Weathering steel suitable for high-temperature and high-humidity marine environment and preparation method thereof

Abstract

The invention provides super weathering steel suitable for a high-temperature and high-humidity marine environment and a preparation method of the super weathering steel, and the super weathering steel suitable for the high-temperature and high-humidity marine environment comprises the following chemical components in percentage by weight: 0.045%-0.065% of C, 0.45%-0.65% of Si, 1.2%-1.40% of Mn, less than or equal to 0.015% of S, 0.075%-0.085% of P, 0.025%-0.035% of Ti, 1.0%-1.2% of Cr, 0.4%-0.5% of Mo, 0.4%-0.5% of Al, 0.6%-0.8% of Ni, 0.35%-0.55% of Cu, 0.18%-0.25% of Sb, 0.1%-0.15% of Sn and the balance of Fe. And the balance of Fe and impurity elements. The weathering steel suitable for the high-temperature and high-humidity marine environment is low in cost and good in local spot corrosion resistance.

Description

Technical Field

[0001] The present application belongs to the field of metallurgical technology, and specifically relates to a weathering steel suitable for high temperature and high humidity marine environment and a preparation method thereof. Background Art

[0002] The tropical marine atmosphere is a harsh corrosive environment among many marine atmospheres. Due to its harsh conditions such as high humidity, strong radiation, long sunshine, and high salt fog, all kinds of metal equipment and reinforced concrete structures in this environment suffer from severe corrosion, which poses a huge threat to their service safety. At the same time, it is also accompanied by many problems such as equipment performance degradation, difficulty in predicting life, and a sharp increase in maintenance costs. Therefore, it is of great significance to develop corrosion-resistant steel suitable for tropical high temperature and high humidity climate environments to reduce the cost of using stainless steel, protective coatings, cathodic protection and other solutions. Summary of the invention

[0003] The present application provides a weathering steel suitable for a high temperature and high humidity marine environment and a preparation method thereof, which can obtain a weathering steel suitable for a high temperature and high humidity marine environment with low cost and strong corrosion resistance, especially good resistance to local pitting corrosion.

[0004] In a first aspect, the present application provides a weathering steel suitable for a high temperature and high humidity marine environment, the weathering steel comprising the following chemical components in weight percentage: C: 0.045% to 0.065%, Si: 0.45% to 0.65%, Mn: 1.2% to 1.40%, S≤0.015%, P: 0.075% to 0.085%, Ti: 0.025% to 0.035%, Cr: 1.0% to 1.2%, Mo: 0.4% to 0.5%, Al: 0.4% to 0.5%, Ni: 0.6% to 0.8%, Cu: 0.35% to 0.55%, Sb: 0.18% to 0.25%, Sn: 0.1% to 0.15%; the rest are Fe and impurity elements.

[0005] In a feasible implementation manner of the first aspect of the present application, the weathering steel includes the following volume fraction structures: 85% to 90% ferrite and 10% to 15% pearlite.

[0006] In a feasible implementation manner of the first aspect of the present application, the thickness of the weathering steel is 2.0-25.0 mm; the yield strength of the weathering steel is 460 MPa-520 MPa, the tensile strength is greater than 600 MPa, the elongation is greater than 18%, and the impact energy at -20°C is greater than 47 J.

[0007] The second aspect of the present application provides a method for preparing weathering steel suitable for high temperature and high humidity marine environment provided by the first aspect of the present application, comprising:

[0008] KR desulfurization: put the molten iron into the desulfurization station, add lime desulfurizer for desulfurization, and obtain desulfurized molten iron. The sulfur content of the desulfurized molten iron is ≤0.010%;

[0009] Converter smelting: Desulfurized molten iron is smelted in a converter, and after converter smelting, argon is blown through a ladle, and the terminal temperature of the argon station is controlled to be 1560℃~1590℃, thus obtaining converter smelting molten steel;

[0010] LF refining: The molten steel smelted in the converter is sent to the LF furnace for refining to obtain refined molten steel;

[0011] RH vacuum treatment: Degas the refined molten steel to obtain degassed molten steel; the oxygen content of the degassed molten steel is less than 300ppm, and the nitrogen content is less than 60ppm;

[0012] Continuous casting: Degassed molten steel is continuously cast at a casting speed of 1.4m / min to 1.7m / min to obtain a slab; the slab is heated in a heating furnace to obtain a furnace-out slab; the temperature of the slab entering the heating furnace is 600℃ to 650℃; the slab is heated at 1180℃ to 1220℃ in the heating furnace for 150min to 250min, and the furnace-out temperature of the slab is 1180℃ to 1220℃; the excess air coefficient of the heating furnace is 0.95-1.05;

[0013] Hot rolling: The steel billet is rolled, cooled, and coiled to obtain weathering steel suitable for high temperature and high humidity marine environments.

[0014] In a feasible implementation manner of the second aspect of the present application, in the continuous casting step, the solution temperature of the slab is 1200° C. to 1220° C., and the solution time is 30 min to 40 min.

[0015] In a feasible implementation manner of the second aspect of the present application, in the hot rolling step, rolling includes rough rolling and finish rolling, the starting rolling temperature of rough rolling is 1150℃~1180℃, and the final rolling temperature of rough rolling is 1050℃~1080℃; the steel billet after rough rolling is finish rolled, the starting rolling temperature of finish rolling is 1000℃~1050℃, and the final rolling temperature of finish rolling is 850℃~900℃.

[0016] In a feasible implementation manner of the second aspect of the present application, in the hot rolling step, cooling the steel billet after finish rolling specifically includes first ultra-fast cooling at 30℃ / s~50℃ / s, and then cooling to 620℃~650℃ by laminar cooling at 10℃ / s~25℃ / s.

[0017] In a feasible implementation manner of the second aspect of the present application, in the continuous casting step, the basicity of the protective slag used for continuous casting is 0.9-1.0, and the viscosity is 1.9-2.2 poise.

[0018] In a feasible implementation manner of the second aspect of the present application, in the refining step, the refining inlet temperature is 1525℃~1585℃, and the refining outlet temperature is 1565℃~1585℃; the refining time is 40min~45min; the temperature of the refined molten steel before entering the RH vacuum treatment is >1540℃.

[0019] In a feasible implementation manner of the second aspect of the present application, in the RH vacuum treatment step, the vacuum degree of the treatment is required to be ≤130 MPa, and the RH cycle time is 28 min to 35 min. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The comparative example is 316L stainless steel at 100ppmCl - Corrosion morphology and pitting measurement values ​​under different environments.

[0021] Figure 2 The comparative example is 316L stainless steel at 1000ppmCl - Corrosion morphology and pitting measurement values ​​under different environments.

[0022] Figure 3 The comparative example is 316L stainless steel at 5000ppmCl - Corrosion morphology and pitting measurement values ​​under different environments.

[0023] Figure 4 The comparative example is 316L stainless steel at 10000ppm Cl - Corrosion morphology and pitting measurement values ​​under different environments.

[0024] Figure 5 Example 1 Super weathering steel at different Cl - Corrosion morphology and corrosion reduction under different environments.

[0025] Figure 6 This is the metallographic structure of the super weathering steel of Example 2. DETAILED DESCRIPTION

[0026] In order to make the invention purpose, technical scheme and beneficial technical effect of the present application clearer, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the embodiments described in this specification are only for explaining the present application, not for limiting the present application.

[0027] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range, and any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0028] In the description herein, when a composition is described as containing, comprising or including specific components, or when a process is described as containing, comprising or including specific process steps, it is expected that the composition of the present application also consists essentially of or consists of the components, and the process of the present application also consists essentially of or consists of the process steps.

[0029] The use of the terms "including," "comprising," "containing," and "having" should generally be interpreted as open ended and non-limiting unless expressly stated otherwise.

[0030] In the description of this article, it should be noted that, unless otherwise specified, “above” and “below” are inclusive of the number itself, and the “multiple” in “one or more” means more than two.

[0031] The above-mentioned summary of the invention of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided by a series of examples, which can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0032] In high Cl - In this environment, 316L is traditionally used. 18% chromium, 10% nickel, 2% molybdenum and other precious alloys are added to the traditional 316 stainless steel formula. The alloy content is as high as 30%, the alloy cost is high, and there is also a weakness of poor local pitting corrosion resistance. Therefore, it is necessary to find a low-alloy corrosion-resistant steel with better pitting corrosion resistance to replace 316L.

[0033] In view of this, the present application provides a weathering steel suitable for high temperature and high humidity marine environment and a preparation method thereof, which can obtain weathering steel suitable for high temperature and high humidity marine environment with low cost, strong corrosion resistance, especially good resistance to local pitting corrosion.

[0034] In a first aspect, the present application provides a weathering steel suitable for a high temperature and high humidity marine environment, the weathering steel comprising the following chemical components in weight percentage: C: 0.045% to 0.065%, Si: 0.45% to 0.65%, Mn: 1.2% to 1.40%, S≤0.015%, P: 0.075% to 0.085%, Ti: 0.025% to 0.035%, Cr: 1.0% to 1.2%, Mo: 0.4% to 0.5%, Al: 0.4% to 0.5%, Ni: 0.6% to 0.8%, Cu: 0.35% to 0.55%, Sb: 0.18% to 0.25%, Sn: 0.1% to 0.15%; the rest are Fe and impurity elements.

[0035] The functions of the components and contents of the weathering steel applicable to high temperature and high humidity marine environment in this application are as follows:

[0036] Carbon: C has a great influence on the phase transformation during the cooling transformation of steel. A higher carbon content can easily form bainite and martensite with higher strength and hardness during the cooling process. However, too high a carbon content will increase the brittleness of the steel and reduce the plasticity and toughness of the steel; too low a carbon content will form softer structures such as ferrite. Considering the comprehensive mechanical properties and castability, the weathering steel in this application has been experimentally studied and demonstrated for many times, and it is best to set the C content in the range of 0.045-0.065%.

[0037] Silicon: Si can be deoxidized during the smelting process, but too high a content will affect weldability and toughness. An appropriate amount of Si solid solution in steel can improve strength, and an appropriate amount of silicon forms Fe in hot-rolled iron oxide scale or rust layer. 2 SiO 4 , which is beneficial to the improvement of corrosion resistance. After many experiments and demonstrations, the Si content of the weathering steel in this application is preferably controlled within the range of 0.45-0.65%.

[0038] Manganese: Mn is a weak carbide-forming element. It usually plays a role of solid solution strengthening in steel. In high-strength steel coils produced by thermomechanical rolling and controlled cooling, Mn dissipates the interface free energy across the diffusion interface, inhibits the diffusion control growth of the end faces of the lamellar phase, and forms refined lamellar bainite, thereby improving the strength, toughness and other comprehensive properties of the steel plate. Too high Mn content will increase the tendency of slab cracking and easily form defects such as longitudinal cracks in slab production, while lower Mn content will increase the hot brittleness of the slab during hot rolling. After many experimental studies and demonstrations, the addition of Mn in the range of 1.2-1.40% can improve the strength and toughness of the steel matrix.

[0039] Chromium: The addition of chromium will increase the strength and hardness of steel, but will reduce plasticity and toughness at the same time. In corrosion-resistant steel, the increase in chromium content can make the self-corrosion potential of the steel matrix shift positively, and as the content increases, it helps to make the surface rust layer denser until a stable passivation film is formed; chromium can change the phase composition of the rust layer and promote the transformation of γ-FeOOH to stable α-FeOOH; chromium can also replace part of the Fe in α-FeOOH. 3+ Formation of Cr-doped α-Fe x CrOOH 1-x The rust layer shows the selective permeability of cations and the corrosive anions Cl - , SO 4 2- The Cr element can effectively inhibit the Fe 3+ The stability of the rust layer is greatly improved by the reduction process. Taking into account the cost and performance requirements, the Cr content is preferably controlled within the range of 1.0-1.2% in this application.

[0040] Molybdenum: The addition of molybdenum can improve the composition of the passive film to improve the passivation ability of steel; on the other hand, it can slow down the anodic dissolution process in the pitting area by forming insoluble oxides. 4 2- The properties of the iron oxide film can be changed from anion selective to cation selective, making H + , Cl - Migrate in the reverse direction, thereby improving the corrosion resistance of the steel; taking all factors into consideration, the present application preferably controls the molybdenum content within the range of 0.4-0.5%.

[0041] Phosphorus: Too high phosphorus will cause grain boundary segregation and increase the brittleness of steel. A small amount of phosphorus can improve the weather resistance of steel. After many experimental studies and demonstrations, the phosphorus content of this weathering steel is preferably controlled within the range of 0.075-0.085%.

[0042] Titanium: During the continuous casting solidification process, titanium combines with nitrogen to form TiN. TiN will inhibit the growth of austenite grains. The presence of TiN can inhibit the coarsening of grains in the heat-affected zone of welding and improve the mechanical properties of the weld. During the continuous rolling process, Ti and C form nano-scale TiC in a lower temperature range. Nano-scale TiC has significant precipitation strengthening and fine grain strengthening effects, which will significantly improve the strength and low-temperature impact performance of the steel plate. When the Ti content is too high, coarse square TiN particles will be formed. When stress is concentrated near the TiN particles, it will form a source of growth for microcracks, reducing the fatigue performance of the steel. On the other hand, the solubility product of TiC in high-temperature ingots is small, and it is difficult to dissolve in the slab heating process, and it does not play a role in precipitation strengthening. Taking all factors into consideration, the Ti content of titanium in this application is preferably controlled at 0.025-0.035%.

[0043] Aluminum: Aluminum is a deoxidizing element in steel. Aluminum and a small amount of boron are conducive to the formation of lath bainite, but too much aluminum will damage the isotropic toughness of steel. At the same time, aluminum in the rust layer of corrosion-resistant steel is in the form of metallic aluminum and spinel oxide Al 2 O 3 It exists in the form of rust layer particles, which effectively improves the resistance of the rust layer. On the other hand, when the aluminum content in the rust layer increases, Al replaces part of the Fe in α-FeOOH. 3+ Formation of α-Fe x Al 1-X OOH can promote the refinement of grains in the rust layer and increase the stability of the rust layer. Taking all factors into consideration, it is best to control its content within the range of 0.4-0.5%.

[0044] Nickel, as a thermodynamically stable element, can promote the positive shift of steel corrosion potential and enhance the corrosion resistance of the steel matrix. Nickel is mainly present in the rust layer in the form of di-oxide Fe 2 NiO 4 The Fe exists in the spinel product of Fe, which promotes the refinement of spinel structure and the refinement of rust layer grains, thereby improving the density of rust layer. 2 NiO 4 The precipitation of CuO and CuO phases in the rust layer provides more sites for the nucleation of FeOOH containing water, promotes the nano-structure of its network structure, and the rust layer particles are closely packed. The rust layer is transformed into a cation selective permeable layer. - The rust layer is "spitted out", and the density of the rust layer is improved. The nickel content of this application is preferably controlled within the range of 0.6-0.8%.

[0045] There are two main mechanisms for copper to improve corrosion resistance in low alloy steel. One is the anode inhibition theory: copper precipitates secondary in the rust layer in the form of a single substance and is enriched at the rust layer / matrix interface to form a Cu-rich barrier layer, which increases the overall polarization resistance of the rust layer and inhibits the intrusion of corrosive media. The second is that Cu can form its own oxide CuO in the inner rust layer, which fills the cracks or pores of the rust layer and blocks the defects of the rust layer, thereby achieving the effect of improving the density of the rust layer. After many experimental studies and demonstrations, the weathering steel of this application is preferably controlled within the above range.

[0046] Antimony, in the rust layer of low alloy steel, is in the form of insoluble Sb 2 O 5 Antimony exists in the form of and works synergistically with Cu to reduce various defects in the rust layer, promote the densification of the rust layer, and improve the corrosion resistance of steel. Antimony can also consume H in the local microenvironment under the rust. + , promoting the conversion of γ-FeOOH to Fe 3 O 4 Antimony itself can also generate Sb 2 O 5 The anode reaction is significantly inhibited, and the corrosion resistance of the steel is improved. After many experimental studies and demonstrations, the antimony content of the weathering steel in this application is preferably controlled within the above range.

[0047] Tin, adding tin to low alloy steel can form Sn in the local acidification zone 2+ and Sn 4+ , inhibiting the anodic dissolution process of steel. The addition of tin can reduce the Fermi energy of the steel matrix and improve the matrix's antioxidant capacity. Tin synergizes with copper and antimony in steel to form a continuous and dense oxidation product layer, improving the density of the rust layer. Taking all factors into consideration, it is best to control the tin content of the present application within the range of 0.1-0.15%.

[0048] Sulfur: Sulfur usually forms MnS and TiS compounds in low alloy steel, which deteriorates the transverse and longitudinal toughness of the steel. As a harmful element, it is generally controlled. In this application, the S content is controlled within the range of 0.015%.

[0049] Gaseous elements such as nitrogen, oxygen, and hydrogen are extremely detrimental to the toughness of steel and should also be strictly controlled. The mass content of nitrogen in the weathering steel of this application is ≤0.0045%, the mass content of oxygen is ≤0.00015%, and the mass content of hydrogen is ≤0.0015%.

[0050] The weathering steel in this application innovatively uses Al to replace part of Cr to form (Fe 1-x-y Cr x Al y)OOH ternary metal oxide rust layer, the density is significantly improved, and the polarization resistance of the rust layer is increased; a trace amount of Cu-Sb-Sn is used to inhibit the anode reaction; Ni-Mo is compounded to form Fe2NiO4 and MO42-metal oxides, so that the rust layer is transformed into a cation selectively passing through, blocking the passage of anions, and improving the ability of the low-alloy steel rust layer to protect the matrix from three dimensions, so that it is suitable for the service environment of high temperature, high humidity, marine climate and high salt. After the innovative design of the protective performance of the rust layer and the proportion of the steel matrix, the cost of the steel in this application has obvious cost advantages compared with 316L stainless steel, and the local pitting corrosion resistance is far better than 316L stainless steel.

[0051] In some embodiments, the weathering steel includes the following volume fractions of the microstructure: 85% to 90% ferrite, 10% to 15% pearlite.

[0052] The ferrite within the above volume fraction range ensures that the steel coil has sufficient plasticity and provides a tissue basis for forming. The pearlite within the above volume fraction range provides the material with a good yield strength ratio.

[0053] In some embodiments, the thickness of the weathering steel is 2.0-25.0 mm; the yield strength of the weathering steel is 460 MPa-520 MPa, the tensile strength is greater than 600 MPa, the elongation is greater than 18%, and the impact energy at -20°C is greater than 47 J.

[0054] In some embodiments, the weathering steel has a Cl content of 1000ppm to 10000ppm. - The service pitting depth is less than that of 316L stainless steel, and the service thinning amount is 0.10mm-0.15mm / year.

[0055] The second aspect of the present application provides a method for preparing weathering steel suitable for high temperature and high humidity marine environment provided by the first aspect of the present application, comprising:

[0056] KR desulfurization: put the molten iron into the desulfurization station, add lime desulfurizer for desulfurization, and obtain desulfurized molten iron. The sulfur content of the desulfurized molten iron is ≤0.010%;

[0057] Converter smelting: Desulfurized molten iron is smelted in a converter, and after converter smelting, argon is blown through a ladle, and the terminal temperature of the argon station is controlled to be 1535℃~1500℃, thereby obtaining converter smelting molten steel;

[0058] LF refining: The molten steel smelted in the converter is sent to the LF furnace for refining to obtain refined molten steel;

[0059] RH vacuum treatment: Degas the refined molten steel to obtain degassed molten steel; the oxygen content of the degassed molten steel is less than 300ppm, and the nitrogen content is less than 60ppm;

[0060] Continuous casting: Degassed molten steel is continuously cast at a casting speed of 1.4m / min to 1.7m / min to obtain a slab; the slab is heated in a heating furnace to obtain a furnace-out slab; the temperature of the slab entering the heating furnace is 600℃ to 650℃; the slab is heated at 1180℃ to 1220℃ in the heating furnace for 150min to 250min, and the furnace-out temperature of the slab is 1180℃ to 1220℃; the excess air coefficient of the heating furnace is 0.95-1.05;

[0061] Hot rolling: The steel billet is rolled, cooled, and coiled to obtain weathering steel suitable for high temperature and high humidity marine environments.

[0062] The temperature of the heating furnace and the temperature of the slab out of the furnace need to be kept at a high temperature, and the furnace time should be more than 30 minutes. The long furnace time can fully dissolve the elements such as Cr, Ni, Cu, Mo, Al, Sb, Sn, etc., so as to form uniform and fine α-(Fe 1-x-y Cr x Al y )OOH prepares uniform composition, thereby improving strength and corrosion resistance. The above-mentioned air excess coefficient range of the heating furnace can make the gas in the heating furnace burn fully, while maintaining a reducing atmosphere, thereby controlling the thickness of the oxide scale on the surface of the slab, on the one hand reducing the burning loss and improving the yield rate, on the other hand, it is conducive to descaling and reducing the oxide pressure on the surface of the steel plate.

[0063] In some embodiments, in the continuous casting step, the solution temperature of the slab is 1200° C. to 1220° C., and the solution time is 30 min to 40 min.

[0064] In some embodiments, the steel slabs are descaled with high pressure water before entering the rough rolling mill to remove the primary iron oxide scale on the surface of the slabs, and the descaling pressure is greater than 200 bar to ensure that the oxide scale is completely removed.

[0065] In some embodiments, after the slab is descaled, it can be reverse rolled for 5 passes, and the thickness of the intermediate slab is 50 mm.

[0066] Optionally, the continuous rolling adopts 7-stand continuous rolling, and the thickness of the rolled steel plate is 2-25mm. If 7 stands are used, too few stands cannot provide sufficient pressure reduction and cannot achieve the production of ultra-thin specifications; if there are too many stands, on the one hand, the investment is too large, and on the other hand, the stability of the rolling process will be reduced.

[0067] In some embodiments, in the hot rolling step, the rolling includes rough rolling and finish rolling, the starting rolling temperature of the rough rolling is 1150℃~1180℃, and the final rolling temperature of the rough rolling is 1050℃~1080℃; the steel billet after rough rolling is finish rolled, the starting rolling temperature of the finish rolling is 1000℃~1050℃, and the final rolling temperature of the finish rolling is 850℃~900℃.

[0068] Hot rolling is based on metal deformation, phase change and other processes. It completes hardening measures such as solid solution strengthening, precipitation strengthening, dislocation strengthening, and refinement strengthening under specified deformation and temperature conditions to obtain steel plates with excellent comprehensive performance.

[0069] On the basis of adopting the slab heating temperature process of the present application and combining it with the above-mentioned continuous casting and rolling process, the grain size of the steel plate produced is one level lower than that of the conventional production line. The grains are refined, and high strength and high toughness are obtained, which is also beneficial to the improvement of corrosion resistance. At the same time, it also has good precision cold bending forming, welding and other properties.

[0070] In some embodiments, in the hot rolling step, cooling the steel billet after finish rolling specifically includes first ultra-fast cooling at 30°C / s to 50°C / s, and then cooling to 620°C to 650°C by laminar cooling at 10°C / s to 25°C / s.

[0071] The steel plate of the present application is ultra-fast cooled at 30℃ / s-50℃ / s after final rolling, and then cooled to 620℃-650℃ by laminar cooling at 10℃ / s-25℃ / s. The purpose of ultra-fast cooling is to obtain a finer grain size of the finished product. A laminar cooling rate of more than 25℃ / s will cause greater internal stress in the steel plate, resulting in poor plate shape. A laminar cooling rate of less than 10℃ / s will cause coarse organization and fluctuation of performance.

[0072] This application optimizes the alloy type ratio, reduces the use of precious alloys, and reduces manufacturing costs. It fully utilizes the rolling and cooling capabilities of the continuous rolling mill and adopts controlled rolling and controlled cooling to achieve the best effect through deformation recrystallization of the high-temperature austenite zone, deformation of the low-temperature austenite non-recrystallization zone, and accelerated cooling after rolling.

[0073] In some embodiments, in the continuous casting step, the basicity of the mold slag used in the continuous casting is 0.9-1.0 and the viscosity is 1.9-2.2 poise.

[0074] In some embodiments, in the refining step, the refining inlet temperature is 1525°C to 1585°C, and the refining outlet temperature is 1565°C to 1585°C; the refining time is 40min to 45min; and the temperature of the refined molten steel before entering the RH vacuum treatment is greater than 1540°C.

[0075] In some embodiments, in the RH vacuum treatment step, the vacuum degree of the treatment is required to be ≤130 MPa, and the RH cycle time is 28 min to 35 min.

[0076] Example

[0077] The following examples more specifically describe the disclosure of the present application, which are intended for illustrative purposes only, as it will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the disclosure of the present application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0078] Example 1

[0079] The method for preparing weathering steel suitable for high temperature and high humidity marine environment in this embodiment comprises the following steps:

[0080] KR desulfurization: molten iron enters the desulfurization station, lime desulfurizer is added, and the rotary stirring method is used for desulfurization. After the sulfur content is reduced to below 0.010%, it enters the converter process for smelting;

[0081] Converter smelting: The desulfurized molten iron is smelted in a 210-ton top and bottom double-blown converter. After converter smelting, argon is blown through the ladle. The terminal temperature of the argon station is controlled at 1580℃.

[0082] LF refining: inlet temperature 1570℃, LF outlet temperature 1580℃, refining time 42 minutes, refining outside the furnace and fine-tuning of composition to the target composition, the molten steel temperature entering RH is required to be greater than 1545℃.

[0083] RH vacuum treatment: Before degassing the molten steel, the vacuum degree of the vacuum chamber is required to be ≤130MPa, and the RH cycle time is 40min to ensure that the oxygen in the molten steel is less than 300ppm and the nitrogen is less than 60ppm to avoid fluctuations in steel performance.

[0084] The smelted molten steel (chemical composition weight percentage of the molten steel: C 0.056%, Si 0.52%, Mn 1.30%, S < 0.015%, P 0.08%, Ti 0.030%, Cr 1.15%, Mo 0.48%, Ni 0.7%, Al 0.45%, Sb 0.22%, Sn 0.13%) is cast into a 230 mm thick slab, the continuous casting speed is 1.5 m / min, the slab hot charging furnace temperature is 600 ° C, the slab is sent to a walking beam heating furnace for heating, the slab furnace time is 200 min, the slab furnace temperature is 1200 ° C, the slab solution temperature is 1200 ° C, the solution time is 35 min, and the air excess coefficient of the heating furnace is 1.05.

[0085] The billet is rolled with a rough rolling inlet temperature of 1180°C and a rough rolling outlet temperature of 1070°C; the finishing rolling inlet temperature is 1030°C and the finishing rolling outlet temperature is 890°C. After leaving the finishing rolling stand, it is first ultra-fast cooled at 35°C / s, then cooled to 640°C by laminar cooling at 25°C / s for coiling, and finally rolled into a steel coil with a thickness of 8mm. After cooling to room temperature, it is straightened and flattened into a steel plate.

[0086] After testing, the material grain grade is 14, the steel plate yield strength is 485MPa, the tensile strength is 635MPa, the elongation is 22%, the -20℃ impact energy is 105J, d=2a, and the cold bending is qualified.

[0087] Example 2

[0088] The method for preparing weathering steel suitable for high temperature and high humidity marine environment in this embodiment comprises the following steps:

[0089] KR desulfurization: molten iron enters the desulfurization station, lime desulfurizer is added, and the rotary stirring method is used for desulfurization. After the sulfur content is reduced to below 0.010%, it enters the converter process for smelting;

[0090] Converter smelting: The desulfurized molten iron is smelted in a 210-ton top and bottom double-blown converter. After converter smelting, argon is blown through the ladle. The terminal temperature of the argon station is controlled at 1580℃.

[0091] LF refining: inlet temperature 1572℃, LF outlet temperature 1582℃, refining time 42 minutes, refining outside the furnace and fine-tuning of composition to the target composition, the molten steel temperature entering the RH is required to be greater than 1545℃.

[0092] RH vacuum treatment: Before degassing the molten steel, the vacuum degree of the vacuum chamber is required to be ≤130MPa, and the RH cycle time is 40min to ensure that the oxygen in the molten steel is less than 300ppm and the nitrogen is less than 60ppm to avoid fluctuations in steel performance.

[0093] The smelted molten steel (chemical composition weight percentage of the molten steel: C 0.050%, Si 0.50%, Mn 1.38%, S < 0.015%, P 0.082%, Ti 0.033%, Cr 1.12%, Mo 0.45%, Ni 0.68%, Al 0.48%, Sb 0.23%, Sn 0.11%) was cast into a 230 mm thick slab, the continuous casting speed was 1.6 m / min, the slab hot charging furnace temperature was 630 ° C, the slab was sent to a walking beam heating furnace for heating, the slab solution temperature was 1200 ° C, and the solution time was 35 min. The slab was in the furnace for 200 min, and the slab was out of the furnace at a temperature of 1200 ° C. The excess air coefficient of the heating furnace was 1.0.

[0094] The billet has a rough rolling inlet temperature of 1180℃ and a rough rolling outlet temperature of 1070℃; a finishing rolling inlet temperature of 1030℃ and a finishing rolling outlet temperature of 890℃. After leaving the finishing rolling mill, it is first cooled at 35℃ / s by ultra-fast cooling, then cooled to 630℃ by laminar cooling at 25℃ / s for coiling, and finally rolled into a steel coil with a thickness of 12mm. After cooling to room temperature, it is straightened and flattened into a steel plate.

[0095] The material grain grade is 14, the steel plate yield strength is 500MPa, the tensile strength is 640MPa, the elongation is 21%, the -20℃ impact energy is 95J, d=2a, and the cold bending is qualified.

[0096] Example 3

[0097] The method for preparing weathering steel suitable for high temperature and high humidity marine environment in this embodiment comprises the following steps:

[0098] KR desulfurization: molten iron enters the desulfurization station, lime desulfurizer is added, and the rotary stirring method is used for desulfurization. After the sulfur content is reduced to below 0.010%, it enters the converter process for smelting;

[0099] Converter smelting: The desulfurized molten iron is smelted in a 210-ton top and bottom double-blown converter. After converter smelting, argon is blown through the ladle. The terminal temperature of the argon station is controlled at 1580℃.

[0100] LF refining: inlet temperature 1575℃, LF outlet temperature 1580℃, refining time 42 minutes, refining outside the furnace and fine-tuning of composition to the target composition, the molten steel temperature entering the RH is required to be greater than 40℃.

[0101] RH vacuum treatment: Before degassing the molten steel, the vacuum degree of the vacuum chamber is required to be ≤130MPa, and the RH cycle time is 42min to ensure that the oxygen in the molten steel is less than 300ppm and the nitrogen is less than 60ppm to avoid fluctuations in steel performance.

[0102] The smelted molten steel (chemical composition weight percentage of the molten steel: C 0.048%, Si 0.51%, Mn 1.33%, S < 0.015%, P 0.078%, Ti 0.031%, Cr 1.08%, Mo 0.42%, Ni 0.75%, Al 0.43%, Sb 0.21%, Sn 0.13%) was cast into a 230 mm thick slab, the continuous casting speed was 1.45 m / min, the slab hot charging furnace temperature was 620 ° C, the slab was sent to a walking beam heating furnace for heating, the slab solution temperature was 1200 ° C, and the solution time was 40 min. The slab was in the furnace for 200 min, and the slab was out of the furnace at a temperature of 1200 ° C. The excess air coefficient of the heating furnace was 0.95.

[0103] The billet has a rough rolling inlet temperature of 1180℃ and a rough rolling outlet temperature of 1070℃; a finishing rolling inlet temperature of 1030℃ and a finishing rolling outlet temperature of 890℃. After leaving the finishing rolling mill, it is first cooled at 35℃ / s by ultra-fast cooling, then cooled to 620℃ by laminar cooling at 25℃ / s for coiling, and finally rolled into a steel coil with a thickness of 16mm. After cooling to room temperature, it is straightened and flattened into a steel plate.

[0104] After testing, the material grain grade is 14, the steel plate yield strength is 510MPa, the tensile strength is 650MPa, the elongation is 21%, the impact energy at -20℃ is 85J, d=2a, and the cold bending is qualified.

[0105] The corrosion performance comparison results are as follows.

[0106] When the pH value of the super weathering steel and 316L in the embodiment of the present application is 6, Cl - The corrosion morphology comparison results after immersion for 720 hours at 100ppm, 1000ppm, 5000ppm, and 10000ppm are as follows: Figure 1 to Figure 5 shown.

[0107] Figure 1 to Figure 4 Respectively, 316L stainless steel in a corrosive immersion environment at 100ppm, 1000ppm, 5000ppm, 10000ppmCl - The corrosion morphology is shown in the figure. The corrosion morphology is characterized by local pitting corrosion, and the pitting pit depths are 9.942μm, 14.243μm, 30.759μm, and 46.560μm, respectively. With the increase of chloride ion concentration, the depth and size of the pitting pit gradually increase. It is very sensitive to chloride ions and has the risk of service failure over time.

[0108] Figure 5 The super weathering steel of Example 1 of the present application is Cl at 100ppm, 1000ppm, 5000ppm, 10000ppm -The corrosion morphology in the environment is uniform corrosion, and a thin rust layer is formed on the surface. After rust removal, the calculated rust layer thicknesses are 75μm, 78μm, 65μm, and 80μm, respectively, without any corrosion pits. The rust layer of the corrosion-resistant steel of the present application has a stable rust layer thickness in different chloride ion solutions. After the stable rust layer is formed, it is insensitive to the corrosion of chloride ions and has good protection for the substrate. The weathering steel of the present application has better applicability in high temperature and high humidity marine environments.

[0109] The above embodiments of the present application are merely examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A weathering steel suitable for high temperature and high humidity marine environment, characterized in that: The weathering steel includes the following chemical components in weight percentage: C: 0.045%-0.065%, Si: 0.45%-0.65%, Mn: 1.20%-1.40%, S≤0.015%, P: 0.075%-0.085%, Ti: 0.025%-0.035%, Cr: 1.0%-1.2%, Mo: 0.4%-0.5%, Al: 0.4%-0.5%, Ni: 0.6%-0.8%, Cu: 0.35%-0.55%, Sb: 0.18%-0.25%, Sn: 0.1%-0.15%; the rest are Fe and impurity elements.

2. The weathering steel suitable for high temperature and high humidity marine environment according to claim 1, characterized in that: The weathering steel comprises the following volume fraction structures: 85% to 90% ferrite and 10% to 15% pearlite.

3. The weathering steel suitable for high temperature and high humidity marine environment according to claim 1, characterized in that: The thickness of the weathering steel is 2.0-25.0 mm; the yield strength of the weathering steel is 460 MPa-520 MPa, the tensile strength is greater than 600 MPa, the elongation is greater than 18%, and the impact energy at -20°C is greater than 47 J.

4. The method for preparing weathering steel suitable for high temperature and high humidity marine environment according to any one of claims 1 to 3, characterized in that: The preparation method comprises: KR desulfurization: the molten iron is fed into the desulfurization station, lime desulfurizer is added for desulfurization, and desulfurized molten iron is obtained, wherein the sulfur content of the desulfurized molten iron is ≤0.010%; Converter smelting: the desulfurized molten iron is subjected to converter smelting, and after converter smelting, argon is blown through a ladle, and the terminal temperature of the argon station is controlled to be 1560°C to 1590°C, thereby obtaining converter smelting molten steel; LF refining: sending the converter smelted molten steel into the LF furnace for refining to obtain refined molten steel; RH vacuum treatment: degassing the refined molten steel to obtain degassed molten steel; the oxygen content of the degassed molten steel is less than 300ppm, and the nitrogen content is less than 60ppm; Continuous casting: the degassed molten steel is continuously cast at a casting speed of 1.4m / min to 1.7m / min, and the obtained slab is slowly cooled to 600°C to 650°C; the slab is heated in a heating furnace to obtain a furnace steel slab; the temperature of the slab entering the furnace is 600°C to 650°C, the slab is heated at 1180°C to 1220°C in the heating furnace for 150min to 250min, and the temperature of the slab out of the furnace is 1180°C to 1220°C; the excess air coefficient of the heating furnace is 0.95-1.05; Hot rolling: rolling, cooling and coiling the steel billet to obtain the weathering steel suitable for high temperature and high humidity marine environment.

5. The method for preparing weathering steel suitable for high temperature and high humidity marine environment according to claim 4, characterized in that: In the continuous casting step, the solution temperature of the slab is 1200° C. to 1220° C., and the solution time is 30 min to 40 min.

6. The method for preparing weathering steel suitable for high temperature and high humidity marine environment according to claim 4, characterized in that: In the hot rolling step, the rolling includes rough rolling and finish rolling, the starting rolling temperature of the rough rolling is 1150℃~1180℃, and the final rolling temperature of the rough rolling is 1050℃~1080℃; the steel billet after the rough rolling is finish rolled, the starting rolling temperature of the finish rolling is 1000℃~1050℃, and the final rolling temperature of the finish rolling is 850℃~900℃.

7. The method for preparing weathering steel suitable for high temperature and high humidity marine environment according to claim 4, characterized in that: In the hot rolling step, cooling the steel billet after finish rolling specifically includes first ultra-fast cooling at 30°C / s to 50°C / s, and then cooling to 620°C to 650°C by laminar cooling at 10°C / s to 25°C / s.

8. The method for preparing weathering steel suitable for high temperature and high humidity marine environment according to claim 4, characterized in that: In the continuous casting step, the basicity of the protective slag used in the continuous casting is 0.9-1.0, and the viscosity is 1.9-2.2 poise.

9. The method for preparing weathering steel suitable for high temperature and high humidity marine environment according to claim 4, characterized in that: In the refining step, the refining inlet temperature is 1525°C to 1585°C, and the refining outlet temperature is 1565°C to 1585°C; the refining time is 40min to 45min; and the temperature of the refined molten steel before entering the RH vacuum treatment is greater than 1540°C.

10. The method for preparing weathering steel suitable for high temperature and high humidity marine environment according to any one of claims 4 to 9, characterized in that: In the RH vacuum treatment step, the vacuum degree of the treatment is required to be ≤130MPa, and the RH cycle time is 28min to 35min.

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