Q620-grade high-toughness and high-corrosion-resistance steel plate and production method thereof

Abstract

The invention discloses a Q620-grade high-toughness and high-corrosion-resistance steel plate and a production method thereof. The steel plate comprises the following chemical components in percentage by weight: 0.08 to 0.09 percent of C, 0.15 to 0.40 percent of Si, 1.35 to 1.45 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.003 percent of S, less than or equal to 0.005 percent of Nb, less than or equal to 0.005 percent of Ti, 0.08 to 0.10 percent of Als, 0.30 to 0.70 percent of Cu, 0.7 to 1.5 percent of Ni, 0.04 to 0.05 percent of V, 0.40 to 0.45 percent of Mo, 0.30 to 0.35 percent of Cr, 0.001 to 0.002 percent of B and 0.08 to 0.30 percent of Sb. The core performance and the fatigue performance are improved by adopting a Nb-free and Ti-free design technology, the process parameters are improved through an in-situ analysis technology, the core quality of the steel plate is improved through the specific design of chemical components, and the statistical segregation degree of C, Mn, Ni, Cu and Sb is smaller than or equal to 0.05. The method is suitable for producing the steel plate with the thickness specification being smaller than or equal to 100 mm, the yield strength being larger than or equal to 620 MPa, the tensile strength being larger than or equal to 720 MPa and the impact toughness KV2 being larger than or equal to 120 J at the low temperature

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metallurgy and relates to a Q620-grade high-toughness high-corrosion-resistant steel plate and a production method thereof. BACKGROUND

[0002] With the development of island reef infrastructure construction, cross-sea bridge construction, seaside building and marine engineering of ships, the demand for offshore structural steel for marine atmospheric and seawater corrosion environment has greatly increased. According to the unique, complex and changeable marine corrosion environment of high humidity and heat, high salt, high radiation and strong tropical storms, it is one of the key directions of current metallurgical industry research to study the mechanical properties and corrosion resistance of infrastructure and key engineering steels and to develop high-corrosion-resistant alloyed and microstructured steels matching the steels.

[0003] Chinese patent CN102586686B discloses a clean corrosion-resistant marine engineering steel and a production method thereof, but the steel provided in the technical solution has a high P content, which is not conducive to the toughness of the base material and the heat-affected zone of welding. Chinese patent CN104419871B discloses a welding structural steel with excellent marine environment corrosion resistance and a manufacturing method thereof, but the steel provided in the technical solution adds a large amount of Cu and Mo, Cu increases the casting crack of the casting blank during continuous casting, excessive Mo increases the production cost of raw materials, and at the same time increases the hardness after welding and increases the post-weld crack sensitivity. The technical solution adopts a low-carbon component design TMCP + tempering process for production, and the impact toughness of the thick steel plate is difficult to stabilize due to the influence of the cold speed in the center of the thick steel plate.

[0004] Chinese patent CN112746216B discloses a marine environment seawater dry-wet alternating corrosion-resistant steel plate, which is produced by a low-carbon component design TMCP process, and the impact toughness of the thick steel plate is difficult to stabilize, the P content is high, and the toughness of the base material and the heat-affected zone of welding is not conducive.

[0005] Based on the above-mentioned status quo of the prior art, how to provide an improved high-toughness high-corrosion-resistant steel plate is a problem to be solved in the art. SUMMARY

[0006] The application aims to provide a Q620-grade high-toughness high-corrosion-resistant steel plate and a production method thereof, the produced steel plate has a yield strength ReL≥620MPa, a tensile strength Rm≥720MPa, an elongation after fracture A≥30%, a low-temperature-60℃ impact toughness KV2≥120J, a low-temperature-60℃ impact toughness KV2≥120J at 1 / 2 thickness of the steel plate, and a lamellar tearing resistance Z≥35%.

[0007] To achieve the above-mentioned purpose, the application adopts the following technical solution: A Q620 grade high-toughness and high-corrosion-resistant steel plate has the following chemical composition by weight percentage: C=0.08~0.09, Si=0.15%~0.40%, Mn=1.35%~1.45%, P≤0.020%, S≤0.003%, Nb≤0.005%, Ti≤0.005%, Als=0.08%~0.10%, Cu=0.30%~0.70%, Ni=0.7%~1.5%, V=0.04%~0.05%, Mo=0.40%~0.45%, Cr=0.30%~0.35%, B=0.001%~0.002%, Sb=0.08%~0.30%, with the remainder being Fe and unavoidable impurity elements.

[0008] The steel plate has a yield strength ReL≥620MPa, tensile strength Rm≥720MPa, elongation after fracture A≥30%, and low-temperature impact toughness KV2≥120J at -60℃; the low-temperature impact toughness KV2≥120J at 1 / 2 thickness of the steel plate at -60℃; and resistance to lamellar tearing Z≥35%.

[0009] A production method for Q620 grade high-toughness and high-corrosion-resistant steel plate includes the following production process: hot metal pretreatment → converter steelmaking → ladle refining (LF) → vacuum treatment (RH) → continuous casting → heating → rolling → controlled rolling cooling → quenching → tempering → finishing. Key process steps include: Continuous casting: The superheat of molten steel is less than 15℃; continuous casting adopts full protective casting, secondary cooling stirring is adopted in the continuous casting process, and the solidification end heavy pressure reduction technology is adopted to improve the internal segregation and internal porosity of the slab; Heating: The heating furnace adopts a reducing atmosphere, with a heating section temperature of 1100~1240℃, a soaking section temperature of 1100~1200℃, and a soaking section holding time of ≥30min; Rolling: The roughing rolling adopts a large reduction regime, with a reduction rate of ≥14% in three consecutive passes after widening; the finishing rolling temperature is 750~820℃, and the reduction rate of the first three passes in the finishing rolling is ≥10%; Controlled rolling cooling: Direct immersion in water, reddening temperature 600~660℃, cooling rate 3~10℃ / s; Quenching: Quenching at 900~920℃, furnace time is plate thickness mm×(1.4~2.5)min / mm, water cooling, quenching ensures that the high pressure section of the quenching machine is ≥8bar, the low pressure section is ≥3.5bar, and the surface temperature of the steel plate after quenching is ≤40℃; Tempering: Temper at 670~690℃, furnace time is plate thickness mm×(2.0~3.5)min / mm, air cooling + stack cooling, stack cooling after tempering, stack cooling temperature 200~300℃, stack cooling time ≥24 hours before destacking; Antimony-iron alloy is added in conjunction with the converter steelmaking, ladle refining (LF), and continuous casting processes.

[0010] Furthermore, the reducing atmosphere mentioned in the above heating step is a mixed gas.

[0011] Furthermore, antimony-iron alloy is added in conjunction with the converter steelmaking, ladle refining (LF), and continuous casting processes. The antimony-iron alloy has a block size of 20-30mm. 80% of the alloy is added during the steel tapping process after converter deoxidation, and 20% is added before leaving the LF station. Bottom-blown argon is used for thorough stirring, and secondary cooling stirring is used during the continuous casting process.

[0012] The Q620 grade high-toughness and high-corrosion-resistant steel plate produced by the above method has a thickness ≤100mm. The steel plate has a yield strength ≥620MPa, tensile strength ≥720MPa, elongation after fracture A ≥30%, low-temperature impact toughness KV2 ≥120J at -60℃, low-temperature impact toughness KV2 ≥120J at 1 / 2 thickness of the steel plate at -60℃, and resistance to lamellar tearing Z ≥35%.

[0013] This invention employs a Ni-Cu-Sb corrosion-resistant alloy design, and its application principle is as follows: Ni is a relatively stable element. Adding Ni can shift the self-corrosion potential of steel in a positive direction, increasing its stability. Atmospheric exposure tests show that a Ni content of around 4% can significantly improve the atmospheric corrosion resistance of nearshore atmospheric corrosion-resistant steel. Enrichment of Ni in the stabilizing rust layer can effectively inhibit Cl... - The intrusion of ions promotes the formation of a protective rust layer and reduces the corrosion rate of steel. However, a higher Ni content inevitably leads to increased steel costs, which is not conducive to large-scale industrial production. Therefore, considering the balance between marine weather resistance and economy, this invention selects a Ni mass percentage of 0.7% to 1.5%.

[0014] Cu is increasingly being added to steel as a strengthening element, especially ultra-low carbon steel. After solution treatment of high-purity copper-containing steel, copper solute atoms are not uniformly distributed in the ferrite matrix, but exist in a non-uniform, short-range ordered form. The presence of ordered domains creates favorable conditions for subsequent aging precipitation, thus influencing the age-hardening behavior of copper-containing steel. Cu is a crucial alloying element for improving the atmospheric corrosion resistance of steel. Adding an appropriate amount of Cu to steel can significantly improve its corrosion resistance, while simultaneously increasing its strength through solid solution strengthening. In this invention, a Cu mass percentage of 0.30% to 0.70% is selected.

[0015] Si is a significant strengthening element in steel, replacing Fe atoms in the crystal lattice to achieve solid solution strengthening. A notable characteristic of solid solution strengthening is that as the number of solute atoms increases, strength and hardness rise, while plasticity and toughness decrease; the greater the strengthening effect, the greater the decrease in plasticity and toughness. Furthermore, research shows that in atmospheric corrosion environments, a high Si content can increase the paramagnetic α-FeOOH content in the protective rust layer, refining α-FeOOH and thus reducing the corrosion rate. The corrosion rate of carbon steel is related to the properties of α-Fe₂O₃ and α-FeOOH. Large α-FeOOH particles and magnetic α-Fe₂O₃ hinder the complete formation of the protective rust layer, leading to an increased corrosion rate. Superparamagnetic α-FeOOH, on the other hand, can refine FeOOH particles, thereby reducing the corrosion rate of carbon steel. In this invention, the mass percentage of Si is selected to be 0.15%~0.40%.

[0016] Manganese (Mn) is a common element in low-carbon steel, and increasing its content within a certain range is beneficial to the performance of low-carbon steel. Mn is one of the cheapest elements for increasing steel strength. In steel, it can significantly expand the austenite phase region, lower the phase transformation temperature, refine the phase transformation microstructure, and change the microstructure. When the carbon content is low, Mn not only improves strength but also effectively ensures plasticity and toughness, and has no significant effect on the corrosion resistance of low-alloy steel. Studies on deformation-strengthening phase transformation in low-carbon manganese steel show that increasing the Mn content delays the austenite-to-ferrite transformation process, increasing the strain required to complete the transformation, but resulting in finer ferrite grains. It is generally believed that during hot deformation, the main recovery mechanism of ferrite is dynamic recovery, and dynamic recrystallization is difficult to occur. Mn expands the austenite phase region of steel, lowers the phase transformation point, and during hot deformation, Mn atoms delay austenite recrystallization and increase the austenite deformation resistance, thus having a certain impact on the phase transformation and austenite deformation and recrystallization behavior during hot working of low-carbon steel. In this invention, the mass percentage of Mn is selected to be 1.35% to 1.45%.

[0017] The presence of Cr significantly accelerates the development of electrochemical corrosion products towards a thermodynamically stable state. Analysis of rust layers revealed that Cr significantly accelerates the transformation process ((FexHYOz)-→γ-FeOOH→α-FeOOH→α-Fe2O3), promoting the formation of spinel compounds. Simultaneously, Cr can partially replace Fe to form chromium-iron hydroxyl oxide CrXFe1-xOOH, giving the α-FeOOH rust layer cation selectivity and preventing Cl- and SO42- from penetrating the substrate surface, thus providing a protective effect. Kamimura used a wet-dry cyclic corrosion test on low-carbon steel under the action of a Cr3+ sulfate electrolyte to study the effect of Cr on atmospheric corrosion of steel. He found that Cr3+ has a significant impact on the corrosion rate, even when the surface polarization potential reaches -200 mV (VS). Even at SCE (Self-Ceramic Erosion), the corrosion rate remains very low. Mussenbaul spectral studies revealed that Cr³⁺ had no significant effect on the composition of the rust layer, but a Cr-rich region existed near the interface between the rust layer and the substrate, consistent with Cr-containing steel. The presence of Cr in the rust layer hinders rust reduction and the formation of intermediate Fe²⁺. However, considering the performance of Cr under marine atmospheric conditions, it should be added sparingly or not at all. This invention selects a Cr mass percentage of 0.30%~0.35%.

[0018] Vitamin V (V) exists primarily in steel as carbides, its main function being to refine the steel's microstructure and grain size. Adding trace amounts of V to steel can refine the grain size, improving strength and toughness. V exhibits good corrosion resistance, resisting seawater erosion. Simultaneously, V increases the tempering stability of quenched steel and produces a secondary hardening effect. The addition of V promotes grain refinement in the rolled steel microstructure, simultaneously improving both strength and toughness, ensuring higher strength levels and stable, excellent impact toughness. In this invention, the mass percentage of V is selected as 0.04% to 0.05%.

[0019] Mo has a strong carbide-forming ability, which can prevent coarse austenitic grains and shift the C-curve to the right, reducing undercooling and greatly improving hardenability, thus facilitating the formation of a full martensitic structure during quenching. When Mo and Nb are added simultaneously, Mo can increase the inhibition of austenite recrystallization during controlled rolling, thereby promoting the refinement of the austenite microstructure. Adding an appropriate amount of Mo also helps improve the atmospheric corrosion resistance of the steel; however, excessive Mo will impair the toughness of the heat-affected zone formed during welding, reducing the weldability of the steel. In this invention, the mass percentage of Mo is selected as 0.40%~0.50%.

[0020] Adding trace amounts of boron (B) can improve the hardenability and strength of steel, ensuring a higher strength level. However, B exceeding 0.0030% can easily cause segregation, forming carboboron compounds, which severely deteriorates the toughness of the steel. This invention selects a B mass percentage of 0.001% to 0.002%.

[0021] Al, as a deoxidizer, can significantly reduce the oxygen content in steel, optimize the addition and yield of Sb, and combine with N in the absence of Nb and Ti. The resulting fine AlN (aluminum nitride) particles can hinder the movement of austenite grain boundaries during heating, thereby preventing excessive grain growth. A high Al content in a Nb- and Ti-free design can eliminate the influence of coarse NbTi(C,N) precipitates in the core of the steel plate, improving core toughness and fatigue performance. In this invention, the mass percentage of Al is selected as 0.08% to 0.10%.

[0022] Sb forms a protective oxide film on the material surface, effectively inhibiting the intrusion of Cl- ions and reducing the corrosion rate of steel. This also increases corrosion resistance in marine climates. However, excessive Sb can negatively impact the surface quality of the cast billet; therefore, this invention uses an Sb concentration of 0.08% to 0.30% by mass to meet the requirements.

[0023] The innovative aspects and beneficial effects of this invention are as follows: 1) This invention overcomes the key technologies of synergistic control of high corrosion-resistant alloy composition design, metallurgical quality, microstructure, and material properties, and develops high-toughness and high-corrosion-resistant steel plates; it solves the problem of unstable impact toughness of thick-gauge low-carbon bainitic steel and preferential corrosion after pearlite formation due to the influence of post-rolling cooling rate; the serialized microstructure design is tempered sorbitic steel; through in-situ analysis technology, the core quality of the steel plate is improved, and the statistical segregation of C, Mn, Ni, Cu, and Sb is ≤0.05; the Nb- and Ti-free design technology is used to improve core performance and fatigue performance.

[0024] 2) This invention employs a reasonable composition design and microalloying strengthening technology, combined with rolling and quenching and tempering processes, to meet the development needs of high corrosion-resistant steel for marine climate environments in island and reef infrastructure construction, cross-sea bridge construction, coastal building construction, and shipbuilding and marine engineering. The steel plate strength grade is Q620, the steel plate thickness is ≤100mm, the yield strength is ≥620MPa, the tensile strength is ≥720MPa, the low-temperature impact toughness KV2≥120J at -60℃ is ≥120J, the low-temperature impact toughness KV2 at 1 / 2 thickness of the steel plate is ≥120J, the elongation after fracture A≥30%, and the resistance to lamellar tearing Z≥35%. Attached Figure Description

[0025] Figure 1 This is a two-dimensional distribution diagram of Sb element content in 1 / 2 thickness, analyzed in situ in Example 3.

[0026] Figure 2 This is a metallographic photograph of a 100mm thick steel plate of Example 3 with a thickness of 1 / 2.

[0027] Figure 3 This is the CCT curve for Example 3.

[0028] Figure 4 The morphology of the inner rust layer after 336 hours of corrosion in Example 3 is shown. Detailed Implementation

[0029] The following description is based on examples and comparative examples.

[0030] The preparation process flow of Examples 1-6 and Comparative Example 1 is as follows: molten iron pretreatment → converter steelmaking → ladle refining (LF) → vacuum treatment (RH) → continuous casting → heating → rolling → controlled rolling cooling → quenching → tempering → finishing → performance testing → ultrasonic flaw detection. Molten iron pretreatment refers to a process of removing impurities from molten iron before it is added to the converter, including desiliconization, desulfurization, and dephosphorization to improve the purity of the molten iron. Converter steelmaking uses molten iron, scrap steel, and ferroalloys as main raw materials. It completes the steelmaking process without external energy, relying on the physical heat of the molten iron itself and the heat generated by the chemical reactions between the molten iron components. During this process, the initial chemical composition is adjusted. Ladle refining (LF) is an external refining technology using electric arc heating under vacuum conditions. Vacuum treatment (RH) is a vacuum circulation degassing method for molten steel, suitable for removing gases from steel and reducing the occurrence of hairline cracks, hydrogen-induced cracks, and lamellar fracture defects. Continuous casting, also known as continuous steel casting, utilizes in-situ analysis techniques for cyclical process improvement to achieve optimal segregation quality of various chemical elements and optimize core properties. Continuous casting employs fully protected casting to prevent contact between molten steel and air, controlling the absorption of nitrogen (N) from the air during casting. The process also utilizes secondary cooling stirring and end-of-solidification heavy pressure techniques to improve internal segregation and porosity in the slab. Heating refers to heating the steel billet to a suitable temperature for the rolling process, providing the necessary conditions for forming. Appropriate heating can significantly refine austenite grains, resulting in a substantial increase in product toughness and optimized core properties. Rolling refers to the deformation process of the steel billet metal; a suitable rolling process can achieve accurate product dimensions and required performance. Controlled rolling and cooling refers to controlling both rolling and cooling; it is an extension of the rolling process and can achieve even more precise product performance. Quenching and tempering are combined heat treatment processes. After heat treatment, tempered sorbite structure is obtained, possessing excellent strength and toughness, as well as enhanced corrosion resistance. Controlling the pressure in the quenching machine ensures thorough quenching of the steel plate, improving the performance at the halfway point. Post-tempering cooling reduces internal stress in the steel plate, resulting in superior machinability. Finishing is a series of operations performed to meet the user's final requirements for product surface quality, dimensions, shape, and certain properties. Performance testing is a series of inspections conducted to verify whether technical requirements are met, used to measure the product's final use. Ultrasonic testing is a non-destructive testing method used to inspect the surface and internal quality of the tested component, used to measure the surface and internal quality of the product.

[0031] In all embodiments, the thickness of the cast billet is 350 mm, and the thickness of the rolled steel plate is 100 mm. Example 1

[0032] The steel plate's chemical composition by weight percentage is: C 0.08%, Si 0.32%, Mn 1.40%, P 0.014%, S 0.001%, Nb 0.002%, Ti 0.001%, Als 0.088%, Cu 0.31%, Ni 0.70%, Cr 0.31%, Mo 0.41%, Sb 0.18%, V 0.046%, B 0.011%, with the remainder being Fe and unavoidable impurities. The key process steps include: Continuous casting: The molten steel is superheated to 12°C; the continuous casting adopts full protective casting to avoid contact between the molten steel and air, so as to control the absorption of N from the air by the molten steel during the casting process; the continuous casting process adopts secondary cooling stirring, and the continuous casting adopts the solidification end heavy pressure technology to improve the internal segregation and internal porosity of the slab; Heating: The heating furnace adopts a reducing atmosphere of mixed coal gas. The temperature of the heating section is 1180℃~1240℃, the temperature of the soaking section is 1200℃, and the soaking section is held for 45 minutes. Rolling: The roughing rolling adopts a large reduction regime, with the reduction rates of the three consecutive passes after widening being 16%, 16%, and 16% respectively; the finishing rolling temperature is 798℃, and the reduction rates of the first three passes of finishing rolling are 12%, 12%, and 11% respectively. Controlled rolling cooling: direct immersion in water, reddening temperature 655℃, cooling rate 3~10℃ / s; Quenching: Quenching at 900℃ for 245 minutes in the furnace, followed by water cooling; the high-pressure section of the quenching machine has a pressure of 8.1 bar, the low-pressure section has a pressure of 3.8 bar, and the surface temperature of the steel plate after quenching is 20℃. Tempering: Temper at 685℃ for 315 minutes, followed by air cooling and stack cooling. After tempering, stack cooling is performed at 248℃ for 38 hours before destacking.

[0033] Example 2 The chemical composition of the steel plate by weight percentage is: C 0.10%, Si 0.39%, Mn 1.45%, P 0.018%, S 0.002%, Nb 0.003%, Ti 0.002%, Als 0.099%, Cu 0.65%, Ni 1.39%, Cr 0.35%, Mo 0.41%, Sb 0.08%, V 0.050%, B 0.002%, with the remainder being Fe and unavoidable impurities. The key process steps include: Continuous casting: The molten steel is superheated by 10°C; the continuous casting adopts full protective casting to avoid contact between the molten steel and air, so as to control the absorption of N from the air by the molten steel during the casting process; the continuous casting process adopts secondary cooling stirring, and the continuous casting adopts the solidification end heavy pressure technology to improve the internal segregation and internal porosity of the slab; Heating: The heating furnace adopts a reducing atmosphere of mixed coal gas. The temperature of the heating section is 1180℃~1240℃, the temperature of the soaking section is 1180℃, and the soaking section is held for 25 minutes. Rolling: The roughing rolling adopts a large reduction regime, with the reduction rates of the three consecutive passes after widening being 16%, 16%, and 16% respectively; the finishing rolling temperature is 745℃, and the reduction rates of the first three passes of finishing rolling are 10%, 12%, and 12% respectively. Controlled rolling cooling: direct immersion in water, reddening temperature 605℃, cooling rate 3~10℃ / s; Quenching: Quenching at 920℃ for 240 minutes in the furnace, followed by water cooling; the high-pressure section of the quenching machine has a pressure of 8.1 bar, the low-pressure section has a pressure of 3.9 bar, and the surface temperature of the steel plate after quenching is 22℃. Tempering: Temper at 688℃ for 255 minutes, followed by air cooling and stack cooling. After tempering, stack cooling is performed at 288℃ for 36 hours before destacking.

[0034] Example 3 The chemical composition (by weight percentage) of the steel plate is: C 0.08%, Si 0.17%, Mn 1.44%, P 0.013%, S 0.002%, Nb 0.003%, Ti 0.001%, Als 0.080%, Cu 0.55%, Ni 1.23%, Cr 0.35%, Mo 0.44%, Sb 0.12%, V 0.041%, B 0.018%, with the remainder being Fe and unavoidable impurities. The key process steps include: Continuous casting: The superheat of molten steel is 11℃; continuous casting adopts full protective casting to avoid contact between molten steel and air, so as to control the absorption of N from the air by molten steel during the casting process; the continuous casting process adopts secondary cooling stirring, and the continuous casting adopts the solidification end heavy pressure technology to improve the internal segregation and internal porosity of the slab; Heating: The heating furnace adopts a reducing atmosphere of mixed coal gas. The temperature of the heating section is 1180℃~1240℃, the temperature of the soaking section is 1160℃, and the soaking section is held for 32 minutes. Rolling: The roughing rolling adopts a large reduction regime, with the reduction rates of the three consecutive passes after widening being 16%, 16%, and 14% respectively; the finishing rolling temperature is 755℃, and the reduction rates of the first three passes of finishing rolling are 12%, 12%, and 11% respectively. Controlled rolling cooling: direct immersion in water, reddening temperature 600℃, cooling rate 3~10℃ / s; Quenching: Quenching at 910℃ for 148 minutes in the furnace, followed by water cooling; the high-pressure section of the quenching machine was 8.1 bar, and the low-pressure section was 3.7 bar. The surface temperature of the steel plate after quenching was 22℃. Tempering: Temper at 690℃ for 300 minutes, followed by air cooling and stack cooling. After tempering, stack cooling is performed at 289℃ for 25 hours before unstacking.

[0035] Example 4: The chemical composition of the steel plate by weight percentage is: C 0.09%, Si 0.22%, Mn 1.35%, P 0.010%, S 0.001%, Nb 0.002%, Ti 0.001%, Als 0.095%, Cu 0.42%, Ni 1.01%, Cr 0.30%, Mo 0.45%, Sb 0.24%, V 0.047%, B 0.018%, with the remainder being Fe and unavoidable impurities. The key process steps include: Continuous casting: The molten steel is superheated to 12°C; the continuous casting adopts full protective casting to avoid contact between the molten steel and air, so as to control the absorption of N from the air by the molten steel during the casting process; the continuous casting process adopts secondary cooling stirring, and the continuous casting adopts the solidification end heavy pressure technology to improve the internal segregation and internal porosity of the slab; Heating: The heating furnace adopts a reducing atmosphere of mixed coal gas. The temperature of the heating section is 1180℃~1240℃, the temperature of the soaking section is 1160℃, and the soaking section is held for 55 minutes. Rolling: The roughing rolling adopts a large reduction regime, with the reduction rates of the three consecutive passes after widening being 14%, 16%, and 16% respectively; the finishing rolling temperature is 750℃, and the reduction rates of the first three passes of finishing rolling are 11%, 12%, and 13% respectively. Controlled rolling cooling: direct immersion in water, reddening temperature 640℃, cooling rate 3~10℃ / s; Quenching: Quenching at 900℃ for 158 minutes in the furnace, followed by water cooling; the high-pressure section of the quenching machine has a pressure of 8.1 bar, the low-pressure section has a pressure of 3.8 bar, and the surface temperature of the steel plate after quenching is 22℃. Tempering: Temper at 670℃ for 205 minutes, followed by air cooling and stack cooling. After tempering, stack cooling is performed at 200℃ for 35 hours before destacking.

[0036] Example 5: The chemical composition of the steel plate by weight percentage is: C 0.08%, Si 0.40%, Mn 1.40%, P 0.0174%, S 0.001%, Nb 0.002%, Ti 0.001%, Als 0.080%, Cu 0.34%, Ni 0.75%, Cr 0.34%, Mo 0.42%, Sb 0.30%, V 0.042%, B 0.017%, with the remainder being Fe and unavoidable impurities; including the following key process steps: Continuous casting: The molten steel is superheated to 12°C; the continuous casting adopts full protective casting to avoid contact between the molten steel and air, so as to control the absorption of N from the air by the molten steel during the casting process; the continuous casting process adopts secondary cooling stirring, and the continuous casting adopts the solidification end heavy pressure technology to improve the internal segregation and internal porosity of the slab; Heating: The heating furnace adopts a reducing atmosphere of mixed coal gas. The temperature of the heating section is 1180℃~1240℃, the temperature of the soaking section is 1160℃, and the soaking section is held for 85 minutes. Rolling: The roughing rolling adopts a large reduction regime, with the reduction rates of the three consecutive passes after widening being 16%, 16%, and 16% respectively; the finishing rolling temperature is 782℃, and the reduction rates of the first three passes of finishing rolling are 12%, 12%, and 14% respectively. Controlled rolling cooling: direct immersion in water, reddening temperature 623℃, cooling rate 3~10℃ / s; Quenching: Quenching at 908℃ for 169 minutes in the furnace, followed by water cooling; the high-pressure section of the quenching machine was 8.2 bar, and the low-pressure section was 3.8 bar. The surface temperature of the steel plate after quenching was 25℃. Tempering: Temper at 675℃ for 255 minutes, followed by air cooling and stack cooling. After tempering, stack cooling is performed at 277℃ for 78 hours before destacking.

[0037] Example 6: The chemical composition of the steel plate by weight percentage is: C 0.09%, Si 0.19%, Mn 1.42%, P 0.009%, S 0.001%, Nb 0.002%, Ti 0.001%, Als 0.085%, Cu 0.49%, Ni 0.89%, Cr 0.34%, Mo 0.40%, Sb 0.10%, V 0.047%, B 0.016%, with the remainder being Fe and unavoidable impurity elements; including the following key process steps: Continuous casting: The molten steel is superheated by 10°C; the continuous casting adopts full protective casting to avoid contact between the molten steel and air, so as to control the absorption of N from the air by the molten steel during the casting process; the continuous casting process adopts secondary cooling stirring, and the continuous casting adopts the solidification end heavy pressure technology to improve the internal segregation and internal porosity of the slab; Heating: The heating furnace adopts a reducing atmosphere of mixed coal gas. The temperature of the heating section is 1180℃~1240℃, the temperature of the soaking section is 1195℃, and the soaking section is held for 65 minutes. Rolling: The roughing rolling adopts a large reduction regime, with the reduction rates of the three consecutive passes after widening being 16%, 18%, and 18% respectively; the finishing rolling temperature is 798℃, and the reduction rates of the first three passes of finishing rolling are 12%, 14%, and 14% respectively. Controlled rolling cooling: direct immersion in water, reddening temperature 618℃, cooling rate 3~10℃ / s; Quenching: Quenching at 917℃ for 224 minutes in the furnace, followed by water cooling; the high-pressure section of the quenching machine was 8.1 bar, and the low-pressure section was 3.9 bar. The surface temperature of the steel plate after quenching was 35℃. Tempering: Temper at 672℃ for 350 minutes, followed by air cooling and stack cooling. After tempering, stack cooling is performed at 266℃ for 99 hours before destacking.

[0038] Comparative Example 1: The production method of bridge steel Q620qENH, the chemical composition of the steel plate by weight percentage is as follows: C 0.08%, Si 0.28%, Mn 1.319%, P 0.009%, S 0.001%, Nb 0.045%, Ti 0.012%, Als 0.038%, Cu 0.30%, Ni 0.48%, Cr 0.40%, Mo 0.22%, V 0.068%, B 0.0011%, Sb 0.004%, with the remainder being Fe and unavoidable impurity elements.

[0039] Continuous casting: molten steel superheated by 8°C; Heating: The heating furnace adopts a reducing atmosphere of mixed coal gas. The temperature of the heating section is 1180℃~1200℃, the temperature of the soaking section is 1185℃, and the soaking section is held for 55 minutes. Rolling: The roughing rolling adopts a large reduction regime, with the reduction rates of the three consecutive passes after widening being 18%, 19%, and 20% respectively; the finishing rolling temperature is 765℃, and the reduction rates of the first three passes of finishing rolling are 14%, 15%, and 14% respectively. Controlled rolling cooling: direct immersion in water, reddening temperature 655℃, cooling rate 3~10℃ / s; Quenching: Quenching at 910℃ for 224 minutes in the furnace, followed by water cooling; Tempering: Temper at 658℃ for 320 minutes in the furnace, followed by air cooling.

[0040] The steel plates prepared in Examples 1-6 and Comparative Example 1 of this invention were subjected to performance tests. The results are shown in Tables 1 and 2. The two-dimensional distribution diagram of Sb element content in the implementation results is shown in Table 1. Figure 1 The metallographic structure of the implementation results is shown in the figure. Figure 2 The CCT curve for the implementation process is shown below. Figure 3 The statistical segregation of C, Mn, Ni, Cu, and Sb in the steel plates prepared in Examples 1-6 and Comparative Example 1 was determined according to the general rules of GB / T 24213-2009 for in-situ statistical distribution of metals. The results are shown in Table 2.

[0041] Corrosion test: The wet and dry immersion test was conducted using a cyclic immersion corrosion test chamber to simulate marine atmospheric corrosion. The experiment lasted for a total of 336 hours, with samples taken at 48h, 96h, 144h, 240h, and 336h. Eight parallel samples were taken for each type of steel in Examples 1-6 and Comparative Example 1. Three of the samples were used for corrosion weight loss measurement. The phase composition of the corrosion rust layer of the three samples was analyzed by X-ray diffraction (XRD). The morphology of the rust layer surface of one sample was observed by scanning electron microscopy (SEM), and the cross-sectional morphology and alloy element distribution of the other sample were observed by SEM.

[0042] The corrosive medium was a 0.5% NaCl solution, and the temperature was kept constant at (42±1)℃. During the drying period, the temperature inside the chamber was (45±1)℃, and the humidity was (30±2)%. Each wet-dry cycle lasted 80 min, including an immersion time of 18 min and a drying time of 62 min.

[0043] The weightless sample was immersed in a prepared rust-removing solution (500ml hydrochloric acid + 500ml distilled water + 20g hexamethylenetetramine) for ultrasonic cleaning. After rust removal, the sample was cleaned with anhydrous ethanol, quickly dried, and weighed, with the weight recorded as W1. The weight was calculated using (W0-W1) / (Sρ) (where S is the corrosion area of ​​the sample, in cm²). 2 ρ is the density of the experimental steel, in g / cm³. 3 The corrosion thinning amount is calculated using K(W0-W1) / (TS ρ) (where K is a constant, chosen here as 8.76×10). 4 (T is the acceleration time, in hours) to calculate the average corrosion rate. Results are shown below. Figure 4 As shown in Table 3.

[0044] In summary, the corrosion-resistant system of this invention incorporates trace amounts of Sb in a Ni-Cu system, improves core quality through in-situ analysis, and enhances core performance and fatigue resistance using a Nb- and Ti-free design technique. Compared to the comparative example, it exhibits superior core toughness and significantly better corrosion resistance, demonstrating promising application prospects in marine atmospheric corrosion resistance.

[0045] Table 1. Performance test results of the steels used in the examples and the comparative steels. .

[0046] Table 2. Statistical segregation of C, Mn, Ni, Cu, and Sb in the Example Steels and Comparative Steels .

[0047] Table 3. Relative corrosion rates (336 h) of the steels used in the examples and the comparative examples. .

Claims

1. A Q620 grade high-toughness, high-corrosion-resistant steel plate, characterized in that: The chemical composition of the steel plate by weight percentage is C=0.08~0.09, Si=0.15%~0.40%, Mn=1.35%~1.45%, P≤0.020%, S≤0.003%, Nb≤0.005%, Ti≤0.005%, Als=0.08%~0.10%, Cu=0.30%~0.70%, Ni=0.7%~1.5%, V=0.04%~0.05%, Mo=0.40%~0.45%, Cr=0.30%~0.35%, B=0.001%~0.002%, Sb=0.08%~0.30%, with the remainder being Fe and unavoidable impurity elements.

2. The Q620 grade high-toughness and high-corrosion-resistant steel plate according to claim 1, characterized in that: The steel plate has a yield strength ReL≥620MPa, tensile strength Rm≥720MPa, elongation after fracture A≥30%, and low-temperature impact toughness KV2≥120J at -60℃; the low-temperature impact toughness KV2≥120J at 1 / 2 thickness of the steel plate at -60℃; and resistance to lamellar tearing Z≥35%.

3. A method for producing Q620 grade high-toughness and high-corrosion-resistant steel plate, the production process including hot metal pretreatment → converter steelmaking → ladle refining (LF) → vacuum treatment (RH) → continuous casting → heating → rolling → controlled rolling cooling → quenching → tempering → finishing, characterized in that... Key process steps include: Continuous casting: The superheat of molten steel is less than 15℃; continuous casting adopts full protective casting, secondary cooling stirring is adopted in the continuous casting process, and the solidification end heavy pressure reduction technology is adopted to improve the internal segregation and internal porosity of the slab; Heating: The heating furnace adopts a reducing atmosphere, with a heating section temperature of 1100~1240℃, a soaking section temperature of 1100~1200℃, and a soaking section holding time of ≥30min; Rolling: The roughing rolling adopts a large reduction regime, with a reduction rate of ≥14% in three consecutive passes after widening; the finishing rolling temperature is 750~820℃, and the reduction rate of the first three passes in the finishing rolling is ≥10%; Controlled rolling cooling: Direct immersion in water, reddening temperature 600~660℃, cooling rate 3~10℃ / s; Quenching: Quenching at 900~920℃, furnace time is plate thickness mm×(1.4~2.5)min / mm, water cooling, quenching ensures that the high pressure section of the quenching machine is ≥8bar, the low pressure section is ≥3.5bar, and the surface temperature of the steel plate after quenching is ≤40℃; Tempering: Temper at 670~690℃, furnace time is plate thickness mm×(2.0~3.5)min / mm, air cooling + stack cooling, stack cooling after tempering, stack cooling temperature 200~300℃, stack cooling time ≥24 hours before destacking; Antimony is added in conjunction with the processes of converter steelmaking, ladle refining (LF), and continuous casting.

4. The method for producing a Q620 grade high-toughness and high-corrosion-resistant steel plate according to claim 3, characterized in that: The reducing atmosphere mentioned in the heating step is a mixed gas.

5. The method for producing a Q620 grade high-toughness and high-corrosion-resistant steel plate according to claim 3, characterized in that: The antimony is selected from antimony-iron alloy with an alloy block size of 20~30mm. 80% is added during the steel tapping process after converter deoxidation, and 20% is added before leaving the LF station. Bottom blowing argon is used for thorough stirring, and secondary cooling stirring is used during the continuous casting process.

6. The method for producing a Q620 grade high-toughness and high-corrosion-resistant steel plate according to claim 3, characterized in that: The thickness of the Q620 grade high-toughness and high-corrosion-resistant steel plate is ≤100mm.

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