Magnetization of a Ferromagnetic Charge during Induction Heating

Abstract

An analysis of the magnetization and heating of a ferromagnetic charge in the crucibles of two types of induction furnaces is given. In induction furnaces, the charge is magnetized by a vertical electromagnetic flux, and in electromagnetic furnaces with a curved U, C or O-shaped magnetic circuit (MCR)—by a horizontal flux. Insufficient knowledge of these largely general processes of magnetization is shown. The importance of the magnetic induction B_i in the charge material is reflected. Difficulties in determining this parameter during the magnetization of a single piece of the charge and other magnetic quantities associated with it are revealed: induction B_m and strength H_m of the demagnetizing field, demagnetization coefficient N, magnetization M, magnetic permeability of the substance μ_i and body μ_b, susceptibility k_m, etc. Difficulties increase with magnetization of charge, which is a porous body with a crucible volume V_b and a filling factor ${{K}_{v}}$ ≤ 0.5 of this volume with ferromagnetic pieces. It also creates a demagnetizing field with induction B_mpb and strength H_mpb. In addition, the pores have an additional demagnetizing effect. Therefore, the induction B_ipb in a porous body is less than the induction B_i in a solid one. To compare the magnetization of a ferromagnetic charge by horizontal and vertical flows with a frequency of 50 Hz, modeling experiments were carried out with samples of unconsolidated shot DSL 08 made of high-carbon steel (GOST 11964–83) with ${{K}_{v}}$ ≈ 0.53. The samples were placed in an inductor and between the poles of a U-shaped magnetic circuit. The induction was measured with cylindrical and flat probes of a Sh115 milliteslameter in air and in a sample. An advantage of the electromagnetic furnace over the induction one in a more uniform distribution of induction В_i in the charge and its significant excess by 1.7 times over the induction B_e in the working cavity of the furnace was found, which indicates a more efficient use of electromagnetic energy in this furnace during heating. It is proposed to control the induction В_i when the charge is heated by the method of an ammeter-voltmeter using a measuring coil made of heat-resistant wire.