 plate to bolt wood to, ie, steel to wood transition on some residential and even commercial buildings?
For what purpose is it being used? Some applications would be far more 'acceptable' than others though none is recommended. Just kind of personally curious what type of application we are talking about and how it caught your attention.
Have a Great Day, Brent
If you did this, or even hot dip galvanized the bolts after fabrication, they would no longer be ASTM A-325 bolts. You would have to re-test the bolts in accordance with the requirements of ASTM A325 after welding or galvanizing. If the P.E. wants to OK the use of your tack welded bolts, that is why he has the state license.
Joe Kane
But, assuming that the drawings are "approved" by the EOR, and if it called for a bolt or nut to be tacked or fillet welded, woulnd't that be proof that he approved of that method?
Doesn't mean it's the right way to go about it, but he approved the drawing, whether he looked at it or not is his responsability.
Chris
Not in My book! If the Engineer missed it-OK he bears some blame. If you the inspector knew about it, and didn't do anything about it, the blame should be on you!
How would you feel if someone got hurt because of a failure???
Joe Kane
Joe, I understand your position and where your coming from, its just that in this day and age I would think that whomever called for this condition and approved it should understand what they are asking for and approving.
There's a certian point due to time, schedules and ease of availableity that it's not always feasible to question every condition. Hopefully this would be picked up early enough in the process to be double checked and RFI'ed to be sure, but I know we don't always have that option. Then again it still could be RFI'd while the parts are being fabricated, and then they can figure out what to do if they have changed their mind.
Respectfully, Chris
eekpod
Chris I understand where you are coming from.
But shouldn't the Fabricator need to develop a procedure before welding? And wouldn't the fabricator need to get the Engineers approval?
Then there would be no questions where the responsibility lies.
Just my ΒΆΒΆ's
Marshall
Regardless of whether the engineer approved shop drawings or not, and the fact that it isn't a good idea to start with, the shop is still on the hook for 2 reasons. The first one is that most contracts have a clause that exceptions need to be pointed out as such. Just putting it on a drawing does not identify it as an exception, so even if the engineer missed it, he has an out if it was not identified as an exception/deviation. Secondly, I have never seen a qualified WPS for tacking or welding fasteners. It is obviously not pre-qualified, but even if you wanted to qualify a WPS, there is not bolt material available in a form that would meet the weld code (such as AWS D1.1) requirements for test plate dimensions, even for fillet welds. So if you are welding fasteners, it is not in accordance with any welding code.
No, it's not at all advisable, nor permitted, for a very simple reason: after the weld and HAZ have cooled down, they (the weld and HAZ) will have lost their High Strength properties and become plain mild steel.
Giovanni S. Crisi
Sao Paulo - Brazil
PS. Thanks to all those who have taught me the past participle of the verb "to lose"
Giovanni
for the verb lose the past participle is "lost"
Marshall
Giovanni,
I think you are looking for the word.... "lost"
edit* whoops...typed too slow again.
John
wish when I went to school typing class wasn't looked upon as a sissy class.LoL
Marshall
I always heard that 10 fingers were much faster than 2 :-)
John
So what you are telling me is you are ambidextrous?
Marshall
Yes, I can use "both" pointer fingers....
Hi-strength bolts should never be welded and for that matter should never be heat-straightened after mechanical damage. This is a common problem on the civil side of projects where high strength bolting is required. It is difficult enough to explain to to the welding fabricators why hi-strength bolts and common plain carbon steel bolts are so different without explaining this to the two of sand and one of cement crowd (or is it two of cement and one of sand? Either way it is not important like welding!)
nantong,
the "two of sand and one of cement crew" (right mixture, although I prefer three of sand and one of cement) isn't the same one that erect and weld structural steel. Here in Brazil the latter is better payed than the former.
Back in my days of erector engineer, I've erected structural steel and prepared and poured concrete, so I'm acquainted with both sides of civil construction. Both deserve respect.
By the way, I'm not a civil engineer, my degree is in chemical engineering.
Giovanni S. Crisi
G. S Crisi
In the USA,I see that a lot of the old weld shop floors appear to have been made with a 1 TO 1 mix ----that is one bag of concrete to one truck load of sand! They even had a name for it---"a one sack load".
Joe Kane
So you Know that a good foundation is critical. Long live concrete and steel!
I took typing class in High School just to meet girls. And I did.
Seriously though, I is an Engineer and we are specifically trained to know about welding on high strength bolts. And we are taught that this is not to be done for all the reasons stated. Sometimes you can get away with a tack, if it is on the non-loaded side of the nut but I don't recommend this. If the EOR says it is O.K. to weld a high strength bolt, that is his contractual responsibility. Although the EOR may be contractually correct, I applaud you in being morally correct to challenge this. And I don't have to tell you that we engineers make mistakes.
Bob G.
Hello All,
It's great to have so many response. and it seems so much is going on.
I had to have some suggestions as I knew it's not a good practice to do.
We are using A36 steel plates connecting with A325 Bolt. Bolt is tacked on Bolt-head to one of the plate.
What about shear strength of this bolt now? Is it same as per ASD book or different?
Thanks again all for your input.
PA
P.S.- I am going to weld Nelson Stud for my application......
If I were you I`d take a look at the tack welds and estimate their length. How long are they? One quarter of an inch or so? I`d leave them where they are.
First. When structural steel is designed, the engineer uses safety factors to compensate for that kind of problems that may occur.
Second. If the engineer has calculated a, say, twenty nine 32nds of an inch bolt diameter, this diameter doesn`t exist, so he`ll go straight to one inch diameter. That`s another safety factor.
Anyway, welding high strength bolts is a practice that shouldn`t be followed.
Giovanni S. Crisi
Agreed. Typically, welding is not allowed on high strength bolts. A325 bolts are subjected to a heat treating process to develop the strength properties necessary to meet the ASTM A325 specification. The heat generated from the welding process can alter the physical property the bolt. When heat is applied in an uncontrolled environment, it's impossible to determine how the heat effects the bolt. The AISC states that anchor bolt material that is quenched and tempered (heat treated) should not be welded or heated. Although A325 bolts are not anchor bolts, it's basically the same principle. ASTM F1554, an anchor bolt specification, prohibits the heating of high strength bolts, stating that hot bending performed on heat treated bar stock shall not have the temperature come within 100 degrees F of the tempering temperature of the heat treat process at any location during hot bending. Any process that applies heat approaching or exceeding the tempering temperature of a high strength bolt may potentially alter the mechanical properties of the fastener and should therefore be avoided.
Topic Welding Industry / Technical Discussions / Welding of High Strength Bolts to Carbon Steel Plates
