JPH11223471A - Induction furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a longer life, by performing a impregnation treatment of a pitch to significantly improve the useful life longevity and to accomplish safe operation of a furnace with a limited amount of a matter adhered onto the internal wall surface of the furnace. SOLUTION: In this induction furnace, a lining material of an electric type induction furnace employs a melted quartz oriented material as main material. A baked refractory, a refractory which is integrally formed with a side wall 1 and fired beforehand, is impregnated with carbon-containing material such as tar, pitch, asphalt or a resin is liquefied by heating and then undergoes a heat treatment at the temperature of 350 deg.C or higher. This impregnation treatment is conducted more than once. The refractory with an permeability of 10 cm.cm/cm<2> .g/cm<3> .sec. or less is arranged as innermost lining material, and the outer circumference part thereof is filled with a monolithic refractory having a thermal expansion coefficient more than equal to that of the lining material to build a two-layer structured furnace.

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 producing zinc oxide powder or zinc powder by melting and refining zinc or evaporating zinc.

[0002]

2. Description of the Related Art Conventionally, in order to produce zinc oxide or zinc powder by melting, refining or evaporating zinc, it has been manufactured by burning gas or heavy oil in a crucible furnace having a crucible and raising the temperature. It is difficult to control the temperature and atmosphere, and this variation produces quality variation, high quality uniformity products, high productivity and a better working environment.In response to these demands, gas using crucibles, Electric induction furnaces have been introduced from heavy oil combustion type crucible furnaces, and improvements have been made.

[0003] However, this induction furnace has an electric induction coil on the outer periphery thereof, a refractory layer for covering and protecting the coil with coil cement is provided inside the induction coil, and a hot water sensor insulating material and a heat insulating material are provided inside the refractory layer. After that, a steel frame (hereinafter referred to as “former”) was placed almost in the center of the furnace,
The refractory layer is used to construct the hearth and furnace wall lining layers. However, the refractory for lining used here is a dry amorphous refractory made by adding a sintering aid such as boric anhydride to a silicon carbide or quartzite material. Has a melting point of 419 ° C and a boiling point of 90.
Low melting point metal with a low melting point of 6 ° C.

[0004] In order to produce powder of zinc oxide, zinc or the like, a temperature of 910 ° C. to 9 ° C., which is higher than the boiling point, is used to evaporate the zinc.
Since it is operated at a temperature of about 70 ° C, extremely low-viscosity zinc and evaporated zinc are filled with vibration-filled lining materials using dry amorphous refractories as of today. Low, and high non-uniformity of filling, easily penetrates into the tissue, and it is detected and activated by the hot water leak sensor arranged on the back of the lining material, and the lining material itself has almost no erosion It cannot be used continuously for safe operation and must be dismantled and replaced with new lining material. For this reason, the life of the lining material is short, and the maintenance work opportunities are increased, which necessitates 3K work. At the same time, the furnace operation rate is reduced and the upper and lower processes are adversely affected. Lower.

Further, the infiltrated material penetrates into the vicinity of the induction coil, adversely affects the induction coil and shortens the service life, and the loss is extremely large, raising the manufacturing cost. For this reason, in the first part, various refractories have been practically tested and studied. The best method is to use a refractory material as the innermost lining material and to install it in a two-layer structure where it is placed almost in the center of the furnace and the outer periphery is filled with siliceous dry amorphous refractory material. However, even if there is almost no erosion, it cannot be used due to the penetration of zinc, and a sufficient effect has not yet been obtained.

[0006]

As mentioned above, the structure of refractory for lining an induction furnace for operation by elevating a low melting point and low boiling point material such as zinc to a temperature of 910 ° C. to 970 ° C. above the boiling point and evaporating the material. It easily penetrates into the inside and generates a heat generation phenomenon due to the induced current, activates the hot water leak sensor, detects even if there is almost no erosion of the lining material, and solves problems such as short life and promoting damage to the induction coil Is a technical task.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned situation, the present inventors have found that the operation of a furnace can be stably performed, the refractory for lining can be fully used, and a long life can be obtained. As a result of various investigations and investigations, it is found that low-melting-point and low-boiling-point metals such as zinc permeate through the refractory structure due to the refractory structure, packing density and air permeability. After obtaining the results of the soldering, first, the vibrating filler for dry amorphous refractory made of silicon carbide-based material and fused quartz-based material and the filling density and ventilation of fused quartz-based shaped refractory which is considered to be the most suitable at present. As a result of examining the air permeability, the vibrating filler of the dry-type amorphous refractory has a packing density of 75% to 82% and a permeability (cm · c).
m / cm ² · g / cm ³ · sec) is around 800, and the fused quartz shaped fired refractory has a packing density of 88% and an air permeability (cm · cm
cm / cm ² · g / cm ³ · sec) is around 12.

[0008] Among general refractories, they belong to the class of materials having a high packing density and a low air permeability, and a great improvement in permeation has been recognized. However, they do not prevent the permeation of zinc, and have a sufficient effect. Although it was not possible, it could be confirmed once again that the packing density and the air permeability of the lining material had a deep relationship with the permeability. From these results, the fused silica-based fired refractory manufactured from the fused silica-based material, which is currently the most suitable material, has a high packing density, a low air permeability, and a low heat spalling property and corrosion resistance. As a result of repeated tests, one or two or more composite materials of asphalt, tar, pitch and other carbon-containing materials were heated on a fixed fired refractory made of the current fused quartz material, And then heat-treated at a temperature of 350 ° C. or higher to remove low volatile components. If necessary, this process is repeated repeatedly, leaving the carbon material in the voids in the structure of the refractory material, filling the material to increase the density and lowering the air permeability, and modifying the material to improve the air permeability (cm · cm / cm ² · g). / Cm ³ · sec)
Is set to 10 or less, it is possible to almost prevent penetration of a low-melting-point metal such as zinc, and it has been found that this is a preferable means for improving a defect without deteriorating the characteristics of the current material, Is mainly impregnated into the bonding voids of the material, and the chemical reactivity can be increased by having it impregnated, and also has the side effect of reducing the adhesion of the melt to the furnace wall surface. I did.

[0009] Specifically, the first step is to produce a fused quartz shaped refractory having at least one molded body of a side wall, and the second step is to apply the raw material at 240 ° C to 270 ° C.
The pitch is melted at a temperature of ℃ C, and the material is immersed in a vacuum or under reduced pressure as a liquid, and then impregnated in the air or under pressure. Remove volatile components and add 2 if necessary
The process is repeated at least twice to leave carbon in the voids of the material structure, increase the packing density, and increase the air permeability (cm · cm / c).
m ² · g / cm ³ · sec) by modifying the material to a low-permeability material of 10 or less, the penetration of low-melting-point metal such as zinc can be controlled and improved, and the service life can be extended. I was able to.

In order to constrain the fixed lining material from the outer periphery at the time of use on the outer peripheral portion of such a molded article having low air permeability as the innermost layer material, the molded product has a thermal expansion coefficient equal to or more than that, and is solidified by receiving heat during use. It is safer and more stable to operate because it is more effective to use non-refractory dry refractories. It is another object of the present invention to provide a means that can prolong the life of the induction coil and solve the current problem.

(Reason for limitation) (1) The air permeability is 10 cm · cm / cm ² · g / cm ³ · s
ec or less. Air permeability is 10cm ・ cm / cm ²・ g
/ Cm ³ · sec or more, melting point 419 ° C., boiling point 90
This is because a metal having a low melting point and a low boiling point of 6 ° C. is heated to a high temperature of 910 to 970 ° C. and used while evaporating. (2) A carbon-containing material such as asphalt, tar, and pitch is heated to be liquefied and impregnated. Asphalt and pitch are solid tars at room temperature and are fluids with strong viscosity.However, it is difficult to impregnate the refractory structure by heating until it can be impregnated to reduce the viscosity. Do. (3) A heat treatment is performed at 350 ° C. or higher after the impregnation step to remove volatile components. If volatile components remain at low temperatures in the impregnated material, a lot of smoke is generated during use, and the working environment is deteriorated. This is for reducing the thermal shock resistance of the. (4) The operating layer is a fired refractory which is formed by molding at least one side wall and fired, and the outer peripheral layer is a two-layer system of a dry amorphous refractory. By forming a molded refractory that is integrally molded and fired, the packing density can be increased and a low-permeability material can be obtained. The outer peripheral portion has flexibility in an unsintered state, so that operational safety is high, and it is possible to easily push out or break from the bottom of the furnace at the time of dismantling, and also keep the heat conductivity low. (5) The dry amorphous refractory used for the outer periphery of the integrally molded and fired fired refractory has a hot linear expansion coefficient equal to or greater than that of the fixed refractory material. The role of the dry amorphous refractory to fill the back is to restrain the inside of the fixed refractory from the back and suppress the generation and development of cracks. To ensure this role, it is desirable that the coefficient of thermal expansion be high to protect the shaped refractory forming the innermost layer. Examples will be described below.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Table 1 shows examples of chemical component values of raw materials used in the examples.

[0013]

[Table 1]

2. Table 2 shows the particle size composition of the refractory used in the examples.

[0015]

[Table 2]

3. Table 3 shows the compounding ratio of the example materials and the form of the refractory.

[0017]

[Table 3]

4. Production method of materials for evaluation test First step (forming of lining material) In the examples of the present invention, the raw materials shown in Table 1 were used, and the particle sizes were adjusted, blended, mixed, and kneaded as shown in Tables 2 and 3. I do. In Embodiment A, the specified materials are blended and mixed to adjust to the dry amorphous refractory. In Embodiment B, predetermined materials are blended, mixed, and kneaded to prepare a wet kneaded clay. Using the materials adjusted as described above, both the embodiments A and B are filled into a 230 mm × 114 mm × 65 mm shape and subjected to a heat treatment to produce a material for evaluation. The embodiment A and the embodiment B of the evaluation material will be described in detail. Embodiment A A steel plate of approximately the same shape as a 1 mm stainless steel plate in a molding die for producing an adjusted dry amorphous refractory in a predetermined shape. After the frame is inserted and fixed on a vibrating table and shake-filled, the entire steel sheet frame is put into an electric furnace and kept at 800 ° C. for 3 hours to be cured and manufactured. Embodiment B To the prepared material, the material is based on a fixed amount of colloidal silica and water, mixed, kneaded to form a wet material, and placed in a container for receiving raw materials in a thickness of 20 to 4 in a receiving container.
Vibration is applied on a shaking table with a thickness of 0 mm, air bubbles in the material are degassed, raw materials are adjusted, and a casting mold having a predetermined size of water absorption performance is set in the shaking table, and is applied while being sequentially charged. After shaking and shaping, leaving it for natural curing for 16 hours or more, it is removed from the mold, pre-dried at 20 ° C. to 50 ° C. for about 24 hours, and then raised to 150 ° C. at a heating temperature of about 30 ° C. per hour. After holding for a period of time and drying, the temperature is raised to 1050 ° C. at 40 ° C. per hour, followed by holding for 6 hours to produce. Second step (impregnation treatment of carbonaceous material) The pitch described in Table 1 was selected as the carbonaceous material, and the material of the embodiment of the present invention produced in the first step was subjected to this second step to obtain the effect of the present invention. Confirm. That is, the manufactured refractory is placed in a vacuum chamber, the pressure in the tissue is reduced to 500 mmHg or more, and air in the tissue is removed. Then, a 270 ° C. solution pitch is introduced into the container, and immersed in the solution pitch. After holding for 1 minute, the pressure was returned to atmospheric pressure, and air pressure of ² kg / cm ^{2 was} further applied to increase the impregnation efficiency. After holding for 60 minutes, the mixture was placed in a heating furnace, heated at 80 ° C. per hour, and heated at 350 ° C. for 10 hours.
One time processing is completed after holding the time. If necessary, this step can be repeated to obtain a material of a high density and low air permeability material. Table 3 shows the results of the evaluation test of the first step materials of the example materials shown in Table 3 produced by the above-described production methods.
The quality characteristic value of the product of the present invention, which was subjected to the second step of the material of the present invention, and the corrosion resistance, Table 4 shows the results of the permeability test.

[0019]

[Table 4]

The test conditions for corrosion resistance and permeation resistance in a high-frequency induction furnace are as follows. 1. Test method Tension test on high frequency induction furnace side wall 2. 2. Size of sample Thickness 60 mm, width 40 mm x length 250 mm Test material Zinc material 4. 4. Melt temperature and holding time 950 ° C ± 10 ° C × 10 hours Number of tests: 10

As described above, in the basic test, the packing density of the comparative material of the same material and the material of the present invention was 77.7.
%, Air permeability (cm · cm / cm ² · g /
(cm ³ · sec) is 13.6 compared to 711.5, which is a significant improvement even for the current material in the case of the vibratory filler of dry amorphous refractory and the shaped fired refractory obtained by wet vibration molding. still,
In an induction furnace lining test in which zinc was dissolved and evaporated, the penetration depth was greatly improved from 56.6 mm to 9.3 mm. The amount of erosion is small and the life is almost determined by the depth of penetration of zinc into the structure of the lining material. The material of the present invention impregnates the pitch with the material in order to suppress this penetration and improve the life, and improved the packing density and the air permeability while applying heat treatment. On the other hand, the air permeability (cm · cm / cm ² · g / cm ³
・ Sec) is 5.5 for 12.3, respectively.
4 and 3.7, and in the corrosion resistance and penetration resistance tests, the penetration depth of zinc is 4.7 mm, 4.1 mm, 38 mm and 50% to 40%, respectively. As a result, a comparative material was used as a practical example in an actual furnace, a material was used, and a material according to the present invention was used using -1 and -4 materials.

Conditions for Practical Use Test Furnace Size 5TON Type Low Frequency Induction Furnace Melting Materials and Usage Production of Powder by Dissolution and Evaporation of Zinc Melt Temperature 950 ± 10 ° C Usage Conditions Fully Continuous Operation

Method of Manufacturing Material for Practical Use Test Material for practical use test is performed in the same manner as the material for evaluation test. Comparative Example Material (Embodiment A) The former is placed almost in the center, and the dry refractory material of the formulation shown in the table is charged into this gap and filled with vibration while knocking from the inside of the former. Production of Materials for Working Examples of the Present Invention (Embodiment B) First Step The base materials based on colloidal silica and water were added to the materials shown in the table, mixed and kneaded, and wet materials were used. The thickness of the raw material was adjusted to 20 to 40 mm, and the raw material adjusted while oscillating on the vibrating table and degassing the air bubbles in the raw material was installed on the vibrating table with a casting mold having a predetermined size of water absorption performance. Vibration cast molding was performed while being poured into the container, and after 48 hours of natural curing, the mold was removed and pre-dried for 72 hours at 20 ° C. to 50 ° C., and then heated at a rate of 30 ° C./hour for 1 hour.
After raising the temperature to 50 ° C. and holding for 10 hours to dry, the baking furnace was filled with nitrogen and heated at a rate of 4050 ° C./hour to 1050 ° C.
The temperature is raised to 0 ° C., the temperature is maintained for 10 hours, and the product is baked. Production of Example Material of the Present Invention (Impregnation Treatment) Second Step The material produced in the first step is put in a vacuum tank and the inside of the tank is filled with 50.
After reducing the pressure to 0 mmHg or more, extracting the air from the material, inserting the pitch, immersing in the pitch, holding for 30 minutes, returning to the atmosphere, pressurizing with air pressure of 2 kg / cm ² and impregnating by holding for 60 minutes After taking out from the tank, the temperature is raised at 80 ° C. per hour in a heating furnace and the temperature is raised at 350 ° C. for 10 hours.
The heat treatment is performed while holding for a time. The material of Example 1 of the present invention was subjected to this treatment once, and the material of Example -4 was subjected to four times to produce a test material for use in the test.

[0024]

According to the present invention, the service life is greatly improved from 36 days to 55 days by forming the material for the lining in advance into a fired refractory which is formed as a single body from the material of the dry amorphous shaking and filling construction and fired. However, the material of the present invention, in which the pitch is impregnated into the fired refractory formed and fired as a single body, is −1 material and -4 material once in the number of times of impregnation, and the total damage amount (melting loss + 0.873 per day for the comparative material
0.428mm and 0.329mm for mm
The total damage ratio was 49.0% and 37.7%, respectively, and the service life of the comparative material was 104 for 55 days.
Days and 129 days, and the service life is 189% and 234%, respectively, by the pitch impregnation treatment of the product of the present invention.
The furnace can be operated safely with a small amount of deposits on the inner wall of the furnace, and the life can be prolonged, thereby reducing the 3K work of dismantling the lining material, improving productivity and reducing production costs. It can greatly contribute to reduction, and its effect is remarkable.

[Table 5]

Claims (1)

[Claims] 1. A refractory for lining of an electric induction furnace for producing zinc powder and zinc oxide powder by dissolving or refining zinc or a low-melting-point, low-boiling-point metal containing zinc as a main component, and evaporating the same. After heating the carbon-containing material such as tar, pitch, asphalt, resin, etc. to a fired refractory that has been formed and fired in advance by forming a side wall with the raw material as a main material, and liquefied and impregnated, the temperature is 350 ° C. or higher. The impregnation process of performing heat treatment at a temperature of at least once is performed, and the air permeability (cm · cm / cm ² · g
/ Cm ³ · sec) is 10 or less as the innermost lining material, and the outer periphery (gap between the furnace body) is filled with a dry amorphous refractory having a thermal expansion coefficient equal to or higher than that of the lining material. An induction furnace characterized by a two-layer structure.