Riser tube, casting mold and use of a riser tube

Abstract

The invention relates to a riser tube for a casting process, in particular for a low pressure die casting process, comprising: at least one substantially cylindrical metal body part (4); at least one substantially cylindrical ceramic body part (6); and at least one metal flange part (8); wherein the at least one substantially cylindrical metal body part (4) and the at least one substantially cylindrical ceramic body part (6) are connected; wherein the at least one cylindrical ceramic body part (6) and the at least one metal flange part (8) are connected. The invention also relates to a casting mold (36) and to the use of a riser tube (2).

Description

[0001] The invention relates to a riser tube for a casting process, in particular for a low pressure die casting process. The invention also relates to a casting mold, in particular to a low pressure (die) casting mold, comprising: at least one pressure chamber for receiving molten metal, a pressure connection for supplying the at least one pressure chamber with a pressurized gas, at least one riser channel in fluid communication with the at least one pressure chamber, wherein the riser channel is configured to guide the molten metal from the at least one pressure chamber, in particular against gravity, into the direction of at least one casting outlet as a result of the pressure in the at least one pressure chamber. The invention also relates to the use of aforementioned riser tube in a casting process, in particular in a low pressure die casting process.

[0002] Casting molds, in particular low pressure die casting molds, are used for casting parts using a low pressure die casting process. In this process, the molten metal is in particular forced against gravity from below from a pressure chamber pressurized with a corresponding overpressure via a riser tube in fluid communication with the pressure chamber into a mold cavity of a casting mold, in particular via a casting outlet of the riser tube. The overpressure is set by means of a pressurized gas, which can be fed into the pressure chamber via a pressure connection.

[0003] The molten metal is in particular a light metal such as aluminum or magnesium as well as corresponding alloys. However, it can also be copper, iron or steel. In addition, the casting mold can be formed as a permanent mold or as a lost mold from molding sand as well as an investment casting mold or shell mold from another molding material. The term gas refers to any gas or combination of gases including atmospheric air, argon, nitrogen or other gasses which may be applied onto molten metals.

[0004] After filling the mold cavity of the casting mold, the pressure in the pressure chamber can be maintained until the casting has solidified to ensure that the casting mold is refilled to prevent shrinkage. The pressure is then reduced until the next casting. The pressure chamber is also opened at regular intervals to refill the molten metal. Low-pressure casting allows for economical casting production, as only a small proportion of the casting is recycled, i.e. only a small amount of solidified recycled material that is not part of the casting has to be melted down again after casting and fed back into the process. Low-pressure casting processes are therefore used, for example, for casting sophisticated cast parts in mass production, such as cylinder crankcases, cylinder heads and wheel rims.

[0005] Several riser tubes can also be used in parallel to fill several separate casting molds in a single operation. The riser tubes are typically installed pressure-tight in a lid or a housing of the casting mold. The lower ends of the riser tubes may protrude into the molten metal in the pressure chamber so that they are for example pulled out of the molten metal when the lid is lifted to refill it and then immersed in it again. Hence, the riser tubes are exposed to increased mechanical and thermal stress. The latter results from the rapid temperature changes during immersion and removal of the molten metal. In particular, the riser tubes form at least a part of the riser channel which connects the pressure chamber with the mold cavity of the casting mold.

[0006] It is known from the prior art to either use metal riser tubes or ceramic riser tubes. Metal riser tubes comprise a high thermal conductivity and therefore the heat of the molten metal may be lost through the thermally conductive metallic material of the riser tube. Ceramic riser tubes comprise a low thermal conductivity, but are mechanically weak and easily damaged by mechanical stress, mechanical shock, thermal shock, and oxidized metal buildup on their surfaces.

[0007] Therefore, the present invention is based on the task of providing a riser tube, a casting mold and a use of a riser tube in such a way that a casting process, in particular a low pressure die casting process can be operated more economically and reliably.

[0008] According to a first aspect said task is solved by a riser tube for a casting process, in particular by a hybrid riser tube (tip) for a low pressure die casting process, comprising: at least one substantially cylindrical metal body part; at least one substantially cylindrical ceramic body part; and at least one metal flange part, wherein the at least one substantially cylindrical metal body part and the at least one substantially cylindrical ceramic body part are connected; and wherein the at least one cylindrical ceramic body part and the at least one metal flange part are connected.

[0009] Hereby, a riser tube may be provided which enables an economically beneficial and reliable casting process, in particular low pressure die casting process. For example, the at least one substantially cylindrical metal body may be disposed in a portion of the riser tube where mechanically advantageous properties are sought. Additionally, the at least one substantially cylindrical ceramic body part may be arranged in a part of the riser tube, in which a high thermal insulation is desired, which may reduce casting defects. Also, the at least one metal flange part may be arranged in a part of the riser tube, in which mechanical properties of metal are desired, in particular to fix the at least one riser tube to the casting mold. Further, a riser tube may be provided which is easily manufacturable.

[0010] Preferably, the metal body part is arranged in an area of the riser tube which higher mechanical stress is to be expected and / or the constructive properties are limiting, for example with regard to the thickness of the riser tube. Preferably, the at least one substantially cylindrical metal body part is arranged at a top part of the riser tube.

[0011] It is further preferred that the at least one substantially ceramic body part is arranged in an area where it is desired to thermally isolate the molten alloy. Preferably, the at least one substantially ceramic body part is arranged in a middle part of the riser tube, particularly preferred at least partly between the at least one substantially cylindrical metal body part and the at least one metal flange part.

[0012] Preferably, the at least one substantially cylindrical metal body part and the at least one substantially cylindrical ceramic body part are directly connected to each other. This enables a preferable connection of said two parts.

[0013] Preferably, the at least one cylindrical ceramic body part and the at least one metal flange part are directly connected to each other. This enables a preferable connection of said two parts.

[0014] Preferably, the inner flow channel of the riser tube is only formed by the at least one substantially cylindrical metal body part and the at least one substantially cylindrical ceramic body part. In particular, during usage of the riser tube only the inner surface / inner sidewall of the at least one substantially cylindrical metal body part and the inner surface / inner sidewall of the at least one substantially cylindrical ceramic body part come into contact with the molten metal. Hereby, both the beneficial properties of the ceramic material and of the metal material may be used similarly.

[0015] It is further preferred that the riser tube may be a riser tube insert which may be arranged, at least partly, in an already present riser channel. Hereby, an already present riser channel may be improved.

[0016] The riser tube preferably may be formed as a riser tube tip, which may be in fluid connection with another riser tube / riser channel or the like.

[0017] According to a preferred embodiment, the at least one substantially cylindrical metal body part and / or the at least one metal flange part comprise a metal alloy, in particular a steel alloy. Hereby, the at least one substantially cylindrical metal body part and / or the at least one metal flange part can be tailored to the specific needs of the riser tube, for example to the mechanical requirement of the riser tube in the specific areas. Further, the durability of the riser tube may be improved. It is further preferred that both the at least one substantially cylindrical metal body part and the at least one metal flange part comprise the same metal alloy. This may reduce the production costs of the at least one substantially cylindrical metal body part and the at least one flange part.

[0018] According to another preferred embodiment, the at least one substantially cylindrical ceramic body part comprises ceramic material, wherein the ceramic material preferably is selected from the group consisting of fired clay, mullite, alumina, zirconia-toughened alumina, zirconia-toughened mullite, silicon carbide, silica-bonded mullite, and / or silica-bonded silicon carbide. Hereby, a thermally insulating material may be provided for in the specific areas of the riser tube, in which a high thermal insulation is beneficial and which additionally comprises sufficient mechanical properties.

[0019] According to another embodiment, the at least one substantially cylindrical metal body part and the at least one substantially cylindrical ceramic body part are connected by form fit. This allows for manufacturing a riser tube in a cost-effective manner. Preferably, the at least one substantially cylindrical metal body part and the at least one substantially cylindrical ceramic body part are connected by a plug connection. This allows for a beneficial assembly of the at least one substantially cylindrical metal body part and the at least one substantially cylindrical ceramic body part. In particular, the at least one cylindrical metal body part and the at least one substantially cylindrical ceramic body part are connected to each other by a press fitting.

[0020] According to another embodiment, the at least one substantially cylindrical ceramic body part and the at least one metal flange are connected by form fit. This allows for manufacturing a riser tube in a cost-effective manner. Preferably, the at least one substantially cylindrical ceramic body part and the at least one metal flange part are connected by a plug connection. This allows for a beneficial assembly of the at least one substantially cylindrical ceramic body part and the at least one metal flange part. In particular, the at least one cylindrical ceramic body part and the at least one metal flange part are connected to each other by a press fitting.

[0021] According to another embodiment, an end region of the at least one substantially cylindrical metal body part comprises a thickness, in particular a sidewall thickness, in a range of 1 to 5 mm, in particular in a range of 2 to 3 mm. By providing a cylindrical metal body part, a thin end region of the riser tube with sufficient strength may be provided in an advantageous manner. The thickness in the aforementioned range is also beneficial with regard to the costs of the riser tube due to less material usage for the manufacturing of the at least one substantially cylindrical metal body part.

[0022] According to another embodiment, the at least one substantially cylindrical metal body part and / or the at least one substantially cylindrical ceramic body part is tube shaped. Preferably, the at least one substantially cylindrical metal body part and / or the at least one substantially cylindrical ceramic body part comprise a thin wall structure, wherein in the thickness of the wall is between 1 and 10 mm, preferably between 2 and 6 mm. Hereby, the space may be used in a beneficial way and sufficient flow of molten metal through the riser tube may be ensured. Additionally, the production costs may be kept low.

[0023] According to another embodiment, the at least one substantially cylindrical metal body part, in particular the inner side surface / inner sidewall of the at least one substantially cylindrical metal body part, and / or the at least one substantially cylindrical ceramic body part, in particular the inner side surface / inner sidewall of the at least one substantially cylindrical ceramic body part, is tapered. A tapered inner side surface / inner sidewall of the at least one substantially cylindrical metal body part and / or the at least one substantially cylindrical ceramic body part may enable beneficial flow characteristics of the molten metal in the riser tube. Preferably, the inner side surface / inner sidewall of the at least one substantially cylindrical metal body part and the inner side surface / inner sidewall of the at least one substantially cylindrical ceramic body part are tapered in opposite directions.

[0024] According to another embodiment, the metal flange part comprises a circumferential rim, and the circumferential rim preferably comprises a plurality of through holes for connecting the riser tube to a casting mold or a pressure chamber. Hereby, a beneficial connection of the riser tube to a casting mold or a pressure chamber is ensured, in particular by the beneficial mechanical properties of the metal flange part.

[0025] According to another embodiment, the at least one substantially cylindrical metal body part, in particular the outer side surface / outer sidewall of the at least one substantially cylindrical metal body part and / or the at least one substantially cylindrical ceramic body part, in particular the outer side surface / outer sidewall of the at least one substantially cylindrical ceramic body part, is configured in steps. This allows for a beneficial connection of the parts with each other, in particular by a plug connection and / or a press fit. Preferably, the at least one substantially cylindrical metal body part and the at least one substantially cylindrical ceramic body part comprise at least one end face which are configured in steps, wherein the stepped end faces of the at least one substantially cylindrical metal body part and the at least one substantially cylindrical ceramic body part correspond to each other, so that the end faces of the at least one substantially cylindrical metal body part and the at least one substantially cylindrical ceramic body part are connectable to each other. Preferably, the at least one substantially cylindrical metal body part is at least partly insertable into the at least one substantially cylindrical ceramic body part.

[0026] According to another embodiment, the at least one substantially cylindrical ceramic body part comprises at least one circumferential flange, wherein preferably the at least one circumferential flange at least partly contacts the at least one metal flange part. This allows for a beneficial connection of the at least one substantially cylindrical ceramic body part to the at least one metal flange part. Preferably, the at least one substantially cylindrical ceramic body part protrudes beyond the at least one circumferential flange, so that the outer sidewall / outer side surface of the protruding portion of the at least one substantially cylindrical ceramic body part additionally contact the at least one metal flange part, in particular an inner sidewall / inner side surface of the at least one metal flange part.

[0027] According to another aspect, aforementioned task is solved by a casting mold, in particular a low pressure die casting mold, comprising: at least one pressure chamber for receiving molten metal, a pressure connection for supplying the at least one pressure chamber with a pressurized gas, at least one riser channel in fluid communication with the at least one pressure chamber, wherein the riser channel is configured to guide the molten metal from the at least one pressure chamber against gravity into the direction of at least one casting outlet and a mold cavity as a result of the pressure in the at least one pressure chamber, wherein the riser channel comprises at least one aforementioned riser tube. Hereby, a casting mold is provided which enables a reliable and cost-effective casting of cast parts. Additionally, the advantages and features described in context with the riser tube apply equally to the casting mold.

[0028] According to another aspect, aforementioned task is solved by the use of an aforementioned riser tube.

[0029] The exemplary embodiments described in this description are also intended to be disclosed with respect to every aspect and in all combinations with one another. In particular, all features mentioned with regard to the riser tube are intended to also disclose respective features for the casting mold and the use of the riser tube.

[0030] Additionally, means for performing a certain method step are also intended to disclose the respective method step.

[0031] Further advantageous exemplary embodiments of the invention are indicated by the following detailed description of a number of practical examples of the present invention, in particular in connection with the figures.

[0032] The figures attached to the application, however, are only intended to be used for the purpose of clarification, and not to determine the scope of protection of the invention.

[0033] The attached drawings are intended only as examples reflecting the general concept of the present invention. In particular, features shown in the figures should not in any way be considered an essential component part of the invention.

[0034] In the following, the invention will be described in more detail with reference to the figures: Fig. 1shows a schematic view of an embodiment of a riser tube in a perspective view; Fig. 2shows a side view of the embodiment of a riser tube depicted in Fig. 1; Fig. 3shows a sectional view along the sectional line III depicted in Fig. 2; Fig. 4shows a partial view of an embodiment of a casting mold in a perspective view; and Fig. 5shows a sectional view along the sectional line V depicted in Fig. 4.

[0035] In the following description of the various embodiments according to the invention, components and elements with the same function and the same mode of operation are provided with the same reference symbols, even if the components and elements may differ in their dimensions or shape in the various embodiments.

[0036] Fig. 1 shows a perspective view of a riser tube 2 for a low pressure die casting process. The riser tube 2 may serve as a sole riser tube or also as a riser insert or as a riser tube tip. The riser tube 2 comprises three parts, namely a substantially cylindrical metal body part 4, a substantially cylindrical ceramic body part 6 and a metal flange part 8.

[0037] The metal body part 4 is arranged at a top of the riser tube 2, wherein the ceramic body part 6 is arranged in a middle of the riser tube 2. Both metal body part 4 and metal flange part 8 are made of a metal alloy, wherein the ceramic body part is made from a ceramic material. It is possible that both metal body part 4 and metal flange part 8 are made from the same material.

[0038] All parts 4, 6 and 8 are connected to each other by form fit, namely by a plug connection. This is in particular depicted in Fig. 3. The outer circumferential sidewall / outer side surface 10 of the metal body part 4 comprises a first step 12. Additionally, the outer sidewall 10 of the metal body part 4 comprises a second step 14 which corresponds to a step 16 of the inner sidewall / inner side surface 18 of the ceramic body part 6. Hereby, metal body part 4 and ceramic body part 6 are connected to each other by a plug connection, in particular by a press fitting.

[0039] The inner sidewall / inner side surface 20 of the metal body part 4 is tapered from a top end face 22 towards the end face directed towards the ceramic body part 6. The inner sidewall 18 of the ceramic body part 6 is tapered from the top end face directed towards the metal body part 4 to the lower end face 24 of the ceramic body part 6. Thus, inner sidewall 18 and inner sidewall 20 are tapered in opposite directions.

[0040] The sidewall of the metal body part 4 comprises a thickness in a range of 1 to 5 mm. In particular, the side wall of the metal body part 4 in an end region 34 comprises a thin wall structure in a range 1 to 3 mm.

[0041] The outer sidewall / outer side surface 26 of the ceramic body part 6 comprises a circumferential flange 28. Said flange 28 enables a plug connection to the metal flange part 8, in particular by a press fitting. The metal flange part 8 comprises a circumferential rim 30 which comprises several through holes 32 for connecting the riser tube 2 to a casting mold 36.

[0042] A partial view of a casting mold 36 is depicted in Figs. 4 and 5. The casting mold 36 comprises a mold cavity 38, wherein the riser tube 2 is connected to the casting mold 36 by several screws 40 arranged in the metal flange part 8 of the riser tube 2. Hereby, the molten metal may be supplied to the mold cavity 38 of the casting mold 36 via the riser tube 2 in a beneficial way. The riser tube 2 forms the riser channel 42.

[0043] The exemplary embodiments / aspects of the present invention described in this specification are intended to be understood as disclosed both individually and in all combinations with each other. In particular, even the description of a feature encompassed by an embodiment - unless explicitly stated to the contrary - is not intended to be understood herein as implying that the feature is indispensable or essential to the function of the embodiment. Potential process steps derivable from this specification may be implemented in various ways.

[0044] Terms used in the patent claims such as "comprising", "having", "including", "containing" and the like do not exclude further elements or steps. The wording "at least in part" or "substantially" covers both the case "in part" and the case "in full". The phrase "and / or" is intended to be understood to disclose both the alternative and the combination, thus "A and / or B" means "(A) or (B) or (A and B)". A plurality of entities, persons or the like means multiple entities, persons or the like in the context of this specification. The use of the indefinite article does not preclude a plural. A single device may perform the functions of multiple units or devices recited in the claims. Reference signs indicated in the patent claims are not to be regarded as limitations of the means and steps employed.

[0045] This solution has been developed under the Nemak Izmir Ar-Ge merkezi initiative.Reference sign list

[0046] 2riser tube 4metal body part 6ceramic body part 8metal flange part 10outer sidewall of the metal body part 12first step of the metal body part 14second step of the metal body part 16step of the inner sidewall of the ceramic body part 18inner sidewall of the ceramic body part 20inner sidewall of the metal body part 22top end face of the metal body part 24lower end face of the ceramic body part 26outer sidewall of the ceramic body part 28circumferential flange 30circumferential rim 32through holes 34end region 36casting mold 38mold cavity 40screw 42riser channel

Claims

1. Riser tube for a casting process, in particular for a low pressure die casting process, comprising: - at least one substantially cylindrical metal body part (4); - at least one substantially cylindrical ceramic body part (6); and - at least one metal flange part (8); - wherein the at least one substantially cylindrical metal body part (4) and the at least one substantially cylindrical ceramic body part (6) are connected; and - wherein the at least one cylindrical ceramic body part (6) and the at least one metal flange part (8) are connected.

2. Riser tube according to claim 1, - wherein the at least one substantially cylindrical metal body part (4) and / or the at least one metal flange part (8) comprise a metal alloy, in particular a steel alloy; and - wherein the at least one substantially cylindrical ceramic body part (6) comprises ceramic material, wherein the ceramic material preferably is selected from the group consisting of fired clay, mullite, alumina, zirconia-toughened alumina, zirconia-toughened mullite, silicon carbide, silica-bonded mullite, and / or silica-bonded silicon carbide.

3. Riser tube according to claim 1 or 2, - wherein the at least one substantially cylindrical metal body part (4) and the at least one substantially cylindrical ceramic body part (6) are connected by form fit; and / or - wherein the at least one substantially cylindrical metal body part (4) and the at least one substantially cylindrical ceramic body part (6) are connected by a plug connection.

4. Riser tube according to one of the claims 1 to 3, - wherein the at the at least one substantially cylindrical ceramic body part (6) and the at least one metal flange part (8) are connected by form fit; and / or - wherein the at least one substantially cylindrical ceramic body part (6) and the at least one metal flange part (8) are connected by a plug connection.

5. Riser tube according to one of the claims 1 to 4, - wherein an end region (34) of the at least one substantially cylindrical metal body part (4) comprises a thickness in a range of 1 to 5 mm, in particular in a range of 2 to 3 mm.

6. Riser tube according to one of the claims 1 to 5, - wherein the at least one substantially cylindrical metal body part (4) and / or the at least one substantially cylindrical ceramic body part (6) is tube shaped; and / or - wherein the at least one substantially cylindrical metal body part (4), in particular the inner side surface (20) of the at least one substantially cylindrical metal body part (4), and / or the at least one substantially cylindrical ceramic body part (6), in particular the inner side surface (18) of the at least one substantially cylindrical ceramic body part (6), is tapered.

7. Riser tube according to one of the claims 1 to 6, - wherein the metal flange part (8) comprises a circumferential rim (30), and - wherein the circumferential rim (30) preferably comprises a plurality of through holes (32) for connecting the riser tube (2) to a casting mold (36).

8. Riser tube according to one of the claims 1 to 7, - wherein the at least one substantially cylindrical metal body part (4), in particular the outer side surface (10) of the at least one substantially cylindrical metal body part (4) and / or the at least one substantially cylindrical ceramic body part (6), in particular the outer side surface (26) of the at least one substantially cylindrical ceramic body part (6), is configured in steps.

9. Riser tube according to one of the claims 1 to 8, - wherein the at least one substantially cylindrical ceramic body part (6) comprises at least one circumferential flange (28), - wherein preferably the at least one circumferential flange (28) at least partly contacts the at least one metal flange part (8).

10. Casting mold, in particular a low pressure die casting mold, comprising: - at least one pressure chamber for receiving molten metal, - a pressure connection for supplying the at least one pressure chamber with a pressurized gas, - at least one riser channel (42) in fluid communication with the at least one pressure chamber, - wherein the riser channel (42) is configured to guide the molten metal from the at least one pressure chamber against gravity into the direction of at least one casting outlet and a mold cavity (38) as a result of the pressure in the at least one pressure chamber, characterized in that - the riser channel (42) comprises at least one riser tube (2) according to one of the claims 1 to 9.

11. Use of a riser tube according to any one of the claims 1 to 9 in a low pressure die casting process.

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