As the core component of automotive transmission, steering, suspension and other systems, the performance of automotive bearings directly affects the safety, reliability and comfort of vehicles. Customized processing of automotive bearings requires precise design of materials, structures, precision, and surface treatment processes based on vehicle models, operating conditions, loads, and other requirements. The following are the key process flows and technical points for customized machining of automotive bearings:
1. Customized design stage
Requirement analysis and working condition matching: Determine the speed, load, and temperature range based on the installation position of the bearing (such as the hub, gearbox, and differential) (such as the hub bearing needing to withstand a temperature difference of -40 ℃~150 ℃). Life target: Set the rated life (such as L10 life ≥ 1 million kilometers), calculate the basic rated dynamic load (C value) and static load (Co value). Lightweight requirements: Use high-strength materials (such as 20CrMnTi carbon steel) or hollow structure design to reduce weight (such as 15% -20% weight reduction for electric vehicle wheel hub bearings).
Structural optimization contact angle design: Adjust the contact angle according to the axial/radial load ratio (such as deep groove ball bearing contact angle of 0 °, tapered roller bearing contact angle of 15 ° -30 °).
.Customized sealing structure: Choose between contact (lip seal) or non-contact (labyrinth seal) seals to balance dust resistance and friction torque (such as electric vehicles that require low friction seals to improve range).
.Retaining frame material: Choose steel (high-speed), engineering plastic (PA66+GF30, lightweight), or copper alloy (high-temperature environment) according to the rotational speed.
.II. Core Processing Technology
1. Ring Processing (Inner/Outer Ring)
Material Selection: High carbon chromium bearing steel (GCr15, hardness HRC60-65) is used for conventional working conditions;
;Permeable carbon steel (20CrMnMoV, surface hardness HRC58-62) is used in impact load scenarios (such as commercial vehicle wheels);
; Stainless steel (9Cr18Mo) is used in corrosion-resistant environments (such as new energy vehicle motor bearings).Processing flow: Forging: using forging or roll forging technology, controlling the grain streamline direction to be consistent with the force direction, and improving fatigue resistance.
.Turning: High precision CNC lathe processes the inner diameter, outer diameter, and groove of the ring, with dimensional tolerances controlled within ± 0.005mm.
.Heat treatment: quenching: salt bath quenching or vacuum quenching, hardness uniformity ≤ 1HRC;
;Tempering: eliminates quenching stress and improves toughness;
; Cryogenic treatment: -196 ℃ liquid nitrogen treatment to reduce residual austenite (target ≤ 5%).Grinding: Coarse grinding: Machining the outer cylindrical grinder to a size tolerance of 0.1-0.2mm;
Fine grinding: Ultra precision grinding (Ra ≤ 0.05 μ m) or electrolytic grinding, controlling the deviation of the channel curvature radius to ± 0.001mm.
2. Rolling element machining (steel ball/roller/needle roller)
Steel ball machining: Cold heading: Cold heading the wire into a ball blank with a diameter tolerance of ± 0.05mm;
Smooth ball: Coarse grinding the hard alloy grinding tool to a sphericity of ≤ 0.005mm;
Filing: Removing surface defects;
;Soft grinding: eliminates filing stress; Heat treatment: quenching+tempering, hardness HRC60-66; Hard grinding: Ultra precision grinding to a dimensional tolerance of ± 0.001mm, with a surface roughness Ra ≤ 0.01 μ m.
Roller machining: turning: CNC lathe machining roller profile, end face parallelism ≤ 0.002mm;
Ultra precision grinding: control roller busbar straightness ≤ 0.001mm/100mm.
.3. Processing of retaining frame
Stamping retaining frame: Material: 08F low-carbon steel plate (thickness 0.5-1.2mm);
Process: Multi station progressive die stamping, aperture tolerance ± 0.02mm, window position tolerance ≤ 0.05mm.
Injection cage: Material: PA66+GF30 (glass fiber reinforced);
;Process: High speed injection molding, mold temperature of 80-100 ℃, injection pressure of 120-150MPa, to avoid shrinkage and burrs.
.4. Assembly and Adjustment
Grouping and Selection: Group according to inner diameter, outer diameter, and rolling element size (usually 5-7 groups), ensuring that the clearance meets the design requirements (such as C3 group clearance of 0.05-0.12mm).
.Fitting: Hydraulic press pressure control (such as deep groove ball bearing pressure installation force of 50-100kN) to avoid deformation of the ring.
.Clearance adjustment: Control axial clearance (such as 0.1-0.3mm axial clearance of tapered roller bearings) by grinding the cage window or adjusting the pre tightening force of the seal.
.III. Surface Treatment and Coating Technology
Rust Prevention Treatment: Phosphating: Manganese based phosphating film thickness of 5-15 μ m, improving salt spray resistance (≥ 72 hours);
; Galvanizing: trivalent chromium passivated galvanized layer, thickness 8-12 μ m, neutral salt spray test ≥ 240 hours. Wear resistant coating: DLC (diamond-like carbon coating): thickness 2-5 μ m, friction coefficient reduced to 0.05-0.1, suitable for high-speed motor bearings; TiN (titanium nitride coating): thickness 3-8 μ m, hardness HV2000-2500, improves anti bite performance. Lubrication enhancement: Solid lubrication: Molybdenum disulfide (MoS ₂) coating, suitable for high temperature or vacuum environments; Micro porous oil storage: Laser drilling technology (aperture 10-50 μ m, density 10 ⁴ -10 ⁵ pieces/cm ²), achieving self-lubricating.IV. Quality Inspection and Control
Dimensional Inspection: CMM detects the position of the groove of the ring ≤ 0.005mm;
Roundness Instrument detects the roundness of the rolling element ≤ 0.001mm.
Performance Testing: Life Test: Accelerated Life Test Machine (speed 10000-20000rpm, load 1.5 times rated dynamic load) verifies L10 life;
;High speed performance: When the speed reaches 30000rpm, the temperature rise is ≤ 15 ℃, and the vibration value is ≤ 2mm/s ²;
Sealing: After the salt spray test (48 hours), there is no rust, and after the dust test (IP6X), there is no foreign object intrusion.
. Non destructive testing: Ultrasonic testing is used to detect internal defects (such as cracks and inclusions) in the sleeve; Magnetic particle inspection for surface cracks (sensitivity ≥ A1 level test piece).Fifth, Typical Application Cases
New energy vehicle electric drive bearings: customized low friction sealing structure, reducing motor energy consumption by 5%;
;Adopting DLC coating, the service life is increased to 300000 kilometers (traditional bearings have 150000 kilometers).
.Commercial vehicle wheel hub bearings: carbon steel rings with ceramic rolling elements, increasing the ability to withstand impact loads by three times;
; Integrate ABS sensor magnetic ring to achieve functional integration.