WO2013086550A2

WO2013086550A2 - Permeable, porous article

Info

Publication number: WO2013086550A2
Application number: PCT/AT2012/000314
Authority: WO
Inventors: Christoph Angerer; Johannes Glätzle; Daniel MEVEC; Andreas SCHWEISSGUT; Josef Thurner
Original assignee: Ceratizit Austria Gesellschaft M.B.H.
Priority date: 2011-12-14
Filing date: 2012-12-12
Publication date: 2013-06-20
Also published as: WO2013086550A3; AT12825U1

Abstract

The invention relates to a permeable, porous article (1) having a base structure (2) of a temperature-resistant material. Said temperature-resistant material is hard metal or cermet.

Description

FLOODABLE, POROUS OBJECT

The present invention relates to a permeable, porous article. The invention relates in particular to a permeable, porous article which can be used as a filter or diffuser in a molten metal.

It is known in metal melts high temperature resistant filter

to use e.g. filter out unwanted particles. in the

Scope of light metal casting, especially in

Aluminum casting processes are further, in addition to the filter function,

high-temperature-resistant, flow-through, porous objects as

Diffusers are used to reduce turbulence in the melt, to ensure a uniform and quiet filling of the casting mold and thus a fine cast structure and to reduce the risk of oxidation defects.

Known such filters or diffusers are commonly used as ceramic foams, e.g. from silicon oxides or aluminum oxides. Although these materials have a high temperature resistance and can be designed such that a sufficient mechanical strength is given, but occurs at least in some applications

insufficiently low chemical resistance to atmospheres or elements to which they are exposed during operation. In practice, there is also a use of elements of the first group of

Periodic table increasingly spread, so that more filters or

Diffusers are required, which are also resistant to alkaline melts. The usual known filters or diffusers made of ceramic materials often do not have sufficient chemical resistance and decompose in alkaline melts.

WO 99/28273 A1 describes a filter for filtering molten metal with a porous carbon foam substrate coated with a refractory metal or a heat resistant compound. It is an object of the present invention to provide an improved permeable, porous article, which is particularly suitable as a filter and / or diffuser for molten metal, as well as a corresponding use and a method for its preparation.

The object is achieved by a permeable, porous article according to claim 1. Advantageous developments are specified in the dependent claims. The flow-through, porous article has a basic structure of a temperature-resistant material. The temperature-resistant material is carbide or cermet.

The term carbide (also referred to as a "cemented carbide") is understood here to mean a material in which hard metal carbides are embedded in a metallic matrix (binder) The metal carbides may be produced in particular by carbides or mixed carbides of the metals of groups IV to VI of FIG

Periodic table of elements, in particular e.g. by carbides or mixed carbides of the metals W, Ti, Zr, Hf, V, Nb, Ta, Mo and Cr. The metallic matrix can e.g. in particular be formed by Co, Ni and / or Fe .. There may also be additives of other hard materials.

Cermet is understood as meaning a material in which ceramic particles, which may be formed in particular by carbonitrides, oxides, borides or carbides, are embedded in a metallic matrix. The ceramic particles may in particular be carbonitrides of titanium (Ti) with different proportions of Ta, W and optionally Mo. The metallic matrix may in particular comprise cobalt (Co), tungsten (W), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), chromium (Cr) and / or nickel (Ni).

Since the material of the basic structure of the permeable, porous article is hard metal or cermet, a very good temperature resistance, especially against rapid temperature changes is given. Furthermore, in a simple manner, for example by material connection, be achieved in particular by a sintering process, a high mechanical strength and toughness. Depending on the intended use, in addition, excellent chemical resistance can be achieved even with respect to aggressive media, either by the material of the basic structure itself or by an optionally applied coating. For applications in the field of metal casting, for example as a filter and / or diffuser, the high density of the carbide or cermet allows a simple reject test, should it come to a breakage of the object. Broken parts settle because of the high density at the bottom, so

that a distance in a post-processing of manufactured castings is made possible or facilitated. Furthermore, the flow-through, porous article is characterized by a high thermal conductivity, so that, if necessary, a targeted heating or cooling to a desired temperature is possible. The provided article can be used in particular in metal melts or as a bedding filter for other chemically aggressive fluids.

According to one embodiment, the basic structure is formed by a plurality of bodies made of the temperature-resistant material. In this case, a particularly simple production of the permeable, porous

In this way, it is possible to obtain objects in which the individual bodies, e.g. can be introduced into a mold. It is e.g. basically possible to arrange the individual bodies unconnected in a flow-through housing or cage, which is also formed of a temperature-resistant material. The bodies may e.g. be introduced as a bed.

If the bodies are materially connected to each other, a particularly high degree of design options in the shaping of the permeable, porous object is given. Further, in this case, high mechanical strength and a high degree of thermal conductivity are achieved throughout the article. In particular, the bodies may be interconnected by sintering. A connection through For carbide and cermet sintering, sintering can be made very reliably and easily with known machining methods.

If the bodies are spheres or hollow spheres, the properties, in particular the achieved porosity, of the permeable, porous material can be determined

Set item very accurately and easily and calculate in advance. For example, For example, the sphere radius of a plurality of identical spheres can be varied, or different types of spheres, e.g. with different radii, used to achieve a desired structure. According to one embodiment, the bodies are a plurality of balls or hollow balls of substantially equal diameter. In this case, a desired porosity of the permeable, porous body can be provided in a particularly simple and predictable manner. According to one embodiment, the bodies have at least two types of ball or hollow ball with different diameters. In this case, the resulting structure of the permeable, porous article can be adjusted very targeted. For example, For example, large diameter balls may be placed in a (densest) ball packing, and other balls may be targeted with a smaller diameter so that they fit into remaining gaps.

According to another embodiment, the basic structure is formed as a foam of the temperature-resistant material. Also in this case, a production of the permeable, porous article with established

Manufacturing methods allows. For example, it is known in relation to the manufacture of filters and / or diffusers for molten metals, a

Polyurethane foam to be provided with a suspension, the

temperature-resistant material and binder, then to dry and to heat the polyurethane foam, so that a foam is formed from the temperature-resistant material. For example, this technique can now be exploited to provide a porous foam of cemented carbide or cermet. According to one embodiment, the basic structure with a chemical

resistant coating provided. In this case, flow-through, porous objects can be provided, which are formed chemically resistant by their coating especially for the particular application. The coating can be applied, for example, by known methods, in particular by means of CVD (chemical vapor deposition). For example, a coating of TiB _{2 can be} provided, in particular for use in aluminum melts, since it has both an excellent chemical resistance and a positive effect on the cast structure.

According to one embodiment, the article is a filter, a diffuser or a catalyst. Preferably, the article may be a filter or a diffuser for molten metal. It can be designed in particular for an aluminum melt.

The object is also achieved by using the permeable, porous article as a filter and / or diffuser in a molten metal. The object is further achieved by a method for producing a

permeable, porous article solved according to claim 13. Advantageous developments are specified in the dependent claims.

The method comprises the steps of introducing a plurality of bodies of cemented carbide or cermet into a mold and materially connecting the plurality of bodies to one another such that a permeable, porous body is formed. It achieves the advantages that have already been described with regard to the permeable, porous article. In particular, a permeable, porous article is achieved, which has both a good chemical resistance and a high mechanical strength and a high thermal conductivity.

According to one embodiment, the material-locking connection takes place by sintering. In this case, a particularly simple production is possible, the Especially suitable for carbide and cermets and it is achieved a high mechanical strength.

According to one embodiment, the method further comprises the step:

Applying a chemically resistant coating. In this case, the flow-through, porous article can be adapted via the coating especially for the purpose, e.g. In particular, be provided with a specially adapted chemical resistance. If one

Coating is applied, which has TiB ₂ , in particular for applications in an aluminum melt at the same time a high chemical resistance and positive effects on the microstructure can be achieved.

Further advantages and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figures.

From the figures show:

Fig. 1: a schematic representation of a permeable, porous

An article according to an embodiment;

2 shows a further schematic representation of the permeable, porous article;

3 is a block diagram for explaining a method for

Producing a permeable, porous article; and FIG. 4 shows a schematic representation of a porous, permeable, flow-through device

Article according to a modification.

An embodiment will be described below with reference to FIGS. 1 and 2.

FIG. 1 and FIG. 2 are schematic representations of a porous object 1 which can be flowed through. FIG. 1 is a schematic representation of the FIG

Item 1 from the side and Fig. 2 is a schematic illustration above. In the illustrated embodiment, the permeable, porous

Article 1 as a filter and diffuser for a molten metal, in particular an aluminum melt formed. In the specific embodiment, the flow-through, porous article is in particular for

Flow calming and cleaning of the melt during the

Casting process formed in aluminum continuous casting.

The flow-through, porous article 1 has a base structure 2 made of a temperature-resistant material. The material of the basic structure 2 is hard metal or cermet. In that shown in Fig. 1

Embodiment, the basic structure 2 is formed by a plurality of bodies 3 made of the temperature-resistant material. The bodies 3 are each formed by balls made of hard metal or cermet. In the illustrated embodiment, the bodies 3 are each formed as balls of hard metal or cermet, which have substantially the same diameter. In this case, the achieved porosity of the permeable, porous

Object 1 can be specified by the selection of the diameter of the body 3 and in particular also be calculated very easily. Although in Fig. 1 balls are shown and a realization of the individual body 3 as balls or hollow spheres brings benefits, the

Body 3 also have other uniform or non-uniform shapes, where appropriate, depending on the shape of an accurate specification of the porosity may be more difficult under certain circumstances.

In the exemplary embodiment, the bodies 3, which form the basic structure 2, are connected to one another in a material-locking manner, so that a high mechanical strength of the permeable, porous article 1 is achieved. In this case, the material-locking connection can be effected in particular by sintering adjoining, loose individual bodies, so that the bodies 3 are connected to one another by sintering. Alternatively, it is also possible, for example, to make a material-fit connection by hot pressing, in particular direct hot pressing; by gluing with a suitable adhesive or by laser sintering, in which the heating is done by a laser, train. As a further alternative, the loose individual bodies can also be connected to one another by soldering, for example by galvanic coating of the individual bodies with a metal (eg cobalt or nickel) and subsequent heating of the adjoining individual bodies, so that the

Basic structure 2 is formed from materially interconnected bodies 3. In addition to realizations with bodies 3 which are materially connected to one another, the basic structure 2 can be made e.g. also by one

Batch of bodies 3 may be formed, which are not materially connected to each other. In this case, e.g. a surrounding cage, which is also made of a heat-resistant and chemically resistant material, be provided to hold the body 3 to the basic structure 2 together.

As schematically illustrated in FIGS. 1 and 2, the basic structure 2 is provided with a chemically resistant coating 4. By doing

Embodiment are first the body 3 material fit

and then the chemically resistant coating 4 has been applied, e.g. through a CVD process

(chemical apour deposition, chemical vapor deposition) can be done reliably. The chemically resistant coating 4 can thereby

in particular be tailored specifically to the application. In the case of a permeable, porous body 1 for use as a filter and / or diffuser for an aluminum melt, as in the exemplary embodiment schematically illustrated in FIGS. 1 and 2, the coating 4 may in particular have an outer layer T1B2. Preferably, the

Coating thereby built up in several layers and e.g. a lowest layer TiN have.

Hereinafter, a method of manufacturing the permeable porous article will be briefly described.

In a first step S1, a plurality of the hard metal or cermet bodies 3 are introduced as a single body into a mold. In the illustrated

Embodiment, the mold may be, for example, a hollow cylinder, in which the Single bodies are introduced as a bed in such a way that they are in contact with each other.

In a second step S2, a material-locking connection of the body 3 is formed by the bodies 3 are sintered.

Subsequently, in a third step S3, the basic structure 2 formed of the plurality of interconnected bodies 3 is cleaned, e.g. can be done by treatment with acetone.

In a subsequent step S4, the coating 4 is applied by means of a CVD method.

example

In one example, carbide balls having an average diameter of 6 mm, as commonly used in an attritor or agitator ball mill, were first cleaned by acetone.

The cleaned hard metal balls were then manually introduced into a hollow cylindrical graphite mold and sintered under pressure by an approximately 4 kg mass at 1500 ° C.

After the sintering process, the basic structure prepared in this way was cleaned again with acetone and then by means of a CVD process with a first layer of titanium nitride (TiN) and an outermost layer

Titanium diborite (T1B2) coated.

In this way, a permeable, porous article was provided which had a substantially cylindrical shape of 40 mm in diameter and 50 mm in height. The article had a high level of chemical

Resistance and at the same time a high mechanical strength. modification

A modification of the previously described embodiment is shown schematically in FIG. The modification differs from the embodiment described with reference to FIGS. 1 and 2 in that it is not a sort of spheres 3 formed by spheres with a uniform one

Diameter is used to form the basic structure 2, but

Body 3 and 3a of different sizes are used. In the example shown in Fig. 4, first spherical bodies 3 having a relatively large diameter and second spherical bodies 3a having a smaller diameter are provided. There are thus two kinds of balls with different diameters. In the illustrated embodiment, the diameter of the second spherical bodies 3a is selected such that the second spherical bodies 3a fit in gaps left when the first spherical bodies 3 are stacked on each other. Also in the modification, the body 3 and 3a are connected by sintering material fit together and there is a coating 4 applied.

Due to the design with bodies 3, 3a of different diameters or different dimensions, the resulting porosity can be set particularly accurately. ^"

Other Variations Besides the above-described embodiment, in which the basic structure 2 is constituted by a plurality of bodies 3, e.g. can also be materially connected to each other, is e.g. in a further modification, a formation of the basic structure 2 by a foam made of hard metal or cermet possible.

The formation of the permeable, porous article 1 with a basic structure 2, which is formed by a foam of hard metal or cermet, will be briefly described below by way of example. To produce such a foam, for example, balls, hollow spheres or other geometric body of a removable material with a

Diameter corresponding to the desired pore size can be used. In one exemplary method, these balls, hollow spheres or other bodies are poured into a mold as a bed. Remaining gaps or cavities are filled with a unsintered carbide or cermet approach. Subsequently, the removable material is removed and by sintering the basic structure 2 of hard metal or cermet is formed.

The removable material may e.g. by a slightly melting metal, e.g. Copper or manganese, which melts below the sintering temperature or evaporates in the case of vacuum sintering. The removable material may e.g. but also by a plastic, as in particular

Polystyrene which pyrolyzes below the sintering temperature, i. can be converted into the gas phase.

According to a further alternative, a through a foam

Cement or cermet formed basic structure 2 also be formed by soaking a foam of removable material with carbide or cermet approach and then by heating the

Removable material and sintering the foam-like basic structure 2 made of hard metal or cermet is formed. Even with a permeable, porous article 1, the one

Basic structure 2, which is formed by a foam of hard metal or cermet, the base structure 2 may preferably be provided with a chemically resistant coating 4. The coating 4 can also be applied in this case by means of a CVD method and, if appropriate, in turn may be multi-layered. When used as a filter and / or diffuser for an aluminum melt may preferably turn a

Be provided coating with an outer layer of T1B2. Although a permeable porous article 1 adapted for use as a filter and diffuser for aluminum melt has been described with respect to the embodiment and its modifications, other applications are possible.

The flow-through porous article 1 may be e.g. also be used as a bedload filter for other chemically aggressive fluids or chemically loaded fluids. It is e.g. also a use as a catalyst possible. By varying the porosity and the optionally provided coating 4, the flow-through, porous article can be adapted for a variety of applications.

Claims

claims

1. flow-through, porous article (1) having a base structure (2) made of a temperature-resistant material, wherein the temperature-resistant material is carbide or cermet.

2. Flow-through, porous article according to claim 1, characterized

in that the basic structure (2) is formed by a plurality of bodies (3, 3a) of the temperature-resistant material.

3. Flow-through, porous article according to claim 2, characterized

characterized in that the bodies (3, 3a) are materially connected to one another.

Flow-through, porous article according to claim 2 or 3, characterized in that the bodies (3, 3a) are interconnected by sintering.

Flow-through, porous article according to one of claims 2 to 4, characterized in that the bodies (3, 3a) are balls or hollow spheres.

A permeable, porous article according to claim 5, characterized in that the bodies (3, 3a) are a plurality of spheres or hollow spheres of substantially equal diameter.

A permeable, porous article according to claim 5, wherein the bodies (3, 3a) comprise at least two types of spherical or hollow spheres

have different diameter.

8. A flow-through, porous article according to claim 1, characterized

characterized in that the basic structure (2) is formed as a foam made of the temperature-resistant material. 9. A flow-through, porous article according to one of the preceding claims, characterized in that the basic structure (2) is provided with a chemically resistant coating (4), in particular with a coating of TiB ₂ .

10. Flow-through, porous article according to one of the preceding claims, characterized in that the object (1) .A filter, a diffuser or a catalyst.

Flow-through, porous article according to one of the preceding claims, characterized in that the article (1) is a filter or a diffuser for a molten metal, in particular a

Aluminum melt, is.

Use of a permeable, porous article (1) according to one of the preceding claims as a filter and / or diffuser in a molten metal.

13. A method for producing a permeable, porous

Item (1) with the steps:

Introducing a plurality of bodies (3) of hard metal or cermet into a mold and

materially connecting the plurality of bodies (3) with each other such that a permeable, porous article (1) is formed.

14. The method according to claim 13, characterized in that the

material-locking connection by sintering takes place. 15. The method according to claim 13 or 14, further comprising the step:

Applying a chemically resistant coating (4), in particular a coating having TiB ₂ .