... mm more than the application of intermediate frequency (0.5-10 KHz) 2,heat treatment, shaft, gear, quenching and annealing ... layer0.2-0.8mm applicable UHF 100-250 KHz, high-frequency 1.0-1.5mm applicable 40-50 ... KHZ20-30mm above the tool to apply high-frequency 10-50 KHZ, super audio 30 mm above the tool applies ... to 1-8 KHZ IF4, melting gold, silver, copper, lead and ...