JPH01242118A - Porous ceramic filter - Google Patents

Abstract

PURPOSE:To sufficiently remove the interposing particles of small diameter by disposing ceramic bone members to intersect each other to form a specified number of stagnation areas at the intersecting part of the bone members through which no streamlines of molten metal flow are allowed to pass. CONSTITUTION:When the cordierite round rods of 1.5mm diameter of cross section are used as the bone members 11, the filter is made by intersecting these bone members 11 each other at right angles. A 2nd layer is formed on a 1st layer by arranging the bone members 11 in such a way that the bone members of the 2nd layer are disposed so as to intersect the bone members of the 1st layer almost at right angles and to have the same distance each other as the 1st layer. Thus, the bone members 11 of each layer are piled up so as to intersect the bone members 11 of the lower layer almost at right angles so that a mesh type porous formation body is formed. In this formation body, the stagnation areas 13 through which no streamlines 12 of molten metal flow are allowed to pass are formed at the parts where the bone members 11 of the upper and the lower layers are intersect each other, and the interposing particles are caught with high efficiency by making the number of these stagnation areas to be >=10/cm<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a porous ceramic filter for filtering and removing unnecessary particulate solid inclusions from molten metal.

[Prior Art] There are mainly three types of mechanisms for removing solid inclusions from molten metal using a filter medium. First, as shown in FIG. 11, there is screen filtration in which inclusions 2 are mechanically removed using a filter medium 1 having a hole diameter smaller than that of the ordinary inclusions. In this case, filtration of inclusions mainly occurs on the surface of the filter medium 1, and inclusions smaller than the hole diameter of the filter medium 1 cannot be removed.

In addition, as shown in FIG. 12, filtration in which inclusions are separated and removed on the surface of the filter material 1 to form a cake layer 2a is called cake filtration. Due to the sudden increase in resistance, large amounts of molten metal cannot be processed.

On the other hand, as shown in FIG. Even fine inclusions 4 can be removed, but in order to increase the collection rate, it is necessary to thicken the filter material, and the entire amount of inclusions cannot be collected. Additionally, if the adhesion force between the inclusions and the aggregate is smaller than the detachment force of the inclusions due to the flow of the molten metal, the trapped inclusions will separate from the filter again due to the flow force of the molten metal and flow out. This will result in

Conventionally, foam type, cross type, honeycomb type, slit type, lotus root type, particle aggregate type, etc. have been used as filter media for molten metal. Since these filter media have different refinements, their filtration ability (amount and size of removable inclusions) and the form of removable inclusions differ from each other.

[Problems to be Solved by the Invention] However, it is difficult to filter molten metal containing granular solid inclusions as unnecessary inclusions using a screen filtration structure using a foam type, cross type, honeycomb type, or lotus root type filter material. When filtered, it is difficult to mechanically remove particulate solid inclusions having a diameter smaller than the pore diameter of these filter media. For this reason, if you try to remove small-sized solid inclusions using a screen filtration mechanism using these filter media, you will need to use a filter with finer mesh. There is a manufacturing limit to making the eyes finer.

For example, it is practically difficult to manufacture a filter medium having a fineness sufficient to mechanically remove particulate solid inclusions having a particle size of 100 μm or less with high efficiency by screen filtration.

Therefore, in order to filter out small particle size solid inclusions,
However, in the case of cake filtration, inclusions smaller than the pore diameter of the filter medium cannot be removed until a cake layer is formed on the surface of the filter medium. This method is not very practical because the resistance to flowing molten metal increases rapidly at the same time as the layer is formed.

Therefore, in order to effectively remove small particle size solid inclusions,
Efficient internal filtration must be used.In the case of internal filtration, the problem is how to keep inclusions attached to the aggregate surface intact. If the filter material is a honeycomb type or lotus root type, it is difficult to retain inclusions on the aggregate surface because the aggregate surface is a plane parallel to the flow of molten metal or a curved surface along streamlines. In the case of the foam type, there are some parts such as the back side of the aggregate that are not easily affected by the flow of molten metal, but because the surface of the aggregate is basically a curved surface due to its manufacturing characteristics, it will not be affected around the curved surface. Since streamlines are likely to occur and most of the flow occurs along the streamlines, it is difficult to retain inclusions on curved aggregate surfaces.

For the above reasons, foam type, cross type,
Applying honeycomb type and lotus root type filter media as filters for removing small particle size inclusions cannot be said to be an effective means.

On the other hand, particle aggregation type filtration materials are structurally capable of being applied to screen filtration with fine mesh. In this particle aggregation type, by making the particles that serve as the aggregate of the filter medium finer, the mesh of the filter medium can be made finer, making it possible to filter out small-sized inclusions by screen filtration. . However, when this filter material is applied to molten metal that has a high viscosity and therefore has a large resistance to flow when passing through the filter material, or to molten metal that has a high melting point and solidifies when the temperature drops at the start of pouring, ,
It becomes clogged at the start of pouring and becomes unusable in a short period of time. Furthermore, even if clogging does not occur at the start of pouring, the flow resistance will rapidly increase due to the adhesion of inclusions, resulting in the problem that the amount of molten metal processed per unit filtered surface area is small. .

Therefore, although this particle aggregation type filter material is used for relatively low-temperature molten metals such as Aρ, it is not practically applicable to molten metals with high molten metal temperatures such as copper-based or iron-based molten metals. I can't.

The present invention has been made in view of such problems, and includes:
Even in high-temperature molten metals such as copper-based or iron-based alloys that have granular inclusions, the fine mesh of the filter material may cause deterioration in liquid permeability during the early stages of casting and flow of the molten metal. It is an object of the present invention to provide a porous ceramic filter for molten metal that avoids the inconvenience of difficulty, suppresses the occurrence of clogging during casting, and has sufficient ability to remove small-sized granular inclusions. shall be.

[Means for Solving the Problems] A porous ceramic filter according to the first invention of the present application is a porous ceramic filter for filtering particulate inclusions in molten metal, by intersecting ceramic aggregates. , this intersection forms a stagnation region through which the streamlines of the molten metal flow do not pass, and this stagnation region has a density of 10 per unit volume (d>
It is characterized by being more than one.

A porous ceramic filter according to the second invention of the present application is a porous ceramic filter for filtering particulate inclusions in molten metal, which comprises 90% by weight or more of ceramic aggregate, and particulate matter fixed to the surface of the aggregate. , and a stagnation area is formed at the fixed part of the granular material through which the streamlines of the molten metal flow do not pass, and it is considered that there are 10 or more stagnation areas per unit volume (CRD).

A porous ceramic filter according to the third invention of the present application is a porous ceramic filter for filtering particulate inclusions in molten metal, in which ceramic aggregates are disposed in an intersecting manner, and the particulate matter is placed on the surface of the aggregates. By fixing the
A stagnation area is formed at the intersection portion and the fixed portion through which streamlines of the molten metal flow do not pass, and the number of stagnation areas is 10 or more per unit volume (cot).

In the first invention of the present application, by intersecting the aggregates, and in the second invention of the present application, 90% by weight
By fixing granular substances to the surface of the above aggregate,
Furthermore, in the third invention of the present application, by intersecting the aggregates and fixing particulate matter to the surface thereof, a stagnation area is formed through which the streamlines of the molten metal flow do not pass. In this case,
In the stagnation region formed in the filter, if particulate inclusions in the molten metal adhere to the surface of the particulate matter fixed to the aggregate and/or filter material, the streamlines generated by the flow of the molten metal are not directly related to the adhered inclusions. Therefore, no force is applied to remove the inclusions, and they are not removed by the flow.
Therefore, the inclusions will be retained as they are on the aggregate surface. Therefore, by providing ten or more such stagnation regions per unit volume (cm3) of the entire filter, inclusions can be collected efficiently and continuously.

In the case of a filter for molten metal, the mesh of the filter needs to be coarsened to some extent to prevent clogging when pouring starts.

Therefore, in the present invention, small particle size (for example, 100 μm or less)
In order to remove inclusions, an internal filtration mechanism must be used.In the case of an internal filtration mechanism, the ability to remove inclusions depends on the frequency with which the inclusions collide with the filter aggregate and the impact of the inclusions on the filter aggregate. is determined by the adhesion force (inclusion retention force of the filter). In particular, the adhesion force of inclusions is generally relatively weak, except in special cases such as chemical adsorption where inclusions react with aggregate, so once inclusions collide with aggregate, However, these inclusions either do not adhere to the aggregate surface and are carried away by the flow of the molten metal, or, after adhering to the aggregate surface, are separated from the aggregate surface by the force of the molten metal flow. Put it away. However, if the part of the aggregate to which the inclusions have adhered is a part where the flow of the molten metal stagnates, the inclusions will not be separated by the flow of the molten metal and will remain as they are on the surface of the aggregate.

The filter according to the present invention has 10 or more regions of stagnation in the flow of molten metal per unit volume (cnt) on the surface of the filter aggregate, and small-sized inclusions are collected in these regions. In addition, when forming a stagnation by intersecting the aggregates that make up the filter, the flow of molten metal can be controlled at the intersection of the aggregates by bringing the aggregates into contact with each other or by making them approach each other at minute intervals of a predetermined distance or less. Stagnation occurs.

This minute interval varies depending on the fluidity of the supplied metal, but it does not necessarily need to be in contact as long as it creates a stagnation area and traps particulate inclusions. be.

[Embodiment 1] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, the aggregate 11 is a cordierite round rod with a cross-sectional diameter of 1.5 ml, and the filter is constructed by crossing the aggregates 11 at right angles to each other. That is, first, this aggregate 11 is placed on the same plane as ICIII.
Next, form a third layer by arranging two aggregates in parallel so that there are two aggregates per length.Next, on top of this second layer, the aggregates are arranged approximately perpendicularly to the aggregate of the first layer at approximately the same intervals as the first layer. Round bar aggregates 11 are arranged to form a second layer. In the same manner, the aggregate 11 of each layer is
By stacking the aggregates so that they are substantially orthogonal to and in contact with the underlying aggregate 11, a mesh-like porous molded body is formed.

In addition, as shown in FIG. 2, the third layer aggregate 11 is located between the first layer aggregates 11, and similarly, the fourth layer aggregate 11 is located between the second layer aggregates 11. 11 so that they are located in the middle.

In the porous molded body configured in this manner, as shown in FIG. 3, a stagnation region 13 is formed where the streamlines 12 of the molten metal flow do not pass through the portion where the upper and lower aggregates 11 intersect.

In the case of a porous molded body with an aggregate diameter of 1.5 mm and an arrangement pitch of 2 pieces/l, the number of stagnation areas 13 where stagnation occurs in the flow of molten metal is equal to the number of areas where aggregates 11 are in contact with each other. Therefore, it is about 27 pieces/cm.

In this filter, when the molten metal passes through, its particulate inclusions adhere to the surface of the aggregate 11. Therefore, the inclusions attached to the parts washed by the streamlines 12 of the molten metal flow tend to separate from the surface of the aggregate 11 even if they are once attached.However, the inclusions attached to the stagnation area 13 are washed away by the molten metal flow. Therefore, by setting the number of stagnation regions 13 to a predetermined value or more (10 pieces/Cr11 or more), the particle size inclusions can be reduced. It can be removed with high efficiency.

Next, the results of an experiment in which molten metal was actually filtered using the porous molded filter shown in FIG. 1 will be described.

On the other hand, for a comparative example, as shown in FIG.
A porous molded body is also available, which forms a smooth curved surface that follows the streamlines of the molten metal flow, and prevents the flow from stagnation. We investigated the difference between

The experimental conditions and results are shown below.

Wari 1 Tosaki O molten metal Tough pitch copper ○ Inclusions to be filtered SiC particles (particle size 100 μm or less) ○ Filter specifications Material: cordierite Dimensions: 100 dragons x 100 mm x 50 dragons Density of stagnation area (micro space); / cn (Example 2 13 pieces/cnt Comparative example 1 0 pieces/cut Comparative example 2 5 pieces/cnt In addition, in Example 2, the stagnation area of Example 1 was half filled and the density of the stagnation area was half that. be.

○ Filter installation method A filter was installed perpendicular to the flow direction in a transfer tub ○ Sampling evaluation method Sample the molten metal before and after filtration with a mold, solidify the sampled molten metal, cut and polish, and observe with an optical microscope Then, the particle size distribution of SiC per unit area in the observed cross section was determined, and the removal rate was determined by comparing the SiC particle size distribution before and after filtration.

The results are shown in Figure 5, with the horizontal axis representing the SiC grain size and the fir axis representing the S
The iC particle removal rate is calculated and shown.

As is clear from Fig. 5, the filter of Comparative Example 1, which has no stagnation part of the molten metal flow, contains fine Si particles with a particle size of 100 μm or less.
It can be seen that Comparative Example 2, which has a low removal ability of C and has 10 or less stagnation areas, has a small effect, but the filters of Examples 1 and 2, which have 10 or more stagnation areas, have extremely high removal ability. . If the removal rate is less than 50%, troubles such as wire breakage or die wear are likely to occur in subsequent Cu wire drawing and rolling steps. In the case of the filter of Example 1.2, it is possible to remove SiC particles with a particle size of 10 μm with a removal rate of 50% or more, so its usefulness is extremely high.

Next, a second embodiment of the present invention (third invention of the present application) will be described with reference to the perspective view of FIG. The shape of the aggregate 11 and its arrangement structure in this example are similar to those of the porous molded body of the first example, but the diameter of the aggregate 11 is 4.5 mm. Os+
m, the arrangement pitch of the aggregates 11 is such that one aggregate 11 is inserted per cra length. The number density of the intersection portions of this porous molded body is 2.5 flW/cnf. That is, as shown in FIG. 7, the number density of the stagnation regions 15 formed in the portions where the aggregates 11 intersect is 2.5 pieces/d.

In addition, the surface of the aggregate 11 of this filter has a diameter of about 0.3
Alumina particles 14 with a thickness of 0.5 to 0.5 am are deposited. The particles 14 form a stagnation region 16 in the region where the particles 14 and the aggregate 11 come into contact.

In the filter configured in this way, by adjusting the amount of attached particles 14, the number density of the total amount of stagnation regions 15.16 can be made to be 10 particles/d or more.

When used for filtering molten iron-based alloy, it is necessary to use a filter with coarse mesh to ensure liquid permeability at the initial stage of pouring and increase the throughput of molten metal. Therefore, in the case of the filter material of the second embodiment, which has a mesh structure similar to that of the first embodiment described above, but whose mesh size is coarser than that of the first embodiment, at the intersection part, Microspace (
The number of stagnation areas 15) is small.

However, as in this embodiment, by attaching the refractory particles 14 to the surface of the aggregate 11, a necessary and sufficient stagnation area 15, 16 can be secured based on the total amount.

Hereinafter, the experimental conditions and results of an experiment in which molten metal was actually filtered using the filter shown in FIG. 6 will be described in detail.

E1 East Star ○ Metal molten metal type; 5i-A, ++ Quilt steel ○ Symbolic grain inclusions; Various oxides ○ Filter specification dimensions; 60+s+iX 60mmX 60im Material;
Density of existence of aluminous microspaces: 30 comparative examples/- 42.5 comparative examples/312 examples of C/422 examples/cn? O filter installation method: A filter weir was provided in a continuous cast steel tundish, and the filter was installed in this weir.

O Sampling: Same O evaluation method as in the first example. The results are shown in FIG. 8, the same as in the first example. As is clear from FIG. 8, in the case of Example 4 where the existence density of micro spaces (stagnation regions) is about 22/-, even if the micro inclusions have a particle size of 20 to 50 μm, the 80
% or more have been removed. Further, at this time, there was no particular problem with the flow of the molten metal, and there was little resistance. In the case of Example 3, the removal efficiency of microparticles is similarly high, and for example, even ultrafine particles with a particle size of 10 μm have a removal rate of 50% or more.

On the other hand, the filter of Comparative Example 2 in which the microspace density is 0 is effective against large inclusions with a particle size of about 100 Jlm, but the removal efficiency significantly decreases for inclusions of 60 μm or less. Similarly, when the density of stagnation regions is lower than 10/- as in Comparative Example 3, the removal rate of fine particles is similarly low.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the technical scope based on the claims of the present invention. For example, the cross-sectional shape of the aggregate may be circular. Of course, there is no limit.

In other words, as shown in FIG. 9, the aggregate 17 has a triangular cross section.
By arranging them so that they intersect, a stagnation region 18 is formed at this intersection. Further, the filter aggregate is not limited to the mesh etc. as in each of the above embodiments, but a foam type aggregate 19 may be used as shown in FIG. 10, and whiskers 20 are arranged on one of the aggregates. By doing so, the stagnation region 21 can be similarly formed.

[Effects of the Invention] The porous ceramic filter according to the present invention has a high ability to capture particulate inclusions in molten metal, especially particulate minute inclusions that could not be filtered conventionally, and has low liquid flow resistance.
The member constituting the stagnation part can be appropriately selected depending on the viscosity of the molten metal, and the use of the porous ceramic filter of the present invention enables highly efficient continuous casting and eliminates granular inclusions peculiar to metals. This reduces manufacturing troubles such as wire breakage in the metal processing process after casting, greatly increasing overall productivity. Further, since the filter is small and has a simple structure, the structure of the tundish equipment incorporating the filter is also simple, which is advantageous in terms of handling and safety.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a porous filter according to the first embodiment of the present invention, FIG. 2 is a side view thereof, FIG. 3 is a schematic diagram explaining the stagnation region, and FIG. 4 is a comparative example. A schematic diagram showing the structure, FIG. 5 is a graph diagram showing the effects of the present invention, FIG. 6 is a perspective view showing a porous filter according to a second embodiment of the present invention, and FIG. 7 is a side view thereof. FIG. 8 is a graph showing the effects of the present invention, FIG. 9 is a side view showing a modified example of the aggregate,
Fig. 10 is a schematic diagram showing a modified example of aggregate, Fig. 11 is a schematic diagram showing a screen filtration mechanism, Fig. 12 is a schematic diagram showing a cake filtration mechanism, and Fig. 13 is a schematic diagram showing an internal filtration mechanism. be. 11.17,19: Aggregate, 12; Streamline, 13°15.1
6, 18, 21; stagnation area, 20; whisker

Claims (7)

[Claims] (1) In a porous ceramic filter that filters particulate inclusions in molten metal, ceramic aggregates are arranged in an intersecting manner to form a stagnation area where streamlines of the molten metal flow do not pass through the intersection. , this stagnation region has a unit volume (c
A porous ceramic filter characterized in that the number of porous ceramic filters is 10 or more per m^3). (2) The porous ceramic filter according to claim 1, wherein the aggregates forming the stagnation region are in contact with each other. (3) The porous ceramic filter according to claim 1, wherein the aggregates forming the stagnation area are spaced apart from each other by a predetermined distance or less. (4) The porous ceramic filter according to claim 1, wherein the aggregate is a plurality of linear bodies. (5) The linear body has a loop shape, and is formed into a planar shape with the centers of the linear rings shifted from each other, and the linear body is constructed by laminating these planar molded bodies. 1. The porous ceramic filter according to 1. (6) A porous ceramic filter for filtering particulate inclusions in molten metal, comprising 90% by weight or more of ceramic aggregate and particulate matter fixed to the surface of this aggregate, A stagnation area is formed in the fixed part through which the streamlines of the molten metal flow do not pass, and this stagnation area has a unit volume (cm^3)
A porous ceramic filter characterized by having 10 or more pieces per porous ceramic filter. (7) In a porous ceramic filter that filters particulate inclusions in molten metal, ceramic aggregates are arranged in an intersecting manner, and the particulate matter is fixed to the surface of the aggregates, so that the intersecting parts and fixed parts A stagnation area is formed through which the streamlines of the molten metal flow do not pass, and this stagnation area has a unit volume (cm^
3) A porous ceramic filter characterized by having 10 or more pieces per porous ceramic filter.