A method for reducing the arsenic and tin content in nickel-based alloy materials

Abstract

This invention discloses a method for reducing the arsenic and tin content in nickel-based alloy materials. Specifically, in the electroslag remelting process during the preparation of nickel-based alloy materials, a pre-melted slag with the following composition is used: CaF2: 38%–45%, CaO: 20%–25%, Al2O3: 20%–30%, ZrO2: 3%–5%, BaF2: 3%–5%, MgO: 1%–3%, SiO2: 1%–3%, with the remainder being unavoidable impurities; the CaO / Al2O3 ratio in the pre-melted slag is 0.8–1; the pre-melted slag also contains 1–1.5% calcium carbide powder in total slag. Using this method, the arsenic and tin removal rate in nickel-based alloy materials can reach over 46%, effectively solving the problem of difficult arsenic and tin removal in nickel-based alloys. This avoids the impact of As and Sn accumulation on product quality during recycling, creating conditions for the reuse of nickel-based alloy recycled materials.

Description

Technical Field

[0001] This invention belongs to the field of metallurgy, and specifically relates to a method for reducing the arsenic and tin content in nickel-based alloy materials. Background Technology

[0002] Arsenic and tin are residual harmful elements in steel and alloys. They have low solubility, high density, and low melting point in the matrix, and easily form low-melting-point eutectics that accumulate in the grain boundary regions. Even in trace amounts, they can cause grain boundary embrittlement, leading to a decline in thermoplasticity, thermal strength, and other properties. Therefore, the arsenic content in steel and alloys must be strictly controlled.

[0003] The current domestic production level of nickel-based alloy materials remains low. However, with rapid economic development and the continuous improvement of industrial levels, the demand for them in aerospace, petrochemical, and nuclear industries is increasing. During the independent research and development of various grades and applications of nickel-based alloy materials, Chinese engineers have discovered that during the recycling process, As and Sn accumulate as trace residual elements in the steel, leading to a deterioration in the performance of the final product. Therefore, effectively controlling the content of arsenic and tin during the smelting process is an urgent problem to be solved in the development and application of such materials.

[0004] High vacuum treatment and the addition of trace additives are currently the main methods for controlling trace harmful elements in alloys. The preparation of nickel-based alloy materials often employs a dual-process smelting method of vacuum induction melting and electroslag remelting. During vacuum induction melting, high-vacuum volatilization can effectively reduce the content of harmful elements such as Bi and Pb. However, arsenic and tin exist in stable forms in nickel-based alloy materials and cannot be removed by high-vacuum treatment. Furthermore, even when adding rare earth elements, magnesium, barium, etc., during the vacuum stage to form compounds with high melting points with harmful elements, special slag systems must be adjusted in the subsequent electroslag process to remove them. Otherwise, the accumulation of harmful elements during subsequent recycling cannot be avoided. This process is complex, and the amount and method of adding microalloys are difficult to control; improper operation can affect the quality of the final product.

[0005] The "slag washing" effect of the slag pool on alloy droplets during the electroslag remelting process provides a new approach for removing As and Sn from alloys. This invention significantly reduces the arsenic and tin content in alloys by simply adjusting the electroslag remelting slag system and fine-tuning the smelting process, avoiding the accumulation of harmful elements in subsequent recycled materials and creating conditions for the reuse of nickel-based alloy recycled materials. Summary of the Invention

[0006] The purpose of this invention is to provide a method for reducing the arsenic and tin content in nickel-based alloy materials. By adjusting the electroslag remelting slag system and fine-tuning the smelting process, the arsenic and tin removal rate in nickel-based alloy materials can reach more than 46%.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for reducing the arsenic and tin content in nickel-based alloy materials is as follows: in the electroslag remelting process of nickel-based alloy material preparation, a pre-melted slag with the following composition is used: CaF2: 38%–45%, CaO: 20%–25%, Al2O3: 20%–30%, ZrO2: 3%–5%, BaF2: 3%–5%, MgO: 1%–3%, SiO2: 1%–3%, with the remainder being unavoidable impurities.

[0009] Furthermore, the CaO / Al2O3 ratio in the pre-melted slag of the present invention is 0.8 to 1, which reduces the permeability of the pre-melted slag while ensuring the high basicity of the molten slag. In addition, the addition of 1% to 3% MgO to the pre-melted slag can form a semi-solidified film on the surface of the slag pool, preventing the slag pool from absorbing oxygen.

[0010] Furthermore, the pre-melted slag of this invention contains 1-1.5% calcium carbide powder by weight of the total slag, the purpose of which is to form free [C] in the slag, increase the activity of [As], and facilitate the arsenic removal reaction in the slag pool. The positive progress.

[0011] Furthermore, the method of the present invention further includes: an electrode preparation stage in the electroslag remelting process, wherein after welding the consumable electrode, aluminum wire is vertically bound to its surface with pure iron wire, the total weight of the aluminum wire being 0.5% to 0.8% of the mass of the pre-melted slag, and the diameter and length of the aluminum wire are determined according to the total mass of the aluminum wire.

[0012] Furthermore, the method of the present invention further includes: the arc-initiating and slag-forming stage of the electroslag remelting process, wherein the arc-initiating scrap and the arc-starting plate are consistent with the consumable electrode base material, and are used after being dried at 150°C for 2 hours in the heating furnace. The constant melting rate melting and hot capping stage is specifically formulated according to the crystallizer diameter and the type of smelting material.

[0013] Furthermore, the method of the present invention further includes: the electroslag remelting process is protected by argon gas throughout the process, and the oxygen content of the smelting atmosphere is controlled below 5 ppm.

[0014] Furthermore, the method of the present invention is applicable to nickel-based alloy materials with As and Sn contents of less than 0.003%.

[0015] The inventive principle and beneficial technical effects of this invention are as follows:

[0016] This invention reduces the permeability of the pre-melted slag by adjusting the CaO / Al2O3 ratio, thereby effectively reducing the oxygenation of the slag pond by the environment. Adding calcium carbide to the slag aims to form free [C] in the slag, increasing the activity of arsenic and facilitating the arsenic removal reaction in the slag pond. The process proceeds in the forward direction; by vertically binding aluminum wire to the surface of the consumable electrode, [O] in the slag is consumed, and the newly generated Al2O3 is adsorbed by the slag pool, thus maintaining the oxygen content in the slag at a low level throughout the smelting process and promoting the arsenic removal reaction. A certain proportion of ZrO2 and BaF2 are added to the slag to react with [Sn] during the remelting process to generate high-melting-point compounds, which can be removed by the slag pool, thus achieving Sn removal; the entire smelting process is protected by argon gas, and the atmospheric oxygen content is controlled below 5 ppm, avoiding atmospheric oxygen supply to the slag pool and creating conditions for arsenic and tin removal reactions.

[0017] The method of this invention is simple to operate and achieves an arsenic and tin removal rate of over 46%, which effectively solves the problem of difficult removal of arsenic and tin from nickel-based alloys. It avoids the impact of As and Sn accumulation on product quality during recycling and creates conditions for the reuse of nickel-based alloy recycled materials. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to specific embodiments.

[0019] A method for reducing the arsenic and tin content in nickel-based alloy materials specifically involves optimizing and controlling the electroslag remelting process during the preparation of nickel-based alloy materials, as follows:

[0020] (1) Electrode preparation: The pretreated consumable electrode is welded to the auxiliary electrode, and aluminum wire is tied vertically on the surface of the consumable electrode with pure iron wire. The total weight of the aluminum wire is 0.5% to 0.8% of the mass of the pre-melted slag.

[0021] (2) Preparation of pre-melted slag: The slag material with the composition of CaF2: 38%~45%, CaO: 20%~25%, Al2O3: 20%~30%, ZrO2: 3%~5%, BaF2: 3%~5%, MgO: 1%~3%, and SiO2: 1%~3% is stirred and mixed, and then placed in a heating furnace for baking and preparation. 1~1.5% of the total slag mass of calcium carbide powder is added to the slag system. The scrap material and arc-starting plate of the same material as the consumable electrode base material used in the arc-starting and slag-forming stage are placed in the heating furnace and dried at 150°C for 2 hours for preparation.

[0022] Arc ignition and slag formation: Place an arc ignition plate on the bottom water tank of the electroslag remelting machine, and place arc ignition chips of the same material in the center of the arc ignition plate. The arc ignition plate and arc ignition chips should be consistent with the base material of the consumable electrode, and the product should be dried at 150°C in the heating furnace for 2 hours before use. Install the crystallizer, protective fume hood, and consumable electrode, ignite the arc, and slowly add slag after the arc light stabilizes.

[0023] Constant melting rate melting: After slag formation, the melting rate is set according to the smelting process. When the consumable electrode has a certain weight remaining, a hot capping operation is performed. After hot capping, the smelting power supply is turned off, and the electroslag ingot is demolded after complete solidification. Argon gas protection is used throughout the electroslag smelting process, and the oxygen content of the smelting atmosphere is controlled below 5 ppm.

[0024] Examples 1-9

[0025] The nickel-based alloy materials and their arsenic and tin contents in each embodiment are shown in Table 1.

[0026] The content of each component in the pre-melted slag used in each embodiment and the amount of aluminum wire added are shown in Table 2.

[0027] After demolding, the electroslag ingots of each embodiment were sliced ​​300mm above the bottom arc-starting plate of the electroslag ingot. One sample was taken from each of the three locations: the center of the cross-section, the R / 2 point, and the edge, and the content of arsenic and tin was tested. The test results are shown in Table 3.

[0028] Table 1. Nickel-based alloy materials and their arsenic and tin contents in each embodiment.

[0029]

[0030]

[0031] Table 2 shows the content of each component in the pre-melted slag and the amount of aluminum wire added in each embodiment.

[0032]

[0033] Note: The CaC and Al lines in Table 2 represent their mass ratios to the pre-melted slag.

[0034] Table 3. Arsenic and tin content and removal rate in electroslag ingots of various embodiments.

[0035]

[0036]

Claims

1. A method of reducing the levels of arsenic and tin in a nickel-based alloy material, characterized in that, The method is characterized in that the following pre-melting slag is used in the electroslag remelting process in the preparation process of the nickel-based alloy material: CaF2: 38-45%, CaO: 20-25%, Al2O3: 20-30%, ZrO2: 3-5%, BaF2: 3-5%, MgO: 1-3%, SiO2: 1-3%, and the rest is inevitable impurities, and 1-1.5% of the total mass of the slag is provided with calcium carbide powder.

2. The method of reducing the content of arsenic and tin in a nickel-based alloy material according to claim 1, characterized in that, The CaO / Al2O3 in the pre-melting slag is 0.8-1.

3. The method of reducing the content of arsenic and tin in a nickel-based alloy material according to claim 1, characterized in that, The method further comprises that in the electrode preparation stage of the electroslag remelting process, after the consumable electrode is welded, pure iron wire is used to bind aluminum wire in the vertical direction on the surface of the electrode, and the total weight of the aluminum wire is 0.5-0.8% of the mass of the pre-melting slag.

4. The method of reducing the content of arsenic and tin in a nickel-based alloy material according to claim 1, characterized in that, The method further comprises that in the arc starting slag stage of the electroslag remelting process, the arc starting scrap and the arc starting plate are consistent with the consumable electrode base material, and are used after being dried at 150 DEG C in the heating furnace for 2 hours.

5. The method of reducing the levels of arsenic and tin in a nickel-based alloy material of claim 1, wherein the method further comprises the step of: The method further comprises that the electroslag remelting process uses argon protection in the whole process, and the oxygen content in the smelting atmosphere is controlled to be less than 5 ppm. ​ 6. The method of reducing the levels of arsenic and tin in a nickel-based alloy material of claim 1, wherein, The method is suitable for nickel-based alloy materials with As and Sn content less than 0.003%.

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