I just scored some 2 1/4" round 4150 for a awomse price..Anyway Im looking for the as quenched hardness and any other tips you may have for 4150..Ive worked with a lot of 4140, Im thinking not much different just higher hardness..Please correct me if Im wrong..Thanks

I LOVE 4150! Used to make a lot of my tooling with a pile I had. Oil quench only, of course. Minimum 400 draw otherwise just depends on use.

Thanks, I picked up eighteen inches of 2 1/4" round for less than $11 shipped on ebay...Couldent believe it...
Im thinking about a couple of hammers and some handles tools...

With 50 points carbon your theoretical maximum hardness is about 60 RC, and of course it'll be pretty deep hardening. That's about all I can tell you.

Quenching temp 1525 -1625ºF.

4140 as-quenched Jominy sample (quenched from 1550F) is 60 Rc at 1/4" from end. 50Rc at 1/2" from end. (per ASM's Atlas.) 4160 should be at least as good.

In the section sizes you have, 4150 will be very nearly through hardening, assuming a sufficiently fast cooling rate. For blacksmith tools requiring good toughness, you will probably want to temper at 900 F or so. For many tools like hardy swages and bolsters you should be able to use it in the as forged or normalized condition. You could also fan cool the grade from the austentizing temperature to get a slightly harder tool than just a straight air cool. This will greatly reduce the risk of quench cracks which are common in this grade if stress risers or significant changes in cross section are present. If higher hardness is desired, such as for a hammer face, then the 400-500 F temper range as Grant suggested will be good. It has sufficient carbon that it will hold a decent, though not great edge. It is not really a grade designed for edge tools. In larger sizes, you may encounter it with a surface hardening treatment such as induction or flame hardening. It will not have the toughness or hardenability of a 4340, but that is probably not a significant concern in the sizes you are dealing with.