Q: I am looking to eventually get a quote for some 3/8″ studs and nuts. I need to have a min yield stress of 29 ksi at 700F.  SA-540 Grade B22 Class 2 or SB-637 should work. Is this something you can provide?

A: These are very different materials: A-540 Grade B22 Class 2 and SB-637 (Inconel 718). For sure the Inconel 718 studs will give you the strength you need of 29 KSI at 700F but it may be a bit overkill. Inconel 625 should be a good fit for your application providing all the strength you need. Inconel 625 studs offer 144ksi ultimate tensile strength and 84ksi yield strength. It is also usable to approximately 1800F.  Inconel 625 fasteners will also be more economic than Inconel 718 fasteners. In addition, they may offer a shorter leadtime.

Q: What stud and nut material should I use with a ANSI 600# Alloy 800 HT pipe class max temperature 1650°F.

A: Given that you are at a high temperature and pressure I would recommend going with an Inconel 625 stud. This will provide the best combination of high temperature strength. Inconel 625 bolting can be used to temperatures of about 1800°F. These fasteners also offer 144ksi ultimate tensile strength. Inconel 625 fasteners are known for their resistance to corrosive environments as well.