Apparatus and method for the production of investment cast parts

Abstract

The present invention relates to an apparatus (10) for producing investment cast parts, the apparatus (10) including a melting chamber (12) having an induction coil assembly (14, 114, 214, 314) disposed therein, the induction coil assembly (14, 114, 214, 314) adapted to melt an electrode (18) at least partially contained therein to produce a continuous ceramic-free melt jet (40) having a melt flow rate MFR of at least 2.5 kg / min. The apparatus further includes a casting chamber (20) downstream of and coupled to the melting chamber (12) and with an investment casting mold contained or receivable within the melting chamber to be filled with the continuous ceramic-free melt jet (40).

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for producing investment cast parts by using a continuous ceramic-free melt jet, in other words, the present invention relates to an apparatus and method for investment casting of molded parts. [Background technology]

[0002] The investment casting plant and the investment casting process carried out therewith are used to produce cast parts made of metal alloys having a relatively high surface quality and dimensional accuracy. In particular, the investment casting plant and the process can be used to produce parts for the aerospace industry, the power generation industry, the automotive industry, the medical technology industry, the chemical industry, and / or the electrical industry. Parts produced using the investment casting process require only minimal post-processing. Furthermore, the investment casting process can be used to produce parts with complex structures.

[0003] In known investment casting plants, the material to be melted is melted in a crucible and then poured into a prepared melt mold. However, in known investment casting plants, undesirable impurities can occur in the molten material that negatively affect the quality of the produced cast parts. Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE PRESENT EMBODIMENT It is therefore an object of the present invention to provide an apparatus and method that overcomes the shortcomings of the prior art.

[0005] In particular, it is an object of the invention to provide an apparatus and a method which allow the production of investment cast parts with improved quality, which here can mean for example a higher material quality and / or a higher surface quality of the part. [Means for solving the problem]

[0006] This object is achieved by the subject matter of the independent claims. Further developments and embodiments of the device and the method are the subject matter of the dependent claims and the following description.

[0007] One aspect of the invention relates to an apparatus or plant for producing investment cast parts, particularly complex cast parts. The apparatus includes a melting chamber including an induction coil assembly disposed therein. The induction coil assembly is adapted to melt an electrode at least partially contained therein to produce a continuous ceramic-free melt jet at a melt flow rate (MFR) of at least 2.5 kg / min. The apparatus further includes a casting chamber downstream of and coupled to the melting chamber and including an investment casting mold contained or capable of being contained within the melting chamber and adapted to be filled with the continuous ceramic-free melt jet.

[0008] The creation and use of a continuous ceramic-free melt jet can prevent contamination of the melt during the process, which serves to both improve the mold filling process and improve the metallurgical properties of the produced cast parts.

[0009] By creating and using a continuous melt jet, a relatively less turbulent mold filling process can be achieved, which reduces the occurrence of ceramic impurities in the melt material and thus in the investment casting due to particles detached from the mold walls. Furthermore, the continuous and uniform filling of the mold allows possible contaminant particles to be carried upward during the casting process, where they have a reduced probability of affecting the quality of the cast part.

[0010] The induction coil assembly can be designed to melt an electrode at least partially contained therein in a manner to produce a continuous ceramic-free melt jet at a melt flow rate MFR of at least 4 kg / min, preferably at least 5 kg / min, more preferably at least 6 kg / min, and even more preferably at least 8 kg / min.

[0011] The induction coil assembly can be designed to melt an electrode at least partially contained therein in a manner to produce a continuous ceramic-free melt jet at a melt flow rate MFR of at most 15 kg / min, preferably at most 12 kg / min, and more preferably at most 10 kg / min.

[0012] In particular, the induction coil assembly can be designed to melt an electrode at least partially contained therein in a manner that produces a continuous ceramic-free melt jet at a melt flow rate MFR of between 2.5 kg / min and 10 kg / min.

[0013] A melt flow rate MFR of at least 2.5 kg / min, specifically in the range of 2.5 kg / min to 10 kg / min, as determined by the inventors, represents a melt flow rate suitable for investment casting applications, which represents an optimal balance between ensuring sufficient superheating of the melt jet, achieving adequate mold filling times, and practically acceptable energy consumption.

[0014] In particular, the inventors of the present invention have recognized that sufficient superheating of the melt jet can be achieved at a melt flow rate MFR of at least 2.5 kg / min. Such a surprising relationship between melt flow rate MFR and superheat was not anticipated based on the prior art known from practice. Rather, it would have been expected that only very low superheats would be achievable due to the relatively short residence time of the molten material inside the coil arrangement as a result of increasing melt flow rates. However, for investment casting applications in order to prevent solidification and agglomeration of the melt before being introduced into the mold, it is required that the melt be superheated to a sufficiently high temperature. At the same time, in investment casting, complete filling within the appropriate mold filling time must be guaranteed in order to produce investment cast parts of the required quality and grade.

[0015] Due to the melt flow rate of at least 2.5 kg / min, in particular 2.5 kg / min to 10 kg / min, of the continuous melt jet generated with the device, a complete filling of the investment casting mold within a reasonable time can be achieved. In other words, the minimum melt flow rate provided by the inventors can reduce the mold filling time to an optimal level. At relatively low melt flow rates, such as those known from conventional continuous melting processes, it seems impossible to guarantee a proper mold filling and thus the production of investment cast parts of sufficient quality. In particular, a proper mold filling time may refer to the mold filling time for common investment cast parts in the aerospace industry (e.g. turbine blades), the power generation industry (e.g. turbine blades), the automotive industry (e.g. turbocharger wheels), the medical technology, chemical and / or electrical industries, etc. The minimum melt flow rate contemplated by the inventors may therefore be highly suitable for the production of such investment cast parts of high quality, but is not limited thereto.

[0016] The investment casting mold is a lost mold. The material of the investment casting mold may be, for example, ceramic or graphite.

[0017] In particular, the meltable electrode may be a rotating electrode that is vertically suspended in the melting chamber and continuously melted under vacuum or inert gas atmosphere by controlled motion at its lower end with an induction coil assembly. The controlled motion may include continuous feeding of the electrode toward the casting chamber in addition to the rotational motion for uniform melting. The induction coil assembly may include a tapered shape toward the lower end of the electrode. The induction coil assembly and the electrode are coaxially disposed with each other.

[0018] In one embodiment, the casting chamber may include a mold heating device configured to heat the investment casting mold during the casting or production process, which may prevent premature and undesired cooling and therefore solidification of the melt jet introduced into the investment casting mold, which may contribute to ensuring complete filling of the investment casting mold and a higher quality of the produced investment cast part.

[0019] The apparatus may include a mold ejection device capable of ejecting the investment casting mold away from the melting chamber. The mold ejection device may be located within or at or below the casting chamber. For example, the mold ejection device may be mounted within a load / unload chamber. The mold ejection device may be used to achieve controlled solidification of the cast part. This may allow for the injection or refilling of liquid metal from the upper portion of the mold into which the melt jet is injected to areas of the mold that are freed due to solidification shrinkage. Moreover, the mold ejection device and controlled solidification may be used to produce directionally solidified castings.

[0020] The apparatus may include a load / unload chamber for loading / unloading the investment casting mold, the load / unload chamber being located downstream from the casting chamber.

[0021] The induction coil assembly may be operated at a power P that satisfies the following conditions:

number

[0022] The induction coil assembly may be operated at a power P that satisfies the following conditions:

number

[0023] The induction coil assembly may be operated with a power P that satisfies the following conditions:

number

[0024] The power P can be set as a function of the diameter of the electrode to be melted according to the above conditions.

[0025] The induction coil assembly may be operated with a power P that satisfies the following conditions, in particular for melting an electrode having a diameter of 150 mm:

number

[0026] The induction coil assembly may be operated with a power P that satisfies the following conditions, in particular for melting an electrode having a diameter of 150 mm:

number

[0027] The induction coil assembly may be operated with a power P of less than or equal to 400 kW, in particular less than or equal to 350 kW, preferably less than or equal to 300 kW.

[0028] The power P mentioned above that can be supplied to or operate the induction coil assembly or induction coil can contribute to optimizing the power consumption and voltage of the device while ensuring a balance between proper mold filling time and optimal heating.

[0029] The induction coil assembly is designed to withstand an overheating temperature T sup may be set to superheat the melt jet according to the melt flow rate MFR such that the following condition is satisfied:

number

[0030] The induction coil assembly is designed to withstand an overheating temperature T sup may be set to superheat the melt jet according to the melt flow rate MFR such that the following condition is satisfied:

number

[0031] The induction coil assembly is designed to withstand an overheating temperature T sup can be set to superheat the melt jet according to the melt flow rate MFR such that the following condition is met:

number

[0032] Superheating temperature T sup can be set as a function of the diameter of the electrode to be melted according to the above conditions.

[0033] The induction coil assembly is heated to a superheat temperature T sup can be set to superheat the melt jet according to the melt flow rate MFR such that the following condition is satisfied:

number

[0034] The induction coil assembly can be set to superheat the melt jet by at least 10° C., preferably by 20° C., preferably by at least 40° C., more preferably by at least 60° C., and even more preferably by at least 80° C. Superheating of over 100° C. is achievable as well.

[0035] The induction coil assembly is heated to a superheat temperature T sup can be set to superheat the melt jet according to the melt flow rate MFR such that the following condition is satisfied:

number

[0036] Here, the superheat may be the time- and volume-averaged superheat of the melt jet.

[0037] The induction coil assembly may be set to superheat the melt jet by no more than 250° C., preferably no more than 200° C., and more preferably no more than 150° C. The superheat can be adjusted depending on the material (relative to the electrode).

[0038] Said superheating of the melt jet can ensure an optimal balance between the energy consumption and voltage of the equipment, between adequate mold filling time and optimal superheating. In particular, a defined superheat as a function of the melt flow rate can provide a measure that can further improve the quality of the investment cast parts.

[0039] The induction coil assembly may be operated at a voltage of 1200 V or less, preferably 1000 V or less. The voltage may be at least 100 V, preferably at least 200 V, more preferably at least 450 V. This upper voltage limit of 1000 V allows the plant to be operated in the low voltage range. Likewise, for example, at such voltages, it is possible to dispense with any insulation between the windings of the induction coil altogether.

[0040] However, in alternative embodiments, higher voltages are possible as well for energizing the induction coil assembly, in particular if the plant is operated under high pressure, higher voltages may be provided, for example 1500V or more.

[0041] The induction coil assembly may be operated at a frequency between 10 kHz and 300 kHz, preferably between 50 kHz and 200 kHz, more preferably between 75 kHz and 125 kHz. In particular, the frequency may be 100 kHz.

[0042] At least the melting chamber may be pressurized with absolute pressure so that the melt jet is generated under absolute pressure. The absolute pressure may be at least 30 mbar, preferably at least 1 bar, more preferably at least 5 bar. The absolute pressure may be less than 10 bar. The absolute pressure may be between 30 mbar and 10 bar, preferably between 1 bar and 10 bar. In particular, in such an embodiment, the induction coil assembly may be operated at a voltage of 1000V or more, preferably 1200V or more, more preferably 1500V or more. The induction coil assembly may include at least one induction coil having four or less series windings, preferably three or less series windings, more preferably two or less (i.e. having only one winding).

[0043] An induction coil having four windings may also be referred to as a four-winding induction coil, which here refers to an induction coil with four serially interconnected windings. An induction coil with three windings may also be referred to as a three-winding induction coil, which here refers to an induction coil with three serially interconnected windings. An induction coil with two windings may also be referred to as a two-winding induction coil, which here refers to an induction coil with two serially linked windings. An induction coil with one winding may also be referred to as a single-winding induction coil.

[0044] The induction coil assembly may include at least one induction coil having at least two parallel windings with a common current draw. Preferably, the induction coil assembly may include an induction coil having exactly two parallel windings with a common current draw. In this case, the induction coil assembly includes a single-winding induction coil with two parallel windings.

[0045] Thus, the above-mentioned embodiments of the induction coil may be combined. For example, the induction coil assembly may include an n×m winding induction coil, where m represents the number of series windings of the induction coil and n represents the number of parallel m-winding arrangements. In one embodiment, the induction coil assembly may include a 2×2 winding induction coil, i.e., an induction coil with a total of four windings, of which two serially interconnected windings are connected in parallel with and have a common current draw with two other serially interconnected windings. In particular, in such an arrangement, the first and last, i.e., the top and bottom or outer windings, are interconnected, and the second and third, i.e., the two middle or inner windings, are interconnected in series. The two outer windings are interconnected in parallel with the two inner windings. In one embodiment, the induction coil assembly may include a 2×1 winding induction coil, i.e., an induction coil with a total of two parallel windings. In one embodiment, the induction coil assembly may include a 1×2 winding induction coil, in other words a two-winding induction coil, ie an induction coil with a total of two series windings.

[0046] An induction coil assembly of the above type can contribute to achieving the desired optimum balance between ensuring sufficient superheating of the melt jet, adequate mold filling time and practically acceptable energy consumption. Thus, an induction coil assembly of the above type, in particular a 2×2 winding induction coil, can contribute to ensuring uniform power input into the electrode tip of electrodes with large electrode diameters (e.g., 150 mm or more), while at the same time avoiding exceeding an upper voltage limit, e.g., 1000 V.

[0047] By using an induction coil with a smaller number of windings (compared to a coil of the same size and with a larger number of windings), it is possible to generate more overheat when operated at a lower voltage, where in particular for example a 2-winding (1×2 winding) induction coil or a 2×2 winding induction coil may be provided.

[0048] The induction coil assembly may include a first induction coil and at least one second induction coil. The two induction coils are separate from each other and each has its own current draw. The first induction coil, at least the second induction coil or the first and at least the second induction coil may be formed with the above-mentioned features. The first induction coil may be supplied or operated with power P1, frequency f1 and voltage U1 (preferably U1≦1000V). The at least second induction coil may be supplied or operated with power P2, frequency f2 and voltage U2 (preferably U2≦1000V).

[0049] In one embodiment, the first induction coil and at least the second induction coil may be arranged in such a way that both induction coils serve to melt the electrode. For this purpose, the two induction coils may be arranged side by side and aligned along an imaginary cylinder or an imaginary cone. In other words, in a cross-sectional view, adjacent winding cross-sections of both induction coils may be aligned along a common axis. The common axis may be arranged substantially parallel to the inclined surface of the fused end portion of the electrode. Both induction coils may have a conical shape. The two induction coils may be embedded in a soft magnetic yoke, thus preventing undesired coil interactions. With such an embodiment, the generated melt flow rate may be increased. That is, P1+P2 leads to an increase in the melt flow rate MFR.

[0050] In one embodiment, the first induction coil may be arranged to help melt the electrode, while the at least second induction coil may be arranged downstream of the first induction coil and to help heat the melt jet. For this purpose, the windings of the first induction coil may be arranged substantially parallel to the inclined surface of the end portion of the electrode to be melted. The first induction coil may have a conical shape. The downstream at least second induction coil may be coaxial with the melt jet generated by the first induction coil and may have a cylindrical shape. The at least second induction coil may be embedded in a soft magnetic yoke. With such an embodiment, the superheating of the generated melt jet can be further enhanced, i.e. P2 helps to enhance the superheating.

[0051] In one embodiment, the first induction coil may be arranged to help melt the electrode, while the second induction coil may be arranged upstream of the first induction coil to help preheat the electrode to be melted. For this purpose, the windings of the first induction coil may be arranged substantially parallel to the inclined surface of the end portion of the electrode to be melted. The first induction coil may have a conical shape. The upstream at least second induction coil may be coaxial with the electrode and may have a cylindrical shape. The at least second induction coil may be embedded in a soft magnetic yoke. With such an embodiment, the superheating of the generated melt jet can be further enhanced, i.e. P2 serves to enhance the superheating. Furthermore, the upstream second induction coil may also at least slightly contribute to the generation of the melt jet, so that P1+P2 contributes to an increase in the melt flow rate MFR.

[0052] In one embodiment, the induction coil assembly may have an average coil diameter of 50 mm or more, preferably 150 mm or more. In particular, the induction coil assembly may be configured to at least partially accommodate an electrode having a diameter of 50 mm or more, preferably 150 mm or more. The use of an electrode with a diameter of 150 mm or more may help provide sufficient material to fill an investment casting mold, since the length of the electrode may be limited due to the system.

[0053] Another aspect of the invention relates to a system for producing investment cast parts including an apparatus of the type described above and an electrode at least partially contained therein.

[0054] The electrode may be a cast electrode. Alternatively, the electrode may be a consolidated electrode that includes a plurality of particles or segments. The particles or segments may be of loose shape, i.e., may have different and nearly any shape. Such electrodes are relatively inexpensive to manufacture. The electrode may be made of or include a metal alloy. The electrode may include or consist of titanium or a titanium alloy, e.g., Ti64. The electrode may include or consist of a nickel-chromium alloy, e.g., IN718. It should be understood that the electrode may include or consist of other metals or metal alloys as well.

[0055] Another aspect of the present invention relates to a method for producing an investment cast component, i.e., an investment casting method, comprising: providing an electrode within a melting chamber; inserting the electrode at least piecewise into an induction coil assembly disposed within the melting chamber; melting the electrode with an induction coil assembly to produce a continuous ceramic-free melt jet at a melt flow rate of at least 2.5 kg / min; providing an investment casting mold in a casting chamber downstream from and coupled to the melting chamber; continuously filling the melt jet into an investment casting mold; Includes.

[0056] The investment casting mold may be heated during the production process using a mold heating device in the casting chamber.

[0057] The investment casting mold may be ejected during continuous filling in a direction away from the molten chamber using a mold ejection device.

[0058] In the method, the induction coil assembly is operable with a power P that satisfies the following conditions:

number

[0059] In the method, the induction coil assembly is operable with a power P that satisfies the following conditions:

number

[0060] In the method, the induction coil assembly is operable with a power P that satisfies the following conditions:

number

[0061] The power P can be set depending on the diameter of the electrode to be melted according to the above conditions.

[0062] In the method, the induction coil assembly can be operated with a power P that satisfies the following conditions, particularly when using electrodes with a diameter of 150 mm:

number

[0063] In the method, the induction coil assembly is heated to a temperature T sup can be used to superheat the melt jet according to the melt flow rate MFR such that the following condition is met:

number

[0064] In the method, the induction coil assembly is heated to a temperature T sup can be used to superheat the melt jet according to the melt flow rate MFR such that the following condition is met:

number

[0065] In the method, the induction coil assembly is heated to a temperature T sup can be used to superheat the melt jet according to the melt flow rate MFR such that the following condition is met:

number

[0066] Superheating temperature T sup can be set according to the diameter of the electrode to be melted according to the above conditions.

[0067] In the method, the induction coil assembly is heated to a temperature T sup can be used to superheat the melt jet according to the melt flow rate MFR in such a way as to satisfy the following conditions, in particular to melt an electrode with a diameter of 150 mm:

number

[0068] The melt jet may be heated by the induction coil assembly by at least 10°C, preferably by 20°C, preferably by at least 40°C, more preferably by at least 60°C, and even more preferably by at least 80°C.

[0069] The induction coil assembly may be operated at a voltage of up to 1200 V, preferably up to 1000 V. The induction coil assembly may be operated at a frequency of 10 kHz to 300 kHz, preferably 50 kHz to 200 kHz, more preferably 75 kHz to 125 kHz.

[0070] At least the melt chamber may be pressurized with absolute pressure so that the melt jet is generated under absolute pressure. The absolute pressure may be at least 30 mbar, preferably at least 1 bar, more preferably at least 5 bar. The absolute pressure may be less than 10 bar. The absolute pressure may be between 30 mbar and 10 bar, preferably between 1 bar and 10 bar.

[0071] A further aspect relates to the structural design of the induction coil assembly. This aspect may be independent of the described embodiment of the overall device and may form a separate subject. The induction coil assembly may include at least one induction coil including up to four series windings, preferably including up to three series windings, more preferably including two or less (i.e. having only one winding). An induction coil having four windings may also be referred to as a four-winding induction coil. Here, it refers to an induction coil with four serially interconnected windings. An induction coil with three windings may also be indicated as a three-winding induction coil. Here, it refers to an induction coil with three serially interconnected windings. An induction coil with two windings may also be indicated as a two-winding induction coil. Here, it refers to an induction coil with two serially linked windings. An induction coil with one winding may also be referred to as a single-winding induction coil.

[0072] The induction coil assembly may include at least one induction coil including at least two parallel windings with a common current draw. Preferably, the induction coil assembly may include an induction coil having exactly two parallel windings with a common current draw. In this case, the induction coil assembly includes a single winding induction coil with two parallel windings.

[0073] Thus, the above-mentioned embodiments of the induction coil may be combined. Thus, the induction coil assembly may include an n×m winding induction coil, where m represents the number of series windings of the induction coil and n represents the number of parallel m-winding arrangements. In one embodiment, the induction coil assembly may include a 2×2 winding induction coil, i.e. an induction coil with a total of four windings, of which two serially interconnected windings are connected in parallel with two other serially interconnected windings and have a common current draw with them. In particular, in such an arrangement, the first and last, i.e. the top and bottom or outer windings, are interconnected, and the second and third, i.e. the two middle or inner windings, are interconnected in series. The two outer windings are interconnected in parallel with the two inner windings. In one embodiment, the induction coil assembly may include a 2×1 winding induction coil, i.e. an induction coil with a total of two parallel windings. In one embodiment, the induction coil assembly may include a 1×2 winding induction coil, in other words a two-winding induction coil, ie an induction coil with a total of two series windings.

[0074] By using an induction coil with a smaller number of windings (compared to a coil of the same size and with a larger number of windings), it is possible to generate more overheat when operated at a lower voltage, where in particular for example a 2-winding (1×2 winding) induction coil or a 2×2 winding induction coil may be provided.

[0075] Although some features, advantages, functions, modes of operation, embodiments and further developments have been explained above only with respect to the device, they correspondingly also apply to the method and vice versa.

[0076] Exemplary embodiments of the invention are explained in more detail below with reference to the accompanying schematic drawings. [Brief description of the drawings]

[0077] [Figure 1]FIG. 1 is a schematic cross-sectional view of an apparatus according to one embodiment of the present invention. [Figure 2A] FIG. 2A is a schematic representation of one embodiment of an induction coil according to the invention for the device of FIG. [Figure 2B] FIG. 2B is a schematic cross-sectional view of the inductive coil of FIG. 2A during operation. [Diagram 3] FIG. 3 is a schematic representation of a first embodiment of an induction coil assembly according to the present invention in operation. [Figure 4] FIG. 4 is a schematic representation of a second embodiment of an induction coil assembly according to the present invention in operation. [Diagram 5] FIG. 5 is a schematic representation of a third embodiment of an induction coil assembly according to the present invention in operation. [Figure 6] FIG. 6 is a graph showing the relationship between superheat temperature and melt flow rate in a device according to the present invention for different electrode materials. [Figure 7] FIG. 7 is a graph showing the relationship between voltage and melt flow rate in a device according to the present invention for different electrode materials. [Figure 8] FIG. 8 is a plot of power versus melt flow rate in a device according to the present invention for different electrode materials. [Figure 9] FIG. 9 is a graph showing the relationship between superheat temperature and melt flow rate in an apparatus according to the present invention for different induction coil designs. [Figure 10] FIG. 10 is a graph showing the relationship between voltage and melt flow rate in an apparatus according to the present invention for different induction coil designs. [Figure 11] FIG. 11 is a graph showing the relationship between power and melt flow rate in an apparatus according to the present invention for different induction coil designs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] 1 shows an apparatus or plant 10 for producing investment cast parts. The apparatus 10 includes a melting chamber 12 that includes an induction coil assembly 14 mounted within the melting chamber 12. A vacuum is applied to the melting chamber 12. Alternatively, the melting chamber 12 may be pressurized with an inert gas atmosphere.

[0079] Above, i.e. upstream of, the melting chamber 12 is arranged an electrode loader 16. It includes an electrode 18 which is movable along its longitudinal axis in the direction of the induction coil assembly 14 and rotatable about its longitudinal axis by means of the electrode loader 16. In this embodiment, the electrode 18 is a titanium alloy electrode. It is understood that electrodes of other metals or metal alloys may be provided as well. The electrode 18 is at least piecewise inserted, more particularly at its lower end portion, into the induction coil assembly 14 during operation of the plant.

[0080] The induction coil assembly 14 is adapted to melt the electrode 18 to produce a continuous ceramic-free melt jet (not shown in FIG. 1, but see, e.g., FIG. 2B). The electrode loading device 16 can be used to feed and simultaneously rotate the electrode 18 to ensure uniform melting of the electrode 18 and the production of a continuous melt jet substantially without interruption.

[0081] The induction coil assembly 14 is operated or controlled to melt the electrode 18 and produce a continuous melt jet at a melt flow rate MFR of at least 2.5 kg / min, specifically between 2.5 kg / min and 10 kg / min.

[0082] The apparatus 10 further includes a casting chamber 20 disposed downstream, i.e., below, and pressure-tightly connected to the melting chamber 12. The casting chamber 20 is adapted to accommodate an investment casting mold (not shown here) that is filled with a melt jet during operation.

[0083] The investment casting mold may have any shape depending on the investment casting to be produced. In particular, the investment casting mold may be a ceramic mold.

[0084] The casting chamber 20 includes a mold heating device 22. The mold heating device 22 is used to heat an investment casting mold provided within the casting chamber 20 prior to the initiation of the melting process or sequence. Additionally, the mold heating device 22 can also be used to further heat the investment casting mold during melting and filling to prevent premature solidification of the melt upon contact with the walls of the investment casting mold, which would negatively impact the quality of the investment cast part.

[0085] A load / unload chamber 24 of the apparatus 10 is formed below and connected to the casting chamber 20. The load / unload chamber 24 is used to insert investment casting molds and remove cast investment cast parts.

[0086] A mold ejection apparatus 26 is formed within the load / unload chamber 24 and can be used to eject an investment casting mold away from the melting chamber 12 .

[0087] FIG. 1 also shows a maintenance platform 28 formed on the device 10 and an operating platform 29 formed on the tool 10 .

[0088] 2A and 2B show an embodiment of the induction coil 30 of the induction coil assembly 14 of FIG. 1. As can be seen from the perspective view of FIG. 2A, the induction coil 30 in this embodiment is formed as a 2×2 winding induction coil. That is, the induction coil 30 includes two parallel two-winding winding arrangements. The windings 32-38 have a common current draw (not shown). The current flow through the induction coil 30, or more precisely its equal division due to the parallel connection, is shown in FIG. 2A by the lines 40 and 42. Moreover, the uniform distribution of the current is indicated in FIG. 2B by the different patterns of the cross sections of the windings 32-38. As can be seen from FIG. 2A and 2B, the windings 32 and 38 are connected in series and in parallel with the windings 34 and 36, which (i.e., the windings 34 and 36) are connected in series.

[0089] By using the 2×2 winding coil configuration shown in Figures 2A and 2B, uniform power input to the electrode 18 to be fused can be achieved. It is understood that other coil configurations may be provided in other embodiments of the invention. In particular, a two-winding, three-winding or four-winding configuration with no parallel windings may be provided. Alternatively, a single-winding coil configuration with or without parallel connection of the windings may be provided (even so, induction coils with two or more parallel single-winding winding arrangements may be referred to herein as single-winding coils).

[0090] In addition to the coil configuration, FIG. 2B also shows an electrode 18 that is piecewise inserted into the induction coil 30 and melted at its lower end with the induction coil 30 to produce a continuous melt jet 40 .

[0091] In Figs. 3-5 different induction coil assemblies 114, 214 and 314 are shown. Each of these induction coil assemblies 114, 214, 314, in addition to the induction coil 30 in the embodiment shown, includes a further induction coil 50, which is only diagrammatically labeled in Figs. 3-5. Each of these can be of single or multi-winding configuration and have the same or different number of windings. The two induction coils 30, 50 are formed and controlled separately from each other in the induction coil assemblies 114, 214, 314 shown. Each of them has its own power supply. In the embodiment shown, the induction coil 30 is operated with power P1, frequency f1 and voltage U1 (here, for example, U1 ≦ 1000V, P1 ≦ 500kw, f1 ≦ 350kHz). The second induction coil 50 is operated with power P2, frequency f2 and voltage U2 (here, for example, U2 ≦ 1000V, P2 ≦ 500kw, f2 ≦ 350kHz).

[0092] In the embodiment shown in FIG. 3, both induction coils 30, 50 are arranged in such a way that they both serve to melt the electrode 18. The induction coils 30, 50 are arranged side by side. In the cross-sectional view shown, the adjacent winding cross-sections of both induction coils are arranged substantially parallel to the inclined surface of the melted end portion of the electrode 18. Both induction coils 30, 50 have a conical shape in FIG. 3. The two induction coils 30, 50 are now embedded in a soft magnetic yoke 52, which prevents undesirable coil interaction. With such an embodiment, the generated melt flow rate MFR can be increased by increasing the powers P1 and P2 of the two induction coils 30, 50.

[0093] In the embodiment shown in FIG. 4, the first induction coil 30 is arranged in such a manner that it serves to melt the electrode 18. The second induction coil 50 may be arranged downstream of the first induction coil and in such a manner that it serves to heat the already melted melt jet 40. The windings of the first induction coil 30 are arranged substantially parallel to the inclined surface of the melted end portion of the electrode 18. The first induction coil 30 has a conical shape. The downstream second induction coil 50 has a cylindrical shape and surrounds the melt jet 40 piecewise. The second induction coil 50 is embedded in a soft magnetic yoke 52. With such an embodiment, the superheating of the generated melt jet can be further enhanced by increasing the power P2 of the second induction coil 50.

[0094] In the embodiment shown in FIG. 5, the first induction coil 30 is arranged in such a way that it serves to melt the electrode 18. The second induction coil 50 is located upstream of the first induction coil 30 and is arranged in such a way that it serves to preheat the electrode 18 to be melted. For this purpose, the windings of the first induction coil 30 are arranged substantially parallel to the inclined surface of the melted end portion of the electrode 18. Here again, the first induction coil 30 has a conical shape. The upstream second induction coil 50 has a cylindrical shape and partly surrounds the electrode 18, more precisely the part of the electrode 18 that has not yet melted. The second induction coil 50 is embedded in a soft magnetic yoke 52. With such an embodiment, the overheating of the generated melt jet can be further enhanced by increasing the power P2 of the second induction coil 50. Additionally, the upstream second induction coil 50 may likewise contribute at least slightly to the generation of the melt jet, and thus increasing P1 and P2 may contribute to an increase in the melt flow rate MFR.

[0095] FIG. 6 shows the superheat temperature T of the melt jet in an apparatus 10 according to the present invention that includes a two-winding induction coil. sup1 shows a diagram illustrating the determined relationship between temperature [°C] and melt flow rate MFR [kg / min]. Line A1 shows this relationship for an electrode 18 made of Ti64. Line A2 shows the relationship for an electrode 18 made of IN718. As can be seen, sufficient overheating can be achieved with a melt flow rate of at least 2.5 kg / min.

[0096] 7 shows a diagram illustrating the determined relationship between the voltage U [V] at which the induction coil is operated and the melt flow rate MFR [kg / min] in an apparatus 10 according to the invention that includes a two-winding induction coil. Line B1 shows this relationship for an electrode 18 made of Ti64. Line B2 shows the relationship for an electrode 18 made of IN718.

[0097] 8 shows a diagram illustrating the determined relationship between the power P [kW] at which the induction coil is operated and the melt flow rate MFR [kg / min] in an apparatus 10 according to the present invention that includes a two-winding induction coil. Line C1 shows this relationship for an electrode 18 made of Ti64. Line C2 shows the relationship for an electrode 18 made of IN718.

[0098] FIG. 9 shows the melt jet superheat temperature T in the apparatus 10 of the present invention including different induction coil designs. sup FIG. 1 shows a diagram illustrating the determined relationship between the melt flow rate MFR [kg / min] and the temperature [°C]. More specifically, this relationship is shown here for induction coil designs with different numbers of turns. Line D1 shows the relationship for a two-winding induction coil (without windings connected in parallel) to generate a melt jet. Line D2 shows the relationship for a three-winding induction coil (without windings connected in parallel) to generate a melt jet. Line D3 shows the relationship for a four-winding induction coil (without windings connected in parallel) to generate a melt jet. As can be seen, by using a smaller number of turns in the induction coil, a larger superheat temperature T sup can be achieved.

[0099] FIG. 10 shows a diagram illustrating the determined relationship between the voltage U [V] at which the induction coil is operated and the melt flow rate MFR [kg / min] in the device 10 according to the present invention with different induction coil designs. More precisely, this relationship is shown here for induction coil designs with different numbers of windings. Line E1 shows the relationship for a two-winding induction coil (without windings connected in parallel) to generate a melt jet. Line E2 shows the relationship for a three-winding induction coil (without windings connected in parallel) to generate a melt jet. Line E3 shows the relationship for a four-winding induction coil (without windings connected in parallel) to generate a melt jet. As can be seen, if there are fewer windings in the induction coil, a lower voltage U is required at the same melt flow rate MFR.

[0100] FIG. 11 shows a diagram illustrating the determined relationship between the power P [kW] at which the induction coil is operated and the melt flow rate MFR [kg / min] in the device 10 according to the present invention with different induction coil designs. More precisely, this relationship is shown here for induction coil designs with different numbers of turns. Line F1 shows the relationship for a two-winding induction coil (without windings connected in parallel) to generate a melt jet. Line F2 shows the relationship for a three-winding induction coil (without windings connected in parallel) to generate a melt jet. Line F3 shows the relationship for a four-winding induction coil (without windings connected in parallel) to generate a molten beam. As can be seen, the different numbers of turns of the induction coil do not have any significant effect on the power P that needs to be applied to generate a given melt flow rate MFR.

[0101] The diagrams in Figures 9 to 11 are based on the used electrodes made of IN718 with an electrode diameter of 150 mm.

[0102] The induction coil frequency set for Figures 6 to 11 was 100 kHz. [Explanation of symbols]

[0103] 10 equipment 12 Melting chamber 14, 114, 214, 314 Induction Coil Assembly 16 Electrode loading device 18 electrodes 20 Casting chamber 22 Mold heating device 24 Load / Unload Chamber 26 Mold removal device 28 Maintenance Platform 29 Operation Platform 30 Induction Coil 32, 34, 36, 38 windings 40, 42 Meltjet 50 Second induction coil 52 Soft magnetic yoke

Claims

1. In an apparatus (10) for producing investment casting parts: A melting chamber (12) containing an induction coil assembly (14, 114, 214, 314) arranged within and at least partially internally accommodating an electrode (18) and adapted to melt the electrode to produce a ceramic-free continuous melt jet (40) at a melt flow rate MFR of at least 2.5 kg / min; A casting chamber (20) downstream of and connected to the melting chamber (12) and containing or capable of containing an investment casting mold accommodated within the melting chamber and filled with the ceramic-free continuous melt jet (40); An apparatus (10) comprising.

2. The apparatus (10) according to claim 1, wherein the casting chamber (20) includes a mold heating device (22) adapted to heat the investment casting mold.

3. The induction coil assembly (14, 114, 214, 314) of 【Number 1】 The apparatus (10) according to claim 1, which is operated at a power P satisfying the following conditions.

4. The induction coil assembly (14, 114, 214, 314) has a temperature T of overheat ｓｕｐ is 【Number 2】 The apparatus (10) according to claim 1, wherein the melt jet (40) is arranged to be superheated according to the melt flow rate MFR in such a manner as to satisfy the following conditions.

5. The induction coil assembly (14, 114, 214, 314) of the apparatus (10) according to claim 1 is operated at a frequency of 10 kHz to 300 kHz, preferably 50 kHz to 200 kHz, more preferably 75 kHz to 125 kHz and at a voltage of 1200 V or less, preferably 1000 V or less.

6. The induction coil assembly (14, 114, 214, 314) of the apparatus (10) according to claim 1 includes at least one induction coil (30, 50) including four or fewer windings, preferably three or fewer windings, more preferably two or fewer windings.

7. The induction coil assembly (14, 114, 214, 314) of the apparatus (10) according to claim 1 includes at least one induction coil (30, 50) including two parallel windings with a common current draw-in.

8. The induction coil assembly (14, 114, 214, 314) includes a first induction coil (30) and at least one second induction coil (50), preferably Are the first induction coil (30) and the second induction coil (50) arranged in such a way that both induction coils help to melt the electrode (18); or, Is the first induction coil (30) arranged in such a way that it helps to melt the electrode (18), and is the second induction coil (50) arranged downstream of the first induction coil (30) and arranged in such a way that it helps to heat the melt jet (40); or, Is the first induction coil (30) arranged in such a way that it helps to melt the electrode (18), and is the second induction coil (50) arranged upstream of the first induction coil (30) and arranged in such a way that it helps to preheat the electrode (18) to be melted? The apparatus (10) according to any one of claims 1 to 7.

9. The apparatus (10) according to claim 1 or 2, wherein the induction coil assembly (14, 114, 214, 314) has an average coil diameter of 50 mm or more.

10. In a method of producing investment casting parts, providing an electrode (18) in a melting chamber (12); at least partially inserting the electrode (18) into an induction coil assembly (14, 114, 214, 314) disposed in the melting chamber (12); generating a ceramic-free continuous melt jet (40) at a melt flow rate of at least 2.5 kg / min by melting the electrode (18) using the induction coil assembly (14, 114, 214, 314); providing an investment casting mold in a casting chamber (20) that is downstream of and connected to the melting chamber (12); continuously filling the investment casting mold with the melt jet (40); A method comprising.

11. The induction coil assembly (14, 114, 214, 314) is [Number 3] operated at a power P that satisfies the conditions, according to the method of claim 10.

12. Using the induction coil assembly (14, 114, 214, 314), the overheat temperature T ｓｕｐ is 【Number 4】 The melt jet (40) is superheated according to the melt flow rate MFR in such a way that the conditions are satisfied, according to the method of claim 10.

13. The method according to claim 10, wherein the melt jet (40) is superheated by at least 10 °C, preferably at least 20 °C, more preferably at least 40 °C, still more preferably at least 60 °C, and even more preferably at least 80 °C using the induction coil assembly (14, 114, 214, 314).

14. The method according to claim 10, wherein the induction coil assembly (14, 114, 214, 314) is operated at a frequency of 10 kHz to 300 kHz, preferably 50 kHz to 200 kHz, more preferably 75 kHz to 125 kHz and at a voltage of 1200 V or less, preferably 1000 V or less.

15. The method according to any one of claims 10 to 14, wherein at least the melting chamber (12) is pressurized at an absolute pressure of at least 30 mbar, preferably at least 1 bar, more preferably at least 5 bar, still more preferably less than 10 bar, such that the melt jet (40) is generated under this absolute pressure.

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