Control method for N08825 aluminum and titanium elements based on protective atmosphere electroslag remelting

Abstract

The invention relates to the field of electroslag special metallurgy, in particular to a control method of N08825 aluminum and titanium elements based on protective atmosphere electroslag remelting, which comprises the following aspects: (1) requirements of slag auxiliary materials: adopting pre-melted slag; (2) protective atmosphere control; (3) the content of original Al and Ti in the electrode; and (4) processing an electroslag smelting electrode blank. The invention designs and provides a process technology for controlling the change of N08825 aluminum and titanium based on the Taihi steel protective atmosphere electroslag furnace, so that the N08825 aluminum and titanium components accurately hit a standard interval, and a predetermined target is achieved.

Description

Technical Field

[0001] The invention relates to the field of electroslag special metallurgy, and in particular to a control method for electroslag remelting N08825 aluminum and titanium elements based on a protective atmosphere. Background Art

[0002] N08825 is a nickel-iron-chromium alloy containing molybdenum, copper, and titanium. Its chemical composition is designed to provide excellent corrosion resistance. The addition of aluminum and titanium stabilizes the alloy under appropriate heat treatment conditions, reducing susceptibility to intergranular corrosion. N08825 exhibits excellent resistance to a wide range of general and localized corrosion environments and is widely used in chemical processing, pollution control, oil and gas recovery, acid production, pickling operations, nuclear fuel reprocessing, and radioactive waste disposal.

[0003] The changes in Al and Ti components during the N08825 electroslag process are difficult to control, and the process is prone to Al and Ti exceeding the standard. The Ti burnout at the arc striking end of the electroslag ingot is significantly higher than that at the feeding end, while the Al content presents the opposite state. How to stably hit the Al and Ti element range while ensuring surface quality is a technical difficulty.

[0004] N08825 requires Al ≤ 0.20 and Ti within the range of 0.60-1.20. Electroslag production of N08825 typically utilizes protective atmosphere remelting to ensure that the changes in the aluminum and titanium compositions during the electroslag remelting process meet standard requirements. However, N08825 electroslag ingots exhibit a general tendency to experience increased aluminum and burned titanium at the bottom. Therefore, a process technology is needed to effectively control the aluminum and titanium compositions, ensuring that the bottom aluminum and titanium compositions return to their normal range with minimal metal consumption, while minimizing the absolute value of increased aluminum and burned titanium.

[0005] This invention aims to effectively control the variation of the aluminum-titanium composition of N08825 electroslag, achieving a preset target aluminum-titanium composition. This is achieved by precisely targeting the target range through slag component setting, protective atmosphere control, raw material electrode composition, and processing control. Summary of the Invention

[0006] The purpose of the present invention is to address the above problems and provide a control method for electroslag remelting N08825 aluminum and titanium elements based on a protective atmosphere.

[0007] The purpose of the present invention is to achieve the following: a control method for electroslag remelting N08825 aluminum titanium element based on protective atmosphere, including the following aspects: (1) requirements for slag auxiliary materials: use pre-melted slag; (2) protective atmosphere control: use 25~30Nm before power supply 3 / h flow of argon gas with dust removal and purge for 90~120min, the oxygen content of the protective cover before power supply is ≤9%, and after smelting, 5~7Nm 3 / h flow rate of argon protection, after the smelting, the oxygen content at the protective cover position is ≤9%; (3) Original Al and Ti content in the electrode: Al is set to operate in the range of 0.11~0.15%, and Ti is set to operate in the range of 1.05~1.15%; (4) Electroslag smelting electrode blank processing: The electroslag remelting process adopts low power, which is 1-2V lower than the conventional power, and the melting rate is 0.8~0.9D smelting, D is the crystallizer diameter, unit mm, and the melting rate unit is Kg / h. The oxygen content of the original oxygen content of the electrode blank and the residual oxygen brought by subsequent processing are controlled to be below 20ppm.

[0008] (1) The content of (FeO+MnO) in the medium pre-melted slag is ≤0.2%, SiO2 is ≤0.8%, and the TiO2 content in the slag is 6-9%.

[0009] The beneficial effects of the present invention are as follows: the present invention designs and provides a process technology for controlling the changes of N08825 aluminum and titanium based on the protective atmosphere electric slag furnace of Taiyuan Iron and Steel Co., Ltd., so that the aluminum and titanium components of N08825 accurately hit the standard range and achieve the predetermined goal.

[0010] The present invention effectively controls the changes of aluminum and titanium, ensuring that the aluminum and titanium components of N08825 reach the predetermined target.

[0011] The present invention proposes internal control requirements for slag components to ensure that the changes in N08825 electroslag remelting aluminum and titanium hit the standard range.

[0012] The present invention completes a scientific evaluation of the internal control of the aluminum and titanium components of the N08825 electrode blank through a large amount of data analysis, matches the electrode blank processing requirements, and can effectively prevent and control the excessive changes in aluminum and titanium.

[0013] After the implementation of this invention, the yield rate is stabilized at about 88%. Based on the annual production of 500 tons, an additional 110 tons can be harvested, realizing a benefit of 8.8 million yuan (the average selling price of N08825 finished products is 160,000 yuan / ton, and the price of scrap steel is 80,000 yuan / ton). DETAILED DESCRIPTION

[0014] This invention relates to a process for controlling the aluminum and titanium compositions of N08825 during electroslag remelting under protective atmosphere. By setting slag components, controlling the protective atmosphere, and controlling the raw material electrode composition and processing, the aluminum and titanium compositions are kept within standard ranges, effectively overcoming production bottlenecks caused by excessive aluminum and titanium variations.

[0015] 1. Requirements for slag auxiliary materials: Pre-melted slag is required, with (FeO+MnO)≤0.2% and SiO2≤0.8% in the slag to minimize the changes in aluminum and titanium caused by the slag. The slag should be matched with 6~9% TiO2 to prevent the oxidation reaction of [Ti].

[0016] The residual [O] in the electrode blank and the [O] in the electroslag atmosphere burn away [Ti] through the slag pool. (Ti3O5) in the slag pool is the determining factor in controlling the [Ti] loss. (Ti3O5) is an unstable oxide that is easily oxidized to form (TiO2). Adding an appropriate amount of Al powder during the electroslag remelting process allows oxygen to react with Al powder, effectively hindering the reaction between oxygen and (Ti3O5) and suppressing titanium loss. However, during the remelting process, due to the protective atmosphere electroslag furnace of Taigang, only a portion of Al powder can be added to the arc starting slag. Excessive addition of Al powder leads to an increase in (Al2O3), which exacerbates the phenomenon of [Ti] loss and [Al] increase. This steel grade requires Al ≤ 0.20, meaning that Al addition should be appropriate to prevent excessive aluminum addition at the tail end, relying solely on the contribution of Al in the electrode blank. According to the reaction conditions, the [Ti] oxidation reaction can only be prevented by adding TiO2 powder to the slag. However, literature research has shown that adding too much TiO2 will increase the slag viscosity and deteriorate the surface quality of the steel ingot. According to practical experience and data analysis, the slag should be matched with 6~9% TiO2.

[0017] 2. Protective atmosphere control: Use 25~30Nm before power on 3 / h flow of argon gas with dust removal and purge for 90~120min, try to minimize the residual oxygen in the protective cover. Based on the protective atmosphere electroslag furnace of Taigang, the oxygen content at the protective cover position before power supply is ≤9%. The process uses 5~7Nm 3 / h flow rate of argon protection, the oxygen content at the process protection cover position is ≤9%.

[0018] 3. The original Al and Ti contents in the electrode, based on TISCO's protective atmosphere electroslag furnace, according to practical experience and data analysis, Al should be operated in the range of 0.11~0.15, and Ti should be operated in the range of 1.05~1.15.

[0019] 4. The impact of electroslag smelting electrode blank processing and melt pool temperature: Low-temperature, low-power smelting (taking a Φ700mm electroslag ingot as an example, conventional varieties require a power of approximately 68V / 12kA, while this variety only requires approximately 65V / 12kA). Temperature naturally decreases as power is reduced. Control the initial oxygen content of the electrode blank and any residual oxygen introduced by subsequent processing (the oxygen content [O] remains constant during processing, and should be below 20ppm). Remelting typically begins and ends with a temperature increase, then stabilizes, and then decreases. Different electrical regimes, especially melting rates, have a significant impact on slag pool temperature.

[0020] The electrical system of the smelting process adopts slag resistance melting of at least 5mohm. On the one hand, the relatively low power helps to reduce the melting temperature and avoid overheating-induced oxidation reaction to proceed in the forward direction (the temperature decreases accordingly, the equilibrium constant K decreases, the reaction proceeds to the left, and Ti is not easily oxidized); on the other hand, it is beneficial to the formation of a complete slag skin and smooth surface quality, avoiding the remelting of the local annular small molten pool on the slag skin and the scarring of surface steel flow.

[0021] Eliminate other factors that may introduce oxygen elements: the oxygen content of the electrode blank shall not be higher than 15ppm, the surface must be polished and sawed evenly, without visible defects such as shrinkage cavities, and the surface shall be free of oil stains and other contamination. Example

[0022] 8+8 atmosphere-protected electroslag furnace in the special metallurgical operation area of TISCO Profile Division.

[0023] By designing four aspects, including slag system design, protective atmosphere control, internal control of aluminum and titanium in raw material electrode billets, electrical system and electrode billet processing requirements, and following specific control methods such as low-power smelting and process oxygen control, 132 N08825 electroslag ingots weighing 685 tons have been produced, and the aluminum and titanium content has been ensured to meet the target requirements.

[0024] The specific operation includes the following aspects: (1) Requirements for slag auxiliary materials: Use pre-melted slag, with (FeO+MnO) of 0.15%, SiO2 of 0.8%, and 7% TiO2 in the slag; (2) Protective atmosphere control: Use 28Nm before power supply; 3 / h flow of argon gas with dust removal and purge for 100 minutes, the oxygen content of the protective cover position before power supply is 8%, and after smelting, 6Nm 3 / h flow rate of argon protection, after the smelting, the oxygen content at the protective cover position is 8%; (3) Original Al and Ti content in the electrode: Al is set to 0.13% and Ti is set to 1.07%; (4) Electroslag smelting electrode blank processing: Φ700mm electroslag ingot, conventional varieties match 68V / 12KA power smelting, this variety can match 65V / 12KA power, the melting rate is 590Kg / h, and the oxygen content of the original oxygen content of the electrode blank and the residual oxygen brought by subsequent processing are controlled to be below 20ppm.

[0025] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by any technician in this field within the scope of the present invention are included in the patent scope of the present invention.

Claims

1. A control method for electroslag remelting N08825 aluminum and titanium elements based on a protective atmosphere, characterized by: Including the following aspects: (1) Requirements for slag auxiliary materials: Use pre-melted slag; (2) Protective atmosphere control: Use 25~30Nm before power supply 3 / h flow of argon gas with dust removal and purge for 90~120min, the oxygen content of the protective cover before power supply is ≤9%, and after smelting, 5~7Nm 3 / h flow rate of argon protection, after the smelting, the oxygen content at the protective cover position is ≤9%; (3) Original Al and Ti contents in the electrode: Al was set to operate in the range of 0.11–0.15%, and Ti was set to operate in the range of 1.05–1.15%; (4) Electroslag smelting electrode blank processing: The electroslag remelting process uses low power, which is 1-2V lower than the conventional power, and the melting rate is 0.8~0.9D. D is the diameter of the crystallizer, unit is mm, and the melting rate is kg / h. The original oxygen content of the electrode blank and the residual oxygen brought by subsequent processing are controlled to be below 20ppm.

2. The control method for N08825 aluminum-titanium element based on protective atmosphere electroslag remelting according to claim 1, characterized in that: (1) The content of (FeO+MnO) in the medium pre-melted slag is ≤0.2%, SiO2 is ≤0.8%, and the TiO2 content in the slag is 6-9%.