A corrosion-resistant rolled composite steel plate for high-temperature equipment and its manufacturing method

Abstract

A corrosion-resistant rolled composite steel plate for high-temperature equipment and its manufacturing method are disclosed. The composite steel plate comprises a base material, a cladding layer, and a transition layer between the base material and the cladding layer. The base material comprises the following components by weight percentage: C: 0.08%–0.18%, Si: 0.01%–0.6%, Mn: 0.30%–0.70%, Ti: 0.009%–0.015%, Als: 0.010%–0.015%, Nb: 0.0010%–0.050%, Cr: 1.85%–3.85%, Mo: 0.5%–1.55%, B: 0.0007%–0.0050%, N: 0.0025%–0.0050%, P≤0.010%, S≤0.010%, O≤0.004%, with the balance including Fe and other unavoidable impurities. This invention fully considers the interface characteristics of composite steel plates and ensures the corrosion resistance of the cladding stainless steel. It is suitable for high-temperature equipment with an operating temperature of 450-530℃ and can be widely used in energy industries such as thermal power, petroleum refining, and chemical industry.

Description

Technical Field

[0001] This invention relates to corrosion-resistant steel and its manufacturing method, specifically to a corrosion-resistant rolled composite steel plate for high-temperature equipment and its manufacturing method, which is suitable for high-temperature equipment with working temperatures of 450 to 530°C in the fields of power, petrochemical and other energy manufacturing. Background Technology

[0002] With the rapid development of my country's economy, the demand for electricity and various energy-related raw materials such as petroleum and fertilizers is increasing. To improve energy production efficiency, the large-scale, high-parameter (higher temperature, higher pressure), and lightweight nature of energy production and processing equipment is imperative. This equipment upgrade demand places higher requirements on the performance of steel plates used in manufacturing these equipment. Specifically, these steel plates must not only have higher strength and hardness, but also excellent toughness, processing and forming properties, and especially better corrosion resistance. Stainless steel has excellent corrosion resistance, while carbon steel has a good balance of strength and toughness. Combining the advantages of stainless steel and carbon steel creates composite materials that possess both high strength and high corrosion resistance. Low-alloy steel combined with various corrosion-resistant materials is a high-performance composite material. Due to its high mechanical strength and strong corrosion resistance, it is frequently used in industries such as crude oil processing and energy chemicals.

[0003] The traditional production process for composite steel plates is explosive bonding. The main problem with this process is that the explosion generates a large amount of harmful gases, which has an adverse impact on the environment, meaning that this type of production process does not meet environmental protection requirements. At the same time, the bonding rate at the interface of the explosively bonded steel plates is low, sometimes failing to meet the requirement of a bonding rate of over 97%. When this type of steel plate is used to manufacture various high-temperature, high-pressure, and large-scale container equipment, there will be significant safety hazards. Once the bonding joint of the composite steel plates separates, the equipment will malfunction, which will have a huge impact on the safety of people's lives and property.

[0004] Compared to explosive bonding, rolled composite steel plates achieve a bonding rate of over 99%, and the production process is more environmentally friendly. Therefore, in recent years, the production scale and engineering applications of rolled composite steel plates have been expanding annually.

[0005] However, regardless of whether it's an explosively bonded steel plate or a rolled composite steel plate, a transition layer will form at the interface between the carbon steel and other corrosion-resistant materials. This transition layer has a complex composition and can negatively impact the strength of the carbon steel matrix and the corrosion resistance of the corrosion-resistant materials. In particular, carbon elements from the base carbon steel material can penetrate the stainless steel at the interface through the transition layer, forming a large amount of carbides and causing intergranular corrosion. When the corrosion resistance of the stainless steel is significantly affected, the corrosion-resistant materials face a high risk of failure, especially under high-temperature conditions. Once the material fails and equipment malfunctions, it could lead to a major industrial accident, causing casualties and huge economic losses.

[0006] Therefore, how to rationally design the alloy composition and production process of carbon steel base layer, and minimize the negative impact of the decrease in corrosion resistance of corrosion-resistant materials caused by the diffusion of carbon elements in the base carbon steel material to stainless steel through the transition layer due to long-term high-temperature service, has become an urgent requirement for improving the comprehensive performance of rolled composite steel plates.

[0007] Chinese Patent Publication No. CN108231273A discloses a method for improving the interface of copper-aluminum composite materials. The main technical solution involves pre-coating or depositing graphene at the copper-aluminum interface, followed by processing and composite bonding of copper, aluminum, and graphene. The coating or deposition method is one of coating, electroplating, or chemical vapor deposition. The composite processing method is one of rolling, extrusion, or drawing. The graphene is in the form of powder or film. This technical solution adds graphene to the copper-aluminum interface, which improves the interface bonding and conductivity while ensuring interfacial bonding and preventing the formation of brittle and poorly conductive intermetallic compounds. Since the materials in this invention are copper and aluminum, and the main purpose of adding graphene at the interface is to improve the conductivity of the materials, the method for improving the interface properties of composite materials described in this patent is not applicable to rolled composite steel plates of low-alloy steel and stainless steel because the properties of copper and aluminum differ significantly from those of low-alloy steel and stainless steel. Furthermore, carbon steel and stainless steel composite plates do not require improved conductivity.

[0008] Chinese Patent Publication No. CN108239725A discloses "A High Shear Strength Rolled Composite Steel Plate and Its Manufacturing Method". This high shear strength rolled composite steel plate comprises a carbon steel base layer and a stainless steel cladding layer rolled onto the carbon steel base layer. The chemical element mass percentages of the carbon steel base layer are: C: 0.17%–0.25%; Si: 0.15%–0.40%; Mn: 1.15%–1.50%; Mo: 0.45%–0.60%; Ni: 0.40%–0.70%; Al: 0.020–0.040%; Ca: 0.0010–0.0030%; with the balance being Fe and other unavoidable impurities. This high shear strength rolled composite steel plate has a tensile strength of 570–690 MPa at room temperature, a yield strength ≥365 MPa at room temperature, a shear strength ≥350 MPa, and an elongation ≥20%. In this patent, the inventors achieved high shear strength in composite steel plates by controlling the microstructure ratio of carbon steel. However, the invention does not mention controlling the microstructure and precipitation at the interface.

[0009] Chinese Patent Publication No. CN108085585A discloses "A High-Strength Corrosion-Resistant Composite Patterned Steel and Its Manufacturing Method." In this rolled composite steel plate, the base layer is carbon steel, and the cladding layer is austenitic stainless steel. The thickness of the composite steel plate is no more than 10mm. The inventor directly assembles carbon steel slabs and austenitic stainless steel slabs, hot-rolls them, and then uses a coiling process to finally obtain the rolled composite plate coil. The target steel grade of this invention patent is a hot-rolled composite plate coil product with a thickness of less than 10mm, and its working temperature is generally room temperature. The invention does not address the impact of high-temperature working conditions on the corrosion resistance of the cladding material at the composite material interface.

[0010] In summary, existing rolled composite steel plate technologies, especially those for carbon steel and stainless steel composite plates, offer little consideration for the transition layer at the interface between the base and cladding materials. Particularly concerning is the diffusion of alloying elements, particularly carbon, from the carbon steel to the interface, which could significantly reduce the corrosion resistance of the stainless steel and ultimately lead to material failure. These issues are almost entirely absent from the published patent solutions. Therefore, the technical solutions generally do not employ specific measures to reduce the likelihood of weakened stainless steel corrosion resistance due to carbide precipitation at the grain boundaries of the stainless steel at the composite material interface. In fact, in the chemical and energy industries, composite steel plate manufacturing equipment often operates at temperatures between 450-530℃. Prolonged operation at such high temperatures can cause further diffusion of elements at the material interface. In particular, carbon from the carbon steel side can diffuse into the stainless steel cladding, forming more and larger carbides, further reducing the corrosion resistance of the stainless steel and creating potential safety hazards. Summary of the Invention

[0011] The purpose of this invention is to provide a corrosion-resistant rolled composite steel plate for high-temperature equipment and its manufacturing method. It fully considers the interface characteristics of the composite steel plate and can ensure the corrosion resistance of the cladding stainless steel. It is suitable for high-temperature equipment with an operating temperature of 450-530℃ and can be widely used in energy industries such as thermal power, petroleum refining, and chemical industry.

[0012] To achieve the above objectives, the technical solution of the present invention is as follows:

[0013] The composite steel plate of the present invention forms a large number of finely dispersed and high-temperature stable MC (M represents one or more of Cr, Mo, Nb, Ti) precipitates in the base carbon steel. These stable carbide precipitates can fix the carbon elements in the steel in the base carbon steel, thereby avoiding the diffusion and migration of carbon elements in the carbon steel to the interface of the rolled composite steel plate under high temperature conditions of 450°C to 530°C. This would lead to an increase in the carbon element concentration in the stainless steel near the interface, and the generation of a large number of carbide precipitates at the stainless steel grain boundaries, inducing intergranular corrosion, and ultimately weakening or even losing the anti-corrosion function of the composite material.

[0014] Specifically, the corrosion-resistant rolled composite steel plate for high-temperature equipment described in this invention comprises a substrate, a cladding layer, and a transition layer between the substrate and the cladding layer; the substrate composition by weight percentage is: C: 0.08%–0.18%, Si: 0.01%–0.6%, Mn: 0.30%–0.70%, Ti: 0.009%–0.015%, Als: 0.010%–0.015%, Nb: 0.0010%–0.050%, Cr: 1.85%–3.85%, Mo: 0.5%–1.55%, B: 0.0007%–0.0050%, N: 0.0025%–0.0050%, P≤0.010%, S≤0.010%, O≤0.004%, with the balance including Fe and other unavoidable impurities;

[0015] The surface microstructure of the composite steel plate substrate consists of 90–95% bainite + 5–10% martensite + MC precipitates, while the central microstructure consists of 90–95% bainite + 0–5% martensite + 0–5% ferrite + MC precipitates. Here, M represents one or more of Cr, Mo, Nb, and Ti. The average major axis length of the MC precipitates is less than 400 nm, and the bulk density of MC precipitates with a major axis length less than 400 nm is greater than 3.0 × 10⁻⁶. 4 pcs / mm 3 ;

[0016] The composite steel plate cladding is made of stainless steel, and its microstructure contains MC precipitates, where M represents one or more of Cr, Mo, Nb, and Ti. The average major axis length of the MC precipitates is less than 700 nm, and the bulk density of the MC precipitates is less than 1.0 × 10⁻⁶. 4 pcs / mm 3 ;

[0017] Preferably, the stainless steel is austenitic stainless steel, ferritic stainless steel, duplex stainless steel, or super stainless steel.

[0018] Furthermore, the remaining component of the composite steel plate substrate is Fe and other unavoidable impurities.

[0019] Furthermore, the composite steel plate substrate also contains at least one of the following chemical elements: 0 < Ca ≤ 0.0055%, 0 < Ni ≤ 0.65%, and 0 < Cu ≤ 0.55%.

[0020] Preferably, the proportion of MC precipitates with a long axis length of less than 400 nm in the composite steel plate substrate is greater than 50% of the total number of MC precipitates.

[0021] Preferably, the proportion of MC precipitates with a major axis length of less than 700 nm in the composite steel plate cladding is greater than 50% of the total number of MC precipitates.

[0022] Furthermore, the microstructure of the composite steel plate cladding may contain a very small amount of σ phase, with the σ phase ratio ≤1.5%, preferably, the σ phase ratio near the transition layer is ≤0.5%.

[0023] Preferably, the thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm; preferably, the thickness of the transition layer is ≤250μm.

[0024] The rolled composite steel plate substrate of the present invention has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the grain size grade of the substrate is not lower than 7.0; and the shear strength of the rolled composite steel plate is ≥330MPa.

[0025] In the composition design of the composite steel plate substrate described in this invention:

[0026] Carbon (C) is an important alloying element. To ensure appropriate strength in carbon steel plates, the mass percentage of C in the steel needs to be controlled to be greater than or equal to 0.08%. Simultaneously, to improve the weldability of the base carbon steel material, the upper limit of C content in the carbon steel needs to be controlled. Furthermore, if the carbon content in the carbon steel base material is high, the difference in carbon concentration gradient between the two materials can lead to large-scale carbon migration at the interface between the base material and the stainless steel cladding material, causing intergranular corrosion in the stainless steel. Therefore, its upper limit is controlled at 0.18%. Additionally, controlling the appropriate carbon content, through composition and process coordination, can form a large number of dispersed nanoscale carbides in the steel, which can also achieve precipitation strengthening, thereby improving the strength of the base carbon steel. Based on this, the present invention controls the C content between 0.08% and 0.18%.

[0027] Si (Si): Si is a commonly used strengthening element in low-alloy steel. Adding a certain amount of Si to steel can improve its strength. Simultaneously, Si also has deoxidizing properties, playing an auxiliary role in deoxidation during the smelting process. Most of the SiO2 products formed after deoxidation are removed into the steel slag and do not affect the steel's properties. Furthermore, adding a certain amount of Si to steel can reduce the solubility of carbon in austenite, thereby promoting carbon desolvation, promoting the formation of MC precipitates, fixing carbon in the steel, and preventing large-scale carbon diffusion to the interface. Therefore, a certain amount of Si needs to be added to the steel. However, excessive Si content will reduce the weldability of the steel. Additionally, Si has a stronger binding affinity with oxygen than iron, easily forming low-melting-point silicates during welding, increasing the fluidity of the slag and molten metal, causing spattering, and affecting the quality of the weld joint. Therefore, controlling the Si content within a certain range helps improve the weldability of the steel. Therefore, this invention controls the Si content to be between 0.01% and 0.6%.

[0028] Mn: Mn is also an important strengthening element, which can effectively improve the strength of the base steel plate. In addition, Mn is an effective austenite stabilizing element; adding a certain amount of Mn can increase the hardenability of steel. Therefore, to ensure the strength of the steel, the lower limit of Mn content is 0.30%. However, Mn is prone to causing center segregation in steel. Excessive addition of Mn will cause severe segregation at the center of the steel plate thickness, reducing the low-temperature toughness of the steel core. Therefore, the upper limit of Mn content is limited to 0.70%. Based on this, the present invention controls the Mn content between 0.30% and 0.70%.

[0029] Ti: As a deoxidizing element, Ti participates in the deoxidation reaction during the smelting process, facilitating precise control of the oxygen level in molten steel. After deoxidation, Ti forms Ti₂O₃ particles, thereby promoting the formation of intragranular ferrite and improving the low-temperature impact toughness of the steel. Simultaneously, Ti is also a strong carbide-forming and nitride-forming element. In this invention, adding an appropriate amount of Ti can, on the one hand, form a stable MC precipitate in the steel, fixing the carbon element in the matrix and preventing its diffusion to the composite material interface. On the other hand, some Ti participates in fixing the free N element in the steel, forming a TiN precipitate. The TiN precipitate can inhibit the growth of austenite grains, refine the grains, and simultaneously improve the strength and toughness of the steel plate. After Ti fixes some of the free nitrogen element, it helps to prevent the combination of B and N elements to form a BN precipitate, thus ensuring that the B element in the steel exists in a free state, improving the hardenability of the steel, and ensuring that the steel plate has excellent strength properties. In the alloy system of this invention, when the Ti content is below 0.009%, the amount of TiN and Ti2O3 formed is relatively small, weakening the pinning effect on austenite grains. Therefore, the Ti content in the steel is controlled to be no less than 0.009%. However, when the Ti content in the steel is too high, the size of the formed TiN and Ti2O3 particles becomes larger, causing these precipitates to lose their ability to hinder austenite growth and the formation of intragranular ferrite. Instead, they easily become the source of crack initiation, reducing the low-temperature impact toughness of the steel. Therefore, the upper limit of Ti is 0.015%. Based on this, the Ti content in this invention is controlled between 0.009% and 0.015%.

[0030] Cr: Adding an appropriate amount of Cr can improve the hardenability of steel plates, ensuring the uniformity of properties across the thickness section after quenching, especially ensuring high strength and toughness in the core of the steel plate. Adding Cr to steel can enhance its oxidation resistance when operating at high temperatures of 450–530℃. Furthermore, as a strong carbide-forming element, Cr in steel can combine with free carbon in the steel plate to form stable MC carbides, fixing the free carbon in the carbon steel and preventing carbon diffusion into the interface, thus affecting the corrosion resistance of the cladding material. When the Cr content in the steel is low, its effect on the hardenability of thick steel plates weakens, and the formation of stable carbides decreases, weakening the fixation effect on free carbon. Therefore, in this invention, the Cr content is not less than 1.85%. However, a high Cr content will reduce the steel plate's resistance to temper embrittlement, which is detrimental to long-term operation at high temperatures. Therefore, the upper limit of Cr is set at 3.85%. Based on the above reasons, this invention controls the Cr content between 1.85% and 3.85%.

[0031] Mo: Mo is a strong carbide-forming element. Mo can improve the high-temperature creep strength of steel plates through solid solution co-solution with interstitial elements such as carbon and nitrogen. Adding an appropriate amount of Mo can also form small, stable MC carbide precipitates, achieving precipitation strengthening on one hand, and fixing free carbon in carbon steel on the other. When the Mo content in the alloy system is below 0.50%, the carbide density is low, reducing precipitation strengthening and carbon fixation. However, when the Mo content in the steel is high, the precipitates are prone to ripening and become larger, weakening the precipitation strengthening effect. Therefore, this invention controls the Mo content between 0.50% and 1.55%.

[0032] Acid-soluble Als: Al is an important deoxidizing element that forms alumina inclusions. Furthermore, Al can combine with nitrogen (N) in steel to form AlN precipitates, reducing the content of free N in the steel. This prevents the combination of boron (B) and nitrogen, promoting the increase of free B content, improving hardenability, and contributing to the strength of the steel plate. However, when the acid-soluble aluminum content in the steel is too high, the size of the deoxidation product, alumina, increases. Due to the strong adsorption capacity between alumina inclusions, large alumina clusters form. These clusters can clog the nozzles during steelmaking, affecting the casting process. If these large clusters enter the steel plate, they will cause the steel plate to fail inclusion rating and flaw detection tests. Therefore, this invention controls the acid-soluble Al content to 0.010–0.015%.

[0033] Nitrogen (Nb): Nitrogen is a strong carbide-forming element. It can combine with carbon in steel to form molybdenum (MC) precipitates, stabilizing the carbon and preventing its diffusion to the interface. Adding an appropriate amount of Nb can also increase the recrystallization temperature of the steel. When the steel is recrystallized and rolled in the austenitic region, the austenitic grains will not grow rapidly, resulting in fine-grained steel with higher strength and toughness. However, if the Nb content in the steel is too high, the resulting MC precipitates will be larger, which will reduce the toughness of the steel plate and worsen the toughness of the weld heat-affected zone. Therefore, this invention controls the Nb content to be between 0.0010% and 0.050%.

[0034] B: Adding an appropriate amount of boron (B) is to compensate for the decrease in dissolved carbon content in steel caused by fixing free carbon in steel with stable carbides, which leads to a decline in the strength properties of the steel plate. If boron exists in steel in a free state, some of it will preferentially occupy grain boundary sites, improving the hardenability of the steel plate. This effect depends on boron existing in a free state in the steel. Therefore, to prevent boron in steel from combining with oxygen and nitrogen to form boron oxide and boron nitride, the oxygen and nitrogen contents in the steel must be carefully controlled, which is a key point in alloy composition design. However, it should be noted that adding excessive boron to steel can easily lead to excessive segregation at grain boundaries, which is detrimental to the toughness of the steel. Therefore, this invention controls the boron content to 0.0007–0.0050%.

[0035] N: In the alloy composition design of this invention, appropriate amounts of Ti and Al elements are added. These two elements can form TiN and AlN precipitates with N elements in the steel. When these precipitates are fine and dispersed, they can refine the austenite grains, thereby improving the strength and toughness of the steel plate. However, when the N content in the steel is too high, the excess N elements will combine with the B elements in the steel to form BN, consuming the free B elements in the steel and reducing the influence of B elements on improving the strength of the steel plate. At the same time, excessive N elements will have an adverse effect on the toughness of the steel, especially when the solid solution N content exceeds 0.005%, which will significantly reduce the low-temperature toughness of the steel plate. Therefore, this invention controls the N content to 0.0025% to 0.0050%.

[0036] Preferably, the rolled composite steel plate substrate for high-temperature equipment described in this invention further contains at least one of the following chemical elements: 0 < Ca ≤ 0.0055%, 0 < Ni ≤ 0.65%, and 0 < Cu ≤ 0.55%.

[0037] In the above technical solution of the present invention, Ca, Ni and Cu elements can all further improve the performance of the high-temperature equipment steel plate of the present invention.

[0038] Ca: Ca is a strong deoxidizing element. Adding an appropriate amount of calcium can control the oxygen content in steel, thereby preventing the oxidation of boron. However, when the Ca content in steel exceeds 0.0055%, large inclusions of calcium oxide and calcium sulfide are easily formed, which is detrimental to the toughness of the steel. Therefore, this invention controls the Ca content to 0 < Ca ≤ 0.0055%.

[0039] Ni: Ni is a typical austenitic stabilizing element that can significantly improve the hardenability of steel plates, as well as their low-temperature toughness. However, Ni is relatively expensive, and considering the overall production cost of steel, excessive Ni should not be added to steel. Therefore, this invention controls the Ni content to 0 < Ni ≤ 0.65%.

[0040] Cu: In the rolled composite steel plate substrate for high-temperature equipment described in this invention, adding an appropriate amount of Cu helps to improve the strength of the steel and enhance its corrosion resistance. However, when the Cu content added to the steel is too high, the steel plate is prone to high-temperature brittleness at high temperatures. Therefore, this invention controls the Cu content to 0 < Cu ≤ 0.55%.

[0041] It should be noted that the addition of the above-mentioned Ca, Ni and Cu elements will increase the cost of the material. Taking into account both performance and cost control, in the technical solution described in this invention, at least one of the above-mentioned elements can be added preferably.

[0042] The composite steel plate substrate described in this invention contains unavoidable impurities, with P ≤ 0.010%, S ≤ 0.010%, and O ≤ 0.004%.

[0043] P, S, and O are all impurity elements in steel. When technical conditions permit, the content of impurity elements in steel should be reduced as much as possible in order to obtain steel with better performance and higher quality.

[0044] P: P is considered a harmful element for most steel plates. The main reason is that P readily segregates towards grain boundaries, reducing the bonding force between atoms at these boundaries and causing temper embrittlement of the steel plate. This is especially pronounced when the steel plate is used at high temperatures, further exacerbating the temper embrittlement effect of P. Therefore, in the rolled composite steel plate substrate for high-temperature equipment described in this invention, the mass percentage of P is controlled to P ≤ 0.010%.

[0045] Sulfur (S): Sulfur (S) in steel readily combines with manganese (Mn) to form MnS inclusions. The higher the S content, the larger the MnS inclusions, which negatively impacts the strength and toughness of the steel plate. Furthermore, excessively high S content can lead to center segregation in the slab and increase the likelihood of hot cracking. Therefore, in the high-temperature equipment rolled composite steel plate substrate described in this invention, the mass percentage of sulfur (S) is controlled to be ≤0.010%.

[0046] O: Oxygen in steel exists primarily in the form of oxides. When the O content in steel is too high, it indicates an excess of oxides, potentially leading to large inclusions and affecting the strength and toughness of the steel plate. Therefore, in the high-temperature equipment rolled composite steel plate substrate described in this invention, the mass percentage of O is controlled to O ≤ 0.004%.

[0047] The composite steel plate substrate of this invention has a surface microstructure of 90-95% bainite and 5-10% martensite, and a central microstructure of 90-95% bainite (B) and 0-5% martensite (M) + 0-5% ferrite (F). To ensure the tensile strength and low-temperature impact performance of the composite steel plate substrate meet requirements, it is necessary to ensure that 90-95% of the microstructure in both the surface and central areas of the steel plate is bainite. The 5-10% martensite in the surface layer further improves the strength of the surface steel plate, compensating for the strength reduction caused by the conversion of some free carbon elements into carbides during subsequent high-temperature service. The 0-5% ferrite in the central microstructure helps improve its low-temperature impact toughness, compensating for the reduction in toughness in the center of the plate due to segregation.

[0048] The substrate of this invention contains stable MC precipitates, where M represents one or more of Cr, Mo, Nb, and Ti, and the average major axis length of the MC precipitates is less than 400 nm. Since larger precipitate sizes can adversely affect the mechanical properties of the steel plate, especially its low-temperature impact toughness, this invention requires controlling the average major axis length of the MC precipitates in the steel plate to be less than 400 nm. The substrate of this invention aims to form carbide precipitates with the smallest possible size to ensure that while fully utilizing the carbide's carbon fixation function, the precipitation of carbides does not adversely affect the mechanical properties of the steel plate. Therefore, the proportion of MC precipitates with a major axis length less than 400 nm to all MC precipitates is limited to greater than 50%.

[0049] Preferably, the bulk density of the MC precipitate with a major axis length of less than 400 nm in the substrate is greater than 3.0 × 10⁻⁶. 4 pcs / mm 3 The formation of MC precipitates in steel is to fix the free carbon elements in the steel. Therefore, in this invention, it is necessary to ensure that the bulk density of MC with a major axis length of less than 400 nm is greater than 3.0 × 10⁻⁶. 4 pcs / mm 3 Only in this way can the carbon element in the steel be effectively controlled, and the large-scale diffusion of free carbon elements to the stainless steel side be avoided.

[0050] Preferably, the proportion of MC precipitates with a long axis length of less than 400 nm in the substrate is greater than 50% of the total number of MC precipitates. In this invention, the "bulk density" of the MC precipitates is determined according to the method described in the YB / T 5320-2006 standard. This invention aims to form carbide precipitates with the smallest possible size to ensure that while fully utilizing the carbide's carbide fixation function, the precipitation of carbides does not adversely affect the mechanical properties of the steel plate. Therefore, the proportion of MC precipitates with a long axis length of less than 400 nm in the total number of MC precipitates is limited to greater than 50%.

[0051] The composite steel plate cladding material of this invention contains a stable MC precipitate phase, where M represents one or more of Cr, Mo, Nb, and Ti, and the average major axis length of the MC precipitate phase is less than 700 nm. The larger the carbide size in the cladding material, the greater the impact on the corrosion resistance of the stainless steel. Therefore, it is desirable for the carbide precipitate size in the cladding material to be as small as possible. However, during the production process of the cladding material and the rolled composite steel plate, some carbide precipitates are inevitably generated. To ensure the corrosion resistance of the rolled composite steel plate, this invention requires that the average major axis length of the MC precipitate phase in the cladding material be less than 700 nm.

[0052] The bulk density of the MC precipitate in the multilayer material of the present invention is less than 1.0 × 10⁻⁶. 4 pcs / mm 3 From the perspective of controlling the amount of carbide precipitates in composite materials, it is desirable to have as few carbides as possible, that is, to control their bulk density as low as possible. However, some carbides inevitably form during the heat treatment of composite steel plates. Controlling the bulk density of carbides to less than 1.0 × 10⁻⁶ is crucial. 4 pcs / mm 3 This ensures the excellent corrosion resistance of the multilayer material.

[0053] Preferably, in the composite material of the present invention, the proportion of MC precipitates with a long axis length of less than 700 nm to the total number of MC precipitates is greater than 50%. In this invention, the "bulk density" of the MC precipitates is determined according to the method described in the YB / T 5320-2006 standard. To minimize the number of carbide precipitates in the composite material and thus increase its corrosion resistance, the present invention limits the size and quantity of MC precipitates, i.e., the proportion of MC precipitates with a long axis length of less than 700 nm to the total number of MC precipitates is greater than 50%. When the number and size of the carbide precipitates exceed the limit, the corrosion resistance of the composite material will be greatly reduced, affecting the safe service performance of the rolled composite steel plate.

[0054] The cladding layer described in this invention is stainless steel (including austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, duplex stainless steel, super stainless steel, and other stainless steel products). The σ phase in stainless steel is a highly hard, low-ductility intermetallic phase. When it exists in stainless steel, especially when precipitated along grain boundaries, it significantly affects the steel's ductility, leading to a substantial reduction in impact toughness. Therefore, the proportion of the σ phase in stainless steel is ≤1.5%, especially near the bonding interface (transition layer) where the σ phase proportion is ≤0.5%.

[0055] The present invention also provides a method for manufacturing the rolled composite steel plate for high-temperature equipment, which includes the following steps:

[0056] 1) Smelting and casting, preparation of base materials and multilayered billets

[0057] The above-mentioned components are smelted and cast into a base billet. During the smelting process, deoxidizers Si+Mn, Al, and Ti alloys are added sequentially to the molten steel for deoxidation. First, Si+Mn and Al are added for pre-deoxidation. After pre-deoxidation, the oxygen content of the molten steel is 0.0020% to 0.0075%. Then, Ti is added for final deoxidation. After deoxidation, element B is added, followed by other alloys. After homogenization, the billet is cast using the top pouring method. At the same time, a stainless steel clad billet is obtained.

[0058] 2) Billet assembly

[0059] The substrate and the cladding are surface treated, then stacked, and the perimeter of the stacked composite slab is welded and sealed, vacuumed, and sealed again; preferably, the vacuum degree after vacuuming is 8 to 60 Pa.

[0060] 3) Rolling of composite slabs

[0061] The composite slab is heated to 1080-1250℃ and then subjected to two-stage rolling. The total reduction rate of the slab in the first stage rolling is not less than 60%, the total reduction rate in the second stage rolling is not less than 20%, and the reduction rate in the last pass is 8-18%. The total cumulative reduction rate of the two stages of rolling is not less than 80%. The final rolling temperature is above 880℃.

[0062] 4) Heat treatment: Quenching and tempering are performed on the composite steel plate.

[0063] Preferably, in step 2), the surfaces of the substrate and composite casting billet are processed to ensure that the surface of the casting billet is free from obvious surface defects such as oil stains, slag inclusions, and cracks, while ensuring that the roughness of the processed surface of the casting billet is not greater than 2.0Ra.

[0064] Preferably, in step 4), the quenching temperature is 945~985℃, the quenching holding time is T1=(1~1.2)H, and after the holding time is completed, the plate is taken out of the furnace and water-cooled to room temperature. Here, T1 is in min and H is the thickness of the steel plate in mm.

[0065] Preferably, in step 4), the tempering temperature is 690~735℃, the tempering holding time is T2=(1~1.5)H, and after the holding time is completed, the plate is removed from the furnace and cooled to room temperature by water. Here, T2 is in min and H is the thickness of the steel plate in mm.

[0066] In the manufacturing method described in this invention:

[0067] The composite steel plate substrate of this invention requires the generation of a large number of uniformly dispersed nanoscale MC precipitates. These MC precipitates fix the free carbon elements in the carbon steel substrate, preventing excessive diffusion of carbon elements to the substrate-composite interface, which could lead to the formation of carbides in the stainless steel and reduce its corrosion resistance, thereby improving the service safety performance of the rolled composite steel plate for high-temperature equipment. However, free carbon in steel is a major strengthening element in carbon steel substrates. When most of the free carbon elements are fixed in the form of MC, the strength of the carbon steel will decrease. To compensate for the strength loss due to the fixation of carbon elements, it is necessary to add boron (B) to improve the hardenability of the steel plate. The hardenability of B mainly depends on the distribution of free B at the grain boundaries. Since B is an extremely reactive element, it can combine with oxygen in molten steel to form boron oxide; on the other hand, boron also easily combines with nitrogen (N) to form boron carbide. Therefore, in the technical solution of this invention, the deoxidation sequence of molten steel and the timing of the addition of B are specifically designed. During deoxidation, Si and Mn are used for pre-deoxidation, causing most of the silicon oxide and manganese oxide to float to the top slag. Using the strong deoxidizer Al allows for relatively precise control of the oxygen level (measured according to the method for measuring oxygen content in molten steel as described in ISO 14284:1996) between 0.0020% and 0.0075%. Then, Ti is used for final deoxidation, forming a large amount of Ti oxides. Simultaneously, the added Ti can combine with free nitrogen elements in the steel to form TiN. The addition of Ti further reduces the free oxygen concentration in the steel. Within a certain oxygen content range (0.0020–0.0075%), the size of the Ti₂O₃ inclusions formed after deoxidation is suitable (2–5 μm), which is beneficial for the formation of some acicular ferrite structure during solidification and subsequent phase transformation, thus improving the toughness of the steel plate. In addition, Ti can combine with N in the steel to form some TiN, which reduces the adverse effects of dissolved nitrogen on the steel's toughness. Furthermore, TiN can precipitate at high temperatures during solidification, acting as a pinning agent for austenite growth and refining the original austenite grains. Once the oxygen and titanium content in the steel is properly controlled, adding an appropriate amount of B ensures that the added B exists primarily in a free state, guaranteeing high hardenability of the base steel plate and significantly improving its strength. Most importantly, through the aforementioned deoxidizer addition sequence and oxygen site control technology, a large number of uniformly dispersed, fine (2-5 μm), spherical Ti2O3 oxides can be formed in the steel. These oxides can serve as nucleation sites for subsequent carbide precipitation. Because these carbide nucleation sites are uniformly dispersed in the steel, it can be ensured that the precipitated carbides are also uniformly dispersed in the steel, while maintaining a large quantity and small size, thus avoiding any adverse effects on the mechanical properties of the substrate.

[0068] In step 2), the surfaces of the base material and composite slab are processed to ensure that there are no obvious surface defects such as oil stains, slag inclusions, or cracks on the slab surface. At the same time, the surface roughness of the processed slab must not exceed 2.0 Ra. After vacuuming, the vacuum degree is 8-60 Pa, which can ensure the rolling effect of the composite slab.

[0069] In step 3), the composite slab is heated to 1080–1250°C for rolling because: when the heating temperature is below 1080°C, the carbides and nitrides in the base slab cannot be completely dissolved, which reduces the pinning effect of the carbides on the austenite grains during rolling; at the same time, within this temperature range, it is beneficial to the homogenization of austenite in the cladding material, and the carbides in the cladding material are also completely dissolved. However, when the slab heating temperature is above 1250°C, it is easy to cause rapid growth of austenite grains in both the base material and the cladding material, which damages the mechanical properties of the steel.

[0070] In addition, the total reduction rate of the slab in the first stage of rolling shall not be less than 60%, the total reduction rate in the second stage of rolling shall not be less than 20%, the reduction rate in the last pass shall be 8-18%, the total cumulative reduction rate of rolling shall not be less than 80%, and the final rolling temperature shall be above 880℃.

[0071] The first-stage high-temperature and high-reduction rolling process allows the material to fully recrystallize during the rolling deformation process, continuously refining the austenite grains. This inhibits the formation of larger austenite grains in the steel, thereby improving the low-temperature toughness of the steel. When the total reduction rate in the first stage is less than 60%, the austenite grain size in the steel is larger, which is not conducive to the strength and toughness of the steel plate.

[0072] The total reduction rate in the second stage of rolling should not be less than 20%, which can further promote austenite grain refinement. The reduction rate of the final rolling pass should be between 8% and 18%, which can increase the dislocation density in the steel and ensure the strength of the steel plate. If the reduction rate is less than 8%, the dislocation density is low, which is not conducive to strength improvement. If the reduction rate is higher than 18%, the rolling torque is too large, which is detrimental to the rolling equipment. If the final rolling temperature is lower than 880℃, the deformation resistance of the steel plate increases, making it difficult to guarantee a large final rolling reduction rate.

[0073] During the quenching process, when the quenching temperature is below 945℃, the homogenization of austenite in the steel requires a longer time, which reduces heat treatment efficiency. Conversely, if the quenching temperature is above 985℃, some austenite in the carbon steel tends to grow, easily forming a mixed-grain structure, which is detrimental to the uniformity of the steel structure. Correspondingly, when the holding time T1 at the quenching temperature is less than 1 hour, sufficient austenitization cannot occur. Conversely, when the holding time T1 exceeds 1.2 hours, it exceeds the required austenitization time, reducing the efficiency of the quenching process.

[0074] During tempering, when the tempering temperature of the steel is below 690℃, a longer tempering time is required to remove residual quenching stress, which reduces tempering efficiency and slows down the formation rate of MC precipitates in carbon steel. Conversely, when the tempering temperature is above 735℃, the MC precipitates in the steel are prone to Ostwald coarsening and agglomeration, hindering the formation of fine, dispersed MC precipitates. Correspondingly, when the tempering holding time T2 is below 1.0H, the quenching stress in the steel tends not to be completely removed, while when the tempering holding time T2 is above 1.5H, the MC precipitates in the steel tend to coarsen, reducing the production efficiency of the tempering process.

[0075] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0076] This invention utilizes finely dispersed spherical (2-5 μm) Ti₂O₃ oxides formed in steel as nucleation sites for MC carbide precipitates. This results in the formation of numerous dispersed nanoscale MC (M represents one or more of Cr, Mo, Nb, and Ti) precipitates within the steel, fixing free carbon elements in the carbon steel and preventing the diffusion and aggregation of carbon elements at the composite interface (transition layer). This reduces the precipitation of stainless steel grain boundary carbides and ensures the corrosion resistance of the composite rolled steel plate. Specifically, when this rolled composite steel plate is used in high-temperature equipment, under high-temperature conditions of 450℃~530℃, the high-melting-point Ti₂O₃ oxides (melting point 2130℃) remain stable in the steel, continuing to function as nucleation sites for MC carbides. Even free carbon elements present in steel can still react with alloying elements in steel using Ti2O3 oxide as a nucleation core to generate fine MC carbides, thereby further fixing carbon elements, ensuring that carbon elements in carbon steel do not diffuse to the interface, and protecting the corrosion resistance of rolled composite steel plates under long-term high-temperature service conditions.

[0077] Furthermore, regarding the smelting process in the production of low-alloy high-strength steel, the most typical existing smelting technology is aluminum deoxidation killed steel. This involves controlling the oxygen content in the steel within a target range through aluminum deoxidation. Its characteristic is high deoxidation efficiency, but it easily forms large and numerous Al2O3 inclusions in the steel. These inclusions tend to aggregate and form clusters, causing the steel plate to fail flaw detection, mechanical properties, or inclusion rating tests. Simultaneously, most Al2O3 inclusions are irregular polyhedral blocky in shape, failing to act as nucleation sites for carbides and promoting their uniform dispersion. Therefore, in aluminum-killed steel, carbide precipitates tend to aggregate at grain boundaries and are relatively large, adversely affecting both the steel's conventional and high-temperature properties.

[0078] This invention optimizes the production process by controlling the type, sequence, and amount of deoxidizer added during steel smelting. This allows for the production of high-melting-point, finely dispersed spherical (2-5 μm) Ti2O3 oxides in the steel. Compared to Al2O3 inclusions formed in traditional aluminum-killed steel, these oxides are less prone to aggregation and growth, have no sharp edges, and are harmless to the flaw detection and mechanical properties of the steel plate, thus optimizing the microstructure. Furthermore, TiN precipitation refines the austenite grains. By designing the order of alloy addition, the oxidation and nitriding of boron are reduced, allowing for full utilization of the added boron to maximize the hardenability of the steel plate, refine the grains, and ensure high strength and excellent low-temperature toughness.

[0079] Furthermore, through smelting process control, especially by controlling the type, sequence, and amount of deoxidizer added, finely dispersed spherical (2-5 μm) Ti₂O₃ oxides formed in the steel can serve as nucleation sites for MC carbide precipitates. Combined with optimized alloy composition and heat treatment process design, a large number of dispersed nanoscale MC (M represents one or more of Cr, Mo, Nb, and Ti) precipitates can be formed in the steel. This fixes the free carbon elements in the carbon steel, preventing the diffusion and aggregation of carbon elements to the composite interface (transition layer), reducing the precipitation of stainless steel grain boundary carbides, and ensuring the corrosion resistance of the composite rolled steel plate. In particular, when this rolled composite steel plate is used in high-temperature equipment, under high-temperature conditions of 450–530℃, the high-melting-point Ti₂O₃ oxides (melting point of 2130℃) formed due to controlled smelting process can still exist stably in the steel, continuing to function as MC carbide precipitation sites. Even free carbon elements present in steel can still react with alloying elements in steel using Ti2O3 oxide as a nucleation core to generate fine MC carbides, thereby further fixing carbon elements, ensuring that carbon elements in carbon steel do not diffuse to the interface, and protecting the corrosion resistance of rolled composite steel plates under long-term high-temperature service conditions.

[0080] The rolled composite steel plate for high-temperature equipment produced by this invention has excellent corrosion resistance and can be effectively used in the energy and chemical industry as a manufacturing material for high-temperature reaction vessels at 450-530℃. It has great practical significance and a very broad application prospect. Detailed Implementation

[0081] The present invention will be further explained and described below with reference to specific embodiments; however, such explanation and description do not constitute an undue limitation on the technical solution of the present invention.

[0082] The composition of the embodiments of the present invention is shown in Table 1. The remaining quantities include Fe and other unavoidable impurities. In the embodiments and comparative examples, the cladding material of the rolled composite steel plate is described using austenitic stainless steel as an example. The manufacturing process parameters of the embodiments of the present invention are shown in Table 2.

[0083] The manufacturing method of this invention includes the following steps:

[0084] 1) Smelting and casting: Smelting and continuous casting are carried out according to the chemical composition shown in Table 1 to obtain slabs. The smelting equipment is a 500 kg vacuum induction furnace. First, 420 kg of industrial pure iron is added to the vacuum induction furnace. According to the alloy composition ratio of the steel, a certain amount of CaO is added with the furnace (the added CaO is used for slag formation during smelting). Vacuum is drawn, and smelting is carried out under a minimum vacuum of about 25 Pa. Argon gas is required for atmosphere protection during the smelting process. After the pure iron is melted and cleared, deoxidizers Si+Mn and Al are added in sequence for pre-deoxidation. According to the online monitoring results of the steel composition, the amount of deoxidizer added is finely adjusted and the oxygen level of free oxygen in the molten steel is controlled to be 0.0020%~0.0075%. Then, an appropriate amount of Ti is added for final deoxidation. Alloys such as Nb, Cr, and Mo are added for alloying treatment. Finally, B is added. The casting is carried out by top pouring method to form a slab.

[0085] 2) Assembly: The base carbon steel billet and the cladding stainless steel billet are surface treated. The surface roughness of the two materials is ≤2.0Ra. After surface inspection, it is ensured that there are no surface defects such as oil stains, slag inclusions, and cracks. The base carbon steel billet and the cladding stainless steel billet are stacked to form a composite slab. The composite slab is welded around its perimeter and then vacuumed with a vacuum degree of 8-60Pa.

[0086] 3) Rolling: The composite slab is heated at 1080-1250℃ and then rolled in two stages. The total cumulative reduction rate of the rolling is not less than 80%, the total reduction rate of the slab in the first stage of rolling is not less than 60%, the total reduction rate in the second stage of rolling is not less than 20%, the reduction rate of the last pass is 8-18%, and the final rolling temperature is above 880℃.

[0087] 4) Heat treatment: Quenching and tempering of the rolled composite steel plate; Quenching treatment of the composite steel plate at a temperature of 945-985℃ for a holding time T1 of 1-1.2H, and water cooling to room temperature after the holding time is completed; Then tempering treatment at a temperature of 690-735℃ for a holding time T2 of 1-1.5H, and air cooling after the plate is removed from the furnace.

[0088] In this invention, the chemical composition design and related processes of the composite steel plates in Examples 1 to 8 all meet the design specifications of this invention.

[0089] Correspondingly, the composite steel plates of Comparative Examples 1 to 5 were manufactured using the same process steps as in Example 1. The difference was that the alloy element content of the base carbon steel in Comparative Examples 1 to 4 exceeded the design range, while the alloy range of Comparative Example 5 was still within the design range. However, in the smelting and casting operations of step 1) above, the order of adding deoxidizer and alloy B in Comparative Examples 1 to 5 was different; the heat treatment tempering process was also different.

[0090] Electrolytic samples were taken from the carbon steel substrate material and the cladding stainless steel side of the composite steel plates of Examples 1-8 and the control rolled composite steel plates of Comparative Examples 1-5, respectively. The MC precipitates in the carbon steel substrate and the cladding stainless steel were extracted using electrolytic extraction. Precipitates of different sizes were separated by passing them through filter membranes of different particle sizes. The particle size distribution of the precipitates was detected using a laser particle size analyzer, and image analysis software was used to confirm the quantity and size distribution range of the MC precipitates (M represents one or more of Nb, Ti, Cr, and Mo) in the steel plates of each example and comparative example. The observed and analyzed data are listed in Table 3 (substrate material) and Table 4 (cladding material at the interface, i.e., the transition layer).

[0091] As shown in Table 3, the total number of precipitates in the carbon steel substrate of the rolled composite steel plates in Examples 1-8 ranges from 747 to 908, which is significantly higher than the number of precipitates (467-547) in the carbon steel substrate of Comparative Examples 1-5. This indicates that after implementing the technical solution of the present invention, a greater number of MC (M is one or more of Cr, Mo, Ti, and Nb) carbide precipitates can be formed in the carbon steel substrate of Examples 1-8, thereby ensuring the effect of using stable carbides in the carbon steel substrate to fix free carbon in the carbon steel designed in the technical solution. Moreover, the size of the MC precipitates in the carbon steel substrate of the rolled composite steel plates in Examples 1-8 is relatively small, mainly ranging from 100 to 600 nm, with an average major axis length of less than 400 nm and a bulk density of greater than 3.0 × 10⁻⁶. 4 pcs / mm 3 The proportion of MC precipitates with a size smaller than 400 nm is greater than 50% of the total number of MC precipitates. When the precipitate size is small, it can, to some extent, pin the growth of austenite grains, thereby refining the grains and further improving the strength and toughness of the material.

[0092] In contrast, the MC precipitates in the carbon steel substrate of the rolled composite steel plates in Comparative Examples 1-5 are relatively large, with an average major axis length greater than 800 nm. The main precipitate sizes are distributed above 800 nm, and precipitates larger than 1000 nm account for a high proportion. Their pinning effect on austenite grains is poor, leading to larger grain sizes and affecting the strength and toughness of the steel plate. Because the carbon steel materials in Comparative Examples 1-5 have a small number of stable precipitates, the fixation of free carbon in the substrate carbon steel is reduced. This results in a large amount of free carbon segregating towards the bonding interface (transition layer), generating a large number of grain boundary carbides at the cladding material at the bonding interface, reducing the corrosion resistance of the cladding material at the bonding interface.

[0093] As shown in Table 4, in the composite steel plate near-transition layer of the composite steel plates described in Examples 1-8, the number of MC (M being one or more of Cr, Mo, Ti, and Nb) precipitates detected was 145-176, which is far fewer than the 503-544 precipitates in Comparative Examples 1-5. Furthermore, the bulk density of the MC precipitates at the interface of the composite materials in Examples 1-8 is less than 1 × 10⁻⁶. 4 pcs / mm 3 The bulk density of the MC precipitate at the interface of the multilayered materials in Comparative Examples 1–5 is greater than 1.5 × 10⁻⁶. 4 pcs / mm 3 This indicates that the carbides in the base carbon steel materials of Examples 1-8 have a good effect on fixing free carbon elements in the steel, and the amount of free carbon diffusing into the cladding material through the bonding interface is small, thus resulting in a smaller number of MCs formed in the cladding material. In contrast, in Comparative Examples 1-5, the carbide precipitates in the base carbon steel materials are not effective at fixing carbon elements, allowing a large amount of carbon elements in the carbon steel materials to diffuse into the cladding material through the bonding interface, resulting in a larger number of carbides in the corresponding cladding materials and a bulk density greater than 1.5 × 10⁻⁶. 4 pcs / mm 3 Furthermore, Table 4 also shows that in the composite materials at the interface of Examples 1-7, the average major axis length of the MC precipitates is less than 700 nm, and the proportion of MC precipitates with a size less than 700 nm is greater than 50% of the total number of MC precipitates; in contrast, the average size of the MC precipitates obtained in the comparative examples is greater than 900 nm. This further illustrates that the carbides in Examples 1-8 have a much better effect on fixing free carbon than those in Comparative Examples 1-5.

[0094] After analyzing the carbide precipitates of the high-temperature equipment steel plates of Examples 1-8 and the comparative steel plates of Comparative Examples 1-5, the mechanical properties and corrosion resistance of the steel plates of Examples 1-8 and Comparative Examples 1-5 were also tested. The test results are shown in Table 5.

[0095] As shown in Table 5, the composite steel plate substrate of this invention has a yield strength ≥ 455 MPa, tensile strength ≥ 535 MPa, reduction of area ≥ 65%, elongation ≥ 18%, impact absorption energy at -40℃ ≥ 120 J, and impact absorption capacity at -60℃ ≥ 70 J. The shear strength of the composite steel plate is ≥ 330 MPa.

[0096] The yield strength and tensile strength of the comparative carbon steel substrate are lower than those of the examples. This is mainly because the smelting process, alloy addition sequence, and heat treatment process of the comparative carbon steel substrate differ from those of the examples. Consequently, the hardenability of the boron element in the comparative steel cannot be fully utilized, and the different precipitates in the steel have different effects on the microstructure of the steel plate. The surface microstructure of the composite steel plate substrate described in this invention consists of 90-95% bainite + 5-10% martensite + MC precipitates, while the central microstructure of the substrate consists of 90-95% bainite (B) and 0-5% martensite (M) + 0-5% ferrite (F). The microstructure proportions of the carbon steel material in the comparative example are significantly different from those in the examples, with a substantial decrease in the proportions of bainite and martensite and an increase in the proportion of ferrite, which also affects the strength of the steel plate.

[0097] Furthermore, the numerous small-sized precipitates in the carbon steel substrates of Examples 1-8 further refined the austenite grains. The grain size of the carbon steel substrates in the examples was not less than 7.5, while the grain size of the carbon steel substrates in the comparative examples was in the range of 5 to 5.5. It can be seen that the technical solution of the present invention in the examples fully utilized the effect of precipitates pinning austenite and refining grains, which played a certain role in improving the strength and toughness of the steel plate.

[0098] The cladding stainless steel at the interface of the rolled composite steel plates from the examples and comparative examples was subjected to corrosion tests according to ASTM A262 Practice E. The test results are shown in Table 6. These results indicate that the stainless steel at the interface of the rolled composite steel plates prepared according to the requirements of this invention exhibits excellent corrosion resistance. Therefore, the corrosion resistance of the cladding stainless steel plates in Examples 1-8 is significantly better than that in Comparative Examples 1-5.

[0099] In summary, the composite steel plate for high-temperature equipment operating at 450–530℃ described in this invention can generate a large number of dispersed nano-sized MC (M represents one or more of Cr, Mo, Nb, and Ti) precipitates in the base steel by optimizing the composition design and production process, especially by controlling the type, sequence, and amount of deoxidizer added during steelmaking, and by adding element B at the appropriate time and in appropriate amounts, combined with other production processes. These nano-sized MC precipitates can fix the free carbon elements in the base carbon steel, thereby preventing these carbon elements from diffusing to the bonding interface in large quantities, which would lead to the formation of a large number of carbide precipitates in the stainless steel and reduce its corrosion resistance. Therefore, using the technical solution of this invention can ensure the strength and toughness of the carbon steel base material, while also significantly improving the corrosion resistance of the rolled composite steel plate, ensuring the intrinsic safety performance of the rolled composite steel plate during long-term high-temperature service.

[0100] Furthermore, it should be noted that the combination of the various technical features in this invention is not limited to the combination methods described in the claims of this application or the combination methods described in the specific embodiments. All technical features described in this application can be freely combined or combined in any way, unless they contradict each other.

[0101] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

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Claims

1. A corrosion-resistant rolled composite steel plate for high-temperature equipment, comprising a substrate, a cladding layer, and a transition layer between the substrate and the cladding layer; wherein the substrate composition by weight percentage is: C: 0.08%–0.18%, Si: 0.01%–0.6%, Mn: 0.30%–0.70%, Ti: 0.009%–0.015%, acid-soluble Als: 0.010%–0.015%, Nb: 0.0010%–0.050%, Cr: 1.85%–3.85%, Mo: 0.5%–1.55%, B: 0.0007%–0.0050%, N: 0.0025%–0.0050%, P≤0.010%, S≤0.010%, O≤0.004%, with the balance including Fe and other unavoidable impurities; The surface microstructure of the composite steel plate substrate consists of 90-95% bainite + 5-10% martensite + MC precipitates, while the central microstructure consists of 90-95% bainite + 0-5% martensite + 0-5% ferrite + MC precipitates. M represents one or more of Cr, Mo, Nb, and Ti. The average major axis length of the MC precipitate is less than 400 nm, and the bulk density of the MC precipitate with a major axis length less than 400 nm is greater than 3.0 × 10⁻⁶. 4 pcs / mm 3 ; The composite steel plate has a stainless steel cladding layer containing MC precipitates in its microstructure; wherein M represents one or more of Cr, Mo, Nb, and Ti, the average major axis length of the MC precipitates is less than 700 nm, and the bulk density of the MC precipitates is less than 1.0 × 10⁻⁶. 4 pcs / mm 3 .

2. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 1, characterized in that, The composite steel plate substrate also contains at least one of the following chemical elements: 0 < Ca ≤ 0.0055%, 0 < Ni ≤ 0.65%, and 0 < Cu ≤ 0.55%.

3. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 1 or 2, characterized in that, The composite steel plate substrate contains Fe and other unavoidable impurities in its composition.

4. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 1 or 2, characterized in that, In the composite steel plate substrate, the proportion of MC precipitates with a long axis length of less than 400 nm to the total number of MC precipitates is greater than 50%.

5. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 3, characterized in that, In the composite steel plate substrate, the proportion of MC precipitates with a long axis length of less than 400 nm to the total number of MC precipitates is greater than 50%.

6. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 1 or 2, characterized in that, In the composite steel plate cladding, the proportion of MC precipitates with a major axis length of less than 700 nm to the total number of MC precipitates is greater than 50%.

7. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 3, characterized in that, In the composite steel plate cladding, the proportion of MC precipitates with a major axis length of less than 700 nm to the total number of MC precipitates is greater than 50%.

8. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 4, characterized in that, In the composite steel plate cladding, the proportion of MC precipitates with a major axis length of less than 700 nm to the total number of MC precipitates is greater than 50%.

9. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 5, characterized in that, In the composite steel plate cladding, the proportion of MC precipitates with a major axis length of less than 700 nm to the total number of MC precipitates is greater than 50%.

10. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 1 or 2, characterized in that, The microstructure of the composite steel plate cladding also contains a very small amount of σ phase, with the proportion of σ phase ≤ 1.5%.

11. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 3, characterized in that, The microstructure of the composite steel plate cladding also contains a very small amount of σ phase, with the proportion of σ phase ≤ 1.5%.

12. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 4, characterized in that, The microstructure of the composite steel plate cladding also contains a very small amount of σ phase, with the proportion of σ phase ≤ 1.5%.

13. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 5, characterized in that, The microstructure of the composite steel plate cladding also contains a very small amount of σ phase, with the proportion of σ phase ≤ 1.5%.

14. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 6, characterized in that, The microstructure of the composite steel plate cladding also contains a very small amount of σ phase, with the proportion of σ phase ≤ 1.5%.

15. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 7, characterized in that, The microstructure of the composite steel plate cladding also contains a very small amount of σ phase, with the proportion of σ phase ≤ 1.5%.

16. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 8, characterized in that, The microstructure of the composite steel plate cladding also contains a very small amount of σ phase, with the proportion of σ phase ≤ 1.5%.

17. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 9, characterized in that, The microstructure of the composite steel plate cladding also contains a very small amount of σ phase, with the proportion of σ phase ≤ 1.5%.

18. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 10, characterized in that, The σ phase ratio near the transition layer, i.e., the interface, is ≤0.5%.

19. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 11, characterized in that, The σ phase ratio near the transition layer, i.e., the interface, is ≤0.5%.

20. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 12, characterized in that, The σ phase ratio near the transition layer, i.e., the interface, is ≤0.5%.

21. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 13, characterized in that, The σ phase ratio near the transition layer, i.e., the interface, is ≤0.5%.

22. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 14, characterized in that, The σ phase ratio near the transition layer, i.e., the interface, is ≤0.5%.

23. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 15, characterized in that, The σ phase ratio near the transition layer, i.e., the interface, is ≤0.5%.

24. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 16, characterized in that, The σ phase ratio near the transition layer, i.e., the interface, is ≤0.5%.

25. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 17, characterized in that, The σ phase ratio near the transition layer, i.e., the interface, is ≤0.5%.

26. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 1 or 2, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

27. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 3, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

28. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 4, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

29. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 5, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

30. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 6, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

31. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 7, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

32. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 8, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

33. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 9, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

34. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 10, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

35. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 11, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

36. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 12, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

37. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 13, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

38. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 14, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

39. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 15, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

40. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 16, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

41. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 17, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

42. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 18, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

43. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 19, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

44. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 20, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

45. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 21, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

46. ​​The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 22, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

47. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 13, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

48. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 24, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

49. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 25, characterized in that, The thickness of the composite steel plate substrate is ≥6mm, and the thickness of the cladding layer is ≥2mm.

50. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 26, characterized in that, The thickness of the transition layer is ≤250μm.

51. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 27, characterized in that, The thickness of the transition layer is ≤250μm.

52. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 28, characterized in that, The thickness of the transition layer is ≤250μm.

53. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 29, characterized in that, The thickness of the transition layer is ≤250μm.

54. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 30, characterized in that, The thickness of the transition layer is ≤250μm.

55. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 31, characterized in that, The thickness of the transition layer is ≤250μm.

56. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 32, characterized in that, The thickness of the transition layer is ≤250μm.

57. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 33, characterized in that, The thickness of the transition layer is ≤250μm.

58. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 34, characterized in that, The thickness of the transition layer is ≤250μm.

59. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 35, characterized in that, The thickness of the transition layer is ≤250μm.

60. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 36, characterized in that, The thickness of the transition layer is ≤250μm.

61. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 37, characterized in that, The thickness of the transition layer is ≤250μm.

62. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 38, characterized in that, The thickness of the transition layer is ≤250μm.

63. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 39, characterized in that, The thickness of the transition layer is ≤250μm.

64. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 40, characterized in that, The thickness of the transition layer is ≤250μm.

65. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 41, characterized in that, The thickness of the transition layer is ≤250μm.

66. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 42, characterized in that, The thickness of the transition layer is ≤250μm.

67. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 43, characterized in that, The thickness of the transition layer is ≤250μm.

68. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 44, characterized in that, The thickness of the transition layer is ≤250μm.

69. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 45, characterized in that, The thickness of the transition layer is ≤250μm.

70. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 46, characterized in that, The thickness of the transition layer is ≤250μm.

71. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 47, characterized in that, The thickness of the transition layer is ≤250μm.

72. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 48, characterized in that, The thickness of the transition layer is ≤250μm.

73. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 49, characterized in that, The thickness of the transition layer is ≤250μm.

74. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 1 or 2, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

75. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 3, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

76. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 4, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

77. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 5, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

78. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 6, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

79. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 7, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

80. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 8, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

81. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 9, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

82. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 10, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

83. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 11, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

84. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 12, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

85. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 13, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

86. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 14, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

87. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 15, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

88. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 16, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

89. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 17, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

90. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 18, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

91. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 19, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

92. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 20, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

93. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 21, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

94. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 22, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

95. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 23, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

96. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 24, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

97. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 25, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

98. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 26, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

99. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 27, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

100. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 28, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

101. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 29, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

102. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 30, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

103. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 31, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

104. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 32, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

105. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 33, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

106. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 34, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

107. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 35, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

108. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 36, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

109. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 37, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

110. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 38, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

111. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 39, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

112. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 40, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

113. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 41, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

114. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 42, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

115. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 43, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

116. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 44, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

117. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 45, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

118. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 46, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

119. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 47, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

120. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 48, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

121. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 49, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

122. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 50, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

123. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 51, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

124. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 52, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

125. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 53, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

126. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 54, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

127. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 55, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

128. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 56, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

129. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 57, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

130. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 58, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

131. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 59, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

132. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 60, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

133. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 61, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

134. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 62, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

135. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 63, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

136. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 64, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

137. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 65, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

138. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 66, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

139. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 67, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

140. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 68, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

141. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 69, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

142. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 70, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

143. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 71, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

144. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 72, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

145. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 73, characterized in that, The rolled composite steel plate substrate has a yield strength ≥455MPa, tensile strength ≥535MPa, reduction of area ≥65%, elongation ≥18%, impact absorption energy at -40℃ ≥120J, and impact absorption capacity at -60℃ ≥70J; the substrate grain size is not less than grade 7.0; and the shear strength of the composite steel plate is ≥330MPa.

146. The corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 1, characterized in that, The stainless steel is austenitic stainless steel, ferritic stainless steel, duplex stainless steel, or super stainless steel.

147. The method for manufacturing corrosion-resistant rolled composite steel plate for high-temperature equipment as described in any one of claims 1 to 146, characterized in that, Includes the following steps: 1) Smelting and casting, preparation of base materials and multilayered billets The composite steel plate is smelted and cast into a base billet according to its composition. During the smelting process, deoxidizers Si+Mn, Al, and Ti alloy are added sequentially to the molten steel for deoxidation. First, Si+Mn and Al are added for pre-deoxidation. After pre-deoxidation, the oxygen content of the molten steel is 0.0020% to 0.0075%. Then, Ti is added for final deoxidation. After deoxidation, element B is added, followed by other alloys. After homogenization, the steel is cast using the top pouring method. At the same time, a stainless steel clad billet is obtained. 2) Billet assembly The substrate and the cladding are surface treated, then stacked, and the perimeter of the stacked composite slab is welded and sealed, vacuumed, and then sealed again. 3) Rolling of composite slabs The composite slab is heated to 1080-1250℃ and then subjected to two-stage rolling. The total reduction rate of the slab in the first stage rolling is not less than 60%, the total reduction rate in the second stage rolling is not less than 20%, and the reduction rate in the last pass is 8-18%. The total cumulative reduction rate of the two stages of rolling is not less than 80%. The final rolling temperature is above 880℃. 4) Heat treatment: Quenching and tempering heat treatment is performed on the composite steel plate.

148. The method for manufacturing corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 147, characterized in that, In step 2), the surfaces of the substrate and composite casting billet are processed to ensure that there are no obvious oil stains, slag inclusions, cracks or other surface defects on the surface of the casting billet, and at the same time, the roughness of the processed surface of the casting billet is not greater than 2.0Ra.

149. The method for manufacturing corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 147, characterized in that, In step 4), the quenching temperature is 945~985℃, the quenching holding time is T1=(1~1.2)H, and after the holding time is completed, the plate is taken out of the furnace and water-cooled to room temperature; where T1 is in min and H is the thickness of the steel plate in mm.

150. The method for manufacturing corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 147 or 149, characterized in that, In step 4), the tempering temperature is 690~735℃, the tempering holding time is T2=(1~1.5)H, and after the holding time is completed, the steel plate is removed from the furnace and cooled to room temperature by water; where T2 is in min and H is the thickness of the steel plate in mm.

151. The method for manufacturing corrosion-resistant rolled composite steel plate for high-temperature equipment as described in claim 147 or 148, characterized in that, In step 2), after the vacuum is drawn, the vacuum level is 8-60 Pa.

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