A method for improving the solidification quality and cleanliness of electroslag remelted ingots

Abstract

This invention relates to the field of electroslag remelting ingot solidification technology, and discloses a method for improving the solidification quality and cleanliness of electroslag remelting ingots. The invention includes an electroslag remelting crystallizer, with a crystallizer base fixedly connected to its lower surface. Inside the crystallizer, during the electroslag remelting process, an electroslag ingot, a molten metal pool, and a slag pool are formed. An electrode bundle is positioned directly above the slag pool, consisting of several slender electrodes. The gaps between the electrodes are filled with electroslag material to be replenished. By dividing the metal electrodes into several slender electrodes, during the electroslag remelting process, the original single-point, localized dripping of molten metal droplets is transformed into stable, dense, multi-point, uniform dripping. Without affecting the production efficiency of electroslag remelting, this effectively reduces the diameter of the molten metal droplets, improves the inclusion removal efficiency of the electroslag remelting process, and simultaneously increases the width of the molten metal pool, increasing the probability of axial grain growth in the electroslag ingot.

Description

Technical Field

[0001] This invention belongs to the field of solidification technology for electroslag remelting ingots, specifically a method for improving the solidification quality and cleanliness of electroslag remelting ingots. Background Technology

[0002] Electroslag remelting (ESR) is a special metal smelting process. ESR uses the metal ingot to be melted as the electrode, forming a closed circuit with the molten slag and a cooling crystallizer. Due to the high thermal resistance of the slag, the generated heat melts the slag, and the metal electrode inserted into the slag gradually melts as well. The molten metal drips through the slag pool. As the metal droplets come into contact with the slag, inclusions in the droplets are adsorbed by the slag. The metal droplets that have passed through the slag pool converge to form a molten pool, and any remaining inclusions in the molten pool float to the slag pool, achieving inclusion removal. Because ESR can effectively remove large inclusions from steel, it is required for the production of metal components used in harsh environments, such as high-speed rail bearings, nuclear power steel, and aircraft engine alloys. Furthermore, with the development of larger and more efficient equipment, even higher requirements are being placed on the ESR process.

[0003] First, the requirements for inclusions are more stringent. Large-sized castings often correspond to large-section metal electrodes. However, during the heating, melting, and dripping process, the metal electrodes tend to drip in concentrated areas. Moreover, the larger the electrode size, the larger the size of the dripping molten metal droplets becomes due to the surface area effect. The diameter of the molten metal droplets directly affects the adsorption of inclusions in the slag pool and their flotation removal in the molten metal pool. The droplet size, to a certain extent, determines the range of inclusion sizes that the electroslag remelting process can remove; the larger the droplet diameter, the more difficult the inclusion removal. Even changing the power supply parameters to alter the droplet droplet location is unlikely to effectively reduce the droplet diameter.

[0004] Secondly, the quality requirements for electroslag remelted ingots are becoming increasingly stringent. To reduce microscopic porosity defects during ingot solidification, grain growth along the axial direction should be promoted as much as possible, which requires maximizing the width (cross-sectional area) of the molten metal pool. However, concentrated or random dripping of large electrode droplets is detrimental to the stable expansion of the molten metal pool. Even in ultra-large tonnage electroslag remelting furnaces employing multiple electrodes, limitations in electrode size and electrode clamping devices make it difficult to form a uniform dripping area across the entire molten metal pool cross-section, thus negatively impacting the uniform growth of grains along the axial direction.

[0005] Third, during electroslag remelting, the slag is continuously consumed. Current technological solutions involve supplementing the slag with either solid or liquid slag during the smelting process. Supplementing with solid slag disrupts the temperature balance in certain areas of the slag, requiring frequent, small additions, which increases the workload for workers and makes uniform replenishment difficult. Supplementing with liquid slag requires additional slag-melting equipment, increasing equipment investment and wasting significant energy.

[0006] Therefore, we propose a method to improve the solidification quality and cleanliness of electroslag remelted ingots. Summary of the Invention

[0007] The purpose of this invention is to effectively reduce the diameter of molten metal droplets and improve the inclusion removal efficiency of the electroslag remelting process without affecting the production efficiency of electroslag remelting. This application provides a method to improve the solidification quality and cleanliness of electroslag remelted ingots.

[0008] The technical solution adopted in this invention is as follows:

[0009] A method for improving the solidification quality and cleanliness of electroslag remelted ingots includes an electroslag remelting crystallizer, wherein a crystallizer base is fixedly connected to the lower surface of the electroslag remelting crystallizer, and an electroslag ingot, a molten metal pool, and a slag pool are formed inside the electroslag remelting crystallizer during the electroslag remelting process, and an electrode bundle is arranged directly above the slag pool, the electrode bundle being composed of several slender strip electrodes.

[0010] In a preferred embodiment of the invention, the supplementary slag filling gaps are provided between a plurality of the elongated electrodes.

[0011] In a preferred embodiment of the invention, the thickness of the filler slag is 1-10 mm.

[0012] In a preferred embodiment of the invention, the interior of the supplementary slag filling slot is filled with slag material, and the melting point of the slag material is lower than the melting point of the electrode bundle.

[0013] A method for improving the solidification quality and cleanliness of electroslag remelted ingots:

[0014] S1. Cut the large-size electrode ingot produced in the previous process into slender strip electrodes with a cross-section of 50-150mm×50-150mm. The specific cutting size of the cross-section of the slender strip electrode is determined by the cross-sectional size of the electrode to be cut, ensuring that the electrode to be cut is evenly cut into several equal parts. The length of the newly cut slender strip electrode is the length of the large-size electrode ingot produced in the previous process.

[0015] S2. Connect the cut ends of the slender strip electrodes to the electrode clamping device of the electroslag remelting ingot solidification device in sequence. For each slender strip electrode installed, the pre-melted and cooled slag material to be added needs to be coated on the slag filling gap on the surface of the slender strip electrode before installing the next slender strip electrode.

[0016] S3. Once a plurality of the elongated electrodes form an electrode bundle, electroslag remelting can then begin. Since the elongated electrodes are separated by slag, the cross-sectional area of ​​a single elongated electrode is small, and the size of the droplets that accumulate during the melting process is small, which can remove even smaller inclusions.

[0017] S4. Because the elongated electrodes are densely distributed and can stably form multiple dripping areas, a wider cross-section of the molten metal pool can be formed;

[0018] S5. Regarding the pre-melted slag layer between the elongated electrodes, when the elongated electrodes begin to be heated by the molten slag, the pre-melted slag layer between the elongated electrodes also begins to be heated. Since the melting point of the slag to be replenished is 100-200 degrees Celsius lower than the melting point of the electrode material, before the elongated electrodes begin to melt, some of the slag to be replenished melts into slag drops and drips into the molten slag pool at the bottom of the electrode.

[0019] S6. At this time, the temperature of the entire electrode bundle is low at the top and high at the bottom. As the molten slag drips, the electrode bundle also begins to melt and drip. Due to the existence of the temperature gradient of the system, the replenishing slag layer always melts preferentially before the electrode bundle. Therefore, there is no replenishing slag layer in the melting zone at the lower end of the slender electrode. Gaps are formed between the slender electrodes, which is conducive to the independent dripping of different slender electrodes. The molten metal droplets and the slag droplets to be replenished fall together. The collision between the two is also conducive to the capture of inclusions in the steel by the molten slag.

[0020] S7. Since the slag layer to be replenished is heated by the heat dissipated by the electrode bundle and heated to the point of melting, the slag layer to be replenished enters the slag pool in the form of slag droplets, which will not affect the temperature of the slag pool. This is beneficial to the stability of electroslag remelting production, increases the width of the metal pool, and increases the probability of electroslag ingot grains growing in the axial direction.

[0021] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0022] 1. In this invention, the metal electrode is cut into several thin strip electrodes. During the electroslag remelting process, the original single-point localized dripping of the metal droplets is transformed into a stable, dense, multi-point uniform dripping. Without affecting the production efficiency of electroslag remelting, the diameter of the metal droplets is effectively reduced, the inclusion removal efficiency of the electroslag remelting process is improved, and the width of the metal pool is increased, which increases the probability of the electroslag ingot grains growing along the axial direction.

[0023] 2. In this invention, by stabilizing the molten metal droplets and allowing them to fall evenly from multiple points, the cross-sectional area of ​​the molten metal pool is increased, thereby increasing the probability of axial grain growth in the electroslag remelted ingot and improving the solidification quality of the ingot.

[0024] 3. In this invention, the slag material to be replenished is used to fill the gaps between the slender electrodes. On the one hand, this achieves effective isolation of the electrodes, forming a state where molten metal droplets fall from multiple points. On the other hand, it utilizes the heat dissipation of the electrodes themselves to heat and melt them, and then drips them into the slag pool under the action of gravity. Without disrupting the temperature field of the slag pool, it also utilizes the system to dissipate waste heat, which is energy-saving and environmentally friendly. Attached Figure Description

[0025] Figure 1 This is a front cross-sectional view of the present invention;

[0026] Figure 2 This is a cross-sectional view of the electrode bundle in this invention.

[0027] The markings in the diagram are: 1-Electroslag remelting crystallizer, 2-Crystallizer base, 3-Electroslag ingot, 4-Molten metal pool, 5-Slag pool, 6-Electrode bundle, 7-Supplementary slag filling gap, 8-Slender strip electrode. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The following will combine Figure 1 and Figure 2 A method for improving the solidification quality and cleanliness of electroslag remelting ingots according to an embodiment of the present invention will be described in detail.

[0030] Example:

[0031] Reference Figure 1 and Figure 2A method for improving the solidification quality and cleanliness of electroslag remelted ingots includes an electroslag remelting crystallizer 1, a crystallizer base 2 fixedly connected to the lower surface of the electroslag remelting crystallizer 1, an electroslag ingot 3, a molten metal pool 4, and a slag pool 5 formed inside the electroslag remelting crystallizer 1 during the electroslag remelting process, an electrode bundle 6 arranged directly above the slag pool 5, the electrode bundle 6 being composed of several slender strip electrodes 8, and supplementary slag filling gaps 7 being arranged between the several slender strip electrodes 8, the thickness of the supplementary slag filling gaps 7 being 1-10 mm, and the supplementary slag filling gaps 7 being coated with pre-melted and cooled slag to be supplemented. Slag material; The large-sized electrode ingots produced in the previous process are cut into slender strip electrodes 8 with a cross-section of 50-150mm × 50-150mm. The specific cutting size of the cross-section of the slender strip electrode 8 is determined by the cross-sectional size of the electrode to be cut. The composition of the slag material to be added between the slender strip electrodes 8 is determined by the metal material of the electroslag remelting. The spacing between the slender strip electrodes 8 is determined by the thickness of the slag material layer to be added, which is between 1-10mm. The specific value is determined by the amount of slag material to be added. The axial length of the slag material layer to be added is determined by the length of the slender strip electrode 8.

[0032] Reference Figure 1 and Figure 2 The process continues until several slender electrodes 8 form an electrode bundle 6, at which point electroslag remelting can begin. Because the slender electrodes 8 are separated by slag, the cross-sectional area of ​​a single slender electrode 8 is small, and the size of the molten droplets that accumulate during melting is small, which can remove even smaller inclusions. Because the slender electrodes 8 are densely distributed and can stably form multiple droplet areas, a wider cross-section of the molten metal pool 4 can be formed. As for the pre-melted slag layer between the slender electrodes 8, it also begins to be heated after the slender electrodes 8 are heated by the molten slag. The interior of the slag filling gap 7 is filled with slag, and the melting point of the slag is lower than that of the electrode bundle 6. Since the melting point of the slag to be replenished is 100-200 degrees Celsius lower than that of the electrode material, some of the slag to be replenished melts into droplets and falls into the molten slag pool 5 below the electrode before the slender electrodes 8 begin to melt.

[0033] Reference Figure 1 and Figure 2The temperature of the entire electrode bundle 6 exhibits a pattern of lower temperature at the top and higher temperature at the bottom. As molten slag drips, the electrode bundle 6 also begins to melt and drip. Due to the temperature gradient within the system, the replenishing slag layer always melts preferentially before the electrode bundle 6. Therefore, there is no replenishing slag layer in the melting zone at the lower end of the slender electrodes 8, creating gaps between them. This facilitates the independent dripping of different slender electrodes 8. The molten metal droplets and the replenishing slag droplets fall together, and their collision helps to capture inclusions in the steel. Since the replenishing slag layer is heated by the heat dissipated from the electrode bundle 6 and melts, it enters the slag pool 5 as dripping slag, without affecting the temperature of the slag pool 5, thus contributing to the stability of the electroslag remelting production. By optimizing the consumable electrode, without changing the overall dripping speed, the metal droplets are made to drop in a small-sized, multi-point manner, expanding the dripping area, widening the cross-sectional area of ​​the metal pool 4, promoting grain growth along the radial direction of the ingot, improving solidification quality, increasing the removal rate of inclusions in the electroslag remelting process, and increasing the width of the metal pool 4, thereby increasing the probability of the electroslag ingot grains growing along the axial direction.

[0034] The implementation principle of the method for improving the solidification quality and cleanliness of electroslag remelted ingots in this application is as follows:

[0035] During electroslag remelting, because the slender electrodes 8 are separated by slag material, the cross-sectional area of ​​each individual slender electrode 8 is small. The resulting molten droplets are also small, allowing for the removal of even smaller inclusions. The width of the molten metal pool 4 is determined by the size of the electrode bundle 6 formed by all the slender electrodes 8. Increasing the cross-sectional width of the molten metal pool 4 effectively promotes the radial growth of grains in the electroslag remelted ingot, reducing solidification defects.

[0036] For the pre-melted slag layer between adjacent slender electrodes 8, when the slender electrodes 8 begin to be heated by the molten slag, the pre-melted slag layer between the slender electrodes 8 also begins to be heated. Since the melting point of the slag to be replenished is 100-200 degrees Celsius lower than the melting point of the electrode material, some of the slag to be replenished melts into slag droplets and falls into the molten slag pool 5 at the bottom of the electrode before the slender electrodes 8 begin to melt. The temperature of the entire electrode bundle 6 is low at the top and high at the bottom. As the molten slag drips, the electrode bundle 6 also begins to melt and drip. Due to the existence of the temperature gradient of the system, the replenished slag layer always melts preferentially before the electrode bundle 6. Therefore, there is no replenished slag layer in the melting zone at the bottom of the slender electrodes 8. Gaps are formed between the slender electrodes 8, which is conducive to the independent dripping of different slender electrodes 8. The molten metal droplets and the slag droplets to be replenished fall together, and their mutual collision is also conducive to the capture of inclusions in the steel by the molten slag.

[0037] Since the slag layer to be replenished is heated by the heat dissipated by the electrode bundle 6 and heated to the point of melting, the effect of waste heat utilization and energy saving and environmental protection is achieved. The slag layer to be replenished enters the molten slag pool 5 in the form of slag dripping, which will not affect the temperature of the molten slag pool 5 and is conducive to the stability of electroslag remelting production.

[0038] By optimizing the consumable electrode, without changing the overall dripping speed, the metal droplets are made to drop in a small-sized, multi-point manner, expanding the dripping area, widening the cross-sectional area of ​​the metal pool 4, promoting grain growth along the radial direction of the ingot, improving solidification quality, increasing the removal rate of inclusions in the electroslag remelting process, and increasing the width of the metal pool 4, thereby increasing the probability of the electroslag ingot grains growing along the axial direction.

[0039] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0040] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electroslag remelting ingot casting solidification device comprising an electroslag remelting crystallizer (1), characterized in that: The lower surface of the electroslag remelting crystallizer (1) is fixedly connected with a crystallizer bottom plate (2), the inside of the electroslag remelting crystallizer (1) is formed with an electroslag ingot (3), a metal molten pool (4) and a molten slag pool (5) during the electroslag remelting process, an electrode beam (6) is arranged above the molten slag pool (5), the electrode beam (6) is composed of a plurality of slender strip electrodes (8), a supplementary slag filling gap (7) is arranged between the plurality of slender strip electrodes (8), the thickness of the supplementary slag filling gap (7) is 1-10 mm, the inside of the supplementary slag filling gap (7) is filled with slag material, and the melting point of the slag material is lower than that of the electrode beam (6).

2. A method of improving the solidification quality and cleanliness of electroslag remelted ingots, characterized in that The device as claimed in claim 1 is applied: S1. The large-size electrode ingot produced in the preceding procedure is cut into the slender strip electrodes (8) with a cross section of 50-150 mm x 50-150 mm, and the specific cutting size of the cross section of the slender strip electrode (8) is determined by the cross section size of the electrode to be cut, to ensure that the electrode to be cut is evenly cut into several equal parts, and the length of the newly cut slender strip electrode (8) is the length of the large-size electrode ingot produced in the preceding procedure; S2. The end of the cut slender strip electrode (8) is sequentially connected to the electrode clamping device of the electroslag remelting ingot solidification device, and the supplementary slag filling gap (7) on the surface of the slender strip electrode (8) needs to be coated with the pre-melted and cooled supplementary slag material every time one slender strip electrode (8) is installed, and then the next slender strip electrode (8) is installed; S3. Until the plurality of slender strip electrodes (8) form an electrode beam (6), and then the electroslag remelting can be started, since the plurality of slender strip electrodes (8) are separated by the slag material, the cross-sectional area of the single slender strip electrode (8) is small, the size of the gathered dripping droplets in the melting process is small, and the size of the inclusions can be removed; S4. Since the slender strip electrodes (8) are densely distributed and can stably form a plurality of dripping areas, a wider cross section of the metal molten pool (4) can be formed; S5. For the pre-melted slag layer between the slender strip electrodes (8), when the pre-melted slag layer between the slender strip electrodes (8) starts to be heated after the slender strip electrodes (8) start to be heated by the molten slag, since the melting point of the supplementary slag material is 100-200 degrees Celsius lower than that of the electrode material, part of the supplementary slag material is melted into slag droplets and dripped into the molten slag pool (5) below the electrode before the slender strip electrodes (8) start to be melted. S6. At this time, the temperature of the whole electrode bundle (6) presents a state of low-high-low, accompanied by the dropping of the slag, the electrode bundle (6) also starts to melt and drop, due to the existence of the system temperature gradient, the supplementary slag layer is always preferentially melted than the electrode bundle (6), so there is no supplementary slag layer in the lower end of the melting zone of the elongated electrode (8), gaps are formed between the elongated electrodes (8), which is beneficial to the independent dropping of different elongated electrodes (8), the metal droplets and the to-be-supplemented slag droplets fall down, and the mutual collision of the two is also beneficial to the capture of the inclusions in the steel by the slag; S7. Since the to-be-supplemented slag layer is heated by the electrode bundle (6) to dissipate heat and is heated to melt, the to-be-supplemented slag layer enters the slag pool (5) in the form of slag droplet dropping, which does not affect the temperature of the slag pool (5), is beneficial to the stability of the electroslag remelting production, and increases the width of the metal pool (4) and the probability of the growth of the electroslag ingot crystal in the axial direction.

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