EP0911426B1 - Production of mouldings - Google Patents

Description

The invention relates to a method for producing molded parts.

In industrial production, molded parts or moldings are very different Geometry needed. The requirements for the properties of the molded parts are included differently. The production of molded parts is particularly difficult made of or with difficult to form materials.

EP 911424 A1 with the same priority has a method for producing Composite bodies described in which an object by thermal spraying is made from two different materials.

EP 911425 A1 with the same priority has a method for coating Substrate materials described by thermal spraying, in which special gases and special temperatures are used.

DE 195 20 885 C1 describes a method for thermal spraying Layer of a metal or a metal alloy described. With this Processes can spray layers with a thickness of 20 mm and more getting produced. The spray layer can be bonded to the substrate be used. At least 60% by weight of the wettable powder particles have the Impact on the substrate at a temperature between the solidus and the liquidus temperature of the metal alloy or up to 80 ° C below the Melting temperature is.

The present invention is based on the object of a method for the production to show molded parts that simplify the manufacture of molded parts, cheaper or made possible at all and / or which contributes significantly to to improve the quality and properties of molded parts. In particular, should the production of molded parts from or with difficult to form materials be made possible.

The object is achieved by a method according to the claims a base body is coated by thermal spraying, a powdered filler material by means of a gas on the to be coated Surface of the base body is passed without the powder particles of the Filler material are melted in the gas jet.

Thermal spraying for coating knows that as process variants autogenous flame spraying or the high speed flame spraying that Arc spraying, plasma spraying, detonation spraying and that Laser spraying.

• Übersicht und Einführung in das "Thermische Spritzen", Peter Heinrich, Linde-Berichte aus Technik und Wissenschaft, 52/1982, Seiten 29 bis 37, oder
• Thermisches Spritzen - Fakten und Stand der Technik, Peter Heinrich, Jahrbuch Oberflächentechnik 1992, Band 48, 1991, Seiten 304 bis 327, Metall-Verlag GmbH,

beschrieben.Thermal spray processes are in general form, for example in

• Overview and introduction to "thermal spraying" , Peter Heinrich, Linde reports from technology and science, 52/1982, pages 29 to 37, or
• Thermal spraying - facts and state of the art, Peter Heinrich, yearbook surface technology 1992, volume 48, 1991, pages 304 to 327, Metall-Verlag GmbH,

described.

Thermal spray processes are essentially characterized in that they enable evenly applied coatings. By thermal spraying Coatings can be applied by varying the spray materials can be adapted to different requirements. The spray materials can can be processed in the form of wires, rods or as powder. With thermal In addition, thermal post-treatment can be provided for spraying.

Recently, another thermal spraying process has also been developed which is also known as cold gas spraying. It is about a kind of further development of high-speed flame spraying with powder. This method is described, for example, in European patent EP 0 484 533 B1 described. A filler material in powder form is used for cold gas spraying Commitment. However, the powder particles are not melted in a gas jet during cold gas spraying. Rather, the temperature of the gas jet is below the melting point the powder particles of the filler material (EP 0 484 533 B1) or only in slightly above the melting temperature of the powder. In the cold gas spray process becomes a "cold" or a compared to the conventional spraying process comparatively colder gas used. Nevertheless, the gas is just as in heated up to conventional methods, but only to temperatures below the melting point of the powder particles of the filler peat or at temperatures of the gas jet from 100 K to 200 K above the melting point of the powder particles of the filler material.

An essential feature of the invention is that the powder particles of Filler material in the gas jet should not be melted. According to the Invention mean that the aim is to have the powder particles of the filler material in the Do not melt the gas jet (i.e. convert it completely into the liquid phase) that but is not aimed that the powder particles of the filler in Gas jet as a mixture of on and / or unmelted particles and on the other hand, composed of molten particles. The statement that the powder particles of the filler material not be melted in the gas jet can be ensured that the Temperature of the gas jet below the melting point of the powder particles Filler material is. But even at temperatures of the gas jet from 100 K to to 200 K above the melting point of the powder particles of the filler material due to the extremely short dwell time of the particles in the gas jet in the range of Milliseconds prevent the powder particles from melting or melting become. The importance of higher gas temperatures or the advantage of Heating of the gas lies in the fact that in hotter gases the speed of sound is higher and the particle speed also becomes comparatively greater as a result.

The cold gas spray process has compared to conventional processes of thermal spraying has a number of advantages. The thermal action and The effect of force on the surface of the substrate material is reduced, as a result unwanted changes in the material properties of the substrate material can be prevented or at least significantly reduced. You can also changes in the structure of the substrate material are largely prevented.

Surprisingly, it has now been found that the numerous process engineering Possibilities of thermal spraying using the cold gas spraying process can be used for the production of molded parts. Through the possibilities opened the use of different powder materials and powder mixtures a wide range for the composition of molded parts.

According to the invention, a base body can be sprayed on by a layer or a layer Coating reinforced to a desired thickness using the cold gas spraying process become. Relatively thin base bodies, e.g. a relatively thin walled after A molded part produced by a conventional method as a starting material be used. This body is then sprayed on same or different material on the inside and / or the outside reinforced to the necessary thickness. Special advantages can be achieved if the Base body has a smaller thickness than that by thermal spraying sprayed-on layer This variant facilitates the production of molded parts or with materials that are difficult to form.

Moldings made of easily plastically deformable are also suitable as base bodies Material, for example copper, aluminum or alloys containing them. The Base bodies can be relatively thin, for example in the range from 0.1 to 10 mm, preferably 0.5 to 5.0 mm. After spraying a particularly heavy malleable material by means of the cold spray process can then Molded articles, for example mechanically or chemically by dissolving, be removed from the sprayed-on layer. In this case, only that Spray layer the desired molded part. This method supports in particular Dimensions the production of molded parts from or with difficult to form materials.

In a further variant of the invention, a raw body according to one of the possibilities described above or produced by a combination. This raw body does not have to have the desired shape of the molded part to be produced, on the contrary, e.g. consist of a flat sheet metal body. After applying the layer by thermal spraying, the workpiece can (the coated raw or basic body or just the layer) in one or several of the known forming processes (drawing, deep drawing, rolling, pressing and the like) are processed further. This is how you finally get that desired molding. The advantage of this variant is that sprayed sheets or raw bodies are very fine-grained and practically texture-free. Your deformation takes place therefore very uniform and allows higher degrees of deformation than with sheet metal were produced by annealing or rolling.

According to the invention, the gas for thermal spraying can be nitrogen, helium, Argon, neon, krypton, xenon, a gas containing hydrogen, a carbon-containing one Gas, especially carbon dioxide, oxygen, an oxygen-containing Contain gas, air, hydrogen or mixtures of the aforementioned gases. Next The gases air and / or helium known from EP 0 484 533 B1 are suitable nitrogen, argon, also for the gas carrying the powdered filler material, Neon, krypton, xenon, oxygen, a gas containing hydrogen, a carbon-containing one Gas, especially carbon dioxide, hydrogen or mixtures of the aforementioned gases and mixtures of these gases with helium. The proportion of helium of the total gas can be up to 90% by volume. A helium content of 10 to 50 vol .-% observed in the gas mixture.

It has been shown that by using different gases to accelerate and carrying the powdered filler the flexibility and Effectiveness of the process can be increased significantly. The so produced Layers adhere very well to a wide variety of substrate materials, for example on metal, metal alloys, ceramics, glass, plastics and composite materials. The coatings produced using the method according to the invention are of high quality, have an extremely low porosity and possess extremely smooth spray surfaces, so that there is usually no need for reworking The gases used according to the invention have a sufficient density and Speed of sound to the required high speeds of the powder particles to be able to guarantee. The gas can be inert and / or reactive gases contain. With the gases mentioned is the production of very dense and special uniform coatings possible, which is also due to their hardness and distinguish strength. The layers have extremely low oxide contents. They have no or at least no pronounced texture, i.e. There is none Preferred orientation of the individual grains or crystals. The substrate becomes further not heated by a flame or a plasma, so no or only extreme minor changes to the base body and no distortion of workpieces due to thermal stress due to thermal spraying.

The gas jet can be heated to a temperature in the range between 30 and 800 ° C are, all known powdery spray materials are used can. The invention is particularly suitable for wettable powders made of metals, metal alloys, Hard materials, ceramics and / or plastics.

In an embodiment of the method according to the invention, the temperature of the gas jet selected between 300 and 500 ° C. These gas temperatures are particularly suitable for the use of reactive gases or reactive Gas constituents. As reactive gas or gas components are in particular Hydrogen admixtures, carbon-containing gases or nitrogenous gases mention.

In a development of the invention, a gas jet with a pressure of 5 to 50 bar used. Above all, working with higher gas pressures brings additional Advantages because the energy transfer in the form of kinetic energy is increased. It gas pressures in the range from 21 to 50 bar are particularly suitable. excellent Spray results were achieved, for example, with gas pressures of around 35 bar. The High pressure gas supply can, for example, by the in the German patent application DE 197 16 414.5 described method or the one described there Gas supply system can be ensured.

In the process according to the invention, the powder particles can run at one speed can be accelerated from 300 to 1600 m / s. Suitable in the process according to the invention speeds of the powder particles between 1000 and 1600 m / s, particularly preferably between 1250 and 1600 m / s, since in this case the Energy transfer in the form of kinetic energy is particularly high.

The powders used in the process according to the invention preferably have Particle sizes from 1 to 100 µm.

The method according to the invention offers the possibility in connection with a Automation and with computer-controlled movement of the base body or Spray gun to produce molded parts particularly quickly and inexpensively (rapid prototyping).

All suitable devices can be used to carry out the method according to the invention are used, in particular this applies to those in EP 0 484 533 B1 described device.

• Formteile, welche einen Grundkörper und eine durch thermisches Spritzen erzeugte Schicht umfassen, wobei der Grundkörper vorzugsweise eine geringere Dicke aufweist als die aufgespritzte Schicht und
• Formteile, welche jeweils aus einer (oder auch mehreren) mittels thermischen Spritzens erzeugten Schicht bestehen.

The following molded parts produced according to the invention have particular advantages over conventional molded parts:

• Molded parts which comprise a base body and a layer produced by thermal spraying, the base body preferably having a smaller thickness than the sprayed-on layer and
• Molded parts, which each consist of one (or more) layer produced by thermal spraying.

The invention and further details of the invention are described below of exemplary embodiments illustrated in the drawings.

Figur 1

ein erfindungsgemäß hergestelltes Formteil aus Grundkörper und Schicht;

Figur 2

ein erfindungsgemäß hergestelltes Formteil bestehend aus der Spritzschicht;

Figur 3

ein erfindungsgemäß hergestelltes Formteil bestehend aus der Spritzschicht nach Umformung mit herkömmlichem Verfahren.

Here show:

Figure 1

a molded part made according to the invention from base body and layer;

Figure 2

a molded part made according to the invention consisting of the spray layer;

Figure 3

a molded part made according to the invention consisting of the spray layer after shaping with a conventional method.

A shaped sheet 1 is shown in FIG. 1 in FIG. This sheet1 is applied a layer 2 by thermal spraying using the cold gas spraying method. The sheet 1 has a smaller thickness than the sprayed-on layer 2. The molding obtained in this way in Figure B consists of base body 1 (sheet metal) and Spray layer 2.

A molded body 1 made of a copper sheet is shown in FIG. After this Applying a thermal spray layer 2 as shown in Figure B, the copper sheet 1 mechanically detached from layer 2 The molded part obtained in this way is shown in Figure C. only from the spray layer 2.

The initially unshaped raw body or sheet 1 from Figure A of Figure 3 is provided with a layer 2 by thermal spraying using the cold gas spraying method (Picture B). After the sheet 1 was mechanically removed from the layer 2 (Figure C), the workpiece consisting of the spray layer 2 is made according to a conventional Forming process deforms and receives, as shown in Figure D, on this Way its desired shape as a molding.

Claims (8)

1. Process for producing shaped parts (1, 2; 2), in which a base body (1) is coated (2) by thermal spraying and a pulverulent additive is passed onto the surface of the base body (1) which is to be coated by means of a gas without the powder particles of the additive being melted in the gas jet and in which the base body (1) is reinforced by spray coating to a desired thickness, the base body (1) having a thickness which is less than that of the layer (2) which is sprayed on by thermal spraying.
2. Process for producing shaped parts (1, 2; 2) according to Claim 1, characterized in that the shaped part (1, 2; 2) which is produced by thermal spraying is subjected to one or more conventional forming processes, in particular by drawing, deep drawing, rolling and/or pressing.
3. Process according to one of Claims 1 or 2, characterized in that the base body (1), after the layer (2) has been sprayed on by thermal spraying, is removed from this layer (2).
4. Process according to Claim 3, characterized in that the base body (1) is removed from the layer (2) by means of a mechanical treatment or chemically by dissolution.
5. Process according to one of Claims 1 to 4, characterized in that the gas used for the thermal spraying contains nitrogen, helium, argon, neon, krypton, xenon, a hydrogen-containing gas, a carbon-containing gas, in particular carbon dioxide, oxygen, an oxygen-containing gas, air, hydrogen or mixtures of the abovementioned gases.
6. Process according to one of Claims 1 to 5, characterized in that the temperature of the gas jet during the thermal spraying lies in the range between 30 and 800°C.
7. Process according to one of Claims 1 to 6, characterized in that the gas jet has a pressure of from 5 to 50 bar during the thermal spraying.
8. Process according to one of Claims 1 to 7, characterized in that the powder particles are accelerated to a velocity of 300 to 1600 m/s during the thermal spraying.

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