JPH11278918A - Basic refractory raw material and basic refractory, its production and metal smelting furnace and baking furnace using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a highly durable basic refractory and its raw material and to provide a metal smelting furnace and a baking furnace lined therewith. SOLUTION: This basic refractory raw material is produced by melting and solidifying raw materials of periclase (MgO) and alumina in an electric furnace. The periclase and spinel are contained as a main composition and the chemical composition contains 3-13% of Al2 O3 and the balance is MgO and inevitable impurities. The method for producing the basic refractory comprises compounding the raw materials with 2-10% of zirconia having <=50 μm particle diameter, kneading and forming the resultant mixture and then baking the formed compact at >=1,700 deg.C. The refractory contains 2.7-12.7% of the Al2 O3 and 2-10% of the ZrO2 and the balance is the MgO and inevitable impurities. The spinel, zirconia and other minerals are present in the grains and grain boundaries of the periclase crystals in the structure and the particle diameter of the zirconia is <=100 μm. The metal smelting furnace and baking furnace use the refractory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a basic refractory raw material, a basic refractory, a method for producing the same, and a metal refining furnace using the same, which are used for refining metals such as iron and steel, and sintering cement and lime. Furnace and firing furnace.

[0002]

2. Description of the Related Art In recent years, in a steel refining process, a strong refining operation such as a strong stirring or a strong reduction has been performed along with an upgradation of steel products and strictness of quality. Along with this, the refractory lining of the refining kiln furnace is greatly worn, so that the basic unit of the refractory has to be increased and the refractory having a high unit price has to be used. In addition, the increase in the frequency of furnace repairs (spray repair of refractories and repair of refills) has led to a decrease in production efficiency. For this reason,
There is a strong demand for improving the durability of refractories and extending the life of refractory linings.

[0003] In the refining of stainless steel, oxygen is blown or blown into a molten stainless steel produced in an electric furnace or a converter while reducing the partial pressure of CO, thereby removing carbon in the molten steel as CO to remove the molten stainless steel. To decarburize. The reason for lowering the CO partial pressure is to prevent the Cr component in the molten steel from being oxidized. At that time, the molten steel is strongly stirred in order to increase the reaction efficiency and obtain a low-carbon molten steel in a short time. After the decarburization is completed, a reduction operation is performed to return the chromium oxide generated during the decarburization process to the molten steel again. As equipment for performing these refining operations, AOD (Argon Oxyg)
en Decarburization) Furnace and VOD
(Vacuum Oxygen Decarburiz
ation) furnaces are often used.

[0004] In the AOD furnace, argon is blown simultaneously with oxygen from a position near the bottom of the side wall to decarbonize while lowering the CO partial pressure and agitate strongly. In a VOD furnace, the molten steel is put into a vacuum vessel together with the ladle and the pressure is reduced.
Reduce O partial pressure. In this case, oxygen is blown from above onto the surface of the molten metal, and Ar
Blow gas and stir the molten steel.

[0005] The reduction operation is performed for both the AOD furnace and the VOD furnace.
This is performed by adding a reducing agent such as l, Si, Ti or an alloy containing these to molten steel. In some AOD furnaces, a decompression function is added in order to increase the decarburization, degassing, and reduction capabilities.

[0006] Magnesia-chrome brick (hereinafter, referred to as magcro brick) is often used as a refractory lining for AOD furnaces and VOD furnaces. Magcro bricks are classified into direct bond bricks, semi-ribbon bricks, and ribbon bricks, depending on the raw materials used during production.

[0007] Direct bonding brick, the Pericles synthesized from smaller ones and seawater relatively SiO ₂ component of the chromium ore (also called magnesia) as a raw material. The raw material of the ribbon brick is an electrofused magcro obtained by temporarily melting, solidifying and pulverizing chromite ore and pericles in an electric furnace. Chromite is defined as chromite (Mg, F
e) A natural refractory raw material obtained by crushing chromitite, which is an aggregate of (Cr, Al) ₂ O ₄ }. Semi-bonded bricks are intermediate between direct-bonded and ribbon-bonded bricks and are made from pericles, chromite ore, and fused magcro. In the case of any of the bricks, the raw materials are blended, kneaded, molded, and fired to produce. The electrofused magcro has the function of accumulating fine chromite between the blended particles during firing of the brick to promote sintering of the brick and to densify it. Brick is highly corrosion resistant. The durability of the magcro brick is determined by the relationship between the properties of the brick and the use environment. AOD furnace and VOD
Under severe operating conditions such as furnaces, the corrosion resistance of refractories is important, and semi-ribbon bricks and ribbon bricks with high corrosion resistance are often used for lining.

[0008]

However, even if the lining of an AOD furnace or a VOD furnace is made using a high corrosion-resistant magcro ribbon brick or semi-ribbon brick as described above, the wear of refractories due to recent severe refining operations is still large. large. The present inventors recovered refractories worn in an AOD furnace or a VOD furnace and investigated the state of wear. The chromium ore near the operating surface of the brick was reduced, and a part of the chrome ore was decomposed into a metallic state. Was often observed. It is considered that such a situation occurred because chromium ore in the brick was also reduced when chromium oxide generated during decarburization of molten stainless steel was reduced. In other words, chromium ore plays a role as an adhesive inside the magcro brick, so when it is decomposed, the strength of the brick decreases significantly,
Further, it is considered that the brick is greatly worn.

[0009] Based on such considerations, the present inventors:
Peripheral technologies related to the above issues were studied. That is, calcia having a CaO composition is a mineral that is more resistant to reduction than chromite constituting chromite ore and can obtain a highly durable refractory material in combination with pericles.
Spinel (refers to a spinel of theoretical composition (MgAl ₂ O ₄ ) containing 28% by mass of MgO and 72% by mass of Al ₂ O ₃ ). Such pericles (Mg
Magnesia-dolomite bricks consisting of O) and calcia (CaO) are widely used next to magcro bricks for AOD furnaces. However, it cannot be overstated that its durability is inferior to magcro brick.

On the other hand, magnesia-spinel bricks composed of pericles (MgO) and spinel (MgAl ₂ O ₄ ) have been developed as substitutes for magcro bricks for cement kilns, and their application to steel refining kiln furnaces has been attempted. Was. However, slag easily penetrates into the brick tissue, causing a structural spall in which the slag infiltration layer peels off due to thermal shock, a deteriorated layer that has lost strength is worn out, and spinel that is relatively weak to slag is prematurely melted and bricks are damaged. The service life is generally low, as the whole is eroded.

As a measure for improving the slag infiltration resistance of such magnesia-spinel bricks, an invention using a spinel clinker containing zirconia and an invention of a refractory using the same are disclosed in JP-A-7-206511. And Japanese Patent Application Laid-Open No. 6-345521. However, when a refractory is formed by combining pericles and a spinel clinker containing zirconia, the zirconia component considered to be effective in suppressing slag infiltration is present only in the spinel clinker. As a result, there is a problem that the slag infiltration resistance of the refractory as a whole is not so high.

On the other hand, magnesia-spinel brick has been developed and used as a substitute for magcro brick which requires detoxification treatment at the time of disposal for a rotary kiln for firing cement or the like. However, magnesia-spinel brick has insufficient adhesiveness and hot strength of the cement coating layer compared to magcro brick, and has a problem in its durability when operating temperature is high or heat load is high. . In addition, this spinel has a disadvantage that it reacts with a cement containing a large amount of CaO to form a low-melting-point substance and is eroded prior to pericles, thereby deteriorating corrosion resistance.

As a method of improving such a problem,
Japanese Patent Publication No. 7-51458 discloses an invention of a refractory containing pericles, spinel and zirconia for a cement kiln. This refractory has a ZrO ₂ content of 0.5 to 1
Since it contains 0%, it reacts with the cement mainly composed of calcia to produce high melting point calcium zirconate (CaZrO ₃ )
To improve the adhesion of the cement coating layer. However, the disadvantage that spinel is eroded ahead of pericles still remains,
The effect of improving the durability is not sufficient.

Accordingly, an object of the present invention is to provide a basic refractory raw material, a basic refractory, a method for producing the same, and a metal refining kiln and a firing furnace using the same, which can advantageously solve the above-mentioned problems. Is what you do.

[0015]

The gist of the present invention to achieve the above object is as follows. (1) Pericles (MgO) and alumina (Al)
A raw material containing ₂ O ₃ ) as a main composition is melted in an electric furnace,
Among the basic refractory raw materials produced by solidification, pericles (MgO) and spinel (MgAl ₂ O ₄ ) are the main compositions, and the remainder is a basic refractory raw material comprising unavoidable minerals and impure compositions. And its chemical composition is A
l ₂ O ₃ in an amount of 3.0 to 13.0% by mass, with the balance being MgO
And a basic refractory raw material, which is an unavoidable impurity.

(2) Two or more zirconia (ZrO ₂ ) particles having a particle size of 50 μm or less are added to the refractory raw material described in (1) above.
A method for producing a basic refractory, comprising mixing 10% by mass, kneading and molding in a conventional manner, and firing at a temperature of 1700 ° C. or more. (3) At the time of mixing the refractory raw material, another refractory particle of 10% by mass or less is further mixed,
The method for producing a refractory according to the above (2).

(4) A basic refractory containing 2.7 to 12.7% by mass of Al ₂ O ₃ and ₂ to 10% by mass of ZrO ₂ , and the remainder having a chemical composition of MgO and unavoidable impurities. The microstructure of spinel (MgAl ₂ O) is formed within and / or at the grain boundaries of pericles (MgO) crystals.
₄ ) A basic refractory, characterized in that zirconia (ZrO ₂ ) and other minerals are present and the zirconia (ZrO ₂ ) has a microstructure having a particle size of 100 μm or less. (5) The basic refractory according to (4), wherein the basic refractory further has a chemical composition of another refractory of 10% by mass or less.

(6) A metal refining kiln characterized by using the basic refractory as described in (4) or (5) above as a lining material. (7) A baking furnace for cement or lime, wherein the basic refractory described in (4) or (5) above is used as a lining material.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the operation of the basic refractory of the present invention will be described below. The refractory of the present invention is a basic refractory raw material produced by melting and solidifying a raw material containing pericles (MgO) and alumina (Al ₂ O ₃ ) as main components in an electric furnace and solidifying the material. MgO) and spinel (MgAl ₂ O ₄₎ as a main composition, the balance is a basic refractory material consisting of unavoidable minerals and impure composition, its chemical composition, 3.0 to the _Al 2 _{O 3} 13.
It is manufactured by using MgO and basic refractory raw material which is an unavoidable impurity, and further blending 2 to 10% by mass of zirconia (ZrO ₂ ) having a particle size of 50 μm or less. The manufactured refractory is made of Al ₂ O ₃
2.7 to 12.7% by mass, ZrO _{2 2} to 10% by mass
The balance is a basic refractory having a chemical composition of MgO and unavoidable impurities, the microstructure of which is spinel (MgAl ₂ O ₄ ), within and / or at the grain boundaries of pericles (MgO) crystals. Zirconia (ZrO ₂ ) and other minerals are present and the zirconia (ZrO ₂ )
Is a microstructure having a particle size of 100 μm or less.

In addition, a raw material mainly made of pericles and spinel is manufactured by electromelting using pericles and alumina as raw materials, and hereinafter, a raw material mainly composed of pericles and spinel is simply referred to as electrofused magspy. It is desirable to use pericles synthesized from seawater or the like as pericles, which is a raw material of electrofused magnespies, but it is also possible to use calcined natural magnesite. Also, the alumina raw material,
Synthetic products are desirable in terms of purity, but natural materials such as calcined bauxite can also be used. These are melted in an electric arc furnace and then cooled and solidified to obtain an ingot. This is crushed and a portion containing less impurities is selected to be used as a refractory raw material.

The microstructure of this raw material, ie, electrofused magspy, is mostly pericles, and spinel is present in the grains and at the grain boundaries of pericles crystals. This is shown in FIG. This is a backscattered electron image of a fused magpie containing 8% by mass of Al ₂ O ₃ by a scanning electron microscope. Spinels (light gray parts) are found in the grains of the pericles crystals (dark gray parts) and at the grain boundaries, and compounds (white parts) containing CaO, an inevitable mineral, are found in some of the grain boundaries. The pores (black portions) are characterized by being scattered, small in volume, and not continuous. Due to such characteristics, even if the electrofused magsp contacts the slag, the slag does not infiltrate through the pores. Therefore, even when the refractory is used, the spinel whose corrosion resistance to slag is lower than that of pericles is also protected, and the corrosion resistance of the refractory is not significantly impaired. Pericles, on the other hand, has the property that slag easily penetrates into its grain boundaries and collapses.However, if spinel is present at the grain boundaries of Pericles, the grain boundaries are protected and the slag is infiltrated. Is effectively suppressed. Further, pericles have a large coefficient of thermal expansion and generate thermal stress with temperature fluctuation. However, spinel at the grain boundary also plays a role of absorbing or releasing thermal stress, so that spall resistance can be improved.

The refractory raw material of the present invention can be produced by a method of melting and solidifying in an electric furnace, but cannot be produced by a sintering method using a powder raw material. What was created by the sintering method,
This is because the porosity is high, the spinel cannot be well distributed at the pericles crystal grain boundaries, and the corrosion resistance, slag infiltration resistance, and spall resistance are poor.

Next, the method for producing a basic refractory of the present invention will be described based on the results of trial production evaluation. First, as a comparative example of the present invention, Japanese Patent Publication No. 7-5145,
A brick manufactured by blending pericles, spinel, and zirconia, which can be conceived from the invention described in Japanese Patent Publication No. 8, was prototyped and evaluated. Table 1 summarizes the blending and evaluation results. The raw materials used in the trial production were electrofused magnesia (MgO), electrofused spinel (MgAl ₂ O ₄ ) having a nearly stoichiometric theoretical composition,
Unstabilized zirconia (ZrO ₂ ), chromia (Cr ₂ O)
₃ ) and alumina (Al ₂ O ₃ ). In each case, those having a purity of 90% by mass or more were used. The particle size of pericles was 5 mm or less, and the electrofused spinel was prepared as a regular product having a particle size of 3 mm or less and fine particles having a particle size of 150 μm or less. The particle diameters of zirconia, chromia and alumina were all 50 μm or less. These were blended in the ratios shown in Table 1, an aqueous polysaccharide solution was added, and the mixture was kneaded.
5 × 114 × 230mm), and after drying, 1800
Fired at ℃. In addition, a magcro semi-ribbon brick was also prepared as a comparative sample.

The evaluation items were general physical properties, hot bending strength, spall resistance, and corrosion resistance. General physical properties, that is, bulk specific gravity,
The apparent specific gravity and apparent porosity were measured in accordance with JIS standard methods. The hot bending strength is 40 × 40 for the sample size.
× 160 mm, gradually heated in an Ar atmosphere, and finally kept at 1500 ° C. for 15 minutes, and then span 100 m
m.

The spall resistance was evaluated by a hot metal immersion test. In the hot metal immersion test, the molten iron
This is a test method in which a test cycle is repeated in which a sample is immersed in hot metal held at 00 ° C. for 1 minute, allowed to cool for 4 minutes after extraction, and the number of repetitions until the lower end of the sample peels off was examined. The sample shape was 40 × 40 × 230 mm, and 110 mm was immersed from the lower end in the longitudinal direction of the sample. The test results were indexed by taking the case of magcro brick as 100 and defined as the Spall index. The higher the value, the better the spall resistance.

The corrosion resistance was evaluated by a vacuum erosion test. 50
A sample processed into a strip shape was lined in a vacuum high-frequency induction melting furnace, and about 15 kg of a stainless steel lump and a small amount of Al were put therein and melted while reducing the pressure to 20 torr or less.
C. and 200 g of slag was injected four times every 30 minutes for a total of 2 hours to erode the sample. The composition of the slag is as follows: basicity C / S (mass ratio) = 1.5, Al ₂ O ₃
= 8% by mass and MgO = 13% by mass. Discharge the molten steel after the experiment, take out the sample after cooling, cut it vertically,
The remaining dimension of the maximum erosion portion was measured and subtracted from the previously measured original thickness to obtain the erosion depth. The results were indexed by setting the case of magcro brick to 100 and used as the erosion index. The smaller the value, the better the corrosion resistance. In addition, the thickness of the portion where the slag was judged not to be infiltrated visually in the maximum erosion portion was measured, and this was subtracted from the remaining dimension to obtain the slag infiltration depth. The slag infiltration index was also indexed by setting the case of magcro brick to 100.
The smaller this value is, the more excellent the slag infiltration resistance is.

[0027]

[Table 1]

According to Table 1, E was slightly higher in corrosion resistance than the comparative magcro brick, but the others were comparable or less. Regarding the slag infiltration resistance, B and D to which chromia was added were bad, but A, C and E were almost equivalent to magcro brick. The spall resistance was all better than the magcro brick. Summarizing the above, simply producing a brick by simply blending pericles, spinel, and zirconia as can be conceived from the invention described in Japanese Patent Publication No. Hei 7-51458,
Nothing greatly surpassed the corrosion resistance of magcro brick. However, it was found that when about 10% of fine-grained spinel was blended as in E, a slightly superior corrosion resistance was obtained. When 10% by mass of fine spinel is blended, even if the slag is affected by relatively weak spinel,
It was considered that the volume occupied by the spinel was small, and it was fine and dispersed, so that the damage to the entire brick was small and the corrosion resistance was improved.

[0029] The present inventors have found that in achieving protection weak spinel slag material to the electrostatic infusible believe effective to a tissue spinel is surrounded by Pericles, MgO is the main composition Al ₂ O A refractory raw material of an electrofused magspi containing 14% by mass of No. ₃ was experimentally produced. The amount of spinel contained in this raw material was about 20% by mass. As a raw material, see Table 1 above.
In addition to those used in the trial production, sintered spinel coarse particles having a purity of 90% by mass and chromium ore having a Cr ₂ O ₃ content of about 50% by mass were also used. In each case, the particle size was 1 to 3 mm.
Using each raw material, a brick was prototyped in the same manner as the previous time, and various characteristics of the brick were evaluated. Table 2 shows the composition and evaluation results.

[0030]

[Table 2]

According to Table 2, there was no corrosion resistance higher than that of magcro brick, but K obtained by adding zirconia to electrofused magspita was relatively excellent in corrosion resistance. G or H obtained by adding chromia or chromite to the electrofused magpi had poor corrosion resistance. Regarding the slag infiltration resistance, J obtained by adding spinel coarse particles to electrofused magspi was inferior, but the others were comparable or superior to magcro brick. Although the spall resistance was superior to the magcro brick in all cases, G was relatively inferior to the other prototypes. To summarize the above, A
All the bricks using electrofused magspi containing 14% by mass of l ₂ O ₃ were inferior to magcro bricks in terms of corrosion resistance. This is due to the concentration of Al ₂ O ₃ in the electrofused
That is, it is considered that the spinel amount was too large. However, rather than simply combining MS with pericles, spinel, and zirconia, K with electrofused magspi and zirconia was compared.
It was thought that the use of electrofused magspi was effective because of the higher corrosion resistance.

Therefore, two kinds of electrofused magpies having a small content of Al ₂ O ₃ were trial-produced, and bricks using these were trial-produced and evaluated. Table 3 shows the chemical composition of the electrofused magspy.
The electrofused magspy A has a main composition of MgO and contains 8% by mass of Al ₂ O ₃ (about 11% by mass in terms of spinel).
The electrofused magspi B has a main composition of MgO and contains 13.0% by mass of Al ₂ O ₃ (about 18% by mass in terms of spinel). Using these and the above-described electrofused magnesia, unstabilized zirconia, and alumina, bricks were prototyped and evaluated in the same manner as in the past. Table 4 shows the composition and the evaluation results. In addition, many electrofused magnesia is added to P, Q, R, S and U. This was an attempt to dilute Al ₂ O _3, or spinel, in the brick to improve corrosion resistance.

[0033]

[Table 3]

[0034]

[Table 4]

According to Table 4, the corrosion resistance of all bricks containing the electrofused magspi exceeded that of the magcro brick. For slag infiltration resistance, L, M, N, T
Magcro was better than brick. However, in P, Q, R, S, and U to which electrofused magnesia was added, the slag infiltration resistance deteriorated according to the added amount. Regarding the spall resistance, those using electrofused magspi exceeded the magcro brick in all cases. U with a large amount of electrofused magnesia
Had relatively low spall resistance. Summarizing the above, when using an electrofused magspy having a maximum Al ₂ O ₃ content of 13.0% by mass and blending with zirconia of approximately 3.0 to 5.0% by mass, a high corrosion resistance and a high corrosion resistance can be obtained. It was found that a refractory having both slag infiltration and spall resistance could be obtained.

The upper limit of the content of Al ₂ O _{3 in} the electrofused magpie is 13.0% by mass as described above. On the other hand, the lower limit is 3.0% by mass. Below this, the slag infiltration increases as in samples P, Q, R, S and U to which electrofused magnesia is added. The Al ₂ O ₃ content of the electrofused magsp is desirably 5.0 to 10.0% by mass. The basic refractory of the present invention using the electrofused magspy as a refractory raw material has an Al content of Al ₂ O ₃ converted from the above electrofused magspy.
_It contains 2.7 to 12.7% by mass of ₂ O ₃ . If the amount of zirconia exceeds 10% by mass, the corrosion resistance decreases, and if it is less than 2% by mass, the corrosion resistance and the slag infiltration resistance deteriorate. In addition, the compounding quantity of zirconia is desirably 3 to 8% by mass.

Refractory particles other than electrofused magspy and zirconia can be added up to 10% by mass. For example, as shown in M of Table 4, alumina (Al
It is also possible to add ₂ O ₃ ). In addition to alumina, spinel, chromite, chromia (Cr ₂ O ₃ ), mullite (Al ₆ Si ₂ O ₁₃ ), zircon (ZrSiO
₄ ), silica stone (main component SiO ₂ ), silica (SiO ₂ ),
Calcia (CaO), Dolomite II (Ca, Mg)
It is also possible to add O｝ or a mixture obtained by electromelting them, a metal, a carbide, a boride, a nitride, or the like. However, in that case, it is necessary to adjust the addition amount and the particle size so that corrosion resistance, slag infiltration resistance, and spall resistance are not impaired. The upper limit of the amount added is 10% by mass.
Beyond this, corrosion resistance, slag infiltration resistance,
This is because the spall resistance is impaired.

A reflection piece of the refractory of the present invention was prepared, and a fine structure was observed by a reflection electron image with a scanning electron microscope. 2, 3 and 4 show the reflected electron images of N in Table 4 as representative examples. In FIG. 2, large electrofused magspy particles having a particle size of several thousand μm are seen from the center to the lower right, and about one quarter of the upper left.
It can be seen that は is approximately 300 μm or less in particle size and that the grain boundary is made of zirconia (white portion). FIG. 3 is an enlarged view of the central part of FIG. 2 in order to examine the distribution of spinels. The edge of a large electrofused magpie is visible. It can be seen that the electrofused magspi is composed of pericles (dark gray part), spinels (light gray part) dispersed therein, and zirconia. Also,
A large amount of zirconia is seen at the grain boundary of the fused magspi in the upper left, and it can be seen that spinel is accompanied around the zirconia. The particle size of zirconia is approximately 50 μm or less, but it is connected and coarsened, and the major axis is about 100 μm.
Some are acceptable. FIG. 4 is an enlarged view of the center of FIG. 3 slightly closer to the right in order to examine the spinel distribution in detail. Crossing the center slightly to the right from top to bottom in the shape of a "<" is the spinel of the pericles grain boundary. It is thought that what originally existed in the electrofused magpie remained after the brick was manufactured. Fine spinel and zirconia are distributed in the right and left pericles crystal grains of this band.

The spinel in the refractory of the present invention exists inside the pericles crystal and at the grain boundaries. Spinel is relatively easy to be attacked by slag, but the amount is small,
Moreover, since it is protected by pericles, the corrosion resistance of the brick is hardly impaired. On the other hand, since spinel is present at the grain boundaries of pericles where slag is easily infiltrated, slag hardly penetrates along the grain boundaries of pericles.
In addition, spinel effectively reduces thermal stress generated in pericles having a large thermal expansion coefficient. Fine-grained zirconia that is present in a dispersed form dissolves into the infiltrated slag,
Alternatively, by suspending in the slag, the viscosity of the intruding slag is increased, and further infiltration is suppressed.

The refractory of the present invention can be handled in the same manner as a conventionally used refractory, for example, a magcro brick, to build a refractory lining such as a kiln. The joint material is desirably made of magnesia, but it can also be constructed at an empty joint. However, Cr ₂ O ₃ is 20% by mass.
Since the degree of thermal expansion coefficient tends to be larger than that of the contained magcro brick, it is necessary to optimize the arrangement of the expansion allowance. The refractory and refractory lining of the present invention are suitable for stainless steel refining kiln furnaces such as AOD furnaces and VOD furnaces. However, secondary refining facilities such as degassing facilities for RH, etc. It is also suitable for equipment and smelting reduction equipment.

[0041]

(Example 1) N in Table 4 was partially applied to the side wall of a 60 tAOD furnace, and the situation was examined after use. The wear rate estimated from the remaining dimensions of the refractory was about 25% lower than that of the surrounding magcrosemi-ribbon brick, confirming the effectiveness of the present invention. When the bricks were collected and examined, the slag infiltration depth was about half that of the surrounding magcro bricks, and no cracks were observed.

Example 2 Similarly, N in Table 4 was partially applied to the sintering zone of a rotary kiln for cement sintering, and the condition was examined after 6 months of use. The wear rate estimated from the residual size of the refractory was about 20% lower than that of the surrounding magnesia-spinel bricks, confirming the effectiveness of the present invention. Further, when the brick was collected and examined, the thickness of the coating layer was about twice as large as that of the surrounding magcro brick, and no crack was recognized between the brick and the raw material layer.

[0043]

As described in detail above, according to the present invention,
The wear rate of the refractory lining can be reduced, and the life of the lining and the furnace can be prolonged.Thus, it is possible to reduce the cost of refractory and improve the equipment operation rate and productivity by reducing the frequency of furnace repairs. It is possible to reduce the production cost of steel, metal, cement and the like.

[Brief description of the drawings]

FIG. 1 is a photograph showing a microstructure of a refractory raw material of the present invention in a reflected electron image by an electron microscope. Black portions are pores, dark gray portions are pericles crystals, light gray portions are spinels, and white portions are compounds containing CaO.

FIG. 2 is a photograph showing a microstructure of a basic refractory of the present invention as a reflected electron image by an electron microscope. The black parts are pores, the dark gray parts are electrofused magspy particles, and the white parts are zirconia. Large electrofused magspy grains with a particle size of several thousand μm are visible at the lower right from the center.
An electrofused magspy having a particle size of approximately 300 μm or less can be seen, and it can be seen that the grain boundary is made of zirconia.

FIG. 3 is an enlarged photograph of a central portion of FIG. Black portions are pores. It can be recognized that the electrofused magnet of FIG. 1 has a dark gray portion (pericles) and a slightly lighter gray portion (spinel). The zirconia part in FIG. 1 is composed of a white part (zirconia) and a slightly light gray part (spinel) around it.

FIG. 4 is an enlarged photograph of a portion slightly to the right in the center of FIG. 3; The dark gray areas are pericles, the light gray areas are spinels, and the white areas are zirconia. The slightly gray belt-like portion that crosses the center slightly to the right from top to bottom in the shape of a "<" is the spinel of the pericles grain boundary. Fine spinel and zirconia can be seen in the right and left pericles grains of this band.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // B22D 41/02 C04B 35/44 101 (72) Inventor Koichi Shimizu 1-1-1, Higashihama-cho, Yawata-nishi-ku, Kitakyushu-shi, Fukuoka Kurosaki Inside the Ceramics Research Institute (72) Inventor Takeki Yoshitomi 1-1, Higashihama-cho, Yawatanishi-ku, Kitakyushu-city, Fukuoka No. 1 Kurosaki Ceramics Co., Ltd.

Claims (7)

[Claims] 1. A method according to claim 1, wherein pericles (MgO) and alumina (Al) are used.
A raw material containing ₂ O ₃ ) as a main composition is melted in an electric furnace,
Among the basic refractory raw materials produced by solidification, pericles (MgO) and spinel (MgAl ₂ O ₄ ) are the main compositions, and the remainder is a basic refractory raw material comprising unavoidable minerals and impure compositions. And its chemical composition is A
l ₂ O ₃ in an amount of 3.0 to 13.0% by mass, with the balance being MgO
And a basic refractory raw material, which is an unavoidable impurity. 2. The refractory raw material according to claim 1, wherein
₂ to 10% by mass of zirconia (ZrO ₂ ) of 0 μm or less
A method for producing a basic refractory, comprising blending, further kneading, molding, and firing at a temperature of 1700 ° C. or higher. 3. The method according to claim 1, further comprising the step of:
The method for producing a refractory according to claim 2, wherein another refractory particle of 10% by mass or less is blended. 4. An Al ₂ O ₃ content of 2.7 to 12.7% by mass,
₂ to 10% by mass of ZrO ₂ , the balance being a basic refractory having a chemical composition of MgO and unavoidable impurities, the microstructure of which is within the grains and / or grain boundaries of pericles (MgO) crystals, Spinel (MgAl
₂ O ₄ ), zirconia (ZrO ₂ ) and other minerals, and the particle size of the zirconia (ZrO ₂ ) is 100 μm.
m. A basic refractory having a microstructure of not more than m. 5. The basic refractory according to claim 4, wherein the basic refractory further has a chemical composition of another refractory of 10% by mass or less. 6. A furnace for refining a metal, wherein the basic refractory according to claim 4 or 5 is used as a lining material. 7. A firing furnace for cement, lime, etc.,
A firing furnace, wherein the basic refractory according to claim 4 or 5 is used as a lining material.