JPH08217552A - Monolithic refractory for induction furnace - Google Patents

Abstract

PURPOSE: To obtain the refractory having a long service life by sufficiently effectively utilizing the refractory constructing a refractory wall. CONSTITUTION: This lining refractory for an induction furnace consists of 25-93wt.% magnesia-base material, 5-50wt.% chromium-base refractory material and 2-25wt.% alumina-base material contg. >=90wt.% alumina, and the total content of the three kinds is controlled to >=90wt.%. The residual expansion of the refractory is controlled to 0 to 5wt.% when the refractory is applied and heat-treated at 1500 deg.C. Accordingly, the service life is remarkably prolonged, the V-grooved abnormal erosion due to cracking is shallowed or the erosion is never caused, the refractory is sufficiently effectively used, and stabilized operation is conducted safely, and a dramatic effect is produced on durability and operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous furnace refractory for an induction furnace used as a lining for an induction furnace used for melting metal.

[0002]

2. Description of the Related Art In the casting industry, melting efficiency of metal is high in terms of productivity, labor saving, quality of molten metal and working environment. Easy operation and easy labor saving. There are few pollution problems. A molten metal with high quality stability and high homogeneity can be easily obtained. Easy adjustment of composition and temperature. Induction furnaces, which have many advantages, are rapidly becoming widespread.

At present, a crucible type induction furnace has an electric induction heating coil on the outer periphery thereof, and if necessary, the inside of this coil is covered with coil cement for protection, and further a hot water leak sensor, an insulating material, and a heat insulation are provided on the inside. A fireproof wall is constructed with one layer of refractory inside by arranging materials and the like. This refractory wall is generally installed in the furnace by using an inner mold made of steel (hereinafter referred to as a former) designed to have a refractory wall having a predetermined thickness in the furnace body. After the dry powdery amorphous refractory is put into the gap between the furnace body and the former, the refractory is put into the building by vibrating and filling while applying vibration from the inside of the former. The goodness of vibrating and filling of this dry powder indeterminate refractory material greatly affects the life of the refractory material, and it also greatly affects the operating rate of the foundry, which is high for constructing a reliable construction body. Requires skill level. In this way, the refractory used for this is carefully examined along with the quality of the construction, and as a refractory suitable for the usage condition so that a long life can be obtained, a silica stone material, a high alumina material, an alumina material, magnesia, and / or spinel. Each of the materials is used as a high-purity refractory material, and if necessary, a sintering aid such as boric anhydride is added and used. When using it, there is a loss of reaction with the melt,
The dissolved substance penetrates into the tissue to form an altered layer, which causes internal cracks and causes a layered peeling along the operating surface, resulting in severe damage. On the other hand, when these melts penetrate into the structure, the heat resistance is lowered, and the glassy substances increase,
There are many problems such as over-sintering, which leads to volume contraction, large cracks, abnormal groove-like damage, stable operation cannot be performed, and bare metal scales occur from this part, shortening the service life. However, there is a strong demand for these improvements.

[0004]

Currently, in order to melt and refine casting materials such as cast steel and stainless steel, the melt temperature is 1650 ° C.
Since the temperature is as high as ~ 1700 ° C, magnesia materials and / or magnesia-alumina spinel materials are used. As the usage progresses, the penetration of foreign matter into the refractory,
Due to the generation of an altered layer due to heat reception, volume contraction occurs, and cracks occur inside the structure and in the surface layer part, and this crack becomes a groove-like abnormal melt loss and delamination along the operating surface Therefore, it is not possible to withstand the use and cannot fully use the fireproof wall material, and depending on the site, it is forced to replace with a new material while leaving a residual thickness of 60% to 80%. It is a technical subject to eliminate such defects and provide a refractory material for an inner lining which is intended to have a long life.

[0005]

In view of the above situation, the inventors of the present invention have developed a refractory material which can be made to have a long life by fully utilizing the refractory material constructing the refractory wall effectively. As a result of various studies, it has been found that it can be solved by using at least three kinds of composite materials of magnesia material-chromium-containing refractory material-alumina material. Specifically, by combining a magnesia material with a chromium-containing refractory material such as chrome ore, it was possible to suppress heat spalling resistance, foreign matter penetration resistance, and internal cracking, but only with these two types. Since cracks may occur at high temperatures, further mix Al ₂ O ₃ material to form spinel (MgO, Al ₂ O ₃ ) between MgO and Al ₂ O ₃ when used in the structure. The residual swelling property was made possible, and the permeability of foreign matter could be suppressed. The most effective range of the above three materials is MgO
Material 25% to 93% by weight, chromium-containing refractory material 5% to 50
₂ % by weight of alumina material containing 90% or more by weight of Al ₂ O ₃
-25% by weight, the content of these three types is 90% by weight or more made of refractory material, and this work body adjusts to a linear change rate of 0 to 5% at 1500 ° C to allow penetration of foreign matter into the tissue. It is possible to suppress the occurrence of delamination of the working layer, the occurrence of harmful cracks, and the shortening of the life due to ingot insertion due to groove-like abnormal melting damage, improving the stable operation rate of the furnace and extending the service life. It provides refractory materials that can be used.

(Reason for limitation) Magnesia material 25% to 93% a) When it is 25% or less, corrosion resistance is lowered and a sufficient life cannot be obtained. b) When the content is 93% or more, the MgO characteristics are exhibited, and groove-shaped abnormal damage is caused due to the occurrence of internal rupture, peeling, and cracking due to foreign matter intrusion, and the metal insertion phenomenon is likely to occur. Chromium-containing refractory material 5% to 50% a) If it is 5% or less, the effect of suppressing the permeation of foreign matter and the occurrence of cracks cannot be obtained. b) If it exceeds 50%, the heat resistance and corrosion resistance will be poor. c) As the chromium-containing refractory material, any of the refractory materials of 1 MgO, Cr ₂ O ₃ -based refractory material containing ₃ chromium ore 2 Cr ₂ O ₃ 5% or more and 3 McNessia-chromite composite synthetic refractory material can be used. It can be used as a chromium-containing refractory material. Alumina material containing 90% or more of Al ₂ O ₃ 2%
-25% a) 90% or more is because the impurities other than Al ₂ O ₃ form a low-melting material between the base material and the heat resistance and corrosion resistance. b) If it is 2% or less, the effect of suppressing the permeation of foreign matters and residual swelling cannot be expected. c) If it exceeds 25%, Mg is absorbed between MgO and Mg.
With the formation of spinel of O and Al ₂ O ₃ , the structure becomes brittle and becomes porous, and the penetration of foreign substances and the corrosion resistance decrease. 90% or more of the content of three kinds of magnesia material, chrome-containing refractory material, and alumina material If the content of these three kinds is 90% or less, heat resistance and corrosion resistance are deteriorated by mixing other materials.

[0007]

EXAMPLES Next, examples will be shown. 1. The quality characteristics of the materials used in the examples are shown in Table 1.

[0008]

[Table 1]

First of all, using these refractory materials, a primary basic test, a magnesia material, a composite refractory material of a chrome ore material, a secondary basic test, a magnesia material, a composite material of Al ₂ O ₃ Example Magnesia material, The test results of the composite material of chrome ore and aluminum are shown below. The sample preparation for this basic test was 0.5 mm in a 230 × 30 × 114 mm mold on a vibrating table with a frequency of 1800 times / min.
Put the metal case made of stainless steel, and oscillate and fill with static pressure for 5 minutes.
After heating for 2 hours, the sample is taken out from the metal case made of stainless steel and used as a sample, which is heat-treated at 1600 ° C. to check the quality. For the slag erosion test, a sample that has been heat-treated at 800 ° C. for 2 hours is placed in a high-frequency induction furnace separately for each type of material and then tested. The test material has a CaO / SiO ₂ ratio of 1.
5 slag and cast iron 92%, Si3%, Mn2%, C3%
Is dissolved and held at 1600 ° C. for 5 hours. Table 2 shows the results of the primary basic test using magnesia materials and chromium ore materials.

[0010]

[Table 2]

Second by magnesia material and alumina material
The results of the following basic tests are shown in Table 3.

[0012]

[Table 3]

Results of the basic tests of these 2 series Magnesia-chromium ore materials When the content of chromium ore materials is 45%, the strength and compactness tend to decrease, and when it exceeds 55%, it further progresses and becomes structurally weak. It is desirable to set the upper limit to 50%. Magnesia-Alumina Material When the content of the alumina material exceeds 20%, the structure becomes brittle and the strength and density decrease greatly. Therefore, it is desirable to set 20% as the upper limit in terms of quality. The results are shown below. Table 4 shows an example in which 90% by weight or more of the three types of magnesia material-chromium-containing refractory material-alumina material of the present invention is used.

[0014]

[Table 4]

Based on the above results, the various materials of the invention products and the comparative products 1 and 2 were dried in a high frequency induction furnace for 5 hours,
As an irregular refractory material, a wall thickness of 100 mm was vibrated and used. The results are shown in Table 5.

[0016]

[Table 5]

[0017]

EFFECTS OF THE INVENTION At present, the mainstream of basic refractory materials is 100% magnesia material, but most of them are used for the most general surface. As shown in Table 5, the total durability of the steel and the chrome ore material added with the alumina material is shown in Table 5, and the product of the present invention melts per channel as compared with the magnesia material (Comparative product 1). Loss amount is 42.5%, 34
%, The service life is 204% and 270%, and the service life is greatly increased and improved, and the V-shaped groove-like abnormal melting loss due to cracks is also shallow, or the result of not occurring at all can be corrected. It was possible to use the refractories sufficiently, and it was possible to obtain a tremendous effect in terms of durability and operation, such as stable and safe operation.

Claims (2)

[Claims] 1. An induction furnace lining refractory for melting metal, wherein the magnesia material is 25% to 93% by weight, the chromium-containing refractory material is 5% to 50% by weight, and the alumina content is 90% or more. % To 25% by weight, and the content of these three kinds is 90% by weight or more, and an amorphous refractory for an induction furnace. 2. The construction body of a refractory material lined with an induction furnace is 1500.
The amorphous refractory material for an induction furnace according to claim 1, which has a residual expansion of 0 to 5% by heat treatment at ℃.