A method for low-cost converter tapping deoxidation by using high-carbon manganese-containing pig iron
By reacting high-carbon manganese pig iron with oxygen in molten steel to generate CO gas for deoxidation, combined with bottom-blown argon stirring, the problems of high cost and low purity of traditional deoxidizers are solved, realizing an efficient and low-cost converter tapping process, improving resource utilization efficiency and molten steel quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BENGANG STEEL PLATES CO LTD
- Filing Date
- 2026-05-29
- Publication Date
- 2026-07-14
AI Technical Summary
In traditional converter steelmaking, deoxidizers are expensive, molten steel is of low purity, temperature drops are large, alloying effects are limited, and high-carbon pig iron resources are not effectively utilized.
High-carbon manganese pig iron reacts with oxygen in molten steel to generate CO gas for deoxidation. By optimizing the timing of its addition and bottom-blowing argon stirring, efficient and low-cost deoxidation and microalloying are achieved, reducing oxide inclusions and improving the purity of molten steel.
It achieves low-cost and efficient steel deoxidation, improves steel purity, increases manganese recovery rate, reduces deoxidation costs, reduces alloy usage, and stabilizes tapping temperature.
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Abstract
Description
Technical Field
[0001] This invention relates to a low-cost method for deoxidation of steel produced from converter using high-carbon, manganese-containing pig iron, belonging to the field of steelmaking technology. Background Technology
[0002] In traditional converter steelmaking, steel deoxidation primarily relies on specialized deoxidizers such as aluminum, ferrosilicon, and ferromanganese. While these materials offer significant deoxidation effects, they also present several challenges. First, specialized deoxidizers are expensive, increasing smelting costs. Second, the deoxidation reaction generates large amounts of solid deoxidation products such as Al2O3 and SiO2, which can easily form inclusions in the molten steel, affecting its purity and billet quality. Third, the addition of deoxidizers causes a drop in molten steel temperature, hindering temperature control and process stability during smelting. Fourth, specialized deoxidizers have relatively simple compositions, offering limited contribution to steel alloying and easily causing compositional fluctuations. Although existing technologies occasionally attempt to use carbon-containing materials to assist deoxidation, these are mostly limited to low-carbon materials (such as coke and graphite), resulting in limited deoxidation efficiency and posing challenges to controlling the carbon content of the molten steel, making large-scale application difficult for steel grades with stringent composition requirements. High-carbon pig iron (such as pig iron containing manganese, silicon, and chromium) has a high carbon content and contains alloying elements, and theoretically has the dual potential for deoxidation and microalloying. However, due to its complex composition and lack of systematic research on the timing of addition and process control, it has not been able to achieve stable and efficient industrial application for a long time, resulting in the underutilization of resources. The contradiction between deoxidation cost and steel purity remains prominent. Summary of the Invention
[0003] To address the technical problems of high cost, low steel purity, large temperature drop, and limited alloying effect associated with traditional deoxidizers used in existing converter steelmaking processes, this invention provides a low-cost method for converter steelmaking deoxidation using high-carbon manganese-containing pig iron. This invention utilizes the carbon, manganese, and silicon contained in the high-carbon manganese-containing pig iron to react with dissolved oxygen in the molten steel during the converter tapping process, generating CO gas that escapes, achieving efficient deoxidation. Simultaneously, the manganese and silicon elements in the pig iron assist in deoxidation and micro-alloying, improving resource utilization efficiency. Furthermore, by optimizing key process parameters such as the timing and amount of high-carbon manganese-containing pig iron addition and bottom-blowing argon stirring, the contradiction between deoxidation cost and steel purity in existing technologies is resolved, achieving the smelting goals of high efficiency, low cost, and comprehensive resource utilization.
[0004] A method for low-cost deoxidation of converter steel using high-carbon, manganese-containing pig iron includes the following steps:
[0005] (1) Control the oxygen content in the molten steel at the end of the converter smelting process to 300~400 ppm, the carbon content to 0.05%~0.07%, and the temperature to ≥1650℃; (2) When the amount of steel tapped from the converter reaches 1 / 4 to 1 / 2 of the total amount of molten steel, high-carbon manganese pig iron is added and all of it is added before the amount of steel tapped reaches 2 / 3 of the total amount of molten steel. The amount added is 0.8%-1.5% of the mass of molten steel. Then ferromanganese is added and all of it is added before the amount of steel tapped reaches the total amount of molten steel. The amount added is 0.5% to 2.0% of the mass of molten steel. Bottom blowing argon stirring is carried out during the tapping process. After the tapping is completed, bottom blowing argon stirring is continued for 5 to 6 minutes. Then the molten steel is transferred to the LF furnace for refining.
[0006] Preferably, the deoxidation method of the present invention is applicable to the production of Q345B steel.
[0007] Oxygen in molten steel mainly exists in the form of oxides such as FeO and Al2O3. These oxides can contaminate the molten steel and reduce its purity. This invention utilizes the high carbon content of high-carbon manganese pig iron to react with dissolved oxygen in molten steel, generating carbon-containing gases CO / CO2 which are then discharged from the molten steel. This reduces the amount of oxidation products left in the molten steel after alloy deoxidation, thereby lowering the oxide content and improving the purity of the molten steel.
[0008] In the above technical solution, in step (2), the tapping time is used instead of the tapping amount for the input of high carbon manganese pig iron and ferromanganese. Specifically, the total tapping time of the converter is controlled to be 4 to 6 minutes. When the tapping process reaches 1 / 4 to 1 / 2 of the total tapping time, high carbon manganese pig iron is added and all of it is added before the 2 / 3 node of the total tapping time. Then ferromanganese is added, and the ferromanganese must be added completely before the tapping operation is completely finished.
[0009] Preferably, taking 150 t steel as an example, the total tapping time is controlled to be 5 min. High carbon manganese pig iron is added 2.5 min after tapping begins and is completely added before 3.3 min after tapping begins.
[0010] Furthermore, the phrase "all steel added before the tapping amount reaches 2 / 3 of the total molten steel" means that it is not necessary to precisely time the addition of steel at the exact moment the tapping amount reaches 2 / 3 (approximately 66.7%) or the exact moment the tapping operation ends (100%). Instead, it is permissible to complete the addition earlier, allowing for a time buffer equivalent to 10% to 15% of the total molten steel. Similarly, when tapping time is used instead of tapping amount for control, a corresponding buffer time can be reserved.
[0011] The "high-carbon manganese pig iron" mentioned in this invention refers to pig iron products with a carbon content ≥4.0% and a manganese content ≥10.0% obtained by blast furnace smelting; the "ferromanganese" refers to ferromanganese alloys with a manganese content ≥70% and a carbon content ≤3.0%.
[0012] In the above technical solution, the high-carbon manganese pig iron is composed of the following chemical components by mass fraction: C: 4.3%~5.8%, Mn: 11%~16%, Si: 2.0%~6.0%, P: 0.040%~0.075%, S: 0.08%~0.12%, with the remainder being Fe.
[0013] Furthermore, the particle size of the high-carbon manganese-containing pig iron is 10~30 mm.
[0014] In the above technical solution, the manganese iron is composed of the following chemical components by mass fraction: C: 1.5%~2.5%, Mn: 75%~85%, Si: 1%~2%, P: 0.03%~0.06%, S: 0.03%~0.10%, with the remainder being Fe.
[0015] Furthermore, the particle size of the ferromanganese is 10~30 mm.
[0016] In the above technical solution, both the high-carbon manganese pig iron and ferromanganese are added to the ladle via a feeding system along a rotary chute, so as to achieve decentralized addition and avoid centralized input.
[0017] In the above technical solution, in step (2), while adding ferromanganese, ferrosilicon can also be added to adjust the silicon composition according to the target silicon content requirements of molten steel; the ferrosilicon and ferromanganese can be added to the ladle simultaneously, in batches or sequentially, but all of them must be added before the steel tapping operation is completely finished.
[0018] In the above technical solution, in step (2), the argon flow rate of bottom blowing argon stirring during the steel tapping process is 30~60NL / min.
[0019] In the above technical solution, in step (2), after the steel is tapped, bottom blowing argon stirring continues, with an argon flow rate of 30~60 NL / min and a duration of 5~6 min.
[0020] In the above technical solution, in step (2), the molten steel is transferred to the LF furnace for refining, and the composition is adjusted and the temperature is controlled according to the steel grade requirements; after the refining process is completed, bottom blowing argon stirring is performed, and the argon flow rate is 10~20 NL / min.
[0021] In the above technical solution, the total oxygen content of the molten steel after treatment by the method is controlled to ≤35 ppm.
[0022] In the above technical solution, after processing by the method, the manganese element recovery rate is ≥85%.
[0023] The beneficial effects of this invention are as follows: This invention uses high-carbon manganese-containing pig iron to partially replace traditional deoxidizers. High-carbon manganese-containing pig iron contains a high amount of carbon, which can react with oxygen in molten steel to generate gas that is discharged from the molten steel, thus achieving deoxidation and stabilizing the total oxygen content of the molten steel at ≤35 ppm. In contrast, traditional processes (such as Comparative Example 1) use solid deoxidizers, and the reaction products are solid oxide inclusions. These inclusions can only be removed by argon blowing and stirring, floating to the slag layer, and are difficult to completely remove, easily remaining in the molten steel and affecting the quality of the steel. This invention obtains clean molten steel while reducing the amount of alloys such as ferromanganese and ferrosilicon, lowering the deoxidation cost per ton of steel. Furthermore, pig iron contains a large amount of carbon, and the carbon-oxygen reaction releases some heat, which can offset some of the temperature changes caused by the addition of manganese to molten steel at room temperature. The temperature drop of the molten steel after deoxidation is not much different from that of the traditional process (Comparative Example 1), and the tapping temperature can be stably controlled. In addition, the manganese in pig iron is effectively utilized, achieving a manganese recovery rate of ≥85%, reducing the amount of purchased alloys added, and providing a new way to increase the value of similar iron-containing resources. Detailed Implementation
[0024] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.
[0025] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.
[0026] In the following embodiments, taking the smelting of Q345B steel as an example, the chemical composition of the Q345B steel, based on mass fraction, includes the following components: C: 0.18%, Si: 0.30%, Mn: 1.65%, P: 0.018%, S: 0.015%. The smelting method of the Q345B steel can be obtained by conventional technical means in the art, and the present invention does not make any particular limitation thereto.
[0027] Example 1 A method for low-cost deoxidation of converter steel using high-carbon, manganese-containing pig iron includes the following steps: (1) Control the oxygen content in the molten steel at the end of the converter smelting process to 350 ppm, the carbon content at the end to 0.06%, the residual Mn content to 0.05%, and the end temperature to 1660℃.
[0028] (2) In this embodiment, the ladle car does not have a weighing device, so the timing of adding each substance is based on the tapping time. The total tapping time of the 150-ton converter is controlled to 5 minutes. 2.5 minutes after tapping begins, high-carbon manganese pig iron with a particle size of 10-30 mm is added for preliminary deoxidation, and all additions are completed before 3.3 minutes after tapping begins. The amount of high-carbon manganese pig iron added is 1.2% of the mass of the molten steel; according to the mass fraction, the high-carbon manganese pig iron is composed of the following chemical components: C content of 5.2%, Mn content of 14.2%, Si content of 4.6%, P content of 0.053%, S content of 0.088%, and Fe content of 75.859%. Next, ferromanganese with a particle size of 10-30 mm is added for re-deoxidation and to replenish the Mn and C elements required for the target steel grade. The amount added is 1.85% of the molten steel mass. The ferromanganese, by mass fraction, consists of the following chemical composition: Mn: 80%, C: 1.8%, Si: 1.0%, P: 0.3%, S: 0.03%, with the remainder being Fe. According to the composition requirements of Q345B steel, ferrosilicon is added to replenish silicon, at a rate of 0.27% of the molten steel mass. The ferrosilicon, by mass fraction, consists of 80% Si and 20% Fe. Both ferromanganese and ferrosilicon must be added completely within 4 minutes. In this embodiment, all substances are added to the ladle via a dedicated feeding system along a rotary chute, allowing them to disperse with the steel flow and avoid concentrated input. A sliding plate is used to block slag during tapping, and the slag thickness is controlled at 30 mm. During the tapping process, bottom blowing argon stirring in the ladle is started simultaneously, with the argon flow rate controlled at 50 NL / min. After tapping is completed, bottom blowing argon stirring continues, with the argon flow rate at 50 NL / min for 6 minutes to ensure sufficient reaction and the floating of inclusions. The converter temperature at the station is 1580℃.
[0029] (3) After the converter tapping is completed, the molten steel enters the LF furnace for subsequent refining treatment. According to the composition requirements of the target steel grade, the Mn, Si, C and other alloying elements in the molten steel are routinely fine-tuned and the temperature is controlled. After the LF refining treatment is completed, a soft blowing argon process is adopted with an argon flow rate of 20 NL / min and a duration of 12 min to further promote the removal of small inclusions.
[0030] After the above treatment, the total oxygen content in the molten steel was measured to be 28 ppm, and the Mn element recovery rate reached 85.8%.
[0031] Comparative Example 1 A method for deoxidation of steel produced from a converter using high-carbon ferromanganese in a conventional manner includes the following steps: (1) Control the oxygen content in the molten steel at the end of the converter smelting process to 338 ppm, the carbon content at the end to 0.07%, the residual Mn content to 0.05%, and the end temperature to 1660℃.
[0032] (2) In this comparative example, the ladle car does not have a weighing device, so the timing of adding each substance is based on the tapping time. The total tapping time of the 150-ton converter is controlled to 5 minutes. Ferromanganese with a particle size of 10~30 mm is deoxidized and the required Mn and C elements in the steel are added. The amount added is 2.3% of the mass of the molten steel. According to the mass fraction, the ferromanganese is composed of the following chemical composition: Mn: 80%, C: 1.8%, Si: 1.0%, P: 0.3%, S: 0.03%, and the remainder is Fe. According to the composition requirements of Q345B steel, ferrosilicon is added to supplement silicon. The amount added is 0.37% of the mass of the molten steel. According to the mass fraction, the ferrosilicon is composed of 80% Si and 20% Fe. Both ferromanganese and ferrosilicon need to be added completely within 4 minutes. In this comparative example, each substance is added to the ladle through a special feeding system along the rotary chute, so that it is dispersed into the ladle with the steel flow and avoids concentrated input. The tapping process employs a sliding plate slag barrier, with the slag thickness controlled at 30 mm. During tapping, bottom blowing argon agitation is simultaneously initiated in the ladle, with the argon flow rate controlled at 50 NL / min. After tapping, bottom blowing argon agitation continues at a flow rate of 50 NL / min for 6 minutes to ensure sufficient reaction and the floating of inclusions. The converter's temperature at the station is 1578℃.
[0033] (3) After the converter tapping is completed, the molten steel enters the LF furnace for subsequent refining treatment. According to the target steel composition requirements, the Mn, Si, C and other alloying elements in the molten steel are routinely fine-tuned and the temperature is controlled. After the LF refining treatment is completed, a soft blowing argon process is adopted with an argon flow rate of 20 NL / min and a duration of 12 min to further promote the removal of small inclusions.
[0034] After the above treatment, the total oxygen content of the molten steel was found to be 32 ppm, and the manganese recovery rate was 85.8%.
[0035] The statistical analysis included 200 heats each of the converter deoxidation processes for Q345B steel produced using the novel process of this invention (Example 1) and the traditional process (Comparative Example 1). Although the specific process parameters for each heat were not exactly the same as those in Comparative Example 1 and Example 1, the adjustment trend was consistent and did not affect the statistical results' proof of the technical effectiveness of this invention. The statistical results are shown in Table 1: After adopting the process of this invention, the consumption of high-carbon ferromanganese and ferrosilicon was reduced compared to the traditional process. This is because oxygen in molten steel exists in the form of oxides such as FeO and Al2O3, which are the main factors contaminating the molten steel and reducing its purity. This invention utilizes the reaction between carbon in high-carbon manganese pig iron and oxygen in molten steel to generate gas, which is then discharged, thus effectively deoxidizing the steel. The process of this invention reduced the average oxygen content of the molten steel at the final stage by 3.4 ppm, significantly improving the purity of the molten steel.
[0036] Table 1. Average Statistical Results of Deoxidation Effects of Traditional and New Processes in the Production of Q345B Steel
Claims
1. A method for low-cost deoxidation of converter steelmaking using high-carbon, manganese-containing pig iron, characterized in that: Includes the following steps: (1) Control the oxygen content in the molten steel at the end of the converter smelting process to 300~400 ppm, the carbon content to 0.05%~0.07%, and the temperature to ≥1650℃; (2) When the amount of steel tapped from the converter reaches 1 / 4 to 1 / 2 of the total amount of molten steel, high-carbon manganese pig iron is added, and all of it is added before the amount of steel tapped reaches 2 / 3 of the total amount of molten steel. The amount added is 0.8% to 1.5% of the mass of molten steel. Then ferromanganese is added, and all of it is added before the amount of steel tapped reaches the total amount of molten steel. The amount added is 0.5% to 2.0% of the mass of molten steel. Bottom blowing argon stirring is carried out during the tapping process. After tapping, bottom blowing argon stirring continues for 5-6 minutes; then the molten steel is transferred to the LF furnace for refining.
2. The method for low-cost deoxidation of converter steelmaking using high-carbon manganese pig iron according to claim 1, characterized in that: In step (2), the tapping time is used instead of the tapping amount for the input of high-carbon manganese pig iron and ferromanganese. Specifically, the total tapping time of the converter is controlled to be 4 to 6 minutes. When the tapping process reaches 1 / 4 to 1 / 2 of the total tapping time, high-carbon manganese pig iron is added and all of it is added before the 2 / 3 mark of the total tapping time. Then ferromanganese is added, and all of the ferromanganese must be added before the tapping operation is completely finished.
3. The method for low-cost deoxidation of converter steelmaking using high-carbon manganese pig iron according to claim 1, characterized in that: According to mass fraction, the high-carbon manganese pig iron is composed of the following chemical components: C: 4.3%~5.8%, Mn: 11%~16%, Si: 2.0%~6.0%, P: 0.040%~0.075%, S: 0.08%~0.12%, with the remainder being Fe.
4. The method for low-cost deoxidation of converter steelmaking using high-carbon manganese pig iron according to claim 1, characterized in that: The manganese iron, by mass fraction, is composed of the following chemical composition: C: 1.5%~2.5%, Mn: 75%~85%, Si: 1.0%~2.0%, P: 0.03%~0.06%, S: 0.03%~0.10%, with the remainder being Fe.
5. The method for low-cost deoxidation of converter steelmaking using high-carbon manganese pig iron according to claim 1, characterized in that: The high-carbon manganese pig iron and ferromanganese are added to the ladle via a feeding system along a rotary chute to achieve decentralized addition and avoid centralized input.
6. The method for low-cost deoxidation of converter steelmaking using high-carbon manganese pig iron according to claim 1, characterized in that: In step (2), the argon flow rate of bottom blowing argon stirring during the steel tapping process is 30~60 NL / min.
7. The method for low-cost deoxidation of converter steelmaking using high-carbon manganese pig iron according to claim 1, characterized in that: In step (2), after the steel tapping is completed, bottom blowing argon stirring continues, with an argon flow rate of 30~60 NL / min and a duration of 5~6 min.
8. The method for low-cost deoxidation of converter steelmaking using high-carbon manganese pig iron according to claim 1, characterized in that: In step (2), the molten steel is transferred to the LF furnace for refining, and the composition and temperature are adjusted according to the steel grade requirements. After the refining process is completed, bottom blowing argon stirring is performed with an argon flow rate of 10~20 NL / min for a duration of 8~10 min.
9. The method for low-cost deoxidation of converter steelmaking using high-carbon manganese pig iron according to claim 1, characterized in that: The total oxygen content of the molten steel treated by the method is controlled to ≤35 ppm.
10. The method for low-cost deoxidation of converter steelmaking using high-carbon manganese pig iron according to claim 1, characterized in that, After processing by the method described above, the manganese yield is ≥85%.