The simple answer is none. The two specifications were written in tandem to be identical. The only difference between the two bolts is intended application. A193 bolts are intended for high temperature and high pressure applications, while A320 bolts are for cold temperature applications. Both bolt grades are made from type 304 stainless steel, have the same mechanical requirements, identical chemical requirements, and same head markings. If you were to hold one of each bolt in your hand, there would be no way to tell which is which, because they are the same.
This also applies to the common A193/A320 stainless grades including B8M, B8 Class 2, B8M Class 2 that we often provide, but also some of the less common grades such as B8P or B8A.
| Grade | Material | Size | Tensile, ksi, Min | Yield, ksi, min | Elong, %, min | RA, %, min | HBW | HRC |
|---|---|---|---|---|---|---|---|---|
| A193 B8 | 304 Stainless | All | 75 | 30 | 30 | 50 | 223 max | 35 max |
| A320 B8 | 304 Stainless | All | 75 | 30 | 30 | 50 | 223 max | 35 max |
| A193 B8M | 316 Stainless | All | 75 | 30 | 30 | 50 | 223 max | 35 max |
| A320 B8M | 316 Stainless | All | 75 | 30 | 30 | 50 | 223 max | 35 max |
If you have any questions about stainless steel bolts, please give one of our friendly team members a call, and we’ll be happy to help.
Dear Nate,
Do advise what is the main difference in testing of SA320 and SA193 B8 since above is all same but vendor here was offering SS304 for an EYE BOLT whereas client spec called for SA320 B8, kindly confirm
BR,
Nabeel Tahir Butt
Lead Procurement Engineer
Descon Engineering FZE
Hamriyah Free Zone, Phase I, P.O. BOX: 42576, Sharjah, UAE
T +971 6 5269020 EXT 727 M +971 54 7911866 F +971 6 5269053
E nabeel.tahir@descon.com W http://www.descon.com
@Nabeel- A320B8 and A193B8 are virtually identical unless you are using the A320 in the cryogenic range. There are however, differences in manufacturing and testing between A320/A193 bolts and bolts only called out to SS304. ASTM A320 and A193 have testing procedures, mandatory processes (like solution annealing), minimum mechanical properties, and product marking requirements. When you specify a bolt to SS304, you are only specifying the chemistry, nothing else. If your client is needing an A320 B8 bolt, that means it should be manufactured and tested in accordance with A320, so I would not want to substitute a SS304 bolt without specific authorization.