JP2013072137A - Lining structure of vessel for steel making - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent refractory lining structure of a vessel for steel making, which addresses damage increase due to lowering of bath level by increasing thickness of lining immediately beneath a slag line part without diminishing workability of castable, controls heat loss, and sustains in the production of clean steel.SOLUTION: In the lining structure of a vessel for steel making, a steel bath part 2 is composed of an amorphous casting material, and a slag line part 1 is composed of a magnesia-carbonaceous brick. As a connecting brick 3 which connects the upper part of the steel bath part and the lower part of the slag line part, an unfired alumina-magnesia brick which underwent heat treatment at a temperature of 1,200°C or less is used.

Description

  The present invention relates to a lining structure for a steelmaking vessel such as a molten metal refining or transporting vessel in which a steel bath portion is an irregularly shaped casting material and a slag line portion is lined with a refractory brick. The present invention relates to a lining structure of a steelmaking container using an alumina-magnesia castable part.

  For steelmaking containers of domestic blast furnace manufacturers, for example, ladle, an irregular casting material (castable) is generally used for the steel bath part, and magnesia-carbon brick is generally used for the slag line part. Here, the slag line part of the steelmaking container means a part in contact with the molten slag when the molten steel is stored in the steelmaking container, and the slag line part is a magnesia-carbon brick having excellent corrosion resistance against the molten slag. It is lined with. Although a slag line part is based also on the container capacity for steelmaking, it is in the range of about 500 mm of upper and lower sides centering on a slag line. Moreover, as a castable used for a steel bath part, the thing of an alumina-magnesia quality has become mainstream. Alumina-magnesia castable is excellent in corrosion resistance and erosion resistance, expandability using the expansion when spinel is formed by the reaction of alumina and magnesia, and contains a small amount of silica, and creep due to liquid phase generation at high temperature It is an excellent material that can suppress cracks due to shrinkage and breakage due to excessive expansion because of its combined characteristics.

  However, the portion immediately below the magnesia-carbon brick that lines the lining of the slag line portion, particularly about 1000 mm below the lower end of the slag line portion, is susceptible to erosion due to molten slag due to the influence of the lowering of the molten metal surface and the fluctuation of the molten metal surface. Therefore, the lining lining made of alumina-magnesia castable constituting the part is severely damaged and may become a durability neck.

  As a countermeasure, it is considered to expand the lining range of the magnesia-carbon brick used in the slag line part in the lower direction. However, in this case, since a carbon-containing brick having a high thermal conductivity is applied in a wide range, there is a problem that a heat loss from the furnace wall increases and a molten steel temperature is lowered. Furthermore, when the molten steel and the carbon-containing brick are brought into contact with each other, carbon is taken into the molten steel from the brick (carbon pickup), which has been a problem in terms of manufacturing clean steel.

  Another measure is to increase the castable lining thickness. However, in castable, it is necessary to pull out the core for construction after castable hardening. For this reason, there has been a problem that it is necessary to provide a drawing taper for pulling out the core, and it is impossible to obtain a construction body having a thickness of a certain level or more.

  On the other hand, increasing the lining thickness is facilitated by brick construction that does not use a core. Moreover, constructing a third refractory between two different refractories has been practiced. In this case, the third refractory is sometimes called a connecting brick. Other carbon-containing bricks having excellent corrosion resistance (for example, alumina-magnesia-carbonaceous brick or alumina-silica-carbonaceous brick) can be applied to the connecting brick. However, as with magnesia-carbon brick, heat loss and carbon pickup problems occur.

  On the other hand, it is possible to construct bricks that have been generally used for steelmaking, specifically zircon bricks, high alumina bricks, machrome bricks, magnesia bricks and spinel bricks. Each have problems in terms of durability. Zircon bricks and high alumina bricks have low corrosion resistance, and are severely damaged in the portion directly under the slag line, which is a problem, and are not practical. Magchromic bricks, magnesia bricks, and spinel bricks are superior in corrosion resistance but have poor spalling resistance and slag infiltration resistance. There was a problem that it was awakened and sufficient durability could not be obtained. Thus, a general steel-making brick lacks one or more of corrosion resistance, slag infiltration resistance, and spalling resistance, which are necessary characteristics as bricks applied to the part. Therefore, there was a problem that a sufficient life could not be obtained.

Moreover, as an alumina-magnesia refractory brick for a steel ladle, for example, Patent Document 1 uses an magnesia raw material containing 90% by mass or more of an alumina raw material and a fine powder of 0.5 mm or less, and Al ₂ O ₃ and The total amount of magnesia is 90% by mass or more, MgO is 4 to 16% by mass, SiO ₂ is 0.5 to 5% by mass, and the total amount of Na ₂ O and K ₂ O is 0.3 to ₂ % by mass. Contained, the balance being inevitable impurities and Al ₂ O ₃ , heat-treated at 100 ° C. or higher and 1150 ° C. or lower after press molding, and having a thermal expansion coefficient at 1500 ° C. of 2 to 5% under a load of 1 MPa A refractory brick having an expansion rate of -6 to 1% is disclosed.

In addition, in the Japanese Patent Application No. 2010-173458, the present applicant uses an alumina raw material and a magnesia raw material containing 90% by mass or more of fine powder having a particle size of 0.5 mm or less, and Al ₂ O ₃ and MgO as chemical components. And the total amount of MgO is 4 to 20% by mass, SiO ₂ is 0.5 to 5% by mass, Na ₂ O and K ₂ O are the total amount of 0.3 to ₂ % by mass, and C is Alumina-magnesia refractory brick characterized by being 0.5% by mass or more and less than 7% by mass (Claim 1); expansion coefficient at 1500 ° C. under a load of 1 MPa is −6 to 2%, The alumina-magnesia refractory brick according to claim 1 (claim 2); an alumina material and a magnesia material containing 90% by mass or more of fine powder having a particle size of 0.5 mm or less, and Al ₂ O ₃ as a chemical component. Amount of MgO and MgO 85 mass% or more, MgO 4 to 20 wt%, SiO ₂ 0.5 to 5 mass%, 0.3 to 2 wt% Na ₂ O and _{K 2} O is in total, C 0.5 wt% As mentioned above, various raw materials are mixed and kneaded so as to be less than 7% by mass, the obtained kneaded product is press-molded, and then heat-treated at a temperature range of 100 to 1150 ° C. A brick manufacturing method (claim 3) is proposed.

Japanese Patent No. 4470207

  The purpose of the present invention is to increase the lining thickness directly under the slag line without impairing the castability, to cope with the increase in damage due to the lowering of the molten metal level, and to withstand clean steel production by suppressing heat loss. Another object is to provide a lining refractory lining structure for a steelmaking container.

  In order to solve the above-mentioned problems, the inventors of the present invention have a steel bath part with an irregular casting material, and a slag line part made of refractory bricks at the upper part of the steel bath part and the lower part of the slag line part. By applying unfired alumina-magnesia bricks that have the same materials and properties as the irregular casting material, it is possible to ensure sufficient lining thickness to cope with corrosion resistance, and to prevent peeling and cracking. It has been found that they are not a factor for determining the lifetime, and as a result, sufficient durability can be obtained, and the present invention has been achieved.

  That is, according to the present invention, in the lining structure of a steelmaking container in which the steel bath part is an irregular casting material and the slag line part is made of magnesia-carbon brick, the upper part of the steel bath part and the lower part of the slag line part are provided. In the lining structure of a steelmaking container, unfired alumina-magnesia brick heat-treated at a temperature of 1200 ° C. or less is used as a connecting brick.

Moreover, the lining structure of the steelmaking container of the present invention uses a magnesia raw material in which the unfired alumina-magnesia brick contains an alumina raw material and 90% by mass or more of fine powder of 0.5 mm or less, and has a chemical composition. The total amount of Al ₂ O ₃ and MgO is 90% by mass or more, MgO 4 to 16% by mass, SiO ₂ 0.5 to 5% by mass, Na ₂ O and K ₂ O in total amount Contains 0.3 to 2% by mass, contains C (carbon) less than 5% by mass (including zero), the balance is made of inevitable impurities, and is heat-treated at 100 ° C. or higher and 1200 ° C. or lower after being press-molded. The thermal expansion coefficient at 1500 ° C. is 2 to 5%, and the expansion coefficient under load at 1 MPa is −6 to 1%.

  According to the lining refractory lining structure of a steelmaking container of the present invention, it is possible to cope with an increase in damage directly under the slag line part due to a decrease in the molten metal surface and to suppress heat loss without impairing castability workability. An excellent lining that can withstand manufacturing can be obtained, and as a result, the life of the steelmaking container can be dramatically improved.

It is the schematic which shows one embodiment of the lining refractory lining structure of the steelmaking container of this invention. It is the schematic which shows the other embodiment of the lining refractory lining structure of the container for steel manufacture of this invention.

  The inner lining structure of a steelmaking container according to the present invention includes an upper part of a steel bath part composed of an irregular casting material and a lower part of a slag line part composed of magnesia-carbon bricks, that is, a steel bath part and a slag line. A non-fired alumina-magnesia brick (hereinafter referred to as “non-fired alumina-magnesia brick”) that has been heat-treated at a temperature of 1200 ° C. or less is provided as a connecting brick that connects the parts. By disposing the unfired alumina-magnesia brick as a connecting brick, it is possible to secure a lining thickness for obtaining sufficient durability according to the corrosion resistance of the unfired alumina-magnesia brick. Furthermore, by using unfired alumina-magnesia brick, high corrosion resistance and crack resistance / peelability can be imparted. In addition, the thermal conductivity of the unfired alumina-magnesia brick is considerably lower than that of the magnesia-carbon brick, thereby suppressing the heat loss and improving the durability without increasing the heat loss. Furthermore, as will be described later, the unfired alumina-magnesia brick does not contain carbon at all, or even if it contains it, it is a very small amount of less than 5% by mass, so that carbon pickup can be prevented.

Hereinafter, the lining structure of the steelmaking container of the present invention will be described in detail.
1 and 2 show an embodiment of the lining structure of a steelmaking container according to the present invention. 1 and 2, the slag line part (1) of the steelmaking vessel is lined with a conventional magnesia-carbon brick. Further, the steel bath part (2) is lined with a conventional irregular casting material. The connecting brick (3) between the lower end of the slag line portion (1) and the upper end of the steel bath portion (2) is lined with a non-fired alumina-magnesia brick that is heat-treated at 1200 ° C. or less. It has become.

  Here, the connecting brick (3) is not particularly limited in the lining lining zone. For example, it is about 1000 mm, preferably about 700 mm, more preferably 400 mm downward from the lower end of the slag line portion (1). Can be lined with lining. Moreover, the lining thickness of the connecting brick (3) can be adjusted with an arbitrary thickness so as to have the same number of times as the lining refractory of the steelmaking container.

  The maximum thickness of the lining lining of the connecting brick (3) is preferably 110 to 300 when the lining thickness of the steel bath part (2) is 100. If the maximum thickness of the lining of the unfired alumina-magnesia brick (3) is smaller than 110, the effect of increasing the thickness of the lining brick (3) lining is not preferable. Moreover, if it exceeds 300, it can be improved by looking at the durability of only the lower part of the slag line portion (1), or damage of other parts becomes a factor determining the life of the steelmaking container, which is not economical. More preferably, it exists in the range of 120-250.

  The thickness of the lining lining of the connecting brick (3) with respect to the slag line portion (1) is preferably 60 to 180, more preferably 70, when the lining thickness of the slag line portion (1) is 100. ~ 175.

  The shape of the connecting brick (3) is not particularly limited, and various shapes such as a rectangular shape such as a normal brick, a bee shape, a fan shape, and a semi-universal shape can be used. It is also possible to combine. In addition, when viewed in a longitudinal section, in addition to a rectangular one, use a trapezoidal one or an irregular one to provide a lining along the iron skin for a tapered pan You can also. For example, by changing the lining thickness of the connecting brick (3) for each step and adjusting the lining thickness so that the step from the steel bath part (2) to the slag line part (1) becomes smaller, the connecting brick ( 3) and initial peeling of the magnesia-carbon bricks constituting the slag line part (1) can be suppressed. In addition, as in the embodiment shown in FIGS. 1 and 2, when the initial thickness is different from that of the upper and lower connecting bricks (3), the lower corner or the uppermost connecting brick (3) has a corner on the lower side of the furnace inner surface. By taking it, the initial spalling of the connecting brick (3) can also be suppressed.

  In addition, a conventional magnesia-carbonaceous brick can be used for a slag line part (1). The composition of the magnesia-carbon brick is not particularly limited. For example, the amount of carbon is 5 to 20% by mass, 5% by mass or less of metal aluminum and / or metal silicon, and the balance is magnesia material. Those made of inevitable impurities can be used. Moreover, as an amorphous cast material which comprises a steel bath part (2), a conventional alumina-magnesia castable, an alumina-magnesia-spinel castable, etc. can be used. The composition of the alumina-magnesia castable is not particularly limited. For example, magnesia is 4 to 12% by mass, silica is 0.3 to 1.2% by mass, and the balance is made of an alumina material and inevitable impurities. Can be used. The composition of the alumina-magnesia-spinel castable is also not particularly limited. For example, magnesia is 2 to 5% by mass, spinel is 5 to 15% by mass, silica is 0.3 to 1.2% by mass, and the balance. Can be made of an alumina material and inevitable impurities.

Next, non-fired alumina-magnesia brick is used for the lower part of the slag line part (1) and the upper part of the steel bath part (2), that is, the connecting brick (3) used at the boundary between them. The non-fired alumina-magnesia brick is not particularly limited. For example, an alumina raw material and a magnesia raw material containing 90% by mass or more of fine powder of 0.5 mm or less are used, and Al ₂ O ₃ is used as the chemical composition. The total amount of MgO is 90% by mass or more, MgO is 4 to 16% by mass, SiO ₂ is 0.5 to 5% by mass, and the total amount of Na ₂ O and K ₂ O is 0.3 to ₂ % by mass. %, The carbonaceous raw material is in the range of less than 5% by mass (including zero), and it is preferable to use a material having a balance of inevitable impurities.

  Here, since the alumina raw material and the magnesia raw material are aggregates having excellent corrosion resistance by themselves, they are adopted as main aggregates of unfired alumina-magnesia bricks. As the alumina material, natural alumina such as calcined bauxite and calcined clay shale is used in addition to commercially available fused alumina such as white fused alumina and brown fused alumina, sintered alumina, and calcined alumina. It is possible and 1 type, or 2 or more types of these can also be mix | blended. Further, as the magnesia material, any material mainly composed of magnesia such as natural magnesia, sintered magnesia, and electrofused magnesia can be used, and one or more of these may be blended. it can.

The spinel crystal formation reaction by the reaction of corundum, which is an alumina crystal in an alumina raw material, and periclaze, which is a magnesia crystal in a magnesia raw material, is a mixture of non-fired alumina when the mixture is heated from room temperature. -It becomes active from about 1200 ° C, which is slightly lower than the temperature of the working surface when magnesia bricks are used, occurs in the range up to 1400 ° C, and the thermal expansion coefficient and residual expansion coefficient increase with reaction. It is known to go. In the unfired alumina-magnesia brick, the above spinel crystal formation reaction is important in order to obtain an appropriate residual expansion property. Therefore, in the unfired alumina-magnesia brick, the total amount of Al ₂ O ₃ and MgO as a chemical composition is 90% by mass or more. If the total amount of Al ₂ O ₃ and MgO is less than 90% by mass, the spinel formation reaction between alumina (corundum crystal) and magnesia (periclase crystal) and the expansion behavior associated therewith will become unclear, and This is not preferable because the slag wet resistance of the calcined alumina-magnesia brick cannot be greatly improved.

  For unfired alumina-magnesia bricks, the magnesia material is used to form a dense spinel-containing layer near the hot working surface by a spinel-forming reaction with the alumina material. As the magnesia material, a material containing 90% by mass or more of fine powder having a particle size of 0.5 mm or less is used. From the viewpoint of the expandability associated with the generation of spinel and the ease of control thereof, the magnesia material is preferably finer. In practice, if a fine powder having a particle size of 0.5 mm or less is used, the expansion behavior at the time of spinel generation appears to the extent that it is almost the same as when a finer one is used, and its control is also possible. Furthermore, even if particles with a particle size exceeding 0.5 mm are mixed in less than 10% by mass, expansion associated with the generation of spinel appears without any adverse effects, and the adjustment thereof is possible without great difficulty and is practically sufficient. However, if 10% by mass or more of particles having a particle size exceeding 0.5 mm are mixed, the spinel formation reaction does not occur promptly, and the reaction takes time and the final absolute expansion amount is not preferable. In addition, since the spinel generation reaction occurs around the magnesia particles, the spinel is not generated in a state of being uniformly dispersed in the brick structure, so that it is difficult to form a dense spinel-containing layer near the working surface.

  In the unfired alumina-magnesia brick, the content of MgO as the chemical composition is in the range of 4 to 16% by mass, preferably 5 to 10% by mass. If the content of MgO is less than 4% by mass, even if it reacts with the alumina raw material to produce spinel, the absolute amount of production is insufficient, and the amount of expansion associated with this spinel production reaction is also insufficient. For this reason, it is not preferable because it becomes difficult to densify the structure in the vicinity of the working surface sufficient to suppress slag infiltration. On the other hand, if the content of MgO exceeds 16% by mass, slag wetting is increased, which affects the slag wetting resistance.

  In the unfired alumina-magnesia brick, the spinel formation reaction always occurs in a temperature range of about 1200 ° C. or more if the alumina particles and the magnesia particles are in contact with each other in the unfired alumina-magnesia brick structure. When the expansion coefficient is measured in a state in which the unfired alumina-magnesia brick is not restrained at all and the dimensions can be freely changed, it always shows a large expansion as the spinel is generated. The expansion coefficient is usually measured as the linear expansion coefficient, and the value is usually more than 2%. The problem in putting unfired alumina-magnesia bricks into practical use as a kiln lining material relates to the expansion characteristics, but this free expansion under no restriction is not a problem. What is important is the expansion under load in a restrained state, that is, under a load. When the unfired alumina-magnesia brick reaches the temperature range where it is heated in a state where it is lined in the kiln and generates spinel, it tries to expand with the formation of spinel, but the unfired alumina-magnesia brick is bound to the iron skin. Therefore, it will receive a compressive stress for the amount of expansion. The compressive stress at this time can be regarded as the same as a state in which a load is applied to the unfired alumina-magnesia brick. If the expansion under restraint is an expansion amount close to free expansion, a very large stress is generated in the unfired alumina-magnesia brick in the state of being lined in the kiln, and the unfired alumina-magnesia brick is generated. Is destroyed. On the other hand, the fact that the free expansion is large and the expansion in a state where a load is applied is small, that is, the change in the entire volume is small means that it is absorbed by pores in the microstructure. This is because the non-fired alumina-magnesia brick absorbs the volume change due to expansion in the non-fired alumina-magnesia brick structure, and the structure is nothing less than densification. The characteristics of the non-fired alumina-magnesia brick used in the lining structure of the steelmaking container of the present invention are the operation of the non-fired alumina-magnesia brick by controlling such free expansion characteristics and expansion characteristics under load. A dense spinel-containing layer is formed in the vicinity of the surface to greatly improve the slag wet resistance.

In unfired alumina-magnesia bricks, SiO _{2 which} is the main component of the liquid phase is an essential chemical component, but since the liquid phase mainly composed of SiO ₂ has a high melting point, the spinel formation reaction becomes active at around 1200 ° C. In the temperature range, almost no liquid phase is generated. In this state, almost no deformability is imparted to the unfired alumina-magnesia brick, so that it is insufficient to relieve the stress generated with expansion. However, the melting point of SiO ₂ decreases to about 850 ° C. in the presence of an alkali metal oxide such as Na ₂ O or K ₂ O. Therefore, by allowing SiO ₂ to coexist with an alkali metal oxide component such as Na ₂ O or K ₂ O, a sufficient liquid phase can be obtained at a lower temperature.

Alkali metal oxide components such as SiO ₂ , Na ₂ O, and K ₂ O are components that are conventionally avoided from the viewpoint that a liquid phase is generated in the brick structure at high temperatures and the corrosion resistance of the brick is reduced. However, delamination damage equals or exceeds erosion by slag affects the durability of bricks (lined bricks), so the durability can be improved by adding appropriate amounts of these ingredients to the bricks to provide stress relaxation. Can do. In the non-fired alumina-magnesia brick, the spinel formation temperature range includes spinel by containing 0.5 to 5% by mass of the SiO ₂ component and 0.3 to ₂ % by mass of the Na ₂ O component + K ₂ O component as the chemical composition. An appropriate liquid phase can be present in the unfired alumina-magnesia brick to absorb the expansion associated with the formation reaction, and this liquid phase acts as a so-called lubricant and enables movement of particles. It is.

The liquid phase amount when the SiO ₂ component is contained alone does not reach the amount necessary for expansion absorption in the temperature range of 1200 to 1400 ° C. where spinel is generated. At higher temperatures, more glass phase is produced, but it can no longer serve to absorb the expansion associated with spinel formation. When the SiO ₂ component coexists with alkali metal oxide components such as Na ₂ O component and K ₂ O component, a glass phase is formed in a temperature range where spinel is generated by the reaction of alumina and magnesia. The function of absorbing the large expansion accompanying the chemical reaction is obtained. When the SiO ₂ component and alkali metal oxides such as Na ₂ O component and K ₂ O component coexist, a glass phase is formed from a low temperature of about 850 ° C., which is sufficiently lower than the spinel formation reaction temperature. Thereafter, the amount of the glass phase increases with increasing temperature. In the non-fired alumina-magnesia brick, by containing these components that form a glass phase with a low melting point in the above range, the non-fired alumina-magnesia brick has an effect of absorbing expansion and does not deteriorate the corrosion resistance. Therefore, the slag infiltration resistance can be greatly improved.

As the chemical composition, the content of the SiO ₂ component is in the range of 0.5 to 5% by mass, preferably 0.8 to 2% by mass. If the content of the SiO ₂ component is less than 0.5% by mass, the absolute amount of the glass phase is insufficient, and the movement of particles during spinel formation cannot be promoted, and the expansion cannot be absorbed. On the other hand, if the content of the SiO ₂ component exceeds 5% by mass, the liquid phase amount becomes excessive and the corrosion resistance is lowered, which is not preferable.

Alkali metal oxides such as Na ₂ O component and K ₂ O component coexist with the SiO ₂ component to lower the melting point and to lower the viscosity at the same temperature. As a chemical composition, if the total content of the Na ₂ O component and the K ₂ O component is in the range of 0.3 to ₂ % by mass, preferably 0.5 to 1.5% by mass, it is appropriate together with the SiO ₂ component. A glass phase having a high viscosity is formed, and in the temperature range where spinel is generated, the movement of particles is supported, and the expansion due to the generation of spinel is absorbed, so that a spinel-containing layer in the vicinity of a dense working surface can be formed. If the total content of the Na ₂ O component and the K ₂ O component is less than 0.3% by mass, the liquid phase amount cannot be sufficiently secured in the spinel generation temperature range, which is not preferable. Exceeding this is not preferable because the corrosion resistance is lowered.

  In the non-fired alumina-magnesia brick, the content of C (carbon) as the chemical composition is less than 5% by mass (including zero), so that the elution of C (carbon) into the molten steel is suppressed and the non-fired Slag infiltration into the alumina-magnesia brick can be suppressed, and the thermal conductivity necessary for suppressing peeling can be obtained. From the viewpoint of steel cleaning, it is desirable not to contain C (carbon). However, in consideration of compatibility between durability and steel cleanliness, the more preferable content of C (carbon) is less than 4% by mass (zero) More preferably less than 3% by mass (including zero). When the content is 5% by mass or more, the elution of C (carbon) from the unfired alumina-magnesia brick into the molten steel becomes remarkable, which is not preferable.

There are various grades of raw materials for alumina and magnesia, which contain the corresponding impurity components. In the non-fired alumina-magnesia brick, it is preferable that inevitable impurities other than Al ₂ O ₃ component, MgO component, SiO ₂ component, Na ₂ O component, K ₂ O component are not included, but practically cost Relevance must also be considered, and some inevitable impurities cannot be dealt with. The content of inevitable impurities is preferably 6% by mass or less if possible in order to exhibit the corrosion resistance of the original alumina + magnesia. Furthermore, in order to reliably control the expansion characteristics of the unfired alumina-magnesia brick, the content of inevitable impurities is more preferably 5% by mass or less. Moreover, when using a fused alumina raw material etc., in order to exhibit the high corrosion resistance, it is desirable that content of an unavoidable impurity is 4 mass% or less. In addition, since the unfired alumina-magnesia brick is heated at a low temperature, the brick may contain a so-called ignition loss such as crystallization water, and this ignition loss is regarded as an inevitable impurity.

  The unfired alumina-magnesia brick is formed by pressing the kneaded clay having the above composition into a predetermined shape. The pressing method is not particularly limited, and a hydraulic press, a friction press, or the like can be used. You may use vacuum deaeration together. In some cases, it is possible to form by hand. The obtained molded body is heat-treated at 1200 ° C. or lower in order to completely dry a small amount of water necessary for molding. Preferably, heat treatment is performed at a temperature range of 100 to 800 ° C. When the heating temperature exceeds 1200 ° C., the spinelization reaction proceeds, which is not preferable.

  The calcined alumina-magnesia brick thus obtained has a coefficient of thermal expansion at 1500 ° C. of 2 to 5%, preferably 2.5 to 4%. If the thermal expansion coefficient at 1500 ° C. is less than 2%, densification by restraint is not sufficient, and if it exceeds 5%, it may be difficult to control expansion under load, which is not preferable.

 Moreover, the expansion coefficient under a load at 1 MPa of unfired alumina-magnesia brick is in the range of −6 to 1%, preferably −5 to 0%. If the expansion coefficient under load at 1 MPa exceeds 1%, unfired alumina-magnesia bricks are cracked, and further, there is a possibility of cracking and collapse, which is not preferable. Moreover, some shrinkage does not pose a problem under a load of 1 MPa. However, non-fired alumina-magnesia bricks with increased shrinkage tend to have greater erosion loss and therefore preferably not exceed -6%.

  In addition, when constructing the lining structure of the steelmaking container of the present invention, each brick can be applied using mortar such as magnesia mortar and alumina mortar. In addition, brick joints can basically be constructed with empty joints. However, when the construction is difficult due to factors such as distortion of the iron skin, various mortars such as magnesia and alumina can be used in the same manner as the mortar applied to the back of the brick. In this case, the joint thickness is preferably about 2 mm.

Hereinafter, the lining structure of the steelmaking container of the present invention will be described more specifically with reference to Examples and Comparative Examples.
Using a ladle for producing 300 tons of plain steel, a lining lining was applied with the distribution pattern shown in FIG. Here, magnesia-carbon bricks having chemical compositions of MgO: 79% by mass and C: 14% by mass are used for the slag line part (1), and Al ₂ O ₃ : An alumina-magnesia castable having a chemical composition of 88% by mass and MgO: 7% by mass was used. The lining thickness of the slag line part (1) was 200 mm, and the lining thickness of the upper end of the steel bath part (2) was 115 mm.
A non-fired alumina-magnesia brick having the chemical composition shown in Table 1 is used, and a lining brick is applied to the boundary region between the slag line part (1) and the molten steel part (2) over a width of 690 mm (3) Formed. In addition, the comparative example 1 is an example using the alumina-magnesia castable used for the steel bath part (2) for the connecting brick (3). Moreover, the comparative example 2 is an example using the magnesia-carbonaceous brick used for the slag line part (1) for the connecting brick (3). Moreover, the comparative example 3 is an example using the zircon brick described in Table 1 for the connecting brick (3). Furthermore, the comparative example 4 is an example using the magnesia-chrome brick described in Table 1 for the connecting brick (3).

Table 2 shows a structural example and various characteristics of the lining structure of the steelmaking container of the present invention.
In Table 2,
In the amount of carbon pickup, ◎ indicates that the amount of carbon pickup to the molten steel is small, ○ indicates that the amount is slightly large, but is within the allowable range, and X indicates that the amount of carbon pickup is excessive and a steel having the desired composition cannot be obtained;
The evaluation of heat loss was measured by measuring the molten steel temperature from receiving steel to the end of steelmaking, and measuring the amount of decrease in the molten steel temperature of each lining running structure. ◎ is a small amount of decrease, ○ is the amount of decrease Is moderate, △ is a large drop, x is very low, and there are operational problems;
The service life is an index of each service life when the comparative example 1 is set to 100, and the higher the value, the greater the service life;
The form of the bridging brick is an analysis of observation during use and brick collected after use.

  Table 3 shows a structural example and various characteristics of the lining structure of the comparative steelmaking container.

From the results shown in Table 2, Examples 1 to 5 of the present invention using unfired alumina-magnesia bricks as connecting bricks have a thicker lining thickness under the slag line than that of Comparative Example 1 using alumina-magnesia castables. As a result, the durability was remarkably improved. Moreover, there was little heat loss and the amount of carbon pick-up to the molten steel was within an allowable range.
Comparative Example 2 is an example in which the magnesia-carbon brick used in the slag line part is expanded downward, which is excellent in terms of durability, but the amount of carbon pickup exceeds the allowable range, and clean steel production In view of the above, it was unsuitable, and further, heat loss increased.
In Comparative Example 3, zircon brick was used as the connecting brick, but the melting loss of the zircon brick was large and the damage was enormous, and the durability was lower than in Comparative Example 1.
In Comparative Example 4, magnesia-chrome brick was used as a bridging brick, and because it was excellent in corrosion resistance, it was in a good state in the initial stage of operation. The service life decreased.

1 Slag line section, 2 steel bath section, 3 connecting bricks.

Claims (2)

  In a lining structure of a steelmaking container in which a steel bath part is an irregular casting material and a slag line part is made of magnesia-carbon brick, as a connecting brick that connects the upper part of the steel bath part and the lower part of the slag line part, 1200 A lining structure for a steelmaking container, characterized by using non-fired alumina-magnesia bricks heat-treated at a temperature of ℃ or less. A non-fired alumina-magnesia brick heat-treated at a temperature of 1200 ° C. or less uses an alumina material and a magnesia material containing 90% by mass or more of fine powder of 0.5 mm or less, and has a chemical composition of Al ₂ O ₃ and the total amount of the MgO is not less 90% by mass or more, the MgO 4 to 16 wt%, a SiO ₂ 0.5 to 5 mass%, the _{K 2} O and Na ₂ O in total 0.3 to 2 weight %, C (carbon) less than 5% by mass (including zero), the balance is made of inevitable impurities, and after press molding, heat treatment is performed at 100 ° C. or more and 1200 ° C. or less, and heat at 1500 ° C. An lining structure for a steelmaking container, characterized by an expansion coefficient of 2 to 5%, an expansion coefficient of 1 MPa at a load of -6 to 1%.

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