WO2015176799A1

WO2015176799A1 - Low-pressure casting device and method for the operation thereof

Info

Publication number: WO2015176799A1
Application number: PCT/EP2015/000936
Authority: WO
Inventors: Siegfried Botsch; Yusuf Durak; Tilmann Haug; Timotheus Kaiser; Hermann Pfeifer; Martin SCHÖNBORN; Jörg TIMM; Karl-Ludwig Weisskopf
Original assignee: Daimler Ag
Priority date: 2014-05-23
Filing date: 2015-05-07
Publication date: 2015-11-26
Also published as: HU4956U; HU4955U; RS1514U1; CN205834180U; CN105081276A

Abstract

The invention relates to a low-pressure casting device (10) comprising a casting mold (11) which is fillable with a casting material by means of excess gas pressure via at least one casting runner (12). At least one cooling module (20) is arranged in the casting runner (12) and/or on the casting runner (12) by means of which cooling module a casting material flowing in the casting runner (12) can be cooled in such a way that this casting material solidifies and the casting runner (12) is closed, and/or that at least one check valve (22) is arranged in the casting runner (12) by means of which the casting runner (12) can be mechanically closed by reducing a gas pressure. Using this low-pressure casting device (10), thin-walled components (40, 44) can be produced at high quality.

Description

Low pressure casting apparatus and a method for operating this

The invention relates to a low-pressure casting apparatus and a method for operating the latter, wherein the low-pressure casting apparatus comprises at least one casting mold into which a casting material can be introduced by means of gas overpressure via a casting run. Furthermore, the invention relates to a manufactured using this caster

Cast component.

From the GM 90 15 025.2 a sealing plug for melting and casting vessels is known. The sealing plug comprises a closure body and an attached thereto

Guide rod, wherein the closure plug has a density that makes him float on the melt. The stopper is formed as a ball and the guide rod is connected to the dipping into the melt area of the ball.

The invention has for its object to provide a comparison with the prior art improved Niederdruckgießvorrichtung and a method for their operation. Furthermore, the object of the invention is to provide a cast component, in particular an exhaust gas turbocharger housing, which can be produced using such a device or such a method.

The object is achieved according to the invention in terms of low-pressure casting by the in claim 1, with respect to the method by the in claim 5

Characteristics and with respect to the cast component solved by the features specified in claim 10.

Advantageous developments of the invention are the subject of the dependent claims. A low-pressure casting device according to the invention comprises at least one casting mold into which a casting material can be introduced by means of gas overpressure via a casting run. At least one cooling module is arranged in the casting run, by means of which a casting material flowing in the casting run can be cooled such that it solidifies and the casting run is closed and / or at least one check valve is arranged in the casting run, by means of which the casting run is lowered when a gas pressure is lowered is mechanically closed.

By means of the low-pressure casting device according to the invention, it is possible in a particularly advantageous manner to lower the pressure after completion of the casting mold, without the melt emerging from the casting mold and flowing back into the casting run. As a result, a process time of a casting process with mold filling against gravity can be shortened in a profitable manner: as soon as the run is closed by the cooling module or the check valve, no liquid can

Gusswerkstoff more flow back from the mold. The casting mold can therefore be decoupled from the low-pressure casting plant, and the casting plant is directly available for filling a further casting mold. In this way, unproductive non-productive times can be reduced and cast components, for example cast steel components,

be manufactured comparatively inexpensive.

In the manufacture of metallic components in casting processes there is generally the risk of the formation of so-called voids due to contraction, i. H. a reduction of a volume of a melt, in particular during rapid solidification of the same. To accommodate the resulting from a Lunkervolumendefizit superfluous melt and reduce the number of voids include molds so-called feeders, which are removed after curing of the cast component. To further reduce the risk of voids, it is advantageous to arrange an exothermically reacting substance or an exothermically reacting substance mixture, for example a so-called blown powder in the region of filling openings of the mold and / or feeders before filling the liquid casting material; In this way, the solidification rate of the Gusswerstoffs can be reduced and thus the solidification time can be extended.

Advantageously, the exothermically reacting substance or the exothermic substance mixture is placed in a container which is destroyed in contact with the liquid casting material such that the exothermic substance or the exothermically reacting substance mixture with the molten material in the at least one Feeder and / or transported into the mold. The provision of the exothermically reacting substance or substance mixture in a container enables a process-reliable placement and quantity control of the exothermically reacting substance or mixture in the region of the filling openings. In this way, the effect of the feeder can be significantly increased. When using such a container, the substance or the mixture can be arranged in a constant and defined definable amount and concentration in the region of the filling openings, so that the process has a very low production bandwidth and error rate. The formation of non-metallic inclusions in the cast body to be produced can be considerably reduced. Also, the Feiserwirkung is significantly increased, which also at least a reduction of shrinkage defects in the casting, ie non-metallic inclusions, can be realized. This makes it possible to reduce a volume of the feeder without losing the feeder effect.

Using the low-pressure casting apparatus according to the invention and the method according to the invention, cast components can be produced in a cost-effective manner with short process times, in high quality and low wall thicknesses. For example, thin-walled cast components, in particular exhaust gas turbocharger housings, can be produced in this way, which at least in some areas,

preferably at least 20%, have a wall thickness of 1 to 3.5 mm.

Due to the reduced wall thickness of the material used in the manufacture of such exhaust gas turbocharger housing can be reduced, resulting in a significant

Weight saving leads. For example, the weight of an exhaust gas turbocharger housing produced in this way for a 4-cylinder engine is more than 30% lower than a corresponding exhaust gas turbocharger housing in conventional

Design. In addition, reduced space required for the arrangement of the exhaust gas turbocharger housing in the vehicle is reduced by the reduced wall thickness.

By manufacturing the exhaust gas turbocharger housing in a low-pressure casting process, a scrap exhaust-gas turbine housing produced in a profit-making manner is reduced as compared with a gravity casting method.

For example, the inventive method significantly reduces a scrap rate to less than 10% rejects compared to the typical one

Reject rate of more than 15% rejects in the corresponding gravity casting.

Embodiments of the invention will be explained in more detail with reference to drawings. Showing:

Fig. 1 shows a schematic perspective view of an inventive

Low pressure casting device with a arranged on a run cooling module;

Fig. 2 shows a schematic perspective view of an inventive

Low-pressure casting device with a non-return valve arranged in a runner;

Fig. 3 is a schematic perspective view of one in the

Low-pressure casting of Fig. 1 or Fig. 2 produced cast component.

Corresponding parts are provided in the figures with the same reference numerals.

FIG. 1 shows a low-pressure casting device 10 according to the invention. The low-pressure casting apparatus 10 comprises at least one casting mold 11, the mold cavity of which is not shown in such a way that it corresponds to a mold of a cast component 40 to be produced, for example an exhaust gas turbocharger housing 44 (shown schematically in FIG. 3). Furthermore, the

Low-pressure casting 10 in the present embodiments according to Figures 1 and 2, two runners 12 and, for example, a melting furnace thirteenth

Under low-pressure casting to understand a process in which a cast material, such as aluminum or steel, by means of a runner 12, also called riser, is pressed from below, ie against gravity, from the furnace 13 into the mold cavity of the mold 11. In this case, it may be in the mold 1 1, for example, a mold, a sand mold or a fine casting mold.

An upward movement of the casting material is in this case effected against the force of gravity, preferably according to a gas pressure principle. It is envisaged that after a casting process, ie after a filling of the

Mold cavity of the mold 1 1, the casting 12 is closed to prevent leakage of the casting material from the mold 11.

In the present embodiment according to FIG

Low-pressure casting 10, as described above, two runners 12 through which the casting material is pressed by means of a gas overpressure in the mold 11. Approximately centrally along the longitudinal extent of the runners 12, the cross section of the respective runner 12 in a section 24 is increased. Preferably, a cooling module 20 is arranged at this section 24 of the cross-sectional enlargement.

The cooling module 20 is arranged on the respective run 12, that it rests positively on the runner 12, in particular material, form and / or non-positively attached thereto. In this case, the cooling module 20 is attached to the runner 12 such that it is not completely enclosed by the cooling module 20, for example. For example, a surface portion 25 of the run 12 is exposed. In particular, a geometry of the cooling module 20 depends on this

Geometry of the respective casting run 12.

The cooling module 20 itself is z. B. formed from a molding sand, a metal and / or a ceramic, although other materials may be suitable.

The cooling module 20 serves to remove the casting material flowing in the casting run 12, in particular the casting material passing through the section 24 of the cross-sectional enlargement

Filling the mold cavity, so after completion of the casting process to cool. For this purpose, the heat of the casting material over the enlarged

Cross section of the casting run 12 fed to the cooling module 20 and discharged from the outside. By cooling the casting material this solidifies, whereby the corresponding casting run 12 is closed and thus the casting material can not flow from the casting mold 11 back into the casting runner 12.

In a particularly advantageous embodiment of the low-pressure casting apparatus 10, a cooling device, for example a cooling device, may be provided on the cooling module 20, for example on a lower side 21 of the cooling module 20. B. in the form of a cooling iron (not shown), whereby a heat transfer is accelerated. In a particularly advantageous manner, a surface of the lower side 21 of the cooling module 20 corresponds to a cooling surface of the cooling device facing the underside 21. It is also possible, within the casting mold 11, in particular at an interface between casting mold 11 and casting run 12, to arrange a further cooling module 20, for example with a cooling device, which is particularly preferably switched on and off as required.

Furthermore, it is possible, the cooling surface of the cooling module 20, which rests directly on the casting run 12, d. H. is arranged at this arcuate run, whereby a cooling of the casting material is fluidically optimized.

FIG. 2 shows a further possible embodiment of a device according to the invention

Low pressure casting device 10 '.

In the present exemplary embodiment according to FIG. 2, a check valve 22 in the form of a ball 23 is arranged in each of these for closing the pouring runs 12, which are illustrated transparently. In this case, a geometry of the ball 23 and a geometry of the runner 12 is particularly advantageously chosen so that the ball 23 does not close the casting run 12 in the direction of flow 27 of the casting mold 1 when the gas overpressure prevails in the casting run 12. For example, an unillustrated shut-off element is provided for this purpose, which is a flow of the casting material in

Flow direction 27 is not affected.

In particular, the ball 23 as a check valve 22 in about one half of the

Casting 12 between, for example, furnace 13 and mold 11 is arranged. In particular, the runner 12 in the region of the ball 23 has a space 26 in the form of a formation which extends to each side, d. H. in the flow direction 27 and opposite, tapered. In this space 26, the ball 23 is arranged as a check valve 22.

For example, the ball 23 is formed of metal, ceramic and / or other suitable material.

If the gas pressure of Niederdruckgießvorrichtung 10 'is lowered, in particular after filling the mold cavity, the ball 23 is against the flow direction 27 of the casting material within the space 26 against an opening 28 of the

Casting 12 pressed, wherein at least a portion of the ball 23 closes the opening 28 and thus the runner 12 and the casting material is not from the mold 11th back into the runner 12 can flow. For example, closes the ball 23, the opening 28 of the runner 12 such that in the space 26, in the casting run 12 and in the mold cavity of the mold 1 1 continues to be a gas pressure.

By means of the low-pressure casting apparatus 10, 10 'according to the invention, it is possible in a particularly advantageous manner to lower the gas pressure after filling the casting mold 11 without the casting material flowing out of the casting mold 11, as a result of which a processing time of a casting process can be shortened. That is, the mold 11 can be removed from the low-pressure casting apparatus 10, 10 'without the

Casting material from the mold 1 1 flows out. The low-pressure casting apparatus 10, 10 'with a further casting mold arranged thereon can for example be used immediately for the production of a further cast component.

3 shows a perspective view of an exhaust gas turbocharger housing 44 as an example of a cast component 40 which was produced using the low-pressure casting apparatus 10 "of FIGURE 1 or 2. The exhaust gas turbocharger housing 44 is made of a cast steel and has a wall thickness 43 between 1 mm and at least in sections 3.5 mm.

To an inner cavity 42 of the exhaust gas turbocharger housing 44 during the

Casting process, a lost core is advantageously used, which is made in a so-called cold box process. In the cold box method, a core sand (usually quartz sand) is mixed with a binder and a hardener and cold cured and then arranged as a core in the mold. Using a cast-core produced in the cold-box process is a

Interior 42 of a cast component 40 in a particularly advantageous manner precisely represented.

The low-pressure casting method for producing the exhaust-gas turbocharger housing 44 provides that a pressure, a temperature and / or a mold-filling speed of the

Molten steel and / or other casting material are accurately controlled or will. By controlling the mold filling speed in particular a laminar mold filling can be realized. This means that a molten steel is pressed into the casting mold in a main flow direction and as a result no turbulence and / or transverse flows occur in the mold cavity. By such a laminar mold filling the exhaust gas turbocharger housing 44 can be produced in a high material quality. Furthermore, it is advantageous if the low-pressure casting process for producing the exhaust gas turbocharger housing 44 is carried out under a protective gas atmosphere.

The Niederdruckgießverfahren described allows an increase in

Economics in the production of exhaust gas turbocharger housings 44. Furthermore, the method enables the process-reliable representation of thin-walled structures of cast components 40, whereby the use of materials, in particular a material use of cost-intensive high temperature resistant materials, is reduced during manufacture. Through this reduced use of materials in the production of

Exhaust gas turbocharger housing 44 is a lightweight construction and associated therewith

Weight saving of the exhaust gas turbocharger housing 44 achievable. Compared to manufacture in a gravity casting process, using the described low pressure casting process, the reject rate in the production of

Exhaust turbocharger housings 44 are significantly reduced.

In order to prevent the formation of voids in the cast component 40 during the casting process, the casting mold 11 is advantageously provided with feeders 50 which open into a top surface 55 of the casting tool. In the perspective view of Figure 2, two feeders 50 are indicated by dashed lines. To reduce voids formation in the cast component to be produced, an exothermically reacting substance or an exothermically reacting substance mixture, for example so-called blown powder, is introduced into the feeders 50 together with the material melt. For this purpose 50 containers 53 are arranged in the region of the filling openings 51 of the feeder, which are connected to the

powdered exothermically reacting substance or mixture are filled.

The containers 53 may, for example, be pocket-shaped or formed as a bag and completely cover the filling openings 51 of the feeders 50. The containers 53 with the substance or substance mixture contained therein form so-called pads. These can be machine filled, accurately weighed and dust sealed, and transported and placed mechanically (e.g., by robots).

The containers 53 are formed of a material, for example paper, which is at least partially destroyed in contact with the liquid cast material such that the exothermic substance or the exothermic substance mixture with the melted material in the respective feeder 50 and / or in the mold 11 is transported. In a particularly advantageous manner, the material is designed such that it dissolves without residue on contact with the molten material. That way you will be off The resulting foreign inclusions within the casting component 40 to be produced are avoided.

Depending on the volumes of the feeders 50 and the casting mold 11, depending on the properties of the casting material and depending on process parameters, such as a temperature and a pressure, an amount of the substance or mixture arranged in the respective container 53 is variably predetermined.

Furthermore, depending on the volumes of the feeders 50, depending on the volumes of the casting mold 11, depending on the properties of the casting material and depending on process parameters, the number of containers 53 arranged in the region of the filling openings 51 of the respective feeder 50 is set variably. In the illustrated embodiment, each feeder 50, a single container 53 is provided.

The application of the substance or substance like in the containers 53 allows a precise specification of the amount and concentration of the substance or mixture at the respective filling opening 51 and ensures a fate of the substance or mixture at the respective filling opening 51 until at least partial destruction of the containers 53 through the liquid casting material. The containers 53 may be formed of pressed powdered exothermic reactant or composition; the substance or the substance mixture can be introduced in powder form into these pressed containers 53. This embodiment makes it possible to further reduce the risk of introducing foreign substances into the cast body 40 to be produced.

Claims

claims

1. Low-pressure casting apparatus (10, 10 ', 10 "), comprising a casting mold (1 1) into which a casting material can be introduced by means of gas overpressure via at least one casting run (12),

characterized in that in the run (12) and / or on the run (12) at least one cooling module (20) is arranged, by means of a in the

Casting (12) flowing casting material can be cooled such that it solidifies and the run (12) is closed and / or that in the run (12) at least one check valve (22) is arranged, by means of which the run (12) at lowering a Gas pressure is mechanically closed.

2. Low-pressure casting apparatus according to claim 1,

characterized in that the cooling module (20) of metal, molding sand and / or ceramic is formed.

3. low-pressure casting apparatus according to claim 1 or 2,

characterized in that a cooling device is arranged on the cooling module (20).

4. low-pressure casting apparatus according to claim 3,

characterized in that the cooling device is a cooling iron.

5. A method for producing a cast component by means of low-pressure casting, in which a casting (12) by means of gas pressure a cast material in a

Casting mold (11) is filled, characterized in that by means of at least one in the run (12) arranged cooling module (20) of the flowing

Cast material is cooled so that it solidifies and the run (12) is closed and / or that in the run (12) at least one

Check valve (22) is arranged, by means of which the casting run (12) is mechanically closed when lowering a gas pressure.

6. The method according to claim 5,

characterized in that an exothermically reacting substance or an exothermically reacting substance mixture is arranged in the region of the filling opening (51) of at least one feeder (50) of the casting mold (11) before a material melt is introduced into the casting mold (11).

7. The method according to claim 6,

characterized in that the exothermically reacting substance or the exothermically reacting substance mixture in at least one container (53) is arranged, which is at least partially destroyed in contact with the molten casting material such that the exothermically reacting substance or the exothermically reacting mixture with the casting material in the at least one feeder (50) and / or in the casting mold (1) is transported.

8. The method according to claim 6 or 7,

characterized in that a powdered exothermically reacting substance or a powdery exothermically reacting substance mixture is used.

9. The method according to any one of claims 5 to 8, wherein a cold cured

lost core in the casting mold (11) is arranged and with a cast material, in particular a molten steel, is encapsulated such that the cast component (40) has a wall thickness of 1 to 3.5 mm, at least in some areas.

10. cast component (40), in particular exhaust gas turbocharger housing (44), which in a low-pressure casting at least in some areas thin-walled with a

Wall thickness (43) is made from 1 to 3.5 mm.

11. cast component (40) according to claim 14,

characterized in that the cast component (40) is formed from steel.