JP2000274956A - Induction furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the refractory of an induction furnace which enables the extension of the life of the furnace and the stable operation. SOLUTION: An induction furnace, which is used for the fusion and/or refining of rear earth metal or metal containing rear earth metal, is of multilayer refractory structure, and the refractory for lining of the furnace is made in at least two-layer structure, and its working layer (the innermost part) is made of figurate refractory being manufactured by making at least its sidewall integrally of such material that cerium material of 74 micron or under is 5-50 wt.% and the rest is high alumina material of 75 wt.% or over in alumina content and/or a proper organic or inorganic deflocculant or hardener is added to alumina material and that they are kneaded, and applying heat treatment in a temperature range of 200 deg.C-1000 deg.C to it to put the porosity at 15% or under, and also the outermost part is made of dry amorphous refractory which has hot linear expansion property equivalent to or more than the inner member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing Ce, Pr, N
The present invention relates to an induction furnace used for melting and / or refining a metal containing a rare earth material such as d.

[0002]

2. Description of the Related Art Conventionally, melting and refining of metals containing rare earth materials such as Ce, Pr, Nd and the like are performed at a very high temperature of about 1600 ° C., so that the alumina content is 96% by weight or more at present. Alumina dry refractory or fixed fired refractory (hereinafter called crucible) is used.

[0003] In the installation of a lining material made of a dry type refractory material, the furnace bottom of the induction furnace is hardened, but a vibrating filling is performed and a furnace floor of a predetermined thickness is constructed. A mold made of steel (hereinafter referred to as “former”) is installed almost in the center of the furnace, and the alumina-based dry amorphous material refractory is put between the furnace body and the former, and then crushed or poured at once, and then put into the former at one time. Vibration filling while applying vibration from the inside of the furnace, or when using a crucible, crush and vibrate the bottom of the furnace with a dry amorphous refractory, and then place the crucible almost in the center of the furnace. The gap between the main body and the crucible is crushed or shaken and filled with dry amorphous refractory, and the upper end is sealed with a sealing material. In the former case, the service life is greatly affected by the quality of the construction, and a highly skilled technician is required.
K work is forced. In addition, the porosity is about 20% to 22% and the packing density is low because the construction body itself is constructed by crushing or shaking dry amorphous refractory. The crucible also has a porosity of 16% to 1 from the viewpoint of thermal shock resistance.
8% and a porous body. Secondly, since the material currently used from the use conditions is an alumina-based material, the material has a property of easily penetrating the different component melt as a material. The melting point of the rare earth metal dissolved here is Ce (cerium) of 8
04 ° C, Pr (praseodymium) is 640 ° C, and Nd (neodymium) is 1019 ° C, which are both low-melting metals and easily oxidizable, but are manufactured from alloys of these and Fe-based materials. When melting, the molten metal is in a very low viscosity state because melting and / or refining is performed at a temperature of about 1600 ° C. by a reduced pressure or vacuum induction furnace, and particularly the rare earth metal added is used for furnace wall refractories. It is in a state that easily penetrates into the tissue.

The rare earth metal that has penetrated into the refractory structure easily causes an oxidation phenomenon during the repetition of the furnace operation, causing volume expansion, destroying the refractory structure and weakening it, and at the same time altering the working layer. At the same time, a layer is formed and cracks are formed inside, and at the same time, slag mainly composed of oxides adheres to the working surface. When trying to mechanically remove this slag, the surface layer is irregularly peeled off from the cracks inside and becomes an uneven surface, and it is in a state where it easily penetrates into the tissue and adheres to the surface Damage will increase. Regardless of the degree to which the construction body made of dry amorphous refractory or the crucible is damaged, the damage is large, the service life is short, and the furnace operation is stopped suddenly, which is a great obstacle to production activities. At present, there is a strong demand for an induction furnace with a long service life that can improve this situation and enable smooth production activities.

[0005]

As described above, the present Ce.
As the lining material for induction furnaces for melting and refining metals containing rare earth metals such as Pr and Nd, refractories with an alumina content of 96% by weight or more are most suitable because of their usage conditions, and as dry amorphous refractories. The furnace is baked and baked and filled with shaking, or a fixed-form fired refractory crucible is used.Although alumina material is inherently heat resistant, molten metal and slag penetrate into the tissue when used. In particular, rare earth materials have Ce of 804 ° C. and Pr
Are 640 ° C and Nd is 1019 ° C, all of which are low-melting metals, and are melted and refined at a high temperature of around 1600 ° C. When the furnace is shut down and the metal is repeatedly used, the metal is oxidized by repeated use to weaken the structure of the lining material, or slag easily adheres to the surface layer and cracks occur in the inner layer. The cracks develop and cause surface delamination, increasing the degree of damage to the lining material, forcing a reduction in the service life, and suddenly shutting down the furnace. Under such circumstances, the short life of the lining material increases the chance of severe 3K work for furnace maintenance, and sudden shutdown of the furnace hinders production activities, and both are major problems. ing. In view of this situation, it is a technical object to provide an induction furnace that can extend the life of the furnace and enable stable furnace operation.

[0006]

In view of such a situation, the present inventors have examined the condition of the furnace in detail and made various investigations based on this investigation. It was confirmed that any of the crucibles having the following problems also occurred in the construction of the alumina-based dry amorphous refractory having a weight percentage of at least. Rare earth metals such as Ce, Pr, and Nd, which are low melting metals, easily penetrate into tissues. These permeated metals are conducted and detected by the hot water leak sensor, and the furnace is stopped. These infiltrated metals have a high oxidizing ability, so that they are easily oxidized by repeated use of the furnace to cause weakening of the structure and internal cracks, which causes a peeling phenomenon. When the working layer is partially peeled, the working surface becomes uneven, and the weakened layer is exposed, and the molten metal and slag are attacked, so the penetration and adhesion of the molten metal and slag increase, further increasing the damage. Become. It is the current situation that failures are overlaid on failures.
It has been concluded that preventing the infiltration of the molten metal and / or slag into the tissue is the greatest means for solving these problems.

Based on this result, the present inventors have conducted various studies,
As a result of repeated practical tests, Ce (cerium) becomes an oxide, and its melting point increases from 804 ° C. to 2650 ° C., and becomes a highly heat-resistant material. It was found that the material produced from this cerium oxide had the lowest penetration and the lowest erosion. Based on this result, the result of a test of replacement with the most systematically weak joint as a lining material,
Increasing the amount of addition increases the improvement effect. 5% by weight as material on the lining material (74 microns or less)
It can also be confirmed by experiments that the addition of up to 50% by weight is within an appropriate range. As a lining material for an induction furnace, 5-50% by weight of cerium oxide (CeO2) and the balance of Al
It is preferable to form a molded body using an appropriate organic and / or inorganic binder on an alumina material having a 2O3 content of 90% by weight or more and heat-treat it at 200 ° C to 1000 ° C.
In addition, in order to improve the furnace maintenance workability and the quality safety of the lining material during the dismantling and construction of the furnace, which is an extreme 3K work, at least the side wall of the inner layer part should be a one-piece molded product and the porosity should be 15% or less. The outer layer is made of high-alumina dry amorphous refractory and the outer layer is made of a multi-layered structure to improve service life, stabilize furnace operation, reduce furnace maintenance work, It is an object of the present invention to provide an induction furnace capable of improving the effects of improvement such as vertical startup operation after repair.

[0008]

[Reason for limitation] The particle diameter of the additive material of cerium oxide (CeO2) should be 74 microns or less. Bonding between particles is substantially established in a particle diameter region of 74 microns or less. Since the permeation of the molten metal or slag is concentrated at the inter-particle joints, to prevent this phenomenon, it is effective to configure the particle area with a cerium oxide material. The compounding amount of cerium oxide is 5 to 50% by weight. When the amount of cerium oxide is 5% by weight or less, the improvement of the alumina material is small, and the reason for setting the amount to 50% by weight is that almost all of the coupling member is replaced. The Al2O3 content of the alumina raw material is set to 75% by weight or more. When the Al2O3 content becomes 75% by weight or less, S
Other components mainly composed of iO2 are increased, and the reaction with cerium oxide is increased to form a low melt, thereby deteriorating heat resistance and corrosion resistance. The porosity of the integrally molded product is 15% or less. Even if cerium oxide is used as a material for reducing the permeability of the molten metal slag, if it has high porosity, there is a problem that the penetration becomes large. In order to improve this problem, the porosity is preferably set to 15% or less. The heat treatment of the molded body is set to 200 ° C to 1000 ° C. If the heat treatment temperature is lower than 200 ° C., the removal of the contained water or the hardening of the binder is insufficient, resulting in problems due to the strength of handling and residual moisture during use. A multi-layer system consisting of a furnace wall sleeve and a backing material (dry type refractory). Even if the working layer becomes sintered due to the heat received during use, the back layer can move freely without hardening due to the heat received. In addition, when dismantling, it has a back material that has not been solidified, so that it can be easily dismantled. The outer layer member of the lining material (dry type refractory) has a higher hot linear expansion than or equal to that of the inner layer member (standard refractory). It is more effective that the outer layer member, which restrains the inner layer material (regular refractory) from the outer peripheral portion and has the effect of preventing cracks and cracks, has the same or higher high hot linear expansion. Next, examples will be described.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Table 1 shows the chemical component values of the raw materials used in the examples.
Shown in 2. Table 2 shows an example of the particle size configuration of the refractory used in the examples. 3. Table 3 shows the mixing ratio of the material test materials and the results of the quality characteristic confirmation test. 4. Table 4 shows the results of confirmation of the working examples.

[0010]

[Table 1]

[0011]

[Table 2]

[0012]

[Table 3]

[0013]

[Table 4]

[0014]

[Table 5]

[0015]

[Table 6] 1. Method of Adjusting Raw Materials for Molding The test specimens were prepared using the raw materials shown in Table 1 and adjusted to the compounding ratios and particle sizes shown in Tables 2 and 3. Mixing and kneading must be 74
30% by weight or less of micron particles and 3% by weight of colloidal silica as a deflocculant and / or a curing agent, 0.5% by weight of phosphorus sansoda and 4% by weight of water are mixed and mixed to prepare a mud-like material in advance. And kneading while adding to the raw materials of the above to obtain a forming clay. 2. Shaping method Mold with heat absorption performance (The test material for the first test is 250 × 1
Practical test material of the secondary test with the shape of 14 × 65 mm is the outer diameter φ510 mm of the sleeve material for the induction furnace, the inner diameter φ410 mm,
(Height: 830 mm). This mold is fixed on a vibrating table, and while the mold is vibrated, the kneaded clay adjusted by the above-described method is sequentially charged and subjected to vibration filling molding, and these are naturally cured for about 24 hours after molding and cured. First remove the core mold,
Preliminary drying at a temperature of about 0 ° C. to check the degree of hardening, demolding everything, natural curing, gradually heating and heating at a maximum temperature of 500 ° C. for 15 hours to produce .
Table 3 shows the results of the erosion test.

[0016]

[Practical Examples] As shown in Table 3, the material of the present invention is different from Comparative Example 1 of the fixed refractory in that the cerium is added in an amount of 5% by weight.
The No. 4 material, which was added with 25% by weight of o2 material, had a erosion resistance ratio of 48% and 24% at the slag line portion and a penetration depth of slag of 64% and 35%, respectively. As an example material of the present invention, a test is carried out by using an example material as an example material of the present invention as an example material of the present invention. The integrated molded article used in this practical example was manufactured by the method of manufacturing the test material described in the preceding section, and the construction in the induction furnace was performed by using the integrated molded article comparative material A and the present invention material B. After shaking and filling the lower layer of the furnace bottom with dry amorphous refractory, the integrated molded product is placed at a predetermined location, and the gap between the sleeve and the furnace body is filled with dry amorphous refractory and shaken and filled. Build the furnace.
C of the comparative example using the dry-type amorphous refractory was prepared by first vibrating and filling the hearth material, then arranging a predetermined adjusting former, charging the former with a predetermined gap between the former and the furnace body, and performing vibratory filling. Offer.

[0017]

The most commonly used fixed refractory material of high alumina material (No. 1 in Table 3) was used as a comparative example material. Based on this refractory material, 25 cerium oxide was added to the refractory joint having a particle diameter of 0.074 mm or less. As a result of using the No. 4 material in Table 3 to which the weight% was added as an integrally formed body in advance, the service life in service life was 57 times compared with 35 times without repair, the service rate was 196%, and the repair was performed twice after use. The final life was 93 times compared to 41 times, and a great effect was obtained, such as a total service life of 244%. In addition, compared with the case of dry type refractory construction, the total maintenance time of the furnace lining material and the ratio of the total time required for furnace start-up are 22.8% compared to the No. 6 material of Table 3 which is the same material. In addition, since the service life is increased by 1.9 times, the ratio of the time required for the total maintenance work is limited to 12%.

Claims (1)

[Claims] 1. An induction furnace used for melting and / or refining a rare earth metal and a metal containing a rare earth metal, wherein the refractory for lining the furnace has at least a two-layer structure and its working layer (the innermost part) has a thickness of 74 μm or less. A material obtained by adding a suitable organic and / or inorganic deflocculant or hardening material to a high alumina material and / or alumina material having a cerium oxide material content of 5 to 50% by weight and a balance of alumina content of 75% by weight or more, and kneading the material. At least the side wall is made as an integral molded product, and 2
A fixed refractory having a porosity of 15% or less by heat treatment in a temperature range of 00 ° C to 1000 ° C, and a dry amorphous refractory having an outer layer portion having a high hot linear expansion property equal to or higher than that of the inner layer member. An induction furnace with a multi-layer refractory structure characterized by being constructed.