KR20070022186A - Filler for ladle sliding and opening/closing device - Google Patents

Abstract

Alkali feldspar with a particle size distribution of 0.3 to 1.7 mm is obtained by external addition of 40 to 100 mass% of silica sand with a particle size distribution of 0.3 to 1.7 mm and 60 to 0 mass% of chromite sand with a particle size distribution of 0.1 to 0.85 mm. Filler for ladle sliding switchgear characterized in that the amount is made so as to be 0.3 to 1.5% by mass.

Description

Filler for ladle sliding opening and closing device {Filler for ladle sliding and opening / closing device}

The present invention relates to a filler for a ladle sliding switchgear. More specifically, in the steelmaking process, the present invention is difficult to dissolve by molten steel flowing in the ladle, sintering and molten steel are difficult to penetrate, and the ladle sliding to drop and open holes easily in tundish. It relates to a filler for a switchgear.

In the conventional steelmaking process, a ladle sliding opening and closing device (sliding nozzle or rotary nozzle) is employed for the ladle receiving molten steel. In order to prevent the molten steel from solidifying in the nozzle, the ladle having the ladle sliding opening and closing device needs to fill the nozzle with a filler for the ladle sliding opening and closing device made of fire-resistant granules before taking the molten steel. As the filler, natural silica sand, chromite yarn, zircon yarn, alumina yarn and the like are known, and among these, natural silica yarn, chromite yarn and mixtures thereof are widely used.

In general, natural silica yarns have a relatively high proportion of thick sintered layers formed of molten steel and the formation of unopened pores. Since this unopened hole would interfere with the molten steel discharge of the ladle, the operator had to insert a pipe into the nozzle to open the hole by oxygen cleaning.

However, this work not only brings about the temperature drop of molten steel but is also extremely dangerous work, and in view of the prevention of labor accidents, it is assumed that 100% is the rate at which open holes do not occur (hereinafter referred to as porosity). Is required.

In addition, the unopened holes generated in the nozzle in today's continuous casting equipment caused many troubles in the operation.

In addition, the filler for the ladle sliding switch is required to form a sintered layer of a suitable thickness early by the molten steel surface layer. The reason is that molten steel penetrates into the filling material for the ladle sliding switchgear which does not generate any sintered layer, and there is a possibility that a hole which does not open is formed by forming a penetration layer in which the ladle sliding switch filling material and the molten steel are mixed. to be.

Conventionally, as a filler for a ladle sliding switch, Japanese Patent Application Laid-Open No. 62-244570 (Patent Document 1), Japanese Patent Application Laid-Open No. Hei 1-80776 (Patent Document 2) or Patent No. 3056260 by the present inventors What is described in the publication (patent document 3) is known.

Japanese Patent Application Laid-Open No. 62-244570 discloses a mixture of silica yarns having a content of SiO ₂ of 96% by mass or more and an Al ₂ O ₃ content of 2.0% by mass or less, and the particle size distribution of the mixture has a particle size distribution of 0.71 to 1.68 mm. A filler for a ladle sliding switchgear having 60 to 75 mass% of silica yarn, 25 to 40 mass% of silica yarn having a particle size distribution of 0.10 to 0.71 mm, and 5 mass% or less of silica yarn having a particle size distribution of less than 0.1 mm is disclosed.

Further, Japanese Patent Laid-Open No. Hei 1-80776 discloses a filler for a ladle sliding switchgear having a particle size of 2.38 to 0.125 mm and a porosity of 25 to 50%. Even such a filler for conventional ladle sliding switchgear may generate a hole which does not open, and it was not enough to be satisfied.

In addition, in Patent Publication No. 3056260 by the present inventors, in order to form an appropriate sintered layer, it is preferable to use chromite yarn, so that the ladle composed of chromite sand of 70 to 90 mass% and silica sand of 10 to 30 mass%. A filler for a sliding switch is proposed.

However, the use of a large amount of chromite yarn as in the above patent is concerned about the pollution problem of hexavalent chromium generated at a higher temperature than this, and may tend to keep the use away from the steelmaking process. For this reason, the filler for the ladle sliding switchgear which restrict | limited the use of chromite company as much as possible is calculated | required.

[Initiation of invention]

The inventors of the present invention have found that the thickness of the sintered layer can be unexpectedly adjusted by adding feldspar to the filler for ladle sliding switchgear including silica and chromite yarn.

That is, according to this invention, the particle size distribution is 0.3-1.7 by the external addition of the yarn which consists of 40-100 mass% of silica yarns whose particle size distribution is 0.3-1.7 mm, and 60-0 mass% of chromite yarns whose particle size distribution is 0.1-0.85 mm. Filler for ladle sliding switchgear is provided by mixing 1.7mm feldspar so that the total alkali amount is 0.3 ~ 1.5% by mass.

Best Mode for Carrying Out the Invention

First, the filler for the ladle sliding opening and closing device of the present invention (hereinafter referred to as filler) is composed of silica sand, chromite sand and feldspar with a specific particle size distribution, and also contains a specific amount of the total alkali amount. In the present specification, the total alkali amount refers to the total amount of K ₂ O and Na ₂ O contained in the entire filler.

The silica yarn used in the present invention has a particle size distribution of 0.3 to 1.7 mm, preferably 0.6 mm to 1.7 mm, more preferably 0.9 to 1.5 mm. This is because the particle size distribution has a lower limit of 0.3 mm because the layer thickness of the sintered layer increases at an overpressure distribution of less than 0.3 mm, which causes the nozzles to not open when the molten steel is injected. On the other hand, the particle size distribution is 1.7 mm at the upper limit, because in the particle size distribution larger than 1.7 mm, molten steel mixed with silica condensates due to infiltration, which also generates holes that do not open in the nozzle. In this invention, the silica yarn of particle size distribution different from the said range can be mix | blended. In particular, the use of a mixture of silica particles having a particle size distribution of 1.2 to 1.7 mm, silica particles having a particle size distribution of 0.9 to 1.2 mm, and silica particles having a particle size distribution of 0.3 to 0.9 mm can improve the packing density and prevent penetration of molten steel. At the same time, it is possible to form a sintered layer of an appropriate thickness. It is preferable to use the silica yarn of 100 mass% of the yarn of the particle size distribution of the range of 0.425-1.18 mm substantially.

Here, in this specification, particle size distribution means the value measured according to the particle size test method (Z2602) of the casting company by Japanese Industrial Standard (JIS). To explain this method schematically, a nominal size of sieve superimposes a 1.7 mm sieve on a 0.3 mm sieve, places a silica yarn on a 1.7 mm sieve, and a sieve such as a low-tap sieve machine. Using the sorting machine, the silica yarn remaining between the two sieves is the silica yarn of the present invention.

In addition, the particle size distribution of chromite yarn and feldspar mentioned later is the same except changing the nominal size of a sieve.

The particle shape coefficient of silica is 1.4 or less, Preferably it is the range of 1.2-1.4. By setting the granularity coefficient to 1.4 or less, it is possible to prevent penetration of molten steel without lowering the packing density. In other words, as the number of vertical shapes decreases, the filling density becomes high and the voids in the nozzles decrease, so that the borrowing of molten steel is reduced. The voids formed by the filler are preferably in the range of 30 to 35% when expressed as porosity.

In the present specification, the vertical coefficient refers to a value calculated using a yarn surface area measuring instrument (manufactured by George Fisher). That is, the granularity coefficient refers to a value obtained by dividing the actual four particle surface area per theoretical surface area per gram. Here, the theoretical surface area refers to the surface area in the case where the four particles are assumed to be total spherical. Therefore, the closer to 1, the closer the shape is to the sphere.

In addition, the chemical components contained in the silica used is the content of SiO ₂ more than 95% by weight, preferably not less than 96% by mass.

In the present invention, the silica yarn is not particularly limited as long as it satisfies the above conditions of the particle size distribution, the particle size coefficient and the content of SiO ₂ , and natural silica yarn can be used.

In general, depending on the silica to live Fields, the content of SiO ₂ is distributed in 90 to 99% by weight. In particular, the SiO ₂ content of silica manufactured in Japan is distributed in 90 to 97 mass%, and the SiO ₂ content of silica produced in overseas is distributed in 95 to 99.8 mass%.

As described above, since natural silica yarns vary in content of chemical components depending on the production site, it is preferable to mix these silica yarns in an appropriate manner so as to satisfy the particle size distribution, the grain size coefficient, and the content of SiO ₂ .

Next, the chromite yarn used in the present invention has a particle size distribution of 0.1 to 0.85 mm, preferably 0.3 to 0.6 mm. The blending ratio of this chromat company is 0-60 mass%. Moreover, the filler of 100 mass% of silica sand can be used, without using chromite yarn according to the operating conditions of a steelmaking process.

Here, if the particle size distribution is less than 0.1 mm of chromite yarn, the particle size of the chromite yarn is smaller than that of the silica yarn, and it is difficult to mix the silica yarn uniformly.

On the other hand, when the particle size distribution is between chromites larger than 0.85 mm, the filling property (filling density) is lowered, and molten steel penetrates and coagulates in the voids to form a strong sintered layer, which is not preferable as a filler.

In particular, it is preferable to use the chromite yarn containing 95 mass% or more of the yarns of the particle size distribution of the range of 0.15-0.85 mm, and 65 mass% or more of the yarns of the particle size distribution of the range of 0.212-0.425 mm. In addition, it is preferable to use the yarn whose particle size distribution is less than 0.15 mm, and 5 mass% or less. This is because when the particle size distribution is less than 0.15 mm, which exceeds 5%, unopened holes due to increased sintering properties are likely to occur.

It is also known that the chromite yarn used in the present invention has fire resistance up to about 2,150 ° C., but the sinterability increases as the particle diameter decreases.

In addition, this chromite yarn will not be specifically limited if it satisfy | fills the conditions of the said particle size distribution. Chromite is mainly produced in South Africa, and is used for castings, metallurgy, and chemical uses, but any of these uses can be used in the present invention. Moreover, what is naturally produced can be used as it is.

In addition, the mixing ratio of silica yarn and chromite yarn is 40-100 mass% and 60-0 mass%, respectively, Preferably it is 50-100 mass% and 50-0 mass%. By reducing the mixing ratio of chromite as much as possible, minimizing the use of chromite which may cause industrial pollution such as hexavalent chromium, and reducing the steelmaking cost by using a lot of relatively inexpensive silica yarn. We can plan.

In the present invention, feldspar is added to the filler to adjust the amount of alkali. Here, the silica yarn usually contains an alkali amount, but the filler having the alkali amount contained in the silica yarn without adding feldspar as the scope of the present invention and the filler having the alkali amount as the range in the present invention by adding feldspar In the case where the alkali amounts of both fillers are the same, the latter has an effect superior to the former in that the thickness of the sintered layer can be appropriately adjusted.

In addition, the feldspar used in the present invention has a particle size distribution of 0.3 to 1.7 mm, preferably 0.5 to 1.0 mm, depending on the blending ratio of silica and chromite yarns, and the total alkali amount which is the sum of K ₂ O and Na ₂ O of the entire filler. Since it is externally added so that it is 0.3-1.5 mass%, Preferably it is 0.3-1.2 mass%, the thickness of a sintered layer can be adjusted suitably.

It is preferable that feldspar to add is kali-feldspar. These caliber feldspars include but are not limited to feldspars, silt calibers, sanidines, ice feldspars, and the like. Moreover, it is also possible to use these individually or in combination of 2 or more types.

In the present invention, the particle size distribution of feldspar is limited to a range of 0.3 to 1.7 mm, because if the particle size distribution is less than 0.3 mm, the sintered layer may be formed rapidly, and the hole may not be opened by the strong sintered layer. On the other hand, if the feldspar has a particle size distribution larger than 1.7 mm, it may require more time than necessary to form an appropriate sintered layer, or the sintered layer may become soft, causing molten steel to easily penetrate and cause unopened holes. to be.

Here, since the silica yarn contains alkali powder, it is preferable to adjust suitably so that the total alkali amount may become the range of this invention according to the alkali quantity of the silica yarn to be used.

In addition, in order to make constant the quality of the silica sand, chromite sand and feldspar, grinding sand may be used. In addition, it is natural that 2 or more of the yarn which was not pulverized can be mixed and used.

Any known dry method or wet method can be used for the grinding treatment.

In the dry method, a pneumatic scrubber, such as a sand reclaimer, in which a raw material sand is raised in the apparatus by high velocity airflow and collided with a collision plate, is pulverized by collision and friction between the four particles. The high-speed rotating scrubber apparatus and the four particles which grind | pulverize by the collision and friction which throw in a raw material sand on the apparatus and the rotor which rotates at high speed, and the throwing sand which generate | occur | produces by the centrifugal force and falling input sand And a method using a high speed stirrer such as an agitator mill which is pulverized by friction.

On the other hand, in the wet method, the method by the grinder | pulverizer, such as a truce type | mold which grind | pulverizes by the four particle mutual friction in the trough which rotated the blade | wing, is mentioned.

Of these grinding treatments, it is preferable to use a wet method. This is because water washing at the time of pulverization can remove yarns smaller than a desired particle size at the same time. However, even with the dry method, the yarn of the present invention can be obtained by providing a water washing device in parallel.

In general, it is known that in the filler, if the wettability (inverse of the value repulsing molten steel) other than the fire resistance to molten steel is high, a sintered layer which causes a hole which does not open is likely to occur.

As a method of improving this wettability, the method of externally adding the powder of carbon (for example, impression graphite, earth graphite, carbon black, etc.) to a nozzle filler is known. Specifically, a method of simply mixing carbon (Japanese Patent Laid-Open Publication No. Hei 6-71424), a method of bonding carbon to a yarn using an adhesive as a binder (Japanese Patent Laid-Open Publication No. Hei 10-58126), and A method of coating or adhering carbon on the surface of aggregates by stirring the nozzle filler material, that is, the aggregate by charging the aggregates, that is, the static electricity by charging the aggregates, and then adding carbon to the aggregates (Japanese Patent Laid-Open No. 2000-317625). Etc.

Also in the present invention, carbon black can be electrostatically coated on the surface of silica, chromite, or feldspar. Although carbon black which can be used is not specifically limited, A well-known thing may be sufficient, but it is preferable to use granular carbon black from a viewpoint of a hygiene, a performance of a filler, and a cost. It is more preferable to use what was obtained by granulating by a dry method or a wet method, for example. It is preferable that it is 2000 micrometers or less, and, as for this particle size distribution, it is more preferable that it is 250-2000 micrometers.

Although it does not specifically limit as a method of electrostatically coating carbon black on the surface of silica yarn, chromite yarn, or feldspar, For example, a ribbon type blender separates silica yarn, chromite yarn, or feldspar from the same apparatus. After charging by stirring separately or simultaneously, carbon black is added, followed by further stirring to electrostatic coating. In this case, the potential of static electricity generated in the filler by stirring has an amount of static electricity corresponding to a potential of -0.1kv or more, but preferably it is in the range of -0.1 to -0.05kv. By having a potential of -0.1 kv or more, it is possible to obtain a filler substantially free of free carbon. In addition, by this agitation, carbon black is electrostatically coated on the entire surface or part of the filler.

Carbon black reduces the generation of free carbon and is used in amounts to obtain fillers of desired properties. Specifically, since the alkali amount of silica used in the present invention is in the range of 0.3 to 1.5%, the amount of carbon black added may be 0.3 to 1.0 mass%, preferably 0.5 to 0.9 mass%, based on the filler.

When the addition amount of carbon black exceeds 1.0 mass% with respect to the filler, it becomes difficult to form a sintered layer by the action of carbon, and it becomes the cause of the opening which does not open, and carburization is produced when manufacturing ultra low carbon steel. It is accelerated and a problem arises on the composition of molten steel.

The shape of the ladle sliding opening and closing apparatus using the filler of the present invention, the kind of molten steel, and the like are not particularly limited. In addition, silica sand and chromite sand or feldspar with or without electrostatic coating with carbon black can be filled into the ladle sliding switch separately, respectively, but since they are good in mixing, it is necessary to fill them with uniform mixing. It is good for improving sex.

1 is a graph showing the particle size distribution of chromite yarn and silica yarn constituting the filler for ladle sliding switchgear used in Example 2. FIG.

Next, although the specific shape of this invention is demonstrated by an Example, this invention does not receive any limitation by these Examples.

In addition, the chemical compositions of silica yarn, chromite yarn and feldspar used in the following examples are shown in Tables 1-3.

Furtherance mass% SiO ₂ 97.69 Al ₂ O ₃ 0.85 Fe ₂ O ₃ 0.70 CaO 0.16 MgO 0.27 Na ₂ O 0.07 K ₂ O 0.23

Furtherance mass% Cr ₂ O ₃ 47.03 Fe ₂ O ₃ 26.94 Al ₂ O ₃ 14.23 MgO 9.49 SiO ₂ 0.48

Furtherance mass% SiO ₂ 74.7 Al ₂ O ₃ 13.3 Na ₂ O 2.7 K ₂ O 7.5

In addition, in the case of feldspar having the chemical composition shown in Table 3, since the sum of K ₂ O and Na ₂ O, which are alkali powders, is 10.2% by mass, the amount of alkali increases by adding 1% by mass of feldspar to the filler.

Example 1

As a ladle of molten steel, a hole having an internal diameter of 50 mm and a height of 30 mm was opened at the bottom of a high frequency furnace having a capacity of 30 kg, and various silica yarns having different particle size distributions were filled therein as fillers. After molten steel of 1650 degreeC was inject | poured here and hold | maintained for 1 hour, the thickness of the sintered layer was measured. Table 4 below shows the relationship between the silica yarn content with a particle size distribution of less than 0.3 mm and the layer thickness of the sintered layer, and Table 5 shows the relationship between the silica yarn content with a particle size distribution larger than 1.7 mm and the layer thickness of the sintered layer. . In addition, the particle size coefficient of the used silica company is 1.21.

Silica yarn content of less than 0.3mm (mass%) Sintered Layer Thickness (mm) 0 2.0 5 3.5 10 5.8 20 12.8

Silica yarn content larger than 1.7mm (mass%) Sintered Layer Thickness (mm) 0 2.8 5 4.7 10 7.0 20 15.4

In Table 6, a hole having an inner diameter of 30 mm and a height of 30 mm was opened under a sand mold having an inner diameter of 150 mm and a height of 100 mm, filled with various silica yarns as a filler therein, and then injected and cooled by molten steel at 1650 ° C. The thickness (layer thickness of the penetration layer) which molten steel penetrated into was measured, and the relationship between the particle size coefficient of a silica company and the layer thickness of a penetration layer was shown. In addition, the particle size distribution of the used silica yarn is 0.3-1.7 mm.

Vertical coefficient Penetration layer thickness (mm)  1.2 5.7  1.3 5.9  1.4 6.1  1.5 9.6  1.6 11.4  1.7 13.4

As is apparent from Table 4, the layer thickness of the sintered layer increases as the content of silica yarn having a particle size distribution of less than 0.3 mm increases. Further, as is apparent from Table 5, the layer thickness of the sintered layer increases as the content of silica yarn having a particle size distribution larger than 1.7 mm increases. The increase in the layer thickness of such a sintered layer means that a hole which does not open in a nozzle tends to be formed in accordance with sintering of silica yarn generated at the time of molten steel injection of a real material.

In addition, as apparent from Table 6 above, the layer thickness of the penetration layer of the molten steel increases as the grain coefficient becomes higher with the grain coefficient 1.4 of silica. This means that the filling density is lowered when the standing coefficient is larger than 1.4, so that penetration of molten steel occurs easily, and as a result, an open hole of the nozzle is likely to be formed.

Next, the relationship between the particle size distribution of feldspar and the sintered layer was measured using the same method as the said high frequency furnace. In this test, 9 mass% of feldspar was added to silica, the alkali amount was set to 1.2 mass%, and 5 test results were calculated, respectively. The particle size distribution of feldspar used in Table 7 and its result are shown. The particle size distribution and particle size coefficient of the used silica are 0.3-1.7 mm and 1.21, respectively.

Comparative Example 1 Comparative Example 2 Example 1 Particle size distribution of feldspar mass% mass% mass% Less than 0.4mm 20 0 0 0.4 ~ 1.2mm 80 80 100 Greater than 1.2mm 0 20 0 Thickness of sintered layer (mm) 20-28 10-17 12-13

In addition, the particle size distribution of feldspar used in Example 1 is shown in Table 8.

Particle size distribution (mm) mass% 1.7 ~ 0 1.18 ~ 23.3 0.85- 38.3 0.6 ~ 33.5 0.425 ~ 4.8 0.3 ~ 0.1

As apparent from Table 7 above, by using feldspar having a particle size distribution of 0.3 to 1.7 mm, variations in the layer thickness of the sintered layer can be reduced, and generation of holes that do not open can be suppressed.

Example 2

As shown in Table 9, a filler containing chromite and feldspar was filled in a ladle sliding switch equipped with a 250 t ladle, and molten steel at 1680 ° C. was injected into the ladle and maintained for 1 to 3 hours. After that, the cycle of taking out the molten steel from the ladle sliding switch was repeated 200 times, and the number of times the nozzle was not opened was measured. Table 9 shows the value obtained by dividing the number of times by 200 as the porosity. Incidentally, the particle size distributions of silica, chromite, and feldspar are 0.3 to 1.7 mm, 0.1 to 0.85 mm, and 0.3 to 1.7 mm, respectively, and Fig. 1 shows a graph of the particle size distribution of chromite and silica. Specific particle size distribution of feldspar is shown in Table 8.

Filler composition (mass%) Alkali amount (mass%) Opening rate (%) Silica yarn Chromite Feldspar addition amount 100 0 0 0.3 98.3 100 0 2.0 0.5 98.8 100 0 9.0 1.2 100.0 100 0 12.0 1.5 99.1 80 20 0.6 0.3 98.4 80 20 2.5 0.5 98.8 80 20 6.5 0.9 100.0 80 20 9.8 1.2 98.3 60 40 1.2 0.3 98.8 60 40 3.2 0.4 99.1 60 40 4.2 0.6 100.0 60 40 8.2 1.0 98.3 40 60 1.8 0.3 99.0 40 60 2.8 0.4 100.0 40 60 3.8 0.6 98.1

As is apparent from Table 9, the use of the filler according to the present invention reduces the unopened hole of the nozzle and solves the important problem for stable operation. In addition, in the case of 100 mass% of silica sand, in case of 9.0 mass% of feldspar addition, and 80 mass% of silica sand, in the case of 6.5 mass% of feldspar addition, and 60 mass% of silica sand, 4.2 mass% of feldspar addition, 40 mass% of silica sand In the case of feldspar addition amount of 2.8 mass%, the porosity became 100%.

According to the present invention, by using a filler in which feldspar is added to 40 to 100% by weight of silica sand and 60 to 0% by weight of chromite sand, melting and sintering is difficult with molten steel flowing through the ladle, and molten steel is difficult to penetrate, Moreover, since the thickness of a sintered layer can be adjusted suitably, the unopened hole which arises in a ladle sliding switchgear can be suppressed very favorably and efficiently.

Claims (7)

Alkali feldspar with a particle size distribution of 0.3 to 1.7 mm is obtained by external addition of 40 to 100 mass% of silica sand with a particle size distribution of 0.3 to 1.7 mm and 60 to 0 mass% of chromite sand with a particle size distribution of 0.1 to 0.85 mm. Filler for ladle sliding switchgear characterized in that the amount is made so as to be 0.3 to 1.5% by mass. The filler material for ladle sliding switchgear according to claim 1, wherein the silica yarn has a grain size of 1.4 or less. The filler material for ladle sliding switchgear according to claim 1, wherein the silica, chromite or feldspar is electrostatically coated with 0.3 to 1.0 mass% of carbon black by external addition to the surface thereof. The filler material for a ladle sliding opening and closing device according to claim 1, wherein the feldspar is kali feldspar. The filler for a ladle sliding switch according to claim 1, wherein the silica ₂ content of silica is 95 mass% or more. The said chromite yarn contains 95 mass% or more of yarns of the particle size distribution of the range of 0.15-0.85 mm, 65 mass% or more of yarns of the particle size distribution of the range of 0.425-0.212 mm, The said silica yarn is 0.425- Filler for ladle sliding switchgear consisting of 100% by mass of sag of particle size distribution in the range of 1.18mm. The filler material for a ladle sliding switch according to claim 1, wherein the chromite yarn has a particle size distribution of less than 0.15 mm and 5 mass% or less.

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