Copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel and preparation method thereof

Abstract

The invention discloses low-density corrosion-resisting steel containing copper Fe-Mn-Al-C and a preparation method of the low-density corrosion-resisting steel, and belongs to the technical field of metal material preparation. The corrosion-resistant steel comprises the following chemical components in percentage by mass: 0.3 to 0.8 percent of C, 18 to 22 percent of Mn, 7 to 10 percent of Al, 2.0 to 3.5 percent of Cu and the balance of Fe and inevitable impurities. Meanwhile, the chemical components meet the corrosion-resistant synergistic coefficient K, and K is larger than or equal to 0.09 and equal to Cu / (Mn + Al) and smaller than or equal to 0.11. The corrosion-resistant steel has a single-phase austenite matrix structure, and the Cu element is distributed in a supersaturated solid solution state in the matrix. The method is used for preparing the corrosion-resisting steel, and through the reverse design of'component cooperative locking 'and'forbidden aging solid solution process', pitting corrosion inducements are eliminated while low density is guaranteed, and excellent long-acting chlorine corrosion resistance is achieved.

Description

Technical Field

[0001] This invention belongs to the field of metal material preparation technology, and more specifically, relates to a copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel and its preparation method. Background Technology

[0002] Fe-Mn-Al-C low-density steel has broad application prospects in marine engineering, transportation, and energy equipment due to its high specific strength, excellent ductility and toughness, and lightweight potential. However, corrosion, a typical failure mode of metallic materials, is particularly severe in chloride-containing media (such as seawater and marine atmosphere). In this type of steel, the high content of Mn element is chemically reactive and easily undergoes selective dissolution in chloride-containing environments; at the same time, the oxide film formed solely by Al element is prone to localized cracking under chloride ion attack. Currently, how to improve the long-term corrosion resistance of Fe-Mn-Al-C low-density steel in harsh marine environments has become a major challenge restricting its further widespread application.

[0003] In recent years, significant progress has been made in improving the corrosion resistance of low-density steels, with alloying methods (such as adding Cr, Ni, and Cu) being the mainstream approach. Among these, Cu, as an economical element, has been widely proven to promote the formation of a dense rust layer in weathering steels. However, the mechanism of Cu's action in the special high-manganese, high-alumina Fe-Mn-Al-C system remains largely unexplored and controversial. Existing research indicates that without targeted compositional window locking and controlled hot working processes, Cu readily segregates at grain boundaries, forming copper-rich phases. These microscale copper-rich regions act as strong cathodes electrochemically, accelerating the anodic dissolution of the surrounding matrix and inducing severe intergranular corrosion.

[0004] In addition, existing technologies also offer Cu alloying and hot-cold working / aging treatment solutions for other service failure problems (such as hydrogen-induced delayed fracture / hydrogen embrittlement) in Fe-Mn-Al-C lightweight steels. For example, Chinese patent application number CN202110733786.8, published on October 26, 2021, discloses a method for improving the resistance of Fe-Mn-Al-C lightweight steel to hydrogen-induced delayed fracture. It proposes adding Cu to Fe-Mn-Al-C steel with high Mn, high Al, and relatively high C content, and using processes such as forging, hot rolling, cold rolling, and aging at 450–650℃ to promote the alloying of Cu-rich particles with κ. Carbide precipitation increases the number of irreversible hydrogen traps, thereby improving resistance to hydrogen-induced delayed fracture. However, this type of approach focuses on regulating hydrogen embrittlement behavior, and its chemical composition window and heat treatment path are not consistent with the dominant mechanism of corrosion resistance in chloride-containing media. Furthermore, it does not provide a synergistic strategy for locking the composition window and controlling the final rolling temperature / soaking to eliminate segregation in chloride environments, addressing the risk of Cu segregation in high-manganese aluminum steel that induces pitting / intergranular corrosion.

[0005] It should be noted that such technologies (e.g., schemes aimed at improving hydrogen-induced delayed fracture / hydrogen embrittlement resistance) typically involve aging treatment in the 400-700℃ (e.g., 450-650℃) range after hot rolling / cold rolling to precipitate nanoscale Cu-rich particles or promote κ-carbide formation as a "hydrogen trap." However, the applicant has found that for corrosion resistance in chloride-containing media, Cu-rich precipitates or compositional segregation zones are often the origin of pitting and intergranular corrosion. When Cu segregates in the matrix and transforms into harmful Cu(II) phases (e.g., CuO or Cu2(OH)3Cl) in corrosion products, a stronger cathodic region is formed, accelerating the dissolution of the surrounding matrix (microgalvanic corrosion), leading to rust layer cracking / scraping and reduced long-term corrosion resistance. Therefore, the preparation of corrosion-resistant steels for chloride environments requires a "compositional window locking + solid solution locking process" to suppress Cu segregation / precipitation, rather than following the precipitation strengthening route.

[0006] Chinese patent application number CN202110374699.8, published on July 9, 2021, discloses a lightweight, high-strength, and highly corrosion-resistant Fe-Mn-Al-C-Cr steel. Its chemical composition primarily relies on the addition of 3.0–6.0% Cr to enhance the stability of the passivation film. While this approach improves the material's corrosion resistance to some extent, the high content of Cr, being an expensive alloying element, significantly increases production costs. Furthermore, this approach does not address the technical path of utilizing the economical Cu element to construct a dense rust layer.

[0007] Chinese patent application number CN202310667610.6, published on September 1, 2023, discloses a Fe-Mn-Al-C-Mo-Ni-Cu austenitic steel and its preparation method. This technical solution employs a multi-principal element alloying strategy to achieve high performance, simultaneously adding multiple elements such as Ni, Mo, and Cu. However, this complex composition system is extremely sensitive to process parameters during solidification and hot working, and is highly susceptible to severe compositional segregation due to improper control of cooling rate or final rolling temperature. Furthermore, the addition of large amounts of precious metals (Ni and Mo) leads to high costs, which is inconsistent with the trend towards low-cost industrial manufacturing.

[0008] Both of the above-mentioned schemes improve the corrosion resistance or overall performance of Fe-Mn-Al-C steels through alloying. However, both schemes either rely excessively on expensive Cr, Ni, and Mo elements, leading to a surge in costs, or ignore the risk of Cu segregation in high-manganese steel matrices, resulting in localized corrosion (such as intergranular corrosion). Currently, there is no existing technology that can precisely micro-alloy the economical element Cu and combine it with specific hot working processes to eliminate segregation, thereby constructing a dense monovalent copper protective film in situ in the Fe-Mn-Al-C system. Summary of the Invention

[0009] 1. The problem to be solved To address the insufficient corrosion resistance of existing Fe-Mn-Al-C low-density steels in chlorinated marine environments, and the defects of existing technologies (especially hydrogen embrittlement-resistant modification technologies) that commonly employ aging precipitation processes leading to Cu segregation and thus inducing severe microgalvanic corrosion and intergranular corrosion, this invention provides a copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel and its preparation method. Through the reverse design of "composition synergistic locking" and "anti-aging solution process," the invention eliminates pitting corrosion inducing factors while ensuring low density, achieving excellent long-term chlorine corrosion resistance.

[0010] 2. Technical Solution To solve the above problems, the present invention adopts the following technical solution.

[0011] A copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel, wherein the chemical composition of the corrosion-resistant steel, by mass percentage, is: C: 0.3-0.8%, Mn: 18-22%, Al: 7-10%, Cu: 2.0-3.5%, with the balance being Fe and unavoidable impurities; simultaneously, the chemical composition satisfies the corrosion resistance synergy coefficient K, where 0.09 ≤ K = Cu / (Mn + Al) ≤ 0.11; The corrosion-resistant steel has a single-phase austenitic matrix structure, and the Cu element is distributed in a supersaturated solid solution state in the matrix.

[0012] Furthermore, the mass percentage of Cu is 2.5-3.2%. Furthermore, among the unavoidable impurities, P ≤ 0.02% and S ≤ 0.01%.

[0013] Furthermore, the microstructure of the corrosion-resistant steel is predominantly composed of austenite matrix, with no Cu-rich precipitates or segregation regions at a scale above 100 nm.

[0014] Furthermore, the corrosion product layer formed by the corrosion-resistant steel in a chlorine-containing medium contains a Cu2O phase, and among the Cu elements in the corrosion product layer, monovalent copper Cu(I) accounts for the largest proportion.

[0015] Furthermore, the corrosion-resistant steel satisfies the carbon-to-copper ratio C / Cu ≤ 0.25.

[0016] A method for preparing a copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel includes the following steps: (1) The materials are vacuum induction melted and cast into steel ingots according to the set composition; (2) The steel ingot is subjected to high-temperature homogenization treatment at a temperature of 1180-1220 ℃ and a holding time of 1.5-2.5 h; (3) Perform multiple hot rolling passes on the homogenized steel ingot, and control the initial rolling temperature to be 1100-1150 ℃; (4) After hot rolling, the temperature is forced to continuously cool to below 300°C at a cooling rate of not less than 20°C / s; during the cooling process, the temperature range of 400-700°C is quickly passed through without constant temperature residence, and the aging treatment in the temperature range of 400-700°C is completely excluded in the preparation process.

[0017] Furthermore, the total reduction rate of the multi-pass hot rolling is not less than 60%.

[0018] Furthermore, the single-pass reduction rate is controlled at 15-25%.

[0019] Furthermore, the final rolling temperature is controlled above 1000 ℃.

[0020] 3. Beneficial effects Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel. Compared with steels in the same system that do not contain Cu or contain excessive Cu, the charge transfer resistance Rct in 3.5% NaCl solution is significantly improved (the preferred scheme can reach >1400 Ω·cm²), the corrosion rate is greatly reduced, and the corrosion resistance is significantly improved.

[0021] (2) This invention discloses a low-density corrosion-resistant steel containing copper (Fe-Mn-Al-C). Benefiting from the control of the compositional synergy coefficient and the solid solution locking process, the corrosion product layer is dominated by stable Cu(I), continuous and dense, effectively blocking Cl- penetration, significantly reducing pitting and intergranular corrosion tendencies, and effectively inhibiting localized corrosion. This invention reveals and utilizes for the first time the synergistic regulation mechanism (i.e., the K coefficient) of Mn / Al elements on the corrosion resistance behavior of Cu. Studies have shown that when the K value is controlled between 0.09 and 0.11, the high Mn / Al content in the matrix can effectively regulate the semiconductor properties of the passivation film and inhibit Cu from reaching higher valence states (Cu²⁺). + This transformation induces the formation of a more thermodynamically stable p-type semiconductor, Cu₂O (Cu₂O). +A protective film. This atomic-scale synergistic effect ensures passivation capabilities comparable to stainless steel, even in expensive systems without Cr or Ni.

[0022] (3) The present invention provides a copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel, which mainly uses economical Cu element alloying and does not require the addition of large amounts of precious metals such as Cr, Ni, and Mo. Its preparation path of "hot rolling + continuous cooling" is compatible with existing industrial production lines, does not require complex cold rolling and aging heat treatment, is easy to realize industrial production and promotion, and has the advantages of low cost and good processability. Attached Figure Description

[0023] Figure 1 Potential dynamic polarization curves of steels with different Cu contents in a 3.5% NaCl solution (before immersion / after 7 days of immersion).

[0024] Figure 2 Nyquist plots of electrochemical impedance spectroscopy for steels with different Cu contents in a 3.5% NaCl solution.

[0025] Figure 3 The weight loss corrosion rate of steels with different Cu contents after immersion in a 3.5% NaCl solution for 1, 3, 5, and 7 days is shown.

[0026] Figure 4 Comparison of surface morphology after removal of corrosion products.

[0027] Figure 5 Comparison of surface morphology of corrosion product layers.

[0028] Figure 6 The image shows the corrosion product layer and EDS element distribution on the cross-section after immersion for 7 days.

[0029] Figure 7 The image shows the XRD pattern of the corrosion products after immersion for 7 days.

[0030] Figure 8 The image shows the Cu 2p XPS spectrum of the corrosion product after immersion for 7 days. Detailed Implementation

[0031] Exemplary embodiments of the present invention are described in detail below. While these exemplary embodiments have been described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be implemented and various changes may be made to the invention without departing from its spirit and scope. The more detailed description of embodiments of the invention below is not intended to limit the scope of the claimed invention, but is merely illustrative and does not limit the description of the features and characteristics of the invention, in order to suggest the best mode for carrying out the invention and to enable those skilled in the art to practice it. Therefore, the scope of the invention is defined only by the appended claims.

[0032] A low-density corrosion-resistant steel containing copper (Fe-Mn-Al-C) has the following chemical composition by mass percentage: C: 0.3-0.8%, Mn: 18-22%, Al: 7-10%, Cu: 2.0-3.5%, with the balance being Fe and unavoidable impurities. The chemical composition satisfies the corrosion resistance synergy coefficient K, where 0.09 ≤ K = Cu / (Mn + Al) ≤ 0.11. The corrosion-resistant steel has a single-phase austenitic matrix, with austenitic matrix comprising the largest proportion of the microstructure. Cu is distributed in a supersaturated solid solution state in the matrix, with no Cu-rich precipitates or segregation regions at scales above 100 nm.

[0033] The mass percentage of Cu is preferably 2.5-3.2%, more preferably 2.8-3.0%. Among unavoidable impurities, P ≤ 0.02% and S ≤ 0.01%.

[0034] The corrosion product layer formed by corrosion-resistant steel in a chlorine-containing medium contains Cu2O phase, and the Cu element in the corrosion product layer is mainly monovalent copper Cu(I); according to the XPS characterization of Cu 2p, its main peak is located at about 932.6-933.0 eV, and the characteristic satellite peak of Cu(II) is weak or undetectable.

[0035] In the preferred embodiment, the corrosion-resistant steel satisfies the carbon-to-copper ratio C / Cu ≤ 0.25.

[0036] The preparation method of this copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel includes the following steps: (1) The materials are prepared according to the set composition and then vacuum induction melting and casting into steel ingots.

[0037] (2) The steel ingot is subjected to high-temperature homogenization treatment at a temperature of 1180-1220 ℃ and a holding time of 1.5-2.5 h to eliminate component segregation during solidification.

[0038] (3) The hot-rolled steel ingot is subjected to multiple passes of hot rolling, with the initial rolling temperature controlled at 1100-1150 ℃ and the final rolling temperature not lower than 1000 ℃. In this step, the total reduction rate of the multiple passes of hot rolling is not less than 60%, and the reduction rate of a single pass is controlled at 15-25% to ensure the crushing and recrystallization of austenite grains.

[0039] (4) After hot rolling, the temperature is forced to continuously cool to below 300°C at a cooling rate of not less than 20°C / s; during the cooling process, the temperature range of 400-700°C is quickly passed through without constant temperature residence, and the aging treatment in the temperature range of 400-700°C is completely excluded in the preparation process to avoid Cu-rich phase desolvation and precipitation and κ-carbide formation.

[0040] This invention solves the above problems through the synergistic effect of "component synergistic optimization" and "solid solution locking process": Synergistic Optimization of Composition: The applicant discovered that in the Fe-Mn-Al-C system, the corrosion resistance of Cu depends not only on its absolute content but also on the synergistic relationship with the contents of Mn and Al in the system. In a high-manganese, high-alumina matrix, the diffusion tendency of Cu atoms exhibits a specific nonlinear coupling relationship with the atomic cloud concentration of (Mn + Al) in the matrix. Therefore, this invention proposes the core inventive point of a corrosion resistance synergistic coefficient K = Cu / (Mn + Al) = 0.09-0.11. Under this ratio control, when the Cu content is controlled at 2.0-3.5% (preferably 2.5-3.2%), and when the K value is in the range of 0.09-0.11, the matrix lattice distortion field can effectively anchor the solid-solution Cu atoms, suppressing their microscopic segregation during forced cooling, thereby ensuring the induction of a high-proportion, dense Cu(I) protective film in the early stage of corrosion. If the K value deviates from this range, even with the same cooling rate, it is difficult to simultaneously meet the technical requirements of 'full solid solution of the substrate' and 'high enrichment of the film layer'. A preferred approach also includes controlling the carbon-copper ratio C / Cu ≤ 0.25 to further suppress the precipitation of κ-carbides at grain boundaries and reduce electrochemical inhomogeneity.

[0041] Solution-locking process: Matching the above composition design, this process abandons the aging route aimed at precipitation strengthening and instead adopts a "homogeneous heating-controlled rolling-continuous cooling" solution-locking process. Specifically, this includes: high-temperature homogenization to eliminate compositional segregation, followed by hot rolling with a high reduction rate at a final rolling temperature not lower than 1000℃; after hot rolling, direct continuous cooling (such as air cooling or accelerated cooling) to below 300℃, avoiding isothermal holding or aging treatment of the material in the 400-700℃ temperature range throughout the entire preparation process. Through this process window, the supersaturated solution state of Cu in the austenitic matrix is ​​forcibly maintained, fundamentally inhibiting the precipitation of Cu-rich harmful phases.

[0042] To verify the technical effects of the present invention, especially the interaction between the Cu content window and process parameters, five sets of examples (including three sets of actual measurements and two sets of preferred designs) and two sets of comparative examples were designed.

[0043] 1. Preparation of experimental materials The chemical composition of each embodiment and comparative example is shown in Table 1. The preparation process strictly follows the parameters specified in this invention: (1) Vacuum melting: smelt steel ingots according to the proportion; (2) Homogenization / scaling treatment: hold at 1200℃ for 2 hours (corresponding to the range of 1180-1220℃) to eliminate as-cast segregation; in another preferred embodiment, it can be further held at 1050-1120℃ for 0.5-1.5 hours (double-stage homogenization) to reduce Cu micro-segregation; (3) Hot rolling process: the initial rolling temperature is 1150℃, after 7 passes of rolling, the final rolling temperature is controlled at 1020℃ (and ≥1000℃), the total reduction rate is about 85%, and the final thickness is 4 mm; (4) Cooling: in the embodiment of this invention, the final rolling is directly air-cooled to room temperature; in another preferred embodiment, the final rolling is controlled by two stages of cooling, that is, after the final rolling, it is cooled to 750-850℃ at 10-30℃ / s and held for 30-180 s, and then air-cooled to room temperature.

[0044] Table 1 Measured / Predicted values ​​of chemical composition for each case (wt.%)

[0045] 2. Performance Test Results Full immersion and electrochemical tests were conducted in 3.5% NaCl solution. Key data are summarized in Table 2. Synergistic effect analysis of Example 1 (3Cu): The synergistic coefficient K ≈ 0.102 for the composition ratio of Example 1 (Cu approximately 2.9%, Mn approximately 19.5%, Al approximately 8.8%), which falls within the preferred window (0.09-0.11) of this invention. Electrochemical impedance spectroscopy results show that its Rct is approximately 1850 Ω·cm², significantly higher than that of 0Cu steel (approximately 380 Ω·cm²), demonstrating optimal corrosion resistance. XRD and XPS characterization ( Figure 7 , Figure 8 The corrosion products are mainly stable Cu2O (Cu(I)), and the cross-sectional EDS ( Figure 6 The results show that Cu is more evenly distributed in the rust layer, thus forming a continuous and dense barrier layer and effectively inhibiting Cl- intrusion.

[0046] Table 2 Results of full immersion test and electrochemical test

[0047] 3. Results Analysis and Mechanism Elucidation 1) Failure cause and counter-evidence of Comparative Example 2 (5Cu): The Cu content of Comparative Example 2 is approximately 4.8%, corresponding to a significantly higher synergy coefficient K than the window of this invention (approximately K≈0.17). Despite using the same hot rolling process, excess Cu is more likely to form localized segregation and cathode heterogeneity. EDS surface scanning ( Figure 6 Cu-rich areas can be observed, and the surface morphology after corrosion ( Figure 4 , Figure 5 The rust exhibited significant localized and intergranular corrosion, as well as mud-like cracking. XRD / XPS results showed the presence of harmful Cu(II) phases such as CuO and Cu2(OH)3Cl in the products. The Cu-rich areas acted as strong cathodes, accelerating the dissolution of the surrounding matrix (micro-galvanic corrosion), leading to an unstable rust layer and reducing Rct to approximately 920 Ω·cm². This comparative result conversely demonstrates that controlling the K window and suppressing Cu segregation / precipitation through a solid solution locking process are key to obtaining long-term resistance to chloride corrosion.

[0048] 2) Reasonable predictions for Examples 2 and 3 (2.5Cu, 3.2Cu): Based on the non-monotonic variation trend of 0-3-5%, a high Rct value (>1400 Ω·cm²) can be maintained when the Cu content is in the range of 2.5-3.2%. This indicates that the technical solution of the present invention (2.0-3.5%) is a wide and stable process window. Within this window, combined with the high-temperature final rolling process, Cu can be fully dissolved, avoiding the precipitation of harmful phases.

[0049] 3) Cause of failure in Comparative Example 2 (5Cu): When the Cu content exceeded the standard (4.8%), despite using the same process, the supersaturated Cu still tended to undergo localized segregation during corrosion. XPS data showed the presence of CuO and Cu2(OH)3Cl (divalent copper) in the products. These copper-rich phases acted as strong cathodes, leading to severe localized galvanic corrosion and rust layer cracking.

[0050] In summary, the preferred embodiment of this invention (approximately 2.9% Cu, K ≈ 0.102) exhibits optimal corrosion resistance, with an Rct value (~1850 Ω·cm²) significantly higher than that of Cu-free steel (~380 Ω·cm²), and far superior to the comparative example (~920 Ω·cm²) containing excessive Cu (approximately 4.8%) and exceeding the K value limit. XRD and XPS analyses confirm that the corrosion products of the preferred embodiment are predominantly Cu(I) / Cu₂O and uniformly distributed, while the comparative example shows a harmful Cu(II) phase, which is associated with mud-crack-like rust layer cracking and severe intergranular corrosion. These experimental results collectively confirm the effectiveness and necessity of the proposed "corrosion resistance synergy coefficient K" control window and "solution locking process" in this invention.

[0051] The examples described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. A copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel, characterized in that, The chemical composition of the corrosion-resistant steel, by mass percentage, is: C: 0.3-0.8%, Mn: 18-22%, Al: 7-10%, Cu: 2.0-3.5%, with the balance being Fe and unavoidable impurities; simultaneously, the chemical composition satisfies the corrosion resistance synergy coefficient K, where 0.09 ≤ K = Cu / (Mn + Al) ≤ 0.11; The corrosion-resistant steel has a single-phase austenitic matrix structure, and the Cu element is distributed in a supersaturated solid solution state in the matrix.

2. The copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel according to claim 1, characterized in that, The mass percentage of Cu is 2.5-3.2%.

3. The copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel according to claim 1, characterized in that, Of the unavoidable impurities, P ≤ 0.02% and S ≤ 0.01%.

4. The copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel according to claim 1, characterized in that, The corrosion-resistant steel has the largest proportion of austenite matrix in its microstructure, and there are no Cu-rich precipitates or segregation regions at the scale above 100 nm.

5. The copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel according to claim 1, characterized in that, The corrosion product layer formed by the corrosion-resistant steel in a chlorine-containing medium contains the Cu2O phase, and among the Cu elements in the corrosion product layer, monovalent copper Cu(I) accounts for the largest proportion.

6. A copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel according to claim 1, characterized in that, The corrosion-resistant steel meets the requirement that the carbon-copper ratio C / Cu ≤ 0.

25.

7. A method for preparing copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel according to any one of claims 1-6, characterized in that, Includes the following steps: (1) The materials are vacuum induction melted and cast into steel ingots according to the set composition; (2) The steel ingot is subjected to high-temperature homogenization treatment at a temperature of 1180-1220 ℃ and a holding time of 1.5-2.5 h; (3) Perform multiple hot rolling passes on the homogenized steel ingot, and control the initial rolling temperature to be 1100-1150 ℃; (4) After hot rolling, the temperature is forced to continuously cool to below 300°C at a cooling rate of not less than 20°C / s; during the cooling process, the temperature range of 400-700°C is quickly passed through without constant temperature residence, and the aging treatment in the temperature range of 400-700°C is completely excluded in the preparation process.

8. The method for preparing a copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel according to claim 7, characterized in that, The total reduction rate of the multi-pass hot rolling is not less than 60%.

9. The method for preparing a copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel according to claim 7, characterized in that, The single-pass reduction rate is controlled at 15-25%.

10. A method for preparing a copper-containing Fe-Mn-Al-C low-density corrosion-resistant steel according to claim 6, characterized in that, The final rolling temperature is controlled above 1000 ℃.

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