An electroslag remelting method for stabilizing titanium

Abstract

This invention discloses an electroslag remelting method for stabilizing titanium. The titanium content of the consumable electrode is controlled above the upper limit of the target composition of the electroslag billet, exceeding the target composition upper limit by 10% to 20%. The surface-treated consumable electrode undergoes a coating process, with the coating consisting of an aluminum powder layer and / or a titanium dioxide layer, followed by a corundum powder layer, from the inside out. During the electroslag remelting stage, electroslag is added to the crystallizer, with the average thickness of the slag pool controlled at 1 / 3 to 1 / 2 of the equivalent diameter of the melted consumable electrode, while inert gas is blown into the crystallizer. During the feeding stage, electroslag is added to the crystallizer again, maintaining the slag pool thickness at 1 / 2 to 1.0 of the equivalent diameter of the melted consumable electrode, and the inert gas flow rate is controlled at 10 to 30 L / min. This invention, through control of the consumable electrode composition and surface coating treatment, effectively prevents the oxidation of titanium in the consumable electrode during electroslag remelting and stabilizes the titanium content within a controlled range, solving the problem of poor stability in controlling the burn-off rate of easily oxidized titanium.

Description

Technical Field

[0001] This invention belongs to the field of electroslag metallurgical smelting technology, and specifically relates to an electroslag remelting method for stabilizing titanium. Background Technology

[0002] Electroslag remelting (ESR) is a special smelting method that utilizes the resistance heat generated when an electric current passes through molten slag as a heat source for melting. It possesses unique advantages in producing high-end steels. With its excellent metallurgical reaction conditions and unique solidification process, it can effectively remove harmful inclusions from metals and improve the solidification quality. However, due to the characteristics of the ESR process, precisely controlling the content of easily oxidized elements in the steel is extremely difficult. Currently, the methods for controlling the content of easily oxidized titanium in the ESR process are as follows:

[0003] 1. Pre-action method: Based on the requirements of titanium content in the finished product, the titanium content of the consumable electrode is controlled above the upper limit of the composition limit in advance. According to the control of exceeding the upper limit of the composition requirement, the proportion of titanium loss during the electroslag remelting process is pre-formed into the consumable electrode to control the titanium loss during the electroslag remelting process and ensure the composition requirements of the electroslag billet. However, since the proportion of titanium loss during the electroslag remelting process fluctuates greatly, it is difficult to control the pre-formed proportion of titanium content in the consumable electrode.

[0004] 2. Online Adjustment Method: Based on the requirements for titanium content in the finished product and combined with the empirical value of the burn-off ratio of easily oxidized aluminum powder during electroslag remelting, titanium oxide powder is added to control the titanium content in the molten steel online during electroslag remelting. However, due to different equipment conditions, the empirical value of titanium burn-off ratio fluctuates greatly, and the added aluminum powder is added intermittently, which cannot achieve a continuous addition mode. This addition method is prone to causing fluctuations in slag properties, which in turn causes large fluctuations in titanium yield. Therefore, this method has poor stability in controlling the burn-off of easily oxidized titanium.

[0005] To address the technical challenges of current methods for reducing titanium loss during electroslag remelting, such as difficulty in controlling the pre-fabricated titanium content in the consumable electrode and large fluctuations and poor stability in titanium yield, there is an urgent need to develop a simple, safe, reliable, and efficient process to reduce titanium loss during electroslag remelting, enabling stable control of the titanium content in the consumable electrode and minimizing fluctuations in titanium yield. Summary of the Invention

[0006] The purpose of this invention is to provide a method for stabilizing titanium through electroslag remelting, which reduces titanium burn-off and solves the problem of poor stability in controlling the burn-off rate of easily oxidized titanium.

[0007] To address the above problems, the present invention provides a method for stabilizing titanium through electroslag remelting, comprising the following:

[0008] (1) Consumable electrode composition: In order to offset the loss of some titanium during the electroslag remelting process, the titanium content of the consumable electrode is controlled above the upper limit of the target composition of the electroslag billet, and controlled at 10% to 20% above the upper limit of the target composition.

[0009] (2) Consumable Electrode Coating: A coating is applied to the surface-treated consumable electrode. Since titanium burn-off is mainly caused by the combination of titanium in the consumable electrode with slag and oxygen in the atmosphere, aluminum powder can be used to bind the oxygen in the system to reduce burn-off caused by oxygen combining with titanium. In addition, the burn-off reaction can be suppressed by increasing the content of titanium oxide, which is the product of the titanium burn-off reaction in the system. Finally, to improve the high-temperature resistance of the coating, corundum powder is applied to its outer side, thus determining the coating structure, which consists of an aluminum powder layer and / or a titanium dioxide layer, and a corundum powder layer from the inside out.

[0010] (3) Electroslag remelting: In the electroslag remelting process, the average thickness of the slag pool has a significant impact on the production cost and quality of the electroslag ingot. The larger the equivalent diameter of the consumable electrode, the larger the amount of molten steel melted per unit time, and the thicker the slag pool should be. Electroslag material is added to the crystallizer to control the average thickness of the slag pool to 1 / 3 to 1 / 2 of the equivalent diameter of the consumable electrode being melted. At the same time, inert gas is blown into the crystallizer to control the atmosphere of the crystallizer, and its flow rate is controlled at 5 to 20 L / min.

[0011] (4) Compensation stage:

[0012] During the feeding stage, since the liquid metal is close to the top of the crystallizer, it is easier to absorb oxygen from the environment. To prevent oxygen from entering the environment, electroslag material is added to the crystallizer again, so that the thickness of the slag pool is controlled at 1 / 2 to 1.0 of the equivalent diameter of the consumable electrode being smelted, and the inert gas flow rate is controlled at 10 to 30 L / min.

[0013] Furthermore, the surface roughness Ra of the consumable electrode reaches 0.5 to 3.0 mm, so that the reducing agent coated on the surface of the consumable electrode in subsequent processes has better adhesion.

[0014] Furthermore, the aluminum powder layer has a thickness of 0.5–1.5 mm, the titanium dioxide layer has a thickness of 1.0–3.0 mm, and the corundum powder layer has a thickness of 0.5–1.0 mm.

[0015] Furthermore, the aluminum powder raw material used for the aluminum powder layer has an Al content of ≥99% by weight and a particle size of 50-100 mesh; the titanium dioxide raw material used for the titanium dioxide layer has a TiO2 content of ≥98% by weight and a particle size of 80-150 mesh; and the corundum powder raw material used for the corundum powder layer has an Al2O3 content of ≥95% by weight and a particle size of 100-300 mesh.

[0016] Furthermore, the thickness of the titanium dioxide layer is controlled according to the titanium content in the consumable electrode. When the titanium content in the consumable electrode exceeds the upper limit of the target composition of the electroslag blank by 15% to 20% (inclusive), the coating thickness is controlled at 1.0 to 1.5 mm (inclusive); when the titanium content in the consumable electrode exceeds the upper limit of the target composition of the electroslag blank by 10% to 15% (exclusive), the coating thickness is controlled at 1.5 to 3.0 mm (exclusive).

[0017] Furthermore, the surface of the consumable electrode is treated with a frosted finish, and each coating is applied using an electrostatic powder coating process.

[0018] Furthermore, the weight percentage of the electroslag material is: CaF2 60%–70%, Al2O3 20%–30%, TiO2 5%–10%, and MgO 5%–10%.

[0019] Furthermore, the electroslag material is a pre-melted slag, which is baked at 600-800℃ for 5-8 hours before use.

[0020] Furthermore, the particle size of the electroslag material is between 0.5 and 1.5 mm.

[0021] Furthermore, the inert gas is argon.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This invention effectively prevents the oxidation of titanium in consumable electrodes and stabilizes the range of titanium content during electroslag remelting by controlling the composition of the consumable electrode and applying a spray coating to its surface before electroslag remelting. The process is simple, safe and reliable.

[0024] 2. The coating of this invention contains aluminum powder as a deoxidizer, which can effectively inhibit oxygenation in molten steel and achieve full-process inhibition of oxygenation in molten steel during electroslag remelting, thereby achieving full-process protection of easily oxidized titanium elements in molten steel.

[0025] 3. The coating of this invention contains titanium dioxide, which can increase the activity of TiO2 in the liquid slag and further suppress the burning loss of titanium elements in the consumable electrode.

[0026] 4. The coating of this invention contains corundum powder, which can effectively block the consumable electrode from contacting air, prevent secondary oxidation of the consumable electrode before melting, and achieve full protection of the consumable electrode throughout the electroslag remelting process.

[0027] 5. This invention enables the titanium content in electroslag ingots to be controlled at a 100% pass rate. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The described embodiments are merely some, not all, of the embodiments of this invention. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0029] This invention employs a consumable electrode surface treatment technology to prevent titanium burn-off, combined with conventional atmosphere protection and deoxidation processes, to achieve a comprehensive, efficient, and stable reduction in titanium burn-off during the electroslag remelting process. The specific solution is as follows:

[0030] (1) Preparation of consumable electrode: In order to offset part of the titanium loss during the electroslag remelting process, the titanium content in the consumable electrode is controlled above the upper limit of the finished product composition, and controlled by 10%-20% above the upper limit of the composition.

[0031] (2) Surface treatment of consumable electrode: Use shot blasting, shot peening, sandblasting and other treatment methods to remove residual oil stains, iron oxide scale and other substances from the surface of the consumable electrode. The treatment time is 30-60 minutes. In order to facilitate the subsequent spraying effect of the coating on the surface of the consumable electrode, it is necessary to perform a sanding treatment to make its surface roughness reach 0.5-3.0 mm;

[0032] (3) Coating and Thickness Control: The surface-treated consumable electrode is coated with a three-layer coating. From the inside out, the first layer is an aluminum powder layer with an Al content ≥99% and a particle size of 50-100 mesh, and a coating thickness of 0.5-1.5 mm. The second layer is a titanium dioxide layer with a TiO2 content ≥98% and a particle size of 80-150 mesh. The coating thickness is controlled according to the titanium content in the consumable electrode, with a thickness of 1.0-3.0 mm. When the titanium content exceeds the upper limit, the coating thickness is controlled at the lower limit; when the titanium content exceeds the lower limit, the coating thickness is controlled at the upper limit. The third layer is a corundum powder layer with an Al2O3 content ≥95% and a particle size of 100-300 mesh, and a thickness of 0.5-1.0 mm. All layers are coated using electrostatic powder spraying.

[0033] (4) Preparation of electroslag material: The electroslag material is composed of CaF2, Al2O3, TiO2 and MgO. The content of each component by weight percentage is 60%-70%, 20%-30%, 5%-10% and 5%-10%, respectively. The slag material is pre-melted slag and should be baked at 600-800℃ for 5-8 hours before use. The particle size of the slag material should be controlled at 0.5-1.5mm.

[0034] (5) Electroslag remelting process control: During the electroslag remelting process, the thickness of the slag pool is controlled at 1 / 3 to 1 / 2 of the diameter of the consumable electrode being melted. At the same time, inert argon gas is blown into the crystallizer to control the atmosphere of the crystallizer, and the argon gas flow rate is controlled at 5-20 L / min.

[0035] (6) Feeding stage control: During the feeding stage, refined slag is added to the crystallizer again to control the thickness of the slag pool to 1 / 2 to 1.0 of the diameter of the self-consumable electrode being melted, and the argon flow rate is controlled at 10-30 L / min.

[0036] To further describe the present invention, the following detailed description is provided in conjunction with embodiments:

[0037] In a steel company, a total of 60 heats of titanium-containing alloy steel were produced using an electroslag remelting furnace: 40 heats were completed using conventional processes, and 20 heats were completed using the present invention. The electrode preparation scheme and production test results are as follows:

[0038] Comparative example: (conventional process)

[0039] Electroslag remelting was conducted using conventional processes to reduce titanium loss. Residual oil and iron oxide scale on the consumable electrode surface were treated using shot blasting, shot peening, and sandblasting methods for 25 minutes, resulting in an average surface roughness of 80 μm. The titanium content in the consumable electrode was controlled to the upper limit of 0.2% required for the finished product. All other operations followed conventional procedures.

[0040] Test results: Among the 40 heats of electroslag ingots, 25 heats had titanium content within the required range, while 15 heats had composition discrepancies due to unstable titanium content control. The overall titanium stability control pass rate was 62.5%.

[0041] Example 1:

[0042] The process of this invention controls the titanium content in the consumable electrode to be within 10% of the upper limit, with an average control of 0.22%. The surface of the consumable electrode is cleaned by sandblasting for 40 minutes, followed by abrasive treatment to achieve a surface roughness of 1.0 mm. An electrostatic powder coating is then applied to the surface-treated consumable electrode. The first layer is an aluminum powder layer, requiring an Al content ≥99%, a particle size of 80 mesh, and a coating thickness of 0.8 mm. The second layer is a titanium dioxide layer, with a TiO2 content ≥98%, a particle size of 120 mesh, and a coating thickness controlled according to the titanium content in the consumable electrode, controlled at 2.5 mm. The third layer is a corundum powder layer, with an Al2O3 content ≥95%, a particle size of 150 mesh, and a thickness of 0.6 mm. The pre-melted electroslag material was baked at 650℃ for 7 hours. The electroslag material used consisted of CaF2, Al2O3, TiO2, and MgO, with the following weight percentages: 65%, 21%, 8.5%, and 5.5%, respectively. The particle size of the slag was 0.5-1.5 mm. During the electroslag remelting process, the slag pool thickness was controlled to be 1 / 3 of the diameter of the consumable electrode being melted, and the inert argon gas flow rate in the crystallizer was controlled to be 10 L / min. In the feeding stage, refined slag material was added to the crystallizer again, so that the slag pool thickness was controlled to be 1 / 2 of the diameter of the consumable electrode being melted, and the argon gas flow rate was controlled to be 15 L / min.

[0043] Test results: Among the 5 heats of electroslag ingots, the titanium content was within the required range in all 5 heats, and the titanium stability control pass rate was 100%.

[0044] Example 2:

[0045] The process of this invention controls the titanium content in the consumable electrode to be 20% above the upper limit, with an average control of 0.24%. The surface of the consumable electrode is cleaned by sandblasting for 45 minutes, followed by abrasive treatment to achieve a surface roughness of 2.5 mm. An electrostatic powder coating is then applied to the surface-treated consumable electrode. The first layer is an aluminum powder layer, requiring an Al content ≥99%, a particle size of 60 mesh, and a coating thickness of 1.0 mm. The second layer is a titanium dioxide layer, with a TiO2 content ≥98%, a particle size of 80 mesh, and a coating thickness controlled according to the titanium content in the consumable electrode, controlled at 1.5 mm. The third layer is a corundum powder layer, with an Al2O3 content ≥95%, a particle size of 120 mesh, and a thickness of 0.8 mm. The pre-melted electroslag material was baked at 750℃ for 6 hours. The electroslag material used consisted of CaF2, Al2O3, TiO2, and MgO, with the following weight percentages: 66%, 22%, 5.5%, and 6.5%, respectively. The particle size of the slag was 0.5-1.5 mm. During the electroslag remelting process, the slag pool thickness was controlled to 1 / 3 of the diameter of the consumable electrode being melted, and the inert argon gas flow rate in the crystallizer was controlled to 10 L / min. In the feeding stage, refined slag material was added to the crystallizer again, so that the slag pool thickness was controlled to 1 / 2 of the diameter of the consumable electrode being melted, and the argon gas flow rate was controlled to 15 L / min.

[0046] Test results: Among the 5 heats of electroslag ingots, the titanium content was within the required range in all 5 heats, and the titanium stability control pass rate was 100%.

[0047] Example 3:

[0048] The process of this invention controls the titanium content in the consumable electrode to be 20% above the upper limit, with an average control of 0.24%. The surface of the consumable electrode is cleaned by sandblasting for 40 minutes, followed by abrasive treatment to achieve a surface roughness of 1.5 mm. An electrostatic powder coating is then applied to the surface-treated consumable electrode. The first layer is an aluminum powder layer, requiring an Al content ≥99%, a particle size controlled at 70 mesh, and a coating thickness controlled at 1.2 mm. The second layer is a corundum powder layer, requiring an Al2O3 content ≥95%, a particle size controlled at 180 mesh, and a thickness controlled at 0.7 mm. The pre-melted electroslag material is baked at 700℃ for 6 hours. The electroslag material consists of CaF2, Al2O3, TiO2, and MgO, with weight percentages of 63%, 23%, 6.5%, and 7.5%, respectively, and a particle size of 0.5-1.5 mm. During the electroslag remelting process, the slag pool thickness is controlled to be 2 / 5 of the diameter of the consumable electrode being melted, and the inert argon gas blowing flow rate into the crystallizer is controlled to be 15 L / min. During the feeding stage, refined slag is added to the crystallizer again, so that the slag pool thickness is controlled to be 2 / 3 of the diameter of the consumable electrode being melted, and the argon gas flow rate is controlled to be 20 L / min.

[0049] Test results: Among the 5 heats of electroslag ingots, the titanium content was within the required range in all 5 heats, and the titanium stability control pass rate was 100%.

[0050] Example 4:

[0051] The process of this invention controls the titanium content in the consumable electrode to be 15% above the upper limit, with an average control of 0.23%. The surface of the consumable electrode is cleaned by sandblasting for 45 minutes, followed by abrasive treatment to achieve a surface roughness of 2.0 mm. An electrostatic powder coating is then applied to the surface-treated consumable electrode. The first layer is a titanium dioxide layer with a TiO2 content ≥98% and a particle size controlled at 100 mesh. The coating thickness is controlled according to the titanium content in the consumable electrode, with a thickness of 1.5 mm. The second layer is a corundum powder layer with an Al2O3 content ≥95%, a particle size controlled at 160 mesh, and a thickness of 0.8 mm. The pre-melted electroslag material is baked at 730℃ for 7 hours. The electroslag material consists of CaF2, Al2O3, TiO2, and MgO, with weight percentages of 64%, 21%, 6.5%, and 8.5%, respectively. The particle size of the slag material is 0.5-1.5 mm. During the electroslag remelting process, the slag pool thickness is controlled at 1 / 2 of the diameter of the consumable electrode being melted, and the inert argon gas blowing flow rate into the crystallizer is controlled at 15 L / min. During the feeding stage, refined slag is added to the crystallizer again, so that the slag pool thickness is controlled at 4 / 5 of the diameter of the consumable electrode being melted, and the argon gas flow rate is controlled at 25 L / min.

[0052] Test results: Among the 5 heats of electroslag ingots, the titanium content was within the required range in all 5 heats, and the titanium stability control pass rate was 100%.

[0053] The above production test results show that when the present invention is used to carry out production tests of electroslag remelting of titanium-containing steel, by improving the processes such as the composition of consumable electrode, slag composition, and electrode surface treatment, it is possible to achieve stable control of titanium in titanium-containing steel during electroslag smelting, thus ensuring the qualified rate of titanium-containing steel composition.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for stabilizing titanium through electroslag remelting, characterized in that, Includes the following: (1) Consumable electrode composition: The titanium content of the consumable electrode is controlled above the upper limit of the target composition of the electroslag billet, and controlled at 10%~20% above the upper limit of the target composition. (2) Consumable electrode coating: The surface-treated consumable electrode is coated. The coating consists of an aluminum powder layer and / or a titanium dioxide layer, and a corundum powder layer from the inside out. (3) Electroslag remelting: Add electroslag material into the crystallizer. The weight percentage of the components of the electroslag material is: CaF2 60%~70%, Al2O3 20%~30%, TiO2 5%~10%, MgO 5%~10%. The average thickness of the slag pool is controlled at 1 / 3 to 1 / 2 of the equivalent diameter of the consumable electrode being melted. At the same time, inert gas is blown into the crystallizer, and its flow rate is controlled at 5~20L / min. (4) Feeding stage: Add electroslag material to the crystallizer again, so that the thickness of the slag pool is controlled at 1 / 2 to 1.0 of the equivalent diameter of the consumable electrode being melted, and the inert gas flow rate is controlled at 10 to 30 L / min.

2. The electroslag remelting method for stabilizing titanium element according to claim 1, characterized in that, The surface roughness of the consumable electrode reaches 0.5~3.0 mm.

3. The electroslag remelting method for stabilizing titanium element according to claim 1, characterized in that, The aluminum powder layer has a thickness of 0.5~1.5mm, the titanium dioxide layer has a thickness of 1.0~3.0mm, and the corundum powder layer has a thickness of 0.5~1.0mm.

4. The electroslag remelting method for stabilizing titanium element according to claim 1 or 3, characterized in that, The aluminum powder raw material used for the aluminum powder layer has an Al content of ≥99% by weight and a particle size of 50~100 mesh; the titanium dioxide raw material used for the titanium dioxide layer has a TiO2 content of ≥98% by weight and a particle size of 80~150 mesh; and the corundum powder raw material used for the corundum powder layer has an Al2O3 content of ≥95% by weight and a particle size of 100~300 mesh.

5. The electroslag remelting method for stabilizing titanium element according to claim 1 or 3, characterized in that, The thickness of the titanium dioxide layer is controlled according to the titanium content in the consumable electrode. When the titanium content in the consumable electrode exceeds the upper limit of the target composition of the electroslag blank by 15% to 20% (inclusive), the coating thickness is controlled at 1.0 to 1.5 mm (inclusive); when the titanium content in the consumable electrode exceeds the upper limit of the target composition of the electroslag blank by 10% to 15% (exclusive), the coating thickness is controlled at 1.5 to 3.0 mm (exclusive).

6. The electroslag remelting method for stabilizing titanium element according to claim 1 or 3, characterized in that, The surface of the consumable electrode is treated with a frosted finish, and each coating is applied using an electrostatic powder coating process.

7. The electroslag remelting method for stabilizing titanium element according to claim 1, characterized in that, The electroslag material is a pre-melted slag, which is baked at 600~800℃ for 5~8 hours before use.

8. The electroslag remelting method for stabilizing titanium element according to claim 1, characterized in that, The particle size of the electroslag material is 0.5~1.5mm.

9. The electroslag remelting method for stabilizing titanium element according to claim 1, characterized in that, The inert gas is argon.