JP2816585B2 - Method for producing refractory material containing magnesia - Google Patents

Description

The present invention relates to a container for a molten metal such as a ladle, a converter, an electric furnace, a vacuum degassing apparatus and the like, which has a particularly high basicity of slag. Alternatively, the present invention relates to a magnesia-containing refractory used as a refractory lining a flow passage.

(Prior art) Magnesia (MgO) has a high melting point and shows high corrosion resistance to highly basic slag. For this reason, refractories using magnesia as a main raw material are widely used in steelmaking processes.

Conventionally, seawater obtained by sintering magnesia collected from seawater from natural magnesia obtained by sintering natural magnesite to reduce impurities in magnesia and raise the melting point with the aim of increasing the corrosion resistance of magnesia-containing refractories Conversion to magnesia was made. Further, in order to reduce the specific surface area of the particles to reduce the reaction interface and suppress erosion by slag, electrofused magnesia in which magnesia was once melted and crystallized in an electric furnace was developed. At present, as a magnesia-containing refractory material particularly required to have high durability, high-purity fused magnesia obtained by electromelting this seawater magnesia is used. With this improvement, the durability of refractories based on magnesia has been significantly improved.
(Reference technique Japanese Patent Application Laid-Open No. 60-251168) (Problems to be Solved by the Invention) However, magnesia has the property of reacting and dissolving when it comes in contact with slag having a low basicity. In such a case, it is inevitable that the erosion of the refractory increases and the life of the furnace is shortened.

When magnesia reacts with the slag, the magnesia becomes magnesium ions and diffuses into the slag, causing erosion. Since the magnesium ion has a small radius, the diffusion rate is high, and thus the erosion rate is high.

In addition, slag infiltrates easily in refractories containing magnesia as a main component. It is considered that this is because there are many gaps at the magnesia grain boundary and the energy state of the magnesia particle surface is high. Due to this property, in the magnesia refractory, deterioration and exfoliation due to slag infiltration progress, which is a serious problem.

In the case of magnesia refractories, erosion and infiltration, alteration and delamination of slag due to this low basicity slag are major problems, but these problems cannot be solved by conventional high-purification or electrofusion. Was.

An object of the present invention is to provide a magnesia-containing refractory capable of effectively solving the problems of erosion, slag infiltration, alteration, and peeling of the magnesia-based refractory, particularly by low basicity slag, and a method for producing the same.

(Means for Solving the Problems) In the present invention, in a melting furnace such as an electric furnace, magnesia and zircon are melted together, forsterite is segregated and concentrated, and this is removed in a molten state or after solidification. Thus, a refractory comprising magnesia, zirconia and a small amount of forsterite is obtained, and this is refined.

In magnesia refractories, it is effective to increase the viscosity of the slag in contact with magnesia in order to suppress erosion due to low basicity slag and prevent slag infiltration. That is, in high viscosity slag, the diffusion rate of magnesium ions is slowed to suppress erosion, and high viscosity slag has low fluidity and is difficult to infiltrate.

Materials that promote slag high viscosity include Cr ₂ O ₃ , Zr
O _{2 and the} like. If these substances are present in the refractory, it is considered that when they come into contact with the slag, the effect of increasing the viscosity of the slag in this portion can be obtained. Cr ₂ O ₃ has been put into practical use in the form of magcro brick, but in the case of Cr ₂ O ₃ CaO which is one of the main components of slag
It has a limit in corrosion resistance because it is easily reactive.
On the other hand, ZrO ₂ (zirconia) has excellent corrosion resistance and is promising. However, both magnesia and zirconia have high melting points, and sintering does not proceed during the firing process.
Refractories are difficult to densify, which is disadvantageous for slag penetration. Also, since zirconia is relatively expensive, mixing it with refractories increases the price of refractories,
Economically disadvantaged.

As a result of repeated studies to solve these problems, a method for obtaining a dense magnesia-zirconia fired refractory with almost no increase in price has been found.

In the present invention, ordinary magnesia and zircon (ZrO ₂ · SiO ₂ ) are used as raw materials. Magnesia may be of normal purity, that is, having a MgO component of about 95% or more. There is no problem with zircon as long as it has a quality comparable to that used for ordinary refractories, that is, about 10% or less of impurities. Regarding the particle size, both are such that they do not hinder the work in the melting process, that is, 50 mm
It is desirable that it is less than about.

These raw materials are put together and melted in a melting furnace, for example, an electric furnace. At this time, zircon is decomposed, and zirconia and silica (SiO ₂ ) are generated. Silica reacts with a part of magnesia to form forsterite (2MgO.SiO ₂ ). Since zirconia and magnesia have high melting points, they crystallize early on the part near the furnace wall of the electric furnace. On the other hand, the forsterite component has a relatively low melting point, so it remains in a molten state until later,
Segregates and concentrates near the center of the electric furnace. After the melting operation,
In a molten state or after solidification, the concentrated part of forsterite in the central part is removed, and then a refractory solidified body composed of magnesium, zirconia and a small amount of forsterite is refined to obtain a magnesia-containing refractory material. In addition, when the forsterite component is mixed in a large amount, the corrosion resistance of the refractory using this refractory material is adversely affected. Works effectively as a sintering aid, contributes to densification of the refractory structure, suppresses slag infiltration, and facilitates the prevention of the occurrence of deterioration, peeling, and the like.

If the weight ratio of zircon exceeds 70%, all the magnesia reacts with the silica in the zircon, and a large amount of fired body composed of forsterite, zirconia, and zircon is formed. The corrosion resistance is reduced without exhibiting the property, and the fire resistance is reduced. Therefore, in order to obtain a high-magnesia-containing refractory having a sufficiently high magnesia effect, the amount of added zircon should be at most 70.
It must be up to wt%.

The thus obtained finely divided magnesia-containing refractory material is adjusted to an appropriate particle size, and then kneaded with a binder or other refractory particles as needed, so that it can be used as an amorphous refractory. The refractory particles that can be used here include spinel, alumina, chromite, magcroclinker, magnesia, calcia, dolomite, graphite,
Carbides, borides, nitrides and the like. Further, if it is molded, it can be used as a non-fired refractory, and if it is further fired, it can be used as a fired refractory.

(Example) The magnesia-containing refractory material according to the present invention was used alone and the refractory material was mixed with refractory particles such as spinel, chromite, magcroclinker, magnesia, calcia, dolomite, graphite, etc. as shown in Table 1, By mixing and firing, a fired refractory was prototyped and its properties were investigated.

The results are shown in Table 1 together with Comparative Examples in which the refractory of the present invention was not used.

* After the erosion test, measure the size reduction of the maximum erosion part of each sample,
The reduction amount of Sample 11 (ordinary magnesia brick) as a comparative example was normalized to 100. The smaller the erosion index, the higher the corrosion resistance.

Erosion test experimental conditions Method Lining erosion test by induction furnace Temperature 1600 ° C Time 2 hours Slag C / S = 1.5 Al ₂ O ₃ = 15% 500g × 4 times Steel SS41 Refractory using refractory material according to the present invention The corrosion resistance of this material was improved up to about 40% compared to the comparative product, confirming the effect of this material.

(Effect of the Invention) As described above, a refractory using a material manufactured by the method according to the present invention has high durability and contributes to stabilization of a steel manufacturing process and cost reduction.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuzo Otsuki 1-1-1 Emitsu, Yawatahigashi-ku, Kitakyushu-city, Fukuoka Prefecture Inside the Equipment Engineering Division, Nippon Steel Corporation (72) Inventor Kiyoshi Okawa Higashihata, Kitakyushu-shi, Fukuoka 1-1-1 Kueda Hikari Nippon Steel Corporation Equipment Engineering Headquarters (72) Inventor Takeyuki Tamaki 1-1 Higashihamacho, Yawatanishi-ku, Kitakyushu-shi, Fukuoka Prefecture Kurosaki Ceramics Co., Ltd. Technical Research Institute (72) Inventor Hiroshi Yamamoto 1-1, Higashihama-cho, Yawata-nishi-ku, Kitakyushu-city, Fukuoka Prefecture (56) References JP-A-60-11263 (JP, A) JP-A-51-71312 (JP, A) JP-A-47- 27213 (JP, A) JP-A-48-36210 (JP, A) JP-B-51-24524 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/00-35 / 22 C04B 35/622-35/636

Claims (2)

(57) [Claims] In a melting furnace such as an electric furnace, magnesia and zircon are melted together, forsterite is segregated and concentrated, and this is removed in a molten state or after coagulation, and magnesia and zirconia are removed in a small amount. A method for producing a magnesia-containing refractory material, comprising obtaining a refractory made of stellite and refining the refractory. 2. A method for producing a magnesia-containing refractory, comprising using the magnesia-containing refractory material obtained in claim 1.