JP7456035B1 - Back material for ladle - Google Patents

Abstract

[Problem] In addition to achieving a heat shrinkage rate suitable for fixing the bricks installed on the inner wall of the ladle and strength suitable for dismantling the bricks after use, we also use raw materials that contribute to a recycling-oriented society. We provide backing material for ladle. [Solution] Consists of 80 to 90% by mass of magnesia particles and 10 to 20% by mass of calcium carbonate particles, and the proportion of particles with a particle diameter of less than 2 mm contained in the calcium carbonate particles is 50% or less. A backing material for a ladle featuring the following. It is preferable to use shells for the calcium carbonate particles. [Selection diagram] None

Description

The present invention relates to a filler used for lining a ladle for iron manufacturing (ladle backing material).

A ladle is a refractory container used to transport molten metal and to pour molten metal into molds. In a ladle, it is necessary to provide a fireproof material such as bricks on the inside of the container, and in order to fix the bricks, a ladle backing material is filled between the bricks.

Regarding the structure of the ladle, for example, in Patent Document 1 (Japanese Unexamined Patent Publication No. 5-13656), it is stated that "in a refractory lining structure applied to the inside of a molten steel ladle, at least the main part is a permanent base layer. It has a two-layer structure consisting of a stretched refractory layer and a lining refractory layer applied thereon. The lining refractory layer is formed by constructing a monolithic refractory that has an expansion tendency and excellent mechanical strength compared to the linear expansion/contraction rate, and the lining refractory layer has a residual linear expansion/contraction rate of The permanent refractory layer is formed by constructing a monolithic refractory that has a shrinkage tendency compared to the residual linear expansion/contraction rate of the permanent refractory layer and has excellent corrosion resistance. "A lining structure for a molten steel ladle, characterized in that a release agent is applied to the surface facing the lining refractory layer."

In the lining structure described in Patent Document 1, the permanent refractory layer serving as the base layer and the lining refractory layer formed thereon are constructed by constructing monolithic refractories by a method such as pouring or spraying. It is said that it can be constructed in a shorter time than the conventional method of stacking refractory bricks. Further, a release agent is applied to the surface of the permanent refractory layer facing the lining refractory layer to prevent welding of the permanent refractory layer and the lining refractory layer. It is said that

Japanese Patent Application Publication No. 5-13656

However, the lining structure of the molten steel ladle described in Patent Document 1 is composed of a monolithic refractory, and is different from the structure in which bricks are fixed by a backing material for the ladle. Furthermore, a lining structure made of monolithic refractories cannot be said to have sufficient durability when compared to a lining structure made of bricks. Furthermore, when the lining refractory layer is eroded and high-temperature molten material (iron or slag) reaches the backing material, the erosion cannot be stopped.

Here, since it is necessary to fill the backing material for the ladle so that the bricks do not move, it is required to have little shrinkage after heating. In addition, it is required that it does not melt even when it comes into contact with high-temperature molten materials (iron or slag), has little welding to bricks due to sintering, and does not damage the bricks when dismantling them after use. The reality is that there is no backing material for ladle that is optimized from this point of view. In addition, no consideration has been given to raw materials from the perspective of contributing to a recycling-oriented society.

In view of the problems in the prior art as described above, an object of the present invention is to develop a heat shrinkage rate suitable for fixing bricks installed on the inner wall of a ladle and a strength suitable for dismantling the bricks after use. In addition to this, we also provide ladle backing materials made from raw materials that contribute to a recycling-oriented society.

In order to achieve the above object, the present inventors have conducted extensive research on the composition of ladle backing materials, and have added an appropriate amount of calcium carbonate particles to ladle backing materials whose main raw material is magnesia particles. They have discovered that controlling the particle size of the calcium carbonate particles is extremely effective, and have arrived at the present invention.

That is, the present invention
80 to 90% by mass of magnesia particles,
Consisting of 10 to 20% by mass of calcium carbonate particles,
The proportion of particles with a particle diameter of less than 2 mm contained in the calcium carbonate particles is 50% or less;
To provide a backing material for a ladle, which is characterized by:

In the ladle backing material of the present invention, by containing 10% by mass or more of calcium carbonate particles, it can be easily dismantled after use, and the content of the calcium carbonate particles should be 20% by mass or less. By doing so, it can retain its shape as a backing material. In addition, there are discarded calcium carbonate raw materials such as oyster shells, and utilization of calcium carbonate is preferable from the perspective of contributing to a recycling-oriented society.

In addition, by setting the proportion of particles with a particle diameter of less than 2 mm in the calcium carbonate particles to 50% or less, the heat shrinkage rate of the ladle backing material can be reduced without reducing the amount of calcium carbonate particles added to the backing material. In addition to being able to suppress an excessive increase in size, it is possible to impart appropriate strength to the ladle backing material after heating. The proportion of particles having a particle diameter of less than 2 mm contained in the calcium carbonate particles is more preferably 30% or less.

Further, in the ladle backing material of the present invention, it is preferable that the calcium carbonate particles are shells such as oyster shells. Oyster shells are used as fertilizer, etc., but their usage is limited and most of them are discarded. By utilizing oyster shells, which are mainly composed of calcium carbonate particles, as calcium carbonate particles, it is possible to contribute to a recycling-oriented society.

Further, in the ladle backing material of the present invention, it is preferable that the calcium carbonate particles are limestone. Limestone is a rock mainly composed of calcium carbonate, and is distributed throughout Japan, with many limestone mines in operation. Limestone is a natural resource that is 100% self-sufficient in Japan, which is said to be a resource-poor country, and can contribute to a recycling-oriented society from the perspective of local production and local consumption.

Further, in the ladle backing material of the present invention, it is preferable that the shrinkage rate after heating in the atmosphere at 1400° C. for 48 hours is 20% or less. By setting the shrinkage rate after heating in the atmosphere at 1400° C. for 48 hours to 20% or less, the ladle brick can be firmly held. The shrinkage rate after heating in the atmosphere at 1400° C. for 48 hours is more preferably 18% or less, most preferably 16% or less.

Furthermore, it is preferable that the ladle backing material of the present invention has a compressive strength of 0.5 to 1.5 MPa after being heated in the atmosphere at 1400° C. for 24 hours. By setting the strength of the ladle backing material after firing to 0.5 MPa or more, a structure made of bricks can be given a strength that can withstand practical use. On the other hand, by setting the strength of the backing material for the ladle after firing to 1.5 MPa or less, the structure made of bricks can be easily dismantled, and the consumption of the bricks due to disassembly can be suppressed.

According to the present invention, in addition to exhibiting a heat shrinkage rate suitable for fixing bricks installed on the inner wall of a ladle and strength suitable for dismantling the bricks after use, the present invention contributes to a recycling-oriented society. It is possible to provide a ladle backing material using the raw material.

Hereinafter, typical embodiments of the ladle back material of the present invention will be described in detail, but the present invention is not limited to these.

The ladle backing material of the present invention is a basic filler consisting of 80 to 90% by mass of magnesia particles and 10 to 20% by mass of calcium carbonate particles. By mixing magnesia and calcium carbonate, which are basic substances, the basicity of the ladle backing material increases, and the life of the area constructed using the ladle backing material can be extended. Hereinafter, each component and physical properties of the ladle backing material of the present invention will be explained in detail.

(1) Component (1-1) Main component The main component is magnesia particles, which account for 80 to 90% by mass of the ladle backing material. The shape, size, particle size distribution, etc. of the magnesia particles are not particularly limited as long as they do not impair the effects of the present invention, and various conventionally known magnesia particles used for basic sprayed refractories etc. can be used.

By using magnesia particles as the main component, it is possible to impart excellent corrosion resistance and the like to the ladle backing material. The type of magnesia raw material is not particularly limited as long as it does not impair the effects of the present invention, but for example, fused magnesia, seawater magnesia, natural magnesia, etc. can be used. Furthermore, regarding the purity of the magnesia raw material, it is preferable to use one with a high purity of 90% by weight or more in order to avoid a decrease in corrosion resistance due to impurities and the influence of oversintering.

(1-2) Essential added components In the ladle backing material of the present invention, 10 to 20% by mass of calcium carbonate particles are added. Since calcium carbonate undergoes a decomposition reaction when heated, the heat absorbed during decomposition has the effect of lowering the temperature of the refractory, and wear and tear on the lining of the ladle can be suppressed. Note that, in the present invention, calcium carbonate particles refer to particles containing calcium carbonate as a main component.

Furthermore, since calcium carbonate releases carbon dioxide at high temperatures, micropores are formed in the ladle backing material (coating layer) after firing. The micropores can impart appropriate strength (compressive strength of 0.5 to 1.5 MPa after heating in the atmosphere at 1400° C. for 24 hours) to the ladle backing material after firing.

The proportion of particles with a particle diameter of less than 2 mm contained in the calcium carbonate particles is 50% or less. By setting the proportion of particles with a particle diameter of less than 2 mm in the calcium carbonate particles to 50% or less, the heat shrinkage rate of the ladle backing material increases without reducing the amount of calcium carbonate particles added to the backing material. In addition to being able to suppress overheating, appropriate strength can be imparted to the ladle backing material after heating. The proportion of particles having a particle diameter of less than 2 mm contained in the calcium carbonate particles is more preferably 30% or less.

Moreover, it is preferable to use seashells such as oyster shells as the calcium carbonate particles. Oyster shells are used as fertilizer, etc., but the amount used is limited and most are discarded. By utilizing shells such as oyster shells, which are mainly composed of calcium carbonate particles, as calcium carbonate particles, it is possible to contribute to a recycling-oriented society.

The shells used, such as oyster shells, need to be sufficiently dried so that the moisture content is 1% or less. Further, it is preferable to prevent impurities such as seaweed and garbage from entering as much as possible. Shells such as oyster shells are crushed into flakes.

Moreover, it is preferable to use limestone for the calcium carbonate particles. Limestone is a rock mainly composed of calcium carbonate, and is distributed throughout Japan, with many limestone mines in operation. Limestone is a natural resource that is 100% self-sufficient in Japan, which is said to be a resource-poor country, and can contribute to a recycling-oriented society from the perspective of local production and local consumption.

The pretreatment of the limestone used is not particularly limited as long as it does not impair the effects of the present invention, and conventionally known pretreatments can be applied, but it is necessary to dry it sufficiently so that the adhering moisture is 1% or less. be.

The ladle backing material of the present invention consists of 80 to 90% by mass of magnesia particles and 10 to 20% by mass of calcium carbonate particles, but it is permissible that a small amount of unavoidable impurities such as sea sand and barnacles be included. be done.

The method for manufacturing the ladle backing material of the present invention is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known methods for manufacturing monolithic refractories and the like can be used.

(2) Physical properties (2-1) Heat shrinkage The ladle backing material of the present invention has a heat shrinkage rate that is sufficient to hold bricks after firing.

More specifically, it is preferable that the shrinkage rate of the ladle back material after heating in the atmosphere at 1400° C. for 48 hours is 20% or less. By setting the shrinkage rate after heating in the atmosphere at 1400° C. for 48 hours to 20% or less, the lining bricks can be firmly held. The shrinkage rate after heating in the atmosphere at 1400° C. for 48 hours is more preferably 18% or less, most preferably 16% or less.

Here, the shrinkage rate of the backing material for a ladle can be determined by, for example, filling a crucible with the backing material and measuring the thickness of the backing material. By heating and measuring the thickness of the backing material after heating, the linear change rate can be calculated and evaluated.

(2-2) Strength The ladle backing material of the present invention not only can firmly fix the bricks installed on the inner wall of the ladle, but also has the strength to allow the backing material itself to be easily dismantled after use. can.

More specifically, it is preferable that the compressive strength of the ladle back material after heating in the atmosphere at 1400° C. for 24 hours is 0.5 to 1.5 MPa. By setting the strength of the ladle backing material after firing to 0.5 MPa or more, a structure made of bricks can be given a strength that can withstand practical use. On the other hand, by setting the strength of the ladle backing material after firing to 1.5 MPa or less, the structure made of lining bricks and backing material can be easily dismantled, and the wear of the lining bricks due to disassembly can be reduced. Can be suppressed. It is more preferable that the compressive strength of the ladle back material after heating in the atmosphere at 1400° C. for 24 hours is 0.7 to 1.3 MPa.

Although typical embodiments of the present invention have been described above, the present invention is not limited to these, and various design changes are possible, and all such design changes are included within the technical scope of the present invention. It will be done.

≪Example≫
Raw materials were prepared in the proportions shown in Examples 1 to 4 in Table 1 and kneaded using a Henschel mixer to obtain backing materials for ladle which are examples of the present invention.

Table 1 shows "oyster shell content" and "proportion of particles with a particle diameter of less than 2 mm contained in oyster shells" as raw material characteristics. In the examples, it is 10 to 20% by mass, and the "proportion of particles with a particle diameter of less than 2 mm contained in oyster shells" is 50% by mass or less in all the examples.

[evaluation]
The heat shrinkability and compressive strength after firing were evaluated for each of the obtained ladle backing materials.

(1) Heat shrinkability Fill a crucible with backing material for a ladle, measure the thickness of the backing material, heat it in the atmosphere at 1400°C for 48 hours with a brick placed on the backing material, and then The linear change rate was calculated by measuring the thickness of the backing material, and the shrinkage rate of the ladle backing material after heating in the atmosphere at 1400° C. for 48 hours was measured. The obtained values are shown in Table 1.

(2) Compressive strength Fill a ladle bag material into an alumina tube with an inner diameter of 40 mm and a height of 20 mm, heat it in the air at 1400°C for 24 hours, take out the bag material, and measure the compressive strength. The compressive strength of the ladle backing material was measured after heating in the atmosphere at 1400°C for 24 hours. The obtained values are shown in Table 1.

≪Comparative example≫
Comparative ladle back materials were obtained in the same manner as in the examples except that the raw materials were adjusted in the proportions shown in Comparative Examples 1 to 3 in Table 1. In addition, the heat shrinkability and compressive strength of each comparative ladle backing material were evaluated in the same manner as in the examples. The results obtained are shown in Table 1.

From Table 1, the shrinkage rate after heating in the air at 1400°C for 48 hours is 20% or less for all the ladle backing materials implemented, and the compressive strength after heating in the air at 1400°C for 24 hours is It can be seen that the pressure is within the range of 0.5 to 1.5 MPa.

In contrast, the comparative ladle backing material having the composition of Comparative Example 1, which does not contain oyster shells (calcium carbonate), has too high a compressive strength and does not damage the lining bricks after use. It becomes extremely difficult to dismantle the lining bricks and backing material. In addition, in the comparative ladle back materials having the compositions of Comparative Example 2, which contains a large amount of oyster shells with a particle diameter of less than 2 mm, and Comparative Example 3, which has an oyster shell content of more than 20% by mass, the shrinkage rate was 20%. It cannot be used as a backing material for ladle because the value exceeds , and the brick cannot be fixed sufficiently.

From the above results, we found that adding 10 to 20% by mass of calcium carbonate particles with a controlled particle size to the main raw material, magnesia particles, is suitable for fixing bricks installed on the inner wall of the ladle. It can be seen that the heat shrinkage rate and the strength suitable for dismantling the lining bricks and backing material without damaging the lining bricks after use are revealed. It is also found that oyster shells can be suitably used as calcium carbonate particles.

Claims (6)

80 to 90% by mass of magnesia particles,
Consisting of 10 to 20% by mass of calcium carbonate particles,
The proportion of particles with a particle diameter of less than 2 mm contained in the calcium carbonate particles is 50% or less;
A ladle backing material featuring: the calcium carbonate particles are shells;
The ladle backing material according to claim 1, characterized in that: the calcium carbonate particles are limestone;
The ladle backing material according to claim 1, characterized in that: The proportion of particles having a particle diameter of less than 2 mm contained in the calcium carbonate particles is 30% or less;
The ladle backing material according to claim 1 or 2, characterized in that: The shrinkage rate after heating in the atmosphere at 1400°C for 48 hours is 20% or less,
The ladle backing material according to claim 1 or 2, characterized in that: The compressive strength after heating in the atmosphere at 1400°C for 24 hours is 0.5 to 1.5 MPa,
The ladle backing material according to claim 1 or 2, characterized in that: