20 min at 1800F. You can pull it out sooner or leave it in longer. The longer you leave it in, the more sanding you'll have to do to get back to metal. The sooner you pull it out the less uniform the austenite (if this matters to you).

The advantage of having a temperature-controlled forge is the control of oxygen. In a temp controlled forge you can wrap the blade with a steel foil and basically eliminate the O2 near the blade. I suppose that you could do this with no temperature control, but having visibility of the blade color is key without having some type of temperature readout on the blade.

Crucible Steel has a website that has some basic numbers for heat treating their metals.