Process method for regulating and controlling melting point and viscosity of aluminum deoxidized steel refining slag based on rare earth cerium

Abstract

The invention discloses a technological method for regulating and controlling the melting point and viscosity of aluminum deoxidized steel refining slag based on rare earth cerium, and belongs to the technical field of ferrous metallurgy refining. The redox characteristic of Ce and slag system structure modification are combined, the limitation of traditional single component adjustment is broken through, and the composite oxide effect of Ce is utilized: Ce generates CeO2 and Ce-Al-O composite oxide at high temperature, so that the liquidus temperature of a slag system is remarkably reduced, and the melt structure is optimized; by limiting the addition amount of Ce and balancing the cost and performance, the situation that the oxidability of a slag system is out of control due to excessive Ce is avoided, and the thermodynamic stability of the slag system is improved; the addition of Ce inhibits the generation of high-melting-point calcium aluminate and promotes the formation of a low-melting-point phase; by adding Ce, melting point reduction, viscosity optimization and molten steel purification are achieved at the same time, the additive is superior to an existing single-function additive, traditional fluorite is replaced, and fluorine pollution is reduced. The invention aims to provide the same environment-friendly and efficient method capable of accurately regulating and controlling the physicochemical properties of the slag.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel metallurgy refining, and in particular relates to a process for regulating the melting point and viscosity of aluminum deoxidized steel refining slag based on rare earth cerium. Background Art

[0002] In the refining process of aluminum-deoxidized steel, the melting point and viscosity of the slag have a significant impact on smelting efficiency, molten steel purity, and energy consumption control. In traditional processes, the slag often uses the CaO-SiO2-Al2O3 system, but this slag system has the following problems:

[0003] 1. High melting point: Conventional slag may not be completely melted at refining temperature (1550-1650℃), resulting in poor fluidity and low mass transfer efficiency;

[0004] 2. High viscosity: Unmelted solid particles increase the viscosity of the slag layer, hindering the interface reaction between the molten steel and the slag, making it difficult for inclusions to float up;

[0005] 3. Sensitive to composition fluctuations: Increased Al2O3 content (generated by aluminum deoxidation reaction) can easily cause the slag system to shift toward the high melting point phase region.

[0006] Existing methods for lowering the melting point often involve adjusting the CaO / Al₂O₃ ratio or adding MgO or fluorite (CaF₂). However, these methods pose environmental risks, such as fluorite pollution and reduced slag stability caused by excessive MgO. Therefore, an environmentally friendly, efficient, and precise method for controlling the physicochemical properties of slag is urgently needed. Summary of the Invention

[0007] The purpose of the present invention is to provide a process method for regulating the melting point and viscosity of aluminum deoxidized steel refining slag based on rare earth cerium, with the aim of solving the problem in the background technology by proposing an environmentally friendly, efficient and precise method for regulating the physical and chemical properties of slag.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] The present invention provides a process for regulating the melting point and viscosity of aluminum deoxidized steel refining slag based on rare earth cerium, comprising:

[0010] 1) Combining the redox properties of Ce with slag structure modification, breaking through the limitations of traditional single component adjustment, utilizing Ce's composite oxide effect: Ce generates CeO2 and Ce-Al-O composite oxides at high temperatures, significantly reducing the slag liquidus temperature and optimizing the melt structure;

[0011] 2) By limiting the amount of Ce added, balancing cost and performance, avoiding excessive Ce causing uncontrolled slag oxidation, and improving the thermodynamic stability of the slag system: the addition of Ce inhibits the formation of high-melting-point calcium aluminates and promotes the formation of low-melting-point phases;

[0012] 3) The addition of Ce simultaneously reduces the melting point, optimizes viscosity, and purifies the molten steel, which is superior to existing single-function additives. It replaces the use of traditional fluorite and reduces fluorine pollution.

[0013] The specific steps include:

[0014] Step 1: Slag composition design

[0015] The basic composition of the refined slag is wt%: CaO: 45-55%, SiO2: 10-15%, Al2O3: 20-30%, MgO: 3-8%, and the balance is impurities;

[0016] Add rare earth cerium 0.1-2.0%

[0017] Step 2: When and how to add cerium

[0018] At the initial stage of refining, the molten steel temperature should be ≥1550℃ and added together with other slag-forming agents;

[0019] Use argon injection or mechanical stirring to ensure that Ce is evenly distributed in the slag layer;

[0020] Step 3: Thermodynamic Control Mechanism

[0021] CeO2 reacts with Al2O3 to form CeAlO3 with low melting point, replacing CaO·2Al2O3 with high melting point; Ce 3+ Ions reduce the degree of polymerization of the slag system through the charge compensation effect, reducing [AlO4] 5- Tetrahedral network structure, thus reducing viscosity;

[0022] Step 4: Process parameter control

[0023] Refining temperature: 1580-1650℃;

[0024] Slag layer thickness: 30-50mm;

[0025] Oxygen activity control: ≤5ppm, to avoid excessive oxidation of Ce.

[0026] Furthermore, the Ce addition range is 0.1-2.0%.

[0027] Furthermore, the composition of the refined slag by mass percentage is: CaO 50%, SiO2 12%, Al2O3 25%, MgO 5%, CeO2 0.8%, and the balance is impurities.

[0028] Furthermore, applicable steel types are: low carbon aluminum deoxidized steel, C≤0.08%, Al=0.02-0.06%.

[0029] Furthermore, the composition of the refined slag by mass percentage is: CaO 52%, SiO2 10%, Al2O3 28%, MgO 5%, metal Ce 1.0%, and the balance is impurities.

[0030] Furthermore, applicable steel types are: high-strength steel, Al=0.1-0.2%.

[0031] Furthermore, 0.5-1.2% of rare earth cerium is added.

[0032] Compared with the prior art, the present invention has the following beneficial technical effects:

[0033] 1. Significantly reduce the melting point: the liquidus temperature of the slag system is reduced by 50-100°C, promoting complete melting of the slag layer;

[0034] 2. Viscosity optimization: The slag viscosity at 1600°C is reduced from 0.8-1.2 Pa·s to 0.3-0.5 Pa·s, improving the desulfurization and deoxidation efficiency;

[0035] 3. Improved cleanliness of molten steel: The proportion of inclusions ≤5μm increased to over 90%;

[0036] 4. Environmental protection: Reduce the amount of fluorite by more than 50% and reduce fluoride emissions. DETAILED DESCRIPTION

[0037] In order to more clearly understand the above aspects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with specific embodiments.

[0038] Step 1: Slag composition design

[0039] The basic composition of the refined slag is (wt%): CaO: 45-55%, SiO2: 10-15%, Al2O3: 20-30%, MgO: 3-8%, and the balance is impurities;

[0040] Rare earth cerium (in the form of metallic cerium or CeO2) is added in an amount of 0.1-2.0%, preferably 0.5-1.2%.

[0041] Step 2: When and how to add cerium

[0042] Added together with other slagging agents (such as lime and bauxite) at the initial stage of refining (molten steel temperature ≥ 1550℃);

[0043] Use argon blowing or mechanical stirring to ensure that Ce is evenly distributed in the slag layer.

[0044] Step 3: Thermodynamic Control Mechanism

[0045] CeO2 reacts with Al2O3 to form low melting point CeAlO3 (melting point about 1600℃), replacing high melting point CaO·2Al2O3 (melting point about 1750℃); Ce 3+ Ions reduce the degree of polymerization of the slag system through the charge compensation effect, reducing [AlO4] 5- Tetrahedral network structure, thereby reducing viscosity.

[0046] Step 4: Process parameter control

[0047] Refining temperature: 1580-1650℃;

[0048] Slag layer thickness: 30-50mm;

[0049] Oxygen activity control: ≤5ppm, to avoid excessive oxidation of Ce.

[0050] Example 1:

[0051] Steel type: low carbon aluminum deoxidized steel (C≤0.08%, Al=0.02-0.06%);

[0052] Refining slag composition: CaO 50%, SiO212%, Al2O325%, MgO 5%, CeO20.8%;

[0053] Results: The melting point of the slag dropped from 1680℃ to 1605℃, the viscosity at 1600℃ was 0.4Pa·s, and the total oxygen content in the steel was ≤15ppm.

[0054] Example 2:

[0055] Steel type: high-strength steel (Al=0.1-0.2%);

[0056] Refining slag composition: CaO 52%, SiO2 10%, Al2O3 28%, MgO 5%, metal Ce 1.0%;

[0057] Results: The proportion of CaO·2Al2O3 phase in the slag decreased from 30% to 8%, and the inclusion density decreased by 40%.

[0058] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A process for regulating the melting point and viscosity of aluminum deoxidized steel refining slag based on rare earth cerium, characterized in that: include: 1) Combining the redox properties of Ce with slag structure modification, breaking through the limitations of traditional single component adjustment, utilizing Ce's composite oxide effect: Ce generates CeO2 and Ce-Al-O composite oxides at high temperatures, significantly reducing the slag liquidus temperature and optimizing the melt structure; 2) By limiting the amount of Ce added, balancing cost and performance, avoiding excessive Ce causing uncontrolled slag oxidation, and improving the thermodynamic stability of the slag system: the addition of Ce inhibits the formation of high-melting-point calcium aluminates and promotes the formation of low-melting-point phases; 3) The addition of Ce can simultaneously reduce the melting point, optimize the viscosity and purify the molten steel, which is superior to existing single-function additives, replacing the use of traditional fluorite and reducing fluorine pollution. The specific steps include: Step 1: Slag composition design The basic composition of the refined slag is wt%: CaO: 45-55%, SiO2: 10-15%, Al2O3: 20-30%, MgO: 3-8%, and the balance is impurities; Add rare earth cerium 0.1-2.0% Step 2: When and how to add cerium At the initial stage of refining, the molten steel temperature should be ≥1550℃ and added together with other slag-forming agents; Use argon injection or mechanical stirring to ensure that Ce is evenly distributed in the slag layer; Step 3: Thermodynamic Control Mechanism CeO2 reacts with Al2O3 to form CeAlO3 with low melting point, replacing CaO·2Al2O3 with high melting point; Ce 3+ Ions reduce the degree of polymerization of the slag system through the charge compensation effect, reducing [AlO4] 5- Tetrahedral network structure, thus reducing viscosity; Step 4: Process parameter control Refining temperature: 1580-1650℃; Slag layer thickness: 30-50mm; Oxygen activity control: ≤5ppm, to avoid excessive oxidation of Ce.

2. The process for regulating the melting point and viscosity of aluminum-deoxidized steel refining slag based on rare earth cerium according to claim 1, characterized in that: The Ce addition range is 0.1-2.0%.

3. The process for regulating the melting point and viscosity of aluminum-deoxidized steel refining slag based on rare earth cerium according to claim 1, characterized in that: The composition of the refined slag by mass percentage is: CaO 50%, SiO2 12%, Al2O3 25%, MgO 5%, CeO2 0.8%, and the balance is impurities.

4. The process for regulating the melting point and viscosity of aluminum-deoxidized steel refining slag based on rare earth cerium according to claim 3, characterized in that: Applicable steel types are: low carbon aluminum deoxidized steel, C≤0.08%, Al=0.02-0.06%.

5. The process for regulating the melting point and viscosity of aluminum-deoxidized steel refining slag based on rare earth cerium according to claim 1, characterized in that: The composition of the refined slag by mass percentage is: CaO 52%, SiO2 10%, Al2O3 28%, MgO 5%, metal Ce 1.0%, and the balance is impurities.

6. The process for regulating the melting point and viscosity of aluminum-deoxidized steel refining slag based on rare earth cerium according to claim 4, characterized in that: Applicable steel types: high-strength steel, Al=0.1-0.2%.

7. The process for regulating the melting point and viscosity of aluminum-deoxidized steel refining slag based on rare earth cerium according to claim 1, characterized in that: Add 0.5-1.2% rare earth cerium.