Heavy Plate for Pressure Equipment at 1100 MPa Level, Manufacturing, Forming and Post-Heat Treatment Method

Abstract

The present invention provides a thick steel plate for pressure-bearing equipment at 1100 MPa level, a manufacturing method, a forming method and a post-heat treatment method thereof; the composition of the steel plate is as follows by weight percentage: C 0.17% - 0.21%, Si 0.20% - 0.35%, Mn 0.45% - 0.70%, P ≤ 0.010%, S ≤ 0.003%, Cr 0.85% - 1.20%, Mo 0.45% - 0.60%, Ni 1.15% - 1.30%, B 0.001% - 0.005%, Alt 0.015% - 0.045%, and the balance is Fe and inevitable inclusions; the manufacturing method includes smelting, continuous casting, heating, controlled rolling, controlled cooling, and heat treatment. After the steel plate is hot formed and post-heat treated, (10 - 30) nm grade (Fe, Mn, Cr, Mo)23C6, Mo2C second-phase particles and borides are precipitated in the microstructure of the steel, and their volume percentage content accounts for 15% - 20% of the tissue.

Description

Technical Field

[0001] The present invention belongs to the field of metal materials, and particularly relates to a thick steel plate for pressure-bearing equipment with a strength level of 1100 MPa, its manufacturing, forming and subsequent heat treatment methods. Background Art

[0002] In the fields of clean energy production such as hydropower and hydrogen energy, pressure-bearing equipment, as an important place for medium transmission, storage and transportation, plays an important role in the entire production process chain. For example, when the water in the hydropower station reservoir falls, it generates a huge impact force on the equipment, and high-concentration compressed hydrogen generates a huge internal pressure on the equipment. At this time, the pressure can reach more than 60 MPa. The special equipment industry defines this as ultra-high pressure, and the tensile strength of the steel used to manufacture such equipment is 1100 MPa. In recent years, in order to meet the high-speed development of the pressure-bearing equipment manufacturing industry, pressure-bearing equipment with high-efficiency, high-parameter and high-reliability design requirements has been proposed by design institutes. The steel materials for pressure-bearing equipment with the existing strength levels can no longer meet the design requirements, and ultra-high strength and toughness materials are needed to support the development of high-end equipment.

[0003] For the disclosed invention patent "A Steel for Nuclear Power Pressure-bearing Equipment and Its Manufacturing Method" (publication number CN103160732A), judging from the disclosed composition, production method and beneficial effects, this patent is a steel for pressure-bearing equipment applied in the nuclear power field, and the tensile strength of its steel plate is in the range of 560 - 625 N / mm 2 After simulated post-weld heat treatment, the tensile strength drops to 510 - 600 N / mm 2 In the face of a service environment with higher pressure, this product cannot provide higher strength to support the equipment requirements. In particular, it does not provide a technical solution and data support after forming to show that it has sufficient strength to meet the high-pressure service requirements.

[0004] For the disclosed invention patent "A Hot-rolled Weldable Steel Plate for Pressure-bearing Equipment and Its Production Method" (publication number CN110983175A), judging from the disclosed composition, production method and beneficial effects, the tensile strength of the steel plate involved in this patent in the as-supplied state and the simulated post-weld heat treatment state is 450 - 610 MPa, and its microstructure consists of ferrite and pearlite with relatively low strength. In the face of a service environment with higher pressure, this product cannot provide higher strength to support the equipment requirements. In particular, it does not provide a technical solution and data support after forming to show that it has sufficient strength to meet the high-pressure service requirements.

[0005] The published invention patent "Production Method of Thick Steel Plate for 1100MPa Grade Heavy Machinery Crane Arm" (Publication No. CN113637900A). From the disclosed composition, production method and beneficial effects, although the tensile strength of the patented product reaches 1100MPa, its plastic toughness is poor, the thickness is only 14 - 30mm, and it is mainly applicable to the construction machinery field. Moreover, there are no relevant technical solutions and data after forming to support that it has sufficient strength to meet the requirements of ultra-high pressure service.

[0006] The strength of the above-mentioned invention and the existing steel for pressure-bearing equipment before and after forming can no longer meet the development needs of large-scale and high-parameter pressure-bearing equipment in clean energy such as hydropower and hydrogen energy. Therefore, there is an urgent need to develop high-strength key materials for pressure-bearing equipment with a thickness specification of (40 - 80)mm and having ultra-high strength at room temperature, high strength at high temperature and good plastic toughness after forming, so as to support the development needs of new and high-parameter pressure-bearing equipment or equipment in the energy field of our country. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of insufficient strength of the above-mentioned invention or the inability to provide a technical solution to improve the strength after forming of high-strength pressure-bearing equipment, and to provide a steel plate with a thickness specification of (40 - 80)mm, a steel product for pressure-bearing equipment with a tensile strength of 1100MPa grade after forming, its manufacturing, forming and subsequent heat treatment processes, so as to meet the manufacturing of high-strength pressure-bearing equipment.

[0008] The purpose of the present invention is achieved as follows:

[0009] A thick steel plate for pressure-bearing equipment, the composition of the steel plate is as follows by weight percentage: C 0.17% - 0.21%, Si 0.20% - 0.35%, Mn 0.45% - 0.70%, P ≤ 0.010%, S ≤ 0.003%, Cr 0.85% - 1.20%, Mo 0.45% - 0.60%, Ni 1.15% - 1.30%, B 0.001% - 0.005%, Alt 0.015% - 0.045%, and the balance is Fe and unavoidable inclusions.

[0010] The thickness of the thick steel plate for pressure-bearing equipment is 40 - 80mm.

[0011] The mechanical properties of the thick steel plate for pressure-bearing equipment are 800MPa ≤ R p0.2 ≤ 930MPa, 1100MPa ≤ R m ≤ 1200MPa, and the impact energy at -20°C is KV 2 ≥ 100J.

[0012] The reasons for the composition design of the present invention are as follows:

[0013] C is the most important element for improving the strength of steel. By adding element C, the hardenability of steel is significantly improved. In addition, in the present invention, C combines with strong carbide alloying elements in the steel to play a role in precipitation strengthening, obtaining a secondary hardening effect and ensuring the high-strength requirement of the steel. When the carbon content is lower than 0.13%, the hardenability is relatively low, and it is difficult to obtain a uniform tempered martensite structure during subsequent tempering treatment, and the strength of the steel cannot meet the usage requirements. However, too high a carbon content will affect the machining performance of the steel. Therefore, in the present invention, the carbon content range is limited to 0.17% - 0.21%.

[0014] Si acts as a reducing agent and deoxidizer during steelmaking. Si has a certain influence on the martensite transformation during the tempering process. When the silicon content is higher than 0.5%, it will hinder the activity of C in martensite during the tempering process, causing ε-carbide to form in the martensitic steel instead of M 3 C-type carbide, reducing the hardness and toughness of the steel and increasing the sensitivity to temper brittleness. Therefore, in the present invention, the Si content range is limited to 0.20% - 0.35%.

[0015] Mn is an element that strongly stabilizes austenite. It can effectively reduce the decomposition rate of austenite, improve the hardenability of steel, and strongly increase the strength and hardness of the steel. However, a high Mn content will enhance the temper brittleness of the steel. Therefore, in the present invention, the Mn content range is limited to 0.45% - 0.70%.

[0016] S and P are harmful elements in steel. To ensure the purity, plasticity and toughness of the steel quality, they must be strictly controlled. Therefore, in the present invention, it is limited that S ≤ 0.003% and P ≤ 0.010%.

[0017] Adding a certain amount of Cr to the steel significantly improves the hardenability of the steel and ensures the matrix strength of the steel. In addition, Cr is a strong carbide-forming element. It forms stable carbides with C in the steel, playing a role in improving the pressure-bearing capacity of the pressure-bearing equipment. When the content of Cr is lower than 0.3%, the improvement of hardenability is very small, which is not conducive to the formation of lath martensite structure and cannot meet the high-strength performance requirements of the steel. Therefore, in the present invention, the Cr content range is limited to 0.85% - 1.20%.

[0018] Mo can improve the hardenability of steel, effectively refine the austenite grains, and also strengthen the solid solution strengthening effect of ferrite. Adding a certain amount of Mo can improve the tempering resistance of steel and play a role in suppressing temper embrittlement. At the same time, molybdenum is a strong carbide-forming element. The Mo 2 C carbide formed during tempering has a secondary hardening effect. Therefore, in the present invention, the Mo content range is limited to 0.45% - 0.60%.

[0019] Ni is an alloying element that expands the austenite region. It has the effect of refining ferrite grains and, while ensuring strength, does not reduce the plasticity and toughness of the steel, especially the low-temperature toughness. However, since Ni belongs to precious metal elements, considering the cost performance, the Ni content range in this invention is limited to 1.15% - 1.30%.

[0020] B mainly increases the hardenability of the steel. At the same time, by using the high-hardness borides formed by boron, the strength of the steel is improved. However, when the boron content exceeds 0.007%, it will cause hot brittleness of the steel, affecting the forming and processing performance of pressure-bearing equipment. The B content range in this invention is limited to 0.001% - 0.005%.

[0021] Alt is a commonly used deoxidizer in steel. Adding a small amount of aluminum can refine the grains and improve the strength and impact toughness of the steel. Excessive amounts, however, will affect the hot working performance, welding performance, and machining performance of the steel. The Alt content range in this invention is limited to 0.015% - 0.045%.

[0022] The second technical solution of this invention is to provide a manufacturing method for thick steel plates for 1100 MPa grade pressure-bearing equipment, including smelting, continuous casting, heating, controlled rolling, controlled cooling, and heat treatment;

[0023] Smelting: including hot metal pretreatment - converter dephosphorization - converter decarburization - secondary refining - vacuum degassing - slab continuous casting - stacking slow cooling - billet cleaning - heating - rolling - hot straightening - slow cooling - heat treatment - flaw detection - inspection and testing.

[0024] The steelmaking is carried out in a converter, using high-quality scrap steel and hot metal as raw materials. The hot metal content is controlled at 75 - 85%. At the same time, to effectively reduce the content of harmful element P, dephosphorization and decarburization are carried out separately in the converter. Among them, the oxygen blowing for dephosphorization is controlled at 7 - 10 min, and the oxygen blowing for decarburization is controlled at 8 - 12 min. Finally, the phosphorus mass fraction is reduced to less than 0.006%; deep desulfurization treatment is carried out in the LF refining furnace, and the sulfur content is controlled below 0.002%; degassing is completed in the VD furnace, with a net circulation time of 10 - 15 min and a pre-tapping calming time of 3 - 5 min.

[0025] Casting process: After breaking the vacuum, slab continuous casting machine is used for casting. The superheat is set at 20 - 30°C, and the casting speed during pouring is 1.0 - 1.4 m / min. The cast billet is taken offline for stacking slow cooling, with a stacking slow cooling time of 24 - 36 h and unstacking below 400°C to prevent defects such as cracks in the cast billet caused by rapid cooling.

[0026] Heating: The heating temperature is controlled at 1180 - 1230°C, and the total heating duration is 4.0 - 6.0 hours.

[0027] Controlled rolling: The rolling process adopts a two-stage controlled rolling method. The finishing temperature in the recrystallization zone is ≥1000 °C, and in order to fully fragmentize the structure of the billet core, the total deformation rate is ≥50%. The starting rolling temperature in the non-recrystallization zone is 870 - 930 °C, the finishing rolling temperature is 820 - 870 °C, and the total deformation rate is ≥55%. At this time, the austenite grains are further flattened and elongated. With the increase in the grain boundary area, the nucleation rate of ferrite increases during the subsequent phase transformation process, and the grains are fully refined. The target thickness of the rolled piece is (40 - 80) mm.

[0028] Controlled cooling: To further refine the internal structure of thick-gauge steel plates, a controlled cooling process is adopted for the rolled steel plates. The starting cooling temperature is 800 - 840 °C, the cooling rate is 20 - 30 °C / s, and the reheat temperature is 500 - 550 °C.

[0029] Heat treatment: Since a large amount of solid solution strengthening elements such as C, Mn, Cr, Mo, and Ni are added to the steel, a lath martensite structure with ultra-high strength and hardness can be obtained after rolling the steel plates. However, the grain size of the steel plates is large, and there are concentration of structure stress and thermal stress, which are prone to produce delayed cracks during flame cutting. Therefore, heat treatment should be carried out in a timely manner for softening and stress elimination. The present invention adopts tempering heat treatment to ensure that the strength of the pressure-bearing steel plates is not lost, and at the same time, the steel plates have appropriate plasticity and toughness, which is beneficial to the forming process of the steel plates. Therefore, the tempering heat treatment temperature of the steel is 650 - 700 °C, and the net holding time is 2.0 - 4.0 min / mm.

[0030] The third technical solution of the present invention is to provide a forming process for thick steel plates used in 1100 MPa-class pressure-bearing equipment;

[0031] Steel plate forming process: Hot forming is an essential process for manufacturing pressure-bearing equipment with steel plates. The forming process not only gives it the shape required for the equipment, but also is an important means to improve the final strength of the pressure-bearing equipment. The present invention has formulated the optimal forming heat treatment process for the steel.

[0032] The set parameters and reasons are as follows: In the forming process, it is heated and held at a temperature of 930 - 960 °C, the net holding time is 1.0 - 2.0 min / mm, and after being taken out of the furnace, it is cooled to room temperature in a salt bath. During this process, chemical elements such as C, Mn, Cr, Mo, Ni and alloying elements such as B enter the austenite region. After a period of holding, the alloying elements are dissolved in the austenite matrix, and then it enters a salt bath at 0 - 10 °C and is rapidly cooled at a cooling rate of 30 - 55 °C / s to transform into a fine lath martensite structure. At this time, the steel has ultra-high strength and meets the requirements of pressure-bearing equipment. However, at this time, the plasticity and toughness of the steel are poor and the structure stress is high. By means of short-time tempering heat treatment at 470 - 500 °C for 0.5 - 1.0 h, the quenching stress is eliminated in a timely manner, the structure is softened, and the plasticity and toughness of the steel are improved, thus completing the forming process of the steel. At this time, the microstructure of the steel is tempered martensite.

[0033] The fourth technical solution of the present invention provides a method for post - forming heat treatment of a thick steel plate for pressure - bearing equipment with a strength level of 1100 MPa; to ensure the ultra - high strength and excellent plasticity and toughness of the steel for pressure - bearing equipment, it is also necessary to obtain by further adjusting the size and type of the second - phase particles in the steel, that is, secondary hardening heat treatment. The process is 500 - 530 °C, holding for 2.0 - 4.0 h. At this time, a large number of (Fe, Mn, Cr, Mo) 23 C 6 and Mo 2 C second - phase particles and high - hardness borides are precipitated dispersively in the steel, and the proportion of the structure is 15% - 20%, and the rest is martensite; the (Fe, Mn, Cr, Mo) 23 C 6 and Mo 2 C second - phase particles and high - hardness borides interact with the high - density dislocations in martensite, improving the strength and plasticity of the matrix and ensuring the use requirements of high - strength pressure - bearing equipment.

[0034] The beneficial effects of the present invention are as follows:

[0035] (1) Based on the strengthening elements of C, Si, and Mn, by compounding and adding alloying elements of Cr, Mo, Ni, and B, and strictly controlling the contents of harmful elements P and S, combined with the manufacturing process, the steel plate of the present invention obtains a high - density tempered martensite structure.

[0036] (2) The mechanical properties of the steel plate for pressure - bearing equipment obtained by the unique production process are as follows: at room temperature, 800 MPa ≤ R p0.2 ≤ 930 MPa, 1100 MPa ≤ R m ≤ 1200 MPa, (-20 °C) KV 2 ≥ 100 J.

[0037] (3) After forming and secondary hardening heat treatment, the steel plate of the present invention obtains a complex structure of high - density tempered martensite. At the same time, a large number of (10 - 30) nm - sized (Fe, Mn, Cr, Mo) 23 C 6 and Mo 2 C second - phase particles and high - hardness borides are precipitated dispersively in the steel, and the proportion of the structure is 15% - 20%, ensuring that the steel plate still has a strength level of 1100 MPa and good plasticity and toughness after forming.

[0038] (4) After forming heat treatment of the steel for pressure - bearing equipment of the present invention, the mechanical properties of the steel are as follows: at room temperature, 830 MPa ≤ R p0.2 ≤ 960 MPa, 1100 MPa ≤ R m ≤ 1230 MPa, 500 MPa ≤ R p0.2 (400 °C) ≤ 560 MPa, (-20 °C) KV 2≥120 J.

[0039] (5) The present invention obtains a high-strength steel plate for pressure-bearing equipment with a grade of 1100 MPa and a thickness specification of (40 - 80) mm. Specific embodiments

[0040] The present invention will be further described below through embodiments.

[0041] In the embodiments of the present invention, smelting, continuous casting, heating, controlled rolling and controlled cooling, and heat treatment are carried out according to the component ratios of the technical solutions.

[0042] A manufacturing method for a thick steel plate for pressure-bearing equipment with a grade of 1100 MPa, including smelting, continuous casting, heating, controlled rolling, controlled cooling, and tempering; Heating: The heating temperature is controlled at 1180 - 1230 °C, and the total heating duration is 4 - 6 hours;

[0043] Controlled rolling: The rolling adopts a two-stage controlled rolling method. The finishing temperature in the recrystallization zone is ≥1000 °C, and the total deformation rate is ≥50%; The starting rolling temperature in the non-recrystallization zone is 870 - 930 °C, the finishing rolling temperature is 820 - 870 °C, and the total deformation rate is ≥55%;

[0044] Controlled cooling: The starting cooling temperature is 800 - 840 °C, the cooling rate is 20 - 30 °C / s, and the return red temperature is 500 - 550 °C;

[0045] Tempering: The tempering temperature is 650 - 700 °C, and the net holding time is 2.0 - 4.0 min / mm.

[0046] Furthermore; Smelting: The molten steel is smelted in a converter, using high-quality scrap steel and hot metal as raw materials. The content of hot metal is controlled at 75% - 85%. Dephosphorization and decarburization are carried out separately in the converter. Among them, the oxygen blowing for dephosphorization is controlled at 7 - 10 min, and the oxygen blowing for decarburization is controlled at 8 - 12 min. Finally, the mass fraction of phosphorus is reduced to less than 0.006%; Deep desulfurization treatment is carried out in the LF refining furnace, and the sulfur content is controlled at less than 0.002%; Degassing is completed in the VD furnace, the net circulation time is 10 - 15 min, and the calming time before pouring is 3 - 5 min.

[0047] Furthermore; Continuous casting: The superheat is 20 - 30 °C, and the casting speed during pouring is 1.0 - 1.4 m / min; The cast slab is taken offline and stacked for slow cooling. The stacking slow cooling time is 24 - 36 h, and it is unstacked below 400 °C.

[0048] A forming process for a thick steel plate for pressure-bearing equipment with a grade of 1100 MPa. Steel plate forming: In the forming process, it is heated and held at 930 - 960 °C, the net holding time is 1.0 - 2.0 min / mm, and after being taken out of the furnace, it enters a salt bath and is rapidly cooled at a cooling rate of 30 - 55 °C / s; Then it is tempered, the tempering temperature is 470 - 500 °C, and the net holding time is 0.5 - 1.0 h.

[0049] Furthermore, the microstructure of the steel after rapid cooling in the salt bath is fine lath martensite, and the microstructure of the steel after the steel plate is formed is tempered martensite.

[0050] A post-forming heat treatment process for a thick steel plate used in a 1100 MPa-class pressure-bearing equipment, the heat treatment process being a secondary hardening heat treatment, and the process being: a heating temperature of 500 - 530 °C and a net holding time of 2.0 - 4.0 h.

[0051] Furthermore, 10 - 30 nm-sized (Fe, Mn, Cr, Mo) 23 C 6 , Mo 2 C second-phase particles and high-hardness borides are precipitated in the microstructure of the steel after the secondary hardening heat treatment, and their volume percentage content is 15% - 20% of the tissue ratio.

[0052] The composition of the steel in the embodiments of the present invention is shown in Table 1. The main process parameters of the steel in the embodiments of the present invention are shown in Table 2. The mechanical properties and microstructures of the steel in the embodiments of the present invention are shown in Table 3. The mechanical properties and microstructures of the formed and heat-treated steel in the embodiments of the present invention are shown in Table 4.

[0053] Table 1 Composition of the steel in the embodiments of the present invention (wt%)

[0054] Example C Si Mn P S Cr Mo Ni B Alt 1 0.17 0.27 0.60 0.006 0.001 0.85 0.45 1.25 0.003 0.039 2 0.21 0.28 0.64 0.006 0.002 1.17 0.50 1.16 0.002 0.022 3 0.18 0.30 0.70 0.008 0.003 1.08 0.58 1.24 0.004 0.033 4 0.19 0.33 0.52 0.010 0.001 1.13 0.48 1.30 0.001 0.028 5 0.20 0.25 0.45 0.005 0.002 0.95 0.49 1.18 0.005 0.045 6 0.21 0.31 0.70 0.009 0.001 1.20 0.60 1.29 0.003 0.031 7 0.17 0.33 0.50 0.006 0.001 0.89 0.56 1.20 0.002 0.028 8 0.18 0.24 0.46 0.010 0.002 0.95 0.57 1.22 0.004 0.020 9 0.19 0.35 0.57 0.009 0.003 0.95 0.49 1.15 0.001 0.023 10 0.17 0.20 0.65 0.008 0.001 0.88 0.60 1.25 0.005 0.040

[0055] Table 2 Main process parameters of the steel in the embodiments of the present invention

[0056]

[0057] Table 3 Mechanical properties and microstructures of the steel in the embodiments of the invention

[0058] Example Sampling location <![CDATA[R p0.2. / MPa]]> <![CDATA[R m / MPa]]> A / ％ <![CDATA[(-20℃)KV 2 / J]]> Microstructure 1 T / 4 907 1192 23.0 148 Tempered martensite 2 T / 4 920 1180 22.0 140 Tempered martensite 3 T / 4 853 1153 21.5 135 Tempered martensite 4 T / 4 832 1115 22.0 132 Tempered martensite 5 T / 4 841 1125 21.5 130 Tempered martensite 6 T / 4 876 1171 21.0 139 Tempered martensite 7 T / 4 803 1104 21.0 146 Tempered martensite 8 T / 4 930 1200 23.0 150 Tempered martensite 9 T / 4 884 1168 23.5 152 Tempered martensite 10 T / 4 864 1165 23.0 151 Tempered martensite

[0059] Table 4 Mechanical properties and microstructures of the formed and heat-treated steel plates in the embodiments of the present invention

[0060]

[0061] According to the above results, it can be seen that for the steel plate used in a 1100 MPa-class pressure-bearing equipment produced by applying the present invention, the content of harmful elements P and S is controlled extremely low, and its mechanical properties are expressed as 800 MPa ≤ R p0.2 ≤ 930 MPa at room temperature, 1100 MPa ≤ R m ≤ 1200 MPa, elongation rate A ≥ 21%, and impact energy KV 2 ≥ 100 J at -20 °C. The mechanical properties of the formed and heat-treated steel are expressed as mechanical properties at room temperature of 830 MPa ≤ R p0.2≤960 MPa, 1100 MPa ≤ R m ≤1230 MPa, elongation A ≥ 21%; at 400 °C, 500 MPa ≤ R p0.2 ≤560 MPa; impact energy KV at -20 °C 2 ≥120 J.

[0062] In order to describe the present invention, the present invention has been properly and fully described by way of examples above. The above embodiments are only used to illustrate the present invention and are not a limitation of the present invention. Those of ordinary skill in the relevant technical field can also make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent replacements, improvements, etc. should be included within the protection scope of the present invention. The patent protection scope of the present invention shall be defined by the claims.

Claims

1. A 1100MPa grade thick steel plate for pressure-bearing equipment, characterized in that: The composition of the steel plate is as follows by weight percentage: C 0.17%~0.21%, Si 0.20%~0.35%, Mn 0.45%~0.70%, P ≤0.010%, S ≤0.003%, Cr 0.85%~1.20%, Mo 0.45%~0.60%, Ni 1.15%~1.30%, B 0.001%~0.005%, Alt 0.015%~0.045%, and the balance is Fe and unavoidable inclusions; The manufacturing method of the 1100MPa grade thick steel plate for pressure-bearing equipment comprises smelting, continuous casting, heating, controlled rolling, controlled cooling and tempering; Heating: The heating temperature is controlled at 1180~1230℃, and the total heating time is 4.0~6.0 hours; Controlled rolling: The rolling adopts a two-stage controlled rolling method. The end rolling temperature of the recrystallization zone is ≥1000℃, and the total deformation rate is ≥50%; the starting rolling temperature of the non-recrystallization zone is 870~930℃, the final rolling temperature is 820~870℃, and the total deformation rate is ≥55%; Controlled cooling: cooling temperature 800~840℃, cooling rate 20~30℃ / s, red-return temperature 500~550℃; Tempering: The tempering temperature is 650~700℃, and the net holding time is 2.0~4.0 min / mm.

2. The 1100MPa grade thick steel plate for pressure-bearing equipment according to claim 1, characterized in that: The thickness of thick steel plates used for pressure-bearing equipment is 40~80mm.

3. The 1100MPa grade thick steel plate for pressure-bearing equipment according to claim 1, characterized in that: The mechanical properties of thick steel plates for pressure equipment are 800MPa≤ R p0.2 ≤930MPa、1100MPa≤ R m ≤1200MPa, impact energy at -20℃ KV 2≥100J.

4. The 1100MPa grade thick steel plate for pressure-bearing equipment according to claim 1, characterized in that: Smelting: The smelting of molten steel is carried out in a converter, using high-quality scrap steel and molten iron as raw materials. The molten iron content is controlled at 75%~85%. Dephosphorization and decarburization are smelted separately in a converter, with oxygen blowing for dephosphorization controlled at 7~10min and oxygen blowing for decarburization controlled at 8~12min, ultimately reducing the phosphorus mass fraction to less than 0.006%. Deep desulfurization is carried out in the LF refining furnace, and the sulfur content is controlled below 0.002%. Degassing is completed in a VD furnace, with a net cycle time of 10~15min and a calming time of 3~5min before pouring.

5. The 1100MPa grade thick steel plate for pressure-bearing equipment according to claim 1, characterized in that: Continuous casting: superheat is 20~30℃, and the casting rate during casting is 1.0~1.4m / min. The billets are stacked and slowly cooled after coming off the line. The stacking slow cooling time is 24~36h, and the billets are unstacking below 400℃.

6. A forming process of the 1100MPa grade thick steel plate for pressure-bearing equipment according to claim 1, characterized in that: During the molding process, the heating temperature is 930~960℃, and the net holding time is 1.0~2.0min / mm. After being taken out of the furnace, it enters the salt water bath and is rapidly cooled at a cooling rate of 30~55℃ / s; then it is tempered at a tempering temperature of 470~500℃, and the net holding time is 0.5~1.0h.

7. The forming process of the 1100MPa grade thick steel plate for pressure-bearing equipment according to claim 6, characterized in that: The microstructure of the steel after rapid cooling in a salt water bath is fine lath martensite; The microstructure of the steel after plate forming is tempered martensite.

8. The forming process of the 1100MPa grade thick steel plate for pressure-bearing equipment according to claim 6, characterized in that: After forming, secondary hardening heat treatment is carried out, and the process is as follows: heating temperature 500~530℃, net insulation time 2.0~4.0h.

9. The forming process of the 1100MPa grade thick steel plate for pressure-bearing equipment according to claim 8, characterized in that: After secondary hardening heat treatment, 10~30nm level (Fe, Mn, Cr, Mo) are precipitated in the microstructure of the steel 23 C6, Mo2C second phase particles and borides, their volume percentage is 15%~20%.

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