Method for preparing LF refining slag from magnesium reducing slag

Abstract

The invention provides a method for preparing LF refining slag from magnesium reducing slag, and belongs to the technical field of comprehensive utilization of steel smelting. The LF refining slag provided by the invention comprises the following raw material components in parts by weight: 100 parts of magnesium reducing slag, 10-15 parts of silicon-manganese alloy, 1-3 parts of aluminum powder, 2-5 parts of pulverized coal, 2-5 parts of a binder and 3-7 parts of a fluxing agent. By reasonably proportioning various raw materials, the fluxing effect and the physical property of the refining slag are improved, the resource utilization of the magnesium reducing slag is realized, and the production cost is reduced. The LF refining slag provided by the invention has a better deoxidation effect in steel smelting, and the purity of molten steel is improved. The preparation process of the LF refining slag provided by the invention is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of comprehensive utilization of iron and steel smelting, and particularly relates to a method for preparing LF refining slag from magnesium reduction slag. Background Art

[0002] The LF (ladle furnace refining) process is one of the key technologies for improving the quality of molten steel and optimizing composition control in modern iron and steel production. To achieve efficient refining, refining slag is often added to the molten steel to adjust the composition of the molten steel, promote desulfurization and deoxidation, and absorb inclusions. The raw materials of traditional refining slag mainly rely on natural minerals such as limestone and fluorite, which not only increases the cost but also has an adverse impact on the environment. In recent years, the resource utilization of industrial waste residues has gradually attracted the attention of the research and industrial communities.

[0003] Patent CN106868253A discloses a method for preparing LF furnace refining slag using waste inner lining bricks and aluminum ash from aluminum electrolysis. The waste inner lining of aluminum electrolysis is added with aluminum ash and other components to obtain LF refining slag. This patent uses a common slag-making method by mixing, and the performance of the refining slag is relatively unstable, and the production cost is high. Patent CN102787213A discloses a low-cost calcium-aluminum pre-melted refining slag for steelmaking and its preparation method. This patent uses industrial waste rich in calcium oxide and aluminum oxide to mix and prepare LF refining slag, and the production process is complex and the production cost is relatively high. Summary of the Invention

[0004] To solve the problems existing in the prior art, the present invention aims to provide a method for preparing LF refining slag from magnesium reduction slag. The present invention forms a briquette by reasonably proportioning magnesium reduction slag, ferrosilicon manganese alloy, aluminum powder, pulverized coal, and binder. To improve the melting aid effect of the briquette, CaF2 melting aid is evenly sprayed on the surface, and after drying, the refining slag suitable for LF refining is obtained. By optimizing the raw material composition and process steps, the present invention not only realizes the efficient utilization of magnesium reduction slag but also ensures that the prepared refining slag has good deoxidation and desulfurization effects and an appropriate melting speed during the LF refining process.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention is an LF refining slag. By weight, the raw materials include the following components: 100 parts of magnesium reduction slag, 10 - 15 parts of ferrosilicon manganese alloy, 1 - 3 parts of aluminum powder, 2 - 5 parts of pulverized coal, 2 - 5 parts of binder, and 3 - 7 parts of melting aid.

[0007] Another technical solution of the present invention is a preparation method of the above LF refining slag, including the following steps:

[0008] Mix magnesium reduction slag, ferrosilicon manganese alloy, aluminum powder, pulverized coal, and binder evenly, and then briquette to obtain a briquette.

[0009] Spray an aqueous solution of a flux on the surface of the briquette body, and dry it to obtain the LF refining slag.

[0010] The third technical solution of the present invention is an application of the above LF refining slag in steel smelting.

[0011] The present invention discloses the following technical effects:

[0012] By reasonably proportioning various raw materials, the present invention improves the fluxing effect and physical properties of the refining slag, realizes the resource utilization of magnesium reduction slag, and reduces the production cost.

[0013] The LF refining slag provided by the present invention has a good deoxidation effect in steel smelting and improves the purity of molten steel.

[0014] The preparation process of the LF refining slag provided by the present invention is simple. Specific Embodiments

[0015] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0016] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0017] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0018] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of the present invention are merely exemplary.

[0019] As used herein, terms such as "comprising", "including", "having", "containing", etc. are all open-ended terms, meaning including but not limited to.

[0020] In the present invention, "%" represents mass percentage.

[0021] Magnesium reduction slag refers to the slag remaining after the reduction reaction during the production of metallic magnesium. As a by-product containing various useful components such as magnesium, iron, silicon, and aluminum, magnesium reduction slag has great development potential in the metallurgical field.

[0022] In the first aspect of the present invention, there is provided an LF refining slag. By weight, the raw materials include the following components: 100 parts of magnesium reduction slag, 10 - 15 parts of ferrosilicon manganese alloy, 1 - 3 parts of aluminum powder, 2 - 5 parts of pulverized coal, 2 - 5 parts of binder, and 3 - 7 parts of flux.

[0023] In the present invention, the magnesium reduction slag is the slag remaining after the reduction reaction during the production of metallic magnesium. The magnesium reduction slag obtained by the production processes in the prior art is applicable to the present invention.

[0024] In some embodiments of the present invention, the proportion of the ferrosilicon manganese alloy with a particle size less than 1 mm is 90 - 95%; the silicon content in the ferrosilicon manganese alloy is 60 wt% - 70 wt%, the manganese content is 15 wt - 25 wt%, and the remaining components are impurities.

[0025] The silicon - manganese ratio of the present invention is optimized by balancing the deoxidation ability, cost - effectiveness, and final product performance. Excessive silicon content or insufficient manganese content will lead to a decrease in deoxidation efficiency and process problems, while insufficient silicon or excessive manganese will increase costs and affect the quality of steel. In actual production, the composition range needs to be strictly controlled to ensure the best performance.

[0026] In some embodiments of the present invention, the proportion of the aluminum powder with a particle size less than 0.4 mm is 90 - 95%.

[0027] In some embodiments of the present invention, the fixed - carbon content of the pulverized coal is 70% - 80%; the proportion of the pulverized coal with a particle size less than 0.3 mm is 70 - 100%.

[0028] In some embodiments of the present invention, the binder is water glass; the modulus of the water glass is 2.0 - 2.3.

[0029] In some embodiments of the present invention, the flux is CaF2.

[0030] In the second aspect of the present invention, there is provided a preparation method of the above - mentioned LF refining slag, including the following steps:

[0031] After uniformly mixing magnesium reduction slag, ferrosilicon manganese alloy, aluminum powder, pulverized coal and binder, briquetting is carried out to obtain a briquette body;

[0032] An aqueous solution of a flux is sprayed on the surface of the briquette body and dried to obtain the LF refining slag.

[0033] In the present invention, when preparing the aqueous solution of the flux, the mass ratio of the flux to water is 3:2.

[0034] In the present invention, the compressive strength of the briquette body is 10-15 MPa.

[0035] The present invention does not make special limitations on the drying method, and conventional technical means of those skilled in the art can be selected, for example: natural air drying at normal temperature.

[0036] The technical solutions of the present invention, unless otherwise specified, are all conventional solutions in the art. The reagents or raw materials used, unless otherwise specified, are all purchased from commercial channels or are already public.

[0037] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments only.

[0038] In the embodiment, the proportion of ferrosilicon manganese alloy with a particle size less than 1 mm is 95%, the silicon element content in the ferrosilicon manganese alloy is 60 wt%, the manganese element content is 25 wt%, and the rest are impurities; the proportion of aluminum powder with a particle size less than 0.4 mm is 95%; the fixed carbon content of the pulverized coal is 80%, and the proportion of the pulverized coal with a particle size less than 0.3 mm is 90%.

[0039] The magnesium reduction slag in the embodiment includes the following components by mass percentage: the CaO content is 55 wt%, the SiO2 content is 23 wt%, the Al2O3 content is 12 wt%, the MgO content is 7 wt%, and the rest are impurities.

[0040] In the embodiment, the deoxidation rate calculation formula of the LF furnace molten steel is shown in Formula 1. The measurement method is to take a molten steel sample using a quartz tube sampler (argon protection) before adding the refining slag to the LF furnace molten steel, and prepare an analysis sample after rapid cooling. After the refining is completed (usually 10-15 minutes after adding the slag material), take the molten steel sample again. The oxygen content of the sample is detected and the deoxidation rate is calculated.

[0041]

[0042] In the embodiment, the calculation formula for the deoxidation rate of the molten steel in the LF furnace is shown in Formula 1. The measurement method is as follows: Before adding the refining slag to the molten steel in the LF furnace, a molten steel sample is taken using a quartz tube sampler (protected by argon), and after rapid cooling, it is prepared into an analysis specimen. After the refining is completed (usually 10 - 15 minutes after adding the slag material), a molten steel sample is taken again. The oxygen content of the sample is detected, and the deoxidation rate is calculated. In the embodiment, the calculation formula for the desulfurization rate of the molten steel in the LF furnace is shown in Formula 2. The measurement method is as follows: Before adding the refining slag to the molten steel in the LF furnace, a molten steel sample is taken using a quartz tube sampler (protected by argon), and after rapid cooling, it is prepared into an analysis specimen. After the refining is completed (usually 10 - 15 minutes after adding the slag material), a molten steel sample is taken again. The oxygen content of the sample is detected, and the desulfurization rate is calculated.

[0043]

[0044] Example 1

[0045] In this example, the LF refining slag, by weight, consists of: 100 parts of magnesium reduction slag, 10 parts of ferrosilicon manganese alloy, 1 part of aluminum powder, 2 parts of pulverized coal, 2 parts of water glass (modulus 2.0), and 3 parts of CaF2.

[0046] The preparation method of the LF refining slag is as follows:

[0047] After uniformly mixing the magnesium reduction slag, ferrosilicon manganese alloy, aluminum powder, pulverized coal, and water glass, they are pressed into blocks under a pressure of 80 MPa to obtain a pressed block body with a compressive strength of 10 MPa;

[0048] After dissolving CaF2 in water (the mass ratio of CaF2 to water is 3:2), it is uniformly sprayed on the surface of the pressed block body and air-dried naturally to obtain the LF refining slag. The composition of the LF refining slag is: the CaO content is 44 wt%, the SiO2 content is 18 wt%, the Al2O3 content is 15 wt%, the Si content is 10 wt%, the Mn content is 4 wt%, the CaF2 content is 4 wt%, and the remaining components are impurities. The melting point of the refining slag is 1382 °C, and the viscosity at 1500 °C is 0.213 Pa·S.

[0049] The LF refining slag of this example is added within 5 - 10 minutes after the molten steel enters the furnace. According to the measurement, the deoxidation percentage of the molten steel in the LF furnace is 50%, and the desulfurization rate is 52%.

[0050] Example 2

[0051] In this example, the LF refining slag, by weight, consists of: 100 parts of magnesium reduction slag, 13 parts of ferrosilicon manganese alloy, 2 parts of aluminum powder, 4 parts of pulverized coal, 3 parts of water glass (modulus 2.2), and 5 parts of CaF2.

[0052] The preparation method of the LF refining slag is as follows:

[0053] After uniformly mixing magnesium reduction slag, ferrosilicon manganese alloy, aluminum powder, pulverized coal, and water glass, briquetting is carried out under a pressure of 100 MPa to obtain a briquette body, and the compressive strength of the briquette body is 12 MPa;

[0054] After dissolving CaF2 in water (the mass ratio of CaF2 to water is 3:2), it is uniformly sprayed on the surface of the briquette body and naturally air-dried to obtain the LF refining slag. The composition of the LF refining slag is: the CaO content is 38 wt%, the SiO2 content is 15 wt%, the Al2O3 content is 17 wt%, the Si content is 13 wt%, the Mn content is 6 wt%, the CaF2 content is 6 wt%, and the remaining components are impurities. The melting point of the refining slag is 1343 °C, and the viscosity at 1500 °C is 0.211 Pa·S.

[0055] The LF refining slag of this example is added within 5 - 10 minutes after the molten steel enters the furnace. According to measurement, the deoxidation percentage of the molten steel in the LF furnace is 60%, and the desulfurization rate is 58%.

[0056] Example 3

[0057] For the LF refining slag in this example, by weight, the raw materials are: 100 parts of magnesium reduction slag, 15 parts of ferrosilicon manganese alloy, 3 parts of aluminum powder, 5 parts of pulverized coal, 5 parts of water glass (modulus 2.3), and 7 parts of CaF2.

[0058] The preparation method of the LF refining slag is as follows:

[0059] After uniformly mixing magnesium reduction slag, ferrosilicon manganese alloy, aluminum powder, pulverized coal, and water glass, briquetting is carried out under a pressure of 120 MPa to obtain a briquette body, and the compressive strength of the briquette body is 15 MPa;

[0060] After dissolving CaF2 in water (the mass ratio of CaF2 to water is 3:2), it is uniformly sprayed on the surface of the briquette body and naturally air-dried to obtain the LF refining slag. The composition of the LF refining slag is: the CaO content is 32 wt%, the SiO2 content is 12 wt%, the Al2O3 content is 21 wt%, the Si content is 14 wt%, the Mn content is 7 wt%, the CaF2 content is 8 wt%, and the remaining components are impurities. The melting point of the refining slag is 1332 °C, and the viscosity at 1500 °C is 0.207 Pa·S.

[0061] The LF refining slag of this example is added within 5 - 10 minutes after the molten steel enters the furnace. According to measurement, the deoxidation percentage of the molten steel in the LF furnace is 55%, and the desulfurization rate is 48%.

[0062] Comparative Example 1

[0063] The difference from Example 2 is only that the ferrosilicon manganese alloy is 30 parts, and the remaining steps and parameters are the same as those in Example 2.

[0064] The melting point of the obtained refined slag is 1350 °C, and the viscosity at 1500 °C is 0.25 Pa·s. The LF refined slag of this comparative example was added within 5 - 10 minutes after the molten steel was charged into the furnace. According to the measurement, the deoxidation percentage of the molten steel in the LF furnace was 30%, and the desulfurization rate was 35%.

[0065] Comparative Example 2

[0066] The difference from Example 2 is only that 5 parts of ferrosilicon manganese alloy were used, and the remaining steps and parameters were the same as those in Example 2.

[0067] The melting point of the obtained refined slag is 1405 °C, and the viscosity at 1500 °C is 0.30 Pa·s. The LF refined slag of this comparative example was added within 5 - 10 minutes after the molten steel was charged into the furnace. According to the measurement, the deoxidation percentage of the molten steel in the LF furnace was 27%, and the desulfurization rate was 28%.

[0068] Comparative Example 3

[0069] The difference from Example 2 is only that 5 parts of aluminum powder were used, and the remaining steps and parameters were the same as those in Example 2.

[0070] The melting point of the obtained refined slag is 1368 °C, and the viscosity at 1500 °C is 0.28 Pa·s. The LF refined slag of this comparative example was added within 5 - 10 minutes after the molten steel was charged into the furnace. According to the measurement, the deoxidation percentage of the molten steel in the LF furnace was 34%, and the desulfurization rate was 25%.

[0071] Comparative Example 4

[0072] The difference from Example 2 is only that 10 parts of pulverized coal were used, and the remaining steps and parameters were the same as those in Example 2.

[0073] The melting point of the obtained refined slag is 1320 °C, and the viscosity at 1500 °C is 0.35 Pa·s. The LF refined slag of this comparative example was added within 5 - 10 minutes after the molten steel was charged into the furnace. According to the measurement, the deoxidation percentage of the molten steel in the LF furnace was 28%, and the desulfurization rate was 20%.

[0074] Comparative Example 5

[0075] The difference from Example 2 is only that the water glass modulus was 1.5 parts, and the remaining steps and parameters were the same as those in Example 2.

[0076] The melting point of the obtained refined slag is 1320 °C, and the viscosity at 1500 °C is 0.35 Pa·s. The LF refined slag of this comparative example was added within 5 - 10 minutes after the molten steel was charged into the furnace. According to the measurement, the deoxidation percentage of the molten steel in the LF furnace was 40%, and the desulfurization rate was 32%.

[0077] The present invention prepares an LF refining slag from magnesium reduction slag, successfully verifying its technical feasibility and comprehensive advantages. Using magnesium reduction slag as the core raw material (containing MgO, CaO, etc.), it replaces traditional limestone and fluorite, realizing the resource utilization of industrial waste residues. In the examples, the optimized ratio (10 - 15 parts of ferrosilicon alloy, 1 - 3 parts of aluminum powder, 2 - 5 parts of pulverized coal, and 3 - 7 parts of CaF2) of the refining slag has a deoxidation rate as high as 50% - 60%, a desulfurization rate of 48% - 58%, a melting point of 1332 - 1382 °C, and a viscosity of 0.207 - 0.213 Pa·s, combining high reactivity and process stability.

[0078] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A LF refined slag, characterized in that: The raw materials include the following components by weight: 100 parts of magnesium reduction slag, 10-15 parts of silicon manganese alloy, 1-3 parts of aluminum powder, 2-5 parts of coal powder, 2-5 parts of binder and 3-7 parts of flux.

2. The LF refined slag according to claim 1, characterized in that: The silicon-manganese alloy has a particle size of less than 1 mm, accounting for 90-95%.

3. The LF refined slag according to claim 1, characterized in that: The aluminum powder has a particle size less than 0.4 mm, accounting for 90-95%.

4. The LF refined slag according to claim 1, characterized in that: The fixed carbon content of the coal powder is 70% to 80%; the proportion of the coal powder with a particle size less than 0.3 mm is 70% to 100%.

5. The LF refined slag according to claim 1, characterized in that: The binder is water glass; the modulus of the water glass is 2.0-2.

3.

6. The LF refined slag according to claim 1, characterized in that: The flux is CaF2.

7. A method for preparing LF refined slag according to any one of claims 1 to 6, characterized in that: The following steps are involved: The magnesium reduction slag, silicon-manganese alloy, aluminum powder, coal powder and a binder are uniformly mixed and then pressed into blocks to obtain a pressed block body; The aqueous solution of flux is sprayed on the surface of the compact body and dried to obtain the LF refined slag.

8. Use of the LF refined slag according to any one of claims 1 to 6 in steel smelting.

9. The use of LF refined slag in steelmaking according to claim 8, characterized in that: The LF refining slag is added within 5-10 minutes after the molten steel enters the furnace.

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