9Cr-ODS martensitic steel with enhanced plasticity and preparation method of 9Cr-ODS martensitic steel
Through the combination of specific components and process parameters, the distribution of oxide nanoparticles and martensite structure are controlled, and the problem of high strength but insufficient plasticity of 9Cr-ODS martensite steel is solved, achieving good comprehensive performance in the nuclear reactor environment.
Patent Information
- Application Number
- CN202510517495.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-23
- Publication Date
- 2025-07-01
AI Technical Summary
During the preparation process, excessive grain refinement of traditional 9Cr-ODS martensitic steel leads to stress concentration, making it difficult to accurately control the size and distribution of oxide particles, resulting in high strength but insufficient plasticity, which cannot meet the strict requirements of the fourth-generation nuclear reactor for structural materials.
After the prealloyed powder of specific components is mixed with Y2O3 powder, the distribution of oxide nanoparticles and martensite structure are controlled to improve plasticity by ball milling, degassing, hot isostatic molding and hot rolling deformation processes, combined with annealing treatment.
9Cr-ODS martensitic steel that exhibits good strength and plasticity at both room and high temperatures was prepared to meet the comprehensive performance requirements of nuclear reactors for materials.
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Figure CN120230952A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of oxide dispersion strengthened steel preparation, in particular to a 9Cr-ODS martensitic steel with enhanced plasticity and a preparation method thereof. Background Art
[0002] Oxide dispersion strengthened (ODS) martensitic steel is considered as a key candidate structural material for the fourth generation nuclear reactor system due to its excellent high temperature strength, radiation swelling resistance and creep resistance. Among them, 9Cr-ODS steel has achieved a good balance between corrosion resistance and processing performance with its moderate Cr content, i.e. 8-10 wt.%, and has become a research hotspot in the international nuclear materials field in recent years. This steel effectively introduces oxide particles through a combination of mechanical alloying and hot working processes, achieving a significant strengthening effect.
[0003] However, although the traditional 9Cr-ODS martensitic steel preparation method can obtain 9Cr-ODS martensite with high strength, it has obvious shortcomings in high plasticity. Specifically, during the preparation process, the commonly used mechanical alloying and hot working processes will lead to excessive grain refinement and an increase in grain boundaries, making the material prone to stress concentration when subjected to force, thereby reducing plasticity. In addition, the existing process is difficult to accurately control the size and distribution of oxide particles and their interfacial bonding state with the matrix, which further limits the improvement of the comprehensive performance of the material. Especially in advanced nuclear energy systems, such as the fourth-generation nuclear reactors, the requirements for structural materials are extremely stringent. Not only do they require sufficient strength to withstand high temperature and high pressure, but they also require good plasticity to resist embrittlement and swelling caused by radiation to avoid premature failure.
[0004] Therefore, it is necessary to invent a 9Cr-ODS martensitic steel with enhanced plasticity and a preparation method thereof to solve the above problems. Summary of the invention
[0005] In order to solve the problem that traditional 9Cr-ODS martensitic steel has high strength but insufficient plasticity due to stress concentration caused by excessive grain refinement and difficulty in accurately controlling the size and distribution of oxide particles, the present invention provides a 9Cr-ODS martensitic steel with enhanced plasticity and a preparation method thereof.
[0006] The present invention is achieved by adopting the following technical solutions: A method for preparing 9Cr-ODS martensitic steel with enhanced plasticity comprises the following steps: S1: Using Fe, Cr, W, Mn, V, and C as raw materials, pre-alloyed powder is obtained through atomization powder making. The mass percentages of the raw materials of the pre-alloyed powder are as follows: Cr: 9%, W: 2%, Mn: 0.4%, V: 0.2%, C: 0.08%, and the balance is Fe. The pre-alloyed powder and Y2O3 powder are mixed at a mass ratio of 99.65:0.35, and mechanical ball milling is carried out in a ball mill under argon protection to obtain the ball-milled mixed powder; S2: The ball-milled mixed powder is filled into a stainless-steel jacket, and the powder in the stainless-steel jacket is degassed at a temperature of 450 °C until the vacuum degree of the stainless-steel jacket reaches 0.002 Pa; S3: The stainless-steel jacket with a vacuum degree of 0.002 Pa is sealed and welded, and then put into a hot isostatic pressing equipment for solidification forming. The forming temperature is 1150 °C, the holding time is 3 h, the forming pressure is 150 Mpa. After cooling to room temperature with the furnace, a 9Cr-ODS martensitic steel sample is obtained; S4: The obtained 9Cr-ODS martensitic steel sample is put into a heat treatment furnace for holding. After cooling the held 9Cr-ODS martensitic steel sample, hot rolling deformation is carried out, and then after cooling to room temperature, a rolled 9Cr-ODS martensitic steel is obtained; S5: The rolled 9Cr-ODS martensitic steel is subjected to annealing treatment to obtain a 9Cr-ODS martensitic steel with enhanced plasticity.
[0007] Further, in step S1: The ball-to-material ratio in the ball mill is 10:1.
[0008] Further, in step S1: The ball milling speed of the ball mill is 250 rpm, and the ball milling time is 30 h.
[0009] Further, in step S4: The holding temperature of the heat treatment furnace is 1100 °C, and the holding time is 30 min - 40 min.
[0010] Further, in step S4: The held 9Cr-ODS martensitic steel sample is cooled to 880 °C for hot rolling deformation, and the deformation amount is 60% - 90%.
[0011] Further, in step S5: The annealing temperature of the annealing treatment is 500 °C - 700 °C, and it is held at this temperature for 10 min - 60 min.
[0012] A 9Cr-ODS martensitic steel with enhanced plasticity, which is obtained based on the preparation method of a 9Cr-ODS martensitic steel with enhanced plasticity described in the present invention.
[0013] The key of the present invention lies in the composition design of the pre-alloyed powder, the process parameters of hot rolling, and the process parameters of subsequent annealing treatment. The raw materials and mass percentages of the pre-alloyed powder are: Cr: 9%, W: 2%, Mn: 0.4%, V: 0.2%, C: 0.08%, and the balance is Fe. This determines that the 9Cr-ODS martensitic steel to be prepared can undergo austenite phase transformation during heating and martensite phase transformation during cooling; the process parameters of hot rolling keep the 9Cr-ODS martensitic steel sample in the austenite phase region. During the rolling process with a deformation amount of 60% - 90%, the austenite grains recrystallize. Under the coupling effect of grain boundaries and oxide nanoparticles, the oxide nanoparticles can dissolve and re-precipitate. The precipitated oxide nanoparticles are distributed along the deformation bands in the rolling direction. At the same time, the austenite grains are deformed and elongated, providing more free paths for dislocation slip, thus being beneficial to improving the plasticity of the 9Cr-ODS martensitic steel; the as-rolled 9Cr-ODS martensitic steel obtained after hot rolling deformation and cooling to room temperature has a martensite matrix structure. Through subsequent annealing process, the dislocation recovery in the martensite matrix can be promoted, and the dislocation tangles can be alleviated, thereby further improving the plasticity of the 9Cr-ODS martensitic steel.
[0014] By conducting certain composition design and hot rolling process adjustment on the 9Cr-ODS martensitic steel in the early stage of the present invention, the randomly distributed oxide nanoparticles in the 9Cr-ODS martensitic steel can be distributed along the rolling direction. At the same time, the martensite structure after rolling deformation shows certain layered characteristics, enabling the as-rolled 9Cr-ODS martensitic steel to exhibit good strength and plasticity combinations at room temperature and 650 °C. Through subsequent annealing process adjustment, the room temperature and high temperature plasticity of the 9Cr-ODS martensitic steel can be further improved. The process is simple and purposeful, which is of great significance for preparing 9Cr-ODS martensitic steel with simultaneously improved strength and plasticity. Description of the Drawings
[0015] Figure 1 It is the electron backscatter diffraction (EBSD) photograph of the as-rolled 9Cr-ODS martensitic steel with a deformation amount of 60% obtained in Example 1 of the present invention.
[0016] Figure 2 It is the scanning electron microscopy (SEM) photograph of the as-rolled 9Cr-ODS martensitic steel with a deformation amount of 60% obtained in Example 1 of the present invention.
[0017] Figure 3 It is the tensile property curve graph of the as-rolled 9Cr-ODS martensitic steel with a deformation amount of 60% obtained in Example 1 of the present invention at room temperature and 650 °C.
[0018] Figure 4It is an electron backscatter diffraction (EBSD) photograph of the rolled 9Cr-ODS martensitic steel with a deformation of 85% obtained in Example 2 of the present invention.
[0019] Figure 5 It is a tensile property curve graph of the rolled 9Cr-ODS martensitic steel with a deformation of 85% obtained in Example 2 of the present invention at room temperature and 650 °C.
[0020] Figure 6 It is a tensile property curve graph of the 9Cr-ODS martensitic steel with a high-strength heterogeneous structure obtained in Example 2 of the present invention at room temperature and 650 °C. Detailed implementation mode
[0021] A preparation method of 9Cr-ODS martensitic steel with enhanced plasticity includes the following steps: S1: Using Fe, Cr, W, Mn, V, and C as raw materials, pre-alloyed powder is obtained by atomization powder making. The mass percentages of the raw materials of the pre-alloyed powder are Cr: 9%, W: 2%, Mn: 0.4%, V: 0.2%, C: 0.08%, and the balance is Fe. The pre-alloyed powder and Y2O3 powder are mixed at a mass ratio of 99.65:0.35, mechanically ball milled in a ball mill with a ball-to-material ratio of 10:1, a ball milling speed of 250 rpm, and a ball milling time of 30 h, and argon protection is used to obtain the ball-milled mixed powder; S2: The ball-milled mixed powder is loaded into a stainless steel jacket, and the powder in the stainless steel jacket is degassed at a temperature of 450 °C until the vacuum degree of the stainless steel jacket reaches 0.002 Pa; S3: The stainless steel jacket with a vacuum degree of 0.002 Pa is sealed and welded, put into a hot isostatic pressing device for solidification and forming, the forming temperature is 1150 °C, the holding time is 3 h, the forming pressure is 150 Mpa, and after cooling to room temperature with the furnace, a 9Cr-ODS martensitic steel sample is obtained; S4: The obtained 9Cr-ODS martensitic steel sample is put into a heat treatment furnace for heat preservation, the heat preservation temperature is 1100 °C, the heat preservation time is 30 min to 40 min, the heat-preserved 9Cr-ODS martensitic steel sample is cooled to 880 °C for hot rolling deformation with a deformation of 60% to 90%, and then cooled to room temperature to obtain the rolled 9Cr-ODS martensitic steel.
[0022] S5: The rolled 9Cr-ODS martensitic steel is annealed at an annealing temperature of 500 °C to 700 °C and held at this temperature for 10 min to 60 min to obtain a 9Cr-ODS martensitic steel with enhanced plasticity.
[0023] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the protection scope of the present invention. Example 1
[0024] A preparation method of 9Cr-ODS martensitic steel with enhanced plasticity includes the following steps: S1: Using Fe, Cr, W, Mn, V, and C as raw materials, pre-alloyed powder is obtained through atomization powder making. The mass percentages of the raw materials of the pre-alloyed powder are Cr: 9%, W: 2%, Mn: 0.4%, V: 0.2%, C: 0.08%, and the balance is Fe. The pre-alloyed powder and Y2O3 powder are mixed at a mass ratio of 99.65:0.35, and mechanical ball milling is carried out in a QM-3SP4 planetary ball mill. The ball-to-material ratio is 10:1, the ball milling speed is 250 rpm, the ball milling time is 30 h, and argon protection is adopted to obtain the ball-milled mixed powder.
[0025] S2: The ball-milled mixed powder is filled into a stainless steel jacket, and the powder in the stainless steel jacket is degassed at a temperature of 450°C until the vacuum degree of the stainless steel jacket reaches 0.002 Pa.
[0026] S3: The stainless steel jacket with a vacuum degree of 0.002 Pa is sealed and welded, and then put into a hot isostatic pressing device for solidification molding. The molding temperature is 1150°C, the holding time is 3 h, the molding pressure is 150 Mpa. After cooling to room temperature with the furnace, a 9Cr-ODS martensitic steel sample is obtained.
[0027] S4: The obtained 9Cr-ODS martensitic steel sample is put into a heat treatment furnace for holding. The holding temperature is 1100°C, the holding time is 30 min. The 9Cr-ODS martensitic steel sample after holding is cooled to 880°C for hot rolling deformation, and the deformation amount is 60%. Then, after cooling to room temperature, a rolled 9Cr-ODS martensitic steel with a deformation amount of 60% is obtained.
[0028] Figure 1 This is the electron backscatter diffraction (EBSD) photograph of the rolled 9Cr-ODS martensitic steel with a deformation amount of 60% obtained in this example. It can be seen from the figure that after rolling treatment, the matrix of the rolled 9Cr-ODS martensitic steel is elongated along the rolling direction to a certain extent, and the size differences of the martensite blocks are relatively large.
[0029] Figure 2This is a scanning electron microscopy (SEM) photograph of the as-rolled 9Cr-ODS martensitic steel with a deformation of 60% obtained in this example. Different from the traditional 9Cr-ODS martensitic steel, it can be clearly seen from the figure that the nano-oxide particles are arranged directionally along the rolling direction.
[0030] Figure 3 This is the tensile property curve of the as-rolled 9Cr-ODS martensitic steel with a deformation of 60% obtained in this example at room temperature and 650 °C. At room temperature, the tensile strength of the as-rolled 9Cr-ODS martensitic steel with a deformation of 60% is 1320 MPa, and the elongation is 8%; at 650 °C, the tensile strength of the as-rolled 9Cr-ODS martensitic steel with a deformation of 60% is 338 MPa, and the elongation is 7%. Example 2
[0031] A preparation method of 9Cr-ODS martensitic steel with a high-strength heterogeneous structure includes the following steps: S1: Using Fe, Cr, W, Mn, V, and C as raw materials, pre-alloyed powder is obtained by atomization powder making. The mass percentages of the raw materials of the pre-alloyed powder are Cr: 9%, W: 2%, Mn: 0.4%, V: 0.2%, C: 0.08%, and the balance is Fe. The pre-alloyed powder and Y2O3 powder are mixed at a mass ratio of 99.65:0.35, and mechanical ball milling is carried out in a QM-3SP4 planetary ball mill. The ball-to-material ratio is 10:1, the ball milling speed is 250 rpm, the ball milling time is 30 h, and argon protection is used to obtain the ball-milled mixed powder.
[0032] S2: The ball-milled mixed powder is loaded into a stainless steel jacket, and the powder in the stainless steel jacket is degassed at a temperature of 450 °C until the vacuum degree of the stainless steel jacket reaches 0.002 Pa.
[0033] S3: The stainless steel jacket with a vacuum degree of 0.002 Pa is sealed and welded, and then put into a hot isostatic pressing equipment for solidification molding. The molding temperature is 1150 °C, the holding time is 3 h, the molding pressure is 150 Mpa, and after cooling to room temperature with the furnace, a 9Cr-ODS martensitic steel sample is obtained.
[0034] S4: The obtained 9Cr-ODS martensitic steel sample is put into a heat treatment furnace for holding. The holding temperature is 1100 °C, the holding time is 30 min. After holding, the 9Cr-ODS martensitic steel sample is cooled to 880 °C for hot rolling deformation, and the deformation is 85%. Then, after cooling to room temperature, the as-rolled 9Cr-ODS martensitic steel with a deformation of 85% is obtained.
[0035] Figure 4This is an electron backscatter diffraction (EBSD) photograph of the as-rolled 9Cr-ODS martensitic steel with a deformation of 85% obtained in this example. It can be seen from the figure that compared with the grains of the as-rolled 9Cr-ODS martensitic steel with a deformation of 60% in Example 1, the grains of the as-rolled 9Cr-ODS martensitic steel with a deformation of 85% show certain layered characteristics, and the martensite lath blocks are arranged in a "V" shape or triangle.
[0036] Figure 5 This is the tensile property curve of the as-rolled 9Cr-ODS martensitic steel with a deformation of 85% obtained in this example at room temperature and 650 °C. At room temperature, the tensile strength of the as-rolled 9Cr-ODS martensitic steel with a deformation of 85% is 1307 MPa, and the elongation is 14%; at 650 °C, the tensile strength of the as-rolled 9Cr-ODS martensitic steel with a deformation of 85% is 484 MPa, and the elongation is 13%. By comparison Figure 3 it can be seen that compared with the as-rolled 9Cr-ODS martensitic steel with a deformation of 60%, the plasticity of the as-rolled 9Cr-ODS martensitic steel with a deformation of 85% obtained in this example is significantly improved at room temperature, and both the tensile strength and plasticity at 650 °C are significantly improved.
[0037] S5: Anneal the as-rolled 9Cr-ODS martensitic steel with a deformation of 85% in a muffle furnace at an annealing temperature of 700 °C and hold for 15 min at this temperature to obtain a 9Cr-ODS martensitic steel with enhanced plasticity.
[0038] Figure 6 This is the tensile property curve of the 9Cr-ODS martensitic steel with a high-strength heterogeneous structure obtained in this example at room temperature and 650 °C. At room temperature, the tensile strength of the 9Cr-ODS martensitic steel with a high-strength heterogeneous structure obtained in this example is 845 MPa, and the elongation is 15%; at 650 °C, the tensile strength of the 9Cr-ODS martensitic steel with a high-strength heterogeneous structure obtained in this example is 336 MPa, and the elongation is 24%. By comparison Figure 5 it can be seen that after annealing treatment, compared with the as-rolled 9Cr-ODS martensitic steel with a deformation of 85%, although the tensile strength of the 9Cr-ODS martensitic steel with a high-strength heterogeneous structure obtained in this example at room temperature and 650 °C decreases slightly, the plasticity is significantly improved. By adjusting the annealing temperature and time, 9Cr-ODS martensitic steels with different strength and plasticity combinations can be obtained.
[0039] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and Moreover, the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.
Claims
1. A method for preparing 9Cr-ODS martensitic steel with enhanced plasticity, characterized in that: The following steps are involved: S1: Fe, Cr, W, Mn, V, and C are used as raw materials, and pre-alloyed powder is obtained by atomization powder making, and the mass percentages of the raw materials of the pre-alloyed powder are Cr: 9%, W: 2%, Mn: 0.4%, V: 0.2%, C: 0.08%, and the balance is Fe. The pre-alloyed powder is mixed with Y2O3 powder in a mass ratio of 99.65:0.35, and mechanically ball milled in a ball mill under argon protection to obtain a mixed powder after ball milling; S2: The ball-milled mixed powder is placed in a stainless steel sheath, and the powder in the stainless steel sheath is degassed at a temperature of 450°C until the vacuum degree of the stainless steel sheath reaches 0.002Pa; S3: The stainless steel sheath with a vacuum degree of 0.002Pa was sealed and welded, and then placed in a hot isostatic pressing device for curing and molding. The molding temperature was 1150°C, the holding time was 3h, and the molding pressure was 150Mpa. After cooling to room temperature with the furnace, a 9Cr-ODS martensitic steel sample was obtained; S4: placing the obtained 9Cr-ODS martensitic steel sample in a heat treatment furnace for heat preservation, cooling the 9Cr-ODS martensitic steel sample after heat preservation, and then hot rolling the sample, and then cooling it to room temperature to obtain a rolled 9Cr-ODS martensitic steel; S5: annealing the rolled 9Cr-ODS martensitic steel to obtain a 9Cr-ODS martensitic steel with enhanced plasticity.
2. The method for preparing a 9Cr-ODS martensitic steel with enhanced plasticity according to claim 1, characterized in that: In step S1: the ball-to-material ratio in the ball mill is 10:
1.
3. The method for preparing a 9Cr-ODS martensitic steel with enhanced plasticity according to claim 1, characterized in that: In step S1: the ball milling speed is 250 rpm, and the ball milling time is 30 h.
4. The method for preparing a 9Cr-ODS martensitic steel with enhanced plasticity according to claim 1, characterized in that: In step S4: the heat treatment furnace is kept at a holding temperature of 1100° C. for a holding time of 30 min to 40 min.
5. The method for preparing a 9Cr-ODS martensitic steel with enhanced plasticity according to claim 1, characterized in that: In step S4: the 9Cr-ODS martensitic steel sample after heat preservation is cooled to 880°C and hot rolled, and the deformation amount is 60% to 90%.
6. The method for preparing a 9Cr-ODS martensitic steel with enhanced plasticity according to claim 1, characterized in that: In step S5: the annealing temperature of the annealing treatment is 500°C to 700°C, and the temperature is kept at 10min to 60min.
7. A 9Cr-ODS martensitic steel with enhanced plasticity, wherein the 9Cr-ODS martensitic steel is obtained based on the preparation method of the 9Cr-ODS martensitic steel with enhanced plasticity as claimed in any one of claims 1 to 6.