Method for preventing steel ladle top slag from transferring oxygen to ultra-low carbon steel liquid

Abstract

The invention discloses a method for preventing steel ladle top slag from transferring oxygen into ultra-low carbon steel liquid, which comprises the following steps: in the converter tapping process, adding 2.5-4.5 kg of slaked lime per ton of steel into the liquid steel according to the adding amount, so that the binary alkalinity of the steel ladle top slag reaches 7-20. According to the method, the lime powder is added into the steel ladle top slag to thicken the steel ladle top slag and improve the viscosity of the steel ladle top slag, so that the mass transfer coefficient D of the oxygen element in the steel ladle top slag is reduced, and the purposes of diluting the content of the oxygen element in the steel ladle top slag and indirectly reducing the oxygen concentration gradient are achieved; the mass transfer rate of the oxygen element on the steel ladle top slag and the interface between the steel ladle top slag and the molten steel can be effectively inhibited, and the purpose of preventing the steel ladle top slag from transferring oxygen to the molten steel is achieved. According to the method, the purpose of limiting the mass transfer flux is achieved by reducing the mass transfer coefficient D of the steel slag, the steel ladle top slag can be effectively prevented from transferring oxygen into the molten steel by adopting the method, a traditional steel ladle top slag modifier or other aluminum or aluminum-containing steel ladle top slag modifier is replaced, and the production cost is effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking, in particular to a method for preventing ladle top slag from transferring oxygen to ultra-low carbon steel liquid. Background Art

[0002] Ultra-low carbon steel refers to steel with a carbon content of less than 0.01%, also known as IF steel (interstitial-free steel), which has excellent deep drawing performance and is used in the production of home appliance panels and automotive panels. In order to ensure deep drawing performance and product surface quality, steel products are required to have a low oxygen content, including elemental oxygen and oxides.

[0003] Figure 1 As shown, in the static state, the distribution of air 1, ladle top slag 2 and molten steel 3 in the ladle 4 is from top to bottom. There are two ways for oxygen to be transferred to the molten steel 3. One is that oxygen is transferred to the interface between ladle top slag 2 and air 1 through air 1, oxygen is transferred to the interface between ladle top slag 2 through air 1, oxygen in ladle top slag 2 diffuses to the interface between ladle top slag 2 and molten steel 3, and then is transferred to the molten steel 3 through the interface between ladle top slag 2 and molten steel 3; the other is that oxygen in ladle top slag 2 directly diffuses to the interface between ladle top slag 2 and molten steel 3, and is transferred to the molten steel through the interface between ladle top slag 2 and molten steel 3. According to the diffusion mass transfer formula and the boundary layer film mass transfer formula, in the field of traditional steelmaking, the method of reducing the oxygen content in ladle top slag 2 is adopted to achieve the purpose of preventing ladle top slag 2 from transferring oxygen to molten steel 3. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preventing the ladle top slag from transferring oxygen to ultra-low carbon steel liquid.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: during the converter steelmaking process, 2.5-4.5 kg / ton of slaked lime is added to the molten steel, and the added amount makes the binary basicity of the ladle top slag reach 7-20.

[0006] Furthermore, the slaked lime is added when the steel output reaches 1 / 3 of the total molten steel and is completely added before it reaches 2 / 3.

[0007] Furthermore, the slaked lime composition requires CaO% ≥ 90%, SiO2% ≤ 3%, and MgO% ≤ 3%.

[0008] Furthermore, the slaked lime particle size is required to be 5-30 mm ≥ 90%.

[0009] Furthermore, during the steel tapping process, the ladle bottom blowing argon gas flow rate is required to be in the range of 800NL / min to 1500NL / min.

[0010] The beneficial effect produced by adopting the above technical scheme is that: the present invention adds lime powder to the ladle top slag to thicken the ladle top slag, thereby reducing the oxygen element mass transfer coefficient D in the ladle top slag, and plays the purpose of diluting the oxygen element content in the ladle top slag and indirectly reducing the oxygen concentration gradient. It can effectively inhibit the mass transfer rate of oxygen element in the ladle top slag and at the interface between the ladle top slag and the molten steel, thereby achieving the purpose of preventing the ladle top slag from transferring oxygen to the molten steel.

[0011] The present invention reduces the mass transfer coefficient D of the slag to limit the mass transfer flux. The present invention can effectively prevent the ladle top slag from transferring oxygen to the molten steel, replacing the traditional ladle top slag modifier or other aluminum or aluminum-containing ladle top slag modifier, effectively reducing the production cost. The present invention combines the ladle turnover, rinses the ladle with other varieties, and alternately smelts IF steel, without the need to use a slag-removing agent for adjustment, effectively controlling the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0013] Figure 1 It is a schematic diagram of oxygen transfer from top slag to ultra-low carbon steel liquid according to the present invention.

[0014] In the figure: air 1; ladle top slag 2; molten steel 3; ladle 4. DETAILED DESCRIPTION

[0015] The diffusion mass transfer formula (I) and boundary layer film mass transfer formula (II) for oxygen transfer from top slag to ultra-low carbon steel liquid are as follows: ; Where J is the mass flux, unit is mol / (m 2 ·s); D is the diffusion coefficient, unit is m 2 / s; is the concentration gradient, in mol / m; δe is the boundary layer thickness, in m; C f With C w is the concentration on both sides of the boundary layer, in mol / m 3 .

[0016] According to formulas (I) and (II), reducing the oxygen content in the ladle top slag and reducing the mass transfer coefficient D of the top slag can both achieve the purpose of limiting the mass transfer flux.

[0017] The method for preventing the ladle top slag from transferring oxygen to the ultra-low carbon steel liquid adopts the principle of reducing the mass transfer coefficient D of the steel slag, and the process is as follows: during the converter tapping process, slaked lime is added to the molten steel, with the amount added per ton of steel being 2.5-4.5 kg, and the addition is made after 1 / 3 of the converter tapping is seen and before the tapping amount reaches 2 / 3 of the total molten steel amount; the slaked lime adopts slaked lime powder and / or slaked lime blocks, and the slaked lime composition requirements (wt): CaO% ≥ 90%, SiO2% ≤ 3%, MgO% ≤ 3%, and the rest are impurity elements that do not participate in the reaction, and the particle size requirement is 5-30 mm, accounting for ≥ 90%; the ladle bottom blowing argon gas flow rate range is required to be 800NL / min-1500NL / min during the tapping process.

[0018] The amount of slaked lime added is based on the amount of slag in the steel strip and the diameter of the ladle, with the goal of actually thickening the top slag of the ladle, so that the binary basicity of the top slag of the ladle is 7-20 and it can cover the surface of the molten steel and isolate it from the air.

[0019] This method is applicable to the "converter → RH → continuous casting" smelting process of interstitial-free atomic steel products.

[0020] Embodiment 1-3: (1) The process parameters of each embodiment are shown in Table 1. After steel tapping, the composition of the molten steel, FeO% of the ladle top slag and the molten steel O% are tested and the test results are shown in Table 2;

[0021]

[0022] (2) Before RH treatment, the composition of molten steel, FeO% of ladle top slag and molten steel O% were tested. The test results are shown in Table 3.

[0023]

[0024] Comparing the ladle composition and top slag FeO% before RH treatment and after converter tapping as described in Table 3 and Table 2, it is found that the changes in the two samplings are very small and the results are basically consistent.

[0025] (3) After RH treatment, the composition of molten steel, FeO% of ladle top slag and molten steel O% were tested. The test results are shown in Table 4.

[0026] Comparing the ladle composition and top slag FeO% after RH treatment and after converter tapping as described in Table 4 and Table 2, it is found that the changes in the two samplings are very small and the results are basically consistent.

Claims

1. A method for preventing ladle top slag from transferring oxygen to ultra-low carbon steel liquid, characterized in that: During the converter tapping process, 2.5 to 4.5 kg / ton of steel slaked lime is added to the molten steel in an amount such that the binary basicity of the ladle top slag reaches 7 to 20.

2. The method for preventing oxygen transfer from ladle top slag to ultra-low carbon steel liquid according to claim 1, characterized in that: The slaked lime is added when the steel output reaches 1 / 3 of the total molten steel and is finished before it reaches 2 / 3.

3. The method for preventing oxygen transfer from ladle top slag to ultra-low carbon steel liquid according to claim 1, characterized in that: The slaked lime composition requirements include CaO% ≥ 90%, SiO2% ≤ 3%, and MgO% ≤ 3%.

4. The method for preventing oxygen transfer from ladle top slag to ultra-low carbon steel liquid according to claim 1, characterized in that: The slaked lime particle size is required to be 5-30 mm ≥ 90%.

5. A method for preventing ladle top slag from transferring oxygen to ultra-low carbon steel liquid according to any one of claims 1 to 4, characterized in that: During the steel tapping process, the ladle bottom blowing argon gas flow rate is required to be in the range of 800NL / min to 1500NL / min.

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