Published Rupture and Creep Data for A193 B8M Bolt Material 2

[REP2]

I am looking for published information for the following A193 B8M Class 2 Bolting Material:

- Average stress for creep rate of 0.01% per 1,000 hrs
- Average stress for rupture at end of 10,000 hrs
- Minimum stress for at the end of 100,000 hrs

This is for determining design stress values per ASME B31.3. Any references would be welcomed.

 

[metengr]

REP2;
Why not use allowable stress values published in ASME Boiler and Pressure Vessel Code, Section II, Part D? This leg work has already been done by Section II committee for Sa 193 Grade B8M2.

If you need allowable stress data for a specific service temperature, let me know.

 

[REP2]

Metengr,

Thanks for the reply. I forgot to mention that I was looking for data from 1050F to 1200F. For this material no values are presented. Sorry. I have a B16.5 flange application where I want to use this material and the application is for a Class 600 application and only design stress values are available for a A193 B8M class 1 material.

 

[blacksmith37]

You may really want relaxation data ; The stress in the studs drops, reducing "clamping" force on a flange gasket leading to leaks.

 

[metengr]

This material is not permitted for service temperature above 1000 deg F for Section VIII, Div 1 because the strength properties are signifcantly reduced because this Class requires solution treatment for maximum corrosion resistance followed by strain hardening. You loose the effects of strain hardening over 1000 deg F.

What I am saying is do not use this Class of material above 1000 deg F because it is unpredictable.

 

[REP2]

Metengr,

Thanks again for the reply. I am going to limit the design temperature to 1000F in agreement.

Do you know what is the difference in the B8M class 1 and class 2 material that would allow class 1 material to be permitted over 1200F? Class 2 has a higher minumum yield 50 ksi vs 30 ksi for Class 1. I have seen B8M Class 1 MTRs that have a 51 ksi yield stress. Under B31.3 this material would meet the requirement that flanges class 400 and higher have a minimum yield higher than 30 ksi. Having said this B16.5 requires an intermediate strength bolt which is 50 ksi which this bolt would meet if only yield is considered. For this reason I wanted to compare the elevated temperature properties.

 

[metengr]

Actually, I discovered an error on my part, the SA 193 Grade B8M Class 2 is limited to 800 deg F, not 1000 deg F. If you can get SA 193 Grade B8M2 versus B8M Class 2, you can get to 1000 deg F.

If you review ASME SA 193, the following are RT properties, followed by allowable stresses from Table 3, Part D;

B8M2 Class 2B; 80-95 Ksi UTS, 55-75 Ksi for YS (allowable at 1000 deg F is 18.8 Ksi)

B8M Class 2; 90-110 Ksi UTS, 50-95 Ksi YS (allowable at 800 deg F is 12 Ksi)

B8M Class 1 75 Ksi UTS, 30 Ksi YS (allowable at 1000 deg F and 1200 deg F is 11.3 and 7.4 Ksi, respectively).

Class 1 has no strain hardening requirement as a means to increase tensile strength, so Class 1 can be used safely at elevated temperature, above 1000 deg F.

 

[btrueblood]

"What is the diff. b/n Class 1 and Class 2"

Class 1 is solution annealed material. Class 2 is strain hardened, as metengr. posted earlier. Annealed material is already "soft", and won't anneal further due to heating.

 

[REP2]

Thanks to all for the help!