DE102011120547A1 - Kiln furniture useful as carrier for components during heat treatment, comprises three-dimensional structure with webs, where kiln furniture is made of ceramic material and kiln furniture is designed as monolith or several separate elements - Google Patents

Abstract

Kiln furniture (1) comprises a three-dimensional structure with webs, where the kiln furniture is completely made of ceramic material and is formed as a part, and the kiln furniture is designed as a monolith or several separate elements, which are bonded to each other by sintering.

Description

The invention relates to kiln furniture, as a carrier for components in a heat treatment. The heat treatment is essentially the sintering of metallic or ceramic components. However, the invention can also be used in other heat treatments, in particular in the high temperature range. Kiln furniture are usually used to position components within a furnace and the components are placed on or between kiln furniture, then in a stacked form. It can also be assigned to a kiln furniture several components.

Various requirements are placed on the kiln furniture. Of course, they must be sufficiently temperature stable and withstand the high temperatures during the heat treatment with sufficient strength. They must be resistant to thermal shock and the lowest possible thermal stresses should occur during temperature changes. They should be formed of a material that avoids influencing the component material during the heat treatment. Another important aspect is the heat capacity, which should be kept as small as possible in order not to adversely affect the required energy consumption. The heat input into the component material should also be favorably influenced in order to obtain or maintain a homogeneous material.

For example, kiln furniture made of ceramic materials has been used in the past.

In DE 298 16 572 U1 It is proposed to use a ceramic plate with through holes as kiln furniture. As a result, the mass and consequently the heat capacity is reduced. However, due to the design, there are areas in addition to the passage openings, which have a considerable accumulation of material and locally there is an increased heat capacity. As a result, thermally induced stresses occur, which must be compensated because of the required strength by a corresponding larger dimensions.

In this known technical solution, the handling is disadvantageous when a multi-layer stacked arrangement of components in an oven should be made. For this purpose, a stator assembly is provided, can be arranged in the stator between two plates. This is done in loose composite of several individual parts, which requires increased skill by an operator.

The handleability also poses a problem in the DE 199 31 306 A1 This kit is to be added from a variety of profile parts a component as kiln furniture. The profile parts are to be connected by an adhesive or a ceramic mass. As a result of the design, local areas also occur on which an increased amount of ceramic material occurs, which relates in particular to the connection areas. As a result, the heat capacity is also locally differentiated and increased overall.

It is therefore an object of the invention to provide kiln furniture available which have a low heat capacity, a low intrinsic mass with sufficient mechanical strength and thermal shock resistance. In addition, they should be easy to handle and allow easy loading of a stove.

According to the invention this object is achieved with a kiln furniture, which has the features of claim 1.

Advantageous embodiments and further developments can be achieved with features described in the subordinate claims.

An inventive firing aid is made entirely of ceramic material and as a part. It has a three-dimensional structure with webs. It can be formed as a monolith or from a plurality of individual elements, which are materially interconnected by sintering.

In this case, particularly advantageously all webs or individual elements should have a maximum thickness / wall thickness of 2.5 mm, preferably of not more than 2 mm. As a result, a very low mass and heat capacity can be maintained. Local material accumulations are reduced and are essentially limited to sintered bridge areas, insofar as such areas are present at all on a kiln furniture according to the invention.

This is especially not the case when a monolithic kiln furniture is formed as a deformed three-dimensional structure. In this case, for example, a plate-shaped green body, as may advantageously be a ceramic green sheet, be deformed. It can be a wave, meander, trapezoidal or wedge-shaped geometry formed and this geometry can be maintained after sintering. Such a shaped monolith can already be used as a kiln furniture. In this case, suitable components can be placed and subjected to heat treatment in an oven.

A monolithic kiln furniture can also be a ceramic foam body, which may have a planar surface on which components can be placed. The surface can also be contoured and components can then be held on the kiln furniture with the aid of contour elements in the form of depressions and / or elevations in a more stable manner. A ceramic foam body should be open-pored and have the largest possible pores. The pores supporting ridges or wall portions should have a thickness or diameter, as already mentioned above.

However, it is also possible to attach at least one surface of a ceramic foam body a planar planar element by sintering, so that a flat storage space is obtained for components. The ceramic foam body then forms a support structure. For the planar element can also be used a ceramic green sheet.

It is also possible, the kiln furniture with at least one plate-shaped element, are attached to the vertically or at an obliquely inclined angle aligned rod, fiber, tubular or deformed non-planar plate-like elements materially connected to produce.

The one plate-shaped element can form a base and components can then be placed on the upwardly facing end portions of the elements connected to the plate-shaped element or used in spaces.

If such elements are arranged between two plate-shaped elements and connected with their end faces by sintering with them, they form a support structure with spacer function.

Due to the small thickness or wall thickness of these elements, the heat capacity can be kept small while maintaining good flow conditions of the atmosphere within the furnace, which allows a good and uniform heating and cooling of components again.

In addition, the correspondingly increased mechanical moments of resistance of the elements attached to plate-shaped elements, in the main load axis of the kiln furniture, can be exploited to ensure sufficient mechanical strength at the lowest mass and volume for these elements.

In a debindering of components during the heat treatment, it is advantageous if a plate-shaped element on which a component is placed in a heat treatment or is in touching contact with the component, is porous and / or has openings. As a result, the released gaseous constituents can flow through the respective plate-shaped element and can also be removed therefrom, as a result of which the process of debindering in the components can be made more homogeneous. In addition, porosity can reduce mechanical stress or stress gradients. With existing openings and possibly also with a porosity, the shrinkage of components during sintering as a heat treatment is less hindered. A reduced contact surface between the surface of a kiln furniture and the component disposed thereon also leads to a reduced friction.

In the invention, it is possible to use different ceramic materials for different elements, taking into account the respective different required properties. Thus, a kiln furniture formed of at least one plate-shaped member having at least one member attached thereto may be manufactured with a first ceramic material for the plate-shaped member (s) and a second ceramic material for the member (s) attached thereto be. In this case, the first material may be particularly inert with respect to the component material and the second material may have a correspondingly increased mechanical strength.

Suitable materials for plate-shaped elements are, for example: Al ₂ O ₃ , calcium aluminate, cordierite, mullite, SiC, SiSiC, RSiC, Al ₂ O ₃ -SiO ₂ and ZrO ₂ (MgO-PSZ, CaO-DSZ). PSZ stands for partially stabilized zirconia and FSZ for fully stabilized zirconia.

For attached elements, the same ceramic materials can be used. In contrast to the first materials, the second materials should be densely sintered, since they essentially depend on mechanical strength. The first materials can be processed into a porous material.

In the selection, the respective thermal expansion coefficients and the shrinkage behavior can be taken into account. It is not absolutely necessary to achieve or comply with an almost complete agreement. In the selection, of course, the material costs are taken into account and only expensive materials for elements of a kiln furniture are used for which this is required.

Thus, for example, a suitable deformation of a plate-shaped element, for example a concave curvature which occurs during sintering, can be tolerated or even deliberately exploited in order to obtain a correspondingly curved storage surface of a kiln furniture.

An element connected to a plate-shaped element can form a jacket which protects against direct thermal radiation. In this case, a correspondingly shaped ceramic green sheets with an end face placed on another ceramic green sheet or a ceramic plate-shaped element before sintering and at low Druckkraftbeaufschlagung the two parts are GE and sintered together. Analogously, of course, other elements already described above can also be connected to one another by sintering.

A jacket can also be formed porous and / or with openings.

The deformed non-planar elements already mentioned should have an overall length in a direction at least 1.15 times the length from one end edge to an opposite end edge in the direction perpendicular to the deformations. As a result, a sufficient size of the three-dimensional shape of a kiln furniture, a sufficient permanent strength due to the sufficiently large radii of curvature in corner or edge regions of the contouring can be secured.

The invention can be based on simple established production methods and also suitable semi-finished products, such as the already mentioned ceramic green sheets. A desired shaping can be carried out easily in the green state and the different elements and arrangements mentioned above can be taken into account or formed.

After sintering is advantageous that usually no further shaping post-processing is required.

It is a simple adaptation, in the production of the kiln furniture, to the requirements of the respective components requirements, as regards the geometry and dimensioning, possible. In this case, the required strength and favorable for the heat treatment design of kiln furniture to the respective components to be treated can be considered.

The kiln furniture can be optimized in terms of their volume and their heat capacity. The individual parts, areas and elements made of ceramic material can be very small in size and still have sufficient strength for the application. As a result, temperature gradients can be kept small.

The kiln furniture according to the invention are thermoshock resistant, so that higher heating and cooling rates are available.

The invention will be explained in more detail by way of example in the following.

Showing:

1A and 1B an example of a kiln furniture according to the invention in a perspective view;

2 another example of a kiln furniture according to the invention;

3 an example with a deformed non-planar element;

4 an example with a deformed non-planar element, which is arranged between two plate-shaped elements;

5 an example with a plurality of deformed non-planar elements arranged in different planes and

6 an example with a plurality of deformed non-planar elements arranged in different planes, which are aligned differently.

In the 1A and 1B an example is shown in which tubular elements 3 ' between two plate-shaped elements 2 arranged and sintered through sintered bridges at their ends with the plate-shaped elements 2 are connected. The tubular design of the elements 3 ' is in 1B recognizable. This showed the tubular elements 3 ' a wall thickness of 0.2 mm and the plate-shaped elements 2 have a layer thickness of 0.5 mm.

The plate-shaped elements 2 have a maximum porosity of 90% and the tubular elements 3 ' are so densely sintered that they have a density which is at least 92% of the theoretical density. The plate-shaped elements 2 and the tubular elements 3 ' are formed in this example of calcium aluminate.

The tubular elements 3 ' form a regular row and column arrangement, so that over the surface of the plate-shaped elements 2 an at least nearly constant strength and Stiffness can be achieved. In non-illustrated form but there is also the possibility of an arrangement of tubular elements 3 ' to choose more or tubular elements in certain areas 3 ' are present with higher strength / resistance moment and these areas are then provided for a placement of components, while other then not so firm and rigid areas can be kept free of components.

Instead of the tubular elements 3 ' It is also possible to use other such elements as are mentioned in the general part of the description, as has been previously described.

On a kiln furniture 1 can also have different elements 3 ' to be available.

It can also on the plate-shaped element arranged here above 2 be waived. Then components can be placed directly on the end faces of the tubular elements 3 ' be placed during the heat treatment.

At the in 2 The example shown is a wave-shaped non-planar deformed element 3 between two plate-shaped elements 2 arranged and in the region of the vertically arranged above and below radii of curvature with the plate-shaped elements 2 sintered. The plate-shaped elements 2 in this example have a wall thickness of 0.5 mm and the wall thickness of the element 2 is 0.5 mm. All elements are made of aluminum oxide.

In this case, a single correspondingly shaped non-planar element 3 to be available. But there is also the possibility of this from several parts, as in 2 it is recognizable to produce. In both cases, at least one ceramic green sheet can be used for the production, which can be easily brought into the desired shape.

Also in this embodiment, can on an upper plate-shaped element 2 be waived, as is the case in the 3 example shown is the case. There is a wedge-shaped element 3 with a plate-shaped element 2 connected. Components can be applied directly to the wedge-shaped tips of the element during the heat treatment 3 be placed, creating a very small contact surface between the element 3 and components can be achieved.

In 4 is additionally an upper plate-shaped element 2 with the wedge-shaped element 3 connected, whereby the strength and stability can be increased.

This in 5 Example shown shows a structure in several levels. In each case between two plate-shaped elements 2 wedge-shaped elements 3 present and with the plate-shaped elements 2 connected.

With the in 6 The example shown should clarify that the strength and stability can be further increased if the non-planar deformed here wedge-shaped elements 3 are aligned differently in the different levels. Here is shown a vertical orientation to each other. For additional additional levels, such as an analogous to 5 trained example, an orientation with a smaller angular deviation, for example, 30 ° or 60 ° can be selected in the respective levels.

A similar effect as with the in 6 The arrangement shown can also be used with other elements 3 ' how to achieve, for example, tubular elements in which such elements 3 ' in the different planes offset from each other.

For the elements 3 can be chosen instead of the wedge shape and a trapezoidal geometry. This increases the mechanical strength and stability and the total area associated with one or more plate-shaped elements 2 is in contact and over which the cohesive connection is reached, is also larger.

In the in the 4 to 6 As shown or similar examples, the plate-shaped elements 2 made of calcium aluminate and the non-planar deformed elements 3 be prepared from Al ₂ O ₃ . For all these elements corresponding ceramic green sheets can be used. The shape of the deformed elements 3 Can be done with suitable plant technology in the green state. Subsequently, the plate-shaped elements 2 and the nonplanar deformed elements 3 be joined and pressed with light pressure on each other before a heat treatment is carried out, in which a sintering of the ceramic materials takes place and the cohesive connection is formed via sintered bridges.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 29816572 U1 [0004]
• DE 19931306 A1 [0006]

Claims (10)

A kiln furniture, as a support for components in a heat treatment, wherein the kiln furniture is formed entirely of ceramic material and as a part having a three-dimensional structure with webs, and the kiln furniture as a monolith or of a plurality of individual elements ( 2 . 3 . 3 ' ), which are materially interconnected by sintering, is formed. Kiln furniture according to claim 1, characterized in that all webs or individual elements ( 2 . 3 . 3 ' ) have a thickness / wall thickness of not more than 2.5 mm, preferably of not more than 2 mm. Kiln furniture according to claim 1 or 2, characterized in that a monolithic kiln furniture ( 1 ) is a ceramic foam or a deformed three-dimensional structure. Kiln furniture according to one of the preceding claims, characterized in that the kiln furniture ( 1 ) with at least one plate-shaped element ( 2 ), at the vertically or at an obliquely inclined angle aligned rod, fiber, tubular or deformed non-planar plate-shaped elements ( 3 . 3 ' ) are fastened cohesively, is formed. Kiln furniture according to claim 4, characterized in that a plate-shaped element ( 3 ), on which a component is placed in a heat treatment or is in touching contact with the component, is porous and / or has openings. Kiln furniture according to one of the preceding claims, characterized in that a monolithic kiln furniture ( 1 ) or a deformed non-planar plate-shaped element ( 2 ) is wave-shaped, meandering, trapezoidal or wedge-shaped. Kiln furniture according to one of the preceding claims, characterized in that a kiln furniture ( 1 ) consisting of at least one plate-shaped element ( 2 ) with at least one element attached thereto ( 3 ) is formed with a first ceramic material for the / the plate-shaped element (s) ( 2 ) and a second ceramic material for the element (s) attached thereto ( 3 ) is made. Kiln furniture according to one of the preceding claims, characterized in that a deformed non-planar element ( 3 ) has a total length in a direction at least 1.15 times the length from one end edge to an opposite end edge in the direction perpendicular to the deformations. Kiln furniture according to one of the preceding claims, characterized in that a component is provided against direct heat radiation protective sheathing. Kiln furniture according to one of the preceding claims, characterized in that deformed plate-shaped elements ( 3 ) or otherwise geometrically designed elements ( 3 ' ) at different levels between plate-shaped elements ( 2 ) are arranged offset from each other or are arranged with a different orientation.

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