Carbon additive capable of improving carbon pick-up effect of molten steel and method of using the same

Abstract

This invention relates to a recarburizing agent capable of improving the carbonization effect of molten steel and its application method. The recarburizing agent is prepared from the following raw materials in the following weight ratio: high-crystallinity graphite: silicon carbide: steel scrap = 7-9:1-2:0-2; wherein the high-crystallinity graphite is prepared by mixing graphite ore and perchloric acid, and the fixed carbon content in the high-crystallinity graphite is 98%-99.95%; the graphite crystallinity of the high-crystallinity graphite is above 85%. The steelmaking recarburizing agent of this invention has excellent effects in improving carbonization conditions, increasing carbonization efficiency, improving carbon recovery rate during converter tapping, and reducing the fluctuation range of carbon recovery rate.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, specifically relating to a carbonizer that can improve the carbonization effect of molten steel and its application method. Background Technology

[0002] As a crucial source of carbon in converter steelmaking, recarburizers are essential for improving steel quality through precise control of carbon content. Using recarburizers not only compensates for carbon loss during steelmaking, ensuring the required carbon content for specific steel grades, but also adjusts the carbon content of molten steel after the furnace. Given my country's enormous demand for high-quality steel and increasingly stringent requirements for carbon content control, addressing the issues of increasing carbon recovery rate and stabilizing carbon recovery fluctuations in the recarburizing process is crucial for improving product quality.

[0003] Currently, there are relatively few research reports on carbon-reinforcing materials and processes both domestically and internationally. Existing carbon-reinforcing agents have poor carbon-reinforcing effects and the carbon-reinforcing process is difficult to control. Developing new carbon-reinforcing materials with good carbon-reinforcing effects, low impurity content, low production costs, and high strength has important theoretical and academic value and practical application significance, and also has broad market prospects. Summary of the Invention

[0004] The purpose of this invention is to provide a carbonizer that can improve the carbonization effect of molten steel and its application method. The steelmaking carbonizer of this invention has the excellent effects of improving carbonization conditions, increasing carbonization efficiency, improving carbon recovery rate during converter tapping, and reducing the fluctuation range of carbon recovery rate.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A carbonizer capable of improving the carbonization effect of molten steel is prepared from the following raw materials in the following weight ratio: high crystallinity graphite: silicon carbide: steel scrap = 7-9: 1-2: 0-2; the fixed carbon content in the high crystallinity graphite is 98%-99.95%; and the graphite crystallinity of the high crystallinity graphite is above 85%.

[0007] The high crystallinity graphite is obtained by mixing graphite ore with perchloric acid to obtain a crude purified product, and then adding the crude purified product to a mixed solution of sulfuric acid and hydrofluoric acid and stirring to obtain a refined purified product.

[0008] The ratio of graphite ore to perchloric acid is 1:1.5 to 2 by mass; the mixing reaction temperature is 50 to 70°C; and the mixing reaction time is 1.5 to 3 hours.

[0009] The mass ratio of graphite ore to perchloric acid is 1:1.5-2, the mixing and stirring reaction temperature is 50-70℃, and the mixing and stirring reaction time is 1.5-3h; the mass ratio of crude purified product to mixed solution is 1:1.5-2, the stirring reaction time is 1-2h, and the stirring reaction temperature is 60-95℃.

[0010] The ratio of sulfuric acid to hydrofluoric acid is 1:5 to 9 by mass, with hydrofluoric acid having a mass concentration of 30% to 60% and sulfuric acid having a mass concentration of 6% to 15%.

[0011] The specific process of graphite treatment using the perchloric acid method of this invention is as follows: First, graphite and perchloric acid are mixed in a certain proportion and placed in a reactor equipped with a stirrer to remove impurities and purify the graphite. The stirring reaction time is 1.5–3 hours, and the stirring reaction temperature is 50–70°C. The purified graphite is then washed and filtered to obtain a crude purified product. Next, the crude purified product is mixed and stirred with a hydrofluoric acid solution containing a small amount of sulfuric acid. After treatment, the waste acid is recovered for reuse. After washing, filtering, and drying, the final product is obtained. The stirring reaction time is 1–2 hours, and the stirring reaction temperature is 60–95°C. After treatment, the fixed carbon content of the graphite reaches 98%–99.95%, and XRD scanning observation shows that the graphite crystallinity can reach over 85%.

[0012] Perchloric acid can dissolve many impurities that other acids cannot, and it can react with both metals and non-metals. This invention mainly utilizes HClO4 to react with impurities in graphite, converting insoluble impurities in graphite into soluble chlorides. Hydrofluoric acid has a good ability to dissolve ash in graphite, and the ash removal rate in graphite can reach more than 75%. The ash in graphite is converted into fluoride precipitates and then removed by filtration.

[0013] The high-crystallinity graphite of this invention has a fully arranged hexagonal structure and small interlayer spacing, and is highly similar to silicon carbide. When mixed and added to molten steel, it can significantly increase the carbon content in the molten steel. The fully arranged hexagonal high-crystallinity graphite promotes an increase in the number of carbon nuclei in the molten steel, which can compensate for the decarburization of the molten steel caused by various complex factors during the tapping process and reduce the fluctuation range of the carbon increase rate.

[0014] The particle size of the carbon raiser is ≤30mm.

[0015] The iron content in the steel scrap is 90% to 95%.

[0016] The purity of the silicon carbide is ≥80%.

[0017] A method for using a carburizing agent that can improve the carburizing effect of molten steel, the method comprising:

[0018] High-crystallinity graphite is mixed with silicon carbide and steel scrap, compacted, and then fed into the ladle via a feeder through a hopper. The amount of carbon raiser added is 3-8 kg / t steel.

[0019] The method of adding the carburizing agent is as follows: before tapping the steel, 20% to 40% of the total weight of the carburizing agent is added to the ladle, and the remaining 60% to 80% is added to the ladle together with the molten steel tapped from the converter via a feeder.

[0020] The tapping conditions for steel with carbon added by the new carbon raiser are: [C]: 0.07%~0.14%; [O]: 80ppm~140ppm; tapping temperature: 1620℃~1665℃.

[0021] This new type of carbon raiser is used to increase the carbon content of high-carbon steel during smelting.

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

[0023] This invention employs a recarburizing agent that enhances the carbonization effect of molten steel, exhibiting excellent processing capabilities for steels with different compositions and temperature ranges. High-crystallinity graphite is mixed and compacted with silicon carbide steel scrap, then fed into the ladle via a feeder during the converter tapping process to complete the carbonization. Using this converter steelmaking recarburizing agent improves carbonization conditions, reduces the stringency requirements for the carbon content of the tapped molten steel, and allows the use of this novel recarburizing agent for molten steel with a tapping carbon content of 0.07%–0.14%. The final carbon content can reach 0.73%–0.75%, with a carbon recovery rate of 87.1%–90%, and a carbonization rate fluctuation range of less than or equal to 2.9%. Compared to using common recarburizing agents, this invention significantly improves the converter tapping carbon recovery rate and significantly reduces the carbonization rate fluctuation range. Furthermore, the process of this invention has a wide range of raw material sources, facilitating continuous production. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of the preparation of high crystallinity graphite according to the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to specific embodiments. However, the specific embodiments and related descriptions do not constitute an improper limitation on the technical solutions of this invention.

[0026] Example 1:

[0027] The specific process of treating graphite using perchloric acid is as follows: First, graphite and perchloric acid are mixed in a 1:2 ratio and placed in a reactor equipped with a stirrer to remove impurities and purify the graphite. The stirring reaction time is 2 hours, and the stirring reaction temperature is 60℃. The purified graphite is then washed and filtered to obtain a crude purified product. Next, the crude purified product is mixed and stirred with a hydrofluoric acid solution containing a small amount of sulfuric acid. After treatment, the waste acid is recovered for reuse. After washing, filtering, and drying, the final product is obtained. The stirring reaction time is 1.5 hours, and the stirring reaction temperature is 90℃. After treatment, the fixed carbon content of the graphite reaches 99.4%, and XRD scanning observation shows that the graphite crystallinity can reach 98%.

[0028] A 100-ton converter was used for carbonization treatment with carbon raisers.

[0029] During the converter tapping process, the molten steel temperature was measured at 1625℃, the carbon content was 0.12%, and the total oxygen content was 103 ppm. High-crystallinity graphite, silicon carbide, and steel scrap were mixed and compacted at a weight ratio of 8:1:1, with an addition rate of 7 kg / t steel (700 kg). Of this, 150 kg was added to the ladle before tapping, and the remaining 550 kg was added to the converter via the feeder during the tapping process. At the end of the converter tapping process, the final carbon content was measured at 0.73%, with a carbon recovery rate of 87.1%, indicating a good carbon enrichment effect.

[0030] Example 2:

[0031] The specific process of treating graphite using perchloric acid is as follows: First, graphite and perchloric acid are mixed at a ratio of 1:1.8 and placed in a reactor equipped with a stirrer to remove impurities and purify the graphite. The stirring reaction time is 2.5 hours, and the stirring reaction temperature is 65℃. The purified graphite is then washed and filtered to obtain a crude purified product. Next, the crude purified product is mixed and stirred with a hydrofluoric acid solution containing a small amount of sulfuric acid. After treatment, the waste acid is recovered for reuse. After washing, filtering, and drying, the final product is obtained. The stirring reaction time is 2 hours, and the stirring reaction temperature is 80℃. After treatment, the fixed carbon content of the graphite reaches 99%, and XRD scanning observation shows that the graphite crystallinity can reach 95%.

[0032] A 100-ton converter was used for carbonization treatment with carbon raisers.

[0033] During the converter tapping process, the molten steel temperature was measured at 1660℃, the carbon content was 0.08%, and the total oxygen content was 131 ppm. High-crystallinity graphite, silicon carbide, and steel scrap were mixed and compacted at a weight ratio of 9:1:1, with an addition rate of 5 kg / t steel (500 kg). Of this, 100 kg was added to the ladle before tapping, and the remaining 400 kg was added to the converter via the feeder during the tapping process. At the end of the converter tapping process, the carbon content was 0.52%, with a carbon recovery rate of 88%, indicating a good carbon enhancement effect.

[0034] Example 3:

[0035] The specific process of perchloric acid treatment of graphite is as follows: First, graphite and perchloric acid are mixed at a ratio of 1:1.6 and placed in a reactor equipped with a stirrer to remove impurities and purify the graphite. The stirring reaction time is 2 hours, and the stirring reaction temperature is 68℃. The purified graphite is then washed and filtered to obtain a crude purified product. Next, the crude purified product is mixed and stirred with a hydrofluoric acid solution containing a small amount of sulfuric acid. After treatment, the waste acid is recovered for reuse. After washing, filtering, and drying, the final product is obtained. The stirring reaction time is 1-2 hours, and the stirring reaction temperature is 75℃. After treatment, the fixed carbon content of the graphite reaches 99.92%, and XRD scanning observation shows that the graphite crystallinity can reach 97%.

[0036] A 100-ton converter was used for carbonization treatment with carbon raisers.

[0037] During the converter tapping process, the molten steel temperature was measured at 1645℃, the carbon content was 0.10%, and the total oxygen content was 100ppm. High-crystallinity graphite, silicon carbide, and steel scrap were mixed and compacted at a weight ratio of 8:2:1, with an addition rate of 3 kg / t steel (300 kg). Of this, 100 kg was added to the ladle before tapping, and the remaining 200 kg was added to the converter via the feeder during the tapping process. At the end of the converter tapping process, the final carbon content was 0.37%, with a carbon recovery rate of 90%, indicating a good carbon enrichment effect.

[0038] Example 4:

[0039] The specific process of treating graphite using perchloric acid is as follows: First, graphite and perchloric acid are mixed in a 1:2 ratio and placed in a reactor equipped with a stirrer to remove impurities and purify the graphite. The stirring reaction time is 2 hours, and the stirring reaction temperature is 65℃. The purified graphite is then washed and filtered to obtain a crude purified product. Next, the crude purified product is mixed and stirred with a hydrofluoric acid solution containing a small amount of sulfuric acid. After treatment, the waste acid is recovered for reuse. After washing, filtering, and drying, the final product is obtained. The stirring reaction time is 2 hours, and the stirring reaction temperature is 75℃. After treatment, the fixed carbon content of the graphite reaches 99.90%, and XRD scanning observation shows that the graphite crystallinity can reach 94%.

[0040] A 120-ton converter was used for carbonization treatment with carbon raisers.

[0041] During the converter tapping process, the molten steel temperature was measured at 1625℃, the carbon content was 0.11%, and the total oxygen content was 96ppm. High-crystallinity graphite, silicon carbide, and steel scrap were mixed and compacted at a weight ratio of 8:1:1, with an addition rate of 7 kg / t steel (840 kg). Of this, 240 kg was added to the ladle before tapping, and the remaining 600 kg was added to the converter via the feeder during the tapping process. At the end of the converter tapping process, the final carbon content was measured at 0.73%, with a carbon recovery rate of 88.6%, indicating a good carbon enrichment effect.

[0042] Example 5:

[0043] The specific process of treating graphite using perchloric acid is as follows: First, graphite and perchloric acid are mixed in a 1:2 ratio and placed in a reactor equipped with a stirrer to remove impurities and purify the graphite. The stirring reaction time is 2 hours, and the stirring reaction temperature is 55℃. The purified graphite is then washed and filtered to obtain a crude purified product. Next, the crude purified product is mixed and stirred with a hydrofluoric acid solution containing a small amount of sulfuric acid. After treatment, the waste acid is recovered for reuse. After washing, filtering, and drying, the final product is obtained. The stirring reaction time is 2 hours, and the stirring reaction temperature is 90℃. After treatment, the fixed carbon content of the graphite reaches 99.93%, and XRD scanning observation shows that the graphite crystallinity can reach 99%.

[0044] A 120-ton converter was used for carbonization treatment with carbon raisers.

[0045] The temperature of the molten steel during the converter tapping process was measured at 1620℃ (the tapping temperature was relatively low; steel scrap was not added to the carbonizer during the carbonization process to prevent poor fluidity of the molten steel), the carbon content was 0.14%, and the total oxygen content in the steel was 92ppm. High-crystallinity graphite and silicon carbide were mixed and compacted at a weight ratio of 9:1, with an addition amount of 6.5 kg / t steel, or 800 kg. Of this, 300 kg was added to the ladle before tapping from the converter, and the remaining 500 kg was added to the converter via the feeder during the tapping process. At the end of the converter tapping process, the final carbon content was measured to be 0.7%, and the carbon recovery rate was 89.2%, indicating a good carbonization effect.

[0046] This invention significantly improves the absorption rate and stability of the graphite recarburizer, which has a positive effect on steelmaking production and control. It enables precise control of the recarburizer dosage, thereby reducing steelmaking production costs. Simultaneously, it reduces the fluctuation range of the recarburizer yield, thus decreasing the maximum recarburizer dosage. By increasing carbon yield and reducing recarburizer dosage, it can, to some extent, save energy and material resources consumed by the recarburizing technology.

Claims

1. A carburizing agent capable of improving the carburizing effect of molten steel, characterized in that, The carbon raiser is prepared from the following raw materials in the following weight ratio: high crystallinity graphite: silicon carbide: steel scrap = 7~9: 1~2: 0~2; the fixed carbon content in the high crystallinity graphite is 98%~99.95%; the graphite crystallinity of the high crystallinity graphite is above 85%; The high crystallinity graphite is obtained by mixing graphite ore with perchloric acid to obtain a crude purified product, and then adding the crude purified product to a mixed solution of sulfuric acid and hydrofluoric acid and stirring to obtain a refined purified product.

2. The carburizing agent according to claim 1, which can improve the carburizing effect of molten steel, is characterized in that, The mass ratio of graphite ore to perchloric acid is 1:1.5-2, the mixing and stirring reaction temperature is 50-70℃, and the mixing and stirring reaction time is 1.5-3h; the mass ratio of crude purified product to mixed solution is 1:1.5-2, the stirring reaction time is 1-2h, and the stirring reaction temperature is 60-95℃.

3. A carburizing agent according to claim 1 or 2, characterized in that, The ratio of sulfuric acid to hydrofluoric acid is 1:5 to 9 by mass, with the hydrofluoric acid having a mass concentration of 30% to 60% and the sulfuric acid having a mass concentration of 6% to 15%.

4. The carburizing agent according to claim 1, characterized in that, The particle size of the carbon raiser is ≤30mm.

5. A carburizing agent according to claim 1 that can improve the carburizing effect of molten steel, characterized in that, The iron content in the steel scrap is 90% to 95%.

6. A carburizing agent according to claim 1, characterized in that, The purity of the silicon carbide is ≥80%.

7. A method for using a carburizing agent as described in any one of claims 1-6, capable of improving the carburizing effect of molten steel, characterized in that the method... include: 1) Mix high-crystallinity graphite with silicon carbide and steel scrap, and compact the mixture. The amount of carburizing agent added is 3-8 kg / t. steel; 2) Before tapping, 20% to 40% of the total carburizing agent weight is added to the ladle, and the remaining 60% to 80% is added to the ladle along with the molten steel tapped from the converter via a feeder; 3) When tapping the steel, the C content in the molten steel is 0.07% to 0.14%; the O content is 80ppm to 140ppm; and the tapping temperature is 1620℃ to 1665℃.

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