A method for producing a Mo-containing slag steel for molten steel alloying

Abstract

This invention belongs to the field of metallurgy and steelmaking technology, and relates to a method for preparing Mo-containing slag steel for steel alloying. The invention first adds molybdenum oxide blocks to a segmented slag basin, and then pours in ladle casting residue. The casting residue basin is then hoisted to the cooling zone, and after cooling, the Mo-containing slag steel is produced, with each block containing 4% to 8% molybdenum. This invention utilizes the steel scrap and alloying elements wasted during steelmaking to reduce molybdenum oxide, reducing reduction costs. The use of Mo-containing slag steel increases the utilization of alloying elements in the slag steel, and the slag in the Mo-containing slag steel is the target slag for refining, not affecting the top slag composition. Simultaneously, it reduces the use of slag-forming materials. The prepared material not only has the advantage of saving ladle top slag, but also shows that the initial Mo recovery rate in the Mo-containing slag steel after use reaches over 98%, and the tested composition meets production requirements, making it a suitable substitute for ferromolybdenum in alloying operations.

Description

Technical Field

[0001] This invention belongs to the field of metallurgy and steelmaking technology, and specifically relates to a method for preparing Mo-containing slag steel for alloying molten steel. Background Technology

[0002] Currently, steelmaking processes often employ alloying with ferromolybdenum or molybdenum-containing alloys, primarily in converters, refining processes, or briquettes. However, due to the limited heat capacity of converter steelmaking, the available alternatives are generally insufficient. Furthermore, these technologies often suffer from the following problems: converter use results in low yields due to the oxidizing atmosphere, refining involves high reduction costs, and briquettes further increase intermediate costs. At the current stage of industry development, the price difference between molybdenum oxide and ferromolybdenum is relatively low, failing to cover these additional costs.

[0003] As the steel industry enters a critical phase of transformation, competition is intensifying, making it increasingly urgent to reduce production costs while ensuring product quality.

[0004] Therefore, researching a molybdenum (Mo) slag steel for molten steel alloying, which can reduce the cost of Mo alloying while ensuring product quality, has become a key issue that my country's steel industry urgently needs to address. Summary of the Invention

[0005] The purpose of this invention is to overcome the technical defects existing in the prior art, thereby providing a Mo-containing slag steel for molten steel alloying. By using the Mo-containing slag steel to replace ferromolybdenum or molybdenum alloys for alloying, stable reduction of molybdenum oxide can be achieved, as well as stability of ladle top slag control and stability of molten steel alloying.

[0006] Based on this invention, the following objectives can be achieved: ① Reduction of molybdenum oxide using waste steel and alloying elements from the steelmaking process, thereby reducing reduction costs; ② Replacing ferromolybdenum or molybdenum-containing alloys with molybdenum oxide for alloying, thereby reducing the alloying costs of Mo; ③ Increasing the utilization of alloying elements in slag steel through the use of Mo-containing slag steel; ④ The slag in Mo-containing slag steel is the target slag for refining and does not affect the composition of the top slag; at the same time, it can reduce the use of slag-forming materials.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides a method for preparing Mo-containing slag steel for alloying molten steel, comprising the following steps:

[0009] (1) Use molybdenum oxide blocks with a Mo content of 55%-60%;

[0010] (2) Divide the slag basin into N pieces using partitions to form N slag basin partitions;

[0011] (3) Add molybdenum oxide blocks from step (1) to the N slag basins divided in step (2). The total amount of molybdenum oxide blocks is based on the capacity of the slag basin in step (2): the total amount of molybdenum oxide blocks added for every 20-30 tons of capacity is 1.5-2.2 tons. When the capacity of the slag basin is increased or decreased, the total amount of molybdenum oxide blocks is increased or decreased proportionally.

[0012] Add ladle casting residue to the casting residue basin containing molybdenum oxide blocks; the amount of ladle casting residue added is based on the total amount of molybdenum oxide blocks used: that is, the mass ratio of molybdenum oxide blocks to ladle casting residue is 1:10~14.

[0013] Among them, the ladle slag is a well-known material in the field. It refers to the mixture of residual molten steel and steel slag left at the bottom of the ladle during the continuous casting process in order to ensure the cleanliness of molten steel and the quality of the billet.

[0014] (4) After the treatment in step (3), the casting residue basin is hoisted to the cooling zone and cooled for no less than 16 hours at room temperature. After cooling, it is naturally divided into N pieces.

[0015] (5) At this point, the production of molybdenum slag steel is completed after cooling, and N pieces of molybdenum slag steel are obtained, with each piece containing 4% to 8% molybdenum.

[0016] Preferably, the capacity of the casting residue basin in step (2) is 20 to 30 tons; where N is a positive integer and the value ranges from 9 to 15.

[0017] Preferably, in step (3), to ensure the sufficiency of the reaction, molybdenum oxide blocks and ladle slag are added alternately in batches. The amount of molybdenum oxide blocks added in each batch can be adjusted as needed and finally evenly distributed to N slag basins.

[0018] The alternating addition process is as follows: After the first batch of molybdenum oxide blocks is added, the corresponding first batch of ladle casting residue is added, evenly distributed into each slag basin compartment. After a reaction of 5-10 minutes, the second batch of molybdenum oxide blocks is added. After this process, the corresponding second batch of ladle casting residue is added, evenly distributed into each slag basin compartment, and reacted again for 5-10 minutes. This alternating addition is repeated until both molybdenum oxide blocks and ladle casting residue are added.

[0019] Preferably, the addition of molybdenum oxide blocks and ladle slag is carried out in 4-5 batches.

[0020] Preferably, the amount of molybdenum oxide blocks added to each slag basin compartment at one time is: total amount ÷ number of batches ÷ N.

[0021] Preferably, the amount of ladle slag added in each batch is the same, and it is evenly added to the slag basin compartment; that is, the amount of ladle slag added in each batch is: total amount ÷ number of batches.

[0022] Preferably, the cooling time in step (4) is 16~24h.

[0023] Preferably, the weight of each piece of molybdenum-containing slag steel in step (5) is 1.5~5t. The weight of each piece of molybdenum-containing slag steel can be controlled by adjusting the number of partitions and slag basins.

[0024] In addition, during actual production, the molybdenum content can be adjusted by changing the use of molybdenum oxide blocks as needed.

[0025] The molybdenum-containing slag steel prepared by this invention is used to replace ferromolybdenum or molybdenum-containing alloys in the steel production process for alloying. The steel includes SCM435, wherein: no Mo alloying is performed when the steel is tapped from the converter; before the refining process, molybdenum-containing slag steel is added to the molten steel, with 1.5 to 1.8 tons of molybdenum-containing slag steel added for every 50 to 58 tons of molten steel.

[0026] The specific usage method is as follows:

[0027] After the converter tapping process, normal slag making (slag material reduced by 1 / 3 year-on-year) and alloying (without adding molybdenum) operations are carried out. After tapping, the calculated amount of molybdenum-containing slag steel is added to the ladle by crane and then refined normally in the LF process. The composition is tested during the refining process, and daily replenishment can be carried out according to the tested composition.

[0028] Beneficial effects:

[0029] In conventional steelmaking processes, when molybdenum oxide is used for alloying, its reduction readily induces reduction reactions with elements such as C, Al, Si, Mn, and Fe, resulting in high reduction costs. Furthermore, the reduction of molybdenum oxide during refining continuously introduces oxygen into the molten steel, leading to a decrease in steel purity. This invention utilizes the ladle residue after continuous casting to reduce molybdenum oxide, providing advantages for preparing molybdenum-containing slag steel.

[0030] ①After the continuous casting ladle residue is sorted and recycled, its top slag composition is consistent with that of the new slag in the new furnace, and will not cause changes in the composition of the ladle top slag.

[0031] ②The temperature of the residual slag in the hot ladle casting is about 1500℃, which can provide the reaction temperature for molybdenum oxide.

[0032] ③ Special steel generally has a ladle casting surplus requirement of ≥2t. After this part of the steel slag is poured into the slag basin, it is usually cooled and then rotated to the converter as scrap steel. Under the high oxygen conditions of the converter, the alloy components remaining in the molten steel in this part of the steel slag will be oxidized, resulting in waste. This invention can utilize alloying elements such as C, Si, Mn, Al, and Fe in this part of the molten steel to reduce molybdenum oxide, which is equivalent to reusing this part of the wasted alloying elements. At the same time, the utilization of unreacted alloys is increased during the process.

[0033] ④ Because molybdenum oxide has a low melting point, the presence of large-scale casting residue during reduction can effectively suppress its volatilization, eliminating the need for separate slag addition.

[0034] ⑤ Because the composition of the molybdenum-containing steel slag used is consistent with that of the refined pre-mixed slag, the cost of slag-making materials can be reduced during use;

[0035] ⑥ When using molybdenum-containing slag steel in the steelmaking process, since the molybdenum oxide has already been pre-reacted and reduced, it is basically the same as using ferromolybdenum alloy and will not affect the composition of the molten steel.

[0036] In summary, the molybdenum-containing slag steel material prepared by this invention not only has the advantage of saving ladle top slag material, but also the initial test results show that the Mo recovery rate in the molybdenum-containing slag steel after use reaches more than 98%. The high recovery rate and the test results meet the production requirements, and it can replace ferromolybdenum or molybdenum-containing alloys for alloying operations. Detailed Implementation

[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0038] It should be understood that the terminology used herein is for describing particular embodiments only and is not intended to limit the invention. Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of the invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0039] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary. Example 1:

[0040] (1) Use molybdenum oxide blocks with a Mo content of 55%;

[0041] (2) Divide the 20-ton casting slag basin into 12 pieces using partitions to form 12 slag basin partitions.

[0042] (3) Add molybdenum oxide blocks from step (1) to the slag basins divided in step (2), with a total amount of 1.5 tons of molybdenum oxide blocks. To ensure sufficient reaction, molybdenum oxide blocks and ladle slag are added alternately. The addition of molybdenum oxide blocks is carried out in four batches, with 31.25 kg added to each slag basin in each batch until the addition is complete. Similarly, ladle slag is also added in four batches, with a total amount of 16 tons, with 4 tons added to each batch.

[0043] The specific operation is as follows: First, add the first batch of molybdenum oxide blocks according to the dosage requirements. Then, pour 4 tons of hot ladle casting residue into the slag basin after adding the first batch of molybdenum oxide blocks. After adding, spread it evenly into each slag basin compartment. After waiting for 10 minutes of reaction, add the second batch of molybdenum oxide blocks. After adding the second batch of 4 tons of ladle casting residue, spread it evenly into each slag basin compartment and react for another 10 minutes. Repeat this alternating addition until the molybdenum oxide blocks and ladle casting residue are added.

[0044] Ladle slag refers to the mixture of residual molten steel and slag left at the bottom of the ladle during continuous casting to ensure the cleanliness of molten steel and the quality of the billet.

[0045] (4) After the treatment in step (3), the slag basin is hoisted to the condensation zone and condensed at room temperature for 16 hours, and then naturally divided into 12 pieces.

[0046] (5) Thus, the production of molybdenum slag steel is completed, and 12 pieces of molybdenum slag steel are obtained, with each piece containing 4.7% molybdenum and weighing 1.5t. Example 2:

[0047] (1) Use molybdenum oxide blocks with a Mo content of 58%;

[0048] (2) Divide the 20-ton casting slag basin into 12 pieces using partitions to form 12 slag basin partitions.

[0049] (3) Add molybdenum oxide blocks from step (1) to the slag basins divided in step (2), with a total amount of 2.4 tons of molybdenum oxide blocks. To ensure sufficient reaction, molybdenum oxide blocks and ladle slag are added alternately. The addition of molybdenum oxide blocks is carried out in five batches, with 40 kg added to each slag basin in each batch until the addition is complete. Similarly, ladle slag is also added in five batches, with a total amount of 20 tons, with 4 tons added to each batch.

[0050] The specific operation is as follows: First, add the first batch of molybdenum oxide blocks according to the dosage requirements. Then, pour 4 tons of hot ladle casting residue into the slag basin after adding the first batch of molybdenum oxide blocks. After adding, spread it evenly into each slag basin compartment. After waiting for 10 minutes of reaction, add the second batch of molybdenum oxide blocks. After adding the second batch of 4 tons of ladle casting residue, spread it evenly into each slag basin compartment and react for another 10 minutes. Repeat this alternating addition until the molybdenum oxide blocks and ladle casting residue are added.

[0051] Ladle slag refers to the mixture of residual molten steel and slag left at the bottom of the ladle during continuous casting to ensure the cleanliness of molten steel and the quality of the billet.

[0052] (4) After the treatment in step (3), the slag basin is hoisted to the condensation zone and condensed at room temperature for 16 hours, and then naturally divided into 12 pieces.

[0053] (5) Thus, the production of molybdenum slag steel is completed, and 12 pieces of molybdenum slag steel are obtained. Each piece of molybdenum slag steel has a molybdenum content of 6.2% and a weight of 1.8t. Example 3:

[0054] (1) Use molybdenum oxide blocks with a Mo content of 60%;

[0055] (2) Divide the 20-ton casting slag basin into 15 pieces using partitions to form 15 slag basin compartments.

[0056] (3) Add the molybdenum oxide blocks from step (1) to the slag basins divided in step (2). The total amount of molybdenum oxide blocks is 2.25 tons. To ensure the sufficiency of the reaction, the molybdenum oxide blocks need to be added in batches, with 30 kg added to each compartment each time, until all the blocks are added.

[0057] (3) Add molybdenum oxide blocks from step (1) to the slag basins divided in step (2), with a total amount of 2.25 tons of molybdenum oxide blocks. To ensure sufficient reaction, molybdenum oxide blocks and ladle slag are added alternately. The addition of molybdenum oxide blocks is carried out in five batches, with 30 kg added to each slag basin in each batch until the addition is complete. Similarly, ladle slag is also added in five batches, with a total amount of 20 tons, with 4 tons added to each batch.

[0058] The specific operation is as follows: First, add the first batch of molybdenum oxide blocks according to the dosage requirements. Then, pour 4 tons of hot ladle casting residue into the slag basin after adding the first batch of molybdenum oxide blocks. After adding, spread it evenly into each slag basin compartment. After waiting for 10 minutes of reaction, add the second batch of molybdenum oxide blocks. After adding the second batch of 4 tons of ladle casting residue, spread it evenly into each slag basin compartment and react for another 10 minutes. Repeat this alternating addition until the molybdenum oxide blocks and ladle casting residue are added.

[0059] Ladle slag refers to the mixture of residual molten steel and slag left at the bottom of the ladle during continuous casting to ensure the cleanliness of molten steel and the quality of the billet.

[0060] (4) After the treatment in step (3), the slag basin is hoisted to the condensation zone and condensed at room temperature for 16 hours, and then naturally divided into 15 pieces.

[0061] (5) Thus, the production of molybdenum slag steel is completed, and 15 pieces of molybdenum slag steel are obtained, with each piece containing 5.9% molybdenum and weighing 1.5 t.

[0062] Application Case: Production Application of SCM435

[0063] Taking the molybdenum-containing slag steel prepared in Example 1 as an example (prepared from the casting residue of SCM435 steel using the same process, with a molybdenum content of 4.8% and a single piece weight of 1.5 tons), the following applications were carried out:

[0064] Application steps:

[0065] ① Lime and calcium aluminate are added to the converter for slag formation (the amount of slag is reduced by 1 / 3 compared with the original process) (the slag in the molybdenum slag steel is the top slag of the ladle of the same series as this steel grade, accounting for 1 / 3 of the weight of the molybdenum slag steel, which can play a normal slag formation role), and other alloys are added normally according to the conventional production process of SCM435 (of which Si, Mn, and Cr are reduced by 0.02% according to the original alloying standard), and Mo alloying is not carried out when the converter is tapped.

[0066] ② When the steel output is between 54 and 58 tons, after the steel output is completed, the ladle car is moved to the ladle position and a piece of steel containing Mo slag (containing 4.8% molybdenum and weighing 1.5 tons) is lifted by a crane.

[0067] ③The ladle is then moved to the refining process for routine refining operations, and LF adds alloys based on the detected composition.

[0068] Performance data determination: Composition analysis was performed on the molten steel after LF refining in step ③.

[0069] Table 1: Composition analysis of molybdenum slag-containing steel after use

[0070]

[0071] As can be seen from the data in Table 1, the molybdenum-containing slag steel material prepared by this invention has the advantage of saving ladle top slag material. At the same time, the Mo recovery rate in the initial test composition after use of the molybdenum-containing slag steel reaches more than 98%. The high recovery rate and the fact that the tested composition meets the production requirements can ensure product quality. This indicates that the initial test composition of the molybdenum-containing slag steel prepared by this invention can replace ferromolybdenum for alloying operations.

[0072] Although this specification has described the invention in detail with reference to the various embodiments described above, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the invention; and all technical solutions and improvements that do not depart from the spirit and scope of the invention should be covered within the scope of the claims of the invention.

Claims

1. A method for preparing Mo-containing slag steel for alloying molten steel, characterized in that, The steps are as follows: (1) Use molybdenum oxide blocks with a Mo content of 55%-60%; (2) Divide the slag basin into N pieces using partitions to form N slag basin partitions; (3) Add molybdenum oxide blocks from step (1) to the N slag basins divided in step (2). The total amount of molybdenum oxide blocks is based on the capacity of the slag basin in step (2): the total amount of molybdenum oxide blocks added for every 20 to 30 tons of capacity is 1.5 to 2.2 tons. When the capacity of the slag basin increases or decreases, the total amount of molybdenum oxide blocks used increases or decreases proportionally. Add ladle casting residue to the casting residue basin containing molybdenum oxide blocks; the amount of ladle casting residue added is based on the total amount of molybdenum oxide blocks used: that is, the mass ratio of molybdenum oxide blocks to ladle casting residue is 1:10~14. (4) After the treatment in step (3), the casting residue basin is hoisted to the cooling zone and cooled for no less than 16 hours at room temperature. After cooling, it is naturally divided into N pieces. (5) At this point, the production of molybdenum slag steel is completed after cooling, and N pieces of molybdenum slag steel are obtained, with each piece containing 4% to 8% molybdenum.

2. The method for preparing Mo-containing slag steel for steel alloying according to claim 1, characterized in that: The capacity of the slag basin mentioned in step (2) is 20 to 30 tons; where N is a positive integer and the value ranges from 9 to 15.

3. The method for preparing Mo-containing slag steel for steel alloying according to claim 1, characterized in that: In step (3), to ensure the sufficiency of the reaction, molybdenum oxide blocks and ladle slag are added alternately in batches. The amount of molybdenum oxide blocks added in each batch can be adjusted as needed and finally evenly distributed to N slag basin compartments. The alternating addition process is as follows: After the first batch of molybdenum oxide blocks is added, the corresponding first batch of ladle casting residue is added, evenly distributed into each slag basin compartment. After a reaction of 5-10 minutes, the second batch of molybdenum oxide blocks is added. After this process, the corresponding second batch of ladle casting residue is added, evenly distributed into each slag basin compartment, and reacted again for 5-10 minutes. This alternating addition is repeated until both molybdenum oxide blocks and ladle casting residue are added.

4. The method for preparing Mo-containing slag steel for steel alloying according to claim 3, characterized in that: The addition of molybdenum oxide blocks and ladle slag is carried out in 4-5 batches.

5. The method for preparing Mo-containing slag steel for steel alloying according to claim 3, characterized in that: The amount of molybdenum oxide blocks added to each slag basin compartment at one time is: total amount ÷ number of batches ÷ N.

6. The method for preparing Mo-containing slag steel for steel alloying according to claim 3, characterized in that: The amount of ladle slag added to each batch is the same, and it is evenly added to the slag basin compartment; that is, the amount of ladle slag added to each batch is: total amount ÷ number of batches.

7. The method for preparing Mo-containing slag steel for steel alloying according to claim 1, characterized in that: The cooling time in step (4) is 16~24h.

8. The method for preparing Mo-containing slag steel for alloying molten steel according to claim 1, characterized in that: In step (5), the weight of each piece of steel containing molybdenum slag is 1.5~5t.

9. The use of the Mo-containing slag steel prepared by any one of claims 1-8 for alloying as a substitute for ferromolybdenum or molybdenum-containing alloys in steel production, characterized in that: The steel includes SCM435, wherein: no Mo alloying is performed on the steel tapped from the converter; before the refining process, molybdenum-containing slag steel is added to the molten steel, with 1.5 to 1.8 tons of molybdenum-containing slag steel added for every 50 to 58 tons of molten steel.

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