Deoxidation method using CO as RH lifting gas
By using CO instead of part of Ar gas during ultra-low carbon IF steel smelting, the reaction of CO+O to generate CO2 is promoted, and the problem of Al2O3 inclusion retention after RH refining and deoxygenation is solved, and the high cleanliness and cost reduction of the steel is achieved.
Patent Information
- Application Number
- CN202411716937.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-27
- Publication Date
- 2025-03-14
AI Technical Summary
During the smelting of ultra-low carbon IF steel, Al2O3 inclusions remain in the steel after RH refining and deoxidation, affecting the surface quality and performance of the steel.
CO is used as RH lifting gas to replace part of Ar gas during the steel water circulation, which promotes the CO2 reaction to generate CO+O, reduces residual oxygen, and reduces the amount of metal aluminum, thereby reducing the formation of Al2O3 inclusions.
It effectively reduces the amount of Al2O3 retained in the steel, improves the cleanliness of the steel liquid, and reduces production costs.
Smart Images
Figure CN119614796A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of steelmaking and refining, and in particular relates to a deoxidation method using CO as RH raising gas. Background Art
[0002] IF steel, the full name of which is Interstitial-Free Steel, is an ultra-low carbon steel. Its main features are excellent deep drawing performance and non-aging properties, which give IF steel a significant advantage in manufacturing parts of complex shapes. In addition, IF steel also has high strength, high toughness and good welding properties, and is widely used in the automotive field, such as manufacturing body panels, structural parts and chassis parts. Its excellent deep drawing performance enables complex-shaped automotive parts to be easily formed, while its non-aging characteristics ensure the dimensional stability of the parts during use. IF steel is also widely used in the home appliance industry, such as the manufacture of washing machines, refrigerators, air conditioners and other products. The characteristics of high strength and high toughness enable IF steel to withstand various loads during the use of home appliances, ensuring the safety and reliability of the products.
[0003] When the current industry smelts ultra-low carbon IF steel, the molten steel circulation process is naturally decarburized under the RH refining vacuum state to remove the carbon in the steel to below 15ppm. The residual oxygen after decarburization needs to be deoxidized with metallic aluminum. Under this process, the deoxidation products of metallic aluminum are mainly Al2O3 inclusions. Most of the deoxidation products Al2O3 can be fully floated, but there are still some fine Al2O3 inclusions retained in the steel. Such inclusions will have adverse effects on the surface quality and performance of the steel. Therefore, in the smelting of ultra-low carbon IF steel, how to reduce the number of Al2O3 inclusions and improve the cleanliness of molten steel has become a key problem for the further development of such products. Summary of the invention
[0004] Aiming at the problem that Al2O3 inclusions are still retained in the steel after the existing RH refining and deoxidation, the present invention provides a deoxidation method using CO as RH lifting gas to solve the above problem. In the RH vacuum treatment process of ultra-low carbon IF steel, the present invention uses CO to replace part of the power gas Ar gas used for molten steel circulation. On the basis of not reducing the power source of molten steel circulation, part of the CO filled in the Ar gas participates in the removal of residual oxygen after the natural decarburization of the molten steel, so as to reduce the metal aluminum used for deoxidation, reduce the amount of Al2O3 generated by aluminum deoxidation, and further reduce the amount of Al2O3 retained in the steel, which can effectively improve the cleanliness of the molten steel.
[0005] The technical solution of the present invention is as follows: A deoxidation method using CO as RH raising gas comprises the following steps: (1) For ultra-low carbon IF steel melt smelted in a top-bottom combined blowing converter, the process manufacturing standard requires that the end point carbon of the steel melt after the converter blowing is 0.03~0.05%, the end point oxygen is 400~600ppm, and the end point temperature is 1660~1690℃.
[0006] (2) After the converter is finished tapping, a top slag modifier is added to modify the top slag to reduce TFe in the slag to 3%~6%.
[0007] (3) The modified molten steel is transported to the RH vacuum treatment station and the ladle is lifted. When the ladle is lifted to a depth of 300-500 mm where the immersion tube is inserted into the molten steel, the system vacuum program is started.
[0008] (4) In the system vacuum program parameter setting, the lifting gas is Ar gas and the circulating gas volume is 120~220Nm 3 / h, used to create good natural decarbonization conditions.
[0009] (5) CO is introduced into the Ar gas pipeline so that CO and Ar can be used together as the power source for the circulation of molten steel.
[0010] (6) After CO is mixed in, the molten steel is recirculated for 2 to 5 minutes to remove some of the residual oxygen in the molten steel using CO.
[0011] (7) After the CO removal of residual oxygen from part of the molten steel is completed, the molten steel is subjected to an oxygen determination operation. Based on the residual oxygen concentration in the molten steel, metallic aluminum is added to remove residual oxygen and alloy the molten steel. Steel samples are then taken for chemical composition testing.
[0012] Furthermore, in step (2), the top slag modifier comprises metallic aluminum, CaO and SiO2, wherein Al≥45%, CaO≥20%, Al2O3≥15%, and SiO2≤5%.
[0013] Furthermore, in step (4), when the oxygen content in the molten steel is ≤400ppm, or the molten steel temperature T is ≤1610°C, oxygen blowing operation is required.
[0014] Furthermore, in step (5), CO is introduced into the Ar gas pipeline, and the carbon content in the molten steel needs to be removed to less than 15 ppm. In order to avoid carbon increase during the pouring process resulting in unqualified components, the carbon is usually removed to below 10 ppm.
[0015] Furthermore, in step (5), the CO introduction rate is carried out at a ratio of CO / Ar=0.1%~0.3%, and the CO and Ar are mixed by mixing through a three-way joint before the gas enters the circulation pipe.
[0016] Furthermore, after the steel liquid temperature, chemical composition and pure degassing time are detected in step (7) and all meet the requirements of the steel grade, the RH vacuum cycle is stopped, the air is broken, and the ladle is separated from the RH treatment station and transported to the continuous casting station.
[0017] The beneficial effects of the present invention are: (1) The lifting gas Ar used in the present invention is filled with CO gas as a power source for the circulation of molten steel, which promotes the reaction of CO+O to generate CO2 in the high-temperature molten steel during the circulation process, thereby removing some residual oxygen in the molten steel. In the reaction of CO+O to generate CO2, the amount of metal aluminum used to remove residual oxygen in the steel can be significantly reduced, which can effectively reduce production costs.
[0018] (2) The reaction product of CO+O generated during the circulation process of the present invention is CO2 gas, which is discharged from the vacuum system, greatly reducing the amount of Al2O3 inclusions generated by metal aluminum deoxidation, and can effectively improve the cleanliness of molten steel. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0020] Figure 1 This is a scanning electron microscope analysis result diagram of inclusions in Example 1 of the present invention.
[0021] Figure 2 This is a scanning electron microscope analysis result diagram of inclusions in Example 2 of the present invention.
[0022] Figure 3 It is a scanning electron microscope analysis result diagram of inclusions in the comparative example of the present invention. DETAILED DESCRIPTION
[0023] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.
[0024] Example 1 A deoxidation method using CO as RH raising gas comprises the following steps: (1) Ultra-low carbon IF steel is smelted in a top and bottom combined blowing converter. After the converter blowing is completed, the end point C = 0.035%, the end point O = 516ppm, and the end point temperature T = 1678℃; (2) After the converter is finished tapping, 300 kg of steel slag modifier with an Al content of 47% is evenly added (spread) to the ladle slag surface. After the modifier is added, the molten steel in this furnace is hoisted to the RH vacuum refining furnace processing station, and the slag sample is taken. The slag sample analysis shows that TFe in the slag is 4.7%; (3) After the molten steel arrives at the RH treatment station, the temperature of the molten steel is measured, T = 1627 ° C, oxygen O = 455 ppm, and after the ladle is raised to the treatment height (the immersion pipe is inserted into the molten steel to a depth of 400 mm), the RH vacuuming program is started to start vacuuming; (4) The circulating gas volume used for vacuuming is 160Nm 3 / h; vacuum for 5 minutes, the vacuum degree reaches 100Pa; after continuing to vacuum for about 20 minutes, when the CO concentration in the tail gas analysis of the RH vacuum system drops to 0.12%, it is considered that the CO reaction in the molten steel has been completed. At this time, the C content in the steel is 0.0008%~0.0010%, the temperature is T=1598℃, and the oxygen concentration is O=261ppm; (5) At this time, CO is mixed into the Ar pipeline at a ratio of CO / Ar = 0.2 through the three-way connecting pipe; (6) After the molten steel continued to circulate under vacuum for 4 minutes, the temperature was measured at T = 1592 ° C and the oxygen was set at O = 135 ppm. 168 kg of aluminum was added (of which 38 kg was used to remove 135 ppm of oxygen in the steel and 130 kg was used for Al = 0.020% to 0.050% in the alloying of the molten steel). After 3 minutes, Ti alloy was added. After the molten steel continued to circulate under vacuum for 7 minutes, the temperature was measured at T = 1582 ° C. The system was broken (the lifting gas was automatically closed). The steel samples were sent to the inspection room for inclusion scanning electron microscopy analysis. The analysis results are detailed in the table. Figure 1 The molten steel is transferred to the continuous casting machine for pouring. Among them, the number of Al2O3 inclusions is 90 / cm 2 .
[0025] Example 2 A deoxidation method using CO as RH raising gas comprises the following steps: (1) Ultra-low carbon IF steel is smelted in a top and bottom combined blowing converter. After the converter blowing is completed, the end point C = 0.031%, the end point O = 533ppm, and the end point temperature T = 1675℃; (2) After the converter is finished tapping, 300 kg of steel slag modifier with an Al content of 47% is evenly added (spread) to the ladle slag surface. After the modifier is added, the molten steel in this furnace is hoisted to the RH vacuum refining furnace processing station, and the slag sample is taken. The slag sample analysis shows that TFe in the slag is 4.2%; (3) After the molten steel arrives at the RH treatment station, the temperature of the molten steel is measured at T = 1632 ° C, the oxygen is set at O = 479 ppm, and after the ladle is raised to the treatment height (the immersion pipe is inserted into the molten steel to a depth of 400 mm), the RH vacuuming program is started to start vacuuming; (4) The circulating gas volume used for vacuuming is 160Nm 3 / h. Vacuum for 5 minutes, the vacuum degree reaches 100Pa; after continuing to vacuum for about 20 minutes, when the CO concentration in the tail gas analysis of the RH vacuum system drops to 0.12%, it is considered that the CO reaction in the molten steel has been completed. At this time, the C content in the steel is 0.0008% to 0.0010%, the temperature is T=1598℃, and the oxygen O=278ppm; (5) At this time, CO is mixed into the Ar pipeline at a ratio of CO / Ar = 0.2 through the three-way connecting pipe; (6) After the molten steel continued to circulate under vacuum for 4 minutes, the temperature was measured at T = 1592 ° C and the oxygen was set at O = 140 ppm. 170 kg of aluminum was added (of which 40 kg was used to remove 140 ppm of oxygen in the steel and 130 kg was used for Al = 0.020% to 0.050% in the alloying of the molten steel). After 3 minutes, Ti alloy was added. After the molten steel continued to circulate under vacuum for 7 minutes, the temperature was measured at T = 1580 ° C. The system was broken (the lifting gas was automatically closed), and steel samples were taken and sent to the inspection room for inclusion scanning electron microscopy analysis. The analysis results are detailed in the table. Figure 2 The molten steel is transferred to the continuous casting machine for pouring. Among them, the number of Al2O3 in the inclusion scanning electron microscope analysis results is 42 / cm 2 .
[0026] Comparative Example The conventional smelting process includes the following steps: (1) Ultra-low carbon IF steel is smelted in a top and bottom combined blowing converter. After the converter blowing is completed, the end point C = 0.033%, the end point O = 572ppm, and the end point temperature T = 1677℃; (2) After the converter is finished tapping, 300 kg of steel slag modifier with an Al content of 47% is evenly added (spread) to the ladle slag surface; after the addition of the modifier is completed, the molten steel in this furnace is hoisted to the RH vacuum refining furnace processing station, and the slag sample is taken. The slag sample analysis shows that TFe=4.4%; (3) After the molten steel arrives at the RH treatment station, the temperature of the molten steel is measured at T = 1629 ° C, the oxygen is set at O = 445 ppm, and after the ladle is raised to the treatment height (the immersion pipe is inserted into the molten steel to a depth of 400 mm), the RH vacuuming program is started to start vacuuming; (4) The circulating gas volume used for vacuuming is 160Nm 3 / h. Vacuum for 5 minutes, the vacuum degree reaches 100Pa; after continuing to vacuum for about 20 minutes, when the CO concentration in the tail gas analysis of the RH vacuum system drops to 0.12%, it is considered that the CO reaction in the molten steel has been completed. At this time, the C content in the steel is 0.0008-0.0010%, the temperature is T=1598℃, and the oxygen O=313ppm; (5) Add 220 kg of aluminum (90 kg of which is used to remove 313 ppm of oxygen from the steel and 130 kg of which is used to add 0.020% to 0.050% of Al in the alloying of the molten steel). After 3 minutes, add the Ti alloy. After the molten steel continues to circulate under vacuum for 7 minutes, the temperature is measured at T = 1586 ° C, the system is vented (the lifting gas is automatically closed), and the steel sample is sent to the inspection room for inclusion scanning electron microscopy analysis. The analysis results are shown in Figure 3 The molten steel is transferred to the continuous casting machine for pouring. Among them, the number of Al2O3 in the inclusion scanning electron microscope analysis results is 280 / cm 2 .
[0027] It can be seen from the final test data of Examples 1 to 2 and the comparative example that after deoxidation by the deoxidation method using part of the CO filled into the Ar gas as the RH-raising gas, the amount of metallic aluminum used for deoxidation is reduced, the amount of Al2O3 produced by aluminum deoxidation is reduced, and the amount of Al2O3 retained in the steel is reduced, thereby effectively improving the cleanliness of the molten steel.
[0028] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.
Claims
1. A deoxidation method using CO as RH raising gas, characterized in that: The following steps are involved: (1) For ultra-low carbon IF steel liquid smelted in a top-bottom combined blowing converter, the final carbon content of the steel liquid after the converter blowing is 0.03-0.05%, the final oxygen content is 400-600 ppm, and the final temperature is 1660-1690°C; (2) After the converter is finished tapping, a top slag modifier is added to modify the top slag to reduce TFe in the slag to 3%~6%; (3) The reformed molten steel is transported to the RH vacuum treatment station, and the ladle is lifted. After the ladle is lifted to a depth of 300-500 mm where the immersion tube is inserted into the molten steel, the system vacuuming procedure is started; (4) In the system vacuum program parameter setting, the lifting gas is Ar gas and the circulating gas volume is 120~220Nm 3 / h; (5) CO is introduced into the Ar gas pipeline so that CO and Ar can be used together as the power source for the circulation of molten steel; (6) After CO is mixed in, the molten steel is recirculated for 2 to 5 minutes; (7) After the CO removal of residual oxygen from part of the molten steel is completed, the molten steel is subjected to an oxygen determination operation. Based on the residual oxygen concentration in the molten steel, metallic aluminum is added to remove residual oxygen and alloy the molten steel. Steel samples are then taken for chemical composition testing.
2. The deoxidation method using CO as RH raising gas according to claim 1, characterized in that: In step (2), the top slag modifier comprises metallic aluminum, CaO and SiO2.
3. The deoxidation method using CO as RH raising gas according to claim 2, characterized in that: The composition of the top slag modifier is: Al≥45%, CaO≥20%, Al2O3≥15%, SiO2≤5%.
4. The deoxidation method using CO as RH raising gas according to claim 1, characterized in that: In step (4), when the oxygen in the molten steel is ≤400ppm or the molten steel temperature T is ≤1610°C, oxygen blowing operation is required.
5. The deoxidation method using CO as RH raising gas according to claim 1, characterized in that: In step (5), CO is introduced into the Ar gas pipeline to remove the carbon content in the molten steel to less than 15 ppm.
6. The deoxidation method using CO as RH raising gas according to claim 1, characterized in that: In step (5), the CO introduction rate is carried out at a ratio of CO / Ar=0.1%~0.3%.
7. The deoxidation method using CO as RH raising gas according to claim 1, characterized in that: In step (5), CO and Ar are mixed by mixing through a three-way joint before the gases enter the circulation pipe.
8. The deoxidation method using CO as RH raising gas according to claim 1, characterized in that: After the steel liquid temperature, chemical composition and pure degassing time are detected in step (7) and all meet the requirements of the steel grade, the RH vacuum cycle is stopped, the air is broken, and the ladle is separated from the RH treatment station and transported to the continuous casting station.