Method for reducing the oxidizability of top slag of ultra-low carbon steel

Abstract

The present application relates to the technical field of steel metallurgy, and in particular, relates to a method for reducing the oxidizability of top slag of ultra-low carbon steel. In the production of ultra-low carbon steel, the top slag of molten steel is strongly modified by static decanting in a converter, and then enters a RH furnace for oxygen blowing and decarburization, thereby controlling the composition of the molten steel and reducing the oxidizability of the top slag of molten steel. The method significantly reduces the oxidizability of the top slag of molten steel, and the modification process does not pollute the molten steel and the on-site environment, and improves the quality of the molten steel and the environmental protection requirements.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, and more particularly to a method for reducing the oxidizability of top slag in ultra-low carbon steel. Background Technology

[0002] The oxidizing properties of ladle top slag are closely related to the quality of steel. The oxidizing properties of ladle top slag directly affect the total oxygen content of molten steel in the tundish, thus impacting the cleanliness of the steel. To ensure the excellent performance of ultra-low carbon steel, the steelmaking and refining processes must strictly control the oxidizing properties of ladle top slag, improve its ability to dissolve and absorb inclusions, reduce inclusions in the molten steel, and thus improve steel quality to better meet market demands. Summary of the Invention

[0003] The purpose of this invention is to provide a method for reducing the oxidizability of top slag in ultra-low carbon steel. In the production of ultra-low carbon steel, the converter strongly modifies the top slag of the molten steel through killed tapping, and then enters the RH furnace for oxygen blowing and decarburization, thereby controlling the composition of the molten steel and reducing the oxidizability of the top slag.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] This invention provides a method for reducing the oxidizability of top slag in ultra-low carbon steel, comprising:

[0006] Converter control:

[0007] a. The tapping temperature is controlled at 1640-1660℃, the oxygen value target value is 500-800ppm, and the carbon value target value is 250-400ppm;

[0008] b. Slag-blocking tapping is used during converter smelting;

[0009] c. Add aluminum wire segments 1-3 minutes after the steel tapping begins;

[0010] d. After tapping, add quicklime, fluorite, and aluminum powder to the surface of the steel slag to modify the top slag;

[0011] e. Use 50-60m 3 Argon gas is blown at a flow rate of / h, and stirred for 5-7 minutes.

[0012] RH control:

[0013] a. Open the RH main valve. Once the RH vacuum level reaches below 0.5 kPa, the oxygen blowing rate should be 1.2-1.3 m³ / h. 3 / ton of steel undergoes decarburization;

[0014] b. After oxygen blowing ends, maintain oxygen levels for 1-2 minutes. If the oxygen content is below 300 ppm, perform supplementary blowing. The supplementary blowing amount is calculated as (300 - oxygen content) / 3.3, where the unit for supplementary blowing amount is meters (m).3 Oxygen content is expressed in ppm.

[0015] c. Control the decarburization time according to the C content of the finished steel:

[0016] If the carbon content of the finished steel meets the requirement of 0.002% < C ≤ 0.01%, the decarburization time is 10-11 minutes after oxygen blowing;

[0017] If the carbon content of the finished steel meets the requirement of C≤0.002%, the decarburization time is 15-17 minutes;

[0018] d. After decarburization, oxygen is determined, and aluminum-added segments are used to kill the molten steel;

[0019] e. After adding the aluminum section for 2-3 minutes, add the alloy according to the target value of the chemical composition;

[0020] f. After the alloy is added, circulate for 3-5 minutes and then break the void.

[0021] g. After RH is completed, aluminum powder is added to the surface of the top slag.

[0022] In the above technical solution, further, during the converter tapping process, the amount of aluminum wire added = (tapping oxygen content + 600) / 1000 * tapping amount + 200, where the unit of the amount of aluminum wire added is kg, the unit of the tapping oxygen content is ppm, and the unit of the tapping amount is t.

[0023] In the above technical solution, further, after the converter tapping is completed, the amount of quicklime added to the surface of the steel slag is 4-5 kg / ton of steel, the amount of fluorite added is 0.4-0.8 kg / ton of steel, and the amount of aluminum powder added is 0.8-1.1 kg / ton of steel.

[0024] In the above technical solution, furthermore, after the converter tapping is completed, the TFe content in the top slag is 2%-6%.

[0025] In the above technical solution, further, after the RH is completed, the amount of aluminum powder added to the surface of the steel slag is 0.7-0.12 kg / ton of steel.

[0026] In the above technical solution, further, in the RH process, the amount of aluminum wire segments added to the killed steel is = oxygen content after decarburization * steel output * 0.0016 + steel output * target Al content / 1000, where the unit of the amount of aluminum wire segments added is kg, the unit of steel output is t, the unit of oxygen content after decarburization is ppm, and the unit of target Al content is ppm.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. The method of this invention significantly reduces the TFe content, i.e., the oxidizing property, of the top slag in ultra-low carbon steel, thereby improving the purity of molten steel;

[0029] 2. The method of this invention improves the pourability of molten steel;

[0030] 3. The method of this invention increases the proportion of ultra-low carbon steel grade O5 plates, thereby improving enterprise efficiency;

[0031] In summary, the method of the present invention significantly reduces the oxidizability of top slag in molten steel, and the modification process does not pollute the molten steel or the on-site environment, thereby improving the quality of molten steel and meeting environmental protection requirements. Attached Figure Description

[0032] Figure 1 Photograph of slag sample from the converter argon station of this invention;

[0033] Figure 2 This is a photograph of the residue sample after the RH process of this invention. Detailed Implementation

[0034] Example 1

[0035] Smelting steel grade IF1 (finished product C≤0.003%, Als 0.04%), process route: converter → argon station → RH → casting machine;

[0036] Converter control:

[0037] a. The final temperature of the converter was 1652℃, the final oxygen value was 621ppm, and the carbon content of the tapped steel was 328ppm.

[0038] b. During converter smelting, slag-blocking is used for steel tapping, and the steel output is 262 tons;

[0039] c. 1 minute and 46 seconds after tapping begins, add 520 kg of aluminum wire segments. The Al content in the argon station is 0.033%.

[0040] d. After tapping, add 1162 kg of quicklime, 135 kg of fluorite, and 233 kg of aluminum powder to the surface of the steel slag to modify the top slag.

[0041] e. Argon gas flow rate at the argon station: 55m³ / h 3 / h, argon blowing and stirring for 6min30s, the top slag is modified to grayish-white, and the TFe content of the top slag is 3.6% after testing;

[0042] RH control:

[0043] a. After the RH main valve is opened, the RH vacuum reaches 0.32 kPa in 2 minutes and 28 seconds, and oxygen is purged at 315 m³ / h. 3 Forced decarbonization;

[0044] b. After oxygen blowing ends, oxygen is stabilized at 270 ppm for 1 minute and 58 seconds, followed by a 9-minute supplemental blow. 3 ;

[0045] c. Decarburization for 10 min 20 s after supplementary blowing;

[0046] d. After decarburization, the oxygen content is 302 ppm, and 231 kg of aluminum-added molten steel is used to kill the steel.

[0047] e. After adding aluminum for 2 minutes and 35 seconds, add 194 kg of metallic manganese and 260 kg of high-titanium iron.

[0048] f. After the alloy is added, circulate the net circulation for 4 minutes and 20 seconds to break the air, then close the RH main valve.

[0049] g. After the molten steel descends out of the vacuum chamber, 210 kg of aluminum powder is added to the surface of the top slag. After the RH is completed, the slag sample is yellow-green. The slag sample is tested and TFe = 5.3%.

[0050] Example 2

[0051] Smelting steel grade ST16 (finished product C≤0.002%, Als 0.04%), process route: converter → argon station → RH → casting machine;

[0052] Converter control:

[0053] a. The converter's final temperature was 1653℃, the final oxygen value was 581ppm, and the carbon content of the tapped steel was 308ppm.

[0054] b. During converter smelting, slag-blocking is used for steel tapping, and the steel output is 260 tons.

[0055] c. 517 kg of aluminum wire segments are added 1 min 48 s after the start of tapping, and the Al content in the argon station is 0.034%.

[0056] d. After tapping, add 1152 kg of quicklime, 130 kg of fluorite, and 230 kg of aluminum powder to the surface of the steel slag to modify the top slag.

[0057] e. Argon gas flow rate at the argon station: 53m³ 3 / h, argon blowing and stirring for 6min32s, the top slag is modified to grayish-white, and the TFe content of the top slag is 3.8% after testing;

[0058] RH control:

[0059] a. After the RH main valve is opened, the RH vacuum reaches 0.42 kPa in 2 minutes and 25 seconds, and oxygen is purged at 313 m³ / min. 3 Forced decarbonization;

[0060] b. After oxygen blowing ends, oxygen content is stabilized at 320 ppm for 1 minute and 48 seconds. No further blowing is required.

[0061] c. Decarburization for 15 min 30 s after supplementary blowing;

[0062] d. After decarburization, the oxygen content is 302 ppm, and 230 kg of aluminum-treated molten steel is added to kill the steel.

[0063] e. After adding aluminum for 2 minutes and 38 seconds, add 174 kg of metallic manganese and 278 kg of high-titanium iron.

[0064] f. After the alloy is added, circulate the net circulation for 4 minutes and 22 seconds to break the air, then close the RH main valve.

[0065] g. After the molten steel descends out of the vacuum chamber, 208 kg of aluminum powder is added to the surface of the top slag. After the RH is completed, the slag sample is yellow-green. The slag sample is tested and TFe = 5.4%.

[0066] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for reducing the oxidizability of top slag in ultra-low carbon steel, characterized in that, include: Converter control: a. The tapping temperature is controlled at 1640-1660℃, the oxygen value target value is 500-800ppm, and the carbon value target value is 250-400ppm; b. Slag-blocking tapping is used during converter smelting; c. Add aluminum wire segments 1-3 minutes after the steel tapping begins; d. After tapping, add quicklime, fluorite, and aluminum powder to the surface of the steel slag to modify the top slag; e. Use 50-60m 3 Argon gas is blown at a flow rate of / h, and stirred for 5-7 minutes. RH control: a. Open the RH main valve. Once the RH vacuum level reaches below 0.5 kPa, the oxygen blowing rate should be 1.2-1.3 m³ / h. 3 / ton of steel undergoes decarburization; b. After oxygen blowing ends, maintain oxygen levels for 1-2 minutes. If the oxygen content is below 300 ppm, perform supplementary blowing. The supplementary blowing amount is calculated as (300 - oxygen content) / 3.3, where the unit for supplementary blowing amount is meters (m). 3 Oxygen content is expressed in ppm. c. Control the decarburization time according to the C content of the finished steel: If the carbon content of the finished steel meets the requirement of 0.002% < C ≤ 0.01%, the decarburization time is 10-11 minutes after oxygen blowing; If the carbon content of the finished steel meets the requirement of C≤0.002%, the decarburization time is 15-17 minutes; d. After decarburization, oxygen is determined, and aluminum-added segments are used to kill the molten steel; e. After adding the aluminum section for 2-3 minutes, add the alloy according to the target value of the chemical composition; f. After the alloy is added, circulate for 3-5 minutes and then break the void. g. After RH is completed, aluminum powder is added to the surface of the top slag.

2. The method for reducing the oxidizability of top slag in ultra-low carbon steel according to claim 1, characterized in that, During the converter tapping process, the amount of aluminum wire added = (tapping oxygen content + 600) / 1000 * tapping amount + 200, where the unit of the amount of aluminum wire added is kg, the unit of tapping oxygen content is ppm, and the unit of tapping amount is t.

3. The method for reducing the oxidizability of top slag in ultra-low carbon steel according to claim 1, characterized in that, After the converter tapping is completed, the amount of quicklime added to the surface of the steel slag is 4-5 kg / ton of steel, the amount of fluorite added is 0.4-0.8 kg / ton of steel, and the amount of aluminum powder added is 0.8-1.1 kg / ton of steel.

4. The method for reducing the oxidizability of top slag in ultra-low carbon steel according to claim 1, characterized in that, After the converter tapping is completed, the TFe content in the top slag is 2%-6%.

5. The method for reducing the oxidizability of top slag in ultra-low carbon steel according to claim 1, characterized in that, After the RH process is completed, the amount of aluminum powder added to the surface of the steel slag is 0.7-0.12 kg / ton of steel.

6. The method for reducing the oxidizability of top slag in ultra-low carbon steel according to claim 1, characterized in that, In the RH process, the amount of aluminum wire added to the killed steel is equal to the oxygen content after decarburization * steel output * 0.0016 + steel output * target Al content / 1000. The unit for the amount of aluminum wire added is kg, the unit for steel output is t, the unit for the oxygen content after decarburization is ppm, and the unit for the target Al content is ppm.

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