Hydropower steel plate and production method therefor

Abstract

The present application discloses a hydropower steel plate and a production method therefor. The steel plate comprises: C: 0.06-0.12%; Si: ≤0.1%; Mn: 1.15-1.55%; Cr: 0.10-0.45%; Ni: 0.5-1.5%; and Mo: 0.15-0.55%. The production method comprises continuous casting billet spraying, heating and descaling, rolling, and heat treatment. Chemical components of an anti-oxidation coating used in the continuous casting billet spraying procedure comprise, in percentage by mass, 55-65% of SiO2, 8-12% of Al2O3, 7-12% of ZrO2, 14-20% of Na2SiO3, and 6-10% of SiC. In the heating and descaling procedure, descaling is performed immediately after heating is completed. In the rolling procedure, descaling is performed on a slab between passes.

Description

Steel sheet for hydroelectric power and method for producing the same

[0001] This application is based on and claims priority to Chinese patent application No. CN202411019274.5, filed on July 29, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to a steel sheet for hydroelectric power and a method for producing the same. BACKGROUND

[0003] The steel sheet for hydroelectric power is mainly used for manufacturing pressure pipes in the dam of a hydroelectric power station, and a part is used for manufacturing auxiliary facilities such as ribbed slabs, branch pipes and volutes. With the large-scale development and use of large-capacity and high-head hydroelectric power stations, the demand for steel pipes that can withstand large flow and high pressure is increasing, which puts higher requirements on the steel sheet for hydroelectric power, and the steel sheet for hydroelectric power needs to have higher strength, better low-temperature toughness and more excellent welding performance.

[0004] In the existing steel sheet for hydroelectric power, in order to ensure that the steel sheet has high strength and good low-temperature toughness at the same time, the content of alloy elements such as Ni in the steel sheet is greatly increased. However, Ni is a relatively difficult element to oxidize in steel. When the steel sheet is oxidized, Fe is preferentially oxidized to form an oxide scale, and Ni enrichment occurs in the inner layer of the oxide scale, forming a rich-Ni metal mesh and particles. These metal mesh and particles will also develop as the temperature rises. This rich-Ni metal mesh connects the oxide scale to the metal matrix. Because its plasticity and thermal expansion coefficient are similar to those of the metal matrix, it is not easy to peel off even under the impact of high-pressure water. In addition, selective oxidation of the grain boundary occurs in the Ni-containing steel, causing FeO, fayalite or eutectic to wedge into the metal matrix along the grain boundary, improving the adhesion of the oxide scale of the Ni-containing steel and causing difficulty in descaling.

[0005] At present, the oxide scale on the surface of the steel sheet is mainly removed by manual grinding in the later stage. However, because the oxide scale penetrates into the steel matrix, excessive grinding is required during descaling, which can easily result in waste products. In addition, grinding requires a large amount of manpower and can also cause serious environmental pollution.

[0006] Any reference in the specification to "prior art" does not indicate that the prior art constitutes part of the common general knowledge in any jurisdiction or that the prior art is considered relevant by those skilled in the art. SUMMARY

[0007] The purpose of the present application is to provide a production method of a steel sheet for hydroelectric power and a steel sheet for hydroelectric power prepared by using the production method.

[0008] To achieve one of the above-mentioned purposes, one embodiment of the present application provides a production method of a steel plate for hydroelectric power, the chemical composition of the steel plate comprising, in mass percentage: C 0.06-0.12%, Si≤0.1%, Mn 1.15-1.55%, Cr 0.10-0.45%, Ni 0.5-1.5%, Mo 0.15-0.55%, and the balance being Fe and inevitable impurities; the production method comprising a continuous casting billet spraying, a heating descaling, a rolling, and a heat treatment procedure in sequence.

[0009] In the continuous casting billet spraying procedure, an anti-oxidation coating is configured into a solution and then sprayed onto the surface of the continuous casting billet to form a coating layer, the chemical composition of the anti-oxidation coating comprising, in mass percentage: SiO255-65%, Al2O38-12%, ZrO27-12%, Na2SiO314-20%, and SiC 6-10%.

[0010] In the heating descaling procedure, the continuous casting billet after the spraying procedure is heated in sequence according to a recovery section, a preheating section, a first heating section, a second heating section, and a third heating section, and descaling is performed immediately after the heating is completed; the heating temperature of the recovery section is 800-950°C, and the heating time is 90-120 min; the heating temperature of the preheating section is 950-1050°C, and the heating time is 50-70 min; the heating temperature of the first heating section is 1050-1150°C, and the heating time is 80-100 min; the heating temperature of the second heating section is 1150-1180°C, and the heating time is 80-100 min; and the heating temperature of the third heating section is 1140-1160°C, and the heating time is 50-70 min.

[0011] In the rolling procedure, descaling is performed on the slab between passes.

[0012] In the heat treatment procedure, quenching and tempering are performed in sequence on the steel plate with a thickness of t obtained from the rolling procedure.

[0013] As a further improvement of one embodiment of the present application, in the continuous casting billet spraying procedure, the thermal expansion coefficient α t of the anti-oxidation coating is greater than the thermal expansion coefficient α p of the continuous casting billet by an absolute value of Δα>25%×α p , Δα=α t -α p .

[0014] As a further improvement of one embodiment of the present application, the thermal expansion coefficient α t of the anti-oxidation coating is calculated by the following formula:

[0015] αt =∑m(i)α(i) / ∑m(i),

[0016] wherein m(i) is the mass percentage of each chemical component in the anti-oxidation coating, and a(i) is the expansion coefficient of each chemical component in the anti-oxidation coating, a(SiO2)=0.5x10 -6 / ℃, a(Al2O3)=8.8x10 -6 / ℃, a(ZrO2)=10x10 -6 / ℃, a(Na2SiO3)=6x10 -6 / ℃, and a(SiC)=4.7x10 -6 / ℃.

[0017] As a further improvement of the embodiment of the present application, the particle size of the anti-oxidation coating is 0.3-0.6 microns.

[0018] As a further improvement of the embodiment of the present application, the anti-oxidation coating is prepared by the following method:

[0019] The chemical components in the anti-oxidation coating are mixed according to the aforementioned mass percentages, then poured into a stainless steel mill jar, grinding media are added, deionized water is added, and planetary ball milling is used to complete the ball milling dispersion, so that the chemical components are mixed and uniform, and sieved to obtain the anti-oxidation coating.

[0020] As a further improvement of the embodiment of the present application, in the spraying process, the anti-oxidation coating is configured into a solution with water in a mass ratio of 1:1 using a spraying machine, and then aged, and then sprayed onto the surface of the continuous casting billet to form a coating, the spraying outlet pressure of the spraying machine is controlled to be 7-8 MPa, and the coating thickness is controlled to be 0.3-0.6 mm.

[0021] As a further improvement of the embodiment of the present application, in the descaling process, the descaling water pressure is controlled to be ≥18 MPa.

[0022] As a further improvement of the embodiment of the present application, in the rolling process, high-pressure water descaling is performed on the slab between passes, and the descaling water pressure is controlled to be ≥15 MPa.

[0023] As a further improvement of the embodiment of the present application, in the heat treatment process, the quenching temperature is 860-900℃, the quenching time T1=1.6xt+(20-45), the unit of T1 is min, after quenching, rapid cooling to room temperature is performed, then tempering is performed, the tempering temperature is 580-620℃, the tempering time T2=3xt+(20-45), the unit of T2 is min, and the unit of t is mm.

[0024] As a further improvement of the embodiment of the present application, the thickness of the steel plate is 25-100 mm, the yield strength is 690-1000 MPa, the tensile strength is 780-1100 MPa, and the elongation after fracture is ≥14%, and the impact energy at -40℃ is ≥100 J.

[0025] To achieve one of the above-mentioned application purposes, the embodiment of the present application further provides a steel plate for hydropower, which is prepared by the production method of the steel plate for hydropower as described above.

[0026] To achieve one of the above-mentioned application purposes, the embodiment of the present application further provides a steel plate for hydropower, which has the following chemical components in percentage by mass: C 0.06-0.12%, Si ≤0.1%, Mn 1.15-1.55%, Cr 0.10-0.45%, Ni 0.5-1.5%, Mo 0.15-0.55%, and the rest is Fe and inevitable impurities.

[0027] As a further improvement of the embodiment of the present application, the thickness of the steel plate is 25-100 mm, the yield strength is 690-1000 MPa, the tensile strength is 780-1100 MPa, and the elongation after fracture is ≥14%, and the impact energy at -40℃ is ≥100 J.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] (1) On the basis of the optimized design of the chemical components, combined with the production process control scheme, the anti-oxidation coating is sprayed on the surface of the continuous casting billet after continuous casting to form an anti-oxidation coating, combined with the segmented control of the heating process, and the scale is removed immediately after heating, and the scale is removed between passes in the rolling process, realizing the comprehensive optimization of the steel plate in strength, toughness, welding performance, production efficiency, etc., and the surface of the steel plate obtained after rolling is free of iron oxide scale, without manual scaling, greatly improving the yield and production efficiency, and saving labor and cost.

[0030] (2) By using the chemical component system of low C and high Ni for the steel plate, combined with the control of the contents of Si, Mn, Cr and Mo alloy elements, the foundation is laid for the steel plate to have high strength, high toughness and excellent welding performance; combined with the chemical component design scheme of the anti-oxidation coating, the chemical components of the coating and the matrix formed by the continuous casting billet can be reasonably matched, not only can the oxidation of the matrix be reduced, but also the coating can be self-stripped during the subsequent heating and descaling, on the one hand, reducing the difficulty of descaling, avoiding the problem of iron oxide scale being pressed into the matrix due to incomplete descaling, saving labor and improving production efficiency, on the other hand, effectively avoiding the surface defect problem caused by descaling, and improving the yield.

[0031] As used herein, the terms "comprise", "comprises" and "comprising", and the terms "include", "includes" and "including", and variations thereof, will be understood to enable the inclusion of further features, ingredients, components, or steps in addition to those expressly stated. BRIEF DESCRIPTION OF DRAWINGS

[0032] Fig. 1 is a surface photo of a steel plate in Example 1;

[0033] Fig. 2 is a surface photo of a steel plate in Example 2;

[0034] Fig. 3 is a surface photo of a steel plate in Example 3. DETAILED DESCRIPTION

[0035] The technical solutions of the present application will be further described below in conjunction with specific embodiments, but the scope of protection is not limited to the description.

[0036] An embodiment of the present application provides a production method of a steel plate for hydropower, and a steel plate for hydropower prepared by using the production method. The steel plate is suitable for manufacturing a pressure conduit in a dam of a hydropower station, or auxiliary facilities such as a ribbed plate, a branch pipe, and a volute.

[0037] In the present application, on the basis of the optimization design of chemical composition, combined with the production process control scheme, an anti-oxidation coating is formed on the surface of the slab by spraying an anti-oxidation coating before heating, combined with the segmented control heating of the heating process, and the scale is removed immediately after heating, as well as the scale is removed between passes in the rolling process, the comprehensive optimization of the steel plate in strength, toughness, welding performance, production efficiency and the like is realized, and the surface of the steel plate obtained after rolling is free of iron oxide scale, without manual scaling, greatly improving the yield and production efficiency, and saving manpower and cost.

[0038] Specifically, in terms of chemical composition, the chemical composition of the steel plate in the present application includes, in mass percentage: C 0.06~0.12%, Si≤0.1%, Mn 1.15~1.55%, Cr 0.10~0.45%, Ni 0.5~1.5%, Mo 0.15~0.55%, and the rest is Fe and unavoidable impurities.

[0039] In this way, by using a low-C high-Ni chemical composition system, combined with the control of the content of Si, Mn, Cr, and Mo alloying elements, a foundation is laid for the steel plate to have high strength, high toughness, and excellent welding performance.

[0040] In an embodiment of the present application, the effects and content control of each chemical composition have the following effects:

[0041] C, Mn: can effectively improve the hardenability and strength of the steel plate, but too much C, Mn will lead to the increase of carbon equivalent and cold crack sensitivity coefficient, resulting in poor low temperature toughness and welding performance. In the present application, the C content is controlled to be 0.06-0.12%, and the Mn content is controlled to be 1.15-1.55%, so that the strength and welding performance of the steel plate can be considered.

[0042] Si: is the main deoxidizing element, but too high Si will cause slab descaling difficulty. In the present application, the Si content is controlled to be Si≤0.1%.

[0043] Cr, Mo: can effectively improve the hardenability of the material, increase the tempering stability, make up for the loss of hardenability and strength caused by low C, Mn content, but too much Cr, Mo will also lead to poor welding performance. In the present application, the Cr content is controlled to be 0.10-0.45%, and the Mo content is controlled to be 0.15-0.55%.

[0044] Ni: has obvious effect of reducing cold brittle transition temperature, is an important alloying element in high-strength hydroelectric steel, can improve the strength and toughness of the steel plate, but is easy to cause high-strength hydroelectric steel descaling difficulty. In the present application, the Ni content is controlled to be 0.5-1.5%.

[0045] In the present embodiment, on the basis of the above chemical composition, the production technology is improved, so that the obtained steel plate is comprehensively optimized in strength, toughness, welding performance, surface quality, production efficiency and the like.

[0046] Specifically, in the production method of the steel plate for water and electricity, the steel smelting, continuous casting, continuous casting billet spraying, heating descaling, rolling and heat treatment processes are sequentially carried out, so that the steel plate finished product can be obtained.

[0047] The production method of the steel plate for water and electricity will be introduced in detail in sequence as follows.

[0048] (1) Steel smelting

[0049] The raw materials are smelted to obtain molten steel, and the chemical composition of the molten steel includes, by mass percent: C 0.06-0.12%, Si≤0.1%, Mn 1.15-1.55%, Cr 0.10-0.45%, Ni 0.5-1.5%, Mo 0.15-0.55%, and the rest is Fe and unavoidable impurities.

[0050] It can be understood that the chemical composition of the molten steel obtained by the molten steel smelting process and the chemical composition of the continuous casting billet obtained by the continuous casting process are the same as the chemical composition of the steel plate, and both conform to the chemical composition described above, which will not be described here.

[0051] (2) Continuous casting process

[0052] The molten steel obtained in the molten steel smelting process is fully protected cast by a continuous casting machine to obtain a continuous casting billet.

[0053] (3) Continuous casting billet spraying process

[0054] After the anti-oxidation coating is configured into a solution, the surface of the continuous casting billet is sprayed to form a coating, and then dried, the chemical components of the anti-oxidation coating include, in percentage by mass: SiO2 55-65%, Al2O3 8-12%, ZrO2 7-12%, Na2SiO3 14-20%, SiC 6-10%.

[0055] By adopting the chemical component system of the anti-oxidation coating, the coating formed can be reasonably matched with the chemical components of the matrix formed by the continuous casting billet, which not only can reduce the oxidation of the matrix, but also can be self-stripped during subsequent heating descaling, on the one hand, reducing the difficulty of descaling, avoiding the problem of iron oxide scale pressing into the matrix due to incomplete descaling, saving labor and improving production efficiency, on the other hand, effectively avoiding the surface defect problem caused by descaling, and improving the yield.

[0056] Specifically, the content control of each chemical component in the anti-oxidation coating has the following effects:

[0057] SiO2 is the main substance of the anti-oxidation coating, and is also the main reason for forming a dense viscous glass film at high temperature. The content of SiO2 determines the melting point and density of the coating. In this application, the content of SiO2 is controlled to be 55-65%.

[0058] Al2O3 can improve the viscosity of the coating at high temperature, and can also improve the softening temperature of the coating and adjust the thermal expansion coefficient of the coating. Al2O3 can form a tetrahedral structure (i.e. Al 3+ ion and four oxygen atoms) to fill into the silicon-oxygen structure of the coating, filling the cracks and leaks formed in the coating at high temperature. In this application, the content of Al2O3 is controlled to be 8-12%.

[0059] ZrO2 has a high melting point and is a high-temperature resistant filler. When the heating temperature reaches 1000°C, ZrO2 will undergo a crystal type conversion from monoclinic phase to tetragonal phase, which is accompanied by a change in volume, thus causing the coating to expand and easily peel off from the surface of the matrix. In this application, the content of ZrO2 is controlled to be 7-12%.

[0060] Na₂SiO₃, as a binder, is beneficial for improving the coating performance and suspension properties of coating materials, and affects the strength and density of the coating. If its content is too low, it will lead to problems such as loose coating structure, bubble formation, pores, and incomplete coating of the substrate surface. If its content is too high, it will increase the bonding force between the coating and the substrate, making it difficult for the coating to detach during the cooling process. In this application, the content of Na₂SiO₃ is controlled at 14~20%.

[0061] SiC: During the heating process, SiC reacts with O2, thereby consuming the oxygen diffused to the coating and creating an oxygen-deficient or oxygen-free state on the substrate surface, reducing substrate oxidation. In this application, the SiC content is controlled at 6~10%.

[0062] Preferably, the coefficient of thermal expansion α of the anti-oxidation coating is... t The coefficient of thermal expansion α of the continuously cast billet p The absolute value of the difference Δα > 25% × α p , Δα=α t -α p By controlling the coefficient of thermal expansion α of the anti-oxidation coating. t The coefficient of thermal expansion α of the continuously cast billet p The relationship between the coating formed by the anti-oxidation coating and the substrate formed by the continuous casting billet is reasonably matched. On the one hand, this is conducive to the coating being able to peel off on its own during subsequent descaling after heating. On the other hand, it can avoid the coating from generating excessive stress during heating, which would cause the coating to crack or peel off, thereby reducing the protective effect.

[0063] Wherein, the coefficient of thermal expansion α of the anti-oxidation coating t It is calculated using the following formula:

[0064] α t =∑m(i)α(i) / ∑m(i),

[0065] Where m(i) is the mass percentage of each chemical component in the anti-oxidation coating. For example, if the mass percentage of SiO2 is 55%, then m(i) = 55%.

[0066] α(i) is the coefficient of thermal expansion of each chemical component in the antioxidant coating, α(SiO2) = 0.5 × 10⁻⁶. -6 / ℃, α(Al2O3)=8.8×10 -6 / ℃, α(ZrO2) = 10 × 10 -6 / ℃, α(Na2SiO3)=6×10 -6 / ℃, α(SiC)=4.7×10 -6 / ℃.

[0067] In this embodiment, the thermal expansion coefficient a of the continuous casting billet p is 12.1 x 10 -6 / ℃~13.0 x 10 -6 / ℃.

[0068] The thermal expansion coefficient of the continuous casting billet can be obtained by using a German NETZSCH DIL 402C thermal dilatometer, and argon protection is adopted during the whole experiment.

[0069] a p is calculated by the following formula:

[0070] ,

[0071] wherein, L0 is the original length of the sample at room temperature T0, and the unit is mm; Li is the length of the sample at temperature Ti, and the unit is mm.

[0072] Preferably, the particle size of the anti-oxidation coating is 0.3-0.6 microns.

[0073] The smaller the particle size of the anti-oxidation coating, the more conducive to subsequent spraying and the protective effect of the coating, but too small particle size will increase the production cost of the coating, and the particle size of the anti-oxidation coating is controlled to be 0.3-0.6 microns in this application.

[0074] The anti-oxidation coating is prepared by the following method:

[0075] The above anti-oxidation coating is mixed with each chemical component according to the mass percentage, then poured into a stainless steel mill jar, added with grinding medium, and then added with deionized water, and the planetary ball mill is used to complete the ball milling dispersion, so that each chemical component is mixed, uniform, and sieved, thereby obtaining the anti-oxidation coating.

[0076] Specifically, the anti-oxidation coating is configured into a solution with water according to a mass ratio of 1:1 by using a spraying machine, and then the solution is aged, and then sprayed on the surface of the continuous casting billet to form a coating.

[0077] Preferably, the spraying outlet pressure of the spraying machine is controlled to be 7-8 MPa, and the coating thickness is controlled to be 0.3-0.6 mm.

[0078] By controlling the spraying outlet pressure of the spraying machine, the spraying flow and the coating thickness are controlled, if the coating is too thin, the anti-oxidation effect is poor, if the coating is too thick, the coating is easy to crack during the drying process after spraying, and the thermal conductivity of the coating is reduced, thereby prolonging the heating time under the same heating temperature.

[0079] (4) Heating and descaling process

[0080] The continuous casting billet after the spraying process is heated in sequence according to a recovery section, a preheating section, a first heating section, a second heating section and a third heating section, and descaling is performed immediately after the heating is completed.

[0081] The heating temperature of the recovery section is 800-950℃, and the heating time is 90-120min; the heating temperature of the preheating section is 950-1050℃, and the heating time is 50-70min; the heating temperature of the first heating section is 1050-1150℃, and the heating time is 80-100min; the heating temperature of the second heating section is 1150-1180℃, and the heating time is 80-100min; and the heating temperature of the third heating section is 1140-1160℃, and the heating time is 50-70min.

[0082] By the multi-section segmented heating, the continuous casting billet can be ensured to be hot through, so as to avoid excessive grain growth. The recovery section and the preheating section are controlled at a lower heating temperature, so as to ensure sufficient heating time, so as to improve the uniformity of the surface and core temperature of the continuous casting billet and the protection effect of the anti-oxidation coating; the first heating section, the second heating section and the third heating section are controlled at a higher heating temperature, so as to shorten the heating time as much as possible under the condition of ensuring complete solid solution of the alloy, so as to avoid the failure of the anti-oxidation coating due to long-time heating.

[0083] Preferably, descaling is performed immediately after the heating is completed, and the descaling water pressure is controlled to be ≥18MPa, so as to remove the anti-oxidation coating and the iron oxide scale on the surface of the continuous casting billet.

[0084] (5) Rolling process

[0085] The continuous casting billet after the heating and descaling process is subjected to two-stage rolling of rough rolling and finish rolling in sequence, to obtain a steel plate with a thickness t of 25-100mm, and descaling is performed on the slab between passes, so as to prevent the iron oxide scale generated at high temperature from affecting the surface quality of the steel plate.

[0086] Preferably, high-pressure water descaling is performed on the slab between passes, and the descaling water pressure is controlled to be ≥15MPa, so as to remove the iron oxide scale on the surface of the continuous casting billet.

[0087] (6) Heat treatment process

[0088] The steel plate obtained in the rolling process is subjected to quenching and tempering in sequence, to obtain a steel plate finished product.

[0089] Preferably, the quenching temperature is 860~900℃, and the quenching time is T1=1.6×t+(20~45), where T1 is in minutes. After quenching, the material is rapidly cooled to room temperature, followed by tempering at 580~620℃ for a time T2=3×t+(20~45), where T2 is in minutes and t is in millimeters. This thorough tempering process ensures that the steel plate obtains a stable tempered martensitic structure.

[0090] Thus, this application, with its low-C, high-Ni chemical composition system for the aforementioned steel plate, combined with the controlled content of Si, Mn, Cr, and Mo alloying elements, lays the foundation for the steel plate to possess high strength, high toughness, and excellent weldability. Furthermore, the chemical composition design of the aforementioned anti-oxidation coating allows for a reasonable match between the coating's chemical composition and the substrate formed by the continuously cast billet. This not only reduces substrate oxidation but also enables the coating to self-peel off during subsequent heating and descaling. This reduces descaling difficulty, avoids the problem of iron oxide scale being pressed into the substrate due to incomplete descaling, saves labor, and improves production efficiency. It also effectively avoids surface defects caused by descaling, increasing the yield. Further, by combining segmented heating control in the heating process with immediate descaling after heating and inter-pass descaling during the rolling process, comprehensive optimization of the steel plate's strength, toughness, weldability, and production efficiency is achieved. Moreover, the surface of the rolled steel plate is free of iron oxide scale, eliminating the need for manual peeling, significantly improving yield and production efficiency, and saving labor and costs.

[0091] Specifically, in this application, after heat treatment, the thickness of the steel plate is 25~100mm, the yield strength is 690~1000MPa, the tensile strength is 780~1100MPa, the elongation after fracture is ≥14%, and the impact energy at -40℃ is ≥100J.

[0092] The following three specific embodiments are provided to further illustrate the technical solution of this application. Of course, these three embodiments are only a part of the many variations contained in this implementation method, and not all of them.

[0093] Each of the three embodiments provides a steel plate. The chemical composition of the steel plates of the three embodiments is shown in Table 1 by mass percentage, with the remainder being iron and unavoidable impurities.

[0094] Table 1

[0095]

[0096] The production process of steel plates includes the following steps.

[0097] (1) Steel smelting

[0098] The raw materials are smelted to obtain molten steel. The chemical composition of the molten steel is shown in Table 1 by mass percentage, with the remainder being iron and unavoidable impurities.

[0099] (2) Continuous casting process

[0100] The molten steel obtained from the steelmaking process is cast under full protection using a continuous casting machine to obtain a continuous casting billet. The chemical composition of the continuous casting billet is shown in Table 1 by mass percentage, with the remainder being iron and unavoidable impurities.

[0101] (3) Spray coating process for continuous casting billets

[0102] First, an anti-oxidation coating is prepared. The chemical composition of the anti-oxidation coating, by mass percentage, includes: SiO2 55~65%, Al2O3 8~12%, ZrO2 7~12%, Na2SiO3 14~20%, and SiC 6~10%.

[0103] The chemical components of the anti-oxidation coating are weighed and mixed, then poured into a stainless steel grinding jar, grinding media are added, and a certain amount of deionized water is added. The mixture is then dispersed by a planetary ball mill under different ball milling parameters to ensure that the chemical components are mixed, homogeneous, and sieved to obtain an anti-oxidation coating with a particle size of 0.3~0.6 micrometers.

[0104] Secondly, the anti-oxidation coating is prepared into a solution.

[0105] The above-mentioned anti-oxidation coating was mixed with water at a mass ratio of 1:1 using a spraying machine to form a solution, which was then left to stand and age.

[0106] Next, a coating is sprayed onto the surface of the continuously cast billet.

[0107] The spraying outlet pressure of the spraying machine is controlled at 7~8MPa, and the coating thicknesses of Examples 1 to 3 are 0.3mm, 0.4mm, and 0.5mm, respectively.

[0108] Finally, dry.

[0109] (4) Heating and descaling process

[0110] The continuously cast billet after the spraying process is heated in sequence through the recovery section, preheating section, first heating section, second heating section and third heating section. After heating is completed, descaling is performed immediately, and the descaling water pressure is ≥18MPa.

[0111] The heating temperatures and heating times of the recovery section, preheating section, first heating section, second heating section, and third heating section are shown in Table 2.

[0112] Table 2

[0113]

[0114] (5) Rolling process

[0115] The continuously cast billet after the heating and descaling process is subjected to a two-stage rolling process of rough rolling and finish rolling to obtain steel plates. High-pressure water descaling is performed on the billets between passes, with the descaling water pressure controlled to be ≥15 MPa. The thicknesses of the steel plates from Examples 1 to 3 are shown in Table 3.

[0116] (6) Heat treatment process

[0117] The steel plate obtained from the rolling process is sequentially quenched and tempered to obtain a finished steel plate with a thickness of t.

[0118] The quenching temperatures of Examples 1-3 were 900℃, 890℃, and 910℃, respectively, and the quenching times of Examples 1-3 were 84min, 65min, and 84min, respectively. After quenching, the samples were rapidly cooled to room temperature and then tempered. The tempering temperatures of Examples 1-3 were 610℃, 620℃, and 590℃, respectively, and the tempering times were 140min, 104min, and 140min, respectively.

[0119] The tensile properties of the steel plates from the above three embodiments were tested according to the GB / T228.1-2021 standard, as follows:

[0120] The tensile strength and elongation after fracture of the steel plate were tested using a tensile testing machine. The test results are shown in Table 3.

[0121] The impact performance of the steel plates from the above three embodiments was tested according to the GB / T229-2020 standard, as follows:

[0122] The impact energy of the steel plate at -40℃ was tested using an impact testing machine, and the test results are shown in Table 3.

[0123] Table 3

[0124]

[0125] As shown in Table 3, the mechanical properties of the steel plates in Examples 1 to 3 meet the requirements for the corresponding strength level of high-strength hydropower steel plates.

[0126] The photographs of the steel plates after painting in Examples 1 to 3 are shown in Figures 1 to 3. As can be seen from the figures, the surface quality of the resulting steel plates is excellent.

[0127] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0128] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of this application, and are not intended to limit the scope of protection of this application. All equivalent implementation methods or modifications made without departing from the spirit of the art of this application should be included within the scope of protection of this application.

Claims

1. A method of producing a steel sheet, characterized by, The chemical composition of the steel plate includes, in mass percentage, C 0.06~0.12%, Si≤0.1%, Mn 1.15~1.55%, Cr 0.10~0.45%, Ni 0.5~1.5%, Mo 0.15~0.55%, and the rest is Fe and inevitable impurities; The production method comprises sequentially performed continuous casting blank spraying, heating descaling, rolling, and heat treatment processes; In the continuous casting blank spraying process, the anti-oxidation coating is configured into a solution, and then the surface of the continuous casting blank is sprayed to form a coating layer, and the chemical composition of the anti-oxidation coating includes, in mass percentage, SiO255~65%, Al2O38~12%, ZrO27~12%, Na2SiO314~20%, and SiC 6~10%. In the heating descaling process, the continuous casting blank after the spraying process is sequentially heated in a recovery section, a preheating section, a first heating section, a second heating section, and a third heating section, and immediately after the heating is completed, descaling is performed; the heating temperature of the recovery section is 800~950℃, and the heating time is 90~120min; the heating temperature of the preheating section is 950~1050℃, and the heating time is 50~70min; the heating temperature of the first heating section is 1050~1150℃, and the heating time is 80~100min; the heating temperature of the second heating section is 1150~1180℃, and the heating time is 80~100min; and the heating temperature of the third heating section is 1140~1160℃, and the heating time is 50~70min. In the rolling process, the slab is descaled between passes. In the heat treatment process, the steel plate with a thickness of t obtained in the rolling process is sequentially quenched and tempered.

2. The method of producing a steel sheet according to claim 1, characterized by, In the continuous casting billet spraying process, the coefficient of thermal expansion α of the anti-oxidation coating is... t The coefficient of thermal expansion α of the continuously cast billet p The absolute value of the difference Δα > 25% × α p , Δα=α t -α p .

3. The method of producing a steel sheet according to claim 2, characterized by, The thermal expansion coefficient a of the oxidation-resistant coating t It is calculated by the following formula: a t =∑m(i)α(i) / ∑m(i), wherein m(i) is the mass percentage of each chemical component in the oxidation-resistant coating, a(i) is the expansion coefficient of each chemical component in the oxidation-resistant coating, a(SiO2) = 0.5 x 10 -6 / ℃, a(Al2O3) = 8.8 x 10 -6 / ℃, a(ZrO2) = 10 x 10 -6 / ℃, a(Na2SiO3) = 6 x 10 -6 / ℃, and a(SiC) = 4.7 x 10 -6 / ℃.

4. The method of producing a steel sheet according to claim 1, characterized by, The particle size of the anti-oxidation coating is 0.3~0.6 microns.

5. The method of producing a steel sheet according to claim 1, characterized by, The anti-oxidation coating is prepared by the following method: The chemical components in the anti-oxidation coating are mixed according to the aforementioned mass percentages, then poured into a stainless steel mill jar, grinding media are added, deionized water is added, and planetary ball milling is performed to mix, uniformly disperse, and sieve the chemical components, thereby obtaining the anti-oxidation coating.

6. The method of producing a steel sheet according to claim 1, characterized by, In the spraying process, the anti-oxidation coating and water are configured into a solution with a mass ratio of 1:1 using a spraying machine, and then the solution is aged and sprayed onto the surface of the continuous casting blank to form a coating layer, the spraying outlet pressure of the spraying machine is controlled to be 7~8MPa, and the coating layer thickness is controlled to be 0.3~0.6mm.

7. The method of producing a steel sheet according to claim 1, characterized by, In the heating descaling process, the descaling water pressure is controlled to be≥18MPa.

8. The method of producing a steel sheet according to claim 1, characterized by, In the rolling process, the slab is descaled by high-pressure water between passes, and the descaling water pressure is controlled to be≥15MPa.

9. The method of producing a steel sheet according to claim 1, characterized by, In the heat treatment process, the quenching temperature is 860~900℃, the quenching time T1=1.6×t+(20~45), the unit of T1 is min, the steel plate is rapidly cooled to room temperature after quenching, and then the steel plate is tempered, the tempering temperature is 580~620℃, the tempering time T2=3×t+(20~45), the unit of T2 is min, and the unit of t is mm.

10. The method of producing a steel sheet according to claim 1, characterized by, The thickness of the steel plate is 25-100mm, the yield strength is 690-1000MPa, the tensile strength is 780-1100MPa, the elongation after fracture is greater than or equal to 14%, and the impact energy at-40 DEG C is greater than or equal to 100J.

11. A steel sheet characterized by comprising, in mass %, The chemical components of the steel plate include, in mass percentage: C 0.06-0.12%, Si less than or equal to 0.1%, Mn 1.15-1.55%, Cr 0.10-0.45%, Ni 0.5-1.5%, Mo 0.15-0.55%, and the rest is Fe and inevitable impurities.

12. Steel sheet according to claim 11, characterized in that, The thickness of the steel plate is 25-100mm, the yield strength is 690-1000MPa, the tensile strength is 780-1100MPa, the elongation after fracture is greater than or equal to 14%, and the impact energy at-40 DEG C is greater than or equal to 100J.

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