EP2720818A1

EP2720818A1 - Casting core for a casting method, and method for removing a casting core

Info

Publication number: EP2720818A1
Application number: EP12728258.0A
Authority: EP
Inventors: Karl-Heinz Horsmann
Original assignee: EGO Elektro Geratebau GmbH
Current assignee: EGO Elektro Geratebau GmbH
Priority date: 2011-06-17
Filing date: 2012-06-15
Publication date: 2014-04-23
Also published as: WO2012172063A1; DE102011077714A1

Abstract

The invention relates to a casting core for a casting method in which the exterior of a cast body is shaped in a casting mold and in which inner cavities, channels, or the like of the cast body are defined by the casting core. The casting core consists of expanded vermiculite and is solidified by means of a binder. The binder, for sample salt, can be dissolved by a solvent or water in order to dissolve away or remove the casting core after the casting process, wherein the casting core dissolves or loses rigidity.

Description

description

Casting core for a casting process and method for removing a

casting core

Field of application and state of the art

The invention relates to a casting core for a casting method in which a cast body in a casting mold receives its outer shape and inner cavities, channels or the like. of the casting are determined by the casting core. Likewise, the invention relates to a method for extracting or removing a casting core.

From WO 2006/042350 A1 it is known, for example, when casting light metal rims for a motor vehicle, to use a casting core of compressed vermiculite. This casting core then remains in the alloy rim or cast body. For this purpose, such a casting core, for example made of vermiculite, similar to one of molding sand, can be brought together with a binder into a solid, stable mold.

Another corresponding casting method is known from DE 201 07 462 U1, wherein also a casting core of vermiculite and a water glass-like binder is pressed and dried. This casting core then remains in the cast body.

In the known so-called Sandkerngießen, however, there is the one hand, the problem that the binder resin for producing the solid casting core of molding sand when heated by the impact of the liquid metal forms gases. These gases interfere with the casting process, as voids may form at the interface between the casting and the casting core, or worse, within the casting itself, which is not noticed during a rough visual inspection. Of the way Although known molding sand often has the disadvantage that it has a lower heat capacity than the metal of a normal mold, but not so much lower. Also, in the area of the casting core, the metal to be cast can cool relatively quickly and then a solid body of the liquid metal can be caused to rapidly solidify in a cast body having a complicated shape and small wall thicknesses and thus problems can arise during the casting process or in the finished cast body.

Field of application and state of the art

The invention has for its object to provide a casting core mentioned above for a casting method and a method for removing a casting core from a finished casting, with which problems of the prior art can be eliminated and in particular an advantageous possibility can be created, a casting core remove a cast body again.

This object is achieved by a casting core with the features of claim 1, 4 or 6 and by a method according to claim 9. Advantageous and preferred embodiments of the invention are the subject of the other claims and are explained in more detail below. Some of the following enumerated features are mentioned only for the casting core or just for the method. However, they should be able to apply independently of such a casting core as well as for such a method. The wording of the claims is incorporated herein by express reference.

It is envisaged that in the casting process, a casting in a casting mold on the one hand receives its outer shape. On the other hand, he should inner cavities, channels or the like. determined by the casting core are. The casting core consists, as described above, of clay mineral or silicate material or phyllosilicate. Vermiculite is used particularly advantageously, in particular exclusively expanded vermiculite. The material of the casting core is brought together with a binder in a solid form, advantageously pressed.

According to the invention, in a first basic embodiment of the invention, the binder is selected or formed in such a way that it can be dissolved by a solvent, preferably water. Thus, after the casting process, the casting core can be removed or removed from the cast body. Thus, on the one hand through the use of a material other than molding sand an advantage can be achieved in the casting process, for example by the lower heat capacity of the alternative materials, especially the vermiculite. Due to the special binder, the casting core or its material can be removed from the cast body again after the casting process, which can bring a weight saving in the cast body, above all. Furthermore, such a cavity or channel can be used functionally in the cast body, which would not be possible with known so-called lost cores. By bringing a solvent on the casting core, the mechanical strength of the binder can be dissolved and thus disintegrate the casting core and in individual small parts, possibly even in a form such as starting material, granular advantageous to be removed from the casting ,

In known casting method with a casting core of molding sand mixed with resin as a binder, although often the temperature of the casting process itself provides for a dissolution of the binder and a subsequent removal of the molding sand from the cast body through a corresponding opening. In the aforementioned materials for the casting core of clay mineral or silicate material or sheet silicate, however This is not so easy, since they have been processed differently so far.

In an advantageous embodiment of the invention, the binder is water-soluble, for example a salt. Different salts can be used, for example KaCl or NaCl. Such salts are relatively heat resistant and have a beneficial bonding effect with the aforementioned core materials. In contact with water as a solvent, however, they dissolve very quickly, so that then the previously bound clay or layered silicate quasi disintegrates and, similar to otherwise known molding sand, can be removed from an opening from the cavity or channel of the casting.

In an alternative embodiment of the invention, a binder may be a synthetic resin or a plastic and be formed so that dissolution by alcohol or ethanol or other similar solvents is possible. In this case, although the chemistry used is somewhat more complex or even provided with more environmental requirements than in the aforementioned case with water and salt. At the same time, however, an attained binding effect can also be greater here in order to produce a firmer casting core, if necessary.

In a second basic embodiment of the invention, the binder may be selected so that it swells or swells in cooperation with water or other liquid. Then, of course, the binding effect is lost. Thus, the casting core can be virtually destroyed on its own and the material can be removed or removed from the casting after the casting process.

An advantageous example of such a binder is a clay mineral, preferably bentonite. This material has the properties that it just absorbs it in contact with small amounts of water and swells it greatly. As a result of this swelling, the previously solid shape of the casting core is destroyed, and the casting core can likewise be easily removed from the cast body, as already described above. In this case, therefore, there is no dissolution of the binder, as described for the first basic embodiment of the invention, since the binder, in particular the bentonite, is in this case still present as a separate constituent after dissolution. Rather, it is a moisture-induced mechanical destruction or in particular self-destruction of the casting core.

In yet another third fundamental embodiment of the invention, a binder for a material for the casting core in the form of clay mineral or phyllosilicate may be thermally dissolvable or lose its binding effect by thermal action. In this case, then, basically similar to known molding sand, either the casting process itself, the casting core can be dissolved and after cooling of the cast body, the material of the casting core are removed. Alternatively, if its thermal resistance is correspondingly high, the binder can be dissolved by subsequent heating or heating, or the material of the casting core can be dissolved out. Here, resins are used as binders.

It can be provided, for example, that such a binder already dissolves at temperatures between 100 ° C and 200 ° C or loses its binding effect with the material of the casting core. In conventional casting processes with conventional temperature ranges then sufficient heating of the entire casting core is already achieved, so that the binding effect is eliminated and the material of the casting core can be removed from the finished casting. In a method for removing a casting core from a finished cast body, on the one hand it can be provided that, as has been described above, water or a solvent is brought to the casting core for its dissolution and detachment. This can be done, for example, such that a jet is directed onto the casting core by means of nozzles or high-pressure nozzles, respectively, by means of an access opening produced during the casting process into the cast body, for example also as a channel or the like provided anyway. Not only does the mechanical impact of the liquid jet on the casting core trigger and flush it out, but the binding effect is dissolved, as described above. Then, either by rinsing out the applied water or solvent itself or by cleaning in the interval mode with short interruptions, the dissolved material of the casting core fall out by itself or be sucked off.

In the case of a thermally dissolvable binder may be dissolved as a separate thermal action either with hot fluid, preferably hot gas, the casting core through an access opening. Alternatively, this may be done by direct flame exposure, which is relatively expensive.

The mentioned casting cores can be produced by pressing the clay mineral or sheet silicate with appropriate binder. The starting material is advantageously present in granular form, for example similar to sand.

These and other features are apparent from the claims and from the description and drawings, wherein the individual features are realized individually or in each case in the form of sub-combinations in an embodiment of the invention and in other fields and advantageous and for themselves represent protectable versions for which protection is claimed here. The subdivision of the application in individual sections as well as intermediate headings do not limit the statements made thereunder in their generality.

Brief description of the drawing

Embodiments of the invention are shown schematically in the drawings and will be explained in more detail below. In the drawings show:

1 is a plan view of a mold including casting core for producing a sanitary fitting,

2 shows a section A through the arrangement of FIG. 1 with only the lower half for clarity,

Fig. 3 is a section B through the arrangement of Fig. 1 with both

Halves of the mold and

A representation, as in the finished sanitary fitting by means

Spray nozzles the casting core is removed.

Detailed description of the embodiments

In Fig. 1, a mold 1 1 is shown in plan view, which has a recess in a known manner, in which a cast body can be cast. As the sectional views of Figure 2 in section A and Fig. 3 in section B show, the mold is also known manner of an upper half 12 and a lower half 13. These are formed here due to the formation of the casting mirror-symmetrical.

In the mold 1 1, for example, fixed in the lower half 13, a casting core 15 is arranged. This casting core 15 consists, as previously from blown and compressed vermiculite to which a binder has been added. The binder may be selected according to one of the aforementioned criteria and will be explained in more detail below.

Thus, in the mold 1 1 a sanitary fitting 17 has been cast as a cast body. The sanitary fitting 17 has a main body 17a and an outlet pipe 17b projecting therefrom. The main body 17a has a large opening 18a at the bottom and a slightly small opening 18b at the top. The outlet pipe 17b has an opening 18c at the free end. The production of the casting core 15 by pressing the expanded vermiculite together with the added binder can, as mentioned above and be easily imagined by the skilled person, take place in a separate form. It can be made much easier than with ordinary foundry sand, which is injected with a binder resin and under enormous pressure into a mold. Since the casting core 15 is arranged only in the interior of the sanitary fitting 17 and here a surface quality and the mapping of possible burrs does not play any significant role, such a casting core can be used very well for such an application.

FIG. 4 shows how the casting core 15 is removed again in the form of a cast sanitary fitting 17 which has been finished out of the casting mold 11. For this purpose, two spray nozzles 22a and 22b are provided at the openings 18c and 18a and directed towards these openings. Depending on the nature of the casting core 15 or of the binder used with the vermiculite or the main material of the casting core, different solvents 23 can be applied with the spray nozzles 22a and 22b.

In a first case described above, in which the binder in the casting core 15 is water-soluble, for example a salt, it can be used as solvent. 23 water with the spray nozzles 22a and 22b are applied. Through the water, the binder or salt of the casting core 15 dissolves and the material can fall out in small pieces of material 24 or be flushed out by the water 23. The casting core 15 dissolves in this case, that the binder itself is dissolved and thus the strength is lost.

As an alternative to salt as a binder, as has already been explained, a binder may also be a synthetic resin or plastic. Then, as a solvent 23, for example, a named alcohol or ethanol is used, which can dissolve the synthetic resin or the plastic.

According to a second embodiment, as has also been explained at the outset, the binder for the material of the casting core 15 may be designed such that it swells in cooperation with water as solvent 23 or another liquid. Even so, it may destroy the strength of the casting core 15 and this then, assisted by the rinsing action of the solvent 23 according to FIG. 4, be rinsed out in the form of pieces of material 24. However, it may be advantageous not to direct the spray nozzle 221 to the rather small opening 18c, but either only to the large conically opened opening 18a or even to the equally large opening 18b. Depending on the Aufquillverhalten the binder together with the material of the casting core, such as vermiculite, it could otherwise come at the openings 18c to problems due to expansion. One possible binder for this example is a clay mineral in the form of bentonite.

As yet another alternative embodiment, the binder may be designed so that it loses its binding effect by thermal action. Then, this could either have already taken place solely by the casting process of the sanitary fitting 17, so that then by means of the pointed nozzles 22a and 22b and a solvent 23, in a In the simplest case water, the casting core 15 into small pieces of material 24 disassemble to rinse them out. Alternatively, either very hot solvent 23 could be used and sprayed on the interior of the casting core 15, or the sanitary fitting 17 together with the casting core 15 could be heated in an oven to dissolve the binder. Then, either by mechanical removal, for example, bubbles with compressed air, or by the pointed nozzles 22 with solvent 23, the material can be removed or rinsed out.

Claims

claims

Casting core for a casting process in which a cast body in a mold maintains its outer shape and inner cavities, channels or the like. of the cast body are determined by the casting core, wherein the casting core consists of clay mineral or silicate material or sheet silicate, in particular vermiculite, and is brought into a solid form or form by a binder, characterized in that the binder is protected by a solvent, in particular by water, is releasable for dissolving or removing the casting core after the casting process.

Cast core according to claim 1, characterized in that the binder is water-soluble and preferably a salt.

Cast core according to claim 1, characterized in that the binder is a synthetic resin or plastic and is soluble by alcohol or ethanol.

Casting core according to the preamble of claim 1, characterized in that the binder is selected so that it swells in co-operation with water or other liquid or swells to destroy the casting core and leaching or removal after the casting process from the casting.

Cast core according to claim 4, characterized in that the binder is a clay mineral, preferably bentonite.

Casting core according to the preamble of claim 1, characterized in that a binder is thermally dissolvable or loses its binding effect by thermal action to remove the casting core after the casting process.

7. Cast core according to claim 6, characterized in that the binder is a synthetic resin.

8. Cast core according to claim 6 or 7, characterized in that the binder dissolves at temperatures between 100 ° C and 200 ° C or loses its binding effect with the material of the casting core or the clay mineral or layered silicate.

9. A method for removing or removing a casting core from a finished casting, characterized in that either water or a solvent is brought to the casting core for its dissolution and dissolution in its individual components or a thermal action takes place for the thermal dissolution of the binder.

10. The method according to claim 9, characterized in that the water or the solvent is brought by an access port produced during the casting process to the casting core by means of high pressure nozzles or the like., Which direct a fine beam through the access opening to the casting core.

1 1. The method according to claim 9, characterized in that in the interval operation, on the one hand, the water or the solvent is brought to the casting core and on the other hand, with stopped supply of water or solvent, the dissolved material of the casting core falls out or is sucked out.