Slagging agents for converter blowing and methods for converter blowing

Abstract

This application relates to the field of iron and steel metallurgical technology, and provides a method for converter blowing, comprising: feeding molten iron into a converter, adding a slagging agent into the converter, then blowing, and feeding the resulting molten steel into a ladle after stopping the blowing; the slagging agent includes a first slagging agent, the composition of which, by mass percentage, includes: MnO≥8.0wt%, SiO2≥25.0wt%, P≤0.030wt%, S≤1.000wt%, H2O≤4.5wt%; the initial slag basicity of the blowing is 2.3~3.0, the final slag basicity is 2.8~4.0, and the final slag MgO content is 8~12wt%; during the converter blowing process, there is no need to modify the existing smelting equipment. By optimizing the slagging agent composition, slag basicity control and other process parameters, the slagging time is shortened, the dephosphorization effect is stable, the risk of sulfur reversion is controllable, and the overall smelting cost is significantly reduced, thereby improving the economic benefits and quality stability of converter smelting.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, and in particular to slagging agents for converter blowing and methods for converter blowing. Background Technology

[0002] Phosphorus causes cold brittleness in steel, affecting its mechanical properties, while sulfur causes hot brittleness. Therefore, both are harmful elements in steel. Dephosphorization and sulfur control are key steps in improving steel quality during converter smelting.

[0003] Meanwhile, the performance of slagging agents directly affects slag formation rate, smelting efficiency, and production costs. Currently, slagging agents widely used in steel enterprises suffer from high costs and slow slag formation rates, making it difficult to simultaneously meet the multiple demands of smelting quality, efficiency, and cost control. Furthermore, traditional slagging agents exhibit insufficient stability in dephosphorization effects across different steel grades, and managing sulfur reversion risks is challenging. In the converter smelting process of steel plants, multiple challenges arise regarding compatibility with various steel grades, slag stability, and cost optimization. Existing slagging agents require large quantities per furnace and have long slag formation times, impacting the converter smelting rhythm.

[0004] Therefore, it is of great significance to provide a slag-forming agent for converter blowing to dephosphorize, control sulfur and improve slag formation rate. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a converter blowing method that can shorten the slag formation time, stabilize the dephosphorization effect, control the risk of sulfur reversion, and significantly reduce the smelting cost.

[0006] In view of this, this application provides a method for converter blowing, comprising:

[0007] Molten iron is fed into a converter, a slag-forming agent is added to the converter, and then blowing is carried out. After blowing is stopped, the resulting molten steel is fed into a ladle.

[0008] The slagging agent includes a first slagging agent, the components of which, by mass percentage, include: MnO ≥ 8.0 wt%, SiO2 ≥ 25.0 wt%, P ≤ 0.030 wt%, S ≤ 1.000 wt%, H2O ≤ 4.5 wt%;

[0009] The initial slag basicity of the blowing process is 2.3~3.0, the final slag basicity is 2.8~4.0, and the final slag MgO content is 8~12wt%.

[0010] In some specific embodiments, the particle size of the first slag-forming agent is 5~50nm.

[0011] In some specific embodiments, the first slag-forming agent includes: MnO 8~10wt%, SiO2 25~35wt%, P≤0.030wt%, S≤1.000wt%, H2O≤4.5wt%.

[0012] In some specific embodiments, the slagging agent also includes an XG-type slagging agent. For 220t of converter molten iron, the amount of the first slagging agent added is ≤500kg / heat.

[0013] In some specific embodiments, the slag-forming agent consists only of the first slag-forming agent, and for 220t of converter molten iron, the amount of the first slag-forming agent added is 0.4~1.0t / heat.

[0014] In some specific embodiments, the initial alkalinity of the alkali residue is 2.4 to 2.8, and / or the final alkalinity of the residue is 2.9 to 3.8.

[0015] In some specific embodiments, the MgO content of the final residue is 9-11 wt%.

[0016] In some specific embodiments, the average MnO content of the converter slag is 1.5~2.5wt%, and the total iron content of the converter slag is ≤18wt%; the amount of S recovered in the molten steel is ≤0.003wt%, and the P content is ≤0.012wt%.

[0017] This application also provides a slagging agent for converter blowing, including a first slagging agent, the composition of which includes: MnO≥8.0wt%, SiO2≥25.0wt%, P≤0.030wt%, S≤1.000wt%, H2O≤4.5wt%.

[0018] In some specific embodiments, the first slag-forming agent comprises: MnO 8~10wt%, SiO2 25~35wt%, P≤0.030wt%, S≤1.000wt%, and H2O≤4.5wt%.

[0019] This application provides a method for converter blowing, in which molten iron is fed into a converter, a slagging agent is added, and then blowing is carried out. After blowing is stopped, the resulting molten steel is fed into a ladle for further refining. During the converter blowing process, by optimizing the composition ratio of the first slagging agent in the slagging agent, the initial slag basicity, the final slag basicity, and the MgO content of the final slag are controlled, achieving efficient slagging in converter blowing, shortening the slagging time, stabilizing the dephosphorization effect, controlling the phosphorus content in the molten steel to below 0.012%, controlling the risk of sulfur reversion, and ensuring that the sulfur reversion in the molten steel is ≤0.003wt%. Moreover, the cost of the first slagging agent is low, reducing the cost of converter smelting. Detailed Implementation

[0020] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0021] Given the problems of existing slagging agents, such as high cost, slow slagging speed, insufficient desulfurization stability, and difficulty in controlling sulfur reversion risk, this application provides a converter blowing method and a converter blowing slagging agent. During the converter blowing process, no modification to existing smelting equipment is required. By optimizing process parameters such as slagging agent composition and slag basicity control, the slagging time is shortened, dephosphorization effect is stable, and sulfur reversion risk is controllable. Simultaneously, the overall smelting cost is significantly reduced, improving the economic efficiency and quality stability of converter smelting. Specifically, this invention discloses a converter blowing method, including:

[0022] Molten iron is fed into a converter, a slag-forming agent is added to the converter, and then blowing is carried out. After blowing is stopped, the resulting molten steel is fed into a ladle.

[0023] The slagging agent includes a first slagging agent, the components of which, by mass percentage, include: MnO ≥ 8.0 wt%, SiO2 ≥ 25.0 wt%, P ≤ 0.030 wt%, S ≤ 1.000 wt%, H2O ≤ 4.5 wt%;

[0024] The initial slag basicity of the blowing process is 2.3~3.0, the final slag basicity is 2.8~4.0, and the final slag MgO content is 8~12wt%.

[0025] In the converter blowing method, high-temperature molten iron is first transferred into the converter. The high-temperature molten iron is obtained in a manner well known to those skilled in the art, and there are no particular restrictions on its source in this application. After the high-temperature molten iron enters the converter, a slagging agent is added to the converter, and then blowing is carried out. In this application, the converter blowing process is basically the same as the prior art, and no adjustment or optimization has been made to the converter blowing process.

[0026] During the converter blowing process, the slagging agent includes a first slagging agent, the composition of which, by mass percentage, includes: MnO ≥ 8.0 wt%, SiO2 ≥ 25.0 wt%, P ≤ 0.030 wt%, S ≤ 1.000 wt%, H2O ≤ 4.5 wt%. In some specific embodiments, the composition of the first slagging agent, by mass percentage, includes: MnO 8~10 wt%, SiO2 25~35 wt%, P ≤ 0.030 wt%, S ≤ 1.000 wt%, H2O ≤ 4.5 wt%. The above five components in the first slagging agent are key control indicators during the converter blowing process, and are not all chemical components. According to actual measurements, they also include CaO, MgO, Al2O3, and total iron (TFe). The above five components directly affect the slagging rate, dephosphorization, and sulfur control. The remaining components are conventional by-products, and this application does not impose special restrictions on the remaining components. In some specific embodiments, the slagging agent can be selected according to the blowing requirements, either by selecting only the first slagging agent mentioned above, or by selecting both the first slagging agent and the XG-type slagging agent as slagging agents. The XG-type slagging agent is a slagging agent well known to those skilled in the art. It is an iron-containing composite fluxing slagging agent, which includes primary dust removal ash from steelmaking, quartz sand, manganese ore powder, and a binder. When the slagging agent consists of a first slagging agent and an XG-type slagging agent, for a converter smelting scale of 220 t / heat, the addition amount of the first slagging agent is ≤500 kg / heat, and the mass ratio of the first slagging agent to the XG-type slagging agent is 1:1. In some specific embodiments, the addition amount of the first slagging agent is 300~390 kg / heat. When the slagging agent consists only of the first slagging agent, for a converter smelting scale of 220 t / heat, the addition amount of the first slagging agent is 0.4~1.0 t / heat. In some specific embodiments, the addition amount of the first slagging agent is 0.6~0.8 t / heat. In some specific embodiments, the particle size of the first slagging agent is 5~50 nm; in some specific embodiments, the particle size of the first slagging agent is 10~40 nm; and in some specific embodiments, the particle size of the first slagging agent is 12~30 nm.

[0027] During the converter blowing process, the slag formation process parameters are controlled as follows: the initial slag basicity is 2.3~3.0, the final slag basicity is 2.8~4.0, and the final slag MgO content is 8~12wt%; in some specific embodiments, the initial slag basicity is 2.4~2.8, the final slag basicity is 2.9~3.8, and the final slag MgO content is 9~11wt%; in some specific embodiments, the initial slag basicity is 2.5~2.7, the final slag basicity is 3.0~3.5, and the final slag MgO content is 10~11wt%. In this application, the initial slag and the final slag are technical terms well known to those skilled in the art. Specifically, the initial slag refers to the slag formed in the early stage of blowing, i.e., from the start of blowing to 1 / 3 of the blowing process, and the final slag refers to the final slag formed at the end of blowing.

[0028] The control of the above-mentioned slag-forming process parameters has a significant effect on slag formation time, dephosphorization effect, and sulfur reversion risk. Specifically, regarding slag formation time: when the above-mentioned slag-forming process parameters are within the specified range, the slag melting point and viscosity are adapted to the smelting conditions, and the slag formation time is shortened by about 20 seconds compared to XG-type slag-forming agent, thus accelerating the smelting pace. Deviation of parameters will lead to delayed slag melting, abnormal viscosity, and a significant slowdown in slag formation speed. Regarding dephosphorization effect: when the above-mentioned slag-forming process parameters are within the specified range, and the basicity is matched with MgO, the slag dephosphorization capacity is stable, and the final P content is lower than that of conventional furnaces and does not exceed the standard, adapting to the dephosphorization requirements of multiple steel grades. Regarding sulfur reversion risk: when the above-mentioned slag-forming process parameters are within the specified range, the sulfur reversion can be controlled within 0.003%, far below the process allowable upper limit of 0.005%, and the sulfur reversion risk is completely controllable.

[0029] The above-mentioned slag-forming process parameters are not within the scope of this application, which may lead to the following problems: 1) Delayed slag formation, prolonging the smelting cycle and disrupting the converter production rhythm; 2) Deterioration of dephosphorization effect, with the final P content exceeding the standard, resulting in unqualified steel quality; 3) The amount of sulfur recovery exceeds the process limit, significantly increasing the subsequent desulfurization cost; 4) Abnormal slag viscosity and melting point, which may easily cause splashing and difficulty in slag removal, increasing the risks of smelting operation and safety; 5) Excessive addition of slag-forming agent, resulting in uncontrolled costs and disordered slag state.

[0030] After the above converter blowing process, the average MnO content in the converter slag is 1.5~2.5wt%, and the total iron content in the converter slag is ≤18wt%; the sulfur content in the molten steel is ≤0.003wt%, and the phosphorus content is ≤0.012wt%. In some specific embodiments, the average MnO content in the converter slag is 1.71~1.72wt%, the total iron content is 17.5~17.7wt%, the sulfur content is 0.002~0.003wt%, and the phosphorus content can reach 0.0081wt%. Meanwhile, the slag formation time during the blowing process is shortened by approximately 20 seconds compared to traditional furnaces using XG-type slag-forming agents, which can improve the converter smelting rhythm and adapt to the production cycle of the continuous casting process.

[0031] Furthermore, this application also provides a slagging agent for converter blowing, including a first slagging agent, the composition of which includes: MnO≥8.0wt%, SiO2≥25.0wt%, P≤0.030wt%, S≤1.000wt%, H2O≤4.5wt%.

[0032] In some specific embodiments, the first slag-forming agent comprises: MnO 8~10wt%, SiO2 25~35wt%, P≤0.030wt%, S≤1.000wt%, H2O≤4.5wt%.

[0033] This application provides a slagging agent for converter blowing and a matching blowing method. By optimizing the composition of the slagging agent and process parameters, it achieves the comprehensive effects of accelerating slagging, stabilizing dephosphorization, improving sulfur control efficiency, and reducing costs.

[0034] To further understand the present invention, the converter blowing method provided by the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0035] Example 1

[0036] The ××× steel plant smelted ××× heats, with a converter final temperature of 1650℃ and a steel output of 220 tons. The 220 tons of molten iron were poured into the converter, and then smelted using a manganese-containing slag-forming agent. The initial slag basicity was 2.5, the final slag basicity was 3.0, and the final slag MgO content was 10wt%. The amount of manganese-containing slag-forming agent added per heat was 400 kg. After smelting was stopped, the resulting molten steel was poured into the ladle. The specific composition of the manganese-containing slag-forming agent is shown in Table 1.

[0037] Table 1. Composition data of manganese-containing slagging agent in Example 1

[0038]

[0039] In the above-mentioned converter blowing process, the slag formation time was shortened by 20 seconds compared with the traditional process, the final P content was reduced to 0.0114wt%, the converter slag MnO content was 1.72wt%, the total iron content was 17.75wt%, and the S recovery amount was 0.0030wt%. All indicators met the process requirements, and the cost of alloy per furnace was reduced by 63.03 yuan.

[0040] The parameters involved in the traditional process are as follows; others are the same as in this application:

[0041] 1. Slag-forming raw materials: Only XG type slag-forming agent is used, without the addition of manganese-containing slag-forming agent; the original cost of slag-forming agent is 480 yuan / ton; the consumption is 4.2 kg / ton of steel.

[0042] 2. Smelting process parameters: The initial slag basicity, final slag basicity, and final slag MgO content shall be implemented according to the existing conventional system, namely, initial slag basicity R (CaO / SiO2): 2.5, final slag basicity R (CaO / SiO2): 3.0, and final slag MgO mass fraction: 10%;

[0043] 3. Smelting indicators: The slag formation time is longer, 20 seconds longer than the process containing manganese slag-forming agents; the average MnO content in the slag is 1.33%, and the average residual manganese at the end point is 0.028%; without deliberate optimization of sulfur and phosphorus control, the slag formation cost is high.

[0044] 4. Operating characteristics: Slow slag formation rate, slow smelting pace, and occasional dry-out phenomenon at the end point.

[0045] Example 2

[0046] The ××× steel plant smelted ××× heats, with a converter final temperature of 1645℃ and a steel output of 220 tons. 220 tons of molten iron were poured into the converter, and then smelted using a manganese-containing slag-forming agent. The initial slag basicity was 2.4, the final slag basicity was 2.9, and the final slag MgO content was 9%. The amount of manganese-containing slag-forming agent added per heat was 400 kg. After smelting was stopped, the resulting molten steel was fed into the ladle. The specific composition of the manganese-containing slag-forming agent is shown in Table 1.

[0047] After converter blowing and smelting, the final P content is reduced to 0.0081wt%, and the MnO content in the converter slag is 1.71wt%. The slag formation rate is fast, the slag viscosity is moderate, which facilitates subsequent slag removal operations. Moreover, the additional cost of desulfurization per furnace is controlled within 48.4 yuan, resulting in significant comprehensive benefits.

[0048] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0049] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for converter blowing, comprising: Molten iron is fed into a converter, a slag-forming agent is added to the converter, and then blowing is carried out. After blowing is stopped, the resulting molten steel is fed into a ladle. The slagging agent includes a first slagging agent, the components of which, by mass percentage, include: MnO ≥ 8.0 wt%, SiO2 ≥ 25.0 wt%, P ≤ 0.030 wt%, S ≤ 1.000 wt%, H2O ≤ 4.5 wt%; The initial slag basicity of the blowing process is 2.3~3.0, the final slag basicity is 2.8~4.0, and the final slag MgO content is 8~12wt%.

2. The method according to claim 1, characterized in that, The particle size of the first slag-forming agent is 5~50nm.

3. The method according to claim 2, characterized in that, The first slag-forming agent comprises: MnO 8~10wt%, SiO2 25~35wt%, P≤0.030wt%, S≤1.000wt%, and H2O≤4.5wt%.

4. The method according to claim 3, characterized in that, The slagging agent also includes XG type slagging agent. For 220t of converter molten iron, the amount of the first slagging agent added is ≤500kg / heat.

5. The method according to claim 3, characterized in that, The slag-forming agent consists only of the first slag-forming agent. For 220t of converter molten iron, the amount of the first slag-forming agent added is 0.4~1.0t / heat.

6. The method according to claim 1, characterized in that, The initial alkalinity of the alkali residue is 2.4~2.8, and / or the final alkalinity of the alkali residue is 2.9~3.

8.

7. The method according to claim 6, characterized in that, The final slag has an MgO content of 9-11 wt%.

8. The method according to any one of claims 1 to 7, characterized in that, The average MnO content in the converter slag is 1.5~2.5wt%, and the total iron content in the converter slag is ≤18wt%; the S content in the molten steel is ≤0.003wt%, and the P content is ≤0.012wt%.

9. A slagging agent for converter blowing, comprising a first slagging agent, wherein the components of the first slagging agent include: MnO≥8.0wt%, SiO2≥25.0wt%, P≤0.030wt%, S≤1.000wt%, H2O≤4.5wt%.

10. The slag-forming agent according to claim 9, characterized in that, The first slag-forming agent comprises: MnO 8~10wt%, SiO2 25~35wt%, P≤0.030wt%, S≤1.000wt%, H2O≤4.5wt%.

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