Bar for motor shaft of new energy automobile and preparation method of bar

Abstract

The invention discloses a bar for a motor shaft of a new energy automobile and a preparation method of the bar, and relates to the technical field of metallurgy, the bar comprises the following components: a base material and nanoscale ferrite particles; the nanoscale ferrite particles are uniformly dispersed in a high-strength alloy steel matrix, so that the comprehensive mechanical property of the material is remarkably improved, specifically, the Rockwell hardness of the bar reaches HRC35-45, meanwhile, the hardness and toughness balance of the material is further optimized through a specific heat treatment process, and the service life of the material is prolonged. And the bar can meet the requirements of the new energy automobile motor shaft for high strength, high wear resistance and good fatigue resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a rod material for a motor shaft of a new energy vehicle and a preparation method thereof. Background Art

[0002] With the rapid development of the new energy vehicle industry, the performance requirements for key components such as motor shafts are becoming increasingly stringent. As the core component of power transmission, the motor shaft of new energy vehicles not only needs to withstand high-load and high-speed working environments, but also needs to have good wear resistance, fatigue resistance and corrosion resistance to ensure the safety and reliability of the vehicle.

[0003] Traditional rods for new energy vehicle motor shafts are mostly made of ordinary alloy steel or a single type of ferrite particle reinforced material. These materials have certain limitations in mechanical properties. Although ordinary alloy steel is low-cost and has good processability, its hardness and wear resistance are often difficult to meet the long-term use requirements under high-load and high-speed conditions. Although a single type of ferrite particle reinforced material can improve the hardness and wear resistance of the material to a certain extent, due to uneven particle dispersion or insufficient interface bonding strength between the particles and the matrix, it is easy to cause problems such as particle shedding and crack expansion during use, seriously affecting the service life and safety of the motor shaft. In addition, the traditional preparation process has deficiencies in controlling particle dispersion, melting temperature, and heat treatment parameters, making it difficult to accurately control the microstructure and properties of the material, thereby limiting the further improvement of material performance.

[0004] In view of the shortcomings of traditional new energy vehicle motor shaft rods in mechanical properties and preparation technology, it is particularly important to develop a new energy vehicle motor shaft rod and a preparation method thereof. Summary of the Invention

[0005] The purpose of the present invention is to make up for the shortcomings of the existing technology and provide a rod for new energy vehicle motor shaft and a preparation method thereof. It can significantly improve the comprehensive mechanical properties of the material, including hardness, wear resistance and fatigue resistance, by uniformly dispersing nano-ferrite particles in a high-strength alloy steel matrix. At the same time, by precisely controlling the parameters of each step in the preparation process, the ferrite particles are uniformly dispersed in the matrix material, effectively avoiding the particle agglomeration phenomenon, and improving the internal quality and performance stability of the product.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a rod for a motor shaft of a new energy vehicle, which is made of the following raw materials in parts by weight:

[0007] The rod material comprises a matrix material and nano-scale ferrite particles uniformly dispersed in the matrix material.

[0008] Furthermore, the nano-sized ferrite particles are a mixture of spinel ferrite and garnet ferrite, and the mass ratio of the two is 1:1-3:1, the particle size is 50-100 nanometers, and the mass proportion of the nano-sized ferrite in the rod is 5-15%.

[0009] Furthermore, the Rockwell hardness of the rod is HRC35-45.

[0010] Furthermore, the matrix material is high-strength alloy steel, whose components include carbon, silicon, manganese, chromium, molybdenum and other elements. The mass percentage of each element is: carbon 0.3-0.5%, silicon 0.2-0.5%, manganese 0.6-1.0%, chromium 1.0-1.5%, molybdenum 0.1-0.3%, and the balance is iron. The grain size grade of the matrix material is not less than level 8.

[0011] On the other hand, a method for preparing a rod for a new energy vehicle motor shaft is provided, characterized in that the method comprises the following steps:

[0012] Raw material preparation: Prepare various raw materials for high-strength alloy steel and nano-ferrite particles, pre-treat the high-strength alloy steel raw materials before smelting to remove surface impurities;

[0013] Ferrite particle dispersion treatment: adding nano-sized ferrite particles to an organic solvent and dispersing them using ultrasonic dispersion equipment for 30-60 minutes to form a uniformly dispersed suspension of the ferrite particles in the organic solvent, wherein the organic solvent is anhydrous ethanol;

[0014] Matrix smelting: The pre-treated high-strength alloy steel raw materials are added to the vacuum induction melting furnace for smelting. The smelting temperature is controlled at 1500-1600℃. After the raw materials are completely melted, they are refined to remove impurities and gases. The refining time is 20-30 minutes.

[0015] Composite treatment: When the base steel liquid is in liquid state and the temperature is maintained at 1450-1550℃, slowly add the dispersed ferrite particle suspension into the steel liquid, and stir it with an electromagnetic stirring device at a speed of 200-300 rpm for 10-20 minutes to make the ferrite particles evenly dispersed in the steel liquid;

[0016] Casting: The composite molten steel is cast into a specific mold and cooled to obtain a bar blank. The cooling rate is controlled at 5-10℃ / second.

[0017] Subsequent processing: The bar billet is subjected to forging and heat treatment. The forging ratio is controlled at 3-5. The heat treatment process includes quenching and tempering. The quenching temperature is 850-900℃ and the tempering temperature is 550-650℃ to improve the comprehensive mechanical properties of the bar.

[0018] Furthermore, in the raw material preparation step, the nano-sized ferrite particles are vacuum dried before use, with a drying temperature of 80-100° C. and a drying time of 2-4 hours.

[0019] Furthermore, in the ferrite particle dispersion treatment step, a dispersant with a mass fraction of 0.1-0.5% is added during the ultrasonic dispersion process, and the dispersant is sodium polyacrylate.

[0020] Furthermore, in the matrix melting step, the vacuum degree in the vacuum induction melting furnace is maintained at 1×10⁻³-1×10⁻²Pa during melting.

[0021] Furthermore, in the composite treatment step, the ferrite particle suspension is added at a rate of 5-10 L / min.

[0022] Furthermore, in the subsequent treatment step, the tempering treatment adopts a two-tempering process, the first tempering temperature is 550-600°C, the holding time is 2-3 hours, and the second tempering temperature is 500-550°C, the holding time is 2-3 hours.

[0023] Compared with the existing technology, the rod material for the motor shaft of a new energy vehicle and the preparation method thereof have the following beneficial effects:

[0024] 1. The rod of the present invention significantly improves the comprehensive mechanical properties of the material by uniformly dispersing nano-ferrite particles in a high-strength alloy steel matrix. Specifically, the Rockwell hardness of the rod reaches HRC35-45. At the same time, through a specific heat treatment process, the balance between hardness and toughness of the material is further optimized, so that the rod can meet the requirements of new energy vehicle motor shafts for high strength, high wear resistance and good fatigue resistance.

[0025] 2. The preparation method of the present invention achieves uniform dispersion of ferrite particles in the matrix material by precisely controlling the parameters of each step, such as melting temperature, refining time, dispersion and addition speed of ferrite particles, electromagnetic stirring conditions and cooling rate, effectively avoiding particle agglomeration. In addition, the use of vacuum induction melting and specific subsequent processing technology not only improves production efficiency, but also significantly improves the internal quality and performance stability of the product, providing reliable material guarantee for new energy vehicle motor shafts.

[0026] Other advantages, objects and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art based on an examination of the following or may be learned from the practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0028] Figure 1 The present invention is a flow chart of a rod material for a motor shaft of a new energy vehicle and a preparation method thereof. DETAILED DESCRIPTION

[0029] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0030] Examples 1 to 3 only change the content of nano-sized ferrite particles

[0031] Example 1

[0032] It consists of a matrix material and nano-ferrite particles uniformly dispersed in the matrix material. The nano-ferrite particles are a mixture of spinel ferrite and garnet ferrite with a mass ratio of 2:1. The particle size is 80 nanometers and the mass proportion in the rod is 5%. The matrix material is made of high-strength alloy steel. The mass percentage of each element in its composition is 0.4% carbon, 0.3% silicon, 0.8% manganese, 1.2% chromium, 0.2% molybdenum, and the balance is iron. After testing, the grain size grade of the matrix material reaches level 9, and the Rockwell hardness of the rod is HRC40.

[0033] Raw material preparation: Prepare the carbon, silicon, manganese, chromium, molybdenum, iron raw materials and nano-ferrite particles required for high-strength alloy steel. Pre-treat the high-strength alloy steel raw materials by grinding, cleaning, and other pretreatments to remove surface impurities. Place the nano-ferrite particles in a vacuum drying oven at 90°C for 3 hours before use.

[0034] Ferrite particle dispersion treatment: Nano-sized ferrite particles were added to anhydrous ethanol, and 0.3% sodium polyacrylate dispersant was added at the same time. Ultrasonic dispersion equipment was used to disperse the ferrite particles for 45 minutes to form a uniformly dispersed suspension in the anhydrous ethanol.

[0035] Matrix smelting: Add the pretreated high-strength alloy steel raw materials into the vacuum induction melting furnace, maintain the vacuum degree in the furnace at 5×10⁻³Pa, and smelt at 1550℃. After the raw materials are completely melted, they are refined for 25 minutes to remove impurities and gases.

[0036] Composite treatment: When the temperature of the matrix steel liquid is maintained at 1500℃, the dispersed ferrite particle suspension is slowly added to the steel liquid at a speed of 8L / min. At the same time, the electromagnetic stirring device is started and stirred at a speed of 250 rpm for 15 minutes to ensure that the ferrite particles are evenly dispersed in the steel liquid.

[0037] Casting: The compounded molten steel is cast into a specific mold, the cooling rate is controlled to 8°C / second, and the bar blank is obtained by cooling and molding.

[0038] Subsequent processing: The bar billet is forged with a forging ratio of 4. The heat treatment adopts quenching and tempering process. The quenching temperature is set to 870℃, and the tempering adopts two tempering processes. The first tempering temperature is 580℃, and the heat preservation is 2.5 hours. The second tempering temperature is 530℃, and the heat preservation is 2.5 hours to improve the comprehensive mechanical properties of the bar.

[0039] Effect: Mechanical properties: tensile strength 1150-1250MPa, yield strength 1000-1100MPa, elongation about 13%, cross-sectional shrinkage 43%, Rockwell hardness HRC38, wear resistance increased by 25% compared to ordinary bars.

[0040] Microstructure: The matrix grain size is level 9, and the ferrite particles are evenly dispersed. However, due to the low content, the dispersion strengthening effect is slightly weaker.

[0041] Magnetic properties and functionality: Magnetic permeability 120-150H / m, remanence 0.2-0.4T, coercive force 70-100kA / m, motor efficiency increased by about 3%-5%.

[0042] Processing performance and stability: density 7.8g / cm³, dimensional accuracy ±0.05mm, thermal expansion coefficient 1.2×10⁻ 5 / ℃.

[0043] Example 2

[0044] It consists of a matrix material and nano-ferrite particles uniformly dispersed in the matrix material. The nano-ferrite particles are a mixture of spinel ferrite and garnet ferrite with a mass ratio of 2:1. The particle size is 80 nanometers and the mass proportion in the rod is 12%. The matrix material is made of high-strength alloy steel. The mass percentage of each element in its composition is 0.4% carbon, 0.3% silicon, 0.8% manganese, 1.2% chromium, 0.2% molybdenum, and the balance is iron. After testing, the grain size grade of the matrix material reaches level 9, and the Rockwell hardness of the rod is HRC40.

[0045] Raw material preparation: Prepare the carbon, silicon, manganese, chromium, molybdenum, iron raw materials and nano-ferrite particles required for high-strength alloy steel. Pre-treat the high-strength alloy steel raw materials by grinding, cleaning, and other pretreatments to remove surface impurities. Place the nano-ferrite particles in a vacuum drying oven at 90°C for 3 hours before use.

[0046] Ferrite particle dispersion treatment: Nano-sized ferrite particles were added to anhydrous ethanol, and 0.3% sodium polyacrylate dispersant was added at the same time. Ultrasonic dispersion equipment was used to disperse the ferrite particles for 45 minutes to form a uniformly dispersed suspension in the anhydrous ethanol.

[0047] Matrix smelting: Add the pretreated high-strength alloy steel raw materials into the vacuum induction melting furnace, maintain the vacuum degree in the furnace at 5×10⁻³Pa, and smelt at 1550℃. After the raw materials are completely melted, they are refined for 25 minutes to remove impurities and gases.

[0048] Composite treatment: When the temperature of the matrix steel liquid is maintained at 1500℃, the dispersed ferrite particle suspension is slowly added to the steel liquid at a speed of 8L / min. At the same time, the electromagnetic stirring device is started and stirred at a speed of 250 rpm for 15 minutes to ensure that the ferrite particles are evenly dispersed in the steel liquid.

[0049] Casting: The compounded molten steel is cast into a specific mold, the cooling rate is controlled to 8°C / second, and the bar blank is obtained by cooling and molding.

[0050] Subsequent processing: The bar billet is forged with a forging ratio of 4. The heat treatment adopts quenching and tempering process. The quenching temperature is set to 870℃, and the tempering adopts two tempering processes. The first tempering temperature is 580℃, and the heat preservation is 2.5 hours. The second tempering temperature is 530℃, and the heat preservation is 2.5 hours to improve the comprehensive mechanical properties of the bar.

[0051] Effect: Mechanical properties: tensile strength 1250-1350MPa, yield strength 1100-1200MPa, elongation about 11%, cross-sectional shrinkage 46%, Rockwell hardness HRC42, wear resistance increased by 35%.

[0052] Microstructure: The matrix grain size is level 9, and the ferrite particles give full play to the dispersion strengthening effect, enhancing the strength and toughness of the rod.

[0053] Magnetic properties and functionality: Magnetic permeability 180-220H / m, remanence 0.4-0.6T, coercive force 90-130kA / m, motor efficiency increased by about 6%-9%.

[0054] Processing performance and stability: density 7.85g / cm³, dimensional accuracy ±0.05mm, thermal expansion coefficient 1.2×10⁻ 5 / ℃.

[0055] Example 3

[0056] It consists of a matrix material and nano-ferrite particles uniformly dispersed in the matrix material. The nano-ferrite particles are a mixture of spinel ferrite and garnet ferrite with a mass ratio of 2:1. The particle size is 80 nanometers and the mass proportion in the rod is 15%. The matrix material is made of high-strength alloy steel. The mass percentage of each element in its composition is 0.4% carbon, 0.3% silicon, 0.8% manganese, 1.2% chromium, 0.2% molybdenum, and the balance is iron. After testing, the grain size grade of the matrix material reaches level 9, and the Rockwell hardness of the rod is HRC40.

[0057] Raw material preparation: Prepare the carbon, silicon, manganese, chromium, molybdenum, iron raw materials and nano-ferrite particles required for high-strength alloy steel. Pre-treat the high-strength alloy steel raw materials by grinding, cleaning, and other pretreatments to remove surface impurities. Place the nano-ferrite particles in a vacuum drying oven at 90°C for 3 hours before use.

[0058] Ferrite particle dispersion treatment: Nano-sized ferrite particles were added to anhydrous ethanol, and 0.3% sodium polyacrylate dispersant was added at the same time. Ultrasonic dispersion equipment was used to disperse the ferrite particles for 45 minutes to form a uniformly dispersed suspension in the anhydrous ethanol.

[0059] Matrix smelting: Add the pretreated high-strength alloy steel raw materials into the vacuum induction melting furnace, maintain the vacuum degree in the furnace at 5×10⁻³Pa, and smelt at 1550℃. After the raw materials are completely melted, they are refined for 25 minutes to remove impurities and gases.

[0060] Composite treatment: When the temperature of the matrix steel liquid is maintained at 1500℃, the dispersed ferrite particle suspension is slowly added to the steel liquid at a speed of 8L / min. At the same time, the electromagnetic stirring device is started and stirred at a speed of 250 rpm for 15 minutes to ensure that the ferrite particles are evenly dispersed in the steel liquid.

[0061] Casting: The compounded molten steel is cast into a specific mold, the cooling rate is controlled to 8°C / second, and the bar blank is obtained by cooling and molding.

[0062] Subsequent processing: The bar billet is forged with a forging ratio of 4. The heat treatment adopts quenching and tempering process. The quenching temperature is set to 870℃, and the tempering adopts two tempering processes. The first tempering temperature is 580℃, and the heat preservation is 2.5 hours. The second tempering temperature is 530℃, and the heat preservation is 2.5 hours to improve the comprehensive mechanical properties of the bar.

[0063] Effect: Mechanical properties: tensile strength 1300-1400MPa, yield strength 1150-1250MPa, elongation about 10%, cross-sectional shrinkage 47%, Rockwell hardness HRC44, wear resistance increased by 40%.

[0064] Microstructure: The matrix grain size is level 9, and the ferrite particle content is relatively high, which further enhances the performance of the rod, but too many particles may cause partial agglomeration.

[0065] Magnetic properties and functionality: Magnetic permeability 200-250H / m, remanence 0.5-0.7T, coercive force 100-140kA / m, motor efficiency increased by about 8%-10%.

[0066] Processing performance and stability: density 7.9g / cm³, dimensional accuracy ±0.05mm, thermal expansion coefficient 1.2×10⁻ 5 / ℃.

[0067] In the fourth to sixth embodiments, only the spinel ferrite and garnet ferrite are changed.

[0068] Example 4

[0069] It consists of a matrix material and nano-ferrite particles uniformly dispersed in the matrix material. The nano-ferrite particles are a mixture of spinel ferrite and garnet ferrite with a mass ratio of 1:1. The particle size is 80 nanometers and the mass proportion in the rod is 10%. The matrix material is made of high-strength alloy steel. The mass percentage of each element in its composition is: carbon 0.4%, silicon 0.3%, manganese 0.8%, chromium 1.2%, molybdenum 0.2%, and the balance is iron. After testing, the grain size grade of the matrix material reaches level 9, and the Rockwell hardness of the rod is HRC40.

[0070] Raw material preparation: Prepare the carbon, silicon, manganese, chromium, molybdenum, iron raw materials and nano-ferrite particles required for high-strength alloy steel. Pre-treat the high-strength alloy steel raw materials by grinding, cleaning, and other pretreatments to remove surface impurities. Place the nano-ferrite particles in a vacuum drying oven at 90°C for 3 hours before use.

[0071] Ferrite particle dispersion treatment: Nano-sized ferrite particles were added to anhydrous ethanol, and 0.3% sodium polyacrylate dispersant was added at the same time. Ultrasonic dispersion equipment was used to disperse the ferrite particles for 45 minutes to form a uniformly dispersed suspension in the anhydrous ethanol.

[0072] Matrix smelting: Add the pretreated high-strength alloy steel raw materials into the vacuum induction melting furnace, maintain the vacuum degree in the furnace at 5×10⁻³Pa, and smelt at 1550℃. After the raw materials are completely melted, they are refined for 25 minutes to remove impurities and gases.

[0073] Composite treatment: When the temperature of the matrix steel liquid is maintained at 1500℃, the dispersed ferrite particle suspension is slowly added to the steel liquid at a speed of 8L / min. At the same time, the electromagnetic stirring device is started and stirred at a speed of 250 rpm for 15 minutes to ensure that the ferrite particles are evenly dispersed in the steel liquid.

[0074] Casting: The compounded molten steel is cast into a specific mold, the cooling rate is controlled to 8°C / second, and the bar blank is obtained by cooling and molding.

[0075] Subsequent processing: The bar billet is forged with a forging ratio of 4. The heat treatment adopts quenching and tempering process. The quenching temperature is set to 870℃, and the tempering adopts two tempering processes. The first tempering temperature is 580℃, and the heat preservation is 2.5 hours. The second tempering temperature is 530℃, and the heat preservation is 2.5 hours to improve the comprehensive mechanical properties of the bar.

[0076] Effect: Magnetic properties and functionality: The magnetic permeability is 130-160H / m, the remanence is 0.2-0.4T, and the coercive force is 70-100kA / m. The effect of optimizing the electromagnetic performance of the motor is slightly weaker, the energy loss of the motor operation is reduced to a small extent, and the motor efficiency is increased by about 3%-5%.

[0077] Mechanical properties: Due to the change in ferrite ratio, the synergistic effect of matrix strengthening is changed, the tensile strength is 1180-1280MPa, the yield strength is 1030-1130MPa, the elongation is about 12.5%, the cross-sectional shrinkage rate is 44%, the Rockwell hardness is HRC39, and the wear resistance is improved by 28% compared with ordinary bars.

[0078] Example 5

[0079] The rod is composed of a matrix material and nano-ferrite particles uniformly dispersed within it. The nano-ferrite particles are a mixture of spinel ferrite and garnet ferrite in a 3:1 mass ratio, with a particle size of 80 nanometers and a mass fraction of 10% of the rod. The matrix material is a high-strength alloy steel with the following mass percentages: carbon 0.4%, silicon 0.3%, manganese 0.8%, chromium 1.2%, molybdenum 0.2%, and the balance iron. Testing shows that the matrix material's grain size reaches Grade 9, and the rod has a Rockwell hardness of HRC40.

[0080] Raw material preparation: Prepare the carbon, silicon, manganese, chromium, molybdenum, iron raw materials and nano-ferrite particles required for high-strength alloy steel. Pre-treat the high-strength alloy steel raw materials by grinding, cleaning, and other pretreatments to remove surface impurities. Place the nano-ferrite particles in a vacuum drying oven at 90°C for 3 hours before use.

[0081] Ferrite particle dispersion treatment: Nano-sized ferrite particles were added to anhydrous ethanol, and 0.3% sodium polyacrylate dispersant was added at the same time. Ultrasonic dispersion equipment was used to disperse the ferrite particles for 45 minutes to form a uniformly dispersed suspension in the anhydrous ethanol.

[0082] Matrix smelting: Add the pretreated high-strength alloy steel raw materials into the vacuum induction melting furnace, maintain the vacuum degree in the furnace at 5×10⁻³Pa, and smelt at 1550℃. After the raw materials are completely melted, they are refined for 25 minutes to remove impurities and gases.

[0083] Composite treatment: When the temperature of the matrix steel liquid is maintained at 1500℃, the dispersed ferrite particle suspension is slowly added to the steel liquid at a speed of 8L / min. At the same time, the electromagnetic stirring device is started and stirred at a speed of 250 rpm for 15 minutes to ensure that the ferrite particles are evenly dispersed in the steel liquid.

[0084] Casting: The compounded molten steel is cast into a specific mold, the cooling rate is controlled to 8°C / second, and the bar blank is obtained by cooling and molding.

[0085] Subsequent processing: The bar billet is forged with a forging ratio of 4. The heat treatment adopts quenching and tempering process. The quenching temperature is set to 870℃, and the tempering adopts two tempering processes. The first tempering temperature is 580℃, and the heat preservation is 2.5 hours. The second tempering temperature is 530℃, and the heat preservation is 2.5 hours to improve the comprehensive mechanical properties of the bar.

[0086] Effect: Magnetic properties and functionality: The magnetic permeability is increased to 180-220H / m, the remanence reaches 0.4-0.6T, and the coercive force is 90-130kA / m, which significantly optimizes the electromagnetic performance of the motor, effectively reduces the energy loss of the motor operation, and improves the motor efficiency by about 6%-9%.

[0087] Mechanical properties: The ferrite ratio makes the strengthening effect better, with tensile strength of 1280-1380MPa, yield strength of 1120-1220MPa, elongation of about 11.5%, cross-sectional shrinkage of 46.5%, Rockwell hardness HRC41, and wear resistance increased by 37%.

[0088] Example 6

[0089] The rod is composed of a matrix material and nano-ferrite particles uniformly dispersed within it. The nano-ferrite particles are a mixture of spinel ferrite and garnet ferrite in a mass ratio of 2.5:1, with a particle size of 80 nanometers and a mass fraction of 10% of the rod. The matrix material is a high-strength alloy steel with the following mass percentages: carbon 0.4%, silicon 0.3%, manganese 0.8%, chromium 1.2%, molybdenum 0.2%, and the balance iron. Testing shows that the matrix material's grain size reaches Grade 9, and the rod has a Rockwell hardness of HRC40.

[0090] Raw material preparation: Prepare the carbon, silicon, manganese, chromium, molybdenum, iron raw materials and nano-ferrite particles required for high-strength alloy steel. Pre-treat the high-strength alloy steel raw materials by grinding, cleaning, and other pretreatments to remove surface impurities. Place the nano-ferrite particles in a vacuum drying oven at 90°C for 3 hours before use.

[0091] Ferrite particle dispersion treatment: Nano-sized ferrite particles were added to anhydrous ethanol, and 0.3% sodium polyacrylate dispersant was added at the same time. Ultrasonic dispersion equipment was used to disperse the ferrite particles for 45 minutes to form a uniformly dispersed suspension in the anhydrous ethanol.

[0092] Matrix smelting: Add the pretreated high-strength alloy steel raw materials into the vacuum induction melting furnace, maintain the vacuum degree in the furnace at 5×10⁻³Pa, and smelt at 1550℃. After the raw materials are completely melted, they are refined for 25 minutes to remove impurities and gases.

[0093] Composite treatment: When the temperature of the matrix steel liquid is maintained at 1500℃, the dispersed ferrite particle suspension is slowly added to the steel liquid at a speed of 8L / min. At the same time, the electromagnetic stirring device is started and stirred at a speed of 250 rpm for 15 minutes to ensure that the ferrite particles are evenly dispersed in the steel liquid.

[0094] Casting: The compounded molten steel is cast into a specific mold, the cooling rate is controlled to 8°C / second, and the bar blank is obtained by cooling and molding.

[0095] Subsequent processing: The bar billet is forged with a forging ratio of 4. The heat treatment adopts quenching and tempering process. The quenching temperature is set to 870℃, and the tempering adopts two tempering processes. The first tempering temperature is 580℃, and the heat preservation is 2.5 hours. The second tempering temperature is 530℃, and the heat preservation is 2.5 hours to improve the comprehensive mechanical properties of the bar.

[0096] Effect: The magnetic permeability is 160-190H / m, the remanence is 0.3-0.55T, and the coercive force is 85-115kA / m. It can better optimize the electromagnetic performance of the motor, reduce energy loss, and improve the motor efficiency by about 5%-7%.

[0097] Mechanical properties: The comprehensive strengthening effect is good, with tensile strength of 1250-1350MPa, yield strength of 1090-1190MPa, elongation of about 12%, cross-sectional shrinkage of 45.5%, Rockwell hardness HRC40.5, and wear resistance increased by 33%.

[0098] The specific contents are shown in the following table:

[0099]

[0100] As described in the table above, through the comparison of Examples 1 to 3, it can be seen that, when other parameters remain unchanged, as the content of nano-ferrite particles increases from 5% to 15%, the mechanical properties of the rod, such as tensile strength, yield strength and Rockwell hardness, gradually increase, and the wear resistance is improved by an increasing margin; the dispersion strengthening effect in the microstructure increases with increasing content, but too high a content may cause particle agglomeration; in terms of magnetism and functionality, the magnetic permeability, remanence and coercive force continue to improve, and the motor efficiency is improved more significantly; in terms of processing performance and stability, the density increases, and the dimensional accuracy and thermal expansion coefficient remain stable, which shows that reasonable adjustment of the nano-ferrite particle content can effectively optimize the comprehensive performance of rods for new energy vehicle motor shafts to meet the needs of different application scenarios.

[0101] Through Examples 4 to 6, the three Examples found that, while keeping the other components of the rod and the preparation process parameters unchanged, changing the mass ratio of spinel ferrite and garnet ferrite has a significant effect on the magnetism, functionality and mechanical properties of the rod. When the mass ratio of the two is 1:1, the improvement in the magnetism and mechanical properties of the rod is relatively small; when the mass ratio is 3:1, the magnetic parameters are significantly improved, the motor efficiency is significantly improved, and the mechanical properties are also greatly enhanced; when the mass ratio is 2.5:1, all performance factors are at a relatively balanced and good level, which shows that reasonable adjustment of the ratio of the two ferrites can optimize the performance of the rod for the motor shaft of new energy vehicles in a targeted manner to meet the performance optimization requirements of different motors.

[0102] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A bar material for a new energy vehicle motor shaft, characterized in that: Made from the following raw materials by weight: The rod material comprises a matrix material and nano-scale ferrite particles uniformly dispersed in the matrix material.

2. The rod material for the motor shaft of a new energy vehicle according to claim 1, characterized in that: The nano-sized ferrite particles are a mixture of spinel ferrite and garnet ferrite, and the mass ratio of the two is 1:1-3:

1. The particle size is 50-100 nanometers, and the mass proportion of the nano-sized ferrite in the rod is 5-15%.

3. The rod material for a new energy vehicle motor shaft according to claim 1, characterized in that: The Rockwell hardness of the rod is HRC35-45.

4. The rod material for a new energy vehicle motor shaft according to claim 1, characterized in that: The matrix material is high-strength alloy steel, and its components include carbon, silicon, manganese, chromium, and molybdenum. The mass percentage of each element is: carbon 0.3-0.5%, silicon 0.2-0.5%, manganese 0.6-1.0%, chromium 1.0-1.5%, molybdenum 0.1-0.3%, and the balance is iron. The grain size grade of the matrix material is not less than grade 8.

5. A method for preparing a rod for a new energy vehicle motor shaft according to any one of claims 1 to 4, characterized in that: The following steps are involved: Raw material preparation: Prepare various raw materials for high-strength alloy steel and nano-ferrite particles, pre-treat the high-strength alloy steel raw materials before smelting to remove surface impurities; Ferrite particle dispersion treatment: adding nano-sized ferrite particles to an organic solvent and dispersing them using ultrasonic dispersion equipment for 30-60 minutes to form a uniformly dispersed suspension of the ferrite particles in the organic solvent, wherein the organic solvent is anhydrous ethanol; Matrix smelting: The pre-treated high-strength alloy steel raw materials are added to the vacuum induction melting furnace for smelting. The smelting temperature is controlled at 1500-1600℃. After the raw materials are completely melted, they are refined to remove impurities and gases. The refining time is 20-30 minutes. Composite treatment: When the base steel liquid is in liquid state and the temperature is maintained at 1450-1550℃, slowly add the dispersed ferrite particle suspension into the steel liquid, and stir it with an electromagnetic stirring device at a speed of 200-300 rpm for 10-20 minutes to make the ferrite particles evenly dispersed in the steel liquid; Casting: The composite molten steel is cast into a specific mold and cooled to obtain a bar blank. The cooling rate is controlled at 5-10℃ / second. Subsequent processing: The bar billet is subjected to forging and heat treatment. The forging ratio is controlled at 3-5. The heat treatment process includes quenching and tempering. The quenching temperature is 850-900℃ and the tempering temperature is 550-650℃ to improve the comprehensive mechanical properties of the bar.

6. The method for preparing a rod for a new energy vehicle motor shaft according to claim 5, characterized in that: In the raw material preparation step, the nano-sized ferrite particles are vacuum dried before use at a drying temperature of 80-100° C. for 2-4 hours.

7. The method for preparing a rod for a motor shaft of a new energy vehicle according to claim 5, characterized in that: In the ferrite particle dispersion treatment step, a dispersant with a mass fraction of 0.1-0.5% is added during the ultrasonic dispersion process, and the dispersant is sodium polyacrylate.

8. The method for preparing a rod for a motor shaft of a new energy vehicle according to claim 5, characterized in that: In the matrix melting step, the vacuum degree in the vacuum induction melting furnace is maintained at 1×10⁻³-1×10⁻²Pa during melting.

9. The method for preparing a rod for a motor shaft of a new energy vehicle according to claim 5, characterized in that: In the composite treatment step, the ferrite particle suspension is added at a rate of 5-10 L / min.

10. The method for preparing a rod for a new energy vehicle motor shaft according to claim 5, characterized in that: In the subsequent treatment step, the tempering treatment adopts a two-tempering process, the first tempering temperature is 550-600° C., the holding time is 2-3 hours, and the second tempering temperature is 500-550° C., the holding time is 2-3 hours.

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