JPH0152348B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a metal smelting furnace in which at least a portion of the lining is made of an unfired refractory manufactured by adding graphite, a thermosetting synthetic resin, and a low-melting point alloy powder to the composition. Conventionally, refractory bricks fired at 1,300 to 1,800℃ have been used for lining electric furnaces and converters, but from the viewpoint of energy saving and cost reduction, some combinations of inorganic and organic materials have been used. Unfired bricks made with additives are used in only a few limited areas. However, refractory linings using these binders have several problems as shown below. If an inorganic binder is used, it is likely to be a source of impurities that are harmful to the quality of the steel, and the binder also reduces its fire resistance and tends to be easily eroded by molten metal and slag. . Furthermore, if an organic binder is used, the organic binder that forms the bond of the refractory will oxidize and decompose at medium to high temperatures during use, causing significant strength deterioration, so the moving surface will suffer wear damage from molten metal. ,
The back side is significantly weakened by oxidation. Therefore, conventional unfired bricks are currently limited to limited steel types and operating conditions, and to locations where the usage conditions are relatively easy. The refractory used in the present invention has improved strength during use when a refractory bond is formed using an organic binder. Note that the organic binder mentioned here refers to all thermosetting materials, but phenolic resins are generally used because of their low cost and high carbonization yield. Organic binders are common in oxidizing atmospheres.
Oxidative decomposition begins at around 300°C and disappears at 500 to 700°C, so conventional unfired bricks, whose refractory bond relies entirely on organic binders, suffer significant strength deterioration at around 700°C. present. To improve this, we added a substance that has a melting point within the range of 200 to 700°C and exists as a single substance or a compound even in the temperature range of 1000°C or higher, and the particle retention function created by softening or melting it. A feature of the present invention is a method of reinforcing the strength and extending the life of the metal smelting furnace by utilizing the above. Conventionally, as an additive substance that satisfies the above conditions, Al (mp660℃ ), Mg (mp650℃)
is the main one (Si has a high melting point of 1410℃,
It is not effective below 800℃), but it is only after 550℃ that it reacts with the aggregate and contributes to the development of strength, and the strength decreases significantly between 400 and 600℃.
Moreover, the oxidation resistance is also insufficient. This is particularly noticeable when using a thermosetting synthetic resin that produces amorphous carbon. The oxide of Al is Al ₂ O ₃ , which becomes an impurity in the basic aggregate, resulting in a decrease in corrosion resistance. In addition, Mg powder has a high risk of explosion, so it is problematic to use it in the brick industry. The present invention relates to alloys of Al and Mg, such as Al-
Mg, Al−Si, Al−Ca, Mg−Ca, Al−Mg−
It is constructed by using one or more of alloys such as Ca, Al-Mg-Si, etc. Al alloy with melting point 200~700℃,
By using an Mg alloy, (1) the melting point is significantly lowered, and the decrease in strength from 400°C, which is about 250°C lower than that of Al alone, is reduced. (2) An important improvement effect of improving oxidation resistance can be obtained. The lowest melting point of a binary system is, for example, Al-Mg alloy 435℃, Al-Si alloy 575℃.
℃, 545℃ for Al-Ca alloy, 450℃ for Mg-Ca alloy (Metal Data Book), and the melting point is 225℃ lower than that of Al single metal. Therefore, by using the above alloy, the reaction with the aggregate occurs in a lower temperature range, and it has excellent spalling resistance, corrosion resistance, oxidation resistance, and high hot strength, completely covering the disadvantages of unfired bricks. Improved unfired bricks can be obtained. Note that the grain size of the alloy to be added is desirably uniformly dispersed in the structure for its purpose, and the finer the particle size, the more advantageous it is, but experience has shown that a particle size of 0.25 mm is sufficient to exhibit its effect. The risk of explosion was prevented by forming Al and Mg into an alloy. To explain the method for manufacturing a refractory according to the present invention, a predetermined amount of a refractory raw material serving as an aggregate, metal powder, and a thermosetting binder are kneaded in a mixer. In order to uniformly disperse the metal powder added at this time, it is desirable to mix the fine aggregate powder and the metal powder in advance. The refractory of the present invention can be obtained by molding the compound after kneading by press molding or, in the case of a complicated shape, by casting, etc., and subjecting it to a conventional heat curing treatment. The appropriate amount of alloy metal powder to be added is 1 to 30% by weight; if it is less than 1% by weight, the effect will not be recognized, and if it exceeds 30% by weight, the metal powder will soften or melt, causing molten metal flow. Accelerates wear or spillage damage. As the alloy metal powder to be added, one type or a combination of two or more types may be used depending on the purpose. The amount of thermosetting organic binder added depends to some extent on the bulk specific gravity of the aggregate;
2 to 15% is appropriate. If the amount added is less than 2%, it will not be possible to mold it into bricks, and 15%
Exceeding this value not only makes it difficult to form, but also increases volatile components, making the refractory structure rough during use, resulting in poor oxidation resistance and a greater tendency to become brittle. Figures 1 and 2 show the results of comparing the hot strength and oxidation resistance of Al-Mg (1:1) alloy and Al in phenol resin bonded magnesia graphite bricks. The amount added is 3% by weight for both, and the particle size is 0.25 mm for the former and 0.044 mm for the latter. As shown in the drawing, the strength of aluminum added increases from around the melting point of aluminum. On the other hand, the present invention has a small strength drop and a small oxidized decarburization layer, and is highly effective. As described above, the refractory of the present invention achieves a significant improvement in the properties of conventional unfired bricks using an organic binder, and has no adverse effect on the quality of steel. Also, by omitting the firing process,
It achieves energy and labor savings, and because used bricks can be recycled, it also makes it possible to save resources. Example As shown in Table 1, as lining bricks for converter,
0.25 mm of Al-Mg (6:4) alloy is added to the mix of high-purity magnesia and flaky graphite (20% by weight) as aggregates.
% by weight and 3.5% of novolac type liquid phenol resin was added to produce unfired bricks. When used on the charging side wall of a converter,
After 1500 heats, the remaining size was approximately 40 mm larger than that of the same type of unfired brick with 4% by weight of Al fine powder added.

【table】

【table】 [Brief explanation of drawings]

Figure 1 is a graph showing the results of comparing the hot strength of Al-Mg (1:1) alloy and Al in phenol resin bonded magnesia-graphite bricks.
FIG. 2 is a graph showing the results of a comparison of oxidation resistance.

Claims (1)

[Claims] 1 55-97% by weight of basic refractory material containing graphite,
Al alloy with a melting point of 200-700℃ with a particle size of 0.5mm or less,
An unfired refractory made of 1 to 30% by weight of one or more types of Mg alloy powder and 2 to 15% by weight of a thermosetting synthetic resin, kneaded, molded, and heat-treated is used for at least part of the lining. A metal smelting furnace characterized by: