Under extreme working conditions such as high temperature, high humidity, and strong corrosion, the performance and life of bearings will be seriously challenged, requiring targeted material selection, structural design, and protection technology. The following are bearing solutions for special environments, combined with typical application scenarios and technical points:
1. Bearing design under high temperature environment
Core challenge: High temperature causes thermal expansion of materials, grease failure, metal softening or oxidation, causing wear, jamming, or fatigue fracture.
Solution:
1. Material selection
High temperature alloys:
High temperature bearing steel (such as SUJ2 improved type, M50 steel): temperature resistance up to 300℃, suitable for medium load scenarios (such as industrial kiln fans).
Nickel-based high temperature alloys (such as Inconel 718): temperature resistance over 650℃, high strength, used in extreme high temperature scenarios such as aircraft engine turbine bearings.
Ceramic materials:
Si3N4 ceramic bearings: temperature resistance up to 1200℃, low thermal expansion coefficient, good self-lubrication, suitable for high-speed and high-temperature environments (such as gas turbines, vacuum furnaces).
Metal-ceramic composite materials (such as Cr3C2-Ni): Combine the high temperature resistance of ceramics with the toughness of metals, and are used in high-temperature corrosion composite environments.
Case: The bearings of a steel plant's continuous casting machine use M50 steel + ceramic balls, and the temperature resistance is increased from 250℃ of traditional steel bearings to 450℃, and the service life is extended by 3 times.
2. Structural design
Thermal expansion compensation:
Adopt "gap adjustable" structure (such as double-row tapered roller bearings), and reserve thermal expansion gap (ΔL=α×L×ΔT, α is the linear expansion coefficient of the material).
The inner and outer rings are separated to allow axial free expansion to avoid thermal stress concentration.
Heat dissipation optimization:
The bearing seat has heat dissipation ribs or built-in cooling channels, and circulating oil/water is passed in for cooling (such as rolling mill bearings).
Spray thermal barrier coating (such as ZrO2) on the surface to reduce heat conduction to the substrate.
3. Lubrication and sealing
Solid lubrication:
High-temperature lubricants such as molybdenum disulfide (MoS2) and graphite are used to attach to the raceway surface by coating (such as ion plating) or inlaying to replace traditional grease.
Case: The conveyor roller bearing of a glass kiln uses MoS2 coating, and the unlubricated operation life reaches 8,000 hours at 600°C.
Air seal:
Labyrinth seal + nitrogen purge is used to prevent high-temperature dust from invading and inhibit lubricant volatilization (such as cement rotary kiln bearings).
II. Bearing design in high humidity environment
Core challenge: Water vapor intrusion causes metal corrosion, grease emulsification failure, rust wear or fretting corrosion.
Solution:
1. Materials and surface treatment
Corrosion-resistant materials:
Stainless steel bearings (such as AISI 440C, 316L): Strong acid corrosion resistance, suitable for humid or chemical medium environments (such as food processing, offshore platforms).
Coating protection:
The surface is plated with nickel-phosphorus (Ni-P) or Dacromet to form a non-porous anti-corrosion layer, and the salt spray test is over 1000 hours.
Case: A coastal wind power bearing uses 316L stainless steel + Ni-P coating, and the service life in a salt spray environment is extended from 2 years of traditional steel bearings to 8 years.
2. Structure and seal design
Liquid intrusion prevention structure:
Double lip seal (contact + non-contact combination) is adopted, the inner lip prevents grease leakage, and the outer lip blocks water vapor (such as washing machine bearings).
Drain holes are designed in the bearing seat to avoid condensation water accumulation.
Lubrication optimization:
Waterproof grease (such as dimethyl silicone oil added to lithium grease) is selected to improve water washing resistance; or oil mist lubrication is used to avoid grease emulsification.