Direct alloying method for converter steelmaking of manganese-rich slag
Through the dual slag smelting process and the optimized design of manganese-rich slag self-reducing blocks, combined with the top-bottom reblowing process and CaCO3 powder wrapping technology, the problem of low manganese yield in manganese-rich slag converter steelmaking is solved, achieving high efficiency The effects of manganese alloying and dephosphorization improve the yield and smelting efficiency of manganese.
Patent Information
- Application Number
- CN202411325599.6
- 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 in the current direct alloying process of manganese-rich slag converter steelmaking is low, and there are problems of low end carbon content and low manganese recovery, which is difficult to meet the requirements of dephosphorization and manganese alloying.
Using the double slag smelting process, by optimizing the selection and ratio of primary slag-making and secondary slag-making materials, manganese alloying is performed using manganese slag-rich self-reducing blocks, combined with the top-bottom reblowing process and CaCO3 powder wrapping technology, the Reduction rate and yield rate of manganese.
The efficient manganese yield is achieved, with a manganese yield of more than 90%, meeting the converter dephosphorization task and reducing smelting costs and environmental load.
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of metallurgy, and more specifically to a direct alloying method for converter steelmaking using manganese-rich slag. Background Art
[0002] Manganese is one of the most important alloying elements in steel. The manganese content of carbon structural steel and low-alloy structural steel, which currently account for the largest production and consumption, is mostly designed to be between 0.5% and 1.5%. The traditional steelmaking process uses manganese-containing ferroalloys such as FeMn and MnSi to be added to the ladle during the converter steelmaking process for manganese alloying. Due to the high energy consumption, high environmental pressure and high production cost of the production process of manganese-containing alloys such as FeMn and MnSi, people began to explore the steelmaking method of direct alloying with manganese-rich slag in the converter.
[0003] Manganese-rich slag is generally green and lumpy, with the main components being MnO, SiO 2 and A1 2 O 3 , and also contains a small amount of CaO, MgO, FeO, MnS, etc. The direct alloying steelmaking process of manganese-rich slag omits the manganese alloy preparation link in the traditional process, transfers the metal Mn reduction process to the converter, omits the intermediate process of manganese alloy preparation, saves energy consumption from manganese alloy smelting to alloying, greatly reduces smelting costs, and reduces environmental load.
[0004] For example, the application case with Chinese patent application number 2022117069225 discloses a method for alloying manganese elements in a converter and refined reduction lean manganese ore. The method of the patent includes the following: the converter composition parameters are as follows: the slag basicity of the lean manganese ore used in the furnace is controlled at 2.4-2.6, the molten iron composition Si: 0.2%-0.4%, and the molten iron Mn: 0.15%-0.35%; the addition of lean manganese ore in the converter blowing is as follows: the lean manganese ore is added to the converter from the high-level silo of the converter; the amount of lean manganese ore added to each furnace is 2.5-4.5kg per ton of steel; within 5-7 minutes of converter blowing, the lean manganese ore is added in 2-3 times to complete the addition of 80% of the total ore; within 9-10 minutes of converter blowing, the remaining amount of lean manganese ore is added. This application reduces the basicity of converter slag under low-silicon and low-manganese iron water conditions, effectively reduces the amount of converter slag, and optimizes the use process of lean manganese ore, so that the manganese recovery rate in the lean manganese ore can reach 40-50%; however, there is still room for further improvement in the manganese recovery rate.
[0005] The steelmaking converter is responsible for dephosphorization. To ensure the dephosphorization effect, a large amount of slag and high oxidizability are required. However, the manganese-rich slag converter direct alloying process requires a small amount of slag and low slag oxidizability. There is a certain contradiction between the two. Therefore, the direct alloying of steelmaking in the manganese-rich slag converter currently generally has the problems of low terminal carbon content and low manganese recovery rate. It is of great significance to further improve the manganese recovery rate in the manganese-rich slag converter direct alloying process for steelmaking. Summary of the invention
[0006] In view of the problem of low manganese recovery rate in the direct manganese alloying process of the converter in the prior art, the present invention provides a direct alloying method for converter steelmaking using manganese-rich slag. The direct manganese alloying method of the present invention is adopted, and the double slag smelting process is optimized and designed. Manganese-rich slag self-reducing briquettes are added to the converter during the secondary slag making process. This not only realizes the direct manganese alloying of molten steel with manganese-rich slag, but also further improves the reduction rate of manganese-rich slag, and the manganese recovery rate is relatively high.
[0007] In order to achieve the above object, the technical solution provided by the present invention is:
[0008] The invention provides a direct alloying method for manganese-rich slag converter steelmaking, comprising: step S1: adding primary slag-making materials for primary slag-making and blowing, the primary slag-making materials comprising lime, dolomite and return material, wherein the addition amounts of lime, dolomite and return material are 15-19 kg / t steel, 8-12 kg / t steel and 18-22 kg / t steel respectively; step S2: blowing until the phosphorus content in the molten steel is within 0.06%, and pouring the slag; step S3: adding secondary slag-making materials and manganese-rich slag self-reducing briquettes after slag discharge for secondary slag-making and blowing and manganese alloying, the secondary slag-making materials comprising lime and light-burned dolomite, wherein the masses of lime, light-burned dolomite and manganese-rich slag self-reducing briquettes are 3.3-4.1 kg / t steel, 2.0-3.0 kg / t steel and 6.0-8.0 kg / t steel respectively; step S4: blowing until the terminal molten steel temperature is 1580-1680 DEG C; and tapping.
[0009] The direct alloying method of converter steelmaking with manganese-rich slag adopts converter double slag smelting. In the first slag blowing, the selection and proportion of the first slag material are optimized and designed, and at the end of the first slag blowing, the phosphorus content of the molten steel is within 0.06%, realizing the basic function of converter dephosphorization; then the second slag blowing is carried out, the selection and proportion of the second slag material are optimized and designed, and the self-reducing briquettes of less slag and manganese-rich slag are used to make up for the defect of insufficient carbon content in the later stage, improve the reduction rate of manganese-rich slag and the manganese content of the terminal molten steel, reduce the subsequent use of manganese alloys for manganese alloying, and thus reduce the converter smelting cost. That is, the technical solution of the present application can realize the direct alloying treatment of manganese on the basis of meeting the requirements of converter dephosphorization tasks, and ensure the recovery rate of manganese.
[0010] Furthermore, both the primary slag blowing and the secondary slag blowing adopt the top and bottom combined blowing process, and the top blowing oxygen supply intensity is 3-4m 3 / (t·min), bottom blowing air supply intensity is 0.01~0.20m 3 / (t·min). The top-bottom combined blowing process is adopted in the blowing process, which can strengthen the stirring in the furnace in the first slag making, promote the interface reaction between slag and steel, and then promote dephosphorization; the top-bottom combined blowing intensity is adopted in the second slag making, which can strengthen the stirring in the furnace, promote the interface reaction between slag and steel, and realize the promotion of dephosphorization and increase of manganese recovery rate.
[0011] Furthermore, in the primary slag making and blowing, the top oxygen lance is at a position of 2.5 to 2.8 m, and the oxygen supply time of the primary slag making and blowing is 5 to 7 min; and / or the top oxygen lance is at a position of 2.0 to 2.8 m during the secondary slag making and blowing. During converter smelting, the oxygen lance uses an oxygen jet to impact the molten pool. Low lance position operation is conducive to strengthening smelting; high lance position operation increases the oxidizability of converter slag, which is conducive to slagging and improving slag fluidity. During the primary slag making, the converter molten pool temperature has not yet risen, and the molten iron temperature is relatively low. A higher lance position can promote converter slaging and control the molten pool temperature from rising too fast, which is conducive to dephosphorization. After dephosphorization is completed, the main purpose of the secondary slag making is to remove impurities in the molten iron, mainly to strengthen smelting, so the lance position of the secondary slag making is lower. And / or the gun is pressed at the end of the secondary slag making and the gun position is maintained at 2.8 m for more than 1 min to reduce the oxidizability of the slag.
[0012] Furthermore, when the carbon content of the molten iron and steel entering the furnace is within 4.6%, the sulfur content is within 0.02%, and the basicity in the furnace is 2.5-2.8, the slag is discharged, the slag discharge ratio is 65-75%, and the slag discharge time is controlled within 3 minutes. By controlling the slag basicity between 2.5 and 2.8, the dephosphorization in the later stage of secondary slag making is promoted and the needs of subsequent slag splashing and furnace protection are met.
[0013] Furthermore, after the secondary slagging, the phosphorus content at the end of blowing is stably controlled within 0.02%, and the carbon mass fraction at the end of the converter is greater than 0.2%.
[0014] Furthermore, the conditions of molten iron entering the converter are w([C]) = 4.05% ~ 4.75%, w([Si]) = 0.12% ~ 0.46%, w([Mn]) = 0.25% ~ 0.35%, w([P]) = 0.107% ~ 0.157%, w([S]) = 0.002% ~ 0.024%, and the temperature is between 1238 ~ 1351 ° C.
[0015] And / or after the first slag making is completed, the composition of the molten iron is w([C])=3.0-3.7%, w([Si])≤0.01%, w([Mn])=0.02-0.12%, w([P])≤0.06%, and w([S])≤0.02%.
[0016] And / or after completing the double slag smelting operation, the semi-steel composition is w([C])=2.55%~3.80%, w([Si])=0~0.08%, w([Mn])=0.043%~0.168%, w([P])≤0.02%, w([S])≤0.01%.
[0017] Furthermore, the manganese-rich slag self-reducing briquette is obtained by pressing and molding a mixed material containing manganese-rich slag, a reducing agent and a flux, and the manganese-rich slag self-reducing briquette is coated with CaCO 3 On the one hand, the manganese-rich slag self-reduction briquette with its own reducing agent breaks the traditional reduction reaction formula C+MnO=Mn+CO↑ in the converter, solving the problem that when the carbon content of the final molten steel is low, the carbon activity and mass transfer rate of the molten steel are reduced, resulting in a low manganese recovery rate; the manganese-rich slag self-reduction briquette is used to reduce the manganese-rich slag with its own reducing agent, thereby improving the manganese reduction rate. On the other hand, by coating CaCO on the surface of the manganese-rich slag self-reduction briquette 3 Powder, during the addition of molten steel, CaCO 3 The powder decomposes when heated to obtain CaO, which can react with the slag layer and S in the molten steel to form a dense CaS shell. The shell can provide a closed space for the reaction between the manganese-rich slag and the reducing agent, and the presence of the shell will not affect the heat transfer, so that the heat in the molten steel can be transferred to the manganese-rich slag self-reduction briquette, thereby ensuring the normal reduction reaction of the manganese-rich slag and making it fully reduced. At the same time, the presence of the shell can effectively prevent the oxidizing atmosphere in the converter from entering and contacting its internal substances, so as to prevent the elemental manganese generated by the reduction from being oxidized again, thereby achieving the purpose of delayed oxidation. In addition, CaCO 3 Powder decomposition to form CO 2 Bubbles and CaO, CO 2 The bubbles are micro-nano bubbles, which can promote the diffusion and uniform distribution of Mn elements, and capture inclusions and purify molten steel. Moreover, the calcium oxide formed by decomposition can further adjust the basicity of the final slag of the converter, which is beneficial to the modification of the refined slag.
[0018] More preferably, the present invention can effectively reduce the melting point of the CaS shell by adding a flux to the manganese-rich slag self-reduction briquette. As the temperature inside the molten steel gradually increases, when the briquette drops to a certain depth, the CaS shell gradually melts, so that the elemental manganese formed by reduction can be released into the molten steel, and the alloying treatment of manganese can be achieved. In addition, under the action of the flux, the melting point and viscosity of the slag can also be reduced, the kinetic conditions in the reduction process of the manganese-rich slag are changed, and the rapidly formed liquid slag wraps the elemental manganese reduced, thereby preventing the volatilization of the metal Mn, and further improving the yield of manganese.
[0019] More preferably, the particle size of the manganese-rich slag self-reduction briquette is designed to be 15-60 mm, which can ensure that the manganese-rich slag self-reduction briquette is between the molten steel and the slag after being added to the converter, which is conducive to promoting the manganese reduction reaction. When the particle size is less than 15 mm, the manganese-rich slag self-reduction briquette will float on the surface of the slag, and will not achieve a good melting and reaction effect, thereby reducing the manganese reduction rate; when the particle size is greater than 60 mm, the manganese-rich slag self-reduction briquette added to the converter will penetrate the slag and enter the molten steel, so that the manganese-rich slag self-reduction briquette enters the molten steel, so that the manganese-rich slag does not fully react with the reducing agent and the elemental manganese generated by the reduction is released prematurely, affecting the manganese recovery rate.
[0020] More preferably, the manganese-rich slag self-reduction briquettes are added to the molten steel in batches. The batch addition can allow the reducing agent inside to fully react with the manganese-rich slag, thereby better controlling the reduction reaction of the manganese-rich slag and achieving the purpose of saving raw materials.
[0021] Furthermore, the components of the manganese-rich slag include: TMn 25% to 36%, TFe 5% to 8%, SiO 2 18%-29%, CaO9%-13%, P≤0.05%, S≤0.03%.
[0022] Furthermore, the reducing agent in the manganese-rich slag self-reduction briquettes is carbon powder, and the ratio of the molar number of carbon in the reducing agent to the sum of the molar number of oxygen combined with manganese and iron in the manganese-rich slag is 1.1-1.3. Under this ratio, it can be ensured that the manganese oxides in the manganese-rich slag self-reduction briquettes are completely reduced by the reducing agent and the amount of the reducing agent is not excessive, thereby ensuring sufficient reduction of the manganese-rich slag and having high economic efficiency.
[0023] and / or flux using CaF 2 The addition amount is 3-7% of the mass of the manganese-rich slag self-reduction briquette. As for the addition amount of flux, when the addition amount is too much, the melting temperature is too low, the manganese-rich slag is not fully reduced in the manganese-rich slag self-reduction briquette and the flux will be wasted; on the contrary, when the addition amount is too little, the melting temperature is too high, the newly generated elemental manganese in the manganese-rich slag self-reduction briquette cannot be released into the molten steel in time, and because the volatility of manganese gradually increases with the increase of temperature, the high melting temperature of the shell will lead to an increase in the volatility of manganese, resulting in a decrease in the metal recovery rate.
[0024] Furthermore, the manganese-rich slag self-reducing briquette surface CaCO 3 The particle size of the powder is 150-250 mesh, and the mass of the coated powder accounts for 18-22% of the mass of the manganese-rich slag self-reduction briquette. By optimizing the particle size of the coated powder and the proportion of the powder mass, when CaCO 3 When the particle size of the powder is too large, it is not conducive to the compactness of the manganese-rich slag self-reduction briquette. When it is too small, it will increase the CaCO 3The grinding cost of the powder; when the mass proportion of the coated powder is too large, the melting temperature will be too high, and the elemental manganese generated by internal reduction cannot be released in time; on the contrary, when the mass proportion of the coated powder is too small, the melting temperature will be too low, the internal manganese-rich slag will not fully react with the reducing agent, and the elemental manganese generated by reduction will be released prematurely, affecting the manganese recovery rate.
[0025] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:
[0026] (1) The present invention optimizes the composition and proportion of the first slag making material, so that the phosphorus content of the molten steel can be stably controlled within 0.06% during slag pouring, thereby achieving the purpose of dephosphorization in an oxidizing atmosphere; on the other hand, by optimizing the composition and proportion of the secondary slag making material, the secondary slag making uses the self-reducing briquettes of less slag and manganese-rich slag with their own reducing agent to make up for the defect of insufficient reducing agent in the later stage, and uses the self-reducing agent to reduce the manganese-rich slag, thereby achieving the direct use of manganese-rich slag for alloying in the converter and improving the reduction rate of the manganese-rich slag. In addition, the phosphorus content at the end point of the secondary slag blowing is stably controlled within 0.02%, the carbon mass fraction at the end point of the converter is greater than 0.2%, and the manganese recovery rate in the manganese-rich slag reaches an average of more than 90%, thereby achieving the purpose of converter dephosphorization and direct manganese alloying.
[0027] (2) The present invention wraps CaCO by self-reducing briquettes made of manganese-rich slag 3 The decomposed CaO can react with the slag layer and S in the molten steel to form a dense CaS shell, which can transfer heat to promote the internal manganese-rich slag to fully react with the reducing agent, and at the same time prevent the oxidizing atmosphere in the converter from entering the shell, thereby preventing the reduced manganese from being oxidized again, reducing the requirements for the amount of converter slag and atmosphere, and ensuring the yield of manganese. At the same time, by adding a flux to the manganese-rich slag, the melting temperature of the shell is reduced. With the increase of the converter temperature, under the coordination of the flux, after the shell melts, the generated elemental manganese is released into the molten steel, and the elemental manganese is quickly surrounded by the surrounding liquid to reduce its volatility, further improving the yield of manganese. DETAILED DESCRIPTION
[0028] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with embodiments.
[0029] The following embodiments and comparative examples are all based on a 200t converter of a certain factory as an example, adopting the double slag smelting method, the average molten iron charging amount is 187t, the molten iron charging fluctuation range is 159-204t, the average scrap steel addition amount is 19.39t, the scrap steel addition amount fluctuation range is 10.4-35.0t, and the average converter steel output is 198t, with a fluctuation range of 180-212t.
[0030] In the following embodiments and comparative examples, the conditions of the molten iron in the converter are: w([C])=4.05%-4.75%, w([Si])=0.12%-0.46%, w([Mn])=0.25%-0.35%, w([P])=0.107%-0.157%, w([S])=0.002%-0.024%, and the temperature is 1238-1351° C. The use of molten iron within this parameter range is only for illustrating the technical effect of the present invention, and it should not be understood that the conditions of the molten iron in the converter are limited to the above range.
[0031] The "reducing agent ratio" referred to in the present invention refers to "the ratio of the molar number of the reducing agent to the sum of the molar numbers of oxygen combined with manganese and iron in the manganese-rich slag". For example, when carbon powder is used as the reducing agent, the reducing agent ratio is the ratio of the molar number of carbon in the carbon powder to the sum of the molar numbers of oxygen combined with manganese and iron in the manganese-rich slag.
[0032] It should also be noted that the shape of the manganese-rich slag self-reducing briquette in the present invention includes but is not limited to square, spherical, cylindrical or irregular block structure, wherein the particle size of the manganese-rich slag self-reducing briquette in the specification is 15-60 mm, and the particle size here refers to the overall size. Specifically, the overall size includes the length, width, height or diameter of the briquette. For example, when the shape of the briquette is spherical, the particle size of the sphere refers to its diameter between 15 and 60 mm, when the shape of the briquette is square, the particle size of the square refers to its length, width or height dimensions are all between 15 and 60 mm, and when the briquette is cylindrical, the particle size of the cylindrical shape refers to its height and diameter are both between 15 and 60 mm.
[0033] Example 1
[0034] In a factory's 200t converter steelmaking, the phosphorus content of the molten iron entering the furnace is 0.107%, the parameters of the molten iron entering the furnace are w([C]) = 4.4%, w([Si]) = 0.28%, w([Mn]) = 0.3%, w([S]) = 0.014%, the temperature is 1310°C, and the specific smelting steps include:
[0035] Step S1: Add the first slag-making material to the converter, the first slag-making material includes lime, dolomite and return material, wherein the amount of lime added is 17kg / t steel, the amount of dolomite added is 10kg / t steel, and the amount of return material added is 20kg / t steel. At this time, the basicity in the furnace reaches 2.5, and the top and bottom combined blowing process is adopted, and the lower lance is used for oxygen blowing. The top blowing oxygen lance position is controlled to 2.5m, and the oxygen supply intensity of the top oxygen lance is 3.4m 3 / (t·min), oxygen supply time is 5min; there are 6 bottom blowing gas supply components at the bottom of the converter, and the bottom blowing flow rate of a single gun is controlled at 40m 3 / h, bottom blowing air supply intensity is 0.02m 3 / (t·min);
[0036] Step S2: when the basicity in the furnace is 2.5-2.8, the carbon content of the molten steel is within 4.6%, the sulfur content is within 0.02%, and the phosphorus content is within 0.04%, the slag pouring operation begins, the slag pouring ratio is 70%, and the slag pouring time does not exceed 3 minutes;
[0037] Step S3: After slag discharge, add secondary slag-making materials and manganese-rich slag self-reducing briquettes. The secondary slag-making materials include lime and dolomite. The amount of lime added is 3.3kg / t steel, and the amount of dolomite added is 3.0kg / t steel. The manganese-rich slag self-reducing briquettes are added from the high-level silo in 3 times, and a total of 6kg / t steel of manganese-rich slag self-reducing briquettes are added. The top and bottom combined blowing process is adopted, in which the top blowing oxygen lance is located at 2.0m, and the oxygen supply intensity of the top blowing oxygen lance is 3.4m 3 / (t·min), the converter is pressed at the end point, the gun position is maintained at 2.8m for more than 1min, and the gas flow rate of the bottom blowing oxygen gun is 0.02m 3 / (t·min);
[0038] Step S4: Blowing until the final molten steel temperature reaches 1580°C and then the steel can be tapped.
[0039] The manganese-rich slag self-reducing briquette used in the above-mentioned manganese-rich slag converter steelmaking direct alloying method includes a mixture of manganese-rich slag, a reducing agent, and a flux, which is pressed into a cylindrical structure. The diameter and height of the cylinder are both 28 mm, wherein the manganese-rich slag includes the following components and their proportions are: TMn 30%, TFe 7%, SiO 2 23%, CaO11%, P≤0.05%, S≤0.03%, and the rest are impurities; the particle size of the mixed material of manganese-rich slag, reducing agent and flux is 150 mesh; the reducing agent is carbon powder, and the ratio of the molar number of carbon in the carbon powder to the molar number of oxygen combined with manganese and iron in the manganese-rich slag is 1.2; the flux is CaF 2 The addition amount accounts for 5% of the mass of the manganese-rich slag self-reducing briquette; the manganese-rich slag self-reducing briquette is wrapped with CaCO 3 Powder; CaCO 3 The particle size of the powder is 150 meshes and the mass of the coated powder accounts for 22% of the mass of the manganese-rich slag self-reduction briquette.
[0040] After the first slag making in the above operation steps was completed, the composition of the molten iron was tested, and the test results were w([C])=3.2%, w([Si])=0.01%, w([Mn])=0.05%, w([P])=0.04%, w([S])=0.014%, the temperature was 1330°C, and the slag basicity was 2.5.
[0041] After the double-slag slag making is completed, the semi-steel composition is tested, and the test results are w([C])=2.8%, w([Si])=0.01%, w([Mn])=0.12%, w([P])=0.02%, and w([S])=0.01%.
[0042] The molten steel after tapping from the converter of this embodiment was tested, and the phosphorus content of the tapped steel was 0.02%, the mass fraction of carbon was 0.2%, and the manganese recovery rate was 92.3%.
[0043] Comparative Example 1
[0044] The manganese-rich slag self-reducing briquette of this comparative example is different from that of Example 1 mainly in that: the product of this comparative example is obtained by pressing and molding a mixed material containing manganese-rich slag, a reducing agent and a flux to obtain a manganese-rich slag self-reducing briquette, and the manganese-rich slag self-reducing briquette is not wrapped with CaCO 3 Powder; the rest of the preparation process and method are the same as in Example 1.
[0045] The molten steel after the converter steel was tapped was tested, and the mass fraction of phosphorus in the steel was 0.02%, the mass fraction of carbon was 0.2%, and the manganese recovery rate in the molten steel after the converter steel was tapped was 87.7%.
[0046] Comparative Example 1 and Comparative Example 1 show that by providing CaCO coated on the surface of the manganese-rich slag self-reducing briquette 3 The powder further improves the manganese recovery rate, and the recovery rate is significantly improved.
[0047] Comparative Example 2
[0048] The manganese-rich slag self-reducing briquette of this comparative example is different from that of Example 1 in that no flux is added to the manganese-rich slag self-reducing briquette, and the manganese-rich slag and reducing agent C are crushed to 150 mesh and then pressed into shape; the rest of the preparation process and method are the same as those of Example 1.
[0049] The molten steel after the converter steel was tapped was tested, and the mass fraction of phosphorus in the steel was 0.02%, the mass fraction of carbon was 0.2%, and the manganese recovery rate in the molten steel after the converter steel was tapped was 90.1%.
[0050] Comparison of no flux and 5% CaF 2 The manganese-rich slag self-reduction briquettes were subjected to manganese-rich slag reduction reaction at different temperatures. 2 It can effectively reduce the melting point of the formed calcium sulfide shell, and reduce the melting point and viscosity of the slag, and change the kinetic conditions of the reduction of manganese-rich slag in the manganese-rich slag self-reduction briquette, so that the rapidly formed liquid slag wraps the reduced elemental manganese, preventing the volatilization of metallic Mn, thereby increasing the Mn recovery rate.
[0051] Example 2
[0052] In a 200t converter steelmaking plant, the phosphorus content of the molten iron entering the furnace is 0.130%, the parameters of the molten iron entering the furnace are w([C]) = 4.05%, w([Si]) = 0.46%, w([Mn]) = 0.35%, w([S]) = 0.024%, and the temperature is 1238°C. The specific smelting steps include:
[0053] Step S1: Add the first slag-making material to the converter, the first slag-making material includes lime, dolomite and return material, wherein the amount of lime added is 19kg / t steel, the amount of dolomite added is 12kg / t steel, and the amount of return material added is 18kg / t steel. At this time, the basicity in the furnace reaches 2.6, and the top and bottom combined blowing process is adopted, and the lower lance is used for oxygen blowing. The top blowing oxygen lance position is controlled to 2.6m, and the oxygen supply intensity of the top oxygen lance is 3m 3 / (t·min), there are 6 bottom blowing gas supply components at the bottom of the converter, and the bottom blowing flow rate of a single gun is controlled at 400m 3 / h, bottom blowing air supply intensity is 0.2m 3 / (t·min), oxygen supply time is 7min;
[0054] Step S2: when the basicity in the furnace is 2.5-2.8, the carbon content of the molten steel is within 4.6%, the sulfur content is within 0.02%, and the phosphorus content reaches 0.06%, the slag pouring operation is started, the slag pouring ratio is 65%, and the slag pouring time does not exceed 3 minutes;
[0055] Step S3: After slag discharge, add secondary slag-making materials and manganese-rich slag self-reducing briquettes. The secondary slag-making materials include lime and dolomite, of which the amount of lime added is 4.1kg / t steel and the amount of dolomite added is 2.0kg / t steel. The manganese-rich slag self-reducing briquettes are added from the high-level silo in 4 times, and a total of 8kg / t steel of manganese-rich slag self-reducing briquettes are added. The top and bottom combined blowing process is adopted, in which the top blowing oxygen lance is located at 2.5m, and the top blowing oxygen supply intensity is 3m 3 / (t·min), converter end point pressure gun, maintain gun position at 2.8m for more than 1min, bottom blowing oxygen gun gas flow rate is 0.20m 3 / (t·min);
[0056] Step S4: Blowing until the final molten steel temperature reaches 1680°C and then the steel can be tapped.
[0057] The manganese-rich slag self-reducing briquette used in the above-mentioned manganese-rich slag converter steelmaking direct alloying method includes a mixture of manganese-rich slag, a reducing agent, and a flux, which is pressed into a cylindrical structure. The diameter and height of the cylinder are both 15 mm, wherein the manganese-rich slag includes the following components and their proportions are: TMn 36%, TFe 5%, SiO 229%, CaO9%, P≤0.05%, S≤0.03%, and the rest are impurities; the particle size of the mixed material of manganese-rich slag, reducing agent and flux is 200 mesh; the reducing agent is carbon powder, and the ratio of the molar number of carbon in the carbon powder to the molar number of oxygen combined with manganese and iron in the manganese-rich slag is 1.1; the flux is CaF 2 The addition amount accounts for 3% of the mass of the manganese-rich slag self-reducing briquette; the manganese-rich slag self-reducing briquette is wrapped with CaCO 3 Powder; CaCO 3 The particle size of the powder is 200 meshes and the mass of the coated powder accounts for 18% of the mass of the manganese-rich slag self-reduction briquette.
[0058] After the first slag making in the above operation was completed, the composition of the molten iron was tested, and the test results were w([C])=3.2%, w([Si])=0.01%, w([Mn])=0.05%, w([P])=0.06%, w([S])=0.02%, the temperature was 1320°C, and the slag basicity was 2.6.
[0059] After the double-slag slag making is completed, the semi-steel composition is tested, and the test results are w([C])=2.8%, w([Si])=0.01%, w([Mn])=0.12%, w([P])=0.02%, and w([S])=0.01%.
[0060] The molten steel after the converter was tapped was tested, and the phosphorus content of the tapped steel was 0.02%, the mass fraction of carbon was greater than 0.2%, and the manganese recovery rate was 91.7%.
[0061] Example 3
[0062] In a 200t converter steelmaking plant, the phosphorus content of the molten iron entering the furnace is 0.157%, the parameters of the molten iron entering the furnace are w([C]) = 4.75%, w([Si]) = 0.12%, w([Mn]) = 0.25%, w([S]) = 0.002%, and the temperature is 1351°C. The specific smelting steps include:
[0063] Step S1: Add the first slag-making material to the converter, the first slag-making material includes lime, dolomite and return material, wherein the amount of lime added is 15kg / t steel, the amount of dolomite added is 8kg / t steel, and the amount of return material added is 22kg / t steel. At this time, the basicity in the furnace reaches 2.8, and the top and bottom combined blowing process is adopted, and the lower lance is used for oxygen blowing. The top blowing oxygen lance position is controlled to 2.8m, and the oxygen supply intensity of the top oxygen lance is 4m 3 / (t·min), oxygen supply time is 6min; there are 6 bottom blowing gas supply components at the bottom of the converter, and the bottom blowing flow rate of a single gun is controlled at 20m 3 / h, bottom blowing air supply intensity is 0.01m 3 / (t·min);
[0064] Step S2: when the basicity in the furnace is 2.5-2.8, the carbon content of the molten steel drops to within 4.6%, the sulfur content drops to within 0.02%, and the phosphorus content reaches 0.03%, the slag pouring operation starts, the slag pouring ratio is 75%, and the slag pouring time does not exceed 3 minutes;
[0065] Step S3: After slag discharge, add secondary slag-making materials and manganese-rich slag self-reducing briquettes. The secondary slag-making materials include lime and dolomite, of which the amount of lime added is 3.8kg / t steel and the amount of dolomite added is 2.5kg / t steel. The manganese-rich slag self-reducing briquettes are added from the high-level silo in 3 times, and a total of 7kg / t steel of manganese-rich slag self-reducing briquettes are added. The top and bottom combined blowing process is adopted, in which the top blowing oxygen lance is located at 2.8m, and the oxygen supply intensity of the top blowing oxygen lance is 4m 3 / (t·min), the gas flow rate of the bottom blowing oxygen gun is 0.01m 3 / (t·min);
[0066] Step S4: Blowing until the final molten steel temperature reaches 1600°C and then the steel can be tapped.
[0067] The manganese-rich slag self-reducing briquette used in the above-mentioned manganese-rich slag converter steelmaking direct alloying method comprises a mixture of manganese-rich slag, a reducing agent, and a flux, which is pressed into a cylindrical structure, and the diameter and height of the cylinder are both 40 mm, wherein the manganese-rich slag comprises the following components and their proportions are: TMn 25%, TFe 8%, SiO 2 18%, CaO13%, P≤0.05%, S≤0.03%, and the rest are impurities; the particle size of the mixed material of manganese-rich slag, reducing agent and flux is 250 mesh; the reducing agent is carbon powder, and the ratio of the molar number of carbon in the carbon powder to the molar number of oxygen combined with manganese and iron in the manganese-rich slag is 1.3; the flux is CaF 2 The addition amount accounts for 7% of the mass of the manganese-rich slag self-reducing briquette; the manganese-rich slag self-reducing briquette is wrapped with CaCO 3 Powder; CaCO 3 The particle size of the powder is 250 meshes and the mass of the coated powder accounts for 20% of the mass of the manganese-rich slag self-reduction briquette.
[0068] After the first slag making in the above operation was completed, the composition of the molten iron was tested, and the test results were w([C])=3.2%, w([Si])=0.01%, w([Mn])=0.05%, w([P])=0.03%, w([S])=0.002%, the temperature was 1340°C, and the slag basicity was 2.8.
[0069] After the double-slag slag making is completed, the semi-steel composition is tested, and the test results are w([C])=2.8%, w([Si])=0.01%, w([Mn])=0.14%, w([P])=0.01%, and w([S])=0.008%.
[0070] The molten steel after tapping from the converter of this embodiment was tested, and the phosphorus content of the tapped steel was 0.01%, the mass fraction of carbon was greater than 0.2%, and the manganese recovery rate was 91.9%.
Claims
1. A direct alloying method for converter steelmaking using manganese-rich slag, characterized in that: include: Step S1: adding primary slag-making materials to carry out primary slag-making blowing, wherein the primary slag-making materials include lime, dolomite and return material, wherein the addition amounts of lime, dolomite and return material are 15-19 kg / t steel, 8-12 kg / t steel and 18-22 kg / t steel respectively; Step S2: blowing until the phosphorus content in the molten steel is within 0.06%, and then pouring the slag; Step S3: After slagging, secondary slag-making materials and manganese-rich slag self-reducing briquettes are added to perform secondary slag blowing and manganese alloying, wherein the secondary slag-making materials include lime and light-burned dolomite, wherein the masses of lime, light-burned dolomite and manganese-rich slag self-reducing briquettes are 3.3-4.1 kg / t steel, 2.0-3.0 kg / t steel and 6.0-8.0 kg / t steel, respectively; Step S4: Blowing until the final molten steel temperature reaches 1580-1680°C; tapping.
2. The direct alloying method for converter steelmaking using manganese-rich slag according to claim 1, characterized in that: The primary slag blowing and the secondary slag blowing both adopt the top and bottom combined blowing process, and the top blowing oxygen supply intensity is 3-4m 3 / (t·min), bottom blowing air supply intensity is 0.01~0.20m 3 / (t·min).
3. The direct alloying method for converter steelmaking with manganese-rich slag according to claim 2, wherein in the primary slag blowing, the top oxygen lance is located at 2.5 to 2.8 m, and the oxygen supply time of the primary slag blowing is 5 to 7 min; And / or during secondary slag blowing, the top-blowing oxygen lance is located at 2.0-2.8m; And / or at the end point of secondary slag blowing, the gun is pressed and the gun position is maintained at 2.8m for more than 1 minute.
4. The direct alloying method for converter steelmaking using manganese-rich slag according to claims 1-3, characterized in that: When the carbon content of the molten iron entering the furnace is within 4.6%, the sulfur content is within 0.02%, and the basicity in the furnace is 2.5-2.8, the slag is discharged, the slag discharge ratio is 65-75%, and the slag discharge time is controlled within 3 minutes.
5. The direct alloying method for converter steelmaking using manganese-rich slag according to claim 4, characterized in that: After secondary slagging, the phosphorus content at the end of blowing is stably controlled within 0.02%; the carbon mass fraction at the end of the converter is greater than 0.2%.
6. The direct alloying method for converter steelmaking with manganese-rich slag according to any one of claims 1 to 3, characterized in that: The conditions of the molten iron in the converter are w([C])=4.05%-4.75%, w([Si])=0.12%-0.46%, w([Mn])=0.25%-0.35%, w([P])=0.107%-0.157%, w([S])=0.002%-0.024%, and the temperature is 1238-1351°C; and / or after the primary slag making is completed, the composition of the molten iron is w([C])=3.0-3.7%, w([Si])≤0.01%, w([Mn])=0.02-0.12%, w([P])≤0.06%, w([S])≤0.02%, and the temperature is 1320-1340°C; And / or complete double slag slag making, the semi-steel composition is w([C])=2.55%~3.80%, w([Si])=0~0.08%, w([Mn])=0.043%~0.168%, w([P])≤0.02%, w([S])≤0.01%.
7. The direct alloying method for converter steelmaking with manganese-rich slag according to any one of claims 1 to 3, characterized in that: The manganese-rich slag self-reducing briquette is obtained by pressing and molding a mixed material containing manganese-rich slag, a reducing agent and a flux, and the outside of the manganese-rich slag self-reducing briquette is coated with CaCO3 powder.
8. The direct alloying method for converter steelmaking using manganese-rich slag according to claim 7, characterized in that: The manganese-rich slag contains the following components in percentage by mass: TMN 25% to 36%, TFe 5% to 8%, SiO2 18% to 29%, CaO 9% to 13%, P ≤ 0.05%, and S ≤ 0.03%.
9. The direct alloying method for converter steelmaking using manganese-rich slag according to claim 7 or 8, characterized in that: The reducing agent in the manganese-rich slag self-reduction briquette is carbon powder or silicon carbide, and the ratio of the carbon mole number of the reducing agent to the sum of the oxygen mole numbers combined with manganese and iron in the manganese-rich slag is 1.1-1.3; And / or the flux is CaF2, and the addition amount thereof is 3-7% of the mass of the manganese-rich slag self-reduction briquette.
10. The direct alloying method for converter steelmaking using manganese-rich slag according to claim 7 or 8, characterized in that: The particle size of the external CaCO3 powder of the manganese-rich slag self-reducing briquette is 150-250 meshes, and the mass of the wrapped powder accounts for 18-22% of the mass of the manganese-rich slag self-reducing briquette.