JP2968542B2 - Refractory - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a refractory material suitable as a lining material for a molten metal container, in particular, a vacuum container.

[Conventional technology]

In the steelmaking process, degassing treatment is performed in DH and RH facilities to remove impurities after refining in a converter. The refractory for lining these vacuum vessels is required to be a material that is particularly stable under high-temperature vacuum.

In general, refractories containing silica as a main component are not suitable for this application because they are easily dissociated under a high-temperature vacuum, but magnesia, spinel, chromite, and the like are stable and suitable for this application. Among them, fired magnesia, magnesia spinel, and magnesia-chromite refractory are particularly suitable from the viewpoint of abrasion resistance to molten steel flow.

Among them, magnesia-chromic brick has excellent spall resistance to chemical erosion due to reaction with slag and molten steel and thermal shock due to temperature change.

Magnesia-chromium refractory materials can be broadly classified into two types, direct bond and ribbon, based on their raw material composition.

The direct bond uses a high-purity magnesia clinker as a magnesia source and a natural chromium ore as a chromium source. These compounds are press-formed and fired at a high temperature of 1800 ° C. or more.

On the other hand, the ribbon is obtained by blending and shaping magnesia clinker, and a low-impurity electrofused magcro, which is obtained by previously melting and cooling the magnesia clinker and chromite in an electric furnace and then pulverizing them.

By the way, porosity is one of the factors which influence the corrosion resistance. That is, foreign components such as slag and molten steel enter the bricks through the pores, and further react with the bricks to form a low melt, and are easily worn and damaged by the slag flow and the melt flow.

In the case of magnesia and chrome bricks, regardless of direct bonding or ribbon bonding, the means of porosity control is to adjust the particle size composition to a closest-packed particle size as before, and then fill with a high-pressure press and then sinter. It is common to fire at an ultra-high temperature to promote

At that time, it is disclosed in Japanese Patent Application Laid-Open No. 62-207757 to use chromium oxide powder and metal chromium in combination to fill pores, promote sintering, and reduce porosity. Although addition is also performed, the porosity is currently 14% in the case of direct bonding and 12% in the case of ribbon bonding at present.

Furthermore, in order to reduce the porosity in the brick structure, there is an improvement in the pressing ability at the time of molding, and furthermore, there is an ultra-high-temperature firing, but all of these are economically limited.

[Problems to be solved by the invention]

The problem to be solved in the present invention is a container for molten metal,
In particular, it is an economical measure to reduce the porosity of the magnesia-chromium refractory for lining the vacuum vessel.

[Means for solving the problem]

The refractory material of the present invention is obtained by adding 1 to 20% by weight of metal aluminum powder to a refractory main component obtained by mixing two or more of magnesia, electrofused magcro and chromite ore, or a refractory main component consisting of electrofused magcro. Then, a spinel in which chromium oxide is formed as a solid solution is formed after firing or during use after being applied without firing.

To the refractory main component, 1 to 50% by weight of one or two kinds of Fe ₂ O ₃ grains and Fe ₃ O ₄ grains can be added.
Alumina powder can be added at 1 to 20% by weight.

[Action]

The refractory material of the present invention uses a material in which metal aluminum is uniformly blended and fired in an oxidizing atmosphere or applied in an unfired state to oxidize the metal during use, further react with magnesia, and utilize the volume expansion at that time. In this case, the porosity is reduced by filling the pores.

On the other hand, blending aluminum powder with magnesia carbon is described in Japanese Patent Publication No. 60-2269, which is used to suppress carbon oxidation and fills pores by expansion due to oxidation. The present invention is fundamentally different from the present invention that attempts to make it more dense.

The reduction of the porosity of a magnesia-chromium direct-bonded brick with addition of metallic aluminum will be described with reference to the accompanying drawings.

FIG. 1 is a view showing a filling state after the material of the present invention is press-formed, and FIG. 2 is a view showing a state after the material is fired.

As shown in FIG. 1, after press molding,
Fine metal aluminum powder 3 is uniformly dispersed between magnesia grains 1 and chromium ore 2.

When this material is fired in an air atmosphere, the metallic aluminum powder 3 is oxidized, and fine-grained spinels 4 in which chromium oxide is newly dissolved are generated (FIG. 2). At this time, since the volume expansion is about 1.3 times, the pores 5 are filled. Further, since the pores 5 are filled, the overall strength is also improved.

Although the case of magnesia-chromium fired brick has been described above, porosity can be similarly reduced in other cases by oxidation of metallic aluminum and further volume expansion accompanying reaction with magnesia.

The refractory material of the present invention can be used as a fired brick if fired after press molding, or as an unfired brick if pressed only, and can be used as it is or as an amorphous refractory if an appropriate binder is added. When used as unfired bricks or amorphous refractories, a series of reactions occur during use, reducing porosity.

By the way, when the refractory material containing metal aluminum is fired as described above, the metal aluminum may not be sufficiently oxidized during firing depending on the firing conditions.
In this part, the metallic aluminum is in the form of the metal as it is, and the structure is coarse, the corrosion resistance is low, and the strength is low.

In order to eliminate unoxidized portions, an oxidizing agent may be added before firing. As an oxidizing agent, it is stable before firing,
It is necessary that the metal be oxidized at the time of sintering, that the sintering furnace not be adversely affected, and that the sintering furnace is not harmed. Fe ₂ O ₃ and Fe ₃ fit these points.
O is _4.

These oxidize other metals during firing and
If it is in the form of FeO and diffuses in magnesia or the like and controls the amount of addition, it does not have a great adverse effect on the corrosion resistance of the refractory. Also, there is no adverse effect on the firing furnace.

If the addition amount of the metal aluminum powder exceeds 20%, cracks due to volume expansion occur during firing or during use, and in some cases, molten metal aluminum may exude during heating. If the addition amount is less than 1%,
It is difficult to uniformly disperse the metal aluminum powder, and the effect of densification is small. Therefore, the proper addition amount is 1
~ 20%.

The particle size of the metal aluminum powder is desirably about 500 μm or less which does not decrease the reaction. Magnesia, chromite or electrofused magcro, which is the main component, may be of a quality within the range normally used. That is, MgO> 90% for magnesia, MgO.
Cr ₂ O ₃ >50%; in the case of electrofused magcro, impurities other than MgO and Cr ₂ O ₃ are 30% or less.

The metal aluminum powder may be an alloy or a mixture containing a metal other than aluminum (for example, iron, magnesium, chromium, etc.) that plays a role of a diluent for uniform dispersion.

There is no effect if the addition amount of Fe ₂ O ₃ and Fe ₃ O ₄ particles is 1% or less,
Addition of more than 50% adversely affects the corrosion resistance of the refractory. Therefore, the appropriate addition amount is 1 to 50%. Also,
The particle size is desirably 500 μm or less because it is necessary to efficiently react with the metal. Concerning the purity, it is preferable that impurities other than iron oxide be about 20% or less from the viewpoint of preventing generation of unnecessary low melting point substances.

〔Example〕

Example 1 Table 1 shows the effect of adding metallic aluminum to magnesia-chromium direct bond bricks.

From the table, it can be seen that the porosity can be reduced, the hot strength can be improved, and the corrosion resistance can be improved when the addition amount of aluminum is 1 to 20% by weight.

Example 3 Table 3 shows the effect of adding Fe ₂ O ₃ to a magnesia-chromic direct bond brick containing 20% by weight of metallic aluminum.

From the table, it can be seen that when the addition amount of Fe ₂ O ₃ is 1 to 50% by weight, it is possible to sufficiently oxidize metallic aluminum and obtain good quality without deterioration in corrosion resistance.

[Effects of the Invention] The refractory material of the present invention has the following effects.

(1) The porosity of the refractory can be remarkably reduced without being impaired at all by blending it with magnesia / chrome or other refractories.

(2) A very dense structure is obtained, and the hot strength is significantly improved.

(3) Slag intrusion is suppressed by the effect of the porosity reduction and the spinel generated at the grain boundary as a result, and the corrosion resistance is remarkably improved.

[Brief description of the drawings]

The drawings are schematic diagrams of porosity reduction of magnesia-chromium direct-bonded bricks added with metallic aluminum, FIG. 1 shows after press molding, and FIG. 2 shows after firing. 1: Magnesia grains, 2: Chromite ore 3: Aluminum powder, 4: Spinel 5: Pores

Continuation of the front page (72) Inventor Takeyuki Tamaki 1-1-1, Higashihama-cho, Yawatanishi-ku, Kitakyushu-shi, Fukuoka (72) Inventor Keisho Asano 1-1-1, Edamitsu, Yawata-higashi-ku, Kitakyushu-shi, Fukuoka No. 1 Nippon Steel Corporation Yawata Works (72) Inventor Kiyoshi Goto 1-1-1, Edamitsu, Yawatahigashi-ku, Kitakyushu-shi, Fukuoka Prefecture Inside Nippon Steel Corporation Yawata Works (56) References JP Akira 63-151660 (JP, A) JP-A-57-27972 (JP, A) JP-A-59-190257 (JP, A) JP-A-52-110713 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/00

Claims (3)

(57) [Claims] 1. A refractory main component comprising a mixture of two or more of magnesia, electrofused magcro and chromite or a refractory main component comprising electrofused magcro, and 1 to 20% by weight of metallic aluminum powder added thereto. A refractory material that forms a spinel with a solid solution of chromium oxide during use after firing or after unfired construction. 2. The refractory main component is one of Fe ₂ O ₃ grains and Fe ₃ O ₄ grains.
The refractory material according to claim 1, wherein 1 to 50% by weight of a seed or a mixture of two kinds is added. 3. A refractory main component comprising 1 to 20% by weight of alumina powder.
The refractory material according to claim 1 or 2, which is added.