Production method of low-manganese raw material pure iron
By employing KR desulfurization, converter smelting, LF refining, and RH refining processes, and utilizing iron oxide scale oxygenating agents and high-alkalinity slag stirring, the problem of high manganese content in raw pure iron has been solved, enabling efficient production of low-manganese raw pure iron, meeting the demands of the high-end market, and protecting equipment.
Patent Information
- Application Number
- CN202410592828.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-14
- Publication Date
- 2025-11-14
AI Technical Summary
Existing technologies cannot effectively control the manganese content in raw pure iron, resulting in low purity that cannot meet the demands of the high-end market. This is especially true for companies without low-manganese ore, where conventional methods disrupt production schedules and cause significant equipment wear and tear.
The process flow adopts KR desulfurization, converter smelting, LF refining and RH refining. By adding oxygenating agents such as iron oxide scale in the LF refining step, the oxygen content of molten steel is controlled, the amount of slag and the stirring intensity are increased, the demanganese removal efficiency is improved, and the equipment requirements and production impact of the converter duplex process are avoided.
Without increasing equipment investment or adjusting blast furnace burden, the manganese content of the finished product can be effectively reduced to below 0.03%, thereby improving the purity of pure iron, maintaining production rhythm and equipment life, and meeting the demands of the high-end market.
Smart Images
Figure CN120945151A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of iron and steel smelting and production technology, and specifically relates to a method for producing pure iron from low-manganese raw materials. Background Technology
[0002] Raw material pure iron is the product with the largest market demand among pure iron series. Benchmark manufacturers (Tangshan Iron & Steel and Taiyuan Iron & Steel) can consistently achieve a total iron content of 3N or higher in their raw material pure iron products, which can be used by customers to produce mid-to-high-end products. The mid-to-high-end market for raw material pure iron is mainly concentrated in the fields of high-performance alloy materials, high-performance magnetic materials, and high-performance electromagnetic shielding materials, and the research and development of high-purity iron (3N grade) is a basic requirement for entering the mid-to-high-end market.
[0003] The national standard for raw material pure iron classifies grades according to the upper limits of each element's composition. Currently, customers using raw material pure iron for high-end applications primarily focus on the total iron content, i.e., purity. For raw material pure iron to reach the 3N level, the control of C, Si, P, and S is a basic requirement. To further improve the purity of pure iron, the control of Mn and residual elements such as Cr, Ni, and Cu in the steel is particularly important. Residual elements such as Cr, Ni, and Cu are mainly controlled through the composition of scrap steel and molten iron. The manganese content in the raw materials entering the converter mainly comes from molten iron and scrap steel. If the blast furnace does not use low-manganese ore, the manganese content in the molten iron is difficult to reach below 0.20%. Similarly, as a commonly used alloying element in steel, the manganese content in scrap steel is generally at a relatively high level. When the manganese content in the molten iron reaches above 0.20%, except for using a twin-tank converter, other conventional production methods make it difficult to reduce the manganese content to below 0.03% through converter smelting. The twin-converter process requires one converter for dephosphorization of molten iron and another converter for decarburization and temperature increase, with the two converters operating in tandem for production. However, adopting the twin-converter method will seriously affect the overall production rhythm of the steel plant.
[0004] Regarding the manganese content of raw material pure iron, steel mills that do not frequently produce low-manganese steel generally do not specifically prepare low-manganese ore for ironmaking and cannot use a converter duplex process. This is because adjusting the amount of low-manganese ore in molten iron typically requires increasing the raw material supply at least two days in advance, resulting in extremely high adjustment costs. Therefore, steel mills that do not frequently produce low-manganese steel find it difficult to produce raw material pure iron with very low manganese content. When enterprises without low-manganese ore produce raw material pure iron, the high manganese content in the molten iron leads to a high manganese content in the final product, resulting in lower purity of the pure iron and failing to meet customer requirements. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a method for producing pure iron from low-manganese raw materials.
[0006] The first aspect of the present invention provides a method for producing low-manganese raw material pure iron, the method comprising the following steps: subjecting the raw material molten iron to KR desulfurization, converter smelting, LF refining, RH refining, and continuous casting to obtain low-manganese raw material pure iron;
[0007] In the LF refining step, an oxygenating agent is added to the ladle to control the oxygen content in the molten steel to be >600ppm, the mass fraction of manganese in the raw iron is 0.25-0.35%, and the mass fraction of manganese in the resulting low-manganese raw material pure iron is ≤0.030%.
[0008] According to the production method of the first aspect, the oxygenating agent is an oxide of iron;
[0009] Preferably, the oxygenating agent is iron oxide scale.
[0010] According to the production method of the first aspect, in the converter smelting step, the oxygen content before tapping the steel from the converter is 550 to 800 ppm.
[0011] According to the production method of the first aspect, the manganese content of the steel produced by the converter smelting is ≤0.08%, and no slag is discharged during the converter tapping process.
[0012] According to the production method of the first aspect, in the LF refining step, top slag is added for slag formation.
[0013] According to the production method of the first aspect, the basicity of the LF refining residue is ≥4.0.
[0014] According to the production method in the first aspect, the amount of LF refining slag is ≥20kg / t.
[0015] According to the production method of the first aspect, the proportion of FeO in the LF refining slag is ≥16%.
[0016] According to the production method of the first aspect, maximum gas volume stirring is used in the LF refining step.
[0017] According to the production method in the first aspect, the oxygen content of the molten steel entering the RH refining step is >500ppm.
[0018] The method of the present invention has, but is not limited to, the following beneficial effects:
[0019] This invention effectively removes manganese from molten steel without increasing equipment investment or adjusting the blast furnace burden. It involves controlling converter slag feeding, controlling the oxygen content in tapped steel, increasing the oxidizability of molten steel by adding an "oxygenating agent" during the LF refining process, increasing the oxidizability of the LF refining slag, increasing the LF slag production, and increasing atmospheric stirring. Compared to existing technologies, this method eliminates the need for blast furnace burden adjustments, increases equipment investment, disrupts normal production, and prevents severe erosion of the converter lining. Furthermore, it increases the free oxygen content in the RH refining process, preventing insufficient oxygen content from affecting the vacuum level during OB oxygen blowing in the RH refining process, thus avoiding impacts on decarburization and production schedule.
[0020] This invention effectively solves the problem that when enterprises without low-manganese ore produce pure iron from raw materials, the high manganese content in the molten iron leads to high manganese content in the final product, resulting in lower purity of pure iron and failing to meet customer requirements. The low-manganese raw material pure iron production method of this invention can effectively reduce the manganese content of the finished product and improve the purity of the raw material pure iron without adjusting the blast furnace feed material or using a double converter. Attached Figure Description
[0021] Figure 1 A schematic diagram of the production process of pure iron from low-manganese raw materials according to the present invention is shown. Detailed Implementation
[0022] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.
[0023] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.
[0024] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.
[0025] Before describing the technical solution of this invention, the terms used herein are defined as follows:
[0026] The term "KR desulfurization" refers to the Kambara Reactor process for desulfurization.
[0027] The term "LF refining" refers to Ladle Furnace refining, a ladle refining technology that utilizes electric arc heating under vacuum conditions.
[0028] The term "RH refining" refers to the vacuum circulation degassing method for molten steel, which is a ladle refining method for molten steel jointly designed and developed by Ruhrstahl and Hereaeus.
[0029] The term "iron oxide scale" refers to iron oxides that form on the surface of steel after the rolled steel is rapidly cooled by water during the steel rolling process. It is mainly composed of FeO, Fe3O4 and Fe2O3.
[0030] To address the issue of high manganese content in molten iron and the inability to employ a dual-converter manganese reduction process, this patented invention utilizes an LF refining demanganese removal process. This process solves several problems: first, it addresses the inability to produce low-manganese raw material pure iron due to high manganese content in molten iron; second, it overcomes the limitation of production schedules that do not allow for dual-converter demanganese removal; third, it resolves the issue of severe erosion of the converter lining by post-blowing; and fourth, it addresses the low demanganese removal rate achieved with conventional processes. Using this patented method to produce raw material pure iron, the process involves KR desulfurization → converter → LF refining → RH refining → continuous casting, achieving a demanganese removal efficiency of over 90%. For molten iron with a manganese content of 0.25-0.35%, the method described in this patent can stably produce raw material pure iron with a finished manganese content below 0.030%, further improving the purity of the raw material pure iron.
[0031] This invention provides a method for producing low-manganese raw material pure iron, the method comprising the following steps: KR desulfurization of raw material molten iron, converter smelting, LF refining, RH refining, and continuous casting to obtain low-manganese raw material pure iron;
[0032] In the LF refining step, an oxygenating agent is added to the ladle to control the oxygen content in the molten steel to be >600ppm, the mass fraction of manganese in the raw iron is 0.25-0.35%, and the mass fraction of manganese in the resulting low-manganese raw material pure iron is ≤0.030%.
[0033] In existing technologies, when the manganese content of the raw iron is high, demanganese removal is usually carried out through a double converter or a double-slag converter. This method has high requirements for equipment conditions and low demanganese removal efficiency. The method of this invention includes converter, LF and RH processes, without using a double converter or double-slag converter process. Instead, it uses an LF refining furnace to produce the equipment. In addition to its heating and slag-forming functions, the demanganese removal capacity is maximized by adjusting the operating process, so that the demanganese removal rate in the LF refining process reaches more than 60%, and the manganese content of the finished pure iron is reduced to below 0.030%.
[0034] In one embodiment, the oxygenating agent is an iron oxide;
[0035] Preferably, the oxygenating agent is iron oxide scale.
[0036] In one specific embodiment, an oxygenating agent is added to the ladle during the LF refining step to control the oxygen content in the molten steel to <1200ppm. For example, the oxygen content in the LF process can be 700ppm, 800ppm, 900ppm, 1000ppm, or 1100ppm.
[0037] In existing technologies, post-converter oxygenation or the addition of iron oxide scale for demanganese removal during iron tapping is commonly used. However, post-converter oxygenation leads to significant blowing losses, and the addition of iron oxide scale during iron tapping results in poor dust removal efficiency, failing to meet environmental protection requirements. This invention, after tapping from the converter, adds an oxygenating agent, such as iron oxide scale, to the ladle based on the pre-tapping oxygen determination results. This increases the oxygen content of the molten steel, and a certain amount of top slag is added. Oxygenation through the post-converter oxygenating agent reduces iron loss, has minimal impact on converter lifespan, and provides comprehensive dust removal measures during the refining stage. The addition of iron oxide scale does not generate excessive dust.
[0038] In one embodiment, during the converter smelting step, the oxygen content before tapping the steel is set at 550–800 ppm.
[0039] Before tapping steel from the converter, the oxygen content is controlled at 550-800 ppm to ensure a certain oxygen content and not exceed the upper limit, thereby reducing furnace lining erosion.
[0040] In one embodiment, the manganese content of the steel produced by the converter smelting is ≤0.08%, and no slag is discharged during the converter tapping process.
[0041] In one embodiment, top slag is added during the LF refining step to form slag.
[0042] In one embodiment, the basicity of the LF refining residue is ≥4.0.
[0043] This invention improves the manganese removal efficiency by creating high-alkalinity slag, thereby increasing the manganese distribution coefficient in the refining slag.
[0044] In one implementation, the amount of LF refining slag is ≥20kg / t.
[0045] This invention produces a large amount of high-basicity slag through LF refining, thereby increasing the capacity for manganese by increasing the amount of slag.
[0046] In one embodiment, the proportion of FeO in the LF refining slag is ≥16%. This invention increases the oxidizability of molten steel by using an oxygenating agent, thereby maintaining a high oxygen content in the molten steel and improving demanganese removal efficiency and effect; simultaneously, it enhances the oxidizability of the refining slag, thereby increasing the fixation effect on manganese and preventing manganese reversion.
[0047] In one implementation, maximum gas volume stirring is used in the LF refining step.
[0048] In the LF refining step of this invention, maximum gas volume stirring is used to promote a faster and more complete demanganese reaction.
[0049] In one implementation, the oxygen content of the molten steel entering the RH refining step is >500ppm, and the decarburization process requires no or only a small amount of oxygen blowing.
[0050] Examples 1-5
[0051] Examples 1 to 5 below illustrate the preparation method of low-manganese raw material pure iron according to the present invention.
[0052] (1) KR desulfurization: KR desulfurization is carried out on raw iron with a manganese content of 0.25-0.35%, and the sulfur content of the desulfurized iron is 0.001-0.003%.
[0053] (2) Converter smelting: The molten iron obtained in step (1) is smelted in a converter. The oxygen content is controlled at 550-800 ppm before the steel is tapped from the converter, and the manganese content is ≤0.08% when the steel is tapped from the converter.
[0054] (3) LF refining: The molten steel obtained in step (2) is fed into the LF furnace, and the oxygenating agent iron oxide scale is added to make the oxygen content in the LF refining molten steel > 600ppm, and the proportion of FeO in the LF refining slag is increased and top slag is added. The top slag composition is: CaO: 44-50%, MgO: 8-10%, SiO2: 8-15%, Al2O3 < 4%, to create a large amount of high basicity slag, so that the basicity of the LF refining slag is ≥ 4.0, and the amount of LF refining slag is ≥ 20kg / t. The maximum gas volume is used for stirring in the LF refining step (determined according to the equipment capacity). The gas volume used in Examples 1 to 5 of this invention is 100-150L / min.
[0055] (4) RH refining: The molten steel obtained in step (3) enters the RH refining step, and the oxygen content of the molten steel is >500ppm.
[0056] (5) Continuous casting: The cooling method is water cooling, and the casting speed is 2.0m / min.
[0057] The process parameters and manganese content (mass fraction) of Examples 1 to 5 are shown in Table 1.
[0058] Table 1. Process parameters and Mn content of Examples 1-5
[0059]
[0060] Comparative Examples 1-5
[0061] Using the same method as Examples 1-5, some process parameters were adjusted to conduct experiments in Comparative Examples 1-5, and the results are shown in Table 2.
[0062] Table 2. Process parameters and Mn content of Comparative Examples 1-5
[0063]
[0064]
[0065] In Comparative Example 1, the oxygen content in the LF process is low, with the oxygen content in the converter tapping steel below 550 ppm and the oxygen content in the LF process below 600 ppm. In Comparative Example 2, the oxygen content in the converter tapping steel is below 550 ppm, and the amount of LF refining slag is below 20 kg / t. In Comparative Example 5, the oxygen content in the converter tapping steel is below 300 ppm, and the oxygen content in the LF process is below 600 ppm. The oxygen content in the molten steel is insufficient, resulting in poor demanganese removal. In Comparative Example 3, the FeO content in the LF refining slag is below 16%, indicating poor oxidizing properties of the refining slag, leading to severe manganese reversion. In Comparative Example 4, the basicity of the refining slag is below 4.0, which reduces the manganese partition coefficient between the slag and the molten steel, increasing the manganese content in the molten steel and making it impossible to obtain finished steel with a Mn content below 0.03%.
[0066] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.
Claims
1. A method for producing pure iron from low-manganese raw materials, characterized in that, The method includes the following steps: KR desulfurization, converter smelting, LF refining, RH refining, and continuous casting of raw molten iron to obtain low-manganese raw pure iron; In the LF refining step, an oxygenating agent is added to the ladle to control the oxygen content in the molten steel to be >600ppm, the mass fraction of manganese in the raw iron is 0.25-0.35%, and the mass fraction of manganese in the resulting low-manganese raw material pure iron is ≤0.030%.
2. The production method according to claim 1, characterized in that, The oxygenating agent is an iron oxide; Preferably, the oxygenating agent is iron oxide scale.
3. The production method according to claim 1, characterized in that, In the converter smelting process, the oxygen content before tapping the steel is 550-800 ppm.
4. The production method according to claim 1, characterized in that, The steel produced by the converter has a manganese content of ≤0.08%, and no slag is discharged during the converter tapping process.
5. The production method according to claim 1, characterized in that, In the LF refining step, top slag is added to form slag.
6. The production method according to claim 5, characterized in that, The basicity of LF refining residue is ≥4.
0.
7. The production method according to claim 5, characterized in that, LF refining slag quantity ≥ 20 kg / t.
8. The production method according to claim 5, characterized in that, The proportion of FeO in LF refining slag is ≥16%.
9. The production method according to claim 1, characterized in that, The LF refining process uses maximum gas volume stirring.
10. The production method according to claim 1, characterized in that, The oxygen content of the molten steel entering the RH refining step is >500ppm.