Low si, low mn steel reclamation electroslag process

Abstract

The present application relates to a kind of low Si, low Mn steel reuses electroslag process, using raw material is except Si, Mn element lower than using standard, other main elements all meet the requirements of steel, electroslag process slag when with slag electrolytic manganese is added, remelted every hour again electrolytic manganese is added, the amount of electrolytic manganese is added according to the Mn content calculated according to the required received, silicon iron powder is used as deoxidizer in the process of remelting and is deoxidized, its total amount is calculated according to the actual required Si element content 1.5 times;Electroslag remelting slag system weight percentage is CaF2:60~70%, Al2O3:15~25%, CaO:5~15%, electroslag remelting melting speed is controlled according to the 0.65~0.75 times coefficient of average diameter of crystallizer;Remelting process control current is ≤1000A;With slag 2% of silica is added;Effectively reduce the moisture and unstable oxide in slag material, electrolytic manganese is added in batches, increase Mn while preventing tail to produce larger deviation of Mn in two ends, while reducing Mn element segregation.

Description

Technical Field

[0001] This invention belongs to the field of electroslag metallurgy technology, and specifically relates to an electroslag process for the reuse of low-Si and low-Mn steel after it has been scrapped. Background Technology

[0002] Si and Mn, common elements in steel, are closely related to the performance of steel ingots. For steel grades where Si and Mn are among the main elements, levels below the usage standards will affect the performance of the ingot, rendering it unusable. Furthermore, Si and Mn are major deoxidizing elements in steel ingots; levels below the usage standards will lead to a high oxygen (O) content within the ingot. For steel grades used in specialized fields, the requirements for O content are very strict. To reduce losses, a re-electroslag remelting process is employed to control the Si and Mn elements in the ingot within the standard range, while simultaneously effectively reducing the O content of the steel grade, thus achieving the goal of reuse. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a low-Si, low-Mn electroslag process for reuse. It adopts a fully pre-melted slag, and electrolytic manganese and silicon dioxide are added with the slag during slag formation. Argon gas is blown down before arc initiation and slag formation to purge the air in the crystallizer and control the melting rate and current stability. After the electrode blanks are alternated, ferrosilicon powder is added for deoxidation. Electrolytic manganese is added every hour during the remelting process.

[0004] The technical solution of this invention is implemented as follows: an electroslag remelting process for reusing low-Si, low-Mn steel. The process involves re-electroslag remelting a steel whose Si and Mn content is below the required level to bring its Si and Mn content to the required range and controlling the oxygen content below 20 ppm. The specific steps of the process are as follows: Step 1) Cast or forge steel with all major elements except Si and Mn below the usage standard into electrode blanks of suitable specifications. After welding dummy electrodes, bake them in a preheating furnace at 450°C for 4 hours. Step 2) The electroslag remelting slag system used is a fully pre-melted slag, with the specific slag system weight percentages being CaF2: 60~70%, Al2O3: 15~25%, and CaO: 5~15%. The slag weight is determined according to the diameter of the selected crystallizer, and the slag layer thickness is controlled at 200~220mm inside the crystallizer. The slag system is baked at 400℃ for 4 hours and then kept at above 300℃ until use. Step 3) During the electroslag process, electrolytic manganese and 1.5%-3% of the total slag amount of silicon dioxide need to be added along with the slag. After remelting, electrolytic manganese is added every hour. The specific amount of electrolytic manganese added is calculated based on the required Mn content. Specifically, 1 / 4 is added during slag formation, and the remainder is added evenly according to the remelting time. Step 4) In the electroslag remelting process, ferrosilicon powder is used as a deoxidizer to deoxidize, which increases Si while effectively reducing the O content in the steel. The total amount added is calculated based on 1.5 times the actual required Si element content. Step 5) The electroslag remelting melting rate is controlled by a coefficient of 0.65 to 0.75 times the average diameter of the crystallizer; the current is controlled to be stable during the remelting process, and the actual current fluctuation range is controlled within ≤1000A; Step 6) During the electroslag remelting process, to reduce the oxygen content of the electroslag ingot, argon gas needs to be blown down for 5-10 minutes before electroslag remelting to completely remove the air from the crystallizer. The argon gas flow rate is 10 Nm³. 3 The remelting process is protected by argon gas throughout, and the argon gas is blown down in a decreasing manner according to the height of the molten steel in the crystallizer, with the flow rate controlled at 3-10 Nm³ / h. 3 / h, continue blowing argon gas down for 10 minutes after the power outage.

[0005] The positive effects of the technical solution of this invention are as follows: The electroslag process uses fully pre-melted slag, effectively reducing moisture and unstable oxides in the slag. Electrolytic manganese is added in batches, increasing Mn while preventing large deviations in Mn at both ends of the tail end, and reducing Mn segregation. Ferrosilicon powder is used for deoxidation, increasing Si while effectively reducing O content in the steel. The melting rate of the electroslag process is controlled by a coefficient of 0.65~0.75 times the average diameter of the crystallizer, and the current is kept stable during the remelting process, with the actual current fluctuation range controlled to ≤1000A. Detailed Implementation

[0006] Example 1: An electroslag process for the reuse of low-Si, low-Mn steel, using 30Cr2MnSiNi4Mo steel, ingot size: 2.0 tons, crystallizer: Φ510 / 560mm, quantity: 2 pieces, slag material is fully pre-melted slag, the specific slag system ratio is: CaF2:Al2O3:CaO=65:25:10, slag amount: 110kg.

[0007] The slag is baked at 400℃ for 4 hours. The consumable electrode is Φ160mm scrap steel. The arc-starting agent is carbon steel plate. Graphite electrode is used for arc-starting and slag-forming. During slag-forming, 2% silicon dioxide and 500g of electrolytic manganese are added with the slag. Argon gas is blown down for 5 minutes before slag-forming to purge the air in the crystallizer. After the slag is completely cleared, the consumable electrode blank is replaced and remelted. The average melting rate during the remelting stage is controlled at 360kg / h-380kg / h. The actual fluctuation range of the current during the remelting process is controlled to be ≤10%. Argon gas is blown throughout the process for protection. After the electrode blanks are replaced, 75g of silicon-calcium powder is added every 5 minutes. Electrolytic manganese is added every hour during the remelting process.

[0008] The following are the results of the Si and Mn composition analysis of 30Cr2MnSiNi4Mo scrap steel and electroslag ingots: Table 1. Results of Si and Mn detection Raw material 1 / 0.02 0.08 Raw material 2 / 0.04 0.07 7A2415 2.0t 0.18 0.15 7B2427 2.0t 0.21 0.13 .

Claims

1. An electroslag process for the reuse of low-Si, low-Mn steel, characterized in that: The process involves electroslag re-electroslag refining of steel with Si and Mn content below the required levels to bring the Si and Mn content within the required range and control the oxygen content below 20 ppm. The specific steps of the process are as follows: Step 1) Cast or forge steel with all major elements except Si and Mn below the usage standard into electrode blanks of suitable specifications. After welding dummy electrodes, bake them in a preheating furnace at 450°C for 4 hours. Step 2) The electroslag remelting slag system used is a fully pre-melted slag, with the specific slag system weight percentages being CaF2: 60~70%, Al2O3: 15~25%, and CaO: 5~15%. The slag weight is determined according to the diameter of the selected crystallizer, and the slag layer thickness is controlled at 200~220mm inside the crystallizer. The slag system is baked at 400℃ for 4 hours and then kept at above 300℃ until use. Step 3) During the electroslag process, electrolytic manganese and 1.5%-3% of the total slag amount of silicon dioxide need to be added along with the slag. After remelting, electrolytic manganese is added every hour. The specific amount of electrolytic manganese added is calculated based on the required Mn content. Specifically, 1 / 4 is added during slag formation, and the remainder is added evenly according to the remelting time. Step 4) In the electroslag remelting process, ferrosilicon powder is used as a deoxidizer to deoxidize, which increases Si while effectively reducing the O content in the steel. The total amount added is calculated based on 1.5 times the actual required Si element content. Step 5) The electroslag remelting melting rate is controlled by a coefficient of 0.65 to 0.75 times the average diameter of the crystallizer; the current is controlled to be stable during the remelting process, and the actual current fluctuation range is controlled within ≤1000A; Step 6) During the electroslag remelting process, to reduce the oxygen content of the electroslag ingot, argon gas needs to be blown down for 5-10 minutes before electroslag remelting to completely remove the air from the crystallizer. The argon gas flow rate is 10 Nm³. 3 The remelting process is protected by argon gas throughout, and the argon gas is blown down in a decreasing manner according to the height of the molten steel in the crystallizer, with the flow rate controlled at 3-10 Nm³ / h. 3 / h, continue blowing argon gas down for 10 minutes after the power outage.