Should be fine. What you don't want is to over shoot greatly. Over shooting is a bad thing, it can drive the carbon out and the steel will not harden. Under shooting nothing really happens since the steel did not get hot enough to get the phase change (grain structure) needed to harden.
Thank you Blue. I can easily keep from overshooting by no more than 5 degrees. Like I said, I may well be able to stabilize the temperatures by increasing temperatures slower. The unit turns the heating element on/off I assume based on the voltage modified by a thermocouple in the unit. No way to really tell as old as the unit is. But I assume if I increase the temperature slowly the amount of time the heating elements are on will decrease and so will the temperature swing.
I had to repair some of the insulation inside the unit and I still have to figure out how to seal the hole that the thermocouple goes through. That in and of itself should stabilize the temperature inside the unit and limit the heat loss and as such the temperature swings. I was able to reach 1200 degrees in 45 minutes and it took less than 15 minutes to go from 1200 to 1750 degrees. So, I'll have to watch myself on the annealing process after I shape the piece.
Here are the hardening instructions for the 3V tool steel. I do not have the capacity for the hardest option as my kiln is limited to
below 1900 degrees. I have bolded and minimized the font for the two 'harder' options for 3V steel. I can get to the 'Maximum Toughness' temperatures though it approaches the limit of the temperatures I'm able to reach.
Hardening
Preheating
: 1500-1550°F (816-845°C), equalize.
Austenitizing (High Heat): Heat rapidly from the preheat.
For Maximum Wear Resistance: Furnace or Salt Bath: 2000-2050°F (1093-1121°C)
Soak for 20 minutes minimum at temperature.
For Balanced Wear & Toughness:
Furnace or Salt Bath: 1950°F (1066°C)
Soak for 20 minutes minimum at temperature
For Maximum Toughness:
Furnace or Salt Bath: 1875-1900°F (1024-1038°C)
Soak for 45 minutes minimum at temperature
Quenching: Air,
pressurized gas, warm oil,
or salt.
For pressurized gas, the furnace should have a minimum quench pressure of 4 bars. For oil, quench until black, about 900°F (482°C), then cool in still air to 150-125°F (66-51°C), then cool in still air to 150-125°F (66-51°C).
For salt maintained at 1000-1100°F (538-593°C), equalize in the salt, then cool in still air to 150-125°F (66-51°C).
Tempering: Temper immediately after quenching. Typical temperature range is 1000-1100°F (524-593°C). Do not temper below 950°F (510°C). Hold at temperature for 1 hour per inch of thickness, 2 hours minimum, then air cool to ambient temperature. Double tempering is required.
Triple tempering is recommended when austenitized at 2000°F (1093°C) or above and when tooling will be wire EDM'd from a solid block after heat treatment.
Annealing
Annealing must be performed after hot working and before rehardening.
Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1600-1650°F (871-899°C), and hold at temperature for 1 hour per inch of maximum thickness; 2 hours minimum. Then cool slowly with the furnace at a rate
not exceeding 50°F per hour (28°C per hour) to 1000°F (538°C). Continue cooling to ambient temperature in the furnace or in air. The resultant hardness should be approximately 241 HBW.
