Cr-cu-mo-sb-based high weathering resistance steel and method for manufacturing the same

Abstract

The application relates to a Cr-Cu-Mo-Sb high weather-resistant steel and a preparation method thereof, and belongs to the technical field of weather-resistant steel, and solves the problems of insufficient corrosion resistance and insufficient crevice corrosion resistance of the Cr-Cu weather-resistant steel in the prior art. The application provides a Cr-Cu-Mo-Sb high weather-resistant steel, wherein the components in the high weather-resistant steel are as follows in percentage by mass: C: 0.055-0.080%, Si: 0.23-0.50%, Mn: 0.1-0.8%, Cr: 0.5-3.5%, Cu: 0.18-0.32%, Mo: 0.07-0.35%, Sb: 0.06-0.12%, and the balance is Fe and inevitable impurities. The high weather-resistant steel has excellent uniform corrosion resistance and crevice corrosion resistance, and has excellent strength and toughness matching; the yield strength is 250-440 MPa, the yield strength ratio ranges from 0.68 to 0.82, and the elongation after fracture is 20.5-31.0%.

Description

Technical Field

[0001] This invention relates to the field of weathering steel technology, and in particular to a Cr-Cu-Mo-Sb series high weathering steel and its preparation method. Background Technology

[0002] Weathering steel is a low-alloy steel with good resistance to atmospheric corrosion. Cr and Cu are commonly used alloying elements in weathering steel. The addition of alloying elements such as Cr and Cu promotes the formation of a dense and highly adhesive protective film on the steel surface, thereby slowing down corrosion. Cr-Cu series weathering steels have been widely studied and are gradually being applied. Existing weathering steels have relatively strong resistance to uniform corrosion, but weak resistance to crevice corrosion. In practical use, this can lead to severe corrosion at structural gaps or surface crevices caused by other reasons, thus affecting the overall stability or performance of equipment or structures, and impacting the service life and safety performance of the steel. Currently, research on crevice corrosion resistant weathering steels is still in its early stages both domestically and internationally. Furthermore, existing crevice corrosion resistant weathering steels generally have expensive raw materials and high smelting difficulty, resulting in high overall economic costs. The comprehensive performance, including mechanical properties, resistance to uniform corrosion, and resistance to crevice corrosion, is insufficient to meet the application requirements of special scenarios, especially harsh environments such as the marine atmosphere. Summary of the Invention

[0003] Based on the above analysis, the present invention aims to provide a Cr-Cu-Mo-Sb series high weathering steel and its preparation method, in order to solve at least one of the problems of insufficient crevice corrosion resistance, poor strength-toughness matching, expensive raw materials, and high smelting difficulty of existing weathering steels.

[0004] This invention provides a Cr-Cu-Mo-Sb series high weathering steel, wherein the components of the high weathering steel are as follows by mass percentage: C: 0.055-0.080%, Si: 0.23-0.50%, Mn: 0.1-0.8%, Cr: 0.5-3.5%, Cu: 0.18-0.32%, Mo: 0.07-0.35%, Sb: 0.06-0.12%, with the balance being Fe and unavoidable impurities.

[0005] Specifically, 0.5 wt.% ≤ Cr < 1.5 wt.%, 0.15 wt.% ≤ Mo + Sb < 0.3 wt.%, and 0.9 wt.% ≤ Mn + Cr ≤ 1.9 wt.%.

[0006] Specifically, the microstructure of the high weathering steel includes ferrite and pearlite, wherein the volume percentage of ferrite is 63% to 76% and the volume percentage of pearlite is 24% to 37%.

[0007] Specifically, the high weathering steel has a yield strength range of 250-360 MPa, a yield strength ratio range of 0.76-0.82, and a post-break elongation of 25.5-31.0%.

[0008] Specifically, 1.5wt.%≤Cr≤3.5wt.%, 0.3wt.%≤Mo+Sb≤0.45wt.%, 1.9wt.%≤Mn+Cr≤4.3wt.%.

[0009] Specifically, the microstructure of the high weathering steel includes ferrite, bainite and pearlite, wherein the volume percentage of the ferrite is 62%-71%, the volume percentage of the bainite is 20%-35%, and the rest is the pearlite.

[0010] Specifically, the high weathering steel has a yield strength range of 360-440 MPa, a yield strength ratio range of 0.68-0.75, and a post-break elongation of 20.5-25.0%.

[0011] Specifically, the high weathering steel has a crevice corrosion test according to GB / T 10127-2002, the corrosion solution is FeCl3 solution, the corrosion time is 3h, and the corrosion depth at the crevice is 10-32μm.

[0012] The application further discloses a preparation method of the high weathering steel, which comprises the following steps: smelting, continuous casting, rolling, and cooling.

[0013] In the rolling process, the heating temperature is 1150-1250℃, the rolling pass is 4-6 times, the finish rolling temperature is ≥850℃, and the thickness of the steel plate after the last rolling pass is 4-6mm.

[0014] Further, the cooling step is air cooling, and the cooling rate is 0.25-2℃ / s.

[0015] Compared with the prior art, the application can achieve at least one of the following beneficial effects:

[0016] 1. The high weathering steel provided by the application has good uniform corrosion resistance and crevice corrosion resistance.

[0017] The application proposes a low C+(Cr-Cu)+(Mo-Sb) alloy design scheme aiming at the material demand for high weathering and crevice corrosion resistance. The low C design ensures good plasticity and toughness and low welding crack sensitivity; the Cr-Cu alloy design aims to form a dense oxide film such as Cr2O3 and Cu2O on the surface of the steel to ensure the uniform corrosion performance of the steel. Meanwhile, the increasing concentration of chloride ions in the development process of crevice corrosion is considered, and the corrosion damage risk of the steel is increased, and the Cr content in the rust layer is increased. 3+The increased likelihood of ion hydrolysis under high chloride conditions lowers the pH value in the corresponding area, thus accelerating the corrosion process. Therefore, a Mo-Sb composite additive was designed. On one hand, the addition of Mo and Sb respectively generates dense oxides, jointly strengthening the protective film on the surface, making it more dense and stable, thereby effectively resisting the intrusion of corrosive media. On the other hand, when Cu and Sb coexist, sufficient Sb can form a complex Cu2Sb with Cu, which deposits on the steel surface, hindering chloride ion intrusion and further improving crevice corrosion resistance. Therefore, (Cr-Cu)+(Mo-Sb) not only ensures uniform corrosion performance but also improves crevice corrosion resistance.

[0018] Uniform corrosion resistance: Accelerated atmospheric corrosion tests were conducted according to the periodic immersion corrosion test method for weathering steel for railways (TB / T 2375-1993). High weathering steel with dimensions of 60mm × 40mm × 3mm was periodically immersed in a 0.01mol / L NaHSO3 solution at an experimental temperature of 45±2℃. One cycle lasted 60 minutes, including a 12-minute immersion time. The test cycles were 3 days and 7 days. After 3 days of corrosion, the corrosion rate of the high weathering steel (Example 1) was 1.513 g / m³. 2 • h; After 7 days of corrosion, the corrosion rate was 1.131 g / m 2 ·h. After 7 days, the corrosion morphology of the high weathering steel is as follows: Figure 1 As shown.

[0019] Crevice corrosion resistance: Crevice corrosion tests were conducted according to GB / T 10127-2002 "Test Method for Crevice Corrosion of Stainless Steel with Ferric Chloride". The corrosion solution was FeCl3 solution, and the corrosion time was 3 hours. The corrosion depth in the crevice of the high weathering steel (Example 3) was relatively shallow, ranging from 10 to 20 μm.

[0020] 2. The high weathering steel provided by this invention has a yield strength of 250–440 MPa, a yield strength ratio of 0.68–0.82, and an elongation after fracture of 20.5–31.0%. Its microstructure is mainly ferrite, with a volume percentage of 62%–76%, and the remainder is pearlite or pearlite + bainite. It exhibits excellent resistance to uniform corrosion and crevice corrosion, and a high strength-toughness ratio. Compared with existing crevice corrosion resistant weathering steels, its overall performance is significantly improved, and it can meet the requirements of use under harsh conditions.

[0021] 3. The high weathering steel provided by this invention has a good balance of strength and toughness. The Cr-Cu-Mo-Sb series weathering steel of this invention achieves a balance of mechanical properties for steels of different strength levels through alloy element matching and process design, thus meeting the material selection requirements for weathering steels of different strength levels.

[0022] When 0.5wt.% ≤ Cr < 1.5wt.%, 0.15wt.% ≤ Mo + Sb < 0.3wt.%, and 0.9wt.% ≤ Mn + Cr ≤ 1.9wt.%, the microstructure of the high weathering steel includes ferrite and pearlite, wherein the volume percentage of ferrite is 63%–76% and the volume percentage of pearlite is 24%–37%; the yield strength of the high weathering steel ranges from 250 to 360 MPa, the yield ratio ranges from 0.76 to 0.82, and the elongation after fracture is 25.5%–31.0%.

[0023] When 1.5wt.%≤Cr≤3.5wt.%, 0.3wt.%≤Mo+Sb≤0.45wt.%, and 1.9wt.%≤Mn+Cr≤4.3wt.%, the microstructure of the high weathering steel includes ferrite, bainite, and pearlite, wherein the volume percentage of ferrite is 62%–71%, the volume percentage of bainite is 20%–35%, and the remainder is pearlite; the yield strength of the high weathering steel ranges from 360 to 440 MPa, the yield ratio ranges from 0.68 to 0.75, and the elongation after fracture is 20.5%–25.0%.

[0024] 4. The high weathering steel designed in this invention uses relatively inexpensive and readily available alloy raw materials and has a simple preparation process with mild conditions. Existing equipment can meet the experimental requirements. The smelting difficulty is significantly reduced compared to existing crevice corrosion resistant weathering steels, resulting in a substantial reduction in economic costs. It is suitable for large-scale production and widespread application.

[0025] 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

[0026] 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.

[0027] Figure 1 This is a microstructure diagram of the high weathering steel in Example 1;

[0028] Figure 2 This is a microstructure diagram of the high weathering steel in Example 2;

[0029] Figure 3 The tensile curve of the high weathering steel in Example 3;

[0030] Figure 4 This is a microstructure diagram of the high weathering steel in Example 4;

[0031] Figure 5 The image shows the microstructure of the alloy steel in Comparative Example 1.

[0032] Figure 6 A comparison diagram of uniform corrosion rates for Example 1, Example 5 and Comparative Example 1;

[0033] Figure 7 This is a topographic image of the area near the crevice corrosion crack in the high weathering steel sample of Example 3;

[0034] Figure 8 This is a topographic image of the area near the crevice corrosion crack in the high weathering steel sample of Example 6;

[0035] Figure 9 This is a morphology image of the area near the crevice corrosion in the alloy steel sample of Comparative Example 2. Detailed Implementation

[0036] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application 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.

[0037] This invention provides a Cr-Cu-Mo-Sb series high weathering steel, wherein the components of the high weathering steel are as follows by mass percentage: C: 0.055-0.080%, Si: 0.23-0.50%, Mn: 0.1-0.8%, Cr: 0.5-3.5%, Cu: 0.18-0.32%, Mo: 0.07-0.35%, Sb: 0.06-0.12%, with the balance being Fe and unavoidable impurities.

[0038] Specifically, the basis for determining the effects / synergistic effects and content of each component is as follows:

[0039] C: Carbon is one of the key elements affecting the strength, toughness, and weldability of weathering steel. A low carbon content design ensures high toughness and low sensitivity to weld cracking in weathering steel, improving its service safety factor. However, when the carbon content is below 0.05 wt%, the smelting difficulty gradually increases, raising smelting costs. Therefore, the carbon content range of this invention is 0.055–0.080 wt.%.

[0040] Si: Silicon is mainly used for deoxidation and to ensure the strength and hardness of steel. An appropriate amount of silicon can also improve the corrosion resistance of steel. The copper content in this invention ranges from 0.23 to 0.50 wt.%.

[0041] Mn: Manganese plays a deoxidizing and desulfurizing role in steel, while also improving its strength and toughness. However, excessive manganese content can easily lead to defects such as macroscopic segregation and deteriorate the weldability of weathering steel. The manganese content in this invention ranges from 0.1 to 0.8 wt.%.

[0042] Cr: Adding Cr to weathering steel can form a dense Cr2O3 oxide film. Furthermore, Cr can form more stable products such as α-(Fe,Cr)OOH or FeCr2O4, significantly improving the corrosion resistance of the steel. However, excessive chromium content can lead to deterioration of weldability and increased alloy costs. In addition, excessive chromium content makes it prone to hydrolysis in a chloride ion environment, which is detrimental to improving crevice corrosion resistance. In this invention, the chromium content ranges from 0.5 to 3.5 wt.%, and it is designed to be matched with Mo and Sb to synergistically improve corrosion resistance.

[0043] Cu: Adding Cu to weathering steel helps form a dense oxide layer of Cu₂O or CuFeO₂ on the steel surface, preventing further contact between the corrosive medium and the substrate. Therefore, the addition of copper can enhance the atmospheric corrosion resistance and crevice corrosion resistance of weathering steel. However, excessively high Cu content can easily lead to "copper embrittlement" defects on the surface of weathering steel, affecting its surface quality. The copper content in this invention ranges from 0.18 to 0.32 wt.%.

[0044] Mo: Molybdenum is an important element for enhancing the corrosion resistance of steel, especially in chloride-containing environments, where it effectively improves the weather resistance of steel. However, Mo is expensive, and adding too much significantly increases the cost of steel. The copper content in this invention ranges from 0.07 to 0.35 wt.%.

[0045] Sb: The addition of antimony can improve the corrosion resistance of steel. Antimony can form a protective Sb₂O₅ oxide film on the surface, reducing the corrosion rate of the steel. Furthermore, antimony can synergistically interact with copper in the steel; sufficient Sb can form a Cu₂Sb complex with Cu, which deposits on the steel surface, further enhancing corrosion resistance. However, the addition of antimony will adversely affect weldability and increase the ductile-brittle transition temperature of the steel. In this invention, the antimony content is controlled at 0.06–0.12 wt.%.

[0046] Synergistic effect: The Cr-Cu alloy design aims to form a dense oxide film of Cr2O3 and Cu2O on the steel surface, ensuring uniform corrosion resistance. Simultaneously, it considers the increasing chloride ion concentration during crevice corrosion development, which increases the risk of corrosion damage and the presence of Cr in the rust layer. 3+The increased likelihood of ion hydrolysis under high chloride conditions lowers the pH value of the corresponding area, thus accelerating the corrosion process. Therefore, a Mo-Sb composite additive was designed. On one hand, the addition of Mo and Sb respectively generates dense oxides, jointly strengthening the protective film on the surface, making it more dense and stable, thereby effectively resisting the intrusion of corrosive media. On the other hand, when Cu and Sb coexist, sufficient Sb can form a complex Cu2Sb with Cu, which deposits on the steel surface, hindering chloride ion invasion and further improving crevice corrosion resistance. Therefore, (Cr-Cu)+(Mo-Sb) not only ensures uniform corrosion performance but also improves crevice corrosion resistance.

[0047] In one possible design, 0.5 wt.% ≤ Cr < 1.5 wt.%, 0.15 wt.% ≤ Mo + Sb < 0.3 wt.%, and 0.9 wt.% ≤ Mn + Cr ≤ 1.9 wt.%.

[0048] Specifically, the microstructure of the high weathering steel comprises ferrite and pearlite, wherein the volume percentage of ferrite is 63%–76% and the volume percentage of pearlite is 24%–37%. The high weathering steel has a yield strength ranging from 250 to 360 MPa, a yield strength ratio ranging from 0.76 to 0.82, and an elongation after fracture ranging from 25.5% to 31.0%.

[0049] It should be noted that when the corrosive medium in the service environment is relatively weak, and the requirements for the steel's strength level are low while the requirements for plasticity are high, a lower Cr content is chosen in the design to consider alloy cost, along with lower Mo+Sb and Mn+Cr contents. From a corrosion resistance perspective, the addition of Cr and Cu ensures uniform corrosion resistance in this environment; the combined addition of Mo and Sb, with Mo and Sb respectively generating dense oxides, strengthens the protective film on the surface, making it denser and more stable, thus effectively resisting the intrusion of corrosive media. From a mechanical property perspective, both Mn and Cr elements improve the hardenability of steel. When the Mn and Cr content is high, bainite with higher hardness is easily formed in the steel, resulting in increased strength but decreased plasticity. Therefore, a lower Mn and Cr content is chosen to obtain a microstructure dominated by pearlite and ferrite, achieving high elongation.

[0050] In another possible design, where 1.5 wt.% ≤ Cr ≤ 3.5 wt.%, 0.3 wt.% ≤ Mo + Sb ≤ 0.45 wt.%, and 1.9 wt.% ≤ Mn + Cr ≤ 4.3 wt.%.

[0051] Specifically, the microstructure of the high weathering steel comprises ferrite, bainite, and pearlite, wherein the volume percentage of ferrite is 62%–71%, the volume percentage of bainite is 20%–35%, and the remainder is pearlite. The high weathering steel has a yield strength ranging from 360 to 440 MPa, a yield-to-tensile strength ratio ranging from 0.68 to 0.75, and an elongation after fracture of 20.5%–25.0%.

[0052] It should be noted that when the corrosive medium in the service environment is strong and the strength requirements of the steel are high, the Cr content needs to be increased to improve the resistance to uniform corrosion. Increased Cr content increases the risk of hydrolytic damage to the rust layer of weathering steel, thus adversely affecting its resistance to crevice corrosion. To compensate for the decrease in rust layer stability, the Mo and Sb contents should be appropriately increased. On the one hand, the addition of Mo and Sb can enhance the density and stability of the rust layer, respectively; on the other hand, when Cu and Sb coexist, sufficient Sb can form a complex Cu2Sb with Cu, which deposits on the steel surface, hindering chloride ion invasion and further improving crevice corrosion resistance. Furthermore, when the strength requirements of the steel are increased, the Mn+Cr content needs to be increased to obtain a harder bainitic structure during the cooling process to room temperature after rolling.

[0053] Specifically, the high weathering steel was subjected to a crevice corrosion test according to GB / T 10127-2002. The corrosion solution was FeCl3 solution, the corrosion time was 3 hours, and the corrosion depth in the crevice was 10-32 μm.

[0054] The present invention also discloses a method for preparing the high weathering steel, comprising the following steps: smelting, continuous casting, rolling, and cooling;

[0055] The heating temperature during the rolling process is 1150℃~1250℃, the number of rolling passes is 4~6, the final rolling temperature is ≥850℃, and the thickness of the steel plate after the last rolling pass is 4~6mm.

[0056] It should be noted that when the heating temperature exceeds 1250℃, it leads to abnormal growth of the original austenite grain size, resulting in austenite grain coarsening and deteriorating the properties of weathering steel. When the heating temperature is below 1150℃, the temperature drops rapidly during subsequent rolling, causing the final rolling temperature to be lower than the design requirements. When the final rolling temperature is below 850℃, the weathering steel will deform after a phase transformation, reducing its plasticity and toughness. Similarly, the number of rolling passes should not be excessive, otherwise the final rolling temperature will be lower than the design requirements.

[0057] Furthermore, the cooling step is air cooling, with a cooling rate of 0.25–2 °C / s.

[0058] It should be noted that the steel plate thickness after the last rolling pass is relatively thin, ranging from 4 to 6 mm. When air cooling is used, the cooling rate meets the requirements for microstructure transformation. Moreover, the air cooling rate is relatively slow, which is conducive to uniform cooling of different parts of the steel plate, thereby ensuring the uniformity of the microstructure. In addition, the processing technology is simple. When rapid cooling such as water cooling is used, the requirements for the cooling device are higher.

[0059] Examples and Comparative Examples

[0060] This invention employs different component ratios to design embodiments and comparative examples to illustrate the technical effects of the invention. The specific components of each embodiment and comparative example are shown in Table 1.

[0061] Table 1. Chemical composition of high weathering steel / alloy steel in each embodiment and comparative example.

[0062]

[0063] The preparation process includes smelting, continuous casting, rolling, and cooling, with specific parameters as follows:

[0064] Example 1:

[0065] The smelting process yields a billet, which is heated to 1200℃ and rolled at a final rolling temperature of 887℃. After six rolling passes, the billet is air-cooled to room temperature, resulting in a steel plate thickness of 4mm. The cooling process is air cooling at a rate of 1.8℃ / s.

[0066] Example 2: A billet was obtained by smelting. The billet was heated to 1250°C and rolled to 889°C. After rolling for 4 passes, it was air-cooled to room temperature. The thickness of the steel plate was 5 mm. The cooling step was air cooling, and the cooling rate was 1.3°C / s.

[0067] Example 3: A billet was obtained by smelting. The billet was heated to 1230°C and rolled to 882°C. After rolling for 4 passes, it was air-cooled to room temperature. The thickness of the steel plate was 6 mm. The cooling step was air cooling, and the cooling rate was 0.3°C / s.

[0068] Example 4: A billet was obtained by smelting. The billet was heated to 1150°C and rolled to 882°C. After rolling 5 times, it was air-cooled to room temperature. The thickness of the steel plate was 4 mm. The cooling step was air cooling at a rate of 1.5°C / s.

[0069] Example 5: A billet was obtained by smelting. The billet was heated to 1180°C and rolled to 885°C. After rolling for 4 passes, it was air-cooled to room temperature. The thickness of the steel plate was 5 mm. The cooling step was air cooling, and the cooling rate was 1.3°C / s.

[0070] Example 6: A billet was obtained by smelting. The billet was heated to 1160°C and rolled to 889°C. After rolling 5 times, it was air-cooled to room temperature. The thickness of the steel plate was 4 mm. The cooling step was air cooling, and the cooling rate was 1.5°C / s.

[0071] The preparation process and specific parameters of Comparative Example 1 are the same as those of Example 1; the preparation process and specific parameters of Comparative Example 2 are the same as those of Example 3.

[0072] The microstructure and mechanical properties of each embodiment and comparative example were characterized, and the results are shown in Table 2.

[0073] Table 2. Microstructure and mechanical properties of each embodiment and comparative example.

[0074]

[0075]

[0076] Accelerated atmospheric corrosion tests were conducted on Example 1 and Comparative Example 1 according to TB / T 2375-1993, "Test Method for Cyclic Immersion Corrosion of Weathering Steel for Railways".

[0077] Experimental steel measuring 60mm × 40mm × 3mm was periodically immersed in a 0.01mol / L NaHSO3 solution at a temperature of 45±2℃. Each cycle lasted 60 minutes, including a 12-minute immersion time. The experimental cycles were conducted for 3 and 7 days. The corrosion comparison results between Example 1 and Comparative Example 1 are as follows: Figure 6 As shown. After 3 days of corrosion, the corrosion rates of Example 1 and Comparative Example 1 were 1.513 g / m³, respectively. 2 ·h and 3.021g / m 2 • h; After 7 days of corrosion, the corrosion rates of Example 1 and Comparative Example 1 were 1.131 g / m. 2 ·h and 2.446g / m 2 •h. The example exhibits better resistance to uniform corrosion than the comparative example.

[0078] Crevice corrosion tests were conducted on Examples 3, 6, and Comparative Example 2 in accordance with GB / T 10127-2002 "Test Method for Crevice Corrosion of Stainless Steel with Ferric Chloride".

[0079] The corrosion solution was FeCl3 solution, and the corrosion time was 3 hours. The morphology and depth of the corrosion pits near the crevice after crevice corrosion in Examples 3, 6, and Comparative Example 2 are statistically shown below. Figure 7 , Figure 8 and Figure 9 As shown, the corrosion depth at the crevice of the samples in Examples 3 and 6 was relatively shallow, with a depth of 10–20 μm in Example 3 and 23–32 μm in Example 6. In Comparative Example 2, the corrosion at the crevice was more severe, with a crevice corrosion depth of 45–76 μm. The crevice corrosion resistance of the Examples was superior to that of the Comparative Example.

[0080] In summary, the high weathering steel exhibits excellent resistance to uniform corrosion and crevice corrosion, with a high degree of strength-toughness matching. Its yield strength ranges from 250 to 440 MPa, the yield-to-tensile ratio ranges from 0.68 to 0.82, and the elongation after fracture ranges from 20.5% to 31.0%. Compared to existing crevice corrosion-resistant weathering steels, its overall performance is significantly improved, meeting the requirements for use under harsh conditions.

[0081] 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 Cr-Cu-Mo-Sb series high weathering steel resistant to crevice corrosion, characterized in that, The components of the high weathering steel, by mass percentage, are: C: 0.055–0.071%, Si: 0.23–0.50%, Mn: 0.1–0.8%, Cr: 1.32–3.5%, Cu: 0.24–0.32%, Mo: 0.17–0.35%, Sb: 0.06–0.12%, with the balance being Fe and unavoidable impurities; The high weather-resistant steel adopts a C+(Cr-Cu)+(Mo-Sb) alloy design. The Cr-Cu alloy design enables the formation of a dense oxide film of Cr2O3 and Cu2O on the surface of the steel. The addition of Mo-Sb composite generates dense oxides respectively. Sb and Cu form a complex Cu2Sb, which is deposited on the steel surface and prevents the invasion of chloride ions with continuously increasing concentration during the development of crevice corrosion. The high weathering steel was subjected to a crevice corrosion test according to GB / T 10127-2002. The corrosion solution was FeCl3 solution, the corrosion time was 3 hours, and the corrosion depth in the crevice was 10-32 μm.

2. The high weathering steel according to claim 1, characterized in that, Among them, 1.32 wt.% ≤ Cr < 1.5 wt.%, 0.23 wt.% ≤ Mo + Sb < 0.3 wt.%, and 1.42 wt.% ≤ Mn + Cr ≤ 1.9 wt.%.

3. The high weathering steel according to claim 2, characterized in that, The microstructure of the high weathering steel includes ferrite and pearlite, wherein the volume percentage of ferrite is 63% to 76% and the volume percentage of pearlite is 24% to 37%.

4. The high weathering steel according to claim 2, characterized in that, The high weathering steel has a yield strength range of 250–360 MPa, a yield strength ratio range of 0.76–0.82, and an elongation after fracture of 25.5–31.0%.

5. The high weathering steel according to claim 1, characterized in that, Among them, 1.5 wt.% ≤ Cr ≤ 3.5 wt.%, 0.3 wt.% ≤ Mo + Sb ≤ 0.45 wt.%, and 1.9 wt.% ≤ Mn + Cr ≤ 4.3 wt.%. The microstructure of the high weathering steel includes ferrite, bainite and pearlite, wherein the volume percentage of ferrite is 62% to 67%, the volume percentage of bainite is 20% to 26%, and the remainder is pearlite; The high weathering steel has a yield strength range of 360–440 MPa, a yield strength ratio range of 0.68–0.75, and an elongation after fracture of 20.5–25.0%. The preparation method of the high weathering steel includes the following steps: smelting, continuous casting, rolling, and cooling; The heating temperature during the rolling process is 1150℃~1250℃, the number of rolling passes is 4~6, the final rolling temperature is ≥882℃, and the thickness of the steel plate after the last rolling pass is 4~6mm. The cooling step is air cooling, with a cooling rate of 0.25–2 °C / s.

6. A method for preparing the high weathering steel according to any one of claims 1 to 4, characterized in that, Includes the following steps: Smelting, continuous casting, rolling, cooling; The heating temperature during the rolling process is 1150℃~1250℃, the number of rolling passes is 4~6, the final rolling temperature is ≥850℃, and the thickness of the steel plate after the last rolling pass is 4~6mm.

7. The preparation method according to claim 6, characterized in that, The cooling step is air cooling, with a cooling rate of 0.25–2 °C / s.

Images