Pure iron steel plate as raw material for low-P, S high-purity amorphous ribbon and its production method

Abstract

This invention relates to the field of steel production technology and discloses a low-P, high-purity amorphous ribbon raw material pure iron steel plate. The chemical composition by mass percentage is: C≤0.0015%, Si≥0.50%, Mn≤0.020%, P≤0.004%, S≤0.004%, Als≤0.003%, Cr≤0.008%, Ni≤0.008%, Cu≤0.008%, Ti≤0.005%, [O]≤0.004%, N≤0.003%, with the remainder being Fe and unavoidable impurities. This invention also discloses a method for producing the low-P, high-purity amorphous ribbon raw material pure iron steel plate. This invention, with its low-P, high-purity amorphous ribbon raw material pure iron steel plate and its production method, can obtain ultra-high purity raw material pure iron steel plates while reducing production process costs and increasing material yield.

Description

Technical Field

[0001] This invention relates to the field of steel production technology, specifically to a pure iron steel plate for low-P, high-purity amorphous ribbon and its production method. Background Technology

[0002] Raw material pure iron is a metallic material with a very low carbon content. Its chemical composition is mainly iron, and the lower the levels of other alloying elements, the better. Raw material pure iron has a predominantly ferrite microstructure at room temperature and is mainly used in industries such as amorphous ribbons, powder metallurgy, permanent magnet materials, lithium batteries, and soft magnets—typical high-value-added products. In practice, raw material pure iron is typically melted, and specific precious elements are added to obtain a mixed molten metal, which is then used to produce finished products such as bars, plates, and strips.

[0003] The amorphous ribbon industry requires high Si content while maintaining extremely low C, Mn, P, S, Al, Ti, and O content due to product characteristics. Al is an important deoxidizing material in steelmaking, ensuring good deoxidation, but it inevitably produces Al2O3 inclusions and leaves a certain amount of residual aluminum in the steel. The P, S, Al, and Ti content, as well as Al2O3 inclusions in the raw material pure iron, can cause nozzle blockage or ribbon breakage during amorphous ribbon preparation. C, Mn, and O content significantly reduces the soft magnetic properties of the material. Therefore, reducing the C, Mn, P, S, Al, Ti, and O content in the raw material pure iron is extremely important for the raw material pure iron used in amorphous ribbons.

[0004] Pure iron is used as a smelting raw material, mixed and melted with precious metals in specific weight ratios. Due to equipment limitations, downstream customers demand round bars and small-flame cut billets from the pure iron to improve material yield. Currently, there are two main methods for producing pure iron from raw materials in steel enterprises: one is to use converter smelting and continuous casting to produce slabs, which are then cut into small square billets or further processed into bars with a diameter of φ20mm to 90mm; the other is to use medium-frequency furnaces or electric furnaces to directly produce small square billets or wire rods, which are then rolled into bars with a diameter of φ20mm to 90mm. Due to production process costs and material yield considerations, a small number of pure iron producers also use single-sheet rolling of medium plates, followed by shearing with a shearing machine to avoid material damage from flame cutting, thus producing thick plates for delivery.

[0005] Regarding patents related to the production of pure iron slabs from raw materials using converter smelting and continuous casting, the inventor conducted the following searches:

[0006] Patent CN115261564A discloses a non-aluminum deoxidized raw material pure iron for amorphous soft magnetic thin strips and its preparation method. The industrial pure iron obtained has the following composition by mass percentage: [C]≤0.005%, [Si]≤1.0%, [Mn]≤0.06%, [P]≤0.015%, [S]≤0.010%, [Al]≤0.005%, [Ti]≤0.0040%, [N]≤0.0040%, T[O]≤0.0070%, with the remainder being Fe and unavoidable impurities. The required Si content is ≤1.0%, and the T[O] content is ≤0.0070%. Desulfurized and demanganese molten iron is used, without adding scrap steel, and the manganese content at the converter endpoint is controlled by using a converter double-slag method. At the same time, without using aluminum deoxidation, the silicon content in the molten steel is above 0.65% in order to control the oxygen content of the molten steel. This process does not add scrap steel, but it is more expensive, and the purity of P and S is poor, with a content greater than 80 ppm.

[0007] Patent CN108559905A discloses a raw material pure iron for high-silicon amorphous materials and its production method. The raw material pure iron produced is high in silicon, low in sulfur and low in manganese, and has the characteristics of high quality, which can meet the application of amorphous materials. However, the raw material pure iron has a high content of residual elements C (>20ppm) and P (>100ppm). The high C content has a significant impact on the soft magnetic properties of the subsequent amorphous ribbon, and the high P content affects the stability of the subsequent amorphous ribbon preparation process.

[0008] Regarding patents related to the production of raw material pure iron slabs using medium-frequency furnaces or electric furnaces, the inventors conducted the following searches:

[0009] Patent CN102352421B discloses a process for smelting industrial pure iron using converter waste slag granules. However, this process has limitations due to the use of converter waste slag granules as raw material and the use of a medium-frequency induction furnace or a vacuum induction furnace for smelting. Patent CN105603312B discloses a method for manufacturing ultra-pure industrial pure iron, using an EBT electric furnace for smelting and adding lanthanum-cerium alloy for deoxidation and desulfurization, but this method is costly.

[0010] Regarding patents for producing raw material pure iron using a single-sheet rolling method from medium plates, the inventor conducted the following searches:

[0011] Patent CN114959488A discloses an industrial pure iron medium-thick plate and its production method. The production process route is: molten iron pretreatment - converter smelting + RH vacuum refining - continuous casting - cutting medium slab - billet heating - high pressure water descaling - rolling - air cooling finishing - inspection and delivery. However, the production efficiency is low. Summary of the Invention

[0012] The purpose of this invention is to address the shortcomings of the above-mentioned technologies by providing a raw material pure iron steel plate for low-P, high-purity amorphous ribbon and its production method, which can not only obtain ultra-high purity raw material pure iron steel plate, but also reduce production process costs and increase material yield.

[0013] To achieve the above objectives, the pure iron steel plate for low-P, high-purity amorphous ribbon designed in this invention has the following chemical composition by mass percentage: C≤0.0015%, Si≥0.50%, Mn≤0.020%, P≤0.004%, S≤0.004%, Als≤0.003%, Cr≤0.008%, Ni≤0.008%, Cu≤0.008%, Ti≤0.005%, [O]≤0.004%, N≤0.003%, with the remainder being Fe and unavoidable impurities.

[0014] A method for producing pure iron steel plate as raw material for low P and S high purity amorphous ribbon includes the following steps in sequence: molten iron pretreatment, converter smelting, alloy fine-tuning station, LF refining, RH refining, continuous casting, heating, rolling, cooling, coiling and cross-cutting.

[0015] Preferably, during the pretreatment of molten iron: 300 tons of molten iron with Mn≤0.25% are selected, the target [S] after desulfurization of the molten iron is ≤0.0010%, the scrap steel is low in nickel, copper and chromium content, the amount of scrap steel added is 15-22% of the mass of molten iron, and the total time for adding scrap steel and mixing iron is ≤16min.

[0016] Preferably, the converter smelting adopts the double slag method, the total amount of main blown lime to molten iron mass ratio is ≤5%, the amount of auxiliary blown lime to molten iron mass ratio is ≤0.67%, the converter main blown temperature target is ≤1550℃, the main blown [C] is ≤0.10%, and the final oxygen control is ≥800ppm.

[0017] Preferably, during LF refining, the ratio of bauxite content to molten iron is ≤0.1%, lime is added in batches during vigorous stirring, in batches ≥3 times, with each addition being ≤0.17% of the molten iron by mass, and the outlet temperature is controlled at 1570±5℃.

[0018] Preferably, during RH refining: RH deoxidation is carried out in three stages: early stage aluminum particle deoxidation + mid-stage ferrosilicon deoxidation + late stage aluminum particle deoxidation and sample determination. The total content of aluminum particles added is ≤0.083% by mass of molten iron. Decarburization is carried out using deoxidizing carbon powder. The target temperature for the end of decarburization is 1585±5℃, and the target carbon content for the end of decarburization is ≤15ppm. After the end of decarburization, ferrosilicon is added for deoxidation and alloying. The target oxygen control range is ≤35ppm. Aluminum particles are added according to the oxygen content, and the target oxygen content is ≤25ppm.

[0019] Preferably, during continuous casting, the argon flow rate of the stopper rod is ≥6NI / min, ultra-low carbon steel protective slag is used, and the billet head is cut ≥4.6m and the tail is cut ≥4.6m.

[0020] Preferably, during heating, the slab exit temperature is 1210~1250℃, all descaling inlet and outlet water nozzles are fully opened, all descaling water pressure is ≥180Bar, and the longitudinal temperature difference of R2DT is ≤40℃.

[0021] Preferably, during rolling, the finishing rolling temperature is 920±20℃, the crown is controlled at 40±20μm, the wedge angle is controlled at 0±20μm, and the flatness is controlled at ±150I.

[0022] Preferably, during cooling, a front-end centralized cooling process is adopted, eliminating the uncooled section at the head. The coiling temperature is controlled at 650±20℃, the coiler tower shape is controlled at ±50mm, and the overflow edge is <20mm. After coiling, the coil is air-cooled to room temperature. During cross-cutting, the cross-cutting production speed is 20~40m / s, the steel coil width alignment error is controlled within ±20mm, the longitudinal tilt of the straightening roller is controlled within ±2.0mm, and the transverse tilt is controlled within ±1.0mm.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. It can obtain ultra-high purity raw material pure iron steel plates, significantly reducing production process costs and increasing the material yield for users;

[0025] 2. Its low-magnification structure: central porosity, central cracks, corner cracks, triangular cracks, Al2O3 inclusions, and honeycomb-like bubbles are all grade 0, and central segregation is ≤B0.5 grade; the microstructure is a coarse ferrite structure, in which the ferrite volume fraction is ≥99%, the grain size is ≥6.0 grade, the yield strength of the product is ≥180MPa, the tensile strength is ≥300MPa, the elongation A50 is ≥55%, the yield strength ratio is ≤0.65, the cold bending performance is 180°, and there are no cracks when D=0a. Attached Figure Description

[0026] Figure 1 A typical metallographic structure diagram of the steel plate obtained in Example 1 of the present invention;

[0027] Figure 2 This is a typical tensile curve of the steel plate obtained in Example 1 of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] A pure iron steel plate for use as raw material for low-P, high-purity amorphous ribbon has the following chemical composition by mass percentage: C≤0.0015%, Si≥0.50%, Mn≤0.020%, P≤0.004%, S≤0.004%, Als≤0.003%, Cr≤0.008%, Ni≤0.008%, Cu≤0.008%, Ti≤0.005%, [O]≤0.004%, N≤0.003%, with the remainder being Fe and unavoidable impurities.

[0030] The production method of the above-mentioned pure iron steel plate for low P and S high purity amorphous ribbon is characterized by the following steps in sequence: molten iron pretreatment, converter smelting, alloy fine-tuning station, LF refining, RH refining, continuous casting, heating, rolling, cooling, coiling and cross-cutting.

[0031] During the pretreatment of molten iron: 300 tons of molten iron with Mn≤0.25% are selected, the target [S] after desulfurization of the molten iron is ≤0.0010%, and scrap steel with low content of nickel, copper and chromium is used. The amount of scrap steel added is 15-22% of the mass of molten iron, and the total time for adding scrap steel and mixing iron is ≤16min.

[0032] The converter smelting adopts the double slag method. The total amount of main blown lime is ≤5% of the mass ratio of molten iron, the amount of auxiliary blown lime is ≤0.67% of the mass ratio of molten iron, the target temperature of the converter main blown lime is ≤1550℃, the main blown lime [C] is ≤0.10%, and the final oxygen control is ≥800ppm.

[0033] During LF refining, the ratio of bauxite content to molten iron mass is ≤0.1%. Lime is added in batches during vigorous stirring, with each batch added at least 3 times. The ratio of each addition to molten iron mass is ≤0.17%. The outlet temperature is controlled at 1570±5℃.

[0034] During RH refining: RH deoxidation is carried out in three stages: early stage aluminum particle deoxidation + mid-stage ferrosilicon deoxidation + final stage aluminum particle deoxidation and sample determination. The total content of aluminum particles added is ≤0.083% by mass of molten iron. Decarburization is carried out using deoxidizing carbon powder. The target temperature for the end of decarburization is 1585±5℃, and the target carbon content for the end of decarburization is ≤15ppm. After decarburization, ferrosilicon is added for deoxidation and alloying. The target oxygen control range is ≤35ppm. Aluminum particles are added according to the oxygen content, with a target oxygen content of ≤25ppm.

[0035] During continuous casting, the argon flow rate of the stopper rod is ≥6NI / min, ultra-low carbon steel protective slag is used, and the billet head is cut ≥4.6m and the tail is cut ≥4.6m.

[0036] During heating, the slab exit temperature is 1210~1250℃. All descaling inlet and outlet water nozzles are opened to maintain surface quality. All descaling water pressure is ≥180Bar, and the longitudinal temperature difference of R2DT is ≤40℃.

[0037] During rolling, the finishing rolling temperature is 920±20℃, the crown is controlled at 40±20μm, the wedge is controlled at 0±20μm, and the flatness is controlled at ±150I.

[0038] During cooling, a front-end centralized cooling process is adopted, eliminating the uncooled section at the head. The coiling temperature is controlled at 650±20℃, the coiler tower shape is controlled at ±50mm, and the overflow edge is <20mm. After coiling, the coil is air-cooled to room temperature. During cross-cutting, the cross-cutting production speed is 20~40m / s, the steel coil width alignment error is controlled within ±20mm, the longitudinal tilt of the straightening roller is controlled within ±2.0mm, and the transverse tilt is controlled within ±1.0mm.

[0039] In steelmaking process design, this invention uses scrap steel with low nickel, copper, and chromium content to reduce the content of impurities such as nickel, copper, and chromium in the steel; it employs a double-slag method to minimize the amount of slag in the steel, thereby reducing the return of residual elements from the slag to the molten steel in subsequent processes and improving the purity of the molten steel; the target main blowing temperature of the converter is ≤1550℃, and the main blowing [C] is ≤0.10%. Using a low main blowing temperature is beneficial for the oxidation reaction of Mn. Since the Mn content cannot be obtained in time during converter smelting, it can be predicted based on the C content; the free O content in the molten steel at the converter endpoint is controlled to be above 0.0800%. A high endpoint oxygen value is used to promote the oxidation of Mn into the steel slag, which helps to reduce the manganese content in the molten steel at the converter endpoint, achieving a demanganese removal rate ≥89% and a dephosphorization rate ≥95%; ultra-low carbon steel protective slag is used to reduce the amount of C from the protective slag entering the molten steel, resulting in carbon enrichment; the billet head is cut ≥4.6m, and the tail is cut ≥4.6m to reduce the residual element content in the billet head and tail, avoiding downgrading and reclassification of the billets and improving the yield.

[0040] In the rolling process design of this invention, to maintain the surface quality of the raw pure iron plate, all descaling inlet and outlet water nozzles are fully opened, and all descaling water pressures are ≥180 Bar; the longitudinal temperature difference of R2DT is ≤40℃ to reduce the instability of rolling force caused by temperature fluctuations; the finishing rolling temperature is controlled at 920±20℃ to reduce rolling force fluctuations during rolling caused by microstructure changes, ensuring the rolling stability of subsequent finishing mills; crown is controlled at 40±20μm, wedge at 0±20μm, and straightness at ±150I to ensure a good rolled plate shape; in addition, the cooling adopts a front-end centralized cooling process and eliminates the head non-cooling section. Since the raw pure iron has low strength, there is no need to add a head non-cooling section for auxiliary coiling, which can effectively reduce costs and improve efficiency. In the cross-cutting process design, the cross-cutting production speed is selected as 20-40m / s, the centering error of the steel coil width is controlled within ±20mm, the longitudinal tilt of the straightening roller is controlled at ±2.0mm, and the transverse tilt is controlled at ±1.0mm, which can effectively improve the plate shape and increase the yield.

[0041] Four sets of examples and two sets of comparative examples illustrate the implementation of this process, as shown in Table 1, which contains the chemical composition of the examples and comparative examples:

[0042] Table 1. Measured chemical composition (mass percentage, wt%) of the examples.

[0043] serial number C Si Mn P S Als Cr Ni Cu Ti O N Example 1 0.0015 0.56 0.0188 0.0028 0.0019 0.0030 0.0049 0.0049 0.0071 0.0001 0.0035 0.0020 Example 2 0.0007 0.50 0.0173 0.0029 0.0022 0.0012 0.0044 0.0080 0.0063 0.0005 0.0030 0.0018 Example 3 0.0009 0.60 0.0171 0.0027 0.0025 0.0012 0.0080 0.0044 0.0069 0.0001 0.0040 0.0030 Example 4 0.0010 0.58 0.0200 0.0040 0.0040 0.0013 0.0039 0.0045 0.0080 0.0002 0.0027 0.0018 Comparative Example 1 0.0020 0.21 0.0460 0.0120 0.0050 0.0015 / / / 0.0010 0.0033 0.0035 Comparative Example 2 0.0020 0.25 0.0420 0.0120 0.0040 0.0016 / / / 0.0010 0.0035 0.0030

[0044] Table 2 shows the steelmaking process parameters for the examples and comparative examples:

[0045] Table 2. Main steelmaking parameters for each embodiment and comparative example.

[0046]

[0047] Table 3 shows the main rolling process parameters and mechanical properties of the examples and comparative examples:

[0048] Table 3. Main rolling process parameters and mechanical properties of each embodiment and comparative example.

[0049]

[0050] As shown in Table 3, the product's yield strength is ≥180MPa, tensile strength is ≥300MPa, elongation A50 is ≥55%, and yield strength ratio is ≤0.65. Figure 1 The image shown is a typical metallographic structure of the steel plate obtained in Example 1. In its low-magnification pickling structure, the center segregation is ≤B0.5 grade, while the central porosity, central cracks, corner cracks, triangular cracks, Al2O3 inclusions, and honeycomb bubbles are all grade 0. There is no bright white band. The microstructure is coarse ferrite, with a ferrite volume fraction ≥99% and a grain size ≥6.0 grade. Figure 2 As shown, this is a typical tensile curve of the steel plate obtained in Example 1. The cold bending performance is 180°, and there are no cracks when D=0a.

[0051] It should be noted that the above description of the technical solutions is exemplary, and this specification may be embodied in different forms and should not be construed as limiting it to the technical solutions set forth herein. Rather, providing these descriptions will ensure that the disclosure of this invention is thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Furthermore, the technical solutions of this invention are defined only by the scope of the claims.

[0052] The aspects disclosed in this specification and claims are merely examples, and therefore, this specification and claims are not limited to the details shown. In the foregoing description, detailed descriptions of relevant known functions or configurations have been omitted where it would unnecessarily obscure the focus of this specification and claims.

[0053] When using the terms “comprising,” “having,” and “including” as described in this specification, there may be another part or other part unless used, and the terms used are generally singular but may also be plural.

[0054] Finally, it should be noted that the above description is a further detailed explanation of the invention in conjunction with specific embodiments. It should not be considered that the specific implementation of the invention is limited to these descriptions. For those skilled in the art, any simple substitutions made without departing from the concept of the invention should be considered within the scope of protection of this invention. The above embodiments are merely representative examples of the invention. Obviously, the invention is not limited to the above embodiments and many variations are possible. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the invention should be considered within the scope of protection of this invention.

[0055] It should be noted that the above description of the technical solutions is exemplary, and this specification may be embodied in different forms and should not be construed as limiting it to the technical solutions set forth herein. Rather, providing these descriptions will ensure that the disclosure of this invention is thorough and complete, and will fully convey the scope of this specification to those skilled in the art. Furthermore, the technical solutions of this invention are defined only by the scope of the claims. Features of various embodiments of this invention may be combined or spliced ​​together in part or in whole, and may be implemented in various different configurations as will be fully understood by those skilled in the art. Embodiments of this invention may be implemented independently of each other or may be implemented together in an interdependent relationship.

[0056] For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and the above structures should all be considered to fall within the protection scope of the present invention.

Claims

1. A method for producing pure iron steel plate as raw material for low-P, high-purity amorphous ribbon, characterized in that: The chemical composition (mass percentage) of the raw material pure iron steel plate is as follows: C≤0.0015%, Si≥0.50%, Mn≤0.020%, P≤0.004%, S≤0.004%, Als≤0.003%, Cr≤0.008%, Ni≤0.008%, Cu≤0.008%, Ti≤0.005%, [O]≤0.004%, N≤0.003%, with the remainder being Fe and unavoidable impurities. The production method of the raw material pure iron steel plate includes the following steps in sequence: hot metal pretreatment, converter smelting, alloy fine-tuning station, LF refining, RH refining, continuous casting, heating, rolling, cooling, coiling and cross-cutting. During hot metal pretreatment: Mn≤0.2% is selected. 300 tons of 5% molten iron, with a target [S] ≤ 0.0010% after desulfurization. Low-content nickel, copper, and chromium scrap steel is used, with the scrap steel addition amount being 15-22% of the molten iron mass. The total time for adding scrap steel and mixing iron is ≤ 16 min. During RH refining: RH deoxidation is carried out in a 3-stage mode: early stage aluminum particle deoxidation + mid-stage ferrosilicon deoxidation + late stage aluminum particle deoxidation sampling. The total content of added aluminum particles to the mass ratio of molten iron is ≤ 0.083%. Decarburization is carried out using deoxidizing carbon powder, with a target decarburization temperature of 1585±5℃ and a target carbon content of ≤ 15ppm. After decarburization, ferrosilicon is added for deoxidation and alloying, with a target oxygen control range of ≤ 35ppm. Aluminum particles are added according to the oxygen content, with a target oxygen level of ≤ 25ppm.

2. The method for producing pure iron steel plate as raw material for low-P, S high-purity amorphous ribbon as described in claim 1, characterized in that: The converter smelting adopts the double slag method. The total amount of main blown lime is ≤5% of the mass ratio of molten iron, the amount of auxiliary blown lime is ≤0.67% of the mass ratio of molten iron, the target temperature of the converter main blown lime is ≤1550℃, the main blown lime [C] is ≤0.10%, and the final oxygen control is ≥800ppm.

3. The method for producing pure iron steel plate as raw material for low-P, high-purity amorphous ribbon as described in claim 1, characterized in that: During LF refining, the ratio of bauxite content to molten iron mass is ≤0.1%. Lime is added in batches during vigorous stirring, with each batch added at least 3 times. The ratio of each addition to molten iron mass is ≤0.17%. The outlet temperature is controlled at 1570±5℃.

4. The method for producing pure iron steel plate as raw material for low-P, high-purity amorphous ribbon as described in claim 1, characterized in that: During continuous casting, the argon blowing flow rate of the stopper rod is ≥6 Nl / min, ultra-low carbon steel protective slag is used, and the billet head is cut ≥4.6m and the tail is cut ≥4.6m.

5. The method for producing pure iron steel plate as raw material for low-P, high-purity amorphous ribbon as described in claim 1, characterized in that: During heating, the slab exit temperature is 1210~1250℃, all descaling inlet and outlet water nozzles are opened, all descaling water pressure is ≥180Bar, and the longitudinal temperature difference of R2DT is ≤40℃.

6. The method for producing pure iron steel plate as raw material for low-P, S high-purity amorphous ribbon as described in claim 1, characterized in that: During rolling, the finishing rolling temperature is 920±20℃, the crown is controlled at 40±20μm, the wedge is controlled at 0±20μm, and the flatness is controlled at ±150I.

7. The method for producing pure iron steel plate as raw material for low-P, S high-purity amorphous ribbon as described in claim 1, characterized in that: During cooling, a front-end centralized cooling process is adopted, eliminating the uncooled section at the head. The coiling temperature is controlled at 650±20℃, the coiler tower shape is controlled at ±50mm, and the overflow edge is <20mm. After coiling, the coil is air-cooled to room temperature. During cross-cutting, the cross-cutting production speed is 20~40m / s, the steel coil width alignment error is controlled within ±20mm, the longitudinal tilt of the straightening roller is controlled within ±2.0mm, and the transverse tilt is controlled within ±1.0mm.

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