Actuator for a casting mold for producing a metal part

Abstract

An actuator for casting molds used in the production of metal parts has at least two electrodes in contact with molten metal for generating a local pulsed electric field in the molten metal of the casting mold and introducing a pulsed current into the molten metal.

Description

Technical Field

[0001] The present invention relates to an actuator for a mold used in the production of metal parts, and an apparatus and method for producing metal parts. Background Technology

[0002] To improve the mechanical properties of cast parts, measures were adopted to induce grain refinement in the solidified molten metal.

[0003] One known technique is to increase the cooling rate of the molten metal during solidification, thus reducing the time required for grain growth. However, rapid cooling is not always possible for thick-walled parts, or the mold technology is very complex.

[0004] Another method involves adding grain refiners (such as TiB particles) to the molten metal. These refiners act as nucleation sites, increasing the number of grains and thus limiting grain growth. The disadvantages are high cost and relatively low efficiency (reducing grain size by only about 15%). Furthermore, this technique does not affect the mechanical properties of the component, but it does affect the overall component.

[0005] It can be seen that the underlying problem of this invention is to provide a cost-effective and universal concept for improving the mechanical properties of cast parts. Summary of the Invention

[0006] The potential problems of this invention are solved by the features of the independent claims. Further developments and embodiments of the invention are the subject of the dependent claims.

[0007] Therefore, the actuator for casting molds used to produce metal parts may have at least two electrodes in contact with the molten metal in order to generate a local pulsed electric field in the molten metal of the mold and introduce a pulsed current into the molten metal.

[0008] Existing research has shown that by coupling a pulsed electric field and introducing a pulsed current into the molten metal, grain growth during solidification can be reduced, thereby effectively limiting the average grain size. Proper positioning of the actuator on or within the mold can specifically enhance the local mechanical properties of the component. Due to the simple design of the actuator and its localized application, the concepts presented here can be used for a variety of mold and component engineering tasks.

[0009] The grain-refining effect of a high-pulsed electric field (i.e., pulsed current in the molten metal) on grain growth may be due to the difference in conductivity between the dendrites and the surrounding molten metal, which generates high heat at the dendrite tips, causing them to melt and slowing down grain growth. This melting delays the supercooling time of the molten metal, leading to dendrite growth.

[0010] Dendrite formation and growth are constrained by the solidification-induced concentration gradient and temperature state near their phase interface. This dependence can be described using the concept of compositional supercooling. In the method employed here, weakly discontinuous localized flow is used to achieve concentration and temperature equilibrium near the dendrites. This reduces compositional supercooling, hindering or slowing dendrite growth. In other words, heterogeneous nucleation is suppressed, favoring homogeneous nucleation, leading to grain refinement in the subsequently cast part. This results in maximum isotropic properties of the cast part.

[0011] According to one embodiment, the actuator further includes a magnetic field coil for generating a localized magnetic field in the molten metal. During actuator operation, the magnetic field coil is arranged between at least two electrodes. Grain growth can be further influenced by superimposing a static magnetic field or an alternating magnetic field onto the pulsed electric field.

[0012] Specifically, this allows for targeted movement of the molten metal, resulting in increased mixing of the molten metal, at least in the region near the mold edge. This reduces concentration and temperature differences, slows grain growth, and creates time for increased internal nucleation. The deflection of the molten metal can be very small and exhibits oscillation, so that the molten metal does not move overall.

[0013] In other words, when using (optional) magnetic field coils, the magnetic field generated by the current in the molten metal itself can interact with the externally applied magnetic field generated by the magnetic field coil, thereby generating a repulsive force and forming a field-dependent flow in the molten metal.

[0014] The superposition of pulsed electric field with static magnetic field or alternating magnetic field enables the desired grain refinement to be achieved even under a lower electric field (current intensity) than when there is no magnetic field, which is beneficial for compliance with electromagnetic compatibility.

[0015] For example, during actuator operation, at least two electrodes and a magnetic field coil can be arranged such that the magnetic field is substantially perpendicular to the electric field. Different effects can be achieved in the molten metal through the interaction of the fields and the control of the electrodes and magnetic field coil based on electromagnetic induction. Details are provided below.

[0016] The actuator may have a housing that accommodates a magnetic field coil, the housing being mounted in a recess in the mold wall. The housing (optionally containing at least two electrodes) is anchored in or on the mold. For example, the housing may be cylindrical, thus allowing the mold wall recess to be designed as a simple hole into which the housing is inserted.

[0017] Furthermore, the housing can accommodate a cooling system that uses a coolant. In this way, undesirable heating of the wall area surrounding the mold can be counteracted, especially under high magnetic field strength.

[0018] An apparatus for producing metal parts includes a mold and an actuator of the type described above in an insert mold, the mold having a cavity for casting the metal part. The actuator in the insert mold can be used to improve the mechanical properties of specific areas of the metal part.

[0019] This type of closed mold with a cavity for casting metal parts can have at least two halves forming a cavity between them, from which the metal part can be removed after the casting half is opened. Due to the (closed) cavity, pressure can also be applied to the melt in the mold if needed.

[0020] The mold and actuator can be modularly designed, meaning the actuator can be combined with various different molds. Of course, several actuators can also be used for specific areas of the part. Therefore, for a wide variety of part shapes and mold concepts, cast parts with locally different mechanical properties, suitable for the intended use of the part, can be easily manufactured.

[0021] For example, the mold cavity can define the thickness and surface shape of the component, with the actuator positioned near the locally thickened portion. For instance, in connection areas (such as screws, insert couplings, flanges, etc.), component thickening is required, meaning the component area has locally thicker walls. In these areas, the cast component cools more slowly, resulting in larger grains and potentially lower mechanical properties. Embodiments of the invention provide remedies herein.

[0022] The mold may include at least two holes for at least two electrodes. Therefore, each electrode can be housed within a hole in the mold, and the electrode is in direct electrical contact with the molten metal.

[0023] The mold may also have at least one central recess, such as a hole in the housing for accommodating the actuator's magnetic field coil. At least two electrodes of the actuator are arranged on either side of the central recess. This allows the magnetic field to be superimposed on the electric field generated by the electrodes in a structurally simple manner.

[0024] Embodiments of the present invention can be used in various molds, including high-pressure die-casting molds, low-pressure die-casting molds, or gravity die-casting molds (also known as permanent die-casting molds). Embodiments of the present invention are also particularly suitable for high-pressure die casting, especially aluminum die casting (high-pressure die casting), because the actuator can be anchored in the mold in a pressure-resistant manner. Due to the high operating pressure and high wear, conventional actuators based on direct mechanical excitation or with vibration-transmitting diaphragms are only suitable for high-pressure die casting to a limited extent.

[0025] According to one embodiment of the method for producing metal parts, a mold may be filled with molten metal. A pulsed current is introduced into the molten metal by generating a localized pulsed electric field in the molten metal through at least two electrodes in contact with the molten metal.

[0026] For example, power of 30W (or possibly 50W) to 5kW, preferably 30W to 1kW, and particularly preferably 30W to 200W, can be coupled into the molten metal using an electric field, and / or a pulsed electric field with a pulse frequency of 1 to 2500Hz, preferably 40Hz to 2000Hz, and particularly preferably 40Hz to 500Hz, can be used. Frequencies of 5000Hz or higher are also possible and may also contribute to achieving the effects of this invention (grain refinement), but require more equipment and incur higher costs. Furthermore, in the range above 20kHz, cavitation occurs in the melt (i.e., the formation of voids and jets), resulting in better mixing, but also causing melt degassing, which is therefore useless in closed molds. The generated bubbles / cavity bubbles cannot escape, leading to increased voids and porosity in the cast parts.

[0027] The pulsed current amplitude can be between 2 and 1000 A, preferably between 50 and 800 A, particularly preferably between 90 and 500 A, or even higher. However, when using superimposed current magnetic fields, even smaller current amplitudes such as a maximum of 800 A, 600 A, 400 A, 200 A, or 100 A are sufficient to achieve effective grain refinement. The preferred areal current density is taken from the cross-sectional size of the electrode, and its range can be from a few square millimeters (e.g., 10 mm²). 2 ) to more than 100 or 200mm 2 The voltage range can be between 1 and 10V, and is mainly determined by the contact resistance between the electrode and the molten metal.

[0028] Embodiments of the method also include generating a local magnetic field in the molten metal, wherein a local pulsed electric field and a local magnetic field are superimposed.

[0029] In this case, the magnetic field can couple 10W to 10kW of power into the molten metal, preferably between 10W and 1kW, particularly preferably between 20W and 500W, and / or the magnetic field can have an AC frequency between 5 and 25000Hz, preferably between 30 and 3000Hz, particularly preferably between 30 and 80Hz.

[0030] In specific applications of the method of the present invention, a local pulsed electric field can be generated in the region where the wall of a metal component is locally thickened, and a local magnetic field can be generated when needed. Attached Figure Description

[0031] In the following text, several embodiments and examples of further developments are explained by way of example based on the accompanying drawings, and therefore different degrees of detail are sometimes used in the drawings. Various features of different embodiments and variations thereof can be combined with each other, provided they are not excluded for technical reasons. The same reference numerals denote the same or similar parts.

[0032] Figure 1An embodiment of an actuator with multiple electrodes and an optional magnetic field coil for use in casting is shown.

[0033] Figure 2 Another example of an actuator with two magnetic field coils is shown.

[0034] Figure 3 It shows the electric field, magnetic field, and the direction of the movement of the molten metal.

[0035] Figure 4 The effect of a pulsed electric field on dendrites in a molten metal is shown.

[0036] Figure 5 The effect of a magnetic field on dendrites in a molten metal is shown.

[0037] Figure 6 A perspective cross-sectional view of an actuator embodiment containing a magnetic field coil within a housing is shown.

[0038] Figure 7 An example of an apparatus for producing metal parts (an actuator is inserted into a mold) is shown.

[0039] Figure 8 A partial cross-sectional perspective view of an embodiment of an apparatus for producing metal parts (with an actuator inserted into a mold) is shown.

[0040] Figure 9 An example of the arrangement of electrodes and magnetic field coils as seen from the cavity wall is shown.

[0041] Figure 10 An exemplary process or stage flowchart of a method for producing metal parts is shown.

[0042] Figure 11 A graph showing the effect of the actuator on the molten metal as a function of temperature and time is presented.

[0043] Figure 12 In the diagram shown, the grain size measured in the cast part is displayed as a function of the distance from the actuator center when the actuator is activated, with the actuator not activated as a reference.

[0044] Figure 13 The diagrams shown present the mechanical parameters for tensile tests on cast components with and without activated actuators.

[0045] Figure 14 The measured grain size distribution of cast parts produced using only magnetic excitation, only electrical excitation, or a combination of magnetic and electrical excitation is shown. Detailed Implementation

[0046] Figure 1An example of an actuator 100 for producing a metal part mold is shown. The actuator 100 has at least a first electrode 110_1 and a second electrode 110_2. The two electrodes 110_1 and 110_2 can be electrically controlled to generate a pulsed electric field in the molten metal 120. For this purpose, the two electrodes 110_1, 110_2 can extend through the wall 130_1 of the mold 130, allowing them to make direct electrical contact with the molten metal 120, in which the mold 130... Figure 1 It is not shown in detail in the document.

[0047] The two electrodes 110_1 and 110_2 can be designed as conductive pins that protrude slightly (not shown) (e.g., 1 mm or more) from the wall 130_1 to ensure reliable electrical contact with the molten metal 120, even during the solidification of the molten metal 120 (contraction phase). That is, externally generated electrical signal pulses (current pulses) can be directly introduced into the molten metal 120, or through the molten metal 120 via the electrodes 110_1 and 110_2 in contact with the molten metal 120.

[0048] The protruding conductive pins maintain direct electrical contact with the molten metal until the solid content in the melt reaches approximately 90%.

[0049] The diameter of the stylus can be selected to achieve an appropriate area current density for a given current. For example, the stylus diameter can be in the range of 3 mm to 12 mm, preferably 6 to 8 mm, and can generate 1 to 10 A / mm². 2 Preferably 2 to 4 A / mm 2 Surface current density in the range of approximately 100A.

[0050] The molten metal 120 may be molten aluminum, molten zinc, molten magnesium, or molten brass, or may include aluminum-based alloys, zinc-based alloys, magnesium-based alloys, or copper-based alloys. Other metals such as bronze, tin, chromium, nickel, or other materials may also be present in the molten metal 120 as base metals or alloying additives.

[0051] A pulsed electric field is generated in the molten metal 120 by applying a pulsed voltage to the two electrodes 110_1 and 110_2, thereby generating a pulsed current. This external current is directly introduced into the molten metal 120 via the two electrodes 110_1 and 110_2 (not by eddy currents induced in the molten metal by an alternating magnetic field). This externally introduced current flows in the direction of the electric field, i.e., from one electrode 110_1 to the other electrode 110_2. Therefore, the electric field has a principal component 112, which extends substantially parallel to the wall 130_1 of the mold 130, at least in some regions. The optional polarity change of the voltage applied between the electrodes 110_1 and 110_2 also correspondingly reverses the direction of the electric field and the direction of the current.

[0052] Electrodes 110_1 and 110_2 can pass through the holes in wall 130_1 and be electrically insulated from the mold (wall 130_1).

[0053] Figure 1 An arrangement including a power supply 180 and an actuator 100 is also shown. In operation, the power supply 180 is electrically connected to electrodes 110_1 and 110_2 of the actuator 100. The power supply 180 generates waveforms (pulses) and provides power to signals (such as current pulses or voltage pulses). The power supply 180 can be current-controlled (i.e., a current source) or voltage-controlled (i.e., a voltage source). In the first case, a current pulse of a predetermined level is generated; in the second case, a predetermined voltage value is specified as a target value for the pulse level. In the first variant (current-controlled power supply 180), the contact resistance between electrodes 110_1 and 110_2 and the molten metal 120 does not change the power introduced into the molten metal 120, so the first variant is likely preferred.

[0054] The actuator 100 may optionally include a magnetic field coil 150. The magnetic field coil 150 can generate a magnetic field in the direction of the magnetic field lines 152, such as... Figure 1 As shown in the example, the magnetic field lines 152 can be substantially perpendicular to the wall 130_1 in the region near the wall. Figure 1 The arrangement shown (where magnetic field coil 150 is between electrodes 110_1 and 110_2) ensures that the electric and magnetic fields are superimposed and that field lines 112 and 152 intersect.

[0055] For example, it can be generated through a solenoid. Figure 1 Magnetic field of the type shown.

[0056] Figure 2 A cross-sectional view of another example of actuator 200 is shown. Actuator 200 differs primarily from actuator 100 in that, in addition to the (optional) magnetic field coil 150 on wall 130_1, another magnetic field coil 250 is arranged on wall 130_2 opposite wall 130_1 on the mold 130. In this way, the magnetic field power coupled into the molten metal 120 can be amplified, and a strong magnetic field can penetrate the entire wall thickness of the component.

[0057] Figure 3 The direction of current 312 (corresponding to the direction of the principal component of electric field 112) and the direction of magnetic field (if present) are shown by magnetic field lines 152. Furthermore, Figure 3 The magnetohydrodynamic flow direction 314 of the molten metal 120 is also shown, which can be obtained by superimposing an electric field on a magnetic field. Figure 1 and 2 In the diagram, the flow direction 314 points out of the paper plane (or inward when the electric field is reversed, see [reference]). Figure 2 (The double arrow in the image).

[0058] Figure 4 Several schematic diagrams illustrate the principle of grain refinement by applying a pulsed electric field to molten metal 120. The current pulse (I) generated by the pulsed electric field is shown in... Figure 4 The upper region, relative to time t. Figure 4 The lower left region schematically shows dendrites 410 exposed to the electric field (field line 112) of molten metal 120. At the tip of dendrite 410, a high electric field intensity is generated due to the potential difference between the dendrite crystal (higher conductivity) and molten metal 120 (lower conductivity) (see field line 412). This results in localized excess current in dendrite 410 and Joule heating at the tip of dendrite 410 during current pulses. Heating melts the tip, causing it to round (see...). Figure 4 (The right-hand region shows the circled tip). The rounded tip reduces the surface area of ​​the dendrite 410, thus reducing its heat exchange (cooling) with the molten metal 120. This hinders or delays further dendrite growth. The molten metal 120 solidifies into a fine-grained spherical structure, which has stronger mechanical properties compared to the dendritic base structure.

[0059] The lateral range where this effect occurs can be equal to or less than 150 mm, 100 mm, or 50 mm. This means that localized areas of the component can be well affected by exposure to a high electric field.

[0060] For example, the pulse frequency can be between 1 and 2000 Hz, preferably between 100 and 1000 Hz. The higher the pulse frequency, the higher the energy can be input to the molten metal 120. In practice, it has been found that 1 to 2 kW of power may be sufficient for the actuators 100 and 200. Higher power can also be coupled, but this requires more expensive power electronics, especially at higher desired pulse frequencies.

[0061] Pulses can use different signal shapes:

[0062] The triangular pulse (Dirac pulse) is the ideal signal shape to achieve the desired effect. However, the problem lies in the system's electromagnetic compatibility or shielding, as the external power supply acts as a broadband source of interference.

[0063] Pulse Width Modulation (PWM) generates pulsed DC current, with the power determined by the pulse duration and pause percentage. For PWM signals, frequency refers to the duration of the on / off cycle. For example, the PWM duty cycle can range from 5% to 95%. PWM signals are easy to generate and control and were used in the experiments presented in this paper.

[0064] It is also possible to run an artificial pulse shape that selects the current curve, and the pulse shape can be optimized in the Dirac pulse direction without its interference effect.

[0065] For example, all waveforms can use reverse pulses, meaning the current can change direction after each pulse (or a sequence of pulses of a certain length).

[0066] All signal shapes can be provided as either current or voltage signals. For example, power supply 180 (see...) Figure 1 It can be a low-voltage power supply used in conjunction with a 180-frequency generator for switching the power on / off.

[0067] Figure 5 The effect of alternating magnetic field on grain growth is illustrated, showing the two walls 130_1 and 130_2 of the mold and the molten metal 120 between the walls.

[0068] During the solidification of the molten metal 120, a solidified shell 120_1 forms on the walls 130_1 and 130_2, while the molten metal 120 remains liquid in the inner region 120_2. Due to the magnetic field (magnetic field line 152), a flow 514 forms in the molten metal 120, particularly at the interface between the solidified shell 120_1 and the still molten interior 120_2, which slows down dendrite growth.

[0069] like Figure 5 As shown in the lower part, the flow 514 can be linear or circular, or agitated. The flow 514 causes the dendrites 410 growing at the interface between the shell 120_1 and the interior 120_2 of the molten metal 120 to deform or break. This provides more time for in-situ grain growth, resulting in a fine-grained microstructure with fewer dendrites during solidification.

[0070] For example, the alternating magnetic field can be in the frequency range between 5 and 20,000 Hz or 25,000 Hz. Proper design of the area surrounding the magnetic field coils 150 and 250 can reduce induction heating and limit the maximum achievable frequency (and thus limit the maximum achievable energy input to the molten metal 120). This undesirable heating can be offset by cooling the magnetic field coils 150 and 250 and / or by using a non-ferritic steel as the mold material, which can also take the form of inserts in the mold walls near the magnetic field coils 150 and 250. For example, austenitic steel or stainless steel (with austenitic stabilizing elements such as Cr and / or Ni) can be used as the non-ferritic steel.

[0071] For many applications, a magnetic field power input between 10W and 10kW may be sufficient.

[0072] By superimposing an alternating magnetic field onto a pulsed electric field, an electromagnetic field can be induced, causing cyclic magnetohydrodynamic motion (magnetic agitation) of the molten metal 120. The electromagnetic field induces a current in the molten metal, generating an opposing electromagnetic field. This produces a force that moves the molten metal 120 in a small agitation manner. The magnetohydrodynamic effect on the molten metal 120 can reduce the porosity in the cast part, which is beneficial to the mechanical properties of the cast part and subsequent heat treatment.

[0073] When the current direction is reversed and / or the magnetic field direction in the magnetic field coils 150 and 250 is reversed, the movement of the molten metal can also be achieved by applying a static magnetic field and injecting a high-pulse current (generated by a pulsed electric field) through the molten metal 120. Therefore, the flow direction in the molten metal is alternately reversed. That is, in the same way, an oscillating flow with a low amplitude (e.g., between 100 μm and a few mm) can be obtained in the molten metal 120, large enough to reduce the alloying element concentration difference between the liquid phase and the solidification zone at the growth crystal interface (i.e., between the shell 120_1 and the interior 120_2 of the molten metal 120). In this process, the molten metal oscillates with a small amplitude, and the growth crystal cannot directly follow the movement due to its inertia. This relative movement leads to mixing, thereby achieving concentration and thermal equilibrium at the solidification front.

[0074] In other words, changes in the magnetic field and / or current can induce eddy currents near the crystal (dendritic) interface, thereby causing movement of the molten metal 120. This movement of the molten metal is within the range of ultrasonic vibration, but such ultrasonic vibration is difficult (acoustically) to penetrate deeply into the interior 120_2 of the molten metal 120.

[0075] according to Figure 6 The magnetic field coil 150 (250) may be in the form of a solenoid 650. The solenoid 650 may include a cylindrical winding 650_1 and a central core 650_2. The solenoid 650 is located within a housing 660. The housing 660 may be mounted in a wall recess of the mold (such as wall 130_1 shown). For example, the wall recess may be as follows: Figure 6 The through recess shown may be formed by a recess in an adjacent cavity mold (such as the recess in wall 130_1).

[0076] For example, the housing 660 can be cylindrical, thus facilitating insertion into wall holes (through holes or blind holes). The diameter of the housing 660 can be equal to, less than, or greater than 20 mm, 30 mm, or 50 mm. The length of the housing 660 can be between 80 mm or 100 mm and 200 mm.

[0077] The magnetic core 650_2 directs the magnetic field to the cavity surface 630. A nonferrite plate 640 may be placed between the magnetic core 650_2 and the molten metal 120 to achieve the highest possible magnetic coupling between the magnetic field coil 150(250) (e.g., in the form of a solenoid 650) and the molten metal 120.

[0078] The magnetic field coil 150 (250) can be cooled by a coolant 670 flowing through the housing 660. Oil, water or air can be used as the coolant.

[0079] Although not shown, the mold wall 130_1 can also be cooled near the recess for the housing 660. For example, a magnetic field coil 150 (250) can also be present in a nonferrous insert of the wall 130_1, and a coolant cooling system can be provided.

[0080] Figure 7 A schematic cross-sectional view of an apparatus 700 for producing metal parts in a mold is shown. In the example shown, the mold includes two mold halves 710 and 720. The mold halves 710 and 720 may form walls 130_1 and 130_2 shown in the previous figures. A cavity 730 is located between the mold halves 710 and 720, in which the part to be produced is cast.

[0081] The molds 710 and 720 can be high-pressure die-casting molds, low-pressure die-casting molds, or gravity die-casting molds.

[0082] For example, in Figure 7 In the example shown, the actuator first electrode 110_1 is formed in the first half-mold 710, while the second electrode 110_2 is formed in the second half-mold 720. Of course, electrodes 110_1 and 110_2 can be implemented in either the first half-mold 710 or the second half-mold 720.

[0083] Furthermore, as mentioned above, the actuator can be equipped with a magnetic field coil 150, such as a solenoid 650. This is present in the first half-mode 710 in this example.

[0084] The magnetic field coil 150 inserted into the molds 710 and 720 can be a fixed part or an integral part of the molds 710 and 720, such as... Figure 7 As shown, it can be modularly connected to or detached from molds 710 and 720. In the region of the magnetic field coil 150 (e.g., solenoid 650), the surface 630 of the cavity 730 can be formed of austenitic steel plate (corresponding to non-ferritic plate 640). Mold halves 710 and 720 can be made of ferritic steel. The aforementioned features and functions of actuators 100 and 200 also relate to a device 700 that can be used to produce metal parts.

[0085] Figure 8An apparatus 800 for producing metal parts in molds 710 and 720 is shown. Apparatus 800 is substantially the same as apparatus 700, therefore, please refer to the description above to avoid repetition. Figure 8 The diagram also shows a mold guide 810 and a gate 820 for opening and closing the mold halves 710 and 720, through which molten metal can be introduced into the cavity 730.

[0086] The device 800 includes two actuators. One actuator includes electrodes 110_1 and 110_2 and a magnetic field coil 150, while the other actuator is implemented separately by electrodes 110_3 and 110_4.

[0087] refer to Figure 9 The surface 630 of the casting mold cavity 730 may include multiple electrodes 110_1, 110_2, 110_1′, and 110_2′, which are arranged symmetrically about the magnetic field coil 150 (located behind the nonferrite plate 640). Because the electrodes 110_1, 110_2, 110_1′, and 110_2′ are arranged in a polygonal manner... Figure 9 The mechanical properties of the circular local components around the magnetic field coil 150, for example, which are thickened relative to the magnetic field coil 150 (solenoid 650), can be particularly well affected. The lateral dimensions of the electrode arrangement are scalable and can be particularly small (e.g., equal to or less than 150 mm, 100 mm, or 50 mm). Only minor modifications to the mold are required, so the grain refinement concept here can be implemented very easily and in a variety of ways. Different electrodes can change the direction of the electric field.

[0088] refer to Figure 10 Embodiments of a method for producing metal parts may include the following stages or processes.

[0089] In S1, the mold is closed. For example, it can be a high-pressure die-casting mold, a low-pressure die-casting mold, or a gravity die-casting mold.

[0090] In S2, the mold is filled with molten metal. All the fill types and molten metal materials mentioned can be used.

[0091] In S3, the actuator is activated. The impact phase S4 includes S4_1 coupling of the pulsed electric field and S4_2 optional simultaneous magnetohydrodynamic mixing of the molten metal.

[0092] Impact phase S4 is complete. In S5, the molten metal has solidified, meaning the cast part is in the solid phase.

[0093] In S6, optional further rapid cooling can be performed to improve the mechanical properties of the cast part. This further cooling step is performed in addition to natural cooling by means of a cooling device to dissipate heat.

[0094] In S7, optional demagnetization and impedance measurements are performed for quality monitoring.

[0095] In S8, the completed casting part is removed from the mold. The production cycle can then restart from S1.

[0096] Figure 11 The time sequence of each process stage is illustrated as an example. The temperature T of the cast part is schematically shown on the Y-axis, and the time t is shown on the X-axis.

[0097] When the mold is filled with hot molten metal at S2, the temperature inside the mold suddenly rises to its maximum. This is followed by a cooling and solidification process. At t a At (S4), the actuator is activated, initiating an electrical or electromagnetic impact on the molten metal. At t e At (S4), the actuator is turned off, and the impact process ends.

[0098] During the intermediate stage t(S4), the molten metal undergoes a phase transformation from liquid to solid. During this period, the impact process produces a grain refinement effect in the manner described above.

[0099] Further stages S6 and S7 occur during the solid-state cooling of the cast part. In S8, the cast part is removed, and the next production cycle can begin.

[0100] Figure 12 The effect of magnetohydrodynamics on grain refinement in molten metal is illustrated, where an actuator generates a pulsed electric field (i.e., a pulsed current) and an alternating magnetic field superimposed on it. The average grain size of the cast component samples determined in the experiment is shown as a function of the distance from the actuator (measured along the solenoid axis).

[0101] The experimental data pertain to gravity casting of a molten metal made of AlSi7Mg0.3. The initial temperature of the molten metal was 720°C, and the initial temperature of the mold was 220°C. A 100A pulsed current, with a duty cycle of 20% and a pulse frequency of 50Hz, was used. The power coupled through the magnetic field coil was only 14W. Figure 1 The single actuator 100 (with a magnetic field coil) shown is placed on one of the mold walls.

[0102] Essentially, a grain size reduction of approximately 40% was achieved across the entire component thickness. This equates to an eightfold increase in grain number, resulting in significant improvements in the mechanical properties of the cast component in terms of electromechanical impact and magnetohydrodynamic motion of the molten metal.

[0103] Figure 13The mechanical properties of the cast part, determined by tensile testing, are shown. The tensile tests were conducted according to DIN EN ISO 6892-1, with tensile specimens according to DIN 50125. The cast part was manufactured as described above, but the frequency was increased to 2000 Hz in this test. The wall thickness of the cast part was 6 mm. Compared to a reference part without an activated actuator, the elongation at break (E) increased by 333%, the tensile strength (Rm) [MPa] increased by 66%, and the 0.2% elongation limit (Rp0.2) [MPa] increased by 13%.

[0104] Table 1 below summarizes the measured mechanical properties of cast parts produced using the various excitation parameters given in the table. In this table, (x W / y%) represents the amount of magnetic power coupled into the melt during the solidification process at x watts, and the amount of PWM pulse current coupled into the melt during the solidification process at y% PWM duty cycle. With the PWM pulse current adjusted to 100A and the voltage approximately 1V, i.e., a duty cycle of 30-80%, approximately 30-80W of PWM electrical power is coupled into the melt. The magnetic agitation power is in the range of 10-500W.

[0105] Table 1 (Mechanical Properties)

[0106]

[0107] In Table 1, YS (0.2% offset yield strength) represents the 0.2% yield strength Rp0.2, UTS (ultimate tensile strength) represents the tensile strength Rm, and E (elongation) represents the elongation at break.

[0108] With D5 = 39 μm, D50 = 141 μm, D95 = 809 μm, and Dmax = 1979 μm, the porosity of the reference cast part (actuator not activated) is 0.8284%. In the cast part using electromagnetic excitation, the porosity is 0.1001%, with D5 = 11 μm, D50 = 22 μm, D95 = 86 μm, and Dmax = 135 μm. D50 represents 50% of the particles being smaller than the specified value. Electro- and magnetic excitation significantly reduce porosity and also greatly reduce pore size (large pores can induce cracks), especially the largest pore (Dmax), which is primarily reflected in increased elongation at break.

[0109] Clearly, electromagnetic excitation of the melt improves the mechanical properties. Magnetic agitation leads to a significant increase in UTS and E. Electrical pulses slightly increase YS and result in an even more significant increase in UTS and E. The combination of the two excitations generally achieves the best results in terms of the desired mechanical properties.

[0110] Figure 14The measured grain size distribution of cast parts is shown when magnetic excitation is used only in the range of 1-500W without electromagnetic excitation (reference), when electric excitation is used only in the range of PWM with a duty cycle of 30-80%, or when magnetic and electric excitation are used simultaneously as described above (i.e., with the same values ​​as the curves above in each case).

[0111] As can be seen, compared with the reference distribution without electromagnetic excitation, magnetic stirring alone can achieve a slightly more uniform particle size distribution, but does not show an increase in the frequency of small particles.

[0112] The electrical pulses significantly increased the uniformity of the distribution and the frequency of small grain sizes. The average grain size decreased by 10% to 20%. The grain size was determined according to the specifications of Espinal, Laura, “Porosity and its Measurement,” Material Characterization (2002): 1-10.

[0113] It is noteworthy that the combination of magnetic agitation and electrical pulses not only further improved the uniformity of the distribution but also significantly increased the frequency of small grain size occurrences. The average grain size decreased by more than 30% (measured value decreased by 32%). The percentage figures refer to the reference values ​​without electromagnetic excitation. In other words, in terms of grain size reduction (or small grain size frequency), the combination of magnetic agitation and electrical pulses produced a synergistic effect that significantly exceeded the sum of the effects of the two excitation methods individually.

[0114] In summary, these and other experiments demonstrate that electrical pulses significantly reduce grain size, thus increasing the strength of cast parts. Magnetic agitation alone has little effect on increasing strength, but it can indeed improve the quality of cast parts by reducing porosity and increasing the uniformity of the metal structure. The combination of these two excitations can produce high-strength cast parts with very good casting quality.

Claims

1. An actuator for casting molds used in the production of metal parts, the actuator comprising: At least two electrodes are disposed on the mold wall, the at least two electrodes being in contact with the molten metal present in the mold, for generating a local pulsed electric field in the molten metal and introducing a pulsed current into the molten metal; A magnetic field coil for generating a local magnetic field in a molten metal, the magnetic field coil comprising a cylindrical winding, wherein, during operation of the actuator, the magnetic field coil is arranged on the mold wall and located between at least two electrodes; The arrangement of the magnetic field coil and the at least two electrodes is such that the extension direction of the cylindrical winding is substantially perpendicular to the local pulsed electric field. The local pulsed electric field has a principal component that extends in a direction substantially parallel to the mold wall.

2. The actuator according to claim 1, further comprising: A housing for accommodating the magnetic field coil, the housing being configured and installed in a wall recess of the mold wall.

3. The actuator according to claim 2, further comprising: Coolant cooling conduits housed within the outer casing.

4. An apparatus for producing metal parts, comprising: A mold having walls and cavities for casting metal parts from molten metal; as well as An actuator for a casting mold, the actuator comprising: At least two electrodes are disposed on the mold wall, the at least two electrodes being in contact with the molten metal present in the mold, for generating a local pulsed electric field in the molten metal and introducing a pulsed current into the molten metal; A magnetic field coil for generating a local magnetic field in a molten metal, the magnetic field coil comprising a cylindrical winding, wherein, during operation of the actuator, the magnetic field coil is arranged on the mold wall and located between at least two electrodes; The arrangement of the magnetic field coil and the at least two electrodes is such that the extension direction of the cylindrical winding is substantially perpendicular to the local pulsed electric field. The local pulsed electric field has a principal component that extends in a direction substantially parallel to the mold wall.

5. The apparatus of claim 4, wherein, The mold wall has at least one central groove for accommodating the housing of the actuator magnetic field coil, wherein at least two electrodes of the actuator are arranged on both sides of the central groove.

6. The apparatus of claim 4 or 5, wherein, The mold is a high-pressure die-casting mold, a low-pressure die-casting mold, or a gravity die-casting mold.

7. A method for producing metal parts, comprising: A mold is filled with molten metal, the mold having walls and cavities for casting metal parts from the molten metal; A local pulsed electric field is generated in the molten metal in the mold by at least two electrodes in contact with the molten metal to introduce a pulsed current into the molten metal. The at least two electrodes are disposed on the mold wall. A local magnetic field is generated in the molten metal by means of a magnetic field coil containing cylindrical windings; The magnetic field coil is arranged on the mold wall and located between at least two electrodes; The arrangement of the magnetic field coil and the at least two electrodes is such that the extension direction of the cylindrical winding is substantially perpendicular to the local pulsed electric field. The local pulsed electric field has a principal component that extends in a direction substantially parallel to the mold wall.

8. The method of claim 7, wherein, Power of 30W to 5kW is coupled into the molten metal via an electric field, and / or the pulse frequency of the pulsed electric field is 1 to 2500Hz.

9. The method of claim 8, wherein, Power of 30W to 1kW is coupled into the molten metal via an electric field, and / or the pulse frequency of the pulsed electric field is 40 to 2000Hz.

10. The method of claim 9, wherein, Power of 30 to 200 W is coupled into the molten metal via an electric field, and / or the pulse frequency of the pulsed electric field is 40 to 500 Hz.

11. The method according to any one of claims 7 to 10, characterized in that, Due to the electric field, a pulse current of 2 to 1000 A flows through the molten metal.

12. The method of claim 11, wherein, Due to the electric field, a pulse current of 50 to 800 A flows through the molten metal.

13. The method of claim 12, wherein, Due to the electric field, a pulse current of 90 to 500 A flows through the molten metal.

14. The method according to any one of claims 7 to 10, characterized in that, Power ranging from 10W to 10kW is coupled into the molten metal via a magnetic field, and / or the magnetic field has an AC frequency of 5 to 25000Hz.

15. The method of claim 14, wherein, Power ranging from 10W to 1kW is coupled into the molten metal via a magnetic field, and / or the magnetic field has an AC frequency of 30 to 3000Hz.

16. The method according to claim 15, characterized in that, Power of 20 to 500W is coupled into the molten metal via a magnetic field, and / or the magnetic field has an AC frequency of 30 to 80Hz.

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