Inductive melting system having automatic control

Abstract

A method (200) for operating an inductive melting system (100) which has at least one induction coil (122) for melting an electrode (E), comprises determining (210) a net heating power of the inductive melting system (100) by means of a control device (160) of the inductive melting system (100). The method also comprises determining (220) a melting rate by means of the control device (160), ascertaining (230) a superheating temperature of the melted-off electrode material (S) at least partly on the basis of the net heating power and the melting rate by means of the control device (160), and controlling (240) at least one operating parameter of the inductive melting system (100) on the basis of the ascertained superheating temperature by means of the control device (160).

Description

[0001] Inductive melting plant with automatic control

[0002] The present application relates to a method for operating an inductive melting system. The application also relates to a control device for an inductive melting system and to an inductive melting system.

[0003] Technical background

[0004] Systems for the inductive melting of material are well known. In possible applications, the molten material is either poured into a mold or atomized, for example, for the purpose of powder production. Typically, a current is induced in the material to be melted using one or more coils. The current melts the material, which then acts as an electrode for the induced current. The molten electrode material, typically in the form of a melt jet, is then fed into a mold, for example. In the process known as EIGA (Electrode Induction Melting Inert Gas Atomization), which is used to produce powder, the melt jet is accelerated by means of an inert gas stream and, together with the inert gas stream, is passed through an atomization nozzle. The atomized melt jet then cools to powder.

[0005] The efficiency of an inductive melting process and the quality of the melt produced depend significantly on the existing process conditions. Optimizing the process and achieving consistent results are hampered by the progressive consumption of the starting electrode material during the process. The position of the electrode relative to the coil that causes the induction, as well as the position at which the molten electrode material is exposed to the inert gas stream, for example, in the EIGA process, are therefore variable.

[0006] In order to create approximately consistent process conditions, known inductive melting systems are designed to advance the electrode toward the coil during the melting process. This compensates for material consumption in the melting area and keeps the position of the fixed electrode end, where the electrode melts, within a limited range. Furthermore, in order to achieve the most uniform melting of the electrode, known inductive melting systems are designed to be rotationally symmetrical, particularly rod-shaped, and aligned coaxially to the coil axis and the nozzle axis, and to rotate the electrode around the common axis of the coil and nozzle during the melting process. Difficulties traditionally arise from the fact that the melting process is subject to changing conditions. These arise in part from differences between different electrode materials and sizes.However, they also inevitably arise from the ever-present asymmetries in the mechanical arrangement of the electrode and coil, inhomogeneities in the electrode material used, fluctuations in the coil's operating current, possible fluctuations in the inert gas flow, and similar variable conditions during the operation of an inductive melting system. While a suitable average electrode feed rate can often be determined for a specific process, short-term fluctuations of this kind can nevertheless have a detrimental impact on the production result.

[0007] In many applications, the manufacturing result is sensitive to the aforementioned fluctuations because the electrode material is not only melted, but the melted electrode material must be superheated as precisely as possible beyond the melting temperature by a predetermined temperature, i.e., the so-called superheating temperature, before further processing—in the EIGA process, for example, before passing through the atomizing nozzle. The superheating of the melt is preferably also achieved by means of the coil's magnetic field. The achieved superheating temperature of the melt therefore depends, among other things, on the length of time the flowing melt remains in the coil's magnetic field, absorbing further heat.

[0008] The residence time of the flowing melt in the coil's magnetic field depends, among other things, on the position of the melting zone, i.e., the fixed electrode end on the coil side. This position is variable due to the aforementioned fluctuations in the melting process. Visual monitoring of the position of the fixed electrode end for the purpose of controlling the melting process is also complicated by the fact that the fixed electrode end is typically not visible due to the melt adhering there.

[0009] The task is therefore to provide a solution that mitigates or avoids the aforementioned disadvantages.

[0010] Summary of the invention

[0011] This object is achieved by a method according to claim 1, a control device according to claim 14 and an inductive melting system according to claim 15.

[0012] According to a first aspect, a method for operating an inductive melting system is presented. The inductive melting system comprises at least one induction coil for melting an electrode. The method comprises the step of determining, by means of a control device of the inductive melting system, a net heating power of the inductive melting system. The method further comprises determining, by means of the control device, a melting rate, determining, by means of the control device, a superheating temperature of the melted electrode material at least partially based on the net heating power and the melting rate, and controlling, by means of the control device, at least one operating parameter of the inductive melting system based on the determined superheating temperature.

[0013] The method enables automatic control, in particular automatic regulation or automatic adjustment, of one or more operating parameters of the inductive melting system as a function of an existing, in particular a simultaneous, melting process in the inductive melting system. The method can also enable automatic control without the need for sensory, in particular optosensory, detection of the position of a region of the electrode to be melted.

[0014] This is achieved by taking into account a combined net heating power, a melting rate, and the superheating temperature of the melted electrode material. Control, particularly automatic regulation, can be achieved by comparing the determined superheating temperature with an adjustable and / or stored superheating temperature setpoint.

[0015] The inductive melting system can be an EIGA system for producing powder. The inductive melting system can further comprise at least one nozzle for atomizing the melted electrode material.

[0016] The net heating power can be a heating power contributing to heating and melting the electrode material, as well as to overheating the melted electrode material. The net heating power can correspond to an induced electrical power converted into thermal power in the electrode material and effectively contributing to heating the electrode material. An effective contribution of the induced electrical power to heating the electrode material can correspond to an amount of the induced electrical power converted into thermal power in the electrode material less a heat loss, in particular due to thermal radiation emitted by the electrode material and, optionally, due to heat dissipation within the electrode. The net heating power can be determined at least partially based on a heat loss, in particular due to thermal radiation.The determination of the net heating power may also be based at least in part on at least one of an applied operating power of a coil module of the inductive melting system that includes the induction coil and an electrical power loss of the coil module.

[0017] The coil module can comprise a plurality of induction coils. In particular, a plurality of induction coils of the coil module can be arranged one behind the other in a feed direction of the electrode.

[0018] The electrical power loss of the coil module can be a difference between the applied operating power of the coil module and the induced electrical power converted into heat power in the electrode material. The applied operating power can be determined at an input to an overall resonant circuit of the coil module. The electrical power loss can include a power loss of a capacitor bank of the overall resonant circuit, a power loss of the one or more induction coils of the coil module, a power loss of one or more power lines of the coil module, and / or a power loss due to one or more stray fields.

[0019] Determining the net heating power may be based at least in part on a difference between the applied operating power of the coil module and a combination of the electrical power dissipation of the coil module and the heat power dissipation.

[0020] The inductive melting system may further comprise a cooling circuit for the at least one induction coil. The heat loss, particularly due to thermal radiation, may be determined at least partially based on the heat conversion of the cooling circuit.

[0021] When determining the heat loss, heat flow within the electrode, in particular heat flow from the region of the electrode to be melted, may be disregarded. Alternatively, when determining the heat loss, the heat flow within the electrode may be taken into account according to a heat flow characteristic, in particular according to a constant heat flow characteristic, of the electrode material.

[0022] The inductive melting system may further comprise at least one camera configured to capture image information related to a melting process of the inductive melting system. The camera may be configured to output an image signal indicative of the image information to the control device. The melting rate may be determined at least partially based on the captured image information.

[0023] The melting rate can be determined at least partially based on a photometric evaluation of the acquired image information. The photometric evaluation can be directed at at least one characteristic, in particular at least one width, of a melt jet of the melted electrode material.

[0024] The determination of the superheat temperature may further be based at least in part on an enthalpy of the electrode material.

[0025] Controlling the at least one operating parameter may include comparing the determined superheat temperature with a superheat temperature setpoint, and controlling the at least one operating parameter based on a result of comparing the determined superheat temperature with the superheat temperature setpoint.

[0026] The at least one operating parameter may include at least one of the operating power of the coil module, an operating current of the induction coil, a feed rate of the electrode, and a position of the induction coil relative to the electrode.

[0027] The method can be provided for the automatic monitoring and / or control of the operation of the inductive melting plant.

[0028] According to a further aspect, a control device for an inductive melting system is presented. The control device comprises a processor unit and a memory device operatively connected to the processor unit. The processor unit is configured to carry out a method of the type presented here.

[0029] According to a further aspect, an inductive melting system for producing metal powder is presented. The inductive melting system comprises at least one induction coil for melting an electrode and a control device designed to operate the inductive melting system according to a method of the type presented here.

[0030] Short description of the characters

[0031] Further features, objects, and advantages of the invention will become apparent from the figures and the detailed description. They show:

[0032] Fig. 1 shows an inductive melting system according to an example; Fig. 2 shows a method for operating an inductive melting system according to an example, and

[0033] Fig. 3 shows a control device for an inductive melting system according to an example.

[0034] Detailed description

[0035] Fig. 1 shows a schematic and exemplary inductive melting system 100. In the example shown, the inductive melting system 100 is an EIGA system for producing powder, for example, for producing high-purity metal powder. However, the techniques described below are also advantageously applicable to other types of inductive melting systems, for example, those in which casting of the melted electrode material is provided, unless otherwise indicated in the following description and in Fig. 1.

[0036] In the example shown, the inductive melting system 100 comprises a melting and atomization structure 110. This structure has a melting chamber 112 and an atomization tower 114 arranged underneath.

[0037] A coil module 120, which comprises at least one induction coil 122, is arranged in the melting chamber 112. When the induction coil 122 is supplied with an operating current by means of a power supply device 130 of the inductive melting system 100, a current is induced in an electrode E located in the magnetic field of the induction coil 122. The current induced in the electrode E is partially converted into Joule heat, which causes the electrode material to melt.

[0038] As shown schematically in Fig. 1, in the example shown, the melted electrode material S falls in the form of a melt jet towards the nozzle 118 of the atomization tower 114 arranged below the induction coil 122. When passing the nozzle 118, the melted electrode material S is first atomized into melt droplets and then cools to powder, which collects, for example, in a collecting area of ​​the atomization tower 114.

[0039] The electrode E is clamped in an electrode feed device 116 of the inductive melting system 100. As indicated by the vertical arrow in the area of ​​the electrode E, the electrode feed device 116 enables the electrode E to be advanced toward the induction coil 122. The loss of electrode material caused by the melting of the electrode E in the area of ​​the induction coil 122 can thus be compensated during the process. In particular, the position of the melting zone, i.e., the fixed end of the electrode E on the coil side, relative to the induction coil 122 can be kept at least approximately constant.

[0040] As indicated by the curved arrow in the area of ​​the electrode E, the electrode feed device 116 in the example shown is also designed to rotate the electrode E around its longitudinal axis. Rotating the electrode E promotes uniform melting of the electrode E, for example, in the case of asymmetric heat distribution within the electrode E, for example, due to asymmetries in the magnetic field, the arrangement of the induction coil 122 and the electrode E, the electrode material, etc.

[0041] In the example of the inductive melting system 100 shown, the nozzle 118, the induction coil 122, and the electrode E are each aligned vertically and coaxially with one another. As shown schematically in Fig. 1, the electrode material melted along the underside of the electrode E initially flows together in the region of a lower tip of the electrode E and from there falls towards the nozzle 118 under the effect of gravity. As indicated by the curved arrow in the region of the nozzle 118, the melted electrode material S in the example shown is additionally accelerated by an inert gas stream that is directed from the melting chamber 112 through the nozzle 118 into the atomization tower 114.

[0042] It is understood, however, that the techniques described below are also applicable to inductive melting systems with different arrangements of electrode E, coil module 120, nozzle 118, and / or inert gas stream. The techniques described below are particularly applicable to inductive melting systems in which, instead of atomization, the melted electrode material S is poured, and / or in which the coil module 120 comprises more than one induction coil, for example, two or more induction coils arranged one behind the other in the feed direction of the electrode E. Furthermore, in further examples of the inductive melting system 100, the melted electrode material S is atomized through several nozzles, for example, arranged one behind the other, and / or using a laterally supplied inert gas stream.In further examples of the inductive melting system 100, a clamping of the electrode E that deviates from a vertical orientation of the electrode E is also provided.

[0043] As schematically shown in Fig. 1, the induction coil 122 typically comprises several coil turns that taper in a funnel-like manner in the feed direction of the electrode E. This promotes efficient power input from the induction coil 122 into the electrode material through a dense spatial arrangement of the induction coil 122 and the electrode E. At the same time, this promotes a confluence of the molten electrode material towards the electrode tip and a flow of the melted electrode material S in the form of a concentrated melt jet. This is advantageous for uniform atomization of the melted electrode material S. It also promotes the setting of a specified superheating temperature of the melted electrode material S, particularly by means of the lower coil turns of the induction coil 122.

[0044] As described above, the superheating temperature generated in the melted electrode material S during operation of the inductive melting system 100 depends on various influences that vary during operation of the inductive melting system 100. As explained below, in particular to achieve a constant superheating temperature of the melted electrode material S, a position of the coil-side fixed end of the electrode E that is as constant as possible is desirable, since this advantageously allows for a uniform process.

[0045] The magnetic field of the induction coil 122 becomes weaker with increasing distance from the induction coil 122. As the distance between the electrode E and the induction coil 122 increases, for example as a result of a temporarily too slow feed rate of the electrode feed device 116, the power input in the form of induced current in the electrode E therefore decreases. If melting of electrode material nevertheless occurs, the melted electrode material S is exposed to the magnetic field of the induction coil 122 over a longer falling distance and thus over a longer period of time, resulting in a different overheating temperature of the melted electrode material S. Furthermore, as the distance between the electrode E and the induction coil 122 in the example in Fig. 1 increases, the inert gas flow will act on the melted electrode material S earlier, i.e. over a longer distance, for example until it is atomized.The resulting cooling of the melted electrode material S by the inert gas flow is also altered. The acceleration of the melt flow by the inert gas flow and by gravity is also altered due to the longer drop distance.

[0046] Conversely, if the feed rate of the electrode feed device 116 is temporarily too fast, the distance between the electrode E and the induction coil 122 decreases. This increases the power input in the form of induced current in the electrode E, while the fall distance of the melted electrode material S is shortened.

[0047] Due to the strong dependence of the magnetic field strength on the coil spacing, the melting process is self-stabilizing in that the melting rate adjusts itself over a wide range to the feed rate of the electrode E. However, the position of the melting zone and thus the distance of the coil-side fixed end of the electrode E from the induction coil 122 vary depending on the feed rate.

[0048] Analogously, the melting process is also self-stabilizing with respect to changes in the applied operating power of the coil module. At a given feed rate, the distance between the coil-side fixed end of electrode E and the induction coil 122 also adjusts depending on the applied operating power.

[0049] Controlling the operation of the inductive melting system 100 to ensure a uniform atomization result can generally be achieved via various operating parameters of the inductive melting system 100. These include, for example, an operating current of the induction coil 122, a feed rate of the electrode feed device 116, and / or a speed of the inert gas flow. However, due to the complex effects of varying most of these parameters, it is advantageous to only control the feed rate of the electrode feed device 116 such that the superheat temperature of the melted electrode material S is kept as constant as possible, corresponding to a constant position of the fixed coil-side end of the electrode E relative to the induction coil 122.However, such control of the melting process is made more difficult by the fact that an exact position of the coil-side fixed end of the electrode E is typically not visible due to the melt adhering there.

[0050] Controlling the feed rate of the electrode feed device 116 is described in more detail below with reference to Fig. 1. However, it is understood that the techniques described therein can also be advantageously used to control an inductive melting system in a different manner. In particular, the described techniques can also be used to control at least one other operating parameter of the inductive melting system 100 other than a feed rate and / or for a purpose other than achieving a uniform process result.

[0051] The inductive melting system 100 comprises a control device 160 connected to a cooling circuit 140 of the inductive melting system 100. The cooling circuit 140 is provided for cooling the induction coil 122. The cooling circuit 140 is designed to detect a heat conversion that occurs in the cooling circuit 140 during cooling of the induction coil 122. The cooling circuit 140 is also designed to output a data signal indicating the detected heat conversion to the control device 160. During operation of the inductive melting system 100, the induction coil 122 is heated both by Joule heat generated in the induction coil 122 by the operating current of the induction coil 122 itself, and by heat transferred from the environment of the induction coil 122, in particular by heat radiated by the electrode E and the melted electrode material S.

[0052] The control device 160 of the inductive melting system 100 is designed to control the operating power of the coil module 120. For this purpose, the control device 160 is connected to the power supply device 130 for control purposes. The control device 160 is also connected to the electrode feed device 116 and is designed to control the feed rate of the electrode E by means of the electrode feed device 116.

[0053] In the example of Fig. 1, the inductive melting system 100 also includes a camera 150. The camera 150 is arranged to capture image information related to the melting process. The camera 150 is connected to the control device 160 and configured to output image signals to the control device 160.

[0054] Due to the self-stabilizing properties of the melting process, as explained above, operation of the inductive melting system 100 in the run-in process approximately corresponds to a dynamic equilibrium. There is a direct relationship between the operating power of the coil module 120, the feed rate of the electrode feeder 116, the melting rate (which, as explained above, is proportional to the feed rate assuming dynamic equilibrium), the heat conversion in the cooling circuit 140, and the superheat temperature of the melted electrode material S.

[0055] The amount of heat converted in the cooling circuit 140 depends on the amount of heat present in the induction coil 122. This heat consists of Joule heat due to the operating current of the induction coil 122 and heat transferred to the induction coil 122 by the heated electrode material of the electrode E and the melted electrode material S, primarily through thermal radiation.

[0056] The contribution of Joule heat in the induction coil 122 to the heat conversion in the cooling circuit 140 is determined primarily by the operating power of the induction coil 122. This corresponds to the operating power of the coil module 120 minus the electrical power loss of the coil module 120. Based on the operating power of the coil module 120, which is controlled by the control device 160 via the power supply device 130, the contribution of Joule heat present in the induction coil 122 to the heat conversion detected in the cooling circuit 140 and transmitted to the control device 160 can be calculated by the control device 160. For this purpose, the control device 160 stores, for example, an association between different operating powers of the coil module 120 and a respective portion of the detected heat conversion in the cooling circuit 140 attributable to Joule heat in the induction coil 122.

[0057] The remaining portion of the heat conversion, which is detected in the cooling circuit 140 and transmitted to the control device 160, is attributable to the thermal effect of the heated electrode material on the induction coil 122. The remaining portion of the detected heat conversion therefore indicates the heat loss currently occurring during the melting process, i.e., heat generated in the electrode material and then released again, which thus does not effectively contribute to heating the electrode material to the overheating temperature.

[0058] Based on the operating power of the coil module 120 minus an electrical power loss of the coil module, assumed to be known and stored, for example, in corresponding characteristic diagrams, as well as the Joule heat in the induction coil 112 and the heat loss, which can each be determined from the recorded heat conversion in the cooling circuit 140, for example, also stored in corresponding characteristic diagrams, a net heating power of the inductive melting system 100 for the current process can be determined by means of the control device 160. The net heating power is considered to be that portion of the electrical operating power of the induction coil 122 that is converted into heat in the electrode E and the melted electrode material S and is not released back into the environment until the intended temperature, for example, the intended superheating temperature, is reached.

[0059] During the melting process, the melting rate is also proportional to the feed rate of the electrode E. The feed rate, which is achieved by the electrode feed device 116, is also controlled by the control device 160. Based on the feed rate and the net heating power, the control device 160 can therefore also determine a relationship between the effectively supplied heat and the amount of electrode material that is melted and superheated using this heat. From this, the resulting superheating temperature of the melted electrode material S can be determined by the control device 160, for example, based on the enthalpy specific to the respective electrode material and stored in the control device 160.

[0060] According to the relationships described above, the control device 160 is designed to determine the overheating temperature of the melted electrode material S dynamically, for example according to a variable heat conversion in the cooling circuit 140, based on data that is acquired by the inductive melting system 100 or stored in the control device 160.

[0061] The control device 160 is further configured to control at least one operating parameter of the inductive melting system 100 based on the determined overheating temperature. For example, the control device 160 is configured to regulate at least one operating parameter of the inductive melting system 100 in order to achieve a constant overheating temperature of the melted electrode material S.

[0062] Fluctuations in the heat conversion measured by the cooling circuit 140 while maintaining constant controllable operating parameters of the inductive melting system 100 indicate irregularities in the melting process. These can result, for example, from inhomogeneities in the electrode material or fluctuations in the inert gas flow. In this case, the control device 160 is designed, for example, to vary one or more operating parameters, such as the feed rate of the electrode E by means of the electrode feed device 116, in order to counteract the effect of the irregularities on the overheating temperature of the melted electrode material S.

[0063] In further examples, the control device 160 according to the above allows the control of at least one other or at least one further operating parameter other than the feed rate. In further examples, the control of the at least one operating parameter is also carried out according to a different or further criterion than a constant superheat temperature.

[0064] In some examples, heat flow from a melting zone of the electrode E to more distant regions of the electrode E is also taken into account to determine the net heating power. This is done, for example, using a constant or temperature-dependent characteristic value for the electrode E. In other examples, heat flow from the melting zone of the electrode E is not taken into account when determining the net heating power. This simplifies the determination of the net heating power using the control device 160 and has only a negligible influence in many applications, for example, relevant electrode materials and sizes.

[0065] In the example shown in Fig. 1, the inductive melting system 100 further comprises a camera 150. The camera is connected to the control device 160 and aligned such that it captures image information relating to the melting process and outputs corresponding image data to the control device 160. In this case, the image data are used by the control device 160 additionally or alternatively, i.e. decoupled from the feed rate of the electrode E, to determine the melting rate. For this purpose, the camera 150 captures at least one characteristic, for example a thickness, of the melt jet. For example, a thickness of the melt jet can be determined by photometric evaluation of the image data by means of the control device 160. The thickness of the melt jet varies depending on an existing melting rate.The image information captured by the camera 150 thus allows an improved determination of the actual melting rate, for example when the melting process is not in dynamic equilibrium with respect to the melting rate.

[0066] In further examples of the inductive melting system 100, a position of the induction coil 122 can also be controllably varied. The position of the induction coil can be controllably varied, for example, parallel and / or transversely to the feed direction of the electrode E. By changing the position of the induction coil 122 parallel to the feed direction of the electrode E, a distance of the induction coil 122 from the electrode E can be varied for a short time. At the same time, a drop height of the melted electrode material S can be varied, for example with otherwise constant controllable operating parameters of the inductive melting system 100. By changing the position of the induction coil 122 transversely to the feed direction of the electrode E, an influence of the magnetic field of the induction coil 122 on the electrode E can be varied, for example for a short time, asymmetrically, i.e. eccentrically, to the coil axis, to the longitudinal axis of the electrode E and / or to the nozzle axis.In this case, a drop height of the melted electrode material S can be kept constant, for example. In some examples of the melting system 100, which are provided for atomizing the melted electrode material S, a position of the nozzle 118 can be controllably varied parallel and / or transverse to the feed direction of the electrode E for at least some of the aforementioned purposes.

[0067] Fig. 2 shows a flowchart for a method 200 for operating an inductive melting system. The method 200 can be carried out, for example, using the inductive melting system 100, as described above.

[0068] The method 200 comprises determining a net heating power of the inductive melting system by means of a control device of the inductive melting system, step 210. The method 200 further comprises determining a melting rate by means of the control device, step 220. At least partially based on the net heating power and the melting rate, a superheating temperature of the melted electrode material is determined by means of the control device, step 230. Based on the determined superheating temperature, in the method 200 at least one operating parameter of the inductive melting system is then controlled by means of the control device, step 240. Fig. 3 schematically and exemplarily shows a control device 300 for an inductive melting system 100. The control device 300 is, for example, a control device of the same type as the control device 160 in Fig. 1.

[0069] The control device 300 comprises a processor unit 310 and a memory device 320 operatively connected to the processor unit 310. The processor unit 310 is connected to the memory device 320 such that the processor unit 310 has read access to program code stored in the memory device 320. The processor unit 310 is also programmable using program code stored in the memory device 320. For this purpose, the processor unit 310 is configured to execute program code stored in the memory device 320.

[0070] The control device 300 comprises at least one input interface 312 for receiving data signals by means of the processor unit 310 and at least one output interface 314 for outputting data signals, for example control signals, which are generated by means of the processor unit 310.

[0071] The storage device 320 contains program code which, when executed by the processor unit 310, configures the control device 300 to carry out a method as described above in connection with Figs. 1 and 2, in particular to control at least one operating parameter of an inductive melting system.

[0072] For this purpose, the storage device 320 contains program code which, in cooperation with the processor unit 310, forms a net heating power determination module 322. The net heating power determination module 322 allows the determination of a net heating power of the inductive melting system, for example, according to step 210 of the method 200.

[0073] The storage device 320 also contains program code that, in cooperation with the processor unit 310, forms a melting rate determination module 324. The melting rate determination module 324 allows the determination of a melting rate of the inductive melting system, for example, according to step 220 of the method 200. The storage device 320 further contains program code corresponding to an overheating temperature determination module 326. The overheating temperature determination module 326 allows the determination of an overheating temperature of melted electrode material based at least partially on the net heating power and the melting rate, for example, according to step 230 of the method 200.

[0074] The storage device 320 also contains program code corresponding to an operating parameter control module 328. The operating parameter control module 328 allows the control of at least one operating parameter of the inductive melting system based on the determined superheat temperature, for example, according to step 240 of the method 200.

Claims

Claims 1. A method (200) for operating an inductive melting system (100) comprising at least one induction coil (122) for melting an electrode (E), the method (200) comprising: Determining (210), by means of a control device (160) of the inductive melting system (100), a net heating power of the inductive melting system (100), Determining (220), by means of the control device (160), a melting rate, Determining (230), by means of the control device (160), a superheat temperature of the melted electrode material (S) at least partially based on the net heating power and the melting rate, and Controlling (240), by means of the control device (160), at least one operating parameter of the inductive melting system (100) on the basis of the determined superheating temperature.

2. The method of claim 1, wherein determining (210) the net heating power is based at least in part on at least one of an applied operating power of a coil module (120) of the inductive melting system (100) comprising the induction coil (122) and an electrical power loss of the coil module (120).

3. The method according to claim 1 or claim 2, wherein the determining (210) of the net heating power is further carried out at least partially on the basis of a heat loss power, in particular due to thermal radiation.

4. The method according to claim 3, wherein the inductive melting system (100) further comprises a cooling circuit (140) for the induction coil (122), wherein the heat loss, in particular due to thermal radiation, is determined at least partially on the basis of a heat conversion of the cooling circuit (140).

5. The method according to claim 3 or claim 4, wherein, when determining the heat loss power, a heat flow within the electrode material (E) is not taken into account, or wherein, when determining the heat loss power, a heat flow within the electrode is taken into account according to a heat flow characteristic, in particular according to a constant heat flow characteristic, of the electrode material (E).

6. The method of claim 2 in conjunction with any one of claims 3 to 5, wherein determining (210) the net heating power is based at least in part on a difference between the applied operating power of the coil module (120) and a combination of the electrical power loss of the coil module (120) and the heat loss.

7. Method according to one of the preceding claims, wherein the net heating power is a heating power contributing to heating and melting of the electrode material (E) as well as to overheating of the melted electrode material (S).

8. The method according to any one of the preceding claims, wherein the inductive melting system (100) further comprises at least one camera (150) configured to capture image information related to a melting process of the inductive melting system (100) and to output an image signal indicative of the image information to the control device (160), wherein the determination of the melting rate is performed at least partially on the basis of the captured image information.

9. The method of claim 8, wherein determining the melting rate is based at least in part on a photometric evaluation of the acquired image information.

10. The method according to any one of the preceding claims, wherein the determination of the superheat temperature is further carried out at least partially on the basis of an enthalpy of the electrode material (E).

11. The method according to any one of the preceding claims, wherein controlling (240) the at least one operating parameter comprises: Comparing the determined superheat temperature with a setpoint superheat temperature, and Controlling the at least one operating parameter based on a result of comparing the determined superheat temperature with the setpoint superheat temperature.

12. The method according to any one of the preceding claims, wherein the at least one operating parameter comprises at least one of the operating power of the coil module (120), an operating current of the induction coil (122), a feed rate of the electrode (E) and a position of the induction coil (122) with respect to the electrode (E).

13. Method according to one of the preceding claims, wherein the method is provided for automatically monitoring and / or controlling an operation of the inductive melting plant (100).

14. Control device (160; 300) for an inductive melting system comprising a processor unit (310) and a memory device (320) which is connected to the processor unit (310) is operatively connected, wherein the processor unit (310) is configured to perform the method according to one of the preceding claims.

15. Inductive melting system (100) comprising: at least one induction coil (122) for melting an electrode (E), and a control device (160; 300) which is designed to operate the inductive melting system (100) according to the method according to one of claims 1 to 13.

Images