JPH07247158A - Production of carbon-containing refractory and its antioxidant - Google Patents

Abstract

PURPOSE:To obtain a carbon-containing refractory having improved oxidation resistance by making metallic aluminum into a finer state further while securing safety of the metallic aluminum to be added as an antioxidant in terms of handling. CONSTITUTION:In the carbon-containing refractory prepared by adding 1-50 pts.wt. of a resin or a tar pitch as a binder to 100 pts.wt. of a refractory parent material obtained by mixing a refractory aggregate with a carbonaceous raw material, 0.1-20 pts.wt. of metallic aluminum fine powder having the surface layer coated with a coating film of aluminum nitride as an antioxidant is added to the carbon-containing refractory.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory material, and more particularly to a carbon-containing refractory material containing a carbonaceous raw material.

[0002]

2. Description of the Related Art Carbonaceous raw materials have a higher melting point and a higher thermal conductivity than ordinary refractory aggregates such as alumina and magnesia, a low coefficient of linear expansion, and a property that they are hard to wet even slag. Therefore, in particular, it is blended as a raw material for lining refractory materials such as furnaces for steelmaking and ironmaking, and imparts excellent heat resistance spalling resistance and slag resistance to the refractory material, and also oversinters the refractory material. It also has the effect of preventing

On the other hand, however, the carbonaceous material is
When it is heated in an oxidizing atmosphere such as air, it is extremely easily oxidized and converted into carbon monoxide, which disappears and the brittleness of the matrix in the refractory progresses.

In order to improve the oxidation resistance of such a carbon-containing refractory, it has been attempted to add a substance that forms glass at a predetermined temperature as an antioxidant. According to this configuration, the carbon component in the matrix is coated with the glass melt generated during the temperature rising process during firing or operation after construction of the carbon-containing refractory, thereby oxidizing the carbon component such as oxygen. It is intended to prevent direct contact of the volatile gas.

However, since the carbon component is originally poor in wettability with the glass melt, it is difficult to obtain the desired antioxidation effect, and conversely, the substance having the low melting point exists in the matrix. On the contrary, harmful effects such as reduction in hot strength and corrosion resistance were conspicuous.

Therefore, a metal that is more easily oxidized than carbon has been adopted as another constituent of the antioxidant. An antioxidant composed of such an easily oxidizable metal preferentially undergoes an oxidation reaction with an increase in temperature, so that the oxygen partial pressure in the matrix is lowered and the oxidation of carbon is suppressed.

Further, when a carbide or the like is produced by the reaction with the oxide of the easily oxidizable metal or the carbon component, the volume expansion is accompanied, so that the oxide or the carbide is filled in the pores in the matrix, The densification will be promoted,
It also exerts the effect of blocking the inflow of oxidizing gas from the outside.

The above metals are aluminum and magnesi.
Aluminum, metal silicon, etc. are used, among which aluminum is used.
Nitrogen reacts more easily than other metals and is less expensive.
It is the most used in terms of availability,
In the case of the temperature rise, Al_FourC ₃And Al₂OC generates
In addition, Al at high temperature₂O₃Of the easily oxidizable metal
It condenses in the vicinity and in the pores, and exhibits the effect described above.

[0009]

By the way, when the metallic aluminum is added as an antioxidant to the refractory base material, when the metallic aluminum is added in the form of coarse particles, the above-mentioned carbides and oxides are contained in the coarse particles. It will be generated only in the surface layer, and the unoxidized metallic aluminum evaporates from the cracks of the surface layer film thus formed, and the antioxidant effect commensurate with the added amount of the metallic aluminum cannot be exhibited. Become.

Such a situation can be overcome by increasing the amount of the above-mentioned aluminum metal, but if added in an excessive amount to the refractory aggregate and the carbonaceous raw material, the volume expansion coefficient of the entire refractory increases excessively. However, there is an adverse effect such as a decrease in heat-resistant spalling property, and it is unreasonable to increase the amount of metallic aluminum.

Therefore, in order to further enhance the antioxidation effect of the metallic aluminum, it is desirable to add the metallic aluminum in the form of fine powder to secure a large reaction effective area per unit amount.

However, since too fine aluminum particles have an excessively strong oxygen affinity and are associated with a danger of exploding during handling, for safety reasons, a particle size of about 10 μm is usually used as a lower limit, and a carbon-containing refractory material is used. This is a bottleneck in further improving the durability (oxidation resistance) of.

The present invention has been proposed in view of the above-mentioned conventional circumstances, and by ensuring the handling safety of metallic aluminum added as an antioxidant, and by making it into a finer form, An object of the present invention is to provide a carbon-containing refractory material having improved oxidation resistance.

[0014]

In order to achieve the above object, the present invention employs the following means. That is, in a carbon-containing refractory in which 1 to 50 parts by weight of a resin or tar pitch as a binder is added to 100 parts by weight of a refractory base material formed by mixing a refractory aggregate and a carbonaceous raw material, a surface layer of an aluminum nitride film is used. 0.1 to 20 parts by weight of finely divided metallic aluminum powder coated with is used as an antioxidant.

The above-mentioned antioxidant composed of fine powder of metallic aluminum can be manufactured by pulverizing in a nitrogen gas atmosphere.

[0016]

According to the carbon-containing refractory having the above structure, the oxygen affinity of the metallic aluminum fine powder added as an antioxidant is suppressed by the aluminum nitride coating film, so that the safety when handling the metallic aluminum fine powder is ensured. The burden required to do so is reduced.

Moreover, the required safety can be ensured even if the particle size of the metal aluminum fine powder is 10 μm or less, which is finer than that of the conventional one. The effect is improved.

It has been confirmed that the aluminum nitride coating on the surface layer of the fine metal aluminum powder does not deteriorate the durability of the carbon-containing refractory. The antioxidant having the above-described action can be produced by simply performing a fine pulverization treatment for forming fine powder in a nitrogen gas atmosphere, and further performing a heat treatment in a nitrogen gas atmosphere after pulverization. As a result, a nitrogen aluminum coating having a thickness of several μm to several tens of μm is formed. In addition, about 500-700 degreeC is suitable for this heating temperature.

The amount of the fine powder of metallic aluminum as the above-mentioned antioxidant is appropriately 0.3 to 20 parts by weight per 100 parts by weight of the refractory base material as described above. If it is less than 10 parts by weight, the refractory does not have the required oxidation resistance, and if it exceeds 20 parts by weight, the coefficient of thermal expansion is excessively increased and the heat-resistant spalling property is deteriorated.

In the present invention, the material of the refractory aggregate constituting the refractory base material, the blending amount with the carbonaceous raw material and the like are not particularly limited. For example, as the refractory aggregate, magnesia raw material, alumina raw material, calcia Well-known materials such as carbonaceous raw materials can be used, and as the carbonaceous raw materials, scaly graphite, earth-like graphite and the like can be used.

Furthermore, the present invention is applied to a so-called "carbon bond refractory material" in which resin or tar pitch is adopted as a binder, and the addition amount of the binder is 1 to 100 parts by weight of the refractory base material. 50 parts by weight is preferable, and if the addition amount is less than this, the strength after molding is insufficient, and conversely, if the addition amount is too large, the carbon content in the matrix becomes excessive, and the present invention still further. It becomes impossible to impart the required oxidation resistance.

[0022]

EXAMPLES The present invention will be described below based on examples. The antioxidant added to the carbon-containing refractory material in this example was manufactured by the following procedure prior to kneading with the refractory base material.

That is, a predetermined metal aluminum raw material is charged into a ball mill crusher together with alumina balls, and air in the crusher is degassed, and then nitrogen gas (purity 9
9.9%) was enclosed, a nitrogen gas atmosphere having a nitrogen partial pressure of 1 atm was formed, and a pulverizer was operated for 1 hour in this state to produce metallic aluminum fine powder having an average particle diameter of 10 μm.

Further, metal aluminum fine powder was taken out from the crusher, and subsequently, a heat treatment was carried out at a temperature of 600 ° C. for 24 hours while maintaining the same nitrogen gas atmosphere as above.

The fine metal aluminum powder as an antioxidant thus obtained has an aluminum nitride coating film with a thickness of several μm to several tens of μm formed on the surface thereof.
It was found by observing the fracture surface with an electron microscope.

Table 1 shows the composition of the product of the present invention using the above-mentioned antioxidant and its physical property values, and a comparative product in which conventional metal aluminum fine powder (however, the particle size is 50 μm or less) is added as the antioxidant. Is also described.

As shown in Table 1, the product of the present invention and the comparative product were used as a refractory aggregate of a raw material of fused magnesia (particle size: 5 to 3 mm, 3
~ 1 mm, 1-mm), scaly graphite (particle size: 0.35-mm, 1 mm ~) as a carbonaceous raw material, and phenol resin as a binder in the respective proportions indicated, and then obtained by molding. It is what is done. Further, the molded body thus obtained was dried at a temperature of 200 ° C. for 24 hours.

“Porosity”, “rough specific gravity”, and “bending strength” shown in the lower column of Table 1 are the physical properties of the molded article after drying, which shows that it is between the product of the present invention and the comparative product. There is no difference at all.

Further, when the dried product of the present invention and the comparative product are heat-treated in a reducing atmosphere, the temperature is 700 to 800 ° C.
Al ₄ C ₃ is generated in the tissue from the vicinity, and 1200
X-ray diffraction identified the formation of MgAl ₂ O ₄ (spinel) above ° C.

In Table 1, the symbols VS, S, and W described in each column of X-ray analysis are the corresponding substances (Al ₄ C ₃ , M) in this order.
It indicates that the amount of gAl ₂ O ₄ ) produced is increased (see * mark).

However, the amount of MgAl ₂ O ₄ (spinel) produced was larger in the product of the present invention, and it was confirmed that the reaction useful for preventing the oxidation of the carbonaceous raw material was progressing. Along with this, the flexural strength of the product of the present invention also shows a higher value, demonstrating that the densification of the matrix is further promoted.

From the above experimental results, the antioxidant used in the product of the present invention has an aluminum nitride film formed on the surface thereof, so that the burden on the operator in handling is reduced, but It has no adverse effect on the carbon-containing refractory to which it is applied. Moreover, the formation of the above-mentioned aluminum oxide is remarkable, which can be expected to improve the durability (oxidation resistance) of the carbon-containing refractory.

Furthermore, the product of the present invention is used together with the above-mentioned comparative product.
The thickness of the lining layer was measured after 2100 ch (charge) after using it as a 0t converter lining refractory, whereas the original thickness of the comparison part was reduced from 900mm to 250mm. In the case of the invention product, the thickness of the lining layer of about 400 mm was left, which also revealed the superiority of the antioxidant effect according to the present invention.

The present invention is not limited to the carbon-containing refractory material in which the magnesia raw material is adopted as in the above-mentioned embodiment, and the same effect can be obtained even if the refractory aggregate material having another structure is adopted. It is clear from the above description that the effect is achieved.

[0035]

[Table 1]

[0036]

As described above, according to the present invention, it becomes easier to handle the fine metal aluminum powder used as the antioxidant of the carbon-containing refractory.

Further, since the fine powder of metallic aluminum can be further finely added and added, the effective reaction area in the matrix is remarkably improved as compared with the conventional product, and the oxidation reaction of the fine powder of metallic aluminum is promoted. Therefore, it is effective in significantly improving the oxidation resistance of the carbon-containing refractory.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // C04B 35/043 C04B 35/04 E

Claims (2)

[Claims] 1. A carbon-containing refractory material in which 1 to 50 parts by weight of a resin or tar pitch as a binder is added to 100 parts by weight of a refractory base material formed by mixing a refractory aggregate and a carbonaceous raw material, wherein aluminum nitride is used. A carbon-containing refractory material, characterized in that 0.1 to 20 parts by weight of metallic aluminum fine powder whose surface is covered with a coating is added as an antioxidant. 2. Oxidation of a carbon-containing refractory material, characterized in that metallic aluminum is pulverized in a nitrogen gas atmosphere to have a particle size of 10 μm or less, and further heat-treated at 500 to 700 ° C. in a nitrogen gas atmosphere. Method for producing inhibitor.