SA 307 Gr. B (Yield Stress and allowable Stress) 1

[ksquare]

Hello, can any body tell why there is no minimum specified yield stress for the SA 307 Gr.B in ASME Section II Part D? It has a minimum specified tensile strength of 413 MPa and relatively low allowable stress (only 48.3 MPa, why?). Can any of you explain for this. Any help will be appreciated.

 

[metengr]

Yes. If you review SA 307, this is a material specification for carbon steel bolting and studs that are specified by tensile strength only, and not yield strength.

 

[ksquare]

metengr,
you are right, there is no yield strength for this material. Do you have any idea why this happen? is that mean it don't have any elastic limit? (seem incorrect??) how do i justify its allowable stress by lower down it by some safety factor according to ASME Sect II Part D, (eg, 2/3 Yield, ST/3.5). Code state 48.3 MPa for its allowable stress regardless of its servise temperature and i wonder why such a low allowable stress since its minimum tensile strength is 413 MPa. Thanks in advance.

 

[metengr]

ksquare;
These bolts and studs are intended by ASME B&PV Code for service where local yielding is not permitted. If you look at the allowable stress (7 Ksi) for this material in Table 3, the stress is controlled by TS, and not by YS. Also, this material is not permitted above 450 deg F.

Yes, these studs do have an elastic limit. I would use the allowable stress values for service in accordance with ASME, Section II, Part D, Table 1.

 

[metengr]

Yes, these studs do have an elastic limit. I would use the allowable stress values for service in accordance with ASME, Section II, Part D, Table 1.

correction, Table 3, not Table 1.

 

[ksquare]

metengr,
How about if i'm using it for structural purpose (eg, anchor bolt for skirt vessel) instead of flange bolting? I understanding the code might limit its allowable stress because do not damage the flanges (might be very expensive) due to its overstress on the bolt. My thinking is, will its allowable stress be higher if base on other structural code. some reference book allow the tensile stress go for 20 KSI. Thanks