Electroslag process optimization method for improving pores at bottom of 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 optimization method for electroslag process to improve the pores at the bottom of electroslag ingots. Background Art

[0002] For electroslag remelting, the slag system is crucial. With the rapid development of electroslag remelting and the increasing requirements for the properties of steel grades under various working conditions, ordinary binary and ternary slag systems can no longer meet the needs of electroslag remelting production. Subsequently, the development of various multi-component slag systems such as quaternary slag systems, quinary slag systems, high-resistance slags, and rare-earth slag systems has emerged. The development and application of these slag systems can not only reduce energy consumption, but more importantly, improve the inclusions and segregation of steel grades, greatly improving the quality of electroslag remelting products. However, with the application of multi-component slag systems in some products, unstable oxides in the slag system will cause pores at the tail of electroslag ingots, seriously affecting the quality of products. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies in the production of multi-component slag systems and provide an optimization method for electroslag process to improve the pores at the bottom of electroslag ingots.

[0004] The technical solution of the present invention is realized as follows: An optimization method for electroslag process to improve the pores at the bottom of electroslag ingots, the method is designed specifically for the electroslag smelting of a low-carbon alloy steel, and the slag system of the electroslag smelting process uses a quinary pre-melted slag, and the specific weight percentage of the slag system is: CaF2: 40-60%, Al2O3: 5-15%, CaO: 10-15%, MgO: 10-15%, rare earth: 10-15%; the method is as follows: Step 1), the used slag system needs to be baked at a temperature of 700°C for more than 6 hours before production, and then kept for use at a temperature of 400°C; increase the weight of the slag material by 10-15%; Step 2), the melting speed of electroslag remelting is controlled by a coefficient of 0.70-0.80 times the average diameter of the mold, and the current is kept stable during the remelting process, and the actual current fluctuation range is controlled ≤ 10%; Step 3), the optimization method adopts the method of cold ignition. During the middle stage of slag melting, when cooperating with the slag system to eliminate unstable oxides, 200-500 g of aluminum powder needs to be added as an auxiliary; Step 4), blow inert gas downward for 10-20 minutes before power-on to completely exhaust the air in the mold; Step 5), during the slag melting stage, on the basis of the original slag melting time of the process, increase the current holding time of 6000A-7000A by 10-20 minutes

[0005] ​The positive effects of the technical solution of the present invention are as follows: Increasing the slag amount can increase the thickness of the slag layer, effectively isolating the water vapor in the atmosphere. Baking at 700 °C can fully reduce the crystal water inherent in the pre-melt. Auxiliary addition of aluminum powder can help reduce unstable oxides during slag melting. Increasing the current holding time of 6000 - 7000 A during the slag melting stage can, while effectively submerging the electrode blank in the arc for slag melting, fully discharge the gas in the molten slag to reduce the formation probability of bottom pores. Description of the Drawings

[0006] Figure 1 It is a schematic cross-sectional view of an H13 type electroslag ingot trial-produced without using the optimization method.

[0007] Figure 2 It is a schematic cross-sectional view of an electroslag ingot produced in this batch of the present invention using the optimization method, with significantly reduced tail pores. Detailed Embodiment

[0008] Example 1: An electroslag process optimization method for improving the bottom pores of electroslag ingots. The steel type of H13 is selected, the ingot type specification is 4.8 tons, the mold is Φ660 / 710 mm, the quantity is 1 piece, and the slag material uses a five-element pre-melt slag. The specific weight percentage of its slag system is: CaF2: 50%, Al2O3: 10%, CaO: 15%, MgO: 15%, rare earth: 10%; the slag amount is 210 kg. The slag material is baked at 700 °C for 6 hours. The electrode blank is a Φ500 mm die-cast blank. The arc starter is selected as a carbon steel plate. The electrode blank is started to arc and melt slag in a cold state. Argon is blown down for 10 minutes before slag melting to evacuate the air in the mold; in the middle stage of slag melting, 200 g of aluminum powder is added, and on the basis of the original slag melting time of the process, the current holding time of 6000 A - 7000 A is increased by 15 minutes; the average melting speed in the remelting stage is controlled at 530 kg / h - 550 kg / h, and the actual fluctuation range of the current during the remelting process is controlled ≤ 10%. Argon is blown throughout the process for protection.

[0009] The comparison of sawing the tail end of the electroslag ingot is as follows: Figure 1 It is an H13 type electroslag ingot trial-produced without using the optimization method. Figure 2 It is an electroslag ingot produced in this batch using the optimization method, with significantly reduced tail pores.

Claims

1. An electro-slag process optimization method for improving the porosity at the bottom of an electro-slag ingot, characterized in that: The method is specifically designed for the electroslag smelting of a low-carbon alloy steel. The slag system for the electroslag smelting process uses a five-component premelted slag, and the specific weight percentage of the slag system is as follows: CaF2: 40 - 60%, Al2O3: 5 - 15%, CaO: 10 - 15%, MgO: 10 - 15%, rare earth: 10 - 15%. The method is as follows: Step 1): The used slag system needs to be baked at a temperature of 700 °C for more than 6 hours before production, and then kept for use in an environment of 400 °C; increase the weight of the slag material by 10 - 15%; Step 2): The melting speed of electroslag remelting is controlled by a coefficient of 0.70 - 0.80 times the average diameter of the mold. During the remelting process, the current is controlled to be stable, and the actual current fluctuation range is controlled ≤ 10%; Step 3): The optimization method uses a cold ignition method. During the middle stage of slag melting, when cooperating with the slag system to eliminate unstable oxides, 200 - 500 g of aluminum powder needs to be added as an auxiliary; Step 4): Blow inert gas for 10 - 20 minutes before power-on to completely discharge the air in the mold; Step 5): During the slag melting stage, based on the original slag melting time of the process, increase it by 10 - 20 minutes, the holding time of the current of 6000 A - 7000 A.

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