What's the diff between A193-B8 and A320-B8M for SS stud bolts?

Question

What's the diff between A193-B8 and A320-B8M for SS stud bolts?

KernOily (Petroleum)

(OP)

24 Jun 02 20:20

Do any of you fine fellers know what the difference is between ASTM A193 grade 8M and A320 grade B8M stud bolts in SS? If I am calling out a 316/316L SS stud bolt, what is the difference between these two specs?

Thanks ! ! ! !

Thanks!
Pete

owlscreech (Mechanical) · Answer 1 · 2002-06-24 23:28:26

A193 is the Standard Specification for Alloy-Steel and Stainless Steel Bolting Materials for High-Temperature Service. A320 is the Standard Specification for Alloy/Steel Bolting Materials for Low-Temperature Service. The former is the "standard" most commonly used for valve and flange bolting. The latter usually requires better control on grain structure and passing certain destructive tests to measure low temperature ductility.

B8 designates a chemistry similar to 304
B8M designates a chemistry similar to 316 (where the M stands for molybdenum).

316 is the standard 18Cr-10Ni-2Mo with 0.08C max
316L is basically 316 with .03C max.

The L grade is to increase resistance to intergranular corrosion after welding. (Less carbon means less chance of sensitization). Since bolting is not welded I am not sure you can get it that way.

Therefore, if you are looking for a 316 bolt for high temp then use A193-B8M.

For low temps use A320-B8M.

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What's the diff between A193-B8 and A320-B8M for SS stud bolts?