EP0937525A1 - Low pressure casting process for light metals, particularly aluminium and apparatus for carrying out the method - Google Patents

Abstract

The melt volume forced upwards during closure of the riser pipe (7) and cut-off of the melt column is pressed into the sprue (11) of the casting die. The apparatus includes a closure unit whose motion directly closes the riser pipe.

Description

The invention relates to a low-pressure casting process for Light metals, especially aluminum, by the in one Melting vessel under pressure over a melt dip tube immersed in the melt in another Mouth rising via a casting mold to be connected is promoted and several consecutive Casting molds through a cyclical relative movement between poured them and the melt vessel successively at the end of each pouring cycle that from the riser pipe melt column reaching into the sprue near the mouth of the riser pipe with the same closure is sheared off. Furthermore, the invention relates to a device directed to carry out the procedure.

Light metals, especially aluminum, have in the Increasing past as a construction material Gained meaning. This also applies to motor vehicle construction, especially engine construction. So be in newer Time engine blocks made of aluminum. Due to the Large series production in the automotive industry must also Casting processes and casting plants with high performance for Will be provided. At the same time, in particular highly stressed components a high quality standard to be guaranteed. Because aluminum is mainly in the molten state spontaneously oxidized with atmospheric oxygen, forms open melt surfaces in the presence of oxygen an oxide skin very quickly.

To prevent this from happening as much as possible for example, both for mold casting and for Gravity die casting, especially in the Execution of the rising casting, proven, since this is the Melt not swirled, but the shape or mold is filled with a calm melt front. Thereby can largely include oxide inclusions in the casting be avoided.

With these typical measures for low pressure casting however, there is the disadvantage that performance is relatively small. This is one of the reasons attributable to the pressure in the melt vessel after each casting must be lowered, which in turn with the decline the melt column is connected in the riser. Here atmospheric oxygen from the environment enters the riser pipe on. It forms on the surface, albeit a small one an oxide skin on the melt column, which is The melt column rises to the next pour cycle Wall of the riser creates and on the melt front always replicates. This increases the riser pipe gradually to. At high performance, this requires one regular replacement of the riser pipe in relatively short Time intervals, which in turn leads to a reduction in performance leads. Another crucial disadvantage is that the oxide skin forming on the surface of the melt column is brought into the mold or mold and itself later found in the cast structure.

These disadvantages become apparent in a known device (DE 71 30 820 U1) partially avoided by the fact that between Riser pipe and sprue a coupling piece with slide is arranged interchangeably and the slide vertically can be inserted into the coupling piece to the riser pipe axis is and shears the melt column. Here it’s primarily about making the transition between the Riser pipe and different molds with different Inclination of the mold base through different coupling pieces to bridge. This version is from Disadvantage that part of the melt column between the Slider and the gate remains and either through appropriate measures kept in a liquid state or must be removed before the next pouring cycle. Especially the latter leads to a significant reduction in performance. The melt must also be replaced every time the coupling is replaced lowered and the melt vessel pressure-free be made.

In another known embodiment (WO95 / 20449) the closure primarily the task of swirling in the melt vessel, especially in the above the Avoid melting gas cushions. Of the Closure consists of a at the transition between the riser and pouring lower melting plate to be used Melting point than the aluminum melt. This Sealing plate is liquefied when the melt rises. These liquid foreign components are in the mold infiltrated and lead to highly undesirable inclusions in the cast. This state of the art also goes assume that despite the closure plate above the melt column forms a gas cushion that when rising the melt column in pockets above the mouth of the Riser pipe is displaced. The formation of oxide layers is not avoided. The publication also leaves open, like the riser after the plate has melted is closed. The same also applies to the described execution of a slide closure. In in any case, either the melt front remains in the Riser pipe free or a melt residue remains in the riser pipe between closure and pouring.

The invention has for its object a low-pressure casting process and one to carry it out propose a suitable device that is both a Performance increase, as well as a quality improvement to lead.

This task is carried out in the process mentioned at the beginning solved in that when sheared the melt column upward displaced melt volume in the pouring of the Casting mold is displaced.

There is therefore no melt residue between the riser and the gate, which the quality of the cast when subsequent casting cycle or the performance in casting could affect. The shapes can be immediate be poured one after the other without any dead time.

It is also advantageous if after shearing the Melt column in the melt vessel at least one the melt column maintain overpressure against the shutter becomes.

This ensures that the melt column is always is present at the closure and not by lowering the Melt column above it creates a negative pressure that could lead to the suction of ambient air.

In terms of device technology, the task of the invention solved by the fact that the closure of the mouth of the Riser pipe is immediately movable closing. By the flush closure of the mouth at the gate is the melt displaced by the closure into the gate displaced and there is no melt residue between the Gate and the closure on the riser.

In a preferred embodiment, the riser pipe is angled and has only one relative in the area of the mouth short straight section, in which a piston-like Closure in the axial direction of the gate aligned section of the riser pipe until it is flush Conclusion at the mouth is movable. At this Execution is the sheared residual volume of the melt from the piston-like closure into the mold mold repressed.

Fig. 1

eine schematische Ansicht einer Niederdruck-Gießanlage für den kastenlosen Sandguß in einer ersten Betriebsstellung;

Fig. 2

die Gießanlage gemäß Fig. 1 in einer weiteren Betriebsstellung;

Fig. 3

eine schematische Ansicht einer Niederdruck-Gießanlage für den Kastenguß in einer ersten Betriebsstellung;

Fig. 4, 5

die Gießanlage gemäß Fig. 3 in je einer weiteren Betriebsstellung;

Fig. 6

eine schematische Ansicht einer Niederdruck-Gießanlage für Kastenformen mit seitlichem Einguß;

Fig. 7

eine schematische Ansicht einer Niederdruck-Gießanlage für kastenlosen Guß und

Fig. 8, 9

die Gießanlage gemäß Fig. 7 in je einer weiteren Betriebsstellung.

The invention is described below with reference to some exemplary embodiments shown in the drawing. The drawing shows:

Fig. 1

is a schematic view of a low-pressure casting system for the castless sand casting in a first operating position;

Fig. 2

1 in a further operating position;

Fig. 3

a schematic view of a low-pressure casting system for box casting in a first operating position;

4, 5

3 in a further operating position;

Fig. 6

is a schematic view of a low-pressure casting machine for box molds with side gate;

Fig. 7

is a schematic view of a low pressure casting machine for boxless casting and

8, 9

7 in a further operating position.

The casting plant designed according to the invention is both suitable for mold casting as well as permanent mold casting. The Embodiments shown in the drawings concern only casting in sand molds (with or without molding box).

1 and 2 are the boxless shaped bales 1 on a conveyor 2 successively arranged. The shaped bales 1 are in the direction the arrow 3 to a casting station, where a melt vessel 4, optionally in the form of an oven, is raised and lowered and movable. By doing The light metal melt 5 is located in the melt vessel 4, a gas cushion 6 stands over the melt surface thereof, that is pressurized. Immersed in the melt vessel 4 a riser pipe designated overall by 7, which at this embodiment over an oblique section 8 and a short straight section 9 upwards is enough and ends at a mouth 10. Above this The shaped bales 1 become the mouth by means of the conveyor 2 clocked so that the gate 11 a Form bales in alignment with the short vertical Section 9 of the riser pipe 7 arrives. In this section 9 a closure in the form of a piston 12 is arranged, which is actuated by means of a cylinder 13. From the in Fig. 1 reproduced closed position, the piston is in the casting position shown in Fig. 2 in which he moves releases short vertical section of the riser 7, so that under the effect of the prevailing in the melting vessel 4 Overpressure the melt gets into the mold. After filling the shape of the closure 12 is again in the closed position brought, in which he is located in section 9 Residual volume 14 of the melt in the sprue 11 of the Form displaced. The cast bales leave the Casting station again in the direction of arrow 3.

1 and 2 is also in the embodiment immediately below the shaped bales and in contact with a cooling plate 16 is arranged over which the shaped bales run with the gate 11 so that the melt in Gate 11 is quickly solidified.

The embodiment according to FIGS. 3 to 5 differs 1 essentially only in that Box molds 17 are poured.

The casting system of the embodiment according to FIG. 6 is again provided for box casting, the molding box 17 over lateral pressure plates 18 are held together. In in this case the gate 11 is lateral and horizontal arranged. The riser pipe 7 has one in this case short horizontal section 19 in which the piston-like closure 20 by means of a cylinder 21 is movable. Here, too, is directly in the area of Section 19 of the riser pipe or along the path of the Pouring 11 a cooling plate 22 is arranged. The one in Fig. 6 Piston-like closure 20 shown in the closed position gives after moving in the opposite direction the section 19 free so that the melt from the riser get into this section and from there into the gate 11 can. Here, too, the form 17 is filled with increasing amounts.

7 to 9 are in the embodiment again boxless shaped bales 23 shown, of which however, each has its own closure 24 for the gate 11 owns that from the open position immediately before Cast (Fig. 7) and during casting (Fig. 8) in the Closed position after the casting (Fig. 9) is movable. in the the rest of this closure is transported along with the shaped bales.

In connection with the piston-like closure in the horizontal section 19 of the riser is the mode of operation such that the shaped bale 23 with the open Closure 24 enters the casting station. The still in Closing position 20 is located (Fig. 7) then opened and the melt over the riser 7 pressed into the mold. At the end of the casting cycle, the Closure 20 with the closure 24 still open in the closed position brought and only then the closure 24th closed for the gate 11.

In all of the exemplary embodiments shown in the drawing closes the piston-like closure 12 or 20 in the The closed position is flush with the mouth of the riser on Gate 11 from.

The cooling plate shown in all exemplary embodiments 16, 22 and the mold-side closure 24 are used excluding the increase in performance during the Closure 12, 20 of the riser pipe both for increased performance, as well as quality improvement in particular the casting serves by creating and infiltrating of oxide skin on the surface of the melt acid in the Riser pipe 7 is avoided. Even in the closed position of the closure 12, 20 is advantageously in the melt vessel maintain a certain overpressure that however, can be lower than the casting pressure. This ensures that not by lowering the Melting column in the riser 7 in its upper part Negative pressure arises which leads to the ingress of leaks Atmospheric oxygen.

Claims (4)

Low pressure casting process for light metals, in particular Aluminum by placing it in a melting pot pressurized melt over a in the Melt dip tube into another Mouth via a casting mold to be connected is increasingly promoted and several successive Casting molds through a cyclical relative movement between them and the melting vessel one after the other be poured off, at the end of each pouring cycle the one reaching from the riser pipe into the sprue Melting column near the mouth of the riser pipe below simultaneous closure of the same is sheared off, characterized in that when shearing the Melt column displaced melt volume upwards is displaced into the casting mold. Casting method according to claim 1, characterized in that after shearing the melt column in Melting vessel at least one against the melt column maintain the overpressure holding the shutter becomes. Device for low pressure casting of light metals, especially aluminum, with a pressurized Melting vessel, one in the melting vessel immersing riser pipe with a closure close its outer mouth, and a plurality of Casting molds with gate, by relative tactical movement between them and the melting pot and Alignment of sprue and riser with everyone Pouring cycle to be poured successively, especially to carry out the method according to Claim 1 or 2, characterized in that the Closes the mouth of the riser pipe immediately is movable to close. Device according to claim 3, characterized in that the riser is angled and the closure piston-like in the axial direction of the with the sprue aligned section of the riser pipe up to flush closure at the mouth is movable.

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