A method for improving the recovery rate of returned ore powder in converter steelmaking

Abstract

The invention discloses a method for improving the recovery rate of return ore powder in converter steelmaking, comprising the following steps: S1, after the blowing and firing are started, the gun position is controlled according to 1.3m; S2, whether to add return ore powder is determined according to the silicon content of molten iron; S3, if the silicon content of molten iron is greater than 0.50%, 500-1000kg of return ore powder is added, and the gun position is quickly lowered; S4, the oxygen supply time is controlled to be between 7'00" and 7'30"; S5, at this time, the return ore powder is added in batches, the slag [Fe] element is reduced into molten steel through C-O reaction, and the FeO content of the slag is adjusted at the same time. The method for improving the recovery rate of return ore powder in converter steelmaking determines whether the process temperature is too high according to the furnace gas temperature, and adds return ore powder in batches, adjusts the FeO% content in the slag, effectively suppresses the "drying back" phenomenon, and determines to add return ore powder in the early and middle stages of blowing steel, and fully utilizes the [C] in the molten steel to react with (FeO) in the return ore powder to generate [Fe] which enters the molten steel to achieve the purpose of reducing the consumption of steel materials.

Description

Technical Field

[0001] The invention relates to the technical field of converter smelting technology, in particular to a method for improving the recovery rate of returned ore powder in converter steelmaking. Background Art

[0002] The existing converter steelmaking will have excess heat when the steel consumption is at the level of 800kg / t, and most steel mills use small-particle slag steel (bean steel), dust sludge balls or lump ore to adjust the converter molten pool temperature during the blowing process. In this technology, the return ore powder of ironmaking sintering ore is added, and the particle size is controlled at 3∽6mm (which can effectively prevent dust removal), and then determine whether to pour the early slag or pour the steel in one shot according to the silicon content of the molten iron. The method of adding return ore powder in the steelmaking process is based on the characteristics of converter steelmaking blowing. And effectively achieve the sintering return ore powder recovery rate of more than 80%. The existing converter steelmaking technology has the following main shortcomings:

[0003] When the silicon content of molten iron exceeds 0.50%, return ore powder is added in the early stage. The early slag comes quickly, and the slag layer begins to move up and thicken in about 2 minutes. Slag overflows and splashes after 3 and a half minutes of steelmaking. When pouring the early slag, the furnace often cannot be shaken.

[0004] In the middle stage of converter steelmaking blowing, especially after 7 minutes of blowing, the carbon-oxygen reaction is violent, the converter slag is seriously dried out, and the addition of lump ore or small-particle slag steel (bean steel) often causes the furnace mouth flame to overflow. If too much is added, slag overflow and splashing will occur, which fails to achieve the purpose of reducing steel consumption.

[0005] Adding lump ore or small-particle slag steel (soy steel) in the later stage of converter steelmaking blowing will cause the carbon-oxygen reaction to gradually slow down, resulting in a high FeO% content in the slag, foaming slag, poor furnace condition, high steel consumption, and poor effect.

[0006] Therefore, we propose a method for improving the recovery rate of return ore powder in converter steelmaking in order to solve the above-mentioned problems. Summary of the invention

[0007] The object of the present invention is to provide a method for improving the recovery rate of returned ore powder in converter steelmaking, so as to solve the problems proposed in the above-mentioned background technology that the furnace often cannot be shaken when pouring the early slag, and excessive addition of lump ore or small-particle slag steel will cause slag overflow and splashing, which fails to achieve the purpose of reducing steel consumption, and lump ore or small-particle slag steel (bean steel) is added in the later stage of converter steelmaking blowing, resulting in a high FeO% content in the slag, foaming slag, poor furnace condition, high steel consumption and poor effect due to the gradual slowing down of carbon-oxygen reaction.

[0008] To achieve the above object, the present invention provides the following technical solution: a method for improving the recovery rate of return ore powder in converter steelmaking, comprising the following steps:

[0009] S1. After the blow and ignition are started, the gun position is controlled at 1.3m;

[0010] S2. Determine whether to add return ore powder according to the silicon content of molten iron;

[0011] S3. If the silicon content of molten iron is greater than 0.50%, add 500-1000kg of return ore powder and quickly lower the gun position;

[0012] S4, control the oxygen supply time between 7'00" and 7'30";

[0013] S5. At this time, the return ore powder is added in batches to reduce the slag [Fe] element into the molten steel through the CO reaction, and the FeO content of the slag is adjusted at the same time;

[0014] S6. Calculate the amount of return ore powder added according to the heat balance of steelmaking, and flexibly adjust the amount of return ore powder added by observing the flame temperature to ensure that the molten steel temperature is appropriate. At the same time, strive to complete the addition of return ore powder before 12 minutes of oxygen supply time (complete the addition 3 minutes before the blowing gun is lifted).

[0015] Preferably, in S3, the reaction between oxygen and [Fe] in the molten iron to generate FeO that enters the slag phase is fully suppressed, and 300 kg of slag lime is added at one time to cause slag foaming. After the converter smelting flame is normal, the normal gun position operation is restored. If the slag thickness line rises too fast, the gun position is appropriately raised by 300∽500 mm to reduce the small CO bubbles generated by the CO reaction, which causes the slag thickness line to rise slowly and maintain below the warning line. When the oxygen supply time continues to 4′30″ to 5′30″, it is possible to consider raising the gun and dumping the early slag.

[0016] Preferably, when the silicon content of the molten iron in S3 is less than 0.50%, return ore powder should not be added in the early stage of smelting. First, it is necessary to ensure that the early slag cannot foam severely to cause slag overflow and splashing, especially when the slag thickness line is not more than the warning line when blowing for 5-7 minutes. When the slag thickness line is close to the warning red line, return ore powder cannot be added into the furnace, otherwise large spraying or slag overflow will occur.

[0017] Preferably, the CO reaction in the S4 begins to intensify, the converter flame begins to become straight and "white", "steel flowers" appear from time to time at the oxygen lance nitrogen seal, and the molten pool temperature begins to rise steadily.

[0018] Preferably, the S5 is for eliminating the "drying back" phenomenon of molten steel.

[0019] Preferably, the S6 controls the FeO% content of the final slag to 10%, so that most of the TFe in the added return ore powder is reduced to [Fe] and enters the molten steel.

[0020] Compared with the prior art, the invention has the following beneficial effects: the method for improving the recovery rate of return ore powder in converter steelmaking;

[0021] According to the numerical trend line changes of the converter steelmaking CO-gun position-slag thickness curve, adjust the gun position and small batch feeding, control the appropriate slag pouring time to achieve maximum control of slag overflow. In the middle and late stages of converter blowing, adjust the gun position appropriately according to the CO-gun position-slag thickness curve, and judge whether the process temperature is too high according to the furnace gas temperature, and add return ore powder in batches to adjust the FeO% content in the slag to effectively suppress the "drying back" phenomenon, and determine to add return ore powder in the early and middle stages of steel blowing, so as to make full use of the [C] in the molten steel to react with (FeO) in the return ore powder to generate [Fe] that enters the molten steel to achieve the purpose of reducing steel material consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the gun position after the opening and firing of the present invention according to 1.3m control;

[0023] Figure 2 It is a schematic diagram of the aggravation of large slag spraying or slag overflowing according to the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present invention provides a technical solution: a method for improving the recovery rate of return ore powder in converter steelmaking, comprising the following steps:

[0026] S1. After the blow and ignition are started, the gun position is controlled at 1.3m. Figure 1 (blue line);

[0027] S2. Determine whether to add return ore powder according to the silicon content of molten iron;

[0028] S3. If the silicon content of molten iron is greater than 0.50%, add 500-1000kg of return ore powder and quickly lower the gun position;

[0029] In S3, the reaction between oxygen and [Fe] in molten iron to generate FeO and enter the slag phase is fully suppressed, and 300kg of slag lime is added at one time to cause slag foaming. After the converter smelting flame is normal, the normal gun position operation is restored. If the slag thickness line rises too fast, the gun position is appropriately raised by 300∽500mm to reduce the small CO bubbles generated by the CO reaction, which causes the slag thickness line to rise slowly and maintain below the warning line. When the oxygen supply time lasts for 4′30″ to 5′30″, it can be considered to raise the gun and dump the early slag;

[0030] When the silicon content of molten iron in S3 is less than 0.50%, it is not advisable to add return ore powder in the early stage of smelting. First of all, it is necessary to ensure that the slag in the early stage cannot foam seriously and cause slag overflow and splashing, especially when the slag thickness line cannot exceed the warning line when the blowing reaches 5-7 minutes. When the slag thickness line approaches the warning red line, return ore powder cannot be added into the furnace, otherwise large spraying or slag overflow will occur. Figure 2 (The blue line exceeds the warning line several times) as shown;

[0031] S4, control the oxygen supply time between 7'00" and 7'30";

[0032] The CO reaction in S4 began to intensify, the converter flame began to become straight and "white", "steel flowers" appeared from time to time at the nitrogen seal of the oxygen lance, and the molten pool temperature began to rise steadily;

[0033] S5. At this time, the return ore powder is added in batches (about 200∽500kg at a time), and the slag [Fe] element is reduced into the molten steel through the CO reaction, and the FeO content of the slag is adjusted at the same time, so as to maximize the recovery rate of the return ore powder;

[0034] The main principles are:

[0035] 2

C

[0036] CO + (FeO) = [Fe] + CO2

[0037] CO2+

C

[0038]

C

Fe

[0039] The S5 is to eliminate the phenomenon of "drying back" of molten steel;

[0040] S6. Calculate the amount of return ore powder added according to the heat balance of steelmaking, and flexibly adjust the amount of return ore powder added by observing the flame temperature to ensure that the molten steel temperature is appropriate. At the same time, strive to complete the addition of return ore powder before 12 minutes of oxygen supply time (complete the addition 3 minutes before blowing and lifting the gun). The recovery rate of return ore powder is as high as 80% or more, and it can effectively reduce steel material consumption and processing costs;

[0041] S6 controls the FeO% content of the final slag to 10%, so that most of the TFe in the added return ore powder is reduced to [Fe] and enters the molten steel;

[0042] The FeO content of the slag sample is about 10-12%. Maintaining the normal slag sample level, the consumption of steel materials is significantly reduced; as shown in the following table:

[0043]

[0044] When the oxygen supply time reaches 10'00" to 12'00", the CO reaction in the converter begins to slow down and the flame begins to soften. At this time, the final carbon is already at the level of 0.30%. At this time, the amount of return ore powder added should be mainly for slag removal and temperature adjustment, and the final slag should be thoroughly removed to prevent the molten steel [P] from being too high to hit once. At the same time, the molten steel temperature should reach ≤1630℃. If a large amount of return ore powder is added, the slag thickness line will quickly rush out of the warning line to form final slag overflow and splashing, which will cause the TFe in the overflow slag to reach more than 30%, seriously affecting the recovery rate of return ore powder.

[0045] Therefore, when the oxygen supply time is controlled at 7′00″ to 7′30″, and the return ore powder is added in batches to adjust the FeO% content in the slag, the "drying out" phenomenon is effectively suppressed, and the return ore powder is added in the early and middle stages of steelmaking to fully utilize the [C] in the molten steel to react with (FeO) in the return ore powder to generate [Fe] that enters the molten steel to achieve the purpose of reducing steel material consumption.

[0046] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0047] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving the recovery rate of returned ore powder in converter steelmaking, characterized in that: The following steps are involved: S1. After the blow and ignition are started, the gun position is controlled at 1.3m; S2. Determine whether to add return ore powder according to the silicon content of molten iron; S3. If the silicon content of molten iron is greater than 0.50%, add 500-1000kg of return ore powder and quickly lower the gun position to fully inhibit the reaction of oxygen and [Fe] in molten iron to generate FeO entering the slag phase, and add 300kg of slag lime at a time to cause slag foaming. After the converter smelting flame is normal, resume normal gun position operation. If the slag thickness line rises too fast, appropriately raise the gun position by 300-500mm to reduce the small CO bubbles generated by the CO reaction, which causes the slag thickness line to rise slowly and maintain below the warning line. When the oxygen supply time lasts for 4'30" to 5'30", consider raising the gun to dump the early slag; When the silicon content of molten iron is less than 0.50%, it is not advisable to add return ore powder in the early stage of smelting. First of all, it is necessary to ensure that the slag in the early stage cannot foam seriously and cause slag overflow and splashing. The slag thickness line cannot exceed the warning line when the slag thickness line is close to the warning red line. When the slag thickness line is close to the warning red line, return ore powder cannot be added into the furnace, otherwise large splashing or slag overflow will occur. S4, control the oxygen supply time between 7'00" and 7'30"; S5. At this time, the return ore powder is added in batches to reduce the slag [Fe] element into the molten steel through the CO reaction, and the FeO content of the slag is adjusted at the same time; S6. Calculate the amount of return ore powder added according to the heat balance of steelmaking, and flexibly adjust the amount of return ore powder added by observing the flame temperature to ensure that the molten steel temperature is appropriate. At the same time, strive to complete the addition of return ore powder before the oxygen supply time of 12 minutes.

2. The method for improving the recovery rate of return ore powder in converter steelmaking according to claim 1, characterized in that: The CO reaction in the S4 began to intensify, the converter flame began to become straight and "white", "steel flowers" appeared from time to time at the oxygen lance nitrogen seal, and the molten pool temperature began to rise steadily.

3. The method for improving the recovery rate of return ore powder in converter steelmaking according to claim 1, characterized in that: The S5 is for eliminating the "drying back" phenomenon of molten steel.

4. The method for improving the recovery rate of return ore powder in converter steelmaking according to claim 1, characterized in that: The S6 controls the FeO% content of the final slag to 10%, so that most of the TFe in the added return ore powder is reduced to [Fe] and enters the molten steel.

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