JP2723903B2 - Induction electric furnace - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an induction electric furnace, in particular, an induction coil is provided outside a cylindrical cement container, and the inside of the cement container is provided with a refractory lining. It concerns a covered induction furnace.

[Prior Art] In a conventional induction electric furnace of this type, an amorphous refractory is generally used for a lining made of a refractory provided inside a cement container. In some cases, fixed refractories were also used, in which case, for example, magnesia-spinel fired bricks were used.

[Problems to be Solved] For this reason, there have been problems such as that sufficient durability cannot be obtained with the conventional induction electric furnace.

The present inventors have conducted various studies on lining materials for induction electric furnaces in order to solve these problems, and as a result, have accomplished the present invention.

[Means for Solving the Problems] (1) That is, the present invention relates to an induction coil provided on a substrate, a cylindrical cement container provided inside the induction coil, and an inner peripheral surface of the cement container. An induction electric furnace having a covering lining, wherein the lining is formed of magnesia-carbonaceous fired brick.

Preferably, the cylindrical portion of the lining opposed to the induction coil via the cement container is formed of magnesia-carbonaceous fired brick, and the bottom of the lining opposed to the substrate is magnesia-carbonaceous fired brick or magnesia. -Formed by chromium fired bricks.

(2) The present inventors have attempted to construct the lining of an induction electric furnace from magnesia-carbonaceous brick and utilize the excellent properties of magnesia-carbon in order to solve the above-mentioned problems of the conventional lining. Was. As a result, it has been found that the following problem occurs when unfired magnesia-carbonaceous brick is used.

That is, since magnesia-carbonaceous brick contains carbon (carbon) and has conductivity, it is heated by the heat applied during preheating or melting of the material to be melted.
Gaseous carbon components are generated from unfired magnesia-carbonaceous bricks. The gaseous carbon component leaches out of the cement container through joints of the unfired magnesia-carbonaceous brick constituting the lining and cracks or gaps in the cement container, and precipitates near the induction coil. Since the deposited carbon component has conductivity, it causes a problem of damage (short circuit or corrosion) of the induction coil.

Therefore, the present inventors have conducted further studies to solve these problems, and as a result, when fired magnesia-carbonaceous brick is used, such problems do not occur, and the excellent magnesia-carbon has They found that properties could be used for lining.

(3) In the induction electric furnace of the present invention, since the lining covering the inner peripheral surface of the cement container is formed of magnesia-carbonaceous fired brick, even if the material to be melted is heated during preheating or melting, it is gaseous. Is not generated, or even if it is generated, its amount is so small that it does not matter. For this reason, the precipitation of the carbon component in the vicinity of the induction coil is avoided, and as a result, the problem of short-circuit or corrosion of the induction coil is prevented.

Examples Next, the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment of the induction electric furnace of the present invention.

(Configuration of Induction Electric Furnace) In FIG. 1, reference numeral 10 denotes an induction electric furnace of the present invention,
A substrate 11 formed of an appropriate material, an induction coil 12 disposed on the substrate 11 and connected to an appropriate power supply and having a cooling facility (not shown), and disposed inside the induction coil 12; A cylindrical cement container 13, a mica sheet 14 disposed on an inner peripheral portion of the cement container 13, and a mica sheet
Fiber ceramic sheet placed on the inner circumference of 14
15 and a magnesia-chromium fired brick 16A which is an inner peripheral portion of the fiber ceramic sheet 15 and is provided on the substrate 11 with only an appropriate layer (two layers in FIG. 1) as a "bottom portion" of the lining; 16B and a magnesia-carbonaceous fired brick 17 which is an inner peripheral portion of the fiber ceramic sheet 15 and is disposed on the magnesia-chromium fired bricks 16A and 16B as a `` tube portion '' of the lining. .

The thickness of the cement container 13 may be 20 to 100 mm,
In particular, about 50 mm is preferable. The thickness of the cement container 13 is 20 to
The grounds for 100 mm are (i) if it is smaller than 20 mm, the induction coil 12 may be damaged when the lining (particularly magnesia-carbonaceous fired brick 17) is removed, and (ii) if it is larger than 100 mm. In addition, the inside of the induction electric furnace 10 and thus the volume of the melting space cannot be sufficiently secured.

The mica sheet 14 is provided to facilitate removal of the lining tube, that is, the magnesia-carbonaceous fired brick 17 from the inner periphery of the cement container 13.

The fiber ceramics sheet 15 is provided to absorb the thermal expansion of the lining tubular portion, that is, the magnesia-carbonaceous fired brick 17, and to prevent the induction coil 12 from being deformed or damaged. Therefore, the thickness of the fiber ceramic sheet 15 is appropriately determined according to the coefficient of thermal expansion of the lining (particularly, the magnesia-carbonaceous fired brick 17).

(Procedure for Producing Induction Electric Furnace Brick) Next, the procedure for producing the brick used in the induction electric furnace 10 of the present invention will be described.

The magnesia-carbon fired brick 17 is manufactured as follows.

For 100 parts by weight of a magnesia material having a maximum particle size of 5 mm having at least one kind of magnesia clinker, electrofused magnesia or natural magnesia clinker, a carbon material 5 having a maximum particle size of 0.2 mm having a maximum particle size of 0.2 mm is used. Up to 25 parts by weight and at least one of aluminum, silicon, magnesium, etc.
1 to 5 parts by weight of an antioxidant additive of 2 mm and 2 to 10 parts by weight of a binder such as a phenol resin are put into a kneader and kneaded with each other. The kneaded product is formed into a predetermined shape by a press device such as a friction press or a hydraulic press, heated and dried, and then fired in a reducing atmosphere.

Thus, the magnesia-carbon fired brick 17 is manufactured.

The magnesia-chromium fired bricks 16A and 16B are manufactured as follows.

For 100 parts by weight of a magnesia material having a maximum particle size of 5 mm having at least one kind of magnesia clinker, electrofused magnesia or natural magnesia clinker, and having a maximum particle size of 3 mm comprising chromite or electrofused magnesia-chromium And 10 to 50 parts by weight of a chromium material, together with 2 to 5 parts by weight of a binder such as a phenol resin, are put into a kneader and kneaded with each other. The kneaded product is formed into a predetermined shape by a press device such as a friction press or a hydraulic press, and dried by heating.
Bake at an ultra-high temperature.

Thus, magnesia-chromic fired bricks 16A, 16B
Is manufactured.

(Guidelines for Construction of Induction Electric Furnace) The induction electric furnace 10 of the present invention includes the magnesia-carbon-fired brick 17 and the magnesia-
It is constructed as follows using the chromium fired bricks 16A and 16B.

First, a cement tube is provided inside an induction coil 12 provided on a substrate 11 formed of a suitable material and having a suitable cooling facility, thereby forming a cylindrical cement container 13.

Next, the mica sheet 14 and the fiber ceramic sheet 15 are sequentially arranged along the inner peripheral surface of the cement container 13.

Thereafter, a plurality of magnesia-chromium fired bricks 16A and 16B are sequentially arranged on the inner side of the fiber ceramic sheet 15 and on the upper surface of the substrate 11 using, for example, mortar, and laminated in two layers. This forms the “bottom” of the lining. Note that the magnesia-chromium fired brick does not need to have two layers. At least one layer is sufficient.

Finally, a plurality of magnesia-carbonaceous fired bricks 17 are placed inside the fiber ceramic sheet 15 and on the magnesia-chrome fired bricks 16A, 16B (i.e., the "bottom" of the lining) using, for example, mortar. To form the "tubing" of the lining.

Thus, the induction electric furnace 10 having the configuration shown in FIG. 1 is constructed.

(Guidelines for Using Dielectric Electric Furnace) The procedure for using the induction electric furnace 10 of the present invention is as follows.

In the induction furnace 10, magnesia-chromium fired bricks
The lining formed by 16A, 16B and magnesia-carbonaceous fired brick 17 forms a cylindrical melting space with an open upper surface. Therefore, the material to be melted is introduced into the cylindrical melting space. In this state, when an alternating current having an appropriate frequency is supplied to the induction coil 12, the material to be melted generates heat in the melting space, and as a result, the material to be melted is melted appropriately.

The material to be melted into a liquid state by heating is supplied to the induction electric furnace 10
By tilting it, it can be moved to the following device.

(Confirmation test) Using the induction electric furnace 10 of the present invention, a confirmation test of the operation and effect of the present invention was performed in the following manner.

First, 85 parts by weight of magnesia clinker having a maximum particle size of 5 mm or less and 10 parts by weight of scale graphite were mixed with each other, and kneaded while adding 5 parts by weight of a phenol resin as a binder. Thereafter, the resulting kneaded product was subjected to pressure molding by a press device, and then dried. Next, the obtained compact was stored in a gold slaughter box at 900 ° C.
And fired for reduction for 10 hours. Thus, a magnesia-carbon fired brick 17 was obtained.

Also, after mixing magnesia clinker with a maximum particle size of 5 mm or less and 70 parts by weight and chromite ore with a maximum particle size of 3 mm or less and 30 parts by weight, 5 parts by weight of a phenol resin as a binder Was added and kneaded.
Thereafter, the resulting kneaded product was subjected to pressure molding by a press device, and then dried. Next, the obtained molded body was fired at an extremely high temperature in a tunnel-type firing furnace to obtain magnesia-chromium fired bricks 16A and 16B.

In addition, the inside diameter of the cooling device is located on the substrate 11.
Inside a 1800 mm copper induction coil 12, a cylindrical cement container 13 having an inner diameter of 1700 mm and a thickness of 50 mm was formed. Then, on the inner peripheral surface of the cement container 13, a mica
A sheet 14 was provided, and a fiber ceramic sheet 15 having a thickness of 2 mm was further provided inside.

Subsequently, inside the cement container 13, magnesia-chromium fired bricks 16A and 16B were disposed on the substrate 11 so as to have a two-layer structure, and a bottom portion of the lining was constructed.

Finally, on the magnesia-chromium fired bricks 16A and 16B, a magnesia-carbon fired brick 17 was arranged along the inside of the fiber ceramic sheet 15 to construct a lining cylinder.

Thus, the induction electric furnace 10 of the present invention having the configuration of FIG.
I got The inner diameter of the cylindrical space (namely, the melting space) formed by the magnesia-carbonaceous fired brick 17 (namely, the cylindrical portion of the lining) was 1500 mm.

In the melting space of the induction electric furnace 10 of the present invention thus obtained,
The process of heating and melting 30 tons of ferrochrome per time was repeated, and even if heating and melting were repeated 120 times, there was no short-circuit accident of the induction coil 12 caused by carbon deposition. Was.

On the other hand, as the induction electric furnace of the comparative example, a magnesia-carbonaceous unfired brick having the same composition as that of the above magnesia-carbonaceous fired brick 17 but not firing was used to form the cylindrical portion and the bottom portion of the lining. . Otherwise, the configuration was the same as that of the induction electric furnace 10 in FIG. The size of the melting space was set to be the same as that of the induction electric furnace 10 shown in FIG.

The process of heating and melting 30 tons of ferrochrome per time was repeated for the induction furnace of the comparative example thus constructed in the same manner as in the case of the induction furnace 10 of the present invention. A short-circuit accident of the induction coil occurred due to carbon deposition.

From this result, the induction electric furnace 10 of the present invention, in which the lining cylinder was formed using the fired magnesia-carbonaceous brick 17, formed the lining cylinder and the bottom using the unfired magnesia-carbonaceous brick. It was confirmed that it had excellent durability as compared with the induction electric furnace of the comparative example.

In the above embodiment, the cylindrical portion of the lining is formed by a plurality of magnesia-carbon fired bricks 17, and the bottom of the lining is formed by a plurality of magnesia-chrome fired bricks 16A, 16B. Is not limited to this. (I) At least one of the tubular portion and the bottom portion of the lining is integrally formed,
The present invention also encompasses a case where the remainder is formed of a plurality of magnesia-carbonaceous fired bricks or a plurality of magnesia-chrome-based fired bricks, and (ii) a case where both the cylindrical portion and the bottom portion of the lining are integrally formed as a whole. You. Also, (iii) the case where both the tubular portion and the bottom portion of the lining are formed of magnesia-carbonaceous fired bricks is included in the present invention.

Further, in the above embodiment, the cylindrical cement container
A mica sheet 14 and a fiber ceramic sheet 15 are arranged between the lining 13 and the lining, but the present invention is not limited to this. If desired, mica
At least one of the sheet and the fiber ceramic sheet may be removed.

[Effects of the Invention] As is clear from the above description, in the induction electric furnace of the present invention, it is possible to improve durability while preventing problems related to the induction coil such as short-circuit or corrosion of the induction coil.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of an induction electric furnace according to the present invention. 10 Induction electric furnace 11 Substrate 12 Induction coil 13 Cement container 14 Mica sheet 15 Fiber ceramic sheet 16A, 16B Magnesia chrome-based fired brick 17 Magnesia carbon-based fired brick

Claims (4)

(57) [Claims] An induction electric furnace comprising an induction coil provided on a substrate, a cylindrical cement container provided inside the induction coil, and a lining covering an inner peripheral surface of the cement container. The induction electric furnace, wherein the lining is formed of magnesia-carbonaceous fired brick. 2. An induction electric furnace comprising an induction coil provided on a substrate, a cylindrical cement container provided inside the induction coil, and a lining covering an inner peripheral surface of the cement container. The cylinder of the lining facing the induction coil through the cement container is formed of magnesia-carbon fired brick, and the bottom of the lining facing the substrate is magnesia-carbon fired brick or magnesia-fired brick. An induction electric furnace characterized by being formed of chromium fired brick. 3. A car seat according to claim 1, wherein a car seat is disposed between said cement container and said lining.
Item 3. The induction electric furnace according to Item 2 or 2. 4. The induction electric furnace according to claim 1, wherein a mica sheet and a fiber ceramic sheet are disposed between the cement container and the lining.