Method for reducing the arsenic content of molten steel in excess and billets obtained thereby

Abstract

The application discloses a method for reducing the content of arsenic in overproof molten steel and a billet obtained by the method. The method comprises the following steps: providing overproof molten steel, wherein the content of arsenic in the overproof molten steel is higher than 0.015%; providing scrap steel, wherein the scrap steel comprises one or more of carbon scrap steel and low-alloy scrap steel; providing refined molten steel, wherein the content of impurity elements in the refined molten steel is lower than 0.013%, and the impurity elements comprise one or more of As, Cu, Mo and Ni; mixing the overproof molten steel, the scrap steel and the refined molten steel in a refining furnace; and adding a dearsenization agent after deoxidization and desulfurization treatment to obtain clean molten steel, wherein the content of arsenic in the clean molten steel is lower than 0.015%. According to the embodiment of the application, the content of arsenic in molten steel can be reduced at low cost, the production rhythm can be stabilized, and the quality of steel can be improved.

Description

Technical Field

[0001] This application relates to a method for reducing the arsenic content in molten steel that exceeds the standard, and the resulting steel billet. Background Technology

[0002] In steelmaking, a "high scrap ratio" refers to the high proportion of scrap steel in the total raw materials (molten iron + scrap steel) during the steelmaking process, typically exceeding 20% ​​or even higher. This concept is one of the core technological directions for the steel industry's green and low-carbon transformation. Its core lies in reducing dependence on iron ore and increasing the recycling rate of scrap steel, thereby achieving resource conservation and reducing carbon emissions.

[0003] However, most of my country's iron ore is arsenic-containing iron ore, which can lead to excessive arsenic content in molten iron. This can cause problems such as surface cracking during hot working of steel, increased brittleness of steel, and reduced impact value and plasticity of steel. Summary of the Invention

[0004] This application provides a method for reducing the arsenic content in molten steel that exceeds the standard, and the resulting steel billet. This method can reduce the arsenic content in molten steel at low cost, stabilize the production rhythm, and improve the quality of steel.

[0005] In a first aspect, embodiments of this application provide a method for reducing the arsenic content in molten steel exceeding the standard, comprising: providing molten steel exceeding the standard, wherein the arsenic content in the molten steel exceeds the standard by more than 0.015%; providing scrap steel, wherein the scrap steel includes one or more of carbon scrap steel and low alloy scrap steel; providing refined molten steel, wherein the impurity elements in the refined molten steel are less than 0.013%, and the impurities include one or more of As, Cu, Mo and Ni; placing the molten steel exceeding the standard, the scrap steel and the refined molten steel in a refining furnace for mixing treatment; after deoxidation and desulfurization treatment, adding an arsenic removal agent to obtain clean molten steel, wherein the arsenic content in the clean molten steel is less than 0.015%.

[0006] In some embodiments, the mass ratio of substandard molten steel to refined molten steel is (0.10-0.20):1, and the mass ratio of scrap steel to refined molten steel is (0.05-0.15):1.

[0007] In some embodiments, the mass ratio of substandard molten steel to refined molten steel is (0.10-0.15):1, and the mass ratio of scrap steel to refined molten steel is (0.10-0.15):1.

[0008] In some embodiments, the arsenic removal agent comprises an Al-Mg-Ca alloy, wherein the Al-Mg-Ca alloy comprises Al, Mg, Ca and Fe, with Al accounting for 42% to 47% by mass, Mg accounting for 1.5% to 2.5% by mass, Ca accounting for 10% to 20% by mass, and Fe accounting for 37% to 42% by mass.

[0009] In some embodiments, the ratio of the mass of the arsenic removal agent to the total mass of the substandard molten steel, scrap steel and refined molten steel is (0.0015 to 0.0025):1.

[0010] In some embodiments, the step of mixing substandard molten steel, scrap steel, and refined molten steel in a refining furnace includes: heating the substandard molten steel to 1580–1630°C and adding it to a refining furnace containing refined molten steel, then adding scrap steel heated to 400–600°C, and melting the scrap steel through refining to obtain diluted molten steel after mixing.

[0011] In some embodiments, the refining process is carried out at a temperature of 1580–1630°C for a time of 50–100 min.

[0012] In some embodiments, the step of heating the substandard molten steel to 1580–1630°C and then adding it to a refining furnace containing refined molten steel further includes turning on argon gas at a rate of 250–350 L / min at the bottom of the refining furnace.

[0013] In some embodiments, the mass percentage of oxygen after deoxidation and desulfurization treatment is less than 0.005%, and the mass percentage of sulfur is less than 0.01%.

[0014] Secondly, embodiments of this application provide a steel billet, comprising a steel billet obtained by continuous casting of clean molten steel obtained by the method provided in the first aspect. Detailed Implementation

[0015] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0016] Many specific details are set forth in the following description in order to provide a full understanding of this application, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0017] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0018] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0019] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0020] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0021] Unless otherwise specified, in this application, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0022] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0023] In the description of the embodiments of this application, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0024] In view of the problems in the background technology, this application provides a method for reducing the arsenic content in molten steel that exceeds the standard and the resulting steel billet, which can reduce the arsenic content in molten steel at low cost, stabilize the production rhythm, and improve the quality of steel.

[0025] Methods to reduce arsenic content in molten steel

[0026] A method for reducing the arsenic content in molten steel exceeding the standard includes: providing molten steel exceeding the standard, wherein the arsenic content in the molten steel is higher than 0.015%; providing scrap steel, wherein the scrap steel includes one or more of carbon scrap steel and low alloy scrap steel; providing refined molten steel, wherein the impurity elements in the refined molten steel are less than 0.013%, and the impurities include one or more of As, Cu, Mo, and Ni; mixing the molten steel exceeding the standard, the scrap steel, and the refined molten steel in a refining furnace; after deoxidation and desulfurization treatment, adding an arsenic removal agent to obtain clean molten steel, wherein the arsenic content in the clean molten steel is less than 0.015%.

[0027] A high scrap steel ratio refers to a high proportion of scrap steel in the total raw materials (molten iron + scrap steel) during steelmaking. This process can improve the recycling rate of scrap steel, thereby achieving resource conservation and reducing carbon emissions. However, most of my country's iron ore is arsenic-containing, which leads to excessive arsenic content in molten iron, resulting in excessive arsenic content in molten steel with a high scrap steel ratio. Related technologies typically employ processes such as molten iron pretreatment oxidation, vacuum refining, and rare earth purification to reduce arsenic content, but these are costly and detrimental to production line stability.

[0028] This application embodiment dilutes the arsenic content in excessive molten steel, scrap steel, and refined molten steel at low cost by mixing them. Then, after deoxidation and desulfurization treatment, an arsenic removal agent is added, utilizing the physical and chemical adsorption of arsenic by the agent to further reduce the arsenic content. Since the dilution effect of the scrap steel and refined molten steel already reduces the arsenic content to some extent, the amount of arsenic removal agent used can be reduced, further lowering the arsenic removal cost. Simultaneously, the dilution effect of the scrap steel and refined molten steel also reduces the possibility of arsenic hindering adsorption on the surface of the arsenic removal agent.

[0029] The refining furnace of this application embodiment can melt scrap steel in a very short time to fully mix and dilute the substandard molten steel with the refined molten steel; then the mixed molten steel is deoxidized and desulfurized to reduce the oxygen and sulfur content in the mixed molten steel, thereby reducing the possibility that oxygen and sulfur will cause the arsenic removal agent to fail.

[0030] The molten steel exceeding the standard in this application embodiment may be molten steel with excessive arsenic content in the LF refining furnace.

[0031] The scrap steel in this embodiment includes one or more of carbon scrap steel and low-alloy scrap steel, both with low alloy element content, which reduces the possibility of introducing impurities. Specifically, carbon scrap steel is mainly composed of iron and carbon, with an alloy element content of less than 0.5%; low-alloy scrap steel contains alloy elements ranging from 0.5% to 5%, which allows for the utilization of recycled alloy elements while reducing the possibility of introducing impurities and minimizing the use of additives.

[0032] The refined steel in this application refers to high-quality liquid steel produced through a secondary refining process that deeply purifies, fine-tunes the composition, and optimizes the temperature of primary steel refined in a converter or electric furnace. This is a crucial step in the production of clean steel and special steel. The refined steel in this application has a low arsenic content and can be categorized according to steel type as stainless steel refined steel, carbon steel refined steel, and alloy steel refined steel.

[0033] In some embodiments, the mass ratio of substandard molten steel to refined molten steel is (0.10 to 0.20):1, for example, it can be 0.10:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1, 0.20:1, or any range of the above values; the mass ratio of scrap steel to refined molten steel is (0.05 to 0.15):1, for example, it can be 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.10:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, or any range of the above values.

[0034] Optionally, the mass ratio of substandard molten steel to refined molten steel is (0.10-0.15):1, and the mass ratio of scrap steel to refined molten steel is (0.10-0.15):1.

[0035] Alternatively, the mass ratio of substandard molten steel to refined molten steel is 0.10:1, and the mass ratio of scrap steel to refined molten steel is 0.15:1.

[0036] A suitable ratio of substandard molten steel, refined molten steel, and scrap steel can better dilute the substandard molten steel to reduce the arsenic content in the system. At the same time, it can reduce dependence on iron ore and improve the recycling rate of scrap steel, thereby achieving resource conservation and carbon emission reduction.

[0037] In some embodiments, the arsenic removal agent comprises an Al-Mg-Ca alloy, wherein the Al-Mg-Ca alloy comprises Al, Mg, Ca and Fe, with Al accounting for 42% to 47% by mass, Mg accounting for 1.5% to 2.5% by mass, Ca accounting for 10% to 20% by mass, and Fe accounting for 37% to 42% by mass.

[0038] Al-Mg-Ca alloy is a lightweight metallic material with Al as the matrix and Mg and Ca as the main alloying elements. Al-Mg-Ca alloys with a suitable composition can effectively remove arsenic (As) through chemical reactions and adsorption. Specifically, Al reacts with As to form stable AlAs, reducing the As content; Mg reacts with As to form Mg3As2, further reducing the As content; Ca reacts with As to form Ca3As2, enhancing the arsenic removal effect; and the porous structure of Al-Mg-Ca alloys can physically adsorb arsenic and its compounds, further improving the arsenic removal efficiency.

[0039] In some embodiments, the ratio of the mass of the arsenic removal agent to the total mass of the molten steel exceeding the standard, scrap steel, and refined molten steel is (0.0015 to 0.0025):1, for example, it can be 0.0015:1, 0.0016:1, 0.0017:1, 0.0018:1, 0.0019:1, 0.0020:1, 0.0021:1, 0.0022:1, 0.0023:1, 0.0024:1, 0.0025:1, or any range of the above values.

[0040] Arsenic removal agents with appropriate content can better reduce the arsenic content in molten steel, while also reducing the possibility of excessive alloy residues contaminating the molten steel.

[0041] In some embodiments, the step of mixing substandard molten steel, scrap steel, and refined molten steel in a refining furnace includes: heating the substandard molten steel to 1580–1630°C and adding it to a refining furnace containing refined molten steel, then adding scrap steel heated to 400–600°C, and melting the scrap steel through refining to obtain diluted molten steel after mixing.

[0042] In this embodiment, when mixing substandard molten steel, scrap steel, and refined steel, heating the substandard molten steel can reduce the possibility of solid phase precipitation. Heating the scrap steel to a suitable temperature can increase the oxygen content in the scrap steel, thereby oxidizing the arsenic impurities in the molten steel and further reducing the arsenic content. It also reduces the risk of scrap steel sticking together. In contrast, related technologies only heat the scrap steel to around 100°C to reduce the amount of iron oxide generated, thus reducing the amount of aluminum blocks needed for deoxidation, lowering costs. However, this process is limited by production schedule and heating equipment, resulting in short heating times and temperatures only reaching 100°C. Deoxidation is then performed later, with the aim of reducing the oxygen content in the scrap steel.

[0043] In some embodiments, the refining process is carried out at a temperature of 1580–1630°C for a time of 50–100 min.

[0044] Optionally, the refining temperature is independently selected from any value of 1580°C, 1590°C, 1600°C, 1610°C, 1620°C, or a range between any two.

[0045] Optionally, the refining time is independently selected from any value or a range between 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, 95 min, and 100 min.

[0046] The refining process described in this application, with appropriate temperature and time, can utilize the electric arc heat of the refining furnace to convert scrap steel into molten steel, thereby fully mixing it with the substandard molten steel and refined molten steel to achieve the purpose of diluting the arsenic content; it can also increase the chemical reaction rate of the arsenic removal agent to improve the arsenic removal effect of the arsenic removal agent.

[0047] In some embodiments, the step of heating the substandard molten steel to 1580–1630°C and then adding it to a refining furnace containing refined molten steel further includes turning on argon gas at a rate of 250–350 L / min at the bottom of the refining furnace. For example, the argon gas rate can be 250 L / min, 260 L / min, 270 L / min, 280 L / min, 290 L / min, 300 L / min, 310 L / min, 320 L / min, 330 L / min, 340 L / min, 350 L / min, or any range of the above values.

[0048] In this embodiment of the application, before adding substandard molten steel to the refining furnace containing refined molten steel, 250-350 L / min of argon gas is turned on at the bottom of the refining furnace to reduce the possibility of cold steel forming in the refining furnace.

[0049] In some embodiments, the mass percentage of oxygen after deoxidation and desulfurization treatment is less than 0.005%, and the mass percentage of sulfur is less than 0.01%.

[0050] The embodiments of this application perform deoxidation and desulfurization treatment on mixed molten steel, which can reduce the content of oxygen and sulfur, thereby reducing the possibility of oxygen and sulfur oxidizing the arsenic removal agent, and thus improving the arsenic removal effect of the arsenic removal agent.

[0051] Example

[0052] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0053] Example 1

[0054] The As content in the molten iron of No. 1 LF refining furnace was 0.023%, which was considered excessive molten steel.

[0055] After raising the temperature of the substandard molten steel to 1620℃, the dispatching room arranged for a crane to lift the substandard molten steel to the No. 3 LF refining furnace. Argon gas was turned on at a rate of 300 L / min at the bottom. The operator directed the crane to slowly pour the substandard molten steel into an empty ladle. Then, the refined molten steel from the No. 2 LF refining furnace was poured into the No. 3 LF ladle. The ladle was then moved to the scrap steel position, and scrap steel heated to 500℃ was added. Refining was carried out at 1580–1630℃ for 55 minutes to obtain diluted molten steel. The quality of the substandard molten steel and the refined molten steel was compared. The mass ratio of scrap steel to refined molten steel is 0.11:1, and the mass ratio of scrap steel to refined molten steel is 0.14:1. At this point, the As content in the diluted molten steel is 0.0208%. The diluted molten steel is then desulfurized and deoxidized until the sulfur content is 0.007% and the oxygen content is 22%. An arsenic removal agent, Al-Mg-Ca alloy, is added, and the mass ratio of the arsenic removal agent to the total mass of the diluted molten steel is 0.0020:1, resulting in clean molten steel with an As content of 0.0136%. The steel is then hoisted onto a continuous casting machine for casting to obtain a steel billet.

[0056] In the Al-Mg-Ca alloy arsenic removal agent, Al accounts for 45% by mass, Mg accounts for 2% by mass, Ca accounts for 14% by mass, and Fe accounts for 39% by mass.

[0057] Examples 2-9

[0058] The experimental procedure was the same as in Example 1, except that the amounts of substandard molten steel, refined molten steel, and scrap steel added, the amount of arsenic removal agent added, and the temperature of the scrap steel were different. See Table 1 for details.

[0059] Comparative Example 1

[0060] The experimental procedure is the same as in Example 1, except that no arsenic removal agent is added. See Table 1 for details.

[0061] Comparative Example 2

[0062] The experimental procedure is the same as in Example 1, except that scrap steel and refined steel are not added. See Table 1 for details.

[0063] Table 1

[0064]

[0065] As can be seen from the examples and comparative examples, the dilution effect of scrap steel and refined molten steel and the physicochemical adsorption effect of the arsenic removal agent can work synergistically to reduce the arsenic content in molten steel at low cost, stabilize the production rhythm, and improve the quality of steel.

[0066] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A method for reducing the arsenic content in molten steel exceeding the standard, characterized in that, include: Providing molten steel that exceeds the standard, wherein the arsenic content in the molten steel is higher than 0.015%. The scrap steel provided includes one or more of carbon scrap steel and low-alloy scrap steel. The refined steel is provided, wherein the impurity elements in the refined steel are less than 0.013%, and the impurity elements include one or more of As, Cu, Mo and Ni; The substandard molten steel, the scrap steel, and the refined molten steel are mixed in a refining furnace. After deoxidation and desulfurization, an arsenic removal agent is added to obtain clean molten steel with an arsenic content of less than 0.015%. The mass ratio of the substandard molten steel to the refined molten steel is (0.10~0.20):1, and the mass ratio of the scrap steel to the refined molten steel is (0.05~0.15):

1. The arsenic removal agent comprises an Al-Mg-Ca alloy, wherein the Al-Mg-Ca alloy comprises Al, Mg, Ca, and Fe, with Al accounting for 42%~47% of the mass, Mg accounting for 1.5%~2.5% of the mass, Ca accounting for 10%~20% of the mass, and Fe accounting for 37%~42% of the mass. The mass ratio of the arsenic removal agent to the total mass of the substandard molten steel, the scrap steel, and the refined molten steel is (0.0015~0.0025):

1.

2. The method according to claim 1, characterized in that, The mass ratio of the substandard molten steel to the refined molten steel is (0.10~0.15):1, and the mass ratio of the scrap steel to the refined molten steel is (0.10~0.15):

1.

3. The method according to claim 1, characterized in that, The step of mixing the substandard molten steel, the scrap steel, and the refined molten steel in a refining furnace includes: The substandard molten steel is heated to 1580~1630℃ and then added to a refining furnace containing the refined molten steel. Then, scrap steel heated to 400~600℃ is added. After refining, the scrap steel is melted to obtain diluted molten steel.

4. The method according to claim 3, characterized in that, The refining process is carried out at a temperature of 1580~1630℃ for 50~100 minutes.

5. The method according to claim 3, characterized in that, The step of heating the substandard molten steel to 1580~1630℃ and then adding it to a refining furnace containing the refined molten steel also includes turning on argon gas at a rate of 250~350L / min at the bottom of the refining furnace.

6. The method according to claim 1, characterized in that, After the deoxygenation and desulfurization treatment, the mass percentage of oxygen is less than 0.005%, and the mass percentage of sulfur is less than 0.01%.

7. A steel billet, characterized in that, The steel billet is obtained by the method described in any one of claims 1-6.

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