Method for preparing layered structure RAFM steel with excellent strength and plasticity

Abstract

The application belongs to the field of metal material preparation and specifically relates to a preparation method of layered structure RAFM steel with excellent strength and plasticity, and the manufacturing method comprises the following steps: 1) keeping a cast ingot at 1100 DEG C-1200 DEG C for more than 2 hours; 2) performing hot rolling treatment on the steel, and super-fast cooling the steel to room temperature after five passes of hot rolling; and 3) tempering the rolled steel below the recrystallization temperature, so that a high-strength and high-plasticity layered structure RAFM steel is finally obtained; the RAFM steel is any one of CLAM steel, CLF-1 steel, 9Cr2WVTa steel, EUROFER97 steel, F82H steel or JLF-1 steel. The preparation process of the RAFM steel overcomes technical prejudice, the rolled steel billet is not subjected to solid solution treatment or high-temperature tempering, but is directly tempered below the recrystallization temperature, the plasticizing mechanism of the layered structure is utilized, the strength and plasticity of the steel are improved, and the strength and plasticity of the steel are improved under the conditions of room temperature and -196 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of metal material preparation, specifically relating to a method for preparing layered RAFM steel with excellent strength and plasticity. Background Technology

[0002] Low-activation ferritic / martensitic steel (RAFM steel) retains excellent mechanical properties, thermal conductivity, and resistance to thermal expansion under strong irradiation conditions, making it considered the preferred structural material for nuclear fusion reactors. However, after long-term service under irradiation, the microstructure of RAFM steel undergoes radiation hardening, significantly reducing its toughness and continuously increasing its ductile-brittle transition temperature. When the ductile-brittle transition temperature exceeds room temperature, it risks brittle fracture at room temperature. Therefore, improving the room temperature and low-temperature strength and ductility of RAFM steel is extremely important.

[0003] Patent document CN109457095A discloses a strengthening treatment method for CLAM steel. By rolling in the non-recrystallization zone and rapidly cooling after rolling, the size of subgrain boundaries and carbides in the steel can be effectively refined, thereby significantly improving the yield strength and tensile strength of the steel. However, the maximum elongation of the steel is also reduced accordingly.

[0004] Patent document CN117123789A discloses a method for preparing heat-resistant and radiation-resistant ultrafine-grained martensitic steel by adding nano-sized Sc4Zr3O12 ceramic oxide powder to CLAM steel. The precipitation of nano-sized Sc4Zr3O12 effectively improves the strength of the steel, but the maximum elongation of the steel is also significantly reduced.

[0005] From the existing technologies described above, refining the subgrain and precipitate sizes in steel can effectively improve its yield and tensile strength; however, this also reduces its plasticity. This mismatch between strength and plasticity severely limits its practical applications. In traditional equiaxed steels, the larger atomic mismatch at grain boundaries effectively hinders dislocation movement, thus increasing the steel's strength. However, this hindering of dislocations by grain boundaries can also easily cause localized stress concentration, promoting crack initiation and reducing the elongation after fracture. To improve the room-temperature / low-temperature yield strength and plasticity of martensitic steel, it is urgent to develop a new technology that overcomes the existing contradiction between strength and plasticity, simultaneously improving the strength and plasticity of steel at both room temperature and low temperatures. Summary of the Invention

[0006] The purpose of this invention is to propose a method for preparing layered RAFM steel with excellent strength and plasticity, overcoming the shortcomings of existing technologies. Addressing the contradiction between strength and plasticity in martensitic steel, this invention forms layered grain boundaries different from equiaxed grains within the steel, allowing stress and cracks to propagate uniformly along the grain boundary direction, avoiding localized stress concentration, delaying crack initiation and propagation, and improving the strength and plasticity of the steel at room temperature and -196℃.

[0007] To achieve the above technical objectives, the present invention is implemented through the following technical solution:

[0008] A method for preparing layered RAFM steel with excellent strength and plasticity includes the following steps: 1) homogenizing and annealing the RAFM steel ingot at 1100℃-1200℃ for 2-4 hours; 2) subjecting the homogenized and annealed steel ingot to initial rolling treatment, with an initial rolling temperature of 1120-1180℃, rolling the steel from 60-67mm to 35-40mm in two passes, with a single reduction of 23-26%, and a final rolling temperature of 1030-1160℃, after which the rolling is paused in a waiting zone; 3) The steel billet after the initial rolling is subjected to a second rolling process. The initial rolling temperature for the second rolling is 830-870℃. The steel is rolled from 35-40mm to 10-16mm in three passes, with a single reduction of 23-26%. The final rolling temperature is 790-850℃, which is lower than the recrystallization temperature. 4) After hot rolling, the steel is cooled to room temperature using a water cooling process. 5) The cooled steel plate is tempered at 700-730℃ for 15-30 minutes. After tempering, a layered RAFM steel with excellent strength and plasticity is obtained.

[0009] The initial rolling process is as follows: the initial rolling temperature is 1150℃, the final rolling temperature is 1050℃, and the steel is rolled from 65mm to 37mm in two passes, with a deformation of 25% in each pass.

[0010] The secondary rolling process involves an initial rolling temperature of 850°C and a final rolling temperature of 800°C. The steel is rolled from 37mm to 15mm in three passes, with a deformation of 25% per pass.

[0011] In step 4), the cooling water temperature is room temperature, the water pressure is 0.35-0.6MPa, and the water volume is 180-300m3.

[0012] The layered RAFM steel has a layered grain size of 8-10 μm, a ferrite subgrain size of 150-170 nm, and an M23C6 carbide size of 25-30 nm, with a volume fraction of 0.25-0.3%.

[0013] The layered RAFM steel has a room temperature yield strength of 900-980 MPa and an elongation after fracture of 25-27%, and a yield strength of 1350-1400 MPa and an elongation after fracture of 23-26% at -196℃.

[0014] The RAFM steel is any one of CLAM steel, CLF-1 steel, 9Cr2WVTa steel, EUROFER97 steel, F82H steel or JLF-1 steel.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0016] 1) The layered grain structure martensitic steel of the present invention overcomes technical biases without sacrificing the plasticity of the steel. The rolled billet does not undergo solution treatment or high-temperature tempering, but is directly tempered below the recrystallization temperature. At this temperature, the layered grains will not recrystallize to form equiaxed grains, but the martensite will completely transform into ferrite, and carbides can be fully precipitated, thereby obtaining martensitic steel with a layered grain structure. This layered structure effectively suppresses the local concentration of stress and cracks, continuously refines the subgrain and carbide size of the steel, thereby improving the strength of the steel.

[0017] 2) The room temperature yield strength of the layered martensitic steel of this invention is increased by more than 40% compared with traditional equiaxed CLAM steel without sacrificing plasticity. At -196℃, its plasticity and yield strength are increased by at least 100% and 30% respectively compared with traditional equiaxed CLAM steel. 3) The layered grain structure RAFM steel prepared by this invention exhibits a strength-plasticity matching at -196℃ that surpasses almost all current steel materials, and its yield strength also surpasses that of current high-entropy alloys. Although its -196℃ plasticity is lower than that of high-entropy alloys, its raw material cost is significantly lower than that of high-entropy alloys because it does not contain precious metal elements such as Co and Ni. Attached Figure Description

[0018] Figure 1 This is a photograph of the grain morphology of the layered CLAM steel in Example 1 of the present invention;

[0019] Figure 2 These are photographs of the subgrain and M23C6 carbide morphology of the layered CLAM steel in Example 1 of this invention;

[0020] Figure 3 This is a comparison of the engineering stress-strain curves at room temperature and -196℃ between the layered CLAM steel in Example 1 of the present invention and the conventional equiaxed CLAM steel in Comparative Example 1. Figure 4 This invention provides a comparison of the strength / plasticity, strength / raw material cost of the layered CLAM steel at -196℃ in Example 1 with current high-entropy alloys and traditional low-temperature steels. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the specific embodiments used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the specific embodiments described below are some embodiments of the present invention. For those skilled in the art, other specific embodiments can be obtained based on these specific embodiments without creative effort.

[0023] The components of the embodiments of the invention described and shown in the specific embodiments herein can be arranged and designed in countless different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the specific embodiments is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0024] Example 1

[0025] This invention discloses a method for preparing layered RAFM steel with excellent strength and plasticity, specifically comprising the following steps:

[0026] Step 1: Homogenize and anneal the CLAM steel ingot at 1100℃-1200℃ for 2 hours; the chemical composition (wt.%) of the CLAM steel used is: Fe 8.91%, Cr 1.4%, W 0.54%, Mn 0.15%, Ta 0.15%, V 0.09%, C 0.06%, Si 0.06%.

[0027] Step 2: The steel ingot after homogenization and annealing is subjected to initial rolling treatment. The initial rolling temperature is 1150℃. The steel is rolled from 65mm to 37mm in two passes, with a single reduction of 25%. The final rolling temperature is 1050℃. After that, the rolling is suspended in the waiting zone.

[0028] Step 3: The steel plate after the initial rolling is rolled a second time. The initial rolling temperature for the second rolling is 850℃. The steel is rolled from 37mm to 15mm in three passes, with a single reduction of 25%. The final rolling temperature is 800℃ (below the recrystallization temperature).

[0029] Step 4: After secondary rolling, the steel plate is ultra-rapidly cooled to room temperature. The ultra-rapid cooling process is a water cooling process, where the water temperature is room temperature, the water pressure is not less than 0.4 MPa, and the water volume is not less than 200 m³. 3 ;

[0030] Step 5: Temper the rolled steel at 700℃ for 15 minutes. After tempering, a layered CLAM steel with excellent strength and plasticity is finally obtained. The layered grain morphology of the steel is as follows: Figure 1 As shown, subcrystalline and M 23 C6 carbide morphology as follows Figure 2 As shown, the layered grain size, ferrite subgrain size, and M in layered CLAM steel are analyzed.23 Table 1 shows the statistical data on C6 carbide size and volume fraction. A comparison of the room temperature yield strength, maximum elongation, and -196℃ yield strength and maximum elongation of the steel with Comparative Example 1 is shown in Figure 1. Figure 3 As shown in Table 2, the specific properties of layered CLAM steel are as follows. At room temperature, the yield strength of layered CLAM steel is increased by more than 40% without sacrificing plasticity, and the plasticity and yield strength at -196℃ are increased by more than 100% and 30% respectively compared with traditional equiaxed CLAM steel.

[0031] Example 2

[0032] This invention discloses a method for preparing layered RAFM steel with excellent strength and plasticity, specifically comprising the following steps:

[0033] Step 1: Homogenize and anneal the CLAM steel ingot at 1160℃-1200℃ for 3 hours; the chemical composition (wt.%) of the CLAM steel used is: Fe 8.91%, Cr 1.4%, W 0.54%, Mn 0.15%, Ta 0.15%, V 0.09%, C 0.06%, Si 0.06%.

[0034] Step 2: The homogenized annealed steel ingot is hot rolled at an initial rolling temperature of 1120℃. The steel is rolled from 65mm to 37mm in two passes with a single reduction of 23%. The final rolling temperature is 1040℃. After that, the rolling process is paused in the waiting zone.

[0035] Step 3: The steel after primary rolling is subjected to secondary rolling. The initial rolling temperature for secondary rolling is 830℃. The steel is rolled from 37mm to 15mm in three passes, with a single reduction of 23%. The final rolling temperature is 790℃ (below the recrystallization temperature).

[0036] Step 4: After five passes of hot rolling, the water is rapidly cooled to room temperature. The rapid cooling process is a water cooling process, where the water temperature is room temperature, the water pressure is not less than 0.4 MPa, and the water volume is not less than 200 m³. 3 ;

[0037] Step 5: Temper the rolled steel at 715℃ for 30 minutes. After tempering, a layered CLAM steel with excellent strength and plasticity is finally obtained. The layered grain size, ferrite subgrain size, and M... 23 Table 1 shows the statistics of C6 carbide size and volume fraction. Table 2 shows the room temperature yield strength, maximum elongation, and -196℃ yield strength and maximum elongation of the steel. At room temperature, the yield strength of layered CLAM steel is increased by more than 40% without sacrificing plasticity, and the plasticity and yield strength at -196℃ are increased by more than 100% and 30% respectively compared with traditional equiaxed CLAM steel.

[0038] Example 3

[0039] This invention discloses a method for preparing layered RAFM steel with excellent strength and plasticity, specifically comprising the following steps:

[0040] Step 1: Homogenize and anneal the CLAM steel ingot at 1100℃-1180℃ for 4 hours; the chemical composition (wt.%) of the CLAM steel used is: Fe 8.91%, Cr 1.4%, W 0.54%, Mn 0.15%, Ta 0.15%, V 0.09%, C 0.06%, Si 0.06%.

[0041] Step 2: The homogenized annealed steel ingot is hot rolled at an initial rolling temperature of 1160℃. The steel is rolled from 65mm to 37mm in two passes with a single reduction of 24%. The final rolling temperature is 1060℃. After that, the rolling process is paused in the waiting zone.

[0042] Step 3: The steel after primary rolling is subjected to secondary rolling. The initial rolling temperature of the secondary rolling is 860℃. The steel is rolled from 37mm to 15mm in three passes, with a single reduction of 24%. The final rolling temperature is 810℃ (below the recrystallization temperature).

[0043] Step 4: After five passes of hot rolling, the water is rapidly cooled to room temperature. The rapid cooling process is a water cooling process, where the water temperature is room temperature, the water pressure is not less than 0.4 MPa, and the water volume is not less than 200 m³. 3 ;

[0044] Step 5: Temper the rolled steel at 730℃ for 15 minutes. After tempering, a layered CLAM steel with excellent strength and plasticity is finally obtained. The layered grain size, ferrite subgrain size, and M... 23 Table 1 shows the statistics of C6 carbide size and volume fraction. Table 2 shows the room temperature yield strength, maximum elongation, and -196℃ yield strength and maximum elongation of the steel. At room temperature, the yield strength of layered CLAM steel is increased by more than 40% without sacrificing plasticity, and the plasticity and yield strength at -196℃ are increased by more than 100% and 30% respectively compared with traditional equiaxed CLAM steel.

[0045] Example 4

[0046] This invention discloses a method for preparing a layered RAFM structure with excellent strength and plasticity, specifically comprising the following steps:

[0047] Step 1: Homogenize and anneal the CLF-1 steel ingot at 1190℃-1200℃ for 2 hours; the chemical composition (wt.%) of the CLF-1 steel used is: Fe9%, Cr1.5%, W0.3%, Mn0.08%, Ta0.3%, V0.12%, C0.12%.

[0048] Step 2: The homogenized annealed steel ingot is hot rolled at an initial rolling temperature of 1180℃. The steel is rolled from 65mm to 37mm in two passes with a single reduction of 24%. The final rolling temperature is 1060℃. After that, the rolling process is paused in the waiting zone.

[0049] Step 3: The steel after primary rolling is subjected to secondary rolling. The initial rolling temperature of the secondary rolling is 870℃. The steel is rolled from 37mm to 15mm in three passes, with a single reduction of 26%. The final rolling temperature is 850℃ (below the recrystallization temperature).

[0050] Step 4: After five passes of hot rolling, the water is rapidly cooled to room temperature. The rapid cooling process is a water cooling process, where the water temperature is room temperature, the water pressure is not less than 0.4 MPa, and the water volume is not less than 200 m³. 3 ;

[0051] Step 5: Temper the rolled steel at 720℃ for 20 minutes. After tempering, a layered structure CLF-1 steel with excellent strength and plasticity is finally obtained. The layered grain size, ferrite subgrain size, and M... 23 Table 1 shows the statistics of C6 carbide size and volume fraction. Table 2 shows the room temperature yield strength, maximum elongation, and -196℃ yield strength and maximum elongation of the steel. At room temperature, the yield strength of layered CLF-1 steel is more than 40% higher than that of equiaxed CLAM steel without sacrificing plasticity, while the plasticity and yield strength at -196℃ are more than 100% and 30% higher than those of equiaxed CLAM steel, respectively.

[0052] Example 5

[0053] This invention discloses a method for preparing a layered RAFM structure with excellent strength and plasticity, specifically comprising the following steps:

[0054] Step 1: Homogenize and anneal the 9Cr2WVTa steel ingot at 1120℃-1190℃ for 2 hours; the chemical composition (wt.%) of the 9Cr2WVTa steel used is: Fe9%, Cr2%, W0.5%, Mn0.08%, Ta0.25%, V0.1%, C0.1%.

[0055] Step 2: The homogenized annealed steel ingot is hot rolled at an initial rolling temperature of 1170℃. The steel is rolled from 65mm to 37mm in two passes with a single reduction of 24%. The final rolling temperature is 1150℃. After that, the rolling process is paused in the waiting zone.

[0056] Step 3: The steel after primary rolling is subjected to secondary rolling. The initial rolling temperature of the secondary rolling is 860℃. The steel is rolled from 37mm to 15mm in three passes, with a single reduction of 23%. The final rolling temperature is 810℃ (below the recrystallization temperature).

[0057] Step 4: After five passes of hot rolling, the water is rapidly cooled to room temperature. The rapid cooling process is a water cooling process, where the water temperature is room temperature, the water pressure is not less than 0.4 MPa, and the water volume is not less than 200 m³. 3 ;

[0058] Step 5: Temper the rolled steel at 710℃ for 25 minutes. After tempering, a layered 9Cr2WVTa steel with excellent strength and plasticity is finally obtained. The layered grain size, ferrite subgrain size, and M... 23 Table 1 shows the statistics of C6 carbide size and volume fraction. Table 2 shows the room temperature yield strength, maximum elongation, and -196℃ yield strength and maximum elongation of the steel. At room temperature, the yield strength of layered 9Cr2WVTa steel is more than 40% higher than that of equiaxed CLAM steel without sacrificing plasticity, while the plasticity and yield strength at -196℃ are more than 100% and 30% higher than those of equiaxed CLAM steel, respectively.

[0059] Example 6

[0060] This invention discloses a method for preparing a layered RAFM structure with excellent strength and plasticity, specifically comprising the following steps:

[0061] Step 1: Homogenize and anneal the EUROFER97 steel ingot at 1150℃-1200℃ for 2 hours; the chemical composition (wt.%) of the EUROFER97 steel used is: Fe 8.7%, Cr 1%, W 0.45%, Mn 0.1%, Ta 0.20%, V 0.1%, C 0.1%.

[0062] Step 2: The homogenized annealed steel ingot is hot rolled at an initial rolling temperature of 1160℃. The steel is rolled from 65mm to 37mm in two passes with a single reduction of 23%. The final rolling temperature is 1060℃. After that, the rolling process is paused in the waiting zone.

[0063] Step 3: The steel after primary rolling is rolled a second time. The initial rolling temperature for the second rolling is 840℃. The steel is rolled from 37mm to 15mm in three passes, with a single reduction of 26%. The final rolling temperature is 790℃ (below the recrystallization temperature).

[0064] Step 4: After five passes of hot rolling, the water is rapidly cooled to room temperature. The rapid cooling process is a water cooling process, where the water temperature is room temperature, the water pressure is not less than 0.4 MPa, and the water volume is not less than 200 m³. 3 ;

[0065] Step 5: Temper the rolled steel at 710℃ for 20 minutes. After tempering, a layered structure EUROFER97 steel with excellent strength and plasticity is finally obtained. The layered grain size, ferrite subgrain size, and M... 23Table 1 shows the statistics of C6 carbide size and volume fraction. Table 2 shows the room temperature yield strength, maximum elongation, and -196℃ yield strength and maximum elongation of the steel. At room temperature, the yield strength of layered EUROFER97 steel is more than 40% higher than that of equiaxed CLAM steel without sacrificing plasticity, while the plasticity and yield strength at -196℃ are more than 100% and 30% higher than those of equiaxed CLAM steel, respectively.

[0066] Example 7

[0067] This invention discloses a method for preparing a layered RAFM structure with excellent strength and plasticity, specifically comprising the following steps:

[0068] Step 1: Homogenize and anneal the F82H steel ingot at 1130℃-1150℃ for 2 hours; the chemical composition (wt.%) of the F82H steel used is: Fe 8%, Cr 2%, W 0.45%, Mn 0.05%, Ta 0.20%, V 0.1%, C 0.1%;

[0069] Step 2: The homogenized annealed steel ingot is hot rolled at an initial rolling temperature of 1140℃. The steel is rolled from 65mm to 37mm in two passes with a single reduction of 23%. The final rolling temperature is 1040℃. After that, the rolling process is paused in the waiting zone.

[0070] Step 3: The steel after primary rolling is subjected to secondary rolling. The initial rolling temperature for secondary rolling is 850℃. The steel is rolled from 37mm to 15mm in three passes, with a single reduction of 23%. The final rolling temperature is 800℃ (below the recrystallization temperature).

[0071] Step 4: After five passes of hot rolling, the water is rapidly cooled to room temperature. The rapid cooling process is a water cooling process, where the water temperature is room temperature, the water pressure is not less than 0.4 MPa, and the water volume is not less than 200 m³. 3 ;

[0072] Step 5: Temper the rolled steel at 720℃ for 25 minutes. After tempering, a layered F82H steel with excellent strength and plasticity is finally obtained. The layered grain size, ferrite subgrain size, and M... 23 Table 1 shows the statistics of C6 carbide size and volume fraction. Table 2 shows the room temperature yield strength, maximum elongation, and -196℃ yield strength and maximum elongation of the steel. At room temperature, the yield strength of layered F82H steel is more than 40% higher than that of equiaxed CLAM steel without sacrificing plasticity, while the plasticity and yield strength at -196℃ are more than 100% and 30% higher than those of equiaxed CLAM steel, respectively.

[0073] Example 8

[0074] This invention discloses a method for preparing layered RAFM steel with excellent strength and plasticity, specifically comprising the following steps:

[0075] Step 1: Homogenize and anneal the JLF-1 steel ingot at 1120℃-1190℃ for 2 hours; the chemical composition (wt.%) of the JLF-1 steel used is: Fe 8.8%, Cr 2%, W 0.45%, Mn 0.08%, Ta 0.20%, V 0.1%, C 0.1%;

[0076] Step 2: The homogenized annealed steel ingot is hot rolled at an initial rolling temperature of 1120℃. The steel is rolled from 65mm to 37mm in two passes with a single reduction of 23%. The final rolling temperature is 1050℃. After that, the rolling process is paused in the waiting zone.

[0077] Step 3: The steel after primary rolling is rolled a second time. The initial rolling temperature for the second rolling is 830℃. The steel is rolled from 37mm to 15mm in three passes, with a single reduction of 24%. The final rolling temperature is 810℃ (below the recrystallization temperature).

[0078] Step 4: After five passes of hot rolling, the water is rapidly cooled to room temperature. The rapid cooling process is a water cooling process, where the water temperature is room temperature, the water pressure is not less than 0.4 MPa, and the water volume is not less than 200 m³. 3 ;

[0079] Step 5: Temper the rolled steel at 720℃ for 18 minutes. After tempering, a layered structure JLF-1 steel with excellent strength and plasticity is finally obtained. The layered grain size, ferrite subgrain size, and M... 23 Table 1 shows the statistics of C6 carbide size and volume fraction. Table 2 shows the room temperature yield strength, maximum elongation, and -196℃ yield strength and maximum elongation of the steel. At room temperature, the yield strength of layered JLF-1 steel is more than 40% higher than that of equiaxed CLAM steel without sacrificing plasticity, while the plasticity and yield strength at -196℃ are more than 100% and 30% higher than those of equiaxed CLAM steel, respectively.

[0080] Comparative Example

[0081] The traditional method for preparing CLAM steel with equiaxed structure, step one: holding the CLAM steel ingot at 1200℃ for 2 hours;

[0082] Step 2: The homogenized annealed steel ingot is hot rolled at an initial rolling temperature of 1150℃. The steel is rolled from 65mm to 37mm in two passes with a single reduction of 25%. The final rolling temperature is 1050℃. After that, the rolling process is paused in the waiting zone.

[0083] Step 3: The steel after primary rolling is subjected to secondary rolling. The initial rolling temperature for secondary rolling is 850℃. The steel is rolled from 37mm to 15mm in three passes, with a single reduction of 25%. The final rolling temperature is 800℃ (below the recrystallization temperature).

[0084] Step 4: After five passes of hot rolling, the water is cooled to room temperature using a water cooling process. The water temperature is room temperature, the water pressure is not less than 0.4 MPa, and the water volume is not less than 200 m3.

[0085] Step 5: After the rolled steel is solution-treated at 980℃ for 30 minutes, it is water-quenched to room temperature and then tempered at 730℃ for 30 minutes.

[0086] The comparative example ultimately yielded a CLAM steel with a traditional equiaxed structure. Its solution treatment process prevented the formation of a layered structure. Table 1 shows the statistical analysis of the layered grain size, ferrite subgrain size, M23C6 carbide size, and volume fraction in the traditional equiaxed CLAM steel. Table 2 shows the room temperature yield strength, maximum elongation, and yield strength and maximum elongation at -196℃.

[0087] Table 1

[0088] Example Grain size (μm) Ferrite size (nm) M23C6 carbide size (nm) M23C6 carbide volume fraction (%) 1 8 150 25 25 2 10 165 30 20 3 12 160 28 23 4 9 170 32 26 5 11 185 24 28 6 10 170 25 23 7 7 180 27 22 8 9 185 25 26 Comparative Example 10 300 100 15

[0089] Table 2

[0090] Example Room temperature yield strength (MPa) Maximum elongation % Yield strength at -196℃ (MPa) Maximum elongation at -196℃ (%) 1 900 25 1400 24 2 850 30 1300 28 3 870 28 1350 26 4 875 28 1380 28 5 820 25 1300 23 6 835 27 1305 25 7 850 26 1325 24 8 840 25 1320 26 Comparative Example 600 20 1000 12

Claims

1. A method for preparing layered RAFM steel with excellent strength and plasticity, characterized in that: Includes the following steps: 1) Homogenize and anneal the RAFM steel ingot at 1100℃-1200℃ for 2-4 hours; 2) The steel ingot after homogenization annealing is subjected to initial rolling treatment. The initial rolling temperature is 1120-1180℃. The steel is rolled from 60-67mm to 35-40mm in two passes, with a single reduction of 23-26%. The final rolling temperature is 1030-1160℃. After that, the rolling is suspended in the waiting area. 3) The steel billet after the initial rolling is rolled a second time. The initial rolling temperature of the second rolling is 830-870℃. The steel is rolled from 35-40mm to 10-16mm in three passes. The reduction per pass is 23-26%. The final rolling temperature is 790-850℃, which is lower than the recrystallization temperature. 4) After hot rolling, the material is cooled to room temperature using an ultra-rapid cooling process, which is a water cooling process. 5) After cooling, the steel plate is tempered at 700-730℃ for 15-30 minutes to obtain a layered RAFM steel with excellent strength and plasticity; the layered grain size in the RAFM steel is 8-10μm, the ferrite subgrain size is 150-170nm, and the M... 23 C6 carbides have a wavelength of 25-30 nm and a volume fraction of 0.25-0.3%.

2. The method for preparing layered RAFM steel with excellent strength and plasticity according to claim 1, characterized in that, The initial rolling process is as follows: the initial rolling temperature is 1150℃, the final rolling temperature is 1050℃, and the steel is rolled from 65mm to 37mm in two passes, with a deformation of 25% in each pass.

3. The method for preparing layered RAFM steel with excellent strength and plasticity according to claim 1, characterized in that, The secondary rolling process involves an initial rolling temperature of 850°C and a final rolling temperature of 800°C. The steel is rolled from 37mm to 15mm in three passes, with a deformation of 25% per pass.

4. The method for preparing layered RAFM steel with excellent strength and plasticity according to claim 1, characterized in that: In step 4), the cooling water temperature is room temperature, the water pressure is 0.35-0.6 MPa, and the water volume is 180-300 m³ / h. 3 .

5. The method for preparing layered RAFM steel with excellent strength and plasticity according to claim 1, characterized in that: The layered RAFM steel has a room temperature yield strength of 900-980 MPa and an elongation after fracture of 25-27%, and a yield strength of 1350-1400 MPa and an elongation after fracture of 23-26% at -196℃.

6. The method for preparing layered RAFM steel with excellent strength and plasticity according to claim 1, characterized in that: The RAFM steel is any one of CLAM steel, CLF-1 steel, 9Cr2WVTa steel, EUROFER97 steel, F82H steel or JLF-1 steel.

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