JPH0460942B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a carbon-containing refractory with excellent oxidation resistance. [Background technology] Carbon-containing refractories are difficult to get wet by various types of molten slag, have excellent corrosion resistance, and have high thermal conductivity, so they have traditionally been used as refractory materials for metal scouring containers, etc. Widely used.
Taking advantage of these properties, carbon-containing refractories have also become essential in the field of steel refining, for use in the bottoms of blast furnaces, mixed wash cars, converters, ladle linings, and as refractories for continuous casting. ing. These carbon-containing refractories are usually made into products by kneading the mixture with refractory aggregate using an organic binder and molding the mixture, followed by heat treatment if necessary. Depending on the heat treatment temperature, the organic binder may be carbonized at the time of production and remain as a carbon bond, creating what is called a fired refractory, but recently organic binders have been used to save energy. In many cases, the refractory is heat treated at a low temperature enough to harden it, and the organic binder is present as it is at the shipping stage, so-called unfired refractories. Even with this unfired refractory, when it is heated during use in actual equipment, the organic binder gradually decomposes and after a certain period of time carbonizes to form a carbon bond. It is the same as fired refractories. Typical examples of the organic binder include synthetic resins such as phenol resin and tar pitch, but in recent years resins have been increasingly used due to their ease of use and the performance of refractories. However, on the other hand, oxidative wear is cited as a common drawback in carbon-containing refractories using organic binders. In the case of carbon-containing refractories, in addition to the carbon bonds generated from the organic binders mentioned above, carbon raw materials such as natural graphite, carbon black, and coke powder are usually blended as part of the refractory aggregate to further enhance the corrosion resistance of the carbon bonds. Although many efforts have been made to improve the performance of refractories, carbon bonds are the weakest among these carbon materials in terms of oxidative wear, and the life of refractories is determined by carbon bonds. Oxidative wear has been the biggest problem in carbon-containing refractories using carbon-containing refractories. Therefore, the following measures have been conventionally adopted to improve the oxidation resistance of carbon-containing refractories. Metals that are easily oxidized by combining with O ₂ such as Al and Si disperse into the refractory and enter the refractory.
It takes in _O2 . A finely powdered SiO ₂ -Na ₂ O- (K ₂ O) glass forming agent is dispersed in the refractory, and when heated, it becomes a highly viscous liquid and closes the pores that are the entry route for O ₂ . They can be sealed or covered with refractory carbon bond to prevent oxidation. Impregnating refractories with a refractory liquid reduces breathability. However, it is difficult to sufficiently disperse the metal in the refractory, and when the metal is oxidized, the volume expansion is large and the structure of the refractory is easily destroyed. In order to impart properties, a large amount of glass-forming agent is required, which often impairs the fire-resistant performance of the refractory itself.However, it is difficult to produce an appropriate impregnating agent with fire-resistant properties, and it is difficult to produce a suitable impregnating agent with sufficient acid resistance. There are problems such as the inability to impart chemical properties.
In the end, even with these means, the oxidative wear resistance of carbon-containing refractories cannot be effectively improved. [Object of the Invention] The present invention has been made in view of the above points, and an object of the present invention is to provide an oxidation-resistant carbon-containing refractory having excellent oxidation wear resistance. [Disclosure of the Invention] The oxidation-resistant carbon-containing refractory according to the present invention is a refractory made by kneading and molding a refractory aggregate using at least a part of a phenol resin as a binder. This invention is characterized in that it contains 1% by weight or more of an alkali metal as an alkali metal hydroxide.The present invention will be described in detail below. Among thermosetting resins, phenolic resin is generally used as the resin as a binder, and alkali metals can be contained by, for example, leaving the reaction catalyst used as a reaction catalyst when preparing this resin. can be done. That is, for example, when preparing a phenolic resin by condensing phenols and aldehydes under an alkali catalyst, if an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide is used as the alkali catalyst, this alkali metal compound remains in the resin, and the alkali metal is contained in the resin. Here, for example, in the case of phenolic resin, the alkali catalyst is usually blended in an amount of 0.5% by weight or less based on the resin in terms of alkali metal, but in the present invention, the alkali catalyst is It is necessary to mix the catalyst in an amount of 1% by weight or more based on the resin. In the present invention, the oxidative wear resistance of the refractory is improved by the presence of an alkali metal, but if the alkali metal is present in an amount less than 1% by weight, a sufficient improvement in oxidative wear resistance cannot be expected. Of course, an alkali metal hydroxide may be added to and mixed with the resin prepared to contain the alkali metal. In this way, a resin containing alkali metal is used as a binder, and this is mixed with fire-resistant aggregate and kneaded. At this time, tar, pitch, etc. are used in addition to the resin as a binder. Good too.
In addition, fire-resistant aggregates include natural graphite, alumina,
Any commonly used material such as silica glass can be used. After the refractory aggregate and the binder are kneaded in this way, they are pressed and shaped, and then heat treated to form fired or unfired refractories. That is, when heat treatment is performed at a high enough temperature to carbonize the binder, a fired refractory is formed in which the refractory aggregate is bonded with carbon bonds. Furthermore, if the heat treatment is carried out at a low enough temperature to harden the binder, the binder will remain as it is without being carbonized and will become an unfired refractory. is carbonized to produce carbon bonds. In the refractories obtained in this way, the alkali metals contained in the binder resin are Na ₂ O and K ₂
O, etc., which are susceptible to oxidation reactions, can be incorporated into the refractory, and Na ₂ O and other substances generated in this _way can be taken in.
K ₂ O reacts with the silicic acid component and alumina component in the refractory aggregate to form Na ₂ O-SiO ₂ -Al ₂ O ₃ system and K ₂ O-
Since SiO ₂ -Al ₂ O ₃ -based glass is produced, the carbon bond is covered with this glass, and the effect of O ₂ on the carbon bond can be prevented. Here, ordinary refractory aggregate powder contains a small amount of _SiO2 component,
When the content of SiO ₂ is low, it is preferable to mix at least one of amorphous silica fine powder and metal silicon fine powder as part of the refractory aggregate and disperse well in the refractory. The Si component in this amorphous silica fine powder and metal silicon fine powder
The glass is produced by reacting with Na ₂ O and K ₂ O. If the amount of SiO ₂ component contained in the refractory aggregate is sufficient, there is no particular need to blend amorphous silica fine powder or metallic silicon fine powder. In this way, the oxidative wear resistance of carbon bond can be improved by the action of the alkali metal contained in the resin, but since the alkali metal is contained in the resin that becomes the carbon bond, the carbon The bond can be effectively protected from oxidation, and since the amount of alkali metal is small compared to the entire refractory, there is no risk of impairing the fire resistance of the refractory itself. Here, the blending amount of the resin binder is preferably set so that the carbon content in the refractory is 2% by weight or more. If it is less than 2% by weight, there will be little carbon bond and ceramic bond will be the main component, making it vulnerable to thermal shock. Further, as the alkali metal to be contained in the resin, potassium is preferable since it is effective in terms of oxidation resistance. The reason is K ₂ O
It is thought that this is because there is a difference in viscosity between the glass having the Na ₂ O component and the glass having the Na 2 O component. The invention will now be illustrated by examples. Manufacturing example of binder 1 658 g of phenol and 851 g of 37% formalin were placed in a four-necked flask, and while stirring, 72 g of 50% potassium hydroxide solution was added, and it took 60 minutes for the internal temperature to reach 70.
The temperature was raised to .degree. C., and the reaction was continued for 5 hours. Next, 580 g of water was dehydrated under a reduced pressure of 70 Torr. The obtained resol type phenolic resin was a brown viscous resin with a viscosity of 150 poise at 25°C. Further, this resin contains 2.5% by weight of potassium. Production Example 2 of Binder 85g of 50% potassium hydroxide water was added to 1000g of the resin obtained in Production Example 1, and the mixture was thoroughly stirred and mixed. The obtained resol type phenolic resin was a brown viscous resin with a viscosity of 130 poise at 25°C. Further, this resin contained 5.0% by weight of potassium. Manufacturing example of binder 3 658 g of phenol and 851 g of 37% formalin were placed in a four-necked flask, and while stirring, 165 g of 50% potassium hydroxide solution was added, the temperature was raised to 70°C over about 90 minutes, and the temperature was raised to 70°C. A time reaction was performed. Next, 635 g of water was dehydrated under a reduced pressure of 70 Torr. The obtained resol type phenolic resin was a brown viscous resin with a viscosity of 350 poise at 25°C. By applying ethylene glycol to this resin,
10% by weight was added to obtain a resin having a viscosity of 130 poise at 25°C. Potassium in this resin is 2.5% by weight
It is contained. Binder Production Example 4 940 g of phenol and 649 g of 37% formalin were placed in a four-necked flask, and 7.5 g of oxalic acid was added thereto, followed by reaction under reflux for 120 minutes. Then 150℃
Dehydration was carried out at normal pressure up to a maximum of 660 g, and 660 g was further dehydrated under reduced pressure of 50 Torr. Immediately thereafter, 625 g of ethylene glycol was added, and after cooling to room temperature, 120 g of 50% potassium hydroxide solution was added and mixed well. The obtained novolak type phenolic resin was a brown viscous resin with a viscosity of 170 poise at 25°C. Further, this resin contains 2.5% by weight of potassium. Binder production example 5 Put 658g of phenol and 851g of 37% formalin into a four-necked flask, add 132g of 33% sodium hydroxide solution while stirring, and bring the internal temperature to 70℃ over 90 minutes. The temperature was raised and the reaction continued for 3 hours. Next, 600 g of water was dehydrated under a reduced pressure of 70 Torr. The obtained resol type phenolic resin was a brown viscous resin with a viscosity of 60 poise at 25°C. Moreover, this resin contains 2.5% by weight of sodium. Manufacturing example of binder 6 658g of phenol and 851g of 37% formalin were placed in a four-necked flask, and while stirring, 24g of 33% sodium hydroxide solution was added, and it took 60 minutes for the internal temperature to rise.
The temperature was raised to 70°C, and the reaction was continued for 6 hours. Next, 550 g of water was dehydrated under a reduced pressure of 70 Torr. The obtained resol type phenolic resin was a brown viscous resin with a viscosity of 30 poise at 25°C. Moreover, this resin contains 0.5% by weight of sodium. The resins of Production Examples 1 to 4 and Production Example 6 obtained as described above were kneaded with the fire-resistant aggregate of the composition shown in Table 1, molded using a rubber press, and reduced and fired at 1000°C. Fired refractories were obtained (Examples 1 to 6 and Comparative Example 1). Various properties of this refractory were measured. The results are shown in Table 2. In Table 2, oxidation resistance is measured using a sample of 30 x 30 x 30 mm.
The evaluation was performed by placing the sample in an electric furnace at 1300℃ for 1 hour for oxidation treatment, and then measuring the amount of weight loss and compressive strength ^.
It is expressed as the value divided by (30 x 30 mm).

【table】

[Table] Also, production examples 1, 2, 5, obtained as above,
An unfired refractory was obtained by kneading the resin of No. 6 with the refractory aggregate of the composition shown in Table 3, molding it using a rubber press, and heat-treating it at 200°C for 48 hours to harden the binder resin. (Examples 7 to 10 and Comparative Example 2). Various properties of this refractory were measured.
The results are shown in Table 4.

【table】

[Table] As a result of Tables 2 and 4, in Examples 1 to 6 and Examples 7 to 10, in which the binder resin contained 1% by weight or more of potassium or sodium, the binder resin contained 1% by weight or more of sodium. It is confirmed that the oxidation resistance can be improved compared to Comparative Examples 1 and 2, which contained less than % by weight. [Effects of the Invention] As described above, in the present invention, 1% by weight or more of an alkali metal is contained as an alkali metal hydroxide in the phenolic resin as a binder for the refractory aggregate. Alkali metals are susceptible to oxidation reactions and can incorporate O ₂ that enters the refractory, and alkali metals also react with the silicic acid and alumina components in the refractory aggregate to form glass. This glass can cover the carbon bond and prevent the action of O ₂ on the carbon bond.
The oxidative wear resistance of carbon-containing refractories using resin as a binder can be improved.

Claims (1)

[Scope of Claims] 1. A refractory made by kneading and molding a refractory aggregate using at least part of a phenol resin as a binder, wherein the resin contains at least 1% by weight of an alkali metal. An oxidation-resistant carbon-containing refractory characterized by being contained as a hydroxide. 2 At least one of the amorphous silica fine powder and the metallic silicon fine powder is contained in the refractory aggregate in an amount of 2% by weight.
The oxidation-resistant carbon-containing refractory according to claim 1, wherein the oxidation-resistant carbon-containing refractory contains at least the following. 3. The oxidation-resistant carbon-containing refractory according to claim 1 or 2, characterized in that the carbon content is 2% by weight or more. 4. The oxidation-resistant carbon-containing refractory according to any one of claims 1 to 3, wherein the alkali metal is potassium.