Forming and manufacturing method for high-wear-resistance and impact-resistance high-carbon-chromium bearing of new energy automobile

Abstract

The invention discloses a forming and manufacturing method for a high-wear-resistance and impact-resistance high-carbon-chromium bearing of a new energy automobile. The forming and manufacturing method comprises the steps that S1, a rolled ring piece blank is rolled at the room temperature, and a rolled ring piece is obtained; s2, the rolled ring piece is subjected to carbonitriding; s3, induction heating is conducted on the rolled ring piece, the induction heating temperature of the surface of the rolled ring piece is made to be higher than the induction heating temperature of the core of the rolled ring piece, and gradient partition austenitizing is conducted; s4, the rolled ring piece is subjected to isothermal quenching; and S5, the rolled ring piece is subjected to tempering. By conducting induction heating on the rolled ring piece, the induction heating temperature of the surface of the rolled ring piece is higher than that of a core part, gradient partition austenitizing is conducted, surface carbide of the rolled ring piece is dissolved to be more than that of the core part, the surface layer solid solution strengthening effect is further improved, the surface hardness of the rolled ring piece is higher, and the core part toughness is better; the extreme performance requirements of new energy automobiles on the surface wear resistance of the bearing and the obdurability of the core part are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of bearing manufacturing, and in particular relates to a forming and manufacturing method of a high-carbon chromium bearing for new energy vehicles with high wear resistance and impact resistance. Background Art

[0002] Developing new energy vehicles is a crucial measure to address global climate change and the energy crisis. It is also a key path to promoting economic transformation and upgrading, achieving green and low-carbon development, and breaking down technological barriers. Bearings, as a core component of new energy vehicle drive systems, support the motor rotor and transmit torque, directly determining the drive system's performance and lifespan.

[0003] Compared to traditional fuel-powered vehicles, new energy vehicle bearings face higher speeds and impact service conditions, placing extremely high demands on bearing surface wear resistance and matrix toughness. To improve bearing surface wear resistance, existing methods use surface chemical treatments such as carbonitriding to improve bearing wear resistance. However, due to grain growth during the carbonitriding process, matrix toughness decreases. To improve matrix toughness, existing methods use heat treatments such as austempering to introduce bainite to improve matrix toughness, but this also reduces surface hardness.

[0004] This shows that the high-carbon chromium bearing microstructure achieved through current single-step control methods is difficult to achieve a synergistic improvement in both ultra-high surface wear resistance and excellent matrix toughness. This contradiction limits the comprehensive performance of bearings under complex and demanding operating conditions. New methods are urgently needed 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 rolled ring surface is made higher than the induction heating temperature of the rolled ring core, and gradient zone austenitization is performed. The gradient temperature causes more carbides on the surface of the rolled ring to dissolve than in the core, further enhancing the surface solid solution strengthening effect, making the surface hardness of the rolled ring higher and the core toughness better, thereby meeting the extreme performance requirements of new energy vehicles for bearing surface wear resistance and core toughness.

[0006] The technical solution of the present invention is achieved as follows:

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

[0008] Step S1, rolling a rolled ring blank at room temperature to obtain a rolled ring;

[0009] Step S2, performing carbonitriding on the rolled ring;

[0010] Step S3, induction heating the rolled ring so that the induction heating temperature of the surface of the rolled ring is higher than the induction heating temperature of the core of the rolled ring, and performing gradient zone austenitization;

[0011] Step S4, performing austempering on the rolled ring;

[0012] Step S5: tempering the rolled ring.

[0013] The rolling deformation and rolling speed are determined according to the wall thickness of the rolled ring blank to form a gradient strain of the bearing and refine the grain structure; reasonable carbon and nitrogen gradients are obtained by adjusting the carbonitriding parameters; the alternating current frequency and induction heating time are controlled to achieve gradient temperature heating of the bearing and perform gradient zoned austenitization. The gradient temperature causes more carbides to dissolve on the surface of the rolled ring than in the core, further enhancing the surface solid solution strengthening effect, making the surface hardness of the rolled ring higher and the core toughness better; bainite isothermal quenching is used to introduce gradient distributed bainite, and subsequent martensite quenching is performed to obtain a gradient martensite-bainite duplex structure; the gradient martensite-bainite duplex structure obtained by quenching is tempered and stabilized.

[0014] In response to the high wear resistance / impact resistance service requirements of new energy vehicle bearings, a high wear resistance / toughness gradient multiphase structure is constructed through the organic combination of strain state controllable rolling forming, carbonitriding, induction heating and isothermal quenching and tempering heat treatment, realizing the controlled forming and manufacturing of high wear resistance and toughness structure.

[0015] On the basis of the above technical solution, the step S3 further comprises: winding an induction coil on 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 of the surface of the rolled ring is 20 to 50° C. higher than the induction heating temperature of the core of the rolled ring;

[0016] Wherein, the induction heating temperature of the surface of the rolled ring is 860-880°C.

[0017] On the basis of the above technical solution, further, the alternating current frequency is 4 to 6 kHz.

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

[0019] Controlling the alternating current frequency at 4 to 6 kHz can make the induction heating temperature of the surface of the rolled ring 20 to 50°C higher than the induction heating temperature 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 enhancing the surface solid solution strengthening effect, making the surface hardness of the rolled ring higher and the core toughness better.

[0020] On the basis of the above technical solution, further, the induction heating time is

[0021] 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, ΔT is the temperature increment, P is the power supply of the induction heater, η is the system efficiency, and 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. On the contrary, the carbon content in the core is relatively low, which promotes the formation of core bainite.

[0023] On the basis of the above technical solution, further, step S1 includes: the rolled ring blank is clamped between the cavity formed by the main roller and the core roller, and under the conditions of the rotational movement of the main roller and the continuous feeding of the core roller, the distribution of the rolling force is regulated by adjusting the feeding speed of the core roller, so that the rolled ring blank produces gradient strain during the rolling process.

[0024] On the basis of the above technical solution, further, the rolling deformation is 30% to 45%, and the core roller feed speed is 0.2 to 1 mm / s.

[0025] On the basis of the above technical solution, further, the core roller feeding speed is

[0026] Among them, ε is the rolling deformation, D is the wall thickness of the rolled ring blank, ω is the main roller speed, R is the main roller radius, and r is the real-time outer diameter of the rolled ring blank.

[0027] If the core roller feed speed is too fast, the radial compression of the rolled ring will increase instantly, resulting in uneven metal flow and possible adverse effects such as uneven wall thickness of the rolled ring. If the core roller feed speed is too slow, the friction between the core roller and the ring may be insufficient, and the core roller may not effectively "bite" the metal, causing slippage.

[0028] During room-temperature rolling, the rolled ring blank is clamped between a cavity formed by a main roll and a core roll. The main roll rotates under the influence of a motor, while the core roll advances at a preset feed rate. The rolled ring blank undergoes continuous localized plastic deformation as it passes through the expanded die formed by the main and core rolls. By regulating the distribution of rolling forces while the main rolls rotate and the core rolls advance continuously, the rolled ring blank undergoes gradient strain during the rolling process, achieving progressive deformation and ultimately achieving the desired size and shape. This process requires precise control of the rolling deformation and core roll feed rate to ensure that the final product meets the desired specifications.

[0029] On the basis of the above technical solution, further, the carbonitriding includes:

[0030] Medium-temperature gas carbonitriding is adopted, and the gradient composition of the rolled ring is controlled by regulating carbon potential, nitrogen potential, temperature and co-diffusion time.

[0031] The heating temperature in the carbonitriding stage is 840°C-860°C, the holding time is 240-270 min, the carbon potential is maintained at 1.15%-1.20%, and the NH3 flow rate is maintained at 2.0-2.5 NL / min.

[0032] During 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] On the basis of the above technical solution, further, the carbon potential C P Control methods include:

[0034] Among them, C P is the carbon potential, T is the furnace temperature, a C is carbon activity;

[0035] The calculation formula of the carbon activity is: Among them, P CO is the CO pressure in the furnace, is the CO2 pressure in the furnace, K P is the reaction equilibrium constant;

[0036] The K P It is related to the furnace temperature T, according to the formula Calculated.

[0037] On the basis of the above technical solution, further, the nitrogen potential is:

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

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

[0040] The nitrogen potential determines the "continuity" of the gradient by regulating the surface compound layer structure and nitride precipitation behavior. High nitrogen potential easily forms a sudden interface, while low nitrogen potential promotes solid solution diffusion.

[0041] On the basis of the above technical solution, further, the co-infiltration time is calculated by the formula: Calculated,

[0042] Where, d is the depth of the infiltration layer (mm), t is the co-infiltration time (h), and f(ε) is a function of the rolling deformation.

[0043] f(ε)=1.2ε+1, where ε is the rolling deformation.

[0044] On the basis of the above technical solution, the carbonitriding further includes: cleaning the rolled ring to remove surface oil, rust, etc., and after the rolled ring is loaded into the carbonitriding furnace, exhausting the air in the furnace as soon as possible to prevent oxidation of the parts.

[0045] On the basis of the above technical solution, further, the temperature in the diffusion stage is kept unchanged, kept warm for 120-150 minutes, the carbon potential is adjusted to 1.0%, and the NH3 flow rate is 2.0-2.5NL / min.

[0046] The carbon potential and nitrogen potential control method in the diffusion stage is the same as that in the strong penetration stage, and the high-concentration carbon and nitrogen atoms on the surface are caused to diffuse into the interior of the ring through diffusion, forming a gentle concentration gradient.

[0047] The cooling process includes placing the rolled ring in a carbonitriding furnace for air cooling for 120 minutes, reducing the temperature from 840°C to 860°C to below 180°C, and then taking the rolled ring out of the furnace and naturally cooling it to room temperature.

[0048] On the basis of the above technical solution, further, the induction heating time is

[0049] 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, ΔT is the temperature increment, P is the power supply of the induction heater, η is the system efficiency, and the system efficiency is 10-15%.

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

[0051] On the basis of the above technical solution, further, in the gradient temperature induction heating process, the actual surface hardening layer depth is

[0052] Wherein, d is the actual surface hardened layer depth, α is the thermal diffusion coefficient of the raw material of the rolled ring, t is the induction heating time, T S is the induction heating temperature of the rolled ring surface, T0 is the ambient temperature, T c is the induction heating temperature of the rolled ring core.

[0053] On the basis of the above technical solution, further, the austempering includes:

[0054] A gradient martensite-bainite duplex structure is obtained by introducing a gradient bainite distribution by austempering, followed by oil cooling.

[0055] Austempering temperature is T = 527-270C + ΔT;

[0056] Wherein, T is the austempering temperature, C is the carbon content in the raw material of the rolled ring, and ΔT is a preset temperature range, which is adjusted according to the raw material type, process target, and size of the rolled ring, and has a value range of [0°C, 30°C].

[0057] The austempering time is 10 to 120 minutes.

[0058] On the basis of the previous process, the gradient duplex isothermal quenching forms a gradient duplex structure in the rolled ring by adjusting the quenching parameters, in which the surface is mainly martensite with a large number of carbonitride particles, and the core is mainly bainite, thereby achieving gradient performance of high surface hardness and high toughness in the core.

[0059] On the basis of the above technical solution, further, the oil cooling temperature is 50-70° C., and the oil cooling time is 2-10 minutes.

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

[0061] On the basis of the above technical solution, further, the tempering in step S4 includes: tempering treatment, the tempering temperature is 160° C.-180° C., the tempering time is 120-180 min, and after the insulation is completed, the rolled ring is placed in the air to cool.

[0062] The gradient microstructure tempering stabilization inhibits the decomposition of retained austenite, promotes the stabilization of the Mapei duplex phase gradient microstructure generated during the quenching stage and the homogenization of the composition gradient and microstructure gradient from the surface to the core, while maintaining the high hardness and high wear resistance of the rolled ring, significantly reducing the quenching stress and brittleness of the ring.

[0063] In a second aspect, a bearing prepared using the above method is provided.

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

[0065] (1) The present invention synergistically constructs strain gradient, composition gradient, temperature gradient and tissue gradient through gradient strain control of room temperature rolling forming, gradient composition control of carbonitriding, gradient temperature induction heating, gradient duplex isothermal quenching and gradient tissue tempering stabilization, and finally forms a gradient duplex structure with high hardness martensite on the surface and high toughness bainite below the core, and the tissue gradient is uniform and the grains are fine, which improves the overall performance of the ring while realizing gradient optimization of environmental performance, achieving the requirements of synergistic improvement of ultra-high wear resistance on the surface and good toughness of the matrix, and meeting the special service requirements of new energy vehicle bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order 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. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0067] Figure 1 This is a microscopic metallographic photograph of the surface of the GCr15 bearing ring after treatment in Example 1;

[0068] Figure 2 This is a microscopic metallographic photograph of the GCr15 bearing ring after treatment in Example 1, taken 500 μm from the surface;

[0069] Figure 3 This is a microscopic metallographic photograph of the GCr15 bearing ring after treatment in Example 1 at a distance of 1000 μm from the surface;

[0070] Figure 4 This is a microscopic metallographic photograph of the GCr15 bearing ring after treatment in Example 1 at a distance of 1500 μm from the surface;

[0071] Figure 5 This is a curve diagram showing the hardness of the GCr15 bearing ring after treatment in Example 1 versus the distance from the surface. DETAILED DESCRIPTION

[0072] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0073] The present invention provides a high-wear-resistant and impact-resistant forming and manufacturing method for a high-carbon chromium bearing for a new energy vehicle, comprising the following steps:

[0074] 1. Gradient strain controlled rolling forming

[0075] 1) Cutting:

[0076] The selected high carbon chromium bearing steel is sheared into rolling ring blanks of appropriate size, pickled to remove scale impurities and then placed on a CNC ring rolling machine for room temperature rolling.

[0077] 2) Rolling:

[0078] During room-temperature rolling, the ring blank is clamped between a cavity formed by a main roll and a core roll. The main roll rotates under the influence of a motor, while the core roll advances at a preset feed rate. The ring blank undergoes continuous, localized plastic deformation as it passes through the rolling groove formed by the main and core rolls. By regulating the distribution of rolling forces while the main rolls rotate and the core rolls advance continuously, a gradient strain is generated in the blank during rolling, achieving progressive deformation and ultimately rolling the ring blank to the desired size and shape. This process requires precise control of the rolling deformation and core roll feed rate to ensure that the final product meets the desired specifications.

[0079] The core roller feed speed is calculated according to the following formula:

[0080]

[0081] Among them, ε is the rolling deformation, D is the wall thickness of the rolled ring blank, ω is the main roller speed, R is the main roller radius, and r is the real-time outer diameter of the rolled ring blank.

[0082] The rolling deformation ε is controlled to be 30% to 45%, and the core roller feed speed v is controlled to be 0.2 to 1 mm / s.

[0083] 3) Inspection:

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

[0085] 2. Gradient composition controlled carbonitriding

[0086] 1) Pre-cleaning:

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

[0088] 2) Furnace charging and exhaust:

[0089] After the rolled rings are loaded into the furnace, the air in the furnace must be exhausted as soon as possible to prevent oxidation of the parts.

[0090] 3) Strong penetration stage:

[0091] In view of the chemical composition of high carbon chromium bearing steel, medium temperature gas carbonitriding is used to control the composition gradient inside and outside the rolled ring, and a high carbon and nitrogen concentration gradient is preferentially established on the surface of the rolled ring.

[0092] Heat the temperature in the furnace to 840℃-860℃, keep it warm for 240-270min, and introduce carburizing gas and NH3. The carbon potential is maintained at 1.15%-1.20%, and the NH3 flow rate is maintained at 2.0-2.5NL / min.

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

[0094]

[0095] Where, d is the depth of the infiltration layer (mm), t is the co-infiltration time (h), and f(ε) is a function of the rolling deformation;

[0096] f(ε)=1.2ε+1;

[0097] Among them, f(ε) is a function of rolling deformation, and ε is the ring rolling deformation.

[0098] The carbon potential calculation formula is as follows:

[0099]

[0100] Among them, C P is the carbon potential, T is the furnace temperature (℃), a C is the carbon activity, which is calculated as follows:

[0101]

[0102] Among them, P CO is the CO pressure in the furnace, is the CO2 pressure in the furnace, KP is the reaction equilibrium constant;

[0103] The KP can be calculated by the formula: Where T is the temperature inside the furnace.

[0104] Nitrogen potential (Np) is indirectly controlled by the residual ammonia (NH3) concentration and is calculated as:

[0105]

[0106] Wherein, Np is the nitrogen potential, and are the partial pressures of NH3 and H2 respectively.

[0107] 4) Diffusion stage:

[0108] The temperature remains unchanged and is kept warm for 120-150 minutes. The carbon potential is adjusted to 1.0%, and the NH3 flow rate is 2.0-2.5NL / min. The carbon potential and nitrogen potential control methods are the same as the strong infiltration process.

[0109] Diffusion causes high-concentration carbon and nitrogen atoms on the surface to diffuse toward 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. The cooling time is 120 minutes, and the temperature drops from 840℃-860℃ to below 180℃. The rolled ring is then taken out of the furnace and naturally cooled 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 scale on the surface of rolled rings to avoid local overheating. Add sandblasting or phosphating treatment to improve surface heat absorption efficiency and uniformity.

[0115] 2) Furnace loading and positioning:

[0116] Design the contoured induction coil according to the shape of the rolled ring, wind the induction coil around the rolled ring, ensure that the heating area is consistent with the target surface hardening layer depth, and reasonably adjust the distance between the induction coil and the rolled ring to avoid magnetic field attenuation or local overburning. The distance should be controlled as follows:

[0117]

[0118] Where a is the distance between the induction coil and the rolled ring (mm), D1 is the inner diameter of the induction coil (mm), and D0 is the outer diameter of the rolled ring (mm).

[0119] 2) Induction heating:

[0120] Apply alternating current to perform short-term rapid induction heating on the rolled ring. Control the alternating current frequency to 4-6kHz to form a temperature gradient from the surface to the inside of the workpiece. The surface induction heating temperature is 20-50℃ higher than that of the core, thus achieving gradient austenitization of the rolled ring.

[0121] The induction heating temperature of the rolled ring surface is controlled and set to 860-880°C. The gradient temperature causes more carbides to dissolve on the surface of the bearing ring than in the core, further enhancing the surface solid solution strengthening effect, making the surface hardness of the bearing ring higher and the core toughness better.

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

[0123]

[0124] Among them, t is the heating time (s), C is the specific heat capacity of the rolled ring raw material, m is the mass of the rolled ring (kg), ΔT is the temperature increment (K), P is the power supply of the induction heater (kW), and η is the system efficiency, which is 10-15%.

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

[0126] Determination of actual surface hardening layer depth:

[0127]

[0128] Wherein, d is the actual surface hardening layer depth (mm), α is the thermal diffusivity of the raw material of the rolled ring (mm 2 / s), t is the induction heating time (s), T S is the induction heating temperature of the rolled ring surface (°C), T0 is the ambient temperature (°C), T c is the induction heating temperature of the rolled ring core (°C).

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

[0130] After heating to the target temperature, the temperature is kept at this temperature for 20-30 minutes to fully austenitize the rolled ring and refine the grains.

[0131] 4. Gradient complex phase isothermal quenching

[0132] The rolled ring after induction heating is quenched into a nitrate bath with a composition of 50% KNO3 + 50% NANO2. The holding time is 10-120 minutes. The stirring frequency of the salt bath is 40Hz. The holding temperature is:

[0133] T = 527-270C + ΔT;

[0134] Wherein, T is the austempering temperature, C is the carbon content (%) of the raw material of the rolled ring, and ΔT is the preset temperature range, which is adjusted according to the raw material type, process target and size of the rolled ring, and the value range is [0°C, 30°C].

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

[0136] 5. Tempering stabilization of gradient structure

[0137] The high carbon chromium bearing steel ring treated by the salt bath quenching process is subjected to a tempering process at a tempering temperature of 160° C.-180° C. for a tempering time of 120-180 min. After the insulation is completed, the rolled ring is placed in air for cooling.

[0138] During the tempering process, the Mapei duplex gradient structure tends to stabilize, which refines the size of the tempered carbides of the high carbon chromium bearing steel and inhibits the decomposition of 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 method for forming and manufacturing a high-carbon chromium bearing for a new energy vehicle with high wear resistance and impact resistance, comprising the following steps:

[0141] In this embodiment, the raw material of a new energy vehicle bearing ring 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 blank was pickled to remove scale impurities and then placed on a CNC ring rolling machine for room temperature rolling.

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

[0145] Among them, ε is the rolling deformation, D is the wall thickness of the rolled ring blank, ω is the main roller speed, R is the main roller radius, and r is the real-time outer diameter of the rolled ring blank;

[0146] The rolling deformation is 30%.

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

[0148] 2. Gradient composition controlled carbonitriding

[0149] Clean the rolled rings in advance to remove surface oil and rust. Load the workpieces into the furnace and exhaust the air inside the furnace to prevent oxidation of the parts.

[0150] Perform strong penetration treatment and diffusion treatment on rolled rings:

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

[0152] Where d is the depth of the infiltration layer, t is the co-infiltration time, and f(ε) is a function of the rolling deformation.

[0153] f(ε)=1.2ε+1, where ε is the rolling deformation.

[0154] During the strong penetration stage, the heating temperature in the furnace is maintained at 850℃ and the holding time is 250min.

[0155] The carbon potential C is controlled according to the following formula P ,include:

[0156] Among them, C P is the carbon potential, T is the furnace temperature, a C is carbon activity;

[0157] The calculation formula of the carbon activity is: Among them, P CO is the CO pressure in the furnace, is the CO2 pressure in the furnace, K P is the reaction equilibrium constant;

[0158] The K P It is related to the furnace temperature T, according 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 heating temperature in the furnace remained unchanged, 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 penetration depth was 1.1 mm;

[0162] After the treatment is completed, the rolled ring is placed in a furnace for air cooling. The cooling time is 120 minutes, and the temperature drops to below 180°C. The rolled ring is then taken out of the furnace and naturally cooled to room temperature.

[0163] 3. Gradient temperature induction heating

[0164] Alkaline cleaning agent or ultrasonic cleaning is used to remove surface oil and oxide scale of the rolled parts.

[0165] An induction coil is designed to emulate the rolled ring, which is wound around the surface of the rolled ring. An alternating current is passed through the induction coil to generate an induced electromotive force and eddy current 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 to be 7.5 mm, and induction heating is performed. The alternating current frequency is 5.0 kHz, and the induction heating temperature of the rolled ring surface is controlled to be 860°C, the induction heating temperature of the core is controlled to be 830°C, and the heating power density is 2.0 kW / cm 2 , induction heating time 5s, after heating to the target temperature, keep warm for 20min.

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

[0168] 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, ΔT is the temperature increment, P is the power supply of the induction heater, and v is the system efficiency, which is 12%.

[0169] According to the formula: The calculated hardened layer depth is 0.35mm.

[0170] Wherein, d is the actual surface hardened layer depth, α is the thermal diffusion coefficient of the raw material of the rolled ring, t is the induction heating time, T S is the induction heating temperature of the rolled ring surface, T0 is the ambient temperature, T c is the induction heating temperature of the rolled ring core,

[0171] 4. Gradient complex phase isothermal quenching

[0172] The ring after induction heating is quenched into a nitrate bath with a composition of 50% KNO3 + 50% NANO2. According to the formula T = 527-270C + ΔT, the austempering temperature is calculated to be 240℃.

[0173] Wherein, T is the austempering temperature, C is the carbon content in the raw material of the rolled ring, ΔT is the preset temperature range, and the preset temperature range is 10°C.

[0174] The holding time is 30 min and the stirring frequency of the salt pool is 40 Hz.

[0175] After the insulation is completed, the ring is oil-cooled at 60°C for 3 minutes.

[0176] 5. Tempering stabilization of gradient structure

[0177] The quenched rings are subjected to a tempering process with a tempering temperature of 180°C and a tempering time of 150 min. After the heat preservation is completed, the rolled rings are placed in the air for cooling.

[0178] The bearing ring obtained in the above embodiment was observed by scanning electron microscope. Figure 1 、 Figure 2 、 Figure 3 and Figure 4 These are scanning electron microscope micrographs of the treated surface of the GCr15 bearing ring and at 500μm, 1000μm and 1500μm from the surface.

[0179] Observation revealed that the surface and near-surface of the treated GCr15 bearing ring exhibited not only martensite but also a small amount of newly formed lower bainite and numerous carbonitride particles. The core of the GCr15 bearing ring exhibited a martensite-bainite duplex structure with a low carbonitride content. The treated bearing ring exhibited a distinct compositional and structural gradient from the outside to the inside.

[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 roller feed speed is 0.2-0.8 mm / s.

[0184] 2. Gradient composition controlled carbonitriding

[0185] During the strong penetration stage, the heating temperature in the furnace was maintained at 840°C, 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 heating temperature in the furnace remained unchanged, 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 penetration layer depth was 1.2 mm.

[0187] 3. Gradient temperature induction heating

[0188] The frequency of the alternating current is 4.0 kHz, and the induction heating temperature of the surface of the rolled ring is controlled to be 880°C, and the induction heating temperature of the core is controlled to be 830°C.

[0189] 4. Gradient complex phase isothermal quenching

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

[0191] 5. Tempering stabilization of gradient structure

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

[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 roller feed speed is 0.3 to 1 mm / s.

[0197] 2. Gradient composition controlled carbonitriding

[0198] During the strong penetration stage, the heating temperature in the furnace was maintained at 860°C, 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 heating temperature in the furnace remained unchanged, 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 penetration layer depth was 1.5 mm.

[0200] 3. Gradient temperature induction heating

[0201] The frequency of the alternating current is 6.0 kHz, and the induction heating temperature of the surface of the rolled ring is controlled to be 870°C, and the induction heating temperature of the core is controlled to be 840°C.

[0202] 4. Gradient complex phase isothermal quenching

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

[0204] 5. Tempering stabilization of gradient structure

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

[0206] Comparative Example 1

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

[0208] The core roller feed speed always 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 the surface and core of the rolled ring is 860°C.

[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 to be 860°C, the induction heating temperature of the core is controlled to be 850°C, and the induction heating temperature difference between the surface and the core of the rolled ring is 10°C.

[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 to be 880°C, the induction heating temperature of the core is controlled to be 820°C, and the induction heating temperature difference between the surface and the core of the rolled ring is controlled to be 60°C.

[0218] Performance testing

[0219] The hardness test was performed on the bearing rings obtained in Example 1 and Comparative Examples 1-4. The hardness results at 100, 500, 1000, 1500, and 2000 μm from the surface of the bearing ring are shown in Table 1 below:

[0220] Table 1 Hardness test results of different parts of bearing ring (unit: HV)

[0221] 100μm 500μm 1000μm 1500μm 2000μm Example 1 883.8 817.65 746.25 743.7 741.3 Comparative Example 1 881.6 812.4 791.3 805.2 762.8 Comparative Example 2 870.6 812.5 772.4 778.3 779.1 Comparative Example 3 879.6 803.1 771.4 775.7 780.1 Comparative Example 4 880.3 820.5 730.6 711.8 708.3

[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 1000μm from the surface. This shows that the treated GCr15 bearing ring has a certain performance gradient from the outside to the inside.

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

[0224] By comparing Example 1 with Comparative Example 2, it can be seen that the surface and core of the rolled ring are induction heated at the same temperature, the surface hardness is low, and the hardness gradient distribution is uneven.

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

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

[0227] This shows that: this application realizes a gradient distribution in the performance of bearing rings by constructing strain gradient, composition gradient, temperature gradient and tissue gradient by adopting the above method, achieves the requirements of synergistic improvement of ultra-high wear resistance of the surface and good toughness of the matrix, and meets the use requirements of 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 in the scope of protection of the present invention.

Claims

1. A method for forming and manufacturing a high-carbon chromium bearing for new energy vehicles with high wear resistance and impact resistance, characterized in that: include: Step S1, rolling a rolled ring blank at room temperature to obtain a rolled ring; Step S2, performing carbonitriding on 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 the induction heating temperature of the core of the rolled ring, and performing gradient zone austenitization; Step S4, performing austempering on the rolled ring; Step S5: tempering the rolled ring.

2. A method for forming and manufacturing a high-carbon chromium bearing for new energy vehicles with high wear resistance and impact resistance as claimed in claim 1, characterized in that: The step S3 comprises: winding an induction coil on 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 of the rolled ring surface is 20 to 50° C. higher than the induction heating temperature of the rolled ring core. Wherein, the induction heating temperature of the surface of the rolled ring is 860-880°C.

3. The method for forming and manufacturing a high-carbon chromium bearing for new energy vehicles with high wear resistance and impact resistance according to claim 1, characterized in that: The induction heating time in 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, ΔT is the temperature increment, P is the power supply of the induction heater, η is the system efficiency, and the system efficiency is 10-15%.

4. The method for forming and manufacturing a high-carbon chromium bearing for new energy vehicles with high wear resistance and impact resistance according to claim 1, characterized in that: The step S1 includes: the rolled ring blank is clamped between the cavity formed by the main roller and the core roller, and under the conditions of the rotational movement of the main roller and the continuous feeding of the core roller, the distribution of the rolling force is regulated by adjusting the feeding speed of the core roller, so that the rolled ring blank generates gradient strain during the rolling process.

5. A method for forming and manufacturing a high-carbon chromium bearing for new energy vehicles with high wear resistance and impact resistance as claimed in claim 4, characterized in that: The core roller feed speed is Among them, v is the core roller feed speed, ε is the rolling deformation, D is the wall thickness of the rolled ring blank, ω is the main roller speed, R is the main roller radius, and r is the real-time outer diameter of the rolled ring blank.

6. The method for forming and manufacturing a high-carbon chromium bearing for new energy vehicles with high wear resistance and impact resistance according to claim 1, characterized in that: The carbonitriding comprises: Medium-temperature gas carbonitriding is adopted, and the gradient composition of the rolled ring is controlled by regulating carbon potential, nitrogen potential, temperature and co-diffusion time.

7. A method for forming and manufacturing a high-carbon chromium bearing for new energy vehicles with high wear resistance and impact resistance as claimed in claim 6, characterized in that: The carbon potential C P Control methods include: Among them, C P is the carbon potential, T is the furnace temperature, a C is carbon activity; The calculation formula of the carbon activity is: Among them, P CO is the CO pressure in the furnace, is the CO2 pressure in the furnace, K P is the reaction equilibrium constant; The K P It is related to the furnace temperature T, according to the formula Calculated.

8. The method for forming and manufacturing a high-carbon chromium bearing for new energy vehicles with high wear resistance and impact resistance as claimed in claim 6, characterized in that: The co-infiltration time is expressed by the formula: Calculated, Where d is the depth of the infiltration layer, t is the co-infiltration time, and f(ε) is a function of the rolling deformation. f(ε)=1.2ε+1, where ε is the rolling deformation.

9. The method for forming and manufacturing a high-carbon chromium bearing for new energy vehicles with high wear resistance and impact resistance according to claim 1, characterized in that: The austempering comprises: A gradient martensite-bainite duplex structure is obtained by introducing a gradient bainite distribution by austempering, followed by oil cooling. Austempering temperature is T = 527-270C + ΔT; Wherein, T is the austempering temperature, C is the carbon content in the raw material of the rolled ring, and ΔT is a preset temperature range, which is adjusted according to the raw material type, process target, and size of the rolled ring, and has a value range of [0°C, 30°C]. The austempering time is 10 to 120 minutes.

10. A bearing prepared by the forming and manufacturing method of a high-carbon chromium bearing for new energy vehicles with high wear resistance and impact resistance as described in any one of claims 1 to 9.

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