Yes, there is. A193 and A320 grades B8 and B8M are assumed to be Class 1 unless otherwise specified. Class 1 fasteners are carbide solution treated, while class 2 fasteners are carbide solution treated and strain hardened. The work hardening that occurs in the manufacturing of Class 2 fasteners increases their strength. Class 2 fasteners are differentiated by the letters “SH” after the grade marking on the fastener and an underline for both A193 and A320 fasteners. The marking typically appears on the heads of bolts or the ends of threaded studs. For both A193 and A320, the marking requirement historically was only the underline, the “SH” lettering was added in approximately 2006.
| ASTM Specification | Stainless Grade |
Application | Marking Class 1 |
Marking Class 2 |
|---|---|---|---|---|
| A193 Grade B8 | Type 304 | High temperature / High pressure | B8 | B8SH |
| A320 Grade B8 | Type 304 | Low temperature | B8 | B8 |
| A193 Grade B8M | Type 316 | High temperature / High pressure | B8M | B8MSH |
| A320 Grade B8M | Type 316 | Low temperature | B8M | B8M |
Marking of a320 b8m class2 Is this b8msh underline? Where are the references
@BoSang- Yes, A193 B8M class 2 requires an underline. The marking requirements can be found in table 5 within the ASTM A193 standard.
Hi,
We have 5/8 SS studs stamped with B8M however it is not underlined. Speaking to the suppliers (Australia) they have said (ASSUMED) that all class B8M studs are class 2 because class 1 is pretty much just a standard stainless rod and no one uses them. The Australian standard doesn’t specify the requirement for markings on bolts and requires the manufacturers specifications to be followed which I don’t have. have you ever heard of Class 2 – ‘B8M’ being written without the underline?
@Tom- No, all B8M studs are not class 2. Class 1 is by far the more common of the two. Class 2 are strain hardened and much less common/more expensive. The old requirement for class 2 was for a simple underline, but as of a couple years ago, the marking mas changed to B8MSH with an underline. If your product is nor marked properly, I’d say it does nor meet the standard for class 2.
what is the difference between B8 and B8C bolting?
The addition of Cb & Ta? Why are these elements added?
@Chris- The only difference as far as I can tell, is the additional chemicals you mention. We are not certain as to what these additional chemicals will do to the overall performance of the material.
Hello @Gary/@Dane,,B8 class 1 & 2 is available in ASTM grades both 193 & 320 ??
I mean it is used as per P-T requirements???
@Srivinayak- Yes, A193 and A320 are available in grade B8 in both class 1 and class 2. We are unsure of what P-T requirements are.
Hi ,
What happen if requirement need B8M CL 1 , but we supply B*M CL2 ?
@Noya- ASTM A193 B8M class 2 is stronger, but slightly less ductile than class 1. I wouldn’t think the substitution should be cause for alarm, but to be sure, the project engineer should be asked to approve it.
@Noya,,, Perfect question.. !!!
The allowable stress value is not mensioned about B8M Cl.2 for temperature. over 750 F in Table A-10, ASME B31.1. It is regarded that the Cl.2 is not recommended to use for high temperature. If you want to use those bolts, you’d better to check the service temperature.