JP2013173657A - Dry ramming material and method for manufacturing refractory material using the same - Google Patents

Abstract

[PROBLEMS] To provide a dry ramming material that is a refractory material that has a low thermal conductivity as low as siliceous, suppresses energy costs, does not impair heat resistance, and has improved strength in a high temperature range, and refractory using the same. A method for manufacturing a product is provided.
A dry ramming material comprising a refractory aggregate and a sintering aid, wherein the refractory aggregate comprises 90-99% by mass of silica aggregate, magnesia aggregate, alumina aggregate and alumina- A dry ramming material comprising 1 to 10% by mass of at least one aggregate selected from silica aggregates, and using fused silica particles and natural silica particles in combination as the silica aggregates.
[Selection figure] None

Description

  The present invention relates to a dry ramming material and a method for manufacturing a refractory using the dry ramming material, and more particularly to a dry ramming material having improved strength at high temperature use and a method for manufacturing a refractory using the same.

  The refractory material to be rammed with the rammer is generally called a ramming material (meaning a material for the rammer construction), and there are roughly two types. First, a ramming material that contains a binding liquid such as coal tar pitch and exhibits a certain degree of strength at room temperature after construction is called a wet (wet) ramming material. A ramming material having a low strength is called a dry ramming material.

  The advantage of the dry ramming material is that the construction is very easy and a high packing density can be obtained as compared with the wet ramming material. That is, since it is a material composed of dried grains, it has good fluidity when struck or vibrated, and is easy to fill in the voids. On the other hand, since the wet ramming material is easy to aggregate due to aggregates, poor filling tends to occur.

  The main application of such a dry ramming material is a material for an electric induction heating furnace (hereinafter referred to as a heating furnace). In order to form this heating furnace, firstly, a gap of the necessary lining thickness (the lining thickness is often 100 mm to 150 mm in the crucible furnace) is set between the furnace shell and a metal frame is installed inside the furnace. While putting the dry ramming material into the gap, the metal frame is shaken with a vibration motor, or the input material is tightly filled with a stick with a vibrator attached and filled. Since the strength of the molded body is insufficient at the time of filling, the metal frame is heated and sintered by melting a sintering aid (for example, boric acid) contained in the dry ramming material (molded body). To provide sufficient bonding strength.

  Sintering by heating the metal frame is performed by electric induction heating using an induction furnace (hereinafter referred to as induction heating). Induction heating is a heating method in which an electric field is caused to flow through a coil disposed on the outer periphery of the furnace wall to generate an electric field, and resistance heat is generated in the metal inside the coil. During this heating, a large amount of current flows through the coil, so it is necessary to avoid the presence of a conductive substance in the vicinity of the furnace wall. However, since the dry ramming material does not contain moisture, there is no fear that the current flowing in the coil will be short-circuited, and the induction furnace can be formed by a firing operation with peace of mind.

  However, at this time, a temperature gradient is generated from the furnace toward the furnace wall. That is, although the treated metal generates heat in the furnace and becomes high temperature, the surroundings are cooled by a water cooling structure on the furnace wall side so as not to release heat to the outside. Therefore, the dry ramming material is sintered and has sufficient strength inside the high-temperature furnace, but does not rise to the sintering temperature on the furnace wall side, and the powder composition is only in a dense state, and the strength is high. Because it does not come out, the furnace wall cannot be removed.

  After sintering the dry ramming material, the induction furnace is made by removing the metal frame. After sintering, the metal frame may be heated to a melting temperature and melted in a refractory (inductive heating furnace) formed of a dry ramming material (molded body) and processed as the first treated metal.

  Another advantage of this dry ramming material is low electrical conductivity. In the induction furnace obtained as described above, a target metal is placed inside, and by applying a magnetic field to this metal, an electric current is passed and the metal itself is heated and melted by its resistance heat. Therefore, if moisture is contained in the refractory that comes into contact, there is a possibility that a current flows there and short-circuits. Since the dry ramming material does not originally contain moisture, there is no fear of that.

  The characteristics required for the refractory of the induction furnace are mainly examined from two aspects, an operational aspect and a structural aspect.

  From the operational aspect, during operation, after the treated metal in the furnace is melted, strength against wear when the metal convects in the furnace is required. The strength against wear here has a correlation with the compressive strength of the refractory, and the greater the compressive strength, the higher the wear resistance of the treated metal against convection.

  Further, from the structural aspect, in forming the induction furnace using the dry ramming material, it is required to press the outer periphery due to the expansion of the refractory itself. This is because only the furnace wall constrains the refractory formed by firing, and the powder composition is only densely packed between the fired refractory and the furnace wall. If it contracts, it will lose its support, and in the worst case it will collapse. However, during operation, the oxide constituting the refractory expands at a high temperature, so that there is little problem. The problem is whether or not expansion (hereinafter also referred to as residual expansion) occurs at the time of stopping. In this specification, whether or not there is residual expansion is determined by measuring the linear change rate when cooled from high temperature to room temperature and determining whether or not residual expansion is exhibited.

  In order to improve the durability as described above, it is necessary to directly increase the strength of the refractory, but in the past, it has been improved by the following two methods.

  One method is to increase the amount of sintering aid. The sintering aid has a role of promoting the sintering by lowering the melting point of the refractory aggregate. As the addition amount increases, the sintering is accelerated and the strength increases (see Patent Document 1).

  Another method is to increase the strength of the aggregate. In reality, considering the balance between strength and cost, silica → mullite → alumina and magnesia are selected in this order, and this is also the order in which the strength of the aggregate itself increases, and alumina and magnesia described in parallel are It is properly used depending on the purpose.

Japanese Patent Publication No.59-6368

  However, the method of Patent Document 1 mainly focuses on sintering in a low temperature region such as about 600 ° C., and promoting liquid phase formation in a low temperature region reduces heat resistance itself. As a result, the heat resistance may be insufficient in the operating temperature range near 1600 ° C. where the metal is melted.

  In addition, the order of selection of the aggregate explained in the above-described improvement in strength by the aggregate overlaps with the order in which the thermal conductivity increases, and even if the strength is increased, if the thermal conductivity is large, the heating state at a predetermined temperature is increased. In order to maintain it, extra energy must be applied from the outside. Therefore, the method of increasing the strength of the aggregate has a problem that the energy cost in the operating temperature range increases.

  Therefore, the present invention has been made to solve the above-mentioned problems, and while reducing the thermal conductivity to about the siliceous level, the energy cost is suppressed, the heat resistance is not impaired, and in a high temperature range. It aims at providing the dry ramming material used as the refractory which improved the intensity | strength, and the manufacturing method of a refractory using the same.

  The dry ramming material of the present invention is a dry ramming material composed of a refractory aggregate and a sintering aid, and the refractory aggregate is composed of 90 to 99% by mass of silica aggregate, magnesia aggregate, alumina bone. 1 to 10% by mass of at least one kind of aggregate selected from a material and an alumina-silica aggregate, and as the silica aggregate, fused silica particles and natural silica particles are used in combination. .

  In this dry ramming material, it is preferable to use a magnesia aggregate and an alumina aggregate and / or an alumina-silica aggregate in terms of improving the strength.

  Further, the method for producing a refractory according to the present invention includes a step of filling the above-described dry ramming material between a furnace wall and a mold, and heating the filled dry ramming material by electric induction heating to sinter. And a step of making it.

  According to the dry ramming material of the present invention and the method for producing a refractory using the same, a refractory excellent in strength and energy cost can be provided in the operating temperature range of the furnace.

  Silica aggregate is used as the main aggregate, and by adding a small amount of at least one kind of aggregate selected from magnesia aggregate, alumina aggregate and alumina-silica aggregate, the energy cost can be kept low after construction. The refractory has a heat resistance and sufficient strength in the high temperature operating temperature range, and can improve the durability in the high temperature operating temperature range. Moreover, since fused silica particles and natural silica particles are used in combination as the silica aggregate, it has excellent thermal stability while having residual expansion characteristics.

It is the figure which showed the relationship between the compounding quantity of Examples 1-4, and compressive strength. It is the figure which showed the relationship between the compounding quantity of Examples 1-4 and a linear change rate. It is the figure which showed the relationship between the compounding quantity of Examples 5 and 6, and compressive strength. It is the figure which showed the relationship between the compounding quantity of Examples 5 and 6, and the linear change rate. It is the figure which showed the relationship between the compounding quantity of Examples 7 and 8, and compressive strength. It is the figure which showed the relationship between the compounding quantity of Examples 7 and 8, and the linear change rate. It is the figure which showed the relationship between the compounding quantity of Examples 9 and 10, and compressive strength. It is the figure which showed the relationship between the compounding quantity of Examples 9 and 10, and the linear change rate.

  Hereinafter, the dry ramming material of this invention and the manufacturing method of a refractory using the same are demonstrated in detail.

First, the dry ramming material of the present invention has a refractory aggregate and a sintering aid as a basic structure. As the refractory aggregate, silica aggregate is a main aggregate, and in addition to that, magnesia aggregate and alumina aggregate. Alternatively, at least one aggregate selected from alumina-silica aggregates is used in combination. When at least one aggregate selected from magnesia aggregate, alumina aggregate or alumina-silica aggregate is used, magnesia aggregate, alumina aggregate or alumina-silica is used. It is one of the aggregates. When two types of aggregates are used, it is a case of either a magnesia aggregate and an alumina aggregate, a magnesia aggregate and an alumina-silica aggregate, or an alumina aggregate and an alumina-silica aggregate. When three types of aggregates are used, three aggregates of magnesia aggregate, alumina aggregate, and alumina-silica aggregate are used.
Hereinafter, the refractory aggregate and sintering aid used in the present invention will be described.

  The silica aggregate used in the present invention may be any silica aggregate conventionally used for dry ramming materials. By using this silica aggregate as a main component, the thermal conductivity of the refractory obtained by sintering this dry ramming material can be kept low, which is a preferable blend from the viewpoint of energy cost.

The silica aggregate used here is preferably made of SiO ₂ : 98% by mass or more as a chemical component and other unavoidable impurities contained industrially. This is because if more impurities are contained, the heat resistance in the use temperature range (˜1600 ° C.) required by the present invention may be reduced. The higher the purity of SiO _{2 in} the silica aggregate, the better, and 99% by mass or more is more preferable.

As the silica aggregate, in the present invention, fused silica particles and natural silica particles are used in combination. Here, the fused silica particles are particles made of amorphous silica glass and manufactured by artificial melting, and are excellent in thermal stability but have poor residual expansion characteristics. On the other hand, natural silica particles are composed of 95% by mass or more of SiO ₂ and less than 5% by mass of other materials, and are obtained by pulverizing a natural product mainly composed of quartz, and exhibiting residual expansibility. There is. On the other hand, the thermal stability is poor because the shape changes easily with respect to heat. In the present invention, the fused silica particles and the natural silica particles are used in combination so that the dry ramming material has residual expansibility and thermal stability.

  The blending ratio of the fused silica particles and the natural silica particles is not particularly limited and may be selected according to the desired product characteristics. In general, fused silica has a low thermal expansibility, and natural silica has a high thermal expansibility. Therefore, when the thermal stability of a product is required, the ratio of fused silica is increased, and when the expansibility of a product is desired to be increased, natural silica is used. What is necessary is just to raise the ratio of a silica.

  The blending ratio is preferably, on a mass basis, fused silica particles: natural silica particles = 1: 9 to 9: 1, more preferably fused silica particles: natural silica particles = 2: 8 to 8: 2. Fused silica particles: natural silica particles = 3: 7 to 7: 3 is particularly preferable.

In addition, there is no particular restriction on the particle size composition of the silica aggregate, but considering the filling properties, the raw materials are divided into particle size groups such as 5 to 3 mm, 3 to 1 mm, 1 to 0.1 mm, and less than 0.1 mm. It is preferable to take a method of classifying and selecting the blending ratio each time. Among these, those having a particle size of 1 to 5 mm form a skeleton of the structure, and therefore, the total amount of silica aggregate is preferably 10% by mass or more, more preferably 20% by mass or more, and particularly preferably 25% by mass or more. However, in order to sinter the silica aggregates, fine particles are required. Therefore, those having a particle size of 1 to 5 mm are preferably 70% by mass or less in the entire silica aggregates, and 60% by mass or less. More preferably, it is particularly preferably 50% by mass or less. In this specification, a particle size shall mean the value measured by JISR2552 (1997) method. That is, measurement is performed using a sieve having a predetermined opening.
Moreover, as an upper limit of the average particle diameter of silica aggregate, it is preferable that the average particle diameter calculated by sieving according to JIS R2552 from the viewpoint of availability, cost, etc. is less than 3 mm, and less than 1.5 mm. More preferably, the lower limit of the average particle diameter is preferably 0.6 mm or more, and more preferably 1 mm or more. In this specification, when the average particle diameter is 500 μm or less, it means a value measured with a laser diffraction measuring machine. However, when it exceeds 500 μm, the measurement accuracy is lowered, so sieving (JIS R2552). It shall mean the value calculated by.

  In the present invention, the silica aggregate is used as the main aggregate as the fireproof aggregate, and the silica aggregate is contained in an amount of 90 to 99% by mass with respect to the entire fireproof aggregate.

  In the present invention, the refractory aggregate used in combination with the silica aggregate includes magnesia aggregate, alumina aggregate (typically alumina beads) or alumina-silica aggregate, and at least one of these. One aggregate is contained in an amount of 1 to 10% by mass with respect to the entire refractory aggregate. These magnesia aggregate, alumina aggregate and alumina-silica aggregate will be described below.

  The magnesia aggregate used in the present invention may be a magnesia aggregate conventionally used in dry ramming materials, and the chemical component includes MgO: 94% by mass or more and other industrial inevitable impurities. If it is a thing, it is preferable.

  This magnesia aggregate contributes to improving the strength of the refractory in a high temperature range of 1200 ° C. to 1650 ° C., which is the operating temperature range. The magnesia aggregate forms a compound in a solid phase with the silica aggregate in contact from around 1200 ° C., and is partially liquefied for the first time at 1543 ° C. until it reaches 1695 ° C. and does not become completely liquid. Therefore, it is considered that the silica aggregates can be strengthened in the use temperature range as described above, and the strength of the refractory itself can be improved.

  Sintering aids such as boric anhydride have the effect of promoting the sintering of refractory aggregates, and this effect is due to the promotion of liquid phase formation in the sintering temperature range. It has a function of lowering the melting point to 400 to 800 ° C. by reacting with the refractory aggregate. However, such a sintering aid has substantially no effect of improving the strength in the high temperature range.

  In addition, as described above, the magnesia aggregate may partially become a liquid phase in the operating temperature range, but does not completely become a liquid phase, and thus has an effect of suppressing a decrease in heat resistance of the refractory.

  At this time, the magnesia aggregate must enter the grain boundary of the silica aggregate in order to connect the silica aggregate efficiently. Therefore, the average particle diameter of the magnesia aggregate is preferably 600 μm or less, and the average particle diameter of the magnesia aggregate is more preferably 300 μm or less.

  On the other hand, the average particle size of the magnesia aggregate is preferably 5 μm or more, more preferably 10 μm or more from the viewpoint of preventing aggregation. The average particle size of the magnesia aggregate is particularly preferably 15 μm or more. In addition, in this specification, an average particle diameter means the value measured with the laser diffraction type particle size distribution measuring apparatus unless there is particular notice.

In the present invention, the alumina aggregate refers to an aggregate containing 90% by mass or more of Al ₂ O ₃ and less than 1% by mass of SiO ₂ . A specific example of the alumina aggregate is a particulate aggregate having a relatively smooth surface that does not include those produced by crushing. For example, Al ₂ O ₃ ; 95 mass% or more and other industries High-purity alumina aggregate composed of unavoidable impurities contained therein.

The method for producing this alumina aggregate is not particularly limited, but the method is to dissolve the raw material prepared so as to have the above content in an arc electric furnace or the like and to make it finer with high-speed air or the like at the time of hot water (hereinafter referred to as melting) And a method of spraying the adjusted raw material into particles and sintering them, and the like. Among these, the melting method is preferable because it is advantageous in terms of manufacturing cost. Moreover, the alumina aggregate obtained by the melting method is preferable because it has better heat resistance than the alumina aggregate obtained by crushing from a sintered clinker or electromelted clinker lump. This is because the alumina aggregate particles obtained by the melting method have almost no irregularities on the particle surface and have a smooth surface close to a sphere, whereas the alumina aggregate obtained by the above crushing is on the surface. This is probably because there are many irregularities generated by crushing, and the heat resistance is lowered because the reactivity is high.
There are also aggregates made by the granulation method as having the same advantages as the melting method. The granulation method refers to a method in which powder raw materials adjusted to have the above content are mixed, granules are formed, and fired to produce an aggregate. However, since the granulation method requires the two steps of granulation and firing in order to become an aggregate after adjusting the raw materials, the melting method becomes an aggregate in one step after adjusting the raw materials. In this aspect, the melting method is desirable.

  When the melting method is adopted as the production method, the type of the melting furnace for melting the adjusted raw material is not particularly limited, and examples thereof include a heating type such as a burner, electric resistance, arc, and coke. In particular, the arc type is preferable because it is relatively easy to obtain a high temperature, the homogeneity of the melt is high, the furnace equipment is simple, and the operability is excellent.

  Further, the maximum particle size of the alumina aggregate is preferably less than 3.35 mm, and more preferably less than 1.4 mm. This is because the magnesia aggregate does not need to be in contact with the silica aggregate. The average particle size of the alumina aggregate is preferably 80 μm or more and 90 μm or more from the viewpoint of the role of strengthening the structure as an aggregate, from the viewpoint of strengthening the structure as an aggregate. And more preferred. The average particle size of the alumina aggregate is particularly preferably 95 μm or more. On the other hand, the upper limit of the average particle size of the alumina aggregate is preferably less than 2 mm, more preferably less than 1 mm, and the average particle size calculated by sieving according to JIS R2552 from the viewpoint of availability, cost, etc. Is particularly preferably less than 0.6 mm.

In the present invention, the alumina-silica aggregate is an aggregate mainly composed of Al ₂ O ₃ and SiO ₂ as chemical components, containing at least 1% by mass of SiO ₂ , and the crystal phase is corundum, This includes an amorphous phase in addition to the crystalline phase. Here, the “main component” in the chemical component in the aggregate means that the aggregate component contains 95 mass% or more of two components of Al ₂ O ₃ and SiO ₂ .
The alumina-silica aggregate contains Al ₂ O ₃ : 90 to 99% by mass and SiO ₂ : 1 to 9% by mass in the aggregate particles, and the total amount of both components is 95% by mass or more. It becomes suitable as an aggregate particle having extremely high fire resistance, and its total amount is more preferably 97% by mass or more.

In this alumina-silica aggregate, if the Al ₂ O ₃ content is less than 90% by mass, the heat resistance may be insufficient, such being undesirable. In this alumina-silica aggregate, the Al ₂ O ₃ content is preferably 95% by mass or more from the viewpoint of heat resistance, and the Al ₂ O ₃ content is particularly preferably 97% by mass or more.

On the other hand, in this alumina-silica aggregate, if the Al ₂ O ₃ content exceeds 99% by mass, the effect of containing SiO ₂ may be lost, and this is not preferable. That is, when the SiO ₂ content is less than 1% by mass, the amount of the amorphous phase constituting the structure is decreased, and the strength of the aggregate particles may be decreased, which is not preferable.

  The alumina-silica aggregate is preferably a corundum basically composed of alumina as a crystal phase and substantially does not contain mullite crystals (alumina silicate compound). When no mullite crystal is contained, sufficient heat resistance and thermal conductivity can be obtained.

  In the present specification, the crystal phase is basically corundum (substantially free of mullite crystals), a clear mullite crystal peak is not observed or a peak is temporarily observed by X-ray diffraction measurement. Means that the relative intensity when the intensity of the main peak is 100 is 5 or less.

The alumina-silica aggregate contains an amorphous phase in addition to the corundum crystal phase. The presence of the amorphous phase is confirmed by the fact that a broad reflection peculiar to the amorphous is observed by an X-ray diffractometer. Further, it is speculated that SiO ₂ exists as an amorphous phase even though it contains 1 to 9% by mass of SiO ₂ in terms of structure, and no crystalline mineral containing SiO ₂ is confirmed. Is done.

  This amorphous phase has the role of absorbing volume changes accompanied by corundum thermal expansion due to temperature fluctuations at high temperatures. As the amount of this amorphous phase increases, the particles do not break due to cracking even when subjected to repeated thermal history. However, if the amount is too large, the fire resistance will decrease or an undesirable mullite crystal phase will be formed. There is a risk.

The amorphous phase ratio in the alumina-silica aggregate particles is preferably 10% by mass or less, ideally 5% by mass or less, more preferably 3% by mass or less. When the amorphous phase is reduced to 3% by mass, cracks may occur in the particles after use, but there are cases in which high heat resistance is unavoidable. Here, the amorphous phase ratio means that 50 to 200 particles randomly selected in the field of view of the optical microscope are arranged, and the number of the transparent particles is counted as amorphous particles. And calculated as follows.
(Amorphous phase ratio) = (Number of amorphous particles) / (Number of all particles in the field of view) × 100

Alumina - In silica aggregate, component TiO ₂ and _Fe 2 _{O 3} is often better not possible contained in the aggregate particles, the total amount of TiO ₂ component and _Fe 2 _{O 3} component _{(TiO 2 + Fe 2 O 3} ; less And TF total amount) is 0 to 0.5 mass%, the TiO ₂ component and the Fe ₂ O ₃ component almost generate a low melting point compound between the SiO ₂ component and the Al ₂ O ₃ component. Therefore, it is preferable because problems such as a decrease in heat resistance of the aggregate particles and sintering of the aggregate particles during use do not occur. In the present aggregate particle, the total amount of TF is more preferably 0.3% by mass or less, and further preferably the total amount of TF is 0.1% by mass or less.

  The maximum particle size of the alumina-silica aggregate is preferably less than 3.35 mm, more preferably less than 1.4 mm. The average particle diameter of the alumina-silica aggregate is preferably 80 μm or more, more preferably 90 μm or more from the viewpoint of strengthening the structure as an aggregate. The average particle diameter of the alumina-silica aggregate is particularly preferably 95 μm or more. On the other hand, as the upper limit of the average particle diameter of the alumina-silica aggregate, the average particle diameter calculated by sieving according to JIS R2552 is preferably less than 2 mm from the viewpoint of availability, cost, etc. More preferably, it is especially preferable in it being less than 0.6 mm.

  At least one of the above-mentioned magnesia aggregate, alumina aggregate and alumina-silica aggregate is contained in an amount of 1 to 10% by mass based on the entire refractory aggregate. These magnesia aggregates, alumina aggregates, and alumina-silica aggregates may be used alone and mixed with silica aggregates, but two or more of these aggregates may be used in combination with silica aggregates. Is preferred.

  The combined use of magnesia aggregate and alumina aggregate and / or alumina-silica aggregate is preferable because the strength improvement effect is further increased as compared with the case where magnesia aggregate is added to the silica aggregate alone. This is because the addition of alumina aggregate and / or alumina-silica aggregate promotes sinterability at a high temperature range, and it is not necessary to greatly reduce the content of silica aggregate in the refractory aggregate. For example, in order to obtain the same strength as the strength of the refractory when silica aggregate: 90% by mass and magnesia aggregate: 10% by mass are added in the refractory aggregate, the silica aggregate in the refractory aggregate particles: 95 mass%, magnesia aggregate: 1.5 mass%, and alumina aggregate can be achieved by 3.5 mass%. Thereby, a sufficient amount of silica aggregate with low thermal conductivity can be secured.

  That is, any of the raw materials of magnesia aggregate, alumina aggregate, or alumina-silica aggregate has a large effect of securing the above-mentioned silica aggregate amount because the thermal conductivity is greatly increased as compared with silica aggregate. For example, when the refractory aggregate is composed of only silica aggregate, the calculated thermal conductivity at 1000 ° C. is 1.4 W / (m · K), whereas the refractory aggregate is silica aggregate 90 In the case of 10% by mass and 10% by mass of magnesia aggregate, it increases to 1.7 W / (m · K). When 10% by mass of magnesia aggregate is changed to 5% by mass in total of 1.5% by mass of magnesia aggregate and 3.5% by mass of alumina aggregate, that is, the refractory aggregate is 95% by mass of silica aggregate, magnesia bone In the case of 1.5 mass% of the aggregate and 3.5 mass% of the alumina aggregate, the thermal conductivity is 1.5 W / (m · K), which can be suppressed to the same extent as in the case of the silica aggregate of 100%.

  When the above magnesia aggregate, alumina aggregate, and alumina-silica aggregate (hereinafter referred to as alumina aggregate in combination with alumina aggregate and alumina-silica aggregate) are used in combination, the mixing ratio is , Magnesia aggregate: alumina-based aggregate is preferably 20:80 to 80:20, more preferably 20:80 to 50:50, and particularly preferably 35:65 to 45:55. This mixing improves the balance between compressive strength and thermal conductivity. As described above, it is preferable to contain 50 mass% or more of alumina aggregate (that is, 50 mass% or less of magnesia aggregate) with respect to the total amount of magnesia aggregate and alumina aggregate. More preferably, less than 50% by mass and more alumina-based aggregate than magnesia aggregate, more preferably 20-30% by mass of magnesia aggregate.

  Moreover, this invention mix | blends a sintering auxiliary agent with respect to the above-mentioned fireproof aggregate, and makes it a dry ramming material. The sintering aid used here can be used without particular limitation as long as it has been conventionally used as a sintering aid for dry ramming materials, and examples thereof include boric anhydride, glass frit, and phosphoric acid compounds.

  This sintering aid reacts with the refractory aggregate to lower the melting point and promotes sintering of the refractory aggregate to increase the strength of the refractory. This is due to the promotion of liquid phase formation, and increases the strength at 400 to 800 ° C. during refractory production.

  The amount of the sintering aid is 0.01 to 5% by mass, preferably 0.1 to 3% by mass, based on the total amount of dry ramming material composed of the fireproof aggregate and the sintering aid. %, More preferably 0.4 to 2% by mass.

  The blending amount of the sintering aid here is extremely small, so that the entire structure does not become liquid phase, and the liquid phase is scattered in the structure. These interspersed liquid phases serve as bonds for bonding the aggregate.

  Next, the manufacturing method of the refractory using the above-mentioned dry ramming material is demonstrated.

  In the refractory manufacturing method according to the present invention, first, a gap of a necessary lining thickness (in the crucible furnace, the lining thickness is often 100 mm to 150 mm) is set between the furnace wall and a metal frame is installed inside the furnace. Then, while putting the above-mentioned dry ramming material into the gap, the metal frame is shaken with a vibration motor, or the input material is tightly filled with a stick with a vibrator attached thereto and filled.

  In such a filled state, the molded body does not have a sufficiently large strength, so the sintering aid (for example, boric acid) contained in the dry ramming material (molded body) by heating the metal frame ) After obtaining the bond strength by melting, remove the metal frame. Alternatively, the metal frame is treated as the first molten metal while heating the dry ramming material (molded body) by heating to a temperature at which the metal frame melts.

  The metal frame is heated by induction heating. Induction heating is a heating method in which an electric field is caused to flow through a coil disposed on the outer periphery of the furnace wall to generate an electric field and resistance heat is generated in the metal inside the coil. This induction heating is performed in the same manner as the metal melting in the furnace. At this time, a large amount of current flows through the coil, but in the present application, since a dry ramming material that does not contain moisture is used, there is no fear that the current flowing through the coil will be short-circuited, and the induction furnace is formed by firing without anxiety. Can do.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited at all by this Example.

(Example 1)
12.0 parts by weight of fused silica having a particle size of 3 mm or more and less than 5 mm, 15.0 parts by weight of fused silica having a particle size of 1 mm or more but less than 3 mm, 21.0 parts by weight of fused silica having a particle size of 150 μm to less than 1 mm, as a main aggregate of the refractory aggregate 21.0 parts by mass of fused silica having a particle size of less than 150 μm, 30.0 parts by mass of natural silica having a particle size of less than 5 mm, and 1.0 part by mass of boric acid as a sintering aid were mixed (Table 1). Further, 1,3,5,7,9,10 parts by mass of alumina-silica aggregates were externally added thereto and mixed to prepare dry ramming materials. Table 1 shows the blending amounts of the main aggregate and sintering aid, which are the inner components at this time.

The aggregate used here is fused silica (SiO ₂ : 99.8 mass%, amorphous), natural silica (SiO ₂ : 98 mass%, Al ₂ O ₃ + Fe ₂ O _{3 and} others: 2 mass). %, Crystal phase: quartz), and the alumina-silica aggregate was obtained in the same manner as the method described in WO 2009/072627. Hereinafter, a method for producing an alumina-silica aggregate will be described.

As the melting furnace, an arc melting furnace having a furnace inner diameter of 1.5 m, a height of 1.5 m, and a furnace inner volume of 2.5 m ³ was used, and a 1100 KVA transformer was prepared as a power source. Note that an electrocast refractory having an alumina content of 95% by mass was used as the lining refractory for the melting furnace. Three electrodes having a diameter of 15 cm were used as electrodes.

  Melting conditions were voltage 100V-250V, power 800KW-1000KW, and the amount of 600kg of one time was divided into three times and divided into the furnace at intervals of 10-15 minutes. The total raw material charging time was 30 minutes to 45 minutes. The dissolution time was 80 to 100 minutes. Moreover, as a raw material, it mix | blended and used alumina powder and silica sand powder so that it might become a predetermined composition.

  Next, the melt was granulated by adding 2 L / min of water to compressed air at a pressure of 4 MPa and blowing out from the nozzle, and spraying high-speed compressed air from below the hot water melt onto the hot water. The particles were collected in a metal collection container protected with a refractory, and used as an alumina-silica aggregate for dry ramming. The flow rate of the compressed air at this time was 100 m / sec to 150 m / sec. As for the particle size of the aggregate particles, 85% by mass or more was in the range of 0.1 mm to 1.2 mm.

The obtained alumina-silica aggregate had a chemical composition of Al ₂ O ₃ : 97% by mass, SiO ₂ : 2% by mass, and others: 1% by mass. The chemical component was measured using a fluorescent X-ray apparatus (Rigaku Corporation, trade name: RIX-2000).

[Evaluation 1]
When the crystal phase of this alumina-silica aggregate was specified with an X-ray diffractometer (trade name: RINT-2200VK, manufactured by Rigaku Corporation), only corundum was observed. About this aggregate particle | grain, it embedded in resin, mirror-polished, and when the structure was observed for the cross section with the metal microscope, only the corundum phase was observed visually and the amorphous phase was not able to be confirmed clearly. Furthermore, when the heat resistance of the aggregate particles was evaluated as fire resistance (SK) based on JIS R2204, it was 41+.

(Examples 2 to 4)
Instead of the alumina-silica aggregate of Example 1, alumina aggregate produced by the granulation method (Example 2), magnesia aggregate (Example 3), and alumina aggregate produced by the crushing method (Example 4) were used, respectively. Similarly, a dry ramming material was obtained.

  The aggregate used here is as follows. Alumina aggregate produced by the granulation method (manufactured by Shinto Kogyo Co., Ltd., trade name: 999S, average particle size 1 mm), magnesia aggregate (manufactured by Ube Materials Co., Ltd., trade name: UBE-95, average particle size 46 μm), Alumina aggregate produced by the crushing method (trade name: Moral Kotabular T-60, average particle size 425 μm, manufactured by Armatis).

(Test Example 1)
Samples were prepared for each of the dry ramming materials obtained in Examples 1 to 4, the compression strength and the linear change rate were measured, and the results are shown in FIGS. In the graphs shown in the drawings of the present specification, the horizontal axis indicates the amount of external additive added in each example.

  In addition, after determining the filling bulk specific gravity of the dry ramming material of each example, the sample is added to the dry ramming material by adding 1 to 2 mass% of kerosene and kneaded with a universal mixer, and put into a mold so that a predetermined compression amount is obtained. A sample shape of φ50 mm × 50 mm was formed and fired at 1600 ° C. for 5 hours.

[Compression strength]:
Measured according to JIS R2206-2 (2007).
-Size: φ50mm x 50mm.
Measurement method: Measure the breaking load (Fmax) when compressive stress is applied evenly to the surface of φ50 from above. At this time, the compressive strength (σ) is calculated as follows: σ = Fmax / A
σ: Compressive strength (MPa) Fmax: Fracture load (N) A: Area subjected to stress (mm ² )
In order to apply pressure evenly, a paper board having a thickness of 3 to 7 mm is applied to the top and bottom surfaces of the sample.

[Line change rate]:
Measured according to JIS R2554 (2005).
Measurement is performed when the sample is prepared. First, the height of the sample is measured before firing. In this measurement, the caliper is rotated so that it touches the center of the surface, and the value is read every 90 degrees, and the average of the four values is defined as the height before firing. It measures similarly after baking, and makes this the height after baking.
ΔL = (l−l ′) / l
ΔL: linear change rate (%) l: height before firing (mm) l ′: height after firing (mm)

  From this result, when the crushed alumina aggregate is added, the numerical value of the compressive strength is high as in Example 4 of FIG. 1, but when the blending amount is large as in Example 4 of FIG. Since it will not be shown, it was excluded from the following examination. In addition, the linear change rate was slightly reduced by the addition of magnesia aggregate, but the compressive strength was greatly improved. Further, the addition of the alumina-silica aggregate and the granulated alumina aggregate slightly increased or was almost the same, and the compressive strength was slightly improved.

(Example 5)
Next, instead of the alumina-silica aggregate of Example 1, dry-ramming was performed in the same manner as in Example 1 except that a mixed aggregate containing alumina-silica aggregate and magnesia aggregate in a ratio of 7: 3 was used. The material was obtained.

(Example 6)
Next, instead of the alumina-silica aggregate of Example 1, the same procedure as in Example 1 was used except that a mixed aggregate in which the granulated alumina aggregate and magnesia aggregate were blended at a ratio of 7: 3 was used. A dry ramming material was obtained.

(Example 7)
Next, instead of the alumina-silica aggregate of Example 1, dry-ramming was performed in the same manner as in Example 1 except that a mixed aggregate containing alumina-silica aggregate and magnesia aggregate in a ratio of 5: 5 was used. The material was obtained.

(Example 8)
Next, instead of the alumina-silica aggregate of Example 1, the same procedure as in Example 1 was used except that a mixed aggregate in which the granulated alumina aggregate and magnesia aggregate were mixed at a ratio of 5: 5 was used. A dry ramming material was obtained.

(Example 9)
Next, instead of the alumina-silica aggregate of Example 1, dry-ramming was performed in the same manner as in Example 1 except that a mixed aggregate containing alumina-silica aggregate and magnesia aggregate in a ratio of 3: 7 was used. The material was obtained.

(Example 10)
Next, instead of the alumina-silica aggregate of Example 1, the same procedure as in Example 1 was used except that a mixed aggregate in which the granulated alumina aggregate and magnesia aggregate were blended at a ratio of 3: 7 was used. A dry ramming material was obtained.

(Test Example 2)
About the dry ramming material obtained in Examples 5-10, the compressive strength and the linear expansion coefficient were measured by the same method as Example 1. The results are shown in FIGS. For reference, the results of Example 3 mixed with magnesia aggregate alone are also shown.

  From the above results, as shown in Examples 1 to 10, the silica aggregate is mixed with at least one aggregate selected from alumina aggregate, magnesia aggregate, and alumina-silica aggregate to provide fire resistance. The compressive strength and linear expansion coefficient of the object can be improved, and the balance of refractory properties can be adjusted by adjusting the blending and addition amount of these aggregates. It was found that the dry ramming material thus obtained can exhibit desirable performance under a high temperature use environment.

  The dry ramming material of the present invention and the method for producing a refractory using the same provide an electric induction heating furnace that has improved stability and durability when using a metal melting heating furnace by electric induction heating, and is superior to the conventional one. it can.

Claims (8)

A dry ramming material containing a refractory aggregate and a sintering aid,
The refractory aggregate contains 90 to 99% by mass of silica aggregate, 1 to 10% by mass of at least one aggregate selected from magnesia aggregate, alumina aggregate, and alumina-silica aggregate, and A dry ramming material, wherein fused silica particles and natural silica particles are used in combination as the silica aggregate.   The dry-ramming material according to claim 1, wherein, in addition to the silica aggregate, the magnesia aggregate and the alumina aggregate and / or the alumina-silica aggregate are used in combination as the fireproof aggregate.   The dry ramming material according to claim 2, comprising less than 50 mass% of the magnesia aggregate with respect to a total amount of the magnesia aggregate and the alumina aggregate and / or the alumina-silica aggregate.   The dry-ramming material of Claim 3 which contains 20-30 mass% of said magnesia aggregates with respect to the total amount of the said magnesia aggregate and an alumina aggregate and / or an alumina-silica aggregate.   The dry ramming material according to any one of claims 1 to 4, wherein the alumina aggregate and / or the alumina-silica aggregate is formed into particles by a melting method.   The dry-ramming according to any one of claims 1 to 5, wherein a blending ratio of the fused silica particles and the natural silica particles is, based on mass, fused silica particles: natural silica particles = 1: 9 to 9: 1. Wood. Filling the dry-ramming material according to any one of claims 1 to 6 between a furnace wall and a mold of an electric induction heating furnace;
Heating and sintering the filled dry ramming material by electric induction heating; and
A process for producing a refractory for an electric induction heating furnace, comprising:   The method for producing a refractory for an electric induction heating furnace according to claim 7, wherein the furnace wall side is water-cooled during the electric induction heating.

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