An electroslag casting device and method for direct forming of three-dimensional curved surface blade-like castings

Abstract

The present invention belongs to the field of casting, and particularly relates to an electroslag casting device and method for directly forming three-dimensional curved blade-like castings. The fixed electrode and the movable electrode of the device serve as consumable electrodes. A movable electrode power transmission device is provided at the part of the upper end of the movable electrode extending above the mold. An arc starting section of the movable electrode is provided at the lower end of the movable electrode; a bottom pad is provided at the bottom opening of the mold, and a process section for arc starting is provided on one side of the lower part of the mold in contact with the bottom pad. The arc starting section of the movable electrode at the lower end of the movable electrode extends into the process section corresponding to the bottom pad. The fixed electrode power transmission device is connected to the fixed electrode for power transmission, and the movable electrode power transmission device is connected to the movable electrode for power transmission. During the electroslag casting process, the molten metal melted from the consumable electrodes fills the cavity of the mold, and the casting solidified in the mold after the casting is completed is the casting product. The present invention realizes the high-quality and low-cost production of castings through the mutual cooperation of the consumable electrodes and the cavity of the mold.

Description

Technical Field

[0001] The present invention belongs to the field of casting, and in particular relates to an electroslag casting device and method for directly forming three-dimensional curved blade castings. Background Art

[0002] As a casting process that combines refining and forming, electroslag casting is currently widely used in the manufacturing field of castings with high quality requirements. Its melting and casting generally use a consumable electrode as the melting and casting raw material. The consumable electrode is placed in the mold, and after power is applied, the electrode completes the remelting process in the molten slag layer. This process requires maintaining the process safety distance between the electrode and the inner cavity of the mold. At the same time, the consumable electrode serves as a conductor to keep the molten slag layer in the circuit, and the heat generated by the slag resistance melts the consumable electrode. The molten steel solidifies in the water-cooled mold cavity. As the melting and casting progresses, the consumable electrode gradually melts and fills the mold cavity until the entire melting and casting process is completed.

[0003] For special-shaped parts, here mainly refers to the casting shape where the mold has no common cavity for the movable electrode, that is, the movable consumable electrode cannot move up and down in the mold, which means there is no common cavity between the mold and the electrode. At this time, the consumable electrode cannot fully fill the mold cavity during the melting and casting process. For this, process designers and technicians have been seeking solutions to this problem: One is to add a movable or fixed melting and casting mold cavity outside the casting mold cavity. The casting cavity and the melting and casting mold cavity are connected through a supplementary channel. The molten steel in the melting and casting mold flows into the casting mold through the supplementary channel to complete the forming of the casting. The metal solidified in the supplementary channel and the melting and casting mold cavity after casting does not belong to the casting body, which greatly reduces the material utilization rate of the casting, and the economy of this method is not good. Another is to first produce flat billets by the electroslag casting process, and then manufacture three-dimensional curved blade castings by the secondary method of die pressing. This method requires investment in large-scale hydraulic presses and pressing molds and other tooling equipment, with high manufacturing costs and low material utilization rates. The process difficulty of this method is low, but the economy is even worse.

[0004] For castings with complex shapes such as the movable guide vanes of hydro-generators, the pivot shafts and shaft heads of assembled movable guide vanes, the blades of hydro-generators, the blades of ship propellers, and the blades of rotor propellers, the current process methods have not solved the technical problems of high-quality and low-cost production of three-dimensional curved blade castings. Summary of the Invention

[0005] The object of the present invention is to provide an electroslag casting device and method for directly forming three-dimensional curved surface blade-like castings, to solve the technical problems of high-quality and low-cost production of castings in the electroslag casting process by the mutual cooperation of the consumable electrode and the mold cavity, to solve the electroslag casting forming problem of complex-shaped castings, especially three-dimensional curved surface blade-like castings, to increase the variety of products manufactured by the electroslag casting technology, and to broaden the application field of the electroslag casting technology.

[0006] The technical solution of the present invention is as follows:

[0007] An electroslag casting device for directly forming three-dimensional curved surface blade-like castings, the device includes: a mold, a fixed electrode, a movable electrode, a bottom pad, a movable electrode power transmission device, and a fixed electrode power transmission device. The specific structure is as follows:

[0008] The fixed electrode and the movable electrode serve as consumable electrodes. The safety distance between the adjacent surfaces of the fixed electrode and the movable electrode and the mold cavity is between 1 mm and 100 mm. By adding process subsidies to the local part of the casting, a common cavity that allows the movable electrode to move and transport is provided locally in the mold cavity. The rest of the mold cavity follows the shape of the casting. The casting body is formed by solidification in the mold cavity. The movable electrode is located at the upper end outside the mold and is connected to the power supply through the movable electrode power transmission device or is clamped and connected to the power supply by an electroslag furnace chuck. The fixed electrode is connected to the power supply through the fixed electrode power transmission device. The lower end of the movable electrode is provided with a movable electrode arc starting section in the shape of a semi-cone or a wedge. A bottom pad is arranged at the bottom opening of the mold. A process section for arc starting is arranged on one side of the lower part of the mold in contact with the bottom pad. The process section is communicated with the mold cavity. The movable electrode arc starting section at the lower end of the movable electrode extends into the process section of the mold to start an arc and melt the slag material to form a molten slag material. The movable electrode can be flexible or non-flexible during the electroslag casting process.

[0009] In the electroslag casting device for directly forming three-dimensional curved surface blade-like castings, an insulating block or insulating layer is arranged between the fixed electrode and the inner wall surface of the mold cavity. Insulating blocks or insulating layers are arranged between the adjacent surfaces of the fixed electrode and the movable electrode according to the needs of the electroslag casting process. Insulating blocks or insulating layers are arranged between the movable electrode and the inner wall surface of the mold cavity. The thickness of the insulating block or insulating layer between the fixed electrode, the movable electrode and the inner wall surface of the mold cavity is not greater than the safety distance between the two.

[0010] In the electroslag casting device for directly forming three-dimensional curved surface blade-like castings, the insulating blocks are dispersedly distributed and fixed in the mold cavity to ensure the separation insulation between the movable electrode and the fixed electrode, the movable electrode and the mold cavity, and the fixed electrode and the mold cavity; or, the insulating layer is brushed on one side of the adjacent surfaces of the fixed electrode, the movable electrode and the mold cavity. The brushing area of the insulating layer is the entire area or a partial area of the adjacent surface.

[0011] An electroslag casting method for direct forming of three-dimensional curved surface blade-like castings. According to the shape characteristics of the casting, the blank size of the casting and the cavity size of the mold are designed. The consumable electrode and the power transmission device are designed according to the mold. The cavity of the mold is a single cavity designed according to the shape of the casting. By adding process allowances to the local part of the casting, a common cavity that allows the movable electrode to move is formed in the local part of the designed mold, and the rest of the mold is conforming to the casting. The casting solidifies and forms in the cavity of the mold. The consumable electrode is located in the cavity of the mold. The consumable electrode is composed of the following forms of electrode combinations: a movable electrode that moves relative to the cavity of the mold, and a fixed electrode that is stationary relative to the cavity of the mold. The fixed electrode power transmission device is connected to the fixed electrode for power transmission, and the movable electrode power transmission device is connected to the movable electrode for power transmission. Insulation is maintained between the fixed electrode, the movable electrode and the mold. During the electroslag casting process, the molten metal melted from the consumable electrode fills the cavity of the mold. During the electroslag casting process, the molten metal level continuously rises, causing the fixed electrode to remain in a continuously melting state until the casting is completed. The casting solidified in the mold after the electroslag casting is the casting product.

[0012] When the center of gravity of the consumable electrode itself is not on the same vertical line as the fixed point or the restraint point of the consumable electrode, it is difficult for the consumable electrode to maintain a stable safety distance from the mold under the action of the center of gravity moment. The consumable electrodes are separated by an insulating material between each other or between the consumable electrode and the cavity of the mold. Insulating blocks are pasted or insulating layers are coated on the inner wall surface of the cavity of the mold or on the local part of the consumable electrode to maintain insulation between the consumable electrode and the cavity of the mold. The insulating blocks or insulating layers will melt after contacting the molten slag layer during the electroslag casting process, without affecting the chemical composition of the casting and the integrity of the solidification and forming of the casting surface.

[0013] In the electroslag casting method for direct forming of the three-dimensional curved surface blade-like castings described above, the movable electrode and the fixed electrode exist simultaneously. The lower end of the movable electrode is in the shape of a semi-cone or a wedge-shaped arc starting section that is beneficial for arc starting. At the beginning stage of power supply in the electroslag casting, the movable electrode is responsible for arc starting to melt the solid slag material to form a molten slag layer. A process section for arc starting is provided on one side of the lower end of the casting mold in contact with the bottom pad. This process section is used for the movable electrode to start an arc to form a molten slag layer. The process section is connected to the cavity of the casting mold. The arc starting section of the movable electrode forms a molten slag layer in this section after starting an arc in the process section. As the electroslag casting progresses, the liquid level of the molten slag layer rises, and the fixed electrode continuously melts. The molten steel gradually solidifies in the water-cooled cavity of the mold to form a casting. During the electroslag casting process, the molten slag layer continuously rises as the casting solidifies and forms. The movable electrode and the fixed electrode immersed in the molten slag layer not only keep the molten slag layer in a high-temperature molten state, but also promote the flow and mixing of the melted metal liquid and the filling of the cavity of the mold. During the electroslag casting process, the consumable electrode, the molten slag layer, the melted metal liquid, the solidified casting metal and the casting bottom pad form a conducting circuit. By applying power between the consumable electrode and the bottom pad to provide the power required for the electroslag casting process, the electroslag casting process can proceed continuously.

[0014] The electroslag casting method for direct forming of three-dimensional curved surface blade-like castings, where the consumable electrode is two or more, and the chemical composition of the consumable electrode material is the same as or different from that of the casting; the difference in the chemical composition between the electrode and the casting means that each electrode has a single chemical composition, and during the electroslag casting process, two or more consumable electrodes with different chemical compositions are mixed with each other during melting to enable the casting to meet the required chemical composition requirements; the movable electrode is one or more, and the fixed electrode is one or more.

[0015] The electroslag casting method for direct forming of three-dimensional curved surface blade-like castings, where the movable electrode is flexible or rigid; the movable electrode being flexible means that the electrode is made of strip-shaped thin plates, rod-shaped materials, or wire-shaped materials woven together and is bendable during the electroslag casting process; the movable electrode being rigid means that the electrode is not bendable during the electroslag casting process; when the movable electrode is flexible and long, the remaining part of the movable electrode outside the mold is coiled for storage, so that the length of the movable electrode is not limited; when the movable electrode is not bendable, the electrode needs to be placed vertically; the movable electrode is powered by a power transmission device located at the furnace mouth of the mold or directly clamped on the chuck of the electroslag furnace.

[0016] The electroslag casting method for direct forming of three-dimensional curved surface blade-like castings, when the power transmission device of the movable electrode is located above the furnace mouth of the mold, the metal-to-metal contact form of a pressure roller or a brush is used to connect power to the movable electrode, or a liquid conductive medium is used to connect power to the movable electrode. Connecting power to the movable electrode enables the electroslag casting process to proceed continuously. At this time, the power transmission device of the movable electrode simultaneously controls the conveying direction and conveying speed of the movable electrode; the power transmission device of the fixed electrode is directly connected to the fixed electrode for power transmission.

[0017] The electroslag casting method for direct forming of three-dimensional curved surface blade-like castings, where the movable electrode is a casting manufactured by sand casting, or is manufactured by processes such as rolling, extrusion, or drawing; the adjacent surface of the fixed electrode to the mold cavity is a shape that follows or approximately follows the shape of the mold cavity. The fixed electrode is manufactured by sand casting, or by rolling or welding steel plates together, and according to the needs of the electroslag casting process, plate-shaped materials or strip-shaped materials are welded on the adjacent surface of the fixed electrode to restrict the moving direction of the movable electrode and prevent the movable electrode from contacting the mold cavity.

[0018] The electroslag casting method for direct forming of three-dimensional curved surface blade-like castings, the casting mold is a combined type or split type on both sides. An arc-striking process section is provided at the contact between the lower end of the mold cavity and the bottom pad. The position of the common cavity required for the movement of the consumable electrode should be selected at the position where the process allowance of the casting is increased minimally. At this time, the fixed electrodes are located on both sides of the consumable electrode, so that the molten metal after melting the consumable electrode flows around and the distances to fill the mold cavity are relatively small, which is beneficial to the integrity of the solidification and forming of the casting. After casting, the casting is taken out by separating the mold cavity.

[0019] The design concept of the present invention is:

[0020] As Figures 1 - 3 shown, based on the basic principle of electroslag casting, the present invention proposes to add allowances locally to the casting, so that the mold cavity has a common cavity convenient for the movement of the consumable electrode. Through the mutual cooperation between the consumable electrode and the casting mold cavity, a single casting mold cavity is designed to realize the electroslag casting and forming of three-dimensional curved surface blade-like castings. The adopted casting mold cavity is a single cavity designed according to the shape of the casting. The consumable electrodes are all in the casting mold cavity. During the casting process, the electrode material is remelted, refined and purified, and the chemical composition is homogenized to complete the near-net forming of the casting. According to the shape characteristics of the casting, insulating materials are added between the electrode and the mold cavity to expand the shape of the available electrode. By selecting different forms of consumable electrodes, the forming of complex-shaped castings can be realized, especially the electroslag casting and forming of three-dimensional curved surface blade-like castings.

[0021] The advantages and beneficial effects of the present invention are:

[0022] 1. The present invention solves the technical bottleneck of electroslag casting and expands its electroslag casting and forming for complex-shaped castings. It provides a higher-quality and lower-cost alternative manufacturing method for the manufacturing processes that originally could only use sand casting, die forging, and the process of using electroslag-cast flat billets and then secondary die forging.

[0023] 2. The refined casting of the present invention can meet the mechanical properties and flaw detection requirements of forgings of the same material. The chemical composition is uniform, the structure is dense, the dendrites are refined, there are no defects such as porosity and slag inclusions, the inclusions are dispersed, the fatigue life is better than that of steel refined outside the furnace, and it has the advantage of isotropy that forgings do not have. At the same time, it has higher anti-fatigue performance and higher resistance to crack generation and propagation, and can meet higher flaw detection requirements and longer service life than sand-castings.

[0024] 3. The present invention uses less process allowance for the mold, so the machining allowance of the casting is small, and there is no need for an auxiliary casting mold and a connection channel, which greatly improves the utilization rate of the casting material. There is also no need to adopt the process of secondary die forging, making the production process simpler and the cost lower.

[0025] 4. The process method of the present invention expands the types of castings that can be produced by electroslag casting. Description of the Drawings

[0026] Figure 1 It is a schematic longitudinal cross-sectional view of the electroslag casting process. In the figure: 1 is the mold; 2 is the fixed electrode; 3 is the movable electrode; 4 is the power transmission device for the movable electrode; 5 is the bottom pad; 6 is the insulating block; 7 is the arc starting section of the movable electrode; 8 is the mold cavity; 81 is the common cavity; 9 is the process section.

[0027] Figure 2 It is a schematic top view of a certain cross-section of the mold cavity of the casting and the electrode. In the figure: 21 is the fixed electrode I; 211 is the constraint section I; 22 is the fixed electrode II; 221 is the constraint section II; 31 is the flexible movable electrode; 8 is the mold cavity; 81 is the common cavity.

[0028] Figure 3 It is a three-dimensional schematic diagram of the mold cavity of the casting and the electrode; Figure 4 It is a schematic top view of a certain cross-section of the mold cavity of the casting and the electrode. In the figure: 23 is the fixed electrode III; 24 is the fixed electrode IV; 32 is the rigid movable electrode; 6 is the insulating block; 8 is the mold cavity; 81 is the common cavity; 82 is the process allowance; 9 is the process section. Detailed Embodiment

[0029] As Figures 1 - 4 shown, the electroslag casting device for directly forming three-dimensional curved surface blade-like castings mainly includes: the mold 1, the fixed electrode 2, the movable electrode 3, the bottom pad 5, the arc starting section 7 of the movable electrode, the mold cavity 8, etc. The specific structure is as follows:

[0030] The fixed electrode 2 and the movable electrode 3 are used as consumable electrodes. Two fixed electrodes 2 are arranged opposite to each other to form a common cavity 81. The movable electrode 3 is located in the common cavity 81 between the two fixed electrodes 2. An insulating block 6 or an insulating layer is arranged between the fixed electrode 2 and the inner wall surface of the mold cavity 8, and an insulating block 6 or an insulating layer is arranged on the inner wall surface of the mold cavity 8 adjacent to the movable electrode 3. The fixed electrode 2 is connected to the power supply through the fixed electrode power transmission device. The upper part of the movable electrode 3 extending above the mold 1 is supplied with power by the power transmission device 4 for the movable electrode or is clamped and connected to the power supply by an electroslag furnace chuck. The lower end of the movable electrode 3 is provided with an arc starting section 7 in the shape of a semi-cone or a wedge. A bottom pad 5 is arranged at the bottom opening of the mold 1. A process section 9 for arc starting is arranged on the contact side between the lower part of the mold 1 and the bottom pad 5. The process section 9 is communicated with the mold cavity 8. The arc starting section 7 of the lower end of the movable electrode 3 extends into the process section 9 to start an arc to melt the slag material to form a molten slag material. A bottom water tank is arranged at the bottom of the bottom pad 5. During the casting process, the casting liquid level continuously rises, so that the fixed electrode 2 remains in a continuous melting state until the casting is completed.

[0031] The safety distance maintained between the fixed electrode 2 and the moving electrode 3 and the adjacent surface of the mold cavity 8 is between 1 mm and 100 mm. The thickness of the insulating block 6 or the insulating layer between the fixed electrode 2 and the moving electrode 3 and the inner wall surface of the mold cavity 8 is not greater than the safety distance between them.

[0032] The insulating blocks 6 are dispersedly distributed and fixed in the mold cavity 8 to ensure the separation and insulation between the moving electrode 3 and the mold cavity 8, and between the fixed electrode 2 and the mold cavity 8; alternatively, the insulating layer is painted on one side of the adjacent surface of the fixed electrode, the moving electrode and the mold cavity, and the painted area of the insulating layer is the entire area or a partial area of the adjacent surface.

[0033] As Figures 1 - 4 shown, in the electroslag casting method for direct forming of three-dimensional curved surface blade-like castings of the present invention, according to the shape characteristics of the casting, the blank size of the casting and the cavity size of the mold are designed. The consumable electrode and the power transmission device are designed according to the mold. By adding process allowances to the local part of the casting, a common cavity that allows the movement and transportation of the moving electrode is formed in the local part of the designed mold cavity. The rest of the mold cavity conforms to the shape of the casting. What solidifies and forms in the mold cavity is the casting body. The mold cavity is a single cavity designed according to the shape of the casting. The casting solidifies and forms in the mold cavity. The consumable electrode is located in the mold cavity and is composed of the following forms of electrode combinations: a moving electrode 3 that moves relative to the mold cavity 8, and a fixed electrode 2 that is stationary relative to the mold cavity 8; before the moving electrode 3 enters the mold 1, power is transmitted by connecting the moving electrode power transmission device 4 to the moving electrode 3 or the moving electrode 3 is directly clamped and connected to the power supply by the electroslag furnace chuck. A safety distance needs to be maintained between the fixed electrode 2 and the moving electrode 3 and between the consumable electrode and the mold 1, or they are separated and insulated by insulating materials. During the melting and casting process, the molten metal melted from the consumable electrode fills the mold cavity, and the casting that solidifies in the mold after the melting and casting is completed is the casting product.

[0034] The movable electrode 3 and the fixed electrode 2 exist simultaneously. The lower end of the movable electrode 3 is a semi-conical frustum shape or a wedge-shaped arc-striking section 7 of the movable electrode that is conducive to arc striking. At the beginning stage of power-on in electroslag casting, the movable electrode 3 is responsible for arc striking to melt the solid slag material to form a molten slag layer. On one side where the lower end of the casting mold 1 contacts the bottom pad 5, there is a technological section 9 for arc striking. This technological section 9 is used for the movable electrode 3 to strike an arc to form a molten slag layer. The lower end of the casting mold 1 needs to be designed with the technological section 9 connected to the cavity 8 of the casting mold at an appropriate position. After the arc is struck by the arc-striking section 7 of the movable electrode 3 in the technological section 9, the molten slag layer is formed in this section. As the casting progresses, the molten slag layer gradually flows into the cavity of the casting mold. During the casting process, the molten slag layer continuously rises as the casting solidifies. The movable electrode and the fixed electrode immersed in the molten slag layer can not only keep the molten slag layer in a high-temperature molten state but also promote the flow and mixing of the molten metal liquid and the filling of the mold cavity. During the casting process, the consumable electrode, the molten slag layer, the molten metal liquid, the solidified casting metal, and the casting bottom pad form a conducting circuit. By applying power between the consumable electrode and the bottom pad, the power required for the casting process is provided, enabling the casting process to proceed continuously.

[0035] The consumable electrode can be two or more. The chemical composition of the consumable electrode material can be the same as that of the casting or a material with a different composition from the casting. The difference in the chemical composition between the electrode and the casting means that each electrode has a single chemical composition. During the casting process, electrodes with two or more chemical compositions are mixed with each other during the melting process to enable the casting to meet the required chemical composition requirements.

[0036] The movable electrode can be flexible or rigid. The movable electrode is flexible means that the electrode is made of strip-shaped thin plates, rod-shaped materials, or wire-shaped materials woven together and is bendable during the casting process. The movable electrode is rigid means that the electrode is not bendable during the casting process. When the movable electrode is flexible and long, the remaining part of the movable electrode outside the mold is coiled and stored, so that the length of the movable electrode is not limited. When the movable electrode is not bendable, the electrode needs to be placed vertically. The power transmission device of the movable electrode can apply power to the electrode at a position above the furnace mouth of the mold in the middle of the movable electrode, or the movable electrode can also be directly clamped on the chuck of the electroslag furnace for power supply.

[0037] The adjacent surface of the fixed electrode to the mold cavity is a simple shape that conforms to or approximately conforms to the shape of the mold. There is no specific proportional limit for the cross-sectional area and weight ratio between the movable electrode and the fixed electrode, and it can be designed in any ratio according to the process requirements. The movable electrode can be one or more, and the fixed electrode can be one or more. The quantity and shape of the consumable electrode should adapt to the shape of the mold cavity. The safety distance maintained between the adjacent surfaces of the fixed electrode, the movable electrode, and the mold cavity is between 1 mm and 100 mm, and the adjacent surfaces of the fixed electrode and the movable electrode should maintain a sufficient safety distance according to the process design requirements.

[0038] When the center of gravity of the consumable electrode itself is not on the same vertical line as the fixed point or constraint point of the consumable electrode, it is difficult for the consumable electrode to maintain a stable safety distance from the mold under the action of the center-of-gravity moment. Additional insulating materials are required between the consumable electrodes or between the consumable electrode and the mold cavity. Insulating blocks can be pasted or insulating layers can be coated on the inner wall surface of the mold cavity or on the local part of the consumable electrode. Its function is to maintain the distance between the consumable electrode and the mold cavity. The insulating blocks or insulating layers will melt after contacting the molten slag layer during the electroslag casting process, without affecting the chemical composition of the casting and the integrity of the solidification molding on the surface of the casting.

[0039] The thickness of the insulating block or insulating layer between the consumable electrode and the inner wall surface of the mold cavity is not greater than the safety distance between the two. The thickness of the insulating block is preferably 5 - 50 mm. The insulating blocks or insulating layers are fixedly distributed dispersedly in the mold cavity; for the insulation of the position of the movable electrode, in addition to using physical distance insulation, to prevent the movable electrode from contacting the mold or to prevent the movable electrode from contacting the fixed electrode, the above-mentioned dispersedly distributed insulating blocks can be used to ensure the separation between the two, or the method of brushing insulating materials on the single side of the adjacent surfaces of the fixed electrode, movable electrode and the mold cavity can be adopted. The brushing area of the insulating layer can be the entire area of the adjacent surface or a partial area of the adjacent surface, and the insulating material is brushed to form an insulating layer with a thickness of 0 - 5 mm or thicker.

[0040] A power transmission device can be set above the furnace mouth for the movable electrode, and forms of metal-to-metal contact such as pressure rollers and carbon brushes are used to connect power to the movable electrode, or a liquid conductive medium can be used to connect power to the movable electrode. The movable electrode can also be directly clamped on the chuck of the electroslag furnace to be powered; power connection to the movable electrode can make the electroslag casting process proceed continuously. At this time, the power transmission device of the movable electrode can control the conveying direction and conveying speed of the electrode at the same time; the power transmission device of the fixed electrode is directly connected to the fixed electrode for power transmission.

[0041] The casting of the movable electrode is manufactured by sand casting, or formed by processes such as rolling, extrusion or drawing; the adjacent surface of the fixed electrode and the mold cavity is of a simple shape that follows the contour or approximately follows the contour. The fixed electrode is prepared by sand casting or by rolling and welding of steel plates, and according to the needs of the electroslag casting process, plate profiles or strip profiles are welded on the adjacent surface of the fixed electrode to restrict the moving direction of the movable electrode and prevent the movable electrode from contacting the mold cavity.

[0042] The casting mold is of a combined type or split type on both sides. An arc starting process section is provided at the contact between the lower end of the mold cavity and the bottom pad. The mold cavity surface is made of a material with good heat conduction. Each mold segment has a water cooling channel. After the individual mold segments are assembled, a combined mold is formed. The position of the common cavity required for the movable electrode transportation should be selected at a location where the casting process allowance is increased minimally. At this time, the fixed electrode can be located on both sides of the movable electrode, so that the distance for the molten metal after melting the movable electrode to flow around and fill the mold cavity is relatively small, which is beneficial to the integrity of the casting solidification and forming. After melting and casting, the casting is taken out by separating the mold cavity.

[0043] The casting material can be carbon steel, low alloy steel or stainless steel, including but not limited to the materials described in the following standards (ASTM743, ASTM 483, ASTM 148, EN 10283, GB / T 6967, GB / T 11352, JB / T 5000.6, JB / T10384, JB / T 7349, JB / T 6405). Specific material examples are as follows:

[0044] Carbon steel: ZG230 - 450, ZG270 - 500, ZG310 - 570, etc.;

[0045] Low alloy steel: ZG20SiMn, ZG25Mn18Cr4, etc.;

[0046] Stainless steel: ZG10Cr13, ZG06Cr13Ni4Mo, ZG04Cr13Ni5Mo, ZG06Cr16Ni5Mo, ZG00Cr13Ni4Mo, ZG00Cr16Ni5Mo, ASTM A743 CA6NM, GX4CrNi13 - 4, etc.

[0047] Next, the present invention will be further elaborated in detail through embodiments.

[0048] Embodiment 1

[0049] In this embodiment, for the Francis turbine blade: the material is ZG00Cr13Ni4Mo, the blade weighs 5 tons, the maximum thickness is 280 mm, and the minimum thickness is 50 mm. As Figures 3 - 4As shown in the figure, the mold cavity 8 is designed based on the shape of the casting itself. By adding process allowances on both sides of the middle part of the casting, the middle part of the mold cavity 8 has a common cavity 81 that facilitates the up and down movement of the rigid movable electrode 32, thereby obtaining a conveying space for the rigid movable electrode 32 within the mold cavity 8. The consumable electrodes (fixed electrode III 23, fixed electrode IV 24, and rigid movable electrode 32) are all prepared by sand casting. The fixed electrode III 23, fixed electrode IV 24, and rigid movable electrode 32 are all located within the mold cavity 8 of the casting. Due to the spatial distortion of the casting shape, the fixed electrode III 23 and fixed electrode IV 24 are both approximately in the shape of spatial distortion. To prevent the fixed electrode III 23 and fixed electrode IV 24 from deforming and contacting the mold cavity 8 during the melting and casting process, insulating blocks 6 are locally fixed on the adjacent surfaces of the fixed electrode III 23 and fixed electrode IV 24 and the mold cavity 8, so that the melting and casting process can proceed safely and smoothly. After melting and casting, the casting solidifies into a casting that is consistent with the mold cavity 8. The rigid movable electrode 32 is located in the common cavity 81 at the middle position of the mold cavity 8, which is beneficial to reducing the flow filling distance of the molten metal melted by the rigid movable electrode 32 to both sides of the mold cavity 8, making the casting form full and conducive to the integrity of the casting solidification and forming.

[0050] Example 2

[0051] In this embodiment, the Francis turbine blade: the material is ZG04Cr13Ni5Mo, the blade weighs 1 ton, the maximum thickness is 120 mm, and the minimum thickness is 20 mm. As Figure 2 shown, a certain cross-section of the casting mold and the electrode is designed. The mold cavity 8 is based on the shape of the casting itself, with appropriate additional allowances. Among the consumable electrodes, the fixed electrodes are prepared by sand casting, and the movable electrode is a plate-shaped or cylindrical rolled material, which is a flexible movable electrode 31 with bendability. The fixed electrode I 21, fixed electrode II 22, and flexible movable electrode 31 are all located within the mold cavity 8 of the casting. Structures for restricting the flexible movable electrode 31 are welded on the adjacent surfaces of the fixed electrode I 21, fixed electrode II 22, and flexible movable electrode 31: a restricting section I 211 is perpendicularly welded to one end of the fixed electrode I 21 corresponding to the flexible movable electrode 31, and a restricting section II 221 is perpendicularly welded to one end of the fixed electrode II 22 corresponding to the flexible movable electrode 31. The restricting section I 211 and the restricting section II 221 are relatively arranged on both sides of the flexible movable electrode 31, so that a common cavity 81 is formed by the end face of the fixed electrode I 21, the restricting section I 211, the end face of the fixed electrode II 22, and the restricting section II 221. At this time, the increase in the local process allowance of the casting body caused by this common cavity is smaller. Since the movable electrode is flexible, this common cavity is three-dimensionally distorted and approximately conforms to the shape of the casting, and the flexible movable electrode 31 moves within the common cavity 81.

[0052] The adjacent surfaces of the fixed electrode I 21 and the fixed electrode II 22 and the flexible movable electrode 31 are partially coated with an insulating layer. The flexible movable electrode 31 has a certain degree of bendability and can bend along with the shape of the common cavity during transportation. As Figure 1 shown, the power connection method of the movable electrode 3 (the flexible movable electrode 31 in this embodiment). The movable electrode 3 is powered through the power transmission device 4 above the mold cavity 8 of the mold. The power transmission device 4 controls the transportation speed of the movable electrode 3. After melting and casting, the casting solidifies into a casting consistent with the mold cavity 8 of the mold.

[0053] Example 3

[0054] In this embodiment, a casting material is ZG06Cr16Ni5Mo, the fixed electrode material is ZG06Cr13Ni4Mo, and the movable electrode material is 0Cr18Ni9. By calculating and distributing the weight ratio of the fixed electrode and the movable electrode, the chemical composition after mixing the two is within the required composition range of the casting. As Figure 1 shown, the movable electrode 3 is powered through the power transmission device 4 above the mold cavity 8 of the mold. The lower part of the movable electrode 3 has a movable electrode arc starting section 7 in the shape of a semi-truncated cone or a wedge. After successful arc starting, a molten slag layer is formed. The casting starts to solidify from the bottom pad 5, and the casting is formed in the mold cavity 8 of the mold 1. An insulating block 6 is provided between the fixed electrode 2 and the mold cavity 8 of the mold. The height of the insulating block is 20 mm, so that the melting and casting process proceeds safely and smoothly. After melting and casting, the casting solidifies into a casting consistent with the mold cavity 8 of the mold.

[0055] Example 4

[0056] In this embodiment, a tubular turbine blade: the material is ZG04Cr13Ni5Mo, the blade weighs 8 tons, the flange diameter is 1200 mm, the maximum thickness of the blade part is 270 mm, and the minimum thickness is 50 mm. As Figure 1 shown, design a certain cross-section of the casting mold and the electrode. The mold cavity 8 of the mold is based on the shape of the casting itself and appropriately increases the allowance. Among the consumable electrodes: the fixed electrode is prepared by the sand casting method, the movable electrode is prepared by the sand casting process with a rectangular cross-section. The fixed electrode 2 and the movable electrode 3 are both located in the mold cavity 8 of the casting. The movable electrode 3 is placed in the middle position between the two fixed electrodes 2, so that the flowing distance of the molten steel melted by the movable electrode 3 to both sides is the shortest. The adjacent surface of the fixed electrode 2 and the mold cavity 8 of the mold is partially pasted with an insulating block. The power connection method of the movable electrode 3 is that the movable electrode 3 is powered through the power transmission device 4 above the mold cavity 8 of the mold. The power transmission device 4 controls the transportation speed of the movable electrode 3. After melting and casting, the casting solidifies into a casting consistent with the mold cavity 8 of the mold.

[0057] The above embodiments are only used to illustrate the technical concept and features of the present invention. The purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. An electroslag casting device for direct forming of three-dimensional curved surface blade-like castings, characterized in that, the device includes: a mold, a fixed electrode, a movable electrode, a bottom pad, a movable electrode power transmission device, and a fixed electrode power transmission device. The specific structure is as follows: The fixed electrode and the movable electrode are used as consumable electrodes. The safety distance between the adjacent surfaces of the fixed electrode, the movable electrode and the mold cavity is between 1 mm and 100 mm. By adding process allowances to the local part of the casting, a common cavity for the movement and transportation of the movable electrode is provided locally in the mold cavity. The rest of the mold cavity follows the shape of the casting. The casting body is formed by solidification in the mold cavity. The movable electrode is located at the upper end outside the mold and is connected to the power supply through the movable electrode power transmission device or is clamped and connected to the power supply by an electroslag furnace chuck. The fixed electrode is connected to the power supply through the fixed electrode power transmission device. The lower end of the movable electrode is provided with a movable electrode arc starting section in the shape of a semi-cone or a wedge. A bottom pad is arranged at the bottom opening of the mold. A process section for arc starting is arranged on one side of the lower part of the mold in contact with the bottom pad. The process section is communicated with the mold cavity. The movable electrode arc starting section at the lower end of the movable electrode extends into the process section of the mold to arc and melt the slag material to form a molten slag material. The movable electrode can be flexible or non-flexible during the electroslag casting process; The mold cavity is based on the shape of the casting itself, and process allowances are added on both sides in the middle of the casting. The casting mold is a combined type or split type on both sides. An arc starting process section is provided at the contact between the lower end of the mold cavity and the bottom pad. The position of the common cavity required for the movement of the movable electrode should be selected at the position where the process allowance of the casting is increased minimally. At this time, the fixed electrode is located on both sides of the movable electrode, so that the distances for the molten metal liquid melted by the movable electrode to flow around and fill the mold cavity are all smaller, which is beneficial to the integrity of the solidification and forming of the casting. After electroslag casting, the casting is taken out by separating the mold cavity.

2. The electroslag casting device for direct forming of three-dimensional curved surface blade-like castings according to claim 1, characterized in that, an insulating block or insulating layer is arranged between the fixed electrode and the inner wall surface of the mold cavity. Insulating blocks or insulating layers are arranged between the adjacent surfaces of the fixed electrode and the movable electrode according to the requirements of the electroslag casting process. An insulating block or insulating layer is arranged between the movable electrode and the inner wall surface of the mold cavity. The thickness of the insulating block or insulating layer between the fixed electrode, the movable electrode and the inner wall surface of the mold cavity is not greater than the safety distance between the two.

3. The electroslag casting device for direct forming of three-dimensional curved surface blade-like castings according to claim 2, characterized in that, the insulating blocks are dispersedly distributed and fixed in the mold cavity to ensure the separation insulation between the movable electrode and the fixed electrode, between the movable electrode and the mold cavity, and between the fixed electrode and the mold cavity; or, the insulating layer is brushed on one side of the adjacent surfaces of the fixed electrode, the movable electrode and the mold cavity. The brushing area of the insulating layer is the entire area or a partial area of the adjacent surface.

4. An electroslag casting method for direct forming of three-dimensional curved surface blade-like castings using the device according to any one of claims 1 to 3, characterized in that, According to the shape characteristics of the casting, the blank size of the casting and the cavity size of the mold are designed. The consumable electrode and the power transmission device are designed according to the mold. The cavity of the mold is a single cavity designed according to the shape of the casting. By adding process allowances to local parts of the casting, a common cavity that allows the movable electrode to move is formed in the local part of the designed mold, and the rest of the mold follows the shape of the casting. The casting solidifies and forms in the cavity of the mold. The consumable electrode is located in the cavity of the mold and is composed of the following forms of electrode combinations: a movable electrode that moves relative to the cavity of the mold and a fixed electrode that is stationary relative to the cavity of the mold. The fixed electrode power transmission device is connected to the fixed electrode for power transmission, and the movable electrode power transmission device is connected to the movable electrode for power transmission. Insulation is maintained between the fixed electrode, the movable electrode and the mold. During the casting process, the molten metal melted from the consumable electrode fills the cavity of the mold. During the casting process, the casting liquid level continuously rises, causing the fixed electrode to remain in a continuously melting state until the casting is completed. The casting solidified in the mold after casting is the casting product. When the center of gravity of the consumable electrode itself is not on the same vertical line as the fixed point or the constraint point of the consumable electrode, it is difficult for the consumable electrode to maintain a stable safety distance from the mold under the action of the center of gravity moment. The consumable electrodes or between the consumable electrode and the cavity of the mold are separated by an insulating material. An insulating block or an insulating layer is pasted or coated locally on the inner wall surface of the cavity of the mold or the consumable electrode to maintain insulation between the consumable electrode and the cavity of the mold. The insulating block or the insulating layer will melt after contacting the molten slag layer during the electroslag casting process, without affecting the chemical composition of the casting and the integrity of the solidification and forming of the casting surface.

5. The electroslag casting method for directly forming three-dimensional curved surface blade-like castings according to claim 4, characterized in that, The movable electrode and the fixed electrode exist simultaneously. The lower end of the movable electrode is in the shape of a semi-cone or a wedge-shaped arc-starting section of the movable electrode that is beneficial for arc starting. At the beginning stage of power-on during electroslag casting, the movable electrode is responsible for arc starting to melt the solid slag material to form a molten slag layer. One side of the lower end of the casting mold in contact with the bottom pad is provided with a process section for arc starting. This process section is used for the movable electrode to start an arc to form a molten slag layer. The process section is connected to the cavity of the casting mold. The arc-starting section of the movable electrode forms a molten slag layer here after starting an arc in the process section. As the casting process progresses, the liquid level of the molten slag layer rises, and the fixed electrode continuously melts. The molten steel gradually solidifies in the water-cooled cavity of the mold to form a casting. During the casting process, the molten slag layer continuously rises as the casting solidifies and forms. The movable electrode and the fixed electrode immersed in the molten slag layer not only keep the molten slag layer in a high-temperature molten state, but also promote the flow and mixing of the molten metal and fill the cavity of the mold. During the casting process, the consumable electrode, the molten slag layer, the molten metal, the solidified casting metal and the casting bottom pad form a conducting circuit. By applying power between the consumable electrode and the bottom pad to provide the power required for the casting process, the casting process can proceed continuously.

6. The electroslag casting method for directly forming three-dimensional curved surface blade-like castings according to claim 4, characterized in that, The consumable electrodes are two or more, and the chemical composition of the consumable electrode material is the same as or different from that of the casting; the difference in chemical composition between the electrode and the casting means that each electrode has a single chemical composition, and during the melting and casting process, two or more consumable electrodes with different chemical compositions are mixed with each other during the melting process to make the casting meet the required chemical composition requirements; the movable electrodes are one or more, and the fixed electrodes are one or more.

7. The electroslag casting method for direct forming of three-dimensional curved surface blade-like castings according to claim 4, characterized in that, the movable electrode is flexible or rigid; the movable electrode is flexible means that the electrode is made of strip-shaped thin plates, rod-shaped materials or wire-shaped materials woven together and is bendable during the melting and casting process; the movable electrode is rigid means that the electrode is not bendable during the melting and casting process; when the movable electrode is flexible and long, the remaining part of the movable electrode outside the mold is coiled and stored so that the length of the movable electrode is not limited; when the movable electrode is not bendable, the electrode needs to be placed vertically. The movable electrode is powered by a power transmission device located at the furnace mouth of the mold, or is directly clamped on the chuck of the electroslag furnace for power supply.

8. The electroslag casting method for direct forming of three-dimensional curved surface blade-like castings according to claim 7, characterized in that, when the power transmission device of the movable electrode is located above the furnace mouth of the mold, the metal-to-metal contact form of a pressure roller or a brush is used to connect power to the movable electrode, or a liquid conductive medium is used to connect power to the movable electrode. Connecting power to the movable electrode makes the electroslag casting process continuous. At this time, the power transmission device of the movable electrode simultaneously controls the conveying direction and conveying speed of the movable electrode; the power transmission device of the fixed electrode is directly connected to the fixed electrode for power transmission.

9. The electroslag casting method for direct forming of three-dimensional curved surface blade-like castings according to claim 4, characterized in that, the movable electrode is a casting manufactured by sand casting, or is manufactured by processes such as rolling, extrusion or drawing; the adjacent surface of the fixed electrode to the mold cavity is a conforming or approximately conforming simple shape. The fixed electrode is manufactured by sand casting, or by rolling or steel plate assembly welding, and according to the needs of the electroslag casting process, plate-shaped or strip-shaped materials are welded on the adjacent surface of the fixed electrode to restrict the moving direction of the movable electrode and prevent the movable electrode from contacting the mold cavity.

Images