TWI644882B - Flat plate for casting refractory and rolling nozzle device - Google Patents

Abstract

An object of the present invention is to further improve the corrosion resistance and thermal shock resistance of a refractory for casting of magnesium oxide.

The problem solving means is a casting refractory material containing 40% by mass or more and 85% by mass or less of MgO and 10% by mass or more and 50% by mass or less of Al ₄ O _{4 in} a state of being subjected to heat treatment in a non-oxidizing gas atmosphere at 500 ° C. The refractory for casting of C has a thermal expansion coefficient at 1000 ° C of 0.9% or less, and a difference between an average thermal expansion coefficient of 1100 ° C to 1500 ° C and an average thermal expansion coefficient of room temperature to 1100 ° C is 6 × 10 ^-6 / ° C or less.

Description

Flat plate for casting refractory and sliding nozzle device

The present invention relates to a refractory for casting such as continuous casting of steel, and a flat plate for a sliding nozzle device using the refractory.

A flat plate for a sliding nozzle device (hereinafter referred to as a "slide plate for a sliding nozzle" and a refractory for a flat plate is referred to as a "plate refractory") is widely used as a flow rate controlling member for molten metal, and is carried out in a bucket. Sub-treatment and continuous casting have become commonplace, and refractory products are necessary and not lacking in the iron and steel industry. Since the flat plate for a sliding nozzle is a component for controlling the flow of molten metal such as molten steel, it is required to have excellent performance, and the material must be well-balanced to have various excellent characteristics that can cope with various severe conditions. That is, the flat plate for sliding nozzles is subjected to physical effects such as sharp thermal shock and abrasion caused by the flow of molten metal, and chemical corrosion caused by molten metal and molten slag, and even chemical action. Physically, it is required to have thermal shock resistance, abrasion resistance, corrosion resistance, strength characteristics, and the like as a desired property.

In the past, a flat plate for a sliding nozzle has been widely used as an alumina material containing alumina aggregates and a magnesium oxide material containing magnesium oxide aggregates. Its main body is fire resistant. Among them, the former alumina material is excellent in thermal shock resistance, and therefore it is often used for a flat plate for a sliding nozzle for a bucket. However, for Ca-treated steel or high-oxygen steel, CaO, deoxidation products, slag, and the like are generated. And easy to melt the problem. On the other hand, the latter magnesia carbonaceous material has excellent corrosion resistance to steels having high corrosion resistance as described above, and therefore, it is often used as a sliding nozzle for steels having high corrosion properties such as Ca-treated steel or high-oxygen steel. The flat plate has a high coefficient of thermal expansion and is inferior in thermal shock resistance. Therefore, there is a problem that the use is limited to a flat plate or a small article for a sliding nozzle of a branching groove having a small heat load.

Then, in the technique of improving the durability such as the corrosion resistance and the thermal shock resistance of the flat plate for a sliding nozzle, for example, Patent Documents 1 and 2 disclose a technique of adding a low melting point metal powder such as metal aluminum to an alumina material or a magnesium oxide material. However, these techniques are mainly aimed at improving mechanical strength and oxidation resistance, and have not been sufficiently reviewed for corrosion resistance and thermal shock resistance.

Further, Patent Document 3 discloses a technique for improving the thermal shock resistance of a magnesium oxide material, and discloses a fire-resistant aggregate composed of 35 to 75 mass% of magnesium oxide aggregate and 10 to 50 mass% of alumina aggregate. And a technique in which a thermosetting resin is added and mixed by a mixture of 3 to 8 mass% of metal aluminum and 2 to 10 mass% of carbon. However, this technique still has a high thermal expansion rate and a poor thermal shock resistance, and thus there is a problem that edge defects or cracks are likely to occur. In addition, when it is heated, spinel is formed around the alumina to swell, and there is a problem that the structure is deteriorated due to heat.

Like this, there has been a lot of literature in the past to try to adopt Magnesium oxide material is used to improve the corrosion resistance of Ca-treated steel or high-oxygen steel. However, due to the high thermal expansion property of magnesium oxide, there is a problem that thermal shock resistance is poor. Therefore, there has been an attempt to replace a part of the magnesium oxide aggregate with an alumina aggregate to improve the thermal shock resistance. However, even if the thermal shock resistance is not improved, in addition, the spinel is formed around the alumina aggregate when heated. However, problems such as swelling and deterioration of the structure have not been solved.

On the other hand, Patent Document 4 discloses Al ₄ O ₄ C containing 15 mass% or more and 80 mass% or less, more than 0.5 mass%, 20.0 mass% of AlN, the remainder of the refractory component such as Al ₂ O ₃ as In the refractory for casting, AlN becomes Al ₂ O ₃ due to FeO or the like, suppresses oxidation of Al ₄ O ₄ C, and the like, and also improves corrosion resistance. However, if the technique of Patent Document 4 is directly applied to a magnesium oxide material, in the structure of the MgO main body, AlN forms a plurality of Al ₂ O ₃ layers around Al ₄ O ₄ C, the Al ₂ O ₃ layer and MgO. When a reaction occurs and a large number of spinels are generated, there is a concern that it exhibits high thermal expansion as a refractory.

Further, Patent Document 5 discloses that Al ₄ O ₄ C containing 15% by mass or more and 60% by mass or less contains 1.2% by mass or more and 10.0% by mass or less of the metal Al component, and the balance is Al ₂ O ₃ and free C and other refractory components _{consisting, Al 4 O 4 C, Al} 2 O 3 and Al metal component the total of 85 mass% or more, and the content of the content of Al ₄ O ₄ C of (Al ₄ O ₄ C), metallic Al component The content (C) of (Al) and free C satisfies 1.0 ≦C / (Al ₄ O ₄ C × 0.038 + Al × 0.33) (Formula 1), 1.0 ≧ C / (Al ₄ O ₄ C × 0.13 + Al × 0.67) A refractory for casting in the relationship of (Formula 2). However, in Patent Document 5, similarly to Patent Document 4, since the Al ₂ O ₃ layer generates spinel with MgO, there is a concern that the refractory exhibits high thermal expansion property.

As described above, the corrosion resistance and thermal shock resistance of the magnesium oxide material have not been sufficiently reviewed.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 56-140064

[Patent Document 2] Japanese Patent Publication No. 01-103952

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2004-141899

[Patent Document 4] Japanese Laid-Open Patent Publication No. 2015-193511

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2015-193512

An object of the present invention is to further improve the corrosion resistance and thermal shock resistance of a refractory for casting of magnesium oxide.

The present invention provides the following refractories for casting and flat plates for sliding nozzle devices.

A refractory for casting containing 40% by mass or more and 85% by mass or less of MgO and 10% by mass or more and 50% by mass or less of Al ₄ O ₄ C in a state of being subjected to heat treatment in a non-oxidizing gas atmosphere at 500 ° C. The refractory for casting has a thermal expansion coefficient at 1000 ° C of 0.9% or less, and a difference between an average thermal expansion coefficient of 1100 ° C to 1500 ° C and an average thermal expansion coefficient of room temperature to 1100 ° C is 6 × 10 ^-6 / ° C or less.

2. The refractory for casting according to the above 1, wherein the state after the heat treatment in a non-oxidizing gas atmosphere at 500 ° C contains 1 mass% or more and 15 mass% or less of metal Al.

3. The refractory for casting according to the above 1 or 2, wherein the state after the heat treatment in a non-oxidizing gas atmosphere at 500 ° C contains 0.5% by mass or more and 4% by mass or less of metal Si.

4. The refractory for casting according to any one of the above 1 to 3, wherein the Al ₄ O ₄ C is derived from a raw material particle containing Al ₄ O ₄ C produced by an electrofusion method.

5. The casting system as claimed in size 4 of refractory material, wherein the Al ₄ O ₄ C contained in the Al ₄ O ₄ C crystal material particles sectional area of the Al ₄ O ₄ C crystal in terms of an average diameter of a circle when It is 20 μm or more.

A flat plate for a sliding nozzle device, which is composed of a part or all of the refractory for casting described in any one of the above 1 to 5.

In the present invention, an appropriate amount of Al ₄ O ₄ C is contained in a refractory for casting of magnesium oxide containing 40% by mass or more and 85% by mass or less of MgO in a state of being subjected to heat treatment in a non-oxidizing gas atmosphere at 500 ° C. The thermal expansion rate can be lowered, and the volume expansion of the spinel petrochemical is suppressed, and the destruction of the refractory structure is suppressed, so that the corrosion resistance and the thermal shock resistance are improved.

In the present invention, the chemical component such as MgO is specified in the "state after heat treatment in a non-oxidizing gas atmosphere at 500 ° C", and the purpose thereof is to remove moisture, organic matter, hydrate, carbon and oxygen in the refractory. The volatile component released by the compound and the carbonization of the organic binder component promote the component to a stable state. In other words, in order to suppress the scattering of volatile components such as a resin component in the refractory component, and to generate a new substance without causing a chemical reaction to occur at a temperature exceeding 500 ° C, it is defined as "a non-oxidizing gas atmosphere at 500 ° C. The state after the heat treatment is performed." Specific examples of the heat treatment method in a non-oxidizing gas atmosphere at 500 ° C in accordance with this purpose may be carried out in a crucible filled with a carbonaceous raw material such as coal char, or a nitrogen gas or an argon gas having an oxygen concentration adjusted to 0.1% or less. In an inert gas atmosphere, the method is maintained at 500 ° C for about 1 hour to 5 hours. The specific conditions of the gas environment, the holding time, the sample size, and the like can be determined arbitrarily according to the above purpose.

In order to solve the problem of the refractory for casting of alumina or magnesia as described above, and to improve corrosion resistance and thermal shock resistance, the present invention mainly uses MgO (magnesium oxide) and Al ₄ O ₄ C as refractories. Composition. Here, the average thermal expansion coefficient corresponding to the temperature range of use of the refractory for casting is from 1100 ° C to 1500 ° C, the magnesium oxide is 14 × 10 ^-6 / ° C, and the alumina is 7 × 10 ^-6 / ° C. Al ₄ O ₄ C is 4 × 10 ^-6 / ° C or less, which is about one-third of that of magnesium oxide, and is half of alumina, and has low thermal expansion property. By this low thermal expansion property, Al ₄ O ₄ C can impart excellent thermal shock resistance to the refractory. Further, alumina is easily reacted with magnesium oxide at 1200 ° C or higher to be spinel. Along with the spinel petrification reaction, the volume expansion causes the structure of the refractory to be squeezed out, which causes a problem of deterioration of the structure. On the other hand, Al ₄ O ₄ C does not directly react with magnesium oxide as in the following formulas 1 and 2, and once Al ₄ O ₄ C is decomposed, the produced alumina reacts with magnesium oxide. The spinel petrochemical, therefore, the rate of reaction of the spinel petrification is lower than that of the alumina, and it has the advantage of being less prone to petrochemical and less prone to tissue degradation.

Al ₄ O ₄ C+2CO=2Al ₂ O ₃ +3C. . . Formula 1

2Al ₂ O ₃ +MgO=2Al ₂ O ₃ . MgO. . . Equation 2

Therefore, the present invention suppresses the spinelization reaction in order not to greatly reduce the corrosion resistance of the refractory for casting of magnesium oxide, improve the thermal shock resistance, and improve the thermal shock resistance.

The volume expansion ratio caused by the spinel petrochemical can be expressed as follows. That is, the spinel petrochemical reaction occurs before and after 1100 ° C, and the thermal expansion rate of the refractory at a temperature higher than the temperature at which the spinel petrochemical reaction occurs is caused by the expansion of the refractory aggregate itself and the reaction of the spinel. The expansion of the sum is the value obtained. On the other hand, the thermal expansion rate of the refractory at a temperature lower than the temperature at which the spinel reaction occurs is considered to be the expansion of the aggregate of the refractory itself, so the average thermal expansion coefficient from 1100 ° C to 1500 ° C and the room temperature to 1100 ° C The difference in the average coefficient of thermal expansion can be estimated as the coefficient of thermal expansion caused by the spinel reaction. That is, if the average thermal expansion coefficient of the refractory from 1100 ° C to 1500 ° C is set to α ₁ /° C., and the average thermal expansion coefficient of room temperature to 1100 ° C is set to α ₂ /° C., the refractory is caused by spinel petrochemical. The coefficient of thermal expansion α _s / ° C can be estimated according to the following formula 3. Further, the room temperature may have a fluctuation range of, for example, about 0 to 40 ° C. However, the coefficient of thermal expansion of the refractory is substantially the same in the temperature range of the left and right. Therefore, in the present invention, the measurement of the coefficient of thermal expansion is convenient. Based on room temperature. Of course, the room temperature can be regarded as, for example, 20 ° C to determine the coefficient of thermal expansion.

α _s =α ₁ -α ₂ . . . Equation 3

According to the findings of the present inventors, it is considered that in the case where the α _{s is} larger than 6 × 10 ^-6 / ° C, if the heat is repeatedly heated, the refractory structure is squeezed due to the expansion caused by the spinel reaction and the high porosity. The rate and the low strength are increased, and the high porosity is caused to impair the corrosion resistance, and the oxidation resistance is also impaired.

Here, the aforementioned heat receiving includes providing a case of being heated during operation and a case of being heated during the firing of the refractory manufacturing. Therefore, the present invention can suppress the deterioration of the structure caused by the spinelization caused by the heat at the time of the operation, and can also suppress the deterioration of the structure caused by the spinelization which occurs during the firing process at the time of manufacture of the refractory. Further, in the firing process at the time of manufacture of the refractory, even in the case where spinelization occurs, it is possible to suppress the deterioration of the structure due to the spinelization which is further performed by the heat during the operation. In addition, when the firing temperature at the time of the production of the refractory is 1100 ° C or lower, the deterioration of the structure during the operation is suppressed, and when the firing temperature is 1100 ° C or more, both the structure deterioration during the production and the structural deterioration during the operation are suppressed. . That is, one of the features of the present invention is that it is not limited by the specific firing temperature, and the deterioration of the structure of the refractory caused by the spinelation can be suppressed.

Further, in the present invention, the metal Al is coexisted with the refractory containing Al ₄ O ₄ C as the aggregate, and the metal Al is more preferentially trapped than the Al ₄ O ₄ C to protect the Al ₄ O ₄ C, which can suppress The spinel petrochemical reaction represented by the above formulas 1 and 2 is carried out. That is, according to the present invention, by coexisting the metal Al, the reaction rate of the spinel petrochemical of Al ₄ O ₄ C can be lowered.

Further, the metal aluminum or the metal aluminum alloy which is a source of the metal Al has a melting point of 660 ° C or less. Therefore, according to the present invention, an oxidation resistance effect can be exhibited in a wide temperature range from about 660 ° C to the casting temperature. Therefore, for example, in the case where a low temperature portion exists in the temperature distribution in the flat refractory due to the repeated use of the flat plate for a sliding nozzle, the oxidation resistance can be enhanced. That is, in the temperature region of about 850 ° C or lower in which Al ₄ O ₄ C is oxidized, oxidation of the refractory (carbon component) can be suppressed and prevented, and Al ₄ O can be suppressed and prevented in a temperature region of about 850 ° C or higher. ₄ C oxidation can reduce the reaction rate of spinel.

According to the present invention, by coexisting MgO with Al ₄ O ₄ C in the refractory, high corrosion resistance can be obtained, and the thermal expansion rate of the refractory is lowered, the thermal shock resistance is improved, and the structural deterioration caused by the spinel petrification can be alleviated. . Thereby, the corrosion resistance and thermal shock resistance of the refractory for casting of magnesium oxide can be further improved.

As described above, in order to improve the thermal shock resistance of the refractory for casting of magnesium oxide, in the prior art, a means for using an alumina aggregate and a magnesium oxide aggregate has been conventionally used. However, these prior art techniques have a small effect of improving the thermal shock resistance, and if the addition ratio of the alumina aggregate is increased, the corrosion resistance is greatly lowered. Further, since the spinel around the alumina aggregate expands to squeezing the refractory structure, the corrosion resistance due to high porosity is lowered and the strength is lowered. Relative to these previous According to the present invention, the corrosion resistance of the refractory for casting of magnesium oxide can be maintained, and the thermal shock resistance can be greatly improved, and the corrosion resistance can be suppressed and the strength can be suppressed even by suppressing the spinelization around the aggregate.

As described above, the refractory for casting of the present invention is suitable for an upper nozzle, a lower nozzle, a tuyere, a flat plate for a sliding nozzle for flow rate control, and the like used for casting steel.

Fig. 1 is a microstructural photograph of an Al ₄ O ₄ C composition (aluminum oxide composition) of a raw material produced by an electrofusion method (arc melting) used in the present invention.

In the present invention, by using a material containing magnesium oxide as a main component as a fire-resistant aggregate of a refractory for casting, it is possible to impart sufficient corrosion resistance even for a steel having high corrosion resistance. Therefore, the content of MgO in the state after the heat treatment in a non-oxidizing gas atmosphere at 500 ° C is set to 40% by mass or more and 85% by mass or less. When the amount is less than 40% by mass, sufficient corrosion resistance cannot be imparted to the steel having high corrosion resistance. On the other hand, when it exceeds 85% by mass, the thermal shock resistance is remarkably deteriorated.

The raw material particles containing Al ₄ O ₄ C which can be used in the present invention may be selected such that the particle size, the classification, the blending ratio, and the like are selected in accordance with the respective conditions or requirements of the refractory shape to be applied. For example, it can be classified into 5 mm to 3 mm, 3 mm to 1 mm, 1 mm to 0 mm, or 0.074 mm or more, and these can be used in an arbitrary ratio. In order to improve the effect of lowering the coefficient of thermal expansion of the refractory material, it is preferable to use a raw material particle containing Al ₄ O ₄ C having a low expansion property as a relatively large particle, that is, a so-called coarse aggregate. On the other hand, when Al ₄ O ₄ C is used as the refractory for casting of magnesium oxide, the thermal expansion of the matrix portion of the magnesium oxide material and Al ₄ O ₄ C is poor, and between the Al ₄ O ₄ C and the parent portion of the magnesium oxide material. It is easy to generate micro space. This micro space has the effect of mitigating thermal stress when heated. In the case where the micro space is uniformly dispersed, the effect of this stress relaxation is easily exhibited. Therefore, in order to improve the effect of stress relaxation, it is preferable to use raw material particles containing Al ₄ O ₄ C as relatively small particles, so-called fine particles. That is, in order to improve the effect of lowering the coefficient of thermal expansion and the effect of stress relaxation, the raw material particles containing Al ₄ O ₄ C are preferably used in combination with coarse aggregates and fine particles. The method of separating the particle sizes of Al ₄ O ₄ C is preferably, for example, 3 mm to 1 mm, 40 to 70% by mass, and less than 1 mm, 30 to 60% by mass.

The thermal expansion coefficient and the thermal expansion coefficient of the present invention can be further adjusted by first changing the balance of the respective contents of Al ₄ O ₄ C and MgO, and further adjusting the particle size of each raw material and the blending ratio of the respective materials, that is, respectively, Al ₄ O ₄ C and MgO are obtained by classifying the composition ratio of each of the raw materials of the coarse particles to the fine particles in several stages, and various combinations between Al ₄ O ₄ C and MgO.

The shape of the raw material particles containing Al ₄ O ₄ C is preferably a spherical shape or a shape similar thereto, and may be in the form of a plate. In addition, the size of the Al ₄ O ₄ C crystal in the raw material particles containing Al ₄ O ₄ C is preferably 20 μm or more in terms of the average diameter when the cross-sectional area of the Al ₄ O ₄ C crystal is converted into a circle. Crystal grain size of Al ₄ O ₄ C contained in the Al ₄ O ₄ C material particles is greater, even under conditions of prolonged use, it can be suppressed more highly of alumina Al ₄ O ₄ C, and can be more Reduce the reaction rate of spinel.

The raw material particles containing Al ₄ O ₄ C are raw materials produced by electrofusion (arc melting), and the main constituent components of the electrofused raw material are preferably Al ₄ O ₄ C and corundum (Al ₂ O ₃ ). . The raw material particles containing Al ₄ O ₄ C have poor productivity in the existing sintering method, and it is difficult to industrialize in reality, and it is difficult to produce a raw material which can be made into a dense aggregate having a large crystal grain size of Al ₄ O ₄ C. On the other hand, the productivity of the electro-melt raw material obtained by arc melting is high, and an aggregate raw material of Al ₄ O ₄ C which is dense and has a large crystal grain size and an arbitrary particle size can be obtained. Since it is dense in this manner, the contact area with oxygen or carbon monoxide is small even under high temperature and oxidation conditions, and oxidation and alumina formation of Al ₄ O ₄ C can be suppressed, and the low thermal expansion rate can be maintained for a long period of time. As a result, it is possible to suppress the progress of alumina formation (lower speed) of Al ₄ O ₄ C under conditions of long-term use, and it is also possible to suppress the progress of spinel petrochemical (lower speed).

The raw material Al ₄ O ₄ C composition produced by the electrofusion method (arc melting) contains about 10% by mass of the corundum Al ₂ O ₃ component. Moreover, Al ₄ O ₄ C interacts with Al ₂ O ₃ (corundum) to form a layered and multi-layered structure, and these layers are firmly adhered to each other. The thickness of these layers is an Al ₄ O ₄ C layer>Al ₂ O ₃ layer, and this Al ₂ O ₃ layer can function to hinder oxidation of the Al ₄ O ₄ C layer or reaction with other components (refer to FIG. 1). Therefore, in the Al ₄ O ₄ C composition, Al ₂ O ₃ which is present in the form of raw material particles alone or a tip of Al ₂ O ₃ and MgO formed by, for example, Patent Document 4, Patent Document 5 or the like Compared with the petrochemical reaction, the reactivity can be greatly suppressed.

The content of Al ₄ O ₄ C in the refractory for casting of the present invention is set to be 10% by mass or more and 50% by mass or less in a state of being subjected to heat treatment in a non-oxidizing gas atmosphere at 500 °C. In the case of less than 10% by mass, the effect of lowering the coefficient of thermal expansion is small, and the effect of improving the thermal shock resistance is small. When it exceeds 50% by mass, the content of MgO is relatively small, and the corrosion resistance is remarkably lowered.

In the refractory for casting of the present invention, the content of the metal Al is arbitrary, and in the case where the metal Al is contained, the state after the heat treatment in a non-oxidizing gas atmosphere at 500 ° C is preferably 1% by mass or more and 15% by mass. the following. The content of the metal Al can be adjusted by the amount of metal Al (metal aluminum or metal aluminum alloy) blended in the billet before forming, and the like, for example, the billet can be made, for example, in accordance with each composition, heat treatment conditions, and the like. The metal aluminum may be contained in an amount of from 1% by mass to 20% by mass or less, and the residual amount may be adjusted according to heat treatment conditions or the like.

The metal Al in the refractory for casting exhibits an antioxidant and strength-enhancing effect and a spinel-chemical inhibition effect of Al ₄ O ₄ C. Therefore, the refractory for casting of the present invention preferably contains 1 mass% or more and 15 mass% or less of metal Al after heat treatment in a non-oxidizing gas atmosphere at 500 °C. In addition, when the content of the metal Al is less than 2% by mass, the free C in the refractory tends to be oxidized, and the strength tends to decrease. Therefore, the content of the metal Al is 2% by mass or more and 15% by mass or less. Preferably. However, even when the content of the metal Al is less than 2% by mass, it is possible to ensure the required oxidation resistance or by setting the heat curing treatment temperature to 1000 ° C or higher by means of means for compensating for oxidation resistance or strength. strength. On the other hand, when the content of the metal Al exceeds 15% by mass, the structure may be deteriorated during use. Therefore, when the metal Al is contained, the content thereof is preferably 15% by mass or less.

The metal Al source may be metal aluminum or a metal aluminum alloy, and its particle size or shape may be applied in accordance with the characteristics described below. That is, from the viewpoint of reactivity, the scale is the most excellent, but the formability is lowered. On the other hand, from the viewpoint of formability, it is preferred to use a particulate form (also referred to as "atomization"). In addition, in the case where the maximum length or particle diameter of the metal aluminum or the metal aluminum alloy exceeds 140 μm, the metal aluminum or the metal aluminum alloy is difficult to disperse in the billet, and the densification effect by the reaction of the metal aluminum or the metal aluminum alloy is not easily performed uniformly. Because of the abnormal expansion of a part of the refractory, the refractory may have a possibility of cracking. Therefore, the maximum length or particle diameter of the scaly or particulate metal aluminum or metal aluminum alloy is preferably 140 μm or less.

Further, it is also effective to use a fibrous metal aluminum or a metal aluminum alloy having a high crack suppression effect. However, in the case of a fibrous form, it tends to be more difficult to disperse than a scaly or granular form. Therefore, in the case of using a fibrous form, it differs depending on a kneading machine, a method, etc., and in order to improve dispersibility, it is preferable that the maximum particle diameter is 140 μm or less and the maximum length is equal to or less than the maximum particle diameter of the refractory raw material. The inventors of the present invention have found that the maximum length is the maximum diameter of the refractory raw material in the billet as the boundary, and the dispersibility is different. In general, the maximum particle diameter of the refractory raw material used for the flat plate for sliding nozzles is about 5 mm or less, so the fiber length is preferably 5 mm or less, and the raw material particles in the present invention. The maximum particle size of the sub-particles is preferably 3 mm or less. In short, the metal aluminum or the metal aluminum alloy which is a source of the metal Al may be used in combination with a scaly shape, a particle shape, or a fiber shape in accordance with the balance between formability and reactivity, and other necessary characteristics. Further, in the case of a scaly shape, the thickness is thin and the reactivity is high. Its thickness is not limited.

Incidentally, in the operation of using the refractory for casting of the present invention, in addition to the case where the refractory is used only once, there are cases where it is used repeatedly (repeatedly). In the case where the temperature is lowered during repeated use and during use, there is a case where MgO (magnesium oxide) in the refractory or Al ₄ C ₃ (aluminum carbide) produced is digested (hydrated) to deteriorate or destroy the refractory structure. . In order to suppress deterioration or destruction of the refractory structure caused by the digestion of MgO or Al ₄ C ₃ , the state in which the refractory is heat-treated in a non-oxidizing gas atmosphere at 500 ° C preferably contains 0.5% by mass or more and 4% by mass or less of metal Si. . In the case of MgO-containing refractory, the MgO in ambient temperature and pressure easily reacts with water to produce Mg (OH) ₂ (magnesium hydroxide). In the case of a carbon-containing refractory containing metal Al, in a temperature region of 700 ° C or more, the metal Al reacts with C (carbon) to start generating Al ₄ C ₃ , and the Al ₄ C _{3 is} at normal temperature and normal pressure. It is easy to react with water to produce Al(OH) ₃ (aluminum hydroxide). Such a reaction for producing Mg(OH) ₂ or Al(OH) ₃ is accompanied by an increase in volume and an increase in weight, so that the refractory may collapse (digestion phenomenon). The SiO ₂ (cerium oxide) produced by the oxidation reaction of the metal Si is solid-solubilized in MgO or Al ₄ C ₃ , whereby the digestion of MgO or Al ₄ C ₃ can be prevented. Further, when the metal Si is heated, a reaction such as Si+2CO→SiO ₂ +2C occurs, and the carbon monoxide gas is reduced, and carbon is supplied to the refractory structure, whereby the oxidation resistance can be improved. In addition, the metal Si contributes to the prevention of the aforementioned digestion, and also has an oxidation resistance effect of the refractory structure in a high temperature region (a temperature region exceeding about 1200 ° C). However, since SiO ₂ easily reacts with molten steel or forms a low melting point compound, there is a problem that corrosion resistance is lowered. Therefore, the content of the metal Si is preferably 4% by mass or less.

Next, a method of manufacturing the refractory for casting of the present invention will be described.

In the method for producing a refractory for casting of the present invention, a production method based on a conventional method for producing a refractory material of magnesium oxide or magnesium oxycarbonate can be basically employed. Specifically, the molding material is added such that a phenol resin or the like is added to the raw material blend containing at least the MgO component and the Al ₄ O ₄ C component, and the outer percentage is 1% by mass or more and 7% by mass or less. The thermosetting resin is produced by kneading.

A metal (metal Al source, metal Si source, etc.), a carbonaceous raw material (graphite, carbon black, etc.), and other fire-resistant aggregates (aluminum alumina, etc.) may be blended in the raw material blend. The metal aluminum as the metal Al source may have a scaly shape having a maximum length of 140 μm or less, a particle shape having a particle diameter of 140 μm or less, or a maximum diameter of a cross section of 140 μm or less and a maximum length of the refractory raw material in the billet. The fiber having a maximum particle diameter (generally 5 mm) or less is selected in one form or in combination. Further, part or all of these metal aluminum raw materials may be substituted with a metal aluminum alloy. In this case, the metal aluminum alloy is preferably an aluminum-magnesium alloy or an aluminum-niobium alloy.

Since the raw materials of these metals have different melting points or reactivity, they are fire resistant, such as strength, corrosion resistance, thermal shock resistance, and resistance to damage. The physical properties of things will change. The selection or combination of the raw materials of these metals can be arbitrarily adjusted depending on various operating conditions and characteristics required for various requirements (for example, thermal shock resistance, corrosion resistance, and damage resistance).

The forming can be formed into an arbitrary shape by, for example, uniaxial calendering. The temperature of the heat treatment or the like may be arbitrarily set so as to be suitable for each operation condition, the conditions to be provided, and the like. For example, it can be suitably optimized in a reducing gas atmosphere or an inert gas atmosphere at a temperature region above the temperature at which the resin responsible for carbon bonding hardens.

[Examples]

Adding a phenol resin to a raw material blend of a magnesium oxide raw material, an alumina raw material, a raw material containing Al ₄ O ₄ C, a metal raw material (metal aluminum or metal ruthenium), and other fire-resistant aggregates, as a mixer The kneading was carried out, and it was formed into a flat plate shape for a sliding nozzle using a 500-ton vacuum hydraulic press, dried, and heat-treated at a predetermined temperature to obtain a refractory for casting. Raw material containing Al ₄ O ₄ C, and is used to electrically Al ₄ O ₄ C and melting a raw material mainly composed of alumina particles, and the maximum particle size of 3mm, Al ₄ O ₄ C crystal size of the Al ₄ O ₄ C The average diameter of the cross-sectional area of the crystal when converted into a circle was 50 μm.

The composition of the obtained refractory for casting was analyzed in accordance with the following procedures. That is, in the composition of the refractory, regarding Al ₄ O ₄ C, Al ₂ O ₃ (corundum), Al, and Si, in the case of internal standard methods and standards without X-ray diffraction, The curve obtained by the Tverde method is quantified. Regarding free C (FC), it was quantified in accordance with JIS-R-2012. The other oxides were quantified by fluorescent X-rays in accordance with JIS-R-2216.

Further, a sample having a predetermined shape was cut out from the obtained refractory for casting, and the total specific gravity, the apparent porosity, the coefficient of thermal expansion, and the coefficient of thermal expansion were measured. The overall specific gravity and apparent porosity were measured in accordance with the method of JIS-R-2205. The coefficient of thermal expansion and the coefficient of thermal expansion were measured in accordance with the method of JIS-R-2207.

Further, the obtained refractory for casting was subjected to a corrosion resistance test and a thermal shock resistance test, and the characteristics of the refractory, particularly the refractory for casting, were evaluated.

In the corrosion resistance test, the conventionally produced steel and the black scale (Mill Scale) were used as the eroded material, and the sample prepared above was heated at 1600 ° C for 3 hours by a lining erosion method, and a three-stage evaluation was performed in accordance with the amount of melt loss. In other words, the comparative example 2 of the following Table 1 which is empirically considered to be the corrosion resistance standard or the lower limit under the normal operating conditions is used as the standard, and the corrosion resistance equivalent thereto is rated as "○", which is superior. The situation was rated as "◎", and the case of failing to meet the above criteria was rated as "X".

On the other hand, in the thermal shock resistance test, a sample prepared by the above method of 40 × 40 × 160 mm was immersed in molten iron at 1600 ° C for 3 minutes, and then cooled by air to observe cracks occurring in the sample. The number of the four-stage evaluation. In other words, the above-mentioned Comparative Example 2 which is empirically considered to be a thermal shock resistance standard or a lower limit under normal operating conditions is used as a standard, and the degree of thermal shock resistance exceeding the level of Comparative Example 2 is rated as "△". , will exceed "△" and excellent evaluation When it was "○", the more excellent case was rated as "◎", and the case of the same degree or worse as Comparative Example 2 was rated as "X".

Further, the sample was subjected to heat treatment at 1400 ° C in a carbonaceous material, and then cooled to room temperature (normal temperature), and the bending strength after cooling was measured. The bending strength was measured in accordance with the method of JIS-R-2213.

[Example A]

Example A shows the results of investigation of the coefficient of thermal expansion at 1000 °C. The composition and results of each sample are disclosed in Table 1. In addition, "the coarse particles in Al ₄ O ₄ C" means particles having a particle diameter of 1 mm or more and 3 mm or less (passing through a hole of a 3 mm mesh and remaining on a 1 mm sieve), and "particles in Al ₄ O ₄ C". It refers to particles having a particle size of less than 1 mm (passing through the pores of a 1 mm screen).

In Examples 1 to 4 in which the thermal expansion coefficient at 1000 ° C was 0.9% or less, the thermal shock resistance of either of them exhibited excellent results exceeding the above criteria. In Example 4, which had a coefficient of thermal expansion of 0.9% at 1000 ° C, the result was slightly inferior to the other examples in which the coefficient of thermal expansion at 1000 ° C was less than 0.9%. In Comparative Example 1 and Comparative Example 2 in which the coefficient of thermal expansion at 1000 ° C was more than 0.9%, the thermal shock resistance was poor, and the result was lower than the usable range. From these results, it is understood that the thermal expansion coefficient at 1000 ° C is preferably less than 0.9% in order to improve the thermal shock resistance.

Further, regarding the corrosion resistance, it was found that any of Examples 1 to 4 exhibited excellent results equivalent to or exceeding the criteria. Regarding the bending strength after the heat treatment at 1400 ° C, any of the examples was 20 MPa or more, and it was a grade having no problem at all in use.

[Example B]

Example B to investigate the average thermal expansion coefficient (α ₁₎ 1100 ℃ to 1500 deg.] C in / ℃ and the average thermal expansion coefficient (α ₂₎ from room temperature to 1100 ℃ a / ℃ difference _{(α s = α 1 -α 2} ) / ℃ The result of the impact. Sample composition and results are disclosed in Table 2.

In Example 1, Example 5, and Example 6 in which α _s was 6 × 10 ^-6 / ° C or less, the room temperature bending strength after heat treatment at 1400 ° C was 20 MPa or more, and it was a grade having no problem at all. In Comparative Example 3 in which α _s exceeded 6 × 10 ^-6 / ° C, the room temperature bending strength after heat treatment at 1400 ° C was less than 20 MPa, which was a result lower than the usable range.

Regarding the corrosion resistance and the thermal shock resistance, it was found that any of the examples exhibited excellent results exceeding the above criteria. Further, although the corrosion resistance and the thermal shock resistance of Comparative Example 3 exceeded the above criteria, in Comparative Example 3 in which α _s exceeded 6 × 10 ^-6 /° C, if it was repeatedly heated, the refractory structure deteriorated as described above. In particular, the corrosion resistance (and oxidation resistance, etc.) tends to decrease.

[Example C]

Example C is the result of investigating the effect of MgO content. Sample composition and results are disclosed in Table 3.

In the present Example C, the MgO content was changed in the range of 36% by mass to 88% by mass. In the case where the MgO content was 36% by mass (Comparative Example 4), the corrosion resistance was ×, and in the case of 88% by mass (Comparative Example 5), the thermal expansion coefficient at 1000 ° C exceeded 0.9%, and the thermal shock resistance was ×. In Examples 7, 1 and 8 in which the MgO content is in the range of 40% by mass or more and 85% by mass or less, the corrosion resistance and the thermal shock resistance are both usable, and the room temperature bending strength after heat treatment at 1400 ° C is 20 MPa or more. There is no problem at all.

[Example D]

Example D is the result of investigating the effect of the Al ₄ O ₄ C content. Sample composition and results are disclosed in Table 4.

In the present Example D, the Al ₄ O ₄ C content was changed in the range of 5 mass% to 54 mass%. In the case where the Al ₄ O ₄ C content was 5% by mass (Comparative Example 1), the thermal expansion coefficient at 1000 ° C exceeded 0.9%, and the thermal shock resistance was ×. In the case where the Al ₄ O ₄ C content was 54% by mass (Comparative Example 6), the corrosion resistance was ×. In Examples 9, 1, and 3 in which the Al ₄ O ₄ C content is in the range of 10% by mass or more and 50% by mass or less, the corrosion resistance and the thermal shock resistance are all in the usable range, and the room temperature bending strength after heat treatment at 1400 ° C is 20 MPa. The above is the level at which there is no problem at all.

[Example E]

Example E is the result of investigating the effect of the metal Al content. Sample composition and results are disclosed in Table 5.

In the present Example E, the metal Al content was changed in the range of 0.5% by mass to 16% by mass. In Examples 10 and 11 in which the metal Al content was less than 2% by mass, in order to compensate for oxidation resistance and strength, firing was performed at 1000 °C. In the case where the metal Al content was 0.5% by mass (Example 10), the corrosion resistance and the thermal shock resistance were good, but the room temperature bending strength after the heat treatment at 1400 ° C was lower than the appropriate target value of 20 MPa. Therefore In addition, it is preferable that the metal Al is contained in an amount of 1% by mass or more, and it is preferably contained in an amount of 2% by mass or more. Even if metal Al is not contained, the strength required may vary depending on conditions such as a flat plate shape or a device to be used. Therefore, it is still possible to use it. In the case where the strength is to be further increased, the strength can be sufficiently increased by firing at a high temperature or the addition of boron carbide. Therefore, the inclusion of the metal Al is not a requirement of the present invention. On the other hand, in Example 14 in which the metal Al content was 16% by mass, although the thermal shock resistance was satisfied, a decrease was observed, and it was predicted that the thermal shock resistance would continue to decrease at a higher content, and thus the metal Al content was It is preferably 15% by mass or less.

[Example F]

Example F is a result of investigating the influence of the presence or absence of metal Si and its content. The composition and results of the samples are disclosed in Table 6. In addition, the digestibility shown in Table 6 was obtained by placing the sample in a constant temperature and humidity chamber maintained at a temperature of 40 ° C and a humidity of 90%, and the weight of the sample after 30 days was compared with that before the placement. The weight change rate of the initial weight is evaluated. In the case of having a weight change rate of Example 16 which is empirically considered to be the lower limit of the digestibility standard under normal operating conditions, the case of the same degree or less is represented by "○", and although Although the reference is high, it is considered that the degree of use is at least one time under normal operating conditions is represented by "Δ".

In any of Examples 15 to 19, the thermal expansion rates at 1000 ° C were all 0.9% or less, and α _{s was} 6 × 10 ^-6 / ° C or less. Regarding the digestibility, the case of Example 15 containing no metal Si was "Δ", and any of Examples 16 to 19 containing metal Si was "○", and the resistance to digestion by metal Si was observed. Sexual improvement effect. Further, regarding the content of the metal Si, a decrease in corrosion resistance was observed in Example 19 of 6% by mass, and it was predicted that the corrosion resistance continued to decrease at a higher content, and therefore it was preferably 4% by mass or less.

[Example G]

Example G is the result of investigating the influence of other fire resistant aggregates and the remainder. Sample composition and results are disclosed in Table 7.

Example 20 is an example in which hexagonal calcite is incorporated in a part of the coarse aggregate, Example 21 is an example in which a part of the coarse aggregate is doped with mullite, and Example 22 is a part of the fine powder component in which B ₄ C is incorporated. As an example, Example 23 is an example in which SiC is incorporated in a part of the fine powder component. In the case of any of the constituent materials having these components, the thermal expansion or the spinelization reaction is not affected, and the refractory structure, particularly the apparent porosity, is not significantly changed, and thus is a good result. In addition, differences in the degree of thermal shock resistance or corrosion resistance are observed depending on the characteristics and characteristics of each component.

Claims (6)

A casting refractory material containing 40% by mass or more and 85% by mass or less of MgO and 10% by mass or more and 50% by mass or less of Al ₄ O ₄ C in a state after heat treatment in a non-oxidizing gas atmosphere at 500 ° C The refractory and the coefficient of thermal expansion at 1000 ° C is 0.9% or less, and the difference between the average thermal expansion coefficient of 1100 ° C to 1500 ° C and the average thermal expansion coefficient of room temperature to 1100 ° C is 6 × 10 ^-6 / ° C or less. The refractory for casting according to the first aspect of the invention, wherein the state after the heat treatment in a non-oxidizing gas atmosphere at 500 ° C contains 1 mass% or more and 15 mass% or less of metal Al. The refractory for founding according to claim 1 or 2, wherein the state after the heat treatment in a non-oxidizing gas atmosphere at 500 ° C contains 0.5% by mass or more and 4% by mass or less of metal Si. The refractory for casting according to claim 1 or 2, wherein the Al ₄ O ₄ C is derived from a raw material particle containing Al ₄ O ₄ C produced by an electrofusion method. Cross-sectional area as patent range cast item of a fourth refractory material, wherein the containing Al ₄ O ₄ C in the Al raw material particles ₄ O ₄ C crystal size based the Al ₄ O ₄ C crystal in terms of when the circle is the The average diameter is 20 μm or more. A flat plate for a sliding nozzle device, which is formed in part or in whole by a refractory for casting according to any one of claims 1 to 5.