JPS644978B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is directed to unsintered refractories partially or entirely using dolomite clinker, magnesia clinker, fused calcia, fused magnesia calcia, sintered calcia clinker, etc. containing free CaO. and a method for producing a monolithic refractory or a fired refractory produced by firing these in a non-oxidizing atmosphere. [Prior Art] It is well known that magnesia-carbon bricks have been rapidly becoming popular in steelmaking furnaces such as converters in recent years. Magnesia-carbon brick is an unfired refractory that uses electrofused or sintered magnesia clinker as the magnesia source, natural phosphorous graphite as the carbon source, and phenolic resin as the binder. In addition, it is a refractory with excellent corrosion resistance and spalling resistance, combining the characteristics of graphite with high corrosion resistance and high thermal shock resistance. The wear condition of such magnesia-carbon bricks in an actual furnace is that there is almost no peeling due to spalling, and the bricks are smoothly melted away from the working surface. Factors that affect this erosion rate include:
In addition to factors that depend on chemical reactions such as the CaO/SiO ₂ ratio of the slag and the amount of iron oxide, physical wear associated with the flow of molten steel and molten slag is considered. Graphite in refractories has the property of not being easily wetted by silicates, but has the disadvantage that iron oxides such as FeO in slabs are easily oxidized and disappear. Furthermore, although magnesia is relatively stable against iron oxides, it forms CMS, C ₃ MS ₂ and the like and dissolves against silicates, especially silicates with low C/S.
As described above, it is thought that in molten slag containing iron oxide, oxidation of graphite and erosion of magnesia occur in parallel, leading to progress of erosion. On the other hand, there is a magnesia-calcia-carbon brick as a material having different characteristics from the above-mentioned magnesia-carbon brick. Calcia-containing raw materials, such as magdro clinker and dolomite clinker, have traditionally been used for fired magdro bricks, and have excellent slag penetration resistance and good resistance to structural spalling. It is well known that the furnaces that produce refractories have poor corrosion resistance, and as operating conditions have become more severe, there has been a shift to high magnesia and low calcia refractories. These magnesia-calcia-carbon bricks conventionally manufactured include tar,
There are tar dolomite bricks that use pittuce as a binder. Normally, this refractory is made of magnesia, dolomite, and a small amount of graphite, but because the amount of graphite used is small, it is not sufficient to reduce the iron oxide slag, and if the amount of graphite used is increased. Since the pitches are thermoplastic, they undergo large expansion in the direction perpendicular to the graphite orientation direction during heat treatment, making it difficult to obtain a good structure. Furthermore, when using a phenolic resin such as magnesia-carbon bricks, the resol type is unsuitable because bound water is generated during curing, which causes digestion of the calcia-containing raw material and causes the brick to collapse. When using a novolac type phenolic resin with hexamethylenetetramine as a curing agent, there is no noticeable digestion phenomenon as with the resol type, but digestion still occurs during heat curing or during the process of lining a furnace with refractory material and raising the temperature. This is not preferable because it may cause cracks or structural deterioration. For this reason, magnesia-calcia-carbon refractories using phenolic resin as a binder have not been put into practical use. [Purpose of the Invention] In order to eliminate the various defects described above, the present inventors have discovered that when a refractory containing free CaO contains a large amount of carbon source such as graphite, calcia is not necessarily as large as magnesia. It cannot be said that the corrosion resistance is inferior. That is, among the slag components, iron oxide, which has the most adverse effect on calcia, has a significantly reduced activity due to an oxidation-reduction reaction with carbon contained in the refractory, and is unlikely to cause any adverse effects on calcia. As mentioned above, the slag reduced by carbon, especially its composition, is as low as in the early stage of converter blowing.
With the CaO/ _SiO2 ratio, calcia has the property of temporarily increasing the melting point of the reaction layer by reacting with slag, forming a high melting point reaction layer on the working surface and increasing the magnesia-carbon brick. It can be expected to have the effect of suppressing the continuous erosion seen in Furthermore, from a thermodynamic point of view, calcia has excellent stability in the coexistence of carbon, and we have found that calcia has an advantage under usage conditions where direct reaction between magnesia and carbon is a concern. In this paper, we researched a method to eliminate the above defects using a phenolic resin as a binder. The present inventor investigated the cause of the digestion phenomenon caused by phenolic resin, and made it possible to use raw materials containing free CaO by using a special solvent and phenolic resin together. The decomposition of phenolic resin's hydroxyl group and the use of hydrophilic solvents are thought to be the causes of digestion associated with the use of novolak-type phenolic resins. Generally, monohydric alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol, and polyhydric alcohols such as ethylene glycol, propylene glycol, and glycerin are used as solvents for phenolic resins, but these are all hydrophilic solvents and do not cause calcia. It has hygroscopic properties that are most detrimental to the raw materials it contains. According to research on phenolic resin chemistry, 300℃
It has been reported that a large amount of water is generated in the vicinity. This is presumed to be due to decomposition of phenolic hydroxyl groups. The present invention solves the above-mentioned drawbacks of phenolic resins, which are factors for digestion, at once by using alkylene carbonate as a solvent. [Effects of the Invention] The present invention has excellent corrosion resistance and spalling resistance by using phenolic resin and alkylene carbonate as binders in the production of basic refractories containing free CaO, and
This is a method for producing refractories that are not digestible with phenolic resin. The alkylene carbonate used in the present invention is preferably a colorless, transparent, odorless, non-hygroscopic, non-corrosive, stable liquid alkylene carbonate such as ethylene carbonate or propylene carbonate. The phenolic resin used in the present invention is obtained by reacting common phenol or phenols with a formaldehyde source under a catalyst. Here, the phenols may be compounds having one or more phenolic hydroxyl groups in one molecule and having two or more vacant positions ortho or para to the phenolic hydroxyl groups. More specifically, phenol, cresol, chlorophenol, nonylphenol, butylphenol, phenylphenol, bisphenol A, phenolphthalein,
Examples include resorcinol, methylresorcinol, hydroquinone, naphthol, isopropenylphenol, and the like. Of course, it is also possible to use a mixture of two or more of these phenols. Regarding the form of the phenolic resin, a novolak type is preferable because it generates less condensed water, but even resol types are polymerized through a reaction during resin production.For example, solid resols generate relatively less condensed water during curing. If used in combination with the solvent according to the present invention, it can be used without causing fatal digestion, and in this case, it is even better if the methylol group of the resol is butoxylated with butanol or the like. Of course, it is also possible to use the novolak type and the resol type in combination. Examples of the alkylene carbonate used in combination with the phenolic resin include ethylene carbonate, propylene carbonate, etc., but are not necessarily limited to these, and any alkylene carbonate that is reactive with a phenolic hydroxyl group can be used. There are various methods for using resins and solvents. A suitable amount of alkylene carbonate is added during the reaction completion or cooling process when producing phenolic resin, and a binder adjusted to an appropriate viscosity is used.Alternatively, phenolic resin and alkylene carbonate are added simultaneously during refractory kneading and the alkylene carbonate is added during the kneading process. Although there are methods such as dissolving the resin, the present invention is not limited to this method as long as the premise that the phenol resin and alkylene carbonate coexist is satisfied. There is no limit to the ratio of phenolic resin to alkylene carbonate used, but from the viewpoint of kneading properties of the refractory and performance of the refractory, the weight ratio of phenol resin to alkylene carbonate is preferably in the range of 40:60 to 90:10. If the ratio of alkylene carbonate used is low, there will be a large number of phenolic hydroxyl groups that are not converted into hydroxyalkyl ethers, which is not sufficient to suppress the digestion of calcia-containing raw materials, and conversely, if the ratio of alkylene carbonate used is high, the amount of phenolic hydroxyl groups that will not be converted into hydroxyalkyl ethers will be insufficient to suppress the digestion of calcia-containing raw materials. Since the proportion of the solvent that does not contribute to the refractory increases, the strength structure of the refractory deteriorates, which is undesirable. Further, as a characteristic reaction of the alkylene carbonate used in the present invention, phenolic hydroxyl groups are quantitatively converted into hydroxyalkyl ether during heat curing of the resin. At this time, free CaO in the refractory
serves as a catalyst for this reaction, so the alkylene carbonate used as a solvent efficiently contributes to the reaction. A cured phenolic resin in which phenolic hydroxyl groups were converted to hydroxyalkyl ethers was thermally decomposed at various temperatures in an N ₂ atmosphere, and the amount of water generated was measured by gas chromatography. The cured resin according to the present invention using propylene carbonate as a solvent generates about 1/7 the amount of water at 300°C and about 1/7 at 400°C compared to a normal cured resin using ethylene glycol as a solvent. 6, which was confirmed to have extremely favorable properties for calcia-containing raw materials that have remarkable digestibility. The essential refractory raw materials used in the present invention include one or more calcia-containing raw materials such as magdromite, dolomite, fused or sintered calcia, and fused magnesia-calcia. Oxides such as spinel, and non-oxides such as graphite, carbon black, coke, anthracite, silicon carbide, silicon nitride, and boron carbide can also be used. In addition, metals such as Al, Cr, Ni, Fe, and Si, or their carbides and nitrides may be added, and surfactants, surfactants, etc. may be added to improve the affinity and adhesion between aggregate and resin.
Coupling agents may also be added. The refractory according to the present invention can be provided as an unfired basic refractory dried at a low temperature, or a fired basic refractory fired in a non-oxidizing atmosphere,
It is also possible to produce monolithic refractories. The present invention will be explained in more detail with reference to Examples below. [Examples and Effects] Example 1 A novolac type phenolic resin was produced, and during the cooling process, 15 parts by weight of ethylene carbonate and 20 parts by weight of propylene carbonate were added to 65 parts by weight of the resin to form a liquid at 105 poise/25°C. Resin was obtained.

[Table] Unfired Magdro carbon bricks according to Example 1 in Table 2 were obtained using Magdro clinkers having the chemical compositions in Table 1. In contrast to the conventional resin using ethylene glycol as a solvent (Comparative Example 1), which caused large expansion and cracking due to digestion during drying,
The bricks according to the invention obtained good physical properties. These bricks were used for the trunnion part of a 150-ton converter. While the erosion rate of conventional magnesia-carbon bricks was 0.35 mm/ch, this brick
The corrosion rate was 0.30mm/ch, and an approximately 15% improvement in durability was observed.

【table】

[Table] Examples 2 to 4 A novolak type phenolic resin was manufactured and during the cooling process, 25 parts by weight of propylene carbonate was added to 75 parts by weight of the resin to obtain a liquid resin at 122 poise/25°C. Unfired bricks shown in Table 4 were manufactured using the dolomite clinker and fused calcia clinker shown in Table 3. In the case of ordinary resins using diethylene glycol and methyl alcohol as solvents, cracks occurred due to digestion and the quality could not be measured, whereas in Examples 2 to 4 according to the present invention, good physical properties were obtained. The unfired refractory of Example 3 was used in a 120 ton LF method ladle slag line. Compared to the average life of conventional magnesia-carbon bricks (Comparative Example 3), which was 57 channels, the durability was recorded at 64 channels, and superiority was recognized.

【table】

[Table] Example 5 A maguro-based stamp material was obtained using the maguro clinker and seawater magnesia clinker shown in Table 1. As a result of applying a stamp to a frame of 200 x 200 x 200 mm and treating it at various temperatures, the stamp material according to the present invention had good physical properties as shown in Table 5.

【table】

【table】

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Claims (1)

[Claims] 1. A method for producing a basic refractory comprising using a phenolic resin and an alkylene carbonate in producing a basic refractory containing free CaO.