Refining calcium-free treatment process

Abstract

The invention discloses a refining calcium-free treatment process, and belongs to the technical field of refining and smelting of high-carbon aluminum-containing steel. According to the method, various smelting parameters of the whole steelmaking process are adjusted, sulfur entering a converter is guaranteed in a desulfurization area, tapping carbon, tapping temperature, in-place refining component hit rate, deoxidation degree and tapping phosphorus difference are guaranteed in a converter area, refining treatment time, white slag protection time and soft blowing time are guaranteed in a refining area, the content of Al2O3 in molten steel is reduced, the purity of the molten steel is guaranteed, and the quality of the molten steel is improved. Molten steel calcium-free treatment is achieved, and the quality of molten steel is improved.

Description

Technical Field

[0001] This invention belongs to the field of refining and smelting high-carbon aluminum-containing steel technology, and particularly relates to a calcium-free refining process. Background Technology

[0002] When smelting high-carbon aluminum-containing steel on the No. 7 casting machine at Baogang Steel Plant, the deoxidation product of the molten steel is mainly high-melting-point inclusion Al2O3. During casting, Al2O3 tends to accumulate and adhere to the inner wall of the nozzle, hindering the flow of molten steel. To prevent Al2O3 from accumulating and adhering to the nozzle inner wall, a calcium treatment process is applied to the molten steel. This process transforms the Al2O3 inclusions in the molten steel into low-melting-point 7Al2O3·12CaO, which floats and is removed, thereby reducing the number of large-particle inclusions and alleviating the blockage of the continuous casting submerged entry nozzle. However, the high calcium content in the molten steel reacts with the alumina and carbonaceous material of the casting machine stopper rod to form silicates and calcium aluminates, exacerbating the corrosion of the stopper rod, increasing the distance between the stopper rod and the nozzle bowl, resulting in poor flow control of the casting machine and increasing the likelihood of unplanned casting stoppages. To improve the fluidity of the molten steel while preventing corrosion of the casting machine stopper rod, this invention improves and enhances the calcium treatment process of the molten steel, thereby increasing the number of consecutive casting heats on the casting machine. Summary of the Invention

[0003] The purpose of this invention is to provide a calcium-free refining process that adjusts the entire smelting process from desulfurization to converter to refining, thereby reducing the content of Al2O3 inclusions in molten steel and achieving calcium-free steel treatment.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This invention discloses a calcium-free refining process, comprising:

[0006] 1. Improve the desulfurization rate in the desulfurization zone to ensure that the sulfur content entering the furnace is ≤0.005%;

[0007] Measures: Adjust the stirring head speed, stirring head insertion depth, and quicklime addition amount in the KR desulfurization zone, specifically: stirring head speed 80-90 r / min, stirring head descent depth 300-315 cm, and quicklime addition amount 4-4.5 kg / t;

[0008] 2. The carbon content of the steel tapped from the converter area shall be ≥0.06%, and the tapping temperature shall be ≥1610℃.

[0009] Measures: Monitor the silicon content and temperature of molten iron in advance in the desulfurization area, and adjust the scrap steel structure and cold material addition amount according to the silicon content and temperature of the molten iron entering the furnace;

[0010] By detecting the silicon content and temperature of molten iron in the desulfurization zone, the converter charging operator adjusts the amount of cold material added in the early stage and quickly measures the final temperature and carbon content of molten steel with a temperature probe before the end point, so that the heat meets the requirements of ≥0.06% carbon content and ≥1610℃ at the end point of the converter.

[0011] 3. Ensure deoxidation degree in the converter area and reduce the phosphorus difference in steel output to ≤0.004%;

[0012] Measures: In the converter area, aluminum and iron are added reasonably according to the carbon content at the final tapping point (see table below); dolomite is added before tapping to thicken the slag; slag-blocking plugs are added at the tapping point; and slag-blocking methods such as sliding plate are used to prevent slag from returning to phosphorus.

[0013] Carbon content and corresponding aluminum-iron addition:

[0014] Steel carbon / % Oxygen output / ppm Aluminum and iron addition amount / kg 0.1 250 28 0.09 278 31 0.08 313 35 0.07 357 40 0.06 417 47 0.05 500 56 0.04 625 70

[0015] IV. The refining area ensures rapid slag formation, maintaining white slag for at least 15 minutes.

[0016] Measures: Aluminum and iron are added to the converter according to the final oxygen content to ensure the appropriate deoxidation degree of the molten steel. The first refining heating is carried out by comparing the color of the slag with the color chart. Aluminum particles are used to remove oxygen from the slag to ensure slag formation in one step.

[0017] White residue retention time ≥ 15 min;

[0018] 5. Ensure refining time ≥ 40 min and soft blowing time ≥ 8 min;

[0019] Measures: The main control of the converter-ladle repair-refining-casting machine will promptly report the production status to the shift foreman by watching the production plan and the steel pulling screen of the casting machine. The shift foreman, as the main production organizer, will reasonably arrange the production sequence.

[0020] By improving the steel pulling process and the coordination between various processes, the number of heats with a refining molten steel treatment time of ≥40 minutes and the number of heats with a refining soft blowing time of ≥8 minutes have been significantly improved.

[0021] Furthermore, the stirring head rotates at 85 r / min.

[0022] Furthermore, the stirring head descends to a depth of 310 cm.

[0023] Furthermore, the amount of quicklime added is 4.3 kg / t.

[0024] Furthermore, by adding dolomite before tapping to thicken the slag, adding slag-blocking plugs at the tapping port, and using sliding plate slag blocking, the number of heats with a phosphorus difference of ≤0.004% has been effectively improved.

[0025] Furthermore, add 10-60 kg of deoxidizer according to the color of the final residue.

[0026] Furthermore, by controlling these process parameters, steel mills can refine and smelt high-carbon aluminum steel without calcium treatment, thereby improving the quality of molten steel and reducing production costs.

[0027] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0028] Increase the number of consecutive castings of high-carbon aluminum steel in steelmaking plants, reduce calcium treatment, and avoid poor flow control in casting machines. Attached Figure Description

[0029] The present invention will be further described below with reference to the accompanying drawings.

[0030] Figure 1 This is a production process flow diagram;

[0031] Figure 2 To achieve the desired final slag refining, a deoxidizer must be added according to standards. Detailed Implementation

[0032] By adjusting and controlling various smelting parameters throughout the entire steelmaking process, ensuring sufficient sulfur input in the desulfurization zone, controlling tapping carbon, tapping temperature, deoxidation degree, and tapping phosphorus difference in the converter zone, and controlling refining treatment time, white slag maintenance time, and soft blowing time in the refining zone, calcium-free refining is promoted. Specific measures and effects are as follows:

[0033] 1. Improve the desulfurization rate in the desulfurization zone to ensure that the sulfur content entering the furnace is ≤0.005%.

[0034] Measures: Adjust the stirring head speed, stirring head insertion depth, and quicklime addition amount in the KR desulfurization zone.

[0035] Table 1 Improvement of parameters such as stirring head rotation speed, stirring head insertion depth, and quicklime addition in the desulfurization zone.

[0036] Before improvement After improvement Increase the stirring head speed (r / min) 75r / min 85r / min Depth of stirring head descent (cm) 290㎝ 310㎝ Amount of quicklime added (kg / t) 3.4㎏ / t 4.3㎏ / t

[0037] Results: By adjusting the stirring head speed from 75 r / min to 85 r / min, the stirring head insertion depth decreased by 20 cm, and the amount of quicklime added increased from 3.4 kg / t to 4.3 kg / t. This increased the contact area between the molten iron and the desulfurizing agent, effectively improved the stirring kinetics of desulfurization, ensured the basicity of the slag, and ensured that the sulfur content of the molten iron entering the furnace met the requirement of ≤0.005%.

[0038] 2. The carbon content of the steel tapped from the converter area shall be ≥0.06%, and the tapping temperature shall be ≥1610℃.

[0039] Measures: Monitor the silicon content and temperature of molten iron in advance in the desulfurization area, and adjust the scrap steel structure and cold material addition amount according to the silicon content and temperature of the molten iron entering the furnace.

[0040] Results: By detecting the silicon content and temperature of molten iron in the desulfurization zone, the converter charging operator adjusts the amount of cold material added in the early stage, and the temperature and carbon content of the molten steel are quickly measured by a temperature probe before the end of the process. The number of heats with carbon content ≥0.06% and converter temperature ≥1610℃ at the end of the converter tapping process is effectively increased.

[0041] 3. Ensure deoxidation degree in the converter area and reduce the phosphorus difference in steel output to ≤0.004%.

[0042] Measures: In the converter area, aluminum and iron are added appropriately according to the carbon content at the final tapping point (Formula 1, Table 2). Dolomite is added before tapping to thicken the slag, and slag-blocking plugs and sliding plate slag-blocking methods are used to prevent phosphorus return in the slag.

[0043] 2AI+3[O]=(AI2O3) (Equation 1) Table 2 shows the carbon content of the steel and the corresponding amount of aluminum and iron added.

[0044] Steel carbon / % Oxygen output / ppm Aluminum and iron addition amount / kg 0.1 250 28 0.09 278 31 0.08 313 35 0.07 357 40 0.06 417 47 0.05 500 56 0.04 625 70

[0045] Results: The converter adds aluminum and ferroalloy according to the carbon content at tapping, ensuring a suitable degree of deoxidation in the molten steel, reducing the need for additional aluminum and ferroalloy in refining, and allowing the deoxidation product Al2O3 inclusions to float sufficiently. The converter effectively improves the number of heats with a phosphorus difference ≤0.004% by adding dolomite before tapping to thicken the slag, adding slag-blocking plugs at the tapping spout, and using sliding plate slag blocking. 4. The refining zone ensures rapid slag formation, maintaining white slag for ≥15 minutes.

[0046] Measures: Aluminum and ferroalloys are added to the converter according to the final oxygen content to ensure a suitable degree of deoxidation in the molten steel. The first refining and heating process involves comparing the slag color with a colorimetric card (see...). Figure 2 The process involves removing oxygen from aluminum granules to ensure slag formation in a single step.

[0047] Results: The refining process involves color comparison during the first slag adhesion test, and aluminum granules are added in proportion to achieve rapid slag formation, with a white slag retention time of ≥15 minutes.

[0048] 5. Ensure refining time ≥ 40 min and soft blowing time ≥ 8 min.

[0049] Measures: The main control of the converter-tank repair-refining-casting machine will promptly report the production status to the shift foreman by viewing the production plan and the steel pulling screen of the casting machine. The shift foreman, as the main production organizer, will rationally arrange the production sequence.

[0050] Results: By improving the steel drawing process and the coordination between various processes, the number of heats with a refining molten steel treatment time of ≥40 minutes and the number of heats with a refining soft blowing time of ≥8 minutes were significantly improved.

[0051] By controlling the aforementioned endpoint parameters, steel mills can refine and smelt high-carbon aluminum steel without calcium treatment, thereby improving the quality of molten steel and reducing production costs.

[0052] 6. Economic benefits

[0053] 1) In 2024, the steel plant produced a total of 92,997.63 tons of high-carbon aluminum steel. Each heat of steel was fed 50 meters less wire. According to the 2025 alloy plan price, the price of high-calcium wire is 8,585.85 yuan / ton. Each coil of high-calcium wire is 4,200 meters long and weighs 1.3 tons. Each heat of molten steel is 100 tons.

[0054] Benefit calculation: 1.3 tons * 8585.856 yuan / ton * 50 meters / 4200 meters / 100 tons * 92997.63 tons = 123,600 yuan.

[0055] 2) Poor flow control of the casting machine results in one unplanned shutdown, causing a loss of 30,000 yuan in the tundish. Due to poor flow control, there are 5 unplanned shutdowns throughout the year, resulting in annual cost savings of 3*5=150,000 yuan. Cost reduction: 150,000 yuan.

[0056] 3) One unplanned shutdown of casting results in one heat of steel being recycled. The alloy cost of 1 ton of B2-1 steel is 232.79 yuan. The weight of each heat of molten steel is 105 tons. One recycling results in a loss of alloy cost of 105 * 232.79 = 24,400 yuan. The annual loss cost is 24,400 * 5 = 122,000 yuan.

[0057] 4) An unplanned shutdown and remelting of steel results in a 10% loss of steel material. The cost of the steel material is 2,860 yuan / ton. Each furnace of molten steel weighs 105 tons. One remelting results in a loss of steel material cost of 2,860 * 105 * 10% = 30,000 yuan. The annual production loss is 3 * 5 = 150,000 yuan.

[0058] Total: 12.36 + 15 + 12.2 + 15 = 54.56 million yuan.

[0059] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A refining process for calcium-free treatment, characterized in that, include:

1. Improve the desulfurization rate in the desulfurization zone to ensure that the sulfur content entering the furnace is ≤0.005%; Measures: Adjust the stirring head speed, stirring head insertion depth, and quicklime addition amount in the KR desulfurization zone, specifically: stirring head speed 80-90 r / min, stirring head descent depth 300-315 cm, and quicklime addition amount 4-4.5 kg / t; 2. The carbon content of the steel tapped from the converter area shall be ≥0.06%, and the tapping temperature shall be ≥1610℃. Measures: Monitor the silicon content and temperature of molten iron in advance in the desulfurization area, and adjust the scrap steel structure and cold material addition amount according to the silicon content and temperature of the molten iron entering the furnace; By detecting the silicon content and temperature of molten iron in the desulfurization zone, the converter charging operator adjusts the amount of cold material added in the early stage and quickly measures the final temperature and carbon content of molten steel with a temperature probe before the end point, so that the heat meets the requirements of ≥0.06% carbon content and ≥1610℃ at the end point of the converter.

3. Ensure deoxidation degree in the converter area and reduce the phosphorus difference in steel output to ≤0.004%; Measures: In the converter area, aluminum and iron are added reasonably according to the carbon content at the final tapping point (see table below); dolomite is added before tapping to thicken the slag; slag-blocking plugs are added at the tapping point; and slag-blocking methods such as sliding plate are used to prevent slag from returning to phosphorus. Carbon content and corresponding aluminum-iron addition: IV. The refining area ensures rapid slag formation, maintaining white slag for at least 15 minutes. Measures: Aluminum and iron are added to the converter according to the final oxygen content to ensure the appropriate deoxidation degree of the molten steel. The first refining heating is carried out by comparing the color of the slag with the color chart. Aluminum particles are used to remove oxygen from the slag to ensure slag formation in one step. White residue retention time ≥ 15 min; 5. Ensure refining time ≥ 40 min and soft blowing time ≥ 8 min; Measures: The main control of the converter-ladle repair-refining-casting machine will promptly report the production status to the shift foreman by watching the production plan and the steel pulling screen of the casting machine. The shift foreman, as the main production organizer, will reasonably arrange the production sequence. By improving the steel pulling process and the coordination between various processes, the number of heats with a refining molten steel treatment time of ≥40 minutes and the number of heats with a refining soft blowing time of ≥8 minutes have been significantly improved.

2. The refining process for calcium-free treatment according to claim 1, characterized in that, The stirring head rotates at 85 r / min.

3. The refining process for calcium-free treatment according to claim 1, characterized in that, The stirring head descends to a depth of 310 cm.

4. The refining process for calcium-free treatment according to claim 1, characterized in that, The amount of quicklime added is 4.3 kg / t.

5. The refining process for calcium-free treatment according to claim 1, characterized in that, By adding dolomite before tapping to thicken the slag, adding slag-blocking plugs at the tapping outlet, and using sliding plate slag blocking, the number of heats with a phosphorus difference of ≤0.004% has been effectively improved.

6. The refining process for calcium-free treatment according to claim 1, characterized in that, Add 10-60 kg of deoxidizer according to the color of the final residue.

7. The refining process for calcium-free treatment according to claim 1, characterized in that, By controlling these process parameters, steel mills can refine and smelt high-carbon aluminum steel without calcium treatment, thereby improving the quality of molten steel and reducing production costs.

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