Q: So I was told that 17-4PH Group 630 bolts per ASTM F593 are heat treated to H1150. So how is a 17-4PH F593 bolt any different from the standard 17-4PH H1150 bolt, as they both have the same heat treatment?
A: Great question. Yes, you are correct, they are both are heat treated to H1150. Often when you see F593 listed it will state ASTM F593 Group AH. The AH denotes age harden which is per H1150. The difference between a standard H1150 bolt and one per F593 is that the ASTM F593 specification includes additional requirements for dimensions, sampling, workmanship, testing etc.
To clarify further F593 is a specification that applies to the bolting and is limited to only the H1150 heat treatment. If addition strength and mechanical properties are required beyond those allowed by H1150, you can combine an ASME or DIN dimensional spec with ASTM A564, a raw material spec, which includes additional heat treat/age harden conditions including H1150D, H1150M, H1150, H1100, H1075, H1025, H925 and H900. This combination will give you additional strength options.