Composite slag changing process for LF (ladle furnace)

Abstract

The invention discloses a composite slag changing process for an LF refining furnace, and belongs to the technical field of metallurgy. The technical scheme that the oxygen content is controlled in the converter process and Si return is controlled in the LF refining process is adopted for slab low-silicon aluminum-containing steel with Si smaller than or equal to 0.03%. The oxygen control target range in the converter process is 400-600 ppm; 400-600 kg of lime is added in 2-3 batches in the LF refining process, and aluminum particles, cut aluminum and calcium carbide are adopted for composite slag modification; and the Si control target range is less than or equal to 0.03%. According to the process technology, the slagging and desulfurization rate is increased, the problem of large-bale flocculation flow in the production process of the slab low-silicon aluminum-containing steel is solved, and the quality requirement of the slab low-silicon aluminum-containing steel is met.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a composite slag reforming process for an LF refining furnace. Background Art

[0002] At present, the slab low-carbon, low-silicon aluminum-containing steel production process implements the LF furnace refining process path and adopts the "light desulfurization, no calcium treatment" production mode. The production process is accompanied by the frequent return of large bags of residual water to the furnace at the end of casting, and the large bag flocculation phenomenon is serious, which affects the normal production order and has a great impact on the improvement of production efficiency, reduction of production costs, variety quality control, overall performance, etc., and urgently needs to be improved. Summary of the invention

[0003] In order to overcome the defects of the above-mentioned prior art, the present invention is aimed at low-silicon aluminum-containing steel in slabs with Si≤0.03%, controls the oxygen content in the converter process and controls the return Si in the LF refining process, thereby improving the slag desulfurization rate and solving the large-bag flocculent flow phenomenon in the production process of low-silicon aluminum-containing steel in slabs, thereby meeting the quality requirements of low-silicon aluminum-containing steel in slabs.

[0004] In order to achieve the above-mentioned invention object, the present invention provides a composite slag modification process for LF refining furnace, the process comprising: controlling the oxygen content in the converter process and controlling the return of Si in the LF refining process, adjusting the LF slag system, reducing the Al2O3 ratio in the slag, and improving the slag fluidity, wherein:

[0005] ①Converter process

[0006] ⑴ End point carbon pulling: time ≥ 1min, ensure the carbon pulling gun position, the end point carbon control target is "release upper limit -0.015%", the oxygen control target range is 400 ~ 600ppm, prevent over-blowing and spot blowing.

[0007] (2) When the oxygen content is greater than 600ppm, the aluminum deoxidation and alloying process shall be followed to prevent low carbon and high oxygen at the end point, oxygen retention in the steel making leading to difficulties in refining and increased inclusions and flocculants.

[0008] (3) Argon station: blow argon for 3 minutes, fix oxygen, feed aluminum wire (reference dosage of aluminum wire is: "oxygen value / 1.5+200"m), Al control target range is 0.015%~0.035%.

[0009] ②LF refining process

[0010] ⑴ Lime: Add 400-600kg in 2-3 batches, each batch ≤300kg, and the interval between batches is about 1min; when the S content of molten steel in the converter or argon station process is greater than the "release upper limit -0.002%", the lime can be appropriately increased by 300-500kg / furnace according to the sulfur content.

[0011] (2) Aluminum particles, cut aluminum and calcium carbide are used for composite slag reforming. During slag formation, aluminum particles are added in two batches. The first batch is 15 kg and the second batch is 10-16 kg. 40-60 kg of cut aluminum is added in batches, and calcium carbide is used to submerge the arc to form slag. Rapid slag formation is conducive to the floating of inclusions, ensuring the castability of molten steel and product quality.

[0012] ⑶ Late deoxidation: Use cutting aluminum to add in 4 to 6 batches. The addition of cutting aluminum requires less frequent addition.

[0013] ⑷ Slag condition at leaving the station: good fluidity, slag color is glassy light green slag.

[0014] ⑸ Secondary aluminum adjustment ensures that the power-on time is ≥5min.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention aims at low-silicon aluminum-containing steel with Si≤0.03% in slabs, controls the oxygen content in the converter process and controls the returned Si in the LF refining process, thereby improving the slag desulfurization rate, solving the problem of large bag flocculent flow in the production process of low-silicon aluminum-containing steel in slabs, further reducing the amount of molten steel returned to the furnace, reducing the generation of non-steady-state castings, increasing the number of continuous casting furnaces, and meeting the quality requirements of low-silicon aluminum-containing steel in slabs. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with specific examples, but the present invention is not limited in any way. To avoid redundant description, the raw materials in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0018] Example 1

[0019] A composite slag reforming process for an LF refining furnace, the process scheme comprising: controlling oxygen content in a converter process and controlling Si recovery in an LF refining process, wherein:

[0020] ①Converter process

[0021] The final carbon drawing time is ≥1min, ensuring the position of the carbon drawing gun. The final carbon control target is "release upper limit -0.015%" to prevent over-blowing and spot blowing. When the oxygen content is >600ppm, follow the aluminum deoxidation and alloying process. The final oxygen of the converter is 493ppm, and the carbon deoxidation process is followed. After blowing argon for 3min, the oxygen is set at 3-5ppm at the argon station. The amount of aluminum wire to be fed is calculated according to "oxygen value / 1.5+200"m, and the aluminum content is controlled at 0.010%~0.025%.

[0022] ②LF refining process

[0023] Add 400-600kg of lime in 2-3 batches, with each batch ≤300kg and the interval between batches is about 1min; when the S content of molten steel in the converter or argon station process is greater than the "release upper limit -0.002%", the lime can be appropriately increased by 300-500kg / furnace according to the sulfur content.

[0024] Aluminum particles, cut aluminum and calcium carbide are used for composite slag modification. Slag formation begins during the slag-forming period and turns into green slag after power is turned on. 15kg+10kg of aluminum particles, 10kg+10kg+10kg+10kg of cut aluminum and 40kg of calcium carbide are added in batches.

[0025] The test results of C, Si and Als of the steel sample obtained by adopting the process scheme of Example 1, the calculation results of the desulfurization rate, and the residual water situation of the ladle are shown in Table 1.

[0026] Example 2

[0027] A composite slag reforming process for an LF refining furnace, the process scheme comprising: controlling oxygen content in a converter process and controlling Si recovery in an LF refining process, wherein:

[0028] ①Converter process

[0029] The final carbon drawing time is ≥1min, ensuring the position of the carbon drawing gun. The final carbon control target is "release upper limit -0.015%" to prevent over-blowing and spot blowing. When the oxygen content is >600ppm, it is carried out according to the aluminum deoxidation and alloying process. The final oxygen of the converter is 657ppm, and the converter is carried out according to the aluminum deoxidation and alloying process. After blowing argon at the argon station for 3min, 3-5ppm, the aluminum wire is fed according to the "oxygen value / 1.5+200"m, and the aluminum content is controlled at 0.010%~0.025%.

[0030] ②LF refining process

[0031] Add 400-600kg of lime in 2-3 batches, with each batch ≤300kg and the interval between batches is about 1min; when the S content of molten steel in the converter or argon station process is greater than the "release upper limit -0.002%", the lime can be appropriately increased by 300-500kg / furnace according to the sulfur content.

[0032] Aluminum particles, cut aluminum and calcium carbide are used for composite slag modification. Slag formation begins during the slag-forming period and becomes light green slag after power is turned on. 15kg+16kg of aluminum particles, 10kg+10kg+10kg+10kg+10kg+10kg of cut aluminum and 20kg of calcium carbide are added in batches.

[0033] The test results of C, Si and Als of the steel sample obtained by adopting the process scheme of Example 2, the calculation results of the desulfurization rate, and the residual water situation of the ladle are shown in Table 1.

[0034] Example 3

[0035] A composite slag reforming process for an LF refining furnace, the process scheme comprising: controlling oxygen content in a converter process and controlling Si recovery in an LF refining process, wherein:

[0036] ①Converter process

[0037] The final carbon drawing time is ≥1min, ensuring the position of the carbon drawing gun. The final carbon control target is "release upper limit -0.015%" to prevent over-blowing and spot blowing. When the oxygen content is >600ppm, it is carried out according to the aluminum deoxidation and alloying process. The final oxygen of the converter is 408ppm, and the converter is carried out according to the aluminum deoxidation and alloying process. After blowing argon at the argon station for 3min, 3-5ppm, the aluminum wire is fed according to the "oxygen value / 1.5+200"m, and the aluminum content is controlled at 0.010%~0.025%.

[0038] ②LF refining process

[0039] Add 400-600kg of lime in 2-3 batches, with each batch ≤300kg and the interval between batches is about 1min; when the S content of molten steel in the converter or argon station process is greater than the "release upper limit -0.002%", the lime can be appropriately increased by 300-500kg / furnace according to the sulfur content.

[0040] Aluminum particles, cut aluminum and calcium carbide are used for composite slag modification. Slag formation begins during the slag-forming period and becomes light green slag after power is turned on. 15kg+13kg of aluminum particles, 10kg+10kg+10kg+10kg of cut aluminum and 30kg of calcium carbide are added in batches.

[0041] The test results of C, Si and Als of the steel sample obtained by adopting the process scheme of Example 3, the calculation results of the desulfurization rate, and the residual water situation of the ladle are shown in Table 1.

[0042] Table 1 Test results of elements in steel obtained in Example 1, desulfurization rate, and residual water in ladle

[0043]

[0044] It can be seen from Examples 1-3 that the technical solution optimizes the LF furnace terminal slag system, improves the deoxidation efficiency, desulfurization efficiency and slag fluidity, thereby improving production efficiency, reducing production costs and improving product quality.

[0045] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A composite slag reforming process for LF refining furnace, characterized in that: The process includes a converter process to control oxygen content and a LF refining process to control Si recovery, wherein: ① Converter process: oxygen control target range is 400~600ppm; ②LF refining process: 400-600kg of lime is added in 2-3 batches, and aluminum particles, cut aluminum and calcium carbide are used for composite slag modification; the Si control target range is ≤0.03%.

2. The process according to claim 1, characterized in that The final carbon pulling time in the converter process of step ① is ≥1 min, and the final carbon control target is "the upper limit of the composition requirement -0.015%".

3. The process according to claim 1, characterized in that In the converter process of step ①, when the oxygen content is greater than 600 ppm, the aluminum deoxidation alloying process is followed.

4. The process according to claim 1, characterized in that In step ①, oxygen is fixed and aluminum wire is fed during the converter process, and the amount of the aluminum wire is "oxygen value / 1.5+200" m; the Al control target range is 0.015% to 0.035%.

5. The process according to claim 1, characterized in that In the LF refining process of step ②, the amount of lime added in each batch is ≤300kg, and the batch interval is 1min.

6. The process according to claim 1, characterized in that In step ②, during the LF refining process, when the molten steel S in the converter or argon station is greater than the "upper limit of the composition requirement -0.002%", the amount of lime is increased by 300 to 500 kg.

7. The process according to claim 1, characterized in that During the LF refining process of step ②, aluminum particles are added in two batches during slagging, 15 kg of aluminum particles are added synchronously with lime in the first batch, and 10 to 16 kg of aluminum particles are added in the second batch.

8. The process according to claim 1, characterized in that During the LF refining process in step ②, cutting aluminum is added in 4 to 6 batches of 40 to 60 kg for later deoxidation.

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