JPH10182254A - Monolithic refractory for induction furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refractory for lining an induction furnace capable of improving the operating rate of a plant, production cost and workability. SOLUTION: The innermost side wall part or side wall part and bottom part of the furnace are produced by using a refractory material consisting of 5-30wt.% quartz material, 5-40wt.% silicon carbide material, 30-90wt.% high alumina material or alumina material containing >=55wt.% Al2 O3 and >=90wt.% in total of three materials and, if necessary, properly adding a sintering assistant. The refractory is remarkably small in the occurrence of crack and free from the development the crack to harmful abnormal damage and is safely and stably used. The useful life is drastically prolonged and the stability of operation is effectively improved since abnormal damage is hardly caused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a refractory for lining an induction furnace used for melting and refining copper and copper alloys.

[0002]

2. Description of the Related Art Conventionally, in melting and refining copper and copper alloys, an induction furnace or a crucible furnace equipped with a graphite crucible has been used. In recent years, melting and refining are simpler and more labor-saving, quality adjustment of molten metal is easier, and the working environment is better. 1. High dissolution efficiency 2. Maintenance of melting furnace is easy. 3. Simple furnace operation and labor saving. 4. Low pollution problems 5. Easy adjustment of components and temperature. Induction furnaces, which have various advantages such as high quality stability and easy to obtain molten metal with high homogeneity, are rapidly spreading. In particular, a large induction furnace of 500 kg or more is provided with an electric induction coil on the outer periphery, and if necessary, a coating layer is provided inside the coil with a coil cement for protecting the coil, and a hot water leak sensor, an insulating material, Insulating materials and the like are provided, and a single layer of refractory material wall (lining material) is constructed and used on the innermost side. The method of constructing this lining refractory wall is generally such that a steel inner form (hereinafter referred to as a “former”) designed to have a predetermined wall thickness inside the furnace body is disposed in the furnace body, After the amorphous powdered refractory in the form of dry powder is charged into the gap between the former and the furnace body, the loaded refractory is vibrated from the inside of the former while being vibrated and filled. The quality of construction of the dry powder refractory greatly affects the durability of the lining material and determines the life of the furnace. If the filling degree at the time of construction is low and the filling degree varies, abnormal damage occurs and its service life is short-lived. This unplanned short-life life or large abnormal damage is not limited to the lining material, it is also a serious matter that leads to damage to the furnace body, and also causes a shutdown of the foundry, which has a great effect. In order to perform stable furnace operation, it is necessary to perform more reliable construction. It requires a high level of skill. In this way, the refractory materials used for the purpose of extending the life of the construction and extending the life of the construction, saving labor, and increasing the operation rate of the factory are selected from high alumina, alumina, magnesia, and spinel. Material and silicon carbide material to these materials
A dry amorphous refractory containing 0% by weight of a silicon carbide refractory and, if necessary, a sintering aid such as boric anhydride is used for the purpose. Cracks occur in the lining material due to repeated heating and cooling during operation due to the formation of heterogeneous structures due to the adhesion of slag containing oxides of the main component and the selective penetration of slag into the structure, and oversintering However, ingots penetrate into these cracks and the overall thickness of the furnace wall remains large, but it cannot withstand the durability and the life of the lining material is shortened. During this time, it is difficult to remove the adhered slag unless it is performed at a high temperature, so an extremely high heat operation is required. For this reason, there are many opportunities for furnace wall maintenance and the furnace operation rate is reduced. Furnace maintenance costs are increased, dismantling, and construction work, and the typical work of 3K, which has an extremely poor working environment, is obstructed. Solving these problems, stable furnace operation can be achieved, operation rate is high, running cost is low, work can be performed in a good environment, and the frequency of 3K work such as dismantling and construction of furnace wall materials is low and simple. At present, it is strongly desired to work.

[0003]

As described above, during the operation of the furnace, the slag removal operation in a high heat place where the slag mainly composed of copper oxide adheres to the operating surface of the lining material of the furnace in a large amount. Sudden damage caused by cracks or cracks caused by metal ingots, etc., can lead to a decrease in the furnace operation rate, which in turn affects the operation of the foundry. For this reason, furnace maintenance costs, losses due to short stops are extremely high, and there are many opportunities for typical 3K work such as furnace dismantling and punching work, so operation, furnace costs, 3K work, etc. Have many problems. It is a technical object of the present invention to provide a refractory for lining an induction furnace, which can solve these problems and can improve the operation rate, cost and workability of a factory.

[0004]

In view of such circumstances, the present inventors have made it possible to operate the furnace stably and to reduce the frequency of work under high heat such as slashing to reduce 3K work. The material composition of the refractory for lining is 5 to 30% by weight of fused quartz material and silicon carbide material in order to eliminate the sudden dismantling of the lining material and the construction work, and to maintain higher safety and stable operation. 5 to 40 wt%, with Al ₂ O ₃ content of 55% or more of high alumina material and alumina material 30 to 90 wt%, if needed total amount of the three parties to the refractory material less than 90% The present inventors have found a solution by using a dry powdery amorphous refractory to which an appropriate sintering aid is added. That is, 55
% Of Al ₂ O ₃ and high alumina material, which maintains high corrosion resistance. Adds silicon carbide material to this material to improve corrosion resistance, resistance to penetration of slag into the structure, and high thermal conductivity. The sex comes out. In addition, the addition of fused quartz can reduce the overall coefficient of linear thermal expansion and combine the refractory structure with a significantly different low-expansion material to create an efficiency that enhances the thermal shock resistance and use it. In the inside, the silicon carbide material partially oxidizes due to heat reception from the molten metal, contact with the atmosphere, etc. to generate an oxide such as cristobalite, and fused quartz partially crystallizes from the outer layer portion of the grains. This oxidation phenomenon, the volume due to the crystallization phenomenon expands, the refractory material undergoes volume shrinkage due to sintering, and the occurrence of cracks associated with this can be suppressed, so that good results can be obtained, so that there is little melting loss,
The current problems can be greatly improved by reducing cracks and cracks, and the sticking of slag is reduced, safe and stable operation can be performed, high efficiency work with improved short stop and under high heat The present invention provides an irregular-shaped refractory for an induction furnace which can greatly reduce the slag removal operation.

(Reason for limitation) Addition amount of the silicon carbide material is 5 to 40% by weight. If the addition amount is 5% by weight or less, the effect of improving the adhesion of the noro, the permeability of the noro and the corrosion resistance is small. This is because the conductive material is low in energy efficiency, no improvement in corrosion resistance and thermal shock resistance is recognized, and raw material costs are increased. If the added amount of the fused quartz material is 5 to 30% by weight a 5% by weight or less, it is not possible to bring out the various properties of the fused quartz. b When the content is 30% by weight or more, the heat shock resistance is enhanced, but the corrosion resistance is further reduced. Corrosion resistance is lowered content of Al ₂ O ₃ 55% or more of high alumina material and alumina material 30 to 90 wt% a content of Al ₂ O ₃ 55% or less when it comes. b When the content is 30% by weight or less, the corrosion resistance is low.

[0006]

Embodiments of the present invention will be described below in detail. Table 1 shows the chemical component values of the refractory materials used in the examples, and Table 2 shows the basic particle size composition.

[0007]

[Table 1]

[0008]

[Table 2]

Primary Basic Test Table 3 shows the mixing ratio and test results of the primary basic test for the Al ₂ O ₃ —SiO ₂ -based material and the fused quartz material.

[0010]

[Table 3]

The test specimens were adjusted to the mixing ratios shown in Table 3 using the specified materials shown in Tables 1 and 2, 1% by weight of boric anhydride was added as a sintering aid, and dry-mixed with a mixer. And used as test materials. As a molding method, molding by dry vibration filling was performed. That is, 250 × 40 on a shaking table (equipped with a Eurus motor having a frequency of 1800 times / minute).
A mold in which a 1 mm thick stainless steel metal case was inserted into a × 65 mm steel frame was fixed, and subjected to vibration filling under static pressure for 5 minutes.
After heating for a period of time, it was taken out of the stainless steel metal case to obtain a test body. Using this test body, a quality characteristic value test and an erosion test by a side wall dividing method are performed using a high frequency induction furnace. The quality characteristic values were measured on test specimens that had been subjected to heat treatment at 1000 ° C. for 10 hours. Erosion test conditions Melt Copper Molten metal temperature 1300 ° C Holding time 72 hours From the results of this basic test, A ₂ O ₃ -SiO ₂ material
l ₂ O ₃ 50% containing material has a large melting. In the fused quartz material, the sintering of the working layer progresses, and the amount of erosion is not much different from that of the high alumina material, and the penetration of foreign components is very small. Secondary Basic Test A secondary basic test was performed to determine the appropriate amount of silicon carbide material to be added. Table 4 shows the compounding ratios and test results.

[0012]

[Table 4]

Based on No. 3 and No. 4 of the primary basic test, 30% by weight of an alumina material and 70% by weight of a mullite material were used as reference materials, and the mullite material and the silicon carbide material were replaced. The appropriate amount was determined. Specimens were produced in the same manner as in the primary basic test, and were examined by conducting quality characteristic value tests and erosion tests. From the results of this secondary basic test, the addition amount of silicon carbide material is 5% by weight, and the effect of penetration depth of different components, erosion resistance, and slag resistance is recognized.
Up to 35% by weight, the effect of improvement is increased with an increase in the amount of addition, but at 40% by weight or more, the parallel values are almost the same. Tertiary Basic Test A tertiary basic test was conducted to determine the appropriate blending ratio of fused quartz based on the secondary basic test. Table 5 shows the results.
Silicon carbide material 15 based on the test material of the second basic test
The appropriate blending ratio of the fused quartz material was determined by substituting the fused quartz material with the mullite material, using the weight material, the alumina material 30% by weight, and the mullite material 50% by weight as reference materials. Table 6 shows the results of the heat-resistant spalling test. Specimens were prepared in the same manner as in the primary basic test, and were subjected to a quality characteristic value test erosion test and a heat resistance spalling test based on the rate of change in elastic modulus.

[0014]

[Table 5]

[0015]

[Table 6]

An improvement in spalling resistance is observed when the added amount of the fused quartz material is 5% by weight, but the effect is almost the same when the added amount is 30% by weight or more. Actual furnace use test An actual furnace test of the product of the present invention was performed based on the results of the basic test. Table 7 shows practical results together with comparative examples.

[0017]

[Table 7]

As the practically used products of the present invention, the products of the present invention of No. 2 and No. 4 in the third basic test were used. No. 1 and No. 6 were used as comparative examples. In each case, 1% by weight of boric anhydride was added as a sintering aid in the same manner as in the manufacturing method of the basic test.
Perform dry mixing with a mixer to produce test materials as dry-type irregular shaped materials, throw each test material into the bottom of the induction furnace main body, build the bottom, install a former, and place a former between the furnace main body and the former. (The specified furnace side wall lining thickness) This dry type irregular shaped material is charged, and it is vibrated and filled while applying impact vibration from the inside of the former to build it. , Copper and a copper alloy were kept at 1350 ° C., which is 100 ° C. higher than the normal temperature for melting and refining, for 2 hours, and after performing high-temperature sintering, melting and refining at 1250 ° C. were used repeatedly. The operating conditions of the induction furnace used in the actual furnace test are shown below. Furnace size 2T Melt Copper Molten temperature 1250 ℃

[0019]

As can be seen from the above results, the alumina mullite of the comparative example No. 6 of the working example of Table 7 which is currently generally used: The high alumina-silicon carbide type silicon carbide material cracks during use. The occurrence of many, and develop into abnormal damage in the form of a groove, the metal can not be inserted into this groove to withstand use, but the product of the present invention has very few cracks,
In addition, it can be used safely and stably without developing small and harmful abnormal damage. In addition, the ratio of the amount of damage per 1 channel of the present invention No. 2 and No. 4 is 33% and 36% for the comparative product No. 1 and 63% and 67% for the comparative product No. 6, respectively. The service life is expected to be improved and abnormal damage will be minimized, thereby improving the service life and greatly improving the operational stability.

Claims (1)

[Claims] 1. An induction furnace for melting and refining copper and copper alloys, wherein the innermost wall or the side wall and the bottom of the furnace is 5 to 30% by weight of fused quartz material, 5 to 40% by weight of silicon carbide material, Al
_A suitable sintering aid if necessary for a refractory material having a ₂ O ₃ content of 55% or more and a high alumina material and an alumina material of 30 to 90% by weight, the total of which is 90% by weight or more. An irregular-shaped refractory lining for an induction furnace, characterized by being produced by adding a refractory.