A design method of a superior lf desulfurization refining slag

Abstract

The application discloses a design method of excellent LF desulfurization refining slag, and comprises the following steps: S1, extracting refining slag components of the LF desulfurization refining slag, and calculating complete melting temperature and viscosity of the refining slag components; S2, calculating desulfurization capacity of each refining slag component based on the refining slag components and the corresponding complete melting temperature and viscosity of the refining slag components, and determining a desulfurization range of the refining slag components based on the desulfurization capacity result; and S3, selecting excellent LF desulfurization refining slag components based on the desulfurization range of the refining slag components, and completing the design of the excellent LF desulfurization refining slag. The method calculates the complete melting temperature and viscosity range of the refining slag by using FactSage thermodynamic software, and calculates the theoretical desulfurization capacity of the refining slag by using the FactSage thermodynamic software.

Description

Technical Field

[0001] This invention belongs to the field of steelmaking technology in iron and steel metallurgy, and particularly relates to a design method for an excellent LF desulfurization refining slag. Background Technology

[0002] Sulfur is a crucial factor affecting the various properties of steel. Excessive sulfur content in steel can lead to hot brittleness and cause the precipitation of large-sized MnS inclusions during solidification, severely impacting the steel's mechanical properties. With the exception of a few steel grades, most steel grades require desulfurization treatment. The sulfur content of molten steel must be controlled at a low level, and ladle refining is the final and primary desulfurization process before casting. LF refining is a widely used refining process that, under theoretical conditions, can desulfurize to below 20 ppm.

[0003] Desulfurization of refining slag is a crucial component of steel desulfurization in the LF refining process. Its composition significantly impacts steel cleanliness. High-quality refining slag should possess characteristics such as good fluidity, high inclusion adsorption capacity, and strong desulfurization ability. However, in actual steel production, the formulation of refining slag is often determined through continuous on-site trials to verify the actual desulfurization effect. This method involves long testing cycles and may lead to slag thickening, impacting production and causing economic losses. Summary of the Invention

[0004] To address the above problems, this invention provides a design method for superior LF desulfurization refining slag, comprising:

[0005] Step S1: Extract the refining slag components from the LF desulfurization refining slag, and calculate the complete melting temperature and viscosity of the refining slag components;

[0006] Step S2: Based on the composition of the refining slag and the corresponding complete melting temperature and viscosity of the refining slag, calculate the desulfurization capacity of each refining slag composition, and determine the desulfurization range of the refining slag composition based on the desulfurization capacity results.

[0007] Step S3: After selecting the optimal LF desulfurization refining slag composition based on the desulfurization capacity range of the refining slag composition, analyze the sulfur content in the steel to complete the design of the optimal LF desulfurization refining slag.

[0008] Optionally, in step S1, the process of extracting the refining slag components from the LF desulfurization refining slag and calculating the complete melting temperature and viscosity of the refining slag components specifically includes:

[0009] The main component of the CaO-Al2O3-SiO2-MgO system refining slag is the ternary CaO-Al2O3-SiO2. Using the Phase Diagram module in FactSage 8.2 software, the complete melting range and viscosity of the refining slag with 4%, 6%, 8%, and 10% MgO content at 1400-1600℃ were calculated.

[0010] Optionally, the LF refining temperature of the CaO-Al2O3-SiO2-MgO system refining slag is 1600℃, and refining slag components with temperatures below 1600℃ are selected.

[0011] Optionally, the MgO content of the refining slag in the CaO-Al2O3-SiO2-MgO system does not exceed 6%.

[0012] Optionally, the process of calculating the viscosity of the refining slag components is as follows:

[0013] Viscosity solid+liquid =Viscosity( liquid )·(1-solid fraction) -2.5

[0014] Among them, Viscosity (solid+liquid) Viscosity is the viscosity of the solid-liquid mixture. (liquid) The viscosity of the liquid portion of the slag is given by , and the solid fraction is given by .

[0015] Optionally, the desulfurization capacity range of the refining slag components is calculated using the Equilib equilibrium multi-component and multi-phase equilibrium module of FactSage 8.2 software.

[0016] Optionally, step S3, after selecting superior LF desulfurization refining slag components based on the desulfurization capacity range of the refining slag components, and then analyzing the sulfur content in the steel, specifically includes:

[0017] Refining slag was prepared and pretreated based on the selected superior LF desulfurization refining slag components;

[0018] The composition of the pretreated refining slag was analyzed using XRF equipment.

[0019] Based on the composition analysis results, the sulfur content in the molten steel was calculated using an electrical discharge analyzer.

[0020] Optional preprocessing methods include:

[0021] At the beginning, slag adjustment, and end stages of the LF refining process, steel rods were inserted into the slag layer to obtain the corresponding refining slag. After cooling, the slag was placed in bags for testing. Steel rods were inserted into the molten steel to obtain the corresponding molten steel. After removal, the molten steel was quickly placed in water to cool to room temperature and then removed for testing. The obtained refining slag was then ground into fine powder and pressed into cakes for sample preparation.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The method of the present invention uses FactSage thermodynamic software to calculate the complete melting temperature and viscosity range of the refining slag; (2) The method of the present invention uses FactSage thermodynamic software to calculate the theoretical desulfurization capacity of the refining slag; (3) The method of the present invention obtains the refining slag composition with strong desulfurization capacity that is beneficial to production through theoretical calculation, and verifies it through industrial tests to obtain the refining slag composition that is beneficial to actual production. Attached Figure Description

[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0025] Figure 1 A series of complete melting range diagrams of refining slag designed for embodiments of the present invention;

[0026] Figure 2 A series of complete melting temperature and viscosity diagrams of refining slag designed for embodiments of the present invention;

[0027] Figure 3 A series of theoretical desulfurization capacity diagrams of refining slag designed for embodiments of the present invention;

[0028] Figure 4 This is a flowchart illustrating the steps of a method for designing an excellent LF desulfurization refining slag according to an embodiment of the present invention. Detailed Implementation

[0029] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The terminology used in the embodiments of the present invention is for the purpose of describing specific embodiments only, and is not intended to limit the present invention. The singular forms "a," "described," and "the" as used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0030] Example

[0031] A superior design method for LF desulfurization refining slag, such as Figure 4 As shown, it includes:

[0032] Step S1: Extract the refining slag components from the LF desulfurization refining slag, and calculate the complete melting temperature and viscosity of the refining slag components.

[0033] The main component of the CaO-Al2O3-SiO2-MgO refining slag is the ternary CaO-Al2O3-SiO2 system, with MgO primarily originating from refractory corrosion. Firstly, using the Phase Diagram module in FactSage 8.2 thermodynamic software, the complete melting range of the refining slag at 1400-1600℃ with 4%, 6%, 8%, and 10% MgO content was calculated. Figure 1 As shown, where, Figure 1 (a) represents the complete melting range of Al2O3-CaO-SiO2 system refining slag with a 4% MgO content. Figure 1 (b) represents the complete melting range of Al2O3-CaO-SiO2 system refining slag with a 6% MgO content. Figure 1 (c) represents the complete melting range of Al2O3-CaO-SiO2 system refining slag with 8% MgO content. Figure 1 (d) shows the complete melting range of the Al2O3-CaO-SiO2 refining slag with a 10% MgO content. The complete melting range of the refining slag varies significantly depending on the MgO content. To observe the complete melting range of the refining slag with the corresponding MgO content for different steel grades, this industrial experiment achieved an LF refining temperature of 1600℃. Refining slag compositions below 1600℃ were selected. Refining slag with more than 6% MgO has an extremely high melting temperature; at 1600℃, the slag is solid, affecting actual production. Therefore, it is necessary to strictly avoid the MgO content of the refining slag exceeding 6% during production.

[0034] Based on the actual MgO content of the refining slag in production, the MgO content was set at 5%. The steel grade used in this test station was aluminum deoxidized steel, with high basicity in the refining slag and relatively small variation in SiO2 content, set at 10% and 8%. A series of CaO contents were designed and calculated using the Equilib multi-phase equilibrium module in FactSage 8.2, employing the precipitate targetphase method to sequentially obtain the complete melting temperature of the refining slag components corresponding to the designed CaO contents and the liquid and solid phase ratios of the refining slag at 1600℃ under industrial conditions. The Viscosity module was then used to sequentially calculate the viscosity of the refining slag components corresponding to the designed CaO contents at 1600℃. The designed refining slag components will have a solid component, which was determined using Viscosity. (solid+liquid) =Viscosity (liquid)·(1-solid fraction) -2.5 The formulas sequentially yield the designed viscosity of the refining slag. The calculated complete melting temperature and viscosity of the refining slag are as follows: Figure 2 As shown, Figure 2 (a) is a graph showing the effect of different CaO contents on the complete melting temperature of refining slag. Figure 2 (b) shows the effect of CaO content on the viscosity of refining slag. Calculations show that changes in SiO2 content have a very small impact on the refining slag. In this industrial test, the refining temperature was 1600℃. The CaO content in the refining slag with a complete melting temperature below 1600℃ was less than 58%, and the CaO content in the refining slag with a viscosity below 0.1 was 52%-61%. Under these conditions, to ensure good fluidity of the refining slag, the CaO content needs to be maintained at 52-58%, with an optimal value of approximately 56%.

[0035] The specific process for calculating the viscosity of the refining slag components is as follows:

[0036] Viscosity solid+liquid =Viscosity( liquid )·(1-solid fraction) -2.5 ;

[0037] Among them, Viscosity (solid+liquid) Viscosity is the viscosity of the solid-liquid mixture. (liquid) The viscosity of the liquid portion of the slag is given by , and the solid fraction is given by .

[0038] Step S2: Based on the composition of the refining slag and the corresponding complete melting temperature and viscosity of the refining slag, calculate the desulfurization capacity of each refining slag component, and determine the desulfurization range of the refining slag component based on the desulfurization capacity results.

[0039] Using the Equilib multi-component and multi-phase equilibrium module of FactSage 8.2 software, calculations were performed with a ratio of 100 tons of steel to 1 ton of slag. The MgO content in the refining slag was set at 5%. The theoretical desulfurization capacity of the refining slag was calculated for different CaO and Al2O3 contents at 10% and 8% SiO2 contents. Figure 3 As shown in the figure, the theoretical desulfurization capacity increases with the CaO content. When the CaO content reaches 60%, the theoretical desulfurization capacity of the refining slag reaches its limit, with a desulfurization rate exceeding 90%. Theoretically, the higher the CaO content, the stronger the desulfurization capacity of the refining slag. When the CaO content in the refining slag exceeds 60%, the refining slag can no longer undergo desulfurization.

[0040] Step S3: After selecting the optimal LF desulfurization refining slag composition based on the desulfurization capacity range of the refining slag composition, analyze the sulfur content in the steel to complete the design of the optimal LF desulfurization refining slag.

[0041] Based on the theoretical results of S1 and S2, five types of refining slag composition were designed to verify the calculation results, with CaO content of 50-60%. Practical operation was carried out in the industrial field. At the beginning of the LF refining process, after slag adjustment, and before leaving the station, the corresponding refining slag was obtained by inserting a steel rod into the slag layer. After cooling, it was put into a bag for testing. The corresponding molten steel was obtained by inserting a steel rod into the molten steel in an iron drum. After taking it out, it was quickly placed in water to cool to room temperature and then taken out for testing.

[0042] The refining slag was crushed into powder and made into a cake sample. XRF analysis was used to determine the composition of the slag. A steel sample was removed from the drum sample, cut 10mm from the bottom, and the oxide layer on the upper surface was ground off. The sulfur content in the steel was then determined using an electrical discharge machining (EDM) analyzer. This method yielded the sulfur content of the molten steel at the beginning and end of refining, verifying the theoretical desulfurization rate. Experimental results showed that the desulfurization effect was optimal, exceeding 80%, when the CaO content was 55-57%. Excessively low or high CaO content led to slag viscosity, affecting actual production and further impacting the desulfurization effect. Therefore, it is necessary to strictly control the refining slag within the range of complete melting temperature and good fluidity.

[0043] This disclosure is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A method for designing superior LF desulfurization refining slag, characterized in that, The method specifically includes: Step S1: Extract the refining slag components from the LF desulfurization refining slag, and calculate the complete melting temperature and viscosity of the refining slag components; Step S2: Based on the composition of the refining slag and the corresponding complete melting temperature and viscosity of the refining slag, calculate the desulfurization capacity of each refining slag composition, and determine the desulfurization range of the refining slag composition based on the desulfurization capacity results. Step S3: After selecting the optimal LF desulfurization refining slag composition based on the desulfurization capacity range of the refining slag composition, analyze the sulfur content in the steel to complete the design of the optimal LF desulfurization refining slag. Step S1, the process of extracting the refining slag components from the LF desulfurization refining slag and calculating the complete melting temperature and viscosity of the refining slag components specifically includes: The main component of the CaO-Al2O3-SiO2-MgO refining slag is the ternary CaO-Al2O3-SiO2 system. Using the Phase Diagram module in FactSage 8.2 software, the values ​​of 1400-1600 are calculated. o Complete melting range and viscosity of refining slag with 4%, 6%, 8%, and 10% MgO content under C; The specific process for calculating the viscosity of the refining slag components is as follows: in, The viscosity of the solid-liquid mixture is... The viscosity of the liquid portion of the slag. The viscosity of the solid portion of the slag; Step S3, the process of selecting superior LF desulfurization refining slag components based on the desulfurization capacity range of the refining slag components and then analyzing the sulfur content in the steel, specifically includes: Refining slag was prepared and pretreated based on the selected superior LF desulfurization refining slag components; The composition of the pretreated refining slag was analyzed using XRF equipment. Based on the composition analysis results, the sulfur content in the molten steel was calculated using an electrical discharge analyzer.

2. The design method for superior LF desulfurization refining slag according to claim 1, characterized in that, The LF refining temperature of the CaO-Al2O3-SiO2-MgO system refining slag is 1600. o C, select below 1600 o The refining residue components of C.

3. The design method for superior LF desulfurization refining slag based on claim 2, characterized in that, The MgO content of the CaO-Al2O3-SiO2-MgO system refining slag does not exceed 6%.

4. The design method for superior LF desulfurization refining slag based on claim 1, characterized in that, The desulfurization capacity range of the refining slag components was calculated using the Equilib equilibrium multi-component and multi-phase equilibrium module of FactSage 8.2 software.

5. The design method for superior LF desulfurization refining slag according to claim 1, characterized in that, The specific methods of preprocessing include: At the beginning, slag adjustment, and end stages of the LF refining process, steel rods were inserted into the slag layer to obtain the corresponding refining slag. After cooling, the slag was placed in bags for testing. Steel rods were inserted into the molten steel to obtain the corresponding molten steel. After removal, the molten steel was quickly placed in water to cool to room temperature and then removed for testing. The obtained refining slag was then ground into fine powder and pressed into cakes for sample preparation.

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