WO2004009273A2

WO2004009273A2 - Moulding of a crystallisable material in the liquid or pasty state

Info

Publication number: WO2004009273A2
Application number: PCT/CH2003/000445
Authority: WO
Inventors: Boris Ouriev; Thomas Scheiwiller; Bernhard Aschmann
Original assignee: Bühler AG
Priority date: 2002-07-19
Filing date: 2003-07-07
Publication date: 2004-01-29
Also published as: DE10233067A1; AU2003238328A1; WO2004009273A3

Abstract

The invention relates to a method and a device for the moulding of a crystallisable material, in particular a light metallic material or a polymer material, in the liquid or pasty state, which is left to solidify after the moulding and resultant shaping, whereby the material is made to vibrate, at least in partial regions thereof, before and/or during the moulding and/or the solidification. Where necessary the material is also inoculated with crystallisation seeds, at least in partial regions thereof, during the moulding and/or solidification. A device used for the above comprises a heating element (1, 2), for heating crystallisable material, a moulding unit (5, 6) which defines a moulding cavity (7), a charging unit (3, 4), by means of which the material is pressed into the moulding unit (5, 6) under pressure and a dosing unit (8, 9, 10, 19), for the dosed introduction of the material in the liquid or pasty state from the heater unit (1, 2) into a casting unit (3, 4), whereby the device is provided with at least one unit (S1 - S11) for the generation of mechanical vibrations, at least in partial regions thereof.

Description

Forming a crystallizable material in the liquid or pasty state

The invention relates to a method for shaping a crystallizable material in the liquid or pasty state and to an apparatus for carrying out this method according to the preamble of claim 1 and claim 70.

Such methods and devices, which are usually referred to as casting processes or casting plants, have long been known. Ultimately, it is always a matter of transferring the liquid or pasty material, which is initially present without a defined shape, into a casting mold, the material being deformed and brought to a solid state by solidification during or after shaping. For the material cohesion of the casting, it is important that it is as homogeneous as possible. Therefore, the liquid or pasty mass before solidification and the solidification conditions or crystallization conditions must be as homogeneous as possible.

Important casting processes are permanent mold casting, especially low-pressure permanent mold casting, die casting, centrifugal casting and continuous casting.

In permanent mold casting, a permanent mold, usually made of steel or cast iron, is generally filled without pressure. The shape of the casting is determined by the mold. In the case of full mold casting, mold cores consisting of steel or cast iron are also usually used.

In low-pressure die casting, the mold is filled from below with a slight overpressure or electromagnetically using a riser pipe. After the relatively slow "quiet" filling, the casting solidifies under the excess pressure. During die casting, the melt or paste is pressed mechanically under high pressure and at great speed into a precisely manufactured permanent metal mold. The pressure is maintained until the solidification ends. In contrast to permanent mold casting, die casting is particularly well suited for relatively thin-walled castings.

In centrifugal casting, the melt is guided into a tubular or ring-shaped mold rotating around its axis, in which it solidifies under the influence of centrifugal force. Common castings are rings, pipes, bushings and cylinders, especially also finned cylinders.

In continuous casting, parts with a constant cross-sectional shape and any length, such as Solid or hollow profiles. The melt is poured into a mold that is open on both sides. The melt in the mold cools down so much that a load-bearing outer shell forms on the casting. The partially solidified strand is continuously pulled out of the mold.

The die casting process is characterized by the fact that, in addition to the casting of liquid materials, it is particularly well suited for the "casting" of pasty materials in which solid particles are present, in particular in the crystalline or partially crystalline state. Die casting is particularly well suited for the production of cast parts made of aluminum or aluminum / magnesium alloys.

Common problems with the casting processes mentioned are separation and sedimentation processes and the uneven degassing of the melt. This leads to inhomogeneous castings or even castings with uncontrolled cavities.

Furthermore, the controllability of the concentration, distribution and size of the solidification or crystallization nuclei is generally poor, which leads to an uneven grain structure, ie an inhomogeneous grain size of the cast part. Another problem is the wall friction of the liquid or pasty material, which leads to an uneven speed distribution when metering the material into the mold and thus to an uneven residence time in the filling and dosing area, but also in the different areas of the mold within the casting system. In particular when pressure casting relatively thin-walled and partly filigree cast parts, the wall friction has a strong influence on the flow behavior of the melt or paste within the mold. In order to achieve complete and rapid filling of the mold, a relatively high filling pressure is required.

The invention has for its object to solve these problems of the prior art or at least to reduce their negative effects.

According to the invention, this object is achieved in terms of method in that, in the method described at the outset, the material is excited to vibrate, at least in some areas, before and / or during the forming and / or solidification.

The vibration can be excited in a heating or tempering area, in a degassing area or in a filtering area.

The material may be a molten metal, in particular a melt containing at least aluminum or magnesium, which was produced in a melting furnace area, or it may be a polymer melt, in particular a melt comprising PET, which was melted in an extruder section. However, the shaping is preferably carried out in a casting mold. The liquid or pasty material can additionally contain particles and / or bubbles.

In a particularly advantageous embodiment, the vibration is excited by at least one vibration source for mechanical vibrations, the vibration being excited over a large area via at least one large-area element coupled to the vibration source. As a result, a relatively homogeneous vibration state can be achieved over the entire volume of the solidifying casting. This enables the entire volume of the solidifying to be influenced in a targeted manner Melt or paste. The large-area element is expediently an inner surface (boundary surface) of a plant or machine part of the casting plant bordering on the material to be formed. By influencing the entire fluid volume, the material is compacted so that the dimensional stability is improved during cooling, ie there is less shrinkage of the material after solidification.

The vibration excitation can take place in such a way that the vibration of the inner surface has at least one component tangential to the interface. The tangential component can reduce the influence of the wall, in particular the wall adhesion or wall friction, which leads to a higher speed of the melt or paste in the area of the wall, so that the ideal of the pure plug flow is approached. Since these transverse waves (transverse waves) can practically not spread in a fluid, they are limited to the wall area.

If, on the other hand, the vibration excitation takes place in such a way that the vibration of the inner surface has at least one component normal to the interface, longitudinal waves (longitudinal waves) propagate into the interior of the melt or paste.

By stimulating with specific vibration frequencies both tangentially and normal to the wall, one can specifically act both on the interface of the melt or paste with the inner surface of the mold and on the inside of the melt or paste.

The vibration is advantageously excited in such a way that surface waves are formed at the interface. Similar to the transverse waves, this also enables a local influence on the fluid (melt or paste) that is limited to the interface, whereby the wall adhesion or wall friction of the fluid can also be reduced.

The interface contacting the material to be formed can be the inner wall of a transport channel for the material. However, the vibration excitation can also be carried out selectively via at least one punctiform element coupled to the at least one vibration source. Such selective vibration excitation is helpful, for example, in dead areas and other areas that are difficult to access for the fluid, such as pointed corners, edges or filigree branches of the mold, in order to facilitate the flow of the fluid there and thus complete filling of the mold.

Vibration excitation can work with predetermined frequencies or in predetermined frequency ranges. It is also possible to work with predetermined amplitudes or in predetermined amplitude ranges. In particular, the vibration can be excited by at least one impact pulse acting on the material. This gives you a wide frequency spectrum. In order to ensure sufficient intensity and exposure over a longer period of time, the vibration can be stimulated by several successive impulses e.g. pulsating.

It is particularly advantageous if, for example, in the case of pulsating forming, in die casting, the pulsation of the vibration excitation is in a predetermined relationship to the pulsation of the forming. The pulsation of the forming and the pulsation of the vibration excitation expediently run synchronously with one another. Due to the pressure surges and the simultaneous vibration surges, the fluid is "shaken" during compression. This allows a denser structure in the solidifying material and thus a better quality of the cast part to be achieved. The pulsation can e.g. by means of a pulsating frequency modulation of the excitation frequency and / or a pulsating amplitude modulation of the excitation amplitude. Depending on requirements or acceptable effort, continuous frequency and amplitude distributions or one or more discrete frequencies or amplitudes are used.

In the casting method according to the invention, there is preferably a different vibration excitation depending on the method step or system section. For example, locally influencing the vibration of the interface of the fluid can dominate when metering into the mold, while in relatively large areas the mold dominates the influence of vibrations in the fluid volume. The influencing of the fluid interface can then dominate again in relatively confined areas of the casting mold. Similarly, can also be specific in time, ie the solidification or Crystallization process "accompanying" the vibration excitation in accordance with the respective phase of solidification or crystallization.

A casting system inner wall with a periodically structured, e.g. corrugated, corrugated or ribbed surface can be used, along which the fluid flows. This creates periodic pulsations due to "self-excitation", which spread throughout the fluid. Different inner wall areas can also be equipped with a different periodic structure (spatial frequency). This results in a superposition of pulsations of several frequencies in the fluid, which correspond to the respective spatial frequencies of the corresponding surface structure. The periodic structuring with different spatial frequencies can also be arranged superimposed in one and the same inner wall area. For example, a coarse periodic structure (fundamental spatial frequency) for relatively low-frequency pulsations for the detachment of dendritic crystal structures from tempered inner wall areas can be designed, while a superimposed fine periodic structure can be designed in such a way that the relatively high-frequency pulsations caused by them influence the rheological properties of the fluid (Wall friction, shear viscosity, etc.) come into question.

As a further vibration source, which also works on the principle of "self-excitation", hydrodynamic instabilities, such as e.g. cyclical stalls or cyclical vortex stalls of the fluid are used, which also creates cyclic pulsations. For this purpose, obstacles protruding into the flowing fluid or stepped, in particular asymmetrical constrictions of a flow channel can be provided in the casting system.

In a further advantageous embodiment of the method according to the invention, the material is inoculated with crystallization nuclei at least in some areas during the shaping and / or solidification. In this way, the crystallization of the melt can be influenced in a targeted manner. The crystallization nuclei can have crystallites of the material to be formed. This prevents the casting from being contaminated in some cases. Alternatively, the crystallization nuclei can also have particles made of a material different from the material to be formed. In addition to influencing the crystallization, targeted contamination of the cast part can thus be achieved.

It is particularly advantageous if the required crystallization nuclei in the melt itself, e.g. generated on a tempered inner wall (temperature gradient) of the casting system or in a region of high shear (shear gradient) in the melt. A combination of a high temperature gradient and a high shear gradient is expediently used for the production of the crystallites. This can e.g. can be achieved by generating a strongly sheared melt flow in the area of a strongly cooled inner wall section of the casting installation, preferably upstream of the actual casting mold in the metering area. The shear effect promotes spontaneous crystallization in the shear gradient on the one hand, but on the other hand also promotes tearing and crushing of dendritic crystal structures that grow from the tempered wall into the melt in the temperature gradient. The detachment of such dendrites from the wall can be promoted by additional pulsation of the melt flow.

It is particularly advantageous if foreign particles, in particular fibers such as carbon fibers, possibly with a modified surface, or nanoparticles, are added to the melt. This suspension can have a volume fraction of foreign particles in the range from about 0.01% to about 80%. The theoretical upper limit of the volume fraction of the foreign particles is formed by the densest packing of, for example, spherical particles, in which case a partially thin layer of the melt material between the foreign particles just forms the continuous phase. Depending on the nature of the solid particles, gel-like or colloid-like fluid states can even be produced. Instead of solid foreign particles, liquid foreign particles, ie droplets, can also be present in the melt (emulsion), as is the case, for example, with immiscible alloys. By adding more surface-active Specific substances that accumulate at the interface between the droplets (discontinuous phase) and the melt (continuous phase), the emulsified state can be stabilized and segregation, ie phase separation, can be prevented.

The crystallization nuclei can contain encapsulated crystallites or crystallite agglomerates, the encapsulation preferably consisting of a substance which dissolves in the crystallizable liquid or pasty material during the shaping and / or solidification, so that the crystallites or the crystallite agglomerates in the exposed material and contribute to the crystallization of the material when it solidifies.

In a further advantageous embodiment, an expansion flow is at least temporarily impressed on the material before and / or during its forming, with a reduction in the fluid pressure in the expansion area, and preferably by passing the material through at least one channel-like area with at least one before and / or during its forming Cross-sectional narrowing transported. Alternatively or additionally, a shear flow can be impressed on the material at least temporarily before and / or during its shaping, preferably by transporting the material through at least one channel-like area (e.g. slot or nozzle) with high shear rate before and / or during its shaping , As a further alternative or in addition, a pressure flow with an increase in the fluid pressure in the pressure area can also be impressed on the material at least temporarily before and / or during its shaping, preferably by passing the material through at least one channel-like area before and / or during its shaping transported at least one cross-sectional expansion. Due to the expansion flow, shear flow or pressure flow, agglomerates such as, for example, agglomerated foreign bodies or agglomerated crystals can be deagglomerated or dendritic crystal structures can be detached from a wall. As a result, the particle sizes of the foreign bodies or the crystals are made more uniform and, at the same time, the total number of such particles in the fluid is increased. Stretching flows, shear flows or compression flows are preferably alternately impressed on the material in succession before and / or during its shaping, in particular by at least one cross-sectional constriction, by at least one region with a high shear gradient (gap) or by at least one region with cross-sectional expansion. This different "stressing" of the fluid means that various types of agglomerates in the fluid can also be largely de-agglomerated.

If the material is a multi-phase fluid with at least one compressible component, a compression flow or an expansion flow can be impressed on it, in which the compressible component is compressed or expanded.

In a further advantageous embodiment, the vibration excitation takes place in such a way that, at least in the region of the casting mold, an interference pattern with regions of vibration antinodes and regions of oscillation nodes is formed before and during solidification, the interference pattern preferably being three-dimensional over the entire volume of the casting mold. In this way, specific enrichment or depletion of certain particles in the areas of the antinodes can take place as long as the fluid has not yet solidified. For example, Crystallites of the fluid material or foreign particles in a metal or plastic melt or different metal atoms in an alloy are redistributed and enriched or depleted in particular in certain areas. As with composite materials, specific properties can be impressed on the casting ("quasi-composite material").

The interference pattern is preferably locally shifted and / or distorted before the fluid solidifies, for example by changing the relative phases of several vibration sources. This creates a blending effect. At least segregation is largely prevented. It is expedient to ensure that the interference pattern remains locally unchanged at least at the beginning and during the solidification. This at least prevents the structure of the solidifying fluid from weakening in an uncontrolled manner. A targeted weakening of the structure in However, certain areas of the casting can be deliberate and are made possible by this measure. Alternatively or additionally, the amplitude of the excitation vibrations of the several vibration sources can also be changed during the forming and / or solidification.

In a further advantageous embodiment of the method according to the invention, theological properties (flow and material properties) of the material are recorded in at least one detection area downstream of the excitation partial areas in which the material is vibrated. Preferably, a first detection of rheological properties of the material takes place in a first detection area upstream of the excitation partial areas and a second detection of rheological properties of the material takes place downstream of the excitation partial areas. This allows the results and thus the effectiveness of the vibration excitation to be assessed by comparing the theological properties before and after the vibration excitation in the excitation sections.

The rheological properties are preferably recorded non-intrusively, e.g. by first determining the fluid velocity profiles using an ultrasound Doppler method and additionally measuring the pressure difference in the area of the recorded velocity profile along the direction of flow or measuring the fluid wall shear stress with a suitable sensor. Important theological parameters such as e.g. determine the flow index in the power law model of the fluid or the yield point of the fluid. All these steps are expediently carried out during the shaping and / or solidification of the material.

Alternatively or additionally, the rheological properties of the material can be recorded offline using a capillary rheometer and / or using a rotary rheometer. This is a control for the in-line non-intrusive approach of the previous paragraph. The rheological properties of the material can also be recorded by recording the propagation properties (speed of sound, sound absorption) of mechanical waves (detection waves) in the material. In this way, for example, the crystallite concentration in the melt can be recorded.

It is expedient to use a different frequency or different frequencies for the mechanical waves to record the rheological properties than for the mechanical waves to excite vibrations in the partial excitation areas. This prevents confusion on the sensor (ultrasound receiver).

In exceptional cases, however, the mechanical waves (ultrasonic waves) for recording the rheological properties can have the same frequency or the same frequencies as the mechanical waves for vibration excitation in the excitation sub-areas. As a result, the outlay on equipment (number of ultrasound transmitters) can be kept low.

To determine the rheological properties of the material, the speed of propagation of the detection waves of a certain frequency can be measured. Inhomogeneities or property gradients in the material can be determined by detecting the reflection behavior and / or diffraction behavior of the detection waves. Inhomogeneities or property gradients in the material can also be determined by detecting the damping behavior of the detection waves. To measure the concentration of crystallites and or crystallization nuclei in the material, the ultrasound speed is measured in the material and the relationship with the ultrasound speed is used.

The localization of crystallization fronts in the solidifying material is particularly advantageously carried out by detecting the reflection behavior and / or diffraction behavior of the ultrasound waves in the material.

To determine the viscosity function (shear viscosity) of the material, a determination of the speed field transverse to the transport direction in a region of the material and a determination of the pressure difference along the transport direction of the Material carried out in the area and / or at the edge of the area of the material (combination of ultrasonic Doppler method and pressure difference measurement).

Alternatively, the determination of the viscosity function (shear viscosity) of the material can be carried out by determining the speed field transverse to the direction of transport in a region of the material and determining the shear stress along the direction of transport of the material in the region and / or at the edge of the region of the material.

In a further advantageous embodiment of the method according to the invention, at least one of the following measures or physical parameters are triggered, depending on the rheological properties of the fluid, at least in the excitation subregions:

1) vibration excitation;

2) seed crystallization;

3) delivery pressure difference;

4) absolute pressure;

5) temperature.

In a particularly preferred embodiment, the rheological properties of the material detected in the first detection area upstream of the excitation partial areas and the rheological properties of the material detected in the second detection area downstream of the excitation partial areas are compared with one another and / or with respective rheological reference properties, wherein depending on the result of the comparison or comparisons, feedback takes place within a control loop for controlling the vibration excitation in the excitation sub-areas.

According to the invention, the object of the invention is achieved in that the device having a heating unit, a molding unit, a casting unit and a metering unit is assigned at least in some areas to at least one unit for generating mechanical vibrations. The unit for generating mechanical vibrations preferably has a vibratable surface which is operatively connected to the crystallizable liquid or pasty material, in particular the vibratable surface of the vibration generating unit directly or indirectly adjacent to the crystallizable liquid or pasty material. The immediate bordering of the vibratable surface to the material allows vibrations to be introduced into the material in a locally defined and limited area of the material, while the indirect arrangement causes parts of the device to vibrate (structure-borne noise), so that usually one less Defined and less localized introduction of mechanical vibrations into the material.

In the device according to the invention, at least one unit for generating mechanical vibrations is expediently assigned to the heating unit or the casting unit or the molding unit or the metering unit.

A unit for introducing crystallization nuclei into the material can also be assigned to the device according to the invention, at least in some areas. This is particularly advantageous in the heating area and in the metering area of the device before the material reaches the casting area and the molding area of the device, in which high pressures occur.

Furthermore, the device according to the invention can have at least one cross-sectional constriction or cross-sectional widening along the flow direction of the material in its channel-like regions and / or have a slot or a nozzle. This enables the stretching, pressure or shear flow mentioned above to be generated in the material.

In a further embodiment, the at least one partial area of the device, but in particular the molding unit, can be assigned a plurality of units spaced apart from one another for generating mechanical vibrations. This allows, for example, the interference pattern or three-dimensional standing waves mentioned above in the mold cavity filled with material prior to solidification of the material.

The device according to the invention preferably also has a unit for recording rheological properties of the material contained in it in at least one of its partial areas. This enables monitoring and, if necessary, control and / or regulation of the rheological properties of the material during its processing in the device according to the invention.

It is particularly advantageous if at least one of the mold halves has ejection pins, at least one of which can be set into mechanical vibrations by an oscillation generation unit. Since the ejection pins are in contact with the melt anyway and in some cases even protrude into the melt and thus into the later solidified casting, a particularly good distribution of the mechanical vibration energy in the melt can be achieved.

In the device according to the invention, in particular in a die casting system, a sprue system is arranged between the shot unit and the mold cavity, with the sprue system being assigned at least one vibration generation unit, with which the melt can be conditioned shortly before entering the mold cavity.

Further advantages, features and possible uses of the invention result from the following description of an exemplary embodiment according to the invention, which is not to be understood as restrictive, with reference to a single figure.

In the figure, a cold chamber die casting machine is shown schematically as an illustrative example of a device according to the invention.

In a crucible 1 there is a crystallizable molten material, such as a light metal alloy, in particular an Al-Mg alloy. By means of electrical heating elements 2, which surround the crucible, it was brought into the liquid state and is kept in this state (tempered). The melting pot 1 and the electrical heating elements 2 together form the heating unit of the device according to the invention.

A cylindrical casting piston 3 is slidably mounted in a cylindrical casting chamber 4. Together 3, 4 they form the firing unit of the device according to the invention.

A first mold half 5 and a second mold half 6 lying against it together define a mold cavity 7. The two mold halves 5, 6 together form the mold unit of the device according to the invention.

A pneumatic pressure line 8 enables the supply of compressed air from a pneumatic pressure source 19 into the crucible chamber 10. A riser 9 for the molten material connects the contents of the crucible to the casting chamber 4. Depending on the magnitude of the pressure applied via the pneumatic pressure line 8, more or less much molten material is conveyed into the casting chamber 4. The pneumatic pressure line 8, the pneumatic pressure source 19, the riser 9 and the crucible chamber 10 together form the dosing unit of the device according to the invention.

The first mold half 5 is connected to a movable platen 13, while the second mold half 6 is connected to a fixed platen 14. A release agent spray element 12 is located above the mold unit formed by the two mold halves 5, 6.

The casting piston 3 of the firing unit is connected via a linkage 18 to a hydraulic piston 15 which is slidably mounted in a hydraulic cylinder 16. A hydraulic pressure line 17 connects the hydraulic cylinder 16 to a hydraulic pressure source 11.

The cold chamber die casting machine has a plurality of vibration generating units S1-S11, which are referred to in the following as "unit". Such a unit can, for example, be a piezoelectric element for generating mechanical ones Vibrations in the ultrasonic range. Depending on the needs, large or selective units can be used.

The units S1 and S2 are connected to the top and bottom of the movable first mold half 5. Similarly, the units S3 and S4 are connected to the top and bottom of the fixed second mold half 6, respectively. The unit S5 is assigned to the casting chamber 4, while the unit S6 is assigned to the riser 9. The unit S7 is connected to the crucible chamber 10, and the unit S8 is connected to the hydraulic pressure line 17. In contrast to the units S1-S8, the temperature and pressure-resistant units S9 and S10 are in direct contact with the molten material in the mold cavity 7. Alternatively, the units S5, S6 and S7 can also be designed so that they are in direct contact with the melt.

Similar to the unit S10, the unit S9 can also be arranged directly adjacent to the melt. The ejector pins (not shown) on the movable mold half 5 are preferably used for this purpose. In addition, vibration generating units (not shown) can also be used on the fixed mold half 6, e.g. also in connection with ejector pins (not shown).

At least one unit S11 is also assigned to the sprue system 20 connecting the casting chamber 4 to the mold cavity 7. The melt can thus be conditioned shortly before it enters the mold cavity 7. In the case of a multichannel sprue system consisting of several parallel channels, a total of several separate units can be arranged between the individual channels. In particular, e.g. such a unit can be assigned to each channel.

The cold chamber die casting machine shown is operated cyclically.

First, the two mold halves 5, 6 are in a spaced apart position (not shown), so that the mold cavity 7 is open to the outside and a previously cast object could be removed from the molding unit 5, 6 after it has solidified. The casting piston 3 and the hydraulic piston 15 are located in its rightmost position (not shown). In this open position (not shown), the inner surfaces of the mold cavity 7 are sprayed with release agent by the release agent spray element 12.

In order to cast another object, the two mold halves 5, 6 are brought together by moving the movable platen 13 to the right, so that the mold cavity 7 is closed (except for a degassing opening, not shown). A metered amount of the molten material is then conveyed from the crucible 1 via the riser 9 into the casting chamber 4 by increasing the gas pressure above the liquid surface in the crucible 1 via the pneumatic pressure line 8 for a certain period of time.

As soon as the casting chamber 4 has reached a certain filling level, the hydraulic pressure source 11 is activated in order to exert a hydraulic pressure on the hydraulic piston 15, which then moves from right to left. Via the linkage 18 and the casting piston 3, the melt previously metered into the casting chamber 4 is thus "shot" from the casting chamber 4 into the mold cavity 7, in which it is held until it solidifies for a certain period of time before the molding unit 5, 6 again opened and the cast finished object is removed.

The casting cycle is now repeated for casting another object.

The equipment according to the invention of the cold chamber die casting machine with the vibration generating units S1 - S11 enables the crystallizable molten material to be influenced in different areas of the die casting machine:

With units S1, S2, S3, S4 and especially with unit S9 and possibly also with unit S10, for example, the crystallization behavior of the melt in the mold cavity 7 can be influenced by suitable oscillation frequencies during its cooling. In this way, the microscopic structure and thus the material properties of the casting can be influenced. With units S5, S6 and S10, for example, the flow properties of the melt in the casting chamber 4 or in the riser 9 can be specifically influenced, on the one hand, by influencing the rheological properties of the melt flowing past the vibrating units S5 and S6, and on the other hand, the wall friction between the flowing melt and the vibrating inner wall.

The vibrations originating from the unit S7 and transmitted to the melt via the crucible chamber 10 and the crucible 1 are suitable e.g. to influence the crystallization in the melt. In particular in connection with the addition of seed crystals in the melt, a targeted influencing of the melt can be achieved which is coordinated with the action generated by the units S1-S5.

The unit S8 enables e.g. the superimposition of a high-frequency ultrasonic vibration and its correspondingly high-frequency pressure fluctuations on the one hand with the pressure increase built up by the hydraulic pressure source 11 for the "shot" of the melt from the casting chamber 4 into the mold cavity 7. This, in particular in coordination with the time (not shown) Degassing the mold cavity 7 filling with melt and supported by the action of the units S1, S2, S3, S4 and S9, also improves the penetration of the melt into filigree areas of the mold cavity 7, thereby improving the die casting result achieved or the same result with less Pressure expenditure can be achieved by the hydraulic pressure source 11.

The unit S10 is arranged on the surface of the casting piston 3 facing the molten material in the casting chamber 4 and enables the melt to be conditioned in interaction with the unit S5.

The unit S11 is arranged in the region of the sprue system 20 and also enables the melt to be conditioned shortly before it enters the mold cavity 7.

Due to the large number of vibration generating units S1 - S11 used in different areas of the device according to the invention, this can be processed. material depending on the area in which it is located, with different frequencies and / or amplitudes and each with different spatial distribution of the vibration excitation (selective, large area).

reference numeral

1 crucible

2 electric heating elements

3 casting pistons

4 casting chamber

5 first mold half (movable)

6 second mold half (fixed)

7 mold cavity

8 pneumatic pressure lines

9 riser

10 crucible chamber

1 1 hydraulic pressure source

12 release agent spray element

13 movable platen

14 fixed platen

15 hydraulic pistons

16 hydraulic cylinders

17 hydraulic pressure line

18 rods

19 pneumatic pressure source

20 sprue system

S1-S11 vibration generating unit

Claims

claims

1. A method for shaping a crystallizable material in the liquid or pasty state, which is allowed to solidify after the shaping and shaping, characterized in that the material is excited to vibrate at least in some areas before and / or during the shaping and / or solidification.

2. The method according to claim 1, characterized in that the vibration excitation takes place in a heating or tempering area.

3. The method according to claim 1 or 2, characterized in that the vibration excitation takes place in a degassing area.

4. The method according to any one of claims 1 to 3, characterized in that the vibration excitation takes place in a filtering area.

5. The method according to any one of claims 1 to 4, characterized in that the material is a molten metal, in particular a melt containing at least aluminum or magnesium, which was produced in a melting furnace area.

6. The method according to any one of claims 1 to 4, characterized in that the material is a polymer melt, in particular a melt comprising PET, which was melted in an extruder section.

7. The method according to any one of claims 1 to 6, characterized in that the shaping takes place in a casting mold.

8. The method according to any one of claims 1 to 7, characterized in that the liquid or pasty material additionally contains particles and / or bubbles.

9. The method according to any one of claims 1 to 8, characterized in that the vibration is excited by at least one vibration source for mechanical vibrations.

10. The method according to any one of claims 1 to 9, characterized in that the vibration excitation takes place over a large area via at least one large-area element coupled to the vibration source.

11. The method according to claim 10, characterized in that the vibration source is a casting system inner wall with periodically structured, e.g. corrugated, corrugated or ribbed surface from which pulsations propagate into the fluid as the fluid flows along it.

12. The method according to claim 10 or 11, characterized in that the vibration source is a casting system inner wall with formations on which hydrodynamic instabilities, such as. cyclical stalls or cyclical vortex stalls of the fluid are used, from which cyclic pulsations spread into the fluid.

13. The method according to claim 12, characterized in that the large-area element is an inner surface (interface) of a plant or machine part bordering on the material to be formed.

14. The method according to claim 13, characterized in that the vibration excitation takes place such that the vibration of the inner surface has at least one component tangential to the interface.

15. The method according to claim 13 or 14, characterized in that the vibration excitation takes place in such a way that the vibration of the inner surface has at least one component normal to the interface.

16. The method according to any one of claims 13 to 15, characterized in that the vibration excitation takes place in such a way that surface waves are formed at the interface.

17. The method according to any one of claims 13 to 16, characterized in that the interface contacting the material to be formed is the inner wall of a transport channel for the material.

18. The method according to any one of claims 1 to 9, characterized in that the vibration excitation is carried out selectively via at least one punctiform element coupled to the at least one vibration source.

19. The method according to any one of claims 1 to 18, characterized in that the vibration excitation takes place at predetermined frequencies or in predetermined frequency ranges.

20. The method according to any one of claims 1 to 19, characterized in that the vibration excitation takes place with predetermined amplitudes or in predetermined amplitude ranges.

21. The method according to any one of claims 1 to 20, characterized in that the vibration excitation takes place by at least one impact pulse acting on the material.

22. The method according to claim 21, characterized in that the oscillation is excited by a plurality of successive impact pulses.

23. The method according to any one of claims 1 to 22, characterized in that the vibration excitation takes place pulsating.

24. The method according to claim 23, characterized in that the shaping takes place in a pulsating manner, the pulsation of the oscillation excitation being related to the pulsation of the shaping.

25. The method according to claim 24, characterized in that the pulsation of the forming and the pulsation of the vibration excitation run synchronously.

26. The method according to any one of claims 23 to 25, characterized in that the pulsation is a pulsating frequency modulation of the excitation frequency.

27. The method according to any one of claims 23 to 26, characterized in that the pulsation is a pulsating amplitude modulation of the excitation amplitude.

28. The method according to any one of claims 1 to 27, characterized in that the vibration excitation is different depending on the method step or system section.

29. The method according to any one of the preceding claims, characterized in that the material is inoculated with crystallization nuclei at least in some areas during the forming and / or solidification.

30. The method according to claim 29, characterized in that the nuclei have crystallites of the material to be formed.

31. The method according to claim 29, characterized in that the crystallization nuclei have particles of a different material from the material to be formed.

32. The method according to any one of the preceding claims, characterized in that a combination of high temperature gradients and high shear gradients in the material is used to produce the crystallites.

33. The method according to any one of the preceding claims, characterized in that the melt foreign particles, in particular fibers such as Carbon fibers, possibly with a modified surface, or nanoparticles can be added.

34. The method according to any one of claims 27 to 31, characterized in that the crystallization nuclei contain encapsulated crystallites or crystallite agglomerates.

35. The method according to claim 34, characterized in that the encapsulation consists of a substance which dissolves in the crystallizable liquid or pasty material during the shaping and / or solidification, so that the crystallites or the crystallite agglomerates in the material to be reformed exposed and contribute to the crystallization of the material when it solidifies.

36. The method according to any one of claims 33 to 35, characterized in that the volume fraction of foreign particles is in the range from about 0.01% to about 80%.

37. The method according to any one of the preceding claims, characterized in that an expansion flow is at least temporarily impressed on the material before and / or during its shaping.

38. The method according to claim 37, characterized in that the expansion flow is impressed by transporting the material before and / or during its shaping through at least one channel-like region with at least one cross-sectional constriction.

39. The method according to any one of the preceding claims, characterized in that a shear flow is at least temporarily impressed on the material before and / or during its shaping.

40. The method according to claim 39, characterized in that the shear flow is impressed by transporting the material before and / or during its shaping through at least one channel-like region (e.g. slot or nozzle) with a high shear gradient.

41. The method according to any one of the preceding claims, characterized in that a pressure flow is at least temporarily impressed on the material before and / or during its shaping.

42. The method according to claim 41, characterized in that the pressure flow is impressed by transporting the material before and / or during its shaping through at least one channel-like region with at least one cross-sectional expansion.

43. The method according to any one of the preceding claims, characterized in that the material before and / or during its reshaping alternately expansion flows, shear flows or pressure flows, in particular by at least one cross-sectional constriction, by at least one area with high shear rate (gap) or by at least an area with cross-sectional expansion.

44. The method according to any one of claims 7 to 43, characterized in that the vibration excitation takes place in such a way that, at least in the region of the casting mold, an interference pattern with regions of the antinode and regions of the nodes of oscillation arises before and during solidification.

45. The method according to claim 44, characterized in that the interference pattern is formed three-dimensionally over the entire volume of the casting mold.

46. The method according to claim 44 or 45, characterized in that the interference pattern is locally shifted and / or distorted, for example by changing the relative phases of several vibration sources.

47. The method according to any one of claims 44 to 46, characterized in that the interference pattern remains locally unchanged at least at the beginning and during the solidification.

48. The method according to any one of claims 44 to 47, characterized in that the amplitude of the excitation vibrations of the plurality of vibration sources is changed during the forming and / or solidification.

49. The method as claimed in one of claims 1 to 48, characterized in that rheological properties (flow and material properties) of the material are detected at least one detection area downstream of the excitation subregions in which the material is vibrated.

50. The method according to claim 49, characterized in that a first detection of rheological properties of the material takes place in a first detection area upstream of the excitation partial areas and a second detection of rheological properties of the material takes place downstream of the excitation partial areas.

51. The method according to any one of claims 1 to 50, characterized in that during the forming and / or solidification of the material, its rheological properties are recorded.

52. The method according to any one of claims 49 to 51, characterized in that the rheological properties of the material are recorded by means of a capillary rheometer and / or by means of a rotary rheometer.

53. The method according to any one of claims 49 to 52, characterized in that the rheological properties of the material are detected by detecting the propagation properties of mechanical waves (detection waves) in the material.

54. The method according to claim 53, characterized in that the mechanical waves for detecting the rheological properties have a different frequency or frequencies than the mechanical waves for vibration excitation in the excitation sub-areas.

55. The method according to claim 53, characterized in that the mechanical waves for detecting the rheological properties have the same frequency or the same frequencies as the mechanical waves for vibration excitation in the excitation sub-areas.

56. The method according to any one of claims 53 to 55, characterized in that the mechanical detection waves are ultrasonic waves.

57. The method according to any one of claims 53 to 56, characterized in that the rate of propagation of the detection waves of a certain frequency is measured to determine rheological properties of the material.

58. Method according to one of claims 53 to 57, characterized in that inhomogeneities or property gradients in the material are determined by detecting the reflection behavior and / or diffraction behavior of the detection waves.

59. The method according to any one of claims 53 to 58, characterized in that inhomogeneities or property gradients in the material are determined by detecting the damping behavior of the detection waves.

60. The method according to any one of claims 53 to 59, characterized in that the concentration of crystallites and or crystallization nuclei in the material is carried out by measuring the ultrasonic speed in the material.

61. The method according to any one of claims 53 to 60, characterized in that the localization of crystallization fronts in the material by detecting the Reflection behavior and / or diffraction behavior of the ultrasonic waves takes place in the material.

62. The method according to any one of claims 49 to 61, characterized in that for determining the viscosity of the material, a determination of the speed field transverse to the direction of transport in a region of the material and a determination of the pressure difference along the direction of transport of the material in the region and / or on Edge of the area of the material to be performed

63. The method according to any one of claims 49 to 61, characterized in that for determining the viscosity of the material, a determination of the speed field transverse to the transport direction in a region of the material and a determination of the shear stress along the transport direction of the material in the region and / or on Edge of the area of the material to be performed.

64. The method according to any one of claims 49 to 63, characterized in that, depending on the rheological properties detected, the vibration excitation is activated at least in the excitation subregions.

65. The method according to any one of claims 49 to 64, characterized in that, depending on the rheological properties detected, the seed crystallization is controlled at least in the excitation subregions.

66. The method according to any one of claims 49 to 65, characterized in that, depending on the rheological properties detected, the delivery pressure difference is controlled at least in the excitation subregions.

67. The method as claimed in one of claims 49 to 66, characterized in that, depending on the rheological properties detected, the absolute pressure is controlled at least in the excitation subregions.

68. Method according to one of claims 49 to 67, characterized in that the temperature in the excitation subregions is controlled as a function of the recorded rheological properties.

69. The method according to any one of claims 64 to 68, characterized in that the rheological properties of the material detected in the first detection area upstream from the excitation partial areas and the rheological properties of the material detected in the second detection area downstream from the excitation partial areas and / or can be compared with respective rheological reference properties, depending on the result of the comparison or the comparisons, a feedback takes place within a control loop for controlling the vibration excitation in the excitation partial areas.

70. Device for carrying out the method according to one of claims 1 to 69, which comprises:

> a heating unit (1, 2) for heating crystallizable material in order to bring it into a liquid or pasty state;

> a mold unit (5, 6) which defines a mold cavity (7);

> a shot unit (3, 4) with which the material is pressed under pressure into the molding unit (5, 6);

> A metering unit (8, 9, 10, 19) for metered feeding of the material in the liquid or pasty state from the heating unit (1, 2) into a casting unit (3, 4), characterized in that the device, at least in some areas, has at least one Unit (S1 - S11) is assigned to the generation of mechanical vibrations.

71. Device according to claim 70, characterized in that the at least one unit (S1 - S11) for generating mechanical vibrations has a vibratable surface which is in operative connection with the crystallizable liquid or pasty material.

72. Device according to claim 71, characterized in that the vibratable surface of the vibration generating unit (S5, S6, S7, S9, S10, S11) is directly adjacent to the crystallizable liquid or pasty material.

73. Apparatus according to claim 71, characterized in that the vibratable surface of the vibration generating unit (S1, S2, S3, S4, S8) is indirectly adjacent to the crystallizable liquid or pasty material.

74. Device according to one of claims 70 to 72, characterized in that at least the heating unit (1, 2) or the firing unit (3, 4) or the molding unit (5, 6) or the metering unit (7, 8) has a unit ( S1 - S11) is assigned to generate mechanical vibrations.

75. Device according to one of claims 70 to 74, characterized in that the device is assigned a unit for introducing crystallization nuclei into the material at least in partial areas.

76. Device according to one of claims 70 to 75, characterized in that it has in its channel-like regions at least a cross-sectional constriction or a cross-sectional widening along the flow direction of the material or that it has a slot or a nozzle.

77. Device according to one of claims 70 to 76, characterized in that the at least one partial area of the device is assigned a plurality of units spaced apart from one another for generating mechanical vibrations.

78. Device according to one of claims 70 to 77, characterized in that it has a unit for recording rheological properties of the material in it in at least one of its partial areas.

79. Device according to one of claims 70 to 78, characterized in that at least one of the mold halves (5, 6) has ejection pins, of which min. at least one can be set into mechanical vibrations by a vibration generation unit.

Device according to one of Claims 70 to 79, in which a sprue system (20) is arranged between the shot unit (3, 4) and the mold cavity (7), characterized in that at least one vibration generation unit (S11) is associated with the sprue system (20) ,