A conductive circuit control device and method for electroslag fusion welding

Abstract

The present invention belongs to the field of metallurgy technology, and relates to a conductive circuit control device and method for electroslag fusion welding, the device comprising: a combined crystallizer is arranged on the side and bottom of a welding part; a plate-type consumable electrode is arranged between two welding parts, and the bottom of the plate-type consumable electrode is immersed in a preset depth of a slag pool; a power supply connects the plate-type electrode and a conductive disk; the top / side conductive disk is fixedly pressed on the top / side of the welding part; a top / side conductive circuit switch is arranged between the industrial AC power supply and the top / side conductive disk; during the electroslag fusion welding process, the current density and Joule heat inside the slag pool and the lower part of the fusion zone are reduced by controlling the on-off of the conductive circuit. Its beneficial effect is that the Joule heat in the slag pool is concentrated near the plate-type consumable electrode, the melting rate inside the welding part is reduced, and then the horizontal width of the slag pool is reduced, which is conducive to maintaining the depth of the slag pool, reducing the total volume of the fusion zone, making the stress distribution during the solidification process more uniform, and reducing element segregation.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a conductive circuit control device and method for electroslag fusion welding. Background Art

[0002] As my country's industrial modernization process continues to advance, the demand for heavy equipment in various industries continues to increase, especially the large-scale high-quality special steel manufacturing equipment. In the traditional production method, key components are generally forged from large ingots, which is time-consuming and produces a lot of metal waste. Therefore, how to quickly produce large-scale high-quality special steel equipment that meets quality requirements has become a focus of research in the metallurgical field.

[0003] Electroslag remelting is an important secondary refining process that can effectively remove non-metallic inclusions. At the same time, the remelted steel ingot has the characteristics of dense structure, small macro-segregation and smooth surface, and is often suitable for the production of large steel ingots. However, when producing large steel ingots, due to the large size of the crystallizer used, the central cooling conditions are weakened, which will cause defects such as shrinkage, shrinkage and macro-segregation in the steel ingot. These defects are difficult to eliminate by conventional means, and the use of various smelting control technologies can often only alleviate but not eliminate them, and these defects will be further amplified with the increase of smelting tonnage.

[0004] In order to meet the production needs of large-tonnage electroslag steel and the manufacturing needs of heavy electroslag steel equipment, electroslag fusion welding technology has been developed. As a secondary manufacturing technology for electroslag, electroslag fusion welding is a process in which electroslag ingots or electroslag parts with small size and excellent technical indicators obtained in the first manufacturing are fused and welded through plate-type consumable electrodes and a certain amount of slag at a suitable welding spacing to achieve the fusion welding of two smaller electroslag parts into a larger electroslag product. This electroslag product obtained through secondary manufacturing of electroslag fusion welding technology not only meets the large-scale production needs, but also maintains the excellent performance of small-sized electroslag products.

[0005] Since the plate consumable electrode and the welding parts are made of the same material, the slag pool will melt and extend to the inside of the welding parts during the welding process. That is, as the welding process proceeds, the horizontal cross-sectional area of ​​the slag pool will continue to increase, the depth of the slag pool will continue to decrease, and the slag pool shape will gradually evolve from deep and narrow to wide and shallow. This phenomenon will increase the risk of horizontal penetration of the welding parts, expand the welding affected area, and cause deformation and uneven stress distribution. Therefore, it is necessary to study methods that can effectively improve the slag pool shape. At the same time, because the current density values ​​of the metal molten pool and the lower part of the welding area are still high when the bottom conductive circuit is connected, a certain amount of Joule heat will be generated in this area, which is not conducive to the rapid solidification of the metal and the reduction of the welding affected area. Summary of the invention

[0006] Technical issues to be solved

[0007] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a conductive circuit control device and method for electroslag fusion welding, which solves the technical problem of how to quickly solidify the metal and reduce the fusion welding affected area during electroslag fusion welding.

[0008] Technical Solution

[0009] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0010] In a first aspect, the present invention provides a conductive circuit control device for electroslag fusion welding, comprising:

[0011] Combined crystallizer, arranged on the side and bottom of the welding part, used to cool the liquid metal in the welding area and prevent the liquid metal and slag from leaking out;

[0012] The plate-type consumable electrode is arranged between two welding parts, and the bottom of the plate-type consumable electrode is immersed in the slag pool to a preset depth;

[0013] Industrial AC power supply, connected in series to the top of the plate-type consumable electrode;

[0014] The top conductive plate is fixed and pressed on the top of the welding part;

[0015] The top conductive loop switch is arranged between the industrial AC power supply and the top conductive disk;

[0016] The side conductive disc is fixed and pressed on the side of the welding part;

[0017] The side conductive loop switch is arranged between the industrial AC power supply and the side conductive plate;

[0018] During the electroslag fusion welding process, the current density and Joule heat inside the slag pool and the lower part of the molten welding area are reduced by controlling the opening and closing of the top conductive circuit switch and the side conductive circuit switch.

[0019] Optionally, the combined crystallizer includes a side-sealed crystallizer and a bottom water tank, and the fusion welding area is cooled by flowing cooling water inside the side-sealed crystallizer and the bottom water tank.

[0020] Optionally, the material and shape of the top conductive plate and the side conductive plate are determined according to the geometric size and surface shape of the welding component.

[0021] Optionally, when the conductive disk is made of the same material as the plate-type consumable electrode and the welding component, the top conductive circuit switch is kept closed in the later stage of electroslag fusion welding to keep the top conductive disk in contact with the surface of the welding component;

[0022] When the conductive disk, the plate-type consumable electrode and the welding part are made of different materials, the top conductive circuit switch is disconnected after the side conductive circuit switch is turned on in the later stage of electroslag fusion welding, and the top conductive disk is lifted to be separated from the surface of the welding part.

[0023] Optionally, the industrial AC power supply includes a transformer to convert high voltage electricity into low voltage electricity, and the operating voltage is 35V~60V.

[0024] Optionally, the distance between the welding part and the side sealing crystallizer is greater than or equal to 20 mm, and the thickness of the welding part is greater than or equal to 100 mm.

[0025] In a second aspect, the present invention provides a conductive circuit control method for electroslag fusion welding, which is applicable to a conductive circuit control device for electroslag fusion welding described in the above technical solution, and the method comprises:

[0026] S1: Adjust the relative positions of the welding parts and the plate consumable electrode, and install the bottom water tank and the side-sealed crystallizer;

[0027] S2: Customize or select existing top conductive plates and side conductive plates according to the geometric size and surface shape of the welding component, and connect the top conductive plates and side conductive plates to the conductive loop; fix and press the top conductive plates and side conductive plates on the top and side of the welding component respectively through a mechanical device;

[0028] S3: At the beginning of arcing and electroslag fusion welding, the side conductive circuit switch is turned on separately; the side conductive circuit switch is closed to start the electroslag fusion welding process; if the thickness of the welded part is greater than the height, the side conductive circuit switch is ignored and the top conductive circuit switch is directly turned on;

[0029] S4: After entering the stable period of electroslag fusion welding, turn on the top conductive circuit switch and disconnect the side conductive circuit; if the thickness of the welded part is greater than the height, ignore S4 and enter S5;

[0030] S5: In the late stage of electroslag fusion welding, i.e., the shrinkage feeding period, the side conductive circuit switch is turned on and then the top conductive circuit switch is turned off. Then, the top conductive disk is lifted up by a mechanical device to separate from the welding parts until the shrinkage feeding is completed and the electroslag fusion welding process is ended.

[0031] Beneficial Effects

[0032] The beneficial effects of the present invention are as follows: a conductive circuit control device for electroslag fusion welding of the present invention replaces a conductive disk of a corresponding size according to the geometric dimensions of the welding part, and is fixed and pressed on the top and side of the welding part by a mechanical device. The conductive disk in the conductive circuit control device can be customized according to the top or side surface shape of the welding part to ensure that there is no gap in the contact surface. A closed conductive circuit of a plate-type consumable electrode-slag pool-welding part-top or side conductive disk is completed. Compared with the bottom water tank conductive circuit used in general electroslag fusion welding, the device can concentrate the Joule heat in the slag pool in the area near the plate-type consumable electrode, reduce the melting rate of the inner area of ​​the welding part, and then reduce the horizontal width of the slag pool, which is beneficial to maintain the slag pool depth, reduce the amount of slag used, and improve the welding quality. At the same time, the smaller horizontal melting depth of the slag pool reduces the total volume of the molten welding area, makes the stress distribution during the solidification process more uniform, and reduces element segregation. In addition, changing the conductive circuit from bottom connection to top or side connection can greatly reduce the current density and Joule heat in the molten metal pool and the lower part of the molten welding area, which is beneficial to the rapid solidification of the molten metal pool and improves the quality of fusion welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of the main structure of a conductive circuit control device for electroslag fusion welding provided by an embodiment of the present invention;

[0034] Figure 2 A schematic side structural diagram of a conductive circuit control device for electroslag fusion welding provided by an embodiment of the present invention;

[0035] Figure 3 A schematic diagram of the top view of a conductive circuit control device for electroslag fusion welding provided in an embodiment of the present invention;

[0036] Figure 4 A schematic diagram of the current density distribution when the side conductive loop provided by an embodiment of the present invention is connected;

[0037] Figure 5 A schematic diagram of the current density distribution when the top conductive loop provided by an embodiment of the present invention is connected;

[0038] Figure 6 A schematic diagram of the current density distribution when the bottom water tank conductive circuit is connected in a typical electroslag fusion welding process provided by an embodiment of the present invention.

[0039] Description of Reference Numerals

[0040] 1-industrial AC power supply, 2-top conductive circuit switch, 3-top conductive disk, 4-side conductive circuit switch, 5-plate consumable electrode, 6-side conductive disk, 7-welding parts, 8-slag pool, 9-bottom water tank, 10-side sealed crystallizer. DETAILED DESCRIPTION

[0041] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0042] The function of the conductive crystallizer during electroslag remelting is to make the current distribution in the slag pool more uniform, and then make the Joule heat distribution more uniform, so that the temperature of the molten metal pool in the middle is reduced, and the temperature of the molten metal pool in the area near the crystallizer wall is increased, and finally the shape of the molten metal pool changes from deep and steep to shallow and flat, improving the molten metal pool morphology and the quality of the ingot. Unlike conventional electroslag remelting, the current path of electroslag fusion welding is generally consumable electrode-slag pool upper surface-welding component-molten welding pool lower area-bottom water tank because of the presence of welding components made of the same material as the consumable electrode. Since the conductivity of the welding components is better than that of the slag, the current passing through the middle and lower part of the slag pool is less than that passing through the welding components, and the Joule heat distribution in the middle and lower part of the slag pool is also less than that in the upper part of the slag pool.

[0043] The demand for Joule heat distribution in the slag pool in electroslag fusion welding is exactly the opposite of that in electroslag remelting. The electroslag fusion welding process requires Joule heat to be concentrated near the plate electrode, and most of the heat is used to melt the plate electrode. At the same time, the Joule heat in the edge area of ​​the slag pool should be as little as possible, which can reduce the melting rate of the inner area of ​​the welded parts, and then reduce the horizontal width of the slag pool, which is conducive to maintaining the depth of the slag pool and improving the welding quality. In addition, due to the change of the conductive circuit, the current density and Joule heat value of the metal molten pool and the lower part of the molten welding area are also greatly reduced, which is also conducive to increasing the solidification rate of the metal and reducing the area affected by the molten welding.

[0044] In order to enhance the heat generation of the slag pool near the plate consumable electrode and weaken the heat generation in the edge area of ​​the slag pool, thereby reducing the horizontal melting depth of the slag pool toward the inner side of the welding part during the welding process, reducing the risk of short circuit of the side melting through and the electrode touching the bottom of the metal molten pool, and improving the welding quality; and also to reduce the current density and Joule heat value of the metal molten pool and the lower part of the molten welding area, increase the solidification rate of the metal and reduce the area affected by the molten welding, the present invention provides a conductive circuit control device and method for electroslag fusion welding.

[0045] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0046] In the first aspect, this embodiment provides a conductive circuit control device for electroslag fusion welding, the overall structure of the device and the relative positions of the components are as follows: Figure 1 , Figure 2 and Figure 3 The device comprises:

[0047] Combined crystallizer, arranged on the side and bottom of the welding part 7, used to cool the liquid metal in the welding area and prevent the liquid metal and slag from leaking out;

[0048] A plate-type consumable electrode 5 is arranged between two welding parts, and the bottom of the plate-type consumable electrode is immersed in a slag pool 8 to a preset depth;

[0049] An industrial AC power source 1 is connected in series to the top of a plate-type consumable electrode 5;

[0050] The top conductive plate 3 is fixed and pressed on the top of the welding component 7;

[0051] A top conductive loop switch 2 is arranged between the industrial AC power source 1 and the top conductive plate 3;

[0052] The side conductive plate 6 is fixed and pressed on the side of the welding component 7;

[0053] The side conductive loop switch 4 is arranged between the industrial AC power source 1 and the side conductive plate 6;

[0054] During the electroslag fusion welding process, the current density and Joule heat inside the slag pool and the lower part of the molten welding area are reduced by controlling the opening and closing of the top conductive circuit switch 2 and the side conductive circuit switch 4.

[0055] The welding part 7 needs to be fused and welded into an integral electroslag part.

[0056] The slag pool 8 is formed when the slag is heated to liquid by the Joule heat generated by the smelting current passing through it. The type of slag is selected according to the production requirements of the electroslag fusion welding process.

[0057] Optionally, the combined crystallizer includes a side-sealed crystallizer 10 and a bottom water tank 9, and the melting welding area is cooled by flowing cooling water inside the side-sealed crystallizer 10 and the bottom water tank 9.

[0058] The bottom water tank 9 is a part of the combined crystallizer used in the electroslag fusion welding process, and the temperature of the fusion welding area is reduced by the flow of internal cooling water.

[0059] The side-sealed crystallizer 10 is a part of the combined crystallizer used in the electroslag fusion welding process. It realizes cooling of the fusion welding area through the flow of internal cooling water, and at the same time realizes sealing of the sides of the fusion welding area to prevent liquid slag and metal from leaking from the sides and endangering production safety.

[0060] Optionally, the material and shape of the top conductive plate and the side conductive plate are determined according to the geometric size and surface shape of the welding component.

[0061] The material and shape of the conductive disk are determined according to the geometric size and surface shape of the welded parts. You can also choose the existing top and side conductive disks and connect the conductive disks to the machine device. The top and side conductive disks are fixed and pressed on the top and side of the welded parts by mechanical devices to avoid arcing on the surface of the welded parts and reduce the surface quality of the welded parts.

[0062] Optionally, when the conductive disk, the plate-type consumable electrode and the welding component are made of the same material, the top conductive circuit switch is kept closed in the later stage of electroslag fusion welding to keep the top conductive disk in contact with the surface of the welding component;

[0063] When the conductive disk, the plate-type consumable electrode and the welding parts are made of different materials, the top conductive circuit switch should be disconnected after the side conductive circuit switch is turned on in the later stage of electroslag fusion welding, and the top conductive disk should be lifted to separate from the surface of the welding parts to prevent the liquid slag from directly contacting the top conductive disk, introducing other metal element impurities and damaging the conductive disk.

[0064] Optionally, the industrial AC power supply includes a transformer to convert high voltage electricity into low voltage electricity, and the operating voltage is 35V~60V.

[0065] Optionally, the distance between the welding part and the side sealing crystallizer is greater than or equal to 20 mm, and the thickness of the welding part is greater than or equal to 100 mm.

[0066] The present invention discloses a conductive circuit control device for electroslag fusion welding, which can select an appropriate conductive disk according to the geometric size and surface shape of the welding part, so as to avoid arcing on the surface of the welding part and reduce the surface quality of the welding part. The device comprises a top and side conductive circuit, a switch and a corresponding control system. During the electroslag fusion welding process, the conductive circuit of the system can be controlled to switch on and off as required. The device comprises a side-sealed crystallizer. The component is a part of the electroslag fusion welding combined crystallizer, and the cooling of the fusion welding area is achieved by cooling water entering from the bottom and exiting from the top, and the sealing of the side of the fusion welding area is achieved at the same time, so as to prevent liquid slag and metal from leaking from the side and endangering production safety. The device comprises a bottom water tank. The component is a part of the electroslag fusion welding combined crystallizer, and the cooling of the fusion welding area is achieved by cooling water entering and exiting from the bottom, and the sealing of the bottom surface of the fusion welding area is achieved at the same time, so as to prevent liquid slag and metal from leaking from the bottom side and endangering production safety. The device comprises a plate-type consumable electrode. The length of the component is determined according to the length of the welding component. According to the experimental results, the distance between the welding component and the side sealing crystallizer should be maintained at 20mm or more, and the thickness of the welding component should not be less than 100mm. The device includes a welding component. The geometric shape and size of the component are selected according to production needs to ensure that the inner surface of the welding component is smooth and flat as much as possible. The device includes an industrial AC power supply. The component also includes a transformer, which can convert high-voltage electricity from the power grid into low-voltage electricity. According to the experimental results, the working voltage required for the electroslag fusion welding technology is about 35V~60V.

[0067] The current density distribution when the side, top and bottom conductive circuits are connected during electroslag fusion welding is shown in Figure 2. Figure 4 , Figure 5 and Figure 6 As shown. Figure 4 and Figure 5 They are respectively the predicted distribution of the longitudinal profile current density when the side and top conductive loops are connected during the operation of the device. Figure 6 This is the predicted distribution of the longitudinal current density when the bottom water tank conductive circuit is connected during general electroslag fusion welding. Figure 6 compared to, Figure 4 and Figure 5 The current density distribution in the slag is more concentrated in the upper layer and near the plate consumable electrode, and the current density value in the lower part of the slag pool is smaller. The corresponding Joule heat distribution also conforms to the above law, and the current density and Joule heat values ​​in the lower part of the metal molten pool and the molten welding zone are significantly reduced.

[0068] In a second aspect, a conductive circuit control method for electroslag fusion welding provided in this embodiment is applicable to a conductive circuit control device for electroslag fusion welding described in the above embodiment, and the method comprises the following steps:

[0069] S1: Adjust the relative positions of the welding component 7 and the plate-type consumable electrode 5, and install the bottom water tank 9 and the side sealing crystallizer 10.

[0070] S2: Customize or select the existing top conductive plate 3 and side conductive plate 6 according to the geometric size and surface shape of the welding component 7, and connect the top conductive plate 3 and the side conductive plate 6 to the mechanical device. The top conductive plate 3 and the side conductive plate 6 are fixed and pressed on the top and side of the welding component respectively by the mechanical device.

[0071] S3: Close the side conductive circuit switch 4 to start the electroslag fusion welding process; if the thickness of the welded part is greater than the height, ignore the side conductive circuit switch and directly connect the top conductive circuit switch.

[0072] S4: After entering the stable period of electroslag fusion welding, the top conductive circuit switch 2 is turned on and the side conductive circuit switch 4 is turned off; if the thickness of the welded part is greater than the height, S4 is ignored and S5 is entered.

[0073] S5: In the late stage of electroslag fusion welding, i.e., the shrinkage compensation period, the side conductive circuit switch 4 is turned on and the top conductive circuit switch 2 is turned off, and then the top conductive disk 3 is lifted up by a mechanical device to separate from the welding parts until the shrinkage compensation is completed and the electroslag fusion welding process is completed.

[0074] According to the conductive circuit control method for electroslag fusion welding provided in this embodiment, since it is used to implement the steps of a conductive circuit control device for electroslag fusion welding provided in the first aspect of the present invention, the conductive circuit control method for electroslag fusion welding has all the technical effects of the conductive circuit control device for electroslag fusion welding, which will not be repeated here.

[0075] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention should also include these modifications and variations.

[0076] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A conductive circuit control device for electroslag fusion welding, characterized in that: include: Combined crystallizer, arranged on the side and bottom of the welding part, used to cool the liquid metal in the welding area and prevent the liquid metal and slag from leaking out; The plate-type consumable electrode is arranged between two welding parts, and the bottom of the plate-type consumable electrode is immersed in the slag pool to a preset depth; Industrial AC power supply, connected in series to the top of the plate-type consumable electrode; The top conductive plate is fixed and pressed on the top of the welding part; The top conductive loop switch is arranged between the industrial AC power supply and the top conductive disk; The side conductive disc is fixed and pressed on the side of the welding part; The side conductive loop switch is arranged between the industrial AC power supply and the side conductive plate; During the electroslag fusion welding process, the current density and Joule heat inside the slag pool and the lower part of the molten welding area are reduced by controlling the opening and closing of the top conductive circuit switch and the side conductive circuit switch; The material and shape of the top conductive plate and the side conductive plate are determined according to the geometric size and surface shape of the welding component; When the conductive disk is made of the same material as the plate-type consumable electrode and the welding part, the top conductive circuit switch is kept closed in the later stage of electroslag fusion welding to keep the top conductive disk in contact with the surface of the welding part; When the conductive disk, the plate-type consumable electrode and the welding part are made of different materials, the top conductive circuit switch is disconnected after the side conductive circuit switch is turned on in the later stage of electroslag fusion welding, and the top conductive disk is lifted to be separated from the surface of the welding part.

2. The conductive circuit control device for electroslag fusion welding according to claim 1, characterized in that: The combined crystallizer comprises a side-sealed crystallizer and a bottom water tank, and the melting welding area is cooled by flowing cooling water inside the side-sealed crystallizer and the bottom water tank.

3. The conductive circuit control device for electroslag fusion welding according to claim 2, characterized in that: The industrial AC power supply includes a transformer, which converts high voltage electricity into low voltage electricity, and the working voltage is 35V~60V.

4. The conductive circuit control device for electroslag fusion welding according to claim 3, characterized in that: The distance between the welding part and the side sealing crystallizer is greater than or equal to 20 mm, and the thickness of the welding part is greater than or equal to 100 mm.

5. A method for controlling a conductive circuit of electroslag fusion welding, characterized in that: The conductive circuit control device for electroslag fusion welding according to claim 4, wherein the method comprises: S1: Adjust the relative positions of the welding parts and the plate consumable electrode, and install the bottom water tank and the side-sealed crystallizer; S2: Customize or select existing top conductive plates and side conductive plates according to the geometric size and surface shape of the welding component, and connect the top conductive plates and side conductive plates to the conductive loop; fix and press the top conductive plates and side conductive plates on the top and side of the welding component respectively through a mechanical device; S3: At the beginning of arcing and electroslag fusion welding, the side conductive circuit switch is turned on separately; the side conductive circuit switch is closed to start the electroslag fusion welding process; if the thickness of the welded part is greater than the height, the side conductive circuit switch is ignored and the top conductive circuit switch is directly turned on; S4: After entering the stable period of electroslag fusion welding, turn on the top conductive circuit switch and disconnect the side conductive circuit; if the thickness of the welded part is greater than the height, ignore S4 and enter S5; S5: In the late stage of electroslag fusion welding, i.e., the shrinkage feeding period, the side conductive circuit switch is turned on and then the top conductive circuit switch is turned off. Then, the top conductive disk is lifted up by a mechanical device to separate from the welding parts until the shrinkage feeding is completed and the electroslag fusion welding process is ended.

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