Method for reducing contents of arsenic and tin in nickel-based alloy material

Abstract

The invention discloses a method for reducing the content of arsenic and tin in a nickel-based alloy material. The method specifically comprises the following steps: adopting pre-melted slag comprising the following components in an electroslag remelting procedure in the preparation process of the nickel-based alloy material: 38%-45% of CaF2, 20%-25% of CaO, 20%-30% of Al2O3, 3%-5% of ZrO2, 3%-5% of BaF2, 1%-3% of MgO, 1%-3% of SiO2 and the balance of inevitable impurities; the ratio of CaO to Al2O3 in the pre-melted slag is 0.8-1; and calcium carbide powder accounting for 1-1.5% of the total amount of the pre-melted slag is also prepared in the pre-melted slag. By the adoption of the method, the removal rate of arsenic and tin in the nickel-based alloy material can reach 46% or above, the problem that arsenic and tin in the nickel-based alloy material are difficult to remove is well solved, the influence of accumulation of As and Sn on the product quality in the recycling process is avoided, and conditions are created for recycling of the nickel-based alloy return scrap.

Description

Technical Field

[0001] The invention belongs to the field of metallurgy, and in particular relates to a method for reducing the contents of arsenic and tin in a nickel-based alloy material. Background Art

[0002] Arsenic and tin are the five harmful elements in steel and alloys. They have low solubility, high density and low melting point in the matrix. They are easy to form low-melting eutectics and accumulate in the grain boundary area. Even if their content is very small, they will make the grain boundary of the material embrittled, resulting in the decline of thermoplasticity, thermal strength and other properties. Therefore, the arsenic content in steel and alloys must be strictly controlled.

[0003] The current localization level of nickel-based alloy materials is still relatively low, but with the rapid development of the economy and the continuous improvement of the level of the industrial field, its demand in the fields of aerospace, petrochemicals, nuclear industry, etc. is getting higher and higher. When Chinese technicians independently developed nickel-based alloy materials of various grades and uses, they found that during the recycling process of nickel-based alloy materials, As and Sn would continue to accumulate in the steel as trace residual elements, resulting in the deterioration of the performance of the final product. Therefore, how to effectively control the content of arsenic and tin in 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 means of controlling trace harmful elements in alloys. The preparation of nickel-based alloy materials often adopts a dual smelting process of vacuum induction melting and electroslag remelting. In the vacuum induction melting process, high vacuum volatilization can effectively reduce the content of harmful elements such as trace Bi and Pb, but arsenic and tin exist in nickel-based alloy materials in a stable form and cannot be removed by high vacuum treatment. In addition, rare earths, magnesium, barium, etc. are added in the vacuum stage to form compounds with high melting points with harmful elements. In the subsequent electroslag process, special slag system adjustments must be made to remove them. Otherwise, the accumulation of harmful elements in the subsequent return material utilization process cannot be avoided. This process route is complicated, and the amount and method of adding microalloys are difficult to control. Improper operation will affect the quality of the final product.

[0005] The "slag washing" effect of the slag pool on the alloy droplets in the electroslag remelting process provides a new idea for removing As and Sn from the alloy. The present invention significantly reduces the arsenic and tin contents in the alloy by only adjusting the electroslag remelting slag system and fine-tuning the smelting process, thereby avoiding the accumulation of harmful elements in the subsequent return material utilization process and creating conditions for the reuse of nickel-based alloy return materials. Summary of the invention

[0006] The present invention aims to provide a method for reducing the arsenic and tin contents 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 the nickel-based alloy materials can reach more than 46%.

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

[0008] A method for reducing the arsenic and tin contents in a nickel-based alloy material comprises the following steps: in an electroslag remelting process in a process of preparing the nickel-based alloy material, a pre-melted slag having the following components is used: CaF2: 38% to 45%, CaO: 20% to 25%, Al2O3: 20% to 30%, ZrO2: 3% to 5%, BaF2: 3% to 5%, MgO: 1% to 3%, SiO2: 1% to 3%, and the rest being unavoidable impurities.

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

[0010] Furthermore, the pre-melted slag of the present invention is provided with 1 to 1.5% of the total mass of the slag in the form of calcium carbide powder, 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. is proceeding in the positive direction.

[0011] Furthermore, the method of the present invention further includes: in the electrode preparation stage of the electroslag remelting process, after the consumable electrode is welded, aluminum wire is tied vertically on its surface 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, 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 comprises: in the arcing and slag-forming stage of the electroslag remelting process, the arcing scraps and arc-starting plates are consistent with the consumable electrode base material, and are used after being dried at 150°C for 2 hours in a heating furnace. The constant melting rate smelting and hot capping stage are specifically formulated according to the diameter of the crystallizer and the type of smelting material.

[0013] Furthermore, the method of the present invention further comprises: the electroslag remelting process adopts argon protection throughout the entire 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 less than 0.003%.

[0015] The inventive principle and beneficial technical effects of the present invention are:

[0016] The present invention can effectively reduce the oxygenation of the slag pool by the environment by adjusting the CaO / Al2O3 ratio in the pre-melted slag to reduce the permeability of the pre-melted slag; adding calcium carbide to the slag is aimed at forming free [C] in the slag, increasing the activity of arsenic, and facilitating the arsenic removal reaction in the slag pool. The process is carried out in the positive direction; by tying aluminum wire vertically on the surface of the consumable electrode, [O] in the slag is consumed, and the newly generated Al2O3 will be adsorbed by the slag pool, so that the oxygen content in the slag is maintained at a low level during the whole process of smelting, which promotes the de-arsenicization reaction. A certain proportion of ZrO2 and BaF2 is added to the slag, the purpose of which is to react with [Sn] during the remelting process to generate high-melting point compounds, which can be removed by the slag pool, thus achieving the removal of Sn; the whole smelting process is protected by argon gas, and the oxygen content of the atmosphere is controlled below 5ppm, which avoids the supply of oxygen to the slag pool by the atmosphere, creating conditions for the de-arsenicization and de-tinning reactions.

[0017] The method of the invention is simple to operate, and the removal rate of arsenic and tin reaches more than 46%, which well solves the problem of difficult removal of arsenic and tin in nickel-based alloys, avoids the influence of As and Sn accumulation on product quality during the recycling process, and creates conditions for the recycling of nickel-based alloy return materials. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below in conjunction with specific implementation modes.

[0019] A method for reducing the arsenic and tin content in a nickel-based alloy material, specifically: optimizing and controlling the electroslag remelting process in the preparation process of the nickel-based alloy material, specifically 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-molten slag.

[0021] (2) Preparation of pre-melted slag: Stir and mix slag materials with the components of CaF2: 38%-45%, CaO: 20%-25%, Al2O3: 20%-30%, ZrO2: 3%-5%, BaF2: 3%-5%, MgO: 1%-3%, SiO2: 1%-3%, and put them into a heating furnace for baking for use, and add 1-1.5% of calcium carbide powder to the slag system in an amount of 1% to 1.5% of the total slag mass; the scraps and arc-starting plates of the same quality as the consumable electrode base material used in the arcing and slagging stage are placed in a heating furnace for drying at 150°C for 2 hours for use.

[0022] Arcing and slag removal: Place an arc-starting plate on the electric slag bottom water tank, and place arc-starting chips of the same material in the center of the arc-starting plate. The arc-starting plate and arc-starting chips should be consistent with the consumable electrode base material, and they should be dried at 150℃ in a heating furnace for 2 hours before use; install the crystallizer, protective fume hood, and consumable electrode, power on to start the arc, and slowly add the slag after the arc light is stable.

[0023] Constant melting rate smelting: After slag melting, the melting rate is set according to the smelting process. When the consumable electrode has a certain weight remaining, the hot capping operation is carried out. After the hot capping is completed, the smelting power supply is turned off, and the electroslag ingot is demoulded after it is completely solidified. The whole process of electroslag smelting is protected by argon gas, and the oxygen content of the smelting atmosphere is controlled below 5ppm.

[0024] Examples 1-9

[0025] The nickel-based alloy materials in various embodiments and the arsenic and tin contents therein are shown in Table 1.

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

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

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

[0029]

[0030]

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

[0032]

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

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

[0035]

[0036]

Claims

1. A method for reducing the arsenic and tin contents in a nickel-based alloy material, characterized in that: The method is specifically as follows: in the electroslag remelting process during the preparation of the nickel-based alloy material, a pre-melted slag with the following composition is used: CaF2: 38% to 45%, CaO: 20% to 25%, Al2O3: 20% to 30%, ZrO2: 3% to 5%, BaF2: 3% to 5%, MgO: 1% to 3%, SiO2: 1% to 3%, and the rest are unavoidable impurities.

2. A method for 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-molten slag is 0.8-1.

3. The method for reducing the arsenic and tin contents in nickel-based alloy materials according to claim 1, characterized in that: The pre-melted slag is provided with 1 to 1.5% of the total mass of the slag calcium carbide powder.

4. The method for reducing the arsenic and tin contents in nickel-based alloy materials according to claim 1, characterized in that: The method further comprises: in the electrode preparation stage of the electroslag remelting process, after welding the consumable electrode, aluminum wire is vertically tied to the surface of the consumable electrode with pure iron wire, and the total weight of the aluminum wire is 0.5% to 0.8% of the mass of the pre-melted slag.

5. The method for reducing the arsenic and tin contents in nickel-based alloy materials according to claim 1, characterized in that: The method further comprises: in the arcing and slag-forming stage of the electroslag remelting process, arcing scraps and arc-starting plates are consistent with the consumable electrode base material, and are dried at 150° C. for 2 hours in a heating furnace before use.

6. The method for reducing the arsenic and tin contents in nickel-based alloy materials according to claim 1, characterized in that: The method further comprises: the electroslag remelting process adopts argon protection throughout the entire process, and the oxygen content of the smelting atmosphere is controlled below 5 ppm.

7. The method for reducing the arsenic and tin contents in nickel-based alloy materials according to claim 1, characterized in that: The method is applicable to nickel-based alloy materials with As and Sn contents less than 0.003%.

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