An ultra-high strength cast steel frame for high-speed rail permanent magnet traction motor and a preparation method thereof

Abstract

This application relates to the field of alloy steel technology, specifically disclosing an ultra-high strength cast steel base for a high-speed railway permanent magnet traction motor and its preparation method. The ultra-high strength cast steel base for a high-speed railway permanent magnet traction motor is made from a chemical composition comprising the following weight percentages: C 0.15-0.25%, Si 0.2-0.5%, Mn 1.5-2.5%, Cr 0.5-1.25%, Ni 0.3-0.8%, Mo 0.2-0.5%, Al 0.02-0.06%, V 0.05-0.15%, Ti 0.02-0.08%, Nb 0.01-0.05%, P 0.01-0.02%, S 0.005-0.01%, with the balance being Fe. The ultra-high strength cast steel frame for the high-speed railway permanent magnet traction motor of this application achieves ultra-high strength while maintaining excellent plasticity and toughness and extremely high fatigue limit. This allows designers to use thinner and more optimized frame wall thickness while ensuring safety margin, thereby directly achieving the goal of lightweighting and enabling it to cope with the extreme vibration conditions of high-frequency and high-stress cycles of high-speed railway traction motors.

Description

Technical Field

[0001] This application relates to the field of alloy steel technology, and more specifically, it relates to an ultra-high strength cast steel base for a high-speed railway permanent magnet traction motor and its preparation method. Background Technology

[0002] As global high-speed railways develop towards higher speeds, greater traction power, and greater intelligence, permanent magnet synchronous motors (PMSMs), with their high efficiency, high power density, high control precision, and low maintenance requirements, have become the inevitable choice to replace traditional asynchronous traction motors and are the core equipment of the next generation of high-speed rail traction systems. As a key load-bearing and force-transmitting component of the motor, the frame not only supports the stator core and windings but also transmits the motor's electromagnetic torque to the bogie and withstands complex dynamic loads during operation. Its performance directly determines the motor's reliability, lightweight design, and the overall train's operational efficiency.

[0003] As high-speed rail technology develops towards higher speeds, greater power, and lighter weight, permanent magnet traction motors have placed extremely stringent requirements on the lightweighting and high reliability of structural components: on the one hand, the motor's weight needs to be reduced to improve train energy efficiency and acceleration performance; on the other hand, it needs to withstand high-frequency vibrations, impact loads, and long-term fatigue stress to ensure the motor's safe operation under complex working conditions.

[0004] Traditional high-speed rail traction motor frames are typically made of ductile iron (such as EN-GJS-400-18-LT) or welded steel. While ductile iron frames have a mature casting process, their strength is relatively low, making it difficult to meet the demands of higher power density motors. Welded steel structures, although stronger, suffer from problems such as welding deformation, high residual stress, and limited fatigue life, and are also difficult to design for thin-walled lightweight structures. Therefore, alloy steel, which can be cast integrally and avoids the problems associated with welded structures, is increasingly being developed and used. However, most alloy steels currently used for frames are multi-manganese alloy systems, which often increase strength by increasing the carbon equivalent, but inevitably sacrifice plasticity and toughness. This makes them prone to fatigue cracking under long-term high-frequency, high-load cyclic stress, ultimately leading to brittle fracture, and maintaining stable lightweight design is also difficult.

[0005] Therefore, in order to solve the problem of balancing lightweight, high strength, and long fatigue life in the permanent magnet traction motor base of high-speed railway, it is urgent to propose a solution to address the above-mentioned technical issues. Summary of the Invention

[0006] In order to achieve high strength and lightweight of the frame while ensuring excellent plasticity, toughness and fatigue resistance, and to meet the stringent service requirements of high-speed rail traction motors under high-frequency vibration conditions, this application provides an ultra-high strength cast steel frame for high-speed rail permanent magnet traction motors and its preparation method.

[0007] In the first aspect, this application provides an ultra-high strength cast steel base for a permanent magnet traction motor for high-speed railways, adopting the following technical solution: A high-strength cast steel base for a high-speed railway permanent magnet traction motor is made of a chemical composition comprising the following weight percentages: C 0.15-0.25%; Si 0.2-0.5%; Mn 1.5-2.5%; Cr 0.5-1.25%; Ni 0.3-0.8%; Mo 0.2-0.5%; Al 0.02-0.06%; V 0.05-0.15%; Ti 0.02-0.08%; Nb 0.01-0.05%; P 0.01-0.02%; S 0.005-0.01%; The balance is Fe.

[0008] By adopting the above technical solutions, a suitable carbon content range can provide sufficient strength while avoiding the severe brittleness and quenching cracking tendency caused by high carbon content. Mn is a strong austenite stabilizing element that can significantly improve the hardenability of steel, ensuring a uniform structural structure even in the center of castings with large cross-sections, thus guaranteeing the uniformity of overall performance of thick-walled castings such as machine bases. Si can strengthen ferrite through solid solution, improve tempering stability, and a suitable Si content provides a certain strengthening effect while avoiding the damage to toughness caused by excessive silicon content. Cr and Mo can significantly improve hardenability and form carbides with carbon, providing a secondary hardening effect. The addition of Mo is particularly important, as it can suppress temper brittleness and improve high-temperature strength and creep resistance. Ni does not form carbides and is mainly dissolved in the matrix. Its core role is to significantly improve low-temperature toughness and fracture toughness, effectively preventing crack propagation. Moreover, it can improve strength without significantly reducing plasticity, making it a key element for strengthening and toughening. The aforementioned Cr-Mo-Ni combination effectively mitigates the brittleness that may result from medium-carbon and carbide-forming elements while ensuring sufficient hardenability and strength, thus promoting a synergistic improvement in both strength and toughness. Al plays a role in refining grain size and precipitation strengthening. Furthermore, controlling the P and S content to extremely low levels significantly reduces the number and size of non-metallic inclusions, thereby increasing the purity of the steel.

[0009] Meanwhile, the microalloying combination of V, Ti, and Nb exhibits excellent synergistic effects. Ti has a strong affinity for nitrogen, oxygen, and carbon; in the early stages of steel solidification, Ti preferentially combines with nitrogen to form high-melting-point TiN particles. Nb carbonitrides have high solid solubility; during post-casting cooling or heat treatment heating, undissolved Nb and TiN work together to effectively prevent coarsening of the casting structure and grain growth during heat treatment austenitization, resulting in exceptionally fine and uniform original austenite grains. This not only provides a foundation for achieving high strength and lightweight design but also... Furthermore, the fine-grained structure effectively inhibits the initiation and propagation of fatigue microcracks, significantly improving the fatigue limit and long-life fatigue strength. Subsequently, based on matrix strengthening and fine-grained strengthening, V carbonitrides have high solid solubility and will become supersaturated during rapid cooling. During subsequent tempering, the supersaturated V and Nb will precipitate from the matrix in the form of nanoscale carbonitride particles. These nanoparticles interact strongly with dislocations, producing a huge strengthening effect with little damage to plasticity, thus protecting the toughness reserve brought by the fine-grained Ti / Nb. Therefore, the cooperation among the three is not a simple superposition of functions, but rather a systematic improvement of the material's comprehensive performance from multiple levels, such as crystal structure, microstructure, and defect control, by precisely controlling its existence form, precipitation sequence, and operating temperature range. This ensures that the cast steel achieves ultra-high strength while maintaining excellent plasticity, toughness, and extremely high fatigue limit. Consequently, designers can use thinner and more optimized frame wall thicknesses while ensuring safety margins, thereby directly achieving the goal of lightweighting and enabling it to cope with the extreme vibration conditions of high-frequency, high-stress cycles in high-speed rail traction motors.

[0010] Preferably, the mass ratio of V, Ti, and Nb is (2-5):(1-3):1.

[0011] By adopting the above technical solutions, we can prioritize the dominance of TiN in the lead precipitation and grain refinement, optimize the dual effects of Nb grain boundary pinning and mid-temperature precipitation, give full play to the ultimate precipitation strengthening potential of V, and avoid damage to toughness, thereby achieving optimal performance and achieving the seemingly contradictory comprehensive performance goals of ultra-high strength, high toughness, and high fatigue resistance. This lays the core micromaterial foundation for the safe and lightweight design of the chassis.

[0012] Preferably, the total weight percentage of V, Ti, and Nb is 0.1-0.25%.

[0013] By adopting the above technical solution, V, Nb, and Ti are all valuable microalloying elements, and their market prices are significantly higher than those of conventional alloying elements. Within the above range, it can not only ensure the expected effect, but also help to control costs and meet the practical needs of large-scale equipment manufacturing.

[0014] Preferably, the chemical composition further contains functional additives, which are composed of a combination of B, Cu, and rare earth elements, and the weight percentages of the B, Cu, and rare earth elements are as follows: B 0.001-0.002%; Cu 0.2-0.3%; Rare earth composition 0.005-0.015%; The rare earth composition consists of Ce and La.

[0015] By employing the above technical solutions, trace amounts of boron (B) can significantly reduce the interfacial energy of grain boundaries, greatly improve the hardenability of steel, and enhance grain boundary bonding and strength through the segregation of B atoms at grain boundaries. This is beneficial for preventing intergranular fracture under impact loads. Furthermore, based on the grain refinement strengthening already achieved by V, Nb, and Ti, the addition of B further strengthens the already refined grain boundaries themselves, allowing the toughening and strengthening benefits brought by grain refinement to be fully realized. The addition of Cu further increases the upper limit of the material's strength without sacrificing toughness, and forms a composite precipitation strengthening system with the carbonitride precipitation of V and Nb, enabling the material to maintain high strength and good toughness matching over a wide tempering temperature range. The rare earth composition composed of Ce and La not only purifies grain boundaries and improves toughness through microalloying, but also inhibits the segregation of harmful elements and improves fatigue performance. By combining B, Cu, and rare earth elements as functional additives, a three-dimensional, multi-layered performance guarantee network is formed through the synergistic treatment of grain boundaries between B and rare earth elements and the complementary properties of Cu and rare earth elements. This further achieves the goal of improving strength without compromising toughness and improving toughness without reducing strength, and effectively combats the initiation of fatigue cracks under long-term high-frequency, high-load cyclic stress. As a result, the application quality of ultra-high strength cast steel bases for high-speed railway permanent magnet traction motors is significantly improved.

[0016] Preferably, the weight ratio of Ce to La in the rare earth composition is (2.2-3):1.

[0017] By adopting the above technical solution, Ce utilizes its strongest chemical activity to quickly and thoroughly reduce the oxygen and sulfur content in molten steel, creating a "clean" environment for subsequent reactions; La further optimizes the morphology and distribution of residual inclusions after Ce completes the main purification; when the two are combined within the above ratio range, they can achieve stable and excellent performance with the highest efficiency with limited rare earth addition, and ensure process stability and reproducibility.

[0018] Secondly, this application provides a method for manufacturing an ultra-high strength cast steel base for a high-speed railway permanent magnet traction motor, employing the following technical solution: A method for preparing an ultra-high strength cast steel base for a high-speed railway permanent magnet traction motor includes the following steps: (1) Prepare the raw materials according to the corresponding chemical composition and proportion, melt them, and then cast them into a machine base blank; (2) The blank of the machine base is subjected to solution treatment, followed by quenching, cooling and tempering, and then further cooling. Finally, it is precision machined to obtain the ultra-high strength cast steel machine base for high-speed railway permanent magnet traction motor.

[0019] By adopting the above technical solution, the connection of the above preparation operations aims to accurately transform the microstructure to meet the goals of "high strength, high toughness and plasticity, and high fatigue resistance", and finally transform it into an ultra-high strength cast steel base for high-speed railway permanent magnet traction motor with ultra-high strength, excellent toughness, high fatigue limit and good dimensional stability.

[0020] Preferably, in step (2), during the solution treatment of the machine base blank, the solution treatment temperature is controlled at 880-920℃ and the solution treatment time is 1.5-3h.

[0021] By adopting the above technical solution, solution treatment of the machine base blank can ensure complete austenitization, dissolve harmful as-cast structures, and promote the full dissolution of alloying elements. Controlling the solution treatment temperature to 880-920℃ ensures the complete dissolution of harmful structures and the full dissolution of alloying elements, while preserving the effects of microalloying of V, Ti, and Nb, preventing performance degradation caused by grain coarsening, and setting a perfect tone of "uniform composition, dense structure, and fine grains" for the microstructure of the entire material.

[0022] Preferably, in step (2), after solution treatment and before quenching, high-temperature homogenization treatment and fine normalizing treatment are performed sequentially; wherein, the high-temperature homogenization treatment temperature is 1150-1200℃ and the high-temperature homogenization treatment time is 8-12h; the fine normalizing treatment temperature is 920-940℃ and the fine normalizing treatment time is 3-5h.

[0023] By adopting the above technical solutions, high-temperature homogenization treatment eliminates local weak areas caused by compositional segregation, making the material properties highly consistent at the microscale, significantly improving overall toughness and plasticity, and making the strength performance more stable. The 1150-1200℃ temperature greatly increases the diffusion coefficient and fully dissolves various segregated phases, while 8-12 hours ensures high compositional uniformity at the microscale. Refining normalizing treatment can "reshape" and "refine" the coarse austenite grains that inevitably appear after high-temperature homogenization treatment, while the combination of 920-940℃ and 3-5 hours maximizes the benefits of "refined grain strengthening" and improves microstructure uniformity. Through the combination of the above high-temperature homogenization treatment and refining normalizing treatment, the compositional segregation and coarse microstructure of cast high-alloy steel are greatly improved, ultimately further enhancing the plasticity, toughness, fatigue resistance, and high strength of the ultra-high-strength cast steel base for high-speed railway permanent magnet traction motors, and making it more conducive to lightweighting, with better application performance under high-frequency vibration conditions.

[0024] Preferably, in step (2), the tempering temperature is 580-620℃ and the tempering time is 6-8h.

[0025] By adopting the above technical solutions, tempering after quenching is a decisive step in giving the material its final service performance. By controlling the above conditions, precise phase transformation control of the high-strength matrix can be obtained, and a perfect balance between ultra-high strength and high toughness can be achieved. Ultimately, an ultra-high strength cast steel base for high-speed rail permanent magnet traction motors is forged that is uniform, clean, fine-grained, and dispersedly strengthened at the microscopic level, and has ultra-high strength, high toughness, and high fatigue resistance at the macroscopic level.

[0026] Preferably, in step (2), the cooling operation after the quenching treatment is to place the quenched material in a cryogenic environment of -80℃ to 120℃ for 2-4 hours immediately.

[0027] By adopting the above technical solution, the residual austenite is the most abundant after quenching. At this time, deep cooling has the most significant transformation effect. It also provides a more complete martensitic matrix, a more uniform micro-stress state, and a distribution of solute atoms that may be more conducive to precipitation. This allows the subsequent high-temperature tempering to be carried out from a cleaner and more stable starting point, thereby achieving precipitation strengthening and internal stress elimination more accurately and efficiently.

[0028] In summary, this application has the following beneficial effects: 1. This application utilizes the microalloying of V, Ti, and Nb to leverage their excellent synergistic effect, which systematically improves the comprehensive performance of the material from multiple levels, including crystal structure, microstructure, and defect control. While ensuring that the cast steel achieves ultra-high strength, it still maintains excellent plasticity and toughness and extremely high fatigue limit. This allows designers to use thinner and more optimized frame wall thickness while ensuring safety margins, thereby directly achieving the goal of lightweighting and enabling it to cope with the extreme vibration conditions of high-frequency and high-stress cycles of high-speed rail traction motors. 2. This application uses a combination of B, Cu and rare earth elements as functional additives. Through the mutual cooperation of the three, a three-dimensional, multi-layered performance guarantee network is formed, which further realizes the improvement of strength without compromising toughness and the improvement of toughness without reducing strength. It also effectively resists the initiation of fatigue cracks under long-term high-frequency and high-load cyclic stress, thus significantly improving the application quality of ultra-high strength cast steel base for high-speed railway permanent magnet traction motor. 3. This application performs high-temperature homogenization treatment and fine normalizing treatment sequentially after solution treatment and before quenching treatment, and deep cryogenic treatment after quenching treatment. All of these are conducive to further improving the plasticity, toughness, fatigue resistance and high strength of the ultra-high strength cast steel base for high-speed railway permanent magnet traction motor, and are more conducive to achieving lightweight, thus resulting in better application effect under high frequency vibration conditions. Detailed Implementation

[0029] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0030] Unless otherwise specified, all raw materials used in the embodiments and comparative examples of this application are commercially available.

[0031] Example Example 1

[0032] A high-strength cast steel base for a high-speed railway permanent magnet traction motor is prepared by means of the following steps: The chemical composition and corresponding weight percentages of this base are shown in Table 1. (1) The ingredients are prepared according to the corresponding chemical composition and proportion, and then melted in an electric arc furnace and cast into a machine base blank; (2) The blank of the base is subjected to solution treatment, followed by quenching, water cooling and tempering, and then air cooling. Finally, it is precision machined to obtain the ultra-high strength cast steel base for high-speed railway permanent magnet traction motor.

[0033] Note: In the above operation, in step (2), during the solution treatment of the machine base blank, the solution treatment temperature is controlled at 900℃ and the solution treatment time is 2.25h. The tempering temperature is 600℃ and the tempering time is 7h. Example 2-3

[0034] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that its chemical composition and corresponding weight percentages are shown in Table 1.

[0035] Table 1. Chemical composition and corresponding weight percentage (%) of Examples 1-3 Example 4

[0036] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that the total amount of V, Ti, and Nb remains unchanged, but the mass ratio of V, Ti, and Nb is adjusted to 3.5:2:1. Example 5

[0037] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Embodiment 1 in that the total amount of V, Ti, and Nb remains unchanged, but the mass ratio of V, Ti, and Nb is adjusted to 2:1:1. Example 6

[0038] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Embodiment 1 in that the total amount of V, Ti, and Nb remains unchanged, but the mass ratio of V, Ti, and Nb is adjusted to 5:3:1. Example 7

[0039] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that the ratio of V, Ti, and Nb remains unchanged, the total weight percentage of V, Ti, and Nb is adjusted to 0.175%, and the percentages of other chemical components except Fe remain unchanged, with only the weight percentage of Fe changing. Example 8

[0040] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that the ratio of V, Ti, and Nb remains unchanged, the total weight percentage of V, Ti, and Nb is adjusted to 0.1%, and the percentages of other chemical components, except for Fe, remain unchanged, with only the weight percentage of Fe changing. Example 9

[0041] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that the ratio of V, Ti, and Nb remains unchanged, the total weight percentage of V, Ti, and Nb is adjusted to 0.25%, and the percentages of other chemical components, except for Fe, remain unchanged, with only the weight percentage of Fe changing. Example 10

[0042] A high-strength cast steel base for a permanent magnet traction motor for high-speed rail differs from that in Example 1 in that, in step (2), during the solution treatment of the base blank, the solution treatment temperature is controlled at 880°C and the solution treatment time is 3 hours. Example 11

[0043] A high-strength cast steel base for a permanent magnet traction motor for high-speed rail differs from that in Example 1 in that, in step (2), during the solution treatment of the base blank, the solution treatment temperature is controlled at 920°C and the solution treatment time is 1.5h. Example 12

[0044] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that, in step (2), the tempering temperature is 580℃ and the tempering time is 8h. Example 13

[0045] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that, in step (2), the tempering temperature is 620°C and the tempering time is 6 hours. Example 14

[0046] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that it also contains functional additives in its chemical composition. These functional additives are composed of a combination of B, Cu, and rare earth elements, with the following weight percentages: B 0.0015%; Cu 0.25%; Rare earth composition 0.010%; The rare earth composition is composed of Ce and La, and the weight ratio of Ce to La in the rare earth composition is 2.6:1; The percentages of all chemical components except Fe remained unchanged, with only the weight percentage of Fe changing to ensure 100% of the overall chemical composition. Example 15

[0047] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 14 in that the weight percentages of the B, Cu, and rare earth composition are as follows: B 0.001%; Cu 0.2%; Rare earth composition 0.005%. Example 16

[0048] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 14 in that the weight percentages of the B, Cu, and rare earth composition are as follows: B 0.002%; Cu 0.3%; Rare earth composition 0.015%. Example 17

[0049] A high-strength cast steel base for a permanent magnet traction motor for high-speed rail differs from Example 14 in that the rare earth composition consists of Ce and La, and the weight ratio of Ce to La in the rare earth composition is 2.2:1. Example 18

[0050] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 14 in that the rare earth composition consists of Ce and La, and the weight ratio of Ce to La in the rare earth composition is 3:1. Example 19

[0051] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 14 in that only functional additive B is added. Example 20

[0052] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 14 in that only Cu, a functional additive, is added. Example 21

[0053] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 14 in that it only adds a rare earth composition from the functional additives. Example 22

[0054] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from that in Example 1 in that, in step (2), after solution treatment and before quenching, high-temperature homogenization treatment and fine normalizing treatment are performed sequentially; wherein, the high-temperature homogenization treatment temperature is 1175℃ and the high-temperature homogenization treatment time is 10h; the fine normalizing treatment temperature is 930℃ and the fine normalizing treatment time is 4h. Example 23

[0055] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from that in Example 1 in that, in step (2), after solution treatment and before quenching, high-temperature homogenization treatment and fine normalizing treatment are performed sequentially; wherein, the high-temperature homogenization treatment temperature is 1150℃ and the high-temperature homogenization treatment time is 12h; the fine normalizing treatment temperature is 920℃ and the fine normalizing treatment time is 5h. Example 24

[0056] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from that in Example 1 in that, in step (2), after solution treatment and before quenching, high-temperature homogenization treatment and fine normalizing treatment are performed sequentially; wherein, the high-temperature homogenization treatment temperature is 1200℃ and the high-temperature homogenization treatment time is 8h; the fine normalizing treatment temperature is 940℃ and the fine normalizing treatment time is 3h. Example 25

[0057] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from that in Example 1 in that, in step (2), the cooling operation after quenching is to place the machine in a deep cryogenic environment at -100℃ for 3 hours immediately after quenching. Example 26

[0058] A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from that in Example 1 in that, in step (2), the cooling operation after quenching is to place it in a deep cryogenic environment of -80℃ for 4 hours immediately after quenching. Example 27

[0059] A high-strength cast steel base for a permanent magnet traction motor for high-speed rail differs from that in Example 1 in that, in step (2), the cooling operation after quenching is to place the machine in a cryogenic environment at -120°C for 2 hours immediately after quenching.

[0060] Comparative Example Comparative Example 1 A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that it does not contain V or Ti in its chemical composition.

[0061] Comparative Example 2 A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that it does not contain V or Nb in its chemical composition.

[0062] Comparative Example 3 A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that it does not contain Ti or Nb in its chemical composition.

[0063] Comparative Example 4 A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that it does not contain V in its chemical composition.

[0064] Comparative Example 5 A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that it does not contain Ti in its chemical composition.

[0065] Comparative Example 6 A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that it does not contain Nb in its chemical composition.

[0066] Comparative Example 7 A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 1 in that it does not contain V, Ti, or Nb in its chemical composition.

[0067] Comparative Example 8 A high-strength cast steel base for a high-speed railway permanent magnet traction motor differs from Example 15 in that it does not contain V, Ti, or Nb in its chemical composition.

[0068] Performance testing Test samples: The ultra-high strength cast steel base for high-speed railway permanent magnet traction motors obtained in Examples 1-27 was selected as test sample 1-27, and the ultra-high strength cast steel base for high-speed railway permanent magnet traction motors obtained in Comparative Examples 1-8 was selected as control sample 1-8.

[0069] Test methods: (1) Fatigue resistance test: Plot the data points and fitting curve with stress amplitude (Sa) or maximum stress (Smax) as the vertical axis (logarithmic coordinates) and the number of failure cycles (Nf) as the horizontal axis (logarithmic coordinates). Determine the stress ratio (R=Smin / Smax, usually R=-1). Obtain the fatigue limit value by testing according to ISO 12107: "Statistical scheme and analysis method for fatigue test data of metallic materials". The fatigue limit is the value obtained after a specified number of cycles (10 7 The maximum stress amplitude at which the material does not experience fatigue failure (under [number] stresses).

[0070] (2) High strength performance test, the tensile strength and yield strength are obtained by testing according to ISO 6892-1: Metallic materials, tensile test - Part 1: Test at room temperature.

[0071] (3) Plastic and toughness test: The elongation after fracture is obtained according to ISO 6892-1: "Metallic materials - Tensile testing - Part 1: Test at room temperature"; the impact energy KV2 absorbed by the specimen during fracture is tested at a low temperature of -40℃ according to ASTM E23: "Metallic materials - Standard impact test method".

[0072] After performing the above tests on test samples 1-27 and control samples 1-8, the test results are recorded in Table 2.

[0073] Table 2 Test results of test samples 1-27 and control samples 1-8 As can be seen from Examples 1-13 and Comparative Examples 1-7, and Table 2, the combined use of microalloying of V, Ti, and Nb can significantly improve the fatigue limit, high strength performance, and ductility of the ultra-high strength cast steel frame for high-speed railway permanent magnet traction motors. It was also found that while adding any two of V, Ti, and Nb can improve the effect, the improvement is limited, and the effects are merely additive. Only when all three are synergistically combined can a significant improvement (1+1+1>3) be achieved. This allows designers to use thinner, more optimized frame wall thicknesses while ensuring safety margins, directly achieving the goal of lightweighting and enabling the motor to withstand the extreme vibration conditions of high-frequency, high-stress cycles in high-speed railway traction motors.

[0074] Combining Examples 1 and 14-18 with Table 2, it can be seen that the use of a combination of B, Cu, and rare earth elements (composed of Ce and La) as functional additives in this application significantly improves the application quality of the ultra-high strength cast steel frame for high-speed railway permanent magnet traction motors. The relevant data obtained from the above tests all show significant improvements. Furthermore, combining Examples 19-21 with Table 2, it can be seen that while adding any one of the functional additives (B, Cu, and rare earth elements) can improve the overall effect, the synergistic effect of all three is more significant. The combined effect of B, Cu, and rare earth elements is even better than the sum of the individual effects of the three elements, demonstrating the synergistic effect of the compound. Furthermore, comparing Comparative Examples 7-8 with Table 2, it can be seen that if the ultra-high strength cast steel base for high-speed railway permanent magnet traction motors lacks the combined use of V, Ti, and Nb, the corresponding effects of the functional additives are significantly reduced. This shows that the functional additives have an indispensable synergistic advantage with V, Ti, and Nb, thus ensuring a significant improvement in the application quality of the ultra-high strength cast steel base for high-speed railway permanent magnet traction motors.

[0075] As can be seen from Examples 1 and 22-27 and Table 2, this application performs high-temperature homogenization treatment and fine normalizing treatment sequentially after solution treatment and before quenching treatment, and performs deep cryogenic treatment after quenching treatment. All of these are beneficial to further improving the plasticity, toughness, fatigue resistance and high strength of the ultra-high strength cast steel base for high-speed railway permanent magnet traction motor.

[0076] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-strength cast steel base for a high-speed railway permanent magnet traction motor, characterized in that, Made from chemical components comprising the following weight percentages: C 0.15-0.25%； Si 0.2-0.5%; Mn 1.5-2.5%; Cr 0.5-1.25%； Ni 0.3-0.8%; Mo 0.2-0.5%; Al 0.02-0.06%； V 0.05-0.15%； Ti 0.02-0.08%; Nb 0.01-0.05%; P 0.01-0.02%； S 0.005-0.01%； The balance is Fe.

2. The ultra-high strength cast steel base for high-speed railway permanent magnet traction motor according to claim 1, characterized in that: The mass ratio of V, Ti, and Nb is (2-5):(1-3):

1.

3. The ultra-high strength cast steel base for high-speed railway permanent magnet traction motor according to claim 2, characterized in that: The total weight percentage of V, Ti, and Nb is 0.1-0.25%.

4. The ultra-high strength cast steel base for high-speed railway permanent magnet traction motor according to claim 1, characterized in that: The chemical composition also contains functional additives, which are composed of a combination of B, Cu, and rare earth elements, and the weight percentages of the B, Cu, and rare earth elements are as follows: B 0.001-0.002%； Cu 0.2-0.3%; Rare earth composition 0.005-0.015%; The rare earth composition consists of Ce and La.

5. The ultra-high strength cast steel base for high-speed railway permanent magnet traction motor according to claim 4, characterized in that: The weight ratio of Ce to La in the rare earth composition is (2.2-3):

1.

6. The method for preparing the ultra-high strength cast steel base for high-speed railway permanent magnet traction motor according to claim 1, characterized in that: Includes the following steps: (1) Prepare the raw materials according to the corresponding chemical composition and proportion, melt them, and then cast them into a machine base blank; (2) The blank of the machine base is subjected to solution treatment, followed by quenching, cooling and tempering, and then further cooling. Finally, it is precision machined to obtain the ultra-high strength cast steel machine base for high-speed railway permanent magnet traction motor.

7. The method for preparing the ultra-high strength cast steel base for high-speed railway permanent magnet traction motor according to claim 6, characterized in that: In step (2), during the solution treatment of the machine base blank, the solution treatment temperature is controlled at 880-920℃ and the solution treatment time is 1.5-3h.

8. The method for preparing the ultra-high strength cast steel base for high-speed railway permanent magnet traction motor according to claim 6, characterized in that: In step (2), after solution treatment and before quenching, high-temperature homogenization treatment and fine normalizing treatment are performed in sequence; the high-temperature homogenization treatment temperature is 1150-1200℃ and the high-temperature homogenization treatment time is 8-12h; the fine normalizing treatment temperature is 920-940℃ and the fine normalizing treatment time is 3-5h.

9. The method for preparing the ultra-high strength cast steel base for high-speed railway permanent magnet traction motor according to claim 6, characterized in that: In step (2), the tempering temperature is 580-620℃ and the tempering time is 6-8h.

10. The method for preparing the ultra-high strength cast steel base for high-speed railway permanent magnet traction motor according to claim 6, characterized in that: In step (2), the cooling operation after the quenching treatment is to place the quenched material in a cryogenic environment of -80℃ to 120℃ for 2-4 hours immediately.

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