JP6441685B2 - Castable refractories for lids of molten metal containers - Google Patents

Description

  The present invention relates to a castable refractory used for a lid of a molten metal container such as a molten steel ladle or tundish.

  The lid | cover used for molten metal containers, such as a molten steel ladle and a tundish, is provided in order to suppress the dissipation of the heat from molten metal surfaces, such as molten steel, and the scattering of molten metal or a molten metal droplet. In particular, in the ladle, the molten steel received from the converter is transported to the tundish through the secondary refining equipment and used for injection. It is greatly affected by mechanical shock when attaching and detaching and damage when removing deposits. Further, in the molten steel ladle, since the molten steel is transported by a crane, there is a weight limit, and the weight of the refractory used for the lid is preferably as light as possible. For this reason, the heat insulating lid is required not only to retain heat but also to have various characteristics such as weight reduction, thermal shock resistance, and mechanical shock resistance. Moreover, if these characteristics are to be satisfied, it is difficult to achieve high durability because they must have contradictory characteristics in terms of material design.

  In Japanese Utility Model Publication No. 61-158354 (Patent Document 1), heat radiation from molten steel as a molten metal accommodated in a molten metal pan (hereinafter simply referred to as a ladle) or lining refractories of the ladle is prevented. In order to maintain the working environment well, it is described that a heat insulating lid is placed on the upper end of the ladle.

  In Japanese Patent Laid-Open No. 10-235466 (Patent Document 2), a rear part is rotatably provided at one upper end of the ladle, and the refractory lining of the ladle or the molten steel contained in the ladle is kept warm. There is described a heat insulating lid that has a bottom lower surface made of brick or castable refractory and an inner lower surface made of fiber refractory. According to Patent Document 2, the heat insulating lid is lightweight, does not shorten its life even when it comes into contact with a converter rod or metal, and does not deteriorate maintainability. It is described that it is suitable as a heat insulation lid having a diameter of about 4 to 5 m for a large ladle to be accommodated.

  Japanese Patent Laid-Open No. 2002-162172 (Patent Document 3) discloses that the heat insulating material disposed inside the lid shell is 1200 to 1300 for the purpose of preventing the castable refractory material and the fiber blanket that are heat insulating materials from falling off and maintaining the shape. A heat insulating lid is disclosed which is supported by a steel plate of carbon steel, carbon steel or stainless steel which has heat resistance at ° C.

  As for the material, Japanese Patent Laid-Open No. 6-87666 (Patent Document 4) discloses a heat insulating castable containing ceramic fiber, and describes that it can be used for a furnace wall, a furnace lid, a heating furnace skid pipe, and the like. .

  Insulation lids for molten metal containers, for example, in the case of a molten steel ladle, are frequently placed or removed by a crane etc. every ch or each time passing through the secondary refining equipment, so thermal shock (rapid heating / cooling) It is damaged by various factors such as mechanical impact (particularly drop impact) when the lid is attached / detached, melting loss due to converter rod, molten steel, metal, etc., mechanical wear. When the damage to the heat insulating cover progresses due to these repeated damage factors, and the cover material (part) falls off and the heat insulating property deteriorates or the iron skin is distorted, the heat insulating cover must be replaced. However, since conventional materials are biased in resistance to these damage factors, if the resistance to any of the factors is low, the factors limit the wear, and sufficient durability cannot be obtained.

Japanese Utility Model Publication No. 61-158354 Japanese Patent Laid-Open No. 10-235466 JP 2002-162172 A JP-A-6-87666

  The present invention has various characteristics such as thermal shock resistance, drop impact resistance, mechanical strength, corrosion resistance, etc. while having the basic characteristics required for lid materials such as excellent heat retention and light weight. It is an object of the present invention to provide a castable refractory for a highly durable molten metal container lid that has excellent resistance to damage factors.

  As a result of diligent research in view of the above object, the present inventors have found that by using a specific amorphous refractory, it is possible to achieve both practicability and durability for use as a molten metal container lid. I came up with it.

That is, in the castable refractory for the molten metal container lid of the present invention, the refractory raw material has a bulk specific gravity of 1.30 to 1.70 g / cm ³ and a particle size of 8 to 100% by mass of the refractory raw material. When 0.3 mm refractory particles (particle size 8 to 1 mm is 30 to 45% by mass and particle size 1 to 0.3 mm is 15 to 25% by mass) are 50 to 65% by mass, (B) when heated at 1000 ° C or higher 5-12% by mass of expansive refractory particles that exhibit expansibility, (C) 3-12% by mass of refractory fine particles having a median diameter of 10 μm or less, (D) 15-25% by mass of alumina cement, and ( E) The balance is characterized by comprising refractory particles having a particle size of 0.3 mm or less.

  The refractory fine particles having a median diameter of 10 μm or less preferably contain at least 3% by mass of silica fume.

  The expandable refractory particles are preferably kyanite.

The castable refractory for the molten metal container lid has a bulk specific gravity of 1.70 g / cm ³ or less after heating at 1000 ° C., a thermal conductivity of 1.0 W / m · K or less, a bending strength of 3.0 MPa or more, and a compressive strength of 10.0. It is preferable that it is more than MPa.

The castable refractory for a molten metal container lid of the present invention is a combination of specific refractory particles, refractory fine particles, alumina cement, etc., and when used for a molten metal container lid, the heat retention, refractory weight, etc. Assures excellent durability (ie, the bulk specific gravity after heating at 1000 ° C is 1.70 g / cm ³ or less and the thermal conductivity is 1.0 W / m · K or less). To demonstrate.

The castable refractory material of the present invention suitable for use in a molten metal container lid will be described. The castable refractory of the present invention has a bulk specific gravity after heating at 1000 ° C. of 1.70 g / cm ³ or less, a thermal conductivity of 1.0 W / m · K or less, a bending strength of 3.0 MPa or more, and a compressive strength of 10.0 MPa or more. Have Furthermore, it has excellent thermal shock resistance.

(1) Refractory raw material The refractory raw material used in the castable refractory for the molten metal container lid of the present invention is refractory particles having a particle size of 0.3 mm or more, expansive refractory particles, refractory fine particles having a median diameter of 10 μm or less, alumina It preferably consists of cement and refractory particles having a particle size of 0.3 mm or less. Note that refractory particles with a particle size of 0.3 mm or more are refractory particles that do not pass through a sieve with a mesh size of 0.3 mm, and refractory particles with a particle size of 0.3 mm or less are those that pass through a sieve with a mesh size of 0.3 mm or less. Refractory particles.

The castable refractory for a molten metal container lid of the present invention is characterized by being light in weight with a bulk specific gravity of 1.70 g / cm ³ or less. If the bulk specific gravity is 1.70 g / cm ³ or less, not only the effect of reducing the required construction amount, but also the impact due to its own weight when attaching and detaching is reduced. Furthermore, in order to prevent damage during attachment and detachment or the like, it is preferable that the strength in the entire heating temperature range is equal to or higher than a certain level and the change in strength is small. For example, even if the strength is higher than a certain level on the high temperature side or the low temperature side, if the strength is low in the intermediate temperature range, the portion tends to crack due to external factors. Specifically, it is preferable that the bending strength after heating at 1000 ° C. is 3.0 MPa or more and the compressive strength is 10.0 MPa or more.

(A) Refractory particles having a particle size of 0.3 mm or more As the refractory particles having a particle size of 0.3 mm or more, those having a bulk specific gravity of 1.30 to 1.70 g / cm ³ are used. For example, it is preferable to use a material obtained by firing a mixture of a mineral raw material having an Al ₂ O ₃ content of 40 to 70% by mass and an SiO ₂ content of 25 to 60% by mass and adding an extinction material.

When a refractory particle having a bulk specific gravity of less than 1.30 g / cm ³ is used, shrinkage of the castable refractory after heating at a high temperature (for example, 1400 ° C.) increases. As a result, shrinkage cracks occur on the working surface during use, and this gradually expands to reach the back surface, resulting in partial or extensive dropout due to mechanical impact when the lid is attached / detached, resulting in insufficient durability. . If the bulk density of refractory particles exceeds 1.70 g / cm ³ , not only will the bulk density and thermal conductivity of castable refractories increase, but thermal shock resistance will also deteriorate. Therefore, sufficient durability cannot be obtained.

  The bulk density of refractory particles with a particle size of 0.3 mm or more was obtained by combining refractory particles with a particle size of 0.3 mm or more and other refractory materials, mixing, adding water, kneading, and heating after curing. It is preferable to be equivalent to the bulk specific gravity of the castable refractory.

  Of the refractory particles having a particle size of 0.3 mm or more, it is preferable to use refractory particles having a particle size of 8 mm or less, that is, refractory particles having a particle size of 8 to 0.3 mm. The refractory particles having a particle size of 8 to 0.3 mm are refractory particles that pass through a sieve having an aperture of 8 mm but do not pass through a sieve having an aperture of 0.3 mm. The content of the refractory particles having a particle diameter of 8 to 0.3 mm is preferably 50 to 65% by mass with respect to 100% by mass of the refractory raw material. Among the refractory particles having a particle size of 8 to 0.3 mm, the refractory particles having a particle size of 8 to 1 mm are 30 to 45% by mass with respect to 100% by mass of the refractory raw material, and the fire resistance of 1 to 0.3 mm is the particle size The conductive particles are preferably 15 to 25% by mass with respect to 100% by mass of the refractory raw material.

  If the content of refractory particles with a particle size of 8 to 0.3 mm is less than 50% by mass, the amount of sintering shrinkage after heating at high temperatures increases, shrinkage cracks occur during operation, and when the lid is attached or detached. It becomes easy to drop off. If the content of refractory particles having a particle size of 8 to 0.3 mm exceeds 65% by mass, the fluidity of the castable that has been kneaded by adding water deteriorates and becomes insufficiently filled, or excessive water is added to impart fluidity. Since it is necessary, separation during curing and a decrease in strength due to excess water will occur. The distribution ratio between the particle size of 8 to 1 mm and the particle size of 1 to 0.3 mm is determined as the range in which the balance of fluidity, heat shrinkability, strength, and thermal shock resistance is most excellent.

(B) Expandable refractory particles The castable refractory for a molten metal container lid of the present invention is characterized by being light in weight with a bulk specific gravity of 1.70 g / cm ³ or less. It is also a big feature. However, in the case of a molten metal container lid, since the attachment / detachment frequency is high and the heating / cooling is frequently received, a shrinkage crack develops and drops off from this point. Therefore, it is preferable to apply expandable refractory particles and suppress the heat shrinkage by utilizing the expansion reaction.

  As refractory raw materials that exhibit expansibility, those due to the phase transition of α-quartz contained in silica and wax stone, those due to phase transition to mullite such as kyanite and andalusite, those due to void formation by magnesia The thing by spinel production | generation by reaction of a magnesia and an alumina is known. However, the expansion reaction that occurs in the material is accompanied by the destruction of connective tissue. In particular, the present invention aims to reduce the bulk specific gravity and thermal conductivity, and therefore refrains from using a high-performance water reducing agent (dispersant), and the aggregate strength itself is low, so that the fine powder part due to expansion is reduced. The destruction of the connective tissue is accompanied by a significant decrease in strength, and is easily damaged when attaching and detaching or removing attached metal, etc., so that the control of the expansion reaction is very important.

As the expandable refractory raw material used for the castable refractory for the molten metal container lid of the present invention, kyanite is preferable. Kyanite is an Al ₂ O ₃ -SiO ₂ mineral, but it is produced in nature under high pressure (kyanite Al ₂ SiO ₅ kyanite: specific gravity 3.53-3.65) and is the only stable mineral under normal pressure. It has a higher density than some mullite (mullite Al ₆ Si ₄ O ₁₃ : specific gravity 3.0). Therefore, when heated under normal pressure, it decomposes and rearranges into low density mullite and tridymite and expands accordingly. The effect of suppressing the heat shrinkage due to the expansion reaction varies depending on the particle diameter. The coarser the particle diameter, the larger the expansion amount, and the accompanying strength decrease becomes remarkable. Moreover, when it is coarse, it will apply to the fine aggregate area | region with a particle size of 0.3 mm or more, and the bulk specific gravity of a castable refractory increases. The median diameter is most preferably 0.15 to 0.03 mm, and by adding 5 to 12% by mass with respect to 100% by mass of the refractory raw material, the effect of strength reduction is small and a sufficient shrinkage suppressing effect can be obtained. It becomes like this. If the median diameter is less than 0.03 mm, the effect of imparting expansibility cannot be obtained. If it exceeds 0.15 mm, the effect of imparting expansibility after high-temperature firing will increase, so adding excessively will cause overhanging cracks, and the working surface side (high temperature side) strength will decrease and during attachment / detachment It is easily damaged by the impact of Therefore, the addition amount in this case is preferably 5 to 7% by mass.

Andalusite (andalusite Al ₂ SiO ₅ syenite: specific gravity 3.13-3.16) and sillimanite (sillimanite Al ₂ SiO ₅ silicite: specific gravity 3.23-3.27) also have the effect of expressing expansivity, but the lightweight castable for the lid of the present invention In this case, the effect is small, the amount necessary for suppressing the heat shrinkage is increased, the addition to the aggregate region is required, and the bulk specific gravity is increased.

  In the case of silica stone, large expansibility is expressed at a lower temperature range. For this reason, a sufficient connective tissue cannot be formed, and the influence of strength reduction is large.

  In the case of magnesia, the present invention containing a large amount of silica fume and the like is not preferable because a large amount of a low-melting-point material is generated during high-temperature heating.

(C) Refractory fine particles having a median diameter of 10 μm or less Silica fume is preferably used as the refractory fine particles having a median diameter of 10 μm or less in order to increase the strength without increasing the specific gravity. However, when combined with a high-performance water reducing agent (dispersing agent) commonly used for castable refractories, the dispersibility of the fine particles is improved when the action is extended, and the bulk specific gravity and heat Since conductivity also increases, it is preferable to avoid its use. However, a high-performance water reducing agent can be used for fluidity adjustment as long as the physical properties are not affected.

  The calcined alumina ultrafine powder and kaolinite also exhibit the effect of increasing the strength and are effective in improving fire resistance because the melting point is higher than that of silica fume, and can be used as appropriate. However, since the density is higher than that of silica fume, the amount is limited.

  The amount of the refractory fine particles having a median diameter of 10 μm or less is preferably 3 to 12% by mass with respect to 100% by mass of the refractory raw material. Of these, silica fume is preferably at least 3% by mass. If it is less than 3% by mass, sufficient strength cannot be obtained. Also, if the amount of refractory fine particles having a median diameter of 10 μm or less exceeds 12% by mass, the amount of heat shrinkage increases, shrinkage cracks are generated and expanded, and it tends to fall off early during operation.

(D) Alumina cement Alumina cement is often used as a hardener for castable refractories, but in the present invention, it develops strength while maintaining an appropriate bulk specific gravity and thermal conductivity, and changes in strength with respect to changes in heating temperature. Less is required. With one or two types of alumina cement specified in JIS R2511 (alumina cement for refractory), predetermined characteristics can be obtained without impairing fire resistance and high temperature sinterability.

  The addition amount of the alumina cement is preferably 15 to 25% by mass with respect to 100% by mass of the refractory raw material, and if it is less than 15% by mass, sufficient strength cannot be obtained. On the other hand, if it exceeds 25% by mass, the amount of shrinkage after heating increases, which is not preferable.

(E) Other refractory particles
Other refractory particles can be used to obtain appropriate fluidity by connecting refractory particles having a particle size of 0.3 mm or more with refractory fine particles or alumina cement. The other refractory particles are selected so that the bulk specific gravity, thermal conductivity, strength, etc. of the castable refractory fall within a predetermined range.

  As other refractory particles, it is preferable to use refractory particles having a size of 0.3 mm or less, and fine particles under a 0.075 mm sieve, such as alumina or mullite, can be used. Silica / siliceous and magnesia fine powders are not preferred because they increase shrinkage during heating.

(2) Other additives To the castable refractory for the molten metal container lid of the present invention, it is possible to add a curing regulator such as a retarder or an accelerator, or a thickener, as long as the properties are not impaired. it can. Moreover, especially when mechanical impact is strong, fracture toughness can be improved by adding a steel fiber, and further durability improvement can be performed. However, steel fiber has high density and high thermal conductivity, and it is necessary to add the steel fiber while checking these characteristics.

  Examples of the present invention and comparative examples will be described below. The present invention is not limited to these examples.

(1) Preparation of refractory particles (particle size: 0.3 mm or more) Table 1 shows the characteristics of the refractory particles used in Examples and Comparative Examples.

(2) Examples 1-7 and Comparative Examples 1-17
Tables 2-1 and 2-2 (Examples 1 to 6) and Tables 3-1 to 3-4 (Comparative Examples 1 to 13) show refractory particles, expandable refractory raw materials, silica fume and alumina cement. Formulated as a prescription and prepared a castable refractory. Furthermore, steel fiber was further blended in the formulations shown in Tables 4-1 to 4-2 to the castable refractory compositions (basic blends) of Example 1, Comparative Example 5 and Comparative Example 6, and Example 7 and Comparative Example 14 And the castable refractory of Comparative Example 15 was prepared. Here, the median diameter of the fine powder is a volume-based value measured using a laser diffraction / scattering particle size distribution measuring device manufactured by Seishin Corporation. Each castable refractory is kneaded with the amount of water shown in Table 2-1, Table 2-2, Table 3-1 to Table 3-4 and Table 4-1 to Table 4-2, and cast into a predetermined form. After curing at room temperature for 24 hours, the frame was removed and dried at 110 ° C. for 24 hours.

  For Examples 1 to 6 and Comparative Examples 1 to 13, the dried samples were further heated at 1000 ° C. for 3 hours, and heated at 1400 ° C. for 3 hours. By the method shown below, the residual line change rate after heating, bulk specific gravity, The thermal conductivity, bending strength, compressive strength and thermal shock test were evaluated.

  For the samples of Example 7, Comparative Example 14 and Comparative Example 15, the sample after drying was further heated at 1000 ° C. for 3 hours, and the residual line change rate after heating, bulk specific gravity, thermal conductivity, bending, by the method shown below The strength and compressive strength were evaluated. Further, castable refractories (Comparative Example 16 and Comparative Example 17) were prepared with the compositions described in JP-A-6-87666 and JP-A-2005-314222 and evaluated in the same manner. For the samples of Example 1, Example 7 and Comparative Examples 14-17, the number of times of use in the lid for the molten steel ladle (from the converter to the ladle from the lid immediately after receiving the steel to the next receiving steel is 1 ch. The lid was attached and detached every time secondary refining was performed.

  The results are shown in Table 2-1 and Table 2-2 (Examples 1 to 6), Table 3-1 to Table 3-4 (Comparative Examples 1 to 13), Table 4-1 and Table 4-2 (Example 1, Example 7 and Comparative Examples 14-17 are shown.

注(1) メジアン径
(2) 0.075 mm篩を通過した粒子
(3) 耐火性原料100質量％に対する外割添加水量
(4) 1300℃急熱→急冷3サイクル後の弾性率と、試験前弾性率との比

Note (1) Median diameter
(2) Particles that passed through 0.075 mm sieve
(3) Amount of extra water added to 100% by mass of refractory material
(4) Ratio of elastic modulus after 1300 ° C rapid heating → rapid cooling 3 cycles and pre-test elastic modulus

注(1) メジアン径
(2) 0.075 mm篩を通過した粒子
(3) 耐火性原料100質量％に対する外割添加水量
(4) 1300℃急熱→急冷3サイクル後の弾性率と、試験前弾性率との比

Note (1) Median diameter
(2) Particles that passed through 0.075 mm sieve
(3) Amount of extra water added to 100% by mass of refractory material
(4) Ratio of elastic modulus after 1300 ° C rapid heating → rapid cooling 3 cycles and pre-test elastic modulus

注(1) メジアン径
(2) 0.075 mm篩を通過した粒子
(3) 耐火性原料100質量％に対する外割添加水量
(4) 1300℃急熱→急冷3サイクル後の弾性率と、試験前弾性率との比

Note (1) Median diameter
(2) Particles that passed through 0.075 mm sieve
(3) Amount of extra water added to 100% by mass of refractory material
(4) Ratio of elastic modulus after 1300 ° C rapid heating → rapid cooling 3 cycles and pre-test elastic modulus

注(1) メジアン径
(2) 0.075 mm篩を通過した粒子
(3) 耐火性原料100質量％に対する外割添加水量
(4) 1300℃急熱→急冷3サイクル後の弾性率と、試験前弾性率との比

Note (1) Median diameter
(2) Particles that passed through 0.075 mm sieve
(3) Amount of extra water added to 100% by mass of refractory material
(4) Ratio of elastic modulus after 1300 ° C rapid heating → rapid cooling 3 cycles and pre-test elastic modulus

注(1) メジアン径
(2) 0.075 mm篩を通過した粒子
(3) 耐火性原料100質量％に対する外割添加水量
(4) 1300℃急熱→急冷3サイクル後の弾性率と、試験前弾性率との比

Note (1) Median diameter
(2) Particles that passed through 0.075 mm sieve
(3) Amount of extra water added to 100% by mass of refractory material
(4) Ratio of elastic modulus after 1300 ° C rapid heating → rapid cooling 3 cycles and pre-test elastic modulus

注(1) メジアン径
(2) 0.075 mm篩を通過した粒子
(3) 耐火性原料100質量％に対する外割添加水量
(4) 1300℃急熱→急冷3サイクル後の弾性率と、試験前弾性率との比

Note (1) Median diameter
(2) Particles that passed through 0.075 mm sieve
(3) Amount of extra water added to 100% by mass of refractory material
(4) Ratio of elastic modulus after 1300 ° C rapid heating → rapid cooling 3 cycles and pre-test elastic modulus

(3) Test method
(3-1) Residual line change rate
Measured according to JIS R2654.

(3-2) Bulk specific gravity
Measured according to JIS R2655.

(3-3) Thermal conductivity
Measured according to JIS R2251-1 (hot wire method: orthogonal method).

(3-4) Bending strength
Measured according to JIS R2553.

(3-5) Thermal shock test
Obtained by drying a 40 mm x 40 mm x 160 mm cuboid molded body obtained by molding in accordance with JIS R2553 at 110 ° C, firing at 1300 ° C, and gradually cooling to room temperature. First, the elastic modulus E ₀ before the thermal shock test was measured. The test piece was put into a furnace heated to 1300 ° C., held for 30 minutes, then removed from the furnace, and subjected to a thermal shock test in which one cycle was taken to cool in air. This thermal shock test was conducted for 3 cycles, the elastic modulus E ₃ after 3 cycles was measured, and the elastic modulus ratio E ₃ / E ₀ before and after the test was evaluated. The closer E ₃ / E ₀ is to 1.0, the better the thermal shock resistance. The elastic modulus was measured by a dynamic elastic modulus test method (JIS R1602: bending resonance method).

(4) Evaluation results (Examples 1 to 6 and Comparative Examples 1 to 13)
As shown in Table 2-1 and Table 2-2, 8 to 1 mm refractory particles and 1 to 0.3 mm refractory particles, expansible refractory that develops expansibility when heated above 1000 ° C Examples 1-6, in which a specified amount of refractory particles, refractory fine particles having an average particle size of 10 μm or less and alumina cement are added in a specified amount, all have moderate bulk specific gravity and thermal conductivity, while exhibiting strength Excellent in heat resistance, heat shrinkage inhibiting effect and thermal shock resistance. Since the expandable refractory particles were added, the shrinkage cracks starting from the working surface were less likely to occur if the residual expansion coefficient was about 0 to 0.4% after heating at 1400 ° C., which approximates the working surface temperature.

  Tables 3-1 to 3-4 show the formulations and characteristics of Comparative Examples 1 to 13. Comparative Example 1 and Comparative Example 2 are an example with little refractory fine particles having a median diameter of 10 μm or less and an example not containing silica fume, respectively. All were low in strength and inferior in mechanical shock resistance when the lid was attached or detached.

  Comparative Example 3 is an example in which the total amount of the refractory particles having a particle diameter of 8 to 1 mm and the refractory particles having a particle diameter of 1 to 0.3 mm is less than 50% by mass with respect to 100% by mass of the refractory raw material. Since the shrinkage after heating is large, it is considered that shrinkage cracks are generated and easily fall off due to an impact at the time of attachment / detachment. Also, the thermal shock resistance was low.

Comparative Example 4 and Comparative Example 5 correspond to materials that have been widely used for lids of conventional molten metal containers, and examples where the bulk specific gravity of refractory particles having a particle size of 0.3 mm or more exceeds 1.70 g / cm ³ It is. Comparative Example 5 is an example that does not further contain silica fume. Both are unfavorable because the bulk specific gravity and thermal conductivity of the castable refractory are large, and the required amount of construction and the amount of heat dissipated increase. In addition, the strength after firing at 1000 ° C. is low, and the thermal shock resistance is also deteriorated.

Comparative Example 6 is an example in which the bulk specific gravity of refractory particles having a particle size of 0.3 mm or more is less than 1.30 g / cm ³ . Sintering shrinkage when heating the refractory particles themselves with a particle size of 0.3 mm or more becomes noticeable, or because the shrinkage after heating of the castable refractory is large, shrinkage cracks are generated and expanded, and when attaching and detaching It is thought that it will be easy to drop off due to the impact of.

  Comparative Example 7 is an example where there are few expandable refractory particles. Since the shrinkage after heating is large, it is considered that shrinkage cracks are generated and easily fall off due to an impact at the time of attachment / detachment.

  Comparative Example 8 is an example with a small amount of alumina cement. Since the strength after heating is insufficient, damage during attachment and detachment becomes large, and it is considered that sufficient durability cannot be obtained. Further, since the expansion after heating at 1400 ° C. is large, it is considered that peeling due to protrusion tends to occur.

  Comparative Example 9 is an example with a large amount of alumina cement. In addition to insufficient strength after heating, the shrinkage after heating is large, so that it is considered that shrinkage cracks are likely to occur or fall off due to impact during attachment / detachment.

  Comparative Example 10 is an example using Kyanite having a median diameter of 0.2 mm as the expandable refractory particles. Since the expansion after heating at 1400 ° C is large, it is considered that peeling due to protrusion tends to occur.

  Comparative Example 11 is an example using andalusite as the expandable refractory particles. It is considered that due to insufficient expansion, shrinkage cracks occur and the bulk specific gravity gradually increases.

  Comparative Example 12 is an example in which silica stone is used as the expandable refractory particles. Silica stones are expansible in the low temperature range (500-600 ° C) where almost no effect of strength development can be obtained by heating, so when using silica, the connective structure is easily destroyed, and as the amount added increases, the strength decreases by 1000 ° C cause. For this reason, the amount of addition cannot be increased to such an extent that sufficient expandability can be obtained on the high temperature side.

  Comparative Example 13 is an example using magnesia as the expandable refractory particles. It is thought that at 1400 ° C, the amount of liquid phase produced increases remarkably and softens, resulting in insufficient fire resistance.

(1) 表2-1及び表3-2に記載した実施例及び比較例
(2) 長さ
(3) 耐火性原料100質量％に対する外割添加水量
(4) 溶鋼取鍋用蓋での使用回数。転炉から取鍋に受鋼直後の蓋掛けから次回受鋼までを1chとする。この間、二次精錬を行う毎に蓋の着脱が行われる。

(1) Examples and comparative examples described in Table 2-1 and Table 3-2
(2) Length
(3) Amount of extra water added to 100% by mass of refractory material
(4) Number of times used with a ladle lid. From the converter to the ladle, the cover from immediately after receiving steel to the next receiving steel is 1ch. During this time, the lid is attached and detached each time secondary refining is performed.

(1) 表3-2に記載した比較例
(2) 長さ
(3) 耐火性原料100質量％に対する外割添加水量
(4) 溶鋼取鍋用蓋での使用回数。転炉から取鍋に受鋼直後の蓋掛けから次回受鋼までを1chとする。この間、二次精錬を行う毎に蓋の着脱が行われる。

(1) Comparative examples described in Table 3-2
(2) Length
(3) Amount of extra water added to 100% by mass of refractory material
(4) Number of times used with a ladle lid. From the converter to the ladle, the cover from immediately after receiving steel to the next receiving steel is 1ch. During this time, the lid is attached and detached each time secondary refining is performed.

  The castable refractory for the molten metal container lid of the present invention (Example 1 and Example 7 in which 2% by mass of steel fiber is added to the outer portion thereof) is necessary for construction compared to Comparative Example 14 that has been conventionally used. In addition to being able to reduce the amount by 20% and the amount of heat dissipated by 30%, it was excellent in resistance to various damage factors such as strength development, heat shrinkability, and thermal shock resistance. As a result, cracking and peeling did not easily occur, and the service life was greatly extended.

  In addition, Comparative Example 15 with lower bulk specific gravity and low thermal conductivity, and Comparative Examples 16 and 17 that can also be used for lids, have large heat shrinkage and low strength, so they are frequently affected by cracks and impact during attachment / detachment. Dropout occurred, the heat retention effect deteriorated significantly, and had to be replaced early.

Claims (3)

The refractory raw material is 100% by mass of the refractory raw material,
(A) Refractory particles having a bulk specific gravity of 1.30 to 1.70 g / cm ³ and a particle size of 8 to 0.3 mm (containing 30 to 45% by mass of particles having a particle size of 8 to 1 mm and having a particle size of 1 to 0.3 mm Containing 15 to 25% by mass of particles)) to 50 to 65% by mass,
(B) 5-12% by mass of expansive refractory particles that develop expansibility when heated at 1000 ° C. or higher,
(C) 3 to 12% by mass of refractory fine particles having a median diameter of 10 μm or less,
(D) 15-25% by mass of alumina cement, and
(E) the remainder Ri is Do the following refractory particles with particle sizes of 0.3 mm, the median diameter 10μm or less of the refractory particles is molten metal container closure for castable refractories, characterized in that silica fume is at least 3% by weight or more object. 2. The castable refractory for a molten metal container lid according to claim 1 , wherein the expandable refractory particles are kyanite. The castable refractory for a molten metal container lid according to claim 1 or 2 , wherein the bulk specific gravity after heating at 1000 ° C is 1.70 g / cm ³ or less, the thermal conductivity is 1.0 W / m · K or less, and the bending strength is 3.0 MPa. As described above, a castable refractory for a molten metal container lid, which has a compressive strength of 10.0 MPa or more.