JPH02229515A - Ceramic filter for filtration of molten metal and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field] The present invention includes an open cell foam structure made of a heat-resistant ceramic as a base material, and has a pair of mass flow surfaces that intersect with the mass flow direction of molten metal, and approximately Regarding a ceramic filter for molten metal filtration comprising at least one outer circumferential side surface extending in the mass flow direction, in particular, the ceramic filter is impregnated with a ceramic in the form of a high viscosity slurry into an organic foam material, dried, and then heated. The organic foam material is removed and the remaining ceramic is fired,
Furthermore, the present invention relates to a ceramic filter for filtrating molten metal which is subjected to surface treatment with a refractory material after drying as required. Furthermore, the present invention also relates to a method of manufacturing the above ceramic filter.

[Prior art]

Ceramic filters of the above-mentioned construction are known in the art and are commonly used in the foundry industry to exclude impurities such as slag, sand and refractory materials from the cast products to be manufactured.

Normally, when manufacturing a ceramic filter having an open cell foam structure, an organic foam material such as polyurethane foam is impregnated with a low viscosity slurry of ceramic material, or after being impregnated with a high viscosity slurry, a pair of rollers is used. Push out excess slurry. When using a low viscosity slurry, the ceramic material is distributed approximately evenly throughout the foam structure. On the other hand, high viscosity slug IJ
Depending on the consolidation hardness of the foam material, the roller gap and the rheological properties of the slurry, the slurry mass can be deposited inside the foam structure or along the sides parallel to the direction of conveyance past the rollers. There is a recognized tendency for this to occur.

To ensure that the desired filtration action is achieved, the filter is
It is necessary to provide excellent heat resistance and mechanical strength against molten metal. In known filters, the ceramic is constantly damaged and eroded in the melt at a certain rate depending on the pouring. Such damage/erosion can occur in particular in the area of the side surfaces extending in the direction of flow of the molten metal, even if the accumulation density of the material increases as they pass through the corresponding rollers, as well as towards the outside. This occurs at the hollow bridging portion of the foam structure that is opened. During the process of conveying the foamed material impregnated with slurry to the next processing position, part of the slurry is removed again, and the cell bridge is formed by the vapor pressure generated during the firing process of the foamed material. This originates from the slit-like openings that occur in the.

International Publication No. WO 82/03339 describes a ceramic filter having an open cell foam structure and having a heat-resistant ceramic material as a base material. This known ceramic filter is manufactured by impregnating an organic foam material with a slurry of highly viscous ceramic material, followed by drying, heating and firing to remove the foamable material. In this case, the excess slurry is extruded and removed when the impregnated foam material passes through the roller gap in the roller pair. Furthermore, in order to reliably protect the cell bridges exposed on the surface of the filter from damage, the surface of the dried and impregnated foam material is further impregnated with a slurry of ceramic material. In that case, the heat resistance of the filter is improved. However, this additional impregnation is disadvantageous in that, on the one hand, an additional slurry layer is formed not only in the exposed cell bridging but also in the filter area below it, impairing the filter's permeability; On the other hand, in many embodiments sufficient strength is not obtained, and a tendency to breakage and erosion is still observed due to insufficient strength, especially as the head of the molten metal increases.

[Disclosure of the invention]

The object of the present invention is to propose a ceramic filter of the type mentioned above which has excellent mechanical and thermal stability and durability against molten metal.

In order to solve this problem, the ceramic filter according to the present invention forms a closed layer made of a refractory material with a thickness of 0.5 to 3 mm on the entire surface of at least one outer peripheral side surface extending in the flow direction of the molten metal. It is characterized by the fact that

A filter with the above-mentioned configuration makes it possible to form a closed frame in the surrounding side areas. In particular, the open cell bridges on the flow-through surface are closed off with a covering layer that does not impair the permeability of the filter.

The peripheral lateral area of the organic foam material adapted to the dimensions of the filter to be produced is a cylindrical outer circumferential surface in the case of filters with a circular or oblong base.

By applying a fire-resistant material to the foam material in this side region, the thickness is reduced to 0.000000 over the entire circumferential length of this region.
A closure layer of 5-3 mm is formed. The open cell bridges on the flow-through side of the foam structure can be subsequently coated with a refractory material.

It is preferable to coat the open cell part with a thickness of 0.1 to lm+n, and in particular, the coating mass per unit area is 40
~400 mg/c.

The lateral closure layer, as well as the covering of the open cell bridges,
Preferably, it is formed from the same ceramic slurry used for impregnation. The materials used here include, for example, substances whose main component is Al20, or known substances which are excellent in fire resistance and contain a particularly large amount of aluminum, such as sillimanite, mullite, or chamotte.

Advantageously, the viscosity of the slurry used is between IXIO' and 2xlO' cps at a rotation speed of 2 Orpm. In some cases, slurries of different refractory materials, such as water glass, silica sols, resins, Air-bonded refractory materials such as aluminum phosphate, zirconium oxide chloride, and ethyl silicate can be used.

[Best mode for carrying out the invention]

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

FIG. 1 shows a cross-section of the filter material before firing, which includes a foamed structure l of an organic material such as foamed polyurethane. The foam structure 1 includes, for example, four circumferential side surfaces 2 that are adjacent to each other in sequence, and a pair of end surfaces (through-flow surfaces) 3 that are spaced apart and arranged in parallel.
It is formed into a rectangular parallelepiped shape having Next, the foamed structure 1 is impregnated with a ceramic material 4 in the form of a high viscosity slurry. As will be described later, all side surfaces 2 are provided with a closing layer 5 made of a refractory material and having a thickness of 0.5 to 3 mm.

This refractory material consists in particular of the same slurry ceramic material with which the foam structure is impregnated. Further, a coating layer 7 made of a refractory material is formed on the open cell bridging portion 6 of the flow surface 3. This coating layer 7 is also made of the same slurry ceramic material with which the foamed structure 1 is impregnated. When fired, the foamed structure 1 is burned out and the ceramic material in the form of slurry is hardened.

As shown in FIGS. 2a and 2b, in order to form a closure layer 5 in the area of the side surface 2, a foam structure l impregnated with slurry is stamped with a stamper having the same bottom shape as the foam structure 1. 8 to apply pressure for a predetermined period of time. As a result, the excess slurry reaches the region of the side surface 2 and is concentrated thereon in the form of a partial bead, as shown in FIG. 2a. When the stamper 8 is lifted to release the pressure from the foam structure 1, a frame of slurry closed on all sides is formed. This is because the beads of excess slurry on the circumferential side 2 become evenly distributed on the circumferential side 2 when the pressure is relieved. Next, the foamed structure 1 impregnated with the slurry is dried and fired, and the coating layer 7 is formed before or after firing.

As shown in FIG. 3, the foamed structure 1 may be passed through a pair of open belts 9 after being impregnated with the slurry. That is,
By pressing the foamed structure 1 impregnated with the slurry between the belt pair 9, excess slurry is pushed out to the side surface 2 and a bead is formed on the side surface. As the foam structure 1 passes through the pair of belts 9, the pressure is released so that the beads of slurry become evenly distributed on both sides 2, forming a pair of closure layers 5 on both sides.

In the embodiment shown in FIG. 4, the foamed structure 1 impregnated with slurry and dried is transported by a horizontal transport device 10 and passed through a pair of rollers 11 having a vertical axis to form a closure layer 5. A refractory material, slurry or air bonding material is applied to a pair of side surfaces 2 of the foam structure 1 by a pair of rollers 11 and penetrated into the porous foam structure to a predetermined depth. At that time, by using a doctor blade, a doctor roll, or the like, a coating material layer with as uniform a thickness as possible is formed on the roller surface.

If the above step of forming the closure layer 5 is performed subsequent to the step shown in FIG. 3, the closure layer 5 can be formed on all the outer surfaces 2. However, in order to form the closure layer 5 on all the side surfaces 2, two sets of devices shown in FIG. 4 may be sequentially arranged, and the foamed structure 1 may be rotated by 90 degrees between each device.

As yet another method of forming the closure layer 5, the foam structure 1
It is also possible to glue a further layer of foamed material with a suitable porosity to the side surface 2 or to provide a fine adhesive material on the side surface 2.

When such a foamed structure 1 is impregnated with slurry, the fine pores (voids) in the outer surface area are kept filled with the slurry, so that the closed layer 5 can be easily formed. Become.

The method shown in FIG. 4 can also be applied to the provision of a closure layer 5 of air-bonded refractory material to the outer surface 2 of a filter which has already been subjected to a firing treatment.

Furthermore, the method shown in FIG. 4 can also be used when forming the covering layer 7 by impregnating it with a slurry before performing the post-drying firing, or by providing a layer of air-bonded refractory material after the firing. Can be applied.

When a foamed ceramic filter is used to filter molten metal (for example, molten spheroidal graphite cast iron or gray cast iron in casting equipment), not only thermal stress but also static load acts rapidly on the filter due to the flow of molten metal. The degree of thermal stress is highly dependent on the composition and properties of the slurry used to manufacture the ceramic filter.

Other factors that affect stability and durability are the shape of the laminated surfaces (joint surfaces) of the filter and the unique shape of the filter due to structural constraints. The latter can be significantly improved by the configuration of the present invention without undesirably affecting the mass flow rate of the molten metal.

That is, the filter according to the invention has a much higher load (head and pressure head) in use compared to the conventional one.
can be made to work. This fact has been demonstrated using a test device having the configuration described below.

The test apparatus shown in Figure 5 consists of a tank I receiving liquid material.
2, the bottom of which is closed by a plug 13. A filter receiving member 14 having a mesh 15 of an appropriate standard grade is arranged on the lower side of the tank 12, and with this receiving member, for example, 5Q+nm x 5Qmm
A test filter 16 of mm is supported. Between the tank 12 and the receiving member l4, there is disposed a pouring pipe l7 whose portion 17' can be extended by a predetermined length, for example. The test filter 16 is mounted on the mesh 15, the plug 13 is removed, and a predetermined amount of molten metal is loaded onto the test filter 16 and is allowed to flow.

The ceramic filter according to the present invention was compared with a comparative example ceramic filter according to the prior art using the test apparatus shown in FIG. 5 using gray cast iron as the molten metal. The ceramic filter according to the present invention is formed with predetermined dimensions,
The thickness of the surrounding closing layer 5 is 2 mm, and the thickness of the covering layer 7 is 0.
．． It is set to 5 mm. On the other hand, the ceramic filter of the comparative example was manufactured only by slurry impregnation treatment without forming the closure layer 5 and the covering layer 7, and had substantially the same dimensions and flow through as the one according to the present invention. It has resistance. The weight spectra in both filters were almost identical. Additionally, both filters were placed in the same furnace. The results are shown in the table below.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view showing a partially broken ceramic filter before firing; FIGS. 2a and 2b are explanatory diagrams showing an example of the method for forming a surrounding closure layer; FIGS. Fourth
The figures are explanatory diagrams showing an example of a method for forming a closure layer on a pair of side edge regions, respectively, and FIG. 5 is a front view showing the configuration of a ceramic filter testing apparatus. l... Foamed structure 2... Circumferential side surface 3... Mass flow surface (end face) 4... Slurry ceramic material 5... Closed layer 6... Open cell bridging portion 7... - Covering layer 8... Stamper 9... Belt pair 10... Conveying device 12... Tank 13... Plug 14... Filter receiving member 15... Mesh 16... Sample filter 17 ... Enema tube patent applicant Georg Fischer Akchengesellschaft

Claims (1)

[Scope of Claims] 1. It includes an open-cell foamed structure made of heat-resistant ceramic as a base material, and has a pair of flow-through surfaces (3) that intersect with the flow-through direction of the molten metal, and that extends substantially in the flow-through direction. A ceramic filter for filtrating molten metal comprising at least one outer circumferential side surface (2) in which an organic foam material (1) is impregnated with a ceramic (4) in the form of a high viscosity slurry, dried, and then heated. The organic foamed material (1) is removed and the remaining ceramic (4) is fired, and if necessary, after drying, the surface is treated with a refractory material. A ceramic filter characterized in that a closing layer (5) made of a refractory material with a thickness of 0.5 to 3 mm is formed on the entire surface. 2. The ceramic filter according to claim 1, wherein the cell bridging portion of the organic foam material (1) that is open at the flow-through surface (3) is closed by a coating layer (7) made of a refractory material. filter. 3. The ceramic filter according to claim 1 or 2, wherein the thickness of the coating layer (7) is 0.1 to 1 mm. 4. In the ceramic filter according to any one of claims 1 to 3, the closure layer (5) and/or the covering layer (
A ceramic filter characterized in that the refractory material forming (7) is the same material as the slurry-like ceramic impregnated into the organic foam material (1). 5. A method for manufacturing a ceramic filter according to any one of claims 1 to 4, wherein the organic foam material (1) is formed from a heat-resistant ceramic material and is molded to correspond to the dimensions of the filter to be manufactured. Where the foamed material is impregnated with a highly viscous slurry and then dried, heated and calcined to remove the foamed material and optionally subsequently surface treated with a refractory material, the refractory material is applied in the peripheral side area of the foamed material. A manufacturing method characterized in that a closed layer having a thickness of 0.5 to 3 mm is formed over the entire length of the region in the circumferential direction. 6. The manufacturing method according to claim 5, wherein, as a subsequent surface treatment, a refractory material is applied to the open cell bridging portions on the flow-through surface of the foam structure to form a coating layer. 7. The manufacturing method according to claim 5 or 6, wherein the coating layer of the cell bridging portion is applied with a thickness of 0.1 to 1 mm and a mass of 40 to 400 mg/cm^2 per unit area. manufacturing method. 8. In the manufacturing method according to any one of claims 5 to 7, after pressing the organic foam material impregnated with the slurry with a stamper having the same bottom shape as the stamper, the pressure is removed from the foam material. A manufacturing method characterized by: 9. The manufacturing method according to any one of claims 5 to 7, characterized in that the organic foam material impregnated with the slurry is passed between a pair of open belts in order to extrude excess slurry. Production method. 10. The manufacturing method according to any one of claims 5 to 7, characterized in that the porosity on the side surface of the organic foam material is reduced by forming a closed slurry layer during impregnation. 11. In the manufacturing method according to claim 10, the porosity on the side surface of the organic foam material is reduced by depositing a foam material with a lower porosity corresponding to the thickness of the closed slurry layer on the peripheral side surface of the organic foam material. A manufacturing method characterized by: 12. In the manufacturing method according to claim 10, by applying fine spun yarn to the peripheral side of the organic foam material,
A manufacturing method characterized by reducing the porosity on the side surface. 13. In the manufacturing method according to any one of claims 5 to 7, the unfired foamed material impregnated with the slurry and dried is passed between a pair of rollers having at least a vertical axis, and A manufacturing method characterized in that a viscous slurry is applied to the side surface of a foamed material and penetrated into the foamed material at a predetermined depth. 14. A manufacturing method according to any one of claims 5 to 7, in which the fired filter is passed between a pair of rollers having at least a vertical axis, by which a pneumatically bonded refractory means is applied. A manufacturing method characterized by making the filter penetrate into the filter at a predetermined depth. 15. The manufacturing method according to any one of claims 5 to 14, in which the unfired foamed material impregnated with the slurry and dried is passed between a pair of rollers having a vertical axis, whereby the A manufacturing method characterized by coating an open cell bridge portion with a high viscosity slurry. 16. A manufacturing method according to any one of claims 5 to 15, in which the fired filter is passed between a pair of rollers having a vertical axis, the open cell bridges in the foam material being bonded with air. A manufacturing method characterized by coating with a fire-resistant means.