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Weldable Bolts and Nuts

Weldable Bolts and Nuts

Weldable Bolts and Nuts

Where can information be found regarding what types of bolts and nuts are weldable.  And from that, can these welds be designed using the same parameters as those for "typical" steel members?

We want to use a threaded rod or bolt as a tension/compression member between two pieces of steel approximately 24" from each other.  The bolt would extend through holes in each piece of steel.

Due to accessibility, we prefer to weld a nut to only one side of each piece of structural steel.  With the bolt in tension, the nut would bear directly against the steel.  With the bolt in compression, the nut would transfer forces through a weld (all-around) to the structural member.

RE: Weldable Bolts and Nuts

Depending on how much strength you need, nuts made from ASTM A-36 carbon steel are easily weldable and left as-welded--no PWHT required.  Do NOT use the common A-194 Gr. 2H nuts, even tho they're also carbon steel--the carbon level is too high to leave them as-welded, which I would assume you'd like to do.

You can also weld A-325 type/grade C nuts for higher strength, and also leave them as-welded.

Be advised that fillet welds, such as you plan on using, do not in general have real good fatigue-crack resistance, so if your loads change rapidly/frequently from tension to compression make sure you take that into account.

RE: Weldable Bolts and Nuts

I would contact fastener manufacturers and get information regarding their weld nut products.  For structural applications, you should use projection weld nuts.  These products are designed to be welded and not degrade the material properties.  Some manufacturers to consider are:

Textron Fastening Systems - http://www.textronfasteningsystems.com

Emhart Teknologies - http://www.emhart.com

RE: Weldable Bolts and Nuts

MetalGuy, thanks for the info; is this published any place?  I haven't seen information in typical engineering books, though I haven't looked too hard.

CoryPad, great references.  Unfortunately, the particular loads in this situation are too great for any of their fasteners.  I looked up projection nuts at Buckeye Fasteners / Ohio Nut & Bolt Company, but even they fall short of the particular load we are trying to transfer - about 4500 lbs via a 3/4" threaded rod through a nut and into a plate.

RE: Weldable Bolts and Nuts

Dunno-I suppose it is somewhere.  But what I wrote is probably well known to many metallurgists.

RE: Weldable Bolts and Nuts

If I understand your design correctly, you wish to place a 4500 pound compression load on a 3/4" column 24" long?  Seems kinda risky.  A lot of weight on a relatively small column.
If you are going to weld nuts to both members, how are you going to thread the bolt in place?  Or are they to be welded after the nuts are in place?
If you must pursue this, perhaps use a sleeve over the bolt between the members to increase the compressive capacity.

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