JPH0477446B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a magnetic caster used for magnetic focusing and magnetic shielding in induction furnaces and the like.

(Prior Art) In general, an induction melting furnace for melting metal has a heating coil wound around the outer periphery of a melting chamber made of refractory material.
Furthermore, a plurality of return path cores are arranged radially around this outer periphery and are supported inside the furnace frame.

In this induction melting furnace, magnetic flux is generated when an alternating current is passed from an alternating current power supply connected to a heating coil, and this magnetic flux interlinks with the molten metal (molten material) placed in the melting chamber, causing an induced current to flow. When this induced current flows, Joule heat is generated due to the resistance of the melting material itself, and heating and melting is performed.

In addition, the magnetic flux generated from the heating coil leaks to the outside of the coil in a loop, and metal furnace structures such as the coil holding fittings, furnace frame, and furnace bottom plate are also heated, so the magnetic flux returns to the heating coil. The magnetic flux is focused by the magnetic path core to reduce heat loss.

In addition, in recent years, the mainstream of induction melting furnaces is the increasing capacity of thyristor-type frequency converters, the widespread use of high-power high-frequency furnaces, and the demand for smaller furnace bodies. A problem has arisen in which leakage magnetic flux cannot be absorbed sufficiently.

For this reason, an attempt has been made to increase the space between the heating coil and the metal furnace body structure to prevent heat loss due to induction heating, resulting in an increase in the size and weight of the furnace body.

(Problems to be Solved by the Invention) The present invention solves the above problems and improves heating efficiency by interposing the heating coil and the metal furnace structure to focus leakage magnetic flux and prevent diffusion. The object of the present invention is to provide a magnetic caster which has excellent strength, insulation properties, and fire resistance, and is easy to mold.

[Structure of the Invention] (Means for Solving the Problems) The present invention is characterized in that fine ferromagnetic powder of 10 meshes or more is comprised in a weight ratio of 50 to 85%, and the remainder is made up of a hydraulic castable binder. It is something to do.

Hereinafter, the present invention will be described in detail. As the ferromagnetic powder used in the present invention, for example, water atomized iron powder or electrolytic iron powder is used. In this case, the ferromagnetic powder has a particle size of 10 mesh or more, which is resistant to oxidation, has excellent magnetic properties, is not easily heated by induced current, and does not act as an aggregate for the hydraulic castable binder. can improve the strength of

Note that if coarse ferromagnetic powder with less than 10 meshes is used, it will be easily oxidized by the heat of the molten metal, and its magnetic properties will gradually deteriorate.For example, if a large steel ball such as a shot is used, an induced current will flow through it itself. This is because it will be heated.

Further, as the hydraulic castable binder, alumina-based or silicon oxide-based castable cement is preferable, and if necessary, fibers such as alumina fibers or silica fibers may be mixed therein.

Further, the mixing ratio of the ferromagnetic powder and the hydraulic castable binder is preferably 50 to 85% by weight of the ferromagnetic powder.

A magnetic caster mixed and molded within this range can have excellent magnetic properties, strength, insulation, and fire resistance.

In this case, if the ferromagnetic powder is less than 50%, the magnetic permeability is low and the magnetic flux focusing effect is insufficient, and if the ferromagnetic powder is less than 50%,
If it is added in an amount exceeding 100%, the strength, insulation properties, and fire resistance will decrease, making it impossible to obtain the properties required for a furnace material.

The method for manufacturing the magnetic caster of the present invention involves mixing ferromagnetic powder and hydraulic castable binder in a predetermined ratio, adding water to the mixture, kneading it, pouring it, and then curing and drying it. It is something. This pour molding is done directly in the furnace.
In addition to pouring it, it may also be formed into a block separately and then placed in the furnace.

(Function) The magnetic caster of the present invention is molded by mixing ferromagnetic powder and hydraulic castable binder in a predetermined ratio, and has a particularly high mixing ratio of fine ferromagnetic powder of 10 meshes or more, so it has a magnetic permeability of 10 or more. It has an excellent magnetic focusing effect, prevents magnetic diffusion into the metal furnace structure, and reduces eddy current loss.Furthermore, since it uses fine ferromagnetic powder, it has no directionality.
Oxidation caused by heat can also be prevented.

Furthermore, since the ferromagnetic powder acts as the aggregate of the magnetic caster, the compressive strength is 300 kg/cm ² or more, which is equivalent to or higher than that of refractory bricks. Further, since the ferromagnetic powder has a high specific gravity, even if the powder is mixed in the above-mentioned weight ratio, there is a large amount of porous hydraulic castable in the volume ratio, and the powder has excellent insulation properties and fire resistance.

(Example) 70% by weight of water atomized iron powder of 20 to 250 meshes and 30% by weight of alumina-based hydraulic castable cement are mixed with water, formed into a block shape, and then made into a ring shape as a coil receiving refractory material. on which a heating coil was supported.

Further, a magnetic caster was formed into a ring shape and was interposed between the upper part of the heating coil and the coil holding fitting.

When we measured the magnetic permeability of the magnetic caster molded in this way, it was μ = 14, and the compressive strength was 1500.
Kg/ ^cm2 was also hot.

When the above induction melting furnace was operated, the leakage magnetic flux passing through both ends of the heating coil was focused on the magnetic caster, forming an effective loop passing through the return path iron core, and the magnetic flux linking both ends of the heating coil was reduced. and prevents diffusion to metal body structures.
The heating efficiency of molten metal was improved by 4% compared to the conventional method.

[Effects of the Invention] As explained above, according to the present invention, the heating coil is interposed between the heating coil and the metal body structure to focus leakage magnetic flux and prevent diffusion, thereby improving heating efficiency. , has excellent strength, insulation and fire resistance,
Moreover, it is possible to obtain a magnetic caster that is easy to mold.

Claims (1)

[Claims] 1. A magnetic caster comprising 50 to 85% by weight of fine ferromagnetic powder of 10 or more meshes, with the remainder being a hydraulic castable binder.