Control method for steelmaking continuous casting process of high-rare-earth-content low-alloy steel

Abstract

The invention discloses a control method for a steelmaking continuous casting process of high-rare-earth-content low-alloy steel, which realizes high cleanliness of steel before rare earth alloying through measures such as converter end point oxygen content control, furnace slag washing, LF (ladle furnace) refining and calcium treatment, effectively improves the yield of rare earth elements, improves the production efficiency and ensures continuous casting. Compared with conventional production, the method has the advantages that the problem of high-content rare earth steel flocculation flow is solved, the yield of rare earth elements in the steel is greatly increased, and the yield of the rare earth elements in the steel can be stably controlled to be 50% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking, and in particular relates to a control method for a steelmaking continuous casting process for low-alloy steel with high rare earth content. Background Art

[0002] In recent years, as researchers gradually realize that trace rare earth elements are the only elements in microalloyed steel that can deeply purify molten steel, denature inclusions, improve the internal structure of continuous casting billets, and improve various properties of steel, they have an irreplaceable unique microalloying effect, which has prompted the research on the role of rare earth microalloying to become a hot topic in recent years. Taking advantage of the outstanding role of rare earth in steel, the method of replacing single or composite precious metal elements with rare earth elements is often used to design products, and the development of microalloyed steel with different rare earth contents has become a weather vane for product development. For rare earth microalloyed steel, different smelting addition processes and addition timings affect the stability of rare earth element recovery. In addition, since rare earth elements are extremely easy to oxidize, rare earths added to molten steel will block the pouring system, and the continuous casting process will be forced to be interrupted, seriously affecting the smooth process; after rare earths are added, large-sized and high-density rare earth inclusions are easily formed, resulting in unstable steel performance, which is also a problem that needs to be solved in steelmaking and continuous casting processes. Summary of the invention

[0003] The purpose of the present invention is to provide a control method for the steelmaking continuous casting process of low-alloy steel with high rare earth content, especially the control of the rare earth content and yield in the steel, so as to achieve stable control of the rare earth content yield in the steel at a level above 50% and the rare earth content in the steel at a level above 80ppm, thereby achieving the successful development and stable supply of low-alloy high-strength steel with high rare earth content and high yield.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention provides a control method for a high rare earth content low alloy steel steelmaking continuous casting process, comprising:

[0006] 1) Molten iron conditions: Molten iron temperature ≥ 1350°C, molten iron silicon content 0.25%-0.50%, molten iron sulfur content ≤ 0.030%, molten iron phosphorus content ≤ 0.130%;

[0007] 2) KR desulfurization: desulfurization stirring time ≥ 15min, desulfurizer addition amount 7.00-7.40kg / t, desulfurizer average particle size 1.2mm, desulfurization slag slag twice;

[0008] 3) Converter control: lime addition amount 20-30kg / t, high silicon dolomite addition amount 5-10kg / t, calcined dolomite addition amount 5-10kg / t, iron ball addition amount 20-45kg / t, full argon blowing mode, bottom blowing flow rate 1600-2000Nm3 / h;

[0009] 4) Converter tapping conditions: converter tapping phosphorus content ≤ 0.015%, tapping temperature ≥ 1620°C, tapping oxygen content ≤ 550ppm;

[0010] 5) Washing slag after converter: During the steel-making process, the amount of lime added is 8.00-10.00kg / t, the amount of modifier added is 0.50-0.80kg / t, the amount of micro-carbon aluminum and iron added is 3.50-4.00kg / t, the steel-making mouth is round and the steel-making time is 6-9min / furnace;

[0011] 6) LF refining: the heating argon gas is set to 400min / L-600min / L, the amount of lime added is 8.00-10.00kg / t, the amount of aluminum particles added is 0.50-0.80kg / t, the high calcium wire is fed after refining treatment, and rare earth alloy is added after calcium treatment;

[0012] 7) Final slag composition range: R: 5.5-7.0%, T.Fe+MnO≤0.5%, C / A: 1.5-2.5.

[0013] Furthermore, the desulfurizing agent comprises the following components: CaO≥90%, CaF2≥9%.

[0014] Furthermore, the desulfurizing agent has a particle size between 0.3-1.2 mm accounting for more than 80%, and a particle size between <0.3 mm and >1.2 mm accounting for an average of ≤5%.

[0015] Furthermore, the main components of the steel grade range as follows: smelting key carbon content 0.05-0.09%, silicon content 0.05-0.25%, manganese content 1.20-1.80%, phosphorus content ≤0.015%, sulfur content ≤0.005%, rare earth content ≥0.0080%.

[0016] Furthermore, the recovery rate of rare earth elements in steel can be stably controlled to be above 50%.

[0017] Compared with the prior art, the beneficial technical effects of the present invention are:

[0018] The present invention achieves high cleanliness of steel before rare earth alloying by controlling the oxygen content at the converter end, post-furnace slag washing, LF refining and calcium treatment, effectively improves the recovery rate of rare earth elements, improves production efficiency and ensures continuous casting; compared with conventional production, the use of this method solves the problem of high-content rare earth steel floc flow and greatly improves the recovery rate of rare earth elements in steel, and the recovery rate of rare earth elements in steel can be stably controlled to be above 50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below in conjunction with the accompanying drawings.

[0020] Figure 1 It is a schematic diagram of the implementation process of the present invention in the steelmaking process. DETAILED DESCRIPTION

[0021] Embodiment 1:

[0022] 1. Molten iron conditions: Molten iron temperature 1365℃, molten iron silicon content 0.27%, molten iron sulfur content 0.027%, molten iron phosphorus content 0.124%;

[0023] 2.KR desulfurization: desulfurization stirring time is 15min, desulfurizer addition amount is 7.24kg / t, and desulfurization slag is scraped twice;

[0024] 3. Converter control: lime addition amount 26.49kg / t, high silicon dolomite addition amount 7.75kg / t, calcined dolomite addition amount 9.36kg / t, iron ball addition amount 29.62kg / t, full argon blowing mode, bottom blowing flow rate 1600~2000Nm 3 / h;

[0025] 4.Converter tapping conditions: The phosphorus content of the converter tapping steel is 0.009%, the tapping temperature is 1625℃, and the oxygen content of the tapping steel is 399ppm;

[0026] 5. Slag washing after converter: During the steel-making process, the amount of lime added is 7.09kg / t, the amount of modifier added is 0.71kg / t, the amount of micro-carbon aluminum and iron added is 3.92kg / t, the steel-making mouth is round and the steel-making time is 8.6min / furnace;

[0027] 6.LF refining: the heating argon gas is set to 550min / L, the amount of lime added is 8.69kg / t, and the amount of aluminum particles added is 0.78kg / t;

[0028] 7. Final slag composition range: R: 5.6%, T.Fe+MnO: 0.4%, C / A: 1.9;

[0029] 8. The argon blowing time of the tundish before pouring is 6 minutes; the new graphite sealing ring of the long nozzle is used, and the argon flow rate is 4L / min; the covering agent must be added after temperature measurement and sampling; the casting machine increases nitrogen by 2ppm;

[0030] 9. Set the pulling speed to 1.05m / min and ensure that the pulling speed is constant; the pouring time is controlled at 43min, and the sensitivity of slag detection for large bags is 5%.

[0031] The amount of rare earth alloy added in this furnace is 120kg, the rare earth Ce element content in the rare earth alloy is 30%, the detected amount of rare earth Ce element in the middle package is 0.0080%, the total amount of molten steel in this furnace is 281.77 tons, and the rare earth recovery rate is 62%.

[0032] Embodiment 2:

[0033] 1. Molten iron conditions: Molten iron temperature 1367℃, molten iron silicon content 0.31%, molten iron sulfur content 0.029%, molten iron phosphorus content 0.129%;

[0034] 2.KR desulfurization: desulfurization stirring time is 15min, desulfurizer addition amount is 7.28kg / t, and desulfurization slag is scraped twice;

[0035] 3. Converter control: lime addition amount 24.09kg / t, high silicon dolomite addition amount 9.22kg / t, calcined dolomite addition amount 8.77kg / t, iron ball addition amount 40.84kg / t, full argon blowing mode, bottom blowing flow rate 1600~2000Nm 3 / h;

[0036] 4.Converter tapping conditions: The phosphorus content of converter tapping is 0.011%, the tapping temperature is 1626℃, and the oxygen content of tapping is 517ppm;

[0037] 5. Slag washing after converter: During the steel-making process, the amount of lime added is 7.03kg / t, the amount of modifier added is 0.70kg / t, the amount of micro-carbon aluminum and iron added is 3.90kg / t, the steel-making mouth is round and the steel-making time is 8.3min / furnace;

[0038] 6.LF refining: the heating argon gas is set to 550min / L, the amount of lime added is 8.58kg / t, and the amount of aluminum particles added is 0.61kg / t;

[0039] 7. Final slag composition range: R: 6.2%, T.Fe+MnO: 0.5%, C / A: 2.2;

[0040] 8. The argon blowing time of the tundish before pouring is 6 minutes; the new long nozzle uses a graphite sealing ring, and the argon flow rate is 4L / min; the covering agent must be added after temperature measurement and sampling; the casting machine increases nitrogen by 2ppm;

[0041] 9. Set the pulling speed to 1.05m / min and ensure that the pulling speed is constant; the pouring time is controlled at 38min, and the sensitivity of slag detection for large bags is 5%.

[0042] The amount of rare earth alloy added in this furnace is 160 kg, the rare earth Ce element content in the rare earth alloy is 30%, the detected amount of rare earth Ce element in the middle package is 0.0096%, the total amount of molten steel in this furnace is 284.38 tons, and the rare earth recovery rate is 55%.

[0043] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A control method for a high rare earth content low alloy steel continuous casting process, characterized in that: include: 1) Molten iron conditions: Molten iron temperature ≥ 1350°C, molten iron silicon content 0.25%-0.50%, molten iron sulfur content ≤ 0.030%, molten iron phosphorus content ≤ 0.130%; 2) KR desulfurization: desulfurization stirring time ≥ 15min, desulfurizer addition amount 7.00-7.40kg / t, desulfurizer average particle size 1.2mm, desulfurization slag slag twice; 3) Converter control: lime addition amount 20-30kg / t, high silicon dolomite addition amount 5-10kg / t, calcined dolomite addition amount 5-10kg / t, iron ball addition amount 20-45kg / t, full argon blowing mode, bottom blowing flow rate 1600-2000Nm 3 / h; 4) Converter tapping conditions: converter tapping phosphorus content ≤ 0.015%, tapping temperature ≥ 1620°C, tapping oxygen content ≤ 550ppm; 5) Washing slag after converter: During the steel-making process, the amount of lime added is 8.00-10.00kg / t, the amount of modifier added is 0.50-0.80kg / t, the amount of micro-carbon aluminum and iron added is 3.50-4.00kg / t, the steel-making mouth is round and the steel-making time is 6-9min / furnace; 6) LF refining: the heating argon gas is set to 400min / L-600min / L, the amount of lime added is 8.00-10.00kg / t, the amount of aluminum particles added is 0.50-0.80kg / t, the high calcium wire is fed after refining treatment, and rare earth alloy is added after calcium treatment; 7) Final slag composition range: R: 5.5-7.0%, T.Fe+MnO≤0.5%, C / A: 1.5-2.

5.

2. The control method for high rare earth content low alloy steel steelmaking continuous casting process according to claim 1 is characterized in that: The desulfurizing agent comprises: CaO≥90%, CaF2≥9%.

3. The control method for high rare earth content low alloy steel steelmaking continuous casting process according to claim 1, characterized in that: The desulfurizer particle size is between 0.3-1.2 mm, accounting for more than 80%, and the particle size is less than 0.3 mm and greater than 1.2 mm, accounting for an average of ≤5%.

4. The control method for high rare earth content low alloy steel steelmaking continuous casting process according to claim 1, characterized in that: Main component range of steel grade: smelting key carbon content 0.05-0.09%, silicon content 0.05-0.25%, manganese content 1.20-1.80%, phosphorus content ≤0.015%, sulfur content ≤0.005%, rare earth content ≥0.0080%.

5. The control method for high rare earth content low alloy steel steelmaking continuous casting process according to claim 1, characterized in that: The recovery rate of rare earth elements in steel can be stably controlled at more than 50%.

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