A desulphurization method for a full scrap electric arc furnace process

Abstract

The application relates to a desulfurization method of a full scrap steel electric furnace process, and belongs to the technical field of metal smelting. The method comprises the following steps: smelting full scrap steel by using an electric furnace, performing bubble-foaming slag treatment, and obtaining smelting molten steel; tapping the smelting molten steel, performing slag washing desulfurization, and obtaining intermediate molten steel; performing VD vacuum degassing treatment on the intermediate molten steel, obtaining desulfurized molten steel, and completing desulfurization; the method adopts an electric furnace plus VD vacuum degassing process, rapidly realizes the desulfurization, denitrification and dehydrogenation requirements of high-grade steel, reaches target components, and improves the problem that nitrogen is easily increased in the desulfurization process of electric furnace steelmaking.

Description

Technical Field

[0001] This application relates to the field of metal smelting technology, and in particular to a desulfurization method for an all-scrap electric furnace process. Background Technology

[0002] Currently, the steel industry still heavily relies on coal-based fossil fuels, resulting in large carbon emissions. Therefore, effectively reducing carbon emissions during steel production has become a critical issue that urgently needs to be addressed by the steel industry and the nation as a whole. The low proportion of steel produced by electric arc furnaces is one of the important reasons for the steel industry's high carbon emissions, high energy consumption, and heavy pollution. Developing electric arc furnace short-process steel production offers significant advantages in energy conservation and emission reduction.

[0003] As users increasingly demand higher steel quality, the requirements for molten steel cleanliness are also becoming more stringent, especially regarding sulfur content. Most domestic steel mills use a converter long-process production line, which can desulfurize through hot metal pretreatment. Electric arc furnace (EAF) processes lack desulfurization facilities, thus placing strict requirements on raw materials and refining processes. Furthermore, since EAF processes primarily use scrap steel, which comes from a wide range of sources and contains numerous impurities, desulfurization in EAF production presents challenges. The traditional process uses an EAF combined with LF desulfurization, but the LF refining process is prone to nitrogen accumulation, and denitrification and dehydrogenation are difficult throughout the entire process. Summary of the Invention

[0004] This application provides a desulfurization method for an all-scrap electric arc furnace process to improve the problem of nitrogen increase during the desulfurization process in current electric arc furnace steelmaking.

[0005] This application provides a desulfurization method for an all-scrap electric arc furnace process, the method comprising:

[0006] The scrap steel is smelted in an electric furnace and treated with foamed slag to obtain molten steel.

[0007] The molten steel is tapped and then subjected to slag washing and desulfurization to obtain intermediate molten steel.

[0008] The intermediate molten steel is subjected to VD vacuum degassing treatment to obtain desulfurized molten steel, thus completing the desulfurization process.

[0009] As an optional implementation, the vacuum degree of the VD vacuum degassing treatment is 60 Pa to 80 Pa; and / or

[0010] The VD vacuum degassing treatment time is 10 min to 30 min.

[0011] As an optional implementation, the composition of the scrap steel, by mass fraction, includes: C: 0.03%–20%, Si: 0.15%–0.5%, Mn: 0.10%–0.5%, P: 0.005%–0.045%, S: 0.002%–0.035%, with the remainder being Fe and unavoidable impurities.

[0012] As an optional implementation, the oxygen supply for the smelting process is 25m³. 3 / t steel ~ 42m 3 / t steel; and / or

[0013] The number of oxygen lances used for oxygen supply in the smelting process shall not be less than three.

[0014] As an optional implementation, the foaming slag treatment includes adding a first lime, dolomite, and carbon powder during the smelting process.

[0015] As an optional implementation, the amount of the first lime added is 35 kg / t steel to 40 kg / t steel; and / or

[0016] The amount of dolomite added is 6 kg / t steel to 10 kg / t steel; and / or

[0017] The amount of carbon powder added is 20 kg / t steel to 30 kg / t steel.

[0018] As an optional implementation, the slag washing desulfurization includes adding aluminum, a second lime, and fluorite during the steel tapping process.

[0019] As an optional implementation, the amount of aluminum added is 2 kg / t steel to 2.3 kg / t steel; and / or

[0020] The amount of the second lime added is 12 kg / t steel to 18 kg / t steel; and / or

[0021] The amount of fluorite added is 4 kg / t steel to 8 kg / t steel.

[0022] As an optional implementation, the timing of the steel tapping initiation satisfies at least one of the following:

[0023] a) The carbon content in the molten steel is 0.03% to 0.2% by mass;

[0024] b) The phosphorus content in the molten steel is not higher than 0.02% by mass;

[0025] c) The sulfur content in the molten steel is not higher than 0.12% by mass;

[0026] d) The temperature of the molten steel is 1600℃~1680℃.

[0027] As an optional implementation, the composition of the desulfurized steel liquid, by mass fraction, includes: C: 0.03% to 0.60%, Si: 0.05% to 0.50%, Mn: 0.05% to 0.95%, P: <0.015%, S: <0.010%, Als: 0.010% to 0.050%, with the remainder being Fe and unavoidable impurities.

[0028] The technical solutions provided in this application have the following advantages compared with the prior art:

[0029] The method provided in this application adopts an electric arc furnace plus VD vacuum degassing process to quickly achieve the requirements of desulfurization, denitrification and dehydrogenation of high-grade steel, and achieve the target composition, thereby improving the problem of nitrogen increase during the desulfurization process of electric arc furnace steelmaking. Attached Figure Description

[0030] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0031] To more clearly illustrate the technical solutions in the embodiments of this application 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.

[0032] Figure 1 This is a flowchart illustrating the method provided in an embodiment of this application. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0035] Electric arc furnace (EAF) processes lack desulfurization facilities, thus imposing stringent requirements on raw materials and refining processes. Furthermore, the primary raw material used in EAF processes is scrap steel, which comes from a wide range of sources and contains numerous impurities, posing challenges to desulfurization in EAF production. Traditional methods employ an EAF combined with LF (sulfurization-extraction) desulfurization, but the LF refining process is prone to nitrogen accumulation, and denitrification and dehydrogenation are difficult throughout the entire process.

[0036] Therefore, this application intends to provide a desulfurization method for all-scrap steel electric arc furnace process. Since the raw materials of electric arc furnace have many harmful elements, the process settings have been optimized, and an electric arc furnace plus VD vacuum degassing process is adopted to quickly achieve the requirements of desulfurization, denitrification and dehydrogenation of high-grade steel and achieve the target composition.

[0037] Figure 1 A flowchart illustrating the method provided in the embodiments of this application, as shown below. Figure 1 As shown in the embodiment of this application, a desulfurization method for an all-scrap electric arc furnace process is provided, the method comprising:

[0038] S1. Use an electric furnace (or electric arc furnace) to smelt all scrap steel and treat it with foam slag to obtain molten steel;

[0039] In some embodiments, the composition of the scrap steel, by mass fraction, includes: C: 0.03% to 20%, Si: 0.15% to 0.5%, Mn: 0.10% to 0.5%, P: 0.005% to 0.045%, S: 0.002% to 0.035%, with the remainder being Fe and unavoidable impurities.

[0040] In some embodiments, the oxygen supply during the smelting process is 25m³. 3 / t steel ~ 42m 3 / t steel; the number of oxygen lances supplying oxygen in the smelting process shall not be less than 3.

[0041] For example, the oxygen supply during the smelting process can be 25m³. 3 / t steel, 26m 3 / t steel, 27m 3 / t steel, 28m 3 / t steel, 29m 3 / t steel, 30m 3 / t steel, 31m 3 / t steel, 32m 3 / t steel, 33m 3 / t steel, 34m 3 / t steel, 35m 3 / t steel, 36m 3 / t steel, 37m 3 / t steel, 38m 3 / t steel, 39m 3 / t steel, 40m 3 / t steel, 41m 3 / t steel or 42m 3 / t steel, etc., which can also be 25m 3 / t steel ~ 42m 3 Any value within the range of / t steel. It should be noted that m 3 / t steel refers to the oxygen supply volume per ton of total scrap steel, for example, an oxygen supply of 2.5m³. 3 / t steel refers to the oxygen supply of 25m³ per ton of complete scrap steel. 3 .

[0042] In some embodiments, the foaming slag treatment includes adding a first lime, dolomite, and carbon powder during the smelting process. The first lime is added at a rate of 35 kg / t steel to 40 kg / t steel; the dolomite is added at a rate of 6 kg / t steel to 10 kg / t steel; and the carbon powder is added at a rate of 20 kg / t steel to 30 kg / t steel.

[0043] Lime is an air-hardening inorganic cementing material with calcium oxide as its main component. Lime is produced by calcining products with high calcium carbonate content, such as limestone, dolomite, chalk, and seashells, at 900–1100℃.

[0044] Dolomite's chemical composition includes CaMg(CO3)2, and it is a carbonate mineral belonging to the trigonal crystal system. There are two main types: iron dolomite and manganese dolomite. Dolomite's crystal structure is similar to calcite, with rhombohedral crystals. The crystal faces are often curved into a saddle shape, and polysynthetic twinning is common. It mostly occurs in massive or granular aggregates.

[0045] For example, the amount of carbon powder added can be 20 kg / t steel, 21 kg / t steel, 22 kg / t steel, 23 kg / t steel, 24 kg / t steel, 25 kg / t steel, 26 kg / t steel, 27 kg / t steel, 28 kg / t steel, 29 kg / t steel, or 30 kg / t steel, etc., or any value within the range of 20 kg / t steel to 30 kg / t steel. It should be noted that kg / t steel refers to the mass amount of lime, dolomite, or carbon powder used per ton of total scrap steel. For example, a carbon powder addition of 20 kg / t steel means that the amount of carbon powder used per ton of total scrap steel is 20 kg.

[0046] S2. The molten steel is tapped and then subjected to slag washing and desulfurization to obtain intermediate molten steel;

[0047] In some embodiments, the timing for initiating the tapping is such that at least one of the following conditions is met: a) the carbon content in the molten steel is 0.03% to 0.2% by mass; b) the phosphorus content in the molten steel is not higher than 0.02% by mass; c) the sulfur content in the molten steel is not higher than 0.12% by mass; d) the temperature of the molten steel is 1600°C to 1680°C.

[0048] In some embodiments, the slag washing desulfurization includes adding aluminum, a second lime, and fluorite during the steel tapping process.

[0049] The amount of aluminum added is 2 kg / t steel to 2.3 kg / t steel; the amount of the second lime added is 12 kg / t steel to 18 kg / t steel; and the amount of fluorite added is 4 kg / t steel to 8 kg / t steel.

[0050] S3. Perform VD vacuum degassing treatment on the intermediate molten steel to obtain desulfurized molten steel, thus completing the desulfurization process.

[0051] In some embodiments, the vacuum degree of the VD vacuum degassing treatment is 60 Pa to 80 Pa; the VD vacuum degassing treatment time is 10 min to 30 min. By controlling the vacuum degree and treatment time of the VD vacuum degassing treatment within a suitable range, it is beneficial to achieve sulfur removal and thus achieve the target composition.

[0052] In some embodiments, the composition of the desulfurized molten steel, by mass fraction, includes: C: 0.03%–0.60%, Si: 0.05%–0.50%, Mn: 0.05%–0.95%, P: <0.015%, S: <0.010%, Als: 0.010%–0.050%, with the remainder being Fe and unavoidable impurities.

[0053] Specifically, in this embodiment, the entire desulfurization process of the all-scrap electric arc furnace can be as follows: all scrap steel is added into the electric arc furnace, then the electric arc furnace is powered on (using a 45MVA transformer for power supply) and oxygen is blown in for smelting; during the smelting process, lime, dolomite, and carbon powder are added to create foamy slag until the final tapping requirements are met: carbon 0.03% to 0.20%, phosphorus not exceeding 0.020%, sulfur not exceeding 0.12%, and temperature 1600℃ to 1680℃; then aluminum, lime, and fluorite are added during tapping for slag washing and desulfurization; the molten steel enters the VD vacuum degassing device for vacuum stirring; the vacuum degree is 67Pa, and the vacuum time is 20 minutes.

[0054] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0055] Example 1

[0056] A desulfurization method for an all-scrap electric arc furnace process, the method comprising:

[0057] S1. A 70-ton electric furnace is used to smelt 72 tons of scrap steel. During the smelting process, first lime, dolomite, and carbon powder are added to create foamy slag to obtain molten steel. Among them, the amount of first lime is 2500 kg, the amount of dolomite is 500 kg, and the amount of carbon powder is 50 kg.

[0058] S2. The molten steel is tapped, and aluminum, second lime, and fluorite are added during the tapping process for slag washing and desulfurization to obtain intermediate molten steel; wherein the amount of aluminum is 132 kg, the amount of second lime is 1000 kg, and the amount of fluorite is 200 kg.

[0059] S3. The intermediate molten steel is subjected to VD vacuum degassing treatment to obtain desulfurized molten steel, thus completing the desulfurization process; wherein, the vacuum degree of the VD vacuum degassing treatment is 67 Pa and the vacuum time is 20 minutes.

[0060] The composition of molten steel in each smelting process is shown in the table below:

[0061]

[0062] Example 2

[0063] A desulfurization method for an all-scrap electric arc furnace process, the method comprising:

[0064] S1. A 70-ton electric furnace is used to smelt 72 tons of scrap steel. During the smelting process, first lime, dolomite, and carbon powder are added to create foamy slag to obtain molten steel. Among them, the amount of first lime is 2500 kg, the amount of dolomite is 500 kg, and the amount of carbon powder is 50 kg.

[0065] S2. The molten steel is tapped, and aluminum, second lime, and fluorite are added during the tapping process for slag washing and desulfurization to obtain intermediate molten steel; wherein the amount of aluminum is 132 kg, the amount of second lime is 1000 kg, and the amount of fluorite is 200 kg.

[0066] S3. The intermediate molten steel is subjected to VD vacuum degassing treatment to obtain desulfurized molten steel, thus completing the desulfurization process; wherein, the vacuum degree of the VD vacuum degassing treatment is 67 Pa and the vacuum time is 20 minutes.

[0067] The composition of molten steel in each smelting process is shown in the table below:

[0068]

[0069] Example 3

[0070] A desulfurization method for an all-scrap electric arc furnace process, the method comprising:

[0071] S1. A 70-ton electric furnace is used to smelt 72 tons of scrap steel. During the smelting process, first lime, dolomite, and carbon powder are added to create foamy slag to obtain molten steel. Among them, the amount of first lime is 2500 kg, the amount of dolomite is 500 kg, and the amount of carbon powder is 50 kg.

[0072] S2. The molten steel is tapped, and aluminum, second lime, and fluorite are added during the tapping process for slag washing and desulfurization to obtain intermediate molten steel; wherein the amount of aluminum is 132 kg, the amount of second lime is 1000 kg, and the amount of fluorite is 200 kg.

[0073] S3. The intermediate molten steel is subjected to VD vacuum degassing treatment to obtain desulfurized molten steel, thus completing the desulfurization process; wherein, the vacuum degree of the VD vacuum degassing treatment is 67 Pa and the vacuum time is 20 minutes.

[0074] The composition of molten steel in each smelting process is shown in the table below:

[0075]

[0076]

[0077] Comparative Example 1

[0078] A desulfurization method for an all-scrap electric arc furnace process, the method comprising:

[0079] S1. A 70-ton electric furnace is used to smelt 72 tons of scrap steel. During the smelting process, first lime, dolomite, and carbon powder are added to create foamy slag to obtain molten steel. Among them, the amount of first lime is 2500 kg, the amount of dolomite is 100 kg, and the amount of carbon powder is 50 kg.

[0080] S2. The molten steel is tapped, and aluminum, second lime, and fluorite are added during the tapping process for slag washing and desulfurization to obtain intermediate molten steel; wherein the amount of aluminum is 132 kg, the amount of second lime is 1000 kg, and the amount of fluorite is 200 kg.

[0081] S3. The intermediate molten steel is subjected to LF smelting treatment to obtain desulfurized molten steel, thus completing the desulfurization process.

[0082] The composition of molten steel in each smelting process is shown in the table below:

[0083]

[0084] Comparative Example 2

[0085] A desulfurization method for an all-scrap electric arc furnace process, the method comprising:

[0086] S1. A 70-ton electric furnace is used to smelt 72 tons of scrap steel. During the smelting process, first lime, dolomite, and carbon powder are added to create foamy slag to obtain molten steel. Among them, the amount of first lime is 2500 kg, the amount of dolomite is 100 kg, and the amount of carbon powder is 50 kg.

[0087] S2. The molten steel is tapped, and aluminum, second lime, and fluorite are added during the tapping process for slag washing and desulfurization to obtain intermediate molten steel; wherein the amount of aluminum is 132 kg, the amount of second lime is 1000 kg, and the amount of fluorite is 200 kg.

[0088] S3. The intermediate molten steel is subjected to LF smelting treatment to obtain desulfurized molten steel, thus completing the desulfurization process.

[0089] The composition of molten steel in each smelting process is shown in the table below:

[0090]

[0091] Comparative Example 3

[0092] A desulfurization method for an all-scrap electric arc furnace process, the method comprising:

[0093] S1. A 70-ton electric furnace is used to smelt 72 tons of scrap steel. During the smelting process, first lime, dolomite, and carbon powder are added to create foamy slag to obtain molten steel. Among them, the amount of first lime is 2500 kg, the amount of dolomite is 500 kg, and the amount of carbon powder is 50 kg.

[0094] S2. The molten steel is tapped, and aluminum, second lime, and fluorite are added during the tapping process for slag washing and desulfurization to obtain intermediate molten steel; wherein the amount of aluminum is 132 kg, the amount of second lime is 1000 kg, and the amount of fluorite is 200 kg.

[0095] S3. The intermediate molten steel is subjected to LF smelting treatment to obtain desulfurized molten steel, thus completing the desulfurization process.

[0096] The composition of molten steel in each smelting process is shown in the table below:

[0097]

[0098] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0099] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b or c" or "at least one of a, b and c" can both mean: a, b, c, ab (i.e. a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0100] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. 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 this application. Therefore, this application 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 desulfurization method for an all-scrap electric arc furnace process, characterized in that, The method includes: The scrap steel is smelted in an electric furnace and treated with foamed slag to obtain molten steel. The molten steel is tapped and then subjected to slag washing and desulfurization to obtain intermediate molten steel. The intermediate molten steel is subjected to VD vacuum degassing treatment to obtain desulfurized molten steel, thus completing the desulfurization process; The vacuum degree of the VD vacuum degassing treatment is 60Pa~80Pa; the VD vacuum degassing treatment time is 10min~30min; The timing for initiating steel tapping shall satisfy at least one of the following: a) The carbon content in the molten steel is 0.03%~0.2% by mass; b) The phosphorus content in the molten steel is not higher than 0.02% by mass; c) The sulfur content in the molten steel is not higher than 0.12% by mass; d) The temperature of the molten steel is 1600℃~1680℃; The foaming slag treatment includes adding first lime, dolomite and carbon powder during the smelting process; the amount of first lime added is 35 kg / t steel to 40 kg / t steel; the amount of dolomite added is 6 kg / t steel to 10 kg / t steel; and the amount of carbon powder added is 20 kg / t steel to 30 kg / t steel.

2. The desulfurization method for the all-scrap electric arc furnace process according to claim 1, characterized in that, The composition of the scrap steel, by mass fraction, includes: C: 0.03%~20%, Si: 0.15%~0.5%, Mn: 0.10%~0.5%, P: 0.005%~0.045%, S: 0.002%~0.035%, with the remainder being Fe and unavoidable impurities.

3. The desulfurization method for the all-scrap electric arc furnace process according to claim 1, characterized in that, The oxygen supply for the smelting process is 25 m³. 3 / t steel ~42 m 3 / t steel; and / or The number of oxygen lances used for oxygen supply in the smelting process shall not be less than three.

4. The desulfurization method for the all-scrap electric arc furnace process according to claim 1, characterized in that, The slag washing desulfurization includes adding aluminum, a second lime, and fluorite during the steel tapping process.

5. The desulfurization method for the all-scrap electric arc furnace process according to claim 4, characterized in that, The amount of aluminum added is 2 kg / t steel to 2.3 kg / t steel; and / or The amount of the second lime added is 12 kg / t steel to 18 kg / t steel; and / or The amount of fluorite added is 2 kg / t steel to 4 kg / t steel.

6. The desulfurization method for the all-scrap electric arc furnace process according to claim 1, characterized in that, The composition of the desulfurized molten steel, by mass fraction, includes: C: 0.03%~0.60%, Si: 0.05%~0.50%, Mn: 0.05%~0.95%, P: <0.015%, S: <0.010%, Als: 0.010%~0.050%, with the remainder being Fe and unavoidable impurities.

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