Weathering steel for marine atmospheric environment and preparation method thereof

Abstract

The present application relates to the technical field of weathering steel production, and in particular to a weathering steel for use in marine atmospheric environments and a preparation method thereof. The chemical composition of the weathering steel includes: C, Si, Mn, Cu, Cr, N, Mo, Sb, P, Ti, S, and Fe; wherein, by mass fraction, the C content is 0.02-0.05%, the Si content is 0.30-0.70%, the Mn content is 0.3-0.6%, the Cu content is 0.2-0.5%, the Cr content is 2.5-4.5%, the Ni content is 0.2-0.5%, the Mo content is 0.2-0.5%, the Sb content is 0.1-0.2%, the P content is 0.04-0.10%, the Ti content is 0.05-0.10%, and the S content is ≤0.002%. The present application solves the technical problem that existing weathering steel for use in marine atmospheric environments has difficulty in achieving both high strength and high corrosion resistance.

Description

Technical Field

[0001] The present application relates to the technical field of weathering steel production, and in particular to a weathering steel for marine atmospheric environment and a preparation method thereof. Background Art

[0002] Based on the different corrosive media in the atmospheric environment, atmospheric corrosion types are divided into rural atmosphere, industrial atmosphere, marine atmosphere, etc., among which the marine atmosphere is the most severe atmospheric corrosion environment. The marine atmosphere contains high concentrations of chloride ions, which severely corrode steel structures in the area. Commonly used atmospheric corrosion-resistant steel, also known as weathering steel, has corrosion resistance between ordinary steel and stainless steel. It is smelted from ordinary carbon steel with a small amount of corrosion-resistant alloying elements such as Cu, Cr, and Ni. There are two main systems: 9CuPCrNi and 09CuPTiRe. Currently, the highest grade of weathering steel specified in the GB / T4171-2008 "Weathering Structural Steel" standard is Q550NH, with a yield strength of 550MPa, and the highest grade of high-weathering steel is Q355GNH, with a yield strength of 355MPa. In practical applications, these weathering steels have excellent atmospheric corrosion resistance in rural and industrial atmospheres.

[0003] However, the corrosion resistance of steel has not been significantly improved in marine atmospheric environments. Furthermore, as countries around the world increase their requirements for low-carbon and environmental protection, the demand for high-strength and lightweight structural steel is growing. Therefore, it is of great significance to obtain high-strength weathering steel for use in marine atmospheric environments through alloy element blending and microstructure control to improve the strength and service life of structural steel in marine atmospheric environments. Summary of the Invention

[0004] The present application provides a weathering steel for marine atmospheric environment and a preparation method thereof, so as to solve the technical problem that the existing weathering steel for marine atmospheric environment is difficult to achieve both high strength and high corrosion resistance.

[0005] In a first aspect, the present application provides a weathering steel for use in a marine atmospheric environment, wherein the chemical composition of the weathering steel comprises:

[0006] C, Si, Mn, Cu, Cr, N, Mo, Sb, P, Ti, S and Fe; among them, in terms of mass fraction,

[0007] The C content is 0.02-0.05%, the Si content is 0.30-0.70%, the Mn content is 0.3-0.6%, the Cu content is 0.2-0.5%, the Cr content is 2.5-4.5%, the Ni content is 0.2-0.5%, the Mo content is 0.2-0.5%, the Sb content is 0.1-0.2%, the P content is 0.04-0.10%, the Ti content is 0.05-0.10%, and the S content is ≤0.002%.

[0008] Optionally, in the chemical composition of the weathering steel, calculated by mass fraction, the C content is 0.026-0.030%, the Si content is 0.38-0.65%, the Mn content is 0.38-0.45%, the Cu content is 0.29-0.40%, the Cr content is 3.1-4.2%, the Ni content is 0.25-0.37%, the Mo content is 0.3-0.5%, the Sb content is 0.15-0.18%, the P content is 0.06-0.078%, and the Ti content is 0.061-0.078%.

[0009] Optionally, the metallographic structure of the weathering steel is acicular ferrite, and the grain size of the weathering steel is ≥12.

[0010] Optionally, the inclusion level of the weathering steel is ≤0.5.

[0011] Optionally, the yield strength R of the weathering steel t0.5 620~720MPa, tensile strength R m 750~850MPa, yield strength ratio R t0.5 / Rm ≤0.85, elongation after fracture A 50mm ≥22%, -20℃ impact energy KV2 ≥120J.

[0012] In a second aspect, the present application provides a method for preparing weathering steel for use in a marine atmospheric environment, which is used to prepare the weathering steel described in any embodiment of the first aspect, the method comprising:

[0013] The casting billet is heated under the condition of set temperature;

[0014] The heated ingot is rolled to obtain a hot-rolled plate; wherein the rolling comprises:

[0015] performing rough rolling on the heated ingot, and controlling the starting temperature and the ending temperature of the rough rolling to obtain a first steel plate;

[0016] performing finish rolling on the first steel plate, and controlling a start temperature and an end temperature of the finish rolling;

[0017] The hot-rolled plate is subjected to laminar cooling, and the process parameters of the laminar cooling are controlled, and then coiled to obtain weathering steel for marine atmospheric environment.

[0018] Optionally, the set temperature is 1150-1210°C.

[0019] Optionally, the starting temperature of the rough rolling is 1000-1150°C, and / or the ending temperature of the rough rolling is 880-930°C.

[0020] Optionally, the starting temperature of the finish rolling is 850-880°C, and / or the ending temperature of the finish rolling is 800-850°C.

[0021] Optionally, the process parameters of the laminar cooling include: cooling rate and cooling end temperature; wherein,

[0022] The cooling rate is 15-25°C / s, and / or the cooling end temperature is 500-550°C.

[0023] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0024] The marine atmospheric weathering steel provided in the embodiment of the present application has an appropriate amount of alloying elements such as Cu, Cr, Ni, Mo, Sb, and P added to the basic component system of C, Si, and Mn. On the one hand, it increases the self-corrosion potential of the weathering steel and reduces the surface corrosion activity of the steel in the early stage of corrosion; on the other hand, it makes the rust layer on the steel surface dense and stable, effectively blocking the chloride ion corrosion in the marine atmosphere. The marine atmospheric weathering steel has high strength, low yield strength ratio, good toughness and excellent corrosion resistance. Mechanical properties: Yield strength R t0.5 620~720MPa, tensile strength R m 750~850MPa, yield strength ratio R t0.5 / Rm ≤0.85, elongation after fracture A 50mm ≥22%, -20℃ impact energy KV2 ≥120J. Tested according to GB / T 19746-2018 "Corrosion of Metals and Alloys - Periodic Immersion in Salt Solutions" standard. The corrosion rate after 7 days of immersion is less than 0.1mm / a, which is no more than 20% of the corrosion rate of ordinary carbon steel Q345. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] Figure 1 A schematic flow chart of a method for preparing weathering steel for marine atmospheric environment provided in an embodiment of the present application;

[0028] Figure 2 This is a metallographic structure diagram of a weathering steel for marine atmospheric environment provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0030] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0031] In this application, unless otherwise specified, the directional words used, such as "upper" and "lower", refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to 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, c can be single or multiple.

[0032] 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.

[0033] In a first aspect, the present application provides a weathering steel for use in a marine atmospheric environment, wherein the chemical composition of the weathering steel comprises:

[0034] C, Si, Mn, Cu, Cr, N, Mo, Sb, P, Ti, S and Fe; among them, in terms of mass fraction,

[0035] The C content is 0.02-0.05%, the Si content is 0.30-0.70%, the Mn content is 0.3-0.6%, the Cu content is 0.2-0.5%, the Cr content is 2.5-4.5%, the Ni content is 0.2-0.5%, the Mo content is 0.2-0.5%, the Sb content is 0.1-0.2%, the P content is 0.04-0.10%, the Ti content is 0.05-0.10%, and the S content is ≤0.002%.

[0036] In the examples of this application, the positive effect of controlling the C content to 0.02-0.05% is that carbon is the most economical and basic strengthening element, but too high a carbon content may negatively affect the ductility, corrosion resistance, and weldability of the steel. Specifically, the C content can be 0.02%, 0.03%, 0.04%, 0.05%, etc.

[0037] The positive effect of controlling the Si content to 0.30-0.70% is that silicon has a strong solid solution strengthening effect, which can improve the strength and toughness of steel within a certain range. However, excessive silicon may reduce the impact toughness and weldability of the steel. Specifically, the Si content can be 0.30, 0.50, 0.70, etc.

[0038] The positive effect of controlling the Mn content to 0.3-0.6% is that manganese plays a role in solid solution strengthening, compensating for the strength loss caused by low carbon or ultra-low carbon. However, excessive manganese can easily cause structural segregation. Specifically, the Mn content can be 0.3%, 0.4%, 0.5%, 0.6%, etc.

[0039] Controlling the Cu content to 0.2-0.5% has the positive effect of copper not only providing solid solution strengthening but also synergizing with phosphorus to improve the corrosion resistance of steel. However, excessive Cu content does not provide additional corrosion resistance and may even cause hot brittleness of the steel. Specifically, the Cu content can be 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0040] Controlling the Cr content to 2.5-4.5% has the following positive effects: chromium can accumulate in the corrosion product film, reducing the electrode reaction rate and refining the α-FeOOH crystals, which facilitates the formation of a dense protective inner rust layer and improves resistance to marine atmospheric corrosion. However, adding large amounts of chromium may reduce the steel's toughness and weldability. Specifically, the Cr content can be 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, etc.

[0041] The positive effect of controlling the Ni content to 0.2-0.5% is that nickel can significantly improve the corrosion resistance of steel in marine atmospheric environment. On the one hand, nickel increases the self-corrosion potential of weathering steel and reduces the corrosion activity of steel surface in the early stage of corrosion. On the other hand, nickel can be enriched in the rust layer, thereby changing the ion selectivity of the rust layer and blocking Cl - However, too much nickel may slow down the improvement of corrosion resistance and significantly increase the production cost of weathering steel. Specifically, the Ni content can be 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0042] The positive effects of controlling the Mo content to 0.2-0.5% include: Molybdenum can enhance the hardenability of steel and improve its pitting corrosion resistance. During marine atmospheric corrosion, the molybdenum in steel is oxidized to insoluble molybdates, resulting in a dense and ion-selective rust layer, which prevents chloride ions from reaching the substrate and reduces the corrosion rate. However, molybdenum can reduce welding performance. Specifically, the Mo content can be 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0043] The positive effects of controlling the Sb content to 0.1-0.2% are: Antimony significantly improves steel's resistance to marine atmospheric corrosion. Antimony forms stable Sb2O3 and Sb2O5 oxides in the rust layer, promoting the conversion of γ-FeOOH in the rust layer to α-FeOOH and Fe3O4, enhancing the stability of the rust layer and improving its density and continuity. However, when Sb is added above 0.3%, corrosion resistance decreases. Specifically, the Sb content can be 0.1%, 0.2%, etc.

[0044] Controlling the phosphorus content to 0.04-0.10% has positive effects: phosphorus works synergistically with copper to enhance the steel's resistance to marine atmospheric corrosion. Furthermore, phosphorus, when enriched in the rust layer, acts as an anodic depolarizer and stabilizes the rust layer, making it denser and more stable, acting as a protective barrier against chloride ions on the steel surface. However, excessive phosphorus levels negatively impact the steel plate's low-temperature toughness and weldability. Specifically, the Sb content can be 0.04%, 0.06%, 0.08%, 0.10%, etc.

[0045] Controlling the Ti content to 0.05-0.10% has the following positive effects: Titanium facilitates deoxidation of steel and reduces inclusions. It also improves the impact toughness of steel. Titanium is also a corrosion-resistant alloying element, and its addition increases the steel's self-corrosion potential, improving its resistance to marine atmospheric corrosion. However, exceeding a certain titanium content can lead to the precipitation strengthening effect of TiC, reducing the steel's low-temperature toughness. Specifically, the Sb content can be 0.05%, 0.07%, 0.10%, etc.

[0046] The positive effect of controlling the sulfur content to ≤ 0.002% is that sulfur is a harmful element in steel. The resulting manganese sulfide inclusions not only reduce the steel's mechanical properties but also its resistance to marine atmospheric corrosion. Specifically, the sulfur content can be 0.002%, 0.0018%, 0.0019%, etc.

[0047] In some embodiments, the chemical composition of the weathering steel is, by mass fraction, the C content is 0.026-0.030%, the Si content is 0.38-0.65%, the Mn content is 0.38-0.45%, the Cu content is 0.29-0.40%, the Cr content is 3.1-4.2%, the Ni content is 0.25-0.37%, the Mo content is 0.3-0.5%, the Sb content is 0.15-0.18%, the P content is 0.06-0.078%, and the Ti content is 0.061-0.078%.

[0048] The above chemical compositions are preferred embodiments.

[0049] In some embodiments, the metallographic structure of the weathering steel is acicular ferrite, see Figure 2 The grain size grade of the weathering steel is ≥12.

[0050] In the embodiment of the present application, the fine acicular ferrite structure steel has high strength and toughness, which makes up for the toughness loss caused by high phosphorus. The positive effect of controlling the grain size of weathering steel to ≥12: After grain refinement, the strength, plasticity and toughness of weathering steel are improved, ensuring that the mechanical performance indicators of weathering steel in the implementation of this application are achieved, that is, the yield strength R t0.5 620~720MPa, tensile strength R m 750~850MPa, yield strength ratio R t0.5 / R m ≤0.85, elongation after fracture A50mm≥22%, and impact energy KV2 at -20°C≥120 J. Specifically, the grain size of the weathering steel can be grade 12, grade 13, etc.

[0051] In some embodiments, the inclusion level of the weathering steel is ≤ 0.5.

[0052] In the embodiments of this application, controlling the inclusion level of weathering steel to ≤ 0.5 has the following positive effects: on the one hand, a smaller inclusion level ensures the continuity of the steel, reduces the impact of inclusions on the steel, and improves the mechanical properties of the material. On the other hand, controlling inclusions reduces corrosion initiation and improves the corrosion resistance of the steel. Specifically, the grain size of the weathering steel can be 0.5, 0.4, etc.

[0053] In some embodiments, the yield strength R of the weathering steel t0.5 620~720MPa, tensile strength R m 750~850MPa, yield strength ratio R t0.5 / Rm ≤0.85, elongation after fracture A 50mm ≥22%, -20℃ impact energy KV2 ≥120J.

[0054] The weathering steel for marine atmospheric environment of the embodiment of the present application has high strength, low yield ratio, good toughness and excellent corrosion resistance.

[0055] In the second aspect, this application provides a method for preparing weathering steel for marine atmospheric environment, see Figure 1 , used to prepare the weathering steel according to any one of the embodiments of the first aspect, the method comprising:

[0056] In the examples of this application, RH vacuum treatment of molten steel combined with titanium microalloying creates a large number of fine, dispersed non-metallic inclusions, which induce ferrite nucleation. Combined with the TMCP process and a rapid cooling rate, a fine, acicular ferrite structure is ultimately achieved. This fine acicular ferrite structure provides steel with high strength and toughness, compensating for the toughness loss associated with high phosphorus content.

[0057] S1. Heating the ingot at a set temperature;

[0058] In some embodiments, the set temperature is 1150-1210°C.

[0059] The "set temperature" refers to the temperature at which the ingot is heated. Controlling this temperature between 1150°C and 1210°C has the positive effect of ensuring sufficient solid solution of microalloying elements and preventing austenite grain coarsening. Specifically, this heating temperature can be 1150°C, 1170°C, 1190°C, 1210°C, etc. Prior to step S1, the process includes converter smelting, RH vacuum calcium treatment, and casting into ingots.

[0060] S2. Rolling the heated ingot to obtain a hot-rolled plate; wherein the rolling comprises:

[0061] performing rough rolling on the heated ingot, and controlling the starting temperature and the ending temperature of the rough rolling to obtain a first steel plate;

[0062] performing finish rolling on the first steel plate, and controlling a start temperature and an end temperature of the finish rolling;

[0063] In the above rough rolling, the total reduction rate is 70-80%; in the above finishing rolling, the cumulative reduction rate is not less than 70%, and the steel plate is rolled into a 1.5-10 mm thick steel plate through 7-12 passes.

[0064] In some embodiments, the starting temperature of the rough rolling is 1000-1150°C, and / or the ending temperature of the rough rolling is 880-930°C.

[0065] In some embodiments, the start temperature of the finish rolling is 850-880°C, and / or the end temperature of the finish rolling is 800-850°C.

[0066] The positive effect of controlling the start temperature of rough rolling to 1000-1150°C is that rolling above the recrystallization temperature improves microstructure uniformity. The positive effect of controlling the end temperature of rough rolling to 880-930°C is that the end temperature is ensured to be above the austenite to ferrite transformation temperature Ar3. Specifically, the start temperature of rough rolling can be 1000°C, 1050°C, 1100°C, 1150°C, etc., and the end temperature of rough rolling can be 880°C, 900°C, 930°C, etc.

[0067] The positive effect of controlling the start temperature of finish rolling to 850-880°C is that rolling within the recrystallization temperature range promotes uniform microstructure and grain refinement. The positive effect of controlling the end temperature of finish rolling to 800-850°C is that it avoids large deformation at low temperatures and prevents the formation of hardened austenite. Specifically, the start temperature of finish rolling can be 850°C, 860°C, 870°C, 880°C, etc., and the end temperature of finish rolling can be 800°C, 830°C, 850°C, etc.

[0068] S3. laminar cooling is performed on the hot-rolled plate, and process parameters of the laminar cooling are controlled, and then coiling is performed to obtain weathering steel for marine atmospheric environment.

[0069] In some embodiments, the process parameters of the laminar cooling include: cooling rate and cooling end temperature; wherein,

[0070] The cooling rate is 15-25°C / s, and / or the cooling end temperature is 500-550°C.

[0071] Controlling the cooling rate to 15-25°C / s has the positive effect of controlling the phase transformation of hardened austenite to fine ferrite. Controlling the cooling endpoint temperature to 500-550°C has the positive effect of ensuring the formation of fine acicular ferrite. Specifically, the cooling rate can be 15°C / s, 20°C / s, 25°C / s, etc., and the cooling endpoint temperature can be 500°C, 530°C, 550°C, etc.

[0072] The preparation method of weathering steel for marine atmospheric environment is based on the above-mentioned weathering steel for marine atmospheric environment. The specific chemical composition of the weathering steel for marine atmospheric environment can be referred to the above-mentioned embodiment. Since the preparation method of weathering steel for marine atmospheric environment adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be repeated here.

[0073] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0074] The steel is smelted in a converter, treated with calcium in a RH vacuum, and then cast into billets. The chemical composition of weathering steel for marine atmospheric environments is shown in Table 1.

[0075] Table 1 Chemical composition (wt%) of weathering steel for marine atmospheric environment, the rest is Fe and unavoidable impurities

[0076]

[0077] Specific implementation steps:

[0078] S1. Heating the ingot at a set temperature;

[0079] S2. Rolling the heated ingot to obtain a hot-rolled plate; wherein the rolling comprises:

[0080] performing rough rolling on the heated ingot, and controlling the starting temperature and the ending temperature of the rough rolling to obtain a first steel plate;

[0081] performing finish rolling on the first steel plate, and controlling a start temperature and an end temperature of the finish rolling;

[0082] S3. Laminar cooling the hot-rolled plate, controlling the laminar cooling process parameters, and then coiling the hot-rolled plate to obtain weathering steel for marine atmosphere environments. The laminar cooling process parameters include cooling rate and cooling endpoint temperature. For specific process parameters, see Table 2.

[0083] Table 2 Preparation process parameters of weathering steel for marine atmospheric environment

[0084]

[0085]

[0086] The mechanical properties of weathering steel for marine atmospheric environment were tested, see Table 3.

[0087] Table 3 Test results of main transverse mechanical properties of weathering steel for marine atmospheric environment

[0088] Example <![CDATA[R t0.5 / MPa]]> <![CDATA[R m / MPa]]> <![CDATA[R t0.5 / R m ]]> <![CDATA[A 50mm / %]]> <![CDATA[-20℃KV2 / J]]> 1 620 750 0.83 22 120 2 720 850 0.85 31 122 3 690 835 0.83 24 125 4 675 810 0.83 25 130 5 680 850 0.80 24 126 6 600 750 0.80 26 135 7 710 845 0.84 28 132 8 630 765 0.82 29 128 9 675 840 0.80 30 127 10 642 780 0.82 27 136 Comparative Example 1 (Q550NH) 566 610 0.93 20 85 Comparative Example 2 (Q355GNH) 365 405 0.90 17 95

[0089] Tests were conducted in accordance with GB / T 19746-2018, "Corrosion of Metals and Alloys - Salt Solution Cyclic Immersion Test," to determine the corrosion rates of the Examples and Comparative Examples over a seven-day immersion period in a 3.5% sodium chloride solution. The average corrosion rate of plain carbon steel Q345 was 5.25 mm / yr. The corrosion rates of the Examples and Comparative Examples relative to Q345 were calculated as: average corrosion rate of the Examples or Comparative Examples / 5.25 mm / yr × 100%. See Table 4.

[0090] Table 4 Test results of cyclic immersion corrosion rate of weathering steel for marine atmospheric environment

[0091]

[0092]

[0093] The marine atmospheric weathering steel of the present invention exhibits not only excellent mechanical properties but also excellent corrosion resistance. Table 4 shows that the corrosion rate after 7 days of immersion is less than 0.1 mm / year, which is less than 20% of the corrosion rate of ordinary carbon steel Q345. The comparative example, on the other hand, exhibits inferior mechanical properties and corrosion resistance compared to the examples.

[0094] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present 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 the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A weathering steel for marine atmospheric environment, characterized in that: The chemical composition of the weathering steel is: in mass fraction, The content of C is 0.02-0.05%, the content of Si is 0.30-0.70%, the content of Mn is 0.3-0.6%, the content of Cu is 0.2-0.5%, the content of Cr is 2.5-4.5%, the content of Ni is 0.2-0.5%, the content of Mo is 0.2-0.5%, the content of Sb is 0.1-0.2%, the content of P is 0.04-0.10%, the content of Ti is 0.05-0.10%, the content of S is ≤0.002%, and the rest is Fe and unavoidable impurities; the metallographic structure of the weathering steel is acicular ferrite, the grain size grade is ≥12, and the yield strength R t0.5 620~720MPa, tensile strength R m 750~850MPa, yield strength ratio R t0.5 / Rm ≤0.85, elongation after fracture A 50mm ≥22%, -20℃ impact energy KV2≥120J; the preparation method of the weathering steel comprises laminar cooling of the hot-rolled plate, controlling the cooling rate of the laminar cooling to 15-25℃ / s, the cooling end temperature to 500-550℃, and then coiling.

2. The weathering steel according to claim 1, characterized in that The chemical composition of the weathering steel is, by mass fraction, that of C is 0.026-0.030%, that of Si is 0.38-0.65%, that of Mn is 0.38-0.45%, that of Cu is 0.29-0.40%, that of Cr is 3.1-4.2%, that of Ni is 0.25-0.37%, that of Mo is 0.3-0.5%, that of Sb is 0.15-0.18%, that of P is 0.06-0.078%, and that of Ti is 0.061-0.078%.

3. The weathering steel according to claim 1, characterized in that The inclusion level of the weathering steel is ≤ level 0.

5.

4. A method for preparing weathering steel for marine atmospheric environment, characterized in that: For preparing the weathering steel according to any one of claims 1 to 3, the method comprises: The casting billet is heated under the condition of set temperature; The heated ingot is rolled to obtain a hot-rolled plate; wherein the rolling comprises: performing rough rolling on the heated ingot, and controlling the starting temperature and the ending temperature of the rough rolling to obtain a first steel plate; performing finish rolling on the first steel plate, and controlling a start temperature and an end temperature of the finish rolling; The hot-rolled plate is subjected to laminar cooling, and the process parameters of the laminar cooling are controlled, and then coiled to obtain weathering steel for marine atmospheric environment.

5. The method according to claim 4, characterized in that The set temperature is 1150-1210°C.

6. The method according to claim 4, characterized in that The starting temperature of the rough rolling is 1000-1150°C, and / or the ending temperature of the rough rolling is 880-930°C.

7. The method according to claim 4, characterized in that The start temperature of the finish rolling is 850-880°C, and / or the end temperature of the finish rolling is 800-850°C.

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