JPH02280958A - Lining structure for bottom part in ladle - Google Patents

Abstract

PURPOSE:To prolong the service life of a ladle by making a convex lens form of bedding wear layer and a concave lens form of permanent layer positioned at lower layer and forming brick laying structure of refractory brick, etc., for forming the bedding wear layer to reverse arch structure. CONSTITUTION:In case of using high alumina brick or basic brick having errosion resistance to the bed in the ladle, the boundary face between the permanent layer and wear layer is made to the structure having curving face, spherical face or inclined face corresponding to these. The wear layer 3 is made to the convex lens form and the permanent layer 4 is made to the concave lens form. By this construction, errosive balance of the lining brick is made uniform, i.e., the service life as the whole of the ladle lining can be lengthened. Further, it is effective to apply large-sized block to the permanent layer below the boundary face in order to surely secure wedging effect. As the center of the bedding wear layer, at the center part of the bedding, the brick having triangle shape in the vertical cross section is set. By this method, the errosive balance of the bedding wear layer is secured and trouble of detaching and floating-up of the refractory can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a lining structure for the bottom of a ladle that receives molten metal, particularly molten steel.

(Prior Art) A ladle is a kiln that receives molten steel after refining in a converter, transports it by crane to a casting machine, and taps the steel. The lining structure has an extremely large effect on the life of the ladle, and by taking into consideration various conditions such as the cost of the lining refractory material, heating at the initial stage of use, and cooling during use, conventionally, chamots The entire interior of the ladle is lined with the same material, such as waxite or zirconite bricks. Specifically, the cross section thereof has a pot-like shape as shown in FIG.
and a side wall wear layer 1, and a permanent bed layer 4 and a bed wear layer 3 are formed at the bottom. The bottom part has a horizontal, generally disk-shaped structure. In this way, the ladle shown in Fig. 5 is lined with a wear layer and a permanent layer, which are made of different materials, like other kilns.
Compared to other kilns, such as converters, the lining is thinner and the amount of heat dissipated is greater.

As can be seen from its structure, ladle has traditionally been positioned as a means to connect the refining process and casting process in the steel process, and has been used for ease of handling, such as ease of transportation and maintenance. It has been designed and used with emphasis on ease of use.

However, with the remarkable spread of continuous casting methods in recent years, the demand for higher quality steel has increased, and methods such as vacuum degassing using a ladle, bubbling in a ladle, and injection treatment methods are now widely used. It's starting to look like this. Along with this, there has been a new requirement for the purpose of using the ladle to support a part of the refining process, that is, high-temperature steel tapping, extension of the residence time of molten steel, etc. Therefore, as the usage conditions have changed and become more severe, damage to the refractory lining of high-silicic acid ladles has become significant.

As a measure to deal with this situation, for example,
As disclosed in Japanese Patent Application No. 1-269968, a highly corrosion-resistant high alumina brick or a basic brick such as Mg0-C brick is inserted into the side wall wear layer centered on the slag line portion, which has poor corrosion resistance. Attempts have been made to improve the corrosion resistance by coating.

In addition, from the viewpoint of ensuring the balance of erosion loss between the side wall and the bottom of the ladle, by adding a small amount of St C, Cry's, Zr0z, etc. to the conventionally used high silicic acid refractory, the side wall can be improved. Attempts have also been made to reduce damage, ensure the above-mentioned melting loss balance, and improve the corrosion resistance of the ladle as a whole.

Furthermore, from the viewpoint of labor saving, progress has been made in making refractories amorphous and mechanizing them, and high alumina and basic refractory materials have also been made into amorphous shapes.

On the other hand, the lifespan of the bottom of the ladle (hereinafter referred to as "bed") has been improved and extended in the same way as the side wall. The wear layer on the bottom is the part that receives both the impact during receiving steel and the contact with slag at the end of casting, so its lifespan is generally shorter than that of the sidewall wear layer.For this reason, the material of the wear layer is changed. The effect of improving corrosion resistance is not as pronounced as in the side wall portion, and the current situation is that the frequency of repair is still higher than that of the side wall portion. Relatively speaking, the unbalance in durability with the side wall portion is considered to have expanded more than in the past.

Furthermore, as disclosed in JP-A No. 61-235064, when basic refractories are used as lining furnace materials, damage to the refractories can be reduced by limiting heating conditions, etc. However, with this method, temperature fluctuations (temperature drop, reheating, etc.) inevitably occur when repairing the flooring, which causes damage to the unrepaired side wall portion.

(Problem to be Solved by the Invention) Various countermeasures have been taken to address the actual situation of ladle beds by means other than improving the material, but the situation has not always been satisfactory.

For example, a method has been proposed in which the part that receives the impact of the receiving steel is thickly wound, but this method is only effective in ensuring the balance of melting loss, and therefore, it is difficult to prevent joint erosion in the surrounding area. , the lining bricks tend to peel off and float up.

In addition, in order to reduce the amount of joint insertion, that is, the amount of molten steel inserted into the joint, large blocks of AQgO are used instead of bricks.
Although there is a method using an s-based refractory material, this AQzOs-based refractory material is prone to cracking due to thermal shock.

As described above, although improvements have been made to conventional ladles by changing the material in response to changes in operating conditions, it has not been possible to obtain sufficient durability for the bedding. Furthermore, since the above-mentioned highly corrosion-resistant refractories are all highly thermally conductive materials, simply replacing the material with the conventional lining structure will result in significant heat dissipation, resulting in problems such as a drop in the temperature of the molten steel and metal build-up at the bottom. This is becoming more likely to occur, and is one of the causes of trouble during operation. For this reason, with the exception of some special ladles, most ladle beds are currently made of conventional high silicic acid materials.

An object of the present invention is to provide a lining structure for the bottom of a ladle that can extend the life of a ladle that receives molten metal, especially molten steel, that is, can reduce the frequency of repair of refractories. be.

(Means for Solving the Problems) The present inventor has proposed changing the bottom structure of the current flat-bottom pot from a high-silicate refractory to a high-corrosion-resistant high-alumina or basic refractory. We believe that by changing the material of the refractory, the corrosion resistance of the ladle, that is, the life of the ladle, can be extended. As a result of a detailed study of the points, it was found that there were the following problems: ■, ■, and ■.

■ Conventional waxite-based materials have little volume change in the high temperature range of 800°C or higher, and are highly silicic, so there is little advance erosion at joints (in contrast, there is little infiltration of FeO, etc.)
The above-mentioned highly corrosion-resistant materials have large thermal expansion changes, lack volume stability, and tend to infiltrate frequently. Therefore, design and structural improvements are required depending on the characteristics of these materials.

■Since the thickness of the conventional paving layer is about 200 to 300 mm, the binding force between the bricks weakens as erosion progresses. In other words, with a flat bottom, there is no pressing effect between the bricks, and when a material with a large change in thermal expansion is used, the joints may loosen,
Joints, peeling and floating of bricks are likely to occur, and this is further exacerbated by the expansion reaction forces from the side walls and the perm layer.

■It is a well-known fact that by making the entire bottom of the ladle have a spherical structure like other kilns (for example, pig iron mixers, converters), the above-mentioned pressing effect can be imparted to the bed (in practice). Publication number 63-8737).

However, renewing a new ladle shell to create a spherical structure not only requires a large investment, but also requires the installation of a slide gate horizontally in an existing steel factory, for example in the ladle body. The steel receiving capacity changes due to spheroidization, there are dimensional restrictions with the mating equipment during receiving and casting, and there are also changes in the volume and weight of the ladle. As a result, there are many new problems that arise, such as problems with the capacity of transport cranes and securing routes, making it difficult to provide practical solutions.

Therefore, as a result of various studies in order to solve the problems shown in (1), (2) or (3) above, the present inventors found that in the conventional ladle structure shown in Fig. If the damage progresses and the erosion balance is lost, that is, if erosion progresses and an erosion line as shown in Figure 6 is formed, the bricks will peel off at the uneven parts of the erosion line and the paving will likely lift up. As a result, the binding force between the refractories in the horizontal direction in the bedding is weakened, and due to the reaction force due to thermal expansion of the side walls or the permanent layer of the bedding, the binding force of the wear layer of the bedding becomes uneven, and the refractories in the bedding are It was discovered that this facilitated the separation and surfacing of the material.

Therefore, the interface between the wear layer and the permanent layer of the bed is made to have a structure with an inclined surface to create a pressing effect, and by making it an inverted arch type structure, it is possible to impart a stable and uniform restraining force to the part structure. The present inventors found that it is possible to avoid lifting of individual paving bricks, and furthermore, they found that with such a configuration, the life of the ladle can be extended without changing the material of the refractory material of the paving. Furthermore, as mentioned above, the boundary surface between the wear layer of the bed and the permanent layer has a structure having an inclined surface and an inverted arch type structure, and the wear layer of the bed has a convex lens shape, and the permanent layer The present invention was completed based on the finding that the life of the ladle can be further extended by forming the ladle into a concave lens shape.

Here, the gist of the present invention is a lining structure for the bottom of a ladle having a flat-bottomed iron skin structure, in which (1) the boundary surface between the wear layer and the permanent layer, which are lining materials, is a curved or spherical surface; or an inclined surface corresponding to these, (ii. In at least one diametrical cross section of the bottom of the ladle, the bedding layer has a convex lens shape, and the permanent layer is located in contact with the lower layer of the bedding wear layer. and (iii) the furnace construction structure of the refractory bricks or refractory blocks forming the bedding layer is an inverted arch structure.

In the broadest sense, the present invention relates to a lining structure at the bottom of a ladle having a flat-bottom iron skin structure, in which the boundary surface between the wear layer, which is the lining material, and the permanent layer is a curved surface, a spherical surface, or any of these. The lining structure of the bottom of the ladle is characterized by an inclined surface corresponding to .

Another aspect of the invention is a lining structure for the bottom of a ladle having a flat-bottom iron shell structure, in which the bedding layer has a convex lens-like shape in at least l cross section in the diametrical direction of the bottom of the ladle, and the bedding layer has a convex lens-like shape. This is a ladle bottom lining structure characterized in that the permanent layer located in contact with the lower layer of the wear layer has a concave lens shape.

Furthermore, from another point of view, the lining structure at the bottom of the ladle has a flat-bottom iron shell structure, and the furnace construction structure of refractory bricks or refractory blocks forming the bedding layer is characterized by an inverted arch structure. This is the lining structure at the bottom of the ladle.

The present invention aims to ensure the balance of melting and erosion of the lining material by giving a mutually pressing effect between the furnace materials from the initial stage to the final stage of use, especially in the wear layer of the lining in the existing ladle having a flat-bottomed steel shell structure. , we propose the following lining structure. This structural diagram is shown in Figure 1, namely: (i) a structure in which the boundary surface between the wear layer and the permanent layer, which is the lining material, is a curved surface, a spherical surface, or an inclined surface equivalent to these; (ii) the inner wear layer is a convex lens (iii) The furnace construction structure of the bricks or refractory blocks forming the wear layer is an inverted arch brickwork structure. The above (i
), (ii) and/or (ii).

More preferably, (iv) at least the first permanent block layer (the first permanent block layer in contact with the wear layer) of the permanent layer has a block assembly structure divided into four or more parts, is thinner than other permanent layers, and is fireproof. (v) Bricks with at least one vertical section having a triangular shape are installed in the center of the floor, and the corners that contact the side walls are made of monolithic refractories. The structure further includes a solidified structure.

(Function) Hereinafter, the present invention will be explained in detail along with the function and effect. In this specification, "%" means "% by weight" unless otherwise specified.
” shall mean.

First, a highly corrosion-resistant high alumina brick (AQzO
containing 60% or more of s) or basic (MgOlMgO-Ca
OlMgO-CrzOs, MgO- to Q20. When using bricks (containing 10% or more of organic components), the reason why the boundary surface between the permanent layer and the wear layer is made to have a curved surface, a spherical surface, a structure having an inclined surface corresponding to these, and/or an inverted arch structure will be explained.

In other words, by making the section structure have a structure with an inclined surface, a pressing effect is generated, and by making it an inverted arch type, a stable and uniform restraining force can be applied between each brick, and the It is possible to avoid floating.

Therefore, the result of making the contact part of the receiving steel thicker and bricklaying it in an inverted arch shape is the structure shown in FIG. 2, with the wear layer shaped like a convex lens and the permanent layer shaped like a concave lens.

By adopting such a shape, it is possible to uniformly balance the melting loss of the lining bricks, that is, to extend the life of the entire ladle. Further, in order to fully exhibit the pressing effect, it is effective to form the permanent layer under the boundary surface into large blocks from the viewpoint of securing the surface area, and it is also easy to construct.

Next, in order to prevent excessive heat dissipation, it is desirable to apply a fire-resistant and heat-insulating refractory to the permanent layer where the bottom center area has become thinner.
Since it has a high thermal conductivity of 6 to 1.0 kcal/m ・hr°C, monolithic refractories or block-shaped refractories are made by adding 10 to 40% of hollow refractory particles to reduce the thermal conductivity. It is desirable to use fired refractories, and specific examples include foamed silica or alumina balls.

If the content is less than 10%, the heat insulating effect will be insufficient and it will not be possible to prevent thermal deformation of the iron skin due to heat dissipation.

Moreover, if it exceeds 40%, the strength of the refractory is low and cannot withstand the static pressure of molten steel during receiving.

Furthermore, as the core of the paving layer, bricks with at least one vertical cross-section having a triangular shape are installed in the central part of the paving. This is installed in order to exert the effect of compressing the disc-shaped ladle base in the diametrical direction, that is, the effect of evenly distributing the restraining force of each refractory in the baseware layer. In addition, ramming material or pouring material is used in the structural portion of the outer peripheral portion that contacts the side wall to fill the gap. The purpose of this is to prevent the intrusion of metal, and to evenly distribute the binding force between the shank and the side wall to maintain the pressing effect at the base.

From the above, it is clear that the present invention has solved the defects in the lining structure of the existing ladle bottom, and it is possible to solve the problem of the existing high-grade ladle bottom lining structure without using high-alumina or basic refractories, which have excellent corrosion resistance. It is clear that similar effects can be obtained even when a siliceous refractory is used.

Example 1 A ladle using conventional waxite-zircon fired bricks (
160 ton capacity), high alumina unfired block (A
QgOs 76%, Sing 20%) was constructed and incorporated into normal operation, and its durability was followed up.

That is, as shown in FIG. 3+a+, which is a cross-sectional view, the partial structure in this embodiment is such that the boundary surface between the wear layer and the permanent layer forms an almost perfect spherical surface, and the wear layer has a convex lens shape. The difference in thickness between the center part and the outer peripheral part was 85 m. As shown in Figure 3, which is a plan view of an example of the present invention,
The blocks of each layer were divided into 2 to 3 parts in the circumferential direction and 4 to 8 parts in the diametrical direction.

The above material was cast and cured for 24 hours, dried at 300° C. for 10 hours, and then placed in a ladle.

In addition, a block with a quadrilateral cross-section charging opening was used so that conventional ``first bricks'' could be directly inserted into the casting opening.

The procedure for constructing the furnace was to lay a ceramic sheet within 10 m thick to ensure the levelness of the bottom steel shell, install permanent blocks, and first charge bricks. Furthermore, the wear blocks were installed from the casting opening to the center and then sequentially to the side walls of the outer periphery. The joint spacing between the blocks was adjusted in the range of 2 to 51, and AQt (h) was filled with 87% alumina mortar.The lining of the side walls was constructed using the conventional procedure after the construction of the lining.Finally, the side walls and The gap between the floor and the floor was filled with 76% AQgOs ramming material.

As a result, during the process of use, abnormal damage at the hot-water contact area was reduced, and the issue of bare metal was eliminated. The melting profile is relatively uniform, reducing the number of repairs to the pad from 3 to 1 over the same period of use.
It was possible to extend the reactor life from the conventional 92 channels to 130 channels.

Example 2 An unfired alumina block (1,2 m
xl, 2m x 230m5, AQtOs 89%)
using medium alumina bricks (8QxOs 60%,
Ladle (1,50 to
n capacity), unfired alumina brick (AQiOx 89
%) was used as the bedding layer.

As shown in Fig. 4 (section 4), the interface between the wear layer and the permanent layer was such that the wear layer was thicker on the slag discharge side (side B in Fig. 4).

The construction procedure was almost the same as in Example 1, but the difference in level between the irregularities of the wear bricks on the top surface of the paving was set to within 25 mm, and the difference in the thickness of the wear bricks was set to within 80 mm. In addition, in the early stages of operation, a slag cart is used to remove the slag layer on the top surface of the molten steel.
It was adjusted to 0m-.

The erosion profile of the ladle during use was as shown in Figure 2. As a result, there was no need for major repairs to the sill,
We were able to extend the reactor life from the conventional 65 channels to 97 channels.

In addition, Fig. 3 + a +, Fig. 4 (4 degrees in al) As a refractory heat-insulating refractory, alumina-based castable with a 60% content is added with 25% alumina hollow holes with a diameter of 2 m + 4 full. It was made into a powder, mixed with 7.9% water, kneaded for 15 minutes, poured into a mold, and molded for 20 hours.
After the above curing, it was dried at 300° C. for 10 hours and then put into an actual furnace.

(Effects of the invention) By applying the lining structure of the present invention to an existing molten steel ladle, the balance of erosion of the cladding layer is ensured, and the problem of peeling and flotation of the refractory is solved, which is better than the conventional example. Compare,
The life of the ladle was significantly improved. Furthermore, since the existing ladle shell is reused, there is no need for large-scale modification of the production process that uses the ladle, making this invention highly practical.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram showing the lining structure of the bottom of the ladle according to the present invention; Fig. 2 is a schematic explanatory diagram showing the erosion state of the lining structure of the ladle bottom according to the present invention; Fig. 3 (Jl ) and 3rd opening) are a schematic sectional view and a schematic plan view of an embodiment of the present invention; FIG. 4 (al and 4th opening) are a schematic sectional view and a schematic plan view of another embodiment of the present invention; 5 and 6 are schematic cross-sectional views showing the conventional lining structure of the bottom of the ladle and its erosion state. 1: Side wall wear layer 2: Side wall perm layer 3: Layout wear layer 4: Layout perm layer 4°: Layout perm (fireproof insulation layer)

Claims (1)

[Scope of Claims] A lining structure for the bottom of a ladle having a flat-bottom iron skin structure, wherein (i) the boundary surface between the wear layer and the permanent layer, which are lining materials, is a curved surface, a spherical surface, or an inclined surface corresponding to these. (ii) In at least one diametrical cross-section of the bottom of the ladle, the bedding layer has a convex lens shape, and the permanent layer located in contact with the lower layer of the bedding wear layer has a concave lens shape. and (iii) a lining structure for the bottom of a ladle, characterized in that the furnace construction structure of the refractory bricks or refractory blocks forming the bedding layer is an inverted arch structure.