Stay away from hot plates and camp stoves under a quench tank (This spells disaster!!!).The tank does not need a heating element,either. Just heat up a bar of steel and stick it in the tank. Do this a few times until the oil is about 120F. That will be fine for maybe 15 minutes. A roasting thermometer clipped to the tank side will tell you the oil temp. If it drops below 100, stick a hot bar of steel in again. The exact temperature of the quench is not all that important. 100 to 130 is the desired range.The proper quenchant is far more important than its temperature.
To make a tank heating tool,do this. Take a round bar of 1/2" mild steel about 3to4' long. Heat it to bright red about 4" up from the end. Bend it back on itself to make a double thickness,4" long. Heat it 4" up again and bend the doubled section back on the shaft. Hammer this all down .The extra mass at the tripled end will heat a bucket of oil fast.One note of caution. When you stick the heating tool (or any red hot seel) into the oil, don't pull it out until it stops gurgling and rumbling. If you pull it out too soon, it will burst into flames as it vaporizes the oil on the hot metal.If this (when this) happens, just stick it back in the oil and let the flames go out. Let it cool down again before removing it.Quenching indoors is a NO-NO unless your shop setup is specifically designed for it.
Stacy