A steel plate for high-temperature resistant and highly homogeneous pressure vessels and its manufacturing method.

Abstract

The present invention discloses a high temperature resistant and high homogeneity steel plate for pressure vessels and a manufacturing method thereof. The main chemical components of the steel plate include C: 0.07%~0.11%, Si: 0.41%~0.49%, Mn: 0.67%~1.04%, Cr: 3.5%~4.6%, Mo: 1.6%~2.1%, Ti: 0.022%~0.029%, W: 0.11%~0.31%, etc. The two-stage TMCP is used, combined with normalizing + high temperature homogenization heat treatment, to obtain a 15~120mm thickness steel plate with room temperature: Rm≥710MPa, Rel≥530Mpa, A%≥22, -40℃: KV 2 (Transverse) ≥200J, 500℃: Rel≥340MPa, grain size 7~9, high homogeneity structure with the total inclusion grade ≤1.0; meets the manufacturing and application requirements of high-performance pressure vessel steel.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal materials, and in particular relates to a high-temperature resistant and high-homogeneity steel plate for a pressure vessel and a manufacturing method thereof. Background Art

[0002] The service environment of steel plates for pressure vessels is relatively complex, such as high temperature, high pressure, hydrogen, and acid-base environment. Therefore, when selecting the main material steel, the smelting, chemical composition, mechanical properties, metallographic structure and welding process of the steel must be strictly controlled. The ability of metal materials to resist high-temperature oxidation is called heat resistance or oxidation resistance; it requires that the metallographic structure of steel is stable under medium and high temperature conditions, otherwise graphitization may occur. When it contains heat-stable carbide-forming elements such as Cr, Mo, Ti and W, the decomposition temperature of cementite in steel can be increased, and graphitization can be prevented, thereby improving the high-temperature service performance of steel. As we all know, the performance of metal materials is closely related to the organization. The uniformity of the organization is a strong guarantee for the high performance of the material; refined organization can improve the strength and toughness of the steel plate, thereby improving the comprehensive service performance of the steel plate.

[0003] With the upgrading of domestic pressure-bearing manufacturing equipment, domestic petrochemical projects are developing in the direction of large-scale and high-performance. The performance of some traditional pressure-bearing equipment steels and the corresponding manufacturing methods can no longer meet the requirements of this development trend. In addition, although some grades can meet the project design requirements at this stage, there is still a need for upgrading in the long run. In addition, with the introduction of the "dual carbon" requirements, the manufacturing of high-performance pressure-bearing equipment steel has also attracted further attention. Therefore, it is urgent to develop a high-strength key material for pressure-bearing equipment that meets the room temperature strength, forming performance, and adapts to complex service environments (such as high temperature, high pressure, etc.) to support the development needs of my country's large-scale new energy equipment or equipment.

[0004] In the prior art, the invention patent with publication number CN104805380A provides a low temper brittleness Cr-Mo series high temperature resistant pressure equipment steel plate and preparation method, which adopts normalizing + tempering heat treatment method to produce thickness specification steel plate with thickness specification of 20~40mm, and does not study the thickness specification steel plate less than 20mm and greater than 40mm, and does not involve the content related to the control of organizational uniformity, and has a narrow scope of application, and the heat treatment process of the steel plate has low production efficiency and is not suitable for large-scale production. The invention patent with publication number CN117127124A provides a method for preparing austenitic stainless steel resistant to high and low temperatures, which is obtained through homogenization treatment, hot rolling, solution treatment, aging treatment, composite metal coating treatment, helium bombardment treatment and carbonitriding and other processes; the production process of the method is too complicated, and the composition design contains precious metals such as Zr, and the production cost is too high, which is not suitable for large-scale batch production application. Summary of the invention

[0005] In order to overcome the defects of the above-mentioned prior art, the present invention adopts a two-stage controlled rolling production and manufacturing process through a new chemical composition design, combined with normalizing + high-temperature homogenization treatment, to obtain a steel plate with room temperature tensile strength ≥710 MPa, yield strength ≥530 MPa, -40°C transverse impact energy KV2 ≥200 J, good high-temperature service performance, grain size of 7 to 9, and a highly homogeneous structure with a total inclusion grade of less than 1.0, that is, a (15 to 120) mm thickness steel plate with excellent strength, toughness, high-temperature service performance and plate shape, which meets the manufacturing and application requirements of high-performance pressure vessel steel.

[0006] In order to achieve the above-mentioned invention object, the present invention provides a high temperature resistant and highly homogeneous steel plate for pressure vessels, wherein the chemical composition mass content range of the steel plate is C: 0.07%~0.11%, Si: 0.41%~0.49%, Mn: 0.67%~1.04%, P≤0.015%, S≤0.01%, Cr: 3.5%~4.6%, Mo: 1.6%~2.1%, Ti: 0.022%~0.029%, W: 0.11%~0.31%, and the balance is Fe and unavoidable inclusions.

[0007] Furthermore, the steel plate for pressure vessels has a room temperature tensile strength of 710-820 MPa, a yield strength of 530-640 MPa, an elongation after fracture of 22≤A%≤30, and a transverse impact energy KV2≥200 J at -40°C.

[0008] Further, the steel plate for pressure vessel, when the steel plate test temperature is 50°C, the yield strength range is 415MPa~455MPa; when the steel plate test temperature is 100°C, the yield strength range is 411MPa~436MPa; when the steel plate test temperature is 150°C, the yield strength range is 401MPa~432MPa; when the steel plate test temperature is 200°C, the yield strength range is 396MPa~435MPa; when the steel plate test temperature is 250°C, the yield strength range is 385MPa~411MPa; when the steel plate test temperature is 300°C, the yield strength range is 383MPa~399MPa; when the steel plate test temperature is 350°C, the yield strength range is 372MPa~393MPa; when the steel plate test temperature is 400°C, the yield strength range is 368MPa~386MPa; when the steel plate test temperature is 450°C, the yield strength range is 361 MPa~373 MPa; when the test temperature of the steel plate is 500℃, the yield strength range is 340 MPa~368 MPa; the strength change trend is small in the test temperature range of 50℃~500℃, and the minimum yield strength value can still reach 340 MPa when the test temperature is 500℃, and the steel plate has excellent high temperature performance.

[0009] Furthermore, the grain size of the steel plate for pressure vessels is in the range of 7 to 9, and the total inclusion grade is below 1.0; 23 The particle sizes of C6, TiC and WC are in the range of 20~80 nm, and the volume percentage of TiC / WC is between 0.25~0.5; the thickness specification is 15~120 mm.

[0010] The reasons for limiting the amount of each chemical element such as C, Si, Mn, P, S, Cr, Mo, Ti, W in steel plates are detailed as follows:

[0011] C is the most important element in steel to improve its strength. If the content is too low, the performance of the steel plate after heat treatment cannot be guaranteed; however, if the carbon content is too high, the machining performance of the steel will be affected, and the supersaturated carbide will become the source of fracture cracks, affecting the toughness and plasticity of the steel plate, and also affecting the welding performance during subsequent use. Therefore, the present invention sets the C content range to 0.07%~0.11%.

[0012] Si acts as a reducing agent and deoxidizer during the steelmaking process. When the silicon content is too high, it is easy to form hard phase compounds, which increases the embrittlement sensitivity of the steel plate and the high-temperature heat treatment brittleness of the welding heat-affected zone, and is prone to cracks during later processing. Therefore, the present invention sets the Si content range to 0.41%~0.49%.

[0013] Mn can be infinitely dissolved with Fe, and is an element that strongly stabilizes austenite, and can strengthen pearlite structure. The effect of Mn and C, while improving the strength of steel, has relatively little effect on plasticity, and can reduce the lower critical point of steel, increase the supercooling when austenite is cooled, thereby refining the structure and improving the mechanical properties of the steel plate. In addition, the price is relatively cheap. However, too high a Mn content will increase the tendency of hard phase MnS inclusions in steel, so the present invention sets the Mn content range to 0.67%~1.04%.

[0014] S and P are harmful elements in steel and must be strictly controlled to ensure the purity and plasticity of the steel. It is known that MnS produced in steel will affect the strength and toughness of the steel plate, and the presence of P will increase the brittleness of the steel plate and have a negative impact on the welding performance. In order to strictly control the generation of harmful inclusions in the steel plate, the present invention is limited to P≤0.015%, S≤0.01%.

[0015] Cr is a stable carbide element, and its presence in steel can improve the hardenability of the steel plate. The Cr-containing carbide formed is relatively stable. When added in an appropriate amount, it can form second-phase particles with smaller size and uniform dispersion distribution, which has the effect of hindering the growth of grains in the steel plate, and significantly improves the strength of the steel plate and reduces the yield point. In addition, because it can still exist stably at high temperature stages, when a certain amount of Cr element is added to the steel, the high-temperature performance of the steel plate can also be significantly improved. Therefore, the present invention sets the Cr content range to 3.5%~4.6%.

[0016] Mo is a weak solid solution strengthening element. Its main function in steel is to increase the supercooling ability of austenite, thereby refining the structure and having a good effect on impact toughness and brittle transition temperature. In addition, the addition of molybdenum improves the tempering resistance or tempering stability of steel, allowing parts to be tempered at higher temperatures, thereby more effectively eliminating (or reducing) residual stress, improving plasticity, and strengthening the high-temperature performance of steel plates. It is used in combination with Cr in steel to ensure the thermal strength of the steel plate. However, excessive Mo has an adverse effect on the welding performance of the steel plate. The present invention sets the Mo content range to 1.6%~2.1%.

[0017] Ti is a strong carbide-forming element, which forms stable Ti (C, N) compound particles in steel. When it is heated in a high temperature section and exists in the form of a solid solution, it can significantly improve the hardenability of the steel plate. Before being dissolved, titanium carbide particles have the effect of preventing grain growth, thereby improving the strength of the steel. After normalizing, the small-sized carbides precipitated can significantly improve the plasticity and impact toughness of the steel. Ti also has a high affinity for O, and can strongly increase the A1 and A3 temperatures of the steel in steel. However, when the Ti content in the steel is too high, large-sized second-phase particles will be generated, increasing the brittleness of the steel plate. Therefore, the present invention controls the Ti content to 0.022%~0.029%.

[0018] W is a carbide stabilizing element. In addition to forming carbides in steel, it partially dissolves into iron to form a solid solution. When used in combination with Ti, the carbides formed are difficult to dissolve when heated, which can strongly hinder the growth of austenite grains, prevent overheating when the steel plate is heated, and improve the strength and toughness of the steel. At the same time, the critical nucleation size of carbonitrides in the austenite region, especially in the high-temperature region, is greatly reduced, the precipitation strengthening effect of carbonitrides is improved, and the high-temperature performance of steel is improved while ensuring the grain size. Therefore, in this technical solution, the volume percentage of TiC / WC in the steel plate matrix is ​​controlled to be between 0.25 and 0.5; considering that the element W is relatively expensive, the content of W is controlled to be within the range of 0.11% to 0.31%.

[0019] A method for manufacturing the above-mentioned high-temperature resistant and high-homogeneity steel plate for pressure vessels, the method comprising the following processes: molten iron pretreatment - converter smelting - refining outside the furnace (LF) - vacuum degassing (VD) - slab heating - controlled rolling and controlled cooling - heat treatment (normalizing treatment - high-temperature homogenization treatment) - flaw detection - inspection. The advanced molten iron pretreatment + efficient slab heating process + two-stage controlled rolling and controlled cold rolling method + two-stage heat treatment process (normalizing treatment - high-temperature homogenization treatment) system is used to produce a pressure vessel steel plate with a thickness of 15 to 120 mm. The steel plate has a uniform and pure structure, a good strength and toughness match, and excellent high-temperature service performance.

[0020] In the above technical scheme, further, the molten iron pretreatment process: in order to improve the smelting efficiency, the molten steel smelting is selected to be carried out in a converter. In order to reduce production costs, high-quality scrap steel and molten iron are used as raw materials, and the molten iron content is controlled at 76%~79%. In order to ensure that the subsequent steel plate structure is uniform and fine, the molten iron is pre-spheroidized. In order to reduce the burning loss and slag amount and reduce the manufacturing cost of the core wire, a cored wire with a Mg content of 28%~32% is selected; in order to reduce the loss of steel plates during production and prevent molten iron from splashing, the height-to-diameter ratio of the molten iron column should be between 1.3~1.4; in order to ensure the spheroidization efficiency and the dense uniformity of the subsequent structure, the wire feeding length is controlled at 26~29 m, and the wire feeding speed is controlled at 28~34 m / min.

[0021] Furthermore, the converter smelting process: in order to ensure the purity of steel, effectively control the content of harmful element P, and ensure the efficiency of decarburization, dephosphorization and decarburization are carried out separately in a converter, wherein the dephosphorization oxygen blowing time is controlled at 8-11 min, and the decarburization oxygen blowing time is controlled at 9-13 min, and finally the P mass fraction is reduced to less than 0.008%; deep desulfurization treatment is carried out in the LF refining furnace, and the sulfur content is strictly controlled below 0.004%; degassing is completed in the VD furnace, the net cycle time is 11-16 min, and the calming time before pouring is 3-7 min.

[0022] Furthermore, the heating process: the continuous casting slab is sent to the heating furnace for heating. Under the premise of ensuring the internal quality of the steel plate, the heating efficiency is improved, and the two-stage heating method of the cast slab is selected, the first stage is 986℃~1000℃, and the insulation time is 2.1~3.3 h; the second stage heating temperature range is 1175℃~1231℃, and the slab insulation time is controlled at 1.3~1.9 h. When the heating temperature is lower than 1175℃, the coarse precipitates in the continuous casting slab cannot be dissolved, the steel plate is not completely austenitized, and the final rolling temperature of the first stage cannot be guaranteed; when the heating temperature is higher than 1231℃ and the heating time in the high temperature section is too long, it is easy to cause the fine precipitates in the continuous casting slab to dissolve again and cause excessive grain growth.

[0023] Furthermore, the rolling process adopts two-stage controlled rolling and controlled cooling, the first stage is rolling in the recrystallization zone, the starting rolling temperature is 1210℃~1230℃, the final rolling temperature is 1100℃~1125℃, the original austenite structure is fully refined, large deformation rapid rolling is adopted, and the single-pass reduction is controlled at 7%~10%; the second stage is rolling in the non-recrystallization zone, the starting rolling temperature is 919℃~935℃, the final rolling temperature is 840℃~860℃, the total reduction is controlled at 40%~52%, and small deformation multi-pass rapid rolling is adopted. At this time, the austenite grains are further flattened and elongated, and the grains are fully refined as the grain boundary area increases; then ACC laminar flow rapid cooling is carried out to room temperature, wherein the starting cooling temperature is controlled at 720℃~780℃, and the cooling rate is controlled at 51℃ / s~62℃ / s, thereby further refining the grains and improving the uniformity of the structure.

[0024] Further, the heat treatment process: due to the addition of C, Si, Mn, P, S, Cr, Mo, Ti, W and other elements to the steel, the steel plate can obtain a ferrite + pearlite structure with excellent strength and toughness after rolling. However, the grain size distribution of the steel plate is uneven, there is concentration of organizational stress and thermal stress, and delayed cracks are easily generated during flame cutting. Therefore, heat treatment should be used in time to homogenize the structure, soften and eliminate stress. In order to further control the internal structure of the steel plate and ensure high production efficiency at the same time, the present invention adopts a combination of normalizing treatment and high-temperature homogenization treatment, which ensures that the strength of the steel plate is not lost while making it have suitable plastic toughness, high-temperature service performance, and good processing performance. Therefore, the first stage of normalizing treatment: control the temperature at 870℃~920℃, and keep warm for 10~30 min; the second stage adopts high-temperature homogenization treatment: control the temperature at 580℃~610℃, and keep warm for 1.5~3 h.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] ① On the basis of strengthening elements of C, Si, and Mn, by adding appropriate amounts of alloying elements of Cr, Mo, Ti, and W, while strictly controlling the content of harmful elements P and S, combined with production process optimization, a refined and pure microstructure is obtained, with uniform fine particle size of 20~80 nm and dispersed second phase Cr 23 C6, TiC, WC particles, and the volume percentage of TiC / WC in the steel plate matrix is ​​between 0.25 and 0.5, which ensures the strength and plasticity of the steel plate.

[0027] ②When the test temperature of the steel plate is 50℃, the yield strength range is 415 MPa~455 MPa; when the test temperature of the steel plate is 100℃, the yield strength range is 411 MPa~436 MPa; when the test temperature of the steel plate is 150℃, the yield strength range is 401 MPa~432 MPa; when the test temperature of the steel plate is 200℃, the yield strength range is 396 MPa~435 MPa; when the test temperature of the steel plate is 250℃, the yield strength range is 385 MPa~411 MPa; when the test temperature of the steel plate is 300℃, the yield strength range is 383 MPa~399 MPa; when the test temperature of the steel plate is 350℃, the yield strength range is 372 MPa~393 MPa; when the test temperature of the steel plate is 400℃, the yield strength range is 368 MPa~386 MPa; when the test temperature of the steel plate is 450℃, the yield strength range is 361 MPa~373 MPa; when the test temperature of the steel plate is 500℃, the yield strength ranges from 340 MPa to 368 MPa; the strength variation trend is small in the test temperature range of 50℃ to 500℃, and the minimum yield strength value can still reach 340 MPa when the test temperature is 500℃, and the steel plate has excellent high temperature performance.

[0028] ③ The high-homogeneity high-temperature resistant pressure vessel steel plate obtained through a unique production process has mechanical properties such as 710 MPa≤Rm≤820 MPa, 530 MPa≤Rel≤640 MPa at room temperature, 22≤ elongation after break A%≤30, -40℃: KV2≥200 J, and excellent high-temperature service performance.

[0029] ④ The present invention produces a steel plate with a thickness of (15-120) mm and excellent plate shape, which can meet the manufacturing and application requirements of high-performance pressure vessel steel. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with specific examples, but the present invention is not limited in any way. To avoid redundant description, the raw materials in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0031] A high-temperature resistant and highly homogeneous steel plate for a pressure vessel, wherein the chemical composition mass content of the steel plate is in the range of C: 0.07%-0.11%, Si: 0.41%-0.49%, Mn: 0.67%-1.04%, P≤0.015%, S≤0.01%, Cr: 3.5%-4.6%, Mo: 1.6%-2.1%, Ti: 0.022%-0.029%, W: 0.11%-0.31%, and the remainder is Fe and unavoidable inclusions.

[0032] A method for manufacturing the above-mentioned high-temperature resistant and high-homogeneity steel plate for pressure vessels, the method comprising the following processes: molten iron pretreatment, converter smelting, refining outside the furnace, vacuum degassing, slab heating, rolling, heat treatment, flaw detection, and inspection;

[0033] The molten iron pretreatment process uses scrap steel and molten iron as raw materials, and pre-spheroidizes the molten iron. The molten iron content is controlled at 76% to 79%, and the height-to-diameter ratio of the molten iron column is between 1.3 and 1.4.

[0034] The converter smelting process: dephosphorization and decarburization are carried out separately, the dephosphorization oxygen blowing is controlled at 8-11 min, and the decarburization oxygen blowing is controlled at 9-13 min, and finally the P mass fraction is reduced to less than 0.008%;

[0035] The slab heating process is as follows: the slab is heated in two stages, the first stage is 986°C~1000°C, and the temperature is kept for 2.1~3.3h; the second stage heating temperature range is 1175°C~1231°C, and the slab insulation time is controlled at 1.3~1.9h;

[0036] The rolling process adopts two-stage controlled rolling and controlled cooling, wherein the first stage is rolling in the recrystallization zone, the start rolling temperature is 1210°C to 1230°C, the final rolling temperature is 1100°C to 1125°C, and the single-pass reduction is controlled at 7% to 10%; the second stage is rolling in the non-recrystallization zone, the start rolling temperature is 919°C to 935°C, the final rolling temperature is 840°C to 860°C, and the total reduction is controlled at 40% to 52%; after rolling, ACC laminar flow rapid cooling is performed to room temperature, the start cooling temperature is controlled at 720°C to 780°C, and the cooling rate is controlled at 51°C / s to 62°C / s;

[0037] The heat treatment process adopts a combination of normalizing treatment and high-temperature homogenization treatment. In the first stage of normalizing treatment, the temperature is controlled at 870°C~920°C and kept warm for 10~30 minutes. In the second stage, high-temperature homogenization treatment is adopted: the temperature is controlled at 580°C~610°C and kept warm for 1.5~3 hours.

[0038] The matters not described in the following embodiments are the same as the description of the above specific implementation methods.

[0039] Example

[0040] A high-temperature resistant and highly homogeneous steel plate for pressure vessels. The chemical composition mass contents of the steel plates for pressure vessels in Examples 1-10 are shown in Table 1.

[0041] Table 1 Chemical composition of steel plates of Examples 1-10 (wt, %)

[0042] Thickness / mm C Si Mn P S Cr Mo Ti W Example 1 16 0.075 0.41 0.68 0.010 0.008 3.51 1.68 0.025 0.31 Example 2 22 0.078 0.42 0.81 0.011 0.006 3.62 1.89 0.028 0.24 Example 3 24 0.106 0.46 0.88 0.009 0.007 4.45 2.08 0.024 0.22 Example 4 34 0.104 0.43 0.89 0.011 0.006 4.28 2.06 0.026 0.28 Example 5 40 0.102 0.49 0.85 0.012 0.005 4.37 1.73 0.023 0.11 Example 6 52 0.085 0.42 0.73 0.008 0.008 4.60 2.04 0.026 0.30 Example 7 78 0.084 0.45 0.71 0.009 0.005 3.83 2.02 0.025 0.27 Example 8 86 0.091 0.46 0.76 0.008 0.007 3.92 1.98 0.023 0.12 Example 9 102 0.093 0.45 0.67 0.010 0.004 4.02 1.99 0.022 0.16 Example 10 120 0.109 0.41 0.75 0.008 0.005 4.56 1.96 0.023 0.19

[0043] A method for manufacturing the above-mentioned high-temperature resistant and high-homogeneity steel plate for pressure vessels adopts a combination of advanced molten iron pretreatment + efficient ingot heating process + two-stage controlled rolling and controlled cold rolling + two-stage heat treatment process (normalizing treatment-high-temperature homogenization treatment). The specific process flow is as follows.

[0044] The hot metal pretreatment and smelting process parameters of the steel of Example 1-10 are shown in Table 2, wherein the Mg content of the cored wire selected in the hot metal pretreatment process is 28% to 32%, the wire feeding length is controlled at 26 to 29 m, and the wire feeding speed is controlled at 28 to 34 m / min. The LF refining furnace is subjected to deep desulfurization treatment, and the sulfur content is controlled below 0.004%; degassing is completed in the VD furnace, the net cycle time is 11 to 16 min, and the calming time before pouring is 3 to 7 min.

[0045] Table 2 Hot metal pretreatment and smelting process parameters of Examples 1-10

[0046] Example 1 2 3 4 5 6 7 8 9 10 Hot metal content / % 78 76 78 79 76 77 78 77 79 76 Mg content of cored wire / % 29 31 30 30 29 31 28 30 29 28 Height-to-diameter ratio of liquid iron column 1.32 1.34 1.33 1.37 1.35 1.38 1.40 1.39 1.36 1.34 Feeding line length / m 26 28 27 29 28 26 27 26 28 29 Feeding speed / (m / min) 29 32 31 33 30 28 31 29 31 32 Decarburization oxygen blowing time / min 11 10 12 9 10 9 11 9 10 12 Dephosphorization oxygen blowing time / min 11 11 9 10 10 8 10 8 11 9 Net cycle time / min 12 11 14 13 12 15 16 12 13 11 Sedation time / min 3 5 6 6 6 7 5 4 6 4

[0047] The heating process parameters of the continuous casting billet of Example 1-10 are shown in Table 3. The billet is heated in two stages, with the first stage at 986°C~1000°C and insulation for 2.1~3.3 h; the second stage heating temperature range is 1175°C~1231°C, and the insulation time of the second stage is controlled at 1.3~1.9 h.

[0048] Table 3 Continuous casting slab heating process parameters of Examples 1-10

[0049] Finished product thickness / mm Temperature of a heating section / ℃ One heating section insulation time / h Second heating section temperature / ℃ Second heating section insulation time / h Example 1 16 990 2.2 1230 1.8 Example 2 22 998 2.3 1223 1.9 Example 3 24 987 2.3 1178 1.5 Example 4 34 988 2.9 1186 1.8 Example 5 40 996 3.2 1198 1.5 Example 6 52 992 2.7 1211 1.3 Example 7 78 1000 2.3 1216 1.5 Example 8 86 989 2.6 1223 1.9 Example 9 102 995 2.4 1225 1.8 Example 10 120 994 3.1 1209 1.7

[0050] The rolling parameters of the steels of Examples 1-10 are shown in Table 4. After rolling, ACC laminar flow rapid cooling to room temperature was performed, the cooling temperature was controlled at 720°C-780°C, and the cooling rate was controlled at 51°C / s-62°C / s.

[0051] Table 4 Rolling process parameters of Examples 1-10

[0052]

[0053] The heat treatment process parameters of the steels of Examples 1-10 are shown in Table 5. Normalizing treatment-high temperature homogenization treatment is adopted to ensure that the strength of the steel plate is not lost while having suitable plasticity, high temperature service performance, and good processing performance.

[0054] Table 5 Heat treatment process parameters of steels in Examples 1-10

[0055]

[0056] The mechanical properties test results of the high temperature resistant and high homogeneity pressure vessel steel plates obtained in Examples 1-10 are shown in Table 6. The room temperature tensile strength of the steel plates is 710-820 MPa, the yield strength is 530-640 MPa, the elongation after fracture is 22≤A%≤30, and the transverse impact energy KV2≥200 J at -40°C.

[0057] Table 6 Mechanical properties test results of steel plates obtained in Examples 1-10

[0058]

[0059] The high temperature tensile properties test results of the high temperature resistant and highly homogeneous pressure vessel steel plates obtained in Examples 1-10 are shown in Table 7. When the test temperature of the steel plate is 50℃, the yield strength range is 415 MPa~455 MPa; when the test temperature of the steel plate is 100℃, the yield strength range is 411 MPa~436 MPa; when the test temperature of the steel plate is 150℃, the yield strength range is 401 MPa~432MPa; when the test temperature of the steel plate is 200℃, the yield strength range is 396 MPa~435 MPa; when the test temperature of the steel plate is 250℃, the yield strength range is 385 MPa~411 MPa; when the test temperature of the steel plate is 300℃, the yield strength range is 383 MPa~399MPa; when the test temperature of the steel plate is 350℃, the yield strength range is 372 MPa~393 MPa; when the test temperature of the steel plate is 400℃, the yield strength range is 368 MPa~386 MPa; when the test temperature of the steel plate is 450℃, the yield strength range is 361 MPa~373MPa; when the test temperature of the steel plate is 500℃, the yield strength range is 340 MPa~368 MPa; the strength change trend is small in the test temperature range of 50℃~500℃, and the minimum yield strength value can still reach 340 MPa when the test temperature is 500℃, and the steel plate has excellent high temperature performance.

[0060] Table 7 High temperature tensile properties test results of the steel plates obtained in Examples 1-10 (unit: MPa)

[0061]

[0062] The results of the evaluation test on the grain size and inclusion grade of the steel plate for high temperature resistant and high homogeneity pressure vessel prepared in Example 1-10 are shown in Tables 8-9. The grain size of the steel plate is in the range of 7 to 9, the total inclusion grade is below 1.0, the uniform fine particle size is in the range of 20 to 80 nm, and the dispersed second phase Cr 23 C6, TiC, WC particles, and the volume percentage of TiC / WC in the steel plate matrix is ​​between 0.25 and 0.5.

[0063] Table 8 Test results of grain size of steel plates obtained in Examples 1-10

[0064]

[0065] Table 9 Test results of structural inclusion grade evaluation of steel plates obtained in Examples 1-10

[0066]

[0067] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A high temperature resistant and high homogeneity steel plate for pressure vessels, characterized in that: The chemical composition of the steel plate is as follows: C: 0.07%~0.093%, Si: 0.41%~0.49%, Mn: 0.67%~0.89%, P≤0.015%, S≤0.01%, Cr: 3.51%~4.60%, Mo: 1.6%~2.1%, Ti: 0.022%~0.029%, W: 0.11%~0.31%, and the balance is Fe and unavoidable inclusions; The manufacturing method of the high temperature resistant and high homogeneity pressure vessel steel plate comprises the following processes: molten iron pretreatment, converter smelting, refining outside the furnace, vacuum degassing, slab heating, rolling, and heat treatment; The molten iron pretreatment process uses scrap steel and molten iron as raw materials, pre-spheroidizes the molten iron, controls the molten iron content to 76%-79%, and the height-to-diameter ratio of the molten iron column is between 1.3 and 1.4; the Mg content of the selected cored wire is 28%-32%, the wire feeding length is controlled at 26-29 m, and the wire feeding speed is controlled at 28-34 m / min; The converter smelting process: dephosphorization and decarburization are carried out separately, the dephosphorization oxygen blowing is controlled at 8-11 min, and the decarburization oxygen blowing is controlled at 9-13 min, and finally the P mass fraction is reduced to less than 0.008%; In the off-furnace refining process, the LF refining furnace performs deep desulfurization treatment, and the sulfur content is controlled below 0.004%; degassing is completed in the VD furnace, the net cycle time is 11-16 minutes, and the calming time before pouring is 3-7 minutes; The slab heating process is as follows: the slab is heated in two stages, the first stage is 986°C~1000°C, and the temperature is kept for 2.1~3.3 hours; the second stage heating temperature range is 1175°C~1231°C, and the slab insulation time is controlled at 1.3~1.9 hours; The rolling process adopts two-stage controlled rolling and controlled cooling, wherein the first stage is rolling in the recrystallization zone, the start rolling temperature is 1210°C to 1230°C, the final rolling temperature is 1100°C to 1125°C, and the single-pass reduction is controlled at 7% to 10%; the second stage is rolling in the non-recrystallization zone, the start rolling temperature is 919°C to 935°C, the final rolling temperature is 840°C to 860°C, and the total reduction is controlled at 40% to 52%; after rolling, ACC laminar flow rapid cooling is performed to room temperature, the start cooling temperature is controlled at 720°C to 780°C, and the cooling rate is controlled at 51°C / s to 62°C / s; The heat treatment process adopts a combination of normalizing treatment and high-temperature homogenization treatment. In the first stage of normalizing treatment, the temperature is controlled at 870°C to 920°C and kept warm for 10 to 30 minutes. In the second stage, high-temperature homogenization treatment is adopted, the temperature is controlled at 580°C to 610°C and kept warm for 1.5 to 3 hours. When the test temperature is 50°C, the yield strength of the steel plate is 415-455 MPa; when the test temperature is 100°C, the yield strength is 411-436 MPa; when the test temperature is 150°C, the yield strength is 401-432 MPa; when the test temperature is 200°C, the yield strength is 396-435 MPa; when the test temperature is 250°C, the yield strength is 385-411 MPa; when the test temperature is 300°C, the yield strength is 383-399 MPa; when the test temperature is 350°C, the yield strength is 372-393 MPa; when the test temperature is 400°C, the yield strength is 368-386 MPa; when the test temperature is 450°C, the yield strength is 361-373 MPa; when the test temperature is 500°C, the yield strength is 340-368 MPa; The grain size of the steel plate is between 7 and 9, and the total inclusion grade is below 1.0; the Cr in the steel plate matrix 23 The particle sizes of C6, TiC and WC are 20~80 nm, and the volume percentage of TiC / WC is between 0.25~0.5; the thickness specification is 15~120 mm.

2. The steel plate for pressure vessel according to claim 1, characterized in that: The steel plate has a room temperature tensile strength of 710-820 MPa, a yield strength of 530-640 MPa, an elongation after fracture of 22≤A%≤30, and a transverse impact energy KV2≥200 J at -40°C.

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