Converter steelmaking slag system capable of increasing content of residual manganese in molten steel and use method of converter steelmaking slag system

Abstract

The invention relates to a converter steelmaking slag system for increasing the content of residual manganese in molten steel and a using method thereof, and belongs to the technical field of steelmaking processes. The slag system comprises the following components in percentage by mass: less than or equal to 4.0% of MgO, less than or equal to 4.5% of MnO, 40-50% of CaO, 12-18% of SiO2, less than or equal to 15% of FeO, Al2O3, CaF2, S and P2O5. By reasonably designing the components of the slag system, the addition of the slag making material light-burned dolomite containing the MgO component is reduced, MgO and MnO are prevented from generating a high-melting-point phase, and the high-melting-point phase is enriched in the slag to form a solid phase, so that MnO can be smoothly reduced by CO to enter the molten steel, and the content of residual manganese in the molten steel is increased.

Description

Technical Field

[0001] The present application relates to the technical field of steelmaking technology, and in particular to a converter steelmaking slag system for increasing the residual manganese content in molten steel and a method for using the same. Background Art

[0002] In order to improve the performance of steel, Mn needs to be added to the molten steel. The molten steel at the end of converter smelting contains a certain content of Mn element. The higher the content, the lower the amount of Mn alloy added, which can reduce the alloying cost of molten steel.

[0003] At present, the commonly used methods for increasing the residual manganese content in molten steel are as follows: 1. Add a certain amount of Mn-containing substances, such as manganese ore, at the beginning of converter smelting, implement low-slag smelting, increase the basicity of slag, etc. during the smelting process to increase the Mn recovery rate. 2. The converter smelting process adopts thermodynamic conditions that are conducive to increasing the Mn recovery rate, such as increasing the temperature of molten steel, reducing the oxygen content in steel, and increasing the carbon content of molten steel. 3. Increase the Mn content of molten iron. At present, no research and reports on a converter steelmaking slag system that can effectively increase the residual manganese content in molten steel have been found. Summary of the invention

[0004] The present application provides a converter steelmaking slag system for increasing the residual manganese content in molten steel and a method for using the same, in order to solve the following technical problem: how to increase the residual manganese content in molten steel.

[0005] In a first aspect, the present application provides a converter steelmaking slag system for increasing the residual manganese content of molten steel. The components of the slag system include, by mass fraction: MgO≤4.0%, MnO≤4.5%, CaO: 40% to 50%, SiO2: 12% to 18%,

[0006] And FeO: ≤15%;

[0007] The components of the slag system also include: Al2O3, CaF2, S and P2O5.

[0008] Optionally, the components of the slag-forming materials of the slag system include: 35kg / t·steel to 40kg / t·steel of lime, 10kg / t·steel to 25kg / t·steel of ore, and 2kg / t·steel to 10kg / t·steel of light-burned dolomite.

[0009] Optionally, the basicity R of the slag system is 2.5 to 3.3.

[0010] In a second aspect, the present application provides a method for using the slag system described in the first aspect, the method comprising:

[0011] placing molten iron in a top-bottom double-blown converter for smelting, and adding the slag-making material to the molten iron during the smelting process to make slag, thereby obtaining molten steel;

[0012] The molten steel is tapped from a converter.

[0013] Optionally, the top-blowing gas supply intensity of the top-bottom combined blowing converter is 3.1m 3 / min / t~3.8Nm 3 / min / t.

[0014] Optionally, the maximum gas supply intensity of the top and bottom combined blowing converter at the end of bottom blowing smelting is 0.03Nm 3 / min / t.

[0015] Optionally, the Mn content in the molten iron is ≥ 0.45% by mass.

[0016] Optionally, the P content in the molten iron is ≤0.18% by mass fraction.

[0017] Optionally, the C content of the molten steel tapped from the converter is ≥ 0.06% by mass.

[0018] Optionally, the temperature of the molten steel tapped from the converter is 1640°C to 1660°C.

[0019] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0020] The present application provides a converter steelmaking slag system for increasing the residual manganese content of molten steel. The components of the slag system include, by mass fraction, MgO≤4.0%, MnO≤4.5%, CaO: 40% to 50%, SiO2: 12% to 18%, FeO: ≤15%, Al2O3, CaF2, S, P2O5. By rationally designing the components of the slag system, the addition of light-burned dolomite, a slag-making material containing MgO components, is reduced, MgO and MnO are prevented from generating a high melting point phase, and are enriched in the slag to form a solid phase, so that MnO can be smoothly reduced by CO and enter the molten steel, thereby increasing the residual manganese content in the molten steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] Figure 1A schematic flow chart of a method for using a converter steelmaking slag system to increase the residual manganese content in molten steel according to some embodiments of the present application; DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0025] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range; in addition, whenever a numerical range is indicated in this document, it is meant to include any cited numbers (fractions or integers) within the indicated range.

[0026] In this document, the terms including "including" and "including" mean "including but not limited to". Relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, and "plurality" means two or more; "at least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items; for example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0027] In a first aspect, the present application provides a converter steelmaking slag system for increasing the residual manganese content of molten steel. The components of the slag system include, by mass fraction: MgO≤4.0%, MnO≤4.5%, CaO: 40% to 50%, SiO2: 12% to 18%,

[0028] And FeO: ≤15%;

[0029] The components of the slag system also include: Al2O3, CaF2, S and P2O5.

[0030] The positive effects of controlling MgO≤4.0% are: it can effectively reduce the amount of slag, providing favorable slag conditions for increasing the residual manganese content of molten steel; reducing the MgO content in the slag can reduce the formation of solid solution between MnO and MgO, and reduce the total amount of Mn element in the slag in solid form. Exemplarily, the MgO content can be 2.8%, 3.0%, 3.4%, 3.8%, 4.0%, etc.

[0031] Positive effect of controlling MnO≤4.5%: In a reducing atmosphere, carbon or other reducing agents in molten steel can reduce MnO in the slag to manganese. Maintaining a moderate MnO content in the slag system is conducive to this reduction reaction, thereby increasing the residual manganese content in the molten steel. For example, the MnO content can be 3.0%, 3.4%, 3.8%, 4.0%, 4.5%, etc.

[0032] The positive effect of controlling the CaO content to 40% to 50% is that as a strong alkaline oxide in the slag system, the increase in the CaO content helps to reduce the oxidizing property of the slag system, thereby creating a more reducing environment. In such an environment, the carbon element in the molten steel can more easily reduce the manganese oxide (MnO) in the slag to manganese element (Mn), thereby increasing the residual manganese content in the molten steel. In addition, a slag system with a high CaO content is conducive to the dephosphorization reaction, because phosphorus is more easily combined with CaO under alkaline conditions to form corresponding compounds, thereby being effectively removed. This helps to reduce the content of harmful element phosphorus in the molten steel and improve the purity and quality of the molten steel. Exemplarily, the CaO content can be 40%, 42%, 44%, 48%, 50%, etc.

[0033] The positive effect of controlling the SiO2 content to 12% to 18% is that a moderate SiO2 content helps maintain the basicity and fluidity of the slag, making the reduction reaction of manganese more complete. Too high a SiO2 content may increase the viscosity of the slag, which is not conducive to the reduction reaction of manganese; while too low a SiO2 content may cause the slag to have too high a basicity, which is not conducive to the fluidity of the slag and the stability of the smelting process. Exemplarily, the SiO2 content can be 12%, 14%, 15%, 17%, 18%, etc.

[0034] Positive effects of controlling FeO≤15%: During the converter smelting process, the manganese element in the molten steel easily combines with oxygen to form manganese oxide (MnO) and enters the slag, causing manganese loss. Controlling the FeO content in the slag system below 15% helps to reduce the oxidizability of the slag, reduce the secondary oxidation of manganese, and retain more manganese in the molten steel. In addition, under a reducing atmosphere, carbon or other reducing agents in the molten steel can reduce the MnO in the slag to manganese element. A lower FeO content is conducive to this reduction reaction, thereby increasing the residual manganese content in the molten steel. Exemplarily, the FeO content can be 7%, 10%, 12%, 13%, 15%, etc.

[0035] In some embodiments, the components of the slag-forming material of the slag system include: 35kg / t·steel to 40kg / t·steel of lime, 10kg / t·steel to 25kg / t·steel of ore, and 2kg / t·steel to 10kg / t·steel of light-burned dolomite.

[0036] The positive effect of controlling the amount of lime to 35kg / t·steel to 40kg / t·steel: Reasonable amount of lime helps to adjust the basicity and chemical composition of the slag, creating good conditions for the recovery of manganese. Appropriate basicity can promote the stability of MnO in the slag, reduce the oxidation loss of manganese, and thus increase the residual manganese content in the molten steel. Exemplarily, the amount of lime can be 35kg / t·steel, 36kg / t·steel, 38kg / t·steel, 40kg / t·steel, etc.

[0037] The positive effect of controlling the amount of ore to 10kg / t·steel to 25kg / t·steel is that it is beneficial to the rapid melting of slag and dephosphorization in the early stage of smelting. For example, the amount of the ore can be 10kg / t·steel, 15kg / t·steel, 20kg / t·steel, 25kg / t·steel, etc.

[0038] The positive effects of controlling the amount of light-burned dolomite to 2kg / t·steel to 10kg / t·steel are: reducing the amount of slag, controlling the MgO content in the slag, and reducing the amount of MnO·MgO high melting point solid solution in the slag. For example, the amount of light-burned dolomite can be 10kg / t·steel, 15kg / t·steel, 20kg / t·steel, 25kg / t·steel, etc.

[0039] In some embodiments, the basicity R of the slag system is 2.5-3.3.

[0040] The positive effect of controlling the basicity R of the slag system to 2.5-3.3: A higher basicity of the slag system is conducive to the dephosphorization reaction, because phosphorus is more easily combined with calcium oxide (CaO) in the slag under alkaline conditions to form calcium phosphate (Ca3(PO4)2), thereby being effectively removed. This helps to reduce the phosphorus content in molten steel and improve the purity of molten steel. Exemplarily, the basicity R of the slag system can be 2.5, 2.6, 2.8, 3.1, 3.3, etc.

[0041] Figure 1 A schematic flow chart of a method for using a converter steelmaking slag system to increase the residual manganese content in molten steel provided in an embodiment of the present application.

[0042] See also Figure 1 In a second aspect, the present application provides a method for using the slag system described in the first aspect, the method comprising:

[0043] S1, placing molten iron in a top and bottom double-blown converter for smelting, and adding the slag-making material to the molten iron during the smelting process to make slag to obtain molten steel;

[0044] In some embodiments, the top-blowing gas supply intensity of the top-bottom combined blowing converter is 3.1m 3 / min / t~3.8Nm 3 / min / t.

[0045] The top blowing air supply intensity is 3.1m 3 / min / t~3.8Nm 3 / min / t positive effect: it can enhance the stirring effect between molten steel and slag, so that the carbon element in the molten steel can be more fully in contact with the manganese oxide (MnO) in the slag, thereby promoting the reduction reaction C+MnO→CO+Mn. This helps to reduce more manganese from the slag to the molten steel and increase the residual manganese content in the molten steel. In addition, moderate top blowing gas supply intensity can improve the mass transfer conditions between molten steel and slag, so that the reduction reaction reaches equilibrium in a shorter time, thereby improving the recovery rate of manganese. Exemplarily, the top blowing gas supply intensity can be 3.1m 3 / min / t, 3.3m 3 / min / t、3.5m 3 / min / t、3.6m 3 / min / t, 3.8Nm 3 / min / t, etc.

[0046] In some embodiments, the maximum gas supply intensity of the top and bottom combined blowing converter at the end of bottom blowing smelting is 0.03Nm 3 / min / t.

[0047] The maximum gas supply intensity at the end of bottom blowing smelting is 0.03Nm3 / min / t positive effect: it can ensure that the bottom gas stirring effect is moderate, neither too strong to cause molten steel splashing, nor too weak to effectively promote the interface reaction between steel and slag. This moderate stirring helps the carbon element in the molten steel to react with the manganese oxide in the slag to generate manganese, thereby increasing the residual manganese content in the molten steel.

[0048] In some embodiments, the Mn content in the molten iron is ≥ 0.45% by mass.

[0049] Positive effects of Mn content in molten iron ≥ 0.45%: High manganese content in molten iron is conducive to increasing the residual manganese content. If the Mn content in molten iron is too low, the residual manganese content at the end of the converter is low and the recovery value is low. Exemplarily, the Mn content in the molten iron can be 0.45%, 0.48%, 0.55%, 0.65%, 0.68%, etc.

[0050] In some embodiments, the P content in the molten iron is ≤ 0.18% by mass.

[0051] The positive effect of controlling the P content in the molten iron to ≤ 0.18% is that if the P content in the molten iron is too high, the P content at the converter end point will be too high, resulting in unqualified molten steel composition. For example, the P content in the molten iron can be 0.08%, 0.12%, 0.16%, 0.18%, etc.

[0052] S2, tapping the molten steel from a converter.

[0053] In some embodiments, the C content of the molten steel tapped from the converter is ≥ 0.06% by mass.

[0054] Positive effects of C content ≥ 0.06% in molten steel: high carbon content in molten steel is conducive to reducing oxygen content in molten steel and increasing residual manganese content. If the C content is ≤ 0.06%, the oxygen content in the steel will be ≥ 0.045%, causing Mn in the molten steel to react chemically with O in the molten steel to generate MnO that enters the slag. If the C content is ≥ 0.06%, the oxygen content in the steel is lower than 0.045%, which will reduce the amount of Mn in the steel reacting with O in the steel and reduce the loss of Mn in the steel. Exemplarily, the C content of the steel tapped from the converter can be 0.06%, 0.08%, 0.10%, 0.12%, 0.14%, etc.

[0055] In some embodiments, the temperature of the molten steel tapped from the converter is 1640°C to 1660°C.

[0056] The positive effect of controlling the temperature of molten steel to 1640°C to 1660°C: within this temperature range, the carbon (C) element in the molten steel has a high reducibility and can reduce manganese oxide (MnO) in the slag to manganese (Mn), that is, the reaction C+MnO→CO+Mn proceeds in the positive direction, thereby increasing the amount of residual manganese in the molten steel. This reduction reaction is more favorable at high temperatures and improves the recovery rate of manganese elements. Excessive molten steel temperature will cause the P content in the tapped steel to exceed the standard. Exemplarily, the molten steel temperature can be 1640°C, 1645°C, 1650°C, 1655°C, 1660°C, etc.

[0057] The present application is further described below in conjunction with specific examples. The experimental methods in the following examples that do not specify specific conditions are usually measured according to industry standards; if there are no corresponding industry standards, they are carried out according to common international standards, conventional conditions, or conditions recommended by the manufacturer.

[0058] This embodiment also provides a method for using a converter steelmaking slag system to increase the residual manganese content in molten steel, comprising the following steps:

[0059] placing molten iron in a top-bottom double-blown converter for smelting, and adding the slag-making material to the molten iron during the smelting process to make slag, thereby obtaining molten steel;

[0060] The molten steel is tapped from a converter.

[0061] The composition of molten iron (wt%), the amount of slag-making material (kg / t·steel) and the molten steel temperature (°C) at steel tapping are shown in Table 1.

[0062] The composition (wt%) of the slag system, the basicity R, the C content and the residual Mn content of the molten steel are shown in Table 2.

[0063] Table 1 Composition of molten iron (wt%), amount of slag-making material (kg / t·steel) and molten steel temperature at tapping (℃)

[0064] Group Mn P lime ore Lightly burned dolomite Molten steel temperature Example 1 0.51 0.130 38 22 5 1645 Example 2 0.55 0.143 35 16 4.5 1650

[0065] Table 2 Composition (wt%) of slag system, basicity R and C content (wt%) and residual Mn content (wt%) of molten steel

[0066] Group FeO CaO <![CDATA[SiO2]]> MnO MgO <![CDATA[P2O5]]> R C YuMn Example 1 12.77 44.51 16.14 3.81 2.2 1.81 2.7 0.12 0.36 Example 2 12.09 48.34 16.52 4.17 3.34 1.78 2.9 0.14 0.38

[0067] It can be seen from Tables 1 and 2 that the composition of the slag system in the embodiment and the process for steelmaking are both within the required range of the present invention, and the residual Mn content in the molten steel after the converter is tapped can reach more than 0.35%, with significant effect.

[0068] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0069] The converter steelmaking slag system can be produced by conventional converter steelmaking methods, the recovery rate of residual manganese is improved, and the converter steelmaking cost is effectively reduced.

[0070] The above is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. It will be apparent to those skilled in the art that various modifications to these embodiments are possible, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features applied for by the present application.

Claims

1. A converter steelmaking slag system for increasing the residual manganese content in molten steel, characterized in that: In terms of mass fraction, the components of the slag system include: MgO≤4.0%, MnO≤4.5%, CaO: 40% to 50%, SiO2: 12% to 18%, and FeO: ≤15%; The components of the slag system also include: Al2O3, CaF2, S and P2O5.

2. The slag system according to claim 1, characterized in that: The components of the slag-forming materials of the slag system include: 35kg / t·steel to 40kg / t·steel of lime, 10kg / t·steel to 25kg / t·steel of ore, and 2kg / t·steel to 10kg / t·steel of light-burned dolomite.

3. The slag system according to claim 1, characterized in that: The basicity R of the slag system is 2.5-3.

3.

4. A method for using the slag system according to any one of claims 1 to 3, characterized in that: The method comprises: placing molten iron in a top-bottom double-blown converter for smelting, and adding the slag-making material to the molten iron during the smelting process to make slag, thereby obtaining molten steel; The molten steel is tapped from a converter.

5. The method according to claim 4, characterized in that The top-blowing gas supply intensity of the top-bottom combined blowing converter is 3.1m 3 / min / t~3.8Nm 3 / min / t.

6. The method according to claim 4, characterized in that The maximum gas supply intensity of the top and bottom combined blowing converter at the end of bottom blowing smelting is 0.03Nm 3 / min / t.

7. The method according to claim 4, characterized in that Calculated by mass fraction, the Mn content in the molten iron is ≥0.45%.

8. The method according to claim 4, characterized in that Calculated by mass fraction, the P content in the molten iron is ≤0.18%.

9. The method according to claim 4, characterized in that Calculated by mass fraction, the C content of the molten steel tapped from the converter is ≥ 0.06%.

10. The method according to claim 4, characterized in that The temperature of the molten steel tapped from the converter is 1640°C to 1660°C.

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