Method for controlling uniformity of chemical components at arcing end of electroslag ingot

Abstract

The invention discloses a method for controlling the uniformity of chemical components at the arcing end of an electroslag ingot, which solves the influence on the uniformity of the chemical components at the arcing end of the electroslag ingot in an electroslag slagging stage. The key technical measures are as follows: (1) setting process parameters in the final stage of slagging, setting the current to be reduced to 500A at 500A / min, and keeping for 5min, so that the molten steel is partially solidified, and the influence on chemical components in the normal remelting stage is reduced; (2) a 20A steel annular base protection plate is adopted, so that the dilution effect of melting on components at the arcing end of the electroslag ingot is reduced; the method has the beneficial effects that the slagging process is innovated, the continuity of a metal molten pool in the electroslag arcing slagging stage and a metal molten pool in the normal remelting stage is blocked, and the influence on chemical components in the normal remelting stage is reduced; by transforming the form of the base protection plate, the dilution effect of melting of the base protection plate on components at the arcing end of the electroslag ingot is reduced; the purpose of controlling the uniformity of chemical components at the arcing end of the electroslag ingot is achieved.

Description

Technical Field

[0001] This invention belongs to the field of electroslag metallurgy technology, specifically relating to a method for controlling the uniformity of chemical composition at the arc-starting end of an electroslag ingot. Background Technology

[0002] The electroslag remelting process is generally divided into three stages: arc initiation and slag formation, electroslag remelting, and electroslag feeding. The arc initiation and slag formation stage is crucial, providing the material and energy basis for electroslag remelting. However, this stage is an unsteady-state melting process characterized by multiphase coexistence, drastic current changes, and complex temperature field distribution. The presence of unstable variable-valence oxides in the slag and shrinkage cavities in most ingot-cast electrodes lead to changes in the chemical elements within the molten metal pool during arc initiation and slag formation, affecting the uniformity of the chemical composition at the arc-starting end of the electroslag ingot. Furthermore, the melting of the base protection plate during arc initiation and slag formation dilutes the chemical composition at the arc-starting end of the electroslag ingot, further impacting its uniformity. Therefore, reducing the impact of the chemical composition during the slag formation stage on the chemical composition during the normal remelting stage, and minimizing the dilution effect of the base protection plate melting on the chemical composition at the arc-starting end of the electroslag ingot, are key to controlling the uniformity of the chemical composition at the arc-starting end of the electroslag ingot. Summary of the Invention

[0003] This invention discloses a method for controlling the uniformity of chemical composition at the arc-starting end of an electroslag ingot, thereby addressing the impact of the electroslag formation stage on the uniformity of chemical composition at the arc-starting end of the electroslag ingot.

[0004] The present invention adopts the following technical solution, specifically including the following steps: (1) Set the process parameters for the final stage of slag formation. The current is set to decrease from 500A / min to 500A and held for 5 minutes to allow partial solidification of the molten steel. Then, the current is increased from 500A / min to the normal slag formation current to complete the slag formation process. See [link to relevant documentation]. Figure 1 .

[0005] (2) Use a 20A steel round plate with a central hole of φ200mm~400mm and a thickness of 15mm~20mm as the base protection plate, see Figure 2 The circular plate should be the same size as the bottom of the crystallizer used. The protective plate should be polished to a metallic luster and placed on the polished electroslag furnace base. See [link / reference]. Figure 3 .

[0006] (3) Place a base pad on the protective plate. The position of the base pad should correspond to the position of the arc-starting end of the consumable electrode. See Figure 3 The composition of the base pad is the same as that of the consumable electrode. The base pad is rectangular in shape, with a size of 300mm×400mm and a thickness of 25mm~35mm. The amount of pre-melted slag used is 3kg~5kg. After assembling the crystallizer, the consumable electrode is brought into contact with the base pad.

[0007] The inventive point of this invention: The key measures to control the uniformity of chemical composition at the arc-starting end of the electroslag ingot are: (1) Breaking the process approach of gradually increasing current during electroslag slagging, setting process parameters at the end of slagging, setting the current to decrease from 500A / min to 500A and maintaining it for 5 minutes, so that part of the molten steel solidifies, interrupting the continuity between the molten pool in the electroslag arc-starting and slagging stage and the molten pool in the normal remelting stage, and reducing the influence of the chemical composition in the electroslag slagging stage on the chemical composition in the normal remelting stage. (2) Reducing the dilution effect of the melting of the base protection plate on the composition at the arc-starting end of the electroslag ingot. The 20A steel protection plate mainly serves to protect the base of the electroslag furnace, but the protection plate and the bottom pad on it will melt during the slagging process. The element content of 20A steel has little effect on the alloy element composition of the electroslag remelted steel but has a greater effect on the concentration. Therefore, the circular protection plate is changed to an annular protection plate, removing the part of the protection plate that can melt during electroslag slagging, thus reducing the dilution effect of the protection plate on the molten pool, that is, the dilution effect on the chemical composition at the arc-starting end of the electroslag ingot. Overall, the first measure is relatively more effective.

[0008] Advantages of this invention: This invention innovates the slag-forming process, interrupting the continuity between the molten metal pool in the electroslag initiation and slag-forming stage and the molten metal pool in the normal remelting stage, thereby reducing the influence of the chemical composition in the electroslag initiation stage on the chemical composition in the normal remelting stage; by modifying the shape of the base protection plate, the dilution effect of the melting of the base protection plate on the composition of the electroslag ingot at the arc-forming end is reduced; thus achieving the goal of controlling the uniformity of the chemical composition at the arc-forming end of the electroslag ingot. Attached Figure Description

[0009] Figure 1 Schematic diagram for setting process parameters at the end of the arc initiation and slag formation stage; Figure 2 A protective plate with holes in the center of the base; Figure 3 For the base pad placed on the protective plate; Figure 4 This is the actual process curve at the end of the arc initiation and slag formation stage; Figure 5 This is a photo of the arc-starting end of the electroslag ingot after ingot removal. Detailed Implementation

[0010] 0005 The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The embodiments use two ingot types: Φ610mm and Φ750mm. Example 1

[0011] Steel grade: 20Cr13 stainless steel; ingot size: Φ610mm; smelting method: constant melting rate electroslag furnace. A 300mm×400mm, 30mm thick 20Cr13 steel base pad was used, with a Φ200mm hole in the center of the base protection plate. The consumable electrode was used for direct arc initiation. The slag-forming process was controlled by current and voltage. Towards the end of slag formation, when the weight of the consumable electrode melted to 150kg, the current was reduced from 500A / min to 500A for 5 minutes, then increased back to the normal slag-forming current at 500A / min to continue slag formation. The actual process curve at the end of arc initiation and slag formation is shown in [link to process curve]. Figure 4 Three samples were taken from the arc-starting end of the electroslag ingot for chemical composition analysis. The samples showed uniformity and met the requirements. The chemical analysis results are shown in Table 1. The state of the arc-starting end of the electroslag ingot after ingot removal is shown in Table 1. Figure 5 . Example 2

[0012] Steel grade: G20Cr2Ni4A bearing steel; ingot size: Φ750mm; smelted in a constant melting rate electroslag furnace. A 300mm×400mm, 35mm thick G20Cr2Ni4A steel base pad was used, with a Φ300mm hole in the center of the base protection plate. The consumable electrode was used for direct arc initiation; the slag-forming process was controlled by current and voltage. Towards the end of slag formation, when the consumable electrode melted to 200kg, the current was reduced from 500A / min to 500A for 5 minutes, then increased back to the normal slag-forming current at 500A / min to continue slag formation. The actual process curve for the arc initiation and final slag-forming stages is shown below. Figure 4 Three samples were taken from the arc-starting end of the electroslag ingot for chemical composition analysis, and the results were uniform and qualified. The chemical analysis results are shown in Table 2. The state of the arc-starting end of the electroslag ingot after ingot removal is shown in [Table 2]. Figure 5 .

[0013]

Claims

1. A method for controlling the uniformity of chemical composition at the arc-starting end of an electroslag ingot, characterized in that, The method includes the following steps: (1) Set the process parameters for the final stage of slag formation. Set the current to decrease from 500A / min to 500A and hold for 5 minutes to allow the molten steel to partially solidify. Then, increase the current to the normal slag formation current from 500A / min to complete the slag formation process. (2) Use a 20A steel round plate with a hole of φ200mm~400mm in the center and a thickness of 15mm~20mm as the base protection plate, see Figure 2; the size of the round plate is the same as the bottom size of the crystallizer used, and the protection plate needs to be polished to a metallic luster and placed on the polished electroslag furnace base. (3) Place a base pad on the protective plate. The position of the base pad should correspond to the position of the arc-starting end of the consumable electrode, as shown in Figure 3. The composition of the base pad is the same as that of the consumable electrode. The base pad is rectangular in shape, with a size of 300mm×400mm and a thickness of 25mm~35mm. The amount of pre-melted slag used is 3kg~5kg. After assembling the crystallizer, make the consumable electrode contact the base pad.

2. The method for controlling the uniformity of chemical composition at the arc-starting end of an electroslag ingot according to claim 1, characterized in that: Steel grade: 20Cr13 stainless steel; ingot size: Φ610mm; smelting is carried out in a constant melting rate electroslag furnace; the consumable electrode is used for direct arc initiation; the slag-forming process is controlled by current and voltage; at the end of slag-forming, when the weight of the consumable electrode melted reaches 150kg, the current is reduced from 500A / min to 500A for 5 minutes, and then the current is increased from 500A / min to the normal slag-forming current to continue slag-forming; a 300mm×400mm, 30mm thick 20Cr13 steel base pad is used, with a Φ200mm hole in the center of the base protection plate.

3. The method for controlling the uniformity of chemical composition at the arc-starting end of an electroslag ingot according to claim 1. The method of sex is characterized by: Steel grade: G20Cr2Ni4A bearing steel; ingot size: Φ750mm; smelted in a constant melting rate electroslag furnace; arc initiation is directly initiated by consumable electrode; the slag-forming process is controlled by current and voltage; at the end of slag-forming, when the weight of the consumable electrode melted reaches 200kg, the current is reduced from 500A / min to 500A for 5 minutes, and then the current is increased from 500A / min to the normal slag-forming current to continue slag-forming; a 300mm×400mm, 35mm thick G20Cr2Ni4A steel base pad is used, with a Φ300mm hole in the center of the base protection plate.

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