Investigation of electromagnetic furnaces with a C-shaped magnetic core

Abstract

The paper describes design features, methodology and results of the study of 10 induction electromagnetic crucible furnaces with a C -shaped magnetic core (MC). The core is covered by turns of an electric coil (EC) of small volume up to ~14.56 dm3. The furnaces have MC from a set of used transformer plates with a working volume of ~ 28.5 – 30.8 dm3, a capacitor bank (CB), the number of turns w = 23 – 50 of copper or aluminum wire, voltage 380 – 390 V, frequency 50 Hz. The water-cooled EC is placed in a rubber tank and creates a horizontal electromagnetic flow with induction of ≈70 mT, which is amplified by MC and directed beyond EC into a larger working volume of ~30.7 dm3 between its poles with induction up to ≈100 mT. When placing a steel crucible in the volume, induction increases up to 125 – 150 mT and the experimental furnace EMC‑30.7‑23A with a capacity of 44 kVA allows melting 21 kg of silumin at a speed of 10 °C/min in 65 min, which is faster than in the resistance furnace СAT‑0.16 with a power of 40 kW in 2 h. With strong compression of MC plates, the noise decreases from 80 – 85 to 40 – 48 dB. To increase the furnace efficiency, it is proposed to use pole plates with a width of 155 mm, mineral wool in the thermal insulation of the crucible, tuning capacitors in CB, and EC from copper cable. For melting of high-temperature alloys, it is advisable to connect this furnace to a step-up transformer in order to increase the current density from 3.7 to the permissible 20 A/mm2, power in the EC – CB circuit, and EC induction. The authors suggest to continue research on electromagnetic furnaces made from cheap transformer scrap to determine the scope.