A seawater corrosion resistant structural steel q500qenhs-i wide and thick steel plate, a production method and application thereof

Abstract

The application discloses a seawater corrosion resistant structural steel Q500qENHS-I wide and thick steel plate and a production method and application thereof. In the application, low-carbon component design is adopted, and elements such as Cr, Cu, Ni, Nb and Mo are added to control microstructure so as to improve the strength and toughness of the steel plate and refine the grain. High-Cr design is adopted to realize that the yield strength is above 530 MPa, the weathering index I value is greater than or equal to 8.5, the welding crack sensitivity index P cm ≤0.25, the structure is a dual-phase structure of fine-grained ferrite + granular sorbite, and the produced steel plate can be used for a cross-sea highway bridge, a railway bridge and a highway-railway combined bridge and a structural steel in a complex environment with high seawater salinity, has certain requirements on the strength, low-temperature toughness, high earthquake resistance and high seawater corrosion resistance of the steel plate, is suitable for application in a general environment in the north and an environmental temperature requirement, can ensure a safe service life, improves the use safety, and has a good prospect.

Description

Technical Field

[0001] This application relates to the field of metallurgical technology, and more specifically, to a seawater corrosion resistant structural steel Q500qENHS-Ⅰ wide and thick steel plate, its production method, and its application. Background Technology

[0002] Q500qENHS-Ⅰ, a seawater corrosion-resistant structural steel, is mainly used for large bridges in special climatic conditions, requiring seawater and marine atmospheric corrosion resistance. Its corrosion resistance is between that of ordinary weathering bridge steel and stainless steel, and its marine atmospheric corrosion resistance is 8-12 times that of ordinary steel of the same grade. A comparative study was conducted using cyclic immersion corrosion tests to investigate the corrosion behavior of the produced seawater corrosion-resistant structural steel Q500qENHS-Ⅰ and traditional weathering steels 09CuPCrNi and Q420qENH in a simulated marine atmospheric environment. Corrosion behavior was analyzed using corrosion morphology observation and electrochemical testing. The results show that microstructure and chemical composition both have a certain influence on the corrosion resistance of the steel matrix. After a protective rust layer forms, corrosion resistance mainly depends on the protective effect of the rust layer. The results of cyclic immersion corrosion tests and the electrochemical impedance spectroscopy and linear polarization curve analysis of rust-bearing tests indicate that the seawater corrosion-resistant structural steel Q500qENHS-Ⅰ has better resistance to marine atmospheric corrosion than 09CuPCrNi steel and Q420qENH. While ensuring good processing performance of the steel plate, a seawater corrosion resistant structural steel Q500qENHS-Ⅰ steel plate was developed, which effectively obtained stable performance and better met the needs of the structural steel market, with significant social and economic benefits.

[0003] Therefore, this application is submitted. Summary of the Invention

[0004] The purpose of this application is to overcome the defects of the prior art and provide a seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate and its production method.

[0005] The technical problem solved by this application is achieved by the following technical solution.

[0006] This application provides a seawater corrosion resistant structural steel Q500qENHS-Ⅰ wide and thick steel plate, containing the following chemical composition by mass percentage: C: 0.04~0.07%, Si: 0.30~0.40%, Mn: 1.10~1.25%, P: 0.012~0.018%, S≤0.005%, Alt: 0.010~0.040%, Nb: 0.035~0.049%, Ni: 1.00~1.20%, Cr: 1.20~1.40%, Cu: 0.26~0.38%, Ti: 0.010~0.020%, Mo: 0.07~0.12%, B≤0.0005%, with the remainder being Fe and residual elements.

[0007] This application also provides a method for producing seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate, the method including: heating, rolling, and post-rolling cooling processes.

[0008] This application also provides an application of the above-mentioned seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate in cross-sea highway bridges, railway bridges and dual-purpose road-rail bridges.

[0009] This application has the following beneficial effects: This application provides a seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate and its production method. The Q500qENHS-Ⅰ thick steel plate provided in this application utilizes a low-carbon composition design, while simultaneously adding elements such as Cr, Cu, Ni, Nb, and Mo to control the microstructure, thereby improving the strength and toughness of the steel plate and refining the grain size. Specifically, the amount of Cr, a highly hardenable element, exceeds 1.20%, and the high-Cr design achieves a yield strength above 530 MPa and a weld crack sensitivity index P. cm With a particle size ≤0.25 and a weathering index I value ≥8.5, the steel plate, designed and prepared by combining controlled rolling and cooling processes to obtain a fine-grained ferrite + granular sorbite dual-phase structure, has excellent mechanical properties and corrosion resistance. It can be used for cross-sea highway bridges, railway bridges and dual-purpose road-rail bridges, as well as complex environments with high seawater salinity, where there are certain requirements for steel plate strength, low-temperature toughness, high seismic resistance and high seawater corrosion resistance. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 Metallographic image (left) and SEM scanned image (right) of the steel plate produced in Example 1 on the surface. Figure 2 Metallographic image of the steel plate produced in Example 1 at 1 / 4 of its thickness; Figure 3 Metallographic image (left) and SEM scan image (right) of the steel plate produced in Example 1 at 1 / 2 thickness. Figure 4 A tensile photograph of the steel plate produced in Example 1; Figure 5Metallographic image of the surface of the steel plate produced for Comparative Example 1; Figure 6 SEM images of the cracks produced in Comparative Example 1; Figure 7 A photograph of the tensile delamination of the steel plate produced in Comparative Example 2; Figure 8 A low-magnification photograph of the steel plate produced in Comparative Example 2 after cold acid treatment; Figure 9 Metallographic images of the surface of the steel plate produced in Comparative Example 3; Figure 10 Metallographic image of the steel plate produced in Comparative Example 3 at 1 / 4 thickness; Figure 11 This is a scanning electron microscope (SEM) image of the fracture surface at the impact point of the steel plate produced in Comparative Example 3. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0013] The following is a detailed description of a seawater corrosion resistant structural steel Q500qENHS-Ⅰ wide and thick steel plate and its production method provided in the embodiments of this application.

[0014] The following is a detailed description of a high-strength, seawater-corrosion-resistant structural steel Q500qENHS-Ⅰ thick steel plate and its production method provided in the embodiments of this application.

[0015] To address the aforementioned technical problems, this application provides a high-strength, seawater-corrosion-resistant structural steel Q500qENHS-Ⅰ thick steel plate. The Q500qENHS-Ⅰ thick steel plate contains the following chemical composition by mass percentage: C: 0.04~0.07%, Si: 0.30~0.40%, Mn: 1.10~1.25%, P: 0.012~0.018%, S≤0.005%, Alt: 0.010~0.040%, Nb: 0.035~0.049%, Ni: 1.00~1.20%, Cr: 1.20~1.40%, Cu: 0.26~0.38%, Ti: 0.010~0.020%, Mo: 0.07~0.12%, B≤0.0005%, with the remainder being Fe and unavoidable residual elements.

[0016] For example, the aforementioned high-strength seawater corrosion-resistant structural steel Q500qENHS-Ⅰ thick steel plate can have the following contents: C content: 0.04%, 0.05%, 0.06%, 0.07%, etc.; Si content: 0.30%, 0.35%, 0.40%, etc.; Mn content: 1.15%, 1.18%, 1.20%, 1.12%, 1.25%; P: 0.012~0.018%; S≤0.005%, etc.; Alt content: 0.015%, 0.020%, 0.030%, 0.040%, etc.; Nb content: 0.030%, 0.035%, 0.045%, etc.; Ni content: [Missing information - likely a typo]. The Cr content can be 1.00%, 1.05%, 1.10%, 1.15%, 1.20%, etc.; the Cu content can be 0.25%, 0.27%, 0.28%, 0.29%, 0.30%, 0.32%, 0.33%, 0.35%, etc.; the Ti content can be 0.011%, 0.013%, 0.015%, 0.010%, 0.016%, 0.018%, 0.019%, 0.020%; and the Mo content can be 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, etc.

[0017] The composition of the aforementioned seawater corrosion resistant structural steel Q500qENHS-Ⅰ wide and thick steel plate also meets the following requirements: weld crack sensitivity index Pcm≤0.25, atmospheric corrosion resistance index I≥8.5, wherein: Pcm=C+Si / 30+Mn / 20+Cu / 20+Ni / 60+Cr / 20+Mo / 15+V / 10+5B....(1) I=26.01(%Cu)+3.88(%Ni)+1.20(%Cr)+1.49(%Si)+17.28(%P)-7.29(%Cu)(%Ni)-9.10(%Ni)(%P)-33.39(%Cu) 2 ........(2).

[0018] The composition of the aforementioned seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate also meets the following requirements: Ni equivalent / Cr equivalent is maintained within the range of 2.10~2.99, wherein: Nickel equivalent Nieq = Ni + 35*C + 20*N + 0.25*Cu.........(3) Chromium equivalent Creq = Cr + 0.25Mo + 0.7 * Nb.........(4) The above-mentioned high-strength seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate has a yield strength ReL≥530MPa, tensile strength Rm≥680MPa, elongation A≥20%; yield strength ratio≤0.80, and longitudinal impact energy at 1 / 2 thickness at -40℃≥120J.

[0019] The microstructure of the aforementioned high-strength, seawater-corrosion-resistant structural steel Q500qENHS-Ⅰ thick steel plate is a composite microstructure of granular sorbite and ferrite.

[0020] The thickness of the aforementioned high-strength bridge seawater corrosion resistant structural steel Q500qENHS-Ⅰ wide and thick steel plate is 20~100mm.

[0021] Meanwhile, this application embodiment also provides a production method for the above-mentioned high-strength seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate, which includes the following processes: steelmaking, continuous casting, thick plate heating, rolling and cooling.

[0022] Its steelmaking process includes: converter smelting → LF furnace refining → RH vacuum treatment. The converter smelting process includes: final composition control C: ≥0.080%; P: 0.012~0.018%, S≤0.025%; ladle tapping temperature 1580~1610℃, and slag blocking during tapping.

[0023] The refining process includes: adding 420-530 kg of refining agent, 650-820 kg of lime, 230-270 kg of submerged arc slag, and 100-160 kg of fluorite; energizing the LF furnace for 5-7 minutes to slag; taking temperature measurements and samples; feeding aluminum wire to create white slag; and maintaining the white slag for 11-15 minutes.

[0024] The vacuum process includes: ensuring a vacuum degree ≤100Pa, vacuum time ≥15min, pure degassing time ≥11min, and setting a hydrogen level at the outlet to ensure that the [H] at the outlet is ≤2ppm; after breaking the vacuum, add ferroboron, then feed 220~270m of pure calcium wire, and after the treatment, gently blow argon for 10~15min, controlling the flow rate of the gently blown argon to ensure the effect of the gently blown argon (the surface of the molten steel should be slightly undisturbed).

[0025] The continuous casting process includes: ensuring proper protection during casting, and preventing the impact zone from turning bright red. Superheating must be maintained between 12 and 28°C. The continuously cast billet must be promptly placed in the pit for slow cooling for 30 to 48 hours. The billet temperature upon entering the pit must not be lower than 550°C. After exiting the pit, the billet should be kept away from hot billets and must not be piled on tuyeres; it must be piled among other cold billets.

[0026] The heating process includes: preheating temperature of billet preheating section ≤890℃, first heating section temperature ≤1155℃, second heating section temperature 1195℃~1265℃, soaking section temperature 1205~1245℃, and total heating time: 330~380 minutes for 300mm billet.

[0027] The rolling process includes: differential temperature rolling in the recrystallization zone + two-stage controlled rolling process in the non-recrystallization zone.

[0028] Differential temperature rolling in the recrystallization zone includes: initial rolling temperature ≥1050℃, final rolling temperature F B ±10℃, the first and third passes utilize a pre-machine cooling device for surface cooling of the steel plate, with a cooling water flow rate of 1350-1550 L / min and a cooling rate A. C1 ±0.50℃ / s, so that the temperature difference between the surface and the core of the steel plate after cooling reaches F. A ±10℃, after cooling, the reduction rate of each of the first to fourth rolling passes is 15%~19%, and the final rolling temperature is F. B ±10℃, the second stage uses non-recrystallization rolling, with an initial rolling temperature of 830~870℃ and a final rolling temperature of F. C ±10℃, cumulative reduction rate 40%~55%, single pass reduction 15~25mm.

[0029] Since the surface temperature of the steel plate has dropped to 940~980℃, but the temperature of the core of the steel plate is still higher than 1050℃, there is a temperature difference between the surface and the core. At this time, temperature difference rolling allows the deformation of the rolling process to penetrate into the core better, increasing the amount of core deformation. This not only increases the probability of welding defects in the core structure, but also improves the core nucleation ability, resulting in a finer core structure.

[0030] The post-rolling cooling process includes: intermittent cooling, specifically: after the steel plate is rolled, the water temperature is ≥826℃, and ACC nozzles are opened intermittently in groups 1-3, 6-8, 11-13, 16-18, and 20-21, for a total of 14 groups. The water volume is 500~550m³ for groups 1-3. 3 / h, 6-8 groups are 440-470m 3 / h, cooling rate A C2 ±0.50℃ / s, groups 11-13 and 16-18 are 240-260m. 3 / h, the 20th-21st groups are 150-170m 3 / h, cooling roller speed 1.0-1.2m / s, cooling rate A C3 ±0.50℃ / s, reddening temperature F after cooling D ±10℃, and after cooling, it is decommissioned at 200~300℃ for 24~48 hours.

[0031] Among them, F A F B F C and F D It refers to the temperature difference between the surface and core after cooling in the roughing stage, the final rolling temperature in the roughing stage, the final rolling temperature in the finishing stage, and the temperature at which the surface reddens after cooling in the cooling stage. AF B F C F D A C1 A C2 and A C3 The calculation formula is as follows: F A =150+20*C+34*Mn+26*Cr............(5) F B =850+20*C+34*Mn+26*Cr+35*Ni+120*Mo+95*Cu............(6) F C =735+20*C+34*Mn+26*Cr+26*Mo+130*Ni.............(7) F D =532+20*C+34*Mn+26*Cr+88*Mo+139*Ni.............(8) A C1 =6.7+(5.689-1.437*C-1.3578*Si-0.796*Mn-1.267*Cr-0.892*Ni) 1 / 2 A C2 =2.3+(5.689-1.437*C-1.3578*Si-0.796*Mn-1.267*Cr-0.892*Ni) 1 / 2 A C3 =1.9+(5.689-1.437*C-1.3578*Si-0.796*Mn-1.267*Cr-0.892*Ni) 1 / 2 .

[0032] In this embodiment, differential temperature rolling is used in the roughing stage, increasing the core deformation of the steel plate. The combination of Mo and Nb can delay the ferrite-pearlite phase transformation, reducing the critical cooling rate for obtaining acicular ferrite and expanding the cooling rate range for acicular ferrite formation. Combined with a suitable controlled rolling and cooling process—that is, roughing in the austenite recrystallization zone with a large pass deformation to obtain fine and uniform austenite grains—and then finishing rolling in a temperature range below the recrystallization temperature Tnr and above the Ar3 temperature, with the largest possible cumulative deformation during the finishing rolling stage and final rolling around Ar3, followed by rapid cooling, a steel plate with a fine-grained ferrite + granular sorbite dual-phase structure is obtained, with an average grain size reaching 50-200 nanometers. Wherein:

[0033] .

[0034] This application also provides an application of the above-mentioned seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate in cross-sea highway bridges, railway bridges and dual-purpose road-rail bridges.

[0035] The present application will be further described below with reference to embodiments.

[0036] Example 1 The high-strength, seawater-corrosion-resistant structural steel Q500qENHS-Ⅰ thick steel plate has a thickness of 60mm. The chemical composition and mass percentage of the steel plate are as follows: C: 0.05%, Si: 0.33%, Mn: 1.17%, P: 0.014%, S: 0.003%, Alt: 0.032%, Nb: 0.039%, Ni: 1.16%, Cr: 1.22%, Cu: 0.34%, Ti: 0.018%, Mo: 0.09%, B: 0.0002%, with the remainder being Fe and residual elements. This ensures a weld crack sensitivity index Pcm ≤ 0.25 and an atmospheric corrosion resistance index I ≥ 8.5. The Ni equivalent / Cr equivalent ratio is maintained within the range of 2.10~2.99.

[0037] Its production method includes heating, rolling, and post-rolling cooling processes, with the specific steps as follows: Heating process: The steel billet containing the above-mentioned smelting components is transported into the heating furnace that has reached the set furnace temperature. The steel billet has an end face size of 295mm. The preheating section temperature is 855℃, the first heating section temperature is 1140℃, the second heating section temperature is 1242℃, the soaking temperature is 1235℃, and the total heating time is 352 minutes.

[0038] Rolling process: The first stage of rolling starts at a temperature of 1058℃. Before the first and third passes, the billet is cooled using a cooling device with a cooling water flow rate of 1360L / min and a cooling rate of 7.12℃ / s. The roll speed is set to 1.0m / s during cooling. After cooling, normal rolling is carried out. The reductions for the first four passes are 32mm, 30mm, 29mm, and 30mm, respectively, with a final rolling temperature of 947℃. The second stage of rolling starts at a temperature of 862℃ and ends at a temperature of 821℃, with a cumulative reduction rate of 53.1%.

[0039] Post-rolling cooling process: Intermittent cooling is adopted. After the steel plate is rolled, the water temperature is 826℃. ACC nozzles are opened intermittently in groups 1-3, 6-8, 11-13, 16-18, and 20-21, for a total of 14 groups. Water volume: 535m³ / h for groups 1-3. 3 / h, 6-8 groups are 480m 3 / h, groups 11-13 and 16-18 are 295m3 / h, group 20-21 is 258m 3 / h, cooling roller speed 1.15m / s, reddening temperature after cooling 622℃, after cooling, offline stacking at 290℃ for 29 hours.

[0040] Example 2 The high-strength, seawater-corrosion-resistant structural steel Q500qENHS-Ⅰ thick steel plate has a thickness of 60mm. The chemical composition and mass percentage of the steel plate are as follows: C: 0.07%, Si: 0.30%, Mn: 1.15%, P: 0.011%, S: 0.003%, Alt: 0.032%, Nb: 0.035%, Ni: 1.17%, Cr: 1.25%, Cu: 0.34%, Ti: 0.015%, Mo: 0.08%, B: 0.0002%, with the remainder being Fe and residual elements. This ensures a weld crack sensitivity index Pcm ≤ 0.25 and an atmospheric corrosion resistance index I ≥ 8.5. The Ni equivalent / Cr equivalent ratio is maintained within the range of 2.10~2.99.

[0041] Its production method includes heating, rolling, and post-rolling cooling processes, with the specific steps as follows: Heating process: The steel billet containing the above-mentioned smelting components is transported into the heating furnace that has reached the set furnace temperature. The steel billet has an end face size of 295mm. The preheating section temperature is 859℃, the first heating section temperature is 1145℃, the second heating section temperature is 1241℃, the soaking temperature is 1238℃, and the total heating time is 372 minutes.

[0042] Rolling process: The first stage of rolling starts at a temperature of 1048℃. Before the first and third passes, the billet is cooled using a cooling device with a cooling water flow rate of 1352L / min and a cooling rate of 7.12℃ / s. The roll speed is set to 1.0m / s during cooling. After cooling, normal rolling is carried out. The reductions for the first four passes are 32mm, 30mm, 29mm, and 30mm, respectively, with a final rolling temperature of 957℃. The second stage of rolling starts at a temperature of 859℃ and ends at a temperature of 828℃, with a cumulative reduction rate of 53.8%.

[0043] Post-rolling cooling process: Intermittent cooling is adopted. After the steel plate is rolled, the water temperature is 820℃. ACC nozzles are opened intermittently in groups 1-3, 6-8, 11-13, 16-18, and 20-21, for a total of 14 groups. Water volume: 535m³ / h for groups 1-3. 3 / h, 6-8 groups are 480m 3 / h, groups 11-13 and 16-18 are 295m 3 / h, group 20-21 is 258m 3 / h, cooling roller speed 1.15m / s, reddening temperature after cooling 622℃, after cooling, offline stacking at 290℃ for 32 hours.

[0044] Example 3 The high-strength, seawater-corrosion-resistant structural steel Q500qENHS-Ⅰ is a 100mm thick wide steel plate. The chemical composition and mass percentage of the steel plate are as follows: C: 0.04%, Si: 0.39%, Mn: 1.25%, P: 0.015%, S: 0.003%, Alt: 0.032%, Nb: 0.035%, Ni: 1.17%, Cr: 1.25%, Cu: 0.34%, Ti: 0.015%, Mo: 0.08%, B: 0.0002%, with the remainder being Fe and residual elements. This ensures a weld crack sensitivity index Pcm ≤ 0.25 and an atmospheric corrosion resistance index I ≥ 8.5. The Ni equivalent / Cr equivalent ratio is maintained within the range of 2.10~2.99.

[0045] Its production method includes heating, rolling, and post-rolling cooling processes, with the specific steps as follows: Heating process: The steel billet containing the above-mentioned smelting components is transported into the heating furnace that has reached the set furnace temperature. The steel billet has an end face size of 295mm. The preheating section temperature is 858℃, the first heating section temperature is 1142℃, the second heating section temperature is 1240℃, the soaking temperature is 1237℃, and the total heating time is 362 minutes.

[0046] Rolling process: The first stage of rolling starts at a temperature of 1053℃. Before the first and third passes, the billet is cooled using a cooling device with a cooling water flow rate of 1345L / min and a cooling rate of 7.12℃ / s. The roll speed is set to 1.0m / s during cooling. After cooling, normal rolling is carried out. The reductions for the first four passes are 32mm, 30mm, 29mm, and 30mm, respectively, with a final rolling temperature of 952℃. The second stage of rolling starts at a temperature of 852℃ and ends at a temperature of 828℃, with a cumulative reduction rate of 50.1%.

[0047] Post-rolling cooling process: Intermittent cooling is adopted. After the steel plate is rolled, the water temperature is 819℃. ACC nozzles are opened intermittently in groups 1-3, 6-8, 11-13, 16-18, and 20-21, for a total of 14 groups. Water volume: 535m³ / h for groups 1-3. 3 / h, 6-8 groups are 480m 3 / h, groups 11-13 and 16-18 are 295m 3 / h, group 20-21 is 258m 3 / h, cooling roller speed 1.15m / s, reddening temperature after cooling 622℃, after cooling, offline stacking at 290℃ for 25 hours.

[0048] Table 1. Mechanical properties of 2500mm wide seawater corrosion resistant structural steel Q500qENHS-Ⅰ steel plates from Examples 1, 2, and 3.

[0049] Combining Table 1 and Figure 1-4 It can be seen that the 60mm, 80mm, and 100mm seawater corrosion resistant structural steel Q500qENHS-Ⅰ steel plates have good mechanical properties at 1 / 4 and 1 / 2 of their thickness, fully meeting the requirements of the corresponding standards, and have a good balance of strength and toughness.

[0050] Table 2. Cyclic acid etching rates of Examples 1, 2, 3, 09CuPCrNi and ordinary Q420qENH relative to Q345B.

[0051] Table 3. Chemical composition of various embodiments of this application and ordinary Q345B, 09CuPCrNi, and Q420qENH.

[0052]

[0053] Table 4. Process parameters during rolling and post-rolling cooling of various embodiments of this application and ordinary Q345B, 09CuPCrNi, and Q420qENH.

[0054] Table 5. Process parameters for smelting, continuous casting, and heating of various embodiments of this application and ordinary Q345B, 09CuPCrNi, and Q420qENH.

[0055] Table 6. Process parameters during rolling and cooling of various embodiments of this application and ordinary Q345B, 09CuPCrNi, and Q420qENH.

[0056] Table 7 Mechanical properties of various embodiments of this application and ordinary Q345B, 09CuPCrNi, and Q420qENH

[0057] Table 8 shows the hydrochloric acid cyclic wetting corrosion resistance of various embodiments of this application and ordinary Q345B, 09CuPCrNi, and Q420qENH.

[0058]

[0059] The experimental results in Tables 7 and 8 show that the high-strength, seawater-corrosion-resistant structural steel Q500qENHS-Ⅰ thick steel plate prepared using the method provided in the embodiments of this invention has good mechanical properties and excellent resistance to hydrochloric acid cyclic wetting corrosion. The metallographic structure of the steel plate prepared in Example 1 at different locations is shown in the figure. Figure 1-3 ,from Figure 1 The right-hand image also shows the precipitation of TiN and NbN. These precipitated particles act as pinning agents, inhibiting grain growth and refining the grains. Tensile photographs of the steel plate from the tensile test are shown below. Figure 4 The designed and manufactured steel plates can be used in cross-sea highway bridges, railway bridges, and dual-purpose road-rail bridges, as well as structural steel in complex environments with high salinity seawater, where certain requirements for steel plate strength, low-temperature toughness, high seismic resistance, and high seawater corrosion resistance are required. Suitable for applications in the common northern environments and with suitable temperature requirements, these plates can ensure safe service life and improve operational safety, demonstrating promising prospects.

[0060] The only difference between Comparative Example 1 and Example 1 is that the C content in the steel plate is 0.12%. The mechanical properties of the steel plate prepared in Comparative Example 1 are shown in Table 7. The three impact values ​​at -40℃ are extremely low, with an average of only 28.6 J, failing to meet the standard requirements. Furthermore, the microstructure shows microcracks and segregation in the middle of the steel plate. This is mainly due to the segregation of C and Cr components and the high C content, which easily leads to the formation of aggregated cementite clusters, such as... Figure 5 Metallographic images of the steel plate produced in Comparative Example 1; Figure 6 This is a SEM image of the crack produced in Comparative Example 1.

[0061] The only difference between Comparative Example 2 and Example 1 is that Ni is 0.46% and the atmospheric corrosion resistance index (I) of the steel plate is 7.82, which does not meet the requirement of I value ≥ 8.5. The mechanical properties of the steel plate prepared in Comparative Example 2 are shown in Table 7. The yield strength is only 525 MPa, and tensile delamination occurs in the longitudinal tensile specimens. Figure 7 A photograph showing the tensile delamination of the steel plate produced in Comparative Example 2. Figure 8 This is a low-magnification photograph of the steel plate produced in Comparative Example 2 after cold acid treatment.

[0062] The only difference between Comparative Example 3 and Example 1 is that: Cr: 0.82%, and the red glow temperature is 762°C, which exceeds the red glow temperature F required by the present application. D The temperature range is ±10℃. The mechanical properties of the steel plate prepared in Comparative Example 3 are shown in Table 7. Its yield strength is only 508 MPa, and it exhibits two high and one low values ​​in transverse impact at -40℃. Metallographic images of the surface and 1 / 4 section of the steel plate prepared in Comparative Example 3 are shown below. Figure 9-10 Furthermore, at lower impact points, the microstructure exhibits obvious cracks, such as... Figure 11This is a scanning electron microscope (SEM) image of the fracture surface at the impact point of the steel plate produced in Comparative Example 3.

[0063] The only difference between Comparative Example 4 and Example 1 is that P: 0.021%. The mechanical properties of the steel plate prepared in Comparative Example 4 are shown in Table 7. The yield strength is only 529 MPa, and the transverse impact at -40℃ shows one high and two low values. The elongation is only 18.9%, which does not meet the standard requirements of yield strength > 530 MPa and elongation > 20%.

[0064] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for producing a seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate, characterized in that, The seawater corrosion resistant structural steel Q500qENHS-Ⅰ wide and thick steel plate contains the following chemical composition by mass percentage: C: 0.04~0.07%, Si: 0.30~0.40%, Mn: 1.10~1.25%, P: 0.012~0.018%, S≤0.005%, Alt: 0.010~0.040%, Nb: 0.035~0.049%, Ni: 1.00~1.20%, Cr: 1.20%. ~1.40%, Cu: 0.26~0.38%, Ti: 0.010~0.020%, Mo: 0.07~0.12%, B≤0.0005%, with the remainder being Fe and unavoidable residual elements. The Ni equivalent / Cr equivalent remains in the range of 2.10~2.99, where: Nieq = Ni + 35*C + 20*N + 0.25*Cu, and Creq = Cr + 0.25Mo + 0.7*Nb. The production method includes the following steps: heating, rolling, post-rolling cooling, and heat treatment. The rolling process includes a two-stage controlled rolling process: differential temperature rolling in the recrystallization zone and rolling in the non-recrystallization zone; The differential temperature rolling in the recrystallization zone includes: an initial rolling temperature ≥1050℃; surface cooling of the steel plate using a pre-machine cooling device in the first and third passes; a cooling water flow rate of 1300-1500 L / min; and a cooling rate A. C1 ±0.5℃ / s, so that the temperature difference between the surface and the core of the steel plate after cooling reaches F. A ±10℃, after cooling, the reduction rate of each of the first to fourth rolling passes is 9%~10%, and the final rolling temperature is F. B ±10℃; The rolling process in the non-recrystallization zone includes: an initial rolling temperature of 800~880℃ and a final rolling temperature of F. C ±10℃, cumulative reduction rate 45%~60%, single-pass reduction 16~29mm; The post-rolling cooling process includes: intermittent cooling, specifically: after the steel plate is rolled, the water temperature is ≥826℃, and ACC nozzles are opened intermittently in groups 1-3, 6-8, 11-13, 16-18, and 20-21, for a total of 14 groups. The water volume is 500~550m³ for groups 1-3. 3 / h, 6-8 groups are 440-470m 3 / h, cooling rate A C2 ±0.5℃ / s, groups 11-13 and 16-18 are 240-260m. 3 / h, the 20th-21st groups are 150-170m 3 / h, cooling roller speed 1.0-1.2m / s, cooling rate A C3 ±0.5℃ / s, reddening temperature F after cooling D ±10℃, after cooling, perform offline stack cooling at 200~300℃ for 24~48 hours; F A F B F C and F D It refers to the temperature difference between the surface and core after cooling in the roughing stage, the final rolling temperature in the roughing stage, the final rolling temperature in the finishing stage, and the temperature at which the surface reddens after cooling in the cooling stage. A F B F C F D A C1 A C2 and A C3 The calculation formula is as follows: F A =150+20*C+34*Mn+26*Cr F B =850+20*C+34*Mn+26*Cr+35*Ni+120*Mo+95*Cu F C =735+20*C+34*Mn+26*Cr+26*Mo+130*Ni F D =532+20*C+34*Mn+26*Cr+88*Mo+139*Ni And C1 =6.7+(5.689-1.437*C-1.3578*Si-0.796*Mn-1.267*Cr-0.892*Ni) 1 / 2 And C2 =2.3+(5.689-1.437*C-1.3578*Si-0.796*Mn-1.267*Cr-0.892*Ni) 1 / 2 And C3 =1.9+(5.689-1.437*C-1.3578*Si-0.796*Mn-1.267*Cr-0.892*Ni) 1 / 2 。 2. The production method according to claim 1, characterized in that, The seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate has a yield strength ReL≥530MPa, tensile strength Rm≥680MPa, elongation A≥20%; yield strength ratio≤0.80, and longitudinal impact energy at -40℃ at 1 / 2 thickness≥120J.

3. The production method according to claim 1, characterized in that, The thickness of the seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate is 10~100mm, and the width is 2500~3500mm. The microstructure of the seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate is a composite microstructure of granular sorbite and ferrite.

4. The production method according to claim 1, characterized in that, The heating process includes: preheating temperature of billet ≤890℃, first heating temperature ≤1140℃, second heating temperature 1190℃~1255℃, soaking temperature 1200~1235℃, and total heating time: ≥335 minutes for 300mm billet.

5. The application of the steel plate prepared by the production method of seawater corrosion resistant structural steel Q500qENHS-Ⅰ thick steel plate according to any one of claims 1-4 in cross-sea highway bridges, railway bridges and dual-purpose road-rail bridges.

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