JPH07214287A - Heat insulating material of molten metal and heat insulating method using the same - Google Patents

Abstract

PURPOSE:To obtain an excellent heat insulating effect by subjecting the surface of molten metal to rapid diffusion covering and to assure an adequate working environment and to reduce a production cost by suppressing generation of smoke and dust at the time of charging a heat insulating material to the surface of the molten metal. CONSTITUTION:Lumped chaff of a grain size 0.1 to 30mm formed by subjecting the consolidated matter obtd. by subjecting dry chaff to a pressure mortar treatment and compression heating and molding treatment further to a crushing treatment is used as the heat insulating material. The surface of the molten metal, such as molten steel or molten iron, is covered by the heat insulating material consisting of such lumped chaff. The pressure mortar treatment is executed under conditions of 150 to 600 deg.C and pressure of 1 to 100ton/cm<2> at need or is otherwise executed by compressing the dry chaff to a volumetric ratio of 1/8 to 1/15 to form a compact body of a thickness 5 to 30mm and introducing this compact body between two kinds of walls moving relatively apart a spacing 5 to 30mm thereby pulverizing this body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat insulating material used to heat a molten metal such as molten iron or steel, and a heat insulating method using the same. The present invention relates to a technique for preventing heat radiation from the surface of molten metal introduced into a torpedo car, a ladle, a tundish, an ingot mold, and the like.

[0002]

2. Description of the Related Art For example, at a steel manufacturing site,
It is customary to repeatedly introduce molten pig iron or molten steel into a ladle, a tundish or the like, and then pour it into a mold. In this work process, in order to prevent rapid heat radiation from the surface of molten iron or molten steel, use of various heat insulating materials such as raw rice husks, burned rice husks, sawdust, and wood powder that can be supplied inexpensively and in large quantities. Is being considered.

Of the various heat insulating materials exemplified above, raw rice husk and burned rice husk are widely used as the most preferable heat insulating material. The main reason is
Since the rice husk, which is the material, contains a large amount of silica, the combustion duration becomes long, and since a large amount of ash is formed and a coating layer is formed on the surface of the molten iron, it has an excellent heat retaining effect. This is because an advantage can be obtained.

However, both the above-mentioned raw rice husks and burned rice husks are bulky and light, and therefore, when they are poured into molten iron or the like, they rise in an updraft due to high temperature, and
There is a problem in that the particles are scattered around and as a result, the work environment is deteriorated.

In particular, when the above-mentioned raw rice husk is put into molten iron or the like, a problem such as generation of a spark is caused, and when it is scattered, it may cause a fire and the safety of the work site is improved. It will be a big obstacle in securing. In addition, when using this raw rice husk as a heat insulating material, it is convenient to use the raw rice husk in a dry state, but it is still customary that it still contains about 12% of water. Therefore, after the raw rice husks are put into the molten iron or the like, there is a problem that smoke is generated.

As an attempt to solve the above-mentioned various problems, for example, according to JP-A-54-18429 and JP-A-50-17326, pelletized rice husks are prepared using an adhesive material. There is an attempt to use the pelletized material as a heat insulating material.

As another example, Japanese Patent Publication No. 52-374.
According to Japanese Patent Laid-Open No. 47, the unburned mineral having thermal expansion properties such as vermiculite and pearlite and the above-mentioned husks are kneaded and molded,
A technique of using the molded product thus obtained as a heat insulating material is disclosed. It is also suggested in the publication that, in actual use, the heat insulating material collapses due to thermal expansion and is pulverized, and along with this, the surface of the molten metal is coated to obtain a good heat insulating effect. ing.

[0008]

However, all of the ones disclosed in the above publications require a kneading and molding apparatus for molding a heat insulating material in the form of pellets or agglomerates, so that the equipment is complicated. At the present time, it has not been popularized because it becomes special and the equipment cost becomes high.

Further, as disclosed in each of the above publications, when using burned rice hulls, there is no problem such as smoke generation as in the case of raw rice hulls, but on the contrary, the rice husks are difficult to burn. The following problems may occur depending on the type of the object to be kept warm. That is, for example, in the manufacturing process of ultra-low carbon steel, when the chaff is added to the molten steel, a problem of carburization occurs due to the high carbon content of the chaff. However, there is a problem that its use is limited.

Japanese Patent Laid-Open No. 4-100671 discloses the use of burned rice hulls having a reduced carbon content and an increased burning degree, but a burned rice hull having such characteristics is disclosed. If it is attempted to be manufactured, it will be extremely disadvantageous in terms of cost and cannot be put to practical use.

The present invention is to deal with the above-mentioned circumstances regarding a heat insulating material and a heat insulating method for a molten metal typified by molten iron or molten steel in the manufacturing process of pig iron, steel, etc. Quickly diffuses on the surface to completely cover the surface, which provides a better heat retention effect than before, while suppressing the generation of smoke and dust to provide a suitable working environment and further reduce manufacturing costs. It is an object of the present invention to provide a heat insulating material that can be used and a heat insulating method using the same.

[0012]

In order to solve the above problems, the present invention takes the following technical means. That is, according to the invention described in claim 1 of the present application, a solidified body obtained by subjecting rice husks as a raw material to pressure crushing treatment and compression heat molding treatment is further crushed to obtain a particle size of 0.
It is characterized in that lumpy rice husks of 1 to 30 mm are used as a heat insulating material.

The invention described in claim 2 of the present application exemplifies a more preferable state of the rice husk as a raw material, and specifically, the above-mentioned rice husk is a dried rice husk.

The invention described in claim 3 of the present application exemplifies the conditions for performing the pressure crushing treatment. Specifically, the temperature is 150 to 600 ° C. and the pressure is 1 to 100 Ton.
/ Cm ² .

The invention described in claim 4 of the present application shows an example of a method different from the above-described crushing at high temperature and high pressure when performing the above-mentioned pressure crushing treatment, and specifically, Rice husk 1
By compressing to a volume ratio of / 8 to 1/15, a thickness of 5
A treatment for producing a dense body of 30 mm and a treatment for pulverizing by a shearing force and a frictional force acting on the dense body introduced between two kinds of walls which relatively move at an interval of 5 to 30 mm. It includes and.

The invention described in claim 5 of the present application relates to a heat insulating method using the above heat insulating material, and specifically, the surface of the molten metal is kept warm according to any one of claims 1 to 4. It was made to cover with material.

The invention described in claim 6 of the present application shows an example of the molten metal applicable to the invention described in claim 5, and more specifically, as the molten metal, molten iron or molten metal is used. It uses steel.

[0018]

According to the invention described in claim 1 of the present application, the lump rice husks having a particle size of 0.1 to 30 mm, preferably 0.2 to 20 mm are used as the heat insulating material. The lumped rice husk is crushed through a pressure crushing process and a compression heating molding process. Therefore,
The bulk specific gravity of this massive rice husk is significantly higher than that of conventional raw rice husks and burned rice husks, which causes the problem that the lumpy rice husks rise and rise in the rising air when they are put on the molten metal surface. It will be difficult. In addition, due to the fact that heating is performed during the above treatment, the water content of this massive rice husk is low, and there is no danger of generating a large amount of water vapor after being put into the furnace, etc. Compared to rice husk, the amount of smoke generated is greatly reduced.

Further, this lumped rice husk is obtained by subjecting the rice husk, which is a raw material, to the above-mentioned treatments only, and is not subjected to firing or the like, and is not kneaded with other substances. It means that it does not contain harmful ingredients. Therefore, unlike the case of using the conventional chaff, there is no risk of carburizing due to the large amount of carbon contained, and even when producing low carbon steel, high quality steel can be obtained. Become. Further, since it is not necessary to use a complicated and special kneading and molding apparatus, the manufacturing cost is reduced, which is extremely advantageous in practical application. Furthermore, when the molten rice is poured onto the surface of the molten metal, the massive rice husks are rapidly diffused to the surface, and the surface is completely covered with the heat-insulating effect. In this case, if the grain size of the lumped rice husks is less than 0.1 mm, the rise and scattering at the time of charging will be large, and if the grain size is larger than 30 mm, it will not be uniformly diffused and will completely cover the surface of the molten metal. It becomes impossible to do so, and the heat retaining effect is hindered.

As described above, according to the first aspect of the present invention, by using the massive rice husks obtained by compression pulverization or the like as the heat insulating material, the high heat insulating property originally possessed by the rice husks is maintained. As a result, the molten metal surface is rapidly disintegrated and diffused, and the amount of dust and smoke generated can be reduced as much as possible. In addition, since a special kneading and forming device is not required, the manufacturing method is simplified and the cost is low, and the low carbon content causes the problem of carburization during the production of ultra-low carbon steel. It will be avoided.

According to the invention described in claim 2 of the present application,
As the rice husk that is the above-mentioned raw material, since the dried rice husk, for example, the dried rice husk having a water content of about 10 to 20% is used, it is possible to appropriately prevent the excessive water content of the lumped rice husk which is the final product. Even if the heating temperature at the time of the above treatment is not significantly increased, the water content of the lumped rice husk is sufficiently reduced, and a more preferable effect for preventing smoke generation can be obtained.

According to the invention described in claim 3 of the present application,
Not only the compression molding treatment is carried out under heating, but also the heating and crushing treatment is carried out under the temperature condition of 150 to 600 ° C. As a result, the moisture content of the massive rice husk is reduced to about 7%. To do. Therefore, taking into consideration that the moisture content can be reduced to only about 12% by simply drying the raw rice husks, the generation of smoke due to the moisture content can be suppressed as much as possible. The heating temperature during the compression molding treatment is 1 as in the above case.
It is preferably 50 to 600 ° C.

In this case, if the temperature is lower than 150 ° C.,
The rice husk that is the raw material does not have a sufficient heating action, resulting in adverse effects such as inadequate removal of water, and when the temperature exceeds 600 ° C, the rice husk is burned and the carbon content increases. And the like, or a problem of equipment for high heating occurs. Furthermore, in addition to such temperature conditions, pressure crushing treatment is performed under a pressure of 1 to 100 ton / cm ² , but if the pressure is less than 1 Ton, the pressing force is insufficient and the lumpy rice husks of sufficient density are obtained. In addition, when it exceeds 100 Ton, the fiber structure of the rice husk as a raw material is adversely affected, or a problem of equipment for high pressurization occurs.

According to the invention described in claim 4 of the present application,
The rice husk, which is the raw material, is compressed and the volume ratio is 1/8 to 1/1
5, the bulk specific gravity of the massive rice husks is 0.4 to 0.
In consideration of the fact that the bulk specific gravity of conventional raw rice husks and burnt rice husks is 0.1, the bulk specific gravity of the massive rice husks is about 4 times, and the bulk density increases at the time of input. It is a value that can appropriately prevent soaring due to the air flow.
And, by receiving such a pressure treatment, a thickness of 5 to 30 which is a convenient size for the subsequent handling.
mm mm dense body is produced. In addition, this dense body is 5
It is pulverized by being subjected to a shearing force and a frictional force by two kinds of walls which move relative to each other with a distance of 30 mm. In this case, if the distance between the two types of walls is less than 5 mm, the amount that can be processed becomes small, and the crushing efficiency is significantly reduced. If the distance is greater than 30 mm, the average of the total thickness is obtained. The shearing force does not act on the densified material, resulting in a large variation in particle size after pulverization. After this, 150-60
A solidified body is produced by heating and compression molding under a temperature condition of 0 ° C., and the solidified body is further crushed to obtain the above-mentioned lumped chaff.

Comparing the lumped rice husks obtained as described above with the conventional husks, as shown in Table 1 below, the large sized rice husks having a particle size of 1.7 mm or more are the lumped rice husks. Is overwhelmingly large, and therefore it is difficult for the powder to rise up due to the large amount of powdery material, and the bulk specific gravity is much higher for the bulky rice husks as described above, so scattering immediately after charging to the molten metal surface is effective. To be prevented.

[0026]

[Table 1]

On the other hand, according to the invention described in claim 5 of the present application, since the surface of the molten metal is covered with the massive rice husk having the excellent heat retaining effect as described above, the surface is completely covered. As a result, the working environment is improved because the adverse effects of dust and smoke are eliminated.

According to the invention of claim 6 of the present application, since the surface of molten iron or molten steel is covered with the above-mentioned massive rice husks, sufficient heat retention for molten iron or the like at the steel manufacturing site is carried out. The effect is obtained, and the working environment at the steel manufacturing site is improved.

From the practical point of view, it is effective to cover the surface of the molten iron or steel with the lumped rice husks, but the surface of the molten metal made of other ferrous alloys, non-ferrous alloys or the like should be covered with the lumped rice husks. It can be inferred that the same effect can be obtained by covering with.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings, but the present invention is not limited to these embodiments.

FIG. 1 shows an example of a manufacturing apparatus for manufacturing the heat insulating material according to the present invention. The manufacturing apparatus 1 includes a first member 2 having a cone-shaped inner surface, and a second member 3 having a cone-shaped outer surface arranged inside the first member 2 so as to have the same axis. An outlet hole 4 is opened at the tip of the first member 2, and
The inner surface of the first member 2 is provided with unevenness 5 at least at the tip side portion thereof. The irregularities 5 are formed in a spiral convex shape.

On the other hand, a spiral ridge 6 is formed on the outer surface of the second member 3. The spiral projection 6 of the second member 3
Has a function of sending the dried rice husks introduced into the annular space 7 between the first member 2 and the second member 3 to the tip outlet side by spiral feeding, and the first side at the tip side portion of the annular space 7. It has a function of applying a shearing force to the dense body in cooperation with the unevenness 5 on the member 2 side. Further, the first member 2 and the second member 3 are relatively rotated around the common axis center when either or both of them are rotationally driven. The direction of this relative rotation takes into consideration the direction of the spiral of the spiral ridge 6 provided on the outer surface of the second member 3, and the dry chaff put between both members 2 and 3 is accompanied by the relative rotation of both. It goes without saying that it should be sent to the exit side.

The annular space 7 between the first member 2 and the second member 3 has a cross-sectional area in the direction orthogonal to the axis thereof in the vicinity of the inlet (cross section aa) to the vicinity of the exit (cross section b-b). ) Is 1/12
Is set to be Furthermore, the annular space 7
The thickness in the vicinity of the outlet is set to 20 mm. The ratio of the vicinity of the inlet and the vicinity of the outlet is 1/8 to 1 /
Other ratios may be used within the range of 15, and the thickness of the annular space 7 near the outlet may be within the range of 5 to 30 mm.

[Manufacturing Example 1 of Heat Insulating Material] As Manufacturing Example 1, a heat insulating material was manufactured using the manufacturing apparatus 1 having the above structure. In the manufacturing process, first, dry rice husks are put into the inlet of the annular space 7, and the dried rice husks are sent to the vicinity of the outlet of the annular space 7 as the members 2 and 3 rotate relative to each other. During this period, the dry chaff is compressed to a volume ratio of 1/12 to obtain a dense body having a thickness of 20 mm. Due to the relative rotation of the members 2 and 3, the shearing force and the frictional force uniformly act on the dense body over the entire area in the thickness direction thereof, so that the dry rice husk as a material is effective. It is crushed into fine powder. The fine powder thus obtained is discharged from the outlet hole 4 of the first member 2.

The fine powder was introduced as an intermediate product into a compression molding machine at a temperature of 250 ° C. to 400 ° C. to obtain a cylindrical solidified body of crushed rice husks. In the compression molding machine used here, for example, a tubular sleeve having an inner surface having substantially the same diameter as the outlet hole 4 is continuously provided at the outlet hole 4 of the first member 2 of the manufacturing apparatus 1 and the tubular sleeve is provided. A heater is installed around the outside of. Further, a screw that is integrally rotatable with the second member 3 is provided in the inner space of the tubular sleeve, and the second member 3 and the screw are relatively opposed to the first member 2 and the tubular sleeve. By the pushing force caused by the rotation, the aggregate of the fine powder is compressed, and the cylindrical solidified body is obtained. The cylindrical solid body obtained at this time had a diameter of 75 mm and a length of 50 to 80.
mm. Then, the cylindrical solid body was further pulverized with a swing hammer mill (D810 type swing hammer mill manufactured by Takeuchi Iron Works Co., Ltd.) and classified using a sieve having 70 mesh, 50 mesh or 4 mesh, nominal size 16 mm, As a result, a particle size of 0.2-5 mm and a particle size of 0.3
Two types of massive rice husks of ˜16 mm were obtained.

[Production Example 2 of heat insulating material] As Production Example 2, a rice husk crushing machine (Huskmaster SHC400B manufactured by Satake Manufacturing Co., Ltd.) having the same configuration as that described in Japanese Patent Publication No. 62-61342. The dried rice husks were used for pressure crushing and compression molding to obtain a cylindrical solidified body of crushed rice husks having a diameter of 75 mm and a length of 50 to 80 mm.
This cylindrical solidified body was further pulverized with a swing hammer mill (D810 type swing hammer mill manufactured by Takeuchi Iron Works Co., Ltd.) and classified in the same manner as in Production Example 1 above, so that particle diameters of 0.2 to 5 mm and 0.3 were obtained. Two types of massive rice husks of ˜16 mm were obtained.

[Example 1] As Example 1 which is a heat retaining method using the above heat retaining material, in a 85 ton ladle (diameter 2.8 m) containing molten steel melted in a converter, 60 kg of massive rice husks having a particle size of 0.2 to 5 mm obtained in the above Production Example 1 was charged. The temperature of the molten steel at this time was 1570 ° C. After this addition, the above-mentioned massive rice husks were completely diffused to uniformly coat the surface of the molten steel in the ladle. And 3
The state of temperature drop of the molten steel after 0 minutes and the state of dust generation when the massive rice husks were charged were observed. The results are shown in Table 2 below.

Example 2 As Example 2, 60 kg of massive rice husks having a particle size of 0.2 to 5 mm, obtained in Production Example 2 above,
In the same manner as in Example 1 above, the molten steel was put into a ladle. As a result, the surface of the molten steel in the ladle was uniformly covered with the above-mentioned massive rice husks. Then, the temperature drop state of the molten steel after 30 minutes and the dust generation state at the time of introducing the lumps of rice husks were observed. The results are shown in Table 2 below.

[Example 3] As Example 3, 60 kg of massive rice husks having a particle size of 0.3 to 16 mm obtained in Production Example 1 above was prepared.
In the same manner as in Example 1 above, the molten steel was put into a ladle. As a result, the massive rice husks uniformly covered the surface of the molten steel. And the temperature drop situation of the molten steel after 30 minutes,
The state of dust generation when lumpy rice husks were added was observed. The results are shown in Table 2 below.

Example 4 As Example 4, 60 kg of massive rice husks having a particle size of 0.3 to 16 mm, obtained in Production Example 2 above,
In the same manner as in Example 1 above, the molten steel was put into a ladle. As a result, the massive rice husks uniformly covered the surface of the molten steel. And the temperature drop situation of the molten steel after 30 minutes,
The state of dust generation when lumpy rice husks were added was observed. The results are shown in Table 2 below.

[Comparative Examples 1 and 2] In Comparative Examples 1 and 2, which are used as the criteria for judging the heat retaining effect of Examples 1 to 4, raw rice husks and burned rice husks are used as the heat insulating materials instead of the massive rice husks did. Then, the raw rice husks and the burned rice husks were placed in a ladle containing molten steel in the same manner as in Example 1. In this case, the temperature drop state of the molten steel after 30 minutes and the dust generation state when the rice husks were charged were observed. The results are shown in Table 2 below.

[0042]

[Table 2]

As is clear from Table 2 above, in all of Examples 1 to 4 according to the present invention, the degree of temperature drop with the passage of time is small, and therefore an excellent heat retaining effect is exhibited. In the case of the raw rice husks of Comparative Example 1, the degree of temperature drop is large, and in the case of the burned rice husks of Comparative Example 2, almost the same degree or slightly large.

Further, in each of the above-mentioned Examples 1 to 4, dust was not generated at the time of charging into molten steel, and a preferable work in terms of hygiene can be performed, whereas in Comparative Examples 1 and 2, dust was generated. However, it becomes a factor that deteriorates the work environment.

Further, in all of the above Examples 1 to 4, the generation of smoke can be suppressed to a slight amount, whereas in the case of the raw rice husks of Comparative Example 1, the degree of smoke generation is severe. become. In addition, in the case of the burned rice hulls of Comparative Example 2, although the generation of smoke can be suppressed to a slight amount, it is inferior in terms of the above-mentioned temperature drop and generation of dust, and the invention of the present application is comprehensively considered. It is clear that Examples 1 to 4 according to 1) have far superior properties.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view of an essential part showing an example of a manufacturing apparatus for manufacturing a heat insulating material according to the present invention.

[Explanation of symbols]

 1 Manufacturing apparatus 2 One wall (first member) that relatively moves 3 The other wall (second member) that relatively moves 7 Between two types of walls (annular space)

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Claims (6)

[Claims] 1. A heat insulating material using rice husks as a raw material, which is used for keeping a temperature of a molten metal, wherein a solidified body obtained by subjecting the raw rice husks to a pressure crushing treatment and a compression heating molding treatment, A heat-insulating material for molten metal, characterized by being lumped rice husks having a particle size of 0.1 to 30 mm obtained by further crushing treatment. 2. The heat insulating material for molten metal according to claim 1, wherein the rice husk is dry rice husk. 3. The pressure crushing treatment is performed at a temperature of 150 to 60.
The heat insulating material for molten metal according to claim 1 or 2, which is performed under the conditions of 0 ° C and a pressure of 1 to 100 Ton / cm ² . 4. The rice husk is ⅛ to 1 in the pressure crushing treatment.
5 to 30 mm by compressing to a volume ratio of / 15
And a process of pulverizing the dense body by a shearing force and a frictional force acting on the dense body, which are introduced between the two kinds of walls that relatively move at an interval of 5 to 30 mm. The heat insulating material for molten metal according to claim 1 or 2, characterized in that 5. A method for retaining heat of molten metal, characterized in that the surface of the molten metal is covered with the heat retaining material according to claim 1, 2, 3 or 4. 6. The method for keeping heat of molten metal according to claim 5, wherein the molten metal is molten iron or molten steel.