Electroslag process optimization method for improving surface quality of large-diameter electroslag ingot

Abstract

The invention relates to an electroslag process optimization method for improving the surface quality of a large-diameter electroslag ingot, which is suitable for producing the electroslag ingot with the average diameter of 1200-1400 mm by 3-4 electrode billets, the filling ratio range in the electroslag smelting process is 0.5-0.6, the electrode billets need to be placed in a furnace to be preheated for more than 6 hours at 600 DEG C before being used, and the electrode billets need to be placed in a furnace to be preheated for more than 6 hours at 600 DEG C; the bottom of an electrode blank and the upper edge of a crystallizer need to be cleaned 5-10 minutes before alternation, redundant oxide skin or impurities need to be removed, after alternation is finished, the electrode blank is controlled to fall on the surface of a slag pool and is inserted into the slag pool by 10-20 mm, closing power transmission is conducted, a transition stage needs to be set from power transmission to remelting, the voltage is set to be 95-100 V, the current is set to be 17000-19000 A, and the time is 20-30 minutes.

Description

Technical Field

[0001] The present invention belongs to the technical field of electroslag metallurgy, and particularly relates to an electroslag process optimization method for improving the surface quality of large-diameter electroslag ingots with an average diameter in the range of 1200 mm to 1400 mm. Background Art

[0002] The production weight of electroslag ingots is determined according to the plan. When producing large-sized electroslag ingots (average diameter 1200 mm to 1400 mm), 2 to 4 electrode blanks are often required to be alternated. With the increase in the number of alternations, it will have a certain impact on the surface and internal quality of the electroslag ingots. Especially when the filling ratio is too small, the power in the initial stage of alternation cannot radiate to the inner edge of the mold. Under the action of cooling water, a slag shell solidifies at the inner edge, and when the molten steel rises, slag grooves are easily formed on the surface of the electroslag ingot. This not only affects the product delivery but also brings risks to subsequent forging. Summary of the Invention

[0003] The purpose of the present invention is to provide an electroslag process optimization method for improving the surface quality of large-diameter electroslag ingots to address the deficiencies in the production of large-sized electroslag ingots. The technical solution of the present invention is implemented as follows: An electroslag process optimization method for improving the surface quality of large-diameter electroslag ingots, which is applicable to products with an electroslag ingot average diameter in the range of 1200 mm to 1400 mm. The filling ratio range in the electroslag smelting process is 0.5 - 0.6, and the slag material uses fully pre-melted slag. The specific weight percentage of the slag system is CaF2: 55 - 65%, Al2O3: 20 - 30%, CaO: 5 - 15%. The weight of the slag material is determined according to the weight of the electroslag ingot produced by the selected mold, specifically 4% - 6% of the electroslag ingot weight. The melting rate kg / h during the smelting process is controlled at 0.8 - 0.85 times the average diameter of the mold. The entire smelting process is completed by 3 - 4 electrode blanks participating in alternation. The specific steps are as follows: Step 1): Bake the slag material at 600 °C for 6 hours. The electrode blank is a die-cast blank. Before use, preheat the electrode blank in a preheating furnace at 600 °C for more than 6 hours. Step 2): Blow argon downward for 10 - 20 minutes before power-on to evacuate the air in the mold. 5 - 10 minutes before alternation, it is necessary to clean the bottom of the electrode blank and the upper edge of the mold to remove excess scale or debris; 2 minutes before alternation, remove the asbestos at the furnace mouth and clean the furnace mouth. Step 3): After alternation, control the electrode blank to fall on the surface of the slag pool and insert it into the slag pool by 10 - 20 mm when the alternation stage ends, then switch on the power supply. Step 4): From power-on to remelting, it is necessary to set a transition stage. The voltage is set to 95 - 100 V, and the current is set Set it to 17000 - 19000A for 20 - 30 minutes. After the final current rises to 20000A, enter normal smelting, and start increasing the current by 100 per minute until the melting rate reaches the setting.

[0004] The positive effects of the technical solution of the present invention are as follows: The electrode blank is preheated at 600°C for more than 6 hours in advance, which can increase the initial temperature of the electrode blank alternation, reduce the temperature difference between the blank and the slag, and make the initial power mainly act on the slag pool; 5 - 10 minutes before alternation, it is necessary to clean the bottom of the electrode blank and the upper edge of the mold to remove excess scale or debris to prevent it from falling into the molten steel and causing inclusions; control the electrode blank to fall on the surface of the slag pool and insert into the slag pool by 10 - 20mm before closing the switch and energizing; after energizing until remelting, the voltage is set to 95 - 100V, the current is set to 17000 - 19000A, and the time is 20 - 30 minutes; the high voltage and low current power continuously act on the slag pool, which can ensure that most of the power acts on the slag pool at this time, effectively radiating the heat energy to the edge of the mold, so that the slag pool will not form a crust due to the water cooling factor before the ingot is heated and melted, thus ensuring the surface quality of the electroslag ingot. Description of the Drawings

[0005] Figure 1 It is a 36.8 - ton electroslag ingot produced without using the optimization method.

[0006] Figure 2 It is an electroslag ingot produced in this batch of the present invention after using the optimization method. Detailed Embodiments

[0007] Example 1: An electroslag process optimization method for improving the surface quality of large - diameter electroslag ingots. Select CrNiMo steel types, ingot type specification: 36.8 tons, mold: Φ1400 / 1450mm, quantity: 1 piece. The slag material uses pre - melted slag, and its specific slag system weight percentage is CaF2: 65%, Al2O3: 25%, CaO: 10%. The slag quantity is 1200kg. The slag material is baked at 600°C for 6 hours. The electrode blank is a Φ800mm die - cast blank. Before use, the electrode blank is preheated at 600°C in a preheating furnace for 8 hours. Argon is blown downward for 10 - 20 minutes before energizing to evacuate the air in the mold. The end of the electrode blank is cleaned before alternation. Two minutes before alternation, the asbestos at the furnace mouth is removed and the furnace mouth is cleaned. When the electrode blank is immersed in the slag surface by 10 - 20mm, the alternation stage ends, and the switch is closed and energized. The voltage is set to 100V, the initial current is set to 17000A, and it increases at a constant power of 66A per minute for 30 minutes. After the final current rises to 20000A, enter normal smelting, and start increasing the current by 100 per minute until the melting rate reaches the setting.

[0008] Comparison of the surface quality of electroslag ingots Figure 1 As shown, it is a 36.8 - ton electroslag ingot produced without using the optimization method.Figure 2 The figure shows the electroslag ingots produced after using the optimized method in this batch, and the surface quality of the electroslag ingots has been significantly improved.

Claims

1. An electroslag process optimization method for improving the surface quality of large-diameter electroslag ingots, characterized in that: The method is applicable to products with the average diameter of electroslag ingots ranging from 1200 mm to 1400 mm. The filling ratio range during the electroslag smelting process is 0.5 to 0.

6. The slag material uses fully pre-melted slag, and the specific weight percentage of the slag system is CaF2: 55 - 65%, Al2O3: 20 - 30%, CaO: 5 - 15%. The weight of the slag material is determined according to the weight of the electroslag ingot produced by the selected mold, specifically 4% - 6% of the weight of the electroslag ingot. The melting rate during the smelting process, in kg / h, is controlled at 0.8 to 0.85 times the average diameter of the mold. The entire smelting process is completed alternately by 3 to 4 electrode billets. The specific steps are as follows: Step 1): Bake the slag material at 600 °C for 6 hours. The electrode billet is a die-cast billet. Before use, preheat the electrode billet in a preheating furnace at 600 °C for more than 6 hours. Step 2): Blow argon downward for 10 - 20 minutes before power-on to evacuate the air in the mold. 5 - 10 minutes before alternation, it is necessary to clean the bottom of the electrode billet and the upper edge of the mold to remove excess scale or debris; 2 minutes before alternation, remove the asbestos at the furnace mouth and clean the furnace mouth. Step 3): After the alternation ends, control the electrode billet to fall on the surface of the slag pool and insert it into the slag pool by 10 - 20 mm, then the alternation stage ends, and switch on the power supply. Step 4): From power-on to remelting, it is necessary to set an intermediate stage. The voltage is set at 95 - 100 V, and the current is set at 17000 - 19000 A for 20 - 30 minutes. After the final current rises to 20000 A, enter normal smelting, and start increasing the current by 100 per minute until the melting rate reaches the set value.

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