A rare earth element cerium doped martensitic stainless steel and a method for manufacturing the same

Abstract

The application discloses a rare earth element cerium doped martensitic stainless steel and a preparation method thereof, and belongs to the field of metal materials.The alloy comprises the following components in percentage by mass: C: 0.10-0.25%, Si: 0.20-1.00%, Mn: 0.30-1.50%, Cr: 11.0-14.0%, Ni: 0.10-2.50%, Mo: 0.10-1.00%, Ce: 0.01-0.05%, and the balance of Fe and inevitable impurities.The application aims at the problems in the prior art, and provides a martensitic stainless steel modified by rare earth element cerium and a preparation method thereof.The stainless steel has excellent comprehensive mechanical properties, corrosion resistance and oxidation resistance.

Description

Technical Field

[0001] This invention relates to the field of metallic materials, specifically to a rare earth element cerium-doped martensitic stainless steel and its preparation method by electric arc melting. Background Technology

[0002] Martensitic stainless steel is an important class of engineering structural materials, possessing high strength, hardness, and certain corrosion resistance, and is widely used in machinery, energy, petrochemical, aerospace, and other fields. Its main alloying components typically include elements such as Cr, N, and Mo. Through appropriate heat treatment, a martensitic structure can be obtained, achieving a good combination of strength and toughness.

[0003] Traditional martensitic stainless steel suffers from insufficient toughness, limited corrosion resistance, weak oxidation resistance, and rapid degradation of high-temperature mechanical properties during use. Especially when operating in harsh environments with high temperature, high pressure, and corrosion for extended periods, its material properties struggle to meet engineering requirements. To address these shortcomings, researchers have explored methods such as alloying design and process optimization to improve the overall performance of martensitic stainless steel.

[0004] Rare earth elements, due to their unique electronic configuration and physicochemical properties, are widely used in the microalloying process of steel materials. Existing research has shown that the addition of appropriate amounts of rare earth elements can purify molten steel, refine grains, improve the morphology and distribution of inclusions, and promote the precipitation of beneficial phases, thereby enhancing the mechanical properties and corrosion resistance of steel. However, rare earth elements are easily oxidized and sulfided in steel, making it difficult to precisely control their effective addition amount, and the influence of different rare earth elements and their addition amounts on the properties of martensitic stainless steel has not yet been systematically elucidated.

[0005] Currently, systematic research on the precise control of cerium doping in martensitic stainless steel and its effects on the microstructure and properties of the steel is insufficient, especially regarding the study of trace additions at low content levels (ppm). Therefore, developing a martensitic stainless steel with precisely controlled cerium doping and its preparation method has significant theoretical and practical value. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the prior art by providing a rare earth element cerium-doped martensitic stainless steel and its preparation method. This stainless steel has excellent comprehensive mechanical properties, corrosion resistance, and oxidation resistance.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A rare earth element cerium-doped martensitic stainless steel, wherein the chemical composition of the martensitic stainless steel by weight percentage is: C: 0.10-0.25%, Si: 0.20-1.00%, Mn: 0.30-1.50%, Cr: 11.0-14.0%, Ni: 0.10-2.50%, Mo: 0.10-1.00%, Ce: 0.01-0.05%, with the balance being Fe and unavoidable impurities.

[0009] Furthermore, the cerium content in the martensitic stainless steel is 0 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm and 500 ppm.

[0010] This invention also provides a method for preparing the above-mentioned rare earth element cerium-doped martensitic stainless steel, comprising the following steps:

[0011] (1) Raw material preparation: Calculate and weigh the corresponding mass of pure iron, chromium, nickel, molybdenum, silicon, manganese, carbon and metallic cerium according to the designed distribution ratio; the chemical composition of the martensitic stainless steel is: C: 0.10-0.25%, Si: 0.20-1.00%, Mn: 0.30-1.50%, Cr: 11.0-14.0%, Ni: 0.10-2.50%, Mo: 0.10-1.00%, Ce: 0.01-0.05%, with the balance being Fe and unavoidable impurities.

[0012] (2) Arc melting: The weighed raw materials are placed sequentially into the copper crucible of the arc melting furnace. After vacuum evacuation, high-purity argon gas is introduced, and arc melting is carried out under argon protection. Each sample is melted 5-8 times, and the sample is turned over during each melting process to ensure compositional uniformity. The arc voltage during arc melting is preferably 20-40V, and the current is preferably 300-500A, depending on the furnace body and crucible size. The addition method of the rare earth element cerium source should ensure its rapid dissolution and uniform dispersion in the molten pool, and minimize volatilization loss. The number of remelting and ingot turning is preferably 2-4 times, and the vacuum degree or inert gas protection must be strictly controlled during each remelting.

[0013] (3) Heat treatment: The heat-processed material is subjected to homogenization annealing, normalizing and tempering in sequence to obtain the final product.

[0014] Furthermore, in step (1), the purity of the raw materials is not less than 99.9%.

[0015] Furthermore, in step (2), the arc melting is carried out under the protection of high-purity argon gas with a purity of not less than 99.999%, and the vacuum degree before arc melting reaches 10. -3 Pa or above.

[0016] Furthermore, in step (3), the homogenization annealing treatment is carried out at a temperature of 1050-1150℃ and a holding time of 2-4h, followed by air cooling.

[0017] Furthermore, in step (3), the normalizing treatment temperature is 950-1050℃, the holding time is 0.5-1h, and then it is air-cooled.

[0018] Furthermore, in step (3), the tempering temperature is 550-650℃, the holding time is 1-2h, and then it is air-cooled.

[0019] The present invention has the following beneficial effects:

[0020] Compared with the prior art, the rare earth element cerium-doped martensitic stainless steel and its preparation method provided by the present invention have the following significant advantages:

[0021] (1) Significantly improved performance: By adding a specific range (0-500 ppm, preferably in increments of 100 ppm) of rare earth element cerium to martensitic stainless steel, the grains can be effectively refined, and the yield strength and tensile strength of the material can be improved. At the same time, by purifying the grain boundaries and forming rare earth oxides, the toughness of the material, especially the impact toughness, is significantly improved, and the oxidation resistance of the material is enhanced in high stress or high temperature service environments.

[0022] (2) Economical and efficient preparation process: The present invention adopts electric arc melting as the core melting method. This process has the advantages of relatively simple equipment, convenient operation, fast melting speed and relatively low cost. It can realize the large-scale production of rare earth element cerium doped martensitic stainless steel, and provide the possibility of reducing manufacturing costs.

[0023] (3) Good process controllability: By precisely controlling the doping amount of rare earth element cerium and optimizing its addition timing and method during the electric arc melting process, the excessive volatilization or formation of unfavorable phases of rare earth element cerium can be effectively avoided, ensuring the stability and reproducibility of material properties.

[0024] (4) Achieve gradient optimization of performance: The doping range with 100 ppm intervals allows users to select the most suitable cerium content according to the needs of specific application scenarios, thereby obtaining the best performance combination. Attached Figure Description

[0025] Figure 1 The XRD patterns of each alloy sample in Experiment Example 1 are shown below.

[0026] Figure 2 The images show the metallographic morphology of the alloy samples in Experimental Example 2, where (a)-(e) are Examples 1-5 respectively; and (f) is Comparative Example 1.

[0027] Figure 3 SEM micrographs of alloys with different Ce contents are shown, where (g) is Comparative Example 1; (h)-(l) are Examples 1-5;

[0028] Figure 4 The table shows the room temperature tensile stress-strain curves of each alloy specimen in Experiment Example 3. Detailed Implementation

[0029] Example 1:

[0030] (1) Raw material preparation: Calculate and weigh the corresponding mass of pure iron, chromium, nickel, molybdenum, silicon, manganese, carbon and metallic cerium according to the designed distribution ratio; the chemical composition of the martensitic stainless steel is: C: 0.10 wt%, Si: 0.25 wt%, Mn: 0.32 wt%, Cr: 12 wt%, Ni: 0.2 wt%, Mo: 0.15 wt%, Ce: 0.01 wt%, with the balance being Fe and unavoidable impurities.

[0031] (2) Arc melting: The weighed raw materials are placed sequentially into the copper crucible of the arc melting furnace. After vacuum evacuation, high-purity argon gas is introduced, and arc melting is carried out under argon protection. Each sample is melted 6 times, and the sample is turned over during each melting process to ensure compositional uniformity. The arc voltage during arc melting is preferably 30V, and the current is 300A, depending on the furnace body and crucible size. The addition method of the rare earth element cerium source should ensure its rapid dissolution and uniform dispersion in the molten pool, and minimize volatilization loss. The remelting and ingot turning is preferably performed 3 times, and the vacuum degree or inert gas protection must be strictly controlled during each remelting.

[0032] (3) Heat treatment: The heat-processed material is subjected to homogenization annealing, normalizing and tempering in sequence to obtain the final product.

[0033] Furthermore, in step (1), the purity of the raw materials is not less than 99.9%.

[0034] Furthermore, in step (2), the arc melting is carried out under the protection of high-purity argon gas with a purity of not less than 99.999%, and the vacuum degree before arc melting reaches 10. -3 Pa or above.

[0035] Furthermore, in step (3), the homogenization annealing treatment is carried out at a temperature of 1050°C for 2 hours, followed by air cooling.

[0036] Furthermore, in step (3), the normalizing temperature is 950°C, the holding time is 1 hour, and then it is air-cooled.

[0037] Furthermore, in step (3), the tempering temperature is 550°C, the holding time is 2 hours, and then it is air-cooled.

[0038] Ultimately, a martensitic precipitation-hardening stainless steel containing 0.01 wt% cerium was obtained.

[0039] Example 2:

[0040] (1) Raw material preparation: Calculate and weigh the corresponding mass of pure iron, chromium, nickel, molybdenum, silicon, manganese, carbon and metallic cerium according to the designed distribution ratio; the chemical composition of the martensitic stainless steel is: C: 0.15 wt%, Si: 0.40 wt%, Mn: 0.75 wt%, Cr: 13.0 wt%, Ni: 0.2 wt%, Mo: 0.50 wt%, Ce: 0.02 wt%, with the balance being Fe and unavoidable impurities.

[0041] (2) Arc melting: The weighed raw materials are placed sequentially into the copper crucible of the arc melting furnace. After vacuum evacuation, high-purity argon gas is introduced, and arc melting is carried out under argon protection. Each sample is melted 5 times, and the sample is turned over during each melting process to ensure compositional uniformity. The arc voltage during arc melting is 40V and the current is 500A, depending on the furnace body and crucible size. The addition method of the rare earth element cerium source should ensure its rapid dissolution and uniform dispersion in the molten pool, and minimize volatilization loss. The remelting and ingot turning is preferably twice, and the vacuum degree or inert gas protection must be strictly controlled during each remelting.

[0042] (3) Heat treatment: The heat-processed material is subjected to homogenization annealing, normalizing and tempering in sequence to obtain the final product.

[0043] Furthermore, in step (1), the purity of the raw materials is not less than 99.9%.

[0044] Furthermore, in step (2), the arc melting is carried out under the protection of high-purity argon gas with a purity of not less than 99.999%, and the vacuum degree before arc melting reaches 10. -3 Pa or above.

[0045] Furthermore, in step (3), the homogenization annealing treatment is carried out at a temperature of 1150°C for 4 hours, followed by air cooling.

[0046] Furthermore, in step (3), the normalizing temperature is 1050°C, the holding time is 1 hour, and then it is air-cooled.

[0047] Furthermore, in step (3), the tempering temperature is 650°C, the holding time is 1 hour, and then it is air-cooled.

[0048] Ultimately, a martensitic precipitation-hardening stainless steel containing 0.02 wt% cerium was obtained.

[0049] Example 3:

[0050] (1) Raw material preparation: Calculate and weigh the corresponding mass of pure iron, chromium, nickel, molybdenum, silicon, manganese, carbon and metallic cerium according to the designed distribution ratio; the chemical composition of the martensitic stainless steel is: C: 0.18 wt%, Si: 0.80 wt%, Mn: 0.45 wt%, Cr: 13.5 wt%, Ni: 2.20 wt%, Mo: 0.55 wt%, Ce: 0.03 wt%, with the balance being Fe and unavoidable impurities.

[0051] (2) Arc melting: The weighed raw materials are placed sequentially into the copper crucible of the arc melting furnace. After vacuum evacuation, high-purity argon gas is introduced, and arc melting is carried out under argon protection. Each sample is melted 8 times, and the sample is turned over during each melting process to ensure compositional uniformity. The arc voltage during arc melting is 20V, and the current is 400A, depending on the furnace body and crucible size. The addition method of the rare earth element cerium source should ensure its rapid dissolution and uniform dispersion in the molten pool, and minimize volatilization loss. The preferred number of remelting and ingot turning is 4 times. The vacuum degree or inert gas protection must be strictly controlled during each remelting.

[0052] (3) Heat treatment: The heat-processed material is subjected to homogenization annealing, normalizing and tempering in sequence to obtain the final product.

[0053] Furthermore, in step (1), the purity of the raw materials is not less than 99.9%.

[0054] Furthermore, in step (2), the arc melting is carried out under the protection of high-purity argon gas with a purity of not less than 99.999%, and the vacuum degree before arc melting reaches 10. -3 Pa or above.

[0055] Furthermore, in step (3), the homogenization annealing treatment is carried out at a temperature of 1100°C for 3 hours, followed by air cooling.

[0056] Furthermore, in step (3), the normalizing temperature is 1000℃, the holding time is -1h, and then air cooling is performed.

[0057] Furthermore, in step (3), the tempering temperature is 600°C, the holding time is 1.5h, and then it is air-cooled.

[0058] Ultimately, a martensitic precipitation-hardening stainless steel containing 0.03 wt% cerium was obtained.

[0059] Example 4:

[0060] (1) Raw material preparation: Calculate and weigh the corresponding mass of pure iron, chromium, nickel, molybdenum, silicon, manganese, carbon and metallic cerium according to the designed distribution ratio; the chemical composition of the martensitic stainless steel is: C: 0.12 wt%, Si: 0.35 wt%, Mn: 1.25 wt%, Cr: 12.05 wt%, Ni: 0.16 wt%, Mo: 0.45 wt%, Ce: 0.04 wt%, with the balance being Fe and unavoidable impurities.

[0061] (2) Arc melting: The weighed raw materials are placed sequentially into the copper crucible of the arc melting furnace. After vacuum evacuation, high-purity argon gas is introduced, and arc melting is carried out under argon protection. Each sample is melted 7 times, and the sample is turned over during each melting process to ensure compositional uniformity. The arc voltage during arc melting is 35V and the current is 400A, depending on the furnace body and crucible size. The addition method of the rare earth element cerium source should ensure its rapid dissolution and uniform dispersion in the molten pool, and minimize volatilization loss. The preferred number of remelting and ingot turning is 4 times. The vacuum degree or inert gas protection must be strictly controlled during each remelting.

[0062] (3) Heat treatment: The heat-processed material is subjected to homogenization annealing, normalizing and tempering in sequence to obtain the final product.

[0063] Furthermore, in step (1), the purity of the raw materials is not less than 99.9%.

[0064] Furthermore, in step (2), the arc melting is carried out under the protection of high-purity argon gas with a purity of not less than 99.999%, and the vacuum degree before arc melting reaches 10. -3 Pa or above.

[0065] Furthermore, in step (3), the homogenization annealing treatment is carried out at a temperature of 1150°C for 2 hours, followed by air cooling.

[0066] Furthermore, in step (3), the normalizing temperature is 1050°C, the holding time is 0.5h, and then it is air-cooled.

[0067] Furthermore, in step (3), the tempering temperature is 550°C, the holding time is 2 hours, and then it is air-cooled.

[0068] Ultimately, a martensitic precipitation-hardening stainless steel containing 0.04 wt% cerium was obtained.

[0069] Example 5:

[0070] (1) Raw material preparation: Calculate and weigh the corresponding mass of pure iron, chromium, nickel, molybdenum, silicon, manganese, carbon and metallic cerium according to the designed distribution ratio; the chemical composition of the martensitic stainless steel is: C: 0.18 wt%, Si: 0.65 wt%, Mn: 1.15 wt%, Cr: 13.25 wt%, Ni: 0.16 wt%, Mo: 0.75 wt%, Ce: 0.05 wt%, with the balance being Fe and unavoidable impurities.

[0071] (2) Arc melting: The weighed raw materials are placed sequentially into the copper crucible of the arc melting furnace. After vacuum evacuation, high-purity argon gas is introduced, and arc melting is carried out under argon protection. Each sample is melted 5 times, and the sample is turned over during each melting process to ensure compositional uniformity. The arc voltage during arc melting is preferably 40V, and the current is preferably 300A, depending on the furnace body and crucible size. The addition method of the rare earth element cerium source should ensure its rapid dissolution and uniform dispersion in the molten pool, and minimize volatilization loss. The remelting and ingot turning is preferably twice, and the vacuum degree or inert gas protection must be strictly controlled during each remelting.

[0072] (3) Heat treatment: The heat-processed material is subjected to homogenization annealing, normalizing and tempering in sequence to obtain the final product.

[0073] Furthermore, in step (1), the purity of the raw materials is not less than 99.9%.

[0074] Furthermore, in step (2), the arc melting is carried out under the protection of high-purity argon gas with a purity of not less than 99.999%, and the vacuum degree before arc melting reaches 10. -3 Pa or above.

[0075] Furthermore, in step (3), the homogenization annealing treatment is carried out at a temperature of 1050°C for 2 hours, followed by air cooling.

[0076] Furthermore, in step (3), the normalizing temperature is 1050°C, the holding time is 1 hour, and then it is air-cooled.

[0077] Furthermore, in step (3), the tempering temperature is 650°C, the holding time is 2 hours, and then it is air-cooled.

[0078] Ultimately, a martensitic precipitation-hardening stainless steel containing 0.05 wt% cerium was obtained.

[0079] Comparative Example 1:

[0080] (1) Raw material preparation: Calculate and weigh the corresponding mass of pure iron, chromium, nickel, molybdenum, silicon, manganese, carbon and metallic cerium according to the designed distribution ratio; the chemical composition of the martensitic stainless steel is: C: 0.19 wt%, Si: 0.55 wt%, Mn: 1.32 wt%, Cr: 12.45 wt%, Ni: 0.60 wt%, Mo: 0.20 wt%, with the balance being Fe and unavoidable impurities.

[0081] (2) Arc melting: The weighed raw materials are placed sequentially into the copper crucible of the arc melting furnace. After vacuum evacuation, high-purity argon gas is introduced, and arc melting is carried out under argon protection. Each sample is melted 5 times, and the sample is turned over during each melting process to ensure compositional uniformity. The arc voltage during arc melting is preferably 40V, and the current is preferably 500A, depending on the furnace body and crucible size. The addition method of the rare earth element cerium source should ensure its rapid dissolution and uniform dispersion in the molten pool, and minimize volatilization loss. The remelting and ingot turning is preferably performed 3 times, and the vacuum degree or inert gas protection must be strictly controlled during each remelting.

[0082] (3) Heat treatment: The heat-processed material is subjected to homogenization annealing, normalizing and tempering in sequence to obtain the final product.

[0083] Furthermore, in step (1), the purity of the raw materials is not less than 99.9%.

[0084] Furthermore, in step (2), the arc melting is carried out under the protection of high-purity argon gas with a purity of not less than 99.999%, and the vacuum degree before arc melting reaches 10. -3 Pa or above.

[0085] Furthermore, in step (3), the homogenization annealing treatment is carried out at a temperature of 1120°C for 3 hours, followed by air cooling.

[0086] Furthermore, in step (3), the normalizing temperature is 980°C, the holding time is 1 hour, and then it is air-cooled.

[0087] Furthermore, in step (3), the tempering temperature is 610°C, the holding time is 1.5h, and then it is air-cooled.

[0088] Ultimately, a martensitic precipitation-hardening stainless steel without cerium was obtained.

[0089] Experimental Example 1: XRD Characterization

[0090] This method aims to perform X-ray diffraction (XRD) analysis on the martensitic stainless steels obtained in Examples 1-5 and Comparative Example 1 to determine their crystal structure, phase composition, and degree of martensitic phase transformation. The testing procedure includes sample preparation (cutting to 10 mm × 10 mm × 2 mm dimensions, sequentially grinding with 80-2000 grit sandpaper, mechanically polishing to a mirror finish, and ultrasonically cleaning with acetone and ethanol); XRD testing is performed using a Cu Kα radiation source (λ = 0.15406 nm), with a working voltage of 40 kV, a current of 40 mA, a scanning angle (2θ) range of 20°-100°, and a step size of 0.02°; finally, the obtained XRD patterns are processed, including background subtraction, peak position determination, phase identification, and quantitative analysis, with a focus on comparing the position and intensity of the martensitic characteristic peaks, the content of retained austenite, and the degree of lattice distortion of each sample.

[0091] See Figure 1 The results showed that XRD analysis of martensitic precipitation-hardening stainless steel containing 0-0.05 wt% cerium revealed that all samples exhibited typical body-centered cubic (BCC) α-Fe structure characteristics, mainly manifested by a strong (110) diffraction peak at approximately 44-45° (2θ), and (200), (211), and (220) diffraction peaks at approximately 64-65°, 82°, and 98-99°, confirming that the main body of the samples was martensitic and no obvious residual austenite was detected. Peak shape analysis showed that all diffraction peaks were relatively sharp with moderate half-width at half-maximum (FWHM), indicating that the martensite grain size was suitable and the crystallinity was good. Notably, as the cerium content increased from 0.01 to 0.05 wt%, the intensity of the main peak did not change significantly, and no characteristic peaks of cerium compounds were observed, suggesting that cerium may exist in solid solution form or form nanoscale precipitates with excessively small size within this content range. The near-absent shift in diffraction peak positions further confirms that cerium did not significantly alter the martensite cell parameters. Furthermore, the XRD pattern did not show obvious diffraction peaks for the precipitated phase, which may be due to the low volume fraction of the precipitated phase, its extremely small particle size, or a coherent / semi-coherent relationship with the matrix.

[0092] Experimental Example 2: Metallographic Characterization

[0093] In this invention, the microstructure of the martensitic stainless steels obtained in Examples 1-5 and Comparative Example 1 was observed using an optical microscope. The metallographic sample size was 10 mm × 10 mm × 5 mm. The sample preparation process included polishing with 80-2000 grit sandpaper, followed by mechanical polishing and chemical etching. Figure 2 The microstructure morphology of all samples is shown, where (a)-(e) correspond to the metallographic microstructure results of Examples 1-5, respectively. Figure (f) shows the metallographic microstructure result of Comparative Example 1.

[0094] Figure 3 SEM micrographs of alloys with different Ce contents: (g) is Comparative Example 1; (h)-(l) are Examples 1-5.

[0095] See Figure 2-3 The results showed that the microstructure of the martensitic precipitation-hardening stainless steel containing 0–0.05 wt% cerium was quenched lath martensite, with significant refinement and homogenization characteristics as the cerium content changed. Without cerium, the martensite laths were coarse and bundled, with numerous and irregularly shaped inclusions, resulting in poor microstructure homogeneity. Adding a small amount of cerium (0.01–0.03 wt%) significantly refined the austenite grains and lath martensite bundles, making the laths finer, more uniform, and more oriented with clear grain boundaries. Simultaneously, inclusions were significantly reduced and tended towards spheroidization, demonstrating excellent grain refinement and purification effects, representing the optimal microstructure range for this steel. When the cerium content continued to increase to 0.04–0.05 wt%, the refining effect weakened, and even localized coarsening of laths and grains occurred, leading to a decrease in microstructure homogeneity. In summary, an appropriate amount of cerium (approximately 0.02–0.03 wt%) can produce the finest, most uniform, and purest martensitic structure.

[0096] Experimental Example 3: Stress-Strain Characterization

[0097] The present invention conducted room temperature tensile property tests on the martensitic stainless steels obtained in Examples 1-5 and Comparative Example 1. Dog-bone shaped specimens with dimensions of 40 mm × 8 mm × 2 mm were used for the tests. The tensile tests were performed at a rate of 1.2 mm / min until the specimens fractured. Figure 4 The figures show the room temperature tensile stress-strain curves of each alloy specimen in the test examples.

[0098] See Figure 4 The results showed that the stress-strain curves of martensitic precipitation-hardening stainless steel containing 0-0.05 wt% cerium exhibited a systematic optimization evolution of the material's mechanical properties with increasing cerium content. Analysis revealed that the yield strength remained relatively stable within the 900-950 MPa range, but the tensile strength significantly increased from approximately 1030 MPa in Comparative Example 1 (without cerium) to approximately 1180 MPa in Example 3 (containing 0.03 wt% Ce), an increase of nearly 17%. Simultaneously, the elongation at break increased dramatically from approximately 8% to approximately 13%, and the plasticity improved by 62.5%, achieving a rare synergistic optimization of strength and plasticity. This rare synergistic optimization further demonstrates that the effect was not simply a matter of adjusting the content, but rather an unexpected technical result produced by the unique role of Ce and the synergistic effect of the steel matrix.

[0099] In terms of curve morphology, the work hardening behavior becomes more pronounced with increasing cerium content. The uniform extension region of high-cerium-content samples (especially Examples 4 and 5) is significantly expanded, the curve rises more steeply after yielding, and the stress decreases more slowly after the maximum stress, indicating that necking development is suppressed and fracture toughness is improved. This comprehensive improvement in mechanical properties may stem from the synergistic effect of multiple microscopic mechanisms: cerium may enhance work hardening capacity by refining the martensitic lath structure (Hall-Petch strengthening), promoting the formation of finer and more uniform nanoprecipitates, strengthening grain boundary bonding to inhibit crack propagation, and regulating dislocation movement.

[0100] Some existing technologies mention the application of La / Ce as rare earth elements in martensitic stainless steel, but their focus is on the short-range attraction between rare earth elements and copper to promote the nucleation of Cu-rich phases. They do not investigate the precise control of Ce in steel or the impact of low Ce content, nor do they focus on the specific mechanisms and effects of Ce in purifying grain boundaries, refining grains, and synergistically improving strength and plasticity in martensitic stainless steel. For martensitic stainless steel, the method in this application avoids the agglomeration or coarse inclusions caused by excessive addition of traditional rare earth elements. Instead, it achieves comprehensive synergistic optimization of toughness, oxidation resistance, and mechanical properties at the microstructure level through the purification effect of Ce (forming fine rare earth oxides / sulfides), grain refinement effect, and regulation of dislocation movement and precipitation behavior.

[0101] This invention is particularly suitable for engineering structural materials that require high strength, high toughness, excellent corrosion resistance and oxidation resistance, and can be widely used in the manufacture of key components in harsh working environments such as energy, petrochemical, aerospace, marine engineering, and nuclear power plants.

Claims

1. A martensitic stainless steel doped with the rare earth element cerium, characterized in that, The chemical composition of the martensitic stainless steel, by weight percentage, includes: C: 0.10-0.25%, Si: 0.20-1.00%, Mn: 0.30-1.50%, Cr: 11.0-14.0%, Ni: 0.10-2.50%, Mo: 0.10-1.00%, Ce: 0.01-0.05%, with the balance being Fe and unavoidable impurities.

2. The rare earth element cerium-doped martensitic stainless steel according to claim 1, characterized in that, The chemical composition of the martensitic stainless steel includes: C: 0.10-0.25 wt%, Si: 0.20-1.00 wt%, Mn: 0.30-1.50 wt%, Cr: 11.0-14.0 wt%, Ni: 0.10-2.50 wt%, Mo: 0.10-1.00 wt%, Ce: 0.02-0.04 wt%, with the balance being Fe and unavoidable impurities.

3. The rare earth element cerium-doped martensitic stainless steel according to claim 1, characterized in that, The chemical composition of the martensitic stainless steel is as follows: C: 0.10-0.25 wt%, Si: 0.20-1.00 wt%, Mn: 0.30-1.50 wt%, Cr: 11.0-14.0 wt%, Ni: 0.10-2.50 wt%, Mo: 0.10-1.00 wt%, Ce: 0.01-0.03 wt%, with the balance being Fe and unavoidable impurities.

4. The method for preparing rare earth element cerium-doped martensitic stainless steel according to any one of claims 1-3, characterized in that, Includes the following steps: Calculate and weigh the corresponding mass of raw materials according to the designed proportions, place the weighed raw materials into the copper crucible of the electric arc melting furnace, perform vacuum evacuation and then fill with high-purity argon gas, and carry out electric arc melting under argon protection. Finally, perform homogenization annealing, normalizing and tempering treatments on the materials in sequence to obtain the final product.

5. The method for preparing rare earth element cerium-doped martensitic stainless steel according to claim 4, characterized in that, The conditions for repeated melting are as follows: the number of repetitions is 5-8 times, the arc voltage during electric arc melting is 20-40V, the current is 300-500A, stirring is carried out during each melting process, and the crucible is turned over after each melting.

6. The method for preparing rare earth element cerium-doped martensitic stainless steel according to claim 4, characterized in that, The homogenization annealing temperature is 1050-1150℃, and the holding time is 2-4h; the normalizing temperature is 950-1050℃, and the holding time is 0.5-1h; the tempering temperature is 550-650℃, and the holding time is 1-2h.

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