EP2723916B1 - Casting component, and method for the application of an anticorrosive layer - Google Patents

Description

The invention relates to a casting component for a device for casting or handling a molten metal, wherein the component has a metallic base body and a surface area which is exposed in the casting operation of the molten metal, and to a method for applying a corrosion protection layer on the casting component.

Such casting components are in the metal casting in many forms in use, for example, as Gießgarnituren, casting containers, melting furnaces, melt delivery units and molds and parts of these Metallgießkomponenten. Usually, a steel material is used for the base body, since such components have a good cost / benefit ratio.
However, it has been found that casting components made of steel in areas where they are in the casting operation with the hot molten metal come in contact, are chemically attacked by the liquid molten metal, ie subject to corrosion. Thus, for example, a noticeable corrosion attack by aluminum melts during aluminum die casting is observed on steel surfaces of casting components coming into contact with it. As a remedy, it is known for casting-piston / casting-cylinder units of metal die-casting machines to manufacture the casting piston and the casting cylinder completely from a ceramic material or from a sintered material, eg from sintered titanium diboride (TiB ₂ ). However, the mechanical strength, heat resistance and impact resistance remained unsatisfactory. As a remedy in the published patent application DE 2 364 809 proposed to manufacture the casting piston and the casting cylinder as a composite sintered component from a mixture of two or more substances from the group of substances, which consists of the carbides, borides and nitrides. In particular, a specific mixture of boron carbide (B ₄ C) with one or more of TiB ₂ , zirconium diboride (ZiB ₂ ) and boron nitride (BN) is given.

In the patent US 4,556,098 For example, this and other sintered materials under investigation are still said to be unsatisfactory and, alternatively, a hot-pressed, high-density, ultra-hard silicon nitride or sialon material is proposed for the casting cylinder and the casting piston. For a crucible made of cast iron, a protective coating against corrosion and oxidation of Ca, Al ₂ O ₃ or other oxides such as Al ₂ O ₃ -TiO ₂ or TiB ₂ , ZaB ₂ , CaB ₂ or other pure or mixed borides or AIN, Si ₃ N ₄ , BN, sialons or other nitrides indicated, for example, is applied from an emulsion or by flame spraying. For conical plugs for closing accessibility holes for the riser and other parts of a casting, the production of such corrosion and erosion resistant materials is also proposed. For parts of the mold that are exposed to molten metal only at lower temperatures, For example, a coating of a dense material of Si ₃ N ₄ , AlN, sialon, BN, graphite or pyrolytic carbon or alloys thereof is proposed.

In the published patent application DE 10 2007 053 284 A1 For example, for a molded article, which may be, for example, a riser for low pressure aluminum casting, there is proposed a permanent, adherent release layer formed by applying a size and curing the applied size by baking at an elevated temperature Suspension of particulate matter comprising 67 to 95% by weight of silicon nitride and 5 to 33% by weight of a SiO ₂ -based high-temperature binder, wherein the SiO ₂ -based high-temperature binder is derived from SiO ₂ precursors and by thermal treatment in a range from 300 to 1300 ° C has been pretreated and this can be obtained by the reaction of a suitable silane compound by the sol-gel method. The separating layer preferably has a thickness of 80 μm to 3,000 μm and may be formed as a multilayer in which an outermost layer has a total oxygen content of at most 21% by weight, while an underlying inner layer has a lower total oxygen content.

The publication DE 10 2006 040 385 A1 discloses a size for producing a high temperature resistant coating comprising a nanoscale inorganic binder system, boron nitride and a solvent. The boron nitride is contained in the form of hexagonal graphite-like boron nitride particles having a primary particle size between 50 nm and 50 μm. The coating can be used, for example, as a mold release layer in die casting.

The publication US 2004/0249039 A1 discloses a method for coating eg casting components, wherein the coating is formed from a precursor layer comprising a silicone resin, a mineral filler and an organic solvent. The filler may be, for example, Al ₂ O ₃ , ZrO ₂ , TiO ₂ , TiB ₂ , ZrB ₂ or boron nitride. The filler can be present in the form of particles in a size between 0.05 .mu.m and 50 .mu.m.

The patent US 5,053,251 discloses a method of repairing a damaged portion of a glass layer of a steel member provided with such a glass layer by a sol-gel process. For this purpose, a first repair agent containing a metal alkoxide is applied and heated to form a first glass layer adhering to the steel substrate. Then, a second repair agent containing a metal alkoxide and an inorganic filler is applied and heated to form a second glass layer. The filler used is preferably a glass or ceramic powder or monocrystalline or multi-crystalline inorganic fiber materials. On the second glass layer, a first liquid-impregnating agent containing a metal alkoxide is applied and heated to fill cavities in the second glass layer. This should fill cavities caused by the filler material.

The invention is based on the technical problem of providing a casting component of the type mentioned above and a method for applying a corrosion layer to a substrate for obtaining a corresponding casting component, wherein the casting component can be produced with relatively little effort and a high corrosion resistance to liquid metal casting melts shows and with the method, a corrosion protection layer with high corrosion resistance, especially against hot molten metal can be applied comparatively easily and with good layer homogeneity even in hard to reach places.

The invention solves this problem by providing a casting component having the features of claim 1 and a corrosion protection layer application method having the features of claim 9.

In the casting-technical component according to the invention, the metallic base body in the melt-contact surface region in which it is exposed to the molten metal in the casting operation is provided with a corrosion-resistant layer which is resistant to the molten metal and characteristically using micro- and / or nanoparticles having an average particle size between 50 nm and 50μm of one or more substances is formed as a filler of a group of substances consisting of borides and carbides of the transition metals and their alloys as well as of boron and silicon. Investigations have shown that a casting component equipped with this special anticorrosive coating exhibits unexpectedly good corrosion resistance to contact with hot, reactive molten metal, especially with respect to aluminum melts. As an explanation, the presence of the one or more anti-corrosive substances in the form of micro- and / or nanoparticles in the layer is primarily assumed. In particular, studies have shown that casting components coated in this way have very high corrosion resistance to aluminum melts and correspondingly long service life, which may be superior to similar components made entirely of a steel material or a ceramic material, or those in a conventional manner with a corrosion protection layer without micro - And / or nanoparticles are provided in the layer structure, even if the same substances are used for the anti-corrosion layer.

Due to the special corrosion protection layer can be used for the main body of the casting component according to a development of the invention, a common steel material, including present also Stainless steel material is to be understood. This allows a simple manufacture of the component compared to the use of ceramic materials. In addition, existing components with such a body made of steel material can be easily retrofitted with the corrosion protection layer. The well-known good mechanical properties of steel for the casting-technical component are retained.

The anticorrosion layer according to the invention is a sol-gel layer, i. a layer applied by a sol-gel process, wherein the micro- and / or nanoparticles act as a filler, with which the sol is loaded in the sol-gel process. The sol-gel layer has a zirconium-based or silicon-based gelling agent. Such anticorrosive coatings can be applied very evenly and with homogeneous layer properties even on relatively difficult to access surface areas of the casting component, which in turn promotes overall corrosion resistance and longevity of the casting component.

Further according to the invention, the sol-gel corrosion protection layer is formed as a multiple layer of several gel layer layers, of which at least one last layer layer is applied without filler. The filler-free layer layer without micro- and / or nanoparticles forms an outer layer layer of the sol-gel layer. The micro- and / or nanoparticles then remain embedded in the underlying layer or layers. Thus, for example, a filler-free outer layer layer can act as a cover layer layer of, for example, silicon oxide or zirconium oxide. In the sol-gel process, all gel layer layers can be subjected to a burn-in process together. With such a multi-layer structure, the properties of the corrosion protection layer can be further optimized with regard to corrosion resistance to hot metal melts.

In one development of the invention, the micro- and / or nanoparticles have an average particle size between 100 nm and 30 μm and more particularly between 150 nm and 30 μm. These particles prove to be very advantageous for the anticorrosion layer designed for resistance to hot, reactive molten metals.

In one development of the invention, the corrosion protection layer contains at least microparticles and / or nanoparticles of TiB ₂ . Based on these TiB ₂ particles built corrosion protection layers, which may optionally contain additional micro- and / or nanoparticles of one or more other substances, show a very high corrosion resistance to corrosion by hot Al melts.

In a further embodiment, the sol-gel corrosion protection layer contains an additionally added alkali metal or alkaline earth metal salt and / or an additionally added, viscosity-adjusting polymer. This contributes to the achievement of the desired good layer properties for the corrosion protection layer on corresponding melt contact surface areas of the casting component.

In one development of the invention, at least two of the layer layers of the sol-gel layer are loaded with micro- and / or nanoparticles of identical or different substances as filler.
In a development of the invention, the casting-technical component is one for a device for casting an aluminum melt. Due to the mentioned, outstanding corrosion resistance against hot aluminum melts, the casting component according to the invention is outstandingly suitable for this purpose.
In a development of the invention, the casting component is one for a metal die casting machine. In particular, it may be a casting assembly, a casting vessel, a melt furnace component, a melt delivery component, a casting component, or a portion of these melt-contacting components of the metal die casting machine. Due to its specific corrosion protection layer, the casting component also has excellent suitability and comparatively long service life for these applications. With the method according to the invention, a corrosion protection layer is applied to a metallic main body of a casting component according to the invention in a melt contact surface area thereof by a sol-gel process using micro- and / or nanoparticles with an average particle size between 50 nm and 50 μm as filler.

According to the method, a plurality of gel layer layers are formed, wherein at least for a last layer layer a filler-free sol material is used. This layer layer then forms a filler-free cover layer layer according to a vitrification baking step common to all layer layers, while the micro- and / or nanoparticles remain embedded in the inner layer layer (s).

In one development of the method, a plurality of gel layer layers are formed with micro- and / or nanoparticles of the same or different substances before the layer layers are subjected together to a curing, vitrification baking step.

In a further development of the method, a vitrification baking process for the one or more gel layer layers is carried out at a temperature between about 500 ° C and about 650 ° C. It has been found that a sol-gel corrosion protection layer formed in this way, when using micro- and / or nanoparticles of suitable substances, has a very high corrosion resistance to chemically-reactive influence of hot metal melts.

Fig. 1

eine Längsschnittansicht durch einen Gießbehälter mit Korrosionsschutzschicht für eine Warmkammer-Druckgussmaschine,

Fig. 2

eine schematische Schnittansicht eines mit der Korrosionsschutzschicht versehenen Bereichs des Gießbehälters und

Fig. 3

ein Flussdiagramm zur Veranschaulichung eines Verfahrens zum Aufbringen einer Korrosionsschutzschicht z.B. für den Gießbehälter von Fig. 1.

Advantageous embodiments of the invention are illustrated in the drawings and will be described below. Hereby show:

Fig. 1

a longitudinal sectional view through a casting container with corrosion protection layer for a hot chamber die-casting machine,

Fig. 2

a schematic sectional view of a provided with the anticorrosion layer portion of the casting container and

Fig. 3

a flow diagram illustrating a method for applying a corrosion protection layer, for example for the casting container of Fig. 1 ,

An in Fig. 1 shown casting container 1 is of a conventional type, as used by the applicant in hot chamber die casting machines, for example, to pour aluminum, magnesium and zinc melts. He has a metallic body 2, which preferably consists of a steel material or stainless steel material as usual and in which various openings or holes are introduced, in particular a piston rod through hole 4, which merges at its lower end in a cylindrical melt chamber bore 5, in which at inlet bore holes 6, is sucked through the melt from a melting furnace or crucible into the melt chamber bore 5, a riser 7, is pressed through the melt from the melt chamber bore 5 to a mold, and access holes 8a, 8b, which serve to introduce the riser channel bore 7 and are closed with sealing plugs, not shown.

In use, the casting container 1 is in the illustrated vertical position up to one in Fig. 1 marked height H used in a melt crucible of the melting furnace of the die-casting machine. This has the consequence that potentially all inner and outer surfaces of the casting container 1 can come into contact with the molten metal to be poured up to this height H. In addition, this melt contact also exists for the surface of the section H of the riser channel 7 above the height H. All of these surface regions which may come into contact with the molten casting in the casting operation are referred to herein as melt-contact surface regions 9 and are described in US Pat Fig. 1 highlighted with thicker drawn lines. In the example shown, these are in particular the surfaces of the melt chamber bore 5 and a subsequent portion of the piston rod passage bore 4 to at least said height H, the inlet holes 3, the riser 7, the access holes 8a, 8b and the outside of the body 2 to the height H.
In these melt-contact surface areas 9, the base body 2 of the casting container 1 is provided with a characteristic, anti-molten metal corrosion protection layer 3, which is formed using micro- and / or nanoparticles of one or more selected substances. These substances are selected from a group of substances consisting of borides and carbides of the transition metals and their alloys as well as of boron and silicon. The micro- and / or nanoparticles have an average particle size between 50 nm and 50 μm, preferably an average particle size between 100 nm and 30 μm and more preferably between 150 nm and 30 μm. Among other things, micro and / or nanoparticles of TiB ₂ prove to be advantageous.
The corrosion protection layer 3 is applied in an advantageous realization by a sol-gel process on the melt-contact surface regions 9 as a substrate, wherein it is said that the substrate is preferably a steel material of the casting container base body 2 as stated. In this case, the sol-gel corrosion protection layer can be realized as a single layer or multiple layer.
Fig. 2 schematically illustrates the anti-corrosive layer 3, for example made of steel or stainless steel applied on the base body 2, in this example as a multilayer with one or more layers forming an outer, filler-free layer part 3b, and one or more layer layers, which covered one of the outer layer part 3b Layer part 3a form, which contains the mentioned micro and / or nanoparticles as a filler of the sol-gel process. As a result, the micro- and / or nanoparticles embedded in the inner layer part 3a of the corrosion protection layer 3, which is covered by the outer layer part as a cover layer layer 3b. Typical preferred layer thicknesses for the anticorrosive layer 3 are in the range between about 1 μm and 500 μm, the mean particle size of the micro- and / or nanoparticles adapted to the desired layer thickness being chosen to be smaller, so that the micro- and / or nanoparticles are not on the surface protrude the corrosion protection layer 3.

Fig. 3 exemplifies a possible advantageous method for applying a corrosion protection layer by a sol-gel process. The anticorrosive layer applied thereby may be the anticorrosion layer 3 of the casting container 1 or, alternatively, any other component used in the casting industry or otherwise having a surface which in use is to be protected from the reactive influence of a liquid molten metal. As shown, first a gel former with a solvent and secondly water with the solvent are mixed in two separate mixing steps 10, 11 on the one hand. The gelling agent used is a zirconium-based or silicon-based gelling agent, for example zirconium propoxide, tetramethoxysilane or tetramethylorthosilicate (TMOS), tetraethoxysilane or tetraethylorthosilicate (TEOS), aminopropyltrimethoxysilane (APS (M)) or aminopropyltriethoxysilane (APS (E)). As the solvent, for example, acetic acid or glacial acetic acid or tetrahydrofuran (THF) can be used. Gelling agent and solvent are typically mixed in approximately equal proportions by weight, the mixing ratio of solvent and water is 1: n mol, where n denotes the amount of gelling agent in moles multiplied by the number of ligands of the gelling agent.

Subsequently, the two mixtures are mixed together, resulting in an exothermic hydrolysis to form the sol as the starting material, see the mixing step 12 in Fig. 3 ,
In order to provide sol laden with filler, in a further mixing step 13, the sol is mixed with the micro- and / or nanoparticles of one or more of the abovementioned particle substances, ie loaded. Average particle sizes are, as stated, in the range of 50 nm to 50 μm and in particular between 100 nm and 30 μm or 150 nm and 30 μm. The micro- and / or nanoparticles are preferably admixed in a proportion by weight which is less than or at most equal to the weight fraction of sol. After a subsequent cooling step, the loaded sol material is ready for use, the processing time typically being at most about 1 hour. During this time, the component to be coated, such as the casting container shown in the melt-contact surface region 3, is coated with a layer layer of the loaded sol material, see step 15 in FIG Fig. 3 , The applied layer layer is then dried for gel formation at a suitable temperature of up to about 100 ° C, see step 16.
The steps 15 and 16 for applying a layer of prepared sol material and conversion to a gel layer layer can be repeated once or several times as needed to prepare the sol-gel layer as a multilayer, with loaded with micro- and / or nanoparticles as needed Sol material or filler-free sol material without these micro- and / or nanoparticles can be used for a respective layer position.
So shows Fig. 3 as an exemplary example, the production of a last, outer layer layer of unloaded, filler-free sol material, as obtained in the mixing step 12. By an appropriate Following coating step 17 and drying step 18, the unloaded sol is applied and dried to gel formation at up to 100 ° C.

It is understood that, in alternative embodiments, any desired combinations of layer layers with unloaded, filler-free sol material and layer layers with loaded sol material can be realized, wherein in the loaded sol material the mentioned micro- and / or nanoparticles of the indicated substance group are contained as filler. Furthermore, it is understood that micro-and / or nanoparticles of exclusively the same substance or alternatively different substances can be contained as needed in the same loaded layer layer and that also in different loaded layer layers as needed micro- and / or nanoparticles of the same substance or may be contained in different substances. Among others, micro and / or nanoparticles of TiB ₂ , Mo ₂ B ₅ , ZrB ₂ and mixtures of these substances have proven to be particularly suitable.

After a desired single-layer or multi-layer layer structure of one or more gel layer layers has been produced in this way, this layer structure is cured in a final stoving step 19 of the sol-gel process and thus compacted to a glassy material. The baking step 19 is preferably carried out at a temperature between 500 ° C and 650 ° C. Preferably, a protective atmosphere is e.g. from argon gas used for the baking process.

If for applying the last layer layer according to the steps 17 and 18 of Fig. 3 an unloaded silicon-based gelling agent is used, it can from the filler-free outer layer layer 3b according to Fig. 2 For example, be realized as a silicon oxide layer.

It is understood that the invention includes other embodiments besides the exemplary embodiments shown and explained above. If necessary, the casting container 1 can also be provided with the anticorrosion layer or another surface layer on further surface regions which are not subject to melt contact. In addition, any other casting components may be provided with the anticorrosive layer, at least in their melt contact surface area, in particular cast sets, melt furnace components, melt delivery components and mold components or parts thereof of hot-chamber or cold-chamber die casting machines and other devices for casting a molten metal. Likewise, any other components may be provided by the method of the invention with a corrosion protection layer in surface areas which, in use, may come in contact with molten metals, e.g. Components or equipment such as those used to handle molten metals in soldering processes, in the manufacture of metal alloys, in the cleaning of molten metals, and in the recovery of solid metals from the melt.

It turns out that the special corrosion protection layer has a very high corrosion resistance, in particular also with respect to hot aluminum melts. When the corrosion protection layer is formed by means of a sol-gel process, the layer can be applied very evenly and homogeneously even in hard to reach surface areas of the casting component to be coated with relatively little effort. If necessary, an alkali or alkaline earth metal salt and / or a viscosity-adjusting polymer may be additionally added to the sol material for the sol-gel layer. In alternative embodiments of the invention, the corrosion protection layer can also be applied by laser cladding, flame spraying or plasma spraying.

Further embodiments of the invention include the application of a multilayer anticorrosion layer, of which at least one, preferably an outer, layer layer is formed by the sol-gel coating method according to the invention and at least one other layer layer by another application method, which is in particular laser cladding, flame spraying or plasma spraying can act. In this way, in appropriate applications, a layer structure adapted optimally to the intended use can be achieved with minimized production outlay. In the same way, according to the invention, any component can be provided, on different surface areas, with in each case one anticorrosive layer which is provided with two different of the four mentioned application methods, i.e. Sol-gel process, laser cladding, flame spraying and plasma spraying are applied. Thus, e.g. the sol-gel process for coating hard-to-reach areas and one of the other three methods mentioned for coating more accessible, flat areas of the component are used. Furthermore, the mentioned variants of the "vertical" or "lateral" combination of layers applied with different methods can also be combined with one another in a corresponding component.

Claims (11)

1. Casting component for a device for casting or handling a metal melt, the component having a metallic basic body (2) and a melt contact surface region (9) which is exposed to the molten metal during a casting operation,
   characterized in that
   the metallic basic body (2) is provided in the melt contact surface region (9) with an anticorrosive layer (3) which is resistant to the metal melt, and which is formed as a sol/gel layer using microparticles and/or nanoparticles as a filler having an average particle size of between 50 nm and 50 µm of one or more substances, which are selected from the group consisting of borides and carbides of the transition metals and their alloys and of boron and silicon, wherein the sol/gel layer has a zirconium-based or silicon-based gel former and is formed by a plurality of gel layer plies, at least one layer ply thereof being formed without microparticles and/or nanoparticles and forming an outer layer ply of the sol/gel layer.
2. Casting component according to claim 1, further characterized in that the microparticles and/or nanoparticles have an average particle size of between 100 nm and 30 µm.
3. Casting component according to claim 1 or 2, further characterized in that the anticorrosive layer is formed using microparticles and/or nanoparticles composed of TiB₂.
4. Casting component according to any one of claims 1 to 3, further characterized in that the sol/gel layer comprises an additionally administered alkali metal salt or alkaline earth metal salt and/or an additionally administered viscosity-setting polymer.
5. Casting component according to any one of claims 1 to 4, further characterized in that at least two layer plies of the sol/gel layer include microparticles and/or nanoparticles of identical or different substances.
6. Casting component according to any one of claims 1 to 5, further characterized in that the basic body is formed from a steel material.
7. Casting component according to any one of claims 1 to 6, further characterized in that the casting component is one for a device for casting an aluminum melt.
8. Casting component according to any one of claims 1 to 7, further characterized in that the casting component is one for a metal die-casting machine, preferably a casting fitting, a casting vessel, a melt furnace constituent, a melt conveying constituent, a casting mold constituent or a part of one of these die-casting machine constituents.
9. Method for applying the anticorrosive layer (3) to the metallic basic body (2) of a casting component according to any one of claims 1 to 8 in a melt contact surface region (9) thereof by means of a sol/gel process using microparticles and/or nanoparticles with an average particle size of between 50 nm and 50 µm as a filler, wherein during the sol/gel process a plurality of gel layer plies are formed, at least a last one thereof being applied filler-free without the microparticles and/or nanoparticles.
10. Method according to claim 9, further characterized in that during the sol/gel process a plurality of gel layer plies are formed, at least two thereof being loaded with the microparticles and/or nanoparticles of identical or different substances as a filler.
11. Method according to claim 9 or 10, further characterized in that, after the formation of one or more gel layer plies, a vitrifying baking step is carried out at a temperature of between 500 °C and 650 °C.

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