Multi-component ultrafine particle reinforced low-activation carbon-free high-nitrogen ODS ferrite martensitic steel and preparation method and application thereof

Abstract

The invention discloses multi-component ultrafine particle reinforced low-activation carbon-free high-nitrogen ODS ferrite martensite steel as well as a preparation method and application of the multi-component ultrafine particle reinforced low-activation carbon-free high-nitrogen ODS ferrite martensite steel. The multi-component ultrafine particle reinforced low-activation carbon-free high-nitrogen ODS ferrite martensite steel is prepared from the following raw material components in percentage by mass: 5.0 to 10.0 percent of Cr, 1.0 to 3.0 percent of W, 0.2 to 0.5 percent of Zr, 0.2 to 0.5 percent of Si, 0.2 to 0.5 percent of Ti, 0.2 to 0.3 percent of N, 0.3 to 0.5 percent of Y2O3, 0.3 to 0.5 percent of TiN and the balance of Fe. A special ball milling process (a two-step method of combining high-energy ball milling with low-energy ball milling), a special ball milling atmosphere (mixing high-purity argon and nitrogen according to a certain proportion in a high-energy ball milling stage) and a special thermal machining process (hot forging and cold rolling are matched with multiple annealing treatments) are adopted; and the multi-component ultrafine particle reinforced low-activation carbon-free high-nitrogen ODS ferrite martensite steel can be obtained. According to the method, the high-temperature strength of the ODS steel is further improved, and the method has high market competitiveness and application prospects.

Description

Technical Field

[0001] This invention relates to the field of high-strength structural materials for high-temperature and high-irradiation environments, and in particular to a low-activation, carbon-free, high-nitrogen ODS ferritic martensitic steel reinforced with multi-component ultrafine particles, its preparation method, and its application. Background Technology

[0002] The fusion reactor blanket and first wall operate in extremely harsh environments, including high temperatures, high-energy neutron radiation, high pressure, thermal shock, and coolant corrosion. This necessitates structural materials with excellent high-temperature strength, radiation resistance, and low activation characteristics to ensure the long-term stable operation of the fusion reactor. Among numerous candidate materials, low-activation ferritic martensitic steel exhibits excellent radiation resistance. Oxide dispersion strengthened (ODS) steel, developed based on this, further enhances the radiation resistance of ferritic martensitic steel by uniformly dispersing a large number of ultrafine nanoscale oxide particles within the steel matrix through specific composition design and processing techniques. In particular, its high-temperature strength is significantly improved, and its maximum service temperature can be 100-150°C higher than similar conventional low-activation steels. Therefore, low-activation ODS steel is considered the most promising structural material for fusion reactor blankets and first walls. Given its excellent radiation resistance and high-temperature strength, ODS steel is also an important candidate material for the cladding of many fourth-generation reactors.

[0003] ODS-modified ferritic martensitic steels contain a large number of dispersed strengthening phases, which significantly hinder phase transformation in the matrix, making it difficult to obtain a martensitic structure. Martensite structure plays a positive role in improving radiation resistance and high-temperature creep resistance. Furthermore, to meet future application requirements, low-activation ODS steels still need further improvements in high-temperature strength and operating temperature window. However, the oxide dispersed particles in ODS steels are mainly distributed within the grains, limiting their grain boundary strengthening effect. How to solve these problems to further improve the performance of ODS ferritic martensitic steels is the focus of current research. Summary of the Invention

[0004] The purpose of this invention is to provide a low-activation, carbon-free, high-nitrogen ODS ferritic martensitic steel (named CZ-ODS steel) reinforced by multi-component ultrafine particles, its preparation method, and its application, so as to solve the problems existing in the prior art and meet the requirements of fusion reactors for high-temperature structural materials.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] One of the technical solutions of the present invention is a multi-component ultrafine particle reinforced low-activation carbon-free high-nitrogen ODS ferritic martensitic steel, wherein the raw material composition by mass percentage is: Cr 5.0-10.0%, W 1.0-3.0%, Zr 0.2-0.5%, Si 0.2-0.5%, Ti 0.2-0.5%, N 0.2-0.3%, Y2O3 0.3-0.5%, TiN 0.3-0.5%, with the balance being Fe.

[0007] Furthermore, the low-activation, carbon-free, high-nitrogen ODS ferritic martensitic steel reinforced by multi-component ultrafine particles has Y-Zr(Ti)-O particles dispersed within the grains and TiN particles dispersed at the grain boundaries.

[0008] Furthermore, the ferrite content in the multi-component ultrafine particle-reinforced low-activation carbon-free high-nitrogen ODS ferritic martensitic steel is 40-30 vol%, and the martensite content is 60-70 vol%.

[0009] Carbon is beneficial for controlling the formation of the austenite phase and its transformation into martensite. Therefore, traditional ODS ferritic martensitic steels often control the content of austenite and martensite phases by controlling the amount of carbon. However, carbon easily generates M23C6, which is unstable under high temperatures and irradiation, thus adversely affecting the properties of ODS ferritic martensitic steels. This invention introduces a certain amount of nitrogen to replace the carbon required in traditional ODS ferritic martensitic steels, promoting the martensitic phase transformation. Its advantages include avoiding the formation of M23C6 particles that easily result from carbon-containing designs. M23C6 consumes Cr, reducing the steel's oxidation resistance, and M23C6 easily coarsens or even decomposes under high temperatures and irradiation, reducing the steel's properties. The nitrogen introduced into the raw materials of this invention helps to form martensite during subsequent heat treatment. The directly introduced TiN can form finer and more stable TiN nitride particles at the grain boundaries (generally, in ODS steel, the oxide strengthening particles formed during mechanical alloying and subsequent heat treatment are mainly distributed within the grains, while the grain boundaries have fewer strengthening particles, becoming weak points and detrimental to its high-temperature creep strength. In this invention, by introducing TiN, nitride dispersed particles are formed at the grain boundaries), thus improving the high-temperature strength of ODS ferritic martensitic steel. Furthermore, the 0.2-0.5% equal content of Zr, Si, and Ti elements added to the raw materials can, together with the added Y2O3, form ultrafine yttrium-rich complex multi-component oxide particles, namely Y-Zr(Ti)-O, during mechanical alloying and subsequent heat treatment. These nano-oxide particles dispersed within the grains have excellent strengthening effects. The addition of W provides solid solution strengthening, thereby improving the high-temperature strength of the alloy.

[0010] Preferably, the raw material composition of the multi-component ultrafine particle reinforced low-activation carbon-free high-nitrogen ODS ferritic martensitic steel, by mass percentage, is: Cr 8.5%, W 1.5%, Zr 0.3%, Si 0.3%, Ti 0.3%, N 0.25%, Y2O3 0.35%, TiN 0.35%, with the balance being Fe.

[0011] Preferably, the raw material composition of the multi-component ultrafine particle reinforced low-activation carbon-free high-nitrogen ODS ferritic martensitic steel, by mass percentage, is: Cr 6.0%, W 2.0%, Zr 0.4%, Si 0.4%, Ti 0.4%, N 0.28%, Y2O3 0.4%, TiN 0.4%, with the balance being Fe.

[0012] The second technical solution of the present invention: a method for preparing low-activation, carbon-free, high-nitrogen ODS ferritic martensitic steel reinforced by the above-mentioned multi-component ultrafine particles, comprising the following steps:

[0013] According to the raw material composition, pre-alloyed powder, Y2O3 powder, and TiN powder containing Cr, W, Zr, Si, Ti, and Fe elements are weighed and subjected to two-step ball milling to obtain nitrogen-containing ball milled powder; the nitrogen-containing ball milled powder is subjected to hot isostatic pressing sintering to obtain hot isostatic pressing steel ingot; the hot isostatic pressing steel ingot is subjected to hot forging, cold rolling, and heat treatment in sequence to obtain the multi-component ultrafine particle reinforced low-activation carbon-free high-nitrogen ODS ferritic martensitic steel;

[0014] The two-step ball milling includes high-energy ball milling and low-energy ball milling, with the high-energy ball milling being carried out in a nitrogen-containing atmosphere.

[0015] Furthermore, the two-step ball milling includes:

[0016] First, the pre-alloyed powder containing Cr, W, Zr, Si, Ti, and Fe elements is mixed with the Y2O3 powder and subjected to high-energy ball milling in a mixed atmosphere of argon and nitrogen. Then, the TiN powder is added and subjected to low-energy ball milling in an argon atmosphere (i.e., using argon as a protective gas).

[0017] The Zr, Ti, and added Y2O3 in the pre-alloyed powder can form ultrafine complex oxide particles during high-energy ball milling and subsequent heat treatment, which are mainly distributed within the grains and play a strengthening role. The N introduced during high-energy ball milling helps to form a ferrite-martensite dual-phase structure during subsequent heat treatment. The TiN added in the later stages of ball milling (i.e., low-energy ball milling) is mainly distributed at the grain boundaries. The nitrogen content specified in the raw material composition of this invention refers to the nitrogen introduced during high-energy ball milling, excluding the nitrogen contained in the raw material TiN; the specified TiN refers entirely to the TiN introduced from the raw material TiN.

[0018] Furthermore, the parameters of the high-energy ball mill include: a ball milling speed of 400-440 rpm, a ball milling time of 30-40 h, and a volume ratio of argon to nitrogen of 1-2:1.

[0019] Furthermore, the parameters of the low-energy ball mill include: a ball milling speed of 200-220 rpm and a ball milling time of 15-20 h.

[0020] Furthermore, the pressure of both the mixed atmosphere and the argon atmosphere is 1-1.1 atmospheres.

[0021] This invention employs a two-step ball milling process. The first stage involves high-energy ball milling under a mixed argon and nitrogen atmosphere to fully mechanically alloy the added oxide (Y₂O₃) with the pre-alloyed powder and introduce a certain nitrogen content. The second stage uses low-energy ball milling under a high-purity argon atmosphere to introduce nano-titanium nitride powder, preventing the decomposition of the added TiN. This two-step ball milling process achieves both sufficient mechanical alloying of the oxide and preserves the size of the subsequently added nano-nitrides, while introducing a controllable nitrogen content to obtain the desired design composition. This allows for the acquisition of a ferrite-martensite dual-phase microstructure during subsequent heat treatment.

[0022] The reason for adding TiN in the low-energy ball milling stage rather than the high-energy ball milling stage is that if it were added in the high-energy ball milling stage, TiN would dissolve into the matrix and thus would not be able to form dispersed particles at the grain boundaries.

[0023] Optionally, the ball-to-material ratio of the high-energy ball mill is 10-15:1, and the grinding media is high-chromium steel grinding balls.

[0024] Furthermore, the conditions for hot isostatic pressing sintering include: a temperature of 1100-1150℃, a pressure of 150-180MPa, and a time of 4-5h.

[0025] Further, the hot forging includes:

[0026] The forging process is repeated 3-4 times. Before each forging process, the material is kept at 1000-1100℃. The deformation amount for each forging process is 20-30%.

[0027] Optionally, the holding time before the first forging deformation is 2-4 hours, and the holding time before the second and third forging deformation is 1-2 hours.

[0028] Furthermore, the total deformation of the cold rolling is 50%, and it is completed in 5-10 passes.

[0029] Further, the heat treatment includes:

[0030] After holding at 1000-1100℃ for 4-6 hours, water quenching is performed, followed by holding at 740-780℃ for 1-2 hours and then air cooling to 400-600℃ followed by sand cooling.

[0031] This invention utilizes hot forging and cold rolling to perform thermomechanical deformation processing on hot isostatically pressed steel ingots, thereby improving the uniformity and density of the alloy microstructure. Furthermore, heat treatment is applied to precipitate nanoparticles and obtain a ferrite-martensite dual-phase microstructure.

[0032] Optionally, the pre-alloyed powder is prepared using gas atomization technology.

[0033] Optionally, the pre-alloyed powder and the Y2O3 powder both have a particle size of 325 mesh (i.e., can pass through a 325 mesh sieve); the TiN powder has a particle size of less than 50 nm.

[0034] This invention utilizes a unique ball milling process (a two-step method combining high-energy and low-energy ball milling), a special ball milling atmosphere (high-purity argon and nitrogen mixed in a specific ratio during the high-energy ball milling stage), and a special thermomechanical processing technique (hot forging and cold rolling combined with multiple annealing treatments) to obtain high-strength, low-activation, high-nitrogen ODS ferritic martensitic steel strengthened by the dispersion of ultrafine multi-component oxides (specifically, ultrafine oxide particles rich in Y, Ti, Zr, and O, i.e., Y-Zr(Ti)-O. Y2O3 powder and alloying elements Ti and Zr are added to the raw material; during mechanical alloying, Y2O3 dissolves into the steel matrix, and during subsequent heat treatment, Y, Ti, Zr, and O nucleate and precipitate multi-component complex oxide particles) and nitride multi-component particles. This preparation method further improves the high-temperature strength of low-activation ODS steel, giving it strong market competitiveness and application prospects.

[0035] The third technical solution of the present invention: the application of the above-mentioned multi-component ultrafine particle reinforced low-activation carbon-free high-nitrogen ODS ferritic martensitic steel in fission reactors or aero engines.

[0036] Optionally, the multi-component ultrafine particle-reinforced low-activation carbon-free high-nitrogen ODS ferritic martensitic steel is used for the preparation of high-temperature hot-end components in fission reactors or aero-engines.

[0037] Optionally, the multi-component ultrafine particle-reinforced low-activation carbon-free high-nitrogen ODS ferritic martensitic steel is used as the cladding or first wall of a fusion reactor.

[0038] The present invention discloses the following technical effects:

[0039] This invention uses low-activation elements (Fe, Cr, Ti, Zr, Si, W) as alloying components, significantly reducing the radiation damage response of steel and minimizing the activation effect of materials under long-term irradiation, thus meeting the low-activation requirements of fusion reactors for structural materials. This invention is a carbon-free design, avoiding the formation of the M23C6 precipitate phase commonly found in traditional steels. This precipitate phase is prone to coarsening and even decomposition in high-temperature and irradiated environments, severely degrading material properties.

[0040] The preparation method of this invention is essentially a carbon-free, nitrogen-controlled, multi-component particle-reinforced method for preparing low-activation ODS steel, which can control the ferrite-martensite dual-phase structure through composition design and preparation steps. Specifically, high-energy ball milling forms ultrafine multi-component oxide particles within the grains, providing intragranular strengthening; ball milling in a special atmosphere introduces a certain amount of nitrogen, which helps in the formation of martensite; and the direct addition of a certain amount of nitrides during low-energy ball milling forms nitrides at grain boundaries, refining the grains and strengthening the grain boundaries. The synergistic effect of the ultrafine multi-component oxide particles within the grains and the nitride particles at the grain boundaries effectively improves the high-temperature mechanical properties of the ODS steel. The preparation method of this invention further improves the high-temperature strength of low-activation ODS steel, giving it strong market competitiveness and application prospects.

[0041] The low-activation, carbon-free, high-nitrogen ODS ferritic martensitic steel prepared by this invention can be applied to the fusion reactor blanket and first wall structure materials with extremely high requirements for high temperature strength and radiation resistance. It can also be used in advanced fission reactor fuel cladding materials, aero-engine structural materials, and other high-temperature structural materials for energy systems. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 Transmission electron microscope (TEM) image of the microstructure of CZ-ODS steel prepared in Example 1.

[0044] Figure 2 The image shows the EDS composition distribution of the CZ-ODS steel prepared in Example 1 under a transmission electron microscope. Detailed Implementation

[0045] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0046] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0047] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0048] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0049] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0050] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0051] In the following embodiments and comparative examples of the present invention, room temperature refers specifically to 20-30°C.

[0052] Unless otherwise specified, all raw materials used in the following embodiments and comparative examples of this invention are commercially available products.

[0053] The pre-alloy powders containing Cr, W, Zr, Si, Ti, and Fe elements, and the pre-alloy powders containing Cr, W, Zr, Si, Ti, Fe, and C elements used in the following embodiments and comparative examples of the present invention were all prepared by gas atomization technology, and the particle size was 325 mesh.

[0054] The Y2O3 powder used in the following examples and comparative examples of the present invention has a particle size of 325 mesh, and the TiN powder has a particle size of 30-50 nm.

[0055] The purity of the high-purity argon and high-purity nitrogen used in the following examples and comparative examples of this invention is 99.999%.

[0056] Example 1

[0057] A multi-component ultrafine particle reinforced low-activation carbon-free high-nitrogen ODS ferritic martensitic steel (i.e., CZ-ODS steel) has the following raw material composition by mass percentage: Cr 8.5%, W 1.5%, Zr 0.3%, Si 0.3%, Ti 0.3%, N 0.25%, Y2O3 0.35%, TiN 0.35%, with the balance being Fe.

[0058] The preparation steps of the above CZ-ODS steel are as follows:

[0059] According to the above raw material composition, weigh out pre-alloyed powder, Y2O3 powder, and TiN powder containing Cr, W, Zr, Si, Ti, and Fe elements; first, add the pre-alloyed powder and Y2O3 powder to a ball mill jar, and add high-chromium steel grinding balls as the grinding medium (ball-to-powder ratio of 10:1). Then, introduce a mixture of high-purity argon and high-purity nitrogen (volume ratio of high-purity argon to high-purity nitrogen of 1:1, pressure of the mixture in the ball mill jar of 1 atmosphere), and ball mill at 430 rpm for 40 hours. Subsequently, add TiN powder and replenish high-chromium steel grinding balls until the ball-to-powder ratio is 10:1, and then ball mill at 210 rpm for 20 hours under a high-purity argon atmosphere (pressure still 1 atmosphere) to obtain nitrogen-containing ball-milled powder (the target nitrogen content in the designed raw material composition is introduced through high-energy ball milling); for the above... Nitrogen-containing ball-milled powder was subjected to hot isostatic pressing (HIP) sintering at 1150℃, 160MPa, and for 4 hours to obtain HIP steel ingots. The HIP steel ingots were then hot-forged using the following process: a first forging deformation was performed after holding at 1050℃ for 3 hours, followed by a second forging deformation after holding at 1050℃ for 1 hour, a third forging deformation after holding at 1050℃ for 1 hour, and a fourth forging deformation after holding at 1050℃ for 1 hour. Each forging deformation involved a 20% reduction in deformation. After hot forging, the hot-forged samples were cold-rolled at room temperature with a total deformation of 50%, completed in 6 passes. The cold-rolled samples were then water-quenched after holding at 1050℃ for 5 hours, followed by air cooling after holding at 750℃ for 2 hours, and finally air-cooled to 600℃ for sand cooling, thus obtaining the desired CZ-ODS steel (abbreviated as ODS-1). Its microstructure is shown in the transmission electron microscope image below. Figure 1 As shown, ferrite in ODS-1 consists of equiaxed crystals with slightly larger grains, accounting for 40 vol%. Martensite consists of finer grains, accounting for 60 vol%. Further magnification and EDS compositional analysis of the dispersed particles under a transmission electron microscope are shown below. Figure 2As shown, EDS analysis reveals nitride particles with a size of 20-50 nm distributed at the grain boundaries, and a large number of ultrafine oxide particles rich in yttrium (Y), titanium (Ti), zirconium (Zr) and oxygen (O) dispersed within the grains, with a size of less than 10 nm.

[0060] Example 2

[0061] A multi-component ultrafine particle reinforced low-activation carbon-free high-nitrogen ODS ferritic martensitic steel (i.e., CZ-ODS steel) has the following raw material composition by mass percentage: Cr 6.0%, W 2.0%, Zr 0.4%, Si 0.4%, Ti 0.4%, N 0.28%, Y2O3 0.4%, TiN 0.4%, with the balance being Fe.

[0062] The preparation steps of the above CZ-ODS steel are as follows:

[0063] According to the above raw material composition, weigh out pre-alloyed powder, Y2O3 powder, and TiN powder containing Cr, W, Zr, Si, Ti, and Fe elements; first, add the pre-alloyed powder and Y2O3 powder to a ball mill jar, and add high-chromium steel grinding balls as the grinding medium (ball-to-powder ratio of 10:1). Then, introduce a mixture of high-purity argon and high-purity nitrogen (volume ratio of high-purity argon to high-purity nitrogen of 1:1, pressure of the mixture in the ball mill jar of 1 atmosphere), and ball mill at 430 rpm for 30 hours. Subsequently, add TiN powder and replenish high-chromium steel grinding balls until the ball-to-powder ratio is 10:1, and then ball mill at 210 rpm for 15 hours under a high-purity argon atmosphere (pressure still 1 atmosphere) to obtain nitrogen-containing ball-milled powder (the target nitrogen content in the designed raw material composition is introduced through high-energy ball milling); for the above... Nitrogen-containing ball milled powder was subjected to hot isostatic pressing (HIP) sintering at 1150℃, 150MPa, and for 4 hours to obtain HIP steel ingots. The HIP steel ingots were then hot-forged using the following process: a first forging deformation was performed after holding at 1050℃ for 3 hours, followed by a second forging deformation after holding at 1050℃ for 1 hour, a third forging deformation after holding at 1050℃ for 1 hour, and a fourth forging deformation after holding at 1050℃ for 1 hour. Each forging deformation involved a 20% reduction in deformation. After hot forging, the hot-forged samples were cold-rolled at room temperature with a total deformation of 50%, completed in 6 passes. The cold-rolled samples were then water-quenched after holding at 1050℃ for 5 hours, followed by air cooling after holding at 760℃ for 2 hours, and finally air-cooled to 600℃ for sand cooling to obtain the desired CZ-ODS steel (abbreviated as ODS-2). Tests showed that ODS-2 contained 35 vol% ferrite and 65 vol% martensite.

[0064] Comparative Example 1 (ODS steel prepared by one-step ball milling with carbon added, but without nitrogen and TiN)

[0065] An ODS steel, by mass percentage, has the following raw material composition: Cr 8.5%, W 1.5%, Zr 0.3%, Si 0.3%, Ti 0.3%, C 0.1%, Y2O3 0.35%, with the balance being Fe.

[0066] The preparation steps for the above-mentioned ODS steel are as follows:

[0067] According to the above-mentioned raw material composition, pre-alloyed powder and Y2O3 powder containing Cr, W, Zr, Si, Ti, Fe, and C elements were weighed. The pre-alloyed powder and Y2O3 powder were added to a ball mill jar, and high-chromium steel grinding balls were added as the grinding media (ball-to-material ratio 10:1). High-purity argon gas was then introduced, and the mixture was ball-milled at 430 rpm for 40 hours under high-purity argon protection to obtain ball-milled powder. The ball-milled powder was then subjected to hot isostatic pressing (HIP) sintering at 1150℃, 160 MPa, and for 4 hours to obtain a hot isostatic pressed steel ingot. The hot isostatic pressed steel ingot was then hot-forged at 1050℃. After holding at 1050℃ for 3 hours, the first forging deformation was performed, followed by a second forging deformation at 1050℃ for 1 hour, a third forging deformation at 1050℃ for 1 hour, and a fourth forging deformation at 1050℃ for 1 hour. The deformation amount in each forging deformation was 20%. After hot forging, the hot-forged sample was cold-rolled at room temperature with a total deformation of 50%, completed in 6 passes. The cold-rolled sample was then water-quenched after holding at 1050℃ for 5 hours, followed by air cooling after holding at 750℃ for 2 hours, and finally air-cooled to 600℃ for sand cooling, thus obtaining the desired ODS steel (abbreviated as ODS-d1). Testing showed that the ferrite content in ODS-d1 was 70 vol%, and the martensite content was 30 vol%.

[0068] Comparative Example 2 (Carbon-free, nitrogen-controlled, TiN-free raw materials, one-step ball milling preparation of ODS steel)

[0069] An ODS steel, by mass percentage, has the following raw material composition: Cr 8.5%, W 1.5%, Zr 0.3%, Si 0.3%, Ti 0.3%, N 0.25%, Y2O3 0.35%, with the balance being Fe.

[0070] The preparation steps for the above-mentioned ODS steel are as follows:

[0071] According to the above-mentioned raw material composition, pre-alloyed powder and Y2O3 powder containing Cr, W, Zr, Si, Ti, and Fe elements were weighed. The pre-alloyed powder and Y2O3 powder were added to a ball mill jar, and high-chromium steel grinding balls were added as the grinding media (ball-to-material ratio of 10:1). Then, a mixture of high-purity argon and high-purity nitrogen (volume ratio of high-purity argon to high-purity nitrogen of 1:1, pressure of the mixture in the ball mill jar of 1 atmosphere) was introduced. High-energy ball milling was performed at 430 rpm for 40 hours to obtain nitrogen-containing ball milled powder (the target nitrogen content in the designed raw material composition was introduced through high-energy ball milling). The above nitrogen-containing ball milled powder was then subjected to hot isostatic pressing sintering at 1150℃, 160 MPa, and for 4 hours. Hot isostatic pressing (HOP) steel ingots were obtained. These ingots were then hot-forged using the following process: a first forging deformation was performed after holding at 1050℃ for 3 hours, followed by a second forging deformation after holding at 1050℃ for 1 hour, a third forging deformation after holding at 1050℃ for 1 hour, and a fourth forging deformation after holding at 1050℃ for 1 hour. Each forging deformation involved a 20% reduction in deformation. After hot forging, the hot-forged samples were cold-rolled at room temperature, with a total deformation of 50%, completed in 6 passes. The cold-rolled samples were then water-quenched after holding at 1050℃ for 5 hours, followed by air cooling after holding at 750℃ for 2 hours, and finally air-cooled to 600℃ for sand cooling, thus obtaining the desired ODS steel (abbreviated as ODS-d2). Testing revealed that ODS-d2 contained 55 vol% ferrite and 45 vol% martensite.

[0072] Comparative Example 3 (No N is introduced during ball milling)

[0073] An ODS steel, by mass percentage, has the following raw material composition: Cr 8.5%, W 1.5%, Zr 0.3%, Si 0.3%, Ti 0.3%, Y2O3 0.35%, TiN 0.35%, with the balance being Fe.

[0074] The preparation steps for the above-mentioned ODS steel are as follows:

[0075] According to the above-mentioned raw material composition, pre-alloyed powder, Y₂O₃ powder, and TiN powder containing Cr, W, Zr, Si, Ti, and Fe elements were weighed out. The pre-alloyed powder and Y₂O₃ powder were added to a ball mill jar, and high-chromium steel grinding balls were added as the grinding media (ball-to-material ratio of 10:1). High-purity argon gas was then introduced, and high-energy ball milling was performed at 430 rpm for 40 hours under high-purity argon protection. Subsequently, TiN powder was added, and high-chromium steel grinding balls were replenished until the ball-to-material ratio reached 10:1. Then, low-energy ball milling was continued at 210 rpm for 20 hours under high-purity argon protection to obtain the ball-milled powder. The above ball-milled powder was subjected to hot isostatic pressing sintering at 1150℃, 160 MPa, and 4 hours to obtain... The hot isostatic pressing (HIP) steel ingots are then hot-forged. The hot forging process is as follows: after holding at 1050℃ for 3 hours, a first forging deformation is performed, followed by a second forging deformation after holding at 1050℃ for 1 hour, a third forging deformation after holding at 1050℃ for 1 hour, and a fourth forging deformation after holding at 1050℃ for 1 hour. The deformation amount in each forging deformation is 20%. After hot forging, the hot-forged samples are cold-rolled at room temperature with a total deformation of 50%, completed in 6 passes. The cold-rolled samples are then water-quenched after holding at 1050℃ for 5 hours, followed by air cooling after holding at 750℃ for 2 hours, and finally air-cooled to 600℃ for sand cooling to obtain the desired CZ-ODS steel (abbreviated as ODS-d3). Testing shows that ODS-d3 has a ferritic structure and no martensite.

[0076] Comparative Example 4

[0077] Similar to Example 1, the only difference is that Zr is omitted from the raw material composition, i.e., the raw material composition is: Cr 8.5%, W 1.5%, Si 0.3%, Ti 0.3%, N 0.25%, Y₂O₃ 0.35%, TiN 0.35%, with the balance being Fe. The ODS steel finally obtained in this comparative example is abbreviated as ODS-d4. Testing showed that the ferrite content in ODS-d4 was 40 vol%, and the martensite content was 60 vol%.

[0078] Comparative Example 5

[0079] Similar to Example 1, the only difference is that W is omitted from the raw material composition, i.e., the raw material composition is: Cr 8.5%, Zr 0.3%, Si 0.3%, Ti 0.3%, N 0.25%, Y₂O₃ 0.35%, TiN 0.35%, with the balance being Fe. The ODS steel finally obtained in this comparative example is abbreviated as ODS-d5. Testing showed that ODS-d5 has a ferrite content of 40 vol% and a martensite content of 60 vol%.

[0080] Comparative Example 6 (One-step ball milling preparation of ODS steel)

[0081] An ODS steel, by mass percentage, has the following raw material composition: Cr 8.5%, W 1.5%, Zr 0.3%, Si 0.3%, Ti 0.3%, N 0.25%, Y2O3 0.35%, TiN 0.35%, with the balance being Fe.

[0082] The preparation steps for the above-mentioned ODS steel are as follows:

[0083] According to the above-mentioned raw material composition, pre-alloyed powder, Y2O3 powder, and TiN powder containing Cr, W, Zr, Si, Ti, and Fe elements were weighed out. The pre-alloyed powder, Y2O3 powder, and TiN powder were added to a ball mill jar, and high-chromium steel grinding balls were added as the grinding media (ball-to-material ratio of 10:1). Then, a mixture of high-purity argon and high-purity nitrogen (volume ratio of high-purity argon to high-purity nitrogen of 1:1, pressure of the mixture in the ball mill jar of 1 atmosphere) was introduced, and high-energy ball milling was performed at 430 rpm for 40 hours to obtain nitrogen-containing ball mill powder (the target nitrogen content in the designed raw material composition was introduced through high-energy ball milling). The above nitrogen-containing ball mill powder was subjected to hot isostatic pressing sintering with sintering parameters of 1150℃ and 160M. Pa, 4h, to obtain a hot isostatically pressed steel ingot; the hot isostatically pressed steel ingot is then hot forged. The hot forging process is as follows: after holding at 1050℃ for 3h, the first forging deformation is performed, followed by holding at 1050℃ for 1h for the second forging deformation, followed by holding at 1050℃ for 1h for the third forging deformation, followed by holding at 1050℃ for 1h for the fourth forging deformation, with a deformation amount of 20% in each forging deformation; after hot forging, the hot-forged sample is cold-rolled at room temperature, with a total deformation amount of 50%, completed in 6 passes; the cold-rolled sample is then water-quenched after holding at 1050℃ for 5h, followed by holding at 750℃ for 2h and then air-cooled, and finally air-cooled to 600℃ for sand cooling, thus obtaining the desired ODS steel (abbreviated as ODS-d6). Testing shows that the ferrite content in ODS-d6 is 35 vol%, and the martensite content is 65 vol%.

[0084] Test case

[0085] Room temperature tensile tests and high temperature tensile tests were conducted on the ODS steels prepared in Examples 1-2 (ODS-1 and ODS-2) and Comparative Examples 1-6 (ODS-d1 to ODS-d6), and the results are shown in Table 1. Creep performance tests were conducted on the ODS steels prepared in Examples 1-2 and Comparative Examples 1-6 under a stress of 800℃ and 100MPa, and the results are shown in Table 2.

[0086] The methods for room temperature tensile testing (according to standard GB / T228.1-2015) and high temperature tensile testing (according to standard GB / T228.2-2015) are as follows: The samples are processed into M6 / 3 circular rod-shaped tensile specimens with a gauge length of 15 mm and a gauge diameter of 3 mm. Three tensile specimens are tested, and the average value is taken. The method for creep testing (according to standard GB / T 2039-2024) is as follows: The samples are processed into M12 circular rod-shaped creep specimens with a gauge length of 25 mm and a gauge diameter of 5 mm. Three creep specimens are tested, and the average value is taken.

[0087] Table 1

[0088]

[0089] Table 2

[0090]

[0091] A comparison of the performance data of Examples 1-2 (ODS-1, ODS-2) and Comparative Examples 1-5 (ODS-d1 to ODS-d5) in Table 1 shows that the ODS steels (ODS-1 and ODS-2) using a carbon-free design, a two-step ball milling method for nitrogen control, and multi-component particle reinforcement exhibit higher tensile strengths at room temperature and 800°C than those prepared by a conventional one-step ball milling method, which are carbon-containing and nitrogen-free or carbon-free and nitrogen-controlled, but without the addition of TiN (ODS-d1 and ODS-d2). In particular, their tensile strengths are significantly higher than those of ODS steels without Zr or W (ODS-d4 or ODS-d5) and ODS steels without the introduction of carbon or nitrogen (ODS-d3). Especially at 800°C, the tensile strengths of ODS-1 and ODS-2 are twice that of ODS-d4 and ODS-d5. This is mainly because the former forms a ferrite-martensite dual-phase structure with a large number of ultrafine multi-component oxide particles dispersed within the grains, and ultrafine nitride strengthening phases distributed at the grain boundaries. The latter, however, has a reduced martensite content, even being dominated by ferrite (ODS-d3); or lacks TiN strengthening particles (ODS-d1, ODS-d2), or lacks elements with strong solid solution strengthening (ODS-d4, ODS-d5). The tensile properties of the ODS steels (ODS-d6) with TiN added via a one-step ball milling method in Examples 1-2 and Comparative Example 6 are similar, although ODS-d6 is slightly lower than ODS-1 and ODS-2. This is because both have similar alloy composition, matrix phase structure, and dispersed particles within the grains, while the difference in grain boundary precipitates has a limited impact on tensile properties.

[0092] As shown in Table 2, compared with tensile properties, the ODS steels (ODS-1 and ODS-2) using a carbon-free design, two-step ball milling method for nitrogen control, and multi-component particle reinforcement exhibit significantly better high-temperature creep performance than the ODS steels in the comparative examples. This is mainly because the former forms a ferrite-martensite dual-phase structure with a large number of ultrafine multi-component oxide particles dispersed within the grains, while ultrafine nitride strengthening phases are distributed at the grain boundaries. In contrast, the latter have reduced martensite content, or even a predominantly ferrite structure (ODS-d3); or lack TiN strengthening particles (ODS-d1, ODS-d2); or lack effective solid solution strengthening elements (ODS-d4, ODS-d5). It is particularly noteworthy that although the tensile properties of Examples 1-2 and Comparative Example 6 are similar, their high-temperature creep properties differ greatly, indicating that the introduction of dispersed strengthening particles at the grain boundaries proposed in this invention is very effective in improving the creep performance of the alloy.

[0093] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A multi-principal element ultrafine-grained, low-activation, carbon-free, high-nitrogen, ODS ferritic-martensitic steel, characterized in that, The raw material components, by mass percentage, are: Cr 5.0-10.0%, W 1.0-3.0%, Zr 0.2-0.5%, Si 0.2-0.5%, Ti 0.2-0.5%, N 0.2-0.3%, Y2O3 0.3-0.5%, TiN 0.3-0.5%, and the balance being Fe.

2. The multi-component ultra-fine grained, strengthened, low-activated, carbon-free, high-nitrogen, ODS ferritic-martensitic steel of claim 1, wherein, The raw material components, by mass percentage, are: Cr 8.5%, W 1.5%, Zr 0.3%, Si 0.3%, Ti 0.3%, N 0.25%, Y2O3 0.35%, TiN 0.35%, and the balance being Fe.

3. The multi-component ultra-fine grained, strengthened, low-activated, carbon-free, high-nitrogen, ODS ferritic-martensitic steel of claim 1, wherein, The raw material components, by mass percentage, are: Cr 6.0%, W 2.0%, Zr 0.4%, Si 0.4%, Ti 0.4%, N 0.28%, Y2O3 0.4%, TiN 0.4%, and the balance being Fe.

4. A method of producing a multi-component ultrafine-grained, low-activated, carbon-free, high-nitrogen, ODS ferritic-martensitic steel according to any one of claims 1 to 3, characterized in that The method comprises the following steps: The pre-alloyed powder containing Cr, W, Zr, Si, Ti, and Fe elements, Y2O3 powder, and TiN powder are weighed according to the raw material component composition, two-step ball milling is performed to obtain nitrogen-containing ball-milled powder; the nitrogen-containing ball-milled powder is subjected to hot isostatic pressing sintering to obtain a hot isostatic pressing steel ingot; and the hot isostatic pressing steel ingot is sequentially subjected to hot forging, cold rolling, and heat treatment to obtain the multi-component ultrafine particle strengthened low-activation carbon-free high-nitrogen ODS ferritic martensitic steel. The two-step ball milling comprises high-energy ball milling and low-energy ball milling, and the high-energy ball milling is performed in a nitrogen-containing atmosphere.

5. The method of making a multi-principal element ultra-fine grained, strengthened, low-activated, carbon-free, high-nitrogen, ODS ferritic martensitic steel of claim 4, wherein, The two-step ball milling comprises: First, the pre-alloyed powder containing Cr, W, Zr, Si, Ti, and Fe elements is mixed with the Y2O3 powder, high-energy ball milling is performed in a mixed atmosphere of argon and nitrogen, and then the TiN powder is added, low-energy ball milling is performed in an argon atmosphere.

6. The method of making a multi-principal element ultra-fine grained, strengthened, low-activated, carbon-free, high-nitrogen, ODS ferritic martensitic steel of claim 5, wherein, The parameters of the high-energy ball milling include: a ball milling rotation speed of 400-440 rpm, a ball milling time of 30-40 h, and a volume ratio of argon to nitrogen of 2-1:1; And / or, the parameters of the low-energy ball milling include: a ball milling rotation speed of 200-220 rpm, a ball milling time of 15-20 h.

7. The method of making a multi-principal element ultra-fine grained, strengthened, low-activated, carbon-free, high-nitrogen, ODS ferritic-martensitic steel of claim 4, wherein, The conditions of the hot isostatic pressing sintering include: a temperature of 1100-1150℃, a pressure of 150-180 MPa, and a time of 4-5 h.

8. The method of making a multi-principal element ultra-fine grained, strengthened, low-activated, carbon-free, high-nitrogen, ODS ferritic martensitic steel of claim 4, wherein, The hot forging comprises: The hot forging comprises:

9. The method of making a multi-principal element ultra-fine grained, strengthened, low-activated, carbon-free, high-nitrogen, ODS ferritic martensitic steel of claim 4, wherein, The heat treatment comprises: After being kept at 1000-1100℃ for 4-6 h, water quenching is performed, and then after being kept at 740-780℃ for 1-2 h, air cooling is performed to 400-600℃ and then sand burying cooling is performed.

10. Use of the multi-component ultrafine particle strengthened low-activation carbon-free high-nitrogen ODS ferritic martensitic steel according to any one of claims 1-3 in a nuclear reactor or an aero-engine.

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