Corrosion-resistant Bauschinger-effect-resistant 890MPa-grade maritime work steel and manufacturing method thereof

Abstract

The invention relates to the technical field of corrosion-resistant Bauschinger-effect-resistant high-strength maritime work steel, in particular to corrosion-resistant Bauschinger-effect-resistant 890MPa-grade maritime work steel and a manufacturing method thereof. Comprising the following chemical components in percentage by weight: 0.08%-0.14% of C, 1.3%-1.8% of Mn, 1.0%-2.5% of Ni, 0.3%-0.8% of Cr, 0.3%-0.8% of Mo and 0.2%-0.5% of Cu. The component design that C, Mn, Ni, Cr, Mo, Cu and microalloy elements are matched is combined with special production processes such as electroslag remelting and forging, the seawater corrosion resistance rate and the marine atmosphere corrosion resistance rate are reduced while the mechanical property of the EH890-grade high-strength steel is kept, and the Bauschinger effect is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of corrosion-resistant and Bauschinger effect-resistant high-strength marine engineering steel, specifically to a corrosion-resistant and Bauschinger effect-resistant 890MPa grade marine engineering steel and its manufacturing method. Background Technology

[0002] In the fields of marine engineering equipment and shipbuilding, EH890 high-strength steel is widely used in key load-bearing structures such as offshore platforms, ship hulls, and subsea pipelines due to its high strength, good weldability, and toughness. However, the marine environment is characterized by high salt spray, high humidity, and periodic wet-dry cycles. The combined effects of chloride ion penetration, microbial adhesion, and wave impact significantly accelerate material corrosion. Traditional EH890 marine engineering steel exhibits significant corrosion resistance during long-term service, with its seawater immersion corrosion rate typically exceeding 0.3 mm / a. In the splash zone and marine atmospheric environment, it is more prone to localized pitting corrosion and stress corrosion cracking, severely affecting structural lifespan. Furthermore, because marine engineering structures often bear alternating loads (such as wind and wave impacts and ship berthing), EH890 steel is susceptible to the Bauschinger effect after plastic deformation, leading to a significant decrease in yield strength under reverse loading (the decrease can reach more than 15% when the residual strain is 2%), reducing the structural load-bearing stability and increasing safety hazards.

[0003] Chinese patent CN108624809B, entitled "Excellent Ultra-High Strength Steel Plate with Excellent Seawater Corrosion Resistance, Fatigue Resistance, and Environmental Brittleness Resistance and its Manufacturing Method," proposes an ultra-high strength steel plate with seawater corrosion resistance and fatigue resistance. It employs a low-C, low-Mn, high-Ni, and high-Cr composition system. While this improves the steel plate's impact toughness and corrosion resistance, its production process still uses conventional smelting, rolling, and heat treatment processes. The steel plate's low-temperature toughness and resistance to the Bauschinger effect cannot meet the requirements for long service life and high reliability in extreme marine environments. Chinese patent CN108707822B, entitled "A High-Strength Steel with Fatigue Stress Amplitude ≥400MPa and its Manufacturing Method," proposes a steel plate with excellent resistance to lamellar tearing, employing a high-C, low-Ni, and high-Cr alloy system. Although the steel plate exhibits excellent fatigue performance, this composition and process can only produce thin-gauge fatigue-resistant steel plates, and it lacks composition and process designs specifically for corrosion resistance and resistance to the Bauschinger effect. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine engineering steel. While maintaining the mechanical properties of EH890 grade high-strength steel, it reduces the seawater corrosion rate to less than 40% of conventional materials and the marine atmospheric corrosion rate to less than 50%, and significantly improves the resistance to the Bauschinger effect (yield strength reduction ≤10% under 2% residual strain), meeting the requirements for long service life and high reliability in extreme marine environments.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A corrosion-resistant and Bauschinger-effect-resistant high-strength marine steel, composed of the following chemical composition by weight percentage:

[0007] C: 0.08%~0.14%, Si: 0.15%~0.35%, Mn: 1.3%~1.8%, P≤0.02%, S≤0.01%, Ni: 1.0%~2.5%, Cr: 0.3%~0.8%, Mo: 0.3%~0.8%, Cu: 0.2%~0.5%, Co: 0.05%~0.15%, Sn: 0.05%~0.2%, Nb: 0.04%~0.09%, V: 0.04%~0.09%, Ti: 0.01%~0.015%, B: 0.0005%~0.001%, with the remainder being Fe and unavoidable impurities.

[0008] The effect of selecting the above alloying elements and their contents:

[0009] 1. The main function of carbon (C) in steel is to form a solid solution structure, increasing the strength of the steel. It also forms carbides, which improve the hardness and stiffness of the steel, making it less prone to plastic deformation under external forces and reducing the Bauschinger effect to some extent. However, excessive addition of C reduces the corrosion resistance of the steel, so the C content must be precisely controlled. Therefore, this invention precisely controls the C content between 0.08% and 0.14%.

[0010] 2. Si can improve the strength of steel plates, and as a deoxidizer, it can reduce the oxygen content. Si can form a dense and stable oxide film, improving corrosion resistance. However, excessive Si content reduces the low-temperature toughness of the steel plate. Therefore, this invention precisely controls the Si content to 0.15%~0.35%.

[0011] 3. Mn has a similar atomic radius to Fe and can dissolve extensively in the Fe matrix, increasing the strength of the steel plate. Mn can refine the grain structure of the steel plate, increase the number of grain boundaries, and improve the low-temperature impact toughness of the steel plate. However, when the Mn content is too high, the hardening effect of Mn will reduce the low-temperature toughness of the core of the thick plate. In this invention, the alloy has high strength, which easily causes segregation in the core of the billet. However, by combining electroslag remelting with forging, the problem of uneven composition and structure in the core of the billet can be effectively solved. Therefore, this invention can appropriately increase the Mn content. Thus, this invention precisely controls the Mn content to 1.3%~1.8%.

[0012] 4. P and S elements have no benefit to the mechanical properties of steel plates, especially elongation. P should be controlled to ≤0.02% and S to ≤0.01%.

[0013] 5. Ni plays a particularly significant role in steel plates. Ni can significantly improve the toughness and corrosion resistance of steel plates. Its addition not only lowers the ductile transition temperature but also works synergistically with microalloying elements such as V to further enhance the strength, toughness, and corrosion resistance of the steel plate. Ni itself possesses excellent corrosion resistance, performing exceptionally well in acidic marine environments. Furthermore, when Ni is used in combination with other elements (such as Cr and Mo), it can effectively improve the hot strength and corrosion resistance of steel. Therefore, this invention precisely controls the Ni content to 1.0%~2.5%.

[0014] 6. The corrosion resistance of Cr in steel is mainly manifested in its ability to form a dense passivation film, significantly improving the corrosion resistance of steel. Combined with elements such as Ni, Co, and Sn, excellent resistance to marine corrosion can be achieved even at low Cr contents. Cr can also effectively increase the strength of steel plates; however, excessively high Cr content will produce a large amount of Cr carbides, reducing the impact toughness of the steel plate and causing temper brittleness after quenching and tempering. Therefore, this invention precisely controls the Cr content to 0.3%~0.8%.

[0015] 7. Mo can enhance corrosion resistance in reducing media, especially resistance to chloride ion corrosion and pitting corrosion, effectively preventing pitting corrosion caused by chloride ions. Mo can combine with carbides, reducing Cr precipitation and thus improving the corrosion resistance of steel plates. Mo can also improve the hardenability of steel plates, and at the same time, Mo can form fine carbides in steel, which can effectively improve the strength of steel plates. Therefore, this invention precisely controls the Mo content at 0.3%~0.8%.

[0016] 8. Cu, along with Cr and P in steel, works synergistically to inhibit pitting and uniform corrosion in steel within saline and humid environments, extending its service life. Cu also helps resist biofouling. However, excessive Cu content can cause Cu brittleness in the billet at high temperatures. Therefore, this invention precisely controls the Cu content to 0.2%~0.5%.

[0017] 9. Co can improve the strength and stiffness of steel plates and enhance their resistance to the Boushinger effect; however, excessive Co addition will reduce the low-temperature toughness of the steel plate. Co also possesses certain antioxidant properties, and when combined with alloying elements such as Ni and Cr, it can further improve the corrosion resistance of the steel plate. Therefore, this invention precisely controls the Co content to 0.05%~0.15%.

[0018] 10. Sn can synergistically work with Ni and Cr in steel to effectively inhibit intergranular corrosion. Sn can form a dense oxide film, which can significantly hinder the transport of corrosive ions. In a chloride ion environment, Sn can accumulate in the rust layer, greatly improving the corrosion resistance of the steel plate. Therefore, this invention precisely controls the Sn content to 0.05%~0.2%.

[0019] 11. Nitrogen (Nb) is an important additive element that increases the strength and high-temperature thermal stability of steel plates. It effectively lowers the transformation temperature from austenite to bainite, reducing the risk of stress corrosion cracking. Simultaneously, it combines with nitrogen (CN) to lower the diffusion thresholds of carbon (C) and nitrogen (N), preventing C and N enrichment at grain boundaries, thereby improving the corrosion resistance of the steel. Furthermore, Nb can synergistically work with elements such as chromium (Cr) and molybdenum (Mo) to further enhance the corrosion resistance of the steel and its ability to resist corrosion in acidic marine environments. Therefore, this invention precisely controls the Nb content to be between 0.04% and 0.09%.

[0020] 12. V is an important alloying element in the steel plate of this invention. V can refine the grain structure and improve the strength and toughness of the steel plate. V, together with C and N, forms V(C,N) particles in the matrix, which can also refine the grains. Adding V to tempered steel plates can significantly improve the core strength and low-temperature toughness of the steel plate. The combination of V and C can prevent C from accumulating around the grain boundaries and improve the steel plate's resistance to intergranular corrosion. Therefore, the V content in this invention is precisely controlled at 0.04%~0.09%.

[0021] 13. Ti can form TiCN with C and N, exhibiting extremely high stability at high temperatures, effectively preventing steel grain growth and thus refining the grain size. Therefore, this invention precisely controls the Ti content to 0.01%~0.015%.

[0022] 14. When boron (B) dissolves in a solid solution, the crystal lattice becomes larger, increasing strength. B inhibits recrystallization diffusion at grain boundaries, increasing the hot strength of steel. B-containing steel exhibits excellent comprehensive mechanical properties after quenching and tempering, including tempering stability, fatigue limit, and hardness. Simultaneously, B can synergistically enhance the corrosion resistance and thermal stability of steel with other alloying elements. Therefore, this invention precisely controls the B content to 0.0005%~0.001%.

[0023] The aforementioned corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine engineering steel has a yield strength ≥890MPa, tensile strength 950~1080MPa, transverse elongation ≥16%, and Charpy impact energy of the steel plate core at -40℃ ≥150J. The steel plate's seawater corrosion resistance rate is less than 40% of that of conventional EH890 marine engineering steel, and its marine atmospheric corrosion resistance rate is less than 50% of that of conventional EH890 marine engineering steel. At 2% residual strain, the yield strength decreases by ≤10%, exhibiting excellent resistance to the Bauschinger effect, uniform elongation ≥6%, and a maximum finished thickness of 50mm.

[0024] The microstructure at half the thickness of the steel plate consists of tempered martensite and retained austenite (3%~8%). Dislocation density ≥10⁻⁶. 10 / cm 2 It has a high-angle grain boundary ratio of ≥55%, an effective grain size of 2~7μm, and good mechanical properties.

[0025] The aforementioned corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine engineering steel is manufactured using a high-cleanliness and alloying smelting + electroslag remelting + forging + high-efficiency rolling + quenching + tempering process. The specific steps of this manufacturing method are as follows:

[0026] 1. Steel refining:

[0027] Molten steel is refined in a converter, LF furnace, RH or VD furnace to further reduce the content of P, S and non-metallic inclusions.

[0028] 2. Electroslag remelting:

[0029] Electroslag remelting uses a ternary slag system, with a slag formation time of 60-100 minutes. Argon gas is started 30-45 minutes in advance, and the entire process is under atmospheric protection with an argon gas flow rate of 30-60 m³ / h. 3 / h, crystallizer cooling water flow rate 10~35m³ 3 / h, the cooling rate of the crystallizer is 0.3~0.8℃ / min, the feeding time is 3~5h, and the electroslag ingot demolding slow cooling is ≥72h.

[0030] Electroslag remelting (ESR) utilizes protective slag, argon protection, and controlled crystallizer water flow and cooling rate to precisely adjust the alloy composition, effectively suppressing the intrusion of harmful gases and reducing alloy oxidation, thereby optimizing the uniformity of the alloy's internal composition. Adjusting the composition and morphology of the protective slag reduces segregation during melting, enhancing the steel plate's resistance to the Bauschinger effect; argon protection helps control oxygen content, improving corrosion resistance; and controlling the argon flow and crystallizer cooling rate further suppresses the oxidation of impurities and gases in the alloy, effectively reducing the alloy potential difference and improving the steel plate's corrosion resistance. These comprehensive measures not only significantly improve the alloy's corrosion resistance and resistance to the Bauschinger effect but also significantly improve the mechanical properties of the steel plate's core.

[0031] 3. Forging:

[0032] Forging heating temperature is 1250~1300℃, heating time is 6~10h, forging billet is upset in three directions, minimum upset amount in each direction is ≥60mm, thickness direction deformation rate is 30%~50%, forging ingot grinding amount is ≥20mm, and forging ingot equiaxed crystal ratio is ≥70%.

[0033] Forging processes significantly improve the homogenization and core mechanical properties of steel plates by controlling temperature, optimizing upsetting direction and upsetting amount, and reducing problems such as segregation and shrinkage cavities. Optimizing the forging reduction amount homogenizes the equiaxed grain structure, improving strength and toughness; slow cooling treatment reduces internal stress and refines grains, further improving mechanical properties.

[0034] 4. Rolling:

[0035] The billet is loaded into the heating furnace at a temperature of 400-700℃, held at low temperature for 1-2 hours, and heated at a rate of 2-7℃ / min. The aim is to maintain a uniform temperature along the thickness of the billet during the low-temperature stage, preparing for a homogeneous microstructure in the high-temperature stage. The heating temperature is 1300-1350℃, and the holding time is 1-3 hours. The initial rolling temperature is 1200-1330℃, the average reduction per pass is 6%-12%, and the final rolling temperature is 900-1150℃. Under the high pressure at high temperature, the steel plate deforms more uniformly, reducing inhomogeneities in the microstructure and thus improving the density and consistency of the material. High-temperature, high-reduction rolling effectively improves the tensile strength and yield strength of the material; and through high-temperature rolling and post-rolling recrystallization, local stress concentration can be reduced, improving the steel plate's resistance to the Baosinger effect. With reasonable control of process parameters, high-temperature, high-reduction rolling can complete large-scale batch production in a shorter time, improving efficiency.

[0036] 5. Quenching and tempering:

[0037] The quenching temperature is 750~900℃, the quenching holding time is 1~1.6min / mm, the cooling rate of the quenched steel plate is 2~6℃ / s, the tempering temperature is 400~700℃, and the tempering holding time is 3~4.5min / mm.

[0038] The purpose of quenching is to refine the rolled microstructure, prepare the microstructure for tempering, further improve the grain size of the tempered microstructure, and enhance the low-temperature toughness of the steel plate core.

[0039] Increasing the tempering temperature and tempering holding time can refine and redistribute fine precipitates while ensuring the strength of the steel plate, thereby maximizing the low-temperature toughness and corrosion resistance of the steel plate. Increased strength and stiffness of the steel plate can effectively prevent plastic deformation. By utilizing fine-grain strengthening and optimized precipitation strengthening, dislocation back pile-up during plastic deformation can be reduced, thus improving the steel plate's resistance to the Bauschinger effect.

[0040] Compared with the prior art, the beneficial effects of the present invention are:

[0041] 1. This invention utilizes the properties of Co and Sn alloys in resisting the Bauschinger effect and improving corrosion resistance. Adding Co increases the strength and stiffness of the steel plate, enhancing its resistance to the Bauschinger effect. Combined with alloying elements such as Ni and Cr, it further improves the corrosion resistance of the steel plate. Sn works synergistically with Ni and Cr in the steel to effectively inhibit intergranular corrosion. Sn can form a dense oxide film that significantly hinders the transport of corrosive ions. In a chloride ion environment, Sn can accumulate in the rust layer, greatly improving the corrosion resistance of the steel plate.

[0042] 2. The electroslag remelting process of this invention improves the alloy's corrosion resistance, resistance to the Bauschinger effect, and the mechanical properties of the steel core by optimizing alloy composition control and gas environment management. By utilizing protective slag, argon protection, and controlling the cooling rate of the crystallizer water, the alloy composition is precisely adjusted, effectively suppressing the intrusion of harmful gases and reducing alloy oxidation, thereby optimizing the uniformity of the alloy's internal composition. These comprehensive measures not only significantly improve the alloy's corrosion resistance and resistance to the Bauschinger effect but also significantly improve the mechanical properties of the steel core.

[0043] 3. The forging process of this invention significantly improves the homogenization and core mechanical properties of steel plates by controlling temperature, optimizing upsetting direction and upsetting amount, and reducing problems such as segregation and shrinkage. Optimizing the forging reduction amount homogenizes the equiaxed grain structure, improving strength and toughness; the slow cooling treatment reduces internal stress and refines the grains, further improving mechanical properties.

[0044] 4. The steel plate of this invention deforms more uniformly under high pressure during the high-temperature stage of the rolling process, reducing inhomogeneity in the microstructure and thus improving the density and consistency of the material. The high-temperature, high-pressure rolling process effectively improves the tensile strength and yield strength of the material; and through high-temperature rolling and post-rolling recrystallization, it reduces local stress concentration and enhances the steel plate's resistance to the Baosinger effect. With reasonable control of process parameters, the high-temperature, high-pressure rolling process can complete large-scale batch production in a shorter time, improving efficiency.

[0045] 5. The purpose of quenching in this invention is to refine the rolled microstructure, preparing it for tempering, further improving the grain size of the tempered microstructure, and enhancing the low-temperature toughness of the steel plate core. Increasing the tempering temperature and tempering holding time can refine and redistribute fine precipitates while ensuring the steel plate's strength, maximizing the steel plate's low-temperature toughness and corrosion resistance. Increased steel plate strength and stiffness can effectively prevent plastic deformation. Utilizing fine-grain strengthening and optimized precipitation strengthening can reduce dislocation back-piling during plastic deformation, thereby improving the steel plate's resistance to the Bauschinger effect.

[0046] In summary, this invention combines a compositional design that integrates C, Mn, Ni, Cr, Mo, Cu with microalloying elements such as Co, Sn, Nb, and V with special production processes such as electroslag remelting and forging to produce marine engineering steel with a maximum thickness of 50 mm. The steel plate has a yield strength ≥ 890 MPa, tensile strength 950~1080 MPa, elongation ≥ 16%, and Charpy impact energy of the core at -40℃ ≥ 150 J. The steel plate's seawater corrosion resistance rate is less than 40% of that of conventional EH890 marine engineering steel, and its marine atmospheric corrosion resistance rate is less than 50% of that of conventional EH890 marine engineering steel. At 2% residual strain, the yield strength decreases by ≤ 10%, exhibits excellent resistance to the Bauschinger effect, and has a uniform elongation ≥ 6%. Attached Figure Description

[0047] Figure 1 This is a metallographic diagram of Embodiment 1 of the present invention. Detailed Implementation

[0048] This invention discloses a corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine engineering steel and its manufacturing method. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0049] The chemical composition of the steel in the embodiments of the present invention is shown in Table 1; the electroslag remelting and forging process in the embodiments of the present invention is shown in Table 2; the rolling process in the embodiments of the present invention is shown in Table 3; the quenching and tempering process in the embodiments of the present invention is shown in Table 4; the mechanical properties of the steel plate in the embodiments of the present invention are shown in Table 5; and the corrosion resistance of the embodiments of the present invention and the comparative examples in the marine environment is shown in Table 6.

[0050] Table 1. Chemical composition (wt%) of steel in the embodiments of the present invention

[0051]

[0052] Table 2 Electroslag remelting and forging processes in embodiments of the present invention

[0053]

[0054] Table 3 Rolling process of embodiments of the present invention

[0055]

[0056] Table 4 Quenching and tempering processes in embodiments of the present invention

[0057]

[0058] Table 5 Mechanical properties of steel plates in embodiments of the present invention

[0059]

[0060] Table 6. Resistance to marine corrosion in the embodiments and comparative examples of the present invention

[0061]

[0062] The full immersion test reference standard is JBT7901, and the salt spray test reference standard is GBT10125. The comparison steel composition is 0.014C~0.2Si~1.40Mn~1.0Ni~0.4Cr~0.4Mo~0.04Nb~0.04V~0.01Ti.

[0063] like Figure 1 As shown, the metallographic structure of Example 1, at half the thickness of the steel plate, consists of tempered martensite + retained austenite (3%~8%). Dislocation density ≥102 10 / cm 2 It has a high-angle grain boundary ratio of ≥55%, an effective grain size of 2~7μm, and good mechanical properties.

[0064] As shown in Table 5, the maximum thickness of the finished steel plate of this invention is 50mm, with a yield strength ≥890MPa, tensile strength 950~1080MPa, elongation ≥16%, and Charpy impact energy of the steel plate core at -40℃ ≥150J. At 2% residual strain, the yield strength decreases by ≤10%, exhibiting excellent resistance to the Bauschinger effect and a uniform elongation ≥6%. As shown in Table 6, the seawater corrosion resistance rate of the steel plate is less than 40% of that of conventional EH890 marine engineering steel, and the marine atmospheric corrosion resistance rate is less than 50% of that of conventional EH890 marine engineering steel. This invention, while maintaining the mechanical properties of EH890 grade high-strength steel, reduces the seawater corrosion resistance rate to less than 40% of conventional materials and the marine atmospheric corrosion resistance rate to less than 50%, and significantly improves the resistance to the Bauschinger effect (yield strength reduction ≤10% at 2% residual strain), meeting the requirements for long service life and high reliability in extreme marine environments.

[0065] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for manufacturing corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine engineering steel, characterized in that, Corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine steel consists of the following chemical composition by weight percentage. composition: C: 0.08%~0.14%, Si: 0.15%~0.35%, Mn: 1.3%~1.8%, P≤0.02%, S≤0.01%, Ni: 1.0%~2.5%, Cr: 0.3%~0.8%, Mo: 0.3%~0.8%, Cu: 0.2%~0.5%, Co: 0.05%~0.15%, Sn: 0.05%~0.2%, Nb: 0.04%~0.09%, V: 0.04%~0.09%, Ti: 0.01%~0.015%, B: 0.0005%~0.001%, with the remainder being Fe and unavoidable impurities; The manufacturing method specifically includes the following steps: 1) Steel refining; 2) Electroslag remelting: Electroslag remelting uses a ternary slag system, with a slag formation time of 60-100 minutes, under constant atmosphere protection, and a crystallizer cooling water flow rate of 10-35 m³ / min. 3 / h, the cooling rate of the crystallizer is 0.3~0.8℃ / min; 3) Forging: Forging heating temperature is 1250~1300℃, heating time is 6~10h; Forging billet is upset in three directions, with a minimum upset amount of ≥60mm in each direction, and the deformation rate in the thickness direction is controlled at 30%~50%; 4) Rolling: The initial rolling temperature is 1200~1330℃, the average reduction per pass is 6%~12%, and the final rolling temperature is 900~1150℃; 5) Quenching and tempering: The quenching temperature is 750~900℃, and the quenching holding time is 1~1.6min / mm; the tempering temperature is 400~700℃, and the tempering holding time is 3~4.5min / mm.

2. The method for manufacturing a corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine engineering steel according to claim 1, characterized in that, The maximum thickness of the finished steel plate is 50mm, with a yield strength ≥890MPa, tensile strength 950~1080MPa, transverse elongation ≥16%, and Charpy impact energy of the steel plate core at -40℃ ≥150J; when the steel plate has 2% residual strain, the yield strength decreases by ≤10%, and the uniform elongation is ≥6%.

3. The manufacturing method of a corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine engineering steel according to claim 1, characterized in that, The microstructure at half the thickness of the steel plate consists of tempered martensite and retained austenite, with the retained austenite comprising 3% to 8%; the dislocation density is ≥10. 10 / cm 2 The proportion of large-angle grain boundaries is ≥55%, and the effective grain size is 2~7μm.

4. The manufacturing method of a corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine engineering steel according to claim 1, characterized in that, In step 1), molten steel is refined through a converter, LF furnace, RH or VD furnace.

5. The method for manufacturing a corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine engineering steel according to claim 1, characterized in that, 2) In the process, start the argon gas 30-45 minutes in advance, with an argon gas flow rate of 30-60 m³ / h. 3 / h; feeding time 3~5h, electroslag ingot demolding and slow cooling ≥72h.

6. The method for manufacturing a corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine engineering steel according to claim 1, characterized in that, 3) The grinding amount of the forged steel ingot is ≥20mm, and the equiaxed crystal ratio of the forged steel ingot is ≥70%.

7. The method for manufacturing a corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine engineering steel according to claim 1, characterized in that, 4) The billet is placed into the heating furnace at a furnace temperature of 400~700℃ and held for 1~2 hours; The heating temperature is 1300~1350℃, the heating rate is controlled at 2~7℃ / min, and the holding time is 1~3h.

8. The method for manufacturing a corrosion-resistant and Bauschinger-effect-resistant 890MPa grade marine engineering steel according to claim 1, characterized in that, 5) In this process, the cooling rate of the quenched steel plate is 2~6℃ / s.

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