Welding of Gr. 5 and/or A325 Bolt

[Unistrut]

I have a project where I need to bolt a fixture to a plate. I have to weld a gr.5 or A325 bolt head to the back side of the plate with the bolt passing thru the plate. Then weld the plate to the top of a HSS column.
the bolt will see a 5000 lbs working load in shear.

Will the weld affect the integrity of the bolt?

 

[MintJulep]

Yes.

 

[Unistrut]

If it will affect the integrity, are there any porducts out there that I can use to still allow me to bolt to the plate?

 

[dik]

Can you use the Flowdrill or Ultra-Twist type of fastener? Alternatively, can you use an adhesive to temporarily hold the bolt? Using A325, are the magnitude of the loads high?

Dik

 

[teb1]

This may be over kill, but why don't you tap the hole through which the bolt is going to pass through, screw the bolt in from the back side and then "tack" weld the bolt head to the back of the plate?

tommy

 

[dik]

I think the point that MintJulep was making was that the welding is a bad idea... even to tack it... If you can obtain A325 with the thread to the head... then it is not necessary to tack... just thread it in...

Dik

 

[GRoberts]

You can weld some mild steel keepers that hold the bolt in and from turning, then you don't have to weld the bolt at all, but it will perform the same function.

 

[redrushin]

What if you have a plain end stud that is already welded down? Is there a standard/formula for calculating a reduced allowable stress?

 

[gtaw]

The magnitude of the load appears to be relatively low. Can you get by with an ASTM A307 bolt? You should have no trouble welding the A307 machine bolt.

The ASTM A325 bolt is quenched and tempered. Welding it will produce untempered martensite in the heat affected zone. If the weld is around the head of the bolt, the heat affected zone may extend to the shank of the bolt and result in a brittleness just where you don't want it, i.e., under the head of the bolt.

Best regards - Al

Best regards - Al

 

[Screwman]

What size bolt are you using? If you have to weld you should use an unheat-treated fastener as gtaw said. Welding hardened fasteners pretty much destroys the factory heat traeatment, so you in effect have grade 2 properties after welding. Except that you potentialy have the martensite that was mentioned. If you have the net strength of a grade two then you should just use a grade two.

 

[dik]

Welding can also promote a brittle fracture with A325 bolts...
not just a softening problem...
Dik