WO2014047664A1

WO2014047664A1 - Method for sintering a workpiece

Info

Publication number: WO2014047664A1
Application number: PCT/AT2013/000133
Authority: WO
Inventors: Axel Reichert
Original assignee: Amann Girrbach Ag
Priority date: 2012-09-27
Filing date: 2013-08-14
Publication date: 2014-04-03
Also published as: DE102012019159A1; EP2900405A1; EP2900405B1

Abstract

The invention relates to a method for sintering at least one workpiece (1), in particular a dental workpiece, using a protective gas atmosphere in a sintering chamber (2), wherein during the sintering process the workpiece (1) is supported in the sintering chamber (2) by a supporting material (3). Ceramic supporting grains (4) together with at least one additional material (5) for reducing the oxygen content in the sintering chamber (2) are used as the supporting material (3).

Description

Method for sintering a workpiece

The present invention relates to a method for sintering at least one, in particular dental, workpiece using a protective gas atmosphere in a sintering chamber, wherein the workpiece is supported in the sintering chamber during the sintering process by a support material.

Furthermore, the invention also relates to a support material with ceramic support grains and an arrangement with a sintering chamber, a workpiece arranged therein and the support material. The sintering and heat treatment of, in particular dental, workpieces e.g. made of sintered metal, requires a virtually oxide-free atmosphere during the sintering process to prevent oxidation of the workpiece at high temperatures. It is known that the oxygen around the workpiece to be sintered by the introduction of inert gases, preferably argon or nitrogen in the

Sintering chamber to displace to a possible oxide-free sintering

enable. In the prior art, large amounts of inert gas are often required to achieve optimum results without residual oxidation on the workpiece. This is in generic methods or corresponding manufacturing processes of

Workpiece an unfavorable cost factor.

The object of the invention is to improve methods of the type mentioned above in such a way that the mentioned problems are reduced.

For this purpose, the invention proposes in a method mentioned above, that supportive ceramic grains together with at least one

Additional material can be used to reduce the oxygen content in the sintering chamber. In other words, in the method according to the invention, a support material is thus used which, on the one hand, has ceramic support grains which rattle the mechanical support or support of the workpiece in the sintering chamber. On the other hand, the support material 1 also comprises an additional material which reduces the oxygen content or residual oxygen content in the sintering chamber. It is favorable in this case if the additional material allows this reduction of the oxygen content in the sintering chamber by the in the

Sinter chamber existing oxygen or residual oxygen attracts and binds. With oxygen or residual oxygen is meant the free, still unbound oxygen, which can lead to an unwanted oxidation of the workpiece. This is, apart from eventuel l oxygen radicals present, in the air usually as a molecule with two oxygen atoms. In this context, particularly preferred inventive

Method that is used as a filler Materia l or a material mixture, which or a higher oxygen affinity than that

Has or have workpiece.

Under oxygen affinity is understood the endeavor of a substance or material to bind oxygen in particular by chemical reaction itself. The higher the oxygen affinity of a substance or material, the sooner and the more oxygen is bound to this substance or material.

In order to equip the additional material with a higher oxygen affinity to the workpiece, there are various possibilities. In a first variant, it is provided that a material or a material mixture which has or have a higher mass-related specific surface area than the workpiece is or are used as additional material. In this case, the higher oxygen affinity essentially results from the larger surface available for corresponding binding of the oxygen. In this

Connection should be mentioned that in the sense of the invention then even sufficient can be that the additional material consists of the same material as the workpiece, the additional material then just should have a higher mass-specific surface than the workpiece. Under the mass related

specific surface is the totality of all in a body or

Material existing surfaces, both outside and inside the pore space, understood, this totality of the surfaces is based on the mass of the body or of the material. The mass-specific surface area can be expressed in units of m ² / kg (square meters per kilogram). When

Alternative to or in combination with a higher specific surface may also be provided that as a supplementary material or a material

Material mixture is used which has at least one chemical element or at least one chemical compound which or which has a higher oxygen affinity than the material of the workpiece or have. This is the case when the material or at least one chemical element or at least one chemical compound thereof has a higher oxygen affinity than the workpiece per se, ie also with the same mass-related specific surface. In this case, the additional material is then a different material or a different material composition than the

Workpiece. Of course, the two possibilities mentioned of providing the higher oxygen affinity can also be combined with one another.

Generally speaking, by using the additional material in the

Support material chemically bound to the additional material despite inert gas atmosphere in the sintering chamber residual oxygen at the additional material so that it is no longer available for oxidation of the workpiece during the sintering process. By the invention is thus achieved that it despite a certain

Residual oxygen content in the inert gas atmosphere comes to no or at least no significant oxidation of the workpiece during the sintering process in the sintering chamber. As a result, the required for the sintering process

Protective gas quantity can be reduced, which is usually a corresponding

Cost advantage is achieved. A protective gas atmosphere is understood to mean a gas composition which has the lowest possible content of free oxygen. To generate this

Inert gas atmosphere in the sintering chamber, as is known,

appropriate inert gases are used. This can e.g. Be nitrogen or noble gases. Particular preference is given to the provision of

Inert gas atmosphere argon and / or nitrogen introduced into the sintering chamber.

Inventive methods are particularly preferably used for sintering dental workpieces. The term of the denta len workpiece includes in particular all those artificially manufactured components which can be used in the denture as a replacement for natural teeth or tooth components, as well as H i lfskörper for fastening and for producing such

Dental prostheses. The workpieces to be sintered are particularly preferably metal or metal alloys. The workpieces can be in

Be sintered green state or Weißlingszustand.

Particularly preferred embodiments of the method according to the invention provide that the ceramic support grains are arranged between the workpiece and the additional material. This avoids that

Additional material adheres to the workpiece during the sintering process.

In addition to the method, the invention also relates to a support material with ceramic support grains, which in addition to the ceramic support grains has an additional material for reducing the oxygen content of the sintering chamber. This

Supplementary material can, as already stated, have a higher oxygen content than the ceramic support grains in order to bind the residual content of molecular oxygen in the protective gas atmosphere, so that it is no longer available for oxidation of the workpiece during the sintering process. This

Support material can be used, for example in its below-described embodiments in the inventive method. But this does not rule out that the support material according to the invention is also suitable for other applications.

The support material according to the invention may consist exclusively of granular,

pourable material. In these embodiments of the invention, therefore, not only the ceramic support grains but also the additional material as well as optional further constituents are present as grains or powders. The various components of the support material may be present as a homogeneous but also as an inhomogeneous mixture. As already stated, it is favorable, in particular in the region in which the workpiece rests directly on the support material, if only or substantially only ceramic support grains are present there. The ceramic support grains are mainly there, the

Wear and support workpiece. They conveniently have, at least when viewed with the naked eye, a rounded and / or smooth outer

Surface on. As support grains, e.g. in the prior art per se known ceramic sintered beads z. B. from partially stabilized with yttrium

Zirconia be used. The ceramic support grains in preferred embodiments have a larger diameter than all other components of the support material. Preferably, their diameter is in the range between 0.4mm and 2mm. The ceramic support grains can also the

Form main component of the support material. Preferably, the support material consists of at least 90% by mass, preferably at least 95% by mass, more preferably at least 98% by mass, of the ceramic

Supporting grains. The ceramic support grains are preferably high

temperature resistant, meaning a temperature resistance of at least 1 600 ° C.

The additional material for reducing the oxygen content in the sintering chamber is preferably metals or metal alloys. They can, in particular with a correspondingly high mass-specific surface area, but for example also be ceramic type. The additional material may be in pills or powder form. But it can also be larger, preferably seventh or lattice-like, preferably porous, body, especially Meta llkörper act. These can also be larger than the diameter of said ceramic support body. It may be, for example. to act cobalt chrome molybdenum or titanium or titanium alloys.

In particular, when the additive material for reducing the oxygen content in the sintering chamber is present as a powder or fine-grained material, preferred embodiments of support materials according to the invention provide that the

Support material additionally comprises a carrier to which the additional material can be stored. It may be e.g. around ceramic materials like

Aluminum corundum act. The carrier substance advantageously has a rough and / or abrasive surface. It can be equipped with a grain diameter between 50 and 1 10 μιτι. Generally speaking, the grain diameter of the carrier is conveniently between the larger grain diameter of the ceramic support grains and the smaller grain diameter of z. B. present in powder form additional material for reducing the oxygen content in the

Sintering chamber before. Due to the rough abrasive surface of the carrier, there is a particularly good attachment of the additional material. Due to the smaller grain diameter, the carrier substance together with the attached thereto

Additional material between the ceramic support grains and its smooth

Slide surfaces through and deposit, at least substantially, under the ceramic support bodies. As a result, the above-mentioned preferred embodiment is achieved, in which the ceramic support grains are arranged between the workpiece and the additional material. This at least largely prevents the workpiece from being able to come into direct physical contact with the additional material during the sintering process. The

Carrier substance, as far as it is present, favorably a proportion of 0, 1 to 2 percent by mass of the support material. The Trägerubsta nz is also favorably high temperature resistant, so preferably has a

Temperature resistance up to at least 1 .600 ° C on. The share of

Additional material for the reduction of the oxygen content in the sintering chamber on Support material is in such, at least three-component mixtures favorably at least 0, 1 percent by mass of the support material.

In addition to the method according to the invention mentioned at the outset and the support material according to the invention now described, the invention also relates to an arrangement having a sintering chamber and at least one workpiece arranged in the sintering chamber, the workpiece being supported in the sintering chamber by a support material according to the invention. It may be all described here embodiments of the support material. In the

Arrangement of the invention provides the support material mainly by means of the ceramic support body for a good storage and support of the workpiece during the sintering process. The additional material deprives the protective gas atmosphere of the free residual oxygen, so that it is no longer for an oxidation of the

Workpiece is available during the sintering process. By the

Distribution of the additional material in the support material is preferred on the one hand

ensures that the additional material does not come into direct contact with the workpiece and thus can not adhere to it. On the other hand that is

Additional material in the support material but during the sintering process in the immediate vicinity or close to the workpiece, so that in particular in the immediate vicinity of the workpiece particularly low free bondable residual oxygen for unwanted oxidation of the workpiece during the sintering process is present. If the support material is in the form of bulk material or a granular mixture with the said two or three components, it can be prepared by a mechanical mixing process by the ceramic

Corresponding portions of additional material and, if appropriate, carrier substance are admixed to support grains as the main component. The addition of the additional material to the carrier substance can take place during the mixing process. The workpiece to be sintered is in the sintering chamber during the sintering process preferably directly on the support material and is thus supported by this. Preferred embodiments of the invention are explained by way of example in the following description of the figures with reference to schematic representations. FIG. 1 shows an enlarged and schematized representation of an inventive device. FIG

Support material in the form of pure bulk material or a grain mixture;

Fig. 2 shows an alternative embodiment of a support material, wherein the

Additional material for reducing the oxygen content in the sintering chamber is designed as a porous solid and

Fig. 3 shows an example of an arrangement according to the invention, in which a workpiece to be sintered rests in a sintering chamber on the support material.

In FIG. 1, the support material 3 according to the invention is completely a grain mixture or bulk material. The ceramic support grains 4 have a completely rounded outer surface. They form the main component of the support material 3 and also have the largest diameter. In the

Interspaces between the ceramic support grains 4 is the additional material 5, which is preferably attached to the carrier substance 6. The diameters of the grains of the additional material 5 and the carrier 6 are significantly smaller than the diameter of the ceramic support grains 4. In the

Embodiment of a support material 3 according to the invention in Fig. 1 is a mixture of said three components 4, 5 and 6.

Fig. 2 shows another embodiment of an inventive

Support material 3. Here are just two components, namely the ceramic

Support grains 4 and the additional material 5 present. The portion forming the additional material 5 is here a coherent porous body on which the ceramic support grains 4 rest. In the intermediate spaces between the ceramic support grains are in this embodiment no further components of the support material 3. Of course, also mixed forms of the variants shown in Fig. 1 and 2 are possible. 3 shows by way of example a very simplified illustrated sintering chamber 2. Through the inlets and outlets 7 can inert gas in the against the outside atmosphere

shielded interior 8 are initiated. By flushing the interior 8 with inert gas via the inlets and outlets 7, the interior 8 can at least in

Essentially filled with protective gas atmosphere. In order to keep the amount of inert gas required as low as possible, in the interior 8 of the sintering chamber 2 in addition to the workpiece 1 to be sintered supporting material 3 is provided, in which the workpiece 1 is embedded during the sintering process or on which it rests. In that shown in Fig. 3

Support material 3 is a bulk-like grain mixture with the three components 4, 5 and 6, as shown in principle in Fig. 1. However, the additional material 5 bound to the carrier substance 6 is deposited substantially downwards on the bottom of the sintering chamber, so that the workpiece 1 is in direct contact substantially only with the ceramic support grains 4. Nevertheless, the additional material 5 bound to the carrier substance 6 is more relative Proximity around the workpiece 1 evenly distributed around and can thus in

in the immediate vicinity of the workpiece 1, the remaining content of free oxygen present in the protective gas atmosphere so that it does not oxidize the

Workpiece 1 while it is sintering available.

Notwithstanding the arrangement according to the invention shown in Fig. 3, of course, other known in the prior art sintering chambers 2 can be used. Of course, the concretely shown in Fig. 3 version of the support material 3 by other inventi ldete invented

Embodiments, in particular by the dargestel in Fig. 2 variant, be replaced. Read the reference numbers

1 workpiece

2 sintering chamber

3 support material

4 ceramic support grains

5 additional material

6 carrier substance

7 inlet and outlet

8 interior

Claims

claims

1 . Method for sintering at least one, in particular dental, workpiece (1) by using a protective gas atmosphere in a sintering chamber (2), the workpiece (1) being supported in the sintering chamber (2) during the sintering process by a support material (3) in that ceramic support grains (4) together with at least one additional material (5) for reducing the oxygen content in the sintering chamber (2) are used as support material (3).

2. The method according to claim 1, characterized in that as additional material (5) a material or a material mixture is used, which or which has a higher oxygen affinity than the workpiece (1) or

exhibit.

3. The method according to claim 1 or 2, characterized in that as

Additional material (5) a material or a material mixture is used, which or have a higher mass-specific surface area than the workpiece (1) or have.

4. The method according to any one of claims 1 to 3, characterized in that as additional material (5) a material or a material mixture is used, which has at least one chemical element or at least one chemical compound, which or a higher oxygen affinity than the material of the workpiece (1) or have.

5. The method according to any one of claims 1 to 4, characterized in that the ceramic support grains (4) between the workpiece (1) and the

Additional material (5) can be arranged.

6. support material (3) with ceramic support grains (4), in particular for

Use in a method according to one of claims 1 to 5, characterized in that in addition to the ceramic support grains (3) it has an additional material (5) for reducing the oxygen content in the sintering chamber (2).

7. Support material (3) according to claim 6, characterized in that the

Additional material (5) has a higher oxygen affinity than the ceramic one

Support grains (4).

8. support material (3) according to claim 6 or 7, characterized in that the ceramic support grains (4) at least when viewed with the naked eye have a rounded and / or smooth outer surface.

9. supporting material (3) according to any one of claims 6 to 8, characterized in that it additionally comprises a carrier substance (6) for attachment of the additional material (5) to the carrier substance (6).

10. Arrangement with a sintering chamber (2) and at least one, in the

Sinterkammer (2) arranged workpiece (1), wherein the workpiece (1) in the sintering chamber (2) is supported by a Stützmateria l, characterized

in that the support material is a support material (3) according to one of claims 6 to 9.