Magnetization of ferromagnetic charge at induction heating

Abstract

The article presents analysis of magnetization and heating of ferromagnetic charge in crucibles of induction furnaces of two types. In inductor furnaces, the charge is magnetized by a vertical electromagnetic flow, and in electromagnetic furnaces with a curved U-, C-, or O-shaped magnetic circuit (MPr) – by a horizontal flow. Knowledge of these largely general magnetization processes is insufficient. Bi magnetic induction in charge material is rather important. There are difficulties in determining this parameter during magnetization of a single piece of charge and other magnetic quantities associated with it: Bm induction and Nm  strength of the demagnetizing field, N demagnetization coefficient, M magnetization, magnetic permeabilities of μi substance and μt body, km susceptibility, etc. Difficulties increase at magnetization, if it is a porous body with crucible volume of ~V t and a factor of filling with ferromagnetic pieces of this volume of Kv ≤ 0.5. It also creates a demagnetizing field with Bmt induction and Hmt strength. Beyond that, pores have an additional demagnetizing effect. Therefore, the induction Вiт in a porous body is less than the induction Вi in a solid one. To compare magnetization of ferromagnetic charge with horizontal and vertical flows with frequency of 50 Hz, modeling experiments were carried out with the samples of DSL08 unconsolidated shot from high-carbon steel (GOST 11964 – 83) with Kv ≈ 0.53. The samples were placed in the inductor and between the poles of a U-shaped core piece. Induction was measured by a cylindrical and flat probe unit of Sh1-15 militeslameter in air and in the sample. An advantage of electromagnetic furnace over an inductor one is more uniform distribution of Bi induction in charge and its significant excess (1.7 times) over the Be induction in a furnace working cavity, which indicates more efficient use of electromagnetic energy in this furnace during heating. The author proposed to control Вi induction when heating the charge by the ammeter-voltmeter method using measuring coil made of heat-resistant wire.