EP1258302A2 - Method and apparatus for producing precision castings - Google Patents

Abstract

A metal casting wheel (1) is used to produce precision castings from a melt, which has an annular distributor channel (4) and several interchangeable casting molds (6), each with at least one pouring opening (6a). The amount of melt per casting is chosen so that the casting molds (6) and the distribution channel (4) are filled with the melt when the casting wheel (1) rotates about its axis (AA), such that the precision castings after the melt has solidified held together by a ring formed in the distribution channel (4) from the casting material, the so-called circulation material for new casting processes, and removed from the casting wheel (1) with the casting molds (6), whereupon the precision castings are separated from the ring. In order to be able to produce precision castings with complicated spatial shapes, in particular with undercuts, the one-time use and destructible molds (6) are selected from a ceramic material and positively and interchangeably attached to the casting wheel (1). As a result, the recycle material can be fed uncontaminated to a recycling process. <IMAGE>

Description

The invention relates to a method for producing precision castings from a melt by means of a metallic casting wheel with an annular Distribution channel and with several interchangeable molds with at least one pouring opening, the amount of melt per Casting is chosen so that the molds and the distribution channel at Rotating the casting wheel around its axis with the melt being filled, such that the precision castings after solidification of the melt a ring formed from the cast material in the distribution channel held and removed from the casting wheel with the molds, whereupon the precision castings are separated from the ring and that Material of the ring is fed to a recycling process.

It is particularly, but not exclusively, about the production of Precision castings made of titanium-containing materials.

A method known from EP 0 686 443 A1 deals primarily with the selection of special molding materials which have an influence on the casting and solidification behavior of melts made of titanium-containing materials, such as Pure titanium, Ti 6 Al 4 V, Ti 6 Al 2 Sn 4 Zr 2 Mo, Ti 5 Al 2.5 Sn Ti 15 V 3 Al 3 Cr 3 Sn, Ti Al 5 Fe 2.5 50 Ti 46 Al 2 Cr 2 Nb Titanium aluminide.

The invention also extends to such cast materials, but is not limited to this. Other materials such as e.g. Nickel-based alloys, heat-resistant nickel aluminides, in particular Why materials that are highly reactive at their casting temperature? also include the above cast materials.

Possible applications are in the field of internal combustion engines, e.g. for oscillating parts such as valves, connecting rods and piston pins, where the mass, noise and temperature behavior a Role play. Applications are also in the field of rotating machines such as turbine wheels, turbine blades, Compressor wheels and their parts, i.e. all mass-produced items for which the Manufacturing costs, the precision and compliance with all product parameters play a crucial role. Other interesting areas of application are biomedical prostheses such as Implants, sports and Leisure articles, tools and the like.

If such workpieces have simple geometries, for example are rotationally symmetrical like valves, can be divisible, reusable metallic shapes can be used as often as required, which are only opened for demolding the castings, but not destroyed Need to become.

In the method known from EP 0 686 443 A1, a central sprue around several wreaths in divisible forms made of castings, which also between the wreaths through the Sprue solidified material into a tree or a cluster of Castings are united. There is also another aspect: the most of the materials described above are at room temperature hard and brittle, solid at temperatures between about 200 ° C and 300 ° C, but still ductile. When demoulding at room temperature, however Brittle fractures occur which lead to rejects.

For single-use ceramic molds that are used for demoulding complicated castings must be destroyed is the known device not provided.

From DE 19 84 678 B2 and the corresponding EP 0 992 305 A1 it is also known, precision castings by pouring melt in to produce split metal molds that are in radial alignment are arranged within an axially divided metallic casting wheel. The arrangement of the molds within the casting wheel formed a distribution channel between its radial walls, the immediate communicates with the mold cavities of the molds. Per Casting, the amount of melt is chosen so that after solidification of the There is also a ring made of cast material in the melt channel, from which the castings protrude radially and with which they are one-piece Form cast body. The castings are made after opening the casting wheel and removing the cast body by removing the arbitrarily often reusable mold parts removed from the mold and separated from the ring. At this. Casting technology that only for non-destructively demouldable castings The melt comes as, for example, engine valves can be used nowhere in contact with ceramic or oxidic materials, so that the quantities of material not belonging to the castings, and this includes in particular the ring, melted again and again can be shed. This material quantities of expensive materials, the so-called "circulation material", amount to about 50 to 70% of the total Amount of material.

As far as the manufacture of complicated, in particular undercut, precision castings that is only under destruction of molds that can be demolded has become casting technology receive new, ceramic or oxidic molds for each cast use. In order to be able to manufacture economically with this, such Casting molds connected by ceramic or oxidic pouring channels, see above that whole grapes or "clusters" of castings arise, their entire Surfaces with the ceramic or oxidic cluster shapes in Have come into contact and have been contaminated. This is for the precision castings themselves still bearable, but makes reuse or the recycling of the remaining material quantities (of the circulating material) problematic because there are the contaminating components accumulate. One had to decide, therefore, such quantities of material to be approved only once for reuse as "recycle material". This makes the manufacturing process extremely expensive, especially when it comes to expensive cast materials such as Titanium-based materials described above, especially the very expensive titanium aluminides.

Titanium in particular has material-related processing temperatures (Because of the embrittlement, it cannot be demolded at room temperature due to its high affinity for oxygen, the property Oxygen and oxygen compounds from the ceramic molding materials record and react yourself with these molding materials. The contact with ceramic materials causes a clear Reduce the ductility of the cast material and make reuse difficult of the "circulating material" or the "return scrap", the consequently only in small quantities in investment casting processes can be added.

The invention is therefore based on the object, a method and a Specify device through which the use of ceramic, once usable molds with high productivity is made possible without that the circulating material is inadmissibly contaminated and the reuse, the recycling of this circulating material is unbearably strong is restricted. To a certain extent, these demands are mutually exclusive diametrically opposite.

The solution to the problem is the one specified at the beginning Method according to the invention in that the casting molds from one ceramic material selected and positive and interchangeable projecting from the casting wheel.

The spatial orientation of the molds or their mold cavities can be radial, oblique or tangential to the casting wheel. Also the molds can have more than one, e.g. have two, gate openings. Casting molds can be used especially for casting turbine blades be a gate at both ends of the mold cavity have. The axis of rotation of the casting wheel does not have to either run horizontally, it can also at an angle to the horizontal or even be aligned vertically. In the latter case then preferably close one side of the casting wheel.

The object is completely achieved by the invention, in particular, the use of ceramic, single-use molds enables with high productivity without the circulating material impermissibly heavily contaminated and the reuse, recycling, this circulating material is intolerably severely restricted. Which diametrically opposed demands are thereby simultaneously solved.

The melt only comes inside the molds, i.e. means only once in contact with ceramic or oxidic materials, but not the quantities of material not belonging to the castings, and this belongs especially the ring, which melted again and shed again can be. These material quantities of expensive materials, the so-called "Circulating material", which is about 50 to 70% of the total amount of material can be used again without any significant restrictions become. An increasing contamination by oxygen and / or oxides is omitted, and the number of precision castings is limited so-called "clusters" is also not required. The invention enables e.g. the simultaneous production of about 50 turbocharger wheels in a process cycle.

This will make the economic manufacture of complicated, in particular undercut, precision castings that only under Destruction of the molds can be demolded. This makes it cheaper the manufacturing process is enormous, especially when it is expensive Cast materials act like, for example, those described at the beginning Titanium-based materials, especially the very expensive titanium aluminides. The ductility of the cast material is preserved and enables that multiple reuse of the "recycle material" or the "return scrap", consequently in large quantities in investment casting processes can be added again.

• als Gießrad ein solches mit zwei Radringen verwendet wird, die an einer ringförmigen Trennfuge aneinanderstoßen, in der sich Ausnehmungen für das Einsetzen der Gießformen befinden, wenn die Radringe nach dem Einsetzen der Gießformen unter Bildung des Verteilerkanals axial zusammengefahren werden und wenn die Radringe nach dem Abguß unter Freigabe des Ringes aus Gußwerkstoff mit den Gießformen und den Präzisionsgußteilen axial auseinander gefahren werden.

In the course of further refinements of the method according to the invention, it is particularly advantageous if:

• as a casting wheel, one with two wheel rings is used, which abut one another at an annular parting line, in which there are recesses for the insertion of the casting molds, if the wheel rings are moved together axially after the casting molds have been inserted to form the distributor channel and if the wheel rings have been cast with the release of the ring made of cast material with the casting molds and the precision castings axially apart.

The invention also relates to a device for producing precision castings from a melt using a metal casting wheel an annular distribution channel and with several interchangeable Casting molds with at least one pouring opening each, the casting molds and the distribution channel when the casting wheel rotates about its axis the melt can be filled, such that the precision castings after Solidification of the melt by a ring formed in the distribution channel the casting material held together and with the molds from the Casting wheel are removable.

To achieve the same object, such a device is in accordance with the invention characterized in that the casting molds from a ceramic Material selected and form-fitting and interchangeable from Casting wheel can be attached to this.

• das Gießrad zwei Radringe aufweist, die an einer ringförmigen Trennfuge aneinanderstoßen, in der sich Ausnehmungen für das Einsetzen der Gießformen befinden, wenn die Radringe nach dem Einsetzen der Gießformen unter Bildung des Verteilerkanals axial zusammenfahrbar sind, und wenn die Radringe nach dem Abguß unter Freigabe des Ringes aus Gußwerkstoff mit den Gießformen und den Präzisionsgußteilen axial auseinander fahrbar sind,
• die Gießformen je einen ihre Eingußöffnungen umgebenden flanschförmigen Rand besitzen, der formschlüssig in die komplementären Ausnehmungen in der Trennfuge des Gießrades parallel zur Achse des Gießrades einsetzbar ist,
• die Radringe an ihren Außenseiten mit Halteringen versehen sind, die die flanschförmigen Ränder der Gießformen auf je einem Teil ihres Umfanges hintergreifen,
• mindestens einer der Halteringe von dem zugehörigen Radring abnehmbar und außerhalb des Gießrades mit den Gießformen bestückbar ist,
• mindestens einer der Halteringe in Sektoren unterteilt ist,
• in mindestens einem der Radringe Gießtrichter angeordnet sind, die den Verteilerkanal mit den Eingußöffnungen der Gießformen verbinden,
• die Gießformen von einem ringförmigen Fangkanal umgeben sind,
• der Fangkanal eine Ringscheibe, eine zylindrische Zarge und einen radial einwärts gerichteten Ringflansch besitzt und wenn der Fangkanal an einem der Radringe befestigt ist,
• an dem jeweils anderen Radring eine weitere Ringscheibe befestigt ist, die bei geschlossenem Gießrad eine öffnung in dem Fangkanal zumindest weitgehend verschließt,
• dem Gießrad eine Beschickungseinrichtung zugeordnet ist, mittels welcher vorgeheizte Gießformen in das Gießrad einsetzbar sind,
• die Beschickungseinrichtung zur Aufnahme mindestens eines der Halteringe ausgebildet ist, und/oder, wenn
• die Beschickungseinrichtung zur Aufnahme von Sektoren mindestens eines der Halteringe ausgebildet ist.

In the course of further refinements of the device according to the invention, it is particularly advantageous if — either individually or in combination:

• the casting wheel has two wheel rings which abut one another at an annular parting line, in which there are recesses for the insertion of the casting molds, if the wheel rings can be moved together axially after the casting molds have been inserted to form the distribution channel, and if the wheel rings after the casting have been released with the release of the Ring made of cast material with the casting molds and the precision castings can be moved axially apart,
• the casting molds each have a flange-shaped edge surrounding their pouring openings, which can be inserted in a form-fitting manner in the complementary recesses in the parting line of the casting wheel parallel to the axis of the casting wheel,
• the wheel rings are provided on their outer sides with retaining rings which engage behind the flange-shaped edges of the casting molds on each part of their circumference,
• at least one of the retaining rings can be removed from the associated wheel ring and can be fitted with the casting molds outside the casting wheel,
• at least one of the retaining rings is divided into sectors,
• pouring funnels are arranged in at least one of the wheel rings, which connect the distribution channel to the pouring openings of the casting molds,
• the casting molds are surrounded by an annular catch channel,
• the catch channel has an annular disc, a cylindrical frame and a radially inwardly directed ring flange and if the catch channel is fastened to one of the wheel rings,
• on the other wheel ring a further washer is attached, which at least largely closes an opening in the catch channel when the casting wheel is closed,
• a feed device is assigned to the casting wheel, by means of which preheated casting molds can be inserted into the casting wheel,
• the loading device is designed to receive at least one of the retaining rings, and / or if
• the loading device is designed to accommodate sectors of at least one of the retaining rings.

The subject of the invention is preferably suitable for centrifugal casting of precision castings.

An embodiment of the subject of the invention and its Mode of operation will be explained in more detail below with reference to FIGS. 1 to 6 explained.

Figur 1

einen halben Axialschnitt entlang der Achse eines Gießrades mit zwei Radringen während eines Abgusses,

Figur 2

das Gießrad nach Figur 1 in geöffnetem Zustand zum Einsetzen der Gießformen und zur Entnahme der Gußteile mit den gefüllten Gießformen,

Figur 3

einen sektorförmigen Ausschnitt aus dem linken Radring mit axialer Blickrichtung gemäß dem Pfeil in Figur 2, jedoch ohne Gießformen,

Figur 4

einen Ausschnitt aus Figur 3 in perspektivischer Darstellung mit einer Gießform vor dem Einschub in den Radring,

Figur 5

eine Prinzipdarstellung eines ersten Ausführungsbeispiels einer automatischen Beschickungseinrichtung für Gießformen mit axialer Blickrichtung und

Figur 6

zwei weitere Ausführungsbeispiele einer automatischen Beschickungseinrichtung für Gießformen mit axialer Blickrichtung.

Show it:

Figure 1

half an axial section along the axis of a casting wheel with two wheel rings during a casting,

Figure 2

1 in the open state for inserting the casting molds and for removing the cast parts with the filled casting molds,

Figure 3

3 shows a sector-shaped section from the left wheel ring with an axial viewing direction according to the arrow in FIG. 2, but without casting molds,

Figure 4

3 shows a detail from FIG. 3 in a perspective representation with a casting mold before insertion into the wheel ring,

Figure 5

a schematic diagram of a first embodiment of an automatic loading device for casting molds with an axial viewing direction and

Figure 6

two further exemplary embodiments of an automatic loading device for casting molds with an axial viewing direction.

FIG. 1 shows a casting wheel 1 which consists of two wheel rings 2 and 3 consists of niobium with a common axis of rotation A-A, which enclose an annular distribution channel 4 between them. The Wheel rings 2 and 3 abut each other at a joint 5. To the Casting wheel 1, numerous casting molds 6 are attached to the circumference thereof Inlet openings 6a are aligned with the distribution channel 4. Details of the Detachable attachment are shown in Figure 4. To do this the wheel rings 2 and 3 corresponding L-shaped retaining rings 2a and 3a, the made of steel or a nickel-based alloy, with the wheel rings 2 and 3 can also be made in one piece from niobium, as shown in FIG. 4 shows.

The wheel rings 2 and 3 have coaxial ones on their outer sides 2b and 3b Steel guide rings 7 and 8, which form ring rails to a certain extent and run in guide rollers 9 and 10, which are distributed over the circumference and only one of which is shown. The leadership roles 9 and 10, at least one of which is driven, are in pedestals 11 and 12 stored, of which the right in the direction of the arrow 13 are displaceable in accordance with the casting wheel 1 in the open position Figure 2 can bring. The casting wheel 1 is according to Figure 1 by a loaded tiltable crucible 14, which with its content, the casting material, is heated by an induction coil 15. The melting pot 14 is designed as a metallic "cold wall crucible" of known construction, see above that the melt cannot be contaminated by crucible material. Such cold wall crucibles consist of hollow, cooled copper sectors are strung together like a palisade on the circumference, so that a "skull" is formed on the inside from the cast material, which each Contamination of the casting material prevented. If necessary between the crucible 14 and the distribution channel 4 another one - here not shown - arranged removable guide for the melt his.

The entire arrangement is to avoid contamination (e.g. oxidation) arranged by gases in a chamber, not shown here, in which will maintain a vacuum or a protective gas atmosphere can. To break one of the ceramic molds or to Another leak is to prevent melt from escaping the casting wheel 1 with all the casting molds 6 from an annular and coaxial Surround catch channel 16, which is fixedly connected to the casting wheel 1, but can be opened according to Figure 2.

Figure 2 shows this condition: The wheel rings 2 and 3 are on theirs radial parting line 5 opened and with respect to this in cross section asymmetrical so that the molds 6 are held reliably and can be used in a form-fitting manner according to FIG. In closed The state according to FIG. 1 also engages under the right retaining ring 3a the right part of the peripheral edge 6b of the molds 6. Also the Catch channel 16 is with regard to an axial, circumferential parting line 17th asymmetrical two-part design and exists on the right side Wheel ring 3 from an annular disc 16a, a cylindrical frame 16b and one of these radially inwardly directed ring flange 16c. To the left wheel ring 2 is attached another washer 18, which at Casting operation according to FIG. 1 into an opening 16d of the ring flange 16c intervenes.

FIG. 3 shows a sector-shaped section from the left wheel ring 2 with an axial viewing direction according to arrow 19 in Figure 2, but without Casting molds 6. With the addition of Figure 4, the following results: The Casting molds 6 have and a radial sprue opening 6a surrounding edge 6b. For this edge 2 are complementary in the wheel part Recesses 20 arranged radially inward to form a pyramid Casting funnels 21 are extended directly into the distribution channel 4 passes. The casting molds 6 can be placed in these recesses 2 insert in the direction of arrow 22 (Figure 4); they are inserted in Position after closing the casting wheel 1 (Figure 1) by the Retaining ring 3a on the right wheel ring 3 held tight and tight.

Figure 5 shows a schematic diagram of an automatic loading device 23 for casting molds 6 in the axial direction of view. On radial Cantilever arms 24 are arranged, which have a corresponding number of Preheated ceramic molds 6 and keep them in front transport the recesses 20 and insert them into them. Here is only one of the molds 6 shown.

Figure 6 shows a schematic diagram of an automatic loading device on the right 23a for casting molds 6 in the axial direction of view. radial Booms 24a serve to hold a retaining ring 2a, which is in reality is closed on the scope. In the left half of Figure 6 is the Retaining ring divided into sectors 26, between which parting lines 26a are located. It is understood that in both cases at the ends of the boom 24a corresponding, but not shown, gripping devices are arranged are. In these cases too, a corresponding number of preheated ones ceramic molds 6 for joint insertion with the retaining ring 2a or the sectors 26 held in the casting wheel 1. Again, there is only one the molds 6 shown.

Heaters with which the casting wheel 1 and the molds 6 on Casting temperature are not heated for the sake of simplicity shown. After the melt solidifies, they are in the molds 6 located castings by the in the pouring funnels 21 and in the Distribution channel 4 located annular material with each other in a star shape connected. This structure can easily be removed from the casting wheel be, if necessary, by automatic means. After removing the molds the castings can be demolded and the material quantities in the Casting funnels 21 and the material in the distribution channel 4 can, since it is not come into contact with the ceramic material of the casting molds 6 is melted down several times and used for new castings become. The degree of utilization of the cast material is thereby considerably increased.

LIST OF REFERENCE NUMBERS

1

casting wheel

2

Radring

2a

retaining ring

3

Radring

3a

retaining ring

4

distribution channel

5

parting line

6

molds

6a

Eingußöffnungen

6b

edge

7

guide ring

8th

guide ring

9

guide rollers

10

guide rollers

11

bearing blocks

12

bearing blocks

13

arrow

14

melting pot

15

induction coil

16

catching channel

16a

washer

16b

frame

16c

annular flange

16d

opening

17

parting line

18

washer

19

arrow

20

recesses

21

sprue

22

arrow

23

feeder

23a

feeder

24

boom

24a

boom

25

grab

26

sectors

26a

joints

A-A

rotation axis

Claims (15)

Process for the production of precision castings from a melt by means of a metallic casting wheel (1) with an annular distributor channel (4) and with several interchangeable molds (6) with at least one pouring opening (6a), the amount of melt per casting being chosen so that the Casting molds (6) and the distribution channel (4) when the casting wheel (1) rotates about its axis (AA) are filled with the melt such that the precision castings after the melt solidifies through a ring formed in the distribution channel (4) Casting material held together and removed from the casting wheel (1) with the casting molds (6), whereupon the precision castings are separated from the ring and the material of the ring is fed to a recycling process, characterized in that the casting molds (6) are made of a ceramic Material selected and positively and replaceably attached to the casting wheel (1). Method according to Claim 1, characterized in that the casting wheel (1) used is one with two wheel rings (2, 3) which abut one another at an annular parting line (5) in which there are recesses (20) for inserting the casting molds ( 6) are that the wheel rings (2, 3) after the insertion of the molds (6) are moved together axially to form the distribution channel (4) and that the wheel rings (2, 3) after the casting with release of the ring made of cast material with the Casting molds (6) and the precision castings are moved apart axially. Device for the production of precision castings from a melt by means of a metallic casting wheel (1) with an annular distributor channel (4) and with several exchangeable molds (6) with at least one pouring opening (6a) each, the casting molds (6) and the distributor channel (4 ) when the casting wheel (1) rotates about its axis (AA) with the melt, such that the precision castings are held together after the solidification of the melt by a ring formed in the distribution channel (4) from the casting material and with the casting molds (6) can be removed from the casting wheel (1), characterized in that the casting molds (6) are selected from a ceramic material and can be attached to the casting wheel (1) in a positive and interchangeable manner. Device according to claim 3, characterized in that the casting wheel (1) has two wheel rings (2, 3) which abut one another at an annular parting line (5) in which there are recesses (20) for inserting the casting molds (6), that the wheel rings (2, 3) can be moved together axially after the insertion of the casting molds (6) to form the distribution channel (4), and that the wheel rings (2, 3) after the casting with release of the ring made of casting material with the casting molds (6 ) and the precision castings can be moved axially apart. Apparatus according to claim 4, characterized in that the casting molds (6) each have a flange-shaped edge (6b) surrounding their pouring openings (6a), which at least has a positive fit in the complementary recesses (20) in the parting line (5) of the casting wheel (1) can be used essentially parallel to the axis (AA) of the casting wheel (1). Apparatus according to claim 5, characterized in that the wheel rings (2, 3) are provided on their outer sides with retaining rings (2a, 3a) which engage behind the flange-shaped edges (6b) of the casting molds (6) on each part of their circumference. Device according to claim 6, characterized in that at least one of the retaining rings (2a, 3a) can be removed from the associated wheel ring (2, 3) and can be fitted with the casting molds (6) outside the casting wheel (1). Device according to claim 6, characterized in that at least one of the retaining rings (2a, 3a) is divided into sectors (26). Apparatus according to claim 4, characterized in that pouring funnels (21) are arranged in at least one of the wheel rings (2, 3) and connect the distributor channel (4) to the sprue openings (6a) of the casting molds (6). Device according to claim 3, characterized in that the casting molds (6) are surrounded by an annular catch channel (16). Device according to claim 10, characterized in that the catch channel (16) has an annular disc (16a), a cylindrical frame (16b) and a radially inwardly directed ring flange (16c) and in that the catch channel (16) is attached to one of the wheel rings (2, 3) is attached. Apparatus according to claim 11, characterized in that a further ring disk (18) is fastened to the respective other wheel ring (2, 3) and at least largely closes an opening (16d) in the catch channel (16) when the casting wheel (1) is closed. Device according to claim 3, characterized in that the casting wheel (1) is assigned a loading device (23) by means of which preheated casting molds (6) can be inserted into the casting wheel (1). Device according to claims 3, 7 and 13, characterized in that the loading device (23) is designed to receive at least one of the retaining rings (2a, 3a). Device according to claims 3, 8 and 13, characterized in that the loading device (23) is designed to receive sectors (26) of at least one of the retaining rings (2a, 3a).

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