Metal molten filter unit

Abstract

The utility model relates to a metal melt filtering unit (1), which comprises a plurality of ceramic filtering pipes (3) and a pair of side plates (2A, 2B), the plurality of ceramic filtering pipes are cylindrical and are approximately arranged in parallel, the sections of the outer surface and the inner surface, which are vertical to the length direction, are approximately circular respectively, and the side plates (2A, 2B) are arranged on the side plates (2A, 2B). The pair of side plates are disposed at both ends in the longitudinal direction of the plurality of ceramic filter tubes, and the plurality of ceramic filter tubes have a first end on one side and a second end on the other side from which the molten metal flows out. When L1 is the length in the longitudinal direction of a portion (3d) of the outer surface of the filter tube exposed to the molten metal, D1 is the outer diameter of the filter tube, L2 is the length in the longitudinal direction of a portion (3c) of the inner surface of the filter tube exposed to the molten metal, and D2 is the inner diameter of the filter tube, the following two relational expressions are satisfied: (i) L1 / D1 > = 8.5; (ii) L2 / D2 > = 22.

Description

Technical Field

[0001] The utility model relates to a molten metal filtering unit for filtering molten metals such as aluminum. Background Art

[0002] In the molten metal such as aluminum used to make castings, non-metallic inclusions such as hydrogen and oxides are usually contained as impurities. For example, the dissolved hydrogen in the molten metal will form casting holes called pores in the casting, and oxides and the like may become inclusions in the casting. These casting holes and inclusions may become the starting point of destruction of the casting, so they are undesirable. Therefore, a filtering device for filtering the molten metal to remove the inclusions and the like contained in the molten metal has been developed.

[0003] To achieve this purpose, a molten metal filtering device is typically used in which a molten metal filtering unit is placed in a filtering chamber, the molten metal filtering unit having a plurality of ceramic filter tubes for filtering impurities from the molten metal, and the filtering chamber is provided with a liquid inlet and a liquid outlet (for example, refer to Patent Document 1). Such a molten metal filtering unit is generally composed of a plurality of ceramic filter tubes and a pair of side plates arranged substantially parallel to each other at both ends of the length direction of the plurality of filter tubes. The molten metal introduced into the filtering chamber from the liquid inlet of the filtering chamber enters from the peripheral wall surface of the filter tube provided with a side plate, where the impurities are filtered out, and flows out from the end on the opposite side of the filter tube provided with another side plate, and then flows out from the liquid outlet of the filtering chamber.

[0004] For the purpose of improving the processing capacity and efficiency of the metal melt filtration unit, an attempt has been made to increase the flow rate of the metal melt while extending the service life of the filter tube. As an example of such an attempt, the following metal melt filtration unit is reported: the metal melt filtration unit has a recess formed on one side of a pair of side plates, into which a plurality of filter tubes are inserted and held, and the ratio of the interval between adjacent recesses to the depth of the recesses is adjusted to within a specified range, and the interval between adjacent recesses is adjusted to within a specified range (see patent document 2). In this document, it is believed that by forming a plurality of filter tubes and the corresponding recesses into such a structure, the effect of improving the filtration efficiency while maintaining the strength of the side plate can be obtained.

[0005] In addition, a filter (filter tube) for molten metal is reported as follows: the filter (filter tube) for molten metal has an average particle size of the filter aggregate within a specified range, a ratio of the average particle size of the inner peripheral surface and the outer peripheral surface of the filter within a specified range, and a porosity that gradually increases from the inner peripheral surface side to the outer peripheral surface side (see Patent Document 3). In this document, it is believed that by appropriately adjusting the average particle size of the inner peripheral surface and the outer peripheral surface of the aggregate constituting the filter for molten metal and the porosity change therebetween, the effect of improving the capture performance of inclusions contained in the molten metal and the life of the filter can be obtained.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 7-004868

[0009] Patent Document 2: Japanese Patent No. 6295108

[0010] Patent Document 3: Japanese Patent No. 6423726 Utility Model Content

[0011] Problems to be solved by the utility model

[0012] However, in the technology of arranging a plurality of tubes inserted into the recesses of the side plates as densely as possible while maintaining the strength of the side plates as in the molten metal filtration unit reported in Patent Document 2, it is desirable to further increase the amount of molten metal flowing through and further extend the service life of the filter tubes. However, if the number of filter tubes is excessively increased, a large number of recesses corresponding to the filter tubes and through holes on the liquid outlet side need to be formed on the side plates, which may make it difficult to maintain sufficient strength of the side plates.

[0013] In addition, the molten metal filter (filter tube) reported in Patent Document 3 seeks to improve the inclusion capture performance and the life of the filter mainly by focusing on the aggregate of the filter. For this patent document, there is room for further improvement of the inclusion removal performance and further extension of the filter life by designing the overall structure of the molten metal filter and the filter unit including the molten metal filter.

[0014] Therefore, a problem to be solved by the present invention is to provide a new type of metal melt filtering unit which does not exist in the prior art.

[0015] In addition, a further problem to be solved by the utility model is to provide a new type of metal melt filter unit which eliminates the above-mentioned disadvantages, that is, can highly maintain the strength of the side plate and can simultaneously achieve a further increase in the flow rate of the metal melt, a further extension of the service life of the filter tube and a further improvement in the removal performance of inclusions contained in the metal melt.

[0016] Means used to solve problems

[0017] The present inventors have conducted intensive research and found that, in a metal melt filtration unit comprising a plurality of cylindrical ceramic filter tubes and a pair of side plates disposed at both ends thereof in a longitudinal direction, the above-mentioned problem can be solved by adjusting, for at least a portion of the plurality of filter tubes, a ratio L1 / D1 of a longitudinal length L1 of a portion of an outer surface of the filter tube exposed to the metal melt relative to an outer diameter D1 of the filter tube to be above a specific lower limit, and by adjusting a ratio L2 / D2 of a longitudinal length L2 of a portion of an inner surface of the filter tube exposed to the metal melt relative to an inner diameter D2 of the filter tube to be above a specific lower limit.

[0018] That is, the inventors have discovered that, according to a molten metal filtration unit having such a structure, the amount of liquid passing through (flow rate) of the molten metal can be further increased by increasing the area of ​​the exposed portion of the outer surface of the filter tube facing the molten metal and reducing (thinning) the inner diameter of the filter tube to a certain extent, and the service life of the filter tube can be further extended by reducing the amount of liquid passing through per unit area of ​​the filter tube. Furthermore, the retention time in the filter tube can be extended by reducing the flow rate of the molten metal, thereby efficiently removing inclusions in the molten metal, thereby completing the utility model.

[0019] A typical embodiment of the present invention is as follows.

[0020] A molten metal filtering unit, wherein:

[0021] The molten metal filtering unit comprises a plurality of ceramic filter tubes and a pair of side plates. The plurality of ceramic filter tubes are cylindrical and arranged approximately in parallel, and the cross-sectional shapes of the outer surfaces and the inner surfaces perpendicular to the longitudinal direction are approximately circular. The pair of side plates are arranged at both ends of the plurality of ceramic filter tubes in the longitudinal direction.

[0022] The plurality of ceramic filter tubes have a first end on one side through which the molten metal flows out and a second end on the other side.

[0023] With respect to at least a portion of the plurality of ceramic filter tubes,

[0024] When the length of the portion of the outer surface of the filter tube exposed to the molten metal is L1, the outer diameter of the filter tube is D1, the length of the portion of the inner surface of the filter tube exposed to the molten metal is L2, and the inner diameter of the filter tube is D2,

[0025] The following two relations are satisfied:

[0026] (1) L1 / D1 ≥ 8.5

[0027] (2)L2 / D2≥22.

[0028] Effect of utility model

[0029] According to the utility model, a novel metal melt filtering unit which does not exist in the prior art is provided.

[0030] Furthermore, according to the preferred embodiment of the present invention, the metal melt filtration unit can obtain the following advantages by appropriately adjusting the relationship between the structural elements of the ceramic filter tube: not only can the strength of the side plate be highly maintained, but also the flow rate of the metal melt can be further increased, the service life of the filter tube can be further extended, and the removal performance of the inclusions contained in the metal melt can be further improved. (The "further improvement of the removal performance" here may be changed to "further improvement of the removal efficiency" in some cases.) BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1( a ) is a schematic diagram of a molten metal filtration unit according to an embodiment of the present invention.

[0032] FIG1( b ) is a schematic cross-sectional view showing the principle of filtering operation of molten metal in the molten metal filtering unit according to one embodiment of the present invention.

[0033] Figure 2 It is a cross-sectional view of a portion of a metal melt filtration unit including a ceramic filter tube and a pair of side plates in one embodiment of the utility model, wherein the ceramic filter tube has a first end on one side for the metal melt to flow out and a second end on the other side, and the pair of side plates are arranged at both ends of the ceramic filter tube in the length direction.

[0034] Figure 3 It is a cross-sectional view of a ceramic filter tube of a molten metal filtration unit according to a modified embodiment of the present invention.

[0035] Figure 4 (a) and (b) are diagrams illustrating the relationship between the opening of the first end of the ceramic filter tube on the side from which the molten metal flows out and the substantially circular through-hole provided on the side plate on the liquid outlet side in the molten metal filtration unit of one embodiment of the present invention. Figure 4 (a) is a cross-sectional view observed from the length direction. Figure 4 (b) is a cross-sectional view observed from a horizontal direction perpendicular to the longitudinal direction.

[0036] Figure 5 This is a cross-sectional view illustrating the relationship between the inner diameter of the filter tube installation side and the inner diameter of the end portion on the liquid outlet side in a substantially circular through hole provided on the side plate on the liquid outlet side of the molten metal filtration unit according to one embodiment of the present invention.

[0037] Figure 6 This is a cross-sectional view for explaining the liquid head heights T0 and T1 of the molten metal for evaluating the filtering performance of the molten metal filtering unit according to one embodiment of the present invention in the examples described later. DETAILED DESCRIPTION

[0038] First, the structure of a molten metal filtration unit and an overview of molten metal filtration according to an embodiment of the present invention are described with reference to Fig. 1(a) and Fig. 1(b). The structure shown in the figure is an example simplified for the purpose of description, and the molten metal filtration unit of the present invention is not limited thereto.

[0039] In FIG. 1(a) and FIG. 1(b), 1 is a metal melt filtering unit, 2A and 2B are a pair of side plates arranged at both ends of the filtering unit (a side plate arranged on a side for the metal melt to flow out and a side plate arranged on the opposite side respectively), 3 is a plurality of ceramic filter tubes (hereinafter also referred to as "filter tubes") for filtering impurities from the metal melt, and 2e is a through hole of the side plate on the liquid outlet side. Although not shown in this figure, a gasket having a shape that can be fitted with them can also be arranged between each end of the filter tube and the corresponding side plate. Although it is not necessary to set such a gasket, it is preferably arranged from the viewpoint of being able to stably fix the filter tube to the side plate and being able to reliably prevent the leakage of the metal melt. The plurality of ceramic filter tubes 3 are cylindrical, arranged approximately parallel to each other, and the cross-sectional shapes of the outer surface and the inner surface perpendicular to the length direction are respectively approximately circular. The filter tube 3 is generally formed of a porous material made of ceramic. As shown by the arrow in Fig. 1(b), foreign matter contained in the molten metal can be filtered and removed by flowing the molten metal between the inner surface and the outer surface of the filter tube 3. And, the purified liquid of the molten metal after filtering the foreign matter is discharged from the through hole 2e of the side plate on the liquid outlet side.

[0040] In the metal melt filtration unit 1 of FIG. 1 (a) and FIG. 1 (b), for ease of explanation, as an example, a structure in which only four ceramic filter tubes 3 are provided is shown, but it is not limited to this. The number of ceramic filter tubes 3 is not particularly limited as long as it is multiple, for example, it can be 2 to 50, or 3 to 40, or 4 to 30, or 5 to 20. As shown in the figure, the cross-sectional shape of the ceramic filter tube 3 is usually roughly circular, but it can also be a mixed combination of cross-sectional shapes other than roughly circular shapes such as a flat roughly elliptical shape or a roughly rectangular shape. In the case of such a mixed combination, the proportion of filter tubes with cross-sectional shapes other than roughly circular shapes can be less than half of the entire filter tube, for example, it can be less than one-third. Multiple ceramic filter tubes 3 are usually arranged horizontally in a roughly horizontal shape and at roughly equal intervals, but adjacent ceramic filter tubes can also be directly in contact in a part. In the case where the ceramic filter tubes 3 arranged horizontally in a roughly horizontal shape and at roughly equal intervals form multiple rows, the multiple rows are preferably also arranged at roughly equal intervals.

[0041] Figure 2 2 shows a cross-sectional view of a molten metal filtration unit according to an embodiment of the present invention observed perpendicularly to the length direction of the filtration tube. Figure 2 In the molten metal filtration unit of the embodiment, a part of the ceramic filter tube is omitted for convenience of illustration, but it has a structure further extending in the longitudinal direction.

[0042] exist Figure 2 In the figure, 1 refers to a molten metal filtration unit, 2A refers to a side plate on the side for the molten metal to flow out, 2B refers to a side plate on the side opposite to the liquid outlet side (without a through hole and is closed), 2e refers to a roughly circular through hole provided on the side plate on the liquid outlet side, 3 refers to a cylindrical ceramic filter tube having roughly circular cross-sectional shapes perpendicular to the length direction on the outer surface and the inner surface, 3a refers to a roughly circular outer end surface at the second end of the filter tube, 3b refers to a roughly circular inner end surface at the second end of the filter tube, 3c refers to a portion of the inner surface of the filter tube exposed to the molten metal, 3d refers to a portion of the outer surface of the filter tube exposed to the molten metal, 3e refers to a roughly circular opening at the first end of the filter tube, 3w refers to a ring-shaped end surface at the first end of the filter tube except for the opening, 4A refers to a gasket for fixing the first end of the filter tube, and 4B refers to a gasket for fixing the second end of the filter tube. Figure 2In the figure, for the sake of explanation, only one of the ceramic filter tubes 3 is shown. The ceramic filter tube 3 is fixed in the form of an end face 3w and its peripheral edge portion other than the opening portion at the first end portion of the filter tube 3 on the side where the molten metal flows out, and an outer end face 3a and its peripheral edge portion at the second end portion on the side opposite to the first end portion, respectively, by fitting with a recess (usually a peripheral wall portion having a substantially circular contour) provided on the side plate 2A on the side where the molten metal flows out and the side plate 2B on the side opposite to the liquid discharge side through a gasket 4A or a gasket 4B. Here, the recess and the gasket 4A provided on the side plate 2A or the recess and the gasket 4B provided on the side plate 2B are formed in a manner matching the shapes of the first end portion of the ceramic filter tube 3 on the side where the molten metal flows out and the second end portion on the opposite side, respectively, and have an opening corresponding to the opening portion of the filter tube on the first end side.

[0043] The gasket 4A and the gasket 4B may be composed of only a contact portion as a flat plate-shaped body in contact with the end surface of the filter tube 3. In the case of such a structure, the peripheral wall portion of the recessed portion opened in the side plate has a substantially circular cross-sectional shape to match the shapes of the first end and the second end of the filter tube 3, and the outer diameter of the tube at the first end and the second end of the filter tube 3 and the diameter of the peripheral wall portion of the recessed portion opened in the corresponding side plate are substantially equal.

[0044] Alternatively, the gasket 4A and the gasket 4B can be composed of a close-fitting portion as a flat plate body in contact with the end face of the filter tube 3 and a sealing portion as an annular body in contact with the edge of the outer surface of the filter tube 3 and the peripheral wall of the recessed portion provided on the side plate. The two parts of the gasket can be formed integrally, or two independent parts can be connected and joined. In such a structure, the close-fitting portion of the gasket has the function of absorbing the dimensional changes in the length direction of the filter tube caused by expansion and contraction due to environmental conditions such as the set temperature of the molten metal, and maintaining the close fit between the filter tube and the side plate. On the other hand, the sealing portion of the gasket has the function of properly maintaining the overall shape of the molten metal filtration unit by sealing and joining the filter tube and the side plate.

[0045] The close-fitting portion of the gasket 4A and / or the gasket 4B can be fixed in a compressed state to the concave portion provided on the side plate 2A and / or the side plate 2B between the end of the filter tube 3 and the side plate 2A and / or the side plate 2B. As for the thickness of the close-fitting portion of the gasket 4A and / or the gasket 4B along the length direction of the filter tube, in a non-compressed state, it can be, for example, 5% or more and 80% or less of the depth of the concave portion provided on the side plate 2A and / or the side plate 2B along the length direction of the filter tube, preferably 10% or more and 70% or less, 15% or more and 60% or less, 18% or more and 50% or less, or 20% or more and 40% or less. The compression ratio (ratio of the thickness of the compressed amount to the thickness when not compressed) of the close-fitting part of the gasket 4A and / or the gasket 4B when compressed relative to the concave part opened on the side plate 2A and / or the side plate 2B can be, for example, greater than 0% and less than 80%, greater than 10% and less than 70%, greater than 20% and less than 60%, or greater than 30% and less than 50%. The thickness of the gasket when compressed can be, for example, greater than 2% and less than 50%, greater than 4% and less than 40%, greater than 5% and less than 30%, greater than 6% and less than 20%, or greater than 7% and less than 15% of the depth of the concave part opened on the side plate 2A and / or the side plate 2B along the length direction of the filter tube.

[0046] exist Figure 2 In the illustrated metal melt filtration unit 1, the side plate 2A on the side for the metal melt to flow out and the side plate 2B on the side opposite to the liquid outlet side only need to have recesses provided so as to be able to fit and fix the first end of the ceramic filter tube 3 on the side for the metal melt to flow out and the second end on the opposite side via the gasket 4A and the gasket 4B, respectively, and their shapes are not particularly limited. The side plate 2A and the side plate 2B can each usually be a flat plate. The bottoms of the side plate 2A and the side plate 2B can also be flat, respectively. Alternatively, when the length direction of the filter tube 3 is set to be approximately horizontal, at least one of the side plate 2A and the side plate 2B has a bottom formed in a manner that the bottom side of one side is set higher in the vertical direction than the bottom side of the other side. The metal melt filtration unit 1 is placed on the hearth ( Figure 2 When the filter unit is mounted on the filter device (not shown in the figure), by setting the bottom of the side plate 2A and / or the side plate 2B to such a structure, the side end surface of the side plate 2A on the liquid outlet side is pressed against the inner wall surface of the filter device by relying on the dead weight of the filter unit, so that the filter unit can be stably placed, so that the through hole 2e (multiple) of the side plate 2A on the liquid outlet side and the liquid outlet provided on the inner wall surface of the filter device can be reliably and continuously connected at the correct position. The details of the embodiment related to the structure of the side plate will be further described in other items later.

[0047] exist Figure 2In FIG. 1 , the ceramic filter tube 3 is exemplified as a cylindrical shape having a substantially circular cross section and having the same outer surface and inner surface from the second end portion to the first end portion.

[0048] exist Figure 2 middle,

[0049] [i] The length of the portion 3d of the outer surface of the filter tube 3 exposed to the molten metal, that is, the length from the end point of the portion of the outer surface of the second end portion of the filter tube 3 on the side opposite to the liquid outlet side that is not covered by the side plate 2B and the gasket 4B on the side opposite to the liquid outlet side to the end point of the portion of the outer surface of the first end portion on the liquid outlet side that is not covered by the side plate 2A and the gasket 4A on the liquid outlet side is set as L1,

[0050] [ii] The length of the portion 3c of the inner surface of the filter tube 3 exposed to the molten metal, i.e., the length from the inner end surface 3b at the second end of the filter tube 3 on the side opposite to the liquid outlet side to the end surface 3w at the first end on the liquid outlet side, is defined as L2;

[0051] [iii] Let the outer diameter of the filter tube 3 (which is the same from the second end to the first end in this figure) be D1,

[0052] [iv] The inner diameter of the filter tube 3 (which is the same from the second end to the first end in this figure) is set to D2,

[0053] At this time, the following relationship is usually satisfied.

[0054] (1) L1 / D1 ≥ 8.5

[0055] (2) L2 / D2 ≥ 22

[0056] Here, the “longitudinal direction” of the filter tube 3 refers to a direction connecting the center of the outer circumference of the end surface 3w at the first end on the liquid outlet side and the center of the outer circumference of the outer end surface 3a at the second end on the opposite side to the liquid outlet side.

[0057] When the cross-sectional shape of the outer surface and / or inner surface of the filter tube 3 perpendicular to the longitudinal direction, i.e., the "substantially circular" shape, is not completely circular, the outer diameter and / or inner diameter is determined by the circumscribed circle of the cross-sectional shape.

[0058] The ceramic filter tube 3 satisfies the above-mentioned relationship (1) so that it is adjusted to extend to a point where the length direction length of the portion of the outer surface of the filter tube exposed to the metal melt has a higher ratio than a specified value relative to the outer diameter of the filter tube. Therefore, by increasing the area of ​​the outer exposed portion, the flow rate of the metal melt can be further increased. At the same time, by reducing the flow rate per unit area of ​​the filter tube, the service life of the filter tube can be further extended, thereby significantly improving the filtering performance of the metal melt.

[0059] In addition, the ceramic filter tube 3 satisfies the above-mentioned relational expression (2) in addition to the above-mentioned relational expression (1), so that the length direction length of the portion of the inner surface of the filter tube exposed to the molten metal has a ratio of a predetermined value or more to the inner diameter of the filter tube (in other words, it is adjusted so that the inner diameter of the filter tube has a ratio of a predetermined value or less to the length direction length of the portion of the inner surface of the filter tube exposed to the molten metal), thereby reducing the flow rate of the molten metal and extending its retention time in the filter tube, and efficiently removing inclusions in the molten metal. As a result, the following advantages can be obtained: while the flow rate of the above-mentioned molten metal is further increased and the service life of the filter tube is further extended, the removal performance of inclusions contained in the molten metal can be further improved.

[0060] Furthermore, by making the ceramic filter tube 3 satisfy the above-mentioned relational expressions (1) and (2), the number of filter tubes installed in the side plates 2A and 2B of the molten metal filtration unit 1 can be increased, and the filtering performance can be further improved.

[0061] In the above relationship (1) L1 / D1≥8.5, from the above viewpoint, preferably L1 / D1≥8.6, L1 / D1≥8.7, L1 / D1≥8.8 or L1 / D1≥8.9, and more preferably L1 / D1≥9.0, L1 / D1≥9.1, L1 / D1≥9.2, L1 / D1≥9.3, L1 / D1≥9.4, L1 / D1≥9.5 1≥9.5, L1 / D1≥9.6, L1 / D1≥9.7, L1 / D1≥9.8, L1 / D1≥9.9, L1 / D1≥10, L1 / D1≥10.5, L1 / D1≥11, L1 / D1≥11.5, L1 / D1≥12, L1 / D1≥12.5, L1 / D1≥13, L1 / D1≥13.5 or L1 / D1≥14. Alternatively, it may be L1 / D1≥14.5, L1 / D1≥15, L1 / D1≥15.5, L1 / D1≥16, L1 / D1≥16.5 or L1 / D1≥17.

[0062] In the above relationship (2) L2 / D2≥22, from the above viewpoint, it is preferably L2 / D2≥22.5, L2 / D2≥23, L2 / D2≥23.5, L2 / D2≥24, L2 / D2≥24.5, L2 / D2≥25, L2 / D2≥25.5 or L2 / D2≥26. Alternatively, it may be L2 / D2≥26.5, L2 / D2≥27, L2 / D2≥27.5, L2 / D2≥28, L2 / D2≥28.5, L2 / D2≥29, L2 / D2≥29.5, L2 / D2≥30, L2 / D2≥30.5, L2 / D2≥31, L2 / D2≥31.5, L2 / D2≥32, L2 / D2≥32.5, L2 / D2≥33, L2 / D2≥33.5, L2 / D2≥34, L2 / D2≥34.5 or L2 / D2≥35.

[0063] When there are a plurality of ceramic filter tubes 3 each having a cylindrical shape with a circular cross section and having the same outer surface and inner surface from the second end to the first end (i.e., having the same outer diameter from the second end to the first end and the same inner diameter from the second end to the first end), the plurality of filter tubes 3 usually have the same outer diameter and inner diameter, but may have different outer diameters and / or inner diameters in at least a portion of the filter tubes. In this case, the outer diameter D1 and / or inner diameter D2 of the filter tube 3 refers to the average value of the outer diameter and / or inner diameter of the plurality of filter tubes as a whole.

[0064] In a modified embodiment, at least a portion of the plurality of ceramic filter tubes 3 may have a circular cross section of an outer surface and / or inner surface different from that at the second end in a portion or substantially the entirety from the second end on the side opposite to the discharge side of the molten metal to the first end, that is, may have an outer diameter and / or inner diameter that changes from the second end. The ratio of the change in the outer diameter and / or inner diameter of the filter tube relative to the outer diameter and / or inner diameter at the second end may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, 15% or less, 10% or less, or 5% or less.

[0065] In this way, the outer diameter D1 and / or inner diameter D2 of the ceramic filter tube 3 in the case where the outer diameter and / or inner diameter change from the second end portion refer to the outer diameter of the outer end surface 3a at the second end portion of the filter tube and / or the inner diameter of the inner end surface 3b at the second end portion of the filter tube. Furthermore, the definition of the outer diameter D1 and / or inner diameter D2 of the plurality of filter tubes 3 based on the average value as described above is also applicable to the case where at least a portion of the plurality of filter tubes has a circular cross section of the outer surface and the inner surface different from that at the second end portion in a portion or substantially the entirety from the second end portion to the first end portion.

[0066] In a mode in which at least a portion of the plurality of ceramic filter tubes 3 has an outer diameter and / or inner diameter that changes from the second end portion in a portion or substantially the entirety from the second end portion on the side opposite to the outlet side of the molten metal to the first end portion, from the viewpoint of promoting the flow of the molten metal (purified liquid) after the filtration treatment of receiving foreign matter to the outlet side, it is preferred that in this portion, the inner diameter of the filter tube increases along the length direction from the second end portion to the first end portion. In other words, from the viewpoint of promoting the flow of the molten metal (purified liquid) after the filtration treatment of receiving foreign matter to the outlet side, it is preferred that in at least a portion of the plurality of ceramic filter tubes 3, the inner diameter at the end face 3w of the first end portion on the outlet side of the molten metal is larger than the inner diameter at the inner end face 3b of the second end portion on the opposite side. With such a structure, the smooth flow of the purified liquid to the outlet side can be promoted, and the filtering performance of the molten metal can be further improved. In addition, in at least a part of the plurality of ceramic filter tubes 3, when the inner diameter at the end face 3w of the first end portion on the side where the molten metal is discharged is larger than the inner diameter at the inner end face 3b of the second end portion on the opposite side, it is more preferred that the outer diameter at the end face 3w of the first end portion on the side where the molten metal is discharged is substantially the same as the outer diameter at the outer end face 3a of the second end portion on the opposite side. With such a structure, the structural strength of the entire filter unit can be maintained well, the design of the recessed portion provided on the side plate can be facilitated, and the spacing and arrangement of the plurality of filter tubes can be optimized to further improve the filtering performance.

[0067] In at least a part of the plurality of ceramic filter tubes 3, the inner diameter at the end surface 3w of the first end portion as the outlet side of the molten metal is larger than the inner diameter at the inner end surface 3b of the second end portion on the opposite side, for example, a method in which a part or substantially the entire filter tube has a so-called inverted cone-like inclination along the length direction from the second end portion to the first end portion to continuously increase the inner diameter, and a method in which the inner diameter is increased in a step-like manner including a plurality of portions where the inner diameter of the filter tube is constant along the length direction from the second end portion to the first end portion. From the viewpoint of further promoting the flow of the molten metal (purified liquid) after the filtration treatment of receiving foreign matter to the outlet side, it is preferred that a part or substantially the entire filter tube has a so-called inverted cone-like inclination along the length direction from the second end portion to the first end portion to continuously increase the inner diameter, and it is more preferred that a so-called inverted cone-like constant inclination is provided in the entire filter tube along the length direction from the second end portion to the first end portion to continuously increase the inner diameter.

[0068] In each embodiment of the utility model including the above-mentioned deformation modes, the longitudinal length L1 of the portion of the outer surface of the ceramic filter tube 3 exposed to the metal melt, the outer diameter D1 of the filter tube 3, the longitudinal length L2 of the portion of the inner surface of the filter tube 3 exposed to the metal melt, and the inner diameter D2 of the filter tube 3 are not particularly limited as long as they satisfy the above-mentioned relationship expressions (1) and (2). For example, these diameters can be in the following ranges.

[0069] The longitudinal length L1 of the portion of the outer surface of the filter tube 3 exposed to the metal melt can generally be, for example, greater than 300 mm and less than 6000 mm, preferably greater than 400 mm and less than 5000 mm, greater than 500 mm and less than 4000 mm, greater than 600 mm and less than 3000 mm, greater than 700 mm and less than 2500 mm, greater than 800 mm and less than 2000 mm, or greater than 850 mm and less than 1500 mm.

[0070] The outer diameter D1 of the filter tube 3 may be, for example, usually 30 mm to 300 mm, preferably 40 mm to 250 mm, 50 mm to 200 mm, 60 mm to 150 mm, or 70 mm to 120 mm.

[0071] The longitudinal length L2 of the portion of the inner surface of the filter tube 3 exposed to the molten metal can generally be, for example, greater than 400 mm and less than 6000 mm, preferably greater than 500 mm and less than 5000 mm, greater than 600 mm and less than 4000 mm, greater than 700 mm and less than 3000 mm, greater than 800 mm and less than 2000 mm, or greater than 850 mm and less than 1600 mm.

[0072] The inner diameter D2 of the filter tube 3 may be, for example, usually 10 mm to 150 mm, preferably 15 mm to 120 mm, 20 mm to 100 mm, 25 mm to 80 mm, or 30 mm to 70 mm.

[0073] exist Figure 3In the figure, as a preferred example of a modified embodiment, the following method is shown: in the ceramic filter tube 3 as a whole, the inner diameter at the end face 3w of the first end portion on the liquid outlet side of the molten metal is larger than the inner diameter at the inner end face 3b of the second end portion on the opposite side, and the outer diameter at the end face 3w of the first end portion on the liquid outlet side of the molten metal is the same as the outer diameter at the outer end face 3a of the second end portion on the opposite side. In the filter tube 3 of this figure, the inner diameter is continuously increased by having a constant inclination of a so-called inverted cone along the length direction from the second end portion to the first end portion. By such a structure of the ceramic filter tube 3, the smooth flow of the molten metal (purified liquid) to the liquid outlet side after the filtration treatment of foreign matter can be further promoted.

[0074] In order to fully perform the filtering treatment of the molten metal and promote the smooth flow of the molten metal (purified liquid) after the filtering treatment of foreign matter to the liquid outlet side, in at least a part of the plurality of ceramic filter tubes 3, the inner diameter at the end face 3w of the first end portion on the liquid outlet side of the molten metal is larger than the inner diameter at the inner end face 3b of the second end portion on the opposite side. Generally, the inner diameter at the first end portion of the filter tube can be greater than 100.5% and less than 150% of the inner diameter at the second end portion. From the viewpoint of fully performing the filtering treatment of the molten metal and further promoting the smooth flow of the purified liquid to the liquid outlet side, thereby further improving the filtering performance, it is preferred that the inner diameter at the first end of the filter tube can be 100.6% to 145%, 100.7% to 140%, 100.8% to 135%, 100.9% to 130%, 101% to 125%, 101.5% to 120%, 102% to 115%, 102.5% to 110%, or 103% to 110% of the inner diameter at the second end.

[0075] Figure 4 (a) and (b) illustrate the relationship between the roughly circular opening portion 3e at the first end of the cylindrical ceramic filter tube 3 on the side from which the molten metal flows out in a molten metal filtration unit of one embodiment and the roughly circular through hole 2e provided on the side plate 2A on the liquid outlet side. Figure 4 (a) is a cross-sectional view observed from the length direction. Figure 4 (b) is a cross-sectional view observed from a horizontal direction perpendicular to the longitudinal direction.

[0076] Here, if Figure 4As shown in (b), a portion 3c of the inner surface of the cylindrical ceramic filter tube 3 extending in the length direction that is exposed to the molten metal forms a substantially circular opening 3e at the edge of the first end portion on the side for the molten metal to flow out. On the other hand, a substantially circular through hole 2e is formed in the side plate 2A on the liquid outlet side, and a recessed portion of a shape that encloses the first end portion of the filter tube 3 is provided at the periphery of the end portion of the through hole 2e on the filter tube installation side. Furthermore, the first end portion of the filter tube 3 is fixedly engaged with the side plate 2A on the liquid outlet side via a gasket 4A in such a manner that the annular end face 3w at the first end portion of the filter tube 3 on the liquid outlet side of the molten metal and the annular periphery of the end portion of the portion 3d of the outer surface of the filter tube 3 extending in the length direction that is exposed to the molten metal are enclosed. Figure 4 In the embodiment shown, the opening shape of the filter tube installation side end of the substantially circular through hole 2e provided on the side plate 2A on the liquid outlet side is the same as the opening shape of the through hole 2e on the side opposite to the filter tube installation side, i.e., the liquid outlet side. Figure 4 In one embodiment, the inner diameter of the liquid outlet end of the substantially circular through hole 2e of the side plate 2A on the liquid outlet side is equal to the inner diameter S of the filter tube arrangement end of the through hole 2e of the side plate 2A. i equal.

[0077] And, in this embodiment, if Figure 4 (b) together with Figure 4 As shown in (a), the shape of the opening 3e at the first end of the ceramic filter tube 3 on the side where the molten metal flows out is such that when viewed from the length direction, the opening shape of the filter tube installation side end of the substantially circular through hole 2e provided on the side plate 2A on the liquid outlet side is enclosed (enclosed inside). That is, the diameter of the opening 3e at the first end of the ceramic filter tube 3 on the side where the molten metal flows out (the inner diameter at the first end of the filter tube 3) D 2y The inner diameter S of the filter tube arrangement side end portion of the through hole 2e of the side plate 2A is i In other words, the inner diameter S of the filter tube arrangement side end portion of the through hole 2e of the side plate 2A is i The diameter D of the substantially circular opening 3e provided at the first end of the filter tube 3 on the side where the molten metal flows out is greater than 2y In this embodiment, as long as S i <D 2y The range of S is not particularly limited. i Relative to D 2y The ratio ((S i / D 2y)×100(%)) can usually be 80% or more and less than 100%, preferably 85% or more and less than 100%, 90% or more and less than 100%, 95% or more and less than 100%, 98% or more and less than 100%, 99% or more and less than 100%, 99.5% or more and less than 100% or 99.9% or more and less than 100%.

[0078] Thus, the inner diameter S of the filter tube placement side end portion passing through the through hole 2e of the side plate 2A is i The diameter D of the opening 3e at the first end of the filter tube 3 on the side where the molten metal flows out is greater than 2y The small structure prevents the inner surface edge of the first end of the filter tube 3 from being exposed to the molten metal, thereby effectively suppressing the deterioration and detachment of the filter tube 3 at this location, and further extending the life of the filter tube.

[0079] In addition, Figure 4 In the embodiment, when the substantially circular cross-sectional shape of the opening 3e of the first end of the filter tube 3 and / or the through hole 2e of the side plate 2A is not completely circular, D is determined by the circumscribed circle of the cross-sectional shape. 2y and / or S i .

[0080] Figure 5 The cross-sectional view shows an example of the inner diameter S of the end portion of the side (i.e., the side where the gasket 4A is arranged) of the ceramic filter tube 3 in the substantially circular through hole 2e provided on the side plate 2A from which the molten metal flows out of the molten metal filtration unit in one embodiment. i The inner diameter S of the end portion on the liquid outlet side ii As shown in the figure, in the present embodiment, in the substantially circular through hole 2e provided on the side plate 2A for the metal melt to flow out, the inner diameter S of the end portion on the liquid outlet side is ii The inner diameter S of the end portion on the side where the filter tube 3 is arranged is formed larger than that of the end portion. i As the inner diameter S of the end of the through hole 2e on the liquid outlet side ii The inner diameter S of the end portion on the side where the filter tube 3 is arranged is i The small means can be set at a constant angle as shown in the figure or set to a variable angle of inclination (tapered shape), or one or more stepped steps can be set.

[0081] exist Figure 5 In the implementation method, as long as S i >S ii The range of S is not particularly limited. ii Relative to S i The ratio ((S ii / Si )×100(%)) can usually be 70% or more and 99.5% or less, preferably 75% or more and 99.4% or less, 80% or more and 99.3% or less, 85% or more and 99.2% or less, 87% or more and 99.1% or more, 88% or more and 99% or less, 89% or more and 99% or less, 90% or more and 99% or less, 91% or more and 99% or more, or 92% or more and 99% or less.

[0082] Thus, in the substantially circular through hole 2e provided on the side plate 2A from which the molten metal flows out, the inner diameter S of the end portion on the liquid outlet side is formed. ii The inner diameter S of the end portion on the side where the filter tube 3 is arranged is i The small structure can suppress the molten metal from flowing out of the filtration unit in a state where the filtration treatment of foreign matter is insufficient, and further reduce the possibility that the purified liquid after the filtration treatment contains foreign matter.

[0083] In this specification, any two or more of the embodiments described above may be combined with each other, and if further desired, they may also be combined with any of the embodiments described later.

[0084] For example, you can Figure 3 The embodiment illustrated in the embodiment (in which, in at least a part of the plurality of ceramic filter tubes 3, the inner diameter of the end surface 3w of the first end portion on the outlet side of the molten metal is larger than the inner diameter of the inner end surface 3b of the second end portion on the opposite side) is different from Figure 4 The illustrated embodiment (an embodiment in which the shape of the opening portion 3e at the first end of the ceramic filter tube 3 on the side for the metal melt to flow out covers / encloses the opening shape of the filter tube side end of the approximately circular through hole 2e provided on the side plate 2A on the liquid outlet side when viewed from the length direction) is combined.

[0085] Alternatively, you can Figure 3 The illustrated embodiments and Figure 5 In the illustrated embodiment (in the substantially circular through hole 2e provided on the side plate 2A from which the molten metal flows out, the inner diameter S of the end portion on the liquid outlet side is ii The inner diameter S is formed larger than the inner diameter S of the end portion on the side where the filter tube 3 is arranged. i Small implementation method) combination.

[0086] Alternatively, you can Figure 4 The illustrated embodiments and Figure 5 Combinations of the illustrated embodiments.

[0087] Alternatively, you can Figure 3 , Figure 4 and Figure 5 The three illustrated embodiments are combined.

[0088] The above advantages that can be obtained through these embodiments respectively are also exerted in an additive manner in the combination of these embodiments, and are not weakened or offset.

[0089] A particularly preferred example is a Figure 3 , Figure 4 and Figure 5 The three embodiments illustrated are: <1> an embodiment in which, in at least a portion of a plurality of ceramic filter tubes 3, the inner diameter at the end face 3w of the first end portion on the liquid outlet side of the molten metal is larger than the inner diameter at the inner end face 3b of the second end portion on the opposite side; <2> an embodiment in which the shape of the opening portion 3e of the first end portion of the ceramic filter tube 3 on the side from which the molten metal flows out is such that when viewed from the length direction, the shape of the opening portion 3e of the filter tube installation side end portion of the substantially circular through hole 2e provided on the side plate 2A on the liquid outlet side is enclosed / enclosed within; <3> an embodiment in which the inner diameter S of the end portion on the liquid outlet side is set to the substantially circular through hole 2e provided on the side plate 2A on the side from which the molten metal flows out. ii The inner diameter S of the end portion on the side where the filter tube 3 is disposed is formed larger than that of the end portion. i An implementation method that is a combination of small implementation methods.

[0090] Thus, all the advantages described for each embodiment can be obtained. That is, according to this embodiment, the smooth flow of the molten metal (purified liquid) after the filtration treatment of foreign matter to the liquid outlet side can be further promoted, and the deterioration and granulation of the filter tube at the inner surface edge of the first end of the filter tube can be effectively suppressed, and the life of the filter tube can be further extended. In addition, the molten metal can be suppressed from flowing out of the filter unit in a state where the filtration treatment of foreign matter is insufficient, and the possibility of foreign matter being contained in the purified liquid after the filtration treatment is further reduced.

[0091] In a preferred embodiment, at least a portion of the plurality of ceramic filter tubes 3 of the metal melt filtration unit 1 can be generally formed of a porous material having a porosity of 25% or more and 50% or less. By forming the filter tube 3 using a porous material having a porosity in such a range, it is possible to achieve an optimal balance between the filter tube's performance of removing / filtering foreign matter in the metal melt and the extension of the filter tube's life (suppression of a decrease in filtration performance in a short period of time), thereby improving the filtration performance. As for the porosity of the porous material forming the filter tube, from the above viewpoint, it is preferably 25% or more and 45% or less, 28% or more and 42% or less, or 30% or more and 40% or less.

[0092] In the embodiment where the ceramic filter tube 3 is formed of a porous material having a porosity within the above range, examples of aggregates constituting the porous material include, but are not limited to, one or more of aluminum oxides such as silicon carbide, fused alumina, and sintered alumina. The aggregates constituting the porous material may preferably be one or more of aluminum oxides such as fused alumina and sintered alumina.

[0093] The average particle size of the aggregate of the porous material constituting the ceramic filter tube 3 is not particularly limited, but can generally be 200 μm or more and 2500 μm or less from the viewpoint of adjusting the porosity within the above range. The average particle size of the aggregate of the ceramic filter tube 3 can preferably be 250 μm or more and 2000 μm or less, and more preferably be 500 μm or more and 1700 μm or less.

[0094] The "average particle size" of the aggregate of the porous material constituting the filter tube herein is a value obtained by taking a SEM (scanning electron microscope) image of a cross section perpendicular to the length direction of the filter tube, measuring the particle size of the aggregate from the SEM image by the intercept method, and averaging the values. Specifically, an arbitrary line is drawn in the SEM image of the cross section of the filter tube, and the major diameter and minor diameter of the aggregate particles intersecting the line are measured. Next, the particle shape is set to an ellipse, and the average value of the major diameter and the minor diameter is set to the particle size of the aggregate. In addition, multiple SEM images of other fields of view are also taken, and the aforementioned measurements are repeated using the multiple SEM images taken. After measuring the particle sizes of more than 500 aggregates, statistical processing is performed to thereby determine the average particle size of the aggregate in the cross-sectional structure of the filter tube. In addition, the "porosity" of the above-mentioned filter tube can be calculated as an actual density based on the size and mass of the filter tube, and calculated as a ratio relative to the theoretical density of the filter tube (for example, composed of ceramic materials such as silicon carbide, alumina, etc. as the main raw materials and a small amount of inorganic binder).

[0095] Hereinafter, examples of materials constituting the respective parts of the molten metal filtration unit 1 except for the ceramic filter tube 3 will be described.

[0096] The close-fitting portion as a flat plate-like body in the liner 4A and the liner 4B of the metal melt filtration unit 1 that contacts the end surface of the filter tube 3 can be formed, for example, by a material made of ceramic fibers such as alumina fibers and ceramic fibers. As a specific example, it can be formed by a reaction product of basic aluminum chloride and silicon dioxide. In addition, the sealing portion as an annular body in the liner 4A and the liner 4B that contacts the edge of the outer surface of the filter tube 3 can be formed, for example, by a fiber-based material. Typically, it can be formed by a material containing an inorganic binder in alumina-silicon dioxide-based ceramic fibers. In the mode in which the close-fitting portion and the sealing portion are integrally formed, it can also be formed by any of the above-mentioned materials.

[0097] Next, a non-limiting example of a method for manufacturing the ceramic filter tube 3 constituting the molten metal filtration unit 1 will be described in general terms.

[0098] The method for producing the ceramic filter tube 3 may include the steps of kneading, molding, drying, degreasing, and sintering.

[0099] The kneading process is, for example, a process of kneading a mixture of raw material particles containing the above-mentioned aggregate and an inorganic binder to prepare raw material soil. Specifically, it can be obtained by kneading a mixture of raw materials containing aggregate particles, an inorganic binder, an organic binder and water and constituting the ceramic filter tube 3 using a kneading device such as a mixer.

[0100] As the aggregate particles, for example, the aggregate particles of the above materials can be used. In addition, as the inorganic binder, for example, one or more of diboron trioxide, aluminum oxide, magnesium oxide and silicon dioxide can be used. Among them, if diboron trioxide and aluminum oxide are used as inorganic binders, sometimes part of them reacts during sintering to generate needle-shaped crystals of 9Al2O3·2B2O3.

[0101] As the organic binder, for example, one or more of starch, cellulose and polysaccharide can be used. As water, deionized water or distilled water with few impurities can be preferably used. In order to properly sinter the aggregate particles, a sintering aid can also be further added for mixing. In addition, as needed, various additives arbitrarily selected from organic pore-forming agents, lubricants, plasticizers and release agents can also be added for mixing.

[0102] The molding process is a process of filling the raw material soil obtained in the kneading process into a mold prepared in advance for molding. The drying process performed next is a process of drying the molded body obtained in the molding process. Through this drying process, water is removed from the molded body.

[0103] The degreasing step is a step of removing organic components such as an organic binder from the molded body from which water has been removed in the drying step. By exposing the molded body to various conditions such as a predetermined temperature and time, the organic components contained in the molded body can be decomposed and removed. In addition, when the organic pore former is removed, pores corresponding to the shape of the organic pore former can be generated.

[0104] The firing step is a step of firing the molded body from which the organic components have been removed in the degreasing step using a firing device. The fired body obtained by firing is subjected to end processing and the like as necessary, thereby obtaining the ceramic filter tube 3 .

[0105] <Additional Embodiments Related to the Structure of the Side Panel>

[0106] The structure of the pair of side plates of the metal melt filtration unit of the utility model is not particularly limited except as specified in the attached claims. In addition to the mode in which each side plate has substantially the same outer shape in the form of a roughly rectangular plate, the two side plates can also satisfy the specific relationship related to shape or size that is carefully designed as exemplified by the following items (1) to (3).

[0107] (1) Additional Embodiment 1 of the Molten Metal Filtration Unit

[0108] As an example of the addition of the molten metal filtration unit, there is a molten metal filtration unit including a pair of side plates defined as follows.

[0109] A molten metal filtering unit, comprising:

[0110] a pair of side panels; and

[0111] a generally cylindrical filter tube connected generally perpendicularly to the pair of side plates;

[0112] Wherein, the pair of side panels comprises:

[0113] A first side plate having a through hole at a portion connected to the filter tube; and

[0114] A second side plate, the portion where the second side plate is connected to the filter tube is closed;

[0115] When the longitudinal direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube,

[0116] At least one of the pair of side plates includes a bottom portion formed such that one of a left bottom side or a right bottom side is provided higher in the vertical direction than a bottom side of the other side.

[0117] The molten metal filtration unit according to this additional embodiment may further include the following non-limiting structures.

[0118] (i)

[0119] When the longitudinal direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube,

[0120] The first side plate has a bottom formed in such a manner that one of the left bottom side or the right bottom side is arranged higher in the vertical direction than the other bottom side.

[0121] In the case where the first side plate has a bottom formed in such a manner that the left bottom side is higher than the right bottom side in the vertical direction, the second side plate has a bottom formed in such a manner that the left bottom side is higher than the right bottom side in the vertical direction, or,

[0122] When the first side plate has a bottom formed such that the right bottom side is higher in the vertical direction than the left bottom side, the second side plate has a bottom formed such that the right bottom side is higher in the vertical direction than the left bottom side.

[0123] (ii)

[0124] When the longitudinal direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube,

[0125] At least one of the pair of side plates includes a step portion formed such that one of the left bottom side or the right bottom side is provided higher in the vertical direction than the bottom side of the other side.

[0126] (iii)

[0127] In the above (ii), when the longitudinal direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube,

[0128] The pair of side plates includes a step portion formed such that a left bottom side is provided higher in the vertical direction than a right bottom side.

[0129] (iv)

[0130] In the above (ii), when the longitudinal direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube,

[0131] The step portion is composed of a first bottom portion as the lowest portion and a second bottom portion formed in a manner to be higher than the first bottom portion in the vertical direction.

[0132] The ratio (W1 / W2) of the horizontal length W1 of the first bottom to the horizontal length W2 of the second bottom is greater than 0.1 and less than 6.0, wherein W1 and W2 are lengths in a direction parallel to the length direction of the filter tube.

[0133] (v)

[0134] In the above (ii), when the longitudinal direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube,

[0135] The step portion is composed of a first bottom portion as the lowest portion and a second bottom portion formed in a manner to be higher than the first bottom portion in the vertical direction.

[0136] The ratio (W1 / H2) of the horizontal length W1 of the first bottom to the vertical length H2 from the first bottom to the second bottom is greater than 0.1 and less than 11, wherein W1 is the length in a direction parallel to the length direction of the filter tube.

[0137] (vi)

[0138] When the longitudinal direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube,

[0139] At least one of the pair of side panels has a bottom, which is formed in a manner that either the left bottom side or the right bottom side is set higher in the vertical direction than the bottom side of the other side, and has a first bottom side as the lowest part and an inclined part connecting the first bottom side to the bottom side set higher in the vertical direction.

[0140] (vii)

[0141] In the above (vi), when the longitudinal direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube,

[0142] The ratio of the horizontal length W1' of the first bottom to the horizontal length W2' of the inclined portion (W1' / W2') is greater than 0 and less than 6.0, wherein W1' and W2' are lengths in a direction parallel to the length direction of the filter tube.

[0143] (viii)

[0144] In the above (vi), when the longitudinal direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube,

[0145] The ratio (W1' / H2') of the horizontal length W1' of the first bottom to the vertical length H2' from the end of the inclined portion in contact with the first bottom to the other end of the inclined portion is greater than 0 and less than 320, wherein W1' is the length in a direction parallel to the length direction of the filter tube.

[0146] (ix)

[0147] In the above (viii), when the longitudinal direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube,

[0148] An angle θ1 formed between the inclined portion and the vertical direction is greater than or equal to 60° and less than or equal to 89°.

[0149] (x)

[0150] In the above (vi), when the longitudinal direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube,

[0151] The pair of side plates includes a bottom portion formed such that a left bottom side is arranged higher than a right bottom side in a vertical direction, and includes a first bottom portion as a lowest portion and an inclined portion connecting from the first bottom portion to the left bottom side.

[0152] (xi)

[0153] In the above (vi), when the longitudinal direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube,

[0154] The pair of side plates includes a bottom portion formed such that a right bottom side is arranged higher than a left bottom side in a vertical direction, and includes a first bottom portion as a lowest portion and an inclined portion connecting from the first bottom portion to the right bottom side.

[0155] (xii)

[0156] A molten metal filtering device is provided with a molten metal outlet, wherein:

[0157] With respect to the molten metal filtration unit described in (ix) above, the pair of side plates has an inclined portion formed in such a manner that the right bottom side is higher than the left bottom side in the vertical direction when the length direction of the filter tube is set to be substantially horizontal and the first side plate is located on the left side of the filter tube and the second side plate is located on the right side of the filter tube, and the first side plate is arranged in such a manner that the first side plate is in contact with the liquid outlet.

[0158] The filtering device includes a wedge-shaped protrusion on the hearth, wherein the wedge-shaped protrusion has an angle θ2 formed between a surface contacting the molten metal filtering unit and a horizontal plane, and θ2 satisfies that the sum of θ1 and θ2 is 61° or more and 114° or less.

[0159] (2) Additional Embodiment 2 of Molten Metal Filtration Unit

[0160] As an example of the addition of the molten metal filtration unit, there is a molten metal filtration unit including a pair of side plates defined as follows.

[0161] A molten metal filtering unit, comprising:

[0162] a pair of side panels; and

[0163] A substantially cylindrical filter tube connected substantially perpendicularly to the pair of side plates;

[0164] Wherein, the pair of side panels comprises:

[0165] A first side plate having a through hole at a portion connected to the filter tube; and

[0166] A second side plate, the portion where the second side plate is connected to the filter tube is closed;

[0167] Each side panel has at least one leg portion vertically arranged from the bottom surface of the side panel.

[0168] When the longitudinal direction of the filter tube is set to be substantially horizontal, the lowest position of the leg portion of the second side plate in the vertical direction is lower than the lowest position of the leg portion of the first side plate in the vertical direction.

[0169] The molten metal filtration unit according to this additional embodiment may further include the following non-limiting structures.

[0170] (i)

[0171] When the longitudinal direction of the filter tube is set to be substantially horizontal, the ratio of the vertical length of the leg portion of the first side plate to the vertical length of the leg portion of the second side plate is greater than or equal to 0.20 and less than 1.0.

[0172] (ii)

[0173] The sum of the ground contact areas of all the legs in the molten metal filtration unit is 0.015 or more and 0.075 or less relative to the sum of the bottom areas of the pair of side plates.

[0174] (iii)

[0175] In the above (ii), the sum of the ground contact areas of all the legs in the molten metal filtration unit is 0.020 or more and 0.060 or less relative to the sum of the bottom areas of the pair of side plates.

[0176] (iv)

[0177] At least two legs are provided on the first side plate, and one leg is provided on the second side plate.

[0178] (v)

[0179] In the above (iv), at least two legs are provided near both ends of the bottom surface of the first side plate in the longitudinal direction, and one leg is provided at a substantially central portion of the bottom surface of the second side plate in the longitudinal direction.

[0180] (3) Additional Embodiment 3 of the Molten Metal Filtration Unit

[0181] As an example of the addition of the molten metal filtration unit, there is a molten metal filtration unit including a pair of side plates defined as follows.

[0182] A molten metal filtering unit, comprising:

[0183] a pair of side panels; and

[0184] A substantially cylindrical filter tube connected substantially perpendicularly to the pair of side plates;

[0185] Wherein, the pair of side panels comprises:

[0186] A first side plate having a through hole at a portion connected to the filter tube; and

[0187] A second side plate, the portion where the second side plate is connected to the filter tube is closed;

[0188] Each side panel has a leg portion vertically arranged from the bottom surface of the side panel,

[0189] The number of the legs included in the first side plate is at least one greater than the number of the legs included in the second side plate.

[0190] The molten metal filtration unit according to this additional embodiment may further include the following non-limiting structures.

[0191] (i)

[0192] The first side plate is provided with two legs, and the second side plate is provided with one leg.

[0193] (ii)

[0194] Two leg portions are provided near both ends of the bottom surface of the first side plate in the longitudinal direction, and one leg portion is provided at a substantially central portion of the bottom surface of the second side plate in the longitudinal direction.

[0195] (iii)

[0196] When the molten metal filtration unit is placed on a horizontal surface and viewed from vertically above, the area of ​​the molten metal filtration unit represented by the product of the length of the molten metal filtration unit in the longitudinal direction of the filter tube and the length of the side plate in the longitudinal direction is denoted as S1.

[0197] The total ground contact area of ​​all legs of the molten metal filtration unit is defined as S2.

[0198] The area ratio S2 / S1 is greater than or equal to 0.0020 and less than or equal to 0.015.

[0199] Example

[0200] Hereinafter, the present invention will be described in more detail with reference to embodiments.

[0201] These embodiments do not constitute any limitation to the present invention and should be understood as examples only.

[0202] Production Example 1 of Ceramic Filter Tube

[0203] 10 parts by mass of inorganic binder were mixed with 100 parts by mass of fused alumina ("aggregate particles") having an average particle size of 600 μm. As inorganic binders, materials containing the following compounds were used: 45% by mass of perboric acid, 20% by mass of alumina, 20% by mass of magnesium oxide, 10% by mass of silicon dioxide, 0.01% by mass of Na2O, 0.01% by mass of K2O3, and 0.2% by mass of CaO. Next, using the raw material soil containing the fused alumina and the inorganic binder, a cylindrical molded body was made, in which the cross-sectional shapes perpendicular to the length direction in the outer surface and the inner surface were circular, and one end (the first end) was open and the other end (the second end) was closed. The molded body was dried at 80°C for 8 hours, and then degreased at 900°C for 6 hours. After that, the molded body that had been dried and degreased was fired at 1250°C for 7 hours in a firing furnace to manufacture a ceramic filter tube. When making the cylindrical molded body, the size of the molded body was adjusted so that the length L1 of the portion of the outer surface of the filter tube exposed to the molten metal was 1400 mm, the outer diameter D1 of the filter tube was 100 mm, the length L2 of the portion of the inner surface of the filter tube exposed to the molten metal was 1430 mm, and the inner diameter D2 of the filter tube was 60 mm. The outer diameter D1 and the inner diameter D2 of the filter tube were constant in the entire length direction. The average particle size of the aggregate of the filter tube was 600 μm, and the porosity was 38% (the same in the subsequent manufacturing examples). The average particle size and porosity were measured in accordance with the above method.

[0204] Production Example 2 of Ceramic Filter Tube

[0205] When making the above-mentioned cylindrical molded body, the size of the molded body was adjusted so that the length L1 of the portion of the outer surface of the filter tube exposed to the metal melt was 1000 mm, the outer diameter D1 of the filter tube was 100 mm, the length L2 of the portion of the inner surface of the filter tube exposed to the metal melt was 1030 mm, and the inner diameter D2 of the filter tube was 30 mm. Except for this, a ceramic filter tube was manufactured in the same manner as in the above-mentioned Manufacturing Example 1.

[0206] Production Example 3 of Ceramic Filter Tube

[0207] When making the above-mentioned cylindrical molded body, the size of the molded body was adjusted so that the length L1 of the portion of the outer surface of the filter tube exposed to the metal melt was 900 mm, the outer diameter D1 of the filter tube was 83 mm, the length L2 of the portion of the inner surface of the filter tube exposed to the metal melt was 930 mm, and the inner diameter D2 of the filter tube was 41.5 mm. Except for this, a ceramic filter tube was manufactured in the same manner as in the above-mentioned Manufacturing Example 1.

[0208] Manufacturing Example 4 of Ceramic Filter Tube

[0209] When making the above-mentioned cylindrical molded body, the size of the molded body was adjusted so that the length L1 of the portion of the outer surface of the filter tube exposed to the metal melt was 1000 mm, the outer diameter D1 of the filter tube was 83 mm, the length L2 of the portion of the inner surface of the filter tube exposed to the metal melt was 1030 mm, and the inner diameter D2 of the filter tube was 41.5 mm. Except for this, a ceramic filter tube was manufactured in the same manner as in the above-mentioned Manufacturing Example 1.

[0210] Production Example 5 of Ceramic Filter Tube

[0211] When making the above-mentioned cylindrical molded body, the size of the molded body was adjusted so that the length L1 of the portion of the outer surface of the filter tube exposed to the metal melt was 1400 mm, the outer diameter D1 of the filter tube was 83 mm, the length L2 of the portion of the inner surface of the filter tube exposed to the metal melt was 1430 mm, and the inner diameter D2 of the filter tube was 41.5 mm. Except for this, a ceramic filter tube was manufactured in the same manner as in the above-mentioned Manufacturing Example 1.

[0212] Manufacturing Example 1C of Ceramic Filter Tube

[0213] When making the above-mentioned cylindrical molded body, the size of the molded body was adjusted so that the length L1 of the portion of the outer surface of the filter tube exposed to the metal melt was 800 mm, the outer diameter D1 of the filter tube was 100 mm, the length L2 of the portion of the inner surface of the filter tube exposed to the metal melt was 830 mm, and the inner diameter D2 of the filter tube was 60 mm. Except for this, a ceramic filter tube was manufactured in the same manner as in the above-mentioned Manufacturing Example 1.

[0214] Manufacturing Example 2C of Ceramic Filter Tube

[0215] When making the above-mentioned cylindrical molded body, the size of the molded body was adjusted so that the length L1 of the portion of the outer surface of the filter tube exposed to the metal melt was 820 mm, the outer diameter D1 of the filter tube was 80 mm, the length L2 of the portion of the inner surface of the filter tube exposed to the metal melt was 850 mm, and the inner diameter D2 of the filter tube was 40 mm. Except for this, a ceramic filter tube was manufactured in the same manner as in the above-mentioned Manufacturing Example 1.

[0216] Manufacturing Example 3C of Ceramic Filter Tube

[0217] When making the above-mentioned cylindrical molded body, the size of the molded body was adjusted so that the length L1 of the portion of the outer surface of the filter tube exposed to the metal melt was 820 mm, the outer diameter D1 of the filter tube was 100 mm, the length L2 of the portion of the inner surface of the filter tube exposed to the metal melt was 850 mm, and the inner diameter D2 of the filter tube was 60 mm. Except for this, a ceramic filter tube was manufactured in the same manner as in the above-mentioned Manufacturing Example 1.

[0218] Manufacturing of molten metal filtration units

[0219] Example 1

[0220] Two side plates formed of a material containing silicon carbide as a main raw material were prepared. Each side plate is a flat plate-shaped body with a thickness of 60 mm, a length of 700 mm, and a width of 720 mm. On a side plate on the side for the molten metal to flow out, three groups of six 60 mm circular through holes (holes with equal inner diameters on the filter tube side of the side plate and the molten metal outlet side on the opposite side) and two groups of five through holes of the same size were arranged along the lateral direction of the side plate in a manner that the interval between each through hole is 55 mm, and the total number of these through holes is 28. No such through holes are arranged on the side plate on the side opposite to the side for the molten metal to flow out. In addition, a recess is arranged on each side plate, and the recess has a peripheral wall surface with a circular cross-section matching the shape (outer diameter) of each end of the filter tube and a flat bottom surface. The depth of the recess relative to the length and width of the side plate (the depth in the direction corresponding to the length direction of the filter tube) is set to 31.3 mm. In one side plate on the side from which the molten metal flows out, the through holes are arranged at the centers of the respective recessed portions.

[0221] A liner made of alumina fiber with a thickness of 6 mm and a circular opening of 60 mm in diameter and a shape matching the bottom surface of the above-mentioned recess was prepared, as well as a liner with the same structure except that it did not have the above-mentioned circular opening. The above-mentioned liner with circular opening was arranged in each recess of the side plate on the side of the metal melt outlet provided with a through hole, and the above-mentioned liner without circular opening was arranged in each recess of the side plate without a through hole. Then, the first end with an opening on the side of the metal melt outlet of the ceramic filter tube of the above-mentioned manufacturing example 1 was embedded and fixed relative to each recess of the side plate on the side of the metal melt outlet provided with a through hole and the above-mentioned liner with circular opening corresponding thereto, and the closed second end of the filter tube was embedded and fixed relative to each recess of the side plate without a through hole and the above-mentioned liner without circular opening corresponding thereto. In order to prevent the leakage of the molten metal, the side plates were pressed from both sides to compress the gasket to 50% of the original thickness, that is, 3 mm, to obtain the molten metal filtration unit of Example 1.

[0222] Examples 2 to 5 and Examples 1C to 3C

[0223] Instead of the ceramic filter tube of the above-mentioned Manufacturing Example 1, the ceramic filter tubes of the above-mentioned Manufacturing Examples 2 to 5 and Manufacturing Examples 1C to 3C were used respectively, and side plates provided with through holes of a size corresponding to the inner diameter of each filter tube (in Examples 3 to 5, the side plates have a total number of through holes of 39) and gaskets having openings of sizes corresponding to the inner diameters were used. Except for this, metal melt filtration units of Examples 2 to 5 and Examples 1C to 3C were obtained in the same manner as Example 1.

[0224] Evaluation of filtration performance

[0225] The following measurements (1) to (3) were performed and evaluated for each of the molten metal filtration units of Examples 1 to 5 and Examples 1C to 3C obtained above. The results are shown in Table 1 below together with the structural parameters of the ceramic filter tubes of these units.

[0226] (1) Determination of the change in the liquid head height of the molten metal in the filtration chamber

[0227] The above-mentioned molten metal filtration unit was placed on a furnace bed of a filtration chamber having a liquid inlet and a liquid outlet for molten metal, and a predetermined amount of molten aluminum (720°C) was supplied to the filter tube of the molten metal filtration unit through the liquid inlet, and the change in the liquid level of the molten aluminum in the filtration chamber (hereinafter also referred to as "liquid top height") was measured. Specifically, the liquid top height T0 of the molten metal in the filtration chamber at the start of filtration was measured, and the liquid top height T1 of the molten metal after 1000 tons of molten metal was circulated was measured (refer to the reference Figure 6 ). In this measurement test, the flow rate of the molten metal to the molten metal filtration unit was set to 25 tons / hour. Figure 6 1 refers to a molten metal filtration unit, 2A refers to a side plate on a liquid discharge side, 2B refers to a side plate on a liquid inlet side, 2e refers to a through hole provided on the side plate on a liquid outlet side, 3 refers to a ceramic filter tube, 5 refers to a filter chamber, 6 refers to a filter bed, 6A and 6B refer to bases provided on a furnace bed, 7 refers to a shell of a filter chamber, I refers to a liquid inlet of the molten metal into the filter chamber, O refers to a liquid outlet of the molten metal from the filter chamber, T0 refers to a liquid top height of the molten metal in the filter chamber at the start of filtration, and T1 refers to a liquid top height of the molten metal after 1000 tons of molten metal has flowed through the molten metal filtration unit.

[0228] The lower the change in the height of the top of the molten metal in the filter chamber (the value of T1-T0), the lower the filtration resistance during continuous liquid flow, and the more stable the use. Therefore, according to the change in the height of the top of the molten metal in the filter chamber, the stability of the filtration was evaluated according to the following three levels of scores. In addition, Table 1 shows the change in the top height (mm) and the score in brackets for each example.

[0229] 3 points: The change in the height of the molten metal top is less than 50 mm.

[0230] 2 points: The change in the height of the molten metal top is 50 mm or more and 100 mm or less.

[0231] 1 point: The change in the height of the molten metal top is greater than 100 mm.

[0232] (2) Determination of the amount of liquid flow until a predetermined change in the height of the molten metal top is achieved (ceramic filter tube) Lifespan evaluation)

[0233] If the flow path for the molten metal to flow is reduced due to the capture of inclusions in the ceramic filter tube, the height of the molten metal liquid head in the filter chamber increases over time. Generally, the filtration of the molten metal is performed by natural flow. When filtering the molten metal with a clogged filter tube, a liquid head height is required to generate a pressure sufficient for the liquid to flow, but if the liquid head height becomes high, it is generally believed that the molten metal is in danger of overflowing from the tank of the filter chamber, and the filtration speed is reduced. In this test, the life of the filter tube was evaluated by measuring the liquid flow rate (tons) until the change in the liquid head height of the molten metal before and after filtration reached 120 mm. In addition, this test continued the measurement test of the molten metal liquid head height in (1) above, and the liquid flow rate (tons) when the final change in the molten metal liquid head height (value of T1-T0) reached 120 mm was calculated. In this test, the life of the filter tube was evaluated according to the following three-level scores based on the liquid flow rate. In addition, Table 1 shows the flow rate (tons) of each example and the fraction in parentheses.

[0234] 3 points: The amount of liquid passed until the change in the height of the molten metal top reaches 120 mm is greater than 2,500 tons (the amount of liquid passed exceeds 2,500 tons).

[0235] 2 points: The amount of liquid passed until the change in the height of the molten metal top reaches 120 mm is 1500 tons to 2500 tons (the amount of liquid passed until the change in the height of the molten metal top reaches 120 mm is 1500 tons or more and 2500 tons or less).

[0236] 1 point: The amount of liquid passed until the change in the height of the molten metal top reaches 120 mm is less than 1,500 tons (the amount of liquid passed is less than 1,500 tons).

[0237] (3) Comprehensive evaluation of the filtration performance of ceramic filter tubes

[0238] The filtration performance of the ceramic filter tube was comprehensively evaluated by the total score of the test results of (1) and (2) above. In the examples of evaluation A and evaluation B, even if the filtration amount of the molten metal increases, the liquid top height during the liquid flow is low, the filtration can be stably performed, and the filtration life is also long, which is relatively good. On the other hand, in the example of evaluation C, if the filtration amount of the molten metal increases, the liquid top height becomes high, so there is a concern that the molten metal overflows from the groove of the filter chamber, etc., and the overall filtration amount is also small, which is not appropriate during operation. In addition, Table 1 shows the evaluation of each example and the total score in brackets.

[0239] A rating: 6 points

[0240] B rating: 4-5 points

[0241] C rating: 3 points or less

[0242] [Table 1]

[0243]

[0244] The results shown in Table 1 verify that by using a molten metal filtration unit comprising a ceramic filter tube that satisfies the relationship (1) L1 / D1≥8.5 and (2) L2 / D2≥22 of the present invention, not only is the flow rate of the molten metal fully ensured, but the life of the filter tube is also greatly improved, compared to a case where neither of these relationship is satisfied.

[0245] Industrial Applicability

[0246] The molten metal filtration unit of the utility model can not only highly maintain the strength of the side plate, but also can simultaneously further increase the flow rate of the molten metal, further extend the service life of the filter tube, and further improve the removal performance of inclusions contained in the molten metal. Therefore, it can be well used to remove inclusions from molten metals such as aluminum in the form of a molten metal filtration device placed in a filter chamber.

[0247] Description of Reference Numerals

[0248] 1: Metal melt filtration unit

[0249] 2A: Side plate on the liquid outlet side

[0250] 2B: Side plate on the side opposite to the liquid outlet side

[0251] 2e: Through hole provided on the side plate on the liquid outlet side

[0252] 3: Ceramic filter tube

[0253] 3a: Outer end surface at the second end of the filter tube

[0254] 3b: Inner end surface at the second end of the filter tube

[0255] 3c: The portion of the inner surface of the filter tube exposed to the molten metal

[0256] 3d: The portion of the outer surface of the filter tube exposed to the molten metal

[0257] 3e: Opening at the first end of the filter tube

[0258] 3w: End surface at the first end of the filter tube

[0259] 4A: Gasket for fixing the first end of the filter tube

[0260] 4B: Gasket for fixing the second end of the filter tube

[0261] L1: The length of the portion of the filter tube outer surface exposed to the molten metal in the longitudinal direction

[0262] L2: The length of the inner surface of the filter tube exposed to the molten metal

[0263] D1: The outer diameter of the filter tube

[0264] D2: Inner diameter of the filter tube

[0265] D 2x : The inner diameter at the second end of the filter tube

[0266] D 2y : The inner diameter of the first end of the filter tube

[0267] S i : The inner diameter of the filter tube installation side end of the through hole of the side plate on the liquid outlet side

[0268] S ii : The inner diameter of the through hole of the side plate on the liquid outlet side at the liquid outlet side end

[0269] 5: Filter chamber

[0270] 6: Filter bed

[0271] 6A, 6B: Base installed on the hearth

[0272] 7: Filter chamber housing

[0273] I: Inlet of molten metal to the filter chamber

[0274] O: The molten metal flows out of the filter chamber.

[0275] T0: The height of the molten metal top in the filter chamber at the beginning of filtration

[0276] T1: The height of the molten metal head after 1000 tons of molten metal is passed through the molten metal filtration unit.

Claims

1. A molten metal filtration unit, characterized in that: The molten metal filtering unit comprises a plurality of ceramic filter tubes and a pair of side plates. The plurality of ceramic filter tubes are cylindrical and arranged approximately in parallel, and the cross-sectional shapes of the outer surfaces and the inner surfaces perpendicular to the longitudinal direction are approximately circular. The pair of side plates are arranged at both ends of the plurality of ceramic filter tubes in the longitudinal direction. The plurality of ceramic filter tubes have a first end on one side through which the molten metal flows out and a second end on the other side. With respect to at least a portion of the plurality of ceramic filter tubes, When the length of the portion of the outer surface of the filter tube exposed to the molten metal is L1, the outer diameter of the filter tube is D1, the length of the portion of the inner surface of the filter tube exposed to the molten metal is L2, and the inner diameter of the filter tube is D2, The following two relations are satisfied: (1) L1 / D1 ≥ 8.5 (2)L2 / D2≥22.

2. The molten metal filtration unit according to claim 1, characterized in that: In at least a portion of the plurality of ceramic filter tubes, the inner diameter at the first end portion is larger than the inner diameter at the second end portion.

3. The molten metal filtration unit according to claim 2, characterized in that: In at least a portion of the plurality of ceramic filter tubes, an inner diameter at the first end portion is 100.5% or more and 150% or less of an inner diameter at the second end portion.

4. The molten metal filtration unit according to claim 1, characterized in that: In at least a portion of the plurality of ceramic filter tubes, the opening shape of the first end portion surrounds the opening shape of the filter tube installation side end portion of the substantially circular through hole provided on the side plate on the liquid outlet side of the pair of side plates when viewed in the longitudinal direction.

5. The molten metal filtration unit according to claim 4, characterized in that: In the through hole of the side plate on the liquid outlet side, the inner diameter of the end of the through hole on the liquid outlet side is smaller than the inner diameter of the end of the through hole on the filter tube installation side.

6. The molten metal filtration unit according to claim 5, characterized in that: In the through hole of the side plate on the liquid outlet side, the inner diameter of the end portion on the liquid outlet side is not less than 70% and not more than 99.5% of the inner diameter of the end portion on the filter tube installation side.

7. The molten metal filtration unit according to claim 1, characterized in that: At least a portion of the plurality of ceramic filter tubes are fitted and fixed to the recessed portion opened in the side plate at each end in the longitudinal direction via a gasket having a shape matching the recessed portion.

8. The molten metal filtration unit according to claim 1, characterized in that: At least a part of the plurality of ceramic filter tubes is formed of a porous material having a porosity of 25% or more and 50% or less.

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