400MPa-grade low-carbon Cr-Cu-Sb-As series high-corrosion-resistance steel for plateau frozen soil environment and preparation method thereof

Abstract

The invention relates to 400MPa-grade low-carbon Cr-Cu-Sb-As series high-corrosion-resistance steel for a plateau frozen soil environment and a preparation method thereof, and belongs to the technical field of steel for the plateau frozen soil environment. The high corrosion-resisting steel comprises the following chemical components in percentage by weight: less than or equal to 0.15 percent of C, 0.5 to 1.0 percent of Cr, 0.1 to 0.3 percent of Cu, 0.05 to 0.10 percent of Sb, 0.05 to 0.25 percent of As, less than or equal to 0.5 percent of Si, less than or equal to 1.2 percent of Mn, less than or equal to 0.10 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.005 percent of N, 0.0008 to 0.0015 percent of B, 0.010 to 0.025 percent of Ti and the balance of Fe. The obtained corrosion-resistant steel not only has higher mechanical properties, but also has industrial atmosphere and frozen soil corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of steel technology for high-altitude permafrost environments, and particularly to a 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for high-altitude permafrost environments and its preparation method. Background Technology

[0002] The complex topography, geology, and climate of plateau regions, along with their harsh environments such as high altitude, extreme cold, permafrost, and frequent earthquakes, pose significant challenges to the long-term safe and reliable service of bridges, tunnels, and road surfaces on plateau highways. Extending the service life of steel used in plateau highways and reducing maintenance workload are of great significance for ensuring the construction and safe operation of these highways.

[0003] The average altitude in high-altitude regions exceeds 4,000 meters, with temperatures reaching as low as -45°C. To ensure the design and operational safety of permafrost highways under these harsh conditions, it is essential to guarantee that the steel used in these highways possesses excellent low-temperature toughness and strength. Furthermore, the steel used in high-altitude highways is exposed to permafrost environments for extended periods, and is susceptible to damage from soluble salts (Cl) in the soil. - SO4 2- Due to factors such as corrosion, steel faces severe corrosion problems, therefore, it is necessary to ensure that the steel has high corrosion resistance.

[0004] Regarding the problem of steel corrosion, existing technologies have confirmed that amorphous, dense rust layer structures can prevent further corrosion of steel. However, Cl in the soil environment has been found to... - It has strong penetrating power, can penetrate rust layers, and accelerates the corrosion of steel, while SO4 2- It will adhere to the surface of steel, reduce the resistance of the solution, and cause damage to the rust layer and pitting corrosion. - and SO4 2- The synergistic effect of these factors can accelerate the corrosion rate of steel. Therefore, currently used steels such as Q355B steel cannot be used in highly corrosive environments. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for use in high-altitude permafrost environments and its preparation method, which has both excellent mechanical properties and resistance to industrial atmosphere and permafrost soil corrosion.

[0006] On the one hand, the present invention provides a 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for use in high-altitude permafrost environments. Its chemical composition, by mass percentage, includes C ≤ 0.15 wt.%, Cr: 0.5–1.0 wt.%, Cu: 0.1–0.3 wt.%, Sb: 0.05–0.10 wt.%, As: 0.05–0.25 wt.%, Si ≤ 0.5 wt.%, Mn ≤ 1.2 wt.%, P ≤ 0.10 wt.%, S ≤ 0.005 wt.%, N ≤ 0.005 wt.%, B: 0.0008–0.0015 wt.%, Ti: 0.010–0.025 wt.%, with the balance being Fe and unavoidable impurities.

[0007] Furthermore, the chemical composition of the 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for use in high-altitude permafrost environments includes C≤0.10wt.%, Cr: 0.5~0.8wt.%, Cu: 0.1~0.22wt.%, Sb: 0.05~0.08wt.%, As: 0.05~0.15wt.%, Si≤0.26wt.%, Mn≤1.0wt.%, P≤0.10wt.%, S≤0.005wt.%, N≤0.005wt.%, B: 0.0010~0.0015wt.%, Ti: 0.010~0.020wt.%, with the balance being Fe and unavoidable impurities.

[0008] Furthermore, the corrosion-resistant steel has a yield strength of 400-460 MPa, a yield strength ratio of ≤0.8, an elongation at break of ≥22%, and an impact energy of ≥100 J at -40℃.

[0009] Furthermore, the microstructure of the corrosion-resistant steel is ferrite and pearlite.

[0010] Furthermore, the ferrite content is 85-95%, and the pearlite content is 5-15%.

[0011] Furthermore, the average corrosion rate of the corrosion-resistant steel against industrial atmospheric corrosion is 1.2328 g / m³. 2 Below h, under the same conditions, its resistance to industrial atmospheric corrosion is more than 2.0 times that of Q355B.

[0012] Furthermore, the average corrosion rate of the corrosion-resistant steel in soil is 0.0473 g / m³. 2 Below h, under the same conditions, its soil corrosion resistance is more than 2.1 times that of Q355B.

[0013] On the other hand, the present invention provides a method for preparing 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for use in high-altitude permafrost environments, comprising the following steps:

[0014] S1: The alloy raw materials are smelted using an electric furnace, converter or vacuum induction furnace to obtain alloy liquid, which is then refined in an LF+RH or VD furnace.

[0015] S2: The billet is prepared by continuous casting or die casting + forging.

[0016] S3: The obtained billet is heated, rolled, cooled to 640-660℃ and then air-cooled to room temperature to obtain corrosion-resistant steel.

[0017] Furthermore, during the forging and rolling processes, the heating temperature is 1120–1200°C, and the final forging and final rolling temperatures are both ≥900°C.

[0018] Furthermore, the deformation during the rolling stage is ≥40%.

[0019] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0020] 1. In this invention, through the synergistic effect of chemical elements and strict control of their content, the resulting corrosion-resistant steel not only possesses high mechanical properties but also exhibits resistance to industrial atmospheric and frozen soil corrosion. The yield strength of the obtained corrosion-resistant steel is 400–460 MPa, yield strength ratio ≤0.8, elongation after fracture ≥22%, and impact energy at -40℃ ≥100 J. The average corrosion rate of the corrosion-resistant steel against industrial atmospheric corrosion is 1.2328 g / m³. 2 Below h, under the same conditions, its resistance to industrial atmospheric corrosion is more than 2.0 times that of Q355B. The average corrosion rate of the corrosion-resistant steel against soil corrosion is 0.0473 g / m³. 2 Below h, under the same conditions, its soil corrosion resistance is more than 2.1 times that of Q355B.

[0021] 2. The addition of elements such as Sb and As to the corrosion-resistant steel of this invention improves its corrosion resistance to a certain extent. Under the synergistic effect of Cu-Sb-As multi-component composite microalloying, the steel's resistance to Cl is significantly enhanced. - SO4 2- The blocking effect enhances the corrosion resistance of steel in frozen soil environments.

[0022] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0023] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0024] Figure 1 The image shows the metallographic structure of the corrosion-resistant steel obtained in Example 1.

[0025] Figure 2 The image shows the metallographic structure of the corrosion-resistant steel obtained in Example 2.

[0026] Figure 3 The image shows the metallographic structure of the corrosion-resistant steel obtained in Example 3.

[0027] Figure 4 Here is a metallographic diagram of the corrosion-resistant steel obtained in Example 4;

[0028] Figure 5 The image shows the metallographic structure of the low-alloy steel obtained in Comparative Example 1. Detailed Implementation

[0029] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0030] The complex topography, geology, and climate of plateau regions, along with their harsh environments such as high altitude, extreme cold, permafrost, and frequent earthquakes, pose significant challenges to the long-term safe and reliable service of bridges, tunnels, and road surfaces on plateau highways. Extending the service life of steel used in plateau highways and reducing maintenance workload are of great significance for ensuring the construction and safe operation of these highways.

[0031] The average altitude in high-altitude regions exceeds 4,000 meters, with temperatures reaching as low as -45°C. To ensure the design and operational safety of permafrost highways under these harsh conditions, it is essential to guarantee that the steel used in these highways possesses excellent low-temperature toughness and strength. Furthermore, the steel used in high-altitude highways is exposed to permafrost environments for extended periods, and is susceptible to damage from soluble salts (Cl) in the soil. - SO4 2- Due to factors such as corrosion, steel faces severe corrosion problems, therefore, it is necessary to ensure that the steel has high corrosion resistance.

[0032] Regarding the problem of steel corrosion, existing technologies have confirmed that amorphous, dense rust layer structures can prevent further corrosion of steel. However, Cl in the soil environment has been found to... - It has strong penetrating power, can penetrate rust layers, and accelerates the corrosion of steel, while SO4 2- It will adhere to the surface of steel, reduce the resistance of the solution, and cause damage to the rust layer and pitting corrosion. - and SO4 2-The synergistic effect of these factors can accelerate the corrosion rate of steel. Therefore, currently used steels such as Q355B steel cannot be used in highly corrosive environments.

[0033] Therefore, this invention provides a 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for use in high-altitude permafrost environments. Its chemical composition, by mass percentage, includes C ≤ 0.15 wt.%, Cr: 0.5–1.0 wt.%, Cu: 0.1–0.3 wt.%, Sb: 0.05–0.10 wt.%, As: 0.05–0.25 wt.%, Si ≤ 0.5 wt.%, Mn ≤ 1.2 wt.%, P ≤ 0.10 wt.%, S ≤ 0.005 wt.%, N ≤ 0.005 wt.%, B: 0.0008–0.0015 wt.%, Ti: 0.010–0.025 wt.%, with the balance being Fe and unavoidable impurities.

[0034] Compared with existing technologies, this invention, through the synergistic effect of chemical elements and strict control of their content, yields a corrosion-resistant steel that not only possesses high mechanical properties but also exhibits resistance to industrial atmospheric and frozen soil corrosion. The resulting corrosion-resistant steel has a yield strength of 400–460 MPa, a yield strength ratio ≤0.8, an elongation after fracture ≥22%, and an impact energy at -40℃ ≥100 J. The average corrosion rate of this corrosion-resistant steel against industrial atmospheric corrosion is 1.2328 g / m³. 2 Below h, under the same conditions, its resistance to industrial atmospheric corrosion is more than 2.0 times that of Q355B. The average corrosion rate of the corrosion-resistant steel against soil corrosion is 0.0473 g / m³. 2 Below h, under the same conditions, its soil corrosion resistance is more than 2.1 times that of Q355B.

[0035] The functions of each element are as follows:

[0036] C: An effective solid solution strengthening element in steel. In this corrosion-resistant steel, excessive C content will form more carbides, reducing corrosion resistance and mechanical properties. Therefore, its content is controlled to be ≤0.15wt.%.

[0037] Si: A strengthening element in steel, but it also reduces elongation, so its content is controlled to be ≤0.5wt.% in this invention.

[0038] Mn: A stable austenite element and also a solid solution strengthening element. The corrosion-resistant steel of this invention has a low carbon composition. In order to ensure the strength requirements, the Mn content is appropriately increased, and its content is controlled to be ≤1.2wt.%.

[0039] P: It can improve strength and also play an effective role in corrosion resistance, but it segregates severely in steel, thereby reducing plasticity and toughness. Taking all factors into consideration, its content should be controlled to ≤0.10wt.%.

[0040] S: Reduces the ductility and toughness of steel, and the MnS generated by it can act as a corrosion source. Considering the high Mn content in this steel, its content is controlled to be ≤0.005wt.%.

[0041] Cr: An effective corrosion-resistant alloying element in steel and a ferrite-forming element. However, excessive Cr content can increase hardenability and make it difficult to control the microstructure. Therefore, its content should be controlled between 0.5 and 1.0 wt.%.

[0042] Sb and As are effective corrosion-resistant elements in steel. They can effectively slow down cathodic reactions and form a dense oxide film on the steel surface, preventing the penetration of corrosive ions such as chloride and sulfate ions. They also promote the formation of α-FeOOH, which plays a protective role in the rust layer, thus improving the corrosion resistance of steel. The combined addition of Sb and As has a synergistic effect, which can further improve the corrosion resistance of steel.

[0043] This invention controls the Sb content to be 0.05–0.10 wt.% and the As content to be 0.05–0.25 wt.%. When the As content is 0.05–0.10 wt.%, the Sb content is controlled at 0.08–0.10 wt.%; when the As content is 0.10–0.25 wt.%, the Sb content is controlled at 0.05–0.08 wt.%.

[0044] B: It exists in steel in a solid solution state and preferentially segregates at grain boundaries. An appropriate amount of B has a grain boundary occupancy effect, which can reduce the segregation of low melting point elements Sb and As at austenite grain boundaries. Excessive B leads to a decrease in steel toughness. In this invention, the content is controlled at 0.0008 to 0.0015 wt.%.

[0045] Ti: Ti combines with N to control and fix N, preventing B from forming BN and ensuring that B is in a solid solution state, thus playing a role in grain boundary occupancy. At the same time, the precipitation of nanoscale TiN has a precipitation strengthening effect, which can effectively improve strength. Excessive Ti will form liquid-precipitated TiN, which becomes a coarse inclusion, impairing toughness and corrosion resistance; if Ti is too low, it cannot fix N well, making it difficult to prevent BN precipitation and failing to play the role of B grain boundary occupancy. In this invention, the content is controlled at 0.010~0.025 wt.%.

[0046] Cu: An effective corrosion-resistant element in steel, but excessive addition can lead to a decrease in plasticity and, in severe cases, even hot-rolling cracking. This invention controls its content to 0.1-0.3 wt.%.

[0047] N: An effective solid solution strengthening element in steel. If the N content is too high, more Ti needs to be added for fixation, which can easily lead to the formation of large-sized TiN precipitates, reducing the toughness and pitting resistance of corrosion-resistant steel. Its content should be controlled below 0.005 wt.%.

[0048] Specifically, by mass percentage, the chemical composition of corrosion-resistant steel includes C ≤ 0.10 wt.%, Cr: 0.5–0.8 wt.%, Cu: 0.1–0.22 wt.%, Sb: 0.05–0.08 wt.%, As: 0.05–0.15 wt.%, Si ≤ 0.26 wt.%, Mn ≤ 1.0 wt.%, P ≤ 0.10 wt.%, S ≤ 0.005 wt.%, N ≤ 0.005 wt.%, B: 0.0010–0.0015 wt.%, Ti: 0.010–0.020 wt.%, with the balance being Fe and unavoidable impurities.

[0049] Specifically, the microstructure of the corrosion-resistant steel is ferrite and pearlite. The ferrite content is 85-95%, and the pearlite content is 5-15%.

[0050] It should be noted that in this invention, the microstructure of the corrosion-resistant steel is a mixture of ferrite and pearlite. Ferrite, as a soft phase, can reduce the yield strength ratio of the steel and improve the seismic performance of the structural steel. When its content reaches more than 85%, the yield strength ratio can be kept below 0.80.

[0051] This invention provides a method for preparing 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for use in high-altitude permafrost environments, comprising the following steps:

[0052] S1: The alloy raw materials are smelted using an electric furnace, converter or vacuum induction furnace to obtain alloy liquid, which is then refined in an LF+RH or VD furnace.

[0053] S2: The billet is prepared by continuous casting or die casting + forging.

[0054] S3: The obtained billet is heated, rolled, cooled to 640-660℃ and then air-cooled to room temperature to obtain corrosion-resistant steel.

[0055] Specifically, during the forging and rolling processes, the heating temperature is 1120–1200℃, the final forging and final rolling temperatures are both ≥900℃, and the final cooling temperature is 640–660℃.

[0056] It should be noted that when the heating temperature exceeds 1200℃, the billet is in the first brittle zone or the high-temperature brittle zone, and the cross-sectional shrinkage rate of the billet decreases rapidly, leading to cracking during rolling or forging. When the heating temperature is below 1120℃, the billet has high deformation resistance, making forging or rolling difficult.

[0057] When the final rolling or forging temperature is below 900℃, the steel billet is in the second brittle zone or the intermediate-temperature brittle zone, and its thermoplasticity decreases, making it prone to rolling or forging cracks. Therefore, the final forging and final rolling temperature should not be lower than 900℃. After rolling, the plate is cooled to 640-660℃, which on the one hand, causes a ferrite phase transformation, increases the ferrite proportion, and reduces the yield strength ratio; on the other hand, it refines the ferrite grain size in the steel, thereby increasing the strength of the steel.

[0058] Specifically, the deformation during the rolling stage shall not be less than 40%.

[0059] To more clearly describe the present invention, the following embodiments and comparative examples are provided for further illustration.

[0060] Examples and Comparative Examples

[0061] The chemical compositions of Examples 1 to 4 of the present invention are shown in Table 1. Q355B produced and sold by the steel mill was selected as Comparative Example 1.

[0062] After smelting and casting, the ends are trimmed, and the steel is held at 1120–1200℃ for 1 hour before forging. The final forging temperature is above 900℃, and the billet dimensions are 120mm (thickness) × 130mm (width). One piece of the forged test steel is cut to 120mm (thickness) × 130mm (width) × 100mm, heated to 1120–1200℃ and held for 2 hours. After removing the oxide scale, it is rolled according to the following tolerances: 60mm-48mm-39mm-31mm-24mm-18mm-15mm-12mm (positive tolerance). The finished product is approximately 1m long, with a final rolling temperature not lower than 900℃. After laminar cooling to 640–660℃, it is air-cooled to room temperature to obtain corrosion-resistant steel. Table 2 shows the specific rolling process parameters for each embodiment.

[0063] Table 1 Chemical composition (wt%) of the examples

[0064] serial number C Si Mn P S Cr Example 1 0.08 0.25 0.98 0.009 0.004 0.52 Example 2 0.08 0.24 0.90 0.010 0.003 0.51 Example 3 0.08 0.25 1.03 0.008 0.004 0.53 Example 4 0.10 0.26 1.01 0.009 0.005 0.52 Comparative Example 1 0.16 0.20 1.10 0.005 0.003 1.0 serial number Sb As B Cu N Ti Example 1 0.10 0.05 0.0015 0.20 0.0034 0.017 Example 2 0.08 0.10 0.0010 0.19 0.0040 0.019 Example 3 0.05 0.15 0.0012 0.22 0.0035 0.018 Example 4 0.05 0.19 0.0013 0.20 0.0037 0.016 Comparative Example 1 / / 0.005 /

[0065] *In Table 1, " / " indicates that it is not added or does not contain.

[0066] Table 2 Specific hot rolling process parameters for the embodiments

[0067] Example Heating temperature Final rolling temperature Final cooling temperature Example 1 1132 937 656 Example 2 1125 919 641 Example 3 1128 926 646 Example 4 1127 930 655 Comparative Example 1 1130 925 650

[0068] The above embodiments and comparative examples were subjected to performance and microstructure tests. The mechanical property test results are shown in Table 3, and the microstructure test results are shown in Table 4.

[0069] Table 3 Mechanical properties of the examples

[0070]

[0071] Table 4 Microstructure of Examples

[0072] serial number Microorganism Example 1 Ferrite 89.4% + Pearlite 10.6% Example 2 Ferrite 90.1% + Pearlite 9.9% Example 3 Ferrite 90.6% + Pearlite 9.4% Example 4 Ferrite 86.5% + Pearlite 13.5% Comparative Example 1 Ferrite 80.2% + Pearlite 19.8%

[0073] Based on Examples 1-4 and Comparative Example 1, and referring to Tables 3 and 4, it can be seen that the microstructure of the low-carbon Cr-Cu-Sb-As high corrosion-resistant steel consists of ferrite and pearlite, with the ferrite content ranging from 75% to 90%, the pearlite content from 85% to 95%, and the pearlite content from 5% to 15%. The corrosion-resistant steel exhibits a yield strength of 400–460 MPa, a yield strength ratio ≤0.8, an elongation at fracture ≥22%, and an impact energy at -40℃ ≥100 J.

[0074] Example 2 and Comparative Example 1 (Q355B) were selected to test corrosion resistance, and the results were evaluated using two different indoor accelerated corrosion tests. The results of the two indoor accelerated corrosion tests are shown in Table 5, and the corresponding test conditions are described below:

[0075] The first type simulates industrial atmospheric corrosion, with the corresponding periodic immersion corrosion conditions as follows: solution: (1.0±0.05)×10 -2 mol / L NaHSO3 solution; RH: 70±5%; test temperature: 45±2℃; cycle time: 60±min, immersion time: 12±1.5min; test period: 72h.

[0076] The second method simulates frozen soil corrosion (salt concentration 5 times that of actual soil). The corresponding full immersion corrosion conditions are as follows: solution: 0.03 mol / L NaHCO3, 0.01 mol / L MgSO4, 0.005 mol / L CaSO4, 0.01 mol / L MaCl2, 0.005 mol / L CaCl2 solution; pH: 9.0; test temperature: 20℃; test period: 720 h.

[0077] Three parallel samples were set up for each group of tests.

[0078] Table 5 Indoor Corrosion Acceleration Test Data

[0079]

[0080]

[0081] Table 5 shows that under both industrial atmospheric and frozen soil corrosion conditions, the corrosion resistance of Example 4 is superior to that of Q355B. Specifically, the industrial atmospheric corrosion resistance of Example 2 is more than 2.0 times that of Q355B, and its soil corrosion resistance is more than 2.1 times that of Q355B. Comparing the industrial atmospheric and soil corrosion resistance of Example 2 and Q355B, it can be seen that the addition of Sb-As results in a higher corrosion potential and a denser rust layer. This dense rust layer prevents the diffusion of chloride and sulfate ions, thereby improving corrosion resistance.

[0082] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for use in high-altitude permafrost environments, characterized in that, The chemical composition, by mass percentage, includes C ≤ 0.15 wt.%, Cr: 0.5–1.0 wt.%, Cu: 0.1–0.3 wt.%, Sb: 0.05–0.10 wt.%, As: 0.05–0.25 wt.%, Si ≤ 0.5 wt.%, Mn ≤ 1.2 wt.%, P ≤ 0.10 wt.%, S ≤ 0.005 wt.%, N ≤ 0.005 wt.%, B: 0.0008–0.0015 wt.%, Ti: 0.010–0.025 wt.%, with the balance being Fe and unavoidable impurities.

2. The 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for high-altitude permafrost environments according to claim 1, characterized in that, The chemical composition, by mass percentage, includes C ≤ 0.10 wt.%, Cr: 0.5–0.8 wt.%, Cu: 0.1–0.22 wt.%, Sb: 0.05–0.08 wt.%, As: 0.05–0.15 wt.%, Si ≤ 0.26 wt.%, Mn ≤ 1.0 wt.%, P ≤ 0.10 wt.%, S ≤ 0.005 wt.%, N ≤ 0.005 wt.%, B: 0.0010–0.0015 wt.%, Ti: 0.010–0.020 wt.%, with the balance being Fe and unavoidable impurities.

3. The 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for use in high-altitude permafrost environments according to claim 1 or 2, characterized in that, The corrosion-resistant steel has a yield strength of 400-460 MPa, a yield strength ratio of ≤0.8, an elongation after fracture of ≥22%, and an impact energy of ≥100 J at -40℃.

4. A 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for use in high-altitude permafrost environments according to claim 1 or 2, characterized in that, The microstructure of the corrosion-resistant steel is ferrite and pearlite.

5. The 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for use in high-altitude permafrost environments according to claim 4, characterized in that, The ferrite content is 85-95%, and the pearlite content is 5-15%.

6. A 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for use in high-altitude permafrost environments according to claim 1 or 2, characterized in that, The average corrosion rate of the corrosion-resistant steel against industrial atmospheric corrosion is 1.2328 g / m³. 2 Below h, under the same conditions, its resistance to industrial atmospheric corrosion is more than 2.0 times that of Q355B.

7. A 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for use in high-altitude permafrost environments according to claim 1 or 2, characterized in that, The average corrosion rate of the corrosion-resistant steel in the soil is 0.0473 g / m³. 2 Below h, under the same conditions, its soil corrosion resistance is more than 2.1 times that of Q355B.

8. A method for preparing 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for high-altitude permafrost environments as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: The alloy raw materials are smelted using an electric furnace, converter or vacuum induction furnace to obtain alloy liquid, which is then refined in an LF+RH or VD furnace. S2: The billet is prepared by continuous casting or die casting + forging. S3: The obtained billet is heated, rolled, cooled to 640-660℃ and then air-cooled to room temperature to obtain corrosion-resistant steel.

9. The method for preparing 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for high-altitude permafrost environments according to claim 8, characterized in that, During the forging and rolling processes, the heating temperature is 1120–1200℃, and the final forging and final rolling temperatures are both ≥900℃.

10. The method for preparing 400MPa grade low-carbon Cr-Cu-Sb-As high corrosion-resistant steel for high-altitude permafrost environments according to claim 8, characterized in that, The deformation during the rolling stage is ≥40%.

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