Hard rock TBM hob cutter ring and preparation method thereof

Abstract

The invention discloses a hard rock TBM hob cutter ring and a preparation method thereof, and belongs to the technical field of key part materials of tunneling equipment. The alloy steel comprises the following chemical components in percentage by weight: 0.50%-0.65% of C, 0.80%-1.20% of Si, 0.50%-0.80% of Mn, 4.50%-5.50% of Cr, 1.20%-1.80% of Mo, 0.80%-1.50% of V, 0.50%-1.20% of W, 0.05%-0.15% of Nb, 0.02%-0.10% of La, 0.03%-0.08% of Y, less than or equal to 0.50% of Ni, less than or equal to 0.020% of P, less than or equal to 0.010% of S and the balance of Fe and inevitable impurities. The preparation method comprises the following steps: adding the lanthanum-iron alloy and the yttrium-iron alloy during smelting in an electric arc furnace, performing electroslag remelting, performing multidirectional forging (the forging ratio is greater than or equal to 5), performing annealing treatment and performing final heat treatment (quenching, subzero treatment at the temperature of between-80 and-196 DEG C, rare earth stabilizing treatment and tempering for three times). According to the invention, W and Nb synergistically separate out nanoscale carbides, La and Y are compounded to realize purification, modification, pinning and stabilization, grains and carbides are refined, the hardness of the cutter ring reaches 60-65 HRC, the impact toughness is greater than or equal to 25 J, the wear resistance and the service life of the cutter ring are obviously improved compared with those of a general H13 steel cutter ring, and the service life and the rock breaking efficiency under hard rock geology are obviously improved.

Description

Technical Field

[0001] This invention belongs to the technical field of key component materials for tunneling equipment, specifically relating to a cutter ring for a hard rock full-face tunnel boring machine (TBM) and its preparation method. Background Technology

[0002] Full-face tunnel boring machines (TBMs) are core equipment in modern tunnel engineering, and their cutterheads are critical wear components that directly contact and break rocks. In hard rock conditions, the cutterheads must withstand extremely high impact loads, enormous compressive stresses, and severe abrasive wear. Premature failure of the cutterheads, such as excessive wear, chipping, or breakage, leads to frequent downtime for cutter replacement, significantly increasing construction costs and severely hindering project progress.

[0003] Currently, the mainstream cutter ring material system is mostly based on hot work die steel, such as the widely used H13 steel. Its typical chemical composition is: C 0.38%-0.42%, Cr 4.80%-5.50%, Mo 1.20%-1.60%, V 0.85%-1.15%. This material exhibits the following significant drawbacks in application: First, its hardness is usually only 52-55 HRC, resulting in insufficient wear resistance, with a wear rate as high as 0.8-1.2 mm / km in actual hard rock tunneling; second, its impact toughness is low, typically 15-18 J, causing the cutter ring to easily chip or break under high impact loads; the overall performance deficiencies result in a short average service life of H13 steel cutter rings, only about 50-80 km, and its replacement cost can account for more than 30% of the total tunnel construction cost.

[0004] To improve the performance of cutting edge rings, existing technologies have explored various approaches. For example, the invention patent with publication number CN1330787C focuses on the Cr-Mo-V system, but does not add W, Nb, or rare earth elements, resulting in a relatively simple composition and limited improvement in wear resistance and toughness. Another example is the invention patent with publication number CN120290981A, which emphasizes vanadium-niobium microalloying to refine grains, but has a high Nb content (V+Nb reaches 1.70%) and lacks W and rare earth elements. Its narrow carbon content range limits further improvement in hardness to some extent. Yet another example is the invention patent with publication number CN117721390A, which optimizes toughness by adding Ce and Ti, but uses a limited variety of alloying elements and a relatively conventional heat treatment process, resulting in limited overall performance improvement.

[0005] In summary, existing cutter ring materials generally suffer from a core contradiction: increasing hardness often sacrifices toughness, leading to increased brittleness; while ensuring toughness makes it difficult to achieve extremely high wear resistance. Therefore, developing a novel cutter ring material and its supporting manufacturing process that can simultaneously possess ultra-high hardness, excellent toughness, and high fatigue resistance to meet the needs of extreme hard rock and high-intensity tunneling has become a key technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0006] The core objective of this invention is to overcome the shortcomings of existing cutter ring materials, such as difficulty in achieving a balance between hardness and toughness, poor wear resistance, and short service life, and to provide a cutter ring for hard rock TBMs and its preparation method. Through the synergistic proportioning of specific components and an optimized preparation process, the cutter ring achieves excellent performance with a hardness of 60-65 HRC and an impact toughness ≥25 J, while its wear resistance is more than 30% higher than that of H13 steel, significantly extending its service life under hard rock geological conditions and improving rock-breaking efficiency.

[0007] To achieve the above objectives, the specific solution adopted by the present invention is as follows: On the one hand, the present invention provides a hard rock TBM cutter ring, the chemical composition of which, by weight percentage, is: C 0.50%–0.65%, Si 0.80%–1.20%, Mn 0.50%–0.80%, Cr 4.50%–5.50%, Mo 1.20%–1.80%, V 0.80%–1.50%, W 0.50%–1.20%, Nb 0.05%–0.15%, La 0.02%–0.10%, Y 0.03%–0.08%, Ni ≤0.50%, P ≤0.020%, S ≤0.010%, with the remainder being Fe and unavoidable impurities.

[0008] Furthermore, the weight percentage of La to Y satisfies: 0.5 ≤ Y / La ≤ 2.0.

[0009] Furthermore, its hardness is 60-65 HRC, and its impact toughness is AKU≥25J.

[0010] On the other hand, the present invention provides a method for preparing the above-mentioned hard rock TBM cutter ring, comprising the following steps: S1. Smelting and refining: Smelting is carried out using an electric arc furnace or a medium-frequency induction furnace, followed by electroslag remelting and refining to obtain steel ingots; S2. Forging: Heat the steel ingot to 1150℃~1200℃ and perform multi-directional upsetting and drawing forging, with a forging ratio ≥5, to form a billet; S3. Annealing treatment: Heat the billet to 860℃~890℃ and hold it at that temperature, then furnace cool it to below 500℃ and air cool it to soften the structure for easier machining. S4. Machining: Rough machining is performed on the annealed billet to form a blade ring blank; S5. Final heat treatment: Perform the following steps in sequence: S51. Quenching: Austenitize in a vacuum furnace at 1020℃~1080℃ and hold for 2~4 hours, then quench to obtain a high-hardness martensitic matrix. S52. Cryogenic treatment: Place the quenched workpiece at -80℃ to -196℃ for 1 to 4 hours to promote the transformation of residual austenite to martensite and improve hardness and dimensional stability. S53. Rare earth stabilization treatment: At 300℃~400℃, keep warm in a vacuum environment or in a protective atmosphere with oxygen partial pressure ≤10Pa for 1~2 hours, then furnace cool to 250℃ and then air cool, so that La and Y elements can be fully segregated at the grain boundaries and phase interfaces to achieve microstructure stabilization. S54. Three temperings: Three temperings are performed at 520℃~580℃, with each tempering holding time not less than 2 hours, in order to promote the dispersion and precipitation of carbides, achieve secondary hardening, and eliminate internal stress. S6. Finishing: The heat-treated cutter ring blank is precision ground to the final size to obtain the final hard rock TBM hobbing cutter ring.

[0011] Furthermore, in step S1, La and Y elements are added in the form of lanthanum-iron alloy and yttrium-iron alloy, respectively.

[0012] Furthermore, the heat preservation time in step S3 is 2 to 5 hours.

[0013] Furthermore, the quenching method in step S51 is high-pressure gas quenching or graded oil quenching.

[0014] Furthermore, the protective atmosphere in step S53 is an inert gas atmosphere or a nitrogen-hydrogen mixed atmosphere.

[0015] Furthermore, the three tempering processes in step S54 are performed consecutively.

[0016] The role of each element in the knife-making circle is explained below.

[0017] Carbon (C): C is the core element that ensures the material obtains a high-hardness martensitic matrix and forms sufficient carbides, which is the basis for the material's wear resistance. The content should be controlled between 0.50% and 0.65%: If the C content is below 0.50%, the hardness of the martensitic matrix will be insufficient, the amount of carbides generated will be reduced, and the wear resistance required for hard rock tunneling will not be met; if the C content is above 0.65%, the material's toughness will decrease significantly, and the cutter ring will be prone to chipping and breakage under impact loads, affecting its service life.

[0018] Silicon (Si) and manganese (Mn): Both act as deoxidizers and solid solution strengthening elements. Si effectively deoxidizes and simultaneously dissolves in the matrix to improve its strength; Mn improves the hardenability of steel and enhances material strength through solid solution strengthening. Si content should be controlled between 0.80% and 1.20%: below 0.80%, deoxidation is ineffective and solid solution strengthening is not significant; above 1.20% leads to decreased toughness and poorer processing performance. Mn content should be controlled between 0.50% and 0.80%: below 0.50%, the improvement in hardenability is limited; above 0.80% easily leads to coarse grains and reduced toughness.

[0019] Chromium (Cr), molybdenum (Mo), and vanadium (V): all three are core carbide-forming elements. Cr primarily improves the hardenability and corrosion resistance of materials, while also forming stable carbides to enhance wear resistance. Mo and V can form fine, dispersed, and stable MC and M2C type carbides (such as Mo2C and VC), producing a strong secondary hardening effect and significantly improving the red hardness, wear resistance, and resistance to tempering softening of materials. Cr content should be controlled between 4.50% and 5.50%: below 4.50%, hardenability and corrosion resistance are insufficient; above 5.50%, it increases the risk of carbide segregation and reduces toughness. Mo content should be controlled between 1.20% and 1.80%: below 1.20%, the secondary hardening effect is weak; above 1.80%, it leads to increased material costs and easily forms coarse carbides. The V content should be controlled between 0.80% and 1.50%. When it is below 0.80%, the amount of carbide generated is insufficient, and the improvement in wear resistance is limited. When it is above 1.50%, the carbide will aggregate and grow, affecting toughness.

[0020] Tungsten (W): Synergistically with Mo, it further improves the high-temperature stability of carbides and the tempering resistance of materials. At the same time, it can form high-hardness carbides (such as WC or W2C), enhancing wear resistance. The W content should be controlled between 0.50% and 1.20%: below 0.50%, the synergistic modification effect is not obvious; above 1.20%, it will increase the material density and easily lead to coarse grains.

[0021] Niobium (Nb): As a strong carbonitride forming element, it can pin grain boundaries during austenitization, refining the original austenite grains and thus improving the strength and toughness of the material. The Nb content should be controlled between 0.05% and 0.15%: below 0.05%, the grain refinement effect is limited; above 0.15%, coarse NbC carbides will form, reducing the material's toughness and processing performance.

[0022] Lanthanum (La): It has a strong tendency to segregate at grain boundaries. It segregates at austenite grain boundaries, which can reduce grain boundary energy and directly inhibit grain boundary migration through the "solute dragging" effect. The La content should be controlled between 0.02% and 0.10%: when it is below 0.02%, the "solute dragging" effect and purification effect are not obvious; when it is above 0.10%, it is easy to cause rare earth element segregation, forming a brittle phase and reducing the toughness of the material.

[0023] Yttrium (Y): The resulting Y₂O₃ particles exhibit extremely high high-temperature stability, providing strong and sustained pinning force and inhibiting grain growth. The Y content should be controlled between 0.03% and 0.08%: below 0.03%, the pinning effect is insufficient; above 0.08%, rare earth compounds will aggregate, affecting the mechanical properties of the material.

[0024] The synergistic mechanism of lanthanum (La) and yttrium (Y): During smelting and heat treatment, La and Y, due to their extremely strong chemical reactivity, preferentially react with impurities such as O, S, and P before carbide-forming elements such as V and Nb, generating high-melting-point, ultra-stable compounds such as La₂O₂S and Y₂O₃. These compounds float to the surface and are removed, achieving deep purification and improving the purity of molten steel. In the early stage of phase transformation during solidification or cooling after austenitization, the dispersed, fine-sized La₂O₂S and Y₂O₃ particles precipitate before carbides such as VC, WC, and NbC, and can act as effective... The heterogeneous nucleation core significantly increases the nucleation rate. During austenitization, these stable rare earth compound particles strongly pin the grain boundaries, while La atoms segregate at the grain boundaries to produce a "solute dragging" effect. Y provides physical pinning, and La provides chemical dragging. The two work together to strongly inhibit the growth of the original austenite grains from different mechanisms, resulting in ultrafine grains. During tempering, La and Y preferentially segregate at the interface between the carbide (such as VC) and the matrix. The strain field generated by their large atomic radius can hinder the diffusion of elements such as V and C, effectively inhibiting the Oswald ripening of carbides like a "coating layer".

[0025] Synergistic effect of combined addition of tungsten (W) and niobium (Nb): W carbides (such as WC or W2C) provide high hardness, while Nb carbides (NbC) inhibit grain growth, together optimizing the strength and toughness ratio.

[0026] Nickel (Ni): An appropriate amount of Ni can improve the toughness of the material, but too much Ni will reduce the hardness and wear resistance of the material. Therefore, Ni should be controlled to be ≤0.50%.

[0027] Phosphorus (P) and sulfur (S): P and S are harmful impurities that tend to agglomerate at grain boundaries, leading to increased grain boundary brittleness and reduced material toughness and fatigue performance. Therefore, P ≤ 0.020% and S ≤ 0.010% should be strictly controlled to reduce grain boundary brittleness and improve material purity.

[0028] Beneficial effects: (1) This invention innovatively introduces the La-Y dual rare earth system, breaking through the limitations of single rare earth modification. The two complement each other and achieve synergistic effects in the four stages of "purifying molten steel, modification treatment, pinning grain boundaries, and stabilizing carbides". Combined with the composite addition of W and Nb (W carbides increase hardness, and Nb carbides refine grains), a deeper and more precise composite control of the microstructure of alloy steel (including grain size and carbide morphology) is achieved.

[0029] (2) Through the above-mentioned composition design and optimization of the entire process of "quenching + deep cryogenic treatment + rare earth stabilization treatment + three tempering", the present invention finally obtains an ideal tempered martensite structure with fine grains, dispersed carbide distribution, and extremely low residual austenite content. This structure enables the blade ring product to achieve a good match between high hardness (60-65HRC) and high impact toughness (≥25J), solving the contradiction that traditional materials cannot achieve both hardness and toughness.

[0030] (3) Due to the simultaneous improvement in hardness and toughness, the cutter ring prepared by this invention exhibits excellent wear resistance, anti-chipping, and anti-fracture capabilities in hard rock tunneling. Its wear resistance and service life are significantly improved compared to the commonly used H13 steel cutter ring. This means that the number of cutter replacements and downtime can be greatly reduced in tunnel construction, thereby significantly reducing construction costs and improving tunneling efficiency. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0032] First, the present invention provides a cutter ring for hard rock TBMs, the chemical composition of which, by weight percentage, is: C 0.50%~0.65%, Si 0.80%~1.20%, Mn 0.50%~0.80%, Cr 4.50%~5.50%, Mo 1.20%~1.80%, V 0.80%~1.50%, W 0.50%~1.20%, Nb 0.05%~0.15%, La 0.02%~0.10%, Y 0.03%~0.08%, Ni ≤0.50%, P ≤0.020%, S ≤0.010%, with the remainder being Fe and unavoidable impurities.

[0033] Preferably, the weight percentages of La and Y satisfy the relationship: 0.5≤Y / La≤2.0, so as to give fuller play to the synergistic modification effect of the two.

[0034] Next, the preparation method of the cutter ring for hard rock TBM is described, which mainly includes the following steps: S1. Smelting and Electroslag Remelting: Primary smelting is performed using an electric arc furnace or a medium-frequency induction furnace, followed by electroslag remelting for refining to obtain high-quality steel ingots with uniform composition and low impurity content. La and Y elements are added as lanthanum-iron alloy and yttrium-iron alloy, respectively, ensuring uniform distribution in the molten steel and maximizing their synergistic effect. The purpose of this step is to achieve initial compositional adjustment through primary smelting, and then further remove impurities and homogenize the composition through electroslag remelting, reducing internal defects in the steel ingot and laying the foundation for subsequent processing and performance improvement. S2. Forging and Forming: The steel ingot is heated to 1150℃~1200℃ and subjected to multi-directional upsetting and drawing forging (including at least two alternating upsetting and drawing processes), with a forging ratio of not less than 5, to obtain a uniform and refined forging structure, initially forming a billet. Heating the steel ingot to this temperature range is to improve the plasticity of the steel, facilitating forging deformation; multi-directional forging with a forging ratio ≥5 can break up coarse grains and carbides in the cast structure, forming a uniform and fine forging structure, while eliminating defects such as porosity and shrinkage cavities inside the steel ingot, improving the density and uniformity of mechanical properties of the material; S3. Annealing: Heat the forged blade blank to 860℃~890℃, hold for 2~5 hours, then cool it in the furnace to below 500℃ and air cool. The purpose of this step is to reduce the material hardness, improve machinability, and facilitate subsequent machining; at the same time, it eliminates the internal stress generated during forging, refines the microstructure, and prepares the microstructure for obtaining excellent properties in the final heat treatment. S4. Machining: Rough machining is performed on the annealed blank to form a blank with the basic geometry of the cutter ring. The purpose of this step is to initially machine the outline of the cutter ring, providing a blank that meets the requirements for subsequent final heat treatment and finishing. S5. Final heat treatment: Perform the following steps in sequence: S51. Quenching: Austenitizing and holding at 1020℃~1080℃ in a vacuum furnace for 2-4 hours is performed, followed by high-pressure gas quenching or staged oil quenching. The purpose of this step is to fully austenitize the material, and then obtain a high-hardness martensitic matrix through rapid cooling, ensuring the final high hardness and high wear resistance of the material. The vacuum environment can avoid oxidation and decarburization during the heating process, and high-pressure gas quenching or staged oil quenching can ensure uniform cooling and reduce the risk of quenching deformation and cracking. S52. Cryogenic Treatment: Immediately place the quenched workpiece into a cryogenic chamber at -80℃ to -196℃ and hold for 1 to 4 hours. The purpose of this step is to promote the transformation of retained austenite into martensite, further improve the material's hardness and dimensional stability, and at the same time refine the martensitic structure and improve the material's toughness. S53. Rare Earth Stabilization Treatment: Hold at 300℃~400℃ under vacuum or a protective atmosphere (oxygen partial pressure ≤10Pa, protective atmosphere is an inert gas atmosphere or a nitrogen-hydrogen mixed atmosphere) for 1-2 hours, then cool with the furnace to 250℃ and air cool. The purpose of this step is to allow La and Y to undergo more complete segregation at grain boundaries and phase interfaces at a lower temperature, achieving a synergistic stabilization effect and preparing for the dispersion precipitation of carbides during subsequent high-temperature tempering; the vacuum or low oxygen partial pressure protective atmosphere can prevent rare earth elements from being oxidized, ensuring that they play a stabilizing role; S54. Three-stage tempering: Three consecutive tempering processes are performed at 520℃~580℃, with each tempering holding time not less than 2 hours. The purpose of this step is to promote further transformation of the retained austenite, eliminate internal stress generated during quenching, and simultaneously allow carbides to precipitate diffusely, achieving secondary hardening and obtaining an ideal microstructure with a large number of nano-scale carbides distributed on a tempered martensitic matrix, ultimately achieving an optimized ratio of material hardness and toughness. S6. Finishing and Inspection: The heat-treated cutter ring is precision ground to its final dimensions and then subjected to non-destructive testing and performance testing. This step ensures the final dimensional accuracy and surface quality of the cutter ring, identifies internal defects through non-destructive testing, and ensures that the cutter ring meets the design requirements for hardness, toughness, and other specifications through performance testing.

[0035] The present invention will be further described in detail below with reference to embodiments and comparative examples, but the scope of protection of the present invention is not limited thereto.

[0036] Example 1 The preparation method of the cutter ring for hard rock TBM mainly includes the following steps: S1. Ingredients: Ingredients are prepared according to the following weight percentages: C 0.55%, Si 1.0%, Mn 0.65%, Cr 5.0%, Mo 1.5%, V 1.2%, W 0.8%, Nb 0.08%, Ni 0.30%, La 0.04%, Y 0.05% (Y / La=1.25), P 0.015%, S 0.005%, Fe as balance; wherein, La and Y are added in the form of lanthanum-iron alloy and yttrium-iron alloy, respectively; S2. Smelting and electroslag remelting: Smelting is carried out in an electric arc furnace. Lanthanum-iron alloy and yttrium-iron alloy are added at 1560℃. After stirring for 10 minutes, the steel is tapped and then electroslag remelted to obtain a Ф500mm steel ingot. S3. Forging and forming: After homogenizing the steel ingot at 1180℃, it is subjected to three upsetting and three drawing multi-directional forging. The final forging temperature is not lower than 900℃, the forging ratio is 6, and the billet is forged into a billet with an outer diameter of 430mm. S4. Annealing treatment: Anneal the blade ring blank at 880℃ for 4 hours, furnace cool to 400℃ and then air cool. S5. Machining: Rough machining is performed on the annealed blank to form the basic geometry of the blade ring; S6. Final heat treatment: Perform the following steps in sequence: S61. Quenching: Hold in a vacuum furnace at 1050℃ for 3 hours, then perform oil quenching; S62. Cryogenic treatment: Immediately place the quenched workpiece into a cryogenic device at -120℃ and keep it at that temperature for 2 hours. S63. Rare earth stabilization treatment: heat at 350℃ in a vacuum environment for 1.5h, cool with the furnace to 250℃ and then air cool. S64, Three temperings: Three consecutive temperings are performed at 550℃, with each tempering holding for 2.5 hours; S7. Finishing and Inspection: The heat-treated blade ring is precision ground to its final dimensions, and then non-destructive testing and performance testing are performed.

[0037] Example 2 The preparation method of the cutter ring for hard rock TBM mainly includes the following steps: S1. Ingredients: Ingredients are prepared according to the following weight percentages: C 0.62%, Si 0.95%, Mn 0.60%, Cr 5.30%, Mo 1.65%, V 1.40%, W 0.75%, Nb 0.09%, La 0.03%, Y 0.045% (Y / La=1.5), Ni 0.25%, P 0.012%, S 0.006%, with the balance being Fe. La and Y are added in the form of lanthanum-iron alloy and yttrium-iron alloy, respectively. S2. Smelting and electroslag remelting: Smelting is carried out in an electric arc furnace. Lanthanum-iron alloy and yttrium-iron alloy are added at 1560℃. After stirring for 10 minutes, the steel is tapped and then electroslag remelted to obtain a Ф500mm steel ingot. S3. Forging and forming: After homogenizing the steel ingot at 1150℃, it is subjected to three upsetting and three drawing multi-directional forging. The final forging temperature is not lower than 900℃, the forging ratio is 6, and the billet is forged into a billet with an outer diameter of 430mm. S4. Annealing treatment: Anneal the blade ring blank at 860℃ for 5 hours, furnace cool to 400℃ and then air cool. S5. Machining: Rough machining is performed on the annealed blank to form the basic geometry of the blade ring; S6. Final heat treatment: Perform the following steps in sequence: S61. Quenching: Hold in a vacuum furnace at 1070℃ for 4 hours, then perform oil quenching; S62. Cryogenic treatment: Immediately place the quenched workpiece into a cryogenic device at -150℃ and keep it at that temperature for 3 hours. S63. Rare earth stabilization treatment: heat at 380℃ in a vacuum environment for 1.5h, cool with the furnace to 250℃ and then air cool. S64, Three temperings: Perform three consecutive temperings at 560℃, with each tempering holding for 2.5 hours; S7. Finishing and Inspection: The heat-treated blade ring is precision ground to its final dimensions, and then non-destructive testing and performance testing are performed.

[0038] Example 3 The preparation method of the cutter ring for hard rock TBM mainly includes the following steps: S1. Ingredients: Ingredients are prepared according to the following weight percentages: C 0.52%, Si 1.15%, Mn 0.70%, Cr 4.90%, Mo 1.75%, W 1.05%, V 1.10%, Nb 0.12%, La 0.055%, Y 0.06% (Y / La=1.1), Ni 0.35%, P 0.010%, S 0.004%, Fe as balance; wherein, La and Y are added in the form of lanthanum-iron alloy and yttrium-iron alloy, respectively; S2. Smelting and electroslag remelting: Smelting is carried out in an electric arc furnace. Lanthanum-iron alloy and yttrium-iron alloy are added at 1560℃. After stirring for 10 minutes, the steel is tapped and then electroslag remelted to obtain a Ф500mm steel ingot. S3. Forging and forming: After homogenizing the steel ingot at 1200℃, it is subjected to three upsetting and three drawing multi-directional forging. The final forging temperature is not lower than 900℃, the forging ratio is 6, and the billet is forged into a billet with an outer diameter of 430mm. S4. Annealing treatment: Anneal the blade ring blank at 890℃ for 2 hours, furnace cool to 400℃ and then air cool. S5. Machining: Rough machining is performed on the annealed blank to form the basic geometry of the blade ring; S6. Final heat treatment: Perform the following steps in sequence: S61. Quenching: Hold in a vacuum furnace at 1040℃ for 2 hours, then perform oil quenching; S62. Cryogenic treatment: Immediately place the quenched workpiece into a cryogenic device at -100℃ and keep it at that temperature for 3 hours. S63. Rare earth stabilization treatment: heat at 360℃ in a vacuum environment for 2 hours, then cool to 250℃ in the furnace and then air cool. S64, Three temperings: Three temperings are performed consecutively at 570℃, with each tempering held for 2 hours; S7. Finishing and Inspection: The heat-treated blade ring is precision ground to its final dimensions, and then non-destructive testing and performance testing are performed.

[0039] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that in step S1, the specific weight percentages are: C 0.55%, Si 1.0%, Mn 0.65%, Cr 5.0%, Mo 1.5%, V 1.2%, W 0.8%, Nb 0.08%, Ni 0.30%, P 0.018%, S 0.008%, La 0% (not added), Y 0.05%, and Fe as the balance.

[0040] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that in step S1, the specific weight percentages are: C 0.55%, Si 1.0%, Mn 0.65%, Cr 5.0%, Mo 1.5%, V 1.2%, W 0.8%, Nb 0.08%, Ni 0.30%, P 0.018%, S 0.008%, Y 0% (not added), La 0.04%, and Fe as the balance.

[0041] Performance testing and results analysis The blade ring samples prepared in Examples 1-3 and Comparative Examples 1-2 were tested for properties such as hardness, impact toughness, and service life. The test results are shown in Table 1. Wherein: Hardness testing was performed using a Rockwell hardness tester (HRC scale) at different locations on the working surface of the tool ring, and the average value was taken.

[0042] Impact toughness test: Standard Charpy U-notch impact test specimens (AKU) were fabricated and impact tests were conducted at room temperature. The average value of the results was taken.

[0043] Wear Resistance Comparison Experiment: To evaluate the practical application effect of the present invention, the cutter rings made in the embodiments and comparative examples of the present invention were compared with H13 steel cutter rings prepared using the typical composition described in the background art (C 0.38%-0.42%, Cr 4.80%-5.50%, Mo 1.20%-1.60%, V 0.85%-1.15%) and conventional processes (quenching + secondary tempering). An equal-life field comparison experiment was conducted under the same TBM equipment and granite tunneling conditions. The cumulative tunneling mileage of the H13 steel cutter ring from its commissioning to failure (excessive wear or chipping) was used as the baseline life (denoted as 1.0 time).

[0044] Table 1 Test Results As shown in Table 1, (1) the composite addition of La and Y in Examples 1-3 of the present invention, combined with optimized processes, successfully achieved a high level of simultaneous improvement in hardness and impact toughness. (2) The performance of Comparative Example 1 (without La) and Comparative Example 2 (without Y) both decreased, proving the indispensable role of La and Y, and the importance of their synergistic effect. The lack of any rare earth element will lead to a loss of hardness, toughness and final service life, and will not achieve the best effect of the present invention. (3) The ultra-long service life of the cutter ring of the present invention in hard rock tunneling verifies its comprehensive advantages of high wear resistance and high reliability, which can effectively solve the problem of frequent machine stoppage and cutter replacement mentioned in the background art, and has significant economic benefits.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention in any way. All equivalent transformations or modifications made in accordance with the essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A hard rock TBM hobbing cutter ring, characterized in that, Its chemical composition by weight percentage is as follows: C 0.50%–0.65%, Si 0.80%–1.20%, Mn 0.50%–0.80%, Cr 4.50%–5.50%, Mo 1.20%–1.80%, V 0.80%–1.50%, W 0.50%–1.20%, Nb 0.05%–0.15%, La 0.02%–0.10%, Y 0.03%–0.08%, Ni ≤0.50%, P ≤0.020%, S ≤0.010%, with the remainder being Fe and unavoidable impurities.

2. The hard rock TBM cutter ring according to claim 1, characterized in that, The weight percentage of La to Y satisfies: 0.5 ≤ Y / La ≤ 2.

0.

3. The hard rock TBM cutter ring according to claim 1, characterized in that, Its hardness is 60-65 HRC, and its impact toughness is AKU≥25J.

4. A method for preparing a hard rock TBM cutter ring as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Smelting and refining: Smelting is carried out using an electric arc furnace or a medium-frequency induction furnace, followed by electroslag remelting and refining to obtain steel ingots; S2. Forging: Heat the steel ingot to 1150℃~1200℃ and perform multi-directional upsetting and drawing forging, with a forging ratio ≥5, to form a billet; S3. Annealing treatment: Heat the billet to 860℃~890℃ and hold it at that temperature, then furnace cool it to below 500℃ and air cool it to soften the structure for easier machining. S4. Machining: Rough machining is performed on the annealed billet to form a blade ring blank; S5. Final heat treatment: Perform the following steps in sequence: S51. Quenching: Austenitize in a vacuum furnace at 1020℃~1080℃ and hold for 2~4 hours, then quench to obtain a high-hardness martensitic matrix. S52. Cryogenic treatment: Place the quenched workpiece at -80℃~-196℃ for 1~4 hours to promote the transformation of residual austenite to martensite and improve hardness and dimensional stability. S53. Rare earth stabilization treatment: At 300℃~400℃, keep warm in a vacuum environment or in a protective atmosphere with oxygen partial pressure ≤10Pa for 1~2 hours, then furnace cool to 250℃ and then air cool, so that La and Y elements can be fully segregated at the grain boundaries and phase interfaces to achieve microstructure stabilization. S54. Three temperings: Three temperings are performed at 520℃~580℃, with each tempering holding time not less than 2 hours, in order to promote the dispersion and precipitation of carbides, achieve secondary hardening, and eliminate internal stress. S6. Finishing: The heat-treated cutter ring blank is precision ground to the final size to obtain the final hard rock TBM hobbing cutter ring.

5. The method according to claim 4, characterized in that, In step S1, La and Y elements are added in the form of lanthanum-iron alloy and yttrium-iron alloy, respectively.

6. The method according to claim 4, characterized in that, The heat preservation time in step S3 is 2 to 5 hours.

7. The method according to claim 4, characterized in that, The quenching method in step S51 is high-pressure gas quenching or graded oil quenching.

8. The method according to claim 4, characterized in that, The protective atmosphere in step S53 is an inert gas atmosphere or a nitrogen-hydrogen mixture atmosphere.

9. The method according to claim 4, characterized in that, The three tempering processes in step S54 are performed consecutively.

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