A control method for a high-rare-earth-content low-alloy steel smelting continuous casting process

Abstract

The application discloses a control method of a high-rare earth content low alloy steel smelting continuous casting process. Through control of converter end point oxygen content, post-furnace slag washing, LF refining and calcium treatment and other measures, high cleanliness of the steel before rare earth alloying is realized, the yield of rare earth elements is effectively improved, the production efficiency is improved, and continuous casting is ensured. By using the method, compared with conventional production, the high-content rare earth steel flocculation is solved, the yield of rare earth elements in the steel is greatly improved, and the yield of rare earth elements in the steel can be stably controlled to be above 50%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steelmaking, and particularly relates to a control method for a high-rare earth content low-alloy steelmaking continuous casting process. BACKGROUND

[0002] In recent years, as researchers gradually realize that trace rare earth elements are the only elements in micro-alloyed steel that can simultaneously purify steel liquid, modify inclusions, improve the internal structure of continuous casting billets and improve the performance of steel, and have an irreplaceable unique micro-alloying effect, the research on rare earth micro-alloying has become a hot topic in recent years. By utilizing the outstanding effect of rare earth in steel, the method of replacing single or composite precious metal elements with rare earth elements is often used in product design, and the development of micro-alloyed steel with different rare earth contents has become a trend in product development. For rare earth micro-alloyed steel, different smelting addition processes and addition timing affect the stability of the rare earth element yield. In addition, since rare earth elements are easily oxidized, the addition of rare earth elements to molten steel blocks the pouring system and forces the continuous casting process to be interrupted, which seriously affects the process. After the addition of rare earth elements, large-size and high-density rare earth inclusions are easily formed, which leads to unstable steel performance, and this is a problem that needs to be solved in the steelmaking and continuous casting processes. SUMMARY

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

[0004] To solve the above technical problems, the present application adopts the following technical scheme:

[0005] The present application is a control method for a high-rare earth content low-alloy steelmaking continuous casting process, comprising:

[0006] 1) Hot metal conditions: hot metal temperature ≥ 1350℃, hot metal silicon content 0.25%-0.50%, hot metal sulfur content ≤ 0.030%, hot metal phosphorus content ≤ 0.130%;

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

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

[0009] 4) Converter tapping conditions: the phosphorus content of converter tapping is less than or equal to 0.015%, the tapping temperature is greater than or equal to 1620 DEG C, and the oxygen content of tapping is less than or equal to 550 ppm;

[0010] 5) Converter post-conversion slag washing: the lime addition amount is 8.00-10.00 kg / t, the modifier addition amount is 0.50-0.80 kg / t, the micro-carbon aluminum iron addition amount is 3.50-4.00 kg / t, the tapping hole is round, and the tapping time is 6-9 min / furnace;

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

[0012] 7) The final slag component range: R: 5.5-7.0%, T.Fe+MnO is less than or equal to 0.5%, and C / A: 1.5-2.5.

[0013] Further, the desulfurizing agent component composition is: CaO is greater than or equal to 90%, and CaF2 is greater than or equal to 9%.

[0014] Further, the desulfurizing agent particle size is more than 80% between 0.3-1.2 mm, and the particle size is less than or equal to 5% on average between <0.3 mm and >1.2 mm.

[0015] Further, the main component range of the steel grade is: the smelting key carbon content is 0.05-0.09%, the silicon content is 0.05-0.25%, the manganese content is 1.20-1.80%, the phosphorus content is less than or equal to 0.015%, the sulfur content is less than or equal to 0.005%, and the rare earth content is greater than or equal to 0.0080%.

[0016] Further, the rare earth element yield in the steel can be stably controlled to be more than 50%.

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

[0018] The present application realizes high cleanliness of the steel before rare earth alloying by controlling the converter end point oxygen content, post-conversion slag washing, LF refining and calcium treatment, effectively improves the rare earth element yield, improves the production efficiency and ensures continuous casting; compared with the conventional production, the present application solves the high content rare earth steel flocculation, the rare earth element yield in the steel is greatly improved, and the rare earth element yield in the steel can be stably controlled to be more than 50%. BRIEF DESCRIPTION OF DRAWINGS

[0019] The present application will be further described below in combination with the description of the drawings.

[0020] Figure 1 The flow chart of the embodiment of the present application in the steelmaking process. DETAILED DESCRIPTION

[0021] Example 1

[0022] 1. Hot metal condition: hot metal temperature 1365℃, hot metal silicon content 0.27%, hot metal sulfur content 0.027%, hot metal phosphorus content 0.124%;

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

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

[0025] 4. Converter tapping condition: converter tapping phosphorus content 0.009%, tapping temperature 1625℃, tapping oxygen content 399 ppm;

[0026] 5. Converter post-furnace slag washing: lime addition amount during tapping 7.09 kg / t, modifier addition amount 0.71 kg / t, micro-carbon ferroaluminum addition amount 3.92 kg / t, tapping mouth roundness and tapping time 8.6 min / furnace;

[0027] 6. LF refining: heating argon setting 550 min / L, lime addition amount 8.69 kg / t, aluminum particle addition amount 0.78 kg / t;

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

[0029] 8. During pouring, argon blowing time in tundish before starting pouring 6 min; long nozzle newly replaced using graphite sealing ring, argon flow rate 4 L / min; after temperature measurement and sampling, covering agent must be added; nitrogen in caster increased by 2 ppm;

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

[0031] The rare earth alloy addition amount in this furnace is 120 kg, the rare earth Ce element content in the rare earth alloy is 30%, the tundish rare earth Ce element detection amount is 0.0080%, the total amount of molten steel in this furnace is 281.77 tons, and the rare earth yield is 62%.

[0032] Example 2:

[0033] 1. Hot metal condition: hot metal temperature 1367°C, hot metal silicon content 0.31%, hot metal sulfur content 0.029%, hot metal phosphorus content 0.129%;

[0034] 2. KR desulfurization: desulfurization stirring time 15 min, desulfurizer addition amount 7.28 kg / t, desulfurization slag skimming two times;

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

[0036] 4. Converter tapping condition: converter tapping phosphorus content 0.011%, tapping temperature 1626°C, tapping oxygen content 517 ppm;

[0037] 5. Converter post-furnace slag washing: lime addition amount during tapping 7.03 kg / t, modifier addition amount 0.70 kg / t, micro-carbon ferroaluminum addition amount 3.90 kg / t, tapping mouth roundness and tapping time 8.3 min / furnace;

[0038] 6. LF refining: heating argon setting 550 min / L, lime addition amount 8.58 kg / t, aluminum particle addition amount 0.61 kg / t;

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

[0040] 8. During pouring, tundish argon blowing time before starting pouring 6 min; long nozzle newly replaced using graphite sealing ring, argon flow rate 4 L / min; after temperature measurement and sampling, covering agent must be added; nitrogen in the caster is increased by 2 ppm;

[0041] 9. Set the pulling speed to 1.05 m / min, and ensure constant pulling speed; pouring time is controlled to be 38 min, and the detection sensitivity of the slag in the ladle is 5%.

[0042] The rare earth alloy addition amount in this heat is 160 kg, the rare earth Ce element content in the rare earth alloy is 30%, the tundish rare earth Ce element detection amount is 0.0096%, the total amount of molten steel in this heat is 284.38 tons, and the rare earth yield is 55%.

[0043] The above described embodiments are only to illustrate the preferred modes of the present application, and are not intended to limit the scope of the present application. Any modification and improvement made by those skilled in the art to the technical solutions of the present application without departing from the design spirit of the present application shall fall within the protection scope of the present application.

Claims

1. A method for controlling a high rare earth content low alloy steel steelmaking continuous casting process, characterized in that, It includes: 1) hot metal conditions: hot metal temperature ≥ 1350℃, hot metal silicon content 0.25%-0.50%, hot metal sulfur content ≤0.030%, hot metal 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 is scraped twice; 3) Converter control: lime addition amount 20-30 kg / t, high-silicon dolomite addition amount 5-10 kg / t, calcined dolomite addition amount 5-10 kg / t, iron skin ball addition amount 20-45 kg / t, adopt full blowing argon mode, bottom blowing flow rate is 1600-2000 Nm 3 / h; 4) converter tapping conditions: converter tapping phosphorus content ≤0.015%, tapping temperature ≥1620℃, tapping oxygen content ≤550ppm; 5) converter post-furnace slag washing: lime addition amount 8.00-10.00kg / t, modifier addition amount 0.50-0.80kg / t, micro-carbon ferroaluminum addition amount 3.50-4.00kg / t, tapping mouth is round and tapping time is 6-9min / furnace; 6) LF refining: heating argon is set to 400L / min-600L / min, lime addition amount 8.00-10.00kg / t, aluminum particle addition amount 0.50-0.80kg / t, 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 of high rare earth content low alloy steel steelmaking continuous casting process according to claim 1, characterized in that, The desulfurizer composition comprises: CaO ≥90%, CaF2 ≥9%.

3. The method of controlling a high rare earth content low alloy steel steelmaking continuous casting process according to claim 1, characterized in that, The desulfurizer particle size is more than 80% between 0.3-1.2mm, and the particle size is ≤5% on average when <0.3mm and >1.2mm.

4. The method of controlling a high rare earth content low alloy steel steelmaking continuous casting process according to claim 1, characterized in that, The 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 method of controlling a high rare earth content low alloy steel steelmaking continuous casting process according to claim 1, characterized in that, The yield of rare earth elements in steel can be stably controlled to be more than 50%.

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