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A320 Stud Specs

A320 Stud Specs

A320 Stud Specs

My company's purchasing department currently specifies A320-GR8 material for low temp service flange studs, and asks for the studs to be stamped 'FB8'.  I have a couple of points I'd appreciate some help on before I jump up and down at them.

1. According to the most recent copy of A320, there isn't a stud material called 'GR8'.  There's a grade 8 nut and washer described in A194, but no bolt or stud by that designation.  Was this once a grade in previous revisions of A320?

2. 'FB8' - Again, my copy of A320 doesn't contain this.  There is a 'B8F'.  Could this be a throwback to a previous edition or is it more likely a typo?

LewTam Inc.
Petrophysicist, Leading Hand, Natural Horseman, Prickle Farmer, Crack Shot, Venerable Yogi.

RE: A320 Stud Specs

Nomenclature of engineering specifications can sometimes be confusing. My guess is that someone was trying to use their own product identification scheme instead of using the Standard Specification product marking requirements. For the SA-320 (Standard Specification for Low Temperature Bolting), Grades are used to describe type of materials, while Classes are used to describe specific strength levels or heat treatment condition pertaining to a Grade of material.

So, for your SA-320 Low Temperature Bolting, you have Grades B8, B8C, etc.. For specific Classes of material Grades you may have Class 1 or 1A, etc.. Marking B8 would suffice for Grade, not GR8. Studs ordered as Grade B8F are sulfur containing, austenitic stainless steel studs for improved machinability, and have nothing to do with application to flange studs using “F”.

Regarding markings for bolting, SA-320 references marking of studs in Section 14 titled “Product Marking”.  

RE: A320 Stud Specs

ASTM A320-97 (in the 1999 Annual Book v. 01.01) also contains B8, B8F, B8FA, etc., and not 'FB8.' Info agrees with that of metengr.

Appears to me that B8F is 303 SS, available in Classes 1, 1A & 2 -- [carbide] solutionized, solutionized in finished condition & solutionized+strain hardened, respectively.

A320/A320M seems to be the most often modified ASTM standard: (20)00, 00a, 00b, 01, 02, 03, 04, 05 & 05a are the most recent versions!

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