An apparatus and method for manufacturing cablan turbine blades by electroslag casting.

Abstract

This application discloses an apparatus and method for manufacturing Cabran-type turbine blades using electroslag casting, belonging to the field of electroslag casting. A free electrode is disposed in the flange area (including the transition area) and arranged between the guide electrodes of a flexible electrode casting system. The cross-sectional profile of the free electrode is adapted to the cavity of the flange area. The free electrode is held in place by a clamping mechanism to maintain its position or move vertically. For the electroslag casting process of turbine blades with a composite cross-section of "blade + flange," this application solves the problems of electrode transition and consumable electrode design in electroslag casting by introducing a dedicated free electrode for the flange area and coordinating with the flexible electrode casting system for partitioned filling. This enables the manufacture of Cabran-type (through-flow and axial-flow) turbine blade castings, i.e., castings with three-dimensional curved surfaces and large cross-sectional area variations, using electroslag casting, thus expanding the application scope of electroslag casting.

Description

Technical Field

[0001] This application relates to the field of electroslag casting technology, and in particular to an apparatus and method for manufacturing cablan turbine blades by electroslag casting. Background Technology

[0002] Electroslag casting (ESC) is a highly efficient casting process that integrates smelting, refining, and near-net-shape forming. With the characteristics of slag pool resistance heating, sequential solidification, and slag washing and purification, the resulting castings have the characteristics of dense structure, high purity, and excellent mechanical properties. It is particularly suitable for key components such as turbine runner blades that have extremely high requirements for fatigue strength and cavitation resistance.

[0003] Kaplan (also known as Kaplan) type (axial-flow propeller) turbine blades and similar fixed-blade blades exhibit significant non-uniformity in their cross-sectional structure. They typically include a three-dimensional variable-curvature airfoil section and a flange (or shaft diameter) section with large cross-sectional dimensions and uniform thickness. Furthermore, the cross-sectional change from the airfoil section to the flange section is extremely abrupt. Traditional electroslag remelting (ESR) casting processes rely on rigid electrodes descending vertically into a fixed cavity, which cannot accommodate the continuous feeding requirements of three-dimensional variable-curvature cavities, and therefore cannot be directly used for the integral ESR casting of such blades.

[0004] To overcome this limitation, existing technologies (such as CN121267146A) have proposed a casting system based on "guide electrode + flexible electrode + driving device + conductive device". This casting system utilizes flexible electrodes continuously conveyed along the guide channel of conformal guide electrodes, successfully achieving direct electroslag casting of the three-dimensional curved surface region of turbine blades. However, when this purely flexible electrode scheme is directly applied to the integral casting of Cabran turbine blades, the following obvious defects are exposed: Since the cross-sectional area of ​​the flange portion of Cabran turbine blades (including through-flow and axial flow types) is much larger than that of the airfoil portion, if (wire / thin plate) flexible electrodes are used entirely as consumable electrodes, the small cross-section of the airfoil portion makes it impossible to arrange a large number of flexible electrodes in a small cross-sectional space. At the same time, the effective melting section ratio of a single flexible electrode is also small. If only these flexible electrodes are used to cast the flange portion of the blade, the small cross-section of the flexible electrodes prevents the increase of casting power, resulting in poor flange formation. Therefore, a casting system using only flexible electrodes cannot cast Cabran turbine blades. Summary of the Invention

[0005] This application aims to solve the problem that the existing pure flexible electrode casting system cannot cast Cabran turbine blades. It provides an apparatus and method for manufacturing Cabran turbine blades by electroslag casting, enabling the manufacture of Cabran turbine blades, i.e., castings with three-dimensional curved surfaces and huge changes in cross-sectional area, using the electroslag casting process, thus expanding the application scope of the electroslag casting process.

[0006] To achieve the above objectives, this application provides the following technical solution.

[0007] On one hand, this application provides an apparatus for manufacturing cabra-type turbine blades by electroslag casting, comprising: The three-dimensional curved blade crystallizer is composed of several crystallizer blocks, and its internal cavity follows the shape of the Caban turbine blade. The cavity is divided into a blade region and a flange region, and the flange region includes a transition area with the blade region. At least one set of flexible electrode casting systems is disposed in the blade region and the flange region; each set of flexible electrode casting systems includes a guide electrode, a flexible electrode passing through the guide electrode, a drive device for driving the flexible electrode to feed continuously, and a conductive device for supplying power to the flexible electrode. At least one free electrode is disposed in the flange area and arranged between the guide electrodes of the flexible electrode casting system; the cross-sectional profile of the free electrode is adapted to the cavity of the flange area; the free electrode is clamped by a clamping mechanism to keep it fixed or to move up and down in the vertical direction; The free electrode, the flexible electrode, and the guiding electrode are all connected to the same electrode polarity of the electroslag casting power supply, and all maintain the required safe distance for insulation from the three-dimensional curved surface blade crystallizer.

[0008] Optionally, the ratio of the cross-sectional area of ​​the free electrode to the cross-sectional area of ​​the flange region ranges from 20% to 80%.

[0009] Optionally, the longitudinal length of the free electrode is set according to the metal supplementation distribution ratio between the blade region and the flange region, and its initial lower end position is located in the transition region between the flange region and the blade region.

[0010] Optionally, the free electrode is formed by stacking and welding steel plates in sheet form, or by integral casting, integral forging, or by casting and welding in separate parts, or by forging and welding in separate parts.

[0011] Optionally, the clamping mechanism includes a clamping assembly, a drive motor, and a transmission component; the clamping assembly is detachably connected to the top of the free electrode; the clamping mechanism is configured to independently control the fixing or lifting of each of the free electrodes.

[0012] On the other hand, this application provides a method for manufacturing Cabran turbine blades by electroslag casting, using the aforementioned apparatus for manufacturing Cabran turbine blades by electroslag casting, the method comprising: The combined crystallizer block forms a cavity that conforms to the shape of the Cabran turbine blade. A guide electrode is fixed inside the cavity and a flexible electrode is inserted. At the same time, a free electrode is arranged in the flange area of ​​the cavity, and the free electrode is located between the guide electrodes of the flexible electrode melting and casting system. The flexible electrode is connected to a conductive device and, together with the guide electrode and the free electrode, is connected to the electroslag melting and casting power source. Molten slag or dry slag is added to the bottom of the cavity and electricity is applied to form a molten slag pool. The drive device is started to continuously transport and melt the flexible electrode downwards, continuously filling the blade area of ​​the cavity. Before the casting begins, the free electrode is placed in the preset initial melting position by the clamping mechanism; during the casting process, the free electrode remains stationary, or the descent of the free electrode is controlled according to the height of the molten slag and the solidification process of the metal; the free electrode and the flexible electrode gradually melt during the melting process to fill the flange area of ​​the cavity. After the entire cavity is completely filled with molten metal and solidifies, the power is turned off, the crystallizer block is disassembled, and the blank of the Cabran turbine blade is removed.

[0013] Optionally, controlling the descent of the free electrode based on the molten slag level and the metal solidification process specifically includes: In the initial stage of casting, when the molten slag level has not risen to contact the lower end of the free electrode or has not risen to the preset safe position, the free electrode remains fixed. When the molten slag level rises to contact the lower end of the free electrode or rises to the preset safe position, the free electrode continues to remain fixed according to the process requirements, or the clamping mechanism is activated to move the free electrode downward as needed, with the moving speed matching the current casting feed rate.

[0014] Optionally, the method for manufacturing Cabran turbine blades by electroslag casting further includes: When more than one free electrode is set, the movement of each free electrode and its movement speed can be controlled individually or synchronously.

[0015] Optionally, the method for manufacturing Cabran turbine blades by electroslag casting further includes: The flexible electrode is responsible for replenishing the molten metal in the blade area, and the metal casting of the blade area is well formed by independently controlling the melting feed rate of the flexible electrode. The melting feed rates of the free electrode and the flexible electrode can be independently controlled. By matching the cross-sectional area ratio and descent speed of the free electrode, the metal casting in the flange area can be well formed.

[0016] Optionally, the method for manufacturing Cabran turbine blades by electroslag casting further includes: The casting current is monitored in real time by a current transformer or Rogowski coil to form a closed-loop feedback control. The descent rate of the flexible electrode and the free electrode is controlled according to the current value. Throughout the descent and melting process, the free electrode maintains a non-contact insulation state with the cavity wall.

[0017] According to the specific embodiments provided in this application, the following technical effects are disclosed: This application provides an apparatus and method for manufacturing Cabran turbine blades by electroslag casting. For the electroslag casting process of Cabran turbine blade castings with composite cross-sectional features of "blade shape + flange," the method introduces a dedicated free electrode and flexible electrode casting system for the flange area to collaboratively fill the space. This enables the manufacture of Cabran turbine blade castings (i.e., castings with three-dimensional curved surfaces and large cross-sectional area variations) using electroslag casting, thus expanding the application scope of the electroslag casting process.

[0018] In addition, while retaining the advantages of flexible electrodes in solving three-dimensional curved surface forming, this application also optimizes the metal filling strategy for large cross-section areas, simplifies the equipment structure, improves casting efficiency, and reduces overall manufacturing costs. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the shape of a Cabran turbine blade, in which... Figure 1 Part (a) is a front view of the blades of a cabrath turbine. Figure 1 Part (b) is a side view of the blades of a cabra turbine; Figure 2 A front view showing the arrangement of free electrodes and guide electrodes at intervals; Figure 3 A side view showing the free electrode and the guide electrode arranged at intervals; Figure 4 A top-view cross-sectional diagram of one type of transverse arrangement of free electrodes; Figure 5 A top view of a cross-section showing another large fill ratio transverse arrangement of free electrodes; Figure 6 This is a schematic diagram of the longitudinal cross-section of two longitudinal arrangement methods for free electrodes; where... Figure 6Part (a) shows the free electrode extending into the airfoil region. Figure 6 Part (b) shows that the free electrode does not extend into the airfoil region; Figure 7 This is a schematic diagram of a single-set flexible electrode casting system. Figure 8 A schematic diagram of a stacked welding structure for free electrodes; Explanation of reference numerals in the attached drawings: 1-cavity; 101-blade area; 102-flange area; 2-guide electrode; 3-flexible electrode; 4-drive device; 5-conductive device; 6-guide channel; 7-free electrode. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] This application aims to solve the problem that the existing pure flexible electrode casting system cannot cast Cabran turbine blades. It provides an apparatus and method for manufacturing Cabran turbine blades by electroslag casting, enabling the manufacture of Cabran turbine blades, i.e., castings with three-dimensional curved surfaces and huge changes in cross-sectional area, using the electroslag casting process, thus expanding the application scope of the electroslag casting process.

[0023] Furthermore, the apparatus and method for manufacturing Cabran turbine blades by electroslag casting provided in this application also aim to overcome the shortcomings of the existing pure flexible electrode casting system when used for casting Cabran turbine blades, such as low flange area filling ratio, complex equipment layout, long casting cycle and high control cost. By introducing a free electrode specifically for the flange area and cooperating with the flexible electrode casting system for partitioned filling, the equipment structure is simplified, the electrode filling rate is improved, the casting cycle is shortened and the process stability is enhanced.

[0024] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this application. In the description of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," and "fixing" should be interpreted broadly, and those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0025] Example 1 This embodiment provides an apparatus for electroslag casting of Cabran turbine blades, applicable to near-net-shape manufacturing of turbine blade castings comprising a composite cross-sectional feature of an airfoil and a flange (or shaft diameter). This apparatus is not only applicable to electroslag casting of Cabran turbine blades, but also to fixed-blade blades with similar shapes to Cabran turbine blades, such as through-flow and axial-flow turbine blades. The characteristic of this type of casting is its significantly non-uniform cross-sectional structure: it typically comprises an airfoil with a complex profile and varying curvature, and a flange (or a shaft diameter in the shape of a cylinder or frustum) with a large cross-sectional dimension. For ease of description, this application refers to turbine blades with this composite cross-sectional feature of "airfoil + flange" as Cabran turbine blades. The shape of Cabran turbine blade castings is as follows... Figure 1 As shown, this is a one-piece casting, divided into a flange (or shaft diameter) section and a blade section based on its cross-sectional shape. For example... Figure 1 As shown, the upper part of the blade is the flange (or shaft diameter) section, characterized by a large cross-section and uniform thickness, with a cross-sectional shape typically rectangular, circular, or a chamfered polygon. The lower part of the blade is the airfoil section, whose cross-sectional shape is typically a three-dimensional curved surface with continuously varying chord length and thickness. The large variation in cross-sectional area between the flange and airfoil sections of this type of Cabran turbine blade casting presents new challenges for electrode design and process power specification in electroslag remelting. Currently available technologies employ flexible electrode casting systems to address the casting process of the airfoil section. However, for the forming of the flange section of Cabran turbine blades, multiple sets of flexible electrode casting systems are required. In this case, the arrangement of the flexible electrode casting systems is highly complex, and it is impossible to cast Cabran turbine blades using only a flexible electrode casting system.

[0026] For turbine blades with composite cross-sectional features including both blade profile and flange (or shaft diameter) sections, this application proposes a specific device structure, mainly composed of three parts: a three-dimensional variable-curvature blade crystallizer (hereinafter referred to as the crystallizer), a flexible electrode casting system, and a free electrode system. The three-dimensional variable-curvature blade crystallizer is composed of several water-cooled crystallizer blocks assembled together, and the cavity 1 formed internally completely conforms to the shape of the Cabran turbine blade. For example... Figures 2 to 6 As shown, based on the cross-sectional geometry of the Cabran turbine blades, cavity 1 is naturally divided from top to bottom into an upper flange region 102 and a lower blade region 101. In this application, for ease of description, the transition area between the flange region 102 and the blade region 101 is also referred to as the flange region 102.

[0027] Several sets of flexible electrode casting systems are arranged within the blade region 101 and flange region 102 of cavity 1. In this embodiment, 6 to 10 sets are preferred, depending on the total cross-sectional width of the blade. Figure 7As shown, each flexible electrode casting system includes: a guide electrode 2, a flexible electrode 3 inserted within the guide electrode 2, a drive device 4 for continuously feeding the flexible electrode 3, and a conductive device 5 for supplying power to the flexible electrode 3. The guide electrode 2 is fixedly installed in a designated vertical position inside the cavity 1, maintaining relative insulation from the cavity wall of the crystallizer. The guide electrode 2 is formed by three-dimensional CNC bending and cold bending of a Φ80×6mm ZG0Cr13Ni4Mo stainless steel tube, or by resin sand casting, and its spatial orientation follows the three-dimensional curved surface cavity curve of the blade region 101. The guide channel 6 extends through the entire length of the guide electrode 2. The flexible electrode 3 is composed of multiple ZG0Cr13Ni4Mo stainless steel wires with diameters of Φ2~9mm or ZG0Cr13Ni4Mo thin metal sheets with thicknesses of 2.0~3.0mm, bundled / stacked in a bundle or layered form, possessing excellent flexibility and tensile strength, and inserted within the guide channel 6. The drive unit 4 is located outside the crystallizer and adopts a six-roll mechanical pressure roller structure driven by a servo motor or a stepping chain pressure plate structure. Each drive unit 4 is linearly arranged along the length of the flexible electrode 3, and is controlled by a PLC program to achieve stepless speed regulation from 1 to 40 mm / s and constant tension clamping, ensuring that the flexible electrode 3 is stably and continuously transported to the melting zone along the guide channel 6. The conductive device 5 uses a double-wheeled copper conductive wheel or a graphite tubular brush, which slides in close contact with the upper outer surface of the flexible electrode 3 to continuously introduce the casting current.

[0028] The free electrode system mainly includes a free electrode 7 and a corresponding clamping mechanism. In this application, the flexible electrode 3 is used simultaneously as the filling electrode for both the blade region 101 and the flange region 102. The free electrode 7 is used only as the filling electrode for the large-section flange region 102. Therefore, the free electrode 7 is only located in the flange region 102 and is arranged between the guide electrodes 2 of the flexible electrode casting system. Furthermore, the cross-sectional profile (including transverse and longitudinal sections) of the free electrode needs to be adapted to the cavity of the flange region 102. The free electrode 7 is clamped by the clamping mechanism to maintain its fixed position or allow it to move vertically (longitudinally).

[0029] In one exemplary embodiment, such as Figures 2 to 6 As shown, within the flange region 102 of the cavity 1, at least one free electrode 7 is arranged between the guide electrodes 2 of adjacent flexible electrode casting systems, i.e., at the interval between adjacent guide electrodes 2. For example... Figures 2 to 4 In the embodiment shown, six sets of flexible electrode casting systems and four free electrodes 7 are arranged. Figure 5 In the illustrated embodiment, seven free electrodes 7 are arranged, compared to Figure 4The illustrated embodiment has a higher filling ratio. To improve filling efficiency, the total cross-sectional area of ​​the multiple free electrodes 7 is proportioned to the cross-sectional area of ​​the flange region 102 to adapt to the casting process, allowing for unequal cross-section designs while ensuring no contact with the flexible electrode casting system. Preferably, the ratio of the cross-sectional area of ​​the free electrode 7 to the cross-sectional area of ​​the flange region 102 is controlled between 20% and 80%.

[0030] The free electrode 7 is typically a plate-shaped electrode, with its thickness direction being plate-like and the other direction simply conforming to the shape of the crystallizer. Each free electrode 7 can move up and down within the flange area 102, or it can be fixed in place. The cross-sectional or longitudinal profile of each free electrode 7 needs to be adapted to the cavity cross-sectional shape of the corresponding flange area 102. It can be manufactured by any of the following methods: by stacking and welding steel plates in sheet form, by integral casting or forging, or by casting or forging separately and then welding them together.

[0031] In one specific implementation, the free electrode 7 can be welded from 40-60mm thick ZG0Cr13Ni4Mo stainless steel plates, or directly cast / forged from the same grade of material. For example... Figure 8 As shown, one of the free electrodes 7 can be formed by stacking and welding four steel plates. The transverse projected cross-sectional area of ​​the free electrode 7 accounts for 20% to 80% of the total cross-sectional area of ​​the corresponding flange area 102 cavity. Figure 4 The example is approximately 45%. Figure 5 The embodiment is approximately 72%, and the proportion should be increased as much as possible within the limits of space arrangement to maximize the amount of metal replenishment per unit time.

[0032] The longitudinal length of the free electrode 7 is set according to the metal supplementation distribution ratio of the blade region 101 and the flange region 102. Its initial lower end position is located in the shallow part of the flange region 102, that is, in the transition area between the flange region 102 and the blade region 101. A non-contact isolation gap can be formed between the sidewall of the free electrode 7 and the outer wall of the guide electrode 2, or they can be in contact with each other. The free electrode 7, the flexible electrode 3, and the guide electrode 2 are all connected to the same electrode polarity of the electroslag casting power supply, and all maintain the required safe distance for insulation from the three-dimensional curved blade crystallizer.

[0033] like Figure 4 and Figure 5 In the illustrated embodiment, a non-contact isolation gap of 15–30 mm is formed between the sidewall of the free electrode 7 and the outer wall of the nearest guide electrode 2. The free electrode 7, the flexible electrode 3, and the water-cooled crystallizer are all kept at a safe insulating distance by insulating ceramic sleeves or fiberglass cloth. The outer wall of the crystallizer block is provided with circulating cooling water channels, and the inner wall is coated with a heat-insulating coating with a thickness of 0.5–1.5 mm to maintain melting and casting thermal balance and prevent electrical short circuits.

[0034] The longitudinal length of the free electrode 7 (typically 1.5–3.0 m) is set according to the metal replenishment distribution ratio between the blade profile region 101 and the flange region 102. Specifically, the blade profile of the cabra turbine blade is mainly supplied with replenished metal by the flexible electrode 3, while the flange or shaft diameter region uses both the free electrode 7 and the flexible electrode 3 as the source of replenished metal. Where space permits, more free electrodes 7 can be installed in the flange or shaft diameter region.

[0035] Figure 6 Parts (a) and (b) show schematic diagrams of a longitudinal cross-section of the free electrode 7, with the shaded area representing the free electrode 7. Figure 6 In part (a), the free electrode 7 extends into the cavity of the leaf-shaped region 101; Figure 6 In part (b), the free electrode 7 does not extend into the cavity of the blade region 101. It should be noted that during initial installation, the lower end of the free electrode 7 (referring to the lower end of the main body of the free electrode 7 that does not extend into the cavity of the blade region 101) is located in the transition area between the flange region 102 and the blade region 101. The free electrode 7 is mainly used for the casting of the flange portion of the cabochon turbine blade, serving as a filler electrode to meet the needs of the large-section casting process. During the casting process, it continuously moves towards the electroslag casting melting zone, and its direction of movement is vertical, depending on the requirements of the casting process, controlling the amount of material it extends into the slag layer.

[0036] The free electrodes 7 of this application are arranged between the guide electrodes 2 within the flange area 102. The free electrodes 7 and guide electrodes 2 can be arranged one after another with intervals, or several free electrodes 7 can be arranged continuously between two adjacent guide electrodes 2, depending on the requirements. During the entire casting process of the blade, the free electrodes 7 can be selected to move or remain stationary, and their movement speed can be adjusted according to the needs of the casting process, thereby completing the entire casting process. The free electrodes 7 and the flexible electrode casting system are respectively connected to a power supply, forming a parallel circuit, meaning that their operation does not interfere with each other and they work together to complete the casting process.

[0037] The clamping mechanism includes a clamping assembly, a drive motor, and a transmission component. The transmission component is connected to both the drive motor and the clamping assembly. The clamping assembly is detachably connected to the top of the free electrode 7. The clamping mechanism is configured to independently control the fixing or raising / lowering of each free electrode 7. Throughout the entire casting process of the blade, each free electrode 7 has the following four operating states: 1) Remaining stationary throughout; 2) Moving continuously throughout; 3) Remaining stationary in the initial stage of casting, and then moving continuously after the molten slag level rises to contact the free electrode 7; 4) Remaining stationary in the initial stage of casting, and then moving intermittently after the molten slag level rises to contact the free electrode 7, adapting to the casting process by switching between moving and not moving the free electrode 7 until the casting process is complete. Furthermore, when more than one free electrode 7 is provided, the multiple free electrodes 7 can move synchronously or asynchronously.

[0038] In an exemplary embodiment, the free electrode 7 is fixed at the start of casting and begins to move and continuously move towards the molten zone once it has melted to a certain point. Therefore, the top of the free electrode 7 needs to be connected to the clamping mechanism via a quick-clamping flange. The clamping mechanism is configured to synchronously drive the lifting and lowering of all free electrodes 7, or to control the stroke and feed speed of each free electrode 7 separately via independent servo axes. Specifically, the clamping mechanism includes a high-thrust servo electric cylinder, a drive motor, and a planetary reduction gear transmission component. The clamping assembly and the top of the free electrode 7 are detachably connected using high-strength bolts. A high-voltage insulating ceramic sleeve and a polytetrafluoroethylene slip ring are provided between the power output end of the clamping mechanism and the clamping assembly to achieve complete isolation between power transmission and the electrical circuit. The free electrode 7 is connected to one pole of the electroslag casting power supply (with the same electrode polarity as the flexible electrode 3) via the clamping section and a flexible cable reel or sliding conductive ring. The bottom of the cabra turbine blade casting and the bottom water tank of the crystallizer are connected to the other pole of the power supply, forming a complete slag resistance melting circuit.

[0039] The free electrode 7 can remain stationary for a period at the beginning of its melting process. Once the molten slag level in the crystallizer reaches a certain height, it gradually moves downwards to melt according to the casting requirements. During electroslag casting, the guide electrode 2, flexible electrode 3, and free electrode 7 all need to be energized. It is precisely because the electrode above the molten slag and the solidified casting below (in the initial casting stage, the bottom water tank) are located at opposite poles of the power supply that the circuit conditions are provided for the slag resistance formed by the molten slag. Therefore, in the above scheme, the guide electrode 2, flexible electrode 3, and free electrode 7 need to be connected to the same electrode polarity of the electroslag casting power supply, while ensuring that each electrode maintains the required safe distance for insulation from the crystallizer.

[0040] This application addresses the electroslag remelting process for Cabran turbine blades. By introducing a dedicated free electrode and flexible electrode remelting system for flange area 102 for coordinated zonal filling, it solves the challenges of electrode transition and consumable electrode design in the electroslag remelting process between the three-dimensional curved blade cavity and the large cross-section flange area. This enables the manufacture of Cabran (through-flow and axial-flow) turbine blades, i.e., castings with three-dimensional curved surfaces and large cross-sectional area variations, using the electroslag remelting process, thus expanding the application scope of the electroslag remelting process.

[0041] Furthermore, directly applying existing pure flexible electrode solutions to the integral casting of Cabran turbine blades reveals the following significant drawbacks. Firstly, the flange area suffers from low filling efficiency and a long casting cycle: the flange cross-sectional area is much larger than the blade section. If relying solely on flexible electrodes (wire / plate-like) as the consumable metal source, the effective melting cross-section of a single flexible electrode is extremely small due to the limited safe process distance between the electrode and the cavity wall. This results in insufficient molten metal replenishment per unit time, significantly extending the flange area casting time. Secondly, the equipment layout is complex and manufacturing costs are high: to cover the large-section flange area and ensure uniform molten metal distribution, dozens of flexible electrode casting systems must be densely arranged. Each system requires independent configuration of guide electrodes, drive devices (multiple pressure rollers / chain pressure plates), and conductive devices, leading to bulky equipment, large footprint, complex control systems, and extremely high subsequent maintenance costs. Thirdly, process coordination and control are difficult: the synchronous feeding and differentiated compensation of multiple flexible electrodes in the flange area are difficult to precisely match, easily causing localized metal accumulation or insufficient filling, affecting the internal density and dimensional accuracy of the casting.

[0042] In this regard, the device provided by this application can also optimize the metal filling strategy for large cross-section areas while retaining the advantages of flexible electrodes in solving three-dimensional curved surface forming. It simplifies the equipment structure, improves the melting and casting efficiency, and reduces the overall manufacturing cost. It solves the defects of the pure flexible electrode melting and casting system in the prior art when used for melting and casting of Cabran turbine blades, such as low flange area filling ratio, complex equipment layout, long melting and casting cycle, and high control cost.

[0043] Example 2 Based on the aforementioned apparatus for manufacturing Cabran turbine blades using electroslag casting, this embodiment provides a method for manufacturing Cabran turbine blades using electroslag casting, comprising the following steps S1 to S4. This embodiment details the process flow and key parameters for manufacturing Cabran turbine blade blanks using the aforementioned apparatus.

[0044] S1. The combined crystallizer block forms a cavity 1 that conforms to the shape of a Cabran turbine blade. A guide electrode 2 is fixed in the blade region 101 and flange region 102 of the cavity 1, and a flexible electrode 3 is inserted therein. At the same time, a free electrode 7 is arranged in the flange region 102 of the cavity 1. The free electrode 7 is located between the guide electrodes 2 of the flexible electrode casting system. The flexible electrode 3 is connected to the conductive device 5, and together with the guide electrode 2 and the free electrode 7, it is connected to the electroslag casting power supply.

[0045] Specifically, the crystallizer blocks are assembled according to the design drawings, and the cooling system is leak-tested. Guide electrodes 2 are fixed at preset coordinates in the blade area 101 and flange area 102 of cavity 1, and flexible electrodes 3 are inserted and connected to the outer drive device 4 and conductive device 5. Free electrodes 7 are suspended and arranged between the guide electrodes 2 in flange area 102, and clamped and fixed to the initial melting position of flange area 102 by a clamping mechanism. The safety clearance between all electrodes and the cavity wall is calibrated to ensure no mechanical interference.

[0046] S2. Add molten slag or dry slag to the bottom of the cavity 1 and energize to form a molten slag pool. Start the drive device 4 to continuously transport and melt the flexible electrode 3 downwards, continuously filling the leaf-shaped area 101 of the cavity 1.

[0047] Specifically, a special molten slag is spread at the bottom of cavity 1, with a typical mass ratio of: CaF2 45%, Al2O3 25%, CaO 20%, MgO 5%, SiO 25%, and a particle size of 0.5–3.0 mm. The initial slag layer thickness is approximately 200 mm. A DC or three-phase AC electroslag power supply is connected, with the operating current set to 12–22 kA and the operating voltage to 38–48 V. The arc-ignition procedure is initiated (usually using iron filings or short-circuit arc initiation). After the slag pool forms, the slag resistance generates heat, causing the temperature to rise rapidly to 1650–1780 °C. The drive device 4 is activated, and the flexible electrode 3 is continuously fed downwards and melted at a speed of 10–50 mm / s. The molten steel droplets pass through the slag pool, are refined, and fall into the molten pool, preferentially filling the blade-shaped area 101 of cavity 1 from bottom to top. During this stage, the free electrode 7 remains stationary or is fed only at a micro-feed rate of ≤0.3 mm / s. The flexible electrode casting system participates in the entire electroslag casting process, and the blade shape of the Cabran turbine mainly relies on the flexible electrode 3 as the source of filler metal.

[0048] S3. Before the casting process begins, the free electrode 7 is placed in the preset initial melting position by the clamping mechanism. During the casting process, the free electrode 7 remains stationary, or the descent of the free electrode 7 is controlled according to the height of the molten slag and the solidification process of the metal. The free electrode 7 and the flexible electrode 3 gradually melt during the casting process to fill the flange area 102 of the cavity 1.

[0049] Specifically, in the initial stage of casting, when the molten slag level has not risen to contact the lower end of the free electrode 7 or has not risen to the preset safe position, the free electrode 7 remains fixed; when the molten slag level rises to contact the lower end of the free electrode 7 or rises to the preset safe position, the free electrode 7 continues to remain fixed according to the process requirements, or the clamping mechanism is activated to move the free electrode 7 downward as needed, with the moving speed matching the current casting feed rate.

[0050] When more than one free electrode 7 is provided, the movement of each free electrode 7 can be controlled individually. When the free electrode 7 needs to move, the movement speed of each free electrode 7 can also be controlled individually or synchronously. Similarly, multiple sets of flexible electrodes 3 can also be selected for individual or synchronous control. The replenishment of molten metal in the blade-shaped region 101 is undertaken by the flexible electrodes 3, and the metal casting of the blade-shaped region 101 is well-formed by independently adjusting the melting feed rate of the flexible electrodes 3. By independently adjusting the melting feed rates of the free electrodes 7 and the flexible electrodes 3, and matching the cross-sectional area ratio and descent speed of the free electrodes 7, the metal casting of the flange region 102 is well-formed.

[0051] In one exemplary embodiment, the free electrode 7 is first lowered to a preset initial melting position using a clamping mechanism, such as... Figure 6 The position is shown in the diagram. Before the slag liquid reaches the preset safe position (shown by the dotted line), the free electrode 7 cannot move because it is very close to the crystallizer cavity 1, and the two cannot come into contact. When the slag liquid exceeds the dotted line, the free electrode 7 can be controlled to move downwards gradually. As the amount of molten metal increases, the slag liquid will rise further, after which the downward movement of the free electrode 7 will be safer and more feasible. The main basis for determining when the free electrode 7 can begin to move is the principle that it must not come into contact with the crystallizer cavity 1. Under this premise, maximizing the proportion of the free electrode 7 relative to each cross-section of the crystallizer helps improve filling efficiency.

[0052] During the casting process, when the molten slag level rises to a preset safe position (i.e., the slag height exceeds the minimum insulation distance critical line between the lower end of the free electrode 7 and the cavity wall, typically the slag layer thickness is ≥100mm), corresponding to... Figure 6After the dotted line position, the clamping mechanism is activated to control the free electrode 7 to move downwards as needed. The free electrode 7 and the flexible electrode 3 are arranged alternately in the flange area 102 of the cavity 1, serving together as a source of filler metal. By independently controlling the melting feed rate of both, matching the cross-sectional area ratio and descent speed of the free electrode 7, the amount of molten metal replenishment in the flange area 102 accounts for 40% to 75% of the total molten casting metal. The molten metal replenishment in the blade-shaped area 101 is mainly undertaken by the flexible electrode 3. The descent speed of the free electrode 7 is typically controlled between 1.0 and 6.0 mm / s, dynamically matching the current molten pool rise rate and slag temperature. It is important to note that both the free electrode 7 and the flexible electrode 3 maintain a safe distance from the crystallizer during the casting process.

[0053] The electroslag remelting process involves melting the electrodes and filling the mold cavity 1 to form the casting. During electroslag remelting, the electrodes melt by being immersed in the molten slag. The free electrode 7 provided in the flange area 102 of this application can improve the electrode filling efficiency and reduce the number of flexible electrodes 3 required. Because the ratio of the electrode's cross-sectional area to the mold cavity 1 is limited, in... Figure 4 and Figure 5 As can be seen, the cross-section of the free electrode 7 largely fills the cross-sectional area of ​​the crystallizer cavity 1, thus improving the electrode filling efficiency during the casting process. That is, the higher the filling ratio per unit time, the more molten electrode is melted, which is more conducive to filling the crystallizer cavity 1 with molten steel. In a specific embodiment, the ratio of the cross-sectional area of ​​the free electrode 7 to the cross-sectional area of ​​the flange region 102 is controlled between 20% and 80%.

[0054] In step S3, the melting current can be monitored in real time using a current transformer or Rogowski coil to form a closed-loop speed feedback control, controlling the descent rate of the flexible electrode 3 and the free electrode 7 based on the current value. It is important to note that the flexible electrode 3 and the free electrode 7 maintain a non-contact, insulated state from the cavity wall throughout the entire descent and melting process.

[0055] Furthermore, in step S3, the displacement of the free electrode 7 and the molten slag level can be monitored in real time using a position sensor, forming a closed-loop feedback control. Specifically, during the casting process, the absolute displacement of the free electrode 7 is monitored in real time using a magnetostrictive displacement sensor mounted on the clamping mechanism support. Simultaneously, a laser level gauge and a multi-point thermocouple array are arranged on the side wall of the crystallizer to obtain the molten slag level and the temperature gradient of the cavity wall in real time. The PLC controller incorporates a "slag level-feed speed" PID control algorithm. When the slag level is detected to be below a safe threshold, the clamping mechanism is forcibly locked, and the free electrode 7 remains fixed. When the slag level exceeds the threshold, the system automatically unlocks and begins descent according to a preset curve. This strategy fundamentally avoids short circuits or crystallizer breakdown accidents caused by the free electrode 7 initially touching the cavity wall during its descent.

[0056] Furthermore, for working conditions where the flange cross-sections of different blades are asymmetrical or have local reinforcing ribs, the clamping mechanism can be configured in a multi-axis independent servo control mode. Based on the real-time melting feedback of each flexible electrode 3 (estimated through current fluctuations and weighing sensors) and the remaining length of each free electrode 7, the descent speed of each independent lifting shaft is dynamically adjusted. If the molten metal replenishment in a certain area is delayed, the descent speed of the corresponding free electrode 7 is automatically increased by 0.5–1.0 mm / s; if the slag temperature is too high, the descent rate is appropriately reduced to prevent overheating and splashing of the molten metal. By integrating the product of the cross-sectional area ratio and the descent speed, the metal replenishment ratio of the flange area 102 is precisely controlled to remain stable within the range of 40%–75%.

[0057] Throughout the descent and melting process, the free electrode 7 maintains a non-contact insulating state with the crystallizer cavity wall via an insulating guide groove and positioning bracket. The sidewalls of the free electrode 7 can be coated with a high-temperature resistant insulating ceramic coating (0.3–0.8 mm thick) to further reduce the risk of localized bridging caused by molten slag splashing. All conductive nodes (conductive device 5, sliding conductive ring / cable reel) are equipped with water-cooling and automatic tensioning mechanisms to ensure that the contact resistance remains stable within the range of 50–150 μΩ under high current (15–25 kA) conditions, preventing localized overheating and melting of the electrode.

[0058] S4. After the entire cavity 1 is completely filled with molten metal and solidifies, turn off the power, disassemble the crystallizer block and remove the Cabran turbine blade blank.

[0059] Electroslag remelting (ESR) uses a water-cooled mold designed to fit the dimensions of the casting. At the start of casting, a slag layer of a certain height forms at the bottom of the crystallizer. This slag layer material is both conductive and provides some slag resistance. When the consumable electrode, powered on, is immersed in the slag layer, a strong current is generated in the slag pool, and the resulting heat raises the temperature of the slag. When the slag temperature exceeds the melting point of the consumable electrode material, the electrode melts. The molten steel, in the form of droplets, flows through the slag pool from the electrode surface under gravity. During this process, the slag pool absorbs harmful elements and inclusions from the molten steel, refining it. The refined and purified steel then pools below the slag pool and rapidly solidifies within the crystallizer cavity, which is cooled by circulating water, forming the casting. Throughout the ESR process, the melting of the consumable electrode, the refining and purification of the molten steel, the filling process, and the sequential solidification continue until the crystallizer is completely filled, completing the entire ESR process.

[0060] When the molten metal level rises to the top overflow port of the crystallizer and cavity 1 is completely filled, the casting current is gradually reduced to 8-12 kA for thermal compression and holding for 15-25 minutes before power is cut off. The crystallizer's water cooling system is used to accelerate sequential solidification, followed by static cooling to below 400°C. The crystallizer block is disassembled, and the Cabran turbine blade blank is removed. The blank undergoes surface sand removal, stress-relieving annealing (holding time depends on the casting thickness), and necessary finishing to obtain the finished product. The produced Cabran turbine blade blank perfectly conforms to the three-dimensional curved surface of the Cabran turbine blade, achieving direct molding of electroslag cast three-dimensional variable-curvature turbine blades in a single casting process. The manufacturing process of the produced Cabran turbine blade blank is simple, with small machining allowances, high material utilization, low manufacturing costs, and excellent internal quality.

[0061] It should be noted that the parameters mentioned above, such as current, voltage, descent speed, slag ratio, and cross-sectional area ratio, are preferred implementation windows for Cabran turbine blades. Those skilled in the art can perform linear interpolation or proportional scaling within the above range based on the specific blade size, material (such as stainless steel, duplex steel, or low-alloy high-strength steel), and crystallizer cooling capacity. Furthermore, the apparatus and method proposed in this application are not limited to Cabran turbine blades but can also be used for blades of other similar shapes, collectively referred to as Cabran turbine blade castings. The welding / casting process of the free electrode 7, the synchronous / independent control mode of the clamping mechanism, and the replacement of the pressure roller / chain structure of the drive device 4 are all equivalent alternatives disclosed in this application. Without departing from the core concept of this application (i.e., "flexible electrode 3 is responsible for the three-dimensional curved surface + free electrode 7 specializes in the collaborative filling of the large-section flange area"), all should fall within the protection scope of this application.

[0062] Compared with the prior art, this application has the following significant technical effects.

[0063] 1) Expanding the application scope of electroslag casting: The apparatus and method for manufacturing cablan turbine blades by electroslag casting provided in this application enable the manufacturing of cablan turbine blade castings (i.e. castings with three-dimensional curved surfaces and huge changes in cross-sectional area) using the electroslag casting process. This solves the long-standing technical problem that the existing pure flexible electrode casting system cannot cast cablan turbine blade castings, thus expanding the application scope of the electroslag casting process.

[0064] 2) Significantly increased flange area filling ratio and shortened casting cycle: The free electrode 7 is specifically designed for the large cross-section flange area 102, with its transverse cross-sectional area accounting for 20-80%, significantly improving the self-consumable electrode filling rate of the flange area 102. The amount of molten metal per unit time increases exponentially, effectively compensating for the slow metal replenishment in the flange area 102 when relying solely on the flexible electrode 3, and shortening the overall casting cycle by 20%-40%.

[0065] 3) Simplified equipment layout, significantly reducing manufacturing and maintenance costs: The flange area 102 no longer requires a dense arrangement of multiple sets of flexible electrodes 3 and their associated complex drive / conductive devices. Only the number of flexible electrode sets required to meet the forming needs of the blade area 101 needs to be retained, and the flange area 102 is supplemented by free electrodes 7 with a simple structure and only single-axis lifting drive. The number of equipment parts is reduced by more than 30%, the control system is simplified, and the footprint and installation and commissioning costs are significantly reduced.

[0066] 4) High process safety and uniform distribution of molten metal: The free electrode 7 and the flexible electrode 3 are arranged at intervals in the flange area 102 of the cavity 1, and the feed rate is independently controlled in each zone to ensure that the molten metal in the flange area 102 rises synchronously and steadily, and there are no defects such as cold shuts and shrinkage porosity inside the casting, and the density of the structure is significantly improved; in conjunction with the linkage control of slag liquid level descent, the risk of cavity short circuit caused by the initial downward exploration of the free electrode 7 is avoided.

[0067] 5) High versatility and adaptability to complex cross-section blades: Applicable to all turbine blades with the characteristics of "three-dimensional curved surface blades + large cross-section flanges / shafts" (such as propeller and fixed-blade turbine blades), one-time casting to near net shape, subsequent machining allowance reduced by more than 50%, material utilization rate improved, in line with the trend of green and efficient manufacturing.

[0068] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An apparatus for manufacturing cablan turbine blades by electroslag remelting, characterized in that, include: The three-dimensional curved blade crystallizer is composed of several crystallizer blocks, and its internal cavity follows the shape of the Caban turbine blade. The cavity is divided into a blade region and a flange region, and the flange region includes a transition area with the blade region. At least one set of flexible electrode casting systems is disposed in the blade region and the flange region; each set of flexible electrode casting systems includes a guide electrode, a flexible electrode passing through the guide electrode, a drive device for driving the flexible electrode to feed continuously, and a conductive device for supplying power to the flexible electrode. At least one free electrode is disposed in the flange area and arranged between the guide electrodes of the flexible electrode casting system; the cross-sectional profile of the free electrode is adapted to the cavity of the flange area; the free electrode is clamped by a clamping mechanism to keep it fixed or to move up and down in the vertical direction; The free electrode, the flexible electrode, and the guiding electrode are all connected to the same electrode polarity of the electroslag casting power supply, and all maintain the required safe distance for insulation from the three-dimensional curved surface blade crystallizer.

2. The apparatus for manufacturing Cabran turbine blades by electroslag casting according to claim 1, characterized in that, The ratio of the cross-sectional area of ​​the free electrode to the cross-sectional area of ​​the flange region ranges from 20% to 80%.

3. The apparatus for manufacturing Cabran turbine blades by electroslag casting according to claim 1, characterized in that, The longitudinal length of the free electrode is set according to the metal supplementation distribution ratio between the blade region and the flange region, and its initial lower end position is located in the transition area between the flange region and the blade region.

4. The apparatus for manufacturing Cabran turbine blades by electroslag casting according to claim 1, characterized in that, The free electrode is formed by stacking and welding steel plates in sheet form, or by integral casting, integral forging, or integral casting followed by welding, or integral forging followed by welding.

5. The apparatus for manufacturing Cabran turbine blades by electroslag casting according to claim 1, characterized in that, The clamping mechanism includes a clamping assembly, a drive motor, and a transmission component; the clamping assembly is detachably connected to the top of the free electrode; the clamping mechanism is configured to independently control the fixing or lifting of each of the free electrodes.

6. A method for manufacturing Cabran-type turbine blades by electroslag casting, characterized in that, The method of manufacturing Cabran turbine blades by electroslag casting using the apparatus described in any one of claims 1 to 5 comprises: The combined crystallizer block forms a cavity that conforms to the shape of the Cabran turbine blade. A guide electrode is fixed inside the cavity and a flexible electrode is inserted. At the same time, a free electrode is arranged in the flange area of ​​the cavity, and the free electrode is located between the guide electrodes of the flexible electrode melting and casting system. The flexible electrode is connected to a conductive device and, together with the guide electrode and the free electrode, is connected to the electroslag melting and casting power source. Molten slag or dry slag is added to the bottom of the cavity and electricity is applied to form a molten slag pool. The drive device is started to continuously transport and melt the flexible electrode downwards, continuously filling the blade area of ​​the cavity. Before the casting begins, the free electrode is placed in the preset initial melting position by the clamping mechanism; during the casting process, the free electrode remains stationary, or the descent of the free electrode is controlled according to the height of the molten slag and the solidification process of the metal; the free electrode and the flexible electrode gradually melt during the melting process to fill the flange area of ​​the cavity. After the entire cavity is completely filled with molten metal and solidifies, the power is turned off, the crystallizer block is disassembled, and the blank of the Cabran turbine blade is removed.

7. The method for manufacturing Cabran turbine blades by electroslag casting according to claim 6, characterized in that, The control of the descent of the free electrode based on the molten slag level and the metal solidification process specifically includes: In the initial stage of casting, when the molten slag level has not risen to contact the lower end of the free electrode or has not risen to the preset safe position, the free electrode remains fixed. When the molten slag level rises to contact the lower end of the free electrode or rises to the preset safe position, the free electrode continues to remain fixed according to the process requirements, or the clamping mechanism is activated to move the free electrode downward as needed, with the moving speed matching the current casting feed rate.

8. The method for manufacturing Cabran turbine blades by electroslag casting according to claim 6, characterized in that, Also includes: When more than one free electrode is set, the movement of each free electrode and its movement speed can be controlled individually or synchronously.

9. The method for manufacturing Cabran turbine blades by electroslag casting according to claim 6, characterized in that, Also includes: The flexible electrode is responsible for replenishing the molten metal in the blade area, and the metal casting of the blade area is well formed by independently controlling the melting feed rate of the flexible electrode. The melting feed rates of the free electrode and the flexible electrode can be independently controlled. By matching the cross-sectional area ratio and descent speed of the free electrode, the metal casting in the flange area can be well formed.

10. The method for manufacturing Cabran turbine blades by electroslag casting according to claim 6, characterized in that, Also includes: By monitoring the casting current in real time through a current transformer or Rogowski coil, a closed-loop feedback control is formed, and the descent rate of the flexible electrode and the free electrode is controlled according to the current value. Throughout the entire process of descent and melting, the free electrode maintains a non-contact, insulated state from the cavity wall.

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