JPH08295572A - Heat treatment of monolithic refractory - Google Patents

Abstract

PURPOSE: To obtain a monolithic refractory which contains a carbonaceous binder and is homogeneous and rigid, and also, has high service durability by adding water to a monolithic refractory contg. a carbonaceous binder and heating the resultant mixture to a specified temp. by irradiating it with a microwave. CONSTITUTION: In this heat treatment, at the time of adding water to a monolithic refractory contg. a carbonaceous binder, kneading the resultant mixture and, thereafter, forming the kneaded material into a formed body, the resultant formed body is dried to remove water by irradiating it with a microwave, and further, heated by continuously performing this irradiation so that the temp. of the back face and surface of the formed body are >=150 deg.C and <=450 deg.C, respectively to solidify the carbonaceous binder. Heating of a material by irradiating it with a microwave is generally classified into dielectric heating and induction heating and, at the time of heating the material with the microwave irradiation, the difference in temp. between the surface and back face of the material is slight and, accordingly, the material can uniformly be heated. At this time, when the surface temp. of the formed body is raised to 150 deg.C at which the volatilization of volatile matter in the surface becomes active, the back face temp. is already >=150 deg.C at which water is completely volatilized. After the complete volatilization of water, the volatile components of the binder is volatilized to solidify the binder. Since oxidation of the carbon component of the binder is rapidly accelerated when the surface temp. exceeds 450 deg.C, it is required to complete the solidification of the binder at <=450 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment method for obtaining an amorphous refractory having excellent durability against molten metal and slag.

[0002]

2. Description of the Related Art In general, an irregular refractory material is constructed by adding water to a powder material having a controlled particle size distribution, kneading, and pouring or spraying. After the completion of molding, moisture is removed by heating, and then the temperature is raised to be used in a portion in contact with molten metal slag or the like. Strength is required in the drying process and also in the heating or preheating process, and various binders are added. Generally, gas burner heating, electric heating, or the like is applied to dry the water, but a drying method using a microwave capable of heating water which is a dielectric is also known (for example, Japanese Patent Publication No. 48-032175). , Tokkyo Sho 49-001
921). In addition, as the binder exhibiting the strength of the amorphous refractory, sodium silicate, a phosphoric acid-based inorganic binder, an organic binder containing carbon such as coal tar, coal tar pitch, or a phenol resin is used.

[0003]

Inorganic refractories are diverse in composition, and conventionally, metal oxide-based materials were overwhelmingly large in terms of the amount used, but recently, carbon-based powders have been used. There is an increasing demand for amorphous refractories to which a carbon-based binder is added. The inclusion of the carbon component has advantages such as improved durability against molten slag, improved thermal conductivity, and improved thermal shock resistance.
However, in the presence of oxygen, there is a weak point that it is oxidized and worn out at a temperature of 450 ° C. or higher and disappears. Therefore, a method has been adopted in which an antioxidant is added and applied to the surface and melted at a high temperature to form a glass layer. When carbon-containing amorphous refractory construction is dried with burner-burned exhaust gas, the surface becomes hot and has a large temperature gradient with the back surface. The back surface is 100 ° C or less, and the surface is 450 ° C even if it still contains water. As described above, oxidation occurs.

Further, when the water on the back surface is vaporized and exists near the surface where the temperature is high, steam oxidation causes
Oxidation is accelerated. When a carbon-based binder is included, the binder component melts, volatilizes, disperses, and solidifies to densify between 150 ° C and 450 ° C, so the temperature rises at the surface due to uneven temperature rise, and when solidified, the back surface The volatile components of the refractory are difficult to escape to the surface, and thus the structure of the refractory is deteriorated, such as explosion and cracking, and fine cracking due to volume change when solidified and densified.

Therefore, it is required to raise the temperature by minimizing the temperature gradient on the front surface and the back surface until the oxidation up to 450 ° C. occurs. An object of the present invention is to provide a heat treatment method for obtaining an amorphous refractory material containing a carbon-based binder, which is uniform, strong, and highly durable.

[0006]

The present invention is a method for heating an amorphous refractory material containing a carbon component using microwaves. The carbon-based binder is a powder or liquid at room temperature that plays the role of a binder containing a volatile component. Irregular refractories that contain a carbon-based binder and are added with water are irradiated with microwaves to minimize the temperature difference between the front and back surfaces, and to completely dry the moisture, then the carbon near the surface. The carbon-based binder is solidified in a temperature range that suppresses oxidative consumption of components as much as possible. Irregular refractories that do not contain water for imparting fluidity and contain solid or liquid carbon-based binders at room temperature are carbon-based within a temperature range that suppresses the oxidation and consumption of carbon components near the surface by microwave irradiation. Allow the binder to solidify. After ensuring the shape retention of the amorphous refractory, quickly raise the temperature to the heat retention temperature for use. In order to promote the elimination of water vapor and volatile components that dissipate during heating with microwaves, it is effective to flow heated air at a temperature close to that of the object to be heated.

That is, (1) by adding water to an amorphous refractory material containing a carbon-based binder, kneading the mixture, and then molding it, irradiate it with microwaves to dry the moisture, and then irradiate it continuously to obtain a back surface. In order to solidify the carbon-based binder by heating at 150 ° C. or higher and at 450 ° C. or lower on the surface. (2) After applying an amorphous refractory containing a carbon-based binder,
Irradiating with microwaves to heat the back surface to 150 ° C. or higher and the front surface to 450 ° C. or lower to solidify the carbon-based binder. (3) The above (1) by irradiating a microwave in the atmosphere,
Solidify the carbon-based binder as in (2). And a heat treatment method for an irregular refractory material.

[0008]

[Function] The heating of the substance by the microwave is roughly classified into dielectric heating and induction heating. In the case of a dielectric material having a low electric conductivity, the dielectric heating is mainly caused by heat generated by internal friction caused by vibration and rotation of molecules, and the higher the permittivity and the dielectric loss angle of the substance, the easier the heating. For this reason, water molecules and liquid organic molecules often generate heat. In the case of a conductor having a high electric conductivity, the dielectric heating causes heat generation due to a dielectric current. Induction heating is mainly used for carbon having high electric conductivity, and dielectric heating is mainly used for carbon having low electric conductivity.
As the microwave, 0.915 GHz or more is often used, and 2.45 GHz is the most common. Microwaves having a higher frequency can be used, but the penetration depth of microwaves into a substance tends to become smaller at higher frequencies.

[0009] In an irregular shaped refractory to be applied after adding water and kneading, by microwave drying, the temperature rises while being soaked, so there is little difference in physical properties between the front and back surfaces, and cracking occurs due to drying shrinkage, etc. There is also no. In addition, when carbon having good electric conductivity is included, induction heating is also added, and heating is efficiently performed in a short time. When a carbon-based binder is included, since the volatile component mainly dissipates from around 150 ° C, the temperature rises rapidly and vapor generation (water dispersal) and volatile dispersal occur at the same time. Voids and other defects are generated in the base material with low strength, and the active carbon during decomposition is oxidized by water vapor, which accelerates the oxidation and deteriorates the structure. It is essential to completely remove the moisture on the backside before the binder volatiles begin to dissipate.

In the case of microwave heating, the temperature difference between the front surface and the back surface is small and uniform heating is possible, and when the temperature reaches 150 ° C. at which the volatilization and dispersion of the surface becomes active, the back surface has already reached 1
Water has been completely dissipated at temperatures above 50 ° C. After the water is completely dissipated, the volatile components of the binder dissipate and solidify. When the surface temperature exceeds 450 ° C., the oxidation of the carbon component rapidly increases, so it is necessary to complete the solidification of the binder at 450 ° C. or lower. At that time, after the water is completely removed on the back surface at 100 ° C or higher, the volatilization dispersion and solidification of the carbon-based binder are promoted at 150 ° C or higher, so that the back surface is in the range of 150 ° C or higher and the surface of 450 ° C or lower. Can be uniformly heated to solidify the carbon-based binder stably and completely.

The temperature range in which uniform heating is particularly required is 150 ° C. or higher on the back side and 450 ° C. or lower on the front side, preferably 200 ° C. or higher on the back side and 400 ° C. or lower on the surface. FIG. 1 shows the heating behavior of a molded product using a carbon-based binder. Here, the results of the test conducted on a molded body in which carbon powder is mixed with a carbon-based binder and water are shown. The horizontal axis shows the heat treatment temperature, and the vertical axis shows the strength and the oxidation rate. After drying with water, the strength is developed by volatilization and dispersion of the carbon-based binder and solidification. 50% strength at 150 ° C, 7% at 200 ° C.
Indicates 0% strength.

On the other hand, the oxidation starts at around 400 ° C. and 4
At 50 ° C., about 5% of oxidation proceeds. Therefore, the range of uniform heating after drying water by microwave is 1
It is 50 ° C to 450 ° C, preferably 200 ° C to 400 ° C. When the carbon-based binder is contained without water, it is not necessary to remove the water, but the effect is similar to the above-mentioned case, and microwaves are used, and the back surface is in the range of 150 ° C. and the surface 450 ° C., preferably 200 ℃ or more and the surface is 400
The carbon-based binder can be solidified safely and completely by uniformly heating in the range of ℃ or less.

By uniformly heating using the microwave heating of the present invention, the carbon-based binder in the amorphous refractory can be solidified safely and completely, and the amorphous refractory having high strength and high durability can be practically used. I was able to In the case of using a carbon binder in an amorphous refractory, the addition of carbon powder tends to improve the strength of carbon bond by firing, and is often used in combination. Also, 45
When the temperature exceeds 0 ° C, it is desirable to rapidly heat to a temperature at which the effect of the antioxidant can be exhibited. At this time, the microwave is used to uniformly raise the temperature and obtain the structure having the highest durability. be able to. However, for heating at a temperature of higher than 450 ° C., it is possible to use the conventional heating method while allowing a slight decrease in characteristics because low cost is desired.

[0014]

【Example】

<Case 1> Example 1 and Comparative Example 1 are shown. As the particle size composition of the powder, the one shown in Table 1 was used.

[Table 1] To 100 parts by weight of this powder, 10 parts of pitch powder as a carbon-based binder, 1 part of antioxidant and 8 parts of water were mixed, and after kneading, vibration molding was performed to obtain 500 × 500 × 250.
A molded body having a size of mm was prepared. 500 x 500 mm
The surface was surrounded by heat insulating bricks and installed in a furnace that enables heating from the surface. The heating was performed by the following two methods. The temperature was measured by installing a temperature sensor on the surface of the molded body.

First method: 15 hours using a gas burner
Raise the temperature to 0 ° C for 1 hour, then raise the temperature to 450 ° C for 1 hour, hold for 1 hour, and then increase from 450 ° C to 1400 ° C 3
The temperature was raised over a period of time, the temperature was maintained for 1 hour, and then the furnace was cooled. Second method: irradiation with microwave (2.45 GHz), heating to 150 ° C. in 1 hour and holding for 1 hour, and then 45 in 1 hour
The temperature was raised to 0 ° C. and maintained for 1 hour. Then, using a gas burner, the temperature was raised from 450 ° C. to 1400 ° C. in 3 hours, held for 1 hour, and cooled in the furnace.

Comparative Example 1 was heat-treated by the first method, and Example 1 was heat-treated by the second method. As a method for evaluating the sample, a bending strength test was carried out after a heating experiment, and a 40 × 40 × 160 mm sample was cut out from the front surface and the back surface of the molded body and subjected to a three-point bending test. The porosity was measured using the sample after the bending test. As a result of visual observation, the surface oxidation was evaluated as × when the degree of deterioration was large and O when the degree of deterioration was small. Corrosion resistance, cut the sample from the surface and back of the molded body after heat treatment,
It was attached to the inside of a cylindrical drum and evaluated by the rotary erosion test method of refractory materials. At that time, using the slag shown in Table 2, it was carried out at 1550 ° C. for 4 hours. Slag was discharged every 30 minutes and new slag was added. After the test, the erosion amount of Comparative Example 1 was set to 100, and the erosion amounts of the following Examples and Comparative Examples were displayed as an index.

[Table 2]

The results are shown in Table 3. As for the strength after heating at 450 ° C., in Example 1, the difference between the front surface and the back surface is small and the strength is large, but in Comparative Example 1, a temperature difference is generated, the water is dissipated from the back surface, and the carbon on the surface is dissipated. Since the change occurs with the change of the system binder, deterioration of the structure occurs and the strength is low. After heating at 1400 ° C., carbon bond is generated by firing, so that the strength is improved. In Example 1 as well, a temperature difference between the front surface and the back surface is generated due to rapid heating by a gas burner at 450 ° C. or more, and the back surface on the low temperature side has lower strength than the surface. In Comparative Example 1, the temperature difference between the front surface and the back surface is large, and while the water content on the back surface still remains, the volatile components of the carbon-based binder dissipate on the surface, and the migration of water content from the back surface also changes the chemical structure. The active carbon component which is about to be oxidized is oxidized.

The surface temperature becomes 450 ° C or higher and becomes 1400 ° C.
Even if the rapid heating up to 1400 is started, there is a large difference in the physical properties between the front surface and the back surface, and defects easily occur in the tissue.
The strength after heating at ℃ is also low. The amount of erosion by the corrosion resistance test is also small in Example 1, but is large in Comparative Example 1, especially the back surface structure where the temperature timing of moisture evaporation and strength development by the binder is not appropriate, and the amount of erosion is the largest. From the above, the superiority of Example 1 in which heat up to 450 ° C. is used as much as possible by using microwaves is recognized.

<Case 2> Example 2 and Comparative Example 2 are shown.
As the particle size composition of the powder, the one shown in Table 1 was used. To 100 parts by weight of this powder, 10 parts of a powdery phenolic resin as a carbon-based binder and 1 part of an antioxidant are mixed, mixed and then pressure-molded at 500 Kg / cm ² ,
A molded body having a size of × 500 × 250 mm was produced. 5
The surface was surrounded by a heat insulating brick with a surface of 00 × 500 mm as a surface, and the furnace was installed in a furnace capable of heating from the surface. The heating method and the evaluation method were the same as in the above-mentioned example.

The results are shown in Table 3. Regarding the strength after heating at 450 ° C., the back surface of Comparative Example 2 is considerably small. This time, only the carbon-based binder is used, and if the solidification of the binder does not proceed smoothly, stable strength cannot be obtained. In Example 2 in which the solidification process of the binder up to 450 ° C. progresses uniformly, the strength after heating at 1400 ° C. is higher than in Comparative Example 2, and the dissipation of volatile components in the binder is stable, so the porosity is small. In the corrosion resistance test, the sample of Example 2 was excellent, and the sample of Comparative Example 2
The back surface of the has a low strength and a large amount of erosion. Regarding the surface oxidation, even in the case of Comparative Example 2, this sample did not add water at the time of molding, and therefore the degree of oxidation resistance was better than that of Comparative Example 1. However, in Comparative Example 2, since the dissipation of volatile components from the back surface continues even when heated to 450 ° C. or higher, the porosity is large, and compared with Example 2, it tends to be oxidized. As described above, according to the present invention, a highly durable amorphous refractory material containing a carbon-based binder can be obtained.

<Case 3> Example 3 and Comparative Example 3 will be described.
As the particle size composition of the powder, the one shown in Table 1 was used. To 100 parts by weight of this powder, 5 parts of pitch powder as a carbon-based binder and 15 parts of liquid phenol resin were added, 1 part of antioxidant was mixed, and after kneading, 500 kg / cm ²
And pressure molding was carried out to prepare a molded body having a size of 500 × 500 × 250 mm. The surface was surrounded by a heat insulating brick with a surface of 500 × 500 mm as a surface, and it was installed in a furnace capable of heating from the surface. The heating method was the same as the first method (Comparative Example 3) and the new third method (Example 3). The evaluation method was the same method as the above example.

Method 3: Irradiation with microwaves (2.45 GHz), heating to 200 ° C. for 2 hours and holding for 1 hour, and then heating to 400 ° C. for 1 hour and holding for 1 hour. Then, using a gas burner, the temperature was raised from 400 ° C. to 1400 ° C. in 3 hours, kept for 1 hour, and then cooled in the furnace. The results are shown in Table 3. The liquid carbon-based binder adheres well to the powder surface when it is sufficiently kneaded, so it is easy to develop uniform strength after firing, but on the other hand, the porosity tends to increase due to the large amount of volatile components dissipated. There is also. In Example 3, after raising the temperature to 200 ° C., emphasis was placed on uniform heating from 200 ° C. to 400 ° C.

Compared with Comparative Example 3, in Example 3 the solidification process of the binder up to 400 ° C. progressed uniformly and the oxidation was small.
The strength after heating at 400 ° C. is high, and the dissipation of volatile components in the binder is stable, so the porosity is also low. In the corrosion resistance test, the sample of Example 3 is excellent, and the back surface of Comparative Example 3 has low strength and high erosion amount. For surface oxidation,
In Comparative Example 3, since the dissipation of volatile matter from the back surface continues even when heated above 450 ° C., the porosity is large, and Example 3
Compared with, it tends to be oxidized. As mentioned above,
According to the present invention, a highly durable amorphous refractory material containing a liquid carbon-based binder can be obtained.

[Table 3]

[0024]

EFFECTS OF THE INVENTION In an amorphous refractory material containing a carbon-based binder, it is indispensable to solidify the binder in a stable manner. On the other hand, if the temperature exceeds 450 ° C. in the presence of oxygen or water, there is a problem that oxidation consumption increases. Therefore, the heating method holds an important key. In the conventional heating method using a gas burner or the like, a temperature difference occurs in the thickness direction of the construction body, and the physical properties particularly on the back surface deteriorate with the deterioration of the structure. Irregular refractory materials melt away from the surface, and when a portion near the back surface is exposed, erosion occurs at once and does not function as a refractory material. Therefore,
By adopting the heating method according to the present invention using microwaves, a uniform, strong and highly durable amorphous refractory material is obtained, and the service life is remarkably improved.

[Brief description of drawings]

FIG. 1 is a diagram showing heat treatment temperature and strength of a molded product containing a carbon-based binder, and the heat treatment temperature and the oxidation rate of the molded product.

Claims (3)

[Claims] 1. An amorphous refractory material containing a carbon-based binder,
When molding after adding water and kneading, microwave irradiation,
By drying the water and continuing irradiation,
A heat treatment method for an amorphous refractory material, which comprises heating the rear surface to 150 ° C. or higher and the front surface to 450 ° C. or lower to solidify the carbon-based binder. 2. After the amorphous refractory material containing a carbon-based binder is applied, it is irradiated with microwaves to heat the back surface at 150 ° C. or higher and the surface at 450 ° C. or lower to solidify the carbon-based binder. A method for heat treatment of an irregular shaped refractory material. 3. The heat treatment method for an amorphous refractory material according to claim 1 or 2, wherein microwave irradiation is performed in the atmosphere.