Are ASTM A 108 and ASTM A 325 materials equal?

[Dinosaur]

On a project under construction in my locality, the engineer specified ASTM A 325 studs to be welded to a baseplate for a later attachment. The Contractor wishes to weld studs using a prequalified process that states the studs have to meet ASTM A 108. Are ASTM A 325 studs and ASTM A 108 studs compatible? Is it then OK to weld ASTM A 325 threaded studs to a plate in much the same fashion as welding stud shear connectors to a top flange? I don't recall ever hearing about welding ASTM A 325 material as has been proposed in this case, but I am no welding expert. Thanks for your help.

 

[metengr]

No, ASTM A325 is a Standard Specification for Structural Steel Bolts that are heat treated. The ASTM A108 Specification is for carbon steel, low alloy steel bar produced to straight length or coil. For your application, I would not have the contractor use a pre-qualified WPS. They need to qualify their WPS on actual A 325 bolt material.

My position on welding of A 325 fasteners is that it is not a good engineering practice. The A 325 fasteners are supplied in a heat treated condition and any welding performed on these fasteners must be carefully considered because the heat from welding will adversely affect mechanical properties.

 

[Dinosaur]

Thanks Metengr. My boss is in agreement with you that we should not be welding A325 material.

The contractor will most likely want to proceed using A108. In further reading today, I have noticed that ASTM A400 calls out the mechanical properties of various grades of ASTM A108 steel studs. Do you have any knowledge regarding which grade most nearly corresponds to A325 material? In this situation, the stud will have to have adequate capacity for total as well as fatigue loadings. Are A108 studs the right thing to use when fatigue loading is significant?

Thanks.

 

[metengr]

Dinosaur;
Why should the contractor proceed with this approach? Who is running the job? If having no other choice in the matter, I would at least select ASTM A 108 material of similar chemical composition and heat treatment as the A 325 fastener material.

 

[metengr]

You need to know the Type (1 or 3) of ASTM A 325 material.

 

[kenvlach]

Agree with metengr that A325 fasteners should not be welded. Have some doubt that such welding is legal (maybe if tested or de-rated), but I'm not a judge.

You should be questioning the engineer as well as the contractor. Especially, if an A325 item is welded to a plate (many times its thermal mass), the Q+T will not restore the original properties. Rather than trying to match the A325's composition, consider air-hardening material.

I also believe it's improper to specify stud or threaded rod as A325 per se. If necessary,
“Threaded rod material with properties meeting ASTM A325, A490, and A449 specifications may be obtained with the use of an appropriate steel (such as ASTM A193, grade B7) quenched and tempered after fabrication.”
--- Manual of Steel Construction, LRFD, vol. II, p. 8-90 (1997).
Note that the foregoing applies to the manufacturer, not necessarily to PWHT.

Questions: Re PWHT of threaded items, are threads protected from oxidation, e.g., using a temporary brush-on coating? If not, should ASTM F2328-05 Standard Test Method for Determining Decarburization and Carburization in Hardened and Tempered Threaded Steel Bolts, Screws and Studs, be considered?
[first version published in 2004, don't have a copy]

http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/F2328.htm?L+mystore+fcfb0840

Happy Holidays!
Ken