Probably not. What combination of properties are you looking for?
Rockwell hardness is often not an end in itself, rather it's a
convenient indicator of the overall properties of a chunk of specific
material. For example, toughness and wear resistance will vary widely
between different materials of equal hardness.
Since you're asking about drawing back to Rc40-45, I assume you're
looking for something relatively strong and tough. In that case, 4140,
or a similar alloy steel, is a possibility. A socket head cap screw is
an example of alloy steel in this hardness range.
I am searching for some easy to get round stock that is dimensionally
correct without having to turn it, and is wear resistant enough to
accept a bearing while enduring heavy side loads. Something like an
axle. I'm aware of prehardened 4140 to RC 35-40 that is still
machinable, but I haven't been very happy with the finish I was able to
turn it to.
If all you need is a straight shaft, Thomson shaft should do the trick.
It has a hard case and a tough core. The usual stuff is .0005-.0010
under nominal, but there are other diameter limits (Thomson call them
"classes") available. McMaster carries the standard class in inch and
metric sizes starting on p.988. The hard case is machinable with
carbide, or it's possible to spot anneal with a torch, though it's best
to do this only on the ends of a piece if you need to maintain
Dowel pins are another possibility if you just need a simple pin.
If you need a more complicated shaft, "stressproof" will approach the
4140 prehard in strength/toughness, but is much nicer to machine. But it
will not be accurate enough as-is to use in a bearing. Look on the
bottom of McMaster page 3441.