Rotary injection passivation Mg-Al alloy powder desulfurization method

Abstract

The invention discloses a rotary injection passivation Mg-Al alloy powder desulfurization method, and belongs to the technical field of metallurgy. In order to solve the problems of low desulfurization rate, low magnesium utilization rate and the like in the prior art, the invention provides a rotary injection passivation Mg-Al alloy powder desulfurization method, which comprises the following steps: adding calcium carbonate into molten aluminum to obtain aluminum coated calcium carbonate; the magnesium-aluminum alloy powder is dispersed in an organic solvent, a passivating agent is added, and passivated magnesium-aluminum alloy powder is obtained; and inserting the rotary spray gun into a ladle, firstly spraying the passivated active lime, then adding the aluminum-coated calcium carbonate particles, and then spraying the passivated magnesium-aluminum alloy powder to finish desulfurization. According to the method, calcium carbonate is wrapped with aluminum, the desulfurization effect is improved, in-situ desulfurization thermodynamic conditions are created through magnesium-aluminum alloy powder, the magnesium vapor pressure is reduced, the retention time of magnesium vapor in molten iron is prolonged, the sulfur content of the molten iron is reduced, the magnesium utilization rate is improved, the material adding conditions are controlled, the desulfurization effect is fully exerted, and the desulfurization effect is remarkably improved through rotary injection.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a desulfurization method for rotary spray passivated Mg-Al alloy powder. Background Art

[0002] Currently, there are two widely used methods for molten iron desulfurization: the injection method and the KR method. The injection method uses an inert gas as a carrier to spray desulfurization powder into the molten iron through a spray gun, causing the desulfurizer to react with the molten iron, achieving desulfurization. However, the desulfurization powder does not fully contact the sulfur in the molten iron, resulting in low desulfurization efficiency and high desulfurizer consumption. Desulfurization using passivated magnesium powder spraying has a short residence time and high desulfurization consumption. The KR method inserts a stirring head into the molten iron to a certain depth. The vortex generated by the intense stirring of a large agitator allows the desulfurization powder to contact and react with the molten iron components, achieving desulfurization. The KR method has higher desulfurization efficiency and lower desulfurization powder consumption, but it also results in a significant temperature drop.

[0003] CN115029511A discloses a calcium oxide-based desulfurizer for spraying complex vanadium-titanium high-sulfur molten iron and its application, wherein the calcium oxide-based desulfurizer is specifically lime powder CaO, calcium carbide CaC2, fluorite CaF2, and AD powder, and has the following components in the following mass ratio: CaO: 68wt%~75wt%, CaC2: 7wt%~8wt%, CaF2: 5wt%~6wt%, Al: 0.5wt%~1.0wt%, Al2O3: 2wt%~3wt%, and the remainder is inevitable impurities; and the amount of desulfurizer added is determined according to the original sulfur content of the molten iron and the molten iron temperature; the mixed calcium oxide-based desulfurizer is sprayed into the molten iron through a spray gun using nitrogen as a carrier gas for desulfurization, solving the problems of low desulfurization rate of complex vanadium-titanium high-sulfur molten iron and long pretreatment time affecting production organization. However, calcium fluoride in this method is not environmentally friendly and there is a risk of increased erosion of refractory materials.

[0004] CN107287377A discloses a composite desulfurizer for hot metal injection desulfurization and its preparation method. The composite desulfurizer comprises the following components by weight: 80-90% passivated magnesium powder, 1-8% metallic aluminum, 2-10% aluminum oxide, and the remainder being unavoidable impurities. This method increases the utilization rate of the passivated magnesium powder in the composite desulfurizer by an average of more than 5%, reducing the cost of hot metal desulfurization. The aluminum component of the composite desulfurizer is derived from metallic aluminum and aluminum oxide found in industrial aluminum ash, significantly reducing the production cost of the composite desulfurizer and enabling the reuse of industrial aluminum ash as waste. However, this method still does not address the issue of low magnesium utilization.

[0005] CN108504821A discloses a vanadium-titanium molten iron composite desulfurizer, which contains the following components in weight percentage: CaO 70-85%, Al2O3 5-20%, Al 2-8%, Mg 1-7%, Na2CO3 2-13%, and the rest are inevitable impurities; the vanadium-titanium molten iron composite desulfurizer is a powder mixed with raw materials containing CaO, Al2O3, Al, Mg and Na2CO3 respectively; desulfurization is carried out by a blowing method.

[0006] CN103789502A discloses a method for preparing a desulfurizer for silicon steel sheets, wherein the desulfurizer is composed of the following components by weight: 50-54 parts of CaO, 18-22 parts of Al, 12-16 parts of MgO, 10-12 parts of SiO2, 3-7 parts of Al2O3, 3-5 parts of Fe2O3, 5-7 parts of CaF2, 5-7 parts of BaO, 10-12 parts of SiO2, 3-7 parts of Al2O3, 3-5 parts of Fe2O3, 5-7 parts of CaF2, 5-7 parts of BaO, 5-7 parts of Mg ...10-12 parts of SiO2, 3-7 parts of Al2O3, 3-5 parts of Fe2O3, 5-7 parts of CaF2, 5-7 parts of BaO, 5- 7-9 parts, the preparation method comprises the following steps: 1) mixing: mixing the materials in proportion; 2) crushing: placing the mixed materials into a crusher for crushing and processing so that the material particle size is ≤0.4mm; 3) passivation: spraying a 30%-50% organic silicone resin solution for passivation protection, the amount of the organic silicone solution is 0.4%-0.8% of the total weight of the material, and after passivation treatment, a passivation film with a thickness of 0.4-0.6um is formed on the surface of the material particles; 4) drying: after crushing and passivation, drying treatment is required, the drying temperature is 120-150°C, and the drying time is 30-60min, so that the organic components of the passivation solution are quickly volatilized and a trace amount of water is discharged at the same time.

[0007] CN1354057A discloses a granular passivated magnesium powder for off-furnace desulfurization in the steel metallurgical industry. The powder is prepared by coating a hydrophobic layer on the surface of granular magnesium powder having a particle size of 0.1 to 2.0 μm, and then adhering a flame retardant layer to the surface of the hydrophobic layer. The hydrophobic agent is an organic substance that is solid at room temperature, such as rosin, asphalt, resin, and mixtures thereof. The amount of the hydrophobic agent is 1 to 10% of the total weight of the passivated magnesium powder. The flame retardant is one or more oxides or salts of Ca, Mg, Al, and Si, such as CaO, MgO, CaCO₃, MgCO₃, Al₂O₃, SiO₂, and mixtures thereof. The flame retardant is a powder having a particle diameter of 0.08 mm or less, preferably 0.03 mm or less. The amount of the flame retardant is 1 to 20% of the total weight of the passivated magnesium powder. The total weight of the hydrophobic agent and flame retardant is 3 to 25% of the total weight of the passivated magnesium powder. Summary of the Invention

[0008] In response to the shortcomings of the existing technology, the present invention proposes a rotary spray passivation Mg-Al alloy powder desulfurization process, which uses Mg-Al alloy powder to create in-situ desulfurization thermodynamic conditions, while reducing the magnesium vapor pressure and extending the residence time in molten iron, thereby reducing the sulfur content of the molten iron and improving the magnesium utilization rate.

[0009] The present invention provides a desulfurization method for rotary spray passivated Mg-Al alloy powder, which comprises the following steps: A. Add calcium carbonate to aluminum liquid under stirring, wrap a layer of aluminum film on the surface of calcium carbonate, and then cool and crush to obtain aluminum-coated calcium carbonate particles; B. Under an inert atmosphere (the entire process of preparing the passivated magnesium-aluminum alloy powder is carried out under an inert atmosphere), a magnesium-aluminum alloy ingot is crushed into magnesium-aluminum alloy powder (the magnesium-aluminum alloy powder can be prepared by mechanical crushing), the magnesium-aluminum alloy powder is dispersed in an organic solvent, a passivating agent is added, and the mixture is reacted under stirring or ultrasonic conditions so that the passivating agent uniformly coats the surface of the magnesium-aluminum alloy powder, and then filtered, dried and crushed to obtain the passivated magnesium-aluminum alloy powder; C. Insert the rotary lance into the molten iron ladle at a distance of 350-550mm from the bottom, rotate at 90-110rpm, and spray in passivation active lime at a rate of 3-4kg / t iron; increase the speed to 100-120rpm, add aluminum-coated calcium carbonate particles at a rate of 1.5-2.5kg / t iron; then spray in passivation magnesium-aluminum alloy powder at a rate of 1.0-1.4kg / t iron to complete desulfurization.

[0010] Wherein, in the above method, in step A, the particle size of the calcium carbonate is ≤1 mm.

[0011] In the above method, in step A, aluminum liquid is used to coat the calcium carbonate. The temperature of the aluminum liquid is generally ≥660°C (generally not higher than 900°C). At this temperature, the calcium carbonate will not be decomposed and the aluminum can be evenly coated with the calcium carbonate.

[0012] In the above method, in step A, the aluminum film thickness of the aluminum-coated calcium carbonate is 0.5-1 mm, and the particle size of the aluminum-coated calcium carbonate is 1-2 mm. In step A, the amount of aluminum liquid used is appropriate to ensure that the aluminum film thickness of the aluminum-coated calcium carbonate is 0.5-1 mm.

[0013] Wherein, in the above method, in step B, the Mg content in the magnesium-aluminum alloy ingot is 70-85wt%, and the Al content is 30-15wt%.

[0014] Wherein, in the above method, in step B, the particle size of the magnesium-aluminum alloy powder is ≤1.0 mm.

[0015] In the above method, in step B, the organic solvent is at least one of ethanol or toluene.

[0016] In the above method, in step B, the passivation agent is at least one of stearic acid, paraffin wax or silane coupling agent.

[0017] In the above method, in step B, the amount of the passivation agent is 5-15% of the mass of the magnesium-aluminum alloy powder.

[0018] In the above method, in step B, the reaction temperature is 50-80 DEG C.

[0019] In the above method, in step C, the particle size of the passivated active lime is less than or equal to 1 mm.

[0020] In the above method, in step C, after desulfurization is completed, the sulfur content of the molten iron is reduced to less than or equal to 15 ppm, and the magnesium utilization rate is greater than or equal to 53%.

[0021] The beneficial effects of the present application are as follows: In the present application, calcium carbonate coated with Al is introduced into the molten iron, Al is dissolved to create conditions for desulfurization, and then calcium carbonate is decomposed to generate active calcium oxide for desulfurization, which has better desulfurization effect than adding Al and calcium carbonate respectively; generally, magnesium powder desulfurization easily produces magnesium vapor, and the utilization rate is not high, the present application uses magnesium-aluminum alloy, which delays the formation of magnesium vapor and reduces the magnesium vapor pressure, and on the other hand, Al in the alloy deoxidizes and promotes in-situ desulfurization, thereby improving the magnesium utilization rate and desulfurization effect.

[0022] In the present application, passivated active lime, aluminum-coated calcium carbonate particles and passivated magnesium-aluminum alloy powder are sequentially sprayed, and the addition conditions and amounts of the three are controlled; when the initial sulfur content is high, passivated active lime is sprayed for desulfurization, and as the sulfur content decreases, aluminum-coated calcium carbonate particles and passivated magnesium-aluminum alloy powder with stronger desulfurization capacity are sequentially added for further deep desulfurization, thereby improving the utilization rate of each material and fully utilizing the desulfurization effect of each material; at the same time, the present application uses rotary injection desulfurization, which has the functions of injection and stirring, powder injection and particle addition, thereby fully utilizing the desulfurization capacity of each material and improving the desulfurization effect.

[0023] The present application has strong operability, and through optimization of desulfurization materials and process, the sulfur content of the molten iron can be reduced to less than or equal to 15 ppm, the magnesium utilization rate is greater than or equal to 53%, the magnesium utilization rate is increased by more than 8%, the cost is reduced, it is suitable for steel enterprises to popularize and apply, and has significant economic benefits. DETAILED DESCRIPTION

[0024] Specifically, a rotary spray passivation Mg-Al alloy powder desulfurization method comprises the following steps: A. Add calcium carbonate to aluminum liquid under stirring, wrap a layer of aluminum film on the surface of calcium carbonate, and then cool and crush to obtain aluminum-coated calcium carbonate particles; B. Under an inert atmosphere (the entire process of preparing the passivated magnesium-aluminum alloy powder is carried out under an inert atmosphere), a magnesium-aluminum alloy ingot is crushed into magnesium-aluminum alloy powder (the magnesium-aluminum alloy powder can be prepared by mechanical crushing), the magnesium-aluminum alloy powder is dispersed in an organic solvent, a passivating agent is added, and the mixture is reacted under stirring or ultrasonic conditions so that the passivating agent uniformly coats the surface of the magnesium-aluminum alloy powder, and then filtered, dried and crushed to obtain the passivated magnesium-aluminum alloy powder; C. Insert the rotary lance into the molten iron ladle at a distance of 350-550mm from the bottom, rotate at 90-110rpm, and spray in passivation active lime at a rate of 3-4kg / t iron; increase the speed to 100-120rpm, add aluminum-coated calcium carbonate particles at a rate of 1.5-2.5kg / t iron; then spray in passivation magnesium-aluminum alloy powder at a rate of 1.0-1.4kg / t iron to complete desulfurization.

[0025] In this method, aluminum is used to coat calcium carbonate before it is added to the molten iron. The aluminum dissolves and deoxidizes the metal, creating conditions for desulfurization. The calcium carbonate then decomposes to produce active calcium oxide, achieving a more effective desulfurization effect than adding aluminum and calcium carbonate separately. In step A, the calcium carbonate has a particle size of ≤1 mm. In step A, aluminum liquid is used to coat the calcium carbonate. The aluminum liquid temperature is generally ≥660°C (generally not higher than 900°C). This temperature prevents calcium carbonate decomposition while ensuring uniform aluminum coating.

[0026] In step A of the present invention, the aluminum film of the aluminum-coated calcium carbonate has a thickness of 0.5 to 1 mm, and the particle size of the aluminum-coated calcium carbonate is 1 to 2 mm. In step A, the amount of aluminum liquid used is appropriate to ensure that the aluminum film of the aluminum-coated calcium carbonate has a thickness of 0.5 to 1 mm.

[0027] The present invention utilizes a magnesium-aluminum alloy to delay magnesium vapor formation and reduce magnesium vapor pressure. It also deoxidizes the aluminum in the alloy, promoting in-situ desulfurization, thereby improving magnesium utilization and desulfurization effectiveness. In step B, the magnesium-aluminum alloy ingot contains 70-85% Mg and 30-15% Al by weight. In step B, the magnesium-aluminum alloy powder has a particle size of ≤1 mm.

[0028] For safety and powder spraying needs, the present invention coats the magnesium-aluminum alloy powder with a passivator. In step B, the organic solvent is at least one of ethanol or toluene. In the present invention, the amount of organic solvent used is appropriate to ensure that the magnesium-aluminum alloy powder can be evenly dispersed and the passivator can be dissolved. Residual organic solvent will be removed by filtration and drying. In step B of the present invention, the passivator is at least one of stearic acid, paraffin, or a silane coupling agent. In step B of the present invention, the amount of the passivator used is 5-15% of the mass of the magnesium-aluminum alloy powder.

[0029] In step B of the present invention, the reaction temperature is 50-80°C.

[0030] In step C of the present invention, the particle size of the passivated active lime is ≤1 mm.

[0031] In step C of the present invention, after desulfurization is completed, the sulfur content of the molten iron is reduced to below 15 ppm, the magnesium utilization rate is ≥53%, and the magnesium utilization rate is increased by more than 8%, which significantly improves the desulfurization effect and the magnesium utilization rate.

[0032] The present invention is further described in detail below through examples, but the protection scope of the present invention is not limited to the scope of the examples.

[0033] Example 1 Calcium carbonate with a particle size of ≤1mm is added to an appropriate amount of aluminum liquid while stirring, and a layer of aluminum film is wrapped on the surface of the calcium carbonate. After cooling and crushing, aluminum-coated calcium carbonate particles with a particle size of 1~2mm are obtained.

[0034] Under an inert atmosphere, a magnesium-aluminum alloy ingot (Mg content 70wt%, Al content 30wt%) was mechanically crushed into a powder with a particle size of less than 1.0mm. The magnesium-aluminum alloy powder was dispersed in an appropriate amount of ethanol, and 10% stearic acid as a passivating agent was added. The mixture was reacted at 50-60°C under stirring to uniformly coat the surface of the magnesium powder with the passivating agent. The powder was then filtered, dried, and crushed to obtain a passivated magnesium-aluminum alloy powder.

[0035] Insert the rotary lance into the molten iron ladle at a distance of 350mm from the bottom, rotate at 90rpm, and spray passivating active lime (particle size less than 1mm) at a rate of 3.0kg / t iron. Increase the speed to 100rpm, add aluminum-coated calcium carbonate particles at a rate of 1.5kg / t iron, and then spray passivating magnesium-aluminum alloy powder at a rate of 1.0kg / t iron. This can reduce the sulfur content of the molten iron to 14ppm, achieve a magnesium utilization rate of 60%, and increase the magnesium utilization rate by more than 15% (the existing process usually uses CaO+Mg mixed injection desulfurization, with a magnesium utilization rate of 35-45%).

[0036] Example 2 Calcium carbonate with a particle size of ≤1mm is added to an appropriate amount of aluminum liquid while stirring, and a layer of aluminum film is wrapped on the surface of the calcium carbonate. After cooling and crushing, aluminum-coated calcium carbonate particles with a particle size of 1~2mm are obtained.

[0037] Under an inert atmosphere, a magnesium-aluminum alloy ingot (Mg content 78wt%, Al content 22wt%) was mechanically crushed into a powder with a particle size of less than 1.0mm. The magnesium-aluminum alloy powder was dispersed in an appropriate amount of toluene, and 12% passivating agent paraffin was added. The mixture was reacted at 70-80℃ under stirring to allow the passivating agent to evenly coat the surface of the magnesium powder. The powder was then filtered, dried and crushed to obtain a passivated magnesium-aluminum alloy powder.

[0038] Insert the rotary lance into the molten iron ladle at a distance of 410mm from the bottom and a rotation speed of 100rpm, and spray passivation active lime (particle size less than 1mm) at a spray rate of 3.5kg / t iron; increase the rotation speed to 110rpm, add aluminum-coated calcium carbonate particles at a dosage of 2.0kg / t iron; then spray passivation magnesium-aluminum alloy powder at a spray rate of 1.2kg / t iron; this can reduce the sulfur content of the molten iron to 12ppm, and the magnesium utilization rate is 56%, which is an increase of more than 11%.

[0039] Example 3 Calcium carbonate with a particle size of ≤1mm is added to an appropriate amount of aluminum liquid while stirring, and a layer of aluminum film is wrapped on the surface of the calcium carbonate. After cooling and crushing, aluminum-coated calcium carbonate particles with a particle size of 1~2mm are obtained.

[0040] Under an inert atmosphere, a magnesium-aluminum alloy ingot (Mg content 85wt%, Al content 15wt%) was mechanically crushed into a powder with a particle size of less than 1.0 mm. The magnesium-aluminum alloy powder was dispersed in an appropriate amount of toluene, and 6% of a passivating silane coupling agent was added. The mixture was reacted at 50-60°C under stirring to uniformly coat the surface of the magnesium powder with the passivating agent. The powder was then filtered, dried, and crushed to obtain a passivated magnesium-aluminum alloy powder.

[0041] Insert the rotary lance into the molten iron ladle at a distance of 550mm from the bottom and at a rotation speed of 110rpm, spray in passivating active lime (particle size less than 1mm) at a rate of 4.0kg / t iron; increase the rotation speed to 120rpm, add aluminum-coated calcium carbonate particles at a rate of 2.5kg / t iron; then spray in passivating magnesium-aluminum alloy powder at a rate of 1.4kg / t iron; this can reduce the sulfur content of the molten iron to 10ppm, achieve a magnesium utilization rate of 53%, and increase the magnesium utilization rate by more than 8%.

Claims

1. A desulfurization method for passivated Mg-Al alloy powder by rotary spraying, characterized in that: The following steps are involved: A. Add calcium carbonate to aluminum liquid under stirring, wrap a layer of aluminum film on the surface of calcium carbonate, and then cool and crush to obtain aluminum-coated calcium carbonate particles; B. Under an inert atmosphere, crushing a magnesium-aluminum alloy ingot into magnesium-aluminum alloy powder, dispersing the magnesium-aluminum alloy powder in an organic solvent, adding a passivating agent, reacting under stirring or ultrasonic conditions so that the passivating agent evenly coats the surface of the magnesium-aluminum alloy powder, and then filtering, drying and crushing to obtain passivated magnesium-aluminum alloy powder; C. Insert the rotary lance into the molten iron ladle at a distance of 350-550mm from the bottom, rotate at 90-110rpm, and spray in passivation active lime at a rate of 3-4kg / t iron; increase the speed to 100-120rpm, add aluminum-coated calcium carbonate particles at a rate of 1.5-2.5kg / t iron; then spray in passivation magnesium-aluminum alloy powder at a rate of 1.0-1.4kg / t iron to complete desulfurization.

2. The desulfurization method of rotary spray passivation Mg-Al alloy powder according to claim 1, characterized in that: In step A, the particle size of the calcium carbonate is ≤1.0 mm.

3. The desulfurization method of rotary spray passivated Mg-Al alloy powder according to claim 1, characterized in that: In step A, the thickness of the aluminum film of the aluminum-coated calcium carbonate is 0.5-1 mm, and the particle size of the aluminum-coated calcium carbonate is 1-2 mm.

4. The desulfurization method of rotary spray passivated Mg-Al alloy powder according to claim 1, characterized in that: In step B, the magnesium-aluminum alloy ingot has a Mg content of 70-85 wt % and an Al content of 30-15 wt %.

5. The desulfurization method of rotary spray passivated Mg-Al alloy powder according to claim 1, characterized in that: In step B, the particle size of the magnesium-aluminum alloy powder is ≤1.0 mm.

6. The desulfurization method of rotary spray passivated Mg-Al alloy powder according to claim 1, characterized in that: In step B, the organic solvent is at least one of ethanol or toluene.

7. The desulfurization method of rotary spray passivated Mg-Al alloy powder according to claim 1, characterized in that: At least one of the following must be met: In step B, the passivating agent is at least one of stearic acid, paraffin or silane coupling agent; In step B, the amount of the passivating agent is 5-15% of the mass of the magnesium-aluminum alloy powder.

8. The desulfurization method of rotary spray passivated Mg-Al alloy powder according to claim 1, characterized in that: In step B, the reaction temperature is 50-80°C.

9. The desulfurization method of rotary spray passivated Mg-Al alloy powder according to claim 1, characterized in that: In step C, the particle size of the passivated active lime is ≤1 mm.

10. The desulfurization method of rotary spray passivated Mg-Al alloy powder according to any one of claims 1 to 9, characterized in that: In step C, after desulfurization is completed, the sulfur content of the molten iron is reduced to below 15 ppm, and the magnesium utilization rate is ≥53%.