Weathering steel and preparation method and application thereof

Abstract

The invention relates to weathering steel and a preparation method and application thereof. The weathering resistant steel comprises the following chemical components in percentage by mass: 0.07%-0.09% of C, 0.30%-0.40% of Si, 0.35%-0.45% of Mn, 0.07%-0.09% of P, less than or equal to 0.008% of S, 0.25%-0.28% of Cu, 0.30%-0.40% of Cr, 0.043%-0.055% of Ti, 0.02%-0.05% of Als, less than or equal to 0.007% of N and the balance of Fe and inevitable impurities. The weather-resistant steel is free of nickel and niobium, low in manganese, low in production cost, high in yield strength, good in weather resistance, good in stability of the whole coil performance and wide in application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy steel, and in particular to a weathering steel and a preparation method and application thereof. Background Art

[0002] Alloy steel refers to an iron-carbon alloy formed by adding an appropriate amount of one or more alloying elements to ordinary carbon steel. Depending on the added elements and the appropriate processing technology, special properties such as high strength, high toughness, wear resistance, corrosion resistance, low temperature resistance, high temperature resistance, and non-magnetic properties can be obtained.

[0003] Weathering steel has good corrosion resistance and can effectively reduce resource waste and secondary environmental pollution caused by metal corrosion. At the same time, metal corrosion will significantly reduce the strength, plasticity, toughness and other properties of metal materials, shorten the service life of equipment, and there are also safety accidents caused by material failure due to severe corrosion. Therefore, weathering steel has good market development prospects.

[0004] With the upgrading and replacement of material strength in various industries, the use of 450MPa grade weathering steel has gradually increased. However, the production of traditional 450MPa grade weathering steel requires the addition of precious metals Ni, Nb and high-content Mn alloys, which is costly and uses a higher coiling temperature, which will result in poor performance stability of the entire coil. Therefore, there is an urgent need to develop a low-cost 450MPa or above weathering steel with good performance stability throughout the coil. Summary of the invention

[0005] Based on this, the present invention provides a weathering steel which is nickel-free, niobium-free, low in manganese, has low production cost, high yield strength, good weather resistance, and good stability of the performance of the entire coil. In addition, a preparation method and application of the weathering steel are provided.

[0006] The technical solution is as follows:

[0007] A weathering steel, whose chemical composition, measured by mass percentage, includes: C: 0.07%-0.09%, Si: 0.30%-0.40%, Mn: 0.35%-0.45%, P: 0.07%-0.09%, S: ≤0.008%, Cu: 0.25%-0.28%, Cr: 0.30%-0.40%, Ti: 0.043%-0.055%, Als: 0.02%-0.05%, N: ≤0.007%, and the balance is Fe and unavoidable impurities.

[0008] In one of the embodiments, the Si content of the weathering steel is 0.31% to 0.40% by mass.

[0009] In one of the embodiments, the Mn content of the weathering steel is 0.36% to 0.45% by mass.

[0010] In one of the embodiments, the P content of the weathering steel is 0.072% to 0.088% by mass.

[0011] In one of the embodiments, the S content of the weathering steel is 0.003% to 0.006% by mass.

[0012] In one of the embodiments, the Ti content of the weathering steel is 0.043% to 0.053% by mass.

[0013] In one of the embodiments, the yield strength of the weathering steel is ≥450 MPa.

[0014] In one of the embodiments, the tensile strength of the weathering steel is ≥550 MPa.

[0015] In one of the embodiments, the elongation of the weathering steel is ≥18%.

[0016] In one of the embodiments, the weathering index of the weathering steel is ≥6.0.

[0017] The present invention also provides a method for preparing the weathering steel as described above, and the technical scheme is as follows:

[0018] A method for preparing weathering steel as described above comprises the steps of heating the steel billet, rough rolling, finish rolling, cooling and coiling.

[0019] In one of the embodiments, in the step of heating the steel billet, the furnace temperature is 1180°C to 1210°C.

[0020] In one of the embodiments, in the rough rolling step, the starting rolling temperature is 1070°C to 1150°C.

[0021] In one of the embodiments, in the rough rolling step, the final rolling temperature is 1030°C to 1100°C.

[0022] In one of the embodiments, in the step of finish rolling, the starting rolling temperature is ≤1030°C.

[0023] In one of the embodiments, in the step of finish rolling, the final rolling temperature is 830°C to 860°C.

[0024] In one of the embodiments, in the cooling step, the front stage adopts a centralized cooling method.

[0025] In one of the embodiments, in the cooling step, the cooling rate is 40°C / s to 60°C / s.

[0026] In one of the embodiments, in the cooling step, the cooling time is 3s to 5s.

[0027] In one of the embodiments, in the coiling step, the coiling temperature is 510°C to 560°C.

[0028] The present invention also provides the application of the weathering steel as described above, and the technical solution is as follows:

[0029] Application of weathering steel as described above in buildings, vehicles, bridges or towers.

[0030] The present invention has at least the following beneficial effects:

[0031] The present invention provides a weathering steel with high yield strength (≥450MPa) by regulating the chemical composition of the weathering steel, especially regulating the types of elements and the percentage of their contents. At the same time, since the chemical composition of the weathering steel of the present invention does not contain precious metals such as Ni and Nb, and the Mn content is low, the alloy cost is greatly reduced. That is, the present invention ensures that the steel has good mechanical properties, corrosion resistance, processability and stability of the performance of the entire coil while also having lower costs, which is convenient for mass industrial production and market promotion and application (especially in atmospheric corrosion resistance environments).

[0032] The weathering steel preparation method of the present invention has the advantages of simple operation, high efficiency, good repeatability, green environmental protection, low energy consumption, low production cost, etc., and is suitable for industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a 500X metallographic structure diagram of the weathering steel prepared in one embodiment of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described in detail below in conjunction with specific embodiments and accompanying drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0036] Where “including,” “having,” and “comprising” are used herein, it is intended to cover a non-exclusive inclusion, and another component may also be added unless explicit limiting terms such as “only,” “consisting of,” etc. are used.

[0037] The words "preferably", "more preferably", "preferably", "better", etc. in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the statement of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention. That is, in the present invention, "preferably", "more preferably", "preferably", "better", etc. are only used to describe implementation methods or examples with better effects, but do not constitute a limitation on the scope of protection of the present invention.

[0038] In the present invention, “further”, “furthermore”, “particularly”, etc. are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present invention.

[0039] In the present invention, "at least one" means more than one, such as one, two and more than two. "Multiple" or "several" means at least two, such as two, three, etc., and "multilayer" means at least two layers, such as two layers, three layers, etc., unless otherwise clearly and specifically defined. In the description of the present invention, "several" means at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0040] When a numerical range is disclosed in the present invention, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when the range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the range can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges included therein. And only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range, and any upper limit can also be combined with any other upper limit to form an unambiguous range. In addition, each individually disclosed point or single value itself can be combined with any other point or single value as a lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0041] If not otherwise specified, all steps of the present invention may be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0042] Unless mentioned to the contrary, terms in the singular may include plural forms and should not be construed as being one in number.

[0043] The temperature parameters in the present invention, if not specifically limited, allow for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the precision range controlled by the instrument.

[0044] The weights of the relevant components mentioned in the embodiments of the present invention description may not only refer to the specific content of each component, but also indicate the weight ratio between the components. Therefore, as long as the content of the relevant components in the embodiments of the present invention description is proportionally enlarged or reduced, it is within the scope disclosed in the embodiments of the present invention description. Specifically, the weights described in the embodiments of the present invention description may be mass units known in the chemical industry such as μg, mg, g, and kg.

[0045] In the present invention, when referring to the unit of the data range, if there is a unit only after the right endpoint, it means that the units of the left endpoint and the right endpoint are the same. For example, 800-850nm means that the units of the left endpoint "800" and the right endpoint "850" are both nm (nanometers).

[0046] In the present invention, "above" or "below" both include the number itself, for example, below 1 means less than or equal to 1 (≤1), and above 1 means greater than or equal to 1 (≥1).

[0047] In the present invention, "A and B are independently selected from x, y or z" means that A and B are independent events, and event A does not affect the occurrence of event B. Therefore, when A is selected from x, B can be selected from any one of x, y or z; when A is selected from y, B can be selected from any one of x, y or z; when A is selected from z, B can be selected from any one of x, y or z.

[0048] Unless mentioned to the contrary, terms in the singular may include plural forms and should not be construed as being one in number.

[0049] The technical solution of the present invention is as follows:

[0050] A weathering steel, whose chemical composition, measured by mass percentage, includes: C: 0.07%-0.09%, Si: 0.30%-0.40%, Mn: 0.35%-0.45%, P: 0.07%-0.09%, S: ≤0.008%, Cu: 0.25%-0.28%, Cr: 0.30%-0.40%, Ti: 0.043%-0.055%, Als: 0.02%-0.05%, N: ≤0.007%, and the balance is Fe and unavoidable impurities.

[0051] Carbon (C): C is an effective economic element for improving the strength of steel. However, if the C content is too high, a brittle structure will be formed, which will reduce the low-temperature impact toughness of the alloy steel, and deteriorate the welding performance and corrosion resistance. An appropriate amount of C and Ti can form a stable nano-scale precipitate TiC. The TiC nano-scale precipitate can produce a strong precipitation strengthening effect and a fine grain strengthening effect, greatly improving the strength of the steel plate. In order to achieve a yield strength of 450MPa, a tensile strength of 550MPa and comprehensively consider the processing performance, welding performance and corrosion resistance, the present invention controls the C content in the steel to 0.07% to 0.09%. It can be understood that the amount includes but is not limited to 0.07%, 0.071%, 0.072%, 0.073%, 0.074%, 0.075%, 0.076%, 0.077%, 0.078%, 0.079%, 0.08%, 0.081%, 0.082%, 0.083%, 0.084%, 0.085%, 0.086%, 0.087%, 0.088%, 0.089% or 0.09%.

[0052] Silicon (Si): Si is dissolved in alloy steel, which can improve the strength of alloy steel and reduce the corrosion rate of steel. However, too high Si content will deteriorate the welding performance of steel and reduce the toughness of the material. Taking all factors into consideration, the Si content in weathering steel is controlled to be 0.30% to 0.40%, which can be understood to include but not limited to 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39% or 0.40%. In one embodiment, the Si content of the weathering steel is 0.31% to 0.40% by mass.

[0053] Manganese (Mn): Mn has a strong solid solution strengthening effect and an obvious fine grain effect. It can improve the strength of alloy steel and the toughness at the same time. However, too high Mn content can easily lead to the segregation of core components, which affects the processing performance and increases the alloy cost. Therefore, in order to make the steel plate have good strength and toughness, avoid the segregation of core components, and reduce the cost of alloy steel, the present invention controls the Mn content in the weathering steel to be 0.35% to 0.45%, which can be understood to include but not limited to 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.40%, 0.41%, 0.42%, 0.43%, 0.44% or 0.45%. In one embodiment, the Mn content of the weathering steel is 0.36% to 0.45% by mass.

[0054] Phosphorus (P): P can increase the corrosion resistance of alloy steel, but will deteriorate the toughness of weathering steel. Taking all factors into consideration, the P content in the weathering steel is controlled to be 0.07% to 0.09%, which may include but is not limited to 0.072%, 0.075%, 0.078%, 0.080%, 0.082%, 0.085%, 0.088% or 0.090%. In one embodiment, the P content of the weathering steel is 0.072% to 0.088% by mass.

[0055] Sulfur (S): S deteriorates the corrosion resistance, ductility and toughness of weathering steel, which is mainly due to the poor plasticity of iron sulfide formed by the combination of sulfur and iron. The present invention controls the S content in weathering steel to be ≤ 0.008%, which can be understood to include but not limited to 0, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007% or 0.008%. In one embodiment, the S content of the weathering steel is 0.003% to 0.006% by mass.

[0056] Copper (Cu): Cu is a strong and effective element for improving the corrosion resistance of steel. Cu can form a dense amorphous oxide protective layer on the surface of steel, thereby improving the corrosion resistance of steel, which is beneficial to extending the working performance and service life of weathering steel, and Cu is beneficial to improving the mechanical properties (such as strength and hardness) of alloy steel, but Cu has a low melting point and is easy to aggregate at the grain boundary during heating. If the Cu content is too high, copper brittleness will occur, resulting in crack defects in the steel plate. Comprehensive consideration, in the present invention, the Cu content in weathering steel is controlled to be 0.25% to 0.28%, which can be understood to include but not limited to 0.25%, 0.26%, 0.27% or 0.28%.

[0057] Chromium (Cr): Cr is a strong carbide-forming element, which can reduce the activity of carbon in alloy steel, improve the anti-oxidation effect of alloy steel, and form a dense passivation film on the surface of steel, thereby improving the corrosion resistance of alloy steel. Cr can significantly increase the strength and hardness of alloy steel, as well as hardenability, but can also increase the temper brittleness tendency of alloy steel, that is, an appropriate amount of Cr can improve mechanical properties, but excessive Cr will cause the toughness of alloy steel to deteriorate. Comprehensively considered, in the present invention, the Cr content in the weathering steel is controlled to be 0.30% to 0.40%, which can be understood to include but not limited to 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39% or 0.40%.

[0058] Titanium (Ti): Ti and N form TiN at high temperatures. When the slab is heated for austenitization, TiN will inhibit the growth of austenite grains. During hot rolling, Ti and C form nano-scale TiC in a lower temperature range. The fine TiC particles have significant precipitation strengthening and fine grain strengthening effects, which are beneficial to improving the strength and toughness of the steel plate. However, when the Ti content is too high, on the one hand, coarse square TiN precipitation will be formed. When the steel plate is subjected to stress, the stress will be concentrated near the TiN particles, which will become the nucleation and growth source of microcracks and reduce the fatigue performance of the steel plate. On the other hand, due to the small solubility product of TiC, it is difficult for Ti to dissolve in the continuous casting billet heating process and it does not play a corresponding role. Comprehensively considered, the Ti content in the weathering steel of the present invention is controlled to be 0.043% to 0.055%, which can be understood to include but not limited to 0.043%, 0.044%, 0.045%, 0.046%, 0.047%, 0.048%, 0.049%, 0.050%, 0.051%, 0.052%, 0.053%, 0.054% or 0.055%. In one embodiment, the Ti content of the weathering steel is 0.043% to 0.053% by mass.

[0059] Aluminum (Al): Al can be used as a deoxidizer to remove oxygen and nitrogen, and can reduce the austenite phase in alloy steel, including acid-soluble aluminum (Als) and acid-insoluble aluminum. In order to improve the performance of weathering steel, the present invention controls the Als content of weathering steel to be 0.015% to 0.050%, including but not limited to 0.015%, 0.020%, 0.025%, 0.030%, 0.035%, 0.040%, 0.045%, or 0.050%. Preferably, the Als content of the weathering steel is 0.020% to 0.045% by mass.

[0060] Nitrogen (N): In alloy steel, N mainly has fine grain strengthening, precipitation strengthening, improved wear resistance and corrosion resistance, and prevents intergranular corrosion or pitting corrosion, but excessive N will increase intergranular corrosion, or form pores in the alloy steel or embrittle the alloy steel and deteriorate weldability. Taking all factors into consideration, the present invention controls the N content of weathering steel to be ≤0.007%, including but not limited to 0, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006% or 0.007%.

[0061] In summary, the present invention regulates the chemical composition of the alloy steel, especially the type of elements and the percentage of content. For example, weather-resistant elements such as Cu, P and Cr are added to achieve weather-resistant effects, without adding precious metals such as Ni and Nb, and lower Mn alloy elements, which greatly reduces the alloy cost and provides a grade of weather-resistant steel that is nickel-free, niobium-free, low in manganese, low in production cost, high in yield strength (≥450MPa), good in weather resistance, and good stability in performance of the entire coil.

[0062] In one of the embodiments, the yield strength of the weathering steel is ≥450 MPa.

[0063] In one of the embodiments, the tensile strength of the weathering steel is ≥550 MPa.

[0064] In one of the embodiments, the elongation of the weathering steel is ≥18%.

[0065] In one of the embodiments, the weathering index of the weathering steel is ≥6.0.

[0066] The present invention also provides a method for preparing the weathering steel as described above, and the technical scheme is as follows:

[0067] A method for preparing weathering steel as described above comprises the steps of heating the steel billet, rough rolling, finish rolling, cooling and coiling.

[0068] In one embodiment, in the step of heating the steel billet, the furnace temperature is 1180° C. to 1210° C. A lower content of strengthening alloy elements can use a lower solution temperature, reduce energy consumption, and lower production costs.

[0069] In one of the embodiments, in the rough rolling step, the starting rolling temperature is 1070°C to 1150°C.

[0070] In one of the embodiments, in the rough rolling step, the final rolling temperature is 1030°C to 1100°C.

[0071] In one of the embodiments, in the finishing rolling step, the starting rolling temperature is ≤1030°C, and the rolling is controlled in the non-recrystallization zone to generate a large number of dislocations, which can increase the nucleation position of the precipitated phase, refine the grains, and improve the uniformity of the grains.

[0072] In one of the embodiments, in the step of finish rolling, the final rolling temperature is 830°C to 860°C.

[0073] In one embodiment, in the cooling step, the front stage adopts a concentrated cooling method. Further, the cooling rate is 40°C / s to 60°C / s. The front stage concentrated cooling and the higher cooling rate can inhibit the growth of proeutectoid ferrite, refine the grains and improve the strength.

[0074] In one of the embodiments, in the cooling step, the cooling time is 3s to 5s.

[0075] In one embodiment, in the coiling step, the coiling temperature is 510°C to 560°C. Further, in the coiling step, the coiling temperature is 510°C to 550°C. Low coiling temperature is conducive to obtaining ferrite and bainite structures, such as Figure 1 As shown, the strength and stability of the entire roll performance are improved.

[0076] The present invention uses the cooling mode of concentrated cold rolling in the front section, and the lower coiling temperature improves the performance stability of the whole coil. A small amount of micro-alloy Ti is added to ensure strength through precipitation strengthening, fine grain strengthening and organizational strengthening, while maintaining good processing performance. Weathering effects are achieved by adding weather-resistant elements such as Cu, P, Cr, etc., and no precious metals such as Ni and Nb are added. The lower Mn alloy element greatly reduces the alloy cost, ensures that the steel has good mechanical properties, corrosion resistance, processability and stability of the whole coil performance while having lower costs, and is convenient for mass industrial production and market promotion and application. Preferably, the present invention is suitable for thin-gauge 450MPa-grade weathering steel with a thickness of ≤6mm.

[0077] The present invention also provides the application of the weathering steel as described above, and the technical solution is as follows:

[0078] Application of weathering steel as described above in buildings, vehicles, bridges or towers.

[0079] It can be understood that there are three main ways to use weathering steel: naked use, painted use and use after rust layer stabilization treatment. The present invention does not impose any special restrictions on this and can be flexibly handled according to actual needs and conditions.

[0080] (1) Naked use:

[0081] The most common way to use weathering steel is to use it in an exposed manner. Generally, after 3 to 10 years, the rust layer on the surface of the weathering steel gradually stabilizes, the corrosion development slows down, and the appearance becomes a beautiful chocolate color.

[0082] (2) Coating use:

[0083] In many departments such as construction, bridges, and vehicles, weathering steel, like ordinary steel, is mostly used after coating. Compared with ordinary steel, the coated weathering steel shows extremely superior corrosion resistance.

[0084] (3) Use after stabilization treatment

[0085] A treatment is applied to the surface of the component at the beginning to shorten the formation process of the stabilized rust layer of weathering steel. This can avoid the phenomenon of yellow rust dripping in the early stage of weathering steel use and prevent pollution, while also forming a stable rust layer.

[0086] The present invention will be further described below with reference to examples.

[0087] (1) Steel weathering index I = 26.01Cu + 3.88Ni + 1.2Cr + 1.49Si + 17.28P - 7.29CuNi - 9.1NiP - 33.39Cu (Since the weathering steel of the present invention does not contain Ni element, the Ni value is 0 when calculating with the formula).

[0088] (2) The mechanical properties of steel are tested by tensile test according to GB / T228.1-2010 and by bending test according to GB / T232-2010.

[0089] Examples 1 to 6 and Comparative Examples 1 to 2

[0090] The process flow is: billet heating, rough rolling, finish rolling, cooling and coiling. The specific operation steps and process parameter control of each process are as follows:

[0091] (1) The chemical composition of the steel billet used in the comparative example is shown in Table 1 below, the remainder is Fe and unavoidable impurities, and the process parameters for preparing the alloy steel are shown in Table 2 below.

[0092] Table 1: Chemical composition (wt%) of the steel billets used in the examples and comparative examples, the balance being Fe and unavoidable impurities

[0093]

[0094] Table 2 Process parameters for preparing alloy steel in Example Comparative Example

[0095]

[0096] (2) The chemical composition of the alloy steels prepared in the comparative examples of the embodiments is shown in Table 3 below, and the performance test results are shown in Table 3 below.

[0097] Table 3 Performance test results of alloy steel obtained by comparative examples of the present invention

[0098]

[0099] In summary, the embodiment of the present invention uses a cooling mode of concentrated cold rolling in the front section, and a lower coiling temperature improves the performance stability of the entire coil, and controls the chemical composition in the alloy steel, specifically, a small amount of microalloy Ti is added, and the strength is ensured by precipitation strengthening, fine grain strengthening and organizational strengthening. The yield strength and tensile strength of the obtained alloy steel are high, while maintaining good processing performance. The weather resistance effect is achieved by adding weather-resistant elements such as Cu, P, Cr, and the weather resistance index is greater than 6.0. No precious metals such as Ni and Nb are added, and the Mn content is low, which can greatly reduce the alloy cost, ensure that the alloy steel has good corrosion resistance, processability and performance stability of the entire coil while having a lower cost, and is suitable for use as weather-resistant steel.

[0100] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0101] The above-described embodiments only express several implementation methods of the present invention, which are convenient for understanding the technical solutions of the present invention in detail, but they cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided by the present invention are all within the protection scope of the claims attached to the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the contents of the attached claims, and the description and drawings can be used to interpret the contents of the claims.

Claims

1. A weathering steel, characterized in that: Measured in percentage by mass, its chemical composition includes: C: 0.07%-0.09%, Si: 0.30%-0.40%, Mn: 0.35%-0.45%, P: 0.07%-0.09%, S: ≤0.008%, Cu: 0.25%-0.28%, Cr: 0.30%-0.40%, Ti: 0.043%-0.055%, Als: 0.02%-0.05%, N: ≤0.007%, and the balance is Fe and unavoidable impurities.

2. The weathering steel according to claim 1, characterized in that: Calculated by mass percentage, the P content of the weathering steel is 0.072% to 0.088%.

3. The weathering steel according to claim 1, characterized in that: Calculated by mass percentage, the Ti content of the weathering steel is 0.043% to 0.053%.

4. The weathering steel according to claim 1, characterized in that: Calculated by mass percentage, one or more of the following (1) to (3) are met: (1) The Si content of the weathering steel is 0.31% to 0.40%; (2) The Mn content of the weathering steel is 0.36% to 0.45%; (3) The sulfur content of the weathering steel is 0.003% to 0.006%.

5. The weathering steel according to any one of claims 1 to 4, characterized in that: Satisfy one or more of the following (1) to (4): (1) The yield strength of the weathering steel is ≥450 MPa; (2) The tensile strength of the weathering steel is ≥550 MPa; (3) The elongation of the weathering steel is ≥18%; (4) The weathering index of the weathering steel is ≥6.

0.

6. A method for preparing weathering steel according to any one of claims 1 to 5, characterized in that: include: The steps of billet heating, rough rolling, finish rolling, cooling and coiling.

7. The method for preparing weathering steel according to claim 6, characterized in that: In the step of heating the steel billet, the furnace temperature is 1180°C to 1210°C.

8. The method for preparing weathering steel according to claim 6, characterized in that: In the rough rolling step, one or more of the following (1) to (2) are satisfied: (1) The rolling temperature is 1070℃~1150℃; (2) The final rolling temperature is 1030℃~1100℃.

9. The method for preparing weathering steel according to any one of claims 6 to 8, characterized in that: In the step of finish rolling, one or more of the following (1) to (2) are satisfied: (1) Rolling temperature ≤ 1030℃; (2) The final rolling temperature is 830℃~860℃.

10. The method for preparing weathering steel according to any one of claims 6 to 8, characterized in that: In the cooling step, one or more of the following (1) to (3) are satisfied: (1) The front section adopts centralized cooling; (2) Cooling rate 40℃ / s~60℃ / s; (3) The cooling time is 3s to 5s.

11. The method for preparing weathering steel according to any one of claims 6 to 8, characterized in that: In the coiling step, the coiling temperature is 510°C to 560°C.

12. Use of the weathering steel according to any one of claims 1 to 5 in buildings, vehicles, bridges or towers.

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