Corrosion-resistant 460 mpa-grade steel plate and production method therefor

Abstract

The present application provides a 460MPa-grade corrosion resistant steel plate and a production method thereof. The steel plate adopts a corrosion-resistant alloying composition system with combined addition of Cr+Ni+Mo+Cu+P, which ensures corrosion resistance and weldability while economizing the use of precious alloys. While strictly controlling impurity elements, one or more rare earth elements selected from La, Ce, Pr, and Nd are used to purify the molten steel, further improving corrosion resistance. Based on the comprehensive design of chemical components, through precise control of process parameters during rolling and cooling processes, accurate control of the steel plate's microstructure, inclusion content and size is achieved, obtaining a 460MPa-grade steel plate for wind tower with excellent comprehensive properties and marine atmospheric corrosion resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of alloy technology, specifically relating to a 460MPa-grade corrosion resistant steel plate and a production method thereof.BACKGROUND

[0002] Compared with onshore wind farms, offshore wind power has advantages such as higher power generation efficiency, less environmental pollution, and no occupation of arable land. However, offshore wind power operates in extremely harsh corrosive environments, especially for steel structure towers in marine atmospheric zones with high humidity and high salt content. Under the influence of capillary action, adsorption, and chemical condensation, water vapor in the marine atmosphere adheres to the steel surface, forming an invisible electrolyte solution with high conductivity, containing dissolved oxygen, chloride ions, sulfate ions, and other salts. Among these, chloride ions have strong penetrating effects, causing localized corrosion such as pitting, stress corrosion, intergranular corrosion, and crevice corrosion, making it difficult for the steel surface to form a long-term stable and dense rust layer, leading to increased corrosion rates. The commonly used anti-corrosion solution is to adopt a long-life anti-corrosion coating system, but coating failure issues occur during service. Therefore, improving the inherent corrosion resistance of steel materials represents a new technical approach to anti-corrosion design.

[0003] In existing production technology for marine atmospheric corrosion resistant steel, the main approach is to add large amounts of P and Ni. However, high P content deteriorates the weldability of steel, making it unsuitable for wind tower steel plates that require extensive welding during fabrication. Adding large amounts of Ni to improve corrosion resistance results in high alloy costs, which is unfavorable for controlling offshore wind turbine costs and makes widespread application difficult. Other steel plates have relatively low strength, making them unsuitable for large-scale offshore wind power construction.SUMMARY

[0004] An object of the present application is to provide a 460MPa-grade corrosion resistant steel plate and a production method thereof.

[0005] The present application provides a production method for a 460MPa-grade corrosion resistant steel plate, wherein chemical components of the steel plate include in percent by mass: C: 0.06~0.09%, Si: 0.2~0.3%, Mn: 0.9~1.0%, Cr: 0.5~0.6%, Ni: 0.30~0.40%, Cu: 0.40~0.45%, Mo: 0.05~0.10%, Nb: 0.02~0.04%, Al: 0.02~0.04%, P: 0.015~0.025%, rare earth elements: 0.015~0.025%, and the balance of Fe and inevitable impurities, wherein some impurity elements include in percent by mass: S≤0.002%, O≤0.002%, N<0.004%; wherein an atmospheric corrosion resistance index I of the steel plate is ≥6.5, and the atmospheric corrosion resistance index I is calculated by the following formula: wherein element symbols in brackets represent mass percentages of corresponding elements, and %element symbol represents mass percentage of corresponding element multiplied by 100; the production method comprises steps of: smelting and casting according to the above chemical component ratio to obtain a bloom; performing two-stage controlled rolling on the bloom to obtain a steel plate, including a first stage of austenite recrystallization zone rolling and a second stage of austenite non-recrystallization zone rolling, wherein a reduction ratio in the first stage of austenite recrystallization zone rolling is controlled to be ≥50%, and a finish rolling temperature in the second stage of austenite non-recrystallization zone rolling is controlled to be 800±20°C; performing cooling on the steel plate, and controlling cooling rate to form a microstructure including acicular ferrite and granular bainite in the steel plate, wherein a content of the acicular ferrite is ≥85%.

[0006] As a further improvement of the present application, a carbon equivalent CE of the steel plate satisfies 0.39≤CE≤0.42, wherein the carbon equivalent CE is calculated by the following formula: CE = % C + % Mn / 6 + % Cr + % Mo + % V / 5 + % Ni + % Cu / 15 wherein element symbols in brackets represent mass percentages of corresponding elements, and %element symbol represents mass percentage of corresponding element multiplied by 100.

[0007] As a further improvement of the present application, in the chemical components of the steel plate, the rare earth elements are one or more of La, Ce, Pr and Nd.

[0008] As a further improvement of the present application, the method comprises: rolling the bloom into a steel plate with a thickness ≤100mm.

[0009] As a further improvement of the present application, performing cooling on the steel plate specifically comprises: water cooling the rolled steel plate with a cooling rate controlled to be 10~28°C / s and a finish cooling temperature of the steel plate controlled to be 350±30°C.

[0010] The present application provides a 460MPa-grade corrosion resistant steel plate, wherein chemical components of the steel plate include in percent by mass: C: 0.06~0.09%, Si: 0.2~0.3%, Mn: 0.9~1.0%, Cr: 0.5~0.6%, Ni: 0.30~0.40%, Cu: 0.40~0.45%, Mo: 0.05~0.10%, Nb: 0.02~0.04%, Al: 0.02~0.04%, P: 0.015~0.025%, rare earth elements: 0.015~0.025%, and the balance of Fe and inevitable impurities, wherein some impurity elements include in percent by mass: S≤0.002%, O≤0.002%, N<0.004%; wherein a microstructure of the steel plate includes acicular ferrite and granular bainite, wherein a content of the acicular ferrite is ≥85%; wherein under test conditions of GB / T 10125-2012, an average corrosion weight loss rate of the steel plate is ≤1.315g / (m 2< ·h); wherein samples are taken according to GB / T2975, and tensile and impact tests are carried out according to GB / T228 and GB / T229, wherein the steel plate has a yield strength ≥460MPa, a tensile strength of 540~720MPa, an elongation after fracture ≥20%, and an impact absorption energy KV2 at -50°C ≥100J.

[0011] As a further improvement of the present application, a length-width product of maximum inclusions in the steel plate is ≤150µm 2< , and under conditions of GB / T10561, grades of A, B, C, and D type inclusions are all ≤1.5, and a sum of grades of A, B, C, and D type inclusions is ≤3.0.

[0012] As a further improvement of the present application, when a welding heat input is ≤80kJ / cm, the steel plate has an impact absorption energy KV2 at -50°C ≥80J in a heat affected zone after welding.

[0013] As a further improvement of the present application, the steel plate has a thickness not greater than 100mm.

[0014] The advantageous effects of the present application are: the present application adopts a corrosion-resistant alloying composition system with combined addition of Cr+Ni+Mo+Cu+P, which ensures corrosion resistance and weldability while economizing the use of precious alloys. While strictly controlling impurity elements, one or more rare earth elements selected from La, Ce, Pr, and Nd are used to purify the molten steel, further improving corrosion resistance. Based on the comprehensive design of chemical components, through precise control of process parameters during rolling and cooling processes, accurate control of the steel plate's microstructure, inclusion content and size is achieved, obtaining a 460MPa-grade steel plate for wind tower with excellent comprehensive properties and marine atmospheric corrosion resistance.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a flow diagram of a production method for a 460MPa-grade corrosion resistant steel plate according to an embodiment of the present application.DETAILED DESCRIPTION

[0016] To make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely below in conjunction with specific embodiments and corresponding drawings of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all of them. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work shall fall within the protection scope of the present application.

[0017] The embodiments of the present application are described in detail below, with examples shown in the accompanying drawings, wherein the same or similar reference numerals throughout denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application and should not be understood as limitations to the present application.

[0018] This embodiment provides a 460MPa-grade corrosion resistant steel plate and a production method thereof. The produced steel plate is particularly suitable for use as marine atmospheric corrosion resistant steel plate. The steel plate provided in this embodiment adopts a corrosion-resistant alloying component system with combined addition of Cr+Ni+Mo+Cu+P, and compared with existing marine atmospheric corrosion resistant steel plates, this embodiment adopts a low P and low Ni alloying component system, improving the weldability of the steel plate while reducing alloy costs. With low additions of P and Ni, during the production process, the present application improves molten steel purity by adding small amounts of rare earth elements, and through control of rolling and cooling process parameters, forms a microstructure dominated by acicular ferrite in the steel plate, thereby improving the corrosion resistance and strength of the steel plate.

[0019] Chemical components of the steel plate provided in this embodiment includes in percent by mass: C: 0.06~0.09%, Si: 0.2~0.3%, Mn: 0.9~1.0%, Cr: 0.5~0.6%, Ni: 0.30~0.40%, Cu: 0.40~0.45%, Mo: 0.05~0.10%, Nb: 0.02~0.04%, Al: 0.02~0.04%, P: 0.015~0.025%, rare earth elements: 0.015~0.025%, the balance of Fe and inevitable impurities, wherein some impurity elements include in percent by mass: S≤0.002%, O≤0.002%, N≤0.004%.

[0020] Specifically, the design principles for the chemical components of the steel plate are explained as follows: C: C is a strengthening element. The C content significantly affects the microstructure of steel and directly influences the strength of the steel plate. However, when C content is high, it deteriorates the low-temperature toughness and weldability of steel. Therefore, in the present application, the C content is controlled at 0.06~0.09%, which, combined with the overall design of other elements, not only ensures strengthening effect but also improves the low-temperature toughness and weldability of the steel plate.

[0021] Si: Si is a solid solution strengthening and deoxidizing element. Currently, there are different views in academia and industry regarding the mechanism of Si's role in steel's corrosion resistance. However, it is generally believed that the three-dimensional network structure of SiO 2 formed by adding Si can promote the formation and grain refinement of α-FeOOH. Additionally, Fe in Fe 3 O 4 in the rust layer can be replaced by Si, forming more stable SiO 2 . Furthermore, when Si is used in combination with Cu, SiO 2 in the rust layer can also increase Cu enrichment, thereby improving industrial atmospheric corrosion resistance. However, when Si content is high, it increases P segregation at grain boundaries, reducing the steel plate's low-temperature toughness and weldability, and weakening P's corrosion resistance effect. Therefore, in the present application, Si content is controlled at 0.2~0.3%, ensuring deoxidation effect while avoiding P segregation.

[0022] Mn: Mn is a solid solution strengthening element that can improve the hardenability of the steel plate, thereby increasing its strength. Meanwhile, Mn can combine with harmful element S to reduce the hot brittleness of the steel plate. However, excessive Mn aggravates the segregation of elements like C and P, forming MnS inclusions in the center of the steel plate, which weakens the corrosion resistance and deteriorates the low-temperature toughness and weldability at the center of the steel plate. Therefore, in the present application, Mn content is controlled at 0.9~1.0%, which can compensate for strength loss due to low carbon content while reducing segregation and inclusion formation, improving the low-temperature toughness and weldability at the center of the steel plate.

[0023] Cr: Cr is one of the common corrosion-resistant elements. Cr can promote the transformation of loose and unstable γ-FeOOH to stable α-FeOOH in the surface rust layer, reducing the occurrence of pores and cracks in the rust layer, improving steel's corrosion resistance. Cr accumulates at the end close to steel plate base of the rust layer, forming a passivation film, reducing the anion selectivity of the rust layer, blocking the penetration of external anions, protecting the steel plate base. Moreover, Cr can work synergistically with Cu to refine rust layer grains, improving the density and stability of the rust layer, and Cr will replace some Fe positions in FeOOH to form CrxFe(1-x)OOH, giving the rust layer cation selectivity, effectively preventing chloride and sulfate ion penetration. However, when Cr content is high, it easily forms carbides, causing pitting corrosion and reducing steel's corrosion resistance. Therefore, in the present application, Cr content is controlled at 0.5~0.6%, ensuring the steel plate's corrosion resistance does not decrease over time.

[0024] Ni: Adding Ni can shift the self-corrosion potential of steel positively, increasing resistance to anodic dissolution reaction while promoting the formation of α-FeOOH phase in the rust layer, refining inner rust layer grains, improving rust layer stability. Moreover, Ni elements may enrich within the rust layer, reducing the anion selectivity of the rust layer, slowing down the corrosion of the steel plate base. Additionally, adding Ni can improve the steel plate's low-temperature toughness and weldability, but excessive Ni results in higher alloy costs. Therefore, in the present application, Ni content is controlled at 0.3~0.4%, ensuring the steel plate's corrosion resistance, low-temperature toughness, and weldability while reasonably controlling alloy costs.

[0025] Cu: Adding Cu to steel significantly improves its corrosion resistance, and due to its low cost, it is widely used in corrosion-resistant steels. Its main mechanisms are multiple: Cu can inhibit crystallization of the rust layer, promoting the formation of α-FeOOH and amorphous Fe 3 O 4 . Furthermore, Cu can enrich at weak points in the rust layer, forming oxides during corrosion that tightly connect the rust layer and steel substrate, reducing cracks and voids in the rust layer, improving pitting resistance. Additionally, Cu elements activate the cathode, causing passivation of the steel substrate and reducing corrosion rate. However, high Cu content adversely affects the steel plate's weldability. Therefore, in the present application, Cu content is controlled at 0.40~0.50%, both improving corrosion resistance and maintaining weldability.

[0026] Mo: Mo can refine grains and improve steel's hardenability. Additionally, Mo can form MoO 4 2-< in the steel's rust layer, giving the inner rust layer cation selectivity, thereby inhibiting Cl -< penetration. When used in combination with Cu, it can promote Cu enrichment at weak points in the rust layer, inhibiting pitting and improving corrosion resistance. Moreover, Mo addition can lower the cooling rate for acicular ferrite formation. However, excessive Mo results in higher alloy costs. Therefore, in the present application, Mo content is controlled at 0.05~0.10%, ensuring steel plate strength and corrosion resistance while reasonably controlling alloy costs.

[0027] Nb: Nb is a grain-refining element and strong carbide-forming element that can prevent C from combining with Cr which would affect the steel plate's corrosion resistance, and Nb can promote rapid formation and increased content of α-FeOOH. Additionally, Nb can increase rare earth elements' solubility in steel, thereby improving corrosion resistance. When Nb content is high, it deteriorates low-temperature toughness in the heat affected zone of welded joints and counteracts corrosion resistance. Therefore, in the present application, Nb content is controlled at 0.02~0.04%, ensuring grain refinement effect and corrosion resistance while avoiding adverse effects on low-temperature toughness in the heat affected zone of welded joints.

[0028] Al: Al is an important deoxidizing element; when content is high, it easily blocks nozzles during casting. In the present application, Al is controlled at 0.02~0.04%, ensuring Al's beneficial effects while reducing smelting difficulty.

[0029] P: P is a typical element for improving steel's corrosion resistance. P can act as an anodic depolarizer, accelerating Fe 2+< oxidation rate and uniform dissolution of steel, effectively helping form uniform α-FeOOH rust layer on the steel plate surface. Moreover, P can form PO 4 3-< , which on one hand can complex with H +< to improve interface pH value, slowing cathodic hydrogen evolution reaction and rust layer dissolution, and on the other hand, PO 4 3-< can combine with Fe 2+< and Mn 2+< during anodic dissolution, forming insoluble phosphate films that block anodic dissolution reaction, acting as a corrosion inhibitor. Additionally, P and Cu have good synergistic corrosion resistance effects, comprehensively improving steel's corrosion resistance. Meanwhile, P is also prone to segregation; when content is too high, it significantly reduces the steel plate's central low-temperature toughness and weldability. Therefore, in the present application, P content is controlled at 0.015~0.025%, ensuring corrosion resistance while avoiding severe segregation that would deteriorate low-temperature toughness and weldability.

[0030] Rare earth elements: Rare earth elements can purify molten steel, refine inclusions in steel, transform elongated manganese sulfides into spherical rare earth sulfides or sulfoxides, and modify high-hardness alumina inclusions into spherical sulfoxides and rare earth aluminates. When used in combination with P, rare earth elements facilitate formation of uniform α-FeOOH rust layer on the steel plate surface, strengthening rust layer-substrate bonding and improving corrosion resistance. Considering cost factors, rare earth content is controlled at 0.015~0.025% in the present application, simultaneously purifying molten steel and improving corrosion resistance.

[0031] In this embodiment, rare earth elements can be one or more of La, Ce, Pr, and Nd. La, Ce, Pr, and Nd are all light rare earth elements with similar ionic radii and identical mechanisms in steel. They occur together naturally, and purifying single rare earth metals is costly. This embodiment uses one or more of La, Ce, Pr, and Nd, ensuring corrosion resistance while reducing rare earth metal costs.

[0032] S, O, and N are impurity elements. Rare earth elements added to steel first react with impurity elements. If impurity content is high, added rare earth elements will be largely consumed, weakening their corrosion resistance effect. Further restricting impurity elements would increase production difficulty. In the present application, S≤0.002%, O≤0.002%, and N≤0.004% are controlled, which, combined with overall chemical components design, ensures effective function of rare earth elements while avoiding excessive production difficulty and high costs from overly strict impurity control requirements.

[0033] Further, the steel plate's atmospheric corrosion resistance index I is ≥6.5, where the atmospheric corrosion resistance index I is calculated by the formula: wherein element symbols in brackets represent mass percentages of corresponding elements, and %element symbol represents mass percentage of corresponding element multiplied by 100.

[0034] The steel plate's carbon equivalent CE satisfies 0.39≤CE≤0.42, ensuring good weldability, where the carbon equivalent CE is calculated by the formula: CE = % C + % Mn / 6 + % Cr + % Mo + % V / 5 + % Ni + % Cu / 15 wherein element symbols in brackets represent mass percentages of corresponding elements, and %element symbol represents mass percentage of corresponding element multiplied by 100.

[0035] In summary, this embodiment adopts a corrosion-resistant alloying composition system with combined addition of Cr+Ni+Mo+Cu+P, and compared with existing marine atmospheric corrosion resistant steel plates, this embodiment uses a low P and low Ni alloying system, improving strength and weldability while reducing alloy costs. With low P and Ni additions, corrosion resistance is further improved by adding small amounts of rare earth elements to increase molten steel purity.

[0036] As shown in Figure 1, the production method includes steps: S1: Smelting and casting according to the above chemical component ratio to obtain a bloom; S2: Performing two-stage controlled rolling on the bloom to obtain a steel plate, including a first stage of austenite recrystallization zone rolling and a second stage of austenite non-recrystallization zone rolling, wherein a reduction ratio in the first stage of austenite recrystallization zone rolling is controlled to be ≥50%, and a finish rolling temperature in the second stage of austenite non-recrystallization zone rolling is controlled to be 800±20°C; S3: Performing cooling on the steel plate, controlling cooling rate to form microstructure including acicular ferrite and granular bainite in the steel plate, wherein a content of the acicular ferrite is ≥85%.

[0037] Step S1 specifically includes: According to chemical component ratio, sequentially performing converter smelting, Ladle Furnace refining, RH-vacuum degasser refining and continuous casting to obtain a bloom.

[0038] In hot metal pre-desulfuration, Kambara Reactor desulfuration is performed to control sulfur content, and after removing desulfuration slag, hot metal is charged into converter for smelting.

[0039] In converter smelting, pre-desulfurized hot metal and scrap steel are used as raw materials to produce molten steel through the converter smelting processs. During smelting, ferrosilicon alloy, metallic manganese and carbon powder are sequentially added for deoxidation and alloying.

[0040] After refining molten steel to meet predetermined requirements, vacuum for circulation degassing is performed.

[0041] Refined molten steel undergoes vacuum for circulation degassing to remove inclusions and further refining.

[0042] After alloying by feeding alloy wire, molten steel is cast into blooms, which are then heated and soaked to ensure uniform temperature distribution, and preparing for rolling.

[0043] Step S2 specifically includes: Two-stage controlled rolling is adopted, including a first stage of austenite recrystallization zone rolling and a second stage of austenite non-recrystallization zone rolling, wherein a reduction ratio in the first stage of austenite recrystallization zone rolling is controlled to be ≥50%, repeated alternating deformation and recrystallization under large reduction thoroughly recrystallizes original austenite grains, gradually refining austenite grains through large reduction to obtain fine equiaxed austenite grains, increasing effective austenite grain boundary area to provide more nucleation sites for austenite-to-ferrite transformation.

[0044] Second stage of rolling is performed below recrystallization temperature with large reduction, increasing recrystallization nucleation sites and driving force, refining original austenite grains, promoting strain-induced precipitation of microalloying elements to achieve austenite grain refinement and work hardening. While austenite grains are elongated, deformation bands and numerous dislocations are produced, accumulating sufficient deformation energy within austenite grains to provide more nucleation sites for transformation, thereby refining grains.

[0045] Specifically, in the second stage of rolling, finish rolling temperature is controlled at 820±15°C, rolling the slab into steel plate with thickness ≤100mm. Combined with the aforementioned microalloying elements composition and addition amount, this can effectively refine grains and improve low-temperature toughness.

[0046] Step S2 specifically includes: Water cooling the rolled steel plate with cooling rate controlled at 10~28°C / s and finish cooling temperature controlled at 350±30°C, controlling cooling rate to form microstructure including acicular ferrite and granular bainite, wherein acicular ferrite content is ≥85%.

[0047] Through high cooling rate, the steel plate forms microstructure dominated by acicular ferrite. Acicular ferrite appears as lath-shaped, a mixed structure with complex phase characteristics. Its grain boundaries are carbon-rich layers with high potential, resistant to corrosion, protecting internal ferrite. Therefore, steel plates dominated by acicular ferrite structure have excellent corrosion resistance. Additionally, during formation, acicular ferrite develops supersaturated solid solution, fine substructure, and multi-directional precipitation morphology, significantly improving strength and toughness. While ensuring high strength, acicular ferrite also has the lowest ductile-brittle transition temperature. Through controlled rolling and cooling processes, utilizing strengthening mechanisms like solid solution strengthening, grain refinement, and precipitation strengthening effectively improves comprehensive properties.

[0048] This embodiment also provides a 460MPa-grade corrosion resistant steel plate manufactured by the above production method. Samples taken according to GB / T2975 and tested according to GB / T228 and GB / T229 for tensile and impact tests show yield strength ≥460MPa, tensile strength 540~720MPa, elongation after fracture ≥20%, and impact absorption energy KV2 at -50°C ≥100J.

[0049] After molten steel purification with rare earth elements, length-width product of maximum inclusions is ≤150µm 2< , and under GB / T10561 conditions, grades of A, B, C, and D type inclusions are all ≤1.5, with sum of grades ≤3.0.

[0050] Under GB / T 10125-2012 test conditions, average corrosion weight loss rate is ≤1.315g / (m 2< ·h).

[0051] When welding heat input is ≤80kJ / cm, impact absorption energy KV2 at -50°C in heat affected zone after welding is ≥80J.

[0052] In summary, this embodiment adopts a corrosion-resistant alloying composition system with combined addition of Cr+Ni+Mo+Cu+P, ensuring corrosion resistance and weldability while economizing precious alloy usage. While strictly controlling impurity elements, one or more rare earth elements from La, Ce, Pr, and Nd are used to purify molten steel, further improving corrosion resistance. Based on comprehensive chemical composition design, through precise control of rolling and cooling process parameters, accurate control of microstructure, inclusion content and size is achieved, obtaining 460MPa-grade wind tower steel plate with excellent comprehensive properties and marine atmospheric corrosion resistance.

[0053] The following further introduces specific embodiments through 4 examples and 3 comparative examples.

[0054] Chemical components of steel plates in Examples 1-4 and Comparative Examples 1-3 are shown in Table 1.

[0055] Comparative Example 1 has rare earth content lower than required 0.02~0.03% in the application.

[0056] Comparative Example 2 has P content lower than required 0.015~0.025% in the application, and Cr content lower than required 0.50~0.60% in the application, and Ni content lower than required 0.30~0.40% in the application, and Cu content lower than required 0.40~0.45% in the application, and atmospheric corrosion resistance index I lower than required 6.5 in the application.

[0057] Comparative Example 3 is ordinary Q460 high-strength steel without Ni, Cu, Mo, rare earth corrosion-resistant elements, and P and Cr contents lower than required in the application. [Table 1]Chemical components in percent by mass (%)CSiMnCrNiCuMoNbAlPrare earth elementsSONCEIExample 10.060.250.920.570.340.420.060.0310.0300.0210.0240.00170.00160.00370.396.58Example 20.070.230.950.580.360.410.080.0320.0270.0170.0250.00160.00140.00320.416.56Example 30.080.270.970.530.340.430.070.0350.0290.0230.0270.00140.00150.00340.416.53Example 40.080.280.960.580.370.420.060.0360.0310.0220.0270.00170.00110.00360.426.67Comparative Example 10.070.250.920.560.350.420.070.030.0320.02100.00170.00150.00340.406.57Comparative Example 20.080.240.950.250.150.240.070.0310.0340.0120.0260.00160.00130.00340.335.46Comparative Example 30.090.251.550.270000.0320.0350.01200.00180.00160.00320.400.90

[0058] Steel plates in Examples 1-4 and Comparative Examples 1-3 were all produced using the above method, with two-stage controlled rolling, and the thicknesses are shown in Table 2.

[0059] In controlled cooling process, reduction ratio in rough rolling stage, finish rolling temperature, finish cooling temperature and cooling rate for Examples 1-4 and Comparative Examples 1-3 are shown in Table 2. [Table 2]Thickness / mmReduction ratio in rough rolling stage / %Finish rolling temperature / °CFinish cooling temperature / °CCooling rate / °C / sExample 12072.781737926.5Example 25053.180535618.2Example 38051.679633713.7Example 41005078432410.6Comparative Example 12071.981537425.9Comparative Example 25056.380735918.4Comparative Example 31005078932810.7

[0060] After cooling of steel plates in Examples 1~4 and Comparative Examples 1~3, samples were taken for testing.

[0061] Inclusion test results for Examples 1~4 and Comparative Examples 1~3 are shown in Table 3. For Examples 1~4 and Comparative Example 2, length-width product of maximum inclusions is ≤150µm 2< , and under GB / T10561 conditions, grades of A, B, C, and D type inclusions are all ≤1.5, with sum of four inclusion type grades A+B+C+D ≤3.0. Comparative Examples 1 and 3 contain no rare earth elements, with sum of four inclusion type grades exceeding 3.0 and length-width product of maximum inclusions exceeding 150µm 2< . [Table 3]Example 1Example 2Example 3Example 4Comparati ve Example 1Comparati ve Example 2Comparati ve Example 3non-metallic inclusionsA typefine0.500.51.01.50.51.5coarse0000000B typefine0.500.501.00.50.5coarse0000000C typefine00.500.50.50.51.5coarse0000000D typefine0.50.51.00.50.50.51.0coarse0000000length-width product of maximum inclusions / µm 2< 3456478915262161

[0062] Samples were taken according to GB / T2975 and tested according to GB / T228 and GB / T229 for tensile and impact tests. Yield strength, tensile strength, elongation after fracture, and impact absorption energy KV2 at -50°C for Examples 1-4 and Comparative Examples 1-3 are shown in Table 4. Examples 1-4 and Comparative Examples 1 and 3 show yield strength ≥460MPa, tensile strength 540~720MPa, elongation after fracture ≥20%, and impact absorption energy KV2 at -50°C ≥100J. Comparative Example 2 has carbon equivalent below 0.39, resulting in yield strength below 460MPa and tensile strength below 540MPa. Comparative Example 3 is ordinary Q460 high-strength steel with microstructure of acicular ferrite and granular bainite, but acicular ferrite content doesn't meet the required ≥85%, resulting in impact absorption energy KV2 at -50°C below 100J.

[0063] Following GB / T 10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test", marine atmospheric corrosion resistance was tested under neutral 50±5g / L NaCl salt spray at 35±2°C. After 72h testing, average corrosion weight loss rates are shown in Table 4. Examples 1-4 show rates of 1.079~1.315g / (m 2< ·h). Comparative Example 1 shows severe pitting with rate of 1.946g / (m 2< ·h). Comparative Example 2 shows 2.975g / (m 2< ·h). Comparative Example 3 (ordinary Q460) shows highest rate at 3.428g / (m 2< ·h). Examples 1-4 show >50% reduction in corrosion rate compared to ordinary Q460. [Table 4]Yield strength / MPaTensile strength / MPaElongation after fracture / %Impact absorption energy KV2 at -50°C / JAverage corrosion weight loss rate / g / (m 2< ·h)Corrosion rate compared to ordinary Q460 / %At 1 / 4 thickness positionAt 1 / 2 thickness positionExample 150760223.4304, 311, 317 / 1.07931Example 248259124.6312, 309, 314321, 316, 3051.31538Example 347557924.7317, 312, 315300, 307, 3141.20935Example 449857723.9298, 307, 317285, 276, 2931.28738Comparative Example 149159825.0311, 315, 307 / 1.94657Comparative Example 242152925.5305, 312, 327325, 309, 3142.97587Comparative Example 348758423.0177, 58, 13916, 27, 203.428100

[0064] Performing double-wire submerged arc welding to the steel palte of example 4 with a welding heat input of 77±3kJ / cm. Low temperature impact energy test results at -50°C for the welding joint heat affected zone at fusion line (FL), FL+2, FL+5, and FL+20 locations are shown in Table 5. [Table 5]FLFL+2FL+5FL+20Near surface95, 103, 188287, 264, 291302, 297, 285295, 299, 304Root97, 93, 105257, 198, 278289, 281, 294301, 297, 275

[0065] It should be understood that while this specification describes embodiments, each embodiment doesn't necessarily contain only one independent technical solution. This description style is merely for clarity. Technical personnel should consider the specification as a whole, and technical solutions in various embodiments can be appropriately combined to form other embodiments understandable to technical personnel.

[0066] The series of detailed descriptions listed above are merely specific explanations of feasible embodiments of the present application and not intended to limit its protection scope. Any equivalent implementations or modifications made without departing from the technical spirit of the present application should be included within its protection scope.

Claims

1. A production method for a 460MPa-grade corrosion resistant steel plate, wherein chemical components of the steel plate include in percent by mass: C: 0.06~0.09%, Si: 0.2~0.3%, Mn: 0.9~1.0%, Cr: 0.5~0.6%, Ni: 0.30~0.40%, Cu: 0.40~0.45%, Mo: 0.05~0.10%, Nb: 0.02~0.04%, Al: 0.02~0.04%, P: 0.015~0.025%, rare earth elements: 0.015~0.025%, and the balance of Fe and inevitable impurities, wherein some impurity elements include in percent by mass: S≤0.002%, O≤0.002%, N<0.004%; wherein an atmospheric corrosion resistance index I of the steel plate is ≥6.5, and the atmospheric corrosion resistance index I is calculated by the following formula: wherein element symbols in brackets represent mass percentages of corresponding elements, and %element symbol represents mass percentage of corresponding element multiplied by 100; the production method comprises steps of: smelting and casting according to the above chemical component ratio to obtain a bloom; performing two-stage controlled rolling on the bloom to obtain a steel plate, including a first stage of austenite recrystallization zone rolling and a second stage of austenite non-recrystallization zone rolling, wherein a reduction ratio in the first stage of austenite recrystallization zone rolling is controlled to be ≥50%, and a finish rolling temperature in the second stage of austenite non-recrystallization zone rolling is controlled to be 800±20°C; performing cooling on the steel plate, and controlling cooling rate to form a microstructure including acicular ferrite and granular bainite in the steel plate, wherein a content of the acicular ferrite is ≥85%.

2. The production method for the 460MPa-grade corrosion resistant steel plate according to claim 1, wherein a carbon equivalent CE of the steel plate satisfies 0.39≤CE≤0.42, wherein the carbon equivalent CE is calculated by the following formula: CE = % C + % Mn / 6 + % Cr + % Mo + % V / 5 + % Ni + % Cu / 15 wherein element symbols in brackets represent mass percentages of corresponding elements, and %element symbol represents mass percentage of corresponding element3. The production method for the 460MPa-grade corrosion resistant steel plate according to claim 1, wherein in the chemical components of the steel plate, the rare earth elements are one or more of La, Ce, Pr and Nd.

4. The production method for the 460MPa-grade corrosion resistant steel plate according to claim 1, further comprising: rolling the bloom into a steel plate with a thickness ≤100mm.

5. The production method for the 460MPa-grade corrosion resistant steel plate according to claim 1, wherein performing cooling on the steel plate specifically comprises: water cooling the rolled steel plate with a cooling rate controlled to be 10~28°C / s and a finish cooling temperature of the steel plate controlled to be 350±30°C.

6. A 460MPa-grade corrosion resistant steel plate, wherein chemical components of the steel plate include in percent by mass: C: 0.06~0.09%, Si: 0.2~0.3%, Mn: 0.9~1.0%, Cr: 0.5~0.6%, Ni: 0.30~0.40%, Cu: 0.40~0.45%, Mo: 0.05~0.10%, Nb: 0.02~0.04%, Al: 0.02~0.04%, P: 0.015~0.025%, rare earth elements: 0.015~0.025%, and the balance of Fe and inevitable impurities, wherein some impurity elements include in percent by mass: S≤0.002%, O≤0.002%, N<0.004%; wherein a microstructure of the steel plate includes acicular ferrite and granular bainite, wherein a content of the acicular ferrite is ≥85%; wherein under test conditions of GB / T 10125-2012, an average corrosion weight loss rate of the steel plate is ≤1.315g / (m2·h); wherein samples are taken according to GB / T2975, and tensile and impact tests are carried out according to GB / T228 and GB / T229, wherein the steel plate has a yield strength ≥460MPa, a tensile strength of 540~720MPa, an elongation after fracture ≥20%, and an impact absorption energy KV2 at -50°C ≥100J.

7. The 460MPa-grade corrosion resistant steel plate according to claim 6, wherein a length-width product of maximum inclusions in the steel plate is ≤150µm2, and under conditions of GB / T10561, grades of A, B, C, and D type inclusions are all ≤1.5, and a sum of grades of A, B, C, and D type inclusions is ≤3.0.

8. The 460MPa-grade corrosion resistant steel plate according to claim 6, wherein when a welding heat input is ≤80kJ / cm, the steel plate has an impact absorption energy KV2 at -50°C ≥80J in a heat affected zone after welding.

9. The 460MPa-grade corrosion resistant steel plate according to claim 6, wherein the steel plate has a thickness not greater than 100mm.

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