KiddT
Nuclear
- Feb 26, 2009
- 8
I was looking at using a forging support that would fall under the jurisdiction of ASME III subsection NF. One of forging materials available was A-668 which is mentioned as an acceptable material for NF in code case N-71. When I was looking up the allowable temperature for this material, I noticed that the Allowable Stress Intensity, Sm, and the Yield Stress, Sy, were given up to at least 650 F. However, the stress values for A-668 for Tensile Strength, Su, and Allowable Stress, S, only go up to 400 F. As the two values only go to 400 F I don't see how I could use this forging for an application exceeding 400 F. But on the other hand why would the Sy and Sm values be listed to a higher temperature than the forging can be used to? I was particularly confused because I thought I'd seen A-668 used in standard supports and rated to 650 F. If anyone can shed any light on this issue it would be greatly appreciated.