High-strength steel plate for marine engineering with corrosion resistance and capable of large heat input welding, and method for producing the same

Abstract

The present invention relates to a corrosion-resistant, high-strength steel plate for marine engineering that can be welded with large heat input, the chemical composition of which is, in mass percent, C: 0.06%-0.09%, Si: 0.15%-0.30%, Mn: 1.45%-1.60%, P: ≦0.012%, S: ≦0.003%, Ni: 0.40%-0.70%, Cu: 0.20%-0.50%, Ti: 0.005%-0.015%, Als: 0.06%-0.09%, and the remainder being Fe and unavoidable impurities. The corrosion-resistant, large heat-input weldable high-strength steel plate for marine engineering according to the present invention is produced by the TMCP thermomechanical controlled rolling and rapid cooling process, has a thickness of 40mm-60mm, and has a KV2(-40℃) of ≧47J in HAZ after 160-210kJ / cm heat input welding, good low-temperature impact toughness, seawater corrosion resistance improved by 35% or more compared to ordinary marine engineering steel, and has the characteristics of high toughness, corrosion resistance, large heat input weldability, and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of low alloy steel. Specifically, the present invention relates to a high-strength steel plate for ocean engineering with corrosion resistance and large heat input weldability, and a manufacturing method thereof. matter (Cross-reference to related applications) This application claims priority based on Chinese Patent Application No. 202111462807.3 filed on December 2, 2021, and all the contents of this Chinese patent application are incorporated herein by reference.

Background Art

[0002] High-strength steel plates for ocean engineering matter are important structural materials in advanced ocean engineering matter and high-tech shipbuilding. Ultra-high strength and excellent low-temperature toughness are the basic requirements for ship and ocean engineering matter steels. As the requirements for the safety of the hull structure are constantly increasing, the strength of shipbuilding steel plates has been gradually improved, gradually increasing from 235 MPa to 315 MPa and 355 MPa, and the steel quality grade has also been improved from grade A to grade E and then to grade F. High-strength steel with large heat input weldability is also one of the hotspots attracting the attention of ship and ocean engineering matter equipment manufacturing enterprises. In order to improve the welding efficiency and shorten the construction cycle, large heat input welding methods, such as vertical electro-gas welding, submerged arc welding, electro-slag welding and other methods, have gradually begun to be used. Under the conditions of large heat input welding, especially when the heat input of welding is greater than 50 kJ / cm, with the increase of the heat input of welding, brittle tissues such as grain boundary ferrite and M-A are formed in the heat affected zone of the weld, and the toughness of the heat affected zone of the weld is significantly reduced, thereby forming a local embrittlement zone. Therefore, the safety of the welded structural members is reduced. Ships and ocean engineering matter equipment not only undergoes the interaction of temperature, humidity and chloride ions during its service process in the marine environment, but also undergoes the combined action of variable loads such as wind force and wave impact, facing the risk of severe corrosion. Therefore, ocean engineering with high strength and toughness, corrosion resistance and large heat input weldability​matter Developing steel for marine engineering is currently a key point for the development of steel for marine engineering. matter It has become a key point for the development of steel for marine engineering.

[0003] In Patent Document CN102839320A and Patent Document CN105256095A, steels with good adaptability to high-heat input welding can be obtained. However, they both need to be micro-alloyed with element B, and element B is difficult to be added in the smelting process and prone to segregation, resulting in higher production difficulty.

[0004] In Patent Document CN102839330A, by adding elements Ni, Cr, and Mo, steel plates that can adapt to welding heat inputs of 40 - 100 kJ / cm with a thickness within 30 mm have been researched and developed. However, the content of the added Ni, Cr, Mo alloy can reach a maximum of 5%, resulting in higher costs. In Patent Document CN102286692A, steel that can be welded with high heat input and has good low-temperature performance is obtained by the DQ + T process, but quenching and tempering heat treatment is required, resulting in higher process costs. The components or production processes related to the above two patent applications have higher costs and are disadvantageous for popularization.

[0005] In Patent Document CN111926259A, by using Ti, Mg, Zr oxide metallurgy technology, fine diffusion composite inclusions of Ti - X - O with a reasonable mixing ratio are formed in the steel, and through the hot working control process, low alloy steel plates with good strength and toughness matching and suitable for high heat input welding of 100 kJ / cm - 200 kJ / cm are obtained. However, this method has drawbacks in terms of the economy of alloy cost and the corrosion resistance of the product.

Summary of the Invention

Problems to be Solved by the Invention

[0006] In view of the drawbacks of the prior art, the present invention provides a high-strength steel plate for marine engineering that has corrosion resistance and can be welded with high heat input. The high-strength steel plate for marine engineering with marine corrosion resistance and weldability with high heat input according to the present invention matter has marine corrosion resistance and can be welded with high heat input. matterThe steel plate has excellent properties such as reasonable design, high toughness of the product, corrosion resistance, and the ability to perform large heat input welding.

Means for Solving the Problem

[0007] In order to achieve the above object, the present invention uses the following technical solutions.

[0008] A high-strength steel plate for marine engineering with corrosion resistance and capable of large heat input welding according to the present invention, the components of which are, by mass percentage, C: 0.06% - 0.09%, Si: 0.15% - 0.30%, Mn: 1.45% - 1.60%, P: ≤0.012%, S: ≤0.003%, Ni: 0.40% - 0.70%, Cu: 0.20% - 0.50%, Ti: 0.005% - 0.015%, Als: 0.06% - 0.09%, and the balance is Fe and inevitable impurity elements, CEV ≤0.40%, and Pcm ≤0.23%. matter Here, CEV = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15, Pcm = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + 5B.

[0009] The present invention can rationally design the contents of alloying elements such as Ni and Cu, form an effective strength effect, improve the low-temperature toughness and welding performance of the steel plate, and significantly improve the corrosion resistance of the steel plate.

[0010] matter In the above high-strength steel plate for marine engineering with corrosion resistance and capable of large heat input welding, as a preferred embodiment, based on the mass of the steel plate, the contents of the inevitable impurity elements are, by mass percentage, H ≤0.0002%, O ≤0.003%, N ≤0.004%, B ≤0.0005%, As ≤0.007%, Sb ≤0.010%, Sn ≤0.020%, Pb ≤0.010%, Bi ≤0.010%.

[0011] ​​The reasons for the selection of the chemical composition of the high-strength steel sheet with corrosion resistance and high heat input weldability according to the present invention are as follows.

[0012] [Regarding Ti] Ti can form carbides, nitrides or carbonitrides with C and N elements, suppress the excessive growth of austenite grain crystals during the heating and manufacturing processes of the slab, has a good grain refinement effect, and can improve the low-temperature toughness of the steel sheet. More importantly, during the welding process, the growth of grain crystals in the heat-affected zone can be suppressed, and the toughness of the heat-affected zone is improved. However, if the Ti content is too high, large particles of TiN are easily formed, eliminating the grain refinement effect. Considering the alloy cost and the performance of the steel sheet comprehensively, the present invention controls the Ti content to be 0.005% - 0.015%.

[0013] [Regarding Cu] It has a strong solid solution strengthening effect, promotes the formation and stability of austenite, and an appropriate amount of Cu can improve the strength without sacrificing the low-temperature toughness and can improve the corrosion resistance performance. In the present invention, Cu plays a precipitation strengthening role during the subsequent cooling process and can compensate for the strength loss caused by the coarsening of the central structure. To ensure the above effects of Cu, the Cu content is set to be 0.20% or more. However, if the Cu content is too high, it will cause hot brittleness during heating, deteriorate the surface quality, and damage the low-temperature toughness of the base material and the heat-affected zone. Therefore, the Cu content is controlled to be 0.20% - 0.50%.

[0014] [Regarding Ni] Promote the formation and stability of austenite, suppress the recrystallization of austenite, and refine the size of crystal grains. Therefore, Ni has the function of simultaneously improving the strength, elongation, and low-temperature toughness of the steel plate. When Ni is added to the steel, it can reduce the copper embrittlement phenomenon of the steel and also reduce the grain boundary cracks during the hot rolling process. Ni can promote the formation of a dense protective rust layer on the surface of the steel plate, thereby improving the corrosion resistance of the steel plate. Therefore, theoretically, the higher the Ni content in the steel within a certain range, the better. However, if the Ni content is too high, it will harden the heat-affected zone of the weld, which is disadvantageous to the weldability of the steel plate. Therefore, the present invention controls the Ni content to be 0.40% - 0.70%.

[0015] [Regarding Als] Al in the steel can fix the free N in the steel, improve the low-temperature toughness of the steel plate and the weld HAZ (Heat-Affected Zone), and the dispersed precipitation of AlN can suppress the growth of austenite crystal grains during the heating process, uniformly refine the size of austenite crystal grains, and improve the impact toughness. Al also has antioxidant and corrosion resistance properties. However, due to too high an Al content, the number of inclusions in the steel increases, the size of the inclusions becomes larger, the internal quality of the steel plate deteriorates, and it has an adverse impact on the hot working performance, welding performance, and cutting performance of the steel. Therefore, the present invention controls the Als content to be 0.06% - 0.09%.

[0016] [Regarding N] If its content is too high, it will form coarse TiN and AlN, which precipitate at the original austenite grain boundaries, damaging the impact toughness and plasticity of the steel plate and the weld heat-affected zone. At the same time, N atoms further enrich at the defects in the steel, forming pores and coarse grains, further deteriorating the mechanical properties of the steel plate. Therefore, considering that it is difficult to completely remove N in the steel, the present invention controls the N content to be ≤0.004%.

[0017] [Regarding B] If its content is too high, it will enrich at the grain boundaries of the steel plate. As a result, the grain boundary energy is reduced, a low-temperature transformation structure is formed in the steel plate during the cooling process, and the low-temperature impact performance and fatigue performance of the steel plate are deteriorated. Therefore, the content of B in the present invention is set to ≤0.0005%.

[0018] [Regarding O] The O element remains in the slab or diffuses to the surface layer, easily oxidizes the grain boundaries to form a brittle oxide intermediate layer, and blocks the austenite grain boundaries, thereby causing grain boundary cracks in subsequent deformation processing, and thereby significantly reducing the strength and plasticity of the steel plate. Therefore, the content of O is controlled as much as possible. In order to ensure the plasticity and low-temperature toughness of the steel plate, inclusions in the steel must be reduced. Since the harm of alumina inclusions is the greatest, the content of O in the steel is set to ≤0.003%.

[0019] [Regarding H] The presence of hydrogen element causes white spots. Therefore, the content of H is controlled to ≤0.0002%.

[0020] [Regarding CEV] The control of the carbon equivalent index contributes to ensuring the strength and weldability of the steel plate. The CEV of the present invention is controlled to ≤0.40%.

[0021] [Regarding Pcm] The control of the cold crack susceptibility coefficient contributes to ensuring the welding performance of the product. The Pcm of the present invention is controlled to ≤0.23%.

[0022] The manufacturing method of the high-strength steel plate with corrosion resistance and large heat input weldability according to the present invention matter for ocean engineering is a steelmaking casting step (1) in which hot metal and steel scraps are steelmaking to obtain molten steel, then the molten steel is refined and cast to obtain a slab, and then the slab is slowly cooled; a slab heating step (2) in which the slowly cooled slab is heated to obtain a hot slab; a rolling step (3) in which the hot slab is rolled to obtain a steel plate A cooling step is performed to cool the steel plate to obtain the corrosion-resistant, large heat input weldable marine construction. matter and (4) obtaining a high strength steel plate for use in a manufacturing process.

[0023] The above-mentioned corrosion-resistant marine construction that can be welded with large heat input matter In the high strength steel plate for use in the present invention, in the step (1), the refining is LF+RH refining, preferably, in the LF refining process, argon gas is blown from the bottom and stirred throughout the entire process, and deoxidized with aluminum particles and calcium carbide, the upper slag is yellowish white slag or white slag before discharge, the holding time of the yellowish white slag or white slag is 10 minutes or more, and the alkalinity of the final slag is controlled to 2.5 or more, preferably, in the LF refining process, the composition is finely adjusted with an alloy such as metal manganese or ferrosilicon, preferably, in the RH refining, the degassing time is 5 minutes or more, and after the RH refining process is completed, calcium aluminum wire is sent to each furnace for 100 to 150 m (for example, 110 m, 120 m, 130 m, 140 m) to perform soft blowing for 12 minutes or more.

[0024] The above-mentioned corrosion-resistant marine construction that can be welded with large heat input matter In the preferred embodiment of the high strength steel plate for use in the casting process, in the step (1), protective casting is used throughout the casting process, the liquidus temperature of this steel is required to be 1514-1524°C (for example, 1516°C, 1518°C, 1520°C, 1522°C), the superheat is required to be less than 25°C, a weak pressing technique is used at the solidification end of the sector segment cast piece, and the cast piece is slowly cooled in a cooling pit for more than 60 hours, thereby sufficiently reducing the structural stress and thermal stress generated in the casting piece during the cooling process.

[0025] The above-mentioned corrosion-resistant marine construction that can be welded with large heat input matterIn the high-strength steel plate for use, as a preferred embodiment, in step (2), the heating time is ≥9 min / cm, the slab is subjected to soaking heat treatment by multi-stage heating and temperature increase, the heating temperature in the first stage is 1020 - 1140°C, the heating temperature in the second stage is 1100 - 1190°C, the temperature in the soaking stage is 1110 - 1170°C, the soaking time is 40 minutes or more, and the slab discharging temperature is 1110 - 1150°C (for example, 1120°C, 1130°C, 1140°C). After taking out the slab from the heating furnace, the hot slab is descaled with high-pressure water.

[0026] The above-mentioned high-strength steel plate with corrosion resistance and large heat input weldability for ocean engineering matter In the high-strength steel plate for use, as a preferred embodiment, in step (3), the rolling is two-stage rolling of rough rolling and finish rolling, the rough rolling is recrystallization rolling, the finish rolling is non-recrystallization rolling. Preferably, in the rough rolling stage, the deformation amount of at least 2 passes is ≥20%, and it is ensured to refine the crystal grains with strong reduction. Preferably, the finish rolling start temperature is 825 - 855°C (for example, 830°C, 835°C, 840°C, 845°C, 850°C), the finish rolling stage has at least 3 passes of deformation within the temperature range of 790 - 760°C (for example, 785°C, 780°C, 775°C, 770°C, 765°C), and it should be ensured that the cumulative deformation amount of the 3 passes is ≥20%, thereby promoting the deformation to progress to the center part to refine ferrite.

[0027] The above-mentioned high-strength steel plate with corrosion resistance and large heat input weldability for ocean engineering matter In the high-strength steel plate for use, as a preferred embodiment, in step (4), by setting the cooling rate to 10 - 15°C / s (for example, 11°C / s, 12°C / s, 13°C / s, 14°C / s), the nucleation rate of ferrite is increased to form fine diffusion precipitation phases, and the strength and toughness of the steel are further improved. The self-tempering temperature is set to 500°C - 550°C (510°C, 520°C, 530°C, 540°C).

Advantages of the Invention

[0028] Compared with the prior art, the advantages of the present invention are as follows.

[0029] 1. The present invention does not require the addition of a large amount of precious metals such as Mo and Cr. It uses Mn element for solid solution strengthening, and fully exerts the solid solution strengthening and precipitation strengthening effects of Ni and Cu elements to obtain a fine and uniformly distributed pearlite + ferrite mixed structure, and can achieve excellent strength, plasticity and low-temperature toughness with a relatively low alloy content, reduce the alloy cost and production cost, and improve the welding performance of the steel plate. At the same time, Ni and Cu elements can effectively promote the formation of a dense and highly adherent protective rust layer on the surface of the steel for marine engineering matter steel, preventing corrosion media such as H2O, O2, and Cl - from penetrating into the steel matrix, thereby improving the corrosion resistance.

[0030] 2. The present invention provides good slab raw materials by controlling the components, purity and gas content in the steelmaking process. The slab is subjected to homogenization heat treatment in the heating furnace by multi-stage heating and temperature rise, the slab discharging temperature is controlled to ensure that the steel slab is sufficiently heated, fully austenitized, and the crystal grains do not coarsen, and each alloy element is fully dissolved, laying a good foundation for subsequent rolling control.

[0031] 3. The present invention is produced by the TMCP thermo-mechanical control rolling and rapid cooling process, and does not require a complicated quenching and tempering heat treatment process. In the rough rolling stage, the crystal grains are refined by strong reduction, and in the finish rolling stage, the control rolling is carried out in the non-recrystallization region, ensuring at least 3 passes of rolling process with strong reduction at low temperature. This promotes the deformation to progress to the center to refine ferrite, and forms a large amount of dislocation to effectively prevent the growth of crystal grains and improve the performance. After rolling, laminar flow cooling is carried out, and the self-tempering temperature after cooling is controlled, thereby increasing the nucleation rate of ferrite and forming fine diffusion precipitation phases to further improve the strength and toughness of the steel.

[0032] The present invention realizes sufficient control of the phase transition process through a reasonable process design, with a thickness of 40 - 60 mm, a yield strength ≥ 355 MPa, a tensile strength of 490 - 630 MPa, and the KV2 (-40 °C) of the HAZ after large heat input welding of 160 - 210 kJ / cm being ≥ 47 J, having good low-temperature impact toughness and a seawater corrosion resistance performance that is more than 35% higher than that of ordinary marine engineering matter steel. matter The product obtained has characteristics such as high strength and toughness, corrosion resistance, weldability with large heat input, and low cost.

Embodiments for Carrying out the Invention

[0033] Hereinafter, a high-strength steel plate for marine engineering with corrosion resistance and weldability with large heat input and its manufacturing method will be described in more detail by specific examples. These examples are only for interpretation, and the present invention is not limited to these examples. matter

[0034] matter According to the embodiments of the present invention, a high-strength steel plate for marine engineering with corrosion resistance and weldability with large heat input and its manufacturing method are provided. Its chemical composition, by weight percentage, is C: 0.06% - 0.09%, Si: 0.15% - 0.30%, Mn: 1.45% - 1.60%, P: ≤ 0.012%, S: ≤ 0.003%, Ni: 0.40% - 0.70%, Cu: 0.20% - 0.50%, Ti: 0.005% - 0.015%, Als: 0.06% - 0.09%, and the rest is Fe and inevitable impurity elements. The present invention uses a low C + Ni, Cu alloying design and a TMCP thermo-mechanical controlled rolling + rapid cooling production process to obtain marine engineering steel with characteristics such as high strength and toughness, corrosion resistance, weldability with large heat input, and low cost. After large heat input welding of 160 - 210 kJ / cm, the impact toughness at -40 °C in the weld heat-affected zone is ≥ 47 J, the low-temperature impact toughness is good, and the seawater corrosion resistance performance is more than 35% higher than that of ordinary marine engineering matter steel. matter After carrying out large heat input welding of 160 - 210 kJ / cm, the impact toughness at -40 °C in the weld heat-affected zone is ≥ 47 J, the low-temperature impact toughness is good, and the seawater corrosion resistance performance is more than 35% higher than that of ordinary marine engineering matter steel.

[0035] The present invention provides a manufacturing method for the above steel plate, which includes steps of steelmaking, continuous casting, slab heating, rolling, and cooling.

[0036] In smelting, the raw materials charged into the furnace must meet the technical requirements of the converter process. The hot metal from the blast furnace is desulfurized by KR pretreatment, and the sulfur content of the hot metal charged into the furnace is ≤ 0.015%. After desulfurization is completed, all the slag on the surface of the hot metal is removed. The hot metal should be accurately weighed and the charging amount should be strictly controlled, with the error of the charging amount being ±2 tons. Nickel plates and copper plates are added together with steel scraps. Primary carbon capture is used, and the slag material is added and completed 3 minutes before the end point. Smelting is carried out by a double slag deep dephosphorization process, and the alkalinity of the final slag is controlled at R = 3.0 - 4.0. The slag is cut off and tapping is carried out to prevent a large amount of slag carry-over. The tapping time should be more than 3 minutes. The steel containing 3.5 - 4.0 kg / t of aluminum - manganese - iron (Al - Mn - Fe) is used for deoxidation. When one - quarter of the molten steel is discharged, ferromanganese and ferrosilicon alloys are added in several portions, and the addition is completed until three - quarters of the molten steel is discharged. During the LF refining process, argon gas is bottom - blown and stirred throughout the whole process, and the molten steel should not be exposed during the whole smelting process to prevent secondary oxidation of the molten steel. Deoxidation is carried out with aluminum particles and calcium carbide. Before tapping, the upper slag should be yellow - white slag or white slag, and the retention time of the yellow - white slag or white slag should be more than 10 minutes. The alkalinity of the final slag should be controlled at 2.5 or more as much as possible. Component fine - tuning is carried out with alloys such as ferromanganese and ferrosilicon to ensure that the components meet the internal control requirements. The LF refining time should be more than 45 minutes. Chemical heating up is avoided during RH refining, and it is ensured that the pure degassing time is more than 5 minutes. After the RH treatment is completed, 100 - 150 m of calcium - aluminum wire is sent per furnace and soft - blown for more than 12 minutes, and the RH smelting cycle is controlled at 40 - 60 minutes.

[0037] In continuous casting, protective casting is used throughout the entire process. When calculating based on the midpoint of the components with intermediate specifications, the liquidus temperature is 1519 °C, and the superheat is required to be less than 25 °C. A weak reduction technique is used at the solidification end of the slab in the segment, and the slab is slowly cooled for 60 hours or more, thereby sufficiently reducing the tissue stress and thermal stress generated during the cooling process of the slab. When the cross-sectional thickness of the slab is 175 mm, the drawing speed is controlled at 1.0 - 1.3 m / min; when the cross-sectional thickness of the slab is 200 mm, the drawing speed is controlled at 1.0 - 1.4 m / min; when the cross-sectional thickness of the slab is 250 mm, the drawing speed is controlled at 1.0 - 1.3 m / min; when the cross-sectional thickness of the slab is 300 mm, the drawing speed is controlled at 0.7 - 0.9 m / min.

[0038] In slab heating, the continuous casting slab is added to the heating furnace for heating. The charging method of the slab into the heating furnace is cold charging, the heating time is ≥ 9 min / cm, the slab is subjected to soaking heat treatment by multi-stage heating and temperature rise, the soaking time is 40 minutes or more, the temperature difference at each point of the steel slab is 20 °C or less, the slab discharging temperature is 1110 - 1150 °C, and after the slab is taken out of the heating furnace, the hot slab is descaled with high-pressure water.

[0039] In rolling, the process is two-stage rolling of rough rolling and finish rolling. The rough rolling is recrystallization rolling, and the finish rolling is non-recrystallization rolling. In the rough rolling stage, the deformation amount of at least 2 passes is ≥ 20%, and strong reduction is ensured to refine the crystal grains. The start temperature of the finish rolling is 825 - 855 °C. In the finish rolling stage, at least 3 passes of deformation are within the temperature range of 790 - 760 °C, and it should be ensured that the cumulative deformation amount of the 3 passes is ≥ 20%, thereby promoting the deformation to progress to the center part and refining the ferrite.

[0040] In cooling, by setting the cooling rate to 10 - 15 °C / s, the nucleation rate of ferrite is increased, and a fine diffusion precipitation phase is formed to further improve the strength and toughness of the steel. The self-tempering temperature is set to 500 - 550 °C. After rolling, it is taken offline as soon as possible and put into a slow cooling pit, stacked and slowly cooled, and the slow cooling time is 48 hours or more.

[0041] Example 1: Steel plate thickness 50 mm The present invention relates to a marine construction material that is corrosion resistant and can be welded with large heat input. matter The present invention provides a high strength steel plate for use in a wide range of applications, the chemical composition and weight percent contents of which are C: 0.085%, Si: 0.19%, Mn: 1.47%, P: 0.0086%, S: 0.0014%, Ni: 0.50%, Cu: 0.35%, Ti: 0.010%, Als: 0.064%, the balance being Fe and unavoidable impurities, CEV=0.39%, Pcm=0.19%.

[0042] The slab discharge temperature is 1140°C, the finish rolling start temperature is 834°C, the deformation of the last three passes of the finish rolling stage is in the temperature range of 775°C to 763°C, the accumulated deformation amount is 22.08%, and the self-tempering temperature is 550°C.

[0043] Example 2: Steel plate thickness 50 mm The present invention relates to a marine construction material that is corrosion resistant and can be welded with large heat input. matter The present invention provides a high strength steel plate for use in a wide range of applications, the chemical composition and weight percent contents of which are C: 0.080%, Si: 0.18%, Mn: 1.48%, P: 0.009%, S: 0.0016%, Ni: 0.55%, Cu: 0.37%, Ti: 0.010%, Als: 0.062%, the balance being Fe and unavoidable impurities, CEV=0.39%, Pcm=0.19%.

[0044] The slab discharge temperature is 1150°C, the finish rolling start temperature is 825°C, the deformation of the last three passes of the finish rolling stage is in the temperature range of 781-769°C, the accumulated deformation amount is 22.65%, and the self-tempering temperature is 523°C.

[0045] The performance of the steel plates and the performance of the welded joints in each embodiment of the present invention are shown in Table 1. The results after immersing the steel grades of the examples in the simulated seawater (3.5% NaCl solution) in the laboratory for 7 days under the condition of a test temperature of (30±2)°C are shown in Table 2. The chemical composition of the conventional EH36 steel for comparison is in weight percentage: C: 0.14%, Si: 0.30%, Mn: 1.25%, P: 0.015%, S: 0.003%, Nb: 0.020%, Al: 0.037%, Ti: 0.015%.

[0046]

Table 1

[0047]

Table 2

[0048] As can be seen from the above, the steel plates of the present invention still have good low-temperature toughness after performing high-heat input welding of 160-210 kJ / cm, creating conditions for efficient welding of the steel plates, and their seawater corrosion resistance performance is more than 35% improved compared with ordinary offshore engineering steel plates, and the service life and safety are greatly improved. matter In short, the high-heat input weldable offshore engineering steel plate with corrosion resistance according to the present invention has excellent comprehensive performance such as high strength and toughness, corrosion resistance, and high-heat input weldability, and has lower cost, simpler process, and is easy to popularize and apply.

[0049] In summary, the corrosion-resistant high-heat input weldable offshore engineering steel plate according to the present invention has excellent comprehensive performance such as high strength and toughness, corrosion resistance, and high-heat input weldability, and has lower cost, simpler process, and is easy to popularize and apply. matter In short, the high-heat input weldable offshore engineering steel plate with corrosion resistance according to the present invention has excellent comprehensive performance such as high strength and toughness, corrosion resistance, and high-heat input weldability, and has lower cost, simpler process, and is easy to popularize and apply.

[0050] For the content not described in detail in the present invention, any ordinary technical knowledge in this field may be used.

[0051] Finally, it should be noted that the above embodiments are merely for explaining the technical solutions of the present invention and do not limit it. Although the present invention has been described in detail with reference to the embodiments, as those skilled in the art will understand, any modification or equivalent substitution made to the technical solutions of the present invention should be included within the scope of the claims of the present invention without departing from the gist and scope of the technical solutions of the present invention.

Claims

1. A high-strength steel plate for marine engineering that is weldable with high heat input and has corrosion resistance, The chemical composition is, by mass percentage, C: 0.06% to 0.09%, Si: 0.15% to 0.30%, Mn: 1.45% to 1.60%, P: ≤0.012%, S: ≤0.003%, Ni: 0.40% to 0.70%, Cu: 0.20% to 0.50%, Ti: 0.005% to 0.015%, Als (acid-soluble Al): 0.06% to 0.09%, and the balance is Fe and inevitable impurity elements, The thickness is 40 to 60 mm, the yield strength ≥355 MPa, the tensile strength is 490 to 630 MPa, and after high heat input welding at 160 to 210 kJ / cm, the KV2 (Charpy impact energy) at -40°C in the HAZ is ≥47 J. A high-strength steel plate for marine engineering that is weldable with high heat input and has corrosion resistance, characterized by this.

2. CEV ≤0.40%, Pcm ≤0.23%. A high-strength steel plate for marine engineering that is weldable with high heat input and has corrosion resistance according to Claim 1, characterized by this.

3. The content of the inevitable impurity elements is, by mass percentage, H ≤0.0002%, O ≤0.003%, N ≤0.004%, B ≤0.0005%, As ≤0.007%, Sb ≤0.010%, Sn ≤0.020%, Pb ≤0.010%, Bi ≤0.010%. A high-strength steel plate for marine engineering that is weldable with high heat input and has corrosion resistance according to Claim 1, characterized by this.

4. A manufacturing method of a high-strength steel plate for marine engineering that is weldable with high heat input and has corrosion resistance according to any one of Claims 1 to 3, A smelting and casting step, which includes primary smelting of hot metal and steel scrap to obtain primary smelted molten steel, then refining and casting the primary smelted molten steel to obtain a slab, and then slow cooling the slab. Step (1); A slab heating step, which includes heating the slow-cooled slab to obtain a hot slab, subjecting the slab to homogenization treatment by multi-stage heating and temperature increase, making the homogenization time 40 minutes or more, and making the slab discharging temperature 1110°C to 1150°C. Step (2); A rolling step, which includes rolling the hot slab to obtain a steel plate, and the rolling is two-stage controlled rolling of rough rolling and finish rolling. The rough rolling is rolling in the recrystallization region, and the finish rolling is rolling in the non-recrystallization region. Step (3); A cooling step, which includes cooling the steel plate to obtain a high-strength steel plate for marine engineering that is weldable with high heat input and has corrosion resistance. Step (4); A method for manufacturing a high-strength steel plate for marine engineering with corrosion resistance and high heat input weldability according to any one of claims 1 to 3, which comprises

5. The refining in step (1) is LF + RH refining, In the LF refining process, stirring is carried out while bottom-blowing argon gas throughout the whole process, deoxidation is carried out with aluminum particles and calcium carbide, the upper slag is yellowish-white slag or white slag before tapping, the holding time of the yellowish-white slag or white slag is 10 minutes or more, the basicity of the final slag is controlled to be 2.5 or more, and in the LF refining process, component fine adjustment is carried out with ferromanganese and / or ferrosilicon alloy, In the RH refining, the degassing time is 5 minutes or more, and after the RH refining treatment is completed, 100 m to 150 m of calcium-aluminum wire is fed per furnace and soft blowing is carried out for 12 minutes or more. The manufacturing method according to claim 4 is characterized by this.

6. In step (1), in the casting process, protective casting is used throughout the whole process, the liquidus temperature is 1514 - 1524 °C, the superheat is less than 25 °C, a weak pressing technique is used at the solidification end of the slab of the segmental mold, the slab is put into the pit, and the slow cooling of the stacked slab is 60 hours or more. The manufacturing method according to claim 4 is characterized by this.

7. In step (2), the heating time is ≥ 9 min / cm, and for the multi-stage heating and temperature rise, the heating temperature in the first stage is 1020 - 1140 °C, the heating temperature in the second stage is 1100 - 1190 °C, and the soaking temperature is 1110 - 1170 °C. The manufacturing method according to claim 4 is characterized by this.

8. In step (3), in the rough rolling stage, the reduction of at least 2 passes is ≥ 20%, and it is ensured that the starting temperature of finish rolling is 825 - 855 °C. In the finish rolling stage, the deformation of at least 3 passes is within the temperature range of 790 - 760 °C, and it is ensured that the cumulative reduction of these 3 passes is ≥ 20% The manufacturing method according to claim 4 is characterized by this.

9. In step (4), the self-tempering temperature is 500 - 550 °C, and the cooling rate is 10 - 15 °C / s. The manufacturing method according to claim 4 is characterized by this.

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