JPH11201654A - Induction furnace lined with glazed shaped material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To modify abnormal phenomenon due to a permeating material and to fully utilize the characteristic of the material by a method wherein ceramics blaze is applied on the back of a molding material sleeve and softened and molten, to provide a low permeability. SOLUTION: In a refractory for lining an electric type induction furnace, an innermost layer working layer is formed of a refractory molded integrally with a side wall. A ceramic glaze having a heat resisting temperature of 700 deg.C or higher is applied on the outer peripheral surface of the molded product, and a glassy layer is formed. Permeability (cm.cm/cm<2> , g/cm<2> , sec) of an integrally molded product is set to 15 or less to form a furnace interior material. The outer peripheral part of the electric type induction furnace is built of dry type amorphous refractories having the coefficiency of hot linear expansion equal to or higher than that of a shaped refractory with which the outer peripheral part thereof is lined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction furnace equipped with a glazed fixed type refractory material used for melting and / or refining metal.

[0002]

2. Description of the Related Art Conventionally, melting and / or refining of cast iron has been mainly performed by melting in a cupola and refining in a pre-furnace or a ladle. In order to respond to these demands in recent years where a better working environment is required than productivity, compared to cupola operation, the melting efficiency is higher and the maintenance opportunities of the furnace and the refractory material of the furnace are less, easy and uniform. Induction furnaces that can obtain a high molten metal and have a good working environment during furnace operation are rapidly spreading. This induction furnace has an induction coil of an electric furnace on the outer periphery.If necessary, a refractory layer for covering and protecting the coil with coil cement is provided inside the coil, and insulation materials for heat leak sensor, heat insulating material, etc. are sequentially arranged. After that, a lining layer is generally formed on the innermost side of the hearth portion and the side wall portion by using one layer of refractory on the innermost side.

In general, a method of applying a lining material with a refractory is to first dry the furnace to a predetermined thickness by using a dry amorphous refractory, or to carry out shaking and filling, followed by a predetermined thickness of a side wall on the upper portion. A steel inner frame (hereinafter referred to as a “former”) with dimensions designed to have a shape is placed at the approximate center of the furnace, and after the dry amorphous refractory is charged into the gap between the former and the furnace body. Vibration is applied directly to the inside of the former, and the refractory that has been injected while being moved up and down is vibrated and filled for construction.

[0004] In this way, the refractory thus constructed has a low filling density and is difficult to construct a highly uniform construction.
Since the life of the furnace tends to fluctuate, the quality of the construction greatly affects the life of the furnace material, so unexpected maintenance work is required and the factory suddenly shuts down. Since the impact on the operation of the factory is large, such as causing loss, it is necessary to perform more reliable construction for stable operation. It requires a high level of skill.

[0005] In addition to the quality of the construction, the refractory used here is also examined especially for various materials such as siliceous material, alumina material, magnesia material and spinel material, and if necessary, sintering of boric anhydride or the like. Dry amorphous refractories to which auxiliary materials have been added are used while being selected according to the usage conditions.However, it is difficult to obtain a uniform or high packing density, so low melting point metals such as zinc contained in gases and cast iron materials When such substances are present at a high temperature, they become very low in viscosity and also cause a partial vaporization phenomenon, which easily causes a penetration phenomenon into the structure of the refractory material lining the furnace.

[0006] At present, the cast iron material to be melted in the induction furnace is replaced by new scrap, and galvanized steel scrap is increasingly used. The melting point of zinc metal is 419.5 ° C,
Since the boiling point is 906 ° C, which is a very low heat-resistant material, the temperature of the cast iron material is as high as 1450-1550 ° C, and it is melted and refined, so that it easily penetrates into the structure of the lining refractory material and is distributed on the back side. It will be detected by the installed hot water leak sensor and will be activated.Even if it is not hot water leak, it can not be judged whether it is hot water leak or not, it can not be used continuously and it can not be safely operated and dismantled, The lining must be replaced. For this reason, there are many opportunities for the maintenance work of the lining material, and the 3K work is inevitable, and the operation of the furnace as well as the upper process and the lower process are affected, thereby lowering the operation of the entire factory. In addition, these low-melting metals such as zinc that have penetrated into the vicinity of the induction coil cause the life of the induction coil to be shortened, and at present, the damage is greatly increased and the manufacturing cost is increased. At present, it is strongly desired that such problems be solved so that a stable furnace operation can be performed and the production cost can be reduced.

[0007]

In view of such a situation, the present inventors have considered that low melting point and low boiling point metals such as zinc mixed in cast iron material during operation as described above make refractory linings of induction furnaces. The water leak sensor, which has penetrated into the tissue and is located on the furnace body side, detects it and detects it as a water leak even though the lining material is in a state that can sufficiently withstand it. It is an object of the present invention to solve the problems such as the occurrence of such a problem that the continuous coil cannot be used continuously and the induction coil is damaged.

[0008]

SUMMARY OF THE INVENTION In view of such circumstances, the present inventors have found that the furnace can be operated stably, the refractory for lining can be used up sufficiently, and a long life can be attained. As a result of various investigations and studies to make it possible, it is found that the phenomenon that a metal with a low melting point and a low boiling point, such as zinc, penetrates the structure of the refractory material is caused by the structure, density and permeability of the refractory. After obtaining the conclusion of wax, firstly, the packing density and the permeability of the material for the lining of the furnace filled with vibration using the current dry type refractory were examined. (Cm · cm / cm ² , g / cm ² , sec) is 8
It was found to be as high as around 00, low density and high air permeability. The results show that the density and permeability of the refractory, 95% by weight of cast iron and 5% of zinc in a small high-frequency induction furnace.
The test was conducted by repeating the test of dissolving the weight percent, maintaining the melt temperature at 1600 ° C., holding the sample for 60 minutes, and then tapping, and repeating the various studies and practical tests on the relationship between the examined zinc permeability and these three factors. cm · cm / cm ² , g / cm ² , s
If ec) is 40 or less, a sleeve is used even if the temperature of the molten metal is 1600 ° C. even when a low melting point and low boiling point metal such as zinc enters, using a zinc-mixed material such as a galvanized steel plate as a cast iron material. The furnace is stopped by the vitreous material applied to the back surface of the furnace, and it is possible to operate the induction furnace without any trouble in the operation of the induction furnace. It was found that the temperature was up to 700 ° C. even at the time of melting and requiring replacement.

As described above, the air permeability (cm · cm / cm ² ,
g / cm ² , sec) To obtain a lining material having a low air permeability of 40 or less, it is necessary to provide a dry-type amorphous refractory, which is the mainstream of the current construction method, with a lining layer having an appropriate thickness for furnace performance. After placing the former designed in the bottom and placing it almost in the center of the furnace, throw it into the gap between the furnace body and the former, and apply vibration to the inside of the former directly while applying vibration to achieve this. Can not. In order to obtain the required low-permeability material, it was achieved in advance by manufacturing the side wall integrally molded body or the side wall and the bottom as an integrally molded body at a factory. A ceramic glaze that can withstand up to 700 ° C. is glazed, softened and melted on the back surface (outer surface) of the sleeve. With this glaze layer, the air permeability (cm
m / cm ² , g / cm ² , sec) A high-quality, stable-quality at least side wall-integrated material sleeve of 15 or less could be produced.

[0010] At present, a general construction body is a lining material in which the density of the lining construction body is low and non-uniformity is liable to occur due to the fact that the vibrating and filling construction is directly performed by using a dry amorphous refractory and a former in the furnace body. Although this has caused a major problem, the integrally molded body manufactured in this way also used a non-refractory dry-type refractory on the lowermost layer of the furnace bottom after glazing the outer surface of the sleeve material. Installed in the center, the inner periphery of which has a two-layered lining material filled with high-density dry amorphous refractory having a coefficient of thermal expansion almost equal to or higher than that of the molded body, thereby improving conventional problems Was found to be the most preferred method.

More specifically, at least a refractory glazed on the back surface is formed at the bottom of the furnace after being formed at least as an integral molded body of the side wall, and is disposed substantially at the center thereof. By injecting the refractory material and directly shaking it with a vibrating bar or filling it with a filling, the low melting point metal such as zinc can reduce the penetration of the lining material (sleeve) into the structure and the sleeve The back glaze layer substantially suppresses further penetration to the outside. In the unlikely event of infiltration or cracking of the innermost layer material due to the two-layer structure, even if the metal infiltrates, the irregular-shaped refractory that forms the second layer is not solidified. Since it enters thinly between the refractories and solidifies, the furnace can be safely operated. Since the low-melting-point metal such as zinc is less likely to penetrate into the tissue of the coil cement and directly adhere to the outer surface of the induction coil, the maintenance work of the induction coil itself is reduced and the life is extended.

Such a molded article having low air permeability is used as the innermost layer material, and has a coefficient of thermal expansion that is equal to or greater than that of the outermost portion in order to restrain the fixed interior material from the outer periphery during use. Due to the fact that it is more effective to use a non-consolidated dry amorphous refractory, safe and stable operation can be achieved, and the effect of prolonging the life of the induction coil can be achieved. A solution that can be provided is provided here.

(Reason for limitation) (1) A ceramic glaze having a heat resistance of 700 ° C. or more is applied to the outer peripheral surface of at least the molded body refractory (sleeve) integrated with the side wall constituting the operating layer. This is because even if a low-melting substance such as zinc permeates into the tissue of the lining material (sleeve), it stays only in the sleeve and can stop the trouble caused by the permeated substance. The heat resistance of 700 ° C. or more is intended to withstand the maximum temperature of the outer peripheral surface. (2) Permeability (cm · cm /
cm ² , g / cm ² , sec) is 15 or less. As the air permeability decreases, the penetration of low-melting substances such as zinc decreases, and is controlled by the glaze applied to the back surface of the sleeve, so that the fixed refractories are balanced with the power input and operate normally. The interval shows characteristic values that can be used safely. (3) The working layer is at least a molded body refractory integral with the side wall,
The outer peripheral layer is a two-layer system made of dry amorphous refractory. (a) The packing density can be increased by forming an integrally molded body, and a low air permeability material can be obtained. (b) The refractory for lining has a high operational stability in that the working layer has a high sintering degree and a high density body, no cracks are generated, and the outer peripheral portion has flexibility in an unsintered state, and During disassembly, it is possible to keep the heat conductivity low, which makes it easier to push out or stiffen from the furnace bottom. (4) The coefficient of linear thermal expansion of the dry amorphous refractory used for the outer periphery of the fixed refractory is equal to or greater than that of the fixed refractory. It is the role of the dry-type amorphous refractory to fill the rear part that the interior fixed refractory is restrained from the back to 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.

[0013]

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

[0014]

[Table 1]

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

[0016]

[Table 2]

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

[0018]

[Table 3]

4. Method of Manufacturing Inner Material 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 to prepare the particle sizes shown in Tables 2 and 3, and blended, mixed or kneaded. Perform In the embodiment A, the determined material ratio is blended and mixed to prepare a dry amorphous refractory. In Embodiment B, a predetermined material is blended, mixed, and kneaded to prepare a wet clay. Embodiment C is prepared by blending, mixing and kneading the specified materials, and using a semi-dry ramming material.

Using the materials prepared as described above, embodiments A, B, and C were all 230 mm × 114 mm × 65 mm
It is filled into a shape, heat-treated, and a material for evaluation is manufactured.
The molding of the evaluation material is described in detail in Embodiments A, B and C. Embodiment A → The prepared dry amorphous refractory is produced into a predetermined shape. Insert a thin steel sheet frame of almost the same shape with a 1 mm stainless steel sheet into the mold, fix it on a shaking table, fill it with vibration, place it in an electric furnace with the inner frame, and hold at 800 ° C for 3 hours. Hardened and manufactured. Embodiment B → To the prepared materials, sodium phosphate and water are added to the prepared materials, and colloidal silica and water are added to the prepared materials in a fixed amount. Mixing and kneading are performed as wet materials, and the thickness is 20 to 4 in a container.
Shake by about 0 mm, prepare the raw material while looking at the bubbles in the material, and shake and cast it while pouring it into a rough casting mold having a predetermined size of water absorption performance, and leave it for 16 hours or more After natural curing, demold, about 24 hours 20 ~
After pre-drying at 50 ° C., increase the temperature to 150 ° C. at a rate of 30 ° C./hour, hold for 10 hours, raise the temperature to 800 ° C. at 40 ° C./hour after drying, and hold for 3 hours. To produce. Embodiment C → The prepared material is mixed with sodium phosphate and water in a mixer and kneaded to prepare the material, and using a mold having a predetermined size, is compacted with an air hammer and manufactured. After natural curing for 16 hours, 150 at 30 ° C per hour
The temperature is raised to 0 ° C., drying is performed for 10 hours, the temperature is increased to 800 ° C. at 40 ° C. per hour, and then the product is held for 3 hours to produce.

Second Step (Step of Glazing Ceramic Glaze on Back Side (Outer Peripheral Surface) of Sleeve Material) Table 4 shows the blending ratio of glaze applied on the back side (outer peripheral surface) of the molded product.

[0022]

[Table 4]

As shown in Table 4, an organic substance, dextrin and sodium phosphate are added to the frit to increase the viscosity and the deflocculating properties of the particles, and the frit is made into a slurry state with water, and this is applied to the back surface of the sleeve. . After applying with a thickness of about 1 mm,
Temperature rises at 100 ° C per hour in an electric furnace, up to 75
The temperature is kept at 0 ° C., and the temperature is kept for 2 hours to cool in a furnace to produce.

The quality characteristic values of the test specimens produced by the above-described production method are separated from each other for the lining of a high-frequency induction furnace using the test specimens, and erosion and penetration tests are performed. The conditions of this split test are as follows. 1. Melted material Cast iron 50%, stamped steel scrap 25%, return material 20%, zinc 5%. 2. Melting temperature 1540 ° C 3. Dissolution time 60 minutes 4. Retention time 30 minutes 5. Number of tests 6. Sample size Width 40 mm, thickness 25 mm, height 250 mm a. The test material is a dry, irregularly shaped material of 60 mm b. The test material is a fixed test material of 25 mm and a dry irregularly shaped material of 35 mm and 60 mm. Table 5 shows the results.

[0025]

[Table 5]

As shown in the above results, the generally used dry-type refractory and vibratory filler have air permeability (cm · cm / cm ² , g / cm ² , sec) of 814 and 715, respectively. Even with the same material, it is as low as 27 and 12 with the wet vibration molded body, and a large difference occurs due to the difference in the molding method. The material B of the present invention, which has a correlation property between the difference in the air permeability and the penetration depth into the tissue, and the backside coated with a ceramic glaze, the material and the material remain in the sample, and the other materials are Due to the effect of the glassy glaze layer, the air permeability (cm · cm / cm ² , g / cm ² , sec) could be set to 5.2 to 7.3, so that there was no permeation to the part of the backing material , With good results. From these results, it was found that setting the air permeability to 15 or less would not prevent penetration or adversely affect the life. Based on this result, of the materials within the scope of the present invention, (2B) and (4B) as practical examples, (2A) as unglazed A and (4A) as comparative examples This is used as a working example.

Use Conditions of Practical Test Furnace size 5TON low frequency induction furnace 2. 2. Melting material Cast iron 20%, Galvanized steel scrap 80%, Carbon 4% 3. Melting and refining rate 1540 ° C ± 10 ° C 4.1 amount of dissolving per day Dewatering time (3 ton + 3 ton + 3 ton + 5 ton = 14 ton in total) Manufacturing method of test material for practical test The material for practical test is performed by the same manufacturing method as the material for evaluation test. First Step (Manufacture of Integrated Molded Body) The materials of the examples are manufactured by the manufacturing method of the embodiment C, and the materials are manufactured by the manufacturing method of the embodiment B. That is, the example material was formed by hardening a material adjusted to the compounding ratio of the material shown in Table 3 with an air hammer using a molding die having a predetermined shape.
After 6 hours of natural curing, 1 hour at 30 ° C
After heating to 50 ° C. and drying for 10 hours,
Hold at 40 ° C per hour up to 800 ° C for 10 hours. The material of Example 4 is manufactured by the manufacturing method of Embodiment B. That is, the Example material 4 is prepared by adding predetermined sodium phosphate and water to the materials prepared in the mixing ratios shown in Table 3, and then mixing and kneading. In addition, the materials were prepared by adding predetermined colloidal silica and water to the materials prepared in the mixing ratio shown in Table 3 and mixing and kneading, and thereafter, immersed in a flat-type raw material container and placed on a shaking table. A thickness of about 20 to 40 is set, vibration degassing is performed, and a molding die for manufacturing the prepared raw materials in a predetermined shape is set on a shaking table. After shaking and filling, the molded product was molded into a side wall integrally, left to cure for 48 hours, then removed from the mold, and pre-heated and dried at 20 to 50 ° C. for approximately 48 hours. The temperature was raised to 150 ° C. at a heating rate of 10 ° C., and kept for 10 hours for drying.
The temperature is increased to 800 ° C. at a temperature rising rate of 0 ° C., and the temperature is maintained for 10 hours to produce a molded body. Second step (glazing of ceramic glaze on the back side of molded body) Table 4 shows the back surface (outer peripheral surface) of the molded body produced in the first step.
Spray the liquid glaze shown in
glazed with a thickness of mm, fired in a single kiln, squeezed, and heat-treated at a maximum temperature of 100 ° C per hour.
Hold at 50 ° C. for 3 hours to soften and / or melt the ceramic glaze. In this way, a molded drug product having the outer peripheral surface ceramic glaze applied thereto is manufactured and used as a practical test material. The example material of the present invention material is an integrally formed body manufactured as described above, and the comparative example material is Table 3, (2A) material, (4)
A) Using a single-piece molded body produced in only the first step as a material, a given siliceous dry amorphous refractory is cast into the furnace bottom to a predetermined thickness, and then substantially at the center of the furnace. After shaking and fixing a dry amorphous refractory of the same material as the furnace low work material into the gap between the furnace body and the molded body, fix the inner bottom to the dry amorphous material of the same material as the side wall Filling is performed by placing and / or vibrating.

As described above, both the examples of the present invention and the comparative examples were formed in advance into compacts having a dense structure, and the materials of the examples of the present invention were formed on the outer peripheral surface with a ceramic glaze applied thereto. The material of the comparative example, which was a low-permeability lining material, was only formed as an integral molded body, and was disposed almost at the center of the furnace, and its outer peripheral portion was filled with a dry type refractory and restrained.
A layer structure was used for practical use. There is no sintering process at low temperature at the time of use, and melting is performed immediately, and only at the time of initial melting, after melting, the temperature is raised by 100 ° C from the normal molten metal temperature and maintained for 2 hours to stabilize the lining material. Was. Table 6 shows the results of actual operation in the induction furnace prepared and constructed with each refractory.

[0029]

[Table 6]

Incidentally, the construction of the lining material of the furnace of the practical embodiment is such that the sleeve material for the interior is 60 mm in both the embodiment of the present invention and the comparative example.
The thickness and the backing material are 40 mm thick and 100 mm in total.

[0031]

According to the present invention, the structure is made in advance as an integrally formed body, and the density of the structure is measured. However, when a low melting point metal such as zinc is melted, it penetrates into the pores, and when it reaches a deep portion, the operation is stopped due to the operation of the leak sensor. However, damage to the induction coil occurs frequently, but glaze is applied to the back surface of the molded material sleeve to soften and melt it to make it less permeable. By making it possible to make full use of the characteristics, even if the refractory of the same material is used, the materials (2B) and (4B) within the scope of the present invention are the same material comparative examples (2A) and (4A). On the other hand, there is no special abnormality and the life of 151% and 176%, respectively, can be obtained, the labor saving of the furnace, stable and safe operation can be achieved, and the long life can be achieved. Reduction of furnace 3K work, planned Etc. which can produce, can also contribute significantly to reduce production costs, there is the effect with enthusiastic.

[Procedure amendment]

[Submission date] January 20, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008]

SUMMARY OF THE INVENTION In view of the above situation, the present inventor has found that the furnace can be operated stably, the refractory for lining can be used up sufficiently, and a long service life can be attained. As a result of various investigations and studies to make it possible, it is found that the phenomenon that a metal with a low melting point and a low boiling point, such as zinc, penetrates the structure of the refractory material is caused by the structure, density and permeability of the refractory. After obtaining the conclusion of wax, firstly, the packing density and the permeability of the material for the lining of the furnace filled with vibration using the current dry type refractory were examined. (Cm · cm / cm ² , g / cm ² , sec) was as high as about 800, indicating low density and high air permeability. From these results, the refractory density and air permeability, and a test in which 95% by weight of cast iron and 5% by weight of zinc were melted in a small high-frequency induction furnace to a temperature of 1600 ° C., held for 60 minutes, and then poured out were repeated. As a result of various studies and practical tests on the relationship between zinc permeability and the three factors, the air permeability (cm · cm / cm ² , g / c)
If m ² , sec) is 40 or less, a low-boiling-point, low-melting-point metal such as zinc may enter even when the temperature of the molten metal is 1600 ° C. using a zinc-mixed material such as galvanized steel sheet as a material for cast iron. However, it is possible to operate the induction furnace without any trouble in the operation of the induction furnace .
It was found that the temperature of the inner wall of the furnace main body was up to 700 ° C. even at the time when the furnace lining material was normally melted and needed to be replaced.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

[0010] At present, a general construction body is a lining material in which the density of the lining construction body is low and non-uniformity is liable to occur due to the fact that the vibrating and filling construction is directly performed by using a dry amorphous refractory and a former in the furnace body. Although this has caused a major problem, the integrally molded body manufactured in this way also used a non-refractory dry-type refractory on the lowermost layer of the furnace bottom after glazing the outer surface of the sleeve material. was placed in the center, by a lining material two-layer structure in which densely packed in dry monolithic refractory having substantially the same or higher coefficient of thermal expansion the outer peripheral portion and the molded body, improving the conventional problem Was found to be the most preferred method.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0025

[Correction method] Change

[Correction contents]

The quality characteristic values of the respective specimens produced by the above-mentioned production method are separated from each other for the lining of a high-frequency induction furnace using the specimens, and erosion and penetration tests are performed. The conditions of this split test are as follows. 1. Melted material Cast iron 50%, punched steel layer 25%, return material 20%, zinc 5%. 2. Melting temperature 1540 ° C 3. Dissolution time 60 minutes 4. Retention time 30 minutes 5. 5. Number of tests 100 Sample size Width 40 mm, thickness 25 mm, height 250 mm a. The test material is a dry, irregularly shaped material of 60 mm b. The test material is a fixed test material of 25 mm and a dry irregularly shaped material of 35 mm and 60 mm. Table 5 shows the results.

Claims (1)

[Claims] 1. A refractory for lining an electric induction furnace for melting and / or refining a metal, wherein an innermost layer (operating layer) is formed as a refractory integrally molded with at least a side wall, and an outer peripheral surface of the molded product has a heat resistant temperature of 700 ° C. or higher. Glazed with a ceramic glaze to form a vitreous layer, and the air permeability (cm
cm / cm ² , g / cm ² , sec) is 15 or less,
An induction furnace equipped with a glazed shaped material, characterized by being made of a furnace interior material and constructed of a dry amorphous refractory material whose outer peripheral portion is equal to or more than a fixed refractory material having a coefficient of linear thermal expansion therein.