A method for simultaneously dephosphorizing and increasing manganese in semi-steel

Abstract

The present invention discloses a method for simultaneously dephosphorizing and increasing manganese content in semi-steel. Manganese ore powder is added during the semi-steel tapping process. This method requires no dedicated dephosphorizing agent or additional equipment and is simple to operate. The method utilizes the heat source and impact kinetic energy of the semi-steel tapping process in a vanadium-extracting converter to melt the manganese ore powder, thereby achieving the dual goals of dephosphorizing and increasing manganese content in the semi-steel. This method can effectively alleviate the dephosphorization burden of the steelmaking converter.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for simultaneously dephosphorizing and increasing manganese in semi-steel. Background Art

[0002] Steel companies using vanadium-titanium magnetite for smelting use semi-steel, the primary raw material for converter steelmaking, as vanadium-extracted semi-steel. The semi-steel obtained after desulfurization and vanadium extraction from vanadium-containing molten iron has a carbon content of 3.4% to 3.8% by weight, and trace amounts of silicon and manganese, elements that form slag during heating, are present in the semi-steel. The temperature of the semi-steel after vanadium extraction fluctuates between 1380-1450°C, and the temperature of the semi-steel added to the steelmaking converter fluctuates between 1300-1350°C. Because the converter vanadium extraction process lacks the ability to remove phosphorus, dephosphorization is primarily performed in the steelmaking converter. Consequently, semi-steel converter steelmaking suffers from issues such as insufficient heat source, a low concentration of slag-forming elements, and high consumption of auxiliary materials.

[0003] To address the heavy dephosphorization workload in semi-steel converter steelmaking, there have been reports of using semi-steel dephosphorization to alleviate this burden. For example, Patent Document CN201310150725, "Semi-steel Dephosphorization Agent and Semi-steel Dephosphorization Method," provides a semi-steel dephosphorization agent and method. The dephosphorization agent described in the patent is composed, by weight, of 35-50 parts lime, 25-45 parts iron oxide scale, and 15-25 parts sodium oxide. The method comprises: uniformly adding the semi-steel dephosphorization agent to the discharged molten steel during tapping, with the amount of the dephosphorization agent added controlled at between 10 and 20 kg / t of semi-steel; blowing nitrogen gas into the bottom of the molten steel after tapping; and performing slag removal after the nitrogen blowing is complete. The advantages of the present invention include: being able to reduce the dephosphorization task during molten steel smelting in a steelmaking converter, thereby creating conditions for smelting low-phosphorus steel and achieving low-slag steelmaking; being able to effectively remove the phosphorus content in semi-steel, with a dephosphorization rate of over 40%, being simple to operate, requiring no additional facilities or equipment, not extending the process time, and reducing the consumption of auxiliary materials for converter steelmaking; being able to effectively avoid the problem of conventional dephosphorization and vanadium extraction agents corroding the converter lining, and simultaneously reducing the sodium content in the vanadium slag.

[0004] Unlike the aforementioned patent, the present invention uses manganese ore to dephosphorize semi-steel while simultaneously increasing the manganese content in the semi-steel. This not only reduces the phosphorus content entering the steelmaking converter, but also facilitates rapid slagging in the semi-steel converter, improving dephosphorization efficiency. No other literature has been reported with content similar to that of the present patent. Summary of the Invention

[0005] This patented method addresses the issues of insufficient heat source, low slag formation, and heavy dephosphorization during semi-steelmaking. It provides a method for simultaneously dephosphorizing and increasing manganese content in semi-steel. This method utilizes the heat source and impact kinetic energy of the semi-steel produced by the vanadium-extraction converter to melt manganese ore powder, achieving the dual goals of dephosphorizing and increasing manganese content in the semi-steel, effectively alleviating the dephosphorization burden of the steelmaking converter.

[0006] A method for simultaneously dephosphorizing and increasing manganese in semi-steel, wherein the semi-steel steelmaking process comprises: vanadium-titanium molten iron → molten iron pretreatment and desulfurization → vanadium extraction in a vanadium extraction converter → semi-steel production (adding manganese ore powder) → slag removal → adding slag to a steelmaking converter for steelmaking.

[0007] Furthermore, the temperature of the semi-steel obtained after vanadium extraction in the converter is between 1380-1450°C.

[0008] Furthermore, the manganese ore powder has the following components in weight percentage: TMn: 30%-45%, iron oxide (FexO): 15%-25%, SiO2: 5%-10%, CaO: 15%-25%, P≤0.050%, S≤0.30%, and the rest are impurities, with a particle size between 100-200 mesh.

[0009] Furthermore, the manganese ore powder is added as follows: after steel is tapped, the amount added is 5-8 kg / t. 半钢 , all added when 1 / 2 of the steel is tapped.

[0010] Furthermore, after the steel is tapped, a slag removal operation is performed, and the dephosphorized and manganese-enriched semi-steel is added to the steelmaking converter for smelting.

[0011] principle:

[0012] Manganese addition: Calculations based on the reaction [C] + (MnO) = [Mn] + CO↑ indicate that when the carbon content of molten iron reaches 3.0% or more, the temperature for this reaction to proceed forward is below 1200°C. However, the temperature for vanadium extraction from semi-steel in the converter is between 1380-1450°C, the carbon content of the semi-steel is above 3.0%, and the oxygen content in the semi-steel is very low. These conditions provide the thermodynamic conditions for manganese reduction in manganese ore, allowing the reaction to proceed forward. Furthermore, the impact kinetic energy of the molten steel provides the stirring dynamics necessary for manganese reduction in the manganese ore, thereby increasing manganese addition to the semi-steel. Manganese addition to the semi-steel occurs through oxidation, releasing heat and increasing the chemical heat of steelmaking. Furthermore, oxidation slag formation expands the liquid phase of the converter slag, promoting rapid slagging and improving dephosphorization efficiency.

[0013] Dephosphorization: The manganese ore powder contains high oxidizing property (FexO), basicity between 2.5-5, and semi-steel temperature between 1380-1450°C, which meets the thermodynamic conditions of low temperature, high basicity, and high oxidizing property. In addition, the impact kinetic energy of the molten steel during tapping and the bubble agitation generated by the reaction [C] + (MnO) = [Mn] + CO↑ enhance the dephosphorization kinetic conditions, achieving a good dephosphorization effect.

[0014] Compared with the prior art, the present invention has the following beneficial effects: the present invention does not require the addition of a dedicated dephosphorization agent, does not require new equipment, is simple to operate, and can increase manganese content in the semi-steel while dephosphorizing the semi-steel. DETAILED DESCRIPTION

[0015] The following non-limiting examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0016] Example

[0017] A certain plant's 120t converter uses vanadium-titanium hot metal for smelting. The production process is as follows: hot metal pretreatment and desulfurization → vanadium extraction in the converter → tapping semi-steel (addition of manganese ore powder) → slag skimming → addition to the steelmaking converter for steelmaking. The semi-steel obtained after desulfurization and vanadium extraction from the vanadium-containing hot metal has a carbon content of 3.4% by weight, slag-forming silicon and manganese of 0.01% and 0.02%, respectively, and a phosphorus content of 0.078%. The tapping temperature is 1400°C. At the start of tapping, 800kg of manganese ore powder (composition by weight: TMn: 35%, iron oxide (FexO): 20%, SiO2: 8%, CaO: 20%, P: 0.030%, S: 0.12%, with the remainder being impurities) is added to the semi-steel tank along with the steel flow. The particle size is between 100-200 mesh. After the steel is tapped, the semi-steel tank is deslagging and a semi-steel sample is taken. The phosphorus content in the semi-steel is found to be 0.040%, and the manganese content in the semi-steel is 0.12%. The semi-steel after dephosphorization and manganese enrichment is added to the steelmaking converter and smelted normally. When the phosphorus content of the final molten steel is 0.008%, the auxiliary material consumption per ton of steel is only 20 kg.

[0018] Comparative Example

[0019] A certain plant's 120t converter uses vanadium-titanium hot metal for smelting. The production process is as follows: vanadium-titanium hot metal → hot metal pretreatment and desulfurization → vanadium extraction in a converter → semi-steel → semi-steel converter steelmaking. The semi-steel obtained after desulfurization and vanadium extraction from the vanadium-containing hot metal has a carbon content of 3.4% by weight, slag-forming silicon and manganese contents of 0.01% and 0.02%, respectively, and a phosphorus content of 0.076%. The semi-steel is tapped at 1400°C and then fed into the steelmaking converter for normal smelting. When the final phosphorus content of the tapped steel is 0.009%, auxiliary material consumption reaches 58kg per ton of steel.

Claims

1. A method for simultaneously dephosphorizing and increasing manganese in semi-steel, characterized in that: The semi-steel steelmaking process is as follows: vanadium-titanium molten iron → molten iron pretreatment and desulfurization → vanadium extraction in vanadium extraction converter → semi-steel production → slag removal → adding slag to steelmaking converter for steelmaking; Manganese ore powder is added during the semi-steel production process; The manganese ore powder has the following components in weight percentage: TMn: 30%-45%, iron oxide (FexO): 15%-25%, SiO2: 5%-10%, CaO: 15%-25%, P≤0.050%, S≤0.30%, and the rest are impurities; The manganese ore powder is added in the steel flow after tapping, with an addition amount of 5-8 kg / t 半钢 , all added when 1 / 2 of the steel is tapped.

2. The method according to claim 1, characterized in that The temperature of the semi-steel obtained after vanadium extraction in the converter is 1380-1450°C.

3. The method according to claim 1, characterized in that The particle size of the manganese ore powder is 100-200 mesh.

4. The method according to claim 1, wherein After the steel is tapped, the slag removal operation is carried out and the dephosphorized and manganese-enriched semi-steel is added to the steelmaking converter for smelting.