Casting component and method for the application of an anticorrosive layer

Abstract

A casting component and method for the application of an anticorrosive layer to a substrate, such as the casting component, are provided. The casting component for a device for casting a metal melt includes a metallic basic body and a melt contact surface region which is exposed to the metal melt during casting operation. In the casting component, the metallic basic body is provided in the melt contact surface region with an anticorrosive layer which is resistant to the metal melt and which is formed, using microparticles and/or nanoparticles of one or more substances from a substance group which includes borides, nitrides and carbides of the transition metals and their alloys and also of boron and silicon and Al.sub.2O.sub.3.

Claims

1. A casting component for a device for casting or handling a metal melt, the component comprising a metallic basic body and a melt contact surface region which is exposed to the metal melt during casting operation, wherein the metallic basic body is provided in the melt contact surface region with an anticorrosive layer which is resistant to the metal melt and which is a sol/gel layer, using, as a filler, at least one of microparticles or nanoparticles of one or more substances selected from the group consisting of borides, nitrides and carbides of the transition metals and their alloys, boron, silicon, and Al.sub.2O.sub.3, wherein the sol/gel layer comprises a plurality of gel layer plies, at least one gel layer ply being formed without the microparticles or nanoparticles, and the at least one gel layer ply formed without the microparticles or nanoparticles constitutes the outer layer ply in a depositing direction of the sol/gel layer.

2. The casting component according to claim 1, wherein the microparticles or nanoparticles have an average particle size of between 50 nm and 50 m.

3. The casting component according to claim 2, wherein the microparticles or nanoparticles have an average particle size of between 100 nm and 30 m.

4. The casting component according to claim 1, wherein the anticorrosive layer is formed, using microparticles or nanoparticles composed of TiB.sub.2.

5. The casting component according to claim 1, wherein the sol/gel layer has a zirconium-based or silicon-based gel former.

6. The casting component according to claim 1, wherein the sol/gel layer contains an additionally administered alkali or alkaline earth metal salt or an additionally administered viscosity-setting polymer.

7. The casting component according to claim 1, wherein at least two of the gel layer plies have microparticles or nanoparticles of identical or different substances.

8. The casting component according to claim 1, wherein the basic body is formed from a steel material.

9. The casting component according to claim 1, wherein the casting component is configured for use in a device for casting an aluminum melt.

10. The casting component according to claim 1, wherein the casting component is configured for use in a metal diecasting machine.

11. A casting component for a device for casting or handling a metal melt, the component comprising a metallic basic body and a melt contact surface region which is exposed to the metal melt during casting operation, wherein the metallic basic body is provided in the melt contact surface region with an anticorrosive layer which is resistant to the metal melt and which is a sol/gel layer, using, as a filler, at least one of microparticles or nanoparticles of one or more substances selected from the group consisting of borides, nitrides and carbides of the transition metals and their alloys, boron, silicon, and Al.sub.2O.sub.3, wherein the sol/gel layer comprises a plurality of gel layer plies, at least one gel layer ply being formed without the microparticles or nanoparticles, and the at least one gel layer ply formed without the microparticles or nanoparticles constitutes the outer layer ply in a depositing direction of the sol/gel layer, and wherein the casting component is configured for use as a casting fitting, a casting vessel, a melt furnace constituent, a melt conveying constituent, or a part of one of these diecasting machine constituents.

12. The casting component according to claim 11, wherein the microparticles or nanoparticles have an average particle size of between 50 nm and 50 m.

13. The casting component according to claim 12, wherein the microparticles or nanoparticles have an average particle size of between 100 nm and 30 m.

14. The casting component according to claim 11, wherein the anticorrosive layer is formed, using microparticles or nanoparticles composed of TiB.sub.2.

15. The casting component according to claim 11, wherein the sol/gel layer has a zirconium-based or silicon-based gel former.

16. The casting component according to claim 11, wherein the sol/gel layer contains an additionally administered alkali or alkaline earth metal salt or an additionally administered viscosity-setting polymer.

17. The casting component according to claim 11, wherein at least two of the gel layer plies have microparticles or nanoparticles of identical or different substances.

18. The casting component according to claim 11, wherein the basic body is formed from a steel material.

19. The casting component according to claim 11, wherein the casting component is configured for use in a device for casting an aluminum melt.

20. The casting component according to claim 11, wherein the casting component is configured for use in a metal diecasting machine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 shows a longitudinal sectional view through a casting vessel with an anticorrosive layer for a hot-chamber diecasting machine,

(3) FIG. 2 shows a diagrammatic sectional view of a region of the casting vessel which is provided with the anticorrosive layer, and

(4) FIG. 3 shows a flowchart to illustrate a method for the application of an anticorrosive layer, for example for the casting vessel of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) A casting vessel 1 shown in FIG. 1 is of a type of construction conventional per se, such as is used by the applicant in hot-chamber diecasting machines, for example in order to cast aluminum, magnesium and zinc melts. It possesses a metallic basic body 2 which is preferably composed, as is customary, of a steel material or high-grade steel material and in which various orifices or bores are introduced, in particular a piston rod leadthrough bore 4 which merges at its lower end into a cylindrical melt chamber bore 5, in which an axially movable casting piston is located when the casting piston rod is inserted, inflow bores 6, via which melt is sucked out of a melt furnace or melt crucible into the melt chamber bore 5, a riser duct 7, via which melt is forced out of the melt chamber bore 5 to a casting mold, and access bores 8a, 8b which serve for introducing the riser duct bore 7 and are closed by means of closure plugs, not shown.

(6) In use, the casting vessel 1 is inserted, in the vertical position shown, into a melt crucible of the melt furnace of the diecasting machine up to a height H marked in FIG. 1. The result of this is that potentially all the inner and outer surfaces of the casting vessel 1 can come into contact up to this height H with the metal melt to be cast. In addition, this melt contact also occurs at the surface of that portion of the riser duct 7 which lies above the height H. All these surface regions which can come into contact with the metallic casting melt during the casting operation are designated in the present case as the melt contact surface regions 9 and are emphasized in FIG. 1 by more thickly drawn lines. In the example shown, these are, in particular, the surfaces of the melt chamber bore 5 and of an adjacent portion of the piston rod leadthrough bore 4 up to at least said height H, of the inflow bores 3, of the riser duct 7, of the access bores 8a, 8b and of the outside of the basic body 2 up to the height H.

(7) In these melt contact surface regions 9, the basic body 2 of the casting vessel 1 is provided with a characteristic anticorrosion layer 3 which is resistant to the metal melt and which is formed, using microparticles and/or nanoparticles of one or a plurality of selected substances. These substances are selected from a substance group which comprises borides, nitrides and carbides of the transition metals and their alloys and also boron and silicon and aluminum oxide (Al.sub.2O.sub.3). The microparticles and/or nanoparticles have an average particle size of between 50 nm and 50 m, preferably an average particle size of between 100 nm and 30 m and more preferably of between 150 nm and 30 m. It proves advantageous to have, inter alia, microparticles and/or nanoparticles composed of TiB.sub.2.

(8) In an advantageous embodiment, the anticorrosion layer 3 is applied to the melt contact surface regions 9 as a substrate by means of a sol/gel process, the substrate preferably being a steel material of the casting vessel basic body 2, as stated. The sol/gel anticorrosive layer can in this case be implemented as a single layer or multiple layer.

(9) FIG. 2 illustrates diagrammatically the anticorrosive layer 3 applied to the basic body 2 made, for example, from steel or high-grade steel, being applied in this example as a multiple layer with one or more layer plies, which form an outer filler-free layer part 3b, and one or more layer plies forming a layer part 3a which is covered by the outer layer part 3b and which contains said microparticles and/or nanoparticles as a filler of the sol/gel process. The microparticles and/or nanoparticles are thereby embedded in the inner layer part 3a of the anticorrosive layer 3, said inner layer part being covered by the outer layer part as a covering layer ply 3b. Typical preferred layer thicknesses for the anticorrosive layer 3 lie in the range between about 1 m and 500 m, the selected average particle size of the microparticles and/or nanoparticles being smaller than this in adaptation to the desired layer thickness, so that the microparticles and/or nanoparticles do not protrude on the surface of the anticorrosive layer 3.

(10) FIG. 3 illustrates by way of example a possible advantageous method for the application of an anticorrosive layer by means of a sol/gel process. The anticorrosive layer thereby applied can be the anticorrosive layer 3 of the casting vessel 1 or, alternatively, any other such component which is used in the casting industry or elsewhere and which has a surface which, in use, has to be protected against the reactive influence of a liquid metal melt. As is shown, for this purpose, first, in two separate mixing steps 10, 11, on the one hand, a gel former is mixed with a solvent and, on the other hand, water is mixed with the solvent. The gel former used is a zirconium-based or silicon-based gel former, for example zirconium propoxide, tetramethoxysilane or tetramethylortho-silicate (TMOS), tetraethoxysilane or tetraethylortho-silicate (TEOS), aminopropyltrimethoxysilane (APS(M)) or aminopropyltriethoxysilane (APS(E)). The solvent which can be used is, for example, acetic acid or glacial acetic acid or tetrahydrofuran (THF). Gel formers and solvents are typically mixed in approximately equal parts by weight, and the mix ratio of solvent and water amounts to 1:n mol, n designating the quantity of gel former in mol multiplied by the number of ligands of the gel former.

(11) The two mixtures are subsequently mixed together, thus resulting in exothermal hydrolysis to form the sol as a starting material, see the mixing step 12 in FIG. 3.

(12) For the preparation of sol loaded with filler, in a further mixing step 13 the sol is mixed, that is to say loaded, with the microparticles and/or nanoparticles of one or more of the abovementioned particle substances. As stated, preferred average particle sizes lie in the range of 50 nm to 50 m and, in particular, between 100 nm and 30 m or 150 nm and 30 m. The microparticles and/or nanoparticles are preferably admixed in a proportion by weight which is smaller than or at most equal to the proportion by weight of sol. After a subsequent cooling step, the loaded sol material is ready for use, the processing time typically amounting to at most approximately 1 h. In this time, the component to be coated, such as the casting vessel shown, is coated in the melt contact surface region 3 with a layer ply of the loaded sol material, see step 15 in FIG. 3. The applied layer ply is then dried for gel formation at a suitable temperature of up to approximately 100 C., see step 16.

(13) Steps 15 and 16 for the application of a layer ply composed of prepared sol material and for conversion into a gel layer ply may, if required, be repeated once or more than once in order to produce the sol/gel layer as a multiple layer, in which case, depending on requirements, sol material loaded with microparticles and/or nanoparticles or filler-free sol material without these microparticles and/or nanoparticles can be used for the respective layer ply.

(14) Thus, FIG. 3 shows by way of example the production of a last outer layer ply composed of nonloaded filler-free sol material, as was obtained in mixing step 12. As a result of an appropriate sequence of the coating step 17 and drying step 18, the nonloaded sol is applied and is dried at up to 100 C. for gel formation.

(15) It will be appreciated that, in alternative embodiments, any combinations of layer plies with a nonloaded filler-free sol material and of layer plies with loaded sol material may be implemented, the loaded sol material containing said microparticles and/or nanoparticles of the specified substance group as a filler. It will be appreciated, further, that, depending on requirements, the same loaded layer ply may contain microparticles and/or nanoparticles solely of the same substance or, alternatively, of different substances, and that, depending on requirements, various loaded layer plies may likewise contain microparticles and/or nanoparticles of the same substance or of different substances. It has proved especially suitable, inter alia, to have microparticles and/or nanoparticles composed of TiB.sub.2, Mo.sub.2B.sub.5, ZrB.sub.2 and mixtures of these substances.

(16) After a desired single-ply or multiple-ply layer make-up has been produced from one or more gel layer plies in this way, this layer make-up is cured in a concluding baking step 19 of the sol/gel process and is consequently compressed into a glass-like material. The baking step 19 preferably takes place at a temperature of between 500 C. and 650 C. A protective atmosphere of, for example, argon gas is preferably used for the baking process.

(17) If a nonloaded silicon-based gel former is used for applying the last layer ply according to steps 17 and 18 of FIG. 3, the filler-free covering layer ply 3b according to FIG. 2 can be formed from this, for example, as a silicon oxide layer.

(18) It will be appreciated that the invention embraces further embodiments in addition to the exemplary embodiments shown by way of example and explained above. Thus, if required, the casting vessel 1 may also be provided with the anticorrosive layer or another surface layer on further surface regions which do not undergo any melt contact. Further, any other casting components may be provided according to the invention with the anticorrosive layer at least in their melt contact surface region, in particular casting fittings, melt furnace constituents, melt conveying constituents and casting mold constituents or their parts of diecasting machines of the hot-chamber or cold-chamber type and of other devices for casting a metal melt. In the same way, any other components may be provided by means of the method according to the invention with an anticorrosive layer in surface regions which may come into contact with metal melts during use, for example components or appliances, such as are employed for the handling of metal melts during soldering processes, in the production of metal alloys, in the purification of metal melts and when solid metals are recovered from the melt.

(19) It is clear that the special anticorrosive layer has very high corrosion resistance, in particular, even with respect to hot aluminum melts. When the anticorrosive layer is formed by means of a sol/gel process, the layer can be applied at relatively low outlay highly uniformly and homogeneously even in surface regions of the casting component to be coated where access is difficult. If required, an alkali or alkaline earth metal salt and/or a viscosity-setting polymer may additionally be administered to the sol material for the sol/gel layer. In alternative embodiments of the invention, the anticorrosive layer may also be applied by laser build-up welding, flame spraying or plasma spraying.

(20) Further embodiments of the invention comprise the application of a multiple-ply anticorrosive layer, of which at least one, preferably an outer, layer ply is formed by means of the sol/gel application method according to the invention and at least one other layer ply is formed by means of another application method which may be, in particular, laser build-up welding, flame spraying or plasma spraying. As a result, in corresponding applications, a layer make-up adapted optimally to the intended use can be achieved with minimized outlay in production terms. In the same way, according to the invention, any component or substrate may be provided on different surface regions in each case with an anticorrosive layer applied by means of two different application methods of the four mentioned, that is to say the sol/gel method, laser build-up welding, flame spraying and plasma spraying. Thus, for example, the sol/gel process may be used for the coating of regions where access is difficult and one of the other three methods mentioned will be used for the coating of surface regions of the substrate where access is easier. Further, said variants of the vertical or lateral combination of layers applied by means of different methods may also be combined with one another in the case of appropriate component or substrate.