Product and method for direct manganese alloying in converter steelmaking
By pressing manganese ore, reducing agent and flux into a block core and wrapping CaO powder to form a CaS shell, the problem of low manganese yield in converter manganese alloying is solved, and the efficient alloying of manganese is achieved, which is suitable for a variety of purposes. The smelting process reduces production costs.
Patent Information
- Application Number
- CN202411325315.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-23
- Publication Date
- 2024-12-27
AI Technical Summary
The manganese yield during the direct manganese alloying process of converter is low and is limited by smelting methods. The existing technology requires high quality and large energy investment, resulting in an increase in production costs.
The block core is pressed from mixed with manganese ore, reducing agent and flux, and the surface is wrapped with CaO powder to form a CaS shell to enclose the reaction space, prevent contact of oxidative atmosphere, improve the reduction rate and yield of manganese, and The melting point of the CaS shell is reduced by flux to promote the alloying of manganese.
On the basis of meeting the converter dephosphorization task, the direct alloying of manganese is realized, which improves the manganese yield, and is suitable for a variety of smelting processes, reducing dependence on smelting processes, and reducing resource and energy investment.
Smart Images
Figure CN119193983A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of metallurgy technology, and more particularly to a product and method for direct manganese alloying in converter steelmaking. Background Art
[0002] Manganese ore alloying steelmaking is a steelmaking process that improves steel performance and quality by adding manganese to molten steel. This addition effectively enhances the steel's hardness, toughness, wear resistance, and corrosion resistance, improving its processing properties and broadening its application areas to meet diverse performance requirements across diverse sectors. However, alloying steelmaking technology is relatively complex, requiring rigorous technical expertise and placing high demands on both production processes and equipment.
[0003] The direct manganese ore alloying steelmaking process eliminates the traditional manganese alloy smelting step and transfers the manganese reduction process to the furnace. This improves the production efficiency of manganese-containing steel and reduces energy consumption. It also avoids the environmental impact of harmful emissions during manganese alloy smelting. This method can improve the quality and process efficiency of manganese alloy products to meet growing market demand.
[0004] For example, the Chinese patent application No. 2019109584186 discloses a method for direct alloying steelmaking with manganese ore in a converter. This application adopts the method of double slag smelting in a converter, adding slag-making materials for the first slag blowing, and then pulling carbon and releasing slag after dephosphorization in the early stage, and then performing secondary slag blowing. During the secondary slag blowing process, slag-making materials, temperature raising agents and manganese ore are added for alloying, and the steel is blown until the terminal molten steel temperature is 1640-1670°C, and the steel is tapped. This application uses the method of low slag + heat compensation to solve the problems of high oxidation in the later stage and low manganese yield of direct alloying of manganese ore through secondary slag making, and jointly achieves dephosphorization and manganese increase in the converter. However, this application is only suitable for secondary slag smelting.
[0005] For example, Chinese patent application No. 2018101477552 discloses a method and apparatus for manganese alloying using manganese ore. This application utilizes a molten electrolytic method to reduce manganese ore for manganese alloying. This method represents a novel green manganese alloying technology; however, its drawbacks include high ore quality requirements and the increased resource and energy input required, which increases production costs. Summary of the Invention
[0006] In response to the technical problems of low manganese yield in the direct manganese alloying process in the converter and the significant limitation of the manganese alloying yield by the smelting method, this solution provides a product and method for direct manganese alloying in converter steelmaking. The direct manganese alloying product of the present invention not only realizes the direct manganese alloying of molten steel using manganese ore, but also is adaptable to more smelting processes.
[0007] In order to achieve the above object, the technical solution provided by the present invention is:
[0008] A first aspect of the present invention provides a product for direct manganese alloying in converter steelmaking, comprising a block core and CaO powder coated on the surface of the block core, wherein the block core is obtained by pressing or pelletizing a mixture of manganese ore, a reducing agent and a flux.
[0009] Traditional steelmaking converters are responsible for dephosphorization, requiring a large slag volume and high oxidizing properties to ensure effective dephosphorization. However, the manganese ore converter direct alloying process requires a small slag volume and low slag oxidizing properties. The present invention achieves direct manganese alloying in converter steelmaking by mixing manganese ore with a reducing agent, then pressing or pelletizing it to form a block core, which is then directly added to molten steel. Furthermore, by coating the block core with a layer of CaO powder, the CaO reacts with the slag layer and sulfur in the molten steel during the addition of molten steel to form a CaS shell. This resulting CaS shell has a dense structure, providing a closed space for the reaction between the manganese ore and the reducing agent. The presence of this shell does not affect heat transfer, allowing heat from the molten steel to be transferred to the block core, thereby ensuring the normal reduction reaction of the manganese ore and achieving full reduction. Furthermore, the presence of the CaS shell effectively prevents the oxidizing atmosphere or oxidizing substances in the converter from entering and contacting the block core, preventing the reduced elemental manganese from being oxidized again, thereby delaying oxidation. That is, the technical solution of the present application can achieve direct alloying treatment of manganese and ensure the manganese yield on the basis of meeting the requirements of converter dephosphorization.
[0010] More preferably, the present invention includes a flux in the block core, thereby effectively lowering the melting point of the CaS shell. As the internal temperature of the molten steel gradually increases and the product descends to a certain depth, the CaS shell gradually melts, thereby releasing the elemental manganese formed by the reduction into the molten steel, achieving manganese alloying. Furthermore, the flux can also lower the melting point and viscosity of the slag, changing the kinetic conditions during the manganese ore reduction process. The rapidly formed liquid slag envelops the reduced metal particles, thereby preventing the volatilization of metallic Mn and further improving the manganese yield.
[0011] In addition, since the newly generated CaS shell is wrapped around the surface of the blocky core with its own reducing agent and can effectively prevent elemental manganese from being oxidized again when in contact with an oxidizing atmosphere, on the one hand, the product can be applied to a variety of converter steelmaking processes, such as the double slag method, the duplex method and the single slag method, and the alloy yield is not limited by the smelting process; on the other hand, the addition timing of the product is less restricted by the oxygen content in the molten steel, which solves the problem in the prior art that the manganese alloying yield can only be guaranteed after deoxidation.
[0012] Furthermore, the particle size of the CaO powder on the surface of the block core is 150-250 mesh mm, and the mass of the coating powder accounts for 18-22% of the mass of the block core. By optimizing the particle size of the coating powder, the coating thickness, or the ratio of powder mass to the block core, when the particle size of the CaO powder on the surface of the block core is too large, it is not conducive to the density of the coating of the block core. Conversely, when the particle size of the CaO powder is too small, the grinding cost of the CaO powder is increased; when the coating thickness is too large, the melting temperature is too high, and the elemental manganese generated by internal reduction cannot be released in time; conversely, when the coating thickness is too small, the melting temperature is too low, the internal manganese ore does not fully react with the reducing agent, and the elemental manganese generated by reduction is released prematurely, affecting the manganese yield.
[0013] Furthermore, the reducing agent is carbon powder, silicon carbide or aluminum powder.
[0014] Furthermore, the reducing agent is preferably silicon carbide. On the one hand, when carbon is selected as the reducing agent, the reducing agent C is in direct contact with manganese oxide and iron oxide, a direct reduction reaction occurs, and CO is generated. As the CO partial pressure in the compact increases, the contact area between manganese oxide and iron oxide and CO increases, an indirect reduction reaction occurs, and the later reduction products block the manganese oxide and iron oxide in the manganese ore from the reducing agent, and the reduction reaction is hindered. Therefore, C as a reducing agent is not conducive to the full progress of the reduction reaction. At the same time, compared to C, the C ions in SiC are more likely to lose electrons and have stronger reducibility. On the other hand, when the ratio of the molar number of the reducing agent used in the block core to the sum of the molar number of oxygen elements bound to manganese and iron in the manganese ore is the same, selecting silicon carbide as the reducing agent can further improve the reduction rate of manganese in the manganese ore.
[0015] When SiC is selected as a reducing agent to prepare the above-mentioned alloyed product, and applied to converter alloying, it is further preferred that the ratio of the number of moles of the reducing agent to the sum of the number of moles of oxygen elements combined with manganese and iron in the manganese ore is 0.4 to 1.0, and more preferably 0.6 to 0.8. This reducing agent ratio is adopted to comprehensively consider the amount of reducing agent used and the manganese yield. Generally speaking, as the amount of reducing agent added increases, the reduction rate of manganese element continues to increase. However, after reaching a certain ratio, the effect of the amount of reducing agent added on the improvement of the metal reduction rate becomes weaker. It has been verified by experiments that the reducing agent ratio is between 0.6 and 0.8, which can not only have a good reduction rate for manganese ore, but also effectively realize the simultaneous reduction of iron, so that it forms an iron-manganese metal mixture, and can save the amount of reducing agent used. A further preferred reducing agent ratio is 0.7, expressed as SiC / O=0.7, where SiC represents the molar number of SiC and O represents the molar number of oxygen elements combined with manganese and iron in the manganese ore. Experimental verification shows that under this reducing agent ratio, both Fe and Mn are effectively reduced to form an iron-manganese metal mixture with a better effect.
[0016] Furthermore, the particle size of the mixed material is 150-250 mesh; when the particle size of the mixed material is too large, it is not conducive to the compactness of the block core; on the contrary, when the particle size is too small, the grinding cost is increased and the speed is too fast. The particle size of the mixed material is 150-250 mesh, which makes the reaction in the block core easy to proceed and convenient for pressing and molding. The shape of the block core includes but is not limited to square, spherical, and cylindrical. Its overall size is 15-60mm. The overall size refers to the length, width, height or diameter of the block briquette, which is 15-60mm. For example, when the block core is spherical, it refers to its diameter of 15-60mm, when the block core is square, it refers to its length (or width) of 15-60mm, and when the block core is cylindrical, it refers to its diameter (or height) of 15-60mm. Products in this size range are placed between molten steel and steel slag in the converter, which is conducive to promoting the reduction reaction of the block core manganese ore. When the size range is less than 15mm, the product will float on the surface of the steel slag, failing to achieve good melting and reaction effects, thereby reducing the manganese reduction rate; on the contrary, when the size range is greater than 60mm, the product will penetrate the steel slag and enter the molten steel, resulting in insufficient reaction between the manganese ore and the reducing agent inside the product and premature release of the elemental manganese generated by the reduction, affecting the manganese recovery rate.
[0017] Furthermore, the flux is selected as CaF2, and its addition amount is 3-7% of the mass of the block core. Regarding the addition amount of flux, if the addition amount is too much, the melting temperature is too low, the manganese ore in the block core is not fully reduced, and the flux is wasted; on the other hand, if the addition amount is too little, the melting temperature is too high, and the newly generated elemental manganese in the block core cannot be released into the molten steel in time. Moreover, since the volatility of manganese gradually increases with increasing temperature, the excessively high melting temperature of the shell will increase the volatility of manganese, resulting in a reduced metal yield.
[0018] Furthermore, the manganese ore includes the following components in proportions: SiO2 56-64%, MnO 15-21%, Al2O3 5-9%, and Fe2O3 10-15%.
[0019] A second aspect of the present invention provides a method for direct manganese alloying in converter steelmaking, comprising: contacting the aforementioned product for direct manganese alloying in converter steelmaking with molten steel during the converter smelting process, utilizing the heat of the molten steel to promote a reduction reaction of the manganese ore by a reducing agent in the blocky core, thereby generating elemental manganese and releasing it into the molten steel. Furthermore, the product for direct manganese alloying is added in the late stages of converter smelting, beginning in the middle to late stages of the oxygen blowing time, and more preferably starting at 4 / 5 of the oxygen blowing time, minimizing the oxidizing atmosphere within the converter, thereby facilitating the alloying of the converter manganese ore and improving the Mn metal yield.
[0020] And / or the product for direct manganese alloying is added in batches, which can ensure that the reducing agent in the block core fully reacts with the manganese ore, better control the progress of the manganese ore reduction reaction, and achieve the purpose of saving raw materials.
[0021] And / or upon contact with molten steel, the following reactions occur: CaO powder on the surface of the block core reacts with sulfur to form a CaS shell; the manganese ore within the block core reacts with a reducing agent to produce elemental manganese; and the CaS shell melts, releasing the resulting elemental manganese into the molten steel. Based on this principle, a product designed for direct manganese alloying in converter steelmaking utilizes the newly generated CaS as a protective shell around the inner block core, isolating it from the oxidizing atmosphere of the external converter. Furthermore, the shelled block core does not melt immediately upon placement in the converter, allowing the heat from the molten steel to accelerate the reduction of the manganese ore within, preventing the reduced elemental manganese from being oxidized again.
[0022] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:
[0023] (1) The present invention presses a mixture of manganese ore, a reducing agent, and a flux into a block core. The surface of the block core is coated with CaO powder. When the CaO passes through the slag layer and reaches the molten steel, it reacts with the slag layer and sulfur in the molten steel to form a CaS shell to isolate the oxidizing atmosphere in the furnace. The CaS shell can transfer heat to promote the full reaction between the manganese ore and the reducing agent in the block core, while preventing the oxidizing atmosphere in the converter from entering the shell, thereby preventing the reduced manganese from being oxidized again. As the temperature of the molten steel increases, the CaS shell melts and the generated elemental manganese is released, thereby completing the direct manganese alloying in converter steelmaking.
[0024] (2) Since the newly generated CaS shell is wrapped around the surface of the block core with its own reducing agent, the purpose of delayed oxidation can be achieved, the influence of the oxidizing atmosphere in the converter on the reduction of manganese ore is reduced, and the block core inside is protected to fully react, thereby reducing the requirements for the amount of converter slag and atmosphere. Therefore, on the one hand, on the basis of ensuring that the oxidizing atmosphere of the converter meets the requirements of the dephosphorization process, direct alloying treatment of manganese can be achieved and the manganese recovery rate in the steel liquid can be guaranteed; on the other hand, by using this alloyed product, the manganese recovery rate is less affected by the smelting process, so it can be applied to a variety of different smelting processes. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 The invention discloses a manganese metal yield obtained by using different reducing agents in a product for direct manganese alloying in converter steelmaking according to the present invention.
[0026] Figure 2 The invention discloses a product for direct manganese alloying in converter steelmaking, wherein the manganese reduction rate and the volatilization rate vary with temperature without adding flux.
[0027] Figure 3 The manganese reduction rate and volatilization rate of CaF2 added to the product for direct manganese alloying in converter steelmaking of the present invention vary with temperature.
[0028] Figure 4 This is a SEM scan of the manganese slag after the reaction in Example 1 of the present invention. DETAILED DESCRIPTION
[0029] In order to further understand the content of the present invention, the present invention is now described in detail with reference to the accompanying drawings and embodiments.
[0030] Example 1
[0031] The direct manganese alloying product for converter steelmaking in this embodiment comprises a block core and CaO powder coated on the surface of the block core. The block core is formed by pressing a mixture of manganese ore, a reducing agent, and a flux. The manganese ore comprises 60% SiO2, 17% MnO, 7% Al2O3, and 13% Fe2O3. The reducing agent is SiC at a ratio of 0.7, and the flux CaF2 accounts for 5% of the mass of the block core. The particle size of the mixture is 200 mesh. In this embodiment, the block core has a cylindrical structure with a diameter and height of 25 mm. The CaO particle size on the surface of the block core is 150 mesh, and the powder mass accounts for 18% of the block core.
[0032] The direct manganese alloying product of this embodiment was used to perform manganese alloying in a converter of a certain factory. Specifically, in the late stage of converter steelmaking, the product for direct manganese ore alloying in converter steelmaking was added from the silo in three batches at 4 / 5 of the oxygen blowing process; the interval between each batch was 2 minutes, and a total of 15 kg / t was added. The temperature at the end of blowing was 1660° C., and steel was tapped.
[0033] Among them: after the product is put into the converter, as the temperature of the molten steel rises to above 1600℃, the CaS shell melts with the cooperation of the flux CaF2.
[0034] The manganese recovery rate in the molten steel after tapping from the converter is 76.2%.
[0035] The manganese slag sample after the reaction in this embodiment was scanned by electron microscope, and the results were as follows: Figure 4 As shown by Figure 4 It can be seen that both Fe and Mn are effectively reduced to form an iron-manganese metal mixture with a good effect.
[0036] Comparative Example 1
[0037] The product for direct manganese alloying in converter steelmaking of this comparative example differs from that of Example 1 mainly in that the product of this comparative example is formed by pressing a mixture comprising manganese ore, a reducing agent, and a flux into a block core, and the block core is not coated with calcium oxide or calcium carbonate powder; the rest of the preparation process and method are the same as those of Example 1.
[0038] The manganese recovery rate in the molten steel after the converter is tapped is 69.5%. Comparison with Example 1 and Comparative Example 1 shows that the manganese recovery rate is further improved by providing calcium oxide powder wrapped on the surface of the block core, and the recovery rate is significantly improved.
[0039] Comparative Example 2
[0040] The product for direct manganese alloying in converter steelmaking of this comparative example differs from that of Example 1 in that no flux is added to the block core, the manganese ore and the reducing agent SiC are crushed to 200 mesh and then mixed; the rest of the preparation process and method are the same as those of Example 1.
[0041] The manganese recovery rate in the molten steel after tapping from the converter is 70.2%.
[0042] The reduction reaction of manganese ore at different temperatures was compared between the block core without flux and the block core with 5% CaF2. The manganese reduction rate and volatility were calculated based on the weight loss and chemical composition test results of the samples before and after the reaction. Figure 2 、 Figure 3 As shown. Figure 2 、 Figure 3 It can be seen that under the condition of adding CaF2, the reduction rate of manganese can be improved and the volatilization rate of manganese can be reduced. This is mainly because by further adding CaF2, the melting point of the formed calcium sulfide shell can be effectively reduced, and the melting point and viscosity of the slag are reduced, which changes the kinetic conditions of manganese ore reduction in the core of the briquette, so that the rapidly formed liquid slag wraps the reduced metal particles and prevents the volatilization of metal Mn.
[0043] Example 2
[0044] The direct manganese alloying product for converter steelmaking in this embodiment comprises a block core and CaO powder coated on the surface of the block core. The block core is obtained by pressing and molding a mixture containing manganese ore, a reducing agent, and a flux. The manganese ore comprises 55% SiO2, 1% MnO2, 35% Al2O3, and 15% Fe2O3. The reducing agent is SiC, with a reducing agent ratio of 0.6. The flux CaF2 accounts for 3% of the mass of the block core, and the particle size of the mixture is 150 mesh. In this embodiment, the block core is spherical with a spherical diameter of 15 mm. The particle size of the CaO powder on the surface of the block core is 200 mesh, and the powder mass accounts for 20% of the mass of the block core.
[0045] The direct manganese alloying product of this embodiment was used to perform manganese alloying in a converter of a certain factory. Specifically, in the late stage of converter steelmaking, the product for direct manganese ore alloying in converter steelmaking was added from the silo in four batches at 4 / 5 of the oxygen blowing process, with an interval of 1.5 minutes between each batch. A total of 18 kg / t of steel was added, and the temperature at the end of blowing was 1680°C.
[0046] Among them: after the product is put into the converter, as the temperature of the molten steel rises to above 1600℃, the CaS shell melts with the help of flux CaF2. The manganese recovery rate in the molten steel after the converter is tapped is 76.1%.
[0047] Example 3
[0048] The direct manganese alloying product for converter steelmaking in this embodiment comprises a block core and CaO powder coated on the surface of the block core. The block core is obtained by pressing and molding a mixture containing manganese ore, a reducing agent, and a flux. The manganese ore comprises 64% SiO2, 15% MnO, 9% Al2O3, and 10% Fe2O3. The reducing agent is SiC, with a reducing agent ratio of 0.8. The flux CaF2 is present at a ratio of 7% to the mass of the block core. The particle size of the mixture is 250 mesh. In this embodiment, the block core has a square structure with a size of 60 mm. The particle size of the CaO powder on the surface of the block core is 250 mesh, and the powder mass accounts for 22% of the block core mass.
[0049] The direct manganese alloying product of this embodiment was used to perform manganese alloying in a converter of a certain factory. Specifically, in the late stage of converter steelmaking, the product for direct manganese ore alloying in converter steelmaking was added from the silo in three batches at 4 / 5 of the oxygen blowing process, with an interval of 2 minutes between each batch. A total of 12 kg / t of steel was added, and the temperature at the end of blowing was 1660°C.
[0050] Among them: after the product is put into the converter, as the temperature of the molten steel rises to above 1600℃, the CaS shell melts with the help of flux CaF2; the manganese recovery rate in the molten steel after the converter is tapped is 76.3%.
[0051] Example 4
[0052] The product for direct manganese alloying in converter steelmaking of this embodiment differs from that of Example 1 mainly in that the reducing agent is C, and the raw material is anthracite; the rest of the preparation process and method are the same as those of Example 1.
[0053] The manganese recovery rate in the molten steel after tapping from the converter is 67.7%.
[0054] Example 5
[0055] The product for direct manganese alloying in converter steelmaking of this embodiment differs from that of Example 1 mainly in that the reducing agent is different, Al is used as the reducing agent, and aluminum particles are used as the raw material; the rest of the preparation process and method are the same as those of Example 1.
[0056] The manganese recovery rate in the molten steel after tapping from the converter is 70.7%.
[0057] In Example 1, Example 4 and Example 5, different reducing agents were used to reduce manganese ore. At 1600°C, the effects of the three reducing agents on the manganese yield were tested as the reducing agent ratio varied. The test results are shown in Figure 2. Figure 1 As shown. Figure 1It can be seen that under the same reducing agent ratio, the manganese oxide recovery rate of the three reducing agents in manganese ore is in the order of: SiC>Al>C. Therefore, using SiC as a reducing agent can achieve better results. Compared with C and Al, it can more effectively improve the manganese recovery rate, thereby increasing resource utilization and reducing the amount of reducing agent used. Specifically, when the SiC / O ratio is 0.5, the manganese recovery rate reaches 75%, when the Al / O ratio is 0.8, the manganese recovery rate is about 70%, and when the C / O ratio is 1.0, the manganese recovery rate is about 67%; where SiC / O, Al / O, and C / O represent the reducing agent ratios when SiC, Al, and C are used as reducing agents, respectively.
[0058] When SiC is used as the reducing agent, the preferred reducing agent ratio is 0.6-0.8, at which the manganese recovery rate reaches over 75%. A further preferred reducing agent ratio is 0.7, at which both Fe and Mn are effectively reduced to form an iron-manganese metal mixture with good results.
Claims
1. A product for direct manganese alloying in converter steelmaking, characterized in that: The product comprises a block core and CaO powder coated on the surface of the block core, wherein the block core is obtained by pressing or pelletizing a mixed material containing manganese ore, a reducing agent and a flux.
2. The product for direct manganese alloying in converter steelmaking according to claim 1, characterized in that: The particle size of the CaO powder on the surface of the block core is 150-250 meshes, and the mass of the wrapped powder accounts for 18-22% of the mass of the block core.
3. The product for direct manganese alloying in converter steelmaking according to claim 1, characterized in that: The reducing agent is carbon powder, silicon carbide or aluminum powder.
4. The product for direct manganese alloying in converter steelmaking according to claim 3, characterized in that: The reducing agent is silicon carbide.
5. The product for direct manganese alloying in converter steelmaking according to claim 4, characterized in that: The ratio of the molar number of the reducing agent to the sum of the molar numbers of oxygen elements combined with manganese and iron in the manganese ore is 0.4 to 1.
0.
6. The product for direct manganese alloying in converter steelmaking according to any one of claims 1 to 5, characterized in that: The particle size of the mixed material is 150-250 meshes, and the shape of the block core obtained after compression molding includes but is not limited to square, spherical, and cylindrical, and the overall size is 15-60 mm.
7. The product for direct manganese alloying in converter steelmaking according to any one of claims 1 to 5, characterized in that: The flux is CaF2, and its addition amount is 3-7% of the mass of the block core.
8. The product for direct manganese alloying in converter steelmaking according to any one of claims 1 to 5, characterized in that: The manganese ore includes the following components in proportion: SiO2 56-64%, MnO 15-21%, Al2O3 5-9%, and Fe2O3 10-15%.
9. A method for direct manganese alloying in converter steelmaking, characterized in that: include: In the converter smelting process, the direct manganese alloying product according to any one of claims 1 to 8 is brought into contact with molten steel to cause a reduction reaction of the manganese ore in the block core to generate elemental manganese and release it into the molten steel.
10. The method for direct manganese alloying in converter steelmaking according to claim 9, characterized in that: The direct manganese alloying product is added in the late stage of converter smelting, starting from the middle and late stages of oxygen blowing time, and more preferably starting from 4 / 5 of the oxygen blowing time; and / or the product for direct manganese alloying is added in batches; And / or after the direct manganese alloying product contacts molten steel, the following reactions occur: The CaO powder on the surface of the block core reacts with the S in the steel slag and the molten steel to form a CaS shell; The manganese ore in the block core reacts with the reducing agent inside the CaS shell to generate elemental manganese; The CaS shell melts to release the generated elemental manganese into the molten steel.