JP2000169247A - Induction furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a refractory having a structure of lining material into which different components are not readily permeated standing even a high- temperature use and prolonging a useful life and a furnace lining material capable of safely and stably carrying out an operation. SOLUTION: In a refractory for lining an induction furnace useful for melting and refining a metal containing a rare-earth metal material and a rare-earth metal component and an alloy of the metal and an iron-based metal, the refractory comprises 3-15 wt.% of silicon carbide 55-97 wt.% of aluminous material and 0-30 wt.% of mullite in which the content of the two or the three is 90 wtr.% and the content of the three components of SiC, Al2O3 and SiO2 is >=85 wt.% and 0-20 wt.% of a sintering auxiliary to give the objective induction furnace comprising a lining material composed of a dry refractory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction furnace used for melting and refining rare earth materials and metals containing rare earth components, and alloy materials of these metals and iron-based metals. .

[0002]

BACKGROUND OF THE INVENTION Conventionally, these metals have been dissolved and / or
Refining is generally carried out at very high temperatures due to alumina (A
l_TwoO_Three  97% by weight or more)
Is used. First, dry lining
Fork-shaped jigs, rammers, and vibrations on the hearth using fire
Using appropriate jigs such as vibration exciter
After that, a steel middle frame (hereinafter referred to as “former”)
And the inner wall of the former and the furnace body,
Put it in the place of the specified lining material thickness and
Construction by vibrating and filling while applying vibration from inside
It is used while gradually heating and sintering the entire foam.
At present, high heat resistance is required for use.
The dry amorphous refractory used has an alumina content of 97
Dry type refractory of more than weight% is generally used
Selects metal and slag components that are molten in the furnace.
Conductive phenomena due to permeated metal by selective absorption
Occasionally, the oxidation phenomenon occurs and the tissue becomes more vulnerable
Defects such as the surface layer peeling phenomenon that makes it unusable for use
It is at present that there is a congruence. Cause these phenomena
With a high degree of damage, the service life is short and stable
If the life is not attained, sometimes catastrophic damage occurs and
Not only does it go away, but if the degree of damage is
It becomes a big problem such as damage. For this reason, furnace shutdown and maintenance
You have to work on this irregular event
Production work has been stopped, causing a major hindrance to production activities.
Add This necessitates maintenance work on the lining material.
The dismantling and construction of the upholstery is a severe 3K work with a lot of dust under high temperature
In industry, this frequency increases. From the above situation,
Furnace operation and stable use of furnace lining materials
Furnace maintenance work, which has a long life and is a severe 3K work
It is currently strongly desired to reduce opportunities for
It is.

[0003]

As described above, refractories generally used at present are dry amorphous refractories having an Al ₂ O ₃ content of 97% by weight or more. During use, the components of the molten metal and slag are selectively absorbed into the structure of the refractory. This infiltration forms an altered layer, or the infiltrated metal partially oxidizes in the tissue, causing deep cracks and cracks parallel to the operating surface, causing a layer-like exfoliation phenomenon and penetrating into the tissue. The oxidized metal causes the metal to become fragile. As these three phenomena are further promoted as use proceeds, damage accelerates and service life is shortened. As described above, a foreign material does not easily penetrate into the structure of the lining material, and it also provides a refractory material that can withstand high-temperature use and has a prolonged service life. The challenge is to reduce the opportunities for

[0004]

In view of such a situation, the present inventor has conducted a detailed investigation of the actual condition of the furnace, conducted various studies on the basis thereof, and conducted various studies. As a result, the refractory used here is currently used. The alumina content of 97% by weight is inherently low in sintering performance, making it impossible to form a dense and strong layer on the operating surface. I have. Suitable refractories have the property that they do not easily absorb and melt the components of the molten metal, and do not cause the weakening of the structure or the occurrence of cracks due to the formation of a deteriorated layer inside and the separation. No residual shrinkage due to heat reception or foreign material penetration during use. The material must always have residual expansion and no cracks. It has been found again that it is necessary to have characteristics such as excellent heat-resistant spoilability. The refractory which can solve the above-mentioned various problems can be obtained by repeating the research on the refractory applicable to these various conditions and conducting a practical test.

That is, the current alumina material (97% by weight of Al ₂ O ₃ ) cannot easily form a dense structure which can prevent the penetration of the molten metal slag component, and is inherently easily permeated. It has various properties that cause problems such as having residual shrinkage ability at high temperature, but its heat resistance has a melting point of 2080.
It has high heat resistance of as high as ° C. and low chemical reactivity in a wide range from general molten metals and acidic to weakly basic. Focusing on this point, the present inventor has conducted various studies to prevent the selective absorption and penetration of the molten metal slag and components by taking advantage of the high heat resistance of the alumina material and the low reactivity of the molten metal with the molten metal slag. It has been found that it can be improved by adding a material to form a composite material.

Further, the addition of the silicon carbide-based material results in a residual expandability in a high-temperature range, and the thermal shock resistance is also improved. In addition, it was also found that the addition of a mullite-based material was effective in further increasing the residual expansion resistance and thermal shock resistance. The proper blending amount of these two or three is that the silicon carbide raw material is 3 to 15% by weight and the alumina raw material is 55 to 55%.
97% by weight of mullite raw material is 0 to 30% by weight, the combined amount of these two or three is 90% by weight or more, and SiO ₂ ,
It was possible to obtain a preferable result that the total amount of the two components of Al ₂ O ₃ was 85% by weight or more. Based on the results, the materials of Examples of the present invention shown in Table 3 are now generally used by applying the raw materials shown in Tables 1 and 2 to dry-shaped amorphous refractories of which the particle size and composition have been adjusted and lining materials of induction furnaces. 97% by weight of the alumina used, 0 to 2% by weight of a dry amorphous refractory to which a suitable sintering additive such as boric anhydride is added, and the effect of improving the defect can be improved and the service life can be improved. It is an object of the present invention to provide an induction furnace capable of resolving various problems at present by greatly improving the above.

Reason for limitation The amount of the silicon carbide material is 3 to 15% by weight. When the content is 1-13% by weight or less, the penetration of the molten metal slag is prevented,
The effect on residual swelling is small and does not lead to comprehensive improvement. 1-2 When the addition is 15% by weight or more, no significant difference is observed in the effect of addition, the improvement is almost the same, and the erosion rate increases as the addition increases. The content of the mullite material is 0 to 30% by weight. The addition of the mullite material allows the sintering to proceed in the case of alumina only due to the heat received during use, but the addition of the mullite material improves the thermal shock resistance due to the composite effect of the material. %, The improvement effect is almost horizontal. On the other hand, as the amount of addition increases, the tendency of erosion to increase increases. The compounding ratio of the alumina material is 55 to 97% by weight. A
This is because 97% by weight of l ₂ O ₃ does not lead to improvement of the permeation phenomenon of the molten metal slag component in the tissue, and if it is 55% by weight or less, the erosion resistance tends to decrease. 0 to 2% by weight of a suitable sintering aid such as boric anhydride. The amount of the sintering additive such as boric anhydride is adjusted depending on the temperature used, but if it exceeds 2% by weight, the heat resistance may be reduced. 2-3 of silicon carbide, alumina, and mullite materials
The total amount of raw materials is 80% by weight or more. The combined amount of the above two or three is 90
If the content is less than 10% by weight, the possibility of impairing the corrosion resistance may occur. If the total amount of the three components of Al ₂ O ₃ , SiC and SiO ₂ exceeds 85% by weight, and if the components other than the above three components exceed 15% by weight, there is a possibility that the corrosion resistance may be reduced.

Next, an embodiment will be described. The required characteristics as a lining material for induction furnaces are: Exhibit residual swelling by receiving heat during use. 2. 2. Low penetration of molten metal slag into tissue. Since properties such as high heat resistance and high corrosion resistance are required, in order to obtain a refractory for lining that meets these conditions, Table 1 shows examples of the chemical composition of the raw materials used, and Table 2 shows the particle configuration values of the test materials. Shown in

[0009]

[Table 1]

[0010]

[Table 2]

(Manufacturing Method of Test Material) The test materials were prepared by using the raw materials shown in Table 1 and weighing a predetermined amount of each ground raw material according to the embodiment of the present invention shown in Table 3 and mixing them by a mixer. . The mixing of the various raw materials may be performed once, but the fineness of 0.1 mm or less may be mixed in advance and then the whole may be mixed. And use it as test material.

[0012]

[0013]

[Table 3]

[0014]

[Table 4]

Table 3 A-1 is an example of the product of the present invention as a comparative material used as a material for lining an induction furnace used under the above conditions. After shaking and filling with a vibrating plate, a copper foamer designed to form a predetermined lining refractory thickness (80 mm) is installed inside the furnace main body, and a flat plate-like vibrator is inserted during this time. A bar is inserted and the refractory is vibrated and filled sequentially while being directly vibrated, and a mixture of sodium silicate and water in a ratio of 1: 1 with the same material at the top of about 50 mm is used as a binder to obtain 6%. After adding and kneading the material with an air rammer and sintering it, it is kept at a low temperature of about 800 ° C. for 10 hours and sintered, and then gradually heated to start melting, and the melting temperature is 1750 ° C. And sintering at high temperature for 120 minutes. The production is performed in the same process. As a result, in the comparative material, sticking of slag became larger than that of about 10 ch, and 1
Partial surface peeling and two vertical cracks occurred on the 4th channel, making it unusable on the 23rd channel while performing repair. However, the material of the present invention had little sticking of noro and no cracking was observed.
From the time past the channel, the adhesion gradually progressed, and the first repair was performed at 35 ch.
The service life up to 2ch was shown.

[0016]

[Table 5] Practical test results Operating conditions Furnace volume 0.6 High frequency induction furnace Melted material ND-Ce-Fe-based material Melting temperature 1650 ± 15 ° C Lining construction method Vibration method using dry amorphous refractory and foamer Sintering Temperature rise at 200 ° C / 60min. 1750 ° C. Hold for 2 hours.

[0017]

Effects of the Invention alumina material (Al ₂ O ₃ 97 wt%) composite of two parties or three parties that the alumina material by weight percent silicon carbide material 3-15 wt% mullite material 0-30 wt% By using the material, the residual shrinkage and thermal shock resistance of the material are improved, and at the same time, the addition of the silicon carbide-based material also suppresses the penetration of the molten metal into the structure. Oxide (noro) adhered to the surface without generation and the service life was greatly improved from 23 ch to 42 ch, and the result of a large improvement of 182.6% was achieved. The furnace shutdown due to the maintenance of the furnace has been halved, production activities have progressed smoothly, and at the same time, the chance of 3K work for lining material maintenance has been reduced to about half. .

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[Procedure amendment]

[Submission date] December 8, 1998 (1998.12.
8)

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[0002]

BACKGROUND OF THE INVENTION Conventionally, the melting and / or refining of these metals is generally at very high temperatures due to alumina (A).
high purity, high dry type amorphous refractory (l ₂ O ₃ 97% by weight or more). Construction of the lining material is first by a dry monolithic refractory hearth portion fork-shaped jig and rammer, vibration
After compacting using a suitable jig such as a vibrator such as a moving plate , a steel middle frame (hereinafter referred to as a “former”) is disposed at a predetermined position, and an inner wall portion of the former and a furnace body is provided. It is installed by applying vibration to the inside of the former while applying vibration to the place where the thickness of the lining material is set, and the former is used while being gradually heated and sintered together with the former. Due to the demand for heat resistance, dry amorphous refractories currently used are generally dry amorphous refractories having an alumina content of 97% by weight or more, but metals and slag that are in a molten state in a furnace The current situation is that the metal that has penetrated by the selective absorption of the component causes a conductivity phenomenon and sometimes causes an oxidation phenomenon, and the tissue becomes brittle, causing a large amount of surface delamination and making it unusable for use. so That. Due to these phenomena, the degree of damage is large, the service life is short, and a stable life cannot be obtained.Sometimes, sudden damage is caused and it is not possible to withstand use. Becomes For this reason, the furnace must be stopped and maintenance work must be performed, and this irregular event causes the casting work in the manufacturing plant to be stopped, which greatly hinders production activities. For this reason, the frequency of the disassembly and construction of the lining material, which necessitates the maintenance work of the lining material, is increased by heavy 3K work with a lot of dust at high temperature. In view of the above situation, it is strongly desired that the above-mentioned problems can be solved and the stable operation of the furnace and the service life of the furnace lining material can be improved and the opportunity for maintenance work of the furnace, which is a heavy 3K operation, can be reduced. That is the current situation.

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Further, the addition of the silicon carbide-based material results in a residual expandability in a high-temperature range, and the thermal shock resistance is also improved. In addition, it was also found that the addition of a mullite-based material was effective in further increasing the residual expansion resistance and thermal shock resistance. The proper blending amount of these two or three is that the silicon carbide raw material is 3 to 15% by weight and the alumina raw material is 55 to 55%.
97% by weight mullite raw material is 0 to 30% by weight, the combined amount of these two or three is 90% by weight or more, and SiO ₂ ,
It was possible to obtain a preferable result that the total amount of the two components of Al ₂ O ₃ was 85% by weight or more. Example material of the present invention shown in Table 3 From the results in Table 1, raw materials used granularity shown in Table 2, by a dry monolithic refractory adjusting the structure and induction furnace lining material construction now commonly 97% by weight of the alumina used, 0 to 2% by weight of a dry amorphous refractory to which a suitable sintering additive such as boric anhydride is added, and the effect of improving the defect can be improved and the service life can be improved. It is an object of the present invention to provide an induction furnace capable of resolving various problems at present by greatly improving the above.

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[0012]

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[0014]

[Table 4]

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(Results of practical test) Comparative materials used as lining materials for induction furnaces used under the above conditions are shown in Table 3 A-
One material is an example of the product of the present invention, and Table 3 and B-3 material are used for vibration-filling with a hearth vibrating plate of an induction furnace, and then the thickness (80 mm) of a predetermined lining refractory is formed inside the furnace body. A copper former designed to be formed is installed, and a flat vibrating rod is inserted while the former is being inserted, and while the refractory is directly vibrated, it is sequentially vibrated and filled while vibrating and filling the refractory material to a thickness of about 50 mm at the top. A mixture of soda and water in a ratio of 1: 1 was used as a binder, and 6% was added. The kneaded material was cast by using an air rammer, and the mixture was sintered at a low temperature of about 800 ° C. for 10 hours. Thereafter, the temperature is gradually increased to start melting, and the melting temperature is maintained at 1750 ° C. for 120 minutes, high-temperature sintering is performed, and the material of the present invention and the comparative material, which are actually used, are manufactured in the same process. As a result, in the comparative material, the adhesion of the slag increased more than around 10 ch, the surface layer was partially peeled off and two vertical cracks occurred at the 14 th channel, and the comparative material became unusable in the 23 ch while performing repair. The adhesion gradually progressed from 28 ch with little adhesion and no occurrence of cracks was observed, the first repair was performed on 35 ch, and the service life up to 42 ch was shown by using the slag while repairing.

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[0016]

[Table 5] Practical test results Operating conditions Furnace volume 0.6 High frequency induction furnace Melted material ND-Ce-Fe-based material Melting temperature 1650 ± 15 ° C Lining method Vibration method using dry amorphous refractory and former Sintering 200 ° C / The temperature rises in 1 minute at 1750 ° C for 60 minutes, and then enters general use after holding for 2 hours. ────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 11, 1999 (1999.1.1)
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[Procedure amendment 1]

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Further, the addition of the silicon carbide-based material results in a residual expandability in a high-temperature range, and the thermal shock resistance is also improved. In addition, it was also found that the addition of a mullite-based material was effective in further increasing the residual expansion resistance and thermal shock resistance. The proper blending amounts of these two or three are 3 to 15% by weight for the silicon carbide raw material and 55 for the alumina raw material.
To 97% by weight , the mullite raw material is 0 to 30% by weight, the combined amount of the two or three is 90% by weight or more, and SiO
2. It was possible to obtain a preferable result that the total amount of the two components of Al2O3 was 85% by weight or more. From these results, the materials of Examples of the present invention shown in Table 3 are now generally used by using the raw materials shown in Tables 1 and 2 and using dry amorphous refractories of which the particle size and composition are adjusted as the lining material of the induction furnace. 97% by weight of alumina used, 0 to 2% by weight
Can improve the effect of improving the defects of dry amorphous refractories to which appropriate sintering aids such as boric anhydride have been added, and can greatly improve the service life and solve various problems that are currently encountered The present invention provides an induction furnace capable of performing the above.

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[0014]

[Table 4]

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[0016]

[Table 5] Practical test results Operating conditions Furnace capacity 0.6 ton high-frequency induction furnace Melted material ND-Ce-Fe-based material Melting temperature 1650 ± 15 ° C Lining construction method Using dry amorphous refractory and foamer Vibration method Sintering Temperature rise at 200 ° C / 60 minutes 1750 ° C, hold for 2 hours, then enter general use.

Claims (1)

[Claims] 1. A refractory for lining an induction furnace used for melting and refining rare earth materials and metals containing rare earth components and alloys of these metals and iron-based metals. 15 wt%, SiC content of 2's or 3's an alumina material with 55-97 wt% mullite material with 0-30% by weight at 90 wt%, Al ₂
When the content of the three components of O ₃ and SiO ₂ is 85% by weight or more,
An induction furnace, wherein a lining material is constructed of a dry-type irregular refractory characterized by comprising 20% by weight of a sintering aid.