JPH0926268A - Method of reducing initial wear of slag line of molten steel ladle lining - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an effective means of reducing the wear rate, especially at the slag line, of the molten steel ladle lining that has been constructed by pouring material, especially to reduce the wear rate at the beginning of use. . [Structure] The slag line part of the ladle lining for unfired steel made by casting castable amorphous refractory material such as alumina-magnesia-spinel material is coated with a basic spraying material, and the slag line for the ladle ladle lining. Reduces initial wear of parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing the wear of cast refractory having an irregular shape, and more particularly to a method for reducing the initial wear of a casting material applied to a slag line portion of a molten steel ladle lining. An advantageous method for extending the life of a line portion is provided.

[0002]

2. Description of the Related Art In recent steelmaking sites, refractory materials are becoming indefinite. For example, in a molten steel ladle, the steel bath part and floor are already indefinite, and if the remaining slag line part is indefinite, nearly 100% of the ladle lining can be constructed with indefinite refractory. Is complete. However, since the lining of the slag line portion is required to have strict corrosion resistance against slag, there is no satisfactory lining until now, and the fact is that the lining has been a brick stacking specification up to the present.

By the way, as a refractory material having excellent corrosion resistance against steelmaking slag, a magnesia-based refractory material has hitherto been tried. However, even with this magnesia-based refractory, the problem of structural spalling caused by slag infiltration and change of the mineral phase of the refractory remains unsolved, and its practical application is delayed. This is because this magnesia-based refractory material has a large slag penetration depth and marked structural spalling. As a preventive measure, a method of further refining the refractory or improving the wettability with the slag by adding carbon has been attempted, but the fact is that the effect is not sufficiently achieved.

On the other hand, recently, alumina-based refractories have attracted attention. Since this alumina refractory has a shallow slag penetration depth, it is one of the preferable materials in that it is better than magnesia in terms of structural spalling and that a uniform wear rate can be expected. However, this alumina-based refractory has a problem in corrosion resistance, and in recent years, significant material improvements have been made. For example, there are an alumina-cement bond type alumina-spinel casting material, an alumina-magnesia casting material, and an alumina-magnesia-spinel casting material. So-called casting materials are those in which magnesia grains and spinel grains are added to the refractory to improve the corrosion resistance, but as mentioned above, the spinel formation reaction occurs at high temperatures and the structural phase due to mineral phase change occurs. There was a risk of polling.

[0005]

In fact, the following problems have been confirmed in the practical tests conducted by the inventors on the above casting material. For example, in the practical test of the above-mentioned alumina-magnesia casting material, since the spinel formation reaction by the alumina fine powder and the magnesia fine powder is added, the physical property change from the operating surface to the thickness direction is large, and structural spalling cannot be completely overcome. It was Although the corrosion resistance was improved, the swelling due to the penetration of the slag component was remarkable, and the seri cracking and the damage due to the structural sprinkling were large.

As described above, the conventional alumina-magnesia and alumina-magnesia-spinel casting materials have not been sufficiently satisfactory in practice.

Therefore, the object of the present invention is to propose a method effective in overcoming the above-mentioned problems of uncalcined alumina-magnesia and uncalcined casting material which undergo a change of mineral phase by reaction during use. Where it is. The specific object of the present invention is, particularly for the location of the slag line in the molten steel ladle lining where the casting material is applied,
It is an object of the present invention to provide an effective means for reducing the wear rate, and particularly for reducing the wear rate in the initial stage of use.

[0008]

The present invention, which was developed as a method for achieving the above-mentioned object, is a method having the following means as its essential constitution. (1) Alumina-magnesia, Alumina-magnesia-
A slag of molten steel ladle lining, characterized in that at least the slag line part of the ladle lining for unfired steel made by pouring spinel-shaped castable refractory is coated with a basic spraying material. Method of reducing initial wear of line parts. (2) The above-mentioned amorphous refractory has MgO: 5 to 30 wt% and Al ₂ O ₃ :
70-95 wt% as the main material and CaO as an additional material:
It is preferable to use one containing at least one selected from 0.5 to 3.0 wt% and SiO ₂ : 0.1 to 1.5 wt%. (3) The above-mentioned amorphous refractory has MgO: 5 to 15 wt% and Al ₂ O ₃ :
45 to 75 wt%, or MgAl ₂ O ₄ : 10 to ₄₀ wt% as a main material, and at least one selected from CaO: 0.5 to 3.0 wt% and SiO ₂ : 0.1 to 1.5 wt% as an additive material. It is preferable to use those containing seeds. (4) The above-mentioned spraying material uses a basic refractory powder composed of MgO: 60 to 90 wt% and Al ₂ O _{3 in an amount of 1 to} 5 wt% with water as a solvent.
SiO ₂ : It is preferable to use one constituted by adding one or two selected from 3 to 10 wt%. (5) The thickness of the coating layer of the above spray material is 3 to 3
Preferably, it is 0 mm.

[0009]

The inventors of the present invention first of all made various types of alumina in an actual machine.
The wear rate of magnesia cast material was investigated.
The result is shown in FIG. Test conditions Test material: MgO-C brick Alumina-magnesia Cast material: A, B, CA A: MgO = 8 wt%, balance mainly Al ₂ O ₃ : 90 wt% B: MgO = 8 wt%, balance mainly Al ₂ O ₃ : 76wt%, MgAl _{2
O 3: 14wt% C: MgO} = 8wt%, the balance main _{Al 2 O 3: 64wt%,} MgAl 2
O _3: 26 wt% Construction member (110 ° C. × 24 hours of drying only) sintered body (sintering 1500 ° C. × 15 hours) Test method: construction the casting material, as a lining of the bottom blown converter by frequency lining method

[0010]

[Table 1] As shown in FIG. 1, the wear rate from the start of use to the 36th charge was the same for all materials and was 40 to 40%.
It turns out that it is about twice as much as 70 charges.

Next, the corrosion resistance test (1700 ° C. × 4) of the lining material applied by the high frequency lining method against the converter slag was performed.
hr) was performed under the same conditions as above. FIG. 2 shows the test results of this corrosion resistance test. This FIG. 2 shows the difference between the time of firing at 1500 ° C. and the time of pouring according to the amount of magnesia added. As shown in this figure, when it is fired at 1500 ° C, the strength is improved, the porosity is decreased, and the spinel formation reaction progresses.
(Index display) is improved. From the above results, it is understood that the casting materials of alumina-magnesia and alumina-magnesia-spinel can be improved in durability by first reducing initial wear and firing.

[0012] Therefore, based on the above test results, the inventors of the present invention, on the slag line portion of the molten steel lining, after the construction of this casting material, the spray material on the surface of the construction body (slag line portion of the lining) Spray and coat,
I came up with the idea of covering the slag line. in this way,
By coating the spray material, it is possible to protect the unfired pouring material in the lower layer in the early stage of use, and the effect of the coating compensates for the lack of strength during firing, resulting in high porosity and unsuccessful spinel formation reaction. It is possible to prevent the deterioration and the like, and further, it is possible to prevent the deterioration of the durability due to the insufficient firing.

That is, the basic idea of the method of the present invention is that by applying a coating layer using a spraying material on the surface (working surface) on which the casting material is applied, significant damage observed during firing in the initial stage of use is prevented. At the same time, the applied casting material is sequentially and sufficiently sintered to the back surface (thickness direction) during firing. And by this action,
It is characterized in that a stable wear rate is obtained from the so-called initial stage of use, which is the same state as the last stage of use when the change in physical properties from the operating surface to the back surface becomes gentle. Therefore, the coating can significantly extend the lining life of the slag line.

The inventors consider that the effect of applying such a spray material is due to the mechanism described below. When using a molten steel ladle lined with unfired amorphous refractory, the casting material applied to the back side of the ladle is gradually heated in the thickness direction during the initial use, while the spray material is eroded. Sintering of the cast material gradually progresses. From this, the rapid heating and drying and sintering as in the past are eliminated, and the physical property changes seen from the operating surface to the thickness direction, which have been seen in the past, become small, which effectively acts to prevent structural spalling and corrosion resistance. I think that. And
In order to fully exhibit the above effects, in the present invention, a spraying material that is basic and has excellent corrosion resistance is used. Incidentally, in general, the lining is repaired by spraying material, but this is strictly for the purpose of extending the life of the furnace at the end of use, while the present invention is intended for the casting material at the beginning of use. The main difference is in the purpose of protection.

The cast amorphous refractory used in the present invention has the following composition. _{That, MgO: 5~15wt%, Al 2} O 3: 45~75wt%, or even MgAl ₂ O _4: comprises 10 to 40 wt% as a main material, and CaO as other added materials: 0.5 ~3.0wt% and SiO ₂ : 0.1-
It is preferable to use the one containing at least one selected from 1.5 wt%. The reason why the above-mentioned components are limited as described above is that in the case of MgO: 5 to 15 wt%, the corrosion resistance is remarkably deteriorated when the content is less than 5 wt%, while the structure deterioration due to the increase in porosity occurs when the content is 15 wt% or more. is there. The reason for limiting Al ₂ O ₃ to the range of 45 to 75 wt% is 45 wt%.
%, The sinterability will be significantly reduced.
This is because if it is more than wt%, the corrosion resistance decreases.

Next, the spray material used in the present invention is
Basic _{MgO: 60~90wt%, Al 2 O} 3: 1~5wt%, Si
O ₂ : 3 to 10 wt% is used. The reason for limiting to this composition is to obtain sufficient seizure with the casting material while maintaining corrosion resistance and thermal conductivity.

In the present invention, the thickness of the basic spraying material to be applied is also important in order to sufficiently exert the above-mentioned effects. For example, if it is 3 mm or less, which is almost the same as the coarse grain size in the sprayed material, there is no effect, and if it is thicker than 30 mm, the wear rate is reduced, but since the corrosion resistance of the sprayed material is low, the economic effect is small.

[0018]

EXAMPLES Examples and comparative examples of the present invention will be described below.
Will be described. Chiba Steel Works ladle lining for steelmaking, and
Alumina-magnesia-cease on the slag line
Pinel casting material (Al_TwoO_Three: 64wt%, MgO: 8wt%,
MgAl _TwoO_Four: 26 wt%, CaO: 1.5 wt%, SiO_Two: 0.5 wt%)
It is poured and constructed, and the construction body surface is explained below.
Basic spraying material (MgO: 86wt%, SiO_Two: 10wt%,
CaO: 1 wt%, Al_TwoO_Three: 3 wt%). (1) Spraying material construction thickness: 20 mm (Example of the present invention) (2) 〃: 2 mm (Comparative example 1) (3) 〃: 5 mm (Example) (4) 〃: 40 mm (Comparative example 2) ( 5) No spraying material (Comparative example 3) (6) Ordinary spraying repair (Comparative example 4) (Repairing for extending the end life) Under the above conditions, construct the slag line part of the ladle lining
And put it into actual operation. During operation, the slag line part is poured
1 from about 100ch until adding and repairing sawdust
The residual thickness was appropriately measured for 50 ch.

FIG. 3 shows the relationship between the treatment conditions on the surface of each construction body and the wear rate. As shown in this figure, it can be seen that when the coating layer of spraying material is applied by 20 mm, the initial wear rate is significantly reduced as compared with the case where the coating layer is not provided, and the life is improved. However, when the construction thickness is 2 mm, such an effect is poor, while when 40 mm, the effect is the same as when 20 mm, and peeling damage was observed at the end stage. In addition, since spray repair for extending the normal end life depends on the durability of the spray material,
It is not economically effective, and the superiority of the initial repair for protecting the refractory lining according to the present invention is clear.

[0020]

As described above, according to the present invention, the basic spraying material is coated on the molten steel ladle slag line portion on which the unfired alumina-magnesia-spinel casting material is applied, so that the slag is used. The initial rate of wear of the line section can be significantly reduced and therefore the life of the slag line section of such a lining can be significantly increased.

[Brief description of drawings]

FIG. 1 is a graph showing changes in wear rate in a slag line portion of an alumina-magnesia casting material.

FIG. 2 is a graph showing the influence of heat treatment conditions of a test piece on a melt loss index during a high frequency lining test.

FIG. 3 is a graph showing the effect of reducing the wear rate of the slag line portion by spray coating.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masato Kumagai, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Technical Research Institute, Kawasaki Steel Co., Ltd. (72) Hajime Suzuki, 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steelmaking Co., Ltd. Chiba Steel Works (72) Inventor Shigeho Tateno 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Works Chiba Works

Claims (5)

[Claims] 1. A basic spraying material for at least the slag line portion of a ladle lining for unfired steel, which is obtained by pouring a castable amorphous refractory of alumina-magnesia or alumina-magnesia-spinel. A method for reducing initial wear of a slag line portion of a molten steel ladle lining, characterized by being coated with. 2. The amorphous refractory is MgO: 5 to 30 wt.
%, Al ₂ O ₃ : 70 to 95 wt% as a main material, and CaO: 0.5 to 3.0 wt% and SiO ₂ : 0.1 to 1.5 wt% as additive materials.
The method for reducing initial wear of a slag line part according to claim 1, which contains at least one selected from the group consisting of: 3. The amorphous refractory is MgO: 5 to 15 wt.
%, Al ₂ O ₃ : 45-75 wt%, or even MgAl ₂ O ₄ : 10-
Contains 40 wt% as main material and CaO: 0.5 as other additive material
The method for reducing initial wear of a slag line part according to claim 1, which contains at least one selected from the group consisting of ˜3.0 wt% and SiO ₂ : 0.1-1.5 wt%. 4. The spraying material is a basic refractory powder composed of MgO: 60 to 90 wt% and Al ₂ O ₃ : 1 to 5 with water as a solvent.
The method for reducing initial wear of a slag line portion according to claim 1, wherein the method is configured by adding one or two selected from wt% and SiO ₂ : 3 to 10 wt%. 5. The method for reducing initial wear of a slag line portion according to claim 1, wherein the thickness of the coating layer made of the spray material is 3 to 30 mm.