Die casting method and systems for agitating molten metal

Abstract

The disclosure inter alia relates to a die casting method comprising: providing molten metal into a dosing container (120) of a die casting system (100) and collecting the molten metal in the dosing container (120); agitating the molten metal within the dosing container (120); and transferring the molten metal from the dosing container (120) into a die casting machine (110) of the die casting system (100). The disclosure further relates to a die casting control system (120, 140) and a die casting system (100).

Description

FIELD OF THE INVENTION

[0001] The present disclosure relates to die casting of metal components.BACKGROUND OF THE INVENTION

[0002] Die casting systems have been used for the fabrication of structural metal components for many years. A constant effort is being made to improve mechanical properties of the resulting components by improving alloy compositions and treatment, conditions. For instance, improved mechanical properties may be achieved with the addition of Sr or Na, Sb (eutectic modifiers) or the use of grain refining fluxes. However, considering the costs, the recyclability and the environmental sustainability, such approaches may not always be possible or desired.

[0003] In view of the above, the approaches of the present disclosure may allow for a sufficient grain refinement and desired mechanical properties of cast metal components. In particular, the approaches of the present disclosure may allow for such improved mechanical properties of cast metal components without the use of (environmentally non friendly) grain refining fluxes and / or the addition of eutectic modifiers.

[0004] According to a first aspect of the present disclosure, a die casting method is disclosed. The method may comprise providing molten metal into a dosing container of a die casting system and collecting the molten metal in the dosing container. The method may further comprise agitating the molten metal within the dosing container. The method may further comprise dosing the molten metal from the dosing container into a die casting machine of the die casting system.

[0005] According to a second aspect of the present disclosure, a die casting control system is disclosed. The control system may comprise a dosing container for collecting molten metal and for dosing the molten metal into the die casting machine. The system may further comprise exciter means configured to agitate the molten metal within the dosing container.

[0006] According to a third aspect a die casting system is disclosed. The die casting system may comprise a die casting control system of the second aspect and a die casting machine. The die casting system may in particular be configured for performing the die casting method of the first aspect.

[0007] The die casting may in particular be a high pressure die casting (HPDC) or a vacuum assisted high pressure die casting. The die casting may in particular be an aluminum die casting. Thus, the molten metal may in particular be molten aluminum. The molten metal may in particular be any suitable aluminum die cast alloy. The die casting machine may for instance comprise a mold cavity, such as a first (e.g. movable) die and a second (e.g. fixed) die. The die casting machine may comprise means for forcing molten metal under pressure into the mold cavity. For instance, the casting machine may comprise a filling chamber. For instance, the die casting machine may comprise a hot-chamber or cold-chamber.

[0008] A dosing container may in particular be a vacuum dosing container. Accordingly, the dosing container may collect the molten metal by sucking the molten metal into the dosing container. The dosing container may be an essentially closed container. The dosing container may be a ceramic container, which has the advantage of withstanding the temperatures of molten metal such as aluminum. Moreover, a closed and / or ceramic dosing container may allow a transfer of melt with only a low drop of temperature during the transfer. The dosing container may be a dosing unit of a dosing system. As will be describe in more detail below, the dosing container may be used with a melting or holding furnace for providing the molten metal to be collected in the dosing container. The dosing container may enable safe outtake and precise dosing of the metal melt into the die casting machine (e.g. a filling chamber of a cold chamber die-casting machine). The dosing container may be movable between a first or intake position (e.g. at the melting or holding furnace) and a second or dosing position (e.g. in order to precisely dose the molten metal into the die casting machine). In an example, the mechanical movement of the dosing container may be realized with a servo-controlled lifting device or swiveling device.

[0009] An agitation of the molten metal may in particular be understood to be an induction of mechanical vibrations into the molten metal. As will be described in more detail below, the molten metal may be agitated by inducing a certain (low) frequency (e.g. a frequency below 100 Hz). For instance, exciter means, which will be described in more detail below as well, may be used for inducing vibrations into the dosing container and thereby agitating the molten metal within the dosing container. That is, the molten metal is agitated indirectly by the exciter means by agitating the dosing container with the exciter means and thereby agitating the molten metal within the dosing container.

[0010] After (or during) agitation of the molten metal in the dosing container, the molten metal is dosed into the die casting machine. For instance, the molten metal may be dosed into a filling chamber of the casting machine. For instance, the molten metal may be dosed into a hot-chamber or cold-chamber of the die casting machine. The molten metal may be dosed into the die casting machine by gravity, e.g. by pouring.

[0011] Microstructural studies have surprisingly shown that a (mechanical) agitation of the molten metal in the dosing container has a positive effect on the grain refinement and thus the mechanical properties of the cast component. As a result, cast components with higher quality can be provided. The agitation or excitation of the molten metal in the dosing container allows the agitation or excitation to take place shortly or directly before the actual casting process in the casting machine. This is in contrast to other approaches where an agitation of the molten metal takes place during the cleaning of the melt, for instance. The agitation of a smaller volume and shortly before the actual casting has been found to have an especially advantageous effect on the grain refinement and mechanical properties of the cast part. In particular, it has been found that the agitation of the molten metal in the dosing container has an advantageous effect on properties such as the tensile strength R m , the yield strength or elastic limit R p0.2 or the elongation At.

[0012] It has been found that advantageous mechanical properties may be achieved even without the addition of modifiers and / or the use of grain refining fluxes. The molten metal may be an aluminum die cast alloy free of modifiers. The aluminum die cast alloy may be free of grain refining fluxes.

[0013] Moreover, it has been found that the dosing accuracy is not negatively affected by the agitation of the molten metal in the dosing container.

[0014] In an example, the molten metal is agitated, while the molten metal is being filled into the dosing container, transferred from a furnace to the die casting machine and / or dosed from the dosing container into the die casting machine (e.g. into a filling chamber or shot sleeve). Accordingly, in an example, the exciter means are arranged such that the molten metal can be agitated while the molten metal is being filled into the dosing container transferred from a furnace to the die casting machine and / or dosed from the dosing container into the die casting machine. In other words, the exciter means may in particular be arranged such that they are able to agitate the dosing container and thereby the molten metal when the dosing container is in an intake position, in which the molten metal is provided or filled into the dosing container. Thus, the time used for filling the dosing container is advantageously used for also performing the agitation of the molten metal within the dosing container with the exciter means. Thus, no or only minimal additional time compared to the time necessary anyways for filling the dosing container is required. In an example, the molten metal is only or exclusively agitated, while the molten metal is being filled into the dosing container, so that no additional time would be required for agitating the molten metal as the whole process of agitation can take place during the process of collecting the molten metal in the dosing container.

[0015] The time of agitation may be less than 1 minute, preferably, less than 40 seconds, more preferably less than 20 seconds. For instance, the metal take-in time into the dosing container and thus the excitation time may be less than 20 seconds (such as 18 seconds).

[0016] In an example, the dosing container is a vacuum dosing container. The molten metal may be provided into the dosing container by sucking the molten metal into the dosing container. Accordingly, the vacuum dosing container may be configured to suck the molten metal into the dosing container. In an example, the dosing container may be part of a dosing system comprising an evacuation device for sucking in the melt. A closure may be provided at the opening of the container. A vacuum dosing container has the advantage of having a degassing effect and reducing the amounts of oxides created. Also, air admission may be avoided during the transfer or dosing of the molten metal again significantly reducing the amount of oxides.

[0017] In an example die casting system, the exciter means are configured to induce vibrations into the dosing container and thereby into the molten metal within the dosing container. Accordingly, in an example die casting method, the molten metal is agitated with exciter means inducing vibrations into the dosing container and thereby into the molten metal within the dosing container. This allows the to agitate the molten metal in a simple manner. In particular, it is also possible to easily retrofit existing casting systems already having a dosing container with exciter means configured for agitating the molten metal by inducing vibrations into the dosing container.

[0018] In an example the exciter means comprise an exciter and a tapping element. The exciter may be configured to periodically push the tapping element against the dosing container to induce the vibrations into the dosing container and the molten metal within the dosing container. Accordingly, in an example method, the molten metal is agitated within the dosing container by the exciter periodically pushing the tapping element against the dosing container to induce the vibrations into the dosing container and the molten metal within the dosing container. The exciter may be configured to provide vibrations in particular in a frequency range as discussed further below. For instance, the exciter may generate a sinusoidal movement or force. The sinusoidal movement or force is then transferred to the dosing container via the tapping element. The force may be at least 50N, preferably at least 75N. It may be sufficient to apply a force of at most 200N, preferably at most 150N. The amplitude or peak to peak displacement generated by the exciter (and thus the tapping element) may be at least 1mm and / or at most 5mm . It may be preferred to generate an amplitude or peak to peak displacement of between 2mm - 3mm. For instance, the amplitude or peak to peak displacement may be between around 2mm, 2.5mm or 3mm. Alternatively, it may also be possible that the exciter generates a random force or displacement.

[0019] The tapping element may for instance be a rod or a bar. The tapping element may allow the exciter to be positioned sufficiently far away (such as at least 50 cm, at least 100 cm or at least 200 cm) from the dosing container e.g. so as to not take any damage from the heat. Nevertheless, a protective shielding may also be provided, which comprises a cut-out for the tapping element to reach trough so that the exciter can be provide behind said shielding.

[0020] The exciter means may comprise further components such as an amplifier, a voltage output module and / or a computer for driving the exciter.

[0021] In an example, the exciter means may comprise a feedback system for measuring the agitation of the dosing container. The feedback system may comprise a sensor arranged at the dosing container for measuring a quantity representative of the vibrations produced by the exciter and induced into the dosing container. The sensor may for instance be an accelerometer for measuring the acceleration of the dosing container. The feedback system may further comprise a signal conditioner, a voltage input module and / or a computer for receiving measurements from the sensor. The feedback system may allow to reliably adjust the exciter to provide the desire frequency to the dosing container and thus to the molten metal.

[0022] In an example, the molten metal is agitated within the dosing container (or the exciter means are configured to agitate the molten metal) with a frequency below 20kHz, preferably below 10kHz, further preferably, below 1kHz, even further preferably below 100 Hz and / or with a frequency above 5Hz, preferably above 10 Hz, further preferably above 15Hz. In an example, the molten metal is agitated with a frequency below 100 Hz, preferably in a frequency range of 5-50 Hz, further preferably in a frequency range of 10-30 Hz, further preferably in a frequency range of 15-25 Hz. The exciter means may in particular be configured to agitate the molten metal at a frequency around 20 Hz. As already mentioned, the frequency in particular refers to a sinusoidal frequency or agitation. It has been found that such frequencies are particularly advantageous to achieve a grain refinement, a more homogenous structure and thus improved mechanical properties.

[0023] In an example, the molten metal is provided into the dosing container from a melting or holding furnace. Alternatively, the molten metal is provided into the dosing container from ladle or transport ladle 8 (e.g. the holding furnace may be skipped). Accordingly, the die casting system may further comprise a melting or holding furnace, wherein dosing container is configured for collecting the molten metal from the melting or holding furnace. As already mentioned, the molten metal may be provided into the dosing container by sucking the molten metal into the dosing container. Generally, the melting or holding furnace may also be a part of a dosing system comprising the dosing container and the melting or holding furnace.

[0024] In an example system, the die casting machine may further comprise a filling chamber and the dosing container may be configured to dose the molten metal into the filling chamber. Accordingly, in an example method, the molten metal may be dosed from the dosing container into a filling chamber of the die casting machine of the die casting system. The molten metal may then be injected into the die, for instance as part of a high pressure die casting process.

[0025] The cast component may then solidify and ejected from the casting machine. The cast component may in particular be an engine block or a cylinder head such as a liner less cylinder head. The cast component may in particular have a tensile strength R m , of at least 200 MPa, preferably at least 220, a yield strength or elastic limit R p0.2 of at least 150 MPa, preferably at least 155 MPa and / or an elongation At of at least 1.2, preferably at least 1.4.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Examples of the invention will now be described in detail with reference to the accompanying drawings, in which: Fig. 1a, 1bshows an example of a die casting system for performing an exemplary die casting method according to the disclosed aspects; Fig. 2shows a flow chart of an exemplary method according to the disclosure; Fig. 3shows exemplary exciter means of a die casting control system; Fig. 4shows a diagram illustrating the advantageous effect of the disclosure on the tensile strength R m ; and Fig. 5shows a diagram illustrating the advantageous effect of the disclosure on the elongation A 5,65 . DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] Figs. 1a, 1b show an exemplary aluminum high pressure die casting system 100 comprising a die casting control system 120, 140 and a casting machine 110 with two die halves 111, 112. The casting machine further comprises a filling chamber 113 (e.g. a shot sleeve) for introducing molten metal (aluminum in this example) into the die. The system further comprises a dosing container 120 for collecting molten metal and for dosing the molten metal into the die casting machine 110 by the die casting control system 120, 140. The molten metal may be provided by a melting or holding furnace 130. The die casting system 100 further comprises exciter means 140 having an exciter 141 and a tapping rod 142. However, other exciter means and tapping elements may be conceivable. Further components of the die casting control system and the exciter means will be described further below with reference to Fig. 3.

[0028] In Fig. 1a, the dosing container 120 is positioned in a first filling or intake position at the melting or holding furnace 130. In this example, the dosing container 120 is a vacuum dosing container configured to suck the molten metal into the dosing container (see also step 210 of flow chart 200 in Fig. 2). The exciter means 140, i.e. the exciter 141 and the tapping rod 142 are arranged such that the molten metal can be agitated while the molten metal is being filled into the dosing container 120. More specifically, the exciter 141 is configured to periodically push the tapping rod 142 against the dosing container 120 to induce the vibrations into the dosing container 120 and thereby into the molten metal within the dosing container (see also step 220 of flow chart 200 in Fig. 2).

[0029] The exciter means are configured to agitate the molten metal within the dosing container with a low frequencies, i.e. in particular with frequencies below 100 Hz. It has been found that the excitation frequency is preferably in the range of 5-50 Hz, and in particular in the frequency range of 10-30 Hz. In the present example a sinusoidal tapping frequency of around 20 Hz is used.

[0030] As illustrated in Fig. 1b, the dosing container 120 can be moved into a second dosing position for dosing the molten metal to the die casting machine 110, i.e. in particular the filling chamber 113 (such as a shot sleeve) of the die casting machine 110 (see also step 230 of flow chart 200 of Fig. 2). A cast component (not illustrated), such as an engine block, a cylinder head or a cylinder head gasket, can then then be cast.

[0031] In an example, an engine block is cast. The excitation of the molten aluminum during the metal intake time into the dosing container 120 is around 18 seconds. Different frequencies such as 10 Hz, 20 Hz and 30 Hz have been used for the exciter 141. The following table shows on the one hand the mechanical properties of an aluminum engine block, which has been cast from molten aluminium agitated in the dosing container with a frequency of 20 Hz during the metal take in time of around 18 seconds (samples 20-1A, 20-2A, 20-3A and samples 20-1, 20-2, 20-3). On the other hand, the table further shows the mechanical properties of comparative aluminum engine block samples (samples III-1A, III-2A, III-3A and III-1, III-2, III-3), for which no metal excitation has been performed in the dosing container but otherwise cast with the same alloy and under the same conditions compared to the respective samples for which a 20 Hz excitation was performed. SampleL 0 [mm]E [GPa]R p0.2 [Mpa]R m [Mpa]A 5,65 [%]A t [%]min. 150min. 20020Hz20-1A3062.7164.35227.041.181.3420-2A3062.0155.93228.741.421.5720-3A3063.6153.38233.051.491.65Standard BlockIII-1A3055.5159.46219.141.241.39III-2A3069.7< 144.33214.721.291.43III-3A3069.3< 135.99220.321.601.7420 Hz20-13064.8166.11227.291.121.2720-23063.5158.37224.531.251.4020-33075.9< 145.62232.821.611.75Standard BlockIII -< 13065.3158.34222.161.211.35III-23065.9< 145.23< 192.380.961.08III-33065.9< 141.92< 193.720.971.09

[0032] Generally, the feasibility of the metal excitation in the dosing container under the serial production conditions could be confirmed. Furthermore, it has been found that the metal excitation did not influence the dosing time and dosing accuracy, i.e. the metal excitation time is equal to the (unchanged) metal take-in time. In the above table, the entries of the samples marked with "<" do not fulfill the desired minimum elastic limit R p0.2 and the desired minimum tensile strength R m . As becomes apparent from the above table, the desired minimum elastic limit R p0.2 of 150 Mpa and the desired minimum tensile strength R m of 200 Mpa could be achieved in nearly every sample of the cast parts for which a metal excitation has been performed (i.e. 5 out of 6 samples fulfill the desired minimum properties), while for various of the comparative examples these minimum requirements could not be achieved (4 out of 6 samples do not fulfill the desired minimum properties). Generally, the above results show that the metal excitation in the dosing container allows for an improved elastic limit R p0.2 , which is increased by around 10 Mpa, an improved tensile strength R m , which is increased by around 18 Mpa and an improved elongation At which is increased by around 0.15%.

[0033] In the following further exemplary components of the exciter means 140 will be described in more detail with reference to Fig. 3. Apart from the exciter means, the dosing container 120 is also again shown in Fig. 3. The exciter means comprise the exciter 141 and the tapping rod 142 already shown in Fig. 1a, 1b. The exciter is in this example a TIRA vib S52110. The exciter is connected a power amplifier 143, in this case a TIRA BAA 120. A computer 145 with a program for generating a sinusoidal signal of different frequencies communicates with the power amplifier 143 using a voltage output module 144.

[0034] The exciter used in the example (SS2110) is an electrodynamic transducer with a wide frequency range capable of generating a sinusoidal force of 100N. The device operates in the frequency range from 2 to 7000Hz, is powered by a sine or random signal, and driven by an amplifier with an output power of 120VA. However, as illustrated above, specifically low frequencies, e.g. below 100 Hz, such as 10, 20 or 30 Hz have been shown to be advantageous for the metal excitation in the dosing container. The exciter is constructed of a self-supporting permanent magnet excited frame with a coil inside. The exciter is rotatable and can be positioned both vertically and horizontally using a turnbuckle.

[0035] In the example shown in Fig. 3, the exciter means 140 of die casting control system further comprise a feedback system comprising a voltage input module 146, a signal conditioner 147 and a sensor 148 (in this case an accelerometer). The accelerometer 148 measures the acceleration generated by the vibrations produced by the exciter 141 and transferred to the dosing container 120. The signal from the sensor 148 is processed by the signal conditioner 147 and then transferred to the computer 145 via the voltage input module 146. The feedback signal may be used by the computer 145 to monitor and / or adjust the signal driving the exciter 141 so as to make sure that the dosing container (and thus the metal melt therein) is agitated with the desired frequency.

[0036] Fig. 4 shows a diagram 400 illustrating experimental results of the advantageous effect of the disclosure on the tensile strength R m . More specifically, Fig. 4 illustrates different excitation frequencies (no excitation "standard", 10Hz and 20Hz) and different excitation amplitudes (1.8mm, 2mm, 2.2mmm, 2.5mm, 2.7mm, 3mm) and their effect on the tensile strength R m in MPa. As can be seen, specifically an excitation of 20Hz and excitation amplitudes of 2mm, 2.5mm and 3mm can significantly increase the tensile strength compared to no excitation or agitation at all. In particular, the standard tensile strength of around 265 - 295 MPa could be increased to up to 310 MPa.

[0037] Fig. 5 shows a diagram 500 illustrating experimental results of the advantageous effect of the disclosure on the elongation A 5,65 . More specifically, Fig. 5 illustrates different excitation frequencies (no excitation "standard", 10Hz and 20Hz) and different excitation amplitudes (1.8mm, 2mm, 2.2mmm, 2.5mm, 2.7mm, 3mm) and their effect on the elongation A 5,65 in %. As can be seen, specifically an excitation of 20Hz and excitation amplitudes of 2.5mm and 3mm can significantly increase the elongation compared to no excitation or agitation at all. In particular, the standard elongation of around 1 - 2.5 % could be increased to up to nearly 3 %.

[0038] It will be understood that the presented embodiments are only examples, and that any feature presented for a particular example embodiment may be used with any aspect on its own or in combination with any feature presented for the same or another particular example embodiment and / or in combination with any other feature not mentioned. In particular, the example embodiments presented in this specification shall also be understood to be disclosed in all possible combinations with each other, as far as it is technically reasonable and the example embodiments are not alternatives with respect to each other. It will further be understood that any feature presented for an example embodiment in a particular category (method / apparatus / system) may also be used in a corresponding manner in an example embodiment of any other category. It should also be understood that presence of a feature in the presented example embodiments shall not necessarily mean that this feature forms an essential feature and cannot be omitted or substituted.

[0039] The sequence of all method actions presented above is not mandatory, also alternative sequences may be possible. Nevertheless, the specific sequence of method actions exemplarily shown in the figures shall be considered as one possible sequence of method actions for the respective embodiment described by the respective figure.

[0040] The subject-matter has been described above by means of example embodiments. It should be noted that there are alternative ways and variations which are obvious to a skilled person in the art and can be implemented without deviating from the scope of the appended claims.

Examples

Embodiment Construction

[0027]Figs. 1a, 1b show an exemplary aluminum high pressure die casting system 100 comprising a die casting control system 120, 140 and a casting machine 110 with two die halves 111, 112. The casting machine further comprises a filling chamber 113 (e.g. a shot sleeve) for introducing molten metal (aluminum in this example) into the die. The system further comprises a dosing container 120 for collecting molten metal and for dosing the molten metal into the die casting machine 110 by the die casting control system 120, 140. The molten metal may be provided by a melting or holding furnace 130. The die casting system 100 further comprises exciter means 140 having an exciter 141 and a tapping rod 142. However, other exciter means and tapping elements may be conceivable. Further components of the die casting control system and the exciter means will be described further below with reference to Fig. 3.

[0028]In Fig. 1a, the dosing container 120 is positioned in a first filling or intake pos...

FIELD OF THE INVENTION

[0001] The present disclosure relates to die casting of metal components.BACKGROUND OF THE INVENTION

[0002] Die casting systems have been used for the fabrication of structural metal components for many years. A constant effort is being made to improve mechanical properties of the resulting components by improving alloy compositions and treatment, conditions. For instance, improved mechanical properties may be achieved with the addition of Sr or Na, Sb (eutectic modifiers) or the use of grain refining fluxes. However, considering the costs, the recyclability and the environmental sustainability, such approaches may not always be possible or desired.

[0003] In view of the above, the approaches of the present disclosure may allow for a sufficient grain refinement and desired mechanical properties of cast metal components. In particular, the approaches of the present disclosure may allow for such improved mechanical properties of cast metal components without the use of (environmentally non friendly) grain refining fluxes and / or the addition of eutectic modifiers.

[0004] According to a first aspect of the present disclosure, a die casting method is disclosed. The method may comprise providing molten metal into a dosing container of a die casting system and collecting the molten metal in the dosing container. The method may further comprise agitating the molten metal within the dosing container. The method may further comprise dosing the molten metal from the dosing container into a die casting machine of the die casting system.

[0005] According to a second aspect of the present disclosure, a die casting control system is disclosed. The control system may comprise a dosing container for collecting molten metal and for dosing the molten metal into the die casting machine. The system may further comprise exciter means configured to agitate the molten metal within the dosing container.

[0006] According to a third aspect a die casting system is disclosed. The die casting system may comprise a die casting control system of the second aspect and a die casting machine. The die casting system may in particular be configured for performing the die casting method of the first aspect.

[0007] The die casting may in particular be a high pressure die casting (HPDC) or a vacuum assisted high pressure die casting. The die casting may in particular be an aluminum die casting. Thus, the molten metal may in particular be molten aluminum. The molten metal may in particular be any suitable aluminum die cast alloy. The die casting machine may for instance comprise a mold cavity, such as a first (e.g. movable) die and a second (e.g. fixed) die. The die casting machine may comprise means for forcing molten metal under pressure into the mold cavity. For instance, the casting machine may comprise a filling chamber. For instance, the die casting machine may comprise a hot-chamber or cold-chamber.

[0008] A dosing container may in particular be a vacuum dosing container. Accordingly, the dosing container may collect the molten metal by sucking the molten metal into the dosing container. The dosing container may be an essentially closed container. The dosing container may be a ceramic container, which has the advantage of withstanding the temperatures of molten metal such as aluminum. Moreover, a closed and / or ceramic dosing container may allow a transfer of melt with only a low drop of temperature during the transfer. The dosing container may be a dosing unit of a dosing system. As will be describe in more detail below, the dosing container may be used with a melting or holding furnace for providing the molten metal to be collected in the dosing container. The dosing container may enable safe outtake and precise dosing of the metal melt into the die casting machine (e.g. a filling chamber of a cold chamber die-casting machine). The dosing container may be movable between a first or intake position (e.g. at the melting or holding furnace) and a second or dosing position (e.g. in order to precisely dose the molten metal into the die casting machine). In an example, the mechanical movement of the dosing container may be realized with a servo-controlled lifting device or swiveling device.

[0009] An agitation of the molten metal may in particular be understood to be an induction of mechanical vibrations into the molten metal. As will be described in more detail below, the molten metal may be agitated by inducing a certain (low) frequency (e.g. a frequency below 100 Hz). For instance, exciter means, which will be described in more detail below as well, may be used for inducing vibrations into the dosing container and thereby agitating the molten metal within the dosing container. That is, the molten metal is agitated indirectly by the exciter means by agitating the dosing container with the exciter means and thereby agitating the molten metal within the dosing container.

[0010] After (or during) agitation of the molten metal in the dosing container, the molten metal is dosed into the die casting machine. For instance, the molten metal may be dosed into a filling chamber of the casting machine. For instance, the molten metal may be dosed into a hot-chamber or cold-chamber of the die casting machine. The molten metal may be dosed into the die casting machine by gravity, e.g. by pouring.

[0011] Microstructural studies have surprisingly shown that a (mechanical) agitation of the molten metal in the dosing container has a positive effect on the grain refinement and thus the mechanical properties of the cast component. As a result, cast components with higher quality can be provided. The agitation or excitation of the molten metal in the dosing container allows the agitation or excitation to take place shortly or directly before the actual casting process in the casting machine. This is in contrast to other approaches where an agitation of the molten metal takes place during the cleaning of the melt, for instance. The agitation of a smaller volume and shortly before the actual casting has been found to have an especially advantageous effect on the grain refinement and mechanical properties of the cast part. In particular, it has been found that the agitation of the molten metal in the dosing container has an advantageous effect on properties such as the tensile strength R m , the yield strength or elastic limit R p0.2 or the elongation At.

[0012] It has been found that advantageous mechanical properties may be achieved even without the addition of modifiers and / or the use of grain refining fluxes. The molten metal may be an aluminum die cast alloy free of modifiers. The aluminum die cast alloy may be free of grain refining fluxes.

[0013] Moreover, it has been found that the dosing accuracy is not negatively affected by the agitation of the molten metal in the dosing container.

[0014] In an example, the molten metal is agitated, while the molten metal is being filled into the dosing container, transferred from a furnace to the die casting machine and / or dosed from the dosing container into the die casting machine (e.g. into a filling chamber or shot sleeve). Accordingly, in an example, the exciter means are arranged such that the molten metal can be agitated while the molten metal is being filled into the dosing container transferred from a furnace to the die casting machine and / or dosed from the dosing container into the die casting machine. In other words, the exciter means may in particular be arranged such that they are able to agitate the dosing container and thereby the molten metal when the dosing container is in an intake position, in which the molten metal is provided or filled into the dosing container. Thus, the time used for filling the dosing container is advantageously used for also performing the agitation of the molten metal within the dosing container with the exciter means. Thus, no or only minimal additional time compared to the time necessary anyways for filling the dosing container is required. In an example, the molten metal is only or exclusively agitated, while the molten metal is being filled into the dosing container, so that no additional time would be required for agitating the molten metal as the whole process of agitation can take place during the process of collecting the molten metal in the dosing container.

[0015] The time of agitation may be less than 1 minute, preferably, less than 40 seconds, more preferably less than 20 seconds. For instance, the metal take-in time into the dosing container and thus the excitation time may be less than 20 seconds (such as 18 seconds).

[0016] In an example, the dosing container is a vacuum dosing container. The molten metal may be provided into the dosing container by sucking the molten metal into the dosing container. Accordingly, the vacuum dosing container may be configured to suck the molten metal into the dosing container. In an example, the dosing container may be part of a dosing system comprising an evacuation device for sucking in the melt. A closure may be provided at the opening of the container. A vacuum dosing container has the advantage of having a degassing effect and reducing the amounts of oxides created. Also, air admission may be avoided during the transfer or dosing of the molten metal again significantly reducing the amount of oxides.

[0017] In an example die casting system, the exciter means are configured to induce vibrations into the dosing container and thereby into the molten metal within the dosing container. Accordingly, in an example die casting method, the molten metal is agitated with exciter means inducing vibrations into the dosing container and thereby into the molten metal within the dosing container. This allows the to agitate the molten metal in a simple manner. In particular, it is also possible to easily retrofit existing casting systems already having a dosing container with exciter means configured for agitating the molten metal by inducing vibrations into the dosing container.

[0018] In an example the exciter means comprise an exciter and a tapping element. The exciter may be configured to periodically push the tapping element against the dosing container to induce the vibrations into the dosing container and the molten metal within the dosing container. Accordingly, in an example method, the molten metal is agitated within the dosing container by the exciter periodically pushing the tapping element against the dosing container to induce the vibrations into the dosing container and the molten metal within the dosing container. The exciter may be configured to provide vibrations in particular in a frequency range as discussed further below. For instance, the exciter may generate a sinusoidal movement or force. The sinusoidal movement or force is then transferred to the dosing container via the tapping element. The force may be at least 50N, preferably at least 75N. It may be sufficient to apply a force of at most 200N, preferably at most 150N. The amplitude or peak to peak displacement generated by the exciter (and thus the tapping element) may be at least 1mm and / or at most 5mm . It may be preferred to generate an amplitude or peak to peak displacement of between 2mm - 3mm. For instance, the amplitude or peak to peak displacement may be between around 2mm, 2.5mm or 3mm. Alternatively, it may also be possible that the exciter generates a random force or displacement.

[0019] The tapping element may for instance be a rod or a bar. The tapping element may allow the exciter to be positioned sufficiently far away (such as at least 50 cm, at least 100 cm or at least 200 cm) from the dosing container e.g. so as to not take any damage from the heat. Nevertheless, a protective shielding may also be provided, which comprises a cut-out for the tapping element to reach trough so that the exciter can be provide behind said shielding.

[0020] The exciter means may comprise further components such as an amplifier, a voltage output module and / or a computer for driving the exciter.

[0021] In an example, the exciter means may comprise a feedback system for measuring the agitation of the dosing container. The feedback system may comprise a sensor arranged at the dosing container for measuring a quantity representative of the vibrations produced by the exciter and induced into the dosing container. The sensor may for instance be an accelerometer for measuring the acceleration of the dosing container. The feedback system may further comprise a signal conditioner, a voltage input module and / or a computer for receiving measurements from the sensor. The feedback system may allow to reliably adjust the exciter to provide the desire frequency to the dosing container and thus to the molten metal.

[0022] In an example, the molten metal is agitated within the dosing container (or the exciter means are configured to agitate the molten metal) with a frequency below 20kHz, preferably below 10kHz, further preferably, below 1kHz, even further preferably below 100 Hz and / or with a frequency above 5Hz, preferably above 10 Hz, further preferably above 15Hz. In an example, the molten metal is agitated with a frequency below 100 Hz, preferably in a frequency range of 5-50 Hz, further preferably in a frequency range of 10-30 Hz, further preferably in a frequency range of 15-25 Hz. The exciter means may in particular be configured to agitate the molten metal at a frequency around 20 Hz. As already mentioned, the frequency in particular refers to a sinusoidal frequency or agitation. It has been found that such frequencies are particularly advantageous to achieve a grain refinement, a more homogenous structure and thus improved mechanical properties.

[0023] In an example, the molten metal is provided into the dosing container from a melting or holding furnace. Alternatively, the molten metal is provided into the dosing container from ladle or transport ladle 8 (e.g. the holding furnace may be skipped). Accordingly, the die casting system may further comprise a melting or holding furnace, wherein dosing container is configured for collecting the molten metal from the melting or holding furnace. As already mentioned, the molten metal may be provided into the dosing container by sucking the molten metal into the dosing container. Generally, the melting or holding furnace may also be a part of a dosing system comprising the dosing container and the melting or holding furnace.

[0024] In an example system, the die casting machine may further comprise a filling chamber and the dosing container may be configured to dose the molten metal into the filling chamber. Accordingly, in an example method, the molten metal may be dosed from the dosing container into a filling chamber of the die casting machine of the die casting system. The molten metal may then be injected into the die, for instance as part of a high pressure die casting process.

[0025] The cast component may then solidify and ejected from the casting machine. The cast component may in particular be an engine block or a cylinder head such as a liner less cylinder head. The cast component may in particular have a tensile strength R m , of at least 200 MPa, preferably at least 220, a yield strength or elastic limit R p0.2 of at least 150 MPa, preferably at least 155 MPa and / or an elongation At of at least 1.2, preferably at least 1.4.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Examples of the invention will now be described in detail with reference to the accompanying drawings, in which: Fig. 1a, 1bshows an example of a die casting system for performing an exemplary die casting method according to the disclosed aspects; Fig. 2shows a flow chart of an exemplary method according to the disclosure; Fig. 3shows exemplary exciter means of a die casting control system; Fig. 4shows a diagram illustrating the advantageous effect of the disclosure on the tensile strength R m ; and Fig. 5shows a diagram illustrating the advantageous effect of the disclosure on the elongation A 5,65 . DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] Figs. 1a, 1b show an exemplary aluminum high pressure die casting system 100 comprising a die casting control system 120, 140 and a casting machine 110 with two die halves 111, 112. The casting machine further comprises a filling chamber 113 (e.g. a shot sleeve) for introducing molten metal (aluminum in this example) into the die. The system further comprises a dosing container 120 for collecting molten metal and for dosing the molten metal into the die casting machine 110 by the die casting control system 120, 140. The molten metal may be provided by a melting or holding furnace 130. The die casting system 100 further comprises exciter means 140 having an exciter 141 and a tapping rod 142. However, other exciter means and tapping elements may be conceivable. Further components of the die casting control system and the exciter means will be described further below with reference to Fig. 3.

[0028] In Fig. 1a, the dosing container 120 is positioned in a first filling or intake position at the melting or holding furnace 130. In this example, the dosing container 120 is a vacuum dosing container configured to suck the molten metal into the dosing container (see also step 210 of flow chart 200 in Fig. 2). The exciter means 140, i.e. the exciter 141 and the tapping rod 142 are arranged such that the molten metal can be agitated while the molten metal is being filled into the dosing container 120. More specifically, the exciter 141 is configured to periodically push the tapping rod 142 against the dosing container 120 to induce the vibrations into the dosing container 120 and thereby into the molten metal within the dosing container (see also step 220 of flow chart 200 in Fig. 2).

[0029] The exciter means are configured to agitate the molten metal within the dosing container with a low frequencies, i.e. in particular with frequencies below 100 Hz. It has been found that the excitation frequency is preferably in the range of 5-50 Hz, and in particular in the frequency range of 10-30 Hz. In the present example a sinusoidal tapping frequency of around 20 Hz is used.

[0030] As illustrated in Fig. 1b, the dosing container 120 can be moved into a second dosing position for dosing the molten metal to the die casting machine 110, i.e. in particular the filling chamber 113 (such as a shot sleeve) of the die casting machine 110 (see also step 230 of flow chart 200 of Fig. 2). A cast component (not illustrated), such as an engine block, a cylinder head or a cylinder head gasket, can then then be cast.

[0031] In an example, an engine block is cast. The excitation of the molten aluminum during the metal intake time into the dosing container 120 is around 18 seconds. Different frequencies such as 10 Hz, 20 Hz and 30 Hz have been used for the exciter 141. The following table shows on the one hand the mechanical properties of an aluminum engine block, which has been cast from molten aluminium agitated in the dosing container with a frequency of 20 Hz during the metal take in time of around 18 seconds (samples 20-1A, 20-2A, 20-3A and samples 20-1, 20-2, 20-3). On the other hand, the table further shows the mechanical properties of comparative aluminum engine block samples (samples III-1A, III-2A, III-3A and III-1, III-2, III-3), for which no metal excitation has been performed in the dosing container but otherwise cast with the same alloy and under the same conditions compared to the respective samples for which a 20 Hz excitation was performed. SampleL 0 [mm]E [GPa]R p0.2 [Mpa]R m [Mpa]A 5,65 [%]A t [%]min. 150min. 20020Hz20-1A3062.7164.35227.041.181.3420-2A3062.0155.93228.741.421.5720-3A3063.6153.38233.051.491.65Standard BlockIII-1A3055.5159.46219.141.241.39III-2A3069.7< 144.33214.721.291.43III-3A3069.3< 135.99220.321.601.7420 Hz20-13064.8166.11227.291.121.2720-23063.5158.37224.531.251.4020-33075.9< 145.62232.821.611.75Standard BlockIII -< 13065.3158.34222.161.211.35III-23065.9< 145.23< 192.380.961.08III-33065.9< 141.92< 193.720.971.09

[0032] Generally, the feasibility of the metal excitation in the dosing container under the serial production conditions could be confirmed. Furthermore, it has been found that the metal excitation did not influence the dosing time and dosing accuracy, i.e. the metal excitation time is equal to the (unchanged) metal take-in time. In the above table, the entries of the samples marked with "<" do not fulfill the desired minimum elastic limit R p0.2 and the desired minimum tensile strength R m . As becomes apparent from the above table, the desired minimum elastic limit R p0.2 of 150 Mpa and the desired minimum tensile strength R m of 200 Mpa could be achieved in nearly every sample of the cast parts for which a metal excitation has been performed (i.e. 5 out of 6 samples fulfill the desired minimum properties), while for various of the comparative examples these minimum requirements could not be achieved (4 out of 6 samples do not fulfill the desired minimum properties). Generally, the above results show that the metal excitation in the dosing container allows for an improved elastic limit R p0.2 , which is increased by around 10 Mpa, an improved tensile strength R m , which is increased by around 18 Mpa and an improved elongation At which is increased by around 0.15%.

[0033] In the following further exemplary components of the exciter means 140 will be described in more detail with reference to Fig. 3. Apart from the exciter means, the dosing container 120 is also again shown in Fig. 3. The exciter means comprise the exciter 141 and the tapping rod 142 already shown in Fig. 1a, 1b. The exciter is in this example a TIRA vib S52110. The exciter is connected a power amplifier 143, in this case a TIRA BAA 120. A computer 145 with a program for generating a sinusoidal signal of different frequencies communicates with the power amplifier 143 using a voltage output module 144.

[0034] The exciter used in the example (SS2110) is an electrodynamic transducer with a wide frequency range capable of generating a sinusoidal force of 100N. The device operates in the frequency range from 2 to 7000Hz, is powered by a sine or random signal, and driven by an amplifier with an output power of 120VA. However, as illustrated above, specifically low frequencies, e.g. below 100 Hz, such as 10, 20 or 30 Hz have been shown to be advantageous for the metal excitation in the dosing container. The exciter is constructed of a self-supporting permanent magnet excited frame with a coil inside. The exciter is rotatable and can be positioned both vertically and horizontally using a turnbuckle.

[0035] In the example shown in Fig. 3, the exciter means 140 of die casting control system further comprise a feedback system comprising a voltage input module 146, a signal conditioner 147 and a sensor 148 (in this case an accelerometer). The accelerometer 148 measures the acceleration generated by the vibrations produced by the exciter 141 and transferred to the dosing container 120. The signal from the sensor 148 is processed by the signal conditioner 147 and then transferred to the computer 145 via the voltage input module 146. The feedback signal may be used by the computer 145 to monitor and / or adjust the signal driving the exciter 141 so as to make sure that the dosing container (and thus the metal melt therein) is agitated with the desired frequency.

[0036] Fig. 4 shows a diagram 400 illustrating experimental results of the advantageous effect of the disclosure on the tensile strength R m . More specifically, Fig. 4 illustrates different excitation frequencies (no excitation "standard", 10Hz and 20Hz) and different excitation amplitudes (1.8mm, 2mm, 2.2mmm, 2.5mm, 2.7mm, 3mm) and their effect on the tensile strength R m in MPa. As can be seen, specifically an excitation of 20Hz and excitation amplitudes of 2mm, 2.5mm and 3mm can significantly increase the tensile strength compared to no excitation or agitation at all. In particular, the standard tensile strength of around 265 - 295 MPa could be increased to up to 310 MPa.

[0037] Fig. 5 shows a diagram 500 illustrating experimental results of the advantageous effect of the disclosure on the elongation A 5,65 . More specifically, Fig. 5 illustrates different excitation frequencies (no excitation "standard", 10Hz and 20Hz) and different excitation amplitudes (1.8mm, 2mm, 2.2mmm, 2.5mm, 2.7mm, 3mm) and their effect on the elongation A 5,65 in %. As can be seen, specifically an excitation of 20Hz and excitation amplitudes of 2.5mm and 3mm can significantly increase the elongation compared to no excitation or agitation at all. In particular, the standard elongation of around 1 - 2.5 % could be increased to up to nearly 3 %.

[0038] It will be understood that the presented embodiments are only examples, and that any feature presented for a particular example embodiment may be used with any aspect on its own or in combination with any feature presented for the same or another particular example embodiment and / or in combination with any other feature not mentioned. In particular, the example embodiments presented in this specification shall also be understood to be disclosed in all possible combinations with each other, as far as it is technically reasonable and the example embodiments are not alternatives with respect to each other. It will further be understood that any feature presented for an example embodiment in a particular category (method / apparatus / system) may also be used in a corresponding manner in an example embodiment of any other category. It should also be understood that presence of a feature in the presented example embodiments shall not necessarily mean that this feature forms an essential feature and cannot be omitted or substituted.

[0039] The sequence of all method actions presented above is not mandatory, also alternative sequences may be possible. Nevertheless, the specific sequence of method actions exemplarily shown in the figures shall be considered as one possible sequence of method actions for the respective embodiment described by the respective figure.

[0040] The subject-matter has been described above by means of example embodiments. It should be noted that there are alternative ways and variations which are obvious to a skilled person in the art and can be implemented without deviating from the scope of the appended claims.

Examples

Embodiment Construction

[0027]Figs. 1a, 1b show an exemplary aluminum high pressure die casting system 100 comprising a die casting control system 120, 140 and a casting machine 110 with two die halves 111, 112. The casting machine further comprises a filling chamber 113 (e.g. a shot sleeve) for introducing molten metal (aluminum in this example) into the die. The system further comprises a dosing container 120 for collecting molten metal and for dosing the molten metal into the die casting machine 110 by the die casting control system 120, 140. The molten metal may be provided by a melting or holding furnace 130. The die casting system 100 further comprises exciter means 140 having an exciter 141 and a tapping rod 142. However, other exciter means and tapping elements may be conceivable. Further components of the die casting control system and the exciter means will be described further below with reference to Fig. 3.

[0028]In Fig. 1a, the dosing container 120 is positioned in a first filling or intake pos...

Claims

1. A die casting method, the method comprising: - providing molten metal into a dosing container (120) of a die casting system (100) and collecting the molten metal in the dosing container (120); - agitating the molten metal within the dosing container (120); - dosing the molten metal from the dosing container (120) into a die casting machine (110) of the die casting system (100).

2. The method of claim 1, wherein the molten metal is agitated, preferably only agitated, while the molten metal is being filled into the dosing container (120), transferred from a furnace to the die casting machine (110) and / or dosed from the dosing container (120) into the die casting machine (110).

3. The method of claim 1 or 2, wherein the dosing container (120) is a vacuum dosing container and wherein the molten metal is provided into the dosing container (120) by sucking the molten metal into the dosing container (120).

4. The method of any of claims 1 to 3, wherein the molten metal is agitated with exciter means (140) inducing vibrations into the dosing container (120) and thereby into the molten metal within the dosing container (120).

5. The method of claim 4, wherein the exciter means (140) comprise an exciter (141) and a tapping element (142), wherein the molten metal is agitated within the dosing container by the exciter (141) periodically pushing the tapping element (142) against the dosing container (120) to induce the vibrations into the dosing container (120) and the molten metal within the dosing container.

6. The method of any of claims 4 or 5, wherein the exciter means (140) comprise a feedback system (146, 147, 148) for measuring the agitation of the dosing container.

7. The method of any of claims 1 to 6, wherein the molten metal is agitated within the dosing container with a frequency below 20kHz, preferably below 10kHz, further preferably, below 1kHz, further preferably below 100 Hz and / or with a frequency above 5Hz, preferably above 10 Hz, further preferably above 15Hz.

8. The method of any of claims 1 to 7, wherein the molten metal is provided into the dosing container (120) from a melting or holding furnace (130) or from a transport ladle.

9. The method of any of claims 1 to 8, wherein the molten metal is dosed from the dosing container (120) into a filling chamber (113), in particular a shot sleeve, of the die casting machine (110) of the die casting system (100).

10. A die casting control system (120, 140), the control system comprising: - a dosing container (120) for collecting molten metal and for dosing the molten metal into a die casting machine (110); - exciter means (140) configured to agitate the molten metal within the dosing container (120).

11. The die casting control system of claim 10, wherein the exciter means (140) are arranged such that the molten metal can be agitated while the molten metal is being filled into the dosing container (120).

12. The die casting control system of claim 10 or 11, wherein the dosing container (120) is a vacuum dosing container configured to suck the molten metal into the dosing container (120).

13. The die casting control system of any of claims 10 to 12, wherein the exciter means (140) are configured to induce vibrations into the dosing container (120) and thereby into the molten metal within the dosing container (120).

14. The die control casting system of claim 13, wherein the exciter means (140) comprise an exciter (141) and a tapping element (142), wherein the exciter (141) is configured to periodically push the tapping element (142) against the dosing container (120) to induce the vibrations into the dosing container (120) and the molten metal within the dosing container.

15. The die casting control system of any of claims 13 or 14, wherein the exciter means (140) comprise a feedback system (146, 147, 148) for measuring the agitation of the dosing container.

16. The die casting control system of any of claims 10 to 15, wherein the exciter means (140) are configured to agitate the molten metal within the dosing container (120) with a frequency below 100 Hz, preferably in a frequency range of 5-50 Hz, further preferably in a frequency range of 10-30 Hz, further preferably in a frequency range of 15-25 Hz.

17. A die casting system (100), in particular configured for performing the die casting method of any of claims 1 to 9, wherein the die casting system (100) comprises: - the die casting control system (120, 140) of any of claims 10 to 16; and - the die casting machine (110).

18. The die casting system of claim 17, wherein the die casting system (100) further comprises a melting or holding furnace (130), wherein dosing container (120) is configured for collecting the molten metal from the melting or holding furnace (130).

19. The die casting system of claim 17 or 18, wherein the die casting machine (110) further comprises a filling chamber (113), wherein dosing container (120) is configured to dose the molten metal into the filling chamber (113).

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