A method for producing low-cost pig iron for steelmaking

Abstract

The application provides a preparation method of low-cost pig iron for steelmaking, and belongs to the field of blast furnace ironmaking. The method comprises the following steps: carrying out blast furnace smelting on blast furnace charging materials to obtain molten iron; controlling the TiO2 load of the blast furnace charging materials to be less than or equal to 9.0 kg / tHM, and controlling the ratio of the Mn load to the TiO2 load of the blast furnace charging materials to be 0.70-0.80, so as to inhibit the reduction of TiO2 in the blast furnace slag; controlling the mass fraction of Al2O3 in the blast furnace slag to be 15.50-18.30%, and controlling the ratio of MgO to Al2O3 in the blast furnace slag to be not less than 0.5 and the binary basicity of the blast furnace slag to be 1.10-1.20, so as to improve the fluidity and desulfurization efficiency of the blast furnace slag; and controlling the physical heat temperature of the molten iron to be higher than 1500 DEG C. Through the technical idea of multi-parameter synergistic optimization, the application realizes the significant reduction of the cost of steelmaking while improving the quality of the molten iron in the blast furnace.

Description

Technical Field

[0001] This application relates to the field of blast furnace ironmaking technology, and in particular to a low-cost method for preparing pig iron for steelmaking. Background Technology

[0002] Integrated steel mills account for over 90% of the nation's steel production capacity. Their core advantages lie in their significantly lower production costs and higher-quality molten iron compared to integrated steel mills and non-blast furnace ironmaking processes. In the blast furnace ironmaking stage, molten iron costs account for 75% to 80% of the total costs for integrated steel mills. Therefore, effectively controlling blast furnace ironmaking costs is crucial for integrated steel mills to reduce costs, increase efficiency, and enhance market competitiveness. This has significant practical implications for sustainable development and technological advancement within the industry.

[0003] However, while existing technologies can ensure stable blast furnace production and molten iron quality, they have significant shortcomings. Strict control over the content of harmful elements in the raw materials leads to a strong dependence on high-quality iron ore, resulting in correspondingly high raw material procurement costs. When comparing steel companies with similar locational advantages, these high raw material requirements make molten iron costs less competitive, hindering companies from continuously reducing costs and increasing efficiency in a fiercely competitive market, and significantly limiting potential for cost reduction. Therefore, how to effectively reduce blast furnace steelmaking costs while improving molten iron quality has become a pressing technical problem to be solved in this field. Summary of the Invention

[0004] This application provides a low-cost method for preparing steelmaking pig iron to solve the following technical problem: how to reduce the cost of blast furnace steelmaking while improving the quality of molten iron.

[0005] This application provides a low-cost method for preparing steelmaking pig iron, the method comprising: The blast furnace charge is smelted in the blast furnace to obtain molten iron, and the following parameters are controlled during the blast furnace smelting process: The TiO2 load of the blast furnace feed is controlled to be ≤9.0 kg / tHM, and the ratio of Mn load to TiO2 load of the blast furnace feed is controlled to be 0.70 to 0.80, so as to suppress the reduction of TiO2 in the blast furnace slag. The mass fraction of Al2O3 in blast furnace slag is controlled to be 15.50-18.30%, and the ratio of MgO to Al2O3 in the blast furnace slag is not less than 0.5 and the binary basicity R2 of the blast furnace slag is controlled to be 1.10-1.20, so as to improve the fluidity and desulfurization efficiency of the blast furnace slag. The physical thermal temperature of the molten iron is controlled to be above 1500℃.

[0006] Optionally, the ratio of MgO to Al2O3 in the blast furnace slag is controlled to be 0.50 to 0.60.

[0007] Optionally, when the ratio of MgO to Al2O3 in the blast furnace slag is controlled to be 0.50 to 0.55, the mass fraction of Al2O3 in the blast furnace slag is controlled to be 16.50 to 17.50%.

[0008] Optionally, when the ratio of MgO to Al2O3 in the blast furnace slag is controlled to be 0.55 to 0.60, the mass fraction of Al2O3 in the blast furnace slag is controlled to be 17.50 to 18.30%.

[0009] Optionally, in the molten iron, by mass fraction, P≤0.12%, S≤0.045%, Ti≤0.090%, Si:0.25~0.50%, Mn≤0.60%.

[0010] Optionally, the blast furnace feed includes iron ore with high Mn content and iron ore with high TiO2 content.

[0011] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a low-cost method for preparing steelmaking pig iron. Through a multi-parameter synergistic optimization approach, it significantly reduces steelmaking costs while improving the quality of blast furnace hot metal. Its core lies in breaking through the path dependence of traditional processes on high-quality raw materials through technological innovation.

[0012] In terms of cost reduction, this application first directly reduces procurement costs by relaxing the quality requirements for raw materials fed into the furnace. Specifically, the limit for TiO2 load is raised from the traditional ≤3.0 kg / tHM to ≤9.0 kg / tHM, meaning that enterprises can use large quantities of relatively inexpensive high-titanium iron ore. Simultaneously, the upper limit for the mass fraction of Al2O3 in the slag is relaxed from 16.5% to 18.3%, and an MgO / Al2O3 ratio of not less than 0.5 is allowed. This reduces the stringent requirements on the aluminum content in the iron ore and the amount of flux added. These adjustments broaden the range of selectable minerals, allowing for the priority selection of iron ore with higher Mn and MgO content among raw materials with similar cost-effectiveness, thereby directly reducing batching costs.

[0013] Regarding improving molten iron quality, this application introduces Mn / TiO2 load ratio control, optimizes slag composition and thermal regime, and ensures or even improves molten iron quality while using low-cost raw materials. Addressing the potential increase in Ti content in molten iron due to the use of high-titanium ore, the ratio of Mn load to TiO2 load is controlled at 0.70~0.80. Utilizing the redox reaction between MnO in the slag and Ti in the molten iron at the slag-iron interface, the reduction of TiO2 in the slag is effectively suppressed, keeping the Ti content in the molten iron stably controlled at a low level not exceeding 0.12%, while simultaneously increasing the Mn content to 0.37%~0.44%, thus improving the fluidity of the molten iron. Addressing the potential decrease in fluidity due to increased Al2O3 in the slag, the MgO / Al2O3 ratio is controlled to be no less than 0.5, and the binary basicity R2 of the slag is reduced to 1.10~1.20. This improves slag fluidity and desulfurization efficiency, reducing the average S content in the molten iron from the original 0.028% to 0.019%. In addition, controlling the physical heat temperature of the molten iron above 1500℃ ensures the stability and activity of the hearth thermal regime, providing a basic condition for the full occurrence of the above-mentioned slag-iron reaction.

[0014] Therefore, this application demonstrates that it has constructed a mutually supportive technical system through the synergistic control of the Mn / TiO2 loading ratio, MgO / Al2O3 ratio, slag basicity, and the physical heat of molten iron. This system, on the one hand, allows the use of raw materials with lower grades and higher content of harmful elements to reduce costs; on the other hand, it ensures that the quality of molten iron is improved rather than reduced through chemical mechanism regulation and slag-iron performance optimization. Ultimately, under the premise that the P, S, Ti, Si, Mn, and other indicators of molten iron fully meet or even exceed the requirements for steelmaking, a significant reduction in molten iron costs is achieved, creating better raw material conditions for downstream steelmaking processes. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0016] This application provides a low-cost method for preparing steelmaking pig iron, the method comprising: The blast furnace charge is smelted in the blast furnace to obtain molten iron, and the following parameters are controlled during the blast furnace smelting process: The TiO2 load in the blast furnace feed should be controlled to be ≤9.0 kg / tHM, and the ratio of Mn load to TiO2 load in the blast furnace feed should be controlled to be 0.70 to 0.80, so as to inhibit the reduction of TiO2 in the blast furnace slag. The mass fraction of Al2O3 in blast furnace slag is controlled at 15.50-18.30%, and the ratio of MgO to Al2O3 in blast furnace slag is controlled at no less than 0.5, and the binary basicity R2 of blast furnace slag is controlled at 1.10-1.20, so as to improve the fluidity and desulfurization efficiency of blast furnace slag. The physical thermal temperature of molten iron is controlled to be above 1500℃.

[0017] It should be noted that the embodiments of this application provide a low-cost method for preparing steelmaking pig iron. This method selects suitable raw materials by optimizing the batching technology, choosing iron ore with high Mn and MgO content among raw materials with similar cost-effectiveness, increasing the Mn load in the furnace feed, and reducing the amount of magnesium oxide flux added in the sintering process. The increase in Mn oxide content in the furnace feed inhibits TiO2 reduction in the furnace and improves slag-iron separation, slag fluidity, and desulfurization during blast furnace smelting. Appropriately reducing slag basicity increases the dealkali removal rate, thereby reducing the quality requirements and cost of the blast furnace feed, thus achieving the goal of reducing iron cost and improving iron quality, and creating favorable conditions for reducing steelmaking costs.

[0018] This application first proposes control requirements for the blast furnace charge load. By controlling the TiO2 load in the blast furnace charge to no more than 9.0 kg / tHM, more low-cost high-TiO2 iron ore can be used, which is the basis for reducing the cost of raw materials. However, simply increasing the TiO2 load will exacerbate the reduction of TiO2 in the furnace, leading to an increase in the titanium content in the molten iron, affecting the quality of the molten iron and potentially damaging the furnace conditions. To resolve this contradiction, this method innovatively introduces and controls the ratio of manganese load to titanium load to be 0.70 to 0.80. The core function of this ratio control is to inhibit the reduction of TiO2 using metallurgical physicochemical principles. When the manganese load in the charge increases, the concentration of MnO in the slag increases accordingly, and a redox reaction occurs at the slag-iron interface: 2(MnO) + [Ti] == 2[Mn] + TiO2. This reaction causes the titanium [Ti] that has been reduced into the molten iron to be reoxidized and enter the slag, while the manganese in the slag is reduced and enters the molten iron. By controlling this ratio within the preferred range of 0.70 to 0.80, the titanium content in molten iron can be effectively controlled at a low level of ≤0.120% without significantly increasing fuel consumption, while the manganese content in molten iron can be increased to 0.37% to 0.44%. This not only improves the quality of molten iron but also clears the way for the large-scale use of high-TiO2 ore.

[0019] Secondly, this method optimizes the composition control of blast furnace slag. The upper limit of the Al2O3 mass fraction in the slag is relaxed from the traditional 16.5% to 18.30%, making it possible to procure inexpensive iron ore with higher Al2O3 content, which is another important way to reduce raw material costs. However, the increased Al2O3 content deteriorates the slag's fluidity and desulfurization capacity. To offset this negative impact, this method adopts a two-pronged approach: first, controlling the MgO to Al2O3 ratio in the slag to be no less than 0.5, by adding an appropriate amount of magnesium-containing flux, utilizing the MgO's characteristic of improving slag fluidity to adapt to high-Al2O3 slag; second, moderately reducing the slag's binary basicity R2 from the traditional 1.20-1.30 to 1.10-1.20. Lowering the basicity helps reduce the slag's viscosity and melting temperature, further improving its fluidity, and working in conjunction with the effect of MgO to jointly ensure the slag has good desulfurization capacity. Through this synergistic control, the study found that when the magnesium-aluminum ratio is not less than 0.5, the furnace operation can be guaranteed within the Al2O3 content range of 15.50% to 18.30%. Furthermore, the reduction in slag basicity also brings a significant benefit: the slag dealkali removal rate increases by 12% to 18%. This means that alkali metals (K2O, Na2O) can be removed from the raw materials more effectively, allowing for a relaxation of restrictions on the alkali metal content of the feedstock and further broadening the range of inexpensive raw materials to be selected.

[0020] Furthermore, this method controls the thermal regime of smelting, requiring the physical heat temperature of the molten iron to be maintained above 1500℃. Sufficient physical heat of the molten iron is a sign of active hearth operation and stable furnace conditions, and is also a necessary condition to ensure good slag-iron separation and the full conduct of various metallurgical reactions (such as the aforementioned desulfurization and displacement reactions). With the dual guarantee of furnace temperature (usually characterized by the silicon content [Si] of the molten iron, controlled between 0.25% and 0.50%) and physical heat, a stable operating platform can be provided for adjusting the aforementioned parameters, ensuring that high-quality molten iron can still be obtained even after relaxing raw material restrictions and adjusting slag composition.

[0021] Therefore, the embodiments of this application construct a mutually supportive and synergistic technical system by suppressing titanium reduction through the manganese-titanium load ratio, optimizing slag performance through the magnesium-aluminum ratio and low basicity, and ensuring thermal regime stability through high physical heat. This system enables the acceptance of raw materials with relatively low grade and high content of harmful elements during blast furnace smelting, ultimately achieving a significant reduction in the cost of molten iron feedstock while ensuring that the quality of molten iron not only meets but even exceeds some steelmaking requirements.

[0022] In some implementations, the ratio of MgO to Al2O3 in the blast furnace slag is controlled to be 0.50 to 0.60.

[0023] The ratio of magnesium oxide to aluminum oxide in blast furnace slag was further limited to between 0.50 and 0.60. This refined range represents a more optimal operating range than the original requirement of no less than 0.5. Within this range, magnesium oxide has the most significant effect on improving the fluidity of high-alumina slag, effectively offsetting the increase in viscosity caused by higher aluminum oxide content, without leading to additional fuel consumption due to excessive magnesium oxide, thus achieving a good balance between smooth furnace operation and economical smelting.

[0024] In some implementations, when the ratio of MgO to Al2O3 in the blast furnace slag is controlled to be 0.50 to 0.55, the mass fraction of Al2O3 in the blast furnace slag is controlled to be 16.50 to 17.50%.

[0025] In some implementations, when the ratio of MgO to Al2O3 in blast furnace slag is controlled to be 0.55 to 0.60, the mass fraction of Al2O3 in blast furnace slag is controlled to be 17.50 to 18.30%.

[0026] Based on the different ratios of magnesium oxide (MgO) to aluminum oxide (ANO), the ANO content in the slag is controlled in different zones. When the ratio is controlled between 0.50 and 0.55, the mass fraction of ANO in the slag is suitable to be controlled between 16.50% and 17.50%; when the ratio is increased to 0.55 to 0.60, the mass fraction of ANO in the slag can be further increased to 17.50% to 18.30%. This stepwise control relationship reveals the synergistic mechanism between the magnesium-aluminum ratio and the aluminum content: at a relatively low magnesium-aluminum ratio, the slag has a correspondingly lower tolerance for aluminum content; while increasing the magnesium-aluminum ratio can effectively support higher levels of aluminum content, while ensuring that the slag has good fluidity and desulfurization capacity, creating conditions for using iron ore with higher aluminum content.

[0027] In some embodiments, the molten iron contains, by mass fraction, P ≤ 0.12%, S ≤ 0.045%, Ti ≤ 0.090%, Si 0.25–0.50%, and Mn ≤ 0.60%.

[0028] This application specifies the quality of the final molten iron: phosphorus content not exceeding 0.12%, sulfur content not exceeding 0.045%, titanium content not exceeding 0.090%, silicon content between 0.25% and 0.50%, and manganese content not exceeding 0.60%. This series of indicators serves as a criterion for verifying the appropriateness of the aforementioned process parameter control, and also demonstrates that this method, while using low-cost raw materials, can still produce high-quality molten iron that fully meets or even exceeds the requirements of the steelmaking process. The silicon content, along with physical heat, ensures the stability of the hearth thermal regime, while the low sulfur and moderate manganese content reduces processing costs for subsequent steelmaking processes.

[0029] In some embodiments, the blast furnace feed includes iron ore with high Mn content and iron ore with high TiO2 content.

[0030] This application explicitly states that the blast furnace feed includes high-manganese iron ore and high-titanium dioxide iron ore. This reveals the specific raw material composition for achieving manganese-titanium load ratio control. By prioritizing and combining these two cost-effective types of iron ore during batching, the overall batching cost can be reduced by utilizing high-titanium ore, while the manganese in high-manganese ore can inhibit titanium reduction, thus solving the technical challenges of high-titanium ore smelting. This raw material combination is the material basis for achieving low-cost smelting.

[0031] In summary, this application provides a low-cost method for preparing pig iron for steelmaking. Its core advantage lies in breaking the dependence of traditional blast furnace smelting on high-quality raw materials through technological innovation. While significantly reducing production costs, it also improves and stabilizes the quality of molten iron, resulting in significant economic, technological, and social benefits.

[0032] From a technical perspective, this method constructs a more flexible and inclusive smelting control model through multi-parameter synergistic optimization. It innovatively overcomes the technical bottleneck of using high-titanium ore by controlling the manganese-titanium load ratio in the furnace charge and utilizing the chemical mechanism of manganese oxide in the slag inhibiting titanium dioxide reduction. This allows for the large-scale use of previously limited, high-cost-performance iron ore. Simultaneously, by combining the magnesium-aluminum ratio in the slag with reduced binary basicity, the fluidity and desulfurization and dealkali removal capabilities of high-alumina slag are effectively improved, thereby relaxing restrictions on harmful elements such as alumina and alkali metals in the furnace charge. This technical approach not only does not sacrifice the quality of molten iron but also reduces the average sulfur content in the molten iron from 0.028% to 0.019% and increases the manganese content from 0.19% to 0.40%, creating better conditions for downstream steelmaking processes and achieving cost reduction at the front end of smelting and efficiency improvement at the back end.

[0033] From an economic perspective, the cost advantage brought by this method is extremely significant. By relaxing the procurement standards for harmful elements in iron ore and allowing the large-scale use of unconventional minerals such as high-titanium ore, the raw material cost of molten iron can be significantly reduced by 30.0 to 45.5 yuan per ton of molten iron.

[0034] From a social benefit perspective, this method promotes the efficient use of resources. It enables the large-scale application of iron ore resources, previously limited by composition and inefficient in utilization or difficult to feed into blast furnaces, thus improving the overall utilization rate of mineral resources and aligning with the concepts of circular economy and sustainable development. Furthermore, this method is based on existing blast furnace equipment, requiring no large-scale equipment modifications, and is easily promoted and applied within the industry. It has significant practical implications for enhancing the competitiveness and greening level of the entire long-process steelmaking process.

[0035] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0036] This embodiment provides a low-cost method for preparing steelmaking pig iron, the method comprising: The blast furnace charge is smelted in the blast furnace to obtain molten iron, and the following parameters are controlled during the blast furnace smelting process: The TiO2 load of the blast furnace feed is controlled to be ≤9.0 kg / tHM, and the ratio of Mn load to TiO2 load of the blast furnace feed is controlled to be 0.70 to 0.80, so as to suppress the reduction of TiO2 in the blast furnace slag. The mass fraction of Al2O3 in blast furnace slag is controlled to be 15.50-18.30%, and the ratio of MgO to Al2O3 in the blast furnace slag is not less than 0.5 and the binary basicity R2 of the blast furnace slag is controlled to be 1.10-1.20, so as to improve the fluidity and desulfurization efficiency of the blast furnace slag. The physical thermal temperature of the molten iron is controlled to be above 1500°C. The control parameters for Examples 1-3 and Comparative Examples 1-4 are shown in Table 1, and the chemical composition of the molten iron obtained in Examples 1-3 and Comparative Examples 1-4 is shown in Table 2.

[0037]

[0038]

[0039] As shown in Tables 1 and 2, the process parameters used in Examples 1 to 3 all fall within the scope of the technical features defined in the claims. Specifically, in the examples, the TiO2 load was controlled between 8.16 and 8.74 kg / tHM, the Mn / TiO2 ratio was between 0.70 and 0.80, the slag binary basicity R2 was between 1.16 and 1.17, the MgO / Al2O3 ratio was between 0.51 and 0.52, the slag Al2O3 content was between 16.55% and 16.65%, and the physical heat temperature of the molten iron was between 1510 and 1515℃. Under the synergistic effect of the above parameters, the chemical composition of the obtained molten iron fully meets the requirements for steelmaking, with a P content of 0.106% to 0.109%, a S content of 0.012% to 0.017%, a Ti content of 0.084% to 0.089%, a Si content of 0.37% to 0.38%, and a Mn content of 0.37% to 0.44%. Compared with the prior art, this embodiment significantly reduces the S content and improves the Mn content to a better level while maintaining stable P and Si indicators, creating favorable conditions for the steelmaking process.

[0040] In Comparative Example 1, the Mn / TiO2 ratio was 0.55, lower than the 0.70 lower limit required by this application, while the other parameters were similar to those in the Example. Due to the relatively insufficient manganese load, the MnO concentration in the slag was low, weakening the inhibitory effect on TiO2 reduction and causing the Ti content in the molten iron to rise to 0.119%, exceeding the control requirement of ≤0.090%. This indicates that when the Mn / TiO2 ratio is below 0.70, it is difficult to effectively suppress the titanium reduction problem caused by high TiO2 load.

[0041] In Comparative Example 2, the Mn / TiO2 ratio was 0.95, which is higher than the upper limit of 0.80 required by this application. Although the resulting molten iron had good quality indicators, with Ti content as low as 0.069% and Mn content reaching 0.55%, the excessively high manganese load is difficult to achieve in natural iron ore and must be achieved by adding more expensive manganese ore, resulting in a significant increase in the cost of raw materials and deviating from the purpose of low-cost smelting.

[0042] In Comparative Example 3, the MgO / Al2O3 ratio was 0.60, and the Al2O3 content in the slag was 17.30%, which is at a relatively high level. Although the molten iron quality indicators are comparable to those of the Example, according to the conclusions of industrial tests, fuel consumption will increase slightly under this combination of magnesium-aluminum ratio and aluminum content, and the overall economic efficiency is not as good as that of the Example.

[0043] In Comparative Example 4, the binary basicity R2 of the slag was 1.08, lower than the lower limit requirement of 1.10, and the physical heat temperature of the molten iron was 1489℃, lower than the requirement of 1500℃. These deviations in key parameters led to a significant decrease in slag desulfurization efficiency, causing the sulfur content in the molten iron to rise to 0.048%, exceeding the control requirement of ≤0.045%, and thus the molten iron quality failed to meet the standards.

[0044] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0045] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. 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 this application. Therefore, this application 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 claimed herein.

Claims

1. A method for preparing low-cost steelmaking pig iron, characterized in that, The method includes: The blast furnace charge is smelted in the blast furnace to obtain molten iron, and the following parameters are controlled during the blast furnace smelting process: The TiO2 load of the blast furnace feed is controlled to be ≤9.0 kg / tHM, and the ratio of Mn load to TiO2 load of the blast furnace feed is controlled to be 0.70 to 0.80, so as to suppress the reduction of TiO2 in the blast furnace slag. The mass fraction of Al2O3 in blast furnace slag is controlled to be 15.50-18.30%, and the ratio of MgO to Al2O3 in the blast furnace slag is not less than 0.5 and the binary basicity R2 of the blast furnace slag is controlled to be 1.10-1.20, so as to improve the fluidity and desulfurization efficiency of the blast furnace slag. The physical thermal temperature of the molten iron is controlled to be above 1500℃.

2. The method for preparing low-cost steelmaking pig iron according to claim 1, characterized in that, The ratio of MgO to Al2O3 in the blast furnace slag is controlled to be 0.50 to 0.

60.

3. The method for preparing low-cost steelmaking pig iron according to claim 2, characterized in that, When the ratio of MgO to Al2O3 in the blast furnace slag is controlled to be 0.50 to 0.55, the mass fraction of Al2O3 in the blast furnace slag is controlled to be 16.50 to 17.50%.

4. The method for preparing low-cost steelmaking pig iron according to claim 2, characterized in that, When the ratio of MgO to Al2O3 in the blast furnace slag is controlled to be 0.55 to 0.60, the mass fraction of Al2O3 in the blast furnace slag is controlled to be 17.50 to 18.30%.

5. The method for preparing low-cost steelmaking pig iron according to claim 1, characterized in that, In the molten iron, by mass fraction, P≤0.12%, S≤0.045%, Ti≤0.090%, Si:0.25~0.50%, Mn≤0.60%.

6. The method for preparing low-cost steelmaking pig iron according to claim 1, characterized in that, The blast furnace feed includes iron ore with high Mn content and iron ore with high TiO2 content.

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