Manufacturing method of high-alloy heat-resistant steel plate

Abstract

The invention relates to a manufacturing method of a high-alloy heat-resistant steel plate, and belongs to the field of metallurgy. The manufacturing process of the steel plate comprises the steps of steel blank electroslag remelting, blank annealing, blank surface cleaning, steel plate rolling, steel plate slow cooling, ultrasonic flaw detection, normalizing and tempering. The steel plate structure is mainly tempered martensite, the tensile strength is 585-760 MPa, the yield strength is larger than or equal to 415 MP, the percentage reduction of area is larger than or equal to 18%, the Brinell hardness is smaller than or equal to 250 HBW, the 630 DEG C high-temperature tensile Rp0.2 is larger than or equal to 220 MPa, and the 20 DEG C impact absorption energy is larger than or equal to 50 J. And when the temperature of the service environment reaches 600 DEG C, the steel plate still has stable persistent plasticity and thermal strength performance, can be used for manufacturing large-diameter steel pipes and pressure containers in a high-temperature environment, and is wider in application scene.

Description

Technical Field

[0001] The invention belongs to the technical field of steel smelting, and in particular relates to a method for manufacturing a heat-resistant steel plate. Background Art

[0002] 9Cr1MoV is a martensitic heat-resistant steel. It is an alloy with a certain amount of niobium, vanadium and nitrogen added to 9Cr-1Mo. Its material grades are SA199 T91, SA213 T91, SA234 WP91, SA335 P91, SA336 F91, SA387 91 Ⅱ, etc. This material has good high-temperature thermal strength and oxidation resistance. At present, it is widely used in large-scale power station boiler reheaters, superheater pipes and headers at home and abroad. It not only has high oxidation resistance and high-temperature steam corrosion resistance, but also has high and stable long-lasting plasticity and thermal strength. When the operating temperature is lower than 620℃, its service stress is higher than that of austenitic stainless steel. It can be used as steel pipes for high-temperature superheaters and reheaters with wall temperatures ≤625℃ for subcritical and supercritical boilers, as well as high-temperature headers and steam pipes with wall temperatures ≤600℃. It can also be used as nuclear power heat exchangers and furnace tubes for petroleum cracking units. The corresponding German steel grade is X10CrMoVNNb91, Japanese steel grade is HCM95, and French steel grade is TUZ10CDVNb0901. T91 steel and P91 steel have been widely used in various regions around the world, but SA387Gr91 series steel plates are less developed and the process is not yet mature.

[0003] Through the electroslag remelting casting process, optimized rolling process and heat treatment process, we have developed high-alloy heat-resistant steel plates with excellent comprehensive performance requirements to meet the use requirements of large-diameter welded pipes in high-temperature and high-pressure working environments. Summary of the invention

[0004] The purpose of the present invention is to provide a method for manufacturing a high alloy heat-resistant steel plate, which solves the problem of using electroslag remelting ingots to produce heat-resistant steel plates with a thickness of 10 to 50 mm. The steel plate produced by the method has a good strength-to-toughness ratio, good high-temperature performance, and excellent welding performance.

[0005] The technical solution adopted by the present invention is: a method for manufacturing a high-alloy heat-resistant steel plate, wherein the mass percentages of the steel plate are as follows: C: 0.08-0.12%, Mn: 0.30-0.60%, Si: 0.20-0.50%, P≤0.020%, S≤0.010%, Cr: 8.00-9.50%, Mo: 0.85-1.05%, Ni≤0.40%, V: 0.18-0.25%, Nb: 0.06-0.10%, N: 0.030-0.070%, Al≤0.020%, Ti≤0.010%, Zr≤0.010%, and the remainder is Fe and unavoidable impurity elements.

[0006] The production thickness of the steel plate is 10-50mm, the steel plate structure is tempered martensite, the tensile strength is 585-760MPa, the yield strength is ≥415MP, the cross-sectional shrinkage is ≥18%, the Brinell hardness is ≤250HBW, and the high temperature tensile strength is R p0.2 ≥220MPa, 20℃ impact absorption energy ≥50J.

[0007] The content of chemical elements in steel plays a key role in the performance of the material. The alloying elements of the steel plate play a role in solid solution strengthening, dispersion strengthening and improving the oxidation resistance and corrosion resistance of the steel. The requirements for the content of chemical elements in the present invention are as follows: Carbon (C): It is the element with the most obvious solid solution strengthening effect in steel. With the increase of carbon content, the short-term strength of steel increases, and the plasticity and toughness decrease. For this series of steels, the increase of carbon content will accelerate the spheroidization and aggregation of carbides, accelerate the redistribution of alloy elements, and reduce the weldability, corrosion resistance and oxidation resistance of steel. Generally, it is hoped to reduce the carbon content, but if the carbon content is too low, the high temperature strength of steel will not be guaranteed. The C content of the present invention is controlled at 0.08-0.12%.

[0008] Silicon (Si): Solid solution in austenite strengthens the structure, improves the hardness and strength of steel, reduces the thermal expansion coefficient of steel, and makes the material less likely to deform due to heat generation in a high temperature environment, thereby improving the heat resistance of the material. Therefore, the Si content of the present invention is controlled to be 0.20-0.50%.

[0009] Manganese (Mn): Manganese carbide formed in steel improves the hardness and rigidity of the material, and can also improve the wear resistance, oxidation resistance and corrosion resistance of the material, and extend the service life of the material, but it increases the carbon equivalent of the material and directly affects the welding performance. Therefore, the Mn content of the present invention is controlled at 0.30-0.60%.

[0010] Phosphorus (P) and sulfur (S): reduce the toughness and plasticity of steel, thus affecting the strength of the material. If the content is too high, surface and internal cracks are likely to occur during processing, and brittle compounds are likely to form during welding, resulting in cracking of the welded joint and even brittle fracture during welding. Therefore, the P content of the present invention is controlled at ≤0.010%, and the S content is controlled at ≤0.010%.

[0011] Chromium (Cr): It mainly significantly improves strength, hardness and wear resistance, but reduces plasticity and toughness at the same time. In heat-resistant steel, Cr can significantly improve the material's oxidation resistance and corrosion resistance. When the chromium content is less than 5.0%, it begins to oxidize violently at 600°C, and when the chromium content reaches 5.0% and above, it has excellent oxidation resistance. When the chromium content is increased to about 9.0%, when the use temperature reaches 650°C, it still has good oxidation resistance, mainly because more Cr content is dissolved in the matrix. The Cr content of the present invention is controlled at 8.00-9.50%.

[0012] Molybdenum (Mo): Molybdenum can refine the grains of steel, improve hardenability and heat resistance, and maintain sufficient strength and creep resistance at high temperatures (long-term stress at high temperatures causes deformation, which is called creep). The addition of molybdenum in the present invention plays a role in solid solution strengthening, which can not only improve the mechanical properties of the material, but also inhibit the brittleness caused by high-temperature tempering. The Mo content of the present invention is controlled at 0.85-1.05%.

[0013] Vanadium (V): Its main function is to refine the structure and grains of steel and increase the grain coarsening temperature, thereby increasing the strength, toughness and wear resistance of steel. The carbides formed by vanadium and carbon can improve the resistance to hydrogen corrosion under high temperature and high pressure. The V content of the present invention is controlled at 0.18-0.25%.

[0014] Niobium (Nb): It is a strong carbide-forming element, which forms fine and stable alloy carbides with carbon, and has a strong dispersion strengthening effect. It refines the grains and reduces the overheat sensitivity and temper brittleness of steel, improves the strength, but reduces the plasticity and toughness. It can also improve the resistance to atmospheric corrosion and the resistance to hydrogen, nitrogen and ammonia corrosion at high temperatures, and has the characteristics of improving welding performance. The Nb content of the present invention is controlled at 0.06-0.10%.

[0015] Nickel (Ni): Nickel can improve the strength of steel while maintaining good plasticity and toughness. Nickel has high corrosion resistance to acids and alkalis, and has rust and heat resistance at high temperatures. However, since nickel is a scarce resource, other alloying elements are generally used as much as possible. The Ni content of the present invention is controlled to be ≤0.40%, preferably 0.20-0.30%.

[0016] Titanium (Ti): Titanium is a strong deoxidizer in steel, which can make the internal structure of steel dense, refine the grains, reduce aging sensitivity and cold brittleness, and improve welding performance. The Ti content of the present invention is controlled to be ≤0.010%.

[0017] Aluminum (Al): Aluminum is a commonly used deoxidizer in steel. Adding a small amount of aluminum to steel can refine the grains and improve impact toughness. Aluminum also has antioxidant and corrosion resistance. Aluminum, chromium, and silicon can significantly improve the high-temperature non-scaling performance and high-temperature corrosion resistance of steel. The Al content of the present invention is controlled to ≤0.020%, preferably 0.010-0.020%.

[0018] Nitrogen (N): Its main role in steel is reflected in two aspects. On the one hand, it plays a role in solid solution strengthening. The solubility of nitrogen in steel at room temperature is very small. During welding heating and post-weld heat treatment, VN solid solution and precipitation processes will occur successively. During welding heating, the austenite structure formed in the heat-affected zone increases nitrogen content due to the dissolution of VN. After that, the supersaturation degree in the structure at room temperature increases. In the subsequent post-weld heat treatment, small VN precipitates, which increases the stability of the structure and improves the endurance strength value of the heat-affected zone. On the other hand, steel contains a small amount of A1, and nitrogen can form AlN with it. A1N is dissolved into the matrix in large quantities above 1100°C, and re-precipitates at a lower temperature, which can play a better dispersion strengthening effect. The N content of the present invention is controlled at 0.030-0.070%.

[0019] The manufacturing process of high alloy heat-resistant steel plate is electroslag remelting → billet annealing → billet surface cleaning → rolling → steel plate cover slow cooling → ultrasonic flaw detection → normalizing + tempering. The specific steps are as follows: (1) Electroslag remelting: alternating current is loaded onto the round billet through a transformer. The conductive circulation generates Joule heat in the slag pool to raise the temperature to a sufficiently high level. The superheated molten slag is then used as a medium to melt the round billet. The conductive slag pool and the droplets of the melting electrode form a molten pool and mix. The density difference is used to separate them. At the same time, the surface tension of the slag pool and the molten pool is relatively large, which hinders the mixing of the slag pool and the solution. After the round billet is melted, droplets are formed that continuously pass through the slag pool and react electrochemically with the liquid slag to separate and fall into the molten pool. The bottom of the molten pool is directionally solidified in a strong water-cooled crystallizer, which controls the balance between the melting rate and the cooling rate of the droplets, increases the uniformity of the chemical elements in the solidification process of the electroslag ingot, reduces the chemical segregation and looseness of the solidification, and forms a dense crystalline structure that lasts until all remelting and solidification are completed.

[0020] (2) Billet annealing: ignite the soaking furnace and simmer for more than 3 hours. When the furnace gas temperature is ≤350℃, load the electroslag remelting ingot into the furnace and heat it to 800±20℃ at a heating rate of ≤35℃ / h. Keep it at this temperature for 5-8h. Cool it to 700±20℃ with the furnace and keep it at this temperature for 7-10h. When the furnace cools to the furnace gas temperature of ≤350℃, open the furnace door. When the billet surface temperature is ≤200℃, take it out of the furnace for cleaning. When the billet surface temperature is ≥150℃,

[0021] (3) Billet rolling: The temperature of the soaking furnace is ≤300℃. The ESR ingot with cleaned surface is loaded into the furnace and kept in the furnace for not less than 5h. After the incubation, the temperature is raised to 650±20℃ at a rate of 20~30℃ / h and kept at this temperature for 2~3h. Then, the temperature is raised to 800±20℃ at a rate of 30~50℃ / h and kept at this temperature for 3~5h. Finally, the temperature is raised to 1250±20℃ at a rate of 80~100℃ / h and kept at this temperature for 10~12h. The billet heating is strictly controlled. Thermal process reduces the risk of cracks caused by heating the billet. The descaling box performs a rough descaling to avoid the pressure of iron oxide scale during rolling. The starting temperature of rough rolling is not less than 1080℃ to ensure high-temperature and high-reduction rolling. The reduction rate of the last 3 passes of rough rolling is ≥15%, which plays a role in improving the loose defects of the billet with large deformation, improving the density of the core and refining the original austenite grains. After rough rolling, it goes directly into the finishing mill without waiting for temperature. The thickness allowance is controlled at (+0.5, 1.5) mm. Finally, the steel plate shape is corrected and the contract size is adjusted. After rolling, the steel plate temperature is ≥400℃ and placed on the cooling bed. It is slow-cooled in the slow cooling cover for more than 96 hours. After the slow cooling, ASME SA578-C+S1 is implemented to detect the steel plate.

[0022] (4) Heat treatment of steel plate: normalizing in a normalizing furnace, the normalizing temperature is 1040-1080℃, the time in the furnace is ≥30min, and the steel plate is cooled in still air after being taken out of the furnace to complete the martensitic transformation of the steel plate; tempering is performed within 4 hours after normalizing the steel plate to prevent the steel plate from cracking due to stress concentration caused by a large number of dislocations and twins generated in the crystals during the phase transformation process, the tempering temperature is 730-780℃, and the time in the furnace is ≥80min; after the heat treatment is completed, the desired steel plate is obtained.

[0023] The present invention reduces the carbon content on the basis of 9Cr1Mo steel, strictly limits the content of sulfur and phosphorus, and adds elements such as vanadium, niobium, and nitrogen. The round billet electroslag remelting method is adopted to control the balance between the droplet melting rate and the cooling rate, thereby increasing the uniformity of chemical elements in the electroslag ingot solidification process, reducing the solidification chemical segregation and looseness, and forming a billet with a dense crystalline structure, thereby ensuring that the core of the steel plate after rolling is uniform and dense, and the performance is stable; the billet annealing process is adopted to avoid the characteristics of this high-alloy steel type with high structural stress and easy stress cracking. Control the billet heating rate and extend the insulation time to ensure that the billet heating process is slow, the stress is fully released, the plasticity is good during rolling deformation, the steel plate shape is excellent, and the size control is precise. The normalizing + tempering heat treatment process is used to produce high-alloy heat-resistant steel plates with a thickness of 10 to 50 mm. The steel plate structure is mainly tempered martensite, with a tensile strength of 585 to 760 MPa, a yield strength of ≥415 MPa, a cross-sectional shrinkage rate of ≥18%, a Brinell hardness of ≤250 HBW, and a high-temperature tensile strength of R p0.2 ≥220MPa, 20℃ impact absorption energy ≥50J.

[0024] Compared with the prior art, the advantages of the present invention are: (1) The present invention provides a new method for producing a high-alloy heat-resistant steel plate with a thickness of 10 to 50 mm.

[0025] (2) The high alloy heat-resistant steel plate manufactured by the method still has stable long-lasting plasticity and thermal strength properties when the service environment temperature reaches 600°C.

[0026] (3) The high-alloy heat-resistant steel plate manufactured by the method can be used for the manufacture of large-diameter steel pipes and pressure vessels in high-temperature environments, and has a wider range of application scenarios. The steel plate can still maintain high and stable long-lasting plasticity and thermal strength in an environment with a service temperature of ≤630°C, meeting the application of large-diameter welded pipes in high-temperature, high-pressure working environments. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with examples. The examples are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention. Example 1

[0028] The thickness of the steel plate in this embodiment is 10 mm, and the chemical composition and mass percentage of the steel plate are: C: 0..09%, Mn: 0.35%, Si: 0.25%, P: 0.008%, S: 0.005%, Cr: 8.5%, Mo: 0.90%, Ni: 0.23%, V: 0.22%, Nb: 0.08%, N: 0.048%, Al: 0.018%, Ti: 0.008%, Zr: 0.005%, and the balance is Fe and unavoidable impurity elements.

[0029] The present embodiment provides a method for manufacturing a high alloy heat-resistant steel plate, wherein the manufacturing process is electroslag remelting → billet annealing → billet surface cleaning → rolling → steel plate cover slow cooling → ultrasonic flaw detection → normalizing + tempering, and the specific process steps are as follows: (1) Electroslag remelting process: alternating current is loaded onto the round billet through a transformer device. The conductive circulation generates Joule heat in the slag pool to raise the temperature to a sufficiently high level. The round billet is then melted with superheated molten slag as a medium. The conductive slag pool and the droplets of the melting electrode form a molten pool and are mixed. The density difference is used to separate them. At the same time, the surface tension of the slag pool and the molten pool is relatively large, which hinders the mixing of the slag pool and the solution. After the round billet is melted, droplets are formed that continuously pass through the slag pool and react electrochemically with the liquid slag to separate and fall into the molten pool. The bottom of the molten pool is directionally solidified in a strong water-cooled crystallizer, which controls the balance between the melting rate and the cooling rate of the droplets, increases the uniformity of the chemical elements in the solidification process of the electroslag ingot, reduces the chemical segregation and looseness of the solidification, and forms a dense crystalline structure, which continues until all remelting and solidification are completed.

[0030] (2) Billet annealing process: The soaking furnace is ignited and simmered for 3.5 hours. When the furnace gas temperature is 348°C, the electroslag remelting ingot is loaded into the furnace and heated to 810°C at a heating rate of 30°C / h. The ingot is kept at this temperature for 6.2 hours. The ingot is cooled to 708°C with the furnace and kept at this temperature for 8.6 hours. When the furnace is cooled to the furnace gas temperature of 350°C, the furnace door is opened. When the surface temperature of the billet is 196°C, the billet is taken out of the furnace for cleaning. When the billet is cleaned, its surface temperature is 163°C.

[0031] (3) Billet rolling process: The temperature of the soaking furnace is 295°C. The electroslag remelting ingot with cleaned surface is loaded into the furnace and stewed for 5.2 hours. After stewing, the temperature is raised to 662°C at a rate of 28°C / h and kept at this temperature for 2.5 hours. Then, the temperature is raised to 806°C at a rate of 48°C / h and kept at this temperature for 4.3 hours. Finally, the temperature is raised to 1248°C at a rate of 95°C / h and kept at this temperature for 11.3 hours. The billet heating process is strictly controlled to reduce the generation of billet heating. In order to prevent the risk of cracks, the descaling box performs a rough descaling to avoid the pressure of iron oxide scale during rolling; the starting temperature of rough rolling is 1105℃ to ensure high temperature and large reduction rolling, and the reduction rates of the last three passes of rough rolling are 16%, 21%, and 25%, which play a role in improving the loose defects of the billet with large deformation, improving the density of the core and refining the original austenite grains; after rough rolling, it goes directly into the finishing mill without waiting for temperature, and the thickness allowance is controlled at (+0.5, 1.5) mm. Finally, the steel plate shape is corrected and the contract size is adjusted. After rolling, the steel plate temperature is 446℃ and cooled on the cooling bed, and then slow-cooled in the slow cooling hood for 102 hours. After the slow cooling, the steel plate is inspected according to ASME SA578-C+S1.

[0032] (4) Heat treatment process of steel plate: normalizing in normalizing furnace, normalizing temperature 1060℃, furnace time 45min, cooling in still air after taking out of furnace to complete martensitic transformation of steel plate; tempering within 4.5 hours after normalizing to prevent cracking of steel plate due to stress concentration caused by a large number of dislocations and twins generated in the crystals during phase transformation, tempering temperature 760℃, furnace time 93min; heat treatment is completed to obtain the required steel plate. Example 2

[0033] The thickness of the steel plate in this embodiment is 33 mm, and the chemical composition of the steel plate and its mass percentage are: C: 0.10%, Mn: 0.45%, Si: 0.38%, P: 0.007%, S: 0.002%, Cr: 9.03%, Mo: 1.03%, Ni: 0.32%, V: 0.24%, Nb: 0.09%, N: 0.065%, Al: 0.018%, Ti: 0.008%, Zr: 0.008%, and the balance is Fe and unavoidable impurity elements.

[0034] The present embodiment provides a method for manufacturing a high alloy heat-resistant steel plate, wherein the manufacturing process is electroslag remelting → billet annealing → billet surface cleaning → rolling → steel plate cover slow cooling → ultrasonic flaw detection → normalizing + tempering, and the specific process steps are as follows: (1) Electroslag remelting process: alternating current is loaded onto the round billet through a transformer device. The conductive circulation generates Joule heat in the slag pool to raise the temperature to a sufficiently high level. The round billet is then melted with superheated molten slag as a medium. The conductive slag pool and the droplets of the melting electrode form a molten pool and are mixed. The density difference is used to separate them. At the same time, the surface tension of the slag pool and the molten pool is relatively large, which hinders the mixing of the slag pool and the solution. After the round billet is melted, droplets are formed that continuously pass through the slag pool and react electrochemically with the liquid slag to separate and fall into the molten pool. The bottom of the molten pool is directionally solidified in a strong water-cooled crystallizer, which controls the balance between the melting rate and the cooling rate of the droplets, increases the uniformity of the chemical elements in the solidification process of the electroslag ingot, reduces the chemical segregation and looseness of the solidification, and forms a dense crystalline structure, which continues until all remelting and solidification are completed.

[0035] (2) Billet annealing process: The soaking furnace is ignited and simmered for 4.1 hours. When the furnace gas temperature is 330°C, the electroslag remelting ingot is loaded into the furnace and heated to 812°C at a heating rate of 30°C / h. The ingot is kept at this temperature for 7.1 hours. The ingot is cooled to 705°C with the furnace and kept at this temperature for 9 hours. When the furnace is cooled to the furnace gas temperature of 340°C, the furnace door is opened. When the surface temperature of the billet is 195°C, the billet is taken out of the furnace for cleaning. When the billet is cleaned, the surface temperature is 180°C.

[0036] (3) Billet rolling process: The temperature of the soaking furnace is 280℃. The electroslag remelting ingot with cleaned surface is loaded into the furnace and stewed for 5.5h. After stewing, the temperature is raised to 665℃ at a rate of 20℃ / h and kept at this temperature for 2.6h. Then, the temperature is raised to 790℃ at a rate of 50℃ / h and kept at this temperature for 4.3h. Finally, the temperature is raised to 1245℃ at a rate of 92℃ / h and kept at this temperature for 11.3h. The billet heating process is strictly controlled to reduce the generation of billet heating. In order to prevent the risk of cracks, the descaling box performs a rough descaling to avoid the pressure of iron oxide scale during rolling; the starting temperature of rough rolling is 1110℃ to ensure high temperature and high reduction rolling, and the reduction rates of the last three passes of rough rolling are 18%, 20% and 23% respectively; it plays a role in improving the loose defects of the billet by large deformation, improving the density of the core and refining the original austenite grains; after rough rolling, it goes directly into the finishing mill without waiting for temperature, and the thickness allowance is controlled at (+0.5, 1.5) mm. Finally, the steel plate shape is corrected and the contract size is adjusted. After rolling, the steel plate temperature is 452℃ and cooled on the cooling bed, and then slow-cooled in the slow cooling hood for 110 hours. After the slow cooling, the steel plate is inspected according to ASME SA578-C+S1.

[0037] (4) Steel plate heat treatment process: normalizing in a normalizing furnace, normalizing temperature 1070°C, furnace time 52 min, cooling in still air after taking out of the furnace to complete the martensitic structure transformation of the steel plate; tempering within 4.5 hours after normalizing to prevent the steel plate from cracking due to stress concentration caused by a large number of dislocations and twins generated in the crystals during the phase transformation, tempering temperature 760°C, furnace time 105 min; after the heat treatment is completed, the desired steel plate is obtained. Example 3

[0038] The thickness of the steel plate in this embodiment is 50 mm, and the chemical composition of the steel plate and its mass percentage are: C: 0.11%, Mn: 0.43%, Si: 0.28%, P: 0.007%, S: 0.005%, Cr: 9.05%, Mo: 0.95%, Ni: 0.35%, V: 0.23%, Nb: 0.09%, N: 0.050%, Al: 0.018%, Ti: 0.008%, Zr: 0.005%, and the balance is Fe and unavoidable impurity elements.

[0039] The present embodiment provides a method for manufacturing a high alloy heat-resistant steel plate, wherein the manufacturing process is electroslag remelting → billet annealing → billet surface cleaning → rolling → steel plate cover slow cooling → ultrasonic flaw detection → normalizing + tempering, and the specific process steps are as follows: (1) Electroslag remelting process: alternating current is loaded onto the round billet through a transformer device. The conductive circulation generates Joule heat in the slag pool to raise the temperature to a sufficiently high level. The round billet is then melted with superheated molten slag as a medium. The conductive slag pool and the droplets of the melting electrode form a molten pool and are mixed. The density difference is used to separate them. At the same time, the surface tension of the slag pool and the molten pool is relatively large, which hinders the mixing of the slag pool and the solution. After the round billet is melted, droplets are formed that continuously pass through the slag pool and react electrochemically with the liquid slag to separate and fall into the molten pool. The bottom of the molten pool is directionally solidified in a strong water-cooled crystallizer, which controls the balance between the melting rate and the cooling rate of the droplets, increases the uniformity of the chemical elements in the solidification process of the electroslag ingot, reduces the chemical segregation and looseness of the solidification, and forms a dense crystalline structure, which continues until all remelting and solidification are completed.

[0040] (2) Billet annealing process: The soaking furnace is ignited and simmered for 3.8 hours. When the furnace gas temperature is 335°C, the electroslag remelting ingot is loaded into the furnace and heated to 806°C at a heating rate of 32°C / h. The ingot is kept at this temperature for 6.8 hours. The ingot is cooled to 712°C with the furnace and kept at this temperature for 8.9 hours. When the furnace is cooled to the furnace gas temperature of 338°C, the furnace door is opened. When the surface temperature of the billet is 196°C, the billet is taken out of the furnace for cleaning. When the billet is cleaned, its surface temperature is 186°C.

[0041] (3) Billet rolling process: The temperature of the soaking furnace is 295°C. The ESR ingot with cleaned surface is loaded into the furnace and kept in the furnace for 5.3 hours. After the end of the furnace, the temperature is raised to 665°C at a rate of 30°C / h and kept at this temperature for 2.2 hours. Then, the temperature is raised to 818°C at a rate of 49°C / h and kept at this temperature for 3.8 hours. Finally, the temperature is raised to 1265°C at a rate of 100°C / h and kept at this temperature for 11.3 hours. The billet heating process is strictly controlled to reduce the billet heating product. In order to reduce the risk of cracks, the descaling box performs a rough descaling to avoid the pressure of iron oxide scale during rolling; the starting temperature of rough rolling is 1095℃ to ensure high temperature and large reduction rolling, and the reduction rates of the last three passes of rough rolling are 20%, 19% and 23% respectively; it plays a role in improving the loose defects of the billet with large deformation, improving the density of the core and refining the original austenite grains; after rough rolling, it goes directly into the finishing mill without waiting for temperature, and the thickness allowance is controlled by (+0.5, 1.5) mm. Finally, the steel plate shape is corrected and the contract size is adjusted. After rolling, the steel plate temperature is 435℃ and cooled on the cooling bed, and then slow-cooled in the slow cooling cover for more than 114 hours. After the slow cooling, the steel plate is inspected according to ASME SA578-C+S1.

[0042] (4) Heat treatment process of steel plate: normalizing in normalizing furnace, normalizing temperature 1060℃, furnace time 56min, cooling in still air after taking out of furnace to complete martensitic microstructure transformation of steel plate; tempering within 4.6 hours after normalizing to prevent cracking of steel plate due to stress concentration caused by a large number of dislocations and twins generated in the crystals during phase transformation, tempering temperature 745℃, furnace time 108min; heat treatment is completed to obtain the required steel plate.

[0043] The properties of the steel plates of Examples 1-3 are shown in Table 1.

[0044] Table 1

Claims

1. A method for manufacturing a high alloy heat-resistant steel plate, characterized in that: The process is steel billet electroslag remelting → billet annealing → billet surface cleaning → steel plate rolling → steel plate slow cooling → ultrasonic flaw detection → normalizing + tempering. The specific steps include: (1) Electroslag remelting: The round billet is used as the raw material, and the electroslag is remelted and solidified into an electroslag ingot as the billet; (2) Annealing of billets: ignite the soaking furnace and simmer for more than 3 hours. When the furnace gas temperature is ≤350℃, load the billets into the furnace and heat them to 800±(0-20)℃ at a heating rate of ≤35℃ / h. Keep them at this temperature for 5-8h. Cool them to 700±(0-20)℃ and keep them at this temperature for 7-10h. When the furnace cools to the furnace gas temperature of ≤350℃, open the furnace door. When the surface temperature of the billets is ≤200℃, take them out of the furnace for cleaning. When cleaning the billets, their surface temperature should be ≥150℃. (3) Rolling: The temperature of the soaking furnace is ≤300℃, the billet is loaded into the furnace and kept in the furnace for not less than 5h; after the end of the furnace, the temperature is raised to 650±(0-20)℃ at a rate of 20-30℃ / h, and kept at this temperature for 2-3h, and then raised to 800±(0-20)℃ at a rate of 30-50℃ / h, and kept at this temperature for 3-5h; finally, the temperature is raised to 1250±(0-20)℃ at a rate of 80-100℃ / h, and kept at this temperature for 10-12h, and the billet is sent to the descaling box for a rough descaling; the starting temperature of the rough rolling is not lower than 1080℃ to ensure high temperature and high reduction rolling, and the single-pass reduction rate of the last three passes of the rough rolling is ≥15%. After the rough rolling, it is directly rolled into the finishing mill without waiting for the temperature, and the thickness allowance is (+0.5,1.5) mm control, final correction of steel plate shape and adjustment of production size, after rolling, the steel plate temperature is ≥400℃, placed on a cooling bed, and then put into a slow cooling cover for slow cooling for more than 96 hours. After the slow cooling, ASME SA578-C+S1 is implemented for steel plate flaw detection; (4) Heat treatment: Normalizing: Normalizing temperature is 1040-1080℃, and the time in the furnace is ≥30min. After taking out of the furnace, it is cooled in still air to complete the martensitic structure transformation of the steel plate; tempering is carried out within 4 hours after normalizing the steel plate, the tempering temperature is 730-780℃, and the time in the furnace is ≥80min. After the heat treatment is completed, the desired steel plate is obtained.

2. The method according to claim 1, characterized in that: The production thickness of steel plates is 10 to 50 mm.

3. The method according to claim 1, characterized in that: The element composition of the billet is in percentage by mass: C: 0.08-0.12%, Mn: 0.30-0.60%, Si: 0.20-0.50%, P≤0.020%, S≤0.010%, Cr: 8.00-9.50%, Mo: 0.85-1.05%, Ni≤0.40%, V: 0.18-0.25%, Nb: 0.06-0.10%, N: 0.030-0.070%, Al≤0.020%, Ti≤0.010%, Zr≤0.010%, and the balance is Fe and unavoidable impurity elements.

4. The method according to claim 1, characterized in that: Ni 0.20~0.30%, Al 0.010~0.020%.

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