EP2049288A2

EP2049288A2 - Flux, and method for the reduction of oxide layers on metallic surfaces

Info

Publication number: EP2049288A2
Application number: EP07725551A
Authority: EP
Inventors: Manfred Laudenklos; Joachim Bohrt
Original assignee: Gelita AG; KS Aluminium Technologie GmbH; KS Kolbenschmidt GmbH
Current assignee: Gelita AG; KS Kolbenschmidt GmbH; KS Huayu Alutech GmbH
Priority date: 2006-07-28
Filing date: 2007-05-25
Publication date: 2009-04-22
Also published as: WO2008011933A3; US20110146845A1; WO2008011933A2; MX2009000610A; KR20090042917A; BRPI0715432A2; JP2009544471A; CN101528389A

Abstract

The invention relates to a flux for application to and the reduction of oxide layers on a metallic solid or molten surface that is composed at least of potassium, fluoride, and moieties of water. The flux is formed from a reactant containing moieties of zirconium fluoride and/or lithium fluoride and/or sodium silicon fluoride and/or potassium cryolite and/or potassium aluminum fluoride (KaAIF4) as well as moieties of salts based on zirconium and/or lithium and/or potassium and/or sodium and/or bismuth and/or boron and/or titanium. The invention further relates to a method for casting basic aluminum alloys as well as the use of the disclosed flux for reducing oxide layers on molten basic aluminum alloys.

Description

DESCRIPTION

Flux and method for reducing oxide layers on metallic surfaces

The invention relates to a flux for applying and for reducing oxide layers on a metallic surface consisting at least of potassium fluoride, sodium fluoride and water. Moreover, the invention relates to a casting process for the production of metallic components, from at least two different materials, of which one material is an iron-based alloy and the other is an aluminum-based alloy, with the process steps:

Applying a metallic layer to an iron-based alloy body, the metallic layer being an aluminum-based alloy and being applied by immersion in an aluminum melt,

Inserting the coated body into a casting mold and casting over the coated body with an aluminum-based alloy, the invention relates to a method in which a liquid light metal alloy is skimmed out of an open mold and filled into a casting mold. Another part of the invention relates to a method for cohesive joining of metallic components, and finally the invention relates to a method for reducing oxide layers on solid or liquid metallic surfaces.

The vast majority of metallic materials form under the influence of the atmosphere and in particular under the influence of oxygen oxide layers. These oxide layers are partially desirable, such as aluminum sheets, but in part, the oxide layers have a detrimental effect on the manufacturing process. If, for example, as is customary when casting in low-pressure casting of aluminum pistons, worked with liquid aluminum alloys, so it forms directly on the surface of the liquid aluminum alloy in the mold, an oxide skin, which in turn adversely affects the casting quality of the castings.

Various manual as well as automated methods for removing the oxide layer on molten aluminum alloys have been known in the past.

Thus, for example, it is common and described in DE 34 11 970, from the crucible in which the liquid aluminum alloy is present to scoop out the aluminum manually by means of a trowel and into the mold, for producing, for example, a piston for an internal combustion engine to fill. If an operator removes the molten aluminum from the crucible, he simultaneously scoops the oxide film formed on the liquid aluminum. This is mitigated by the fact that the operator, the oxide skin, which is also called scabies, skimmed off manually by means of a trowel and thus removed. In the case of aluminum and aluminum alloys in particular, it is the case that this oxide skin is formed directly again, so that complete elimination is virtually impossible.

In order to automate this manual activity, an automatic removal of the dross is further described in DE 34 11 970. Described is a method in which the trowel in the immersed state cooperates with a likewise immersed in the molten metal in the mold puller, which is displaceable for pushing the dross on the trowel against this by an actuator and further the trowel in a vertical plane around a Rotation axis is thrown out of the mold under the action of further drive means for ejecting the recorded dross. As a result, a minimization of the introduced into the casting aluminum oxide is achieved.

In order to reduce in particular the disadvantages of the oxide layers on workpieces to be cast, a method is known from DE 101 13 962 A1 which uses a flux for the deoxidation of oxide layers present on the workpieces. Before the workpiece to be cast is provided with a further metallic layer, a flux is applied to the metallic workpiece. gene, which on the one hand reduces the oxides on the workpiece and on the other hand supports the metallurgical bond of Umgusswerkstoffes with the einzugießenden material, since the oxide layer is broken and thus eliminates the diffusion-inhibiting layer. A problem that arises with such metallurgical bonds is the oxide layer formed between the metallic layer on the body to be infused. The oxide layers of aluminum have a very high melting point, of about 2,000 ⁰ C, whereas conventional aluminum alloys have a melting point, which is usually far below 1000 ⁰ C, in particular below 800 ⁰ C. The encapsulation material can thus not break the oxide layer, which leads to increased binding errors. In order to reduce or dissolve these high-melting oxide layers, flux is applied to the body before casting.

A method for producing a composite casting of an aluminum alloy and a wear-resistant material forming an inner layer is described in DE 2 344 899. The method is characterized in that the core to be coated is immersed in an aluminum melt immediately prior to casting in order to form a diffusion layer of the aluminum and the wear-resistant material. This method has become known as the so-called Alfin method. To bond the aluminum melt, the use of release agents is also described herein. It is described that for better release of the core after the casting process, it is appropriate to coat the core with a release agent prior to coating with the wear-resistant material.

The object of the invention is to provide an agent with a chemical composition with a high potential difference, which allows a reduction of oxide layers in a manner not known and beyond a metallurgical connection between a casting workpiece and a Umgussmaterial significantly improved. In addition, the object is to provide a method in which it is possible to dispense with removing oxide layers in crucibles. In addition, it is an object of the invention to provide a method by means of which the oxide skin on liquid or solid metallic O- surfaces reduced or completely removed. The object of the invention is achieved by providing a flux consisting of proportions of zirconium fluoride and / or lithium fluoride and a reactant of proportions of salts based on zirconium and / or lithium and / or potassium and / or sodium and / or bismuth and / or boron and water is formed. With regard to the method to be improved, the object according to the invention is achieved in that in conventional methods the improved flux is applied directly to the workpieces and / or the flux is applied directly to the surface of the aluminum melt. The inventive composition of the flux, the possibility is now created to completely or almost completely remove the forming oxide layer and to provide permanent protection for the formation of new oxide layers. With regard to the casting process, and the use of the flux on the surface of the molten casting metal, it is now possible to completely dispense with the mechanical removal of the oxide layer. Thus, in particular, the manual removal of the dross from the mirror of the liquid metal and the discharge of the deducted scraps from the mold in a waste bin omitted by the caster.

With respect to the agent, a flux is provided which additionally contains gelatin. In an advantageous development of the invention, the flux additionally contains proportions of zirconium fluoride and / or lithium fluoride, sodium silicon fluoride and / or potassium cryolite and / or potassium aluminum fluoride (KaAIF ₄ ) and amounts of salts based on zirconium and / or lithium and / or Potassium and / or sodium and / or bismuth and / or boron and / or titanium and water is formed. The present in the liquid or granular state mixture of flux, which is in particular a fluorine-based flux, reactants, such as zirconium and bismuth or lithium and bismuth or zirconium, titanium and bismuth, and the gelatin is here in particular for the reduction of aluminum oxides, such as Al ₂ O ₃ , used. The flux known as "NOCOLOK" can be used as flux, the flux NOCOLOK is manufactured and marketed by the company Solvay, and a particular advantage arises when gelatine is added to the flux sold under the trade name "Gelita" of the gelatin group. The use of this gelatin in combination with the flux and the reactant makes it possible, in particular but not exclusively, to reduce oxide layers on light metal alloys, preferably aluminum. The reactant in the flux is formed from proportions of zirconium fluoride and / or lithium fluoride and proportions of salts based on zirconium and / or lithium and / or potassium and / or sodium and / or bismuth and / or boron and / or titanium and water. The proportion of zirconium is between 5 wt .-% to 20 wt .-%, the proportion of lithium between 8 wt .-% and 25 wt .-% and the proportion of potassium between 2 wt .-% and 10 wt. -% and the proportion of sodium between 1 wt .-% and 8 wt .-% and the proportion of bismuth between 0.5 wt .-% to 5 wt .-% and the proportion of boron between 2 wt .-% to 10% by weight. The gelatin additionally added to the flux is formed predominantly of calcium and / or magnesium and organic and inorganic constituents which make a coordinated contribution to the potential equalization during dispersion and to the acceleration of the reaction. The gelatin content is between 0.5% by weight and 5% by weight in the flux. The main constituents of the gelatin are calcium with proportions 3,950 mg per kg and magnesium 1,500 mg per kg.

Furthermore, the invention relates to the use of the flux in a casting process, in which components are formed of different materials. A problem with such methods is that the different materials have different specific properties that adversely affect the casting process. If, for example, a body consisting of an iron-based alloy is encapsulated with a light-alloy, such as aluminum, it is during casting, due to the different melting temperatures, to areas between the different materials that are not metallurgically connected, rather The body of the light alloy alloy surrounded and held there only mechanically in position. A method for better metallurgical bonding of the iron-based body to the aluminum melt surrounding it is the known Alfin process. For better connection of the encapsulation to the body, the body is immersed in an aluminum melt and immediately inserted into the mold. The invention will be explained in relation to the use of the flux in a casting process, hereinafter in an embodiment. It shows:

Figure 1 Two coated with an aluminum layer ring carrier for a

Piston.

A coated in the Alfin process ring carrier as part of a piston is shown in the figure 1. FIG. 1 shows, on the left side, a ring carrier 1 formed of an iron-based alloy and coated with an aluminum layer 2 by means of the Alfin process. The ring carrier has in addition, for mechanical clamping in the Umgussmaterial, circumferential grooves 3, which additionally fix the ring carrier 1 in Umgusswerkstoff.

The ring carrier 1 shown in Figure 1 was immersed in an aluminum melt whose surface was provided with a conventional flux, in this case NOCOLOC. The aim of this experiment was to reduce the oxides on the surface of the molten aluminum, so that the ring carrier could be coated circumferentially and over the entire surface. The application of the agent with the trade name NOCOLOC and the gelatin markedly reduced the dross forming on the aluminum melt, so that only in a few areas 4 did the aluminum layer 2 on the ring carrier 1 become less adherent. The application of the flux according to the invention to the molten aluminum significantly reduces the oxide layer forming on the liquid molten bath, so that a significantly improved result with respect to the alfine layer 2 on the ring carrier 1 can be formed.

The ring carrier 5 on the right side of FIG. 1 was alfined in a molten bath charged with a flux consisting of the conventional flux NOCOLOC _1, a reactant and gelatin. By applying the flux according to the invention as claimed in claim 4, the oxide layer on the molten aluminum could be almost completely and long-term reduced, so that the ring carrier 5 by the flux on the surface of the molten aluminum directly into the molten aluminum of the molten bath ein- could be dipped without depositing oxides on the surface of the ring carrier 5. The alfinierte surface 6 of the ring carrier 5 shows a consistently uniform Alfinschicht, or an aluminum coating that is free of defects. It is thus inventively a casting process for the production of metallic components, made available from at least two different materials, in which an optimal connection of a metallic layer 2, 6 on a body 1, 5 can be deposited.

In order to reduce oxides present on the body 1, 5, it is proposed according to the invention to apply to the body 1, 5 provided with the metallic layer 2, 6 before insertion into the casting mold with a flux according to one of claims 1 to 4. As a result, the oxides forming on the metallic layer 2, 6 can likewise be reduced again, so that a metallurgical bond occurs between the metallic layer 2, 6 and the encapsulation material. As a casting material usually aluminum alloys and preferably aluminum silicon alloys are used. It goes without saying that this is merely an exemplary embodiment; the casting-technical method is, of course, also applicable to other components, such as cylinder liners, crankshaft bearings in cylinder crankcases. The inventive method is particularly applicable where a metallurgical bond between different materials to be achieved.

The flux according to any one of claims 1 to 4 is for this purpose in the liquid or in the granular state to the aluminum melt, e.g. AISi9, AISi12, AI 99.5, applied directly and on the order of 10 to 100 g per square centimeter. By applying the flux to the molten aluminum, the oxide layer is immediately reduced and forms a permanent oxide-free surface on the free surface of the mold of the molten aluminum alloy material.

A further field of use of the flux according to the invention is the use in a method for producing a cast body, in which a liquid light alloy from an open mold is skimmed off and filled into a casting mold. The processes known from the prior art show solutions gene, which show a manual or automatic removal of the oxide layers or dross on the liquid surfaces of the aluminum alloys. A disadvantage of such processes is that, on the one hand, the aluminum oxide layers can never be completely removed and, on the other hand, the aluminum oxide layers reform within a very short time, that is to say within fractions of a second.

The use of the flux according to the invention in a method for producing a cast body, in which a flux according to any one of claims 1 to 4 is applied to the surface of the light alloy prior to skimming the light metal alloy, can completely dispense with a removal of the oxide layer become. The flux reduces or dissolves the oxide layer on the light metal alloy, so that the ladle immersed in an oxide-free surface and also can scoop off oxide-free aluminum or an aluminum alloy. Thus, a casting of castings which is free of oxide layers or at least greatly reduced is made possible.

The flux is applied directly to the open surface of the liquid molten metal mold in an amount of 10 to 100 g, preferably 20 g per square centimeter, the surface having a diameter of about 40 cm. As a result, the oxides on the surface of the molten metal are completely reduced, so that the liquid aluminum alloy metal without oxide layers is available for processing.

In addition to the casting process, the flux according to the invention can be used in methods for the material-locking connection of metallic components. In material bonds, such as welding, oxides on the surfaces of the materials are a hindrance, since the oxides can get into the molten bath or the joining surface, and thus cause errors in the weld. The use of a flux according to any one of claims 1 to 4 reduces the oxide layers on iron-based alloys such as on aluminum-based alloys, in such a way that the joining surfaces are deoxidized sustainable. In addition, the flux can be used to reduce oxide layers on metallic, iron-containing or aluminum-based surfaces formed from an aluminum-based base. The flux according to the invention can thus not only be used on molten aluminum alloys, but also be used on solid metallic surfaces which form oxide layers on their surfaces.

Claims

PATENT APPLICATIONS Extinguishing media and methods for reducing oxide layers on metallic surfaces

1. A flux for applying and for reducing oxide layers on a metallic surface consisting at least of potassium fluoride, sodium fluoride and remaining portions of water, characterized in that the flux contains gelatin.

2. Fluxing agent according to claim 1, characterized in that the flux is a reaction agent of proportions of zirconium fluoride and / or lithium fluoride, sodium silicon fluoride and / or potassium cryolite and / or potassium aluminum fluoride (KaAIF ₄ ) and proportions of salts based on zirconium and / or lithium and / or potassium and / or sodium and / or bismuth and / or boron and / or titanium.

3. flux according to claim 1 or 2, characterized in that the gelatin is formed from calcium and / or magnesium and organic and inorganic constituents and is present in proportions of 0.5 wt .-% and 5% by weight in the flux.

4. flux according to one of claims 1 to 3, characterized in that the flux of 5 wt .-% to 20 wt .-% zirconium and / or 0.1 to 5 wt .-% titanium and / or 8 wt. % to 25 wt .-% lithium and / or 2 wt .-% to 10 wt .-% potassium and / or 1 wt .-% to 8 wt .-% sodium and / or 0.5 wt .-% to 5 wt .-% bismuth and / or 2 wt .-% to 10 wt .-% boron is composed.

5. flux according to one of claims 1 to 4, characterized in that the flux contains gelatin.

5. Casting process for the production of metallic components from at least two different materials, of which one material is an iron-based alloy and the other is an aluminum-based alloy, comprising the steps of applying a metallic layer (2, 6) to a body (1 5) of an iron-based alloy, wherein the metallic layer (2, 6) is an aluminum-based alloy and applied by immersion in an aluminum melt, inserting the coated body (1, 5) into a casting mold and casting over the coated body ( 1, 5) with an aluminum-based alloy, characterized in that prior to immersing the body (1, 5) of an iron-based alloy in the aluminum melt on the surface of the molten aluminum, a flux according to any one of claims 1 to 4 is applied, so that for the reduction or dissolution of the on the aluminum melt bil When the metallic oxide layer penetrates into the aluminum melt, the metallic layer forms a metallurgical bond with the body of iron-based alloys.

6. casting process according to claim 5, characterized in that the flux is applied in the liquid or granular state to the aluminum melt.

7. Casting method according to one of claims 5 and 6, characterized in that on the provided with the metallic layer body of an iron-based alloy prior to insertion into the mold, a flux according to any one of claims 1 to 4 is applied.

8. A method for producing a cast body in which a liquid light metal alloy is skimmed from an open mold and filled into a mold, characterized in that prior to filling the light metal alloy on the surface of the light metal alloy, a flux according to one of Claims 1 to 4 is applied, so that it comes to the reduction or dissolution of the forming on the light metal alloy oxide layer.

9. A method for producing a cast body according to claim 8, characterized in that the flux is applied in an amount of 10 to 100 g to about 0.3 m ² on the open mold.

10. A method for cohesive joining of metallic components, characterized in that a flux according to any one of claims 1 to 4 is applied to the regions of the components to be joined, so that it comes to the reduction or dissolution of the forming on the metallic component oxide layer ,

11. A method for material bonding according to claim 10, characterized in that the method is a welding method.

12. A method for reducing oxide layers on metallic surfaces, characterized in that a flux according to any one of claims 1 to 4 is applied to the metallic surface.

13. A method for reducing oxide layers according to claim 12, characterized in that the metallic surfaces of an aluminum-based alloy or an iron-based alloy is formed.