A method for forming and manufacturing high-carbon chromium bearings for new energy vehicles with high wear resistance and impact resistance

Abstract

This invention discloses a method for forming and manufacturing high-carbon chromium bearings for new energy vehicles with high wear resistance and impact resistance, comprising: step S1, rolling a rolled ring blank at room temperature to obtain a rolled ring; step S2, carbonitriding the rolled ring; step S3, induction heating the rolled ring so that the induction heating temperature of the surface of the rolled ring is higher than that of the core of the rolled ring, performing gradient partitioning austenitization; step S4, isothermal quenching the rolled ring; and step S5, tempering the rolled ring. By induction heating the rolled ring so that the induction heating temperature of the surface of the rolled ring is higher than that of the core, gradient partitioning austenitization is performed, resulting in more carbide dissolution on the surface of the rolled ring than in the core, further improving the surface solid solution strengthening effect, resulting in higher surface hardness and better core toughness of the rolled ring, meeting the extreme performance requirements of new energy vehicles for bearing surface wear resistance and core toughness.

Description

Technical Field

[0001] This invention belongs to the field of bearing manufacturing technology, specifically relating to a method for forming and manufacturing high-carbon chromium bearings for new energy vehicles with high wear resistance and impact resistance. Background Technology

[0002] Developing new energy vehicles is an important measure to address global climate change and the energy crisis, and a key path to promote economic transformation and upgrading, achieve green and low-carbon development, and break through technological barriers. Bearings, as one of the core components of the drive system of new energy vehicles, support the motor rotor and transmit torque, directly determining the service performance and lifespan of the drive system.

[0003] Compared to traditional gasoline-powered vehicles, bearings in new energy vehicles face higher speeds and impact conditions, placing extremely high demands on the wear resistance of the bearing surface and the toughness of the matrix. To improve the wear resistance of the bearing surface, existing methods use surface chemical treatments such as carbonitriding to enhance wear resistance. However, due to grain growth during carbonitriding, the toughness of the matrix decreases. To improve the toughness of the matrix, existing methods use heat treatments such as isothermal quenching to introduce bainite, but this also results in a decrease in surface hardness.

[0004] Therefore, it is evident that the microstructure of high-carbon chromium bearings obtained through current single control methods cannot achieve a synergistic improvement in both ultra-high surface wear resistance and good matrix toughness. This contradiction limits the overall performance of bearings under complex and harsh operating conditions, necessitating the exploration of new methods to overcome this performance bottleneck and meet the current service requirements of new energy vehicles for long-life and impact-resistant bearings. Summary of the Invention

[0005] In view of this, the present invention proposes a method for forming and manufacturing high-carbon chromium bearings for new energy vehicles with high wear resistance and impact resistance. By induction heating the rolled ring, the induction heating temperature of the surface of the rolled ring is made higher than that of the core of the rolled ring, and gradient partitioning austenitization is performed. The gradient temperature causes more carbides to dissolve on the surface of the rolled ring than in the core, further improving the surface solid solution strengthening effect, resulting in higher surface hardness and better core toughness of the rolled ring, which meets the extreme performance requirements of new energy vehicles for bearing surface wear resistance and core toughness.

[0006] The technical solution of this invention is implemented as follows:

[0007] In a first aspect, the present invention provides a method for forming and manufacturing a high-wear-resistant and impact-resistant high-carbon chromium bearing for new energy vehicles, comprising:

[0008] Step S1: The rolled ring blank is rolled at room temperature to obtain the rolled ring;

[0009] Step S2: Perform carbonitriding on the rolled ring;

[0010] Step S3: Induction heating is performed on the rolled ring to make the induction heating temperature on the surface of the rolled ring higher than the induction heating temperature in the core of the rolled ring, thereby performing gradient partitioning austenitization.

[0011] Step S4: Perform isothermal quenching on the rolled ring;

[0012] Step S5: Temper the rolled ring.

[0013] The rolling deformation and rolling speed are determined based on the wall thickness of the rolled ring blank to form a bearing gradient strain and refine the grain structure. A reasonable carbon and nitrogen element gradient is obtained by adjusting the carbonitriding parameters. The bearing gradient temperature heating is achieved by controlling the alternating current frequency and induction heating time, and gradient partitioning austenitization is performed. The gradient temperature causes more carbides to dissolve on the surface of the rolled ring than in the core, further improving the surface solid solution strengthening effect, resulting in higher surface hardness and better core toughness. Bainitic isothermal quenching is used to introduce gradient bainite, followed by martensitic quenching to obtain a gradient martensite-bainite multiphase structure. The gradient martensite-bainite multiphase structure obtained by quenching is then tempered and stabilized.

[0014] To meet the high wear resistance and impact resistance requirements of bearings for new energy vehicles, a gradient multiphase structure with high wear resistance and toughness is constructed by organically combining strain-controlled rolling forming, carbonitriding, induction heating and isothermal quenching and tempering heat treatment, thus achieving controlled forming and manufacturing of high wear resistance and toughness structure.

[0015] Based on the above technical solution, step S3 further includes: winding an induction coil around the surface of the rolled ring, applying an alternating current for induction heating, and controlling the frequency of the alternating current so that the induction heating temperature on the surface of the rolled ring is 20~50℃ higher than the induction heating temperature of the core of the rolled ring.

[0016] The induction heating temperature of the surface of the rolled ring is 860~880℃.

[0017] Furthermore, based on the above technical solution, the frequency of the alternating current is 4~6 kHz.

[0018] If the alternating current frequency is too high, the current will be more concentrated on the metal surface, resulting in a shallow heating depth; if the alternating current frequency is too low, the current will be distributed relatively evenly inside the metal.

[0019] Controlling the alternating current frequency to 4~6 kHz can make the induction heating temperature of the surface of the rolled ring 20~50℃ higher than that of the core of the rolled ring. The gradient temperature causes more carbides to dissolve on the surface of the rolled ring than in the core, further improving the surface solid solution strengthening effect, resulting in higher surface hardness and better core toughness of the rolled ring.

[0020] Based on the above technical solution, the induction heating time is further... ,

[0021] in, t For induction heating time, C The specific heat capacity of the raw material for the rolled ring is given. m The mass of the rolled ring is... For temperature increment, P This refers to the power supply of the induction heater. The system efficiency is 10-15%.

[0022] During the gradient temperature induction heating stage, the surface temperature of the rolled ring is higher than that of the core due to the skin effect. The high surface temperature is conducive to the dissolution of carbon and enhances the surface solid solution strengthening effect. Conversely, the carbon content in the core is relatively low, which promotes the formation of bainite in the core.

[0023] Based on the above technical solution, step S1 further includes: the rolled ring blank is clamped between a cavity formed by a main roll and a core roll, and under the rotational motion of the main roll and the continuous feeding of the core roll, the distribution of rolling force is controlled by adjusting the feeding speed of the core roll, so that the rolled ring blank generates gradient strain during the rolling process.

[0024] Based on the above technical solution, further, the rolling deformation is 30%~45%, and the core roll feed speed is 0.2~1mm / s.

[0025] Based on the above technical solution, the core roller feed speed is further defined as follows: ,

[0026] in, The amount of rolling deformation. For the wall thickness of the rolled ring blank, Main roller speed, Main roller radius, The real-time outer diameter of the rolled ring blank.

[0027] Excessive mandrel feed speed can cause a sudden increase in radial compression of the rolled ring, resulting in uneven metal flow and potentially causing uneven wall thickness in the rolled ring. Insufficient mandrel feed speed may lead to insufficient friction between the mandrel and the ring, preventing effective metal gripping and causing slippage.

[0028] In room temperature rolling, the rolled ring blank is clamped between a cavity formed by a main roll and a mandrel. The main roll rotates under the drive of a motor, while the mandrel feeds at a preset speed. The rolled ring blank undergoes continuous localized plastic deformation through the rolling pass formed by the main roll and mandrel. With the rotation of the main roll and the continuous feeding of the mandrel, the distribution of rolling force is controlled to induce gradient strain in the rolled ring blank during rolling, achieving gradual deformation of the ring and ultimately rolling it into a ring blank of the required size and shape. Precise control of the rolling deformation and mandrel feed speed is crucial to ensure that the final product meets the predetermined requirements.

[0029] Based on the above technical solution, the carbonitriding further includes:

[0030] Medium-temperature gas carbonitriding is used to control the gradient composition of the rolled ring by adjusting the carbon potential, nitrogen potential, temperature and co-infiltration time.

[0031] The carbonitriding process includes a strong infiltration stage and a diffusion stage. The strong infiltration stage is heated to a temperature of 840℃~860℃, held for 240~270 min, with the carbon potential maintained at 1.15%~1.20% and the NH3 flow rate maintained at 2.0~2.5 NL / min.

[0032] In the carbonitriding stage, the rolled ring is heated and carburizing gas and ammonia are introduced to effectively change the chemical composition of the surface of the rolled ring. By adjusting the process parameters, a suitable chemical composition gradient is constructed to obtain a carbonitriding layer depth of more than 1 mm.

[0033] Based on the above technical solution, further, the carbon potential The control methods include: ,

[0034] in, The carbon potential is given. The furnace temperature. Carbon activity;

[0035] The formula for calculating carbon activity is: ,in, The CO pressure inside the furnace, The CO2 pressure inside the furnace, K P It is the reaction equilibrium constant;

[0036] The K P With furnace temperature T Related to the formula Calculated.

[0037] Based on the above technical solution, the nitrogen potential is further defined as follows: ,

[0038] Wherein, Np is the nitrogen potential. and These are the partial pressures of NH3 and H2, respectively.

[0039] Carbon potential mainly affects the "steepness" of the gradient and the thickness of the diffusion layer by controlling the surface carbon concentration and diffusion driving force. High carbon potential tends to form steep gradients and carbide layers, while low carbon potential tends to form gentle gradients.

[0040] The nitrogen potential determines the "continuity" of the gradient by regulating the structure of the surface compound layer and the precipitation behavior of nitrides. High nitrogen potential tends to form abrupt interfaces, while low nitrogen potential promotes solid solution diffusion.

[0041] Based on the above technical solution, the co-percolation time is further specified by the formula: Calculations show that

[0042] in, d The depth of the infiltration layer is in mm. t The co-infiltration time (h) It is a function of the amount of rolling deformation.

[0043] ,in This represents the amount of deformation during rolling.

[0044] Based on the above technical solution, the carbonitriding further includes: cleaning the rolled ring to remove surface oil, rust, etc., and after loading the rolled ring into the carbonitriding furnace, quickly venting the air inside the furnace to prevent oxidation of the parts.

[0045] Based on the above technical solution, further, the temperature of the diffusion stage remains unchanged, and the temperature is maintained for 120~150 min, while the carbon potential is adjusted to 1.0% and the NH3 flow rate is 2.0~2.5 NL / min.

[0046] The carbon and nitrogen potential control method in the diffusion stage is the same as that in the strong infiltration stage. Diffusion promotes the diffusion of high-concentration carbon and nitrogen atoms from the surface into the interior of the ring, forming a gentle concentration gradient.

[0047] Cooling includes placing the rolled ring in a carbonitriding furnace for air cooling for 120 minutes, reducing the temperature from 840°C-860°C to below 180°C, and then removing the rolled ring from the furnace and allowing it to cool naturally to room temperature.

[0048] Based on the above technical solution, the induction heating time is further... ,

[0049] in, t For induction heating time, C The specific heat capacity of the raw material for the rolled ring is given. m The mass of the rolled ring is... For temperature increment, P This refers to the power supply of the induction heater. The system efficiency is 10-15%.

[0050] The temperature increment is the difference between the target temperature and the room temperature.

[0051] Based on the above technical solution, further, during the gradient temperature induction heating process, the actual surface hardening layer depth is... ,

[0052] in, d The actual surface hardened layer depth, The thermal diffusivity of the raw material for the rolled ring is given. t For induction heating time, The induction heating temperature of the surface of the rolled ring is [temperature value missing]. For ambient temperature, The induction heating temperature of the core of the rolled ring is given.

[0053] Based on the above technical solution, the isothermal quenching further includes:

[0054] Isothermal quenching was used to introduce gradient-distributed bainite, followed by oil cooling, to obtain a gradient martensite-bainite multiphase structure.

[0055] Isothermal quenching temperature is ;

[0056] in, This is the isothermal quenching temperature. The carbon content in the raw material of the rolled ring is given. The preset temperature range is adjusted according to the raw material type, process objectives, and size of the rolled ring, and the value range is [0℃, 30℃].

[0057] The isothermal quenching time is 10~120 min.

[0058] Based on the previous process, gradient multiphase isothermal quenching, by adjusting the quenching parameters, forms a gradient multiphase structure in the rolled ring, with the surface mainly composed of martensite and containing a large number of carbonitride particles, and the core mainly composed of bainite, thereby achieving gradient properties of high surface hardness and high core toughness.

[0059] Based on the above technical solution, the oil cooling temperature is 50~70℃ and the oil cooling time is 2~10min.

[0060] After quenching, oil cooling is performed to obtain partial martensite, which facilitates subsequent tempering to obtain a gradient martensite-bainite multiphase structure.

[0061] Based on the above technical solution, the tempering in step S4 further includes: tempering treatment, tempering temperature of 160℃-180℃, tempering time of 120-180 min, and placing the rolled ring in air to cool after the heat preservation is completed.

[0062] Gradient structure tempering stabilization, while suppressing the decomposition of residual austenite, promotes the stabilization of the Mabe multiphase gradient structure generated during the quenching stage and the homogenization of the compositional and structural gradients from the surface to the core. While maintaining the high hardness and high wear resistance of the rolled ring, it significantly reduces the quenching stress and brittleness of the ring.

[0063] Secondly, a bearing prepared using the above method is provided.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] This invention utilizes gradient strain-controlled room temperature rolling, gradient composition-controlled carbonitriding, gradient temperature induction heating, gradient multiphase isothermal quenching, and gradient microstructure tempering stabilization to synergistically construct strain gradient, composition gradient, temperature gradient, and microstructure gradient. Ultimately, it forms a gradient multiphase microstructure with high-hardness martensite as the main component on the surface and high-toughness bainite as the main component below the core. The microstructure gradient is uniform and the grains are fine. This improves the overall performance of the bearing while achieving gradient optimization of environmental performance, meeting the requirements of synergistic improvement of ultra-high surface wear resistance and good toughness of the matrix, and satisfying the special service requirements of bearings for new energy vehicles. Attached Figure Description

[0066] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0067] Figure 1 The image shows the surface microstructure of the GCr15 bearing ring after treatment in Example 1.

[0068] Figure 2 This is a microstructure image of the GCr15 bearing ring after treatment at a distance of 500 μm from the surface in Example 1.

[0069] Figure 3 This is a microstructure image of the GCr15 bearing ring after treatment at a distance of 1000 μm from the surface in Example 1.

[0070] Figure 4 This is a microstructure image of the GCr15 bearing ring after treatment at a distance of 1500 μm from the surface in Example 1.

[0071] Figure 5 This is a graph showing the relationship between the hardness of the GCr15 bearing ring after treatment and the distance from the surface in Example 1. Detailed Implementation

[0072] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0073] This invention provides a method for forming and manufacturing high-wear-resistant and impact-resistant high-carbon chromium bearings for new energy vehicles, comprising the following steps:

[0074] 1. Gradient strain controlled rolling forming

[0075] 1) Material cutting:

[0076] The selected high-carbon chromium bearing steel is cut into rolled ring blanks of appropriate size, pickled to remove oxide scale and impurities, and then placed in a CNC ring rolling mill for room temperature rolling.

[0077] 2) Rolling:

[0078] In room temperature rolling, the rolled ring blank is clamped between a cavity formed by a main roll and a mandrel. The main roll rotates under the drive of a motor, while the mandrel feeds at a preset speed. The ring blank undergoes continuous localized plastic deformation through the rolling pass formed by the main roll and mandrel. With the rotation of the main roll and the continuous feeding of the mandrel, the distribution of rolling force is controlled to induce gradient strain in the blank during rolling, achieving gradual deformation of the ring and ultimately rolling it into a ring blank of the required size and shape. Precise control of the rolling deformation and mandrel feed speed is crucial to ensure the final product meets the predetermined requirements.

[0079] Calculate the core roller feed speed using the following formula:

[0080]

[0081] in, This refers to the amount of rolling deformation. For the wall thickness of the rolled ring blank, Main roller speed, Main roller radius, The real-time outer diameter of the rolled ring blank.

[0082] Controlling rolling deformation =30%~45%, control the core roller feed speed =0.2~1mm / s.

[0083] 3) Inspection:

[0084] After cold rolling (room temperature rolling), inspect the dimensional accuracy of the rolled rings to ensure that the diameter, height, etc. meet the tolerance requirements; check the surface quality to see if there are any defects such as cracks, scratches, pits, etc.; test the hardness to ensure that it meets the specified standards; finally, check the gradient strain state to see if there is any grain refinement and grain morphology change caused by gradient strain, in order to prepare for controlling the carbon and nitrogen concentration gradient in the carbonitriding process.

[0085] 2. Gradient composition control of carbonitriding

[0086] 1) Pre-cleaning:

[0087] Clean the rolled rings to remove surface oil and rust.

[0088] 2) Furnace loading and exhaust:

[0089] After the rolled rings are loaded into the furnace, the air inside the furnace must be vented as soon as possible to prevent the parts from oxidizing.

[0090] 3) Strong infiltration stage:

[0091] Given the chemical composition of high-carbon chromium bearing steel, a medium-temperature gas carbonitriding method is selected to control the composition gradient inside and outside the rolled ring, prioritizing the establishment of a high carbonitridion concentration gradient on the surface of the rolled ring.

[0092] The furnace temperature was heated to 840℃-860℃ and held for 240-270 minutes. Carburizing gas and NH3 were introduced, and the carbon potential was maintained at 1.15%-1.20%, while the NH3 flow rate was maintained at 2.0-2.5 NL / min.

[0093] At a known heating temperature, the formula for calculating the co-percolation time is:

[0094] ;

[0095] in, d The depth of the infiltration layer is in mm. t The co-infiltration time (h) It is a function of the amount of rolling deformation;

[0096]

[0097] in ， It is a function of the amount of rolling deformation. This refers to the deformation during the rolling of the ring.

[0098] The formula for calculating carbon potential is as follows:

[0099]

[0100] in, The carbon potential is given. The temperature inside the furnace is (°C). Carbon activity is calculated using the following formula:

[0101]

[0102] in, The CO pressure inside the furnace, The CO2 pressure inside the furnace, KP It is the reaction equilibrium constant;

[0103] The KP It can be calculated using this formula: ,in, This refers to the temperature inside the furnace.

[0104] Nitrogen potential ( Np ) through residual ammonia ( NH 3 Concentration is indirectly controlled, and the calculation formula is as follows:

[0105]

[0106] in, Np The nitrogen potential ， and These are the partial pressures of NH3 and H2, respectively.

[0107] 4) Diffusion stage:

[0108] Keep the temperature constant and maintain it for 120-150 min. Adjust the carbon potential to 1.0% and the NH3 flow rate to 2.0-2.5 NL / min. The carbon potential and nitrogen potential are controlled using the same methods as in the strong infiltration process.

[0109] Diffusion promotes the diffusion of high concentrations of carbon and nitrogen atoms from the surface to the core of the ring, forming a gentle concentration gradient.

[0110] 5) Cooling:

[0111] After the composition gradient is established, the rolled ring is placed in a furnace for air cooling for 120 minutes, and the temperature drops from 840℃-860℃ to below 180℃. Then the rolled ring is removed from the furnace and allowed to cool naturally to room temperature.

[0112] 3. Gradient temperature induction heating

[0113] 1) Surface pretreatment:

[0114] Use alkaline cleaning agents or ultrasonic cleaning to remove oil and oxide scale from the surface of rolled rings to avoid local overheating. Sandblasting or phosphating can be added to improve surface heat absorption efficiency and uniformity.

[0115] 2) Furnace loading and positioning:

[0116] A contour-following induction coil is designed based on the shape of the rolled ring. The induction coil is wound around the rolled ring, ensuring that the heating area matches the depth of the hardened layer on the target surface. The distance between the induction coil and the rolled ring is adjusted appropriately to avoid magnetic field attenuation or localized overheating. The distance should be controlled as follows:

[0117]

[0118] in, a The distance between the induction coil and the rolling ring is in mm. The inner diameter of the induction coil (mm) The outer diameter (mm) of the rolled ring.

[0119] 3) Induction heating:

[0120] Apply alternating current to the rolled ring for short-term rapid induction heating, control the frequency of alternating current to 4~6 kHz to form a temperature gradient from the surface to the inside of the workpiece, and the surface induction heating temperature is 20~50℃ higher than the core, so as to achieve gradient austenitization of the rolled ring.

[0121] The induction heating temperature of the rolled ring surface is set to 860~880℃. The gradient temperature causes more carbides on the bearing ring surface to dissolve than in the core, further improving the surface solid solution strengthening effect, resulting in higher surface hardness and better core toughness of the bearing ring.

[0122] The induction heating time is calculated based on the thermophysical properties of the raw material of the rolled ring and the equipment process parameters:

[0123]

[0124] in, t Heating time (s) C The specific heat capacity of the raw material for the rolled ring is given. m The mass (kg) of the rolled ring is given. For temperature increment (K). P The power supply for the induction heater is (kW). The system efficiency is 10-15%.

[0125] The temperature increment is the difference between the target temperature and the room temperature.

[0126] Determining the actual depth of the surface hardened layer:

[0127]

[0128] in, d This represents the actual surface hardened layer depth (mm). The thermal diffusivity (mm) of the raw material for the rolled ring is given. 2 / s), t The induction heating time (s) is the time during which the heating process is initiated. The induction heating temperature (°C) of the surface of the rolled ring. The ambient temperature is (°C). The core induction heating temperature (°C) of the rolled ring is given.

[0129] For example, the thermal diffusivity of GGr15 is 11.6 mm. 2 / s.

[0130] After heating to the target temperature, hold for 20-30 minutes to fully austenitize the rolled ring and refine its grains.

[0131] 4. Gradient multiphase isothermal quenching

[0132] The induction-heated rolled ring was quenched in a nitrate bath with a composition of 50% KNO3 + 50% NaNO2, held for 10-120 min, with a stirring frequency of 40 Hz, and held at a temperature of:

[0133]

[0134] in, This is the isothermal quenching temperature. The carbon content (%) of the raw material for the rolled ring is given. The preset temperature range is adjusted according to the type of raw material, process objectives, and size of the rolled ring, with a value range of [0℃, 30℃].

[0135] After quenching, the rolled ring is oil cooled at 60°C for 3 minutes to obtain partial martensite, which facilitates subsequent tempering to obtain a gradient martensite-bainite multiphase structure.

[0136] 5. Gradient-grade tempering stabilization

[0137] The high-carbon chromium bearing steel rings treated by the above salt bath quenching process are subjected to tempering process. The tempering temperature is 160℃-180℃ and the tempering time is 120-180min. After the heat preservation is completed, the rolled rings are placed in air to cool.

[0138] During the tempering process, the Marbe multiphase gradient structure tends to stabilize, which refines the size of the tempered carbides in the high carbon chromium bearing steel and inhibits the decomposition of the retained austenite. While maintaining the high hardness and high wear resistance of the ring, it significantly reduces the quenching stress and brittleness of the ring.

[0139] Example 1

[0140] This embodiment provides a high-wear-resistant and impact-resistant forming manufacturing method for high-carbon chromium bearings for new energy vehicles, including the following steps:

[0141] In this embodiment, the raw material of a bearing ring for a new energy vehicle is GGr15, the outer diameter of the outer ring is 90 mm, the inner diameter is 75 mm, and the wall thickness is 8 mm.

[0142] 1. Gradient strain controlled rolling forming

[0143] The selected GCr15 steel ring blanks are pickled to remove oxide scale and impurities, and then placed in a CNC ring rolling mill for room temperature rolling.

[0144] During the rolling process, according to the following formula: Calculate the core roller feed speed and control it to be 0.2~0.5 mm / s.

[0145] in, This refers to the amount of rolling deformation. For the wall thickness of the rolled ring blank, Main roller speed, Main roller radius, For the real-time outer diameter of the rolled ring blank;

[0146] Rolling deformation amount: 30%.

[0147] After rolling, remove the ring and measure its diameter, height, and surface hardness to see if they meet the requirements. Observe whether there are any defects on the surface of the ring.

[0148] 2. Gradient composition control of carbonitriding

[0149] The rolled rings are pre-cleaned to remove surface oil and rust. The workpieces are then loaded into the furnace, and air is vented from the furnace to prevent oxidation of the parts.

[0150] The rolled rings were subjected to strong infiltration and diffusion treatment:

[0151] Co-osmosis time is determined by the formula: The calculated co-infiltration time was 250 min.

[0152] in, d The depth of the infiltration layer. t For co-infiltration time, It is a function of the amount of rolling deformation.

[0153] ,in This represents the amount of deformation during rolling.

[0154] During the intense infiltration stage, the furnace heating temperature is maintained at 850℃, and the holding time is 250 minutes.

[0155] Control carbon potential using the following formula ,include: ,

[0156] in, The carbon potential is given. The furnace temperature. Carbon activity;

[0157] The formula for calculating carbon activity is: ,in, The CO pressure inside the furnace, The CO2 pressure inside the furnace, K P It is the reaction equilibrium constant;

[0158] The K P With furnace temperature T Related to the formula Calculated.

[0159] The calculated carbon potential is 1.20%.

[0160] The NH3 flow rate was maintained at 2.4 NL / min;

[0161] During the diffusion stage, the furnace heating temperature remained constant, the holding time was 120 min, the carbon potential was controlled at 1.00%, the NH3 flow rate was maintained at 2.0 NL / min, and the diffusion layer depth was 1.1 mm.

[0162] After processing, the rolled ring is placed in a furnace for air cooling for 120 minutes until the temperature drops below 180°C. Then, the rolled ring is removed from the furnace and allowed to cool naturally to room temperature.

[0163] 3. Gradient temperature induction heating

[0164] The surface oil and oxide scale of the rolled parts are removed by using alkaline cleaning agents or ultrasonic cleaning.

[0165] The design incorporates a contour-following induction coil for the rolled ring. The induction coil is wound around the surface of the rolled ring, and an alternating current is passed through the induction coil to generate an induced electromotive force and eddy currents in the rolled ring, thereby causing the rolled ring to heat up rapidly.

[0166] The distance between the induction coil and the rolled ring is controlled at 7.5 mm for induction heating. The alternating current frequency is 5.0 kHz. The induction heating temperature on the surface of the rolled ring is controlled at 860℃, and the induction heating temperature in the core is controlled at 830℃. The heating power density is 2.0 kw / cm². 2 The induction heating time is 5 seconds, and after heating to the target temperature, it is kept warm for 20 minutes.

[0167] According to the formula, the induction heating time is... The calculated induction heating time is 5 seconds.

[0168] in, t For induction heating time, C The specific heat capacity of the raw material for the rolled ring is given. m The mass of the rolled ring is... For temperature increment, P This refers to the power supply of the induction heater. The system efficiency is 12%.

[0169] The calculated hardened layer depth is 0.35 mm.

[0170] in, d The actual surface hardened layer depth, The thermal diffusivity of the raw material for the rolled ring is given. t For induction heating time, The induction heating temperature of the surface of the rolled ring is [temperature value missing]. For ambient temperature, The induction heating temperature of the core of the rolled ring is [temperature value missing].

[0171] 4. Gradient multiphase isothermal quenching

[0172] The induction-heated ring is quenched in a nitrate bath with a composition of 50% KNO3 + 50% NaNO2, according to the formula... The calculated isothermal quenching temperature is 240℃.

[0173] in, This is the isothermal quenching temperature. The carbon content in the raw material of the rolled ring is given. The preset temperature range is 10°C.

[0174] The heat preservation time is 30 minutes, and the stirring frequency of the salt tank is 40 Hz.

[0175] After the heat preservation is completed, the ring is oil-cooled at 60℃ for 3 minutes.

[0176] 5. Gradient-grade tempering stabilization

[0177] The quenched ring is subjected to a tempering process at a temperature of 180℃ for 150 minutes. After the tempering is completed, the rolled ring is placed in air to cool.

[0178] The bearing ring obtained in the above embodiments was observed by scanning electron microscopy. Figure 1 , Figure 2 , Figure 3 and Figure 4 These are scanning electron microscope (SEM) images of the surface of the GCr15 bearing ring after treatment, and at distances of 500 μm, 1000 μm, and 1500 μm from the surface.

[0179] Observations revealed that the treated GCr15 bearing rings, both on the surface and near the surface, contained a small amount of newly formed lower bainite in addition to martensite, along with a large number of carbonitride particles. The core of the GCr15 bearing rings exhibited a martensitic-bainitic dual-phase structure with relatively low carbonitride content. A clear gradient in composition and microstructure was observed from the outside inwards in the treated bearing rings.

[0180] Example 2

[0181] The difference between this embodiment and Embodiment 1 is that:

[0182] 1. Gradient strain controlled rolling forming

[0183] The rolling deformation is 45%, and the core roll feed speed is 0.2~0.8 mm / s.

[0184] 2. Gradient composition control of carbonitriding

[0185] During the strong infiltration stage, the furnace heating temperature was maintained at 840℃, the holding time was 240 min, the carbon potential was controlled at 1.15%, and the NH3 flow rate was maintained at 2.0 NL / min.

[0186] During the diffusion stage, the furnace heating temperature remained constant, the holding time was 150 min, the carbon potential was controlled at 1.00%, the NH3 flow rate was maintained at 2.5 NL / min, and the diffusion layer depth was 1.2 mm.

[0187] 3. Gradient temperature induction heating

[0188] The alternating current frequency is 4.0 kHz, and the induction heating temperature of the surface of the rolled ring is controlled at 880℃, while the induction heating temperature of the core is 830℃.

[0189] 4. Gradient multiphase isothermal quenching

[0190] The heat preservation time is 120 minutes. After the heat preservation is completed, the ring is oil-cooled at 60°C for 3 minutes.

[0191] 5. Gradient-grade tempering stabilization

[0192] Tempering temperature 160℃, tempering time 120 min.

[0193] Example 3

[0194] The difference between this embodiment and Embodiment 1 is that:

[0195] 1. Gradient strain controlled rolling forming

[0196] The rolling deformation is 40%, and the core roll feed speed is 0.3~1mm / s.

[0197] 2. Gradient composition control of carbonitriding

[0198] During the strong infiltration stage, the furnace heating temperature was maintained at 860℃, the holding time was 270 min, the carbon potential was controlled at 1.18%, and the NH3 flow rate was maintained at 2.3 NL / min.

[0199] During the diffusion stage, the furnace heating temperature remained constant, the holding time was 130 min, the carbon potential was controlled at 1.00%, the NH3 flow rate was maintained at 2.3 NL / min, and the diffusion layer depth was 1.5 mm.

[0200] 3. Gradient temperature induction heating

[0201] The alternating current frequency is 6.0 kHz, and the induction heating temperature of the surface of the rolled ring is controlled at 870℃, while the induction heating temperature of the core is 840℃.

[0202] 4. Gradient multiphase isothermal quenching

[0203] The heat preservation time is 10 minutes. After the heat preservation is completed, the ring is oil-cooled at 60°C for 3 minutes.

[0204] 5. Gradient-grade tempering stabilization

[0205] Tempering temperature 170℃, tempering time 180 min.

[0206] Comparative Example 1

[0207] The difference between this embodiment and Embodiment 1 is that:

[0208] The core roller feed speed remains constant at 0.5 mm / s.

[0209] Comparative Example 2

[0210] The difference between this embodiment and Embodiment 1 is that:

[0211] The induction heating temperature of both the surface and the core of the rolled ring is 860℃.

[0212] Comparative Example 3

[0213] The difference between this embodiment and Embodiment 1 is that:

[0214] The induction heating temperature of the surface of the rolled ring is controlled at 860℃, the induction heating temperature of the core is controlled at 850℃, and the temperature difference between the surface and core of the rolled ring is 10℃.

[0215] Comparative Example 4

[0216] The difference between this embodiment and Embodiment 1 is that:

[0217] The induction heating temperature of the surface of the rolled ring is controlled at 880℃, the induction heating temperature of the core is controlled at 820℃, and the temperature difference between the surface and core of the rolled ring is 60℃.

[0218] Performance testing

[0219] The bearing rings obtained in Example 1 and Comparative Examples 1-4 were subjected to hardness tests. The hardness results at distances of 100, 500, 1000, 1500, and 2000 μm from the surface of the bearing rings are shown in Table 1 below.

[0220] Table 1. Hardness test results at different locations on the bearing ring (unit: HV)

[0221]

[0222] The results of Example 1 are as follows Figure 5 As shown in the figure, the surface hardness of the bearing ring is much higher than that of the core, and decreases with increasing distance, with a slow decrease at a distance of 1000 μm from the surface. This indicates that the treated GCr15 bearing ring exhibits a certain performance gradient from the outside to the inside.

[0223] By comparing Example 1 and Comparative Example 1, it can be seen that when the core roller feed speed remains unchanged, the uneven bearing structure leads to uneven hardness distribution.

[0224] By comparing Example 1 and Comparative Example 2, it can be seen that the surface of the rolled ring is heated at the same temperature as the core during induction heating, resulting in lower surface hardness and uneven hardness gradient distribution.

[0225] By comparing Example 1 and Comparative Example 3, it can be seen that the surface and core of the rolled ring have a small difference in induction heating temperature, the surface hardness is slightly lower, and the hardness gradient distribution is uneven.

[0226] By comparing Example 1 and Comparative Example 4, it can be seen that the surface and core of the rolled ring have a large difference in induction heating temperature, and the core is not completely austenitized, resulting in a sharp drop in core hardness.

[0227] This demonstrates that by constructing strain gradient, composition gradient, temperature gradient, and microstructure gradient using the above methods, this application achieves a gradient distribution in the performance of bearing rings, meeting the requirements for synergistic improvement of ultra-high surface wear resistance and good matrix toughness, thus satisfying the requirements for use in new energy vehicle bearings.

[0228] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-wear-resistant impact-resistant new energy vehicle high-carbon chromium bearing forming manufacturing method, characterized by, The application relates to a high-wear-resistance and high-impact new-energy-vehicle high-carbon-chromium-bearing forming manufacturing method. Step S1: rolling a rolling ring blank at room temperature to obtain a rolling ring; Step S2: carbonitriding the rolling ring; Step S3: inductively heating the rolling ring, so that the inductive heating temperature of the surface of the rolling ring is higher than that of the core of the rolling ring, and gradient partitioned austenitizing is carried out; Step S4: isothermal quenching the rolling ring; Step S5: tempering the rolling ring; The step S3 comprises the following steps: winding an induction coil on the surface of the rolling ring, applying alternating current for inductive heating, and controlling the frequency of the alternating current so that the inductive heating temperature of the surface of the rolling ring is 20-50 DEG C higher than that of the core of the rolling ring, Wherein, the inductive heating temperature of the surface of the rolling ring is 860-880 DEG C; The step S1 comprises the following steps: the rolling ring blank is clamped between a hole cavity formed by a main roller and a core roller, under the rotation of the main roller and the continuous feeding of the core roller, the distribution of the rolling force is adjusted by adjusting the feeding speed of the core roller, so that the rolling ring blank generates gradient strain in the rolling process; The core roll feed speed is , wherein, v is the core roll feed speed, is the rolling deformation, is the rolling ring blank wall thickness, is the main roll rotational speed, is the main roll radius, is the rolling ring blank real-time outer diameter; The rolling deformation is 30%-45%, and the feeding speed of the core roller is 0.2-1 mm / s; The carbonitriding comprises the following steps: adopting medium-temperature gas carbonitriding, adjusting the carbon potential, the nitrogen potential, the temperature and the carbonitriding time to control the gradient composition of the rolling ring; The carbonitriding comprises a strong penetration stage and a diffusion stage, the heating temperature of the strong penetration stage is 840 DEG C-860 DEG C, the holding time is 240-270 min, the carbon potential is maintained at 1.15%-1.20%, and the NH3 flow is maintained at 2.0-2.5 NL / min; the temperature of the diffusion stage is kept unchanged, the holding time is 120-150 min, the carbon potential is adjusted to 1.0%, and the NH3 flow is 2.0-2.5 NL / min; The isothermal quenching comprises the following steps: The isothermal quenching is used to introduce gradient distributed bainite, and then oil cooling is carried out to obtain a gradient martensite-bainite complex structure; The isothermal quenching temperature is ; wherein, is an isothermal quenching temperature, is a carbon element content in a raw material of the rolling ring, is a preset temperature interval, the preset temperature interval is adjusted according to a raw material type of the rolling ring, a process target and a size of the rolling ring, and a value interval is [0℃, 30℃]. The isothermal quenching time is 10-120 min.

2. A high wear and impact resistant high carbon chromium bearing forming manufacturing method for new energy vehicles as claimed in claim 1, characterized in that, The induction heating time in the step S3 is , wherein, t is the induction heating time, C is the specific heat capacity of the raw material of the rolled ring, m is the mass of the rolled ring, is the temperature increment, P is the power of the induction heater power supply, is the system efficiency, which is 10-15%.

3. A high wear and impact resistant new energy vehicle high carbon chromium bearing forming manufacturing method according to claim 1, characterized in that, The carbon potential The method of regulating, comprising: , wherein, is the carbon potential, is the in-furnace temperature, is the carbon activity; The calculation formula of the carbon activity is: wherein, is the CO pressure in the furnace, is the CO2 pressure in the furnace, K P is the reaction equilibrium constant; The K P related to the temperature in the furnace T is calculated by the formula .

4. A high wear and impact resistant new energy vehicle high carbon chromium bearing forming manufacturing method according to claim 1, characterized in that, The co-permeation time is calculated by the formula: is calculated, wherein, d is the depth of the diffusion layer, t is the diffusion time, is a function of the amount of rolling deformation, wherein is the amount of rolling deformation.

5. A bearing prepared by the high-wear-resistance and high-impact new-energy-vehicle high-carbon-chromium-bearing forming manufacturing method according to any one of claims 1-4.

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