JPS6126859Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to refractories for lining various high-temperature furnaces, and more particularly to a block-shaped two-layer refractory constructed to protect the surface to be heated and prevent oxidation of the surface area. In the steel manufacturing field, there is a strong demand for high-grade steels, such as low P steel and low S steel, and the operating conditions for hot metal processing and molten steel processing are becoming increasingly severe. cars, ladles, etc.)
The inner fireproof walls formed on the inner surface of the furnace body of molten steel processing furnaces (for example, converters, electric furnace ladles, etc.) are often exposed to extremely severe operating conditions compared to conventional ones.
For this reason, it has become difficult to maintain and extend the operational life of the conventionally frequently used refractories such as syamoto, high alumina, zircon, and pyrolithite, and recently Al ₂ O ₃ -SiC-C and other refractories have For the inner lining, refractory materials containing SiC, C, or SiC and C, such as MgO-C, are increasingly being used. However, despite this trend toward higher-grade refractory materials, it is still difficult to line the inner surface of the furnace body with such refractory materials, dry them, and perform temperature-raising operations such as burner heating in preparation for receiving high-temperature molten metal. It has been found that as the amount of refractory material is added, the SiC and C contained in the innermost surface of the refractory material are oxidized and consumed, forming a brittle layer. The thickness of such a brittle layer depends on the conditions of drying and heating operations (method, temperature, time required, etc.), so it is not always constant, but in any case, the physical and chemical properties It deteriorates significantly and does not function as a fireproof layer at all. In other words, in the part that changes to such a brittle layer, a completely meaningless reinforcing layer has been formed from the beginning, and considering that this covers the entire inner surface of the furnace, the loss in terms of material is extremely large. Then,
Furthermore, the lifespan of the furnace body may be incorrectly judged, which seriously hinders production planning and quality control. This situation is a cause for concern, and examples such as 〓〓〓〓〓
The following countermeasures can be considered. (1) A method of blending and dispersing an antioxidant into the above-mentioned SiC-based high-grade refractory material. (2) Apply antioxidant to the surface of the refractory material (side surface to be heated)
How to apply it. However, method (1) requires an amount of antioxidant that can be uniformly dispersed throughout the refractory material, resulting in an increase in cost. Particularly considering the actual situation during operation, the surface of the refractory material is coated with slag due to the first injection of molten metal after lining, and as a result of this coating, the effect of preventing oxidation of the refractory material is obtained. Method (1) of dispersing the antioxidant to the deep side of the material means that excessive measures are taken to the deep side, and the above-mentioned high cost becomes completely meaningless. On the other hand, method (2) eliminates waste as mentioned above and is efficient in that sense, but whether it is a spraying method or a brush coating method, it imposes a considerable labor burden, especially for mixed iron cars. If the entrance is narrow and the interior is wide, the working environment is poor and there are many problems from an occupational health perspective. In addition, since the SiC and C-based refractory materials mentioned above are easily oxidized, they are generally non-sintered types, and organic binders are often used. This cannot be said to be a satisfactory countermeasure because combustion gas is generated during the process, and the oxidation prevention layer that has been painstakingly applied may peel off. In view of these circumstances, the inventors of the present invention believe that it is necessary to establish a technology for preventing oxidation of fireproof lining materials that does not involve the above-mentioned problems in terms of both durability and construction workability, and have conducted various studies. I did this. As a result, as a means to prevent oxidation from being applied only to the heated side of the refractory material without causing any problems during the construction process, it is possible to form a block-shaped two-layer refractory consisting of a main body part and a protective part. After finding that a suitable method for forming it on the inner surface of the furnace body was suitable, and after further consideration from the material and shape aspects, the present invention was completed. In other words, the block-shaped two-layer refractory according to the present invention is:
A main body made of a refractory material containing one or both of C and SiC; a main body made of a refractory material containing one or both of C and SiC;
and SiC and one or both of boron carbide and an easily oxidizable metal. The gist lies in the fact that they are formed by laminating them. The configuration and effects of the present invention will be explained below based on the drawings of the embodiments. FIG. 1 is a perspective view showing a typical embodiment, in which a main body part 1 and a protection part 2 are directly joined together to form a block-shaped two-layer refractory. As is clear from the above description, the structure of the main body part 1 is a refractory material containing one or both of C and SiC, and there is no particular control on the oxide that constitutes the main component of the refractory material.
Although it can be arbitrarily adopted depending on the application, some typical examples include SiO ₂ , Al ₂ O ₃ ,
MgO, ZrO ₂ , etc. are listed as subcomponents.
It can contain Fe ₂ O ₃ , TiO ₂ , MnO, CaO, Cr ₂ O ₃ , FeO, etc., and more specific examples include silicic refractories, alumina refractories, silica-alumina refractories, and magnesia refractories. Refractories, dolomitic refractories, gnesia-chromia refractories, zirconia refractories, zircon refractories, or various refractories not classified into any of these are used.
A particularly important point is that it contains one or both of C and SiC, and the inclusion of these causes the problem of oxidative deterioration on the heated surface side as described above. By the way, there are no particular restrictions on the content of C or SiC, but the normal content range is considered to be C: 3-28% by weight, SiC: 3-25% by weight, so in the case of the present invention, this is also the case. The content is set according to this, but in the present invention, the above-mentioned structure prevents the main body from weakening as described later, so the lower limit value is set in contrast to the conventional content setting standard, which was set a little higher. It may be further lowered, or conversely, the upper limit value may be further increased for those placed in a relatively small amount. On the other hand, regarding the composition of the protective part 2, there are two cases in which the protective part 2 has essentially the same composition as the main body part 1 (particularly in that it contains one or both of C and SiC), and a case in which the protective part 2 has a composition essentially the same as that of the main body part 1 (particularly in that it contains one or both of C and SiC).
(However, one or both of C and SiC must be included); however, in any case, the presence of C or SiC causes oxidative deterioration. Boron carbide and easily oxidizable gold are considered to be the cause of oxidative deterioration of C and SiC.
It is important to include one or both of the genera. Regarding boron carbide, one considered to be B ₄ C is used, but any of B ₁ to _{B 6} C may be used.
On the other hand, examples of easily oxidizable metals include Al, Mg, Si, and Ti, but the former three are superior in terms of versatility when considering economic efficiency. When using easily oxidizable metals, these metals may be used alone or in combination. When used in combination, the combination is completely free, but they can also be added as an alloy, such as Al-Mg. Also, ferroalloys such as Fe-Si
It can also be blended in the form of Furthermore, the combined use of boron carbide and easily oxidizable metals is considered to be an effective embodiment. Due to the combination of boron carbide and easily oxidizable metals, C and
Although the oxidative deterioration of SiC is prevented, as shown in the examples below, the principle of its action is not necessarily clearly understood. Therefore, these are considered to be selective components in terms of the actual effects that can be obtained, but on the other hand, there are special differences between boron carbide and easily oxidizable metals from the perspective of their blending amounts. In order to achieve the desired effect without any difference, it is necessary to keep the total amount within the range of 0.5 to 5% by weight, regardless of whether they are used alone or in combination. i.e. 0.5% by weight
If it is less than that, oxidation of C and SiC in the protection part 2 cannot be prevented, and the protection part 2 itself becomes brittle. On the other hand, if it exceeds 5% by weight, the corrosion resistance of the protective portion 2 will deteriorate rapidly even though the anti-oxidation effect can be obtained. Next, the thickness t (Fig. 1) of the protective part 2 is at least 5 mm, considering the past application results for pig iron mixed vehicles.
If the thickness t was given, there would be no problem with oxidation deterioration of the main body part 1 during the drying and temperature rising process after construction. Even more preferable lower limit thickness t
It is safer to set it to 10 mm, considering that the conditions of the drying and temperature raising operations may become even more severe. On the other hand, the upper limit should be taken into consideration from the cost perspective, and the total thickness of the block-shaped refractory T ₁
It is recommended to suppress the amount to 20% or less. By the way, as for the main components of the fire-resistant materials constituting the main body part 1 and the protection part 2, it was stated that they may be the same or different, but if they are the same, there is no big difference in the coefficient of thermal expansion between the two. There is no strain stress during manufacturing, drying and temperature rise after construction, or even during actual operation, so there is no risk of peeling, so the flat surfaces are simply brought into close contact as shown in Figure 1. However, if you select a material that causes a difference in the coefficient of thermal expansion between the two, use the fitting method shown in Figures 2 and 3, or an alternative strong bonding method. It is recommended that the design be designed to prevent separation of both parts. However, even in this case, be aware that the unit amount of heat received by the protection part 2 is much larger than the unit amount of heat received by the main body part 1, and the fire-resistant material used for the protection part 2 should have a lower thermal expansion than the fire-resistant material used for the main body part 1. It is necessary to reduce the difference in the amount of thermal deformation between the two by using a coefficient. As for the block-shaped refractories, a rather flat rectangular body has been illustrated (Figs. 1 to 3), but the shape of the applicable furnace depends on the size, the required thickness of the refractory wall, and the construction location (straight sections, corner sections). It goes without saying that various shapes such as rectangular parallelepiped, cubic, fan-shaped, cylindrical, L-shaped, convex, concave, etc. can be made in consideration of differences in curved parts, etc., and in these cases, a protective part is formed on the side to be heated. Of course. The refractory of the present invention can be applied to almost any type of high-temperature furnace, not just the pig iron mixer or ladle as exemplified above. Next, an example of use of the refractory of the present invention will be explained. Main body parts 1-a, 1-b and protection part 2 shown in Table 1
Block-shaped refractories A and B were manufactured by combining 2-a and 2-b in a corresponding manner. Refractory A (main body part 1-a: 280 mm, protective part 2-a: 25 mm), refractory B (main body part 1-b: 400 mm, protective part 2-b: 25
mm) was used to line a mixed pig iron car for receiving and transporting pig iron.
The life-extending effect of charge (15,000 tons in weight) was recognized. In addition, in the conventional example in which only the main body part 1-a is lined, drying and temperature rise (approximately 3
When inspecting the inner surface of the lining, it was found that the temperature was 20 to 40 mm (7 to 7 mm for the total thickness).
A weak oxidation layer was formed over the area (equivalent to 15%). 〓〓〓〓〓

[Table] Next, main body parts 1-c and 1-d with the compositions shown in Table 2.
and protection parts 2-c, 2-c', 2-d, and 2-d' were prepared, and refractories C, C', D, and D' were made. Refractory C,
C' is main body part 1-c: 150mm, protection part 2-c, 2-
c': 10mm, refractories D and D' are main part 1-d: 200
mm, and protective portions 2-d and 2-d': 10 mm, and each was used to line the slag line of the ladle.
As a result, the life extension effect of the refractories C, D, and D' using refractories C, D, and D' was found to be 8 charges on average compared to the conventional example (in which the main body portions 1-c and 1-d were lined alone). In addition, in the conventional example in which only the main body part 1-c was lined, after the lining was applied, it was dried and heated (approximately 1 day, maximum 1200℃), and the inner surface of the lining was investigated. An oxidation brittle layer was formed over an area (equivalent to 7 to 15% of the thickness). On the other hand, in the case of refractory C' which is a combination of main body part 1-c and protective part 2-c', the corrosion resistance is poor due to the high content of boron carbide and easily oxidizable metals in protective part 2-c'. It was not suitable for

[Table] 〓〓〓〓〓
Since the present invention is constructed as described above, it is an inexpensive block in which an oxidation-resistant protective layer is formed on the heated surface side of a refractory layer that is upgraded by containing one or both of C and SiC. With the provision of refractories, it has become possible to reliably prevent oxidative deterioration on the heated surface side. As a result, it became possible to almost completely enjoy the effect of upgrading the refractory material by C and SiC from the surface layer to the deep layer, and the life-extending effect of the lining material was reliably demonstrated.

[Brief explanation of the drawing]

1 to 3 show examples of the present invention, in which FIG. 1 is a perspective view and FIGS. 2 and 3 are plan views. 1... Main body part, 2... Protection part. 〓〓〓〓〓

Claims (1)

[Scope of utility model registration request] A main body made of a refractory material containing one or both of C and SiC, and a refractory material containing one or both of C and SiC, as well as one or both of boron carbide and an easily oxidizable metal. A block-shaped two-layer refractory, characterized in that the protection part is integrally laminated on the heated surface side of the main body part.