A weathering resistant steel and a method for manufacturing and using the same

Abstract

This application relates to a weathering steel, its preparation method, and its application, belonging to the field of steel preparation technology. The chemical composition of the steel includes C 0.030-0.050%; Si ≤0.10%; Mn 1.25-1.70%; P ≤0.020%; S ≤0.003%; Al 0.02-0.05%; Nb 0.010-0.030%; Ti 0.03-0.07%; Ni 0.02-0.05%; Cu 0.2-0.5%; Cr 0.8-1.5%; N ≤0.0040%; Ca 0.001-0.004%. It adopts a reasonable ratio of weathering-resistant elements such as copper, chromium, and nickel added on a low-carbon, low-silicon, and low-manganese basis. The combination of Cu and Cr can form a dense α-FeOOH oxide rust layer on the surface of the steel, preventing further corrosion of the steel matrix.

Description

Technical Field

[0001] This application relates to the field of steel preparation, and more particularly to a weathering steel, its preparation method, and its application. Background Technology

[0002] Weathering steel, also known as atmospheric corrosion resistant steel, is a low-alloy steel series that falls between ordinary steel and stainless steel. It is smelted from ordinary carbon steel with the addition of small amounts of corrosion-resistant elements such as copper and nickel. It possesses the strength, toughness, ductility, formability, weldability, abrasion resistance, high-temperature resistance, and fatigue resistance of high-quality steel. Weathering steel, which uses rust to stop rust, has 2 to 8 times the weather resistance of ordinary carbon steel, and its corrosion resistance becomes more pronounced with longer service life. Due to its excellent corrosion resistance, weathering steel is widely used in steel structures such as railways, vehicles, and bridges that are exposed to the atmosphere for extended periods.

[0003] Solar photovoltaic (PV) brackets are specialized supports designed for placing, installing, and securing solar panels in a solar photovoltaic power generation system. Currently, the most commonly used solar PV brackets in my country are primarily made of three materials: concrete, steel, and aluminum alloy. Concrete brackets are mainly used in large-scale PV power plants, placed outdoors to support massive solar panels. Aluminum alloy brackets are generally used in rooftop solar applications on residential buildings. Aluminum alloys are corrosion-resistant, lightweight, aesthetically pleasing, and durable; however, their price is slightly higher than hot-dip galvanized steel. Steel brackets offer stable performance, mature manufacturing processes, high load-bearing capacity, and easy installation, making them widely used in residential and industrial solar PV and solar power plants. Steel brackets are typically made of carbon steel with a hot-dip galvanized surface treatment, ensuring rust-free outdoor use for 30 years. To meet environmental protection requirements, traditional PV brackets are facing challenges such as high galvanizing costs and long lead times. During the PV boom, the number of galvanizing plants decreased dramatically, and galvanizing costs continued to rise, significantly increasing material costs for bracket manufacturers and compromising the timely supply of qualified brackets.

[0004] It is evident that, in existing technologies, aluminum alloys are expensive, and hot-dip galvanizing of plain carbon steel not only generates large amounts of wastewater and waste acid during production, causing environmental pollution, but also has disadvantages such as long production processes, high prices of raw material zinc, lower strength levels, thicker specifications, and poor low-temperature toughness and fatigue resistance. Summary of the Invention

[0005] This application provides a weathering steel, its preparation method, and its application to replace galvanized steel as a solar photovoltaic support, thereby solving the environmental pollution caused by galvanized steel.

[0006] In one aspect, this application provides a weathering steel.

[0007] Specifically, the chemical composition of the steel, expressed as a mass fraction, includes:

[0008] C: 0.030%-0.050%; Si: ≤0.10%; Mn: 1.25%-1.70%; P: ≤0.020%; S: ≤0.003%;

[0009] Al: 0.02%-0.05%; Nb: 0.010%-0.030%; Ti: 0.03%-0.07%; Ni: 0.02%-0.05%; Cu: 0.2%-0.5%; Cr: 0.8%-1.5%; N: ≤0.0040%; Ca: 0.001%-0.004%; the remainder is Fe and unavoidable impurities.

[0010] As an optional implementation, the chemical composition of the steel, by mass fraction, includes:

[0011] C: 0.035%-0.045%; Si: ≤0.10%; Mn: 1.4%-1.55%; P: ≤0.020%; S: ≤0.003%;

[0012] Al: 0.03%-0.04%; Nb: 0.015%-0.025%; Ti: 0.04%-0.06%; Ni: 0.03%-0.04%; Cu: 0.3%-0.4%; Cr: 1.0%-1.3%; N: ≤0.0040%; Ca: 0.002%-0.003%; the remainder is Fe and unavoidable impurities.

[0013] As an optional implementation, the mass ratio of Ca to S in the steel is 1.5-3.5.

[0014] As an alternative implementation, the microstructure of the steel comprises ferrite and pearlite, wherein nanoscale precipitates are dispersed in the ferrite.

[0015] As an optional implementation, the weather resistance index I of the steel is ≥6.0%, the yield strength of the steel is ≥600MPa, the tensile strength of the steel is ≥700MPa, the elongation at break of the steel is ≥23%, and the impact energy of the steel at -40℃ is ≥47J.

[0016] Secondly, this application provides a method for preparing weathering steel to achieve the preparation of weathering steel as described in any embodiment of the first aspect.

[0017] Specifically, the method includes:

[0018] Heating and holding the continuously cast slab at the desired temperature;

[0019] The continuously cast slab, after being heated and held at a certain temperature, is subjected to rough rolling to obtain an intermediate slab.

[0020] The intermediate slab is precision rolled to obtain strip steel;

[0021] The strip is subjected to laminar flow cooling and coiling to obtain a hot-rolled steel coil;

[0022] The hot-rolled steel coil is slowly cooled to obtain weathering steel.

[0023] As an optional implementation, the continuous casting slab reaches a heating endpoint temperature of 1220-1260℃; and / or

[0024] The heat preservation time is 2.0-2.5 hours.

[0025] As an optional implementation, the exit temperature of the roughing mill is 1050-1090°C; and / or

[0026] The exit temperature of the finishing mill is 830-930℃.

[0027] As an optional implementation, the winding temperature is 600-660°C.

[0028] Thirdly, this application provides a component for implementing the application of weathering steel as described in any embodiment of the first aspect.

[0029] The technical solutions provided in this application have the following advantages compared with the prior art:

[0030] The weathering steel provided in this application adopts a low-carbon, low-silicon, and low-manganese base with a reasonable ratio of added weathering elements such as copper, chromium, and nickel. The combined use of Cu and Cr can form a dense α-FeOOH oxide rust layer on the surface of the steel, preventing further corrosion of the steel matrix. However, the addition of Cu can easily lead to copper embrittlement defects. Therefore, in order to suppress copper embrittlement defects, a certain amount of Ni element is added, which gives the steel excellent cold formability, weldability, fatigue performance, and weather resistance. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 Metallographic images of steel provided for embodiments of this application;

[0034] Figure 2 A flowchart illustrating the method provided in an embodiment of this application. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0037] This application provides a weathering steel, the chemical composition of which, by mass fraction, includes:

[0038] C: 0.030%-0.050%; Si: ≤0.10%; Mn: 1.25%-1.70%; P: ≤0.020%; S: ≤0.003%; Al: 0.02%-0.05%; Nb: 0.010%-0.030%; Ti: 0.03%-0.07%; Ni: 0.02%-0.05%; Cu: 0.2%-0.5%; Cr: 0.8%-1.5%; N: ≤0.0040%; Ca: 0.001%-0.004%; the remainder is Fe and unavoidable impurities.

[0039] The design principles of each chemical element are as follows:

[0040] Carbon (C) is one of the most economical strengthening elements in steel and is essential for ensuring strip strength; this effect is significant when the C content is above 0.03%. On the other hand, higher C content leads to the formation of more coarse tertiary cementite and promotes the transformation of pearlite, resulting in increased inhomogeneity of the steel matrix, which is detrimental to corrosion resistance and reduces the cold formability, low-temperature toughness, and weldability of the strip. Therefore, considering the material's strength, cold formability, weldability, and corrosion resistance, the C content in the steel of this embodiment is controlled at 0.03%-0.05%.

[0041] Si is a solid solution strengthening element. In this embodiment, the main strengthening mechanisms are precipitation strengthening and grain refinement strengthening. The magnitude of Si solid solution strengthening has little impact on strength. However, a high Si content will affect the surface quality of the strip and is also detrimental to the strip's ductility, toughness, and weldability. Therefore, considering all factors, the Si content in the steel in this embodiment is controlled at 0%-0.10%.

[0042] Mn is a solid solution strengthening element that contributes to increased steel strength, influences the interaction between carbon and dislocations, hinders dislocation movement, suppresses the initiation of initial fatigue cracks, and improves fatigue characteristics. To achieve this effect, the Mn content must be ≥1.25%. On the other hand, excessively high Mn content can lead to severe banded microstructure, reducing transverse elongation and affecting cold formability. In particular, when the Mn content exceeds 1.70%, it inhibits ferrite phase transformation, failing to ensure the desired microstructure and excellent formability. Therefore, considering the material's strength, toughness, weldability, and cold formability, this embodiment designs the Mn content to be 1.25%-1.70%.

[0043] P and S are impurity elements in steel. P easily causes center segregation in steel, worsening its weldability and ductility, so it is preferable to minimize its content. S readily forms MnS inclusions with Mn, which reduces the weldability, formability, fatigue performance, and low-temperature toughness of the steel, so it is also preferable to minimize its content. Therefore, considering both the weldability and ductility of the material, the P content in the steel of this embodiment is controlled to ≤0.020%, and the S content is controlled to ≤0.003%.

[0044] Al acts as a deoxidizer during steelmaking and combines with nitrogen (N) in the steel to inhibit austenite grain growth and refine recrystallized grains during hot rolling. The steel grade of this invention requires good cold formability during roll forming. Incomplete deoxidation will lead to a decrease in the material's cold formability. To meet the requirements for steel sheet formability and to obtain a ferrite grain size of approximately 5 μm, the Al content should be ≥0.02%. However, excessive Al content will result in too many AlN inclusions in the steel, reducing the material's elongation and fatigue resistance. Therefore, considering deoxidation, grain size, and inclusion control, the Al content in this embodiment is controlled between 0.02% and 0.05%.

[0045] In steel, Nb and Ti combine with C to form (Nb, Ti) composite carbides, which precipitate out and inhibit the recovery of austenite and the growth of recrystallized grains during hot rolling, thereby controlling the ferrite phase grain size to within 10 μm. Simultaneously, precipitation strengthening increases the steel's strength to over 600 MPa in yield strength. On the other hand, excessively high Nb and Ti contents significantly increase the rolling difficulty during hot rolling, and the strength increase and ductility decrease caused by carbide precipitation become significant. Therefore, considering both rolling difficulty and strengthening effect, the Nb content in the steel of this embodiment is controlled at 0.010%-0.030%, and the Ti content is controlled at 0.03%-0.07%.

[0046] Cr, Ni, and Cu are generally added to steel as corrosion-resistant elements, and usually in combination. When Cu and Cr are used in a specific ratio, they can form a dense α-FeOOH oxide rust layer on the steel surface, preventing further corrosion of the steel matrix. However, the addition of Cu easily leads to copper embrittlement defects; therefore, to suppress these defects, a certain amount of Ni is generally added. Considering production costs, the addition amounts of Ni, Cr, and Cu are as follows: Ni: 0.02%-0.05%; Cu: 0.2%-0.5%; Cr: 0.8%-1.5%.

[0047] Ca has the function of transforming extended inclusions (MnS) into granular inclusions (Ca(Al)S(O)), a process known as inclusion morphology control. This morphology control improves formability and fatigue properties. This effect is significant at Ca contents above 0.001%, but when the content exceeds 0.004%, the number of non-metallic inclusions increases, thus reducing fatigue properties. Therefore, in this embodiment, the Ca content is controlled between 0.001% and 0.004%, and the Ca / S ratio is maintained between 1.5 and 3.5.

[0048] Nitrogen (N) is an element present during the smelting process and needs to be controlled within a certain range. For steel containing Nb and Ti, a high N content can easily lead to crack defects and large TiN precipitates in the slab. Therefore, taking into account the above factors, the N content in the steel in this embodiment is controlled to be ≤0.004%.

[0049] In addition to meeting the above composition design requirements, the following relationships must also be met: the Ca / S ratio is controlled between 1.5 and 3.5; the strip steel has a yield strength ≥ 600 MPa, tensile strength ≥ 700 MPa, elongation at break ≥ 23%, impact energy at -40℃ ≥ 47 J, and a corrosion rate ≤ 30% relative to ordinary structural steel Q345B. To ensure the corrosion resistance of the strip steel, the corrosion resistance index is limited, with a weathering index I ≥ 6.0%. According to ASTM G 101 standard, the formula for evaluating the atmospheric corrosion resistance of low alloy steel is I = 26.01 (% Cu) + 3.88 (% Ni) + 1.20 (% Cr) + 1.49 (% Si) + 17.28 (% P) - 7.29 (% Cu) * (% Ni) - 9.10 (% Ni) - 33.39 (% Cu). 2 .

[0050] The microstructure of weathering steel is ferrite + pearlite; the ferrite grain size is mainly between 3-10 μm, accounting for up to 95%. The ferrite contains nanoscale precipitates, which are mainly precipitates with a particle size distribution of 1-10 nm, and the proportion of nanoscale precipitates is greater than or equal to 80%.

[0051] Generally speaking, the thickness of weathering steel is 1.5-8.0 mm.

[0052] Preferably, the chemical composition of the steel, by mass fraction, includes:

[0053] C: 0.035%-0.045%; Si: ≤0.10%; Mn: 1.4%-1.55%; P: ≤0.020%; S: ≤0.003%; Al: 0.03%-0.04%; Nb: 0.015%-0.025%; Ti: 0.04%-0.06%; Ni: 0.03%-0.04%; Cu: 0.3%-0.4%; Cr: 1.0%-1.3%; N: ≤0.0040%; Ca: 0.002%-0.003%; the remainder is Fe and unavoidable impurities.

[0054] like Figure 2 As shown, based on a general inventive concept, this application also provides a method for preparing weathering steel.

[0055] The method for preparing weathering steel is used to prepare the aforementioned weathering steel. The limitations of the weathering steel can be referred to in the above embodiments. Since the method for preparing weathering steel adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0056] The entire preparation process is as follows: smelting → continuous casting → heating of continuously cast billet → rough descaling → fixed width press → rough rolling → plate coil box → flying shear → fine descaling → fine rolling → laminar flow cooling → coiling into steel coils. This embodiment mainly includes the following improved steps:

[0057] S1. Heating and holding the continuously cast slab at the desired temperature;

[0058] Specifically, the continuously cast slab is heated and held at that temperature; after heating, the temperature of the continuously cast slab is 1220–1260°C; and the holding time is 2.0–2.5 hours.

[0059] S2. The continuously cast slab after heating and heat preservation is rough rolled to obtain an intermediate slab;

[0060] Specifically, the heated continuous casting slab is subjected to rough descaling to remove iron oxide scale from the surface of the strip steel. The descaled continuous casting slab is then rough rolled to obtain an intermediate slab. The rough rolling mode is 1+5, with four descaling passes (1, 2, 3, and 5) initiated. The exit temperature of the rough rolling is 1050–1090℃. The thickness of the intermediate slab is 34–44 mm.

[0061] S3. The intermediate slab is precision rolled to obtain strip steel;

[0062] Specifically, the intermediate slab is descaled under a pressure greater than 18 MPa, and the descaled intermediate slab is then finished rolled to obtain strip steel. The single-pass reduction rate of F1 and F2 in the finishing rolling stage is greater than 40%, and the rolling reduction rate of the last stand is less than 10%. The temperature of the strip steel after the finishing rolling is 830-930°C.

[0063] S4. The strip is subjected to laminar flow cooling and coiling to obtain a hot-rolled steel coil;

[0064] Specifically, the strip steel is subjected to laminar flow cooling; the laminar flow cooling adopts a sparse cooling pattern of 2 sections above and 4 sections below, plus a U-shaped cooling mode; the laminar flow cooled strip steel is then coiled to obtain a hot-rolled steel coil, and the coiling temperature is 600–660℃.

[0065] S5. The hot-rolled steel coil is slowly cooled to obtain weathering steel.

[0066] Specifically, the hot-rolled steel coil is slowly cooled to room temperature to obtain weathering steel.

[0067] By adopting the above design, and by using a reasonable ratio of weather-resistant elements such as copper, chromium, and nickel added to a low-carbon, low-silicon, and low-manganese base, combined with a hot rolling process of high-temperature extrusion, high-temperature final rolling, and high-temperature coiling, hot-rolled strip steel with excellent cold formability, weldability, fatigue performance, and weather resistance is obtained. This ensures that the steel for photovoltaic brackets does not exhibit defects such as forming cracks, oxide scale peeling, and welding cracks during processing, and that it has excellent strength, fatigue performance, low-temperature toughness, and corrosion resistance during use, thus meeting the requirements for structural stability and long service life of the steel for photovoltaic brackets. Through the above-mentioned product composition and process design, the shortcomings of existing technologies, such as the high price of aluminum alloys and the environmental pollution, high price, thick specifications, poor low-temperature toughness and fatigue of hot-dip galvanized carbon steel, are effectively solved. The technology achieves a strip steel yield strength of over 600MPa, tensile strength of over 700MPa, elongation of over 23%, impact energy of ≥47J at -40℃, and a corrosion rate of ≤30% compared to ordinary structural steel Q345B. This technology meets the processing and performance requirements of photovoltaic bracket steel and sets a precedent for the application of high-strength, high-weather-resistant steel in the field of photovoltaic brackets.

[0068] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0069] Examples 1-3

[0070] A method for preparing weathering steel, the method comprising:

[0071] (1) Smelting and continuous casting: Steel is smelted according to the set composition and cast into billets. The chemical elements in each embodiment are shown in the table below by mass percentage:

[0072]

[0073] (2) Slab heating: The continuous casting slab is heated and held at 1220℃~1260℃ for 2.0h-2.5h to fully austenitize and ensure the dissolution of microalloying elements.

[0074] (3) Hot rolling: The roughing rolling adopts the 1+5 mode rolling process. R1 is descaling in one pass, and R2 is descaling in 1, 2, 3 and 5 passes to ensure that the iron oxide scale on the surface of the intermediate billet is completely removed. The exit temperature of the roughing rolling is 1050~1090℃; the thickness of the intermediate billet in the roughing rolling is 34~44mm; the plate coil box is used to reduce the temperature drop of the intermediate billet and reduce the temperature difference between the head and tail; before finishing rolling, high pressure water above 18MPa is used for descaling to completely remove the iron oxide scale on the surface of the strip steel; in the finishing rolling process, the load distribution strategy of each stand adopts the method of decreasing F1~F7 in sequence. The single pass reduction rate of F1 and F2 is greater than 40%, and the reduction rate of F7 is not more than 10%; the finishing rolling end temperature is 830~930℃.

[0075] (4) Laminar flow cooling: adopts a sparse cooling mode of 2 on top and 4 on the bottom + U-shaped cooling mode, the body winding temperature is 600~660℃, and the head and tail are weakly cooled by 30-50℃.

[0076] The process parameters for each embodiment are controlled as follows:

[0077]

[0078]

[0079] Comparative Examples 1-2

[0080] A method for preparing weathering steel, the method comprising:

[0081] (1) Smelting and continuous casting: Steel is smelted according to the set composition and cast into billets. The chemical elements in each embodiment are shown in the table below by mass percentage:

[0082]

[0083] (2) Slab heating: The continuously cast slab is heated and held for 2.0h-2.5h to fully austenitize and ensure the redissolution of microalloying elements.

[0084] (3) Hot rolling: The roughing rolling adopts the 1+5 mode rolling process. R1 is descaling in one pass, and R2 is descaling in 1, 2, 3 and 5 passes to ensure that the iron oxide scale on the surface of the intermediate billet is completely removed. The exit temperature of the roughing rolling is 1050~1090℃; the thickness of the intermediate billet in the roughing rolling is 34~44mm; the plate coil box is used to reduce the temperature drop of the intermediate billet and reduce the temperature difference between the head and tail; before finishing rolling, high pressure water above 18MPa is used for descaling to completely remove the iron oxide scale on the surface of the strip steel; in the finishing rolling process, the load distribution strategy of each stand adopts the method of decreasing F1~F7 in sequence. The single pass reduction rate of F1 and F2 is greater than 40%, and the reduction rate of F7 is not more than 10%; the finishing rolling end temperature is 830~930℃.

[0085] (4) Laminar flow cooling: adopts a sparse cooling mode of 4 on top and 4 on the bottom + U-shaped cooling mode.

[0086] The process parameters for each embodiment are controlled as follows:

[0087]

[0088]

[0089] Relevant experimental and effect data:

[0090] The steels provided in Examples 1-3 and Comparative Examples 1-2 were subjected to mechanical property tests, and the results are shown in the table below:

[0091]

[0092] As shown in the table above, the weathering steel prepared using the method provided in the embodiments of this application has a yield strength greater than 600 MPa, reaching a maximum of 655 MPa; a tensile strength greater than 700 MPa, reaching a maximum of 778 MPa; and an elongation at break greater than or equal to 23.0%, reaching a maximum of 25.0%. Simultaneously, it passes the 180°d=1a cold bending test; the impact energy at half the width at -40℃ is ≥70J; and the corrosion rate relative to ordinary structural steel Q345B is ≤25%. The photovoltaic bracket steel made from this steel strip exhibits excellent cold forming performance, weldability, and corrosion resistance.

[0093] Examples 1-3 all feature a ferrite microstructure with an average grain size of 3-10 μm and an average particle size of 1-10 nm for (Nb, Ti) composite carbonitrides, with a nanoscale precipitate ratio greater than or equal to 80%. The strip surface is free of edge peeling and red iron oxide scale, and the iron oxide scale does not detach during the forming process.

[0094] As can be seen from Comparative Examples 1 and 2, Comparative Example 1, lacking the addition of microalloying corrosion-resistant elements such as Cu, Cr, and Ni, achieved a yield strength of 600 MPa, a tensile strength of 700 MPa, and an impact energy greater than 47 J at -40℃. However, its elongation was only 20%, and its corrosion resistance index was only 90%, indicating a lack of corrosion resistance. Comparative Example 2, using a commonly used photovoltaic support steel with a medium-carbon microalloying composition, suffered from insufficient addition of reinforcing elements such as Nb, Ti, and Cr. Although its elongation at break was as high as 26%, its yield strength and tensile strength were only 470 MPa and 600 MPa, respectively, indicating insufficient strength. Furthermore, its low-temperature toughness did not meet the 47 J requirement, and it also lacked atmospheric corrosion resistance.

[0095] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0096] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0097] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A weathering steel, characterized in that, The chemical composition of the steel, expressed as a mass fraction, includes: C: 0.030%-0.050%; Si: ≤0.10%; Mn: 1.25%-1.70%; P: ≤0.020%; S: ≤0.003%; Al: 0.02%-0.05%; Nb: 0.010%-0.030%; Ti: 0.03%-0.07%; Ni: 0.02%-0.05%; Cu: 0.2%-0.5%; Cr: 0.8%-1.5%; N: ≤0.0040%; Ca: 0.001%-0.004%; the remainder is Fe and unavoidable impurities. The mass ratio of Ca to S in the steel is 1.5-3.5; The microstructure of the steel includes ferrite and pearlite, and nanoscale precipitates are dispersed in the ferrite. The steel has a weather resistance index I ≥ 6.0%, a yield strength ≥ 600 MPa, a tensile strength ≥ 700 MPa, an elongation at break ≥ 23%, and an impact energy at -40℃ ≥ 47 J.

2. The weathering steel according to claim 1, characterized in that, The chemical composition of the steel, expressed as a mass fraction, includes: C: 0.035%-0.045%; Si: ≤0.10%; Mn: 1.4%-1.55%; P: ≤0.020%; S: ≤0.003%; Al: 0.03%-0.04%; Nb: 0.015%-0.025%; Ti: 0.04%-0.06%; Ni: 0.03%-0.04%; Cu: 0.3%-0.4%; Cr: 1.0%-1.3%; N: ≤0.0040%; Ca: 0.002%-0.003%; the remainder is Fe and unavoidable impurities.

3. A method for preparing weathering steel, characterized in that, The weathering steel is the weathering steel according to claim 1 or 2, and the method includes: Heating and holding the continuously cast slab at the desired temperature; The continuously cast slab, after being heated and held at a certain temperature, is subjected to rough rolling to obtain an intermediate slab. The intermediate slab is precision rolled to obtain strip steel; The strip is subjected to laminar flow cooling and coiling to obtain a hot-rolled steel coil; The hot-rolled steel coil is slowly cooled to obtain weathering steel.

4. The method for preparing weathering steel according to claim 3, characterized in that, The continuous casting slab reaches a heating endpoint temperature of 1220-1260℃; and / or The heat preservation time is 2.0-2.5 hours.

5. The method for preparing weathering steel according to claim 3, characterized in that, The exit temperature of the roughing mill is 1050-1090℃; and / or The exit temperature of the finishing mill is 830-930℃.

6. The method for preparing weathering steel according to claim 3, characterized in that, The winding temperature is 600-660℃.

7. A component, characterized in that, At least a portion of the material used to prepare the component includes the weathering steel as described in claim 1 or 2.

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