WO2007028362A1 - Method for casting moulded pieces - Google Patents

Abstract

The invention relates to a method for casting moulded pieces, comprising the following method steps: production of the casting mould (2), comprising a core of moulding material, forming a complete core packet (1), positioning the core packet (1) in a support mould (3) with a separation to the core packet (1), back-filling the space between the core packet (1) and the support mould (3) with a free-flowing bulk material (5), casting the metal melt into the casting mould (2), opening or removing the support mould (3) after the solidification of the melt, removing at least the majority of the bulk material (5) and the multiple thermal insulation of the remaining core packet (1) with the already set moulded piece (7) therein.

Description

 METHOD FOR FORMING SHAPES

The invention relates to a method for casting moldings.

The invention relates generally to the molding of molded parts, i. on the foundry technology. For casting moldings of any kind foundry cores and / or forms are usually made of separate parts, brought together and connected together to form a mold or a Kempaket or mold package. These form / core packages are then filled with molten metal to produce, for example, a metallic workpiece, wherein in series production the molten metal to be filled FormVKakakete successively lined up the production line.

Core and mask shooting machines for manufacturing the cores to be joined together have been known from practice for decades. For example only, reference is made to DE 31 48 461 C1, which discloses a core and mask shooting machine.

So far, moldings are cast in a mold, which in turn consists of cores or a core package. After firing and completing the mold, it is transformed into another core sand, i. in a kind of support form, integrated, namely, to ensure the required mechanical stability can. Especially with gray cast iron or cast steel, the static pressure during casting is so high that a core package alone is not sufficient and the provision of the support form is absolutely necessary. The support form is so far greensand forms in which the Kempaket is inserted. Metallic molds have also been used so far, and such metallic molds are extremely expensive and, moreover, wear out quickly.

Regardless of the actual casting, the mold material / core package forming mold material is then to be removed from the molded molding. Due to a binder, the molding material must be disposed of or recycled in a special way. The same applies to previously used support forms or green sand molds, which are also provided with binder. The recycling of the mold sands / Grünsands associated effort is considerable, especially in expensive treatment plants additives such as bentonite, etc. must be removed.

In addition, there is another problem in the production of the support forms or greensand forms, which are produced on very expensive molding equipment. In addition, the sand processing takes place in very expensive and therefore expensive sand processing plants. The provision of green sand molds for supporting the core package and the sand preparation is therefore disproportionately expensive.

The present invention is therefore based on the object to design the above-discussed generic method in such a way and further that reduces especially in gray cast iron or cast steel the effort to be operated at a reproducible result, especially in relation to the recycling of the materials used. In addition, the residual heat should be used in the solidified molding.

The above object is achieved by a method with the following method steps:

Providing the mold, consisting of cores of molding material completed to form a core package,

Positioning the Kempakets in a spaced apart from the core package support form,

Backfilling of the space between the core package and the support mold with a pourable bulk material,

Casting the metallic melt into the mold,

Opening or removal of the support mold after the solidification of the melt,

- At least largely removing the bulk material and

- Repeated thermal insulation of the remaining core package with the therein already solidified molding.

According to the invention, it has been recognized that, while the support form previously made of greensand is needed, it is necessary, on the one hand, with the manufacture and other On the other hand, the costs associated with recycling, ie the total cost of production, can be considerably reduced. For this purpose, a support form is still provided, which, however, to the core package - aware - spaced. For example, the support form can be generated from plates of different temperature-resistant materials, namely according to the modular principle. For cohesion, the items could be reciprocally adjustable, latched or otherwise fastened together. It is essential that a space remains between the actual casting mold, ie the core package, and the support form. This space between the core package and the support form is backfilled with a pourable bulk material. This bulk material defines an isostatic pressure around the core package on all sides so that, due to this pressure, the core package can withstand the outward pressure created during molten metal casting. With the help of the bulk material is guaranteed in any case that the core package can withstand the pressure generated during casting and it is on top of that guaranteed that any fugitives, cracks or the like through no melt penetrates to the outside. Using simple means, based on isostatic pressure, it is ensured that the metallic melt can be poured into the casting mold without jeopardizing the dimensional stability of the core package.

Furthermore, it has been recognized in accordance with the invention that the energy stored in the melt or in the molding and in the core package is not readily sufficient to carry out a further-reaching process, for example to burn the binder contained in the core package. This is due to the fact that the mass to be heated is too large, not least because of the bulk material inside the support form. Thus, in further inventive manner, the support mold is opened or removed, after the solidification of the melt, so that the actual support function of the support form is no longer necessary. The bulk material is at least largely removed. Thereafter, the remaining core package is again isolated with the already solidified molding therein, so that the residual heat contained therein can be used without the bulk of the bulk material.

Advantageously, the core package is placed on a thermally insulating base as part of the support form for positioning the core package in the support form. These Base remains under the core package. By a thermally insulating wall and a thermally insulating cover part, the base is completed to the support form.

An opening of the support mold or a complete removal of the support form takes place by removing the cover part and the walls. After that, the bulk material can be easily removed. An aspiration of the bulk material is conceivable.

For repeated thermal insulation, a thermally insulating hood is used in an advantageous manner, which may be made in one piece or in several parts. In the case of a one-piece embodiment, this could be put over the core package, for example via a pulley block, a manipulator or with other aids. Specifically, the hood is placed around the core package with the molded part therein on the base and complements the hood with the base for a thermal insulation on all sides. Once the binders of the core package are burned or at least dissolved, the hood is removed again, so that remains on the basis of at least largely freed from the molding sand molding.

In a particularly advantageous manner, the bulk material is essentially the same material as the core-molding material, preferably without any additives. If the cores consist of molding material (for example made of quartz sand) with binder, the same molding material, preferably without binder, can be used as the bulk material. Likewise, the bulk material could have substantially the same grain size as the molding material, so that the molding material together with the bulk material - after recycling the molding material - can be used again with identical or different grain size.

In concrete terms, pure sand, preferably so-called dry sand without additives, could be used as the bulk material, which causes no problems in further processing with the molding sand. This is especially true for identical or nearly identical grain size. As a bulk material, quartz sand is particularly suitable.

The backfilling in the space between the core package and the support form can be achieved by means of funnels or suitable technical aids by merely pouring it in of the bulk material to obtain a bulk density realize. The weight of the bulk material results in an isostatic pressure acting on the core packet which counteracts the outward pressure encountered during casting with molten metal to maintain the shape. The individual cores of the core package will thus hold together securely.

If the bulk density of the bulk material reached by pouring in is insufficient, the backfilling can be done by blowing in the bulk material. As a result, a density of the bulk material can be achieved, which is above the bulk density. Furthermore, it is conceivable, after pouring in of the bulk material to recompress this by means of compressed air.

A further compression of the bulk material, preferably up to the receipt of the tap density, can be achieved if the backfilling is supported by bulk material by vibration. The vibration can be induced, for example, by means of ultrasound or else mechanically, in which case the entire support form or a functional element located therein or in the support form can be used as a resonator. In any case, it is essential that preferably vibration induced by ultrasound promotes the compaction of the bulk material.

It is also conceivable that is mechanically densified for further compression of the Schützguts by namely the bulk material is pressed with mechanical equipment into the mold or even pressed. A punctiform or zonal recompression by means of a punch or the like is conceivable.

In a further advantageous manner, the support mold is used for thermal insulation of the casting mold before and / or after casting and for deliberate use of the process heat within the casting mold or insulation for the controlled treatment of the cast molding and / or of the molding material forming the core pack.

Thus, the process heat can be used to burn the organic or inorganic binder in the molding material, so that special recycling measures are no longer required thereafter. A special disposal of the Form material as special waste is then also no longer necessary, you should not want to continue using the molding material.

Likewise, the process heat can be used for the temperature treatment of the cast molded part.

In a particularly advantageous manner, the molded part could be cooled regulated, with a thermal insulation by the support form along with backfilling plays a very special role.

Likewise, it is conceivable that during the in-situ heat treatment, gases are conducted out of the interior of the mold and / or the insulation or out of the support part together with backfilling.

Of particular importance is another feature, according to which it is advantageous if individual cores are used to form the core package, which are formed as hollow bodies. This has the enormous advantage that the mass of the core sand material is kept as low as possible, so that the energy present in the form of heat within the overall system as far as possible. for the treatment of the cast molding and / or the core package, so for example. For burning the binder, can be used. In addition, significantly less gases from the outset, which can still be collected and sucked.

It is also advantageous if the flue gases produced during combustion of the binder are retained within the device for heat insulation. They can be vacuumed at the end of the isolation process. The concentrated presence of noxious gases considerably facilitates their disposal or destruction, which considerably simplifies the process.

There are now various possibilities for designing and developing the teaching of the present invention in an advantageous manner. On the one hand to the claims subordinate to claim 1 and on the other hand to the following explanation of an embodiment of the invention with reference to the Drawing to refer. In conjunction with the explanation of the preferred embodiment of the invention with reference to the drawing, generally preferred embodiments and developments of the teaching are explained. In the drawing shows

Fig. 1 is a schematic view of the arrangement of a core package with spaced support form and by means of bulk material hinterfülltem space between the core package and the support mold and

Fig. 2 is a schematic view of the arrangement of a core package of FIG. 1, but without bulk material and with it over hood for thermal insulation.

1 shows, to clarify the method according to the invention, in which arrangement the casting mold 2 to be understood as the core package 1 is provided for pouring the melt. The core package 1 comprises a plurality of individual cores, which are completed together to form the core package 1. The core package 1 forms the casting mold 2.

Fig. 1 can further recognize that the core package 1 is positioned in a support mold 3, which in turn is composed of individual parts 4 like a frame or made in one piece. Between the support form 3 and the core package 1, a space is formed, which is backfilled by a flowable bulk material 5 and thus builds between the support form 3 and the core package 1 isostatic pressure defined by the weight. In this state, the metallic melt is poured into the mold or in the core package 1 and ensures that the core package 1 dimensionally stable withstand the resulting internal pressure during casting.

In the embodiment chosen here, the parts 4 of the support form 3 can be used several times. The support of the mold 2 or the core package 1 via the bulk material 5, which is in the concrete to so-called. Dry sand without any additives. As dry sand, quartz sand is an option. preferably with the same grain size as the molding material of the individual cores or of the core package 1.

Furthermore, it should be noted again at this point that the bulk material 5 can be compacted, for example by means of vibration beyond the bulk density, in order to increase the isostatic pressure in relation to the core packet 1. With regard to further measures for the compaction of the bulk material 5, reference is made to avoid repetition in the general part of the description.

Furthermore, the support mold 3 together with bulk material 5 serves for the thermal insulation of the casting mold 2 and can therefore be formed before or after casting for the deliberate use of the process heat within the casting mold or insulation and thus for the controlled treatment of the cast molding and / or of the molding pack Use molding material. However, it has been recognized that the process heat is absorbed too much by the bulk material 5 and also by the support mold 3.

As shown in Fig. 2, the support mold 3 and the bulk material 5 has been removed. Instead, a thermally insulating cover 6 is also placed on the thermally insulating Basjs _8. so that the residual heat held under the hood 6 can be used for example for burning the binder present in the molding material. At the end of the process, the hood 6 is removed and the molding 7 is at least largely freed from the molding material of the former core package 1, namely because the bond between the components of the molding material is canceled.

The method according to the invention has the enormous advantage that on the one hand the process heat is used and on the other hand that no molding installation is required for molding the molding. The process heat utilization is favored by the fact that the sand-to-iron ratio is favored by removing the bulk material.

With regard to further features, which can not be inferred from the figures, reference is made to avoid repetition to the general part of the description. Finally, it should be noted that the embodiment discussed above is merely illustrative of the claimed teaching, but does not limit it to the embodiment.

Claims

Patent claims 1. Method for casting molded parts (7) with the following method steps: Providing the casting mold (2), consisting of cores of molding material, which are completed to form a core packet (1), Positioning the core package (1) in a support form (3) spaced apart from the core package (1), - backfilling of the space between the core package (1) and the support mold (3) with a free-flowing bulk material (5), Casting the metallic melt into the casting mold (2), Opening or removal of the support mold (3) after solidification of the melt, - At least largely removing the bulk material (5) and - But repeated thermal insulation of the remaining Kempakets (1) with the therein already solidified molding (7). 2. The method according to claim 1, characterized in that for positioning of the core package (1) in the support mold (3), the core package (1) on a thermally insulating base (8) is positioned as part of the support mold (3). 3. The method according to claim 2, characterized in that the base (8) by thermally insulating walls and a thermally insulating cover part to the support form (3) is completed. 4. The method according to claim 3, characterized in that the support form (3) is opened by removing the cover part and the walls. 5. The method according to any one of claims 1 to 4, characterized in that for repeated thermal insulation, a thermally insulating hood (6) is used. 6. The method according to claim 5, characterized in that the hood (6) is made in one piece. 7. The method according to claim 5 or 6, characterized in that the hood (6) to the core packet (1) with the molding therein (7) is placed on the base (8). 8. The method according to any one of claims 1 to 7, characterized in that as bulk material (5) is substantially the same mold material as used for core production, preferably without additives. 9. The method according to any one of claims 1 to 8, characterized in that the bulk material (5) has substantially the same grain size as the molding material or a different grain to it. 10. The method according to any one of claims 1 to 9, characterized in that as bulk material (5) pure sand, preferably so-called. Dry sand without additives, is used. 11. The method according to claim 10, characterized in that as bulk material (5) quartz sand or other known in the foundry or usual sands are used. 12. The method according to any one of claims 1 to 11, characterized in that the backfilling is done by pouring the bulk material (5) to obtain a bulk density. 13. The method according to any one of claims 1 to 12, characterized in that the backfilling is done by blowing in the bulk material (5). 14. The method according to claim 12 or 13, characterized in that is compressed to further compression by means of compressed air. 15. The method according to any one of claims 12 to 14, characterized in that for further compression, preferably up to the receipt of the tap density, the backfilling is supported by vibration. 16. The method according to claim 15, characterized in that the vibration is induced by means of ultrasound. 17. The method according to any one of claims 12 to 16, characterized in that for further compression, the bulk material (5) is mechanically recompressed. 18. The method according to any one of claims 1 to 17, characterized in that first the support form (3) for thermal insulation of the mold (2) before and / or after casting and then the hood for the deliberate use of process heat within the mold (2 ) or insulation for the controlled treatment of the cast molded part (4) and / or of the core material (1) forming molding material is used. 19. The method according to claim 18, characterized in that the process heat is used for burning the organic or inorganic binder in the molding material. 20. The method according to claim 18 or 19, characterized in that the process heat for the temperature treatment of the cast molded part (4) is used. 21. The method according to any one of claims 18 to 20, characterized in that the molded part (4) or the entire system is cooled controlled. 22. The method according to any one of claims 18 to 21, characterized in that during the in situ heat treatment of the cast molded part (4) and / or the core core (1) gas is discharged from the interior of the mold and / or from the insulation , 23. The method according to any one of claims 18 to 22, characterized in that during the in-situ heat treatment of the cast molded part (4) and / or of the core packet (1), the gas formed during combustion of the binder is retained within the thermal insulation and is sucked off at the end of the isolation process. 24. The method according to any one of claims 18 to 23, characterized in that during the thermal insulation heat can be supplied. 25. The method according to any one of claims 18 to 24, characterized in that for forming the core package (1) also partially hollow cores are used with reduced mass.