Don't worry about grain size when you are forging... just make sure it stays HOT when you're moving metal. As long as you don't create fractures, normalizing will fix all the "wrong" you've done during the forging process. YOU NEED TO NORMALIZE AFTER FORGING. Start your normalizing at 1650F to make sure everything gets into solution. Then use lower heats during subsequent cycle to refine grain and not undo what we are trying to accomplish. In between cycles the steel only needs to form another structure from which to renucleate... when it becomes magnetic again, you're there! Then you can ramp back up for the next cycle. Here is a good starting regime that will work for most carbon steels...
- Heat to 1650F, cool to magnetic.
- Heat to 1525F, cool to magnetic.
- Heat to 1475F, Quench in warm oil. Medium speed(for O1) if you have it... canola if you don't.
- Heat to 1300F (make sure you don't go non-magnetic) and cool to black. Repeat 2-3 times and quench in oil on the last.
Yes, you end your last normalization cycle with a hardening quench. You don't have to, but I recommend it. If you choose not to, at least quench from black to avoid coarse pearlite and other unwanted structures. That last 1300F bit is a sub-critical anneal(or at least a redneck version of it.) Proper spheroidizing would be best but for those without the equipment, this does the trick.
Now, you have dead-soft annealed steel all set up for a great final quench. For O1, without a controlled kiln, I would forgo any attempt to soak and just heat it to 1500F and quench.
Rick