A method for producing low-carbon steel using VD

Abstract

This application relates to the field of iron and steel smelting technology, and more particularly to a method for producing low-carbon steel using VD (Volatile Dioxide) refining. The method includes: smelting molten iron, followed by tapping to obtain oxygen-containing molten steel; refining the oxygen-containing molten steel using VD to achieve decarburization and deoxidation, followed by alloying to obtain low-carbon steel; and casting the low-carbon steel to obtain low-carbon steel. The VD refining includes decarburization refining, wherein the decarburization vacuum degree is adjusted according to the carbon-oxygen product after decarburization refining, with a decarburization vacuum degree of 0.5 kPa to 50 kPa and a carbon-oxygen product of 0.4 x 10⁻⁶ kPa. ‑8 ~12.2*10 ‑8 By performing VD refining on oxygen-containing molten steel, the decarburization vacuum degree can be adjusted through carbon-oxygen product during the VD refining process. This ensures that the oxygen-containing molten steel is decarburized to the target range under the adjusted decarburization vacuum degree, thereby achieving rapid and precise control of the carbon content of low-carbon steel under VD refining conditions.

Description

Technical Field

[0001] This application relates to the field of iron and steel smelting technology, and in particular to a method for producing low-carbon steel using VD. Background Technology

[0002] A vacuum degassing furnace (VD furnace) is a crucial piece of metallurgical equipment used to refine molten steel from primary furnaces (such as electric arc furnaces, open-hearth furnaces, and converters). It also regulates the temperature and composition of the molten steel, facilitating subsequent continuous casting and rolling processes. VD refining decarburizes, degasses, and fine-tunes the alloy composition of molten steel under vacuum conditions, accelerating production and thus improving overall metallurgical efficiency.

[0003] In the production of low-carbon steel, the carbon content of the steel is usually first reduced to an extremely low range, and then a carbon raiser or high-carbon alloy is added to increase the carbon content of the steel to a low range. However, when using a VD refining furnace for smelting, multiple station changes are required, which not only reduces production efficiency but also makes it impossible to quickly and accurately control the carbon content of low-carbon steel. Therefore, how to quickly and accurately control the carbon content of low-carbon steel under VD vacuum conditions is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] This application provides a method for producing low-carbon steel using VD (Volatile Dioxide) to solve the technical problem in the prior art that the carbon content of low-carbon steel cannot be quickly and accurately controlled under VD refining conditions.

[0005] In a first aspect, this application provides a method for producing low-carbon steel using VD, the method comprising:

[0006] The molten iron is smelted and then tapped to obtain oxygen-containing molten steel.

[0007] The oxygen-containing molten steel is subjected to VD refining to decarburize and deoxidize it, and then alloyed to obtain molten steel with low carbon content.

[0008] The low-carbon steel molten steel is then poured to obtain low-carbon steel;

[0009] The VD refining process includes decarburization refining. The decarburization vacuum degree of the VD refining is adjusted according to the carbon-oxygen product after decarburization refining. The decarburization vacuum degree is 0.5 kPa to 50 kPa, and the carbon-oxygen product is 0.4 * 10^6 kPa. -8 ~12.2*10 -8 .

[0010] Optionally, the decarburization vacuum degree of the VD refining is adjusted according to the carbon-oxygen product after decarburization refining, specifically including:

[0011] If the carbon-oxygen product is 0.4*10 -8 ~0.6*10 -8 The decarburization vacuum degree is then 0.5 kPa.

[0012] If the carbon-oxygen product is 1.0*10 -8 ~1.2*10 -8 The decarburization vacuum degree is then 2 kPa;

[0013] If the carbon-oxygen product is 1.6*10 -8 ~1.8*10 -8 The decarburization vacuum degree is then 5 kPa;

[0014] If the carbon-oxygen product is 2.7*10 -8 ~3.0*10 -8 The decarburization vacuum degree is then 10 kPa;

[0015] If the carbon-oxygen product is 7.3*10 -8 ~7.6*10 -8 The decarburization vacuum degree is then 30 kPa;

[0016] If the carbon-oxygen product is 11.5*10 -8 ~12.2*10 -8 The decarburization vacuum degree is 50 kPa.

[0017] Optionally, the formula for calculating the carbon-oxygen product is:

[0018] w [C] *w [O] =[O0-1.33*(C0-C1+C2)]*(C1-C2)

[0019] In the formula, w [C] *w [O] The carbon-oxygen product is defined as follows: O0 is the oxygen content of the oxygen-containing molten steel, C0 is the carbon content of the oxygen-containing molten steel, C1 is the target carbon content of the low-carbon steel, and C2 is the carbon increase after adding alloys during alloying.

[0020] Optionally, the VD refining further includes deoxidation refining, which includes an oxygen control operation, specifically including:

[0021] Based on the carbon-oxygen product, the oxygen content at the end of VD refining and decarburization is calculated;

[0022] Based on the oxygen content at the end of VD refining and decarburization and the target oxygen content, it is determined whether to oxygenate or deoxidize the oxygen-containing molten steel after decarburization.

[0023] If the oxygen content at the end of the VD refining and decarburization is greater than the target oxygen content, then an oxygenation operation is performed on the oxygen-containing molten steel after decarburization.

[0024] If the oxygen content at the end of the VD refining and decarburization process is less than the target oxygen content, then the oxygen-containing molten steel after decarburization will undergo a deoxidation operation.

[0025] Optionally, the VD refining includes refining for a preset time under the decarburization vacuum condition, wherein the preset time is 5 min to 10 min.

[0026] Optionally, the target carbon content of the decarbonization refining is ≤0.03%, and the total flow rate of the bottom-blown gas in the decarbonization refining is 200L / min to 600L / min.

[0027] Optionally, the VD refining further includes ladle slag modification; the ladle slag modification includes modifying the ladle slag with oxygen-containing molten steel after decarburization refining under the condition of a modifier, wherein the modifier includes at least one of aluminum particles, aluminum granules, aluminum slag ash and low-carbon aluminum slag balls, the ladle slag modification time is ≥3 min, and the amount of modifier added is 100 kg to 700 kg.

[0028] Optionally, the modified ladle slag composition includes FeO and MnO, and the modified ladle slag composition satisfies the following:

[0029] [FeO]+[MnO]≤8%,

[0030] In the formula, FeO is the mass fraction of FeO, and MnO is the mass fraction of MnO.

[0031] Optionally, the total flow rate of the bottom-blown gas for the ladle slag modification is 100L / min to 400L / min.

[0032] Optionally, the temperature of the molten steel entering the VD refining station is 1600℃~1630℃, the thickness of the slag entering the VD refining station is ≤100mm, and the net thickness of the slag entering the VD refining station is 800mm~1500mm.

[0033] The technical solutions provided in this application have the following advantages compared with the prior art:

[0034] This application provides a method for producing low-carbon steel using VD (Vacuum-Deoxidation). The method involves VD refining oxygen-containing molten steel to decarburize and deoxidize it, followed by alloying to adjust the steel's composition. During VD refining, the carbon-oxygen product after decarburization represents the degree of decarburization of the oxygen-containing molten steel, and the decarburization vacuum degree of VD refining determines the final decarburization degree. Therefore, adjusting the decarburization vacuum degree through the carbon-oxygen product ensures that the oxygen-containing molten steel is decarburized to the target range under the adjusted vacuum conditions. This ensures that the carbon content in the low-carbon molten steel remains at a low level, achieving rapid and precise control of the carbon content of low-carbon steel under VD refining conditions. Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A flowchart illustrating the method provided in the embodiments of this application;

[0038] Figure 2 This is a schematic diagram of the oxygen control operation provided in the embodiments of this application. Detailed Implementation

[0039] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0040] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0041] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0042] The creative thinking behind this application is:

[0043] 1) It abandons the traditional method of first removing carbon content to an extremely low range and then adding carbon-replenishing agents or high-carbon alloys to increase carbon content to a low range.

[0044] 2) By controlling the vacuum level of VD, the carbon content of low-carbon steel can be precisely controlled.

[0045] 3) Utilize the favorable vacuum and bottom-blowing conditions of VD to perform rapid VD decarburization.

[0046] The technical solution provided by the embodiments of the present invention is to solve the above-mentioned technical problems, and the general idea is as follows:

[0047] In an optional embodiment of this application, such as Figure 1 As shown, a method for producing low-carbon steel using VD is provided, the method comprising:

[0048] S1. The molten iron is smelted and then tapped to obtain oxygen-containing molten steel;

[0049] S2. The oxygen-containing molten steel is subjected to VD refining to complete decarburization and deoxidation, and then alloyed to obtain molten steel with low carbon content;

[0050] S3. The low-carbon steel molten steel is poured to obtain low-carbon steel;

[0051] The VD refining process includes decarburization refining. The decarburization vacuum degree of the VD refining is adjusted according to the carbon-oxygen product after decarburization refining. The decarburization vacuum degree is 0.5 kPa to 50 kPa, and the carbon-oxygen product is 0.4 * 10^6 kPa. -8 ~12.2*10 -8 .

[0052] In this embodiment, the positive effect of a decarburization vacuum degree of 0.5 kPa to 50 kPa is that within this range, the VD refining process can be guaranteed to decarburize to the target range, thereby ensuring that the carbon content of the oxygen-containing molten steel is at a low level. When the decarburization vacuum degree is greater than the maximum value at the end of this range, the excessively high vacuum degree will result in insufficient oxygen content in the oxygen-containing molten steel after deoxidation refining, leading to insufficient carbon-oxygen reaction and inadequate decarburization of the oxygen-containing molten steel. When the decarburization vacuum degree is less than the minimum value at the end of this range, the excessively low vacuum degree will result in inadequate decarburization of the oxygen-containing molten steel.

[0053] The carbon-oxygen product is 0.4 * 10^4 -8 ~12.2*10 -8The positive effect is that within the range of the carbon-oxygen product, the degree of decarburization in decarburization refining can be guaranteed to be appropriate. When the value of the carbon-oxygen product is greater than the maximum value at the end of the range, it will result in an excessively large carbon-oxygen product, indicating that the degree of decarburization is too large, which will affect the carbon content of the oxygen-containing molten steel. When the value of the carbon-oxygen product is less than the minimum value at the end of the range, it will result in an excessively small carbon-oxygen product, indicating that the degree of decarburization is too low, which will also affect the carbon content of the oxygen-containing molten steel.

[0054] In some optional embodiments, the decarburization vacuum degree of the VD refining is adjusted according to the carbon-oxygen product after decarburization refining, specifically including:

[0055] If the carbon-oxygen product is 0.4*10 -8 ~0.6*10 -8 The decarburization vacuum degree is then 0.5 kPa.

[0056] If the carbon-oxygen product is 1.0*10 -8 ~1.2*10 -8 The decarburization vacuum degree is then 2 kPa;

[0057] If the carbon-oxygen product is 1.6*10 -8 ~1.8*10 -8 The decarburization vacuum degree is then 5 kPa;

[0058] If the carbon-oxygen product is 2.7*10 -8 ~3.0*10 -8 The decarburization vacuum degree is then 10 kPa;

[0059] If the carbon-oxygen product is 7.3*10 -8 ~7.6*10 -8 The decarburization vacuum degree is then 30 kPa;

[0060] If the carbon-oxygen product is 11.5*10 -8 ~12.2*10 -8 The decarburization vacuum degree is 50 kPa.

[0061] In this embodiment of the application, by corresponding the decarburization vacuum degree and the carbon-oxygen product range one-to-one, the decarburization vacuum degree of VD refining can be precisely controlled by the carbon-oxygen product. Since the decarburization vacuum degree can directly affect the decarburization degree of oxygen-containing molten steel, controlling the decarburization vacuum degree can precisely control the carbon content of oxygen-containing molten steel.

[0062] In some optional embodiments, the carbon-oxygen product is calculated using the following formula:

[0063] w [C] *w [O] =[O0-1.33*(C0-C1+C2)]*(C1-C2)

[0064] In the formula, w [C] *w [O] The carbon-oxygen product is defined as follows: O0 is the oxygen content of the oxygen-containing molten steel, C0 is the carbon content of the oxygen-containing molten steel, C1 is the target carbon content of the low-carbon steel, and C2 is the carbon increase after adding alloys during alloying.

[0065] In this embodiment of the application, the positive effect of limiting the calculation formula of carbon-oxygen product is that the accuracy of carbon-oxygen product can be guaranteed under the condition of the calculation formula, thereby facilitating the subsequent control of decarburization vacuum degree and ensuring the degree of decarburization of oxygen-containing molten steel.

[0066] In some alternative implementations, such as Figure 2 As shown, the VD refining further includes deoxidation refining, which includes oxygen control operations, specifically including:

[0067] S101. Calculate the oxygen content at the end of VD refining and decarburization based on the carbon-oxygen product;

[0068] S102. Based on the oxygen content at the end of VD refining and decarburization and the target oxygen content, determine whether to oxygenate or deoxidize the oxygen-containing molten steel after decarburization.

[0069] If the oxygen content at the end of the VD refining and decarburization is greater than the target oxygen content, then an oxygenation operation is performed on the oxygen-containing molten steel after decarburization.

[0070] If the oxygen content at the end of the VD refining and decarburization process is less than the target oxygen content, then the oxygen-containing molten steel after decarburization will undergo a deoxidation operation.

[0071] In this embodiment of the application, the positive effect of limiting the specific oxygen control operation is that if the oxygen content in the oxygen-containing molten steel after decarburization is too high, it will affect the subsequent deoxidation refining process and generate a large number of inclusions, affecting the cleanliness of the molten steel. If the oxygen content in the oxygen-containing molten steel after decarburization is too low, it will lead to excessive carbon addition in the alloy during the alloying process after deoxidation refining, affecting the carbon content of the low-carbon molten steel after the final VD refining.

[0072] In some optional embodiments, the VD refining includes refining for a preset time under the decarburization vacuum condition, the preset time being 5 min to 10 min.

[0073] In this embodiment of the application, the positive effect of setting the time to 5 min to 10 min is to ensure complete decarburization in the decarburization refining process under low-cost conditions. If the time value is greater than or less than the endpoint of this range, it will result in the decarburization refining process being too long, increasing production costs, or the decarburization refining process being insufficient, affecting the carbon content of the final molten steel.

[0074] In some optional embodiments, the target carbon content of the decarbonization refining is ≤0.03%, and the total flow rate of the bottom-blown gas in the decarbonization refining is 200L / min to 600L / min, wherein the bottom-blown gas in the decarbonization refining can be argon.

[0075] In this embodiment of the application, the positive effect of the target carbon content of decarburization refining being ≤0.03% is that within the range of the target carbon content, it indicates that the carbon content of oxygen-containing molten steel after decarburization refining meets the standard of low-carbon steel products.

[0076] The positive effect of a total bottom-blowing gas flow rate of 200L / min to 600L / min in decarburization refining is that if the total bottom-blowing gas flow rate is too high, it will cause splashing and slag overflow of molten steel during the decarburization refining process of VD refining. If the total bottom-blowing gas flow rate is too low, it will cause slow circulation of molten steel and affect the decarburization efficiency of VD refining.

[0077] In some optional embodiments, the VD refining further includes ladle slag modification; the ladle slag modification includes modifying the ladle slag with oxygen-containing molten steel after decarburization refining under the condition of a modifier, wherein the modifier includes at least one of aluminum granules, aluminum beans, aluminum slag ash and low-carbon aluminum slag balls, the ladle slag modification time is ≥3 min, and the amount of modifier added is 100 kg to 700 kg.

[0078] In the embodiments of this application, the positive effect of limiting the type of modifier is that within this range, the complete modification of ladle slag can be guaranteed, while reducing the modifier standard required for ladle slag modification and promoting complete modification of ladle slag.

[0079] The modification time of ladle slag is ≥3 minutes. Within this time range, the modification effect of ladle slag is guaranteed, thereby ensuring that the oxidizability of ladle slag is within a suitable range. If the value of the time is less than the endpoint of this range, it indicates that the modification time of ladle slag is too short, the modification effect of ladle slag is not obvious, and the oxidizability of ladle slag is enhanced.

[0080] The positive effect of adding 100kg to 700kg of modifier is that within this range, the oxidizability of ladle slag and production cost can be kept within a suitable range. If the amount added is greater than or less than the endpoint of this range, it will result in excessive addition of modifier, which will cause waste of raw materials and increase production costs. Alternatively, if the amount added is insufficient, the oxidizability of ladle slag will be enhanced.

[0081] In some optional embodiments, the modified ladle slag comprises FeO and MnO, and the modified ladle slag composition satisfies the following:

[0082] [FeO]+[MnO]≤8%,

[0083] In the formula, FeO is the mass fraction of FeO, and MnO is the mass fraction of MnO.

[0084] In the embodiments of this application, the positive effect of [FeO]+[MnO]≤8% is that within the range of the sum of this mass fraction, the risk of explosive oxidation of molten steel can be reduced, thereby improving the cleanliness of molten steel after VD refining.

[0085] In some optional embodiments, the total flow rate of the bottom-blown gas for ladle slag modification is 100 L / min to 400 L / min, wherein the bottom-blown gas for ladle slag modification can be argon.

[0086] In this embodiment, the positive effect of having a total bottom-blown gas flow rate of 100 L / min to 400 L / min for ladle slag modification is that within this range, the modifier can be fully stirred with the molten steel, ensuring that the ladle slag modification is fully carried out. When the total gas flow rate is greater than or less than the endpoint of this range, the total gas flow rate will be too high, causing the modifier to react directly with the molten steel, failing to achieve the modification effect, or resulting in slow molten steel circulation and poor modification effect.

[0087] In some optional embodiments, the temperature of the molten steel entering the VD refining station is 1600℃~1630℃, the thickness of the slag entering the VD refining station is ≤100mm, and the net thickness of the slag entering the VD refining station is 800mm~1500mm.

[0088] In this embodiment of the application, the positive effect of setting the temperature of the molten steel entering the VD refining station at 1600℃~1630℃ is that if the temperature is too high, the temperature of the molten steel will be high after decarburization, resulting in a thinner billet shell in the casting machine and a risk of molten steel leakage; if the temperature is too low, the temperature of the molten steel will be low after decarburization, and the casting machine will have a risk of freezing.

[0089] Limiting the thickness of the slag entering the VD refining station and the net clearance thickness of the slag at the station has the positive effect of ensuring the decarburization effect while preventing the molten steel from overflowing into the ladle.

[0090] In some alternative embodiments, the chemical composition of the oxygen-containing molten steel, by mass fraction, comprises: C: 0.02% to 0.08%, O: 0.02% to 0.08%, with the remainder being Fe and unavoidable impurities.

[0091] In this embodiment, the specific chemical composition of the oxygen-containing molten steel is defined, which can better facilitate the carbon-oxygen reaction and achieve decarburization of the molten steel.

[0092] In some optional embodiments, the oxygen content after the decarbonization refining is 50 ppm to 250 ppm.

[0093] In this embodiment of the application, the positive effect of having an oxygen content of 50ppm to 250ppm after decarburization refining is that if the oxygen content is too high after decarburization, the cleanliness of the molten steel will be poor; if the oxygen content is too low after decarburization, the carbon content after decarburization will be too high.

[0094] In some alternative embodiments, tapping includes tapping by adding slag material including quicklime, fluorite, and bauxite, and tapping also includes not adding deoxidizer after tapping.

[0095] In this embodiment of the application, the positive effect of limiting the type of slag material used for slag formation is that the stirring effect of the steel flow during the steel tapping process allows the slag and steel to come into full contact, and the slag material to melt into slag quickly.

[0096] The positive effect of not adding deoxidizer after tapping is that if deoxidizer is added, it will cause the steel slag reaction to be more intense during the decarburization and refining stage. The free oxygen in the steel will further oxidize the ladle slag, increasing the oxidizing power of the ladle slag.

[0097] The process parameters for each embodiment and comparative example are shown in Table 1 and Table 2.

[0098] Table 1. Process parameters for decarburization refining in VD refining.

[0099]

[0100] Table 2. Process parameters for ladle slag modification in VD refining.

[0101]

[0102] In Tables 1 and 2, all other parameters not mentioned in Examples 2-3 and Comparative Examples 1-8 are consistent with those in Example 1.

[0103] Detailed analysis of Tables 1 and 2:

[0104] The data from Examples 1-3 show that:

[0105] By performing VD refining on oxygen-containing molten steel, decarburization and deoxidation are achieved. Then, alloying is used to adjust the composition of the molten steel. During the VD refining process, the decarburization vacuum degree is adjusted through carbon-oxygen product, which ensures that the oxygen-containing molten steel is completely decarburized under the adjusted decarburization vacuum degree. This allows for precise control of the carbon content of low-carbon steel under VD refining conditions.

[0106] From the data in Comparative Examples 1-8, we can see that:

[0107] In Comparative Example 1, if the carbon content in the molten steel entering the VD station is low while the oxygen content is high, it indicates that the molten steel entering the station has not undergone pre-deoxidation. The oxygen content after decarburization refining is as high as 722 ppm, indicating that the oxygen content in the molten steel is relatively high after decarburization refining.

[0108] In Comparative Example 2, if oxygen is not added during the oxygen control operation of the VD process, the oxygen content after decarbonization and refining is 43 ppm, which will result in a carbon content as high as 471 ppm after decarbonization and refining.

[0109] In Comparative Example 3, if the decarburization vacuum degree of VD decarburization refining is low, it will result in a low carbon-oxygen product at equilibrium. If the carbon content after decarburization refining is 14 ppm, then carbon replenishment is required.

[0110] In Comparative Example 4, if the decarburization vacuum is maintained for a short time during the VD process, and the carbon-oxygen reaction has not reached equilibrium at this time, the carbon content will be high after the decarburization refining is completed.

[0111] In Comparative Example 5, if the total flow rate of bottom-blown gas in VD decarburization refining is low, the decarburization rate of oxygen-containing molten steel will be slow, and the carbon content after decarburization refining will be as high as 405 ppm.

[0112] In Comparative Example 6, if the amount of modifier added to the ladle slag in VD is too small, the deoxidation effect of the ladle slag will be poor. The sum of the mass fractions of [FeO] and [MnO] in the ladle slag is 9.9%, which will cause the oxidizing property of the ladle slag to become stronger and affect the cleanliness of the molten steel.

[0113] In Comparative Example 7, if the modification time of the ladle slag in VD is too short, the modifier will not react fully. The sum of the mass fractions of [FeO] and [MnO] in the ladle slag is 8.7%, which will cause the oxidizing property of the ladle slag to become stronger and affect the cleanliness of the molten steel.

[0114] In Comparative Example 8, if the total flow rate of bottom-blown gas for ladle slag modification in VD is small, the modification effect of ladle slag will be poor, the oxidizing property of ladle slag will be stronger, and the cleanliness of molten steel will be affected.

[0115] One or more technical solutions in the embodiments of this application have at least the following technical effects or advantages:

[0116] (1) The method provided in this application embodiment is to perform VD refining on oxygen-containing molten steel, and to decarburize and deoxidize the oxygen-containing molten steel by VD refining. Then, the composition of the molten steel is adjusted by alloying. During the VD refining process, the decarburization vacuum degree is adjusted by carbon-oxygen product, which can ensure that the oxygen-containing molten steel is decarburized to the target range under the adjusted decarburization vacuum degree, and achieve precise control of the carbon content of low carbon steel under VD refining conditions.

[0117] (2) The method provided in this application uses the vacuum conditions and bottom blowing conditions in the VD refining process to ensure the rapid progress of decarburization refining. At the same time, it can control the decarburization vacuum degree of VD refining through carbon-oxygen product. This not only enables precise control of the carbon content of low carbon steel, thereby reducing the addition of carbon raisers in the refining stage, but also reduces the smelting cycle of VD refining and alleviates the pressure of converter smelting.

[0118] (3) The method provided in this application embodiment can not only ensure precise control of the carbon content of low carbon steel by VD refining oxygen-containing molten steel, but also control the oxygen content after the decarburization refining in VD refining, ensuring that the oxygen content in low carbon steel is low, thereby improving the cleanliness of molten steel.

[0119] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0120] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0121] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for producing low-carbon steel using VD, characterized in that, The method includes: The molten iron is smelted and then tapped to obtain oxygen-containing molten steel. The oxygen-containing molten steel is subjected to VD refining to decarburize and deoxidize it, and then alloyed to obtain molten steel with low carbon content. The low-carbon steel molten steel is then poured to obtain low-carbon steel; Among them, the VD refining includes decarburization refining, and the decarburization vacuum degree of the VD refining is adjusted according to the carbon-oxygen product after the decarburization refining. The decarburization vacuum degree is 0.5 kPa to 50 kPa, and the carbon-oxygen product is 0.4 10 -8 ~12.2 10 -8 ; The decarburization vacuum degree of the VD refining is adjusted according to the carbon-oxygen product after decarburization refining, specifically including: If the carbon-oxygen product is 0.4 10 -8 ~0.6 10 -8 , then the decarburization vacuum degree is 0.5 kPa; If the carbon-oxygen product is 1.0 10 -8 ~1.2 10 -8 , then the decarburization vacuum degree is 2 kPa; If the carbon-oxygen product is 1.6 10 -8 ~1.8 10 -8 , then the decarburization vacuum degree is 5 kPa; If the carbon-oxygen product is 2.7 10 -8 ~3.0 10 -8 , then the decarburization vacuum degree is 10 kPa; If the carbon-oxygen product is 7.3 10 -8 ~7.6 10 -8 , then the decarburization vacuum degree is 30 kPa; If the carbon-oxygen product is 11.5 10 -8 ~12.2 10 -8 , then the decarburization vacuum degree is 50 kPa; The VD refining includes refining for a preset time under the decarburization vacuum condition, wherein the preset time is 5 min to 10 min; The target carbon content of the decarbonization refining is ≤0.03%, and the total flow rate of the bottom-blown gas in the decarbonization refining is 200L / min to 600L / min; The VD refining also includes ladle slag modification; the ladle slag modification includes modifying the ladle slag with oxygen-containing molten steel after decarburization refining under the condition of a modifier, wherein the modifier includes at least one of aluminum particles, aluminum beans, aluminum slag ash and low-carbon aluminum slag balls, the ladle slag modification time is ≥3 min, and the amount of modifier added is 100 kg to 700 kg; The modified ladle slag comprises FeO and MnO, and the modified ladle slag composition satisfies the following: [FeO]+[MnO]≤8%, In the formula, FeO is the mass fraction of FeO, and MnO is the mass fraction of MnO; The total flow rate of the bottom-blown gas for the ladle slag modification is 100L / min to 400L / min.

2. The method according to claim 1, wherein The formula for calculating the carbon-oxygen product is: w [C] w [O] =[O0-1.33 (C0-C1+C2)] (C1-C2) In the formula, w [C] w [O] The carbon-oxygen product is defined as follows: O0 is the oxygen content of the oxygen-containing molten steel, C0 is the carbon content of the oxygen-containing molten steel, C1 is the target carbon content of the low-carbon steel, and C2 is the carbon increase after adding alloys during alloying.

3. The method according to claim 2, characterized in that, The VD refining process further includes deoxidation refining, which includes oxygen control operations, specifically including: Based on the carbon-oxygen product, the oxygen content at the end of VD refining and decarburization is calculated; Based on the oxygen content at the end of VD refining and decarburization and the target oxygen content, it is determined whether to oxygenate or deoxidize the oxygen-containing molten steel after decarburization. If the oxygen content at the end of the VD refining and decarburization is greater than the target oxygen content, then an oxygenation operation is performed on the oxygen-containing molten steel after decarburization. If the oxygen content at the end of the VD refining and decarburization process is less than the target oxygen content, then the oxygen-containing molten steel after decarburization will undergo a deoxidation operation.

4. The method according to claim 1, characterized in that, The temperature of the molten steel entering the VD refining station is 1600℃~1630℃, the thickness of the slag entering the VD refining station is ≤100mm, and the net thickness of the slag entering the VD refining station is 800mm~1500mm.

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