Sintered Bushing: A Comprehensive Guide

As industrial development progresses, sintered bushings are increasingly utilized in various fields. This article provides insights into sintered bushing materials, their advantages and disadvantages, and the industries where they are applied. We hope this information will be helpful to you.
sintered bushing A Comprehensive Guide

What Is a Sintered Bushing?

A sintered bushing, also known as a sintered bronze bushing, is a type of bearing made from bronze powder. The bronze powder undergoes a process called sintering, where it is compacted under high pressure and then heated at high temperatures to form a solid structure. This process creates a porous structure within the bushing, which is then impregnated with lubricating oil. The oil impregnation allows the sintered bushing to self-lubricate by forming a film of oil between the shaft and the bushing during operation. Known for their low maintenance cost, affordability, and self-lubricating properties, sintered bushings are a staple in many application areas.

How Did Sintered Bushings Evolve?

The history of sintered bushings, particularly sintered bronze bushings, is closely tied to advancements in sintering technology and its application in bearing manufacturing.
In 1930: The Chrysler Corporation developed the Oilite bushing by pressing a mixture of copper, tin, and graphite powder under high pressure, then sintering it in an anaerobic furnace. This sintered bronze technology led to the production of bushings that were an instant success, with sales reaching about 500,000 units in 1930 and approximately 2.5 million the following year.
Sintered bushings represent a key innovation in bearing technology, introducing the concept of self-lubricating bearings which significantly reduced the need for maintenance and lubrication.

What Is Another Term for Sintered Bushing?

Another term for a sintered bushing is “sintered bronze bushing,” “sintered iron bushing,” or “flanged sleeve bearing,” which are more specifically described based on the material and shape used.

What Is the Size Range of Sintered Bushings?

The size of sintered bushings can vary greatly to accommodate different applications. Standard oil-free bushings have internal diameters ranging from less than 10 mm to 30 mm or larger. Custom-sized bushings are also available. Depending on the material, internal diameters can range from 100 mm to 300 mm, all of which our company can provide.

What Is the Tolerance of Sintered Bushings?

The tolerance of sintered bushings varies with the size of the bushing.
For bushings with an internal diameter of 30~50 mm, the internal diameter tolerance is +0.085/+0.045/+0.025 mm, and the external diameter tolerance is 0/+0.062 mm. In this case, the tolerance of the bushing bore can be denoted as “H7,” a universal standard.

How Are Sintered Bushings Manufactured?

Sintered Bushings Manufactured Process

Sintered bushings are produced through a process known as powder metallurgy, which involves several key steps to transform metal powder into a finished sintered bushing.

  1. Mixing and Blending of Metal Powders: This process starts with the mixing of metal powders such as copper, tin, and graphite in predetermined proportions. Organic lubricants are sometimes added to the mixture to facilitate molding operations.
  2. Pressing – Mold Compaction: After mixing, the powder is compacted in a mold under high pressure to form a green compact or pressed item. This pressing process ensures the powder acquires the desired shape and sufficient strength for handling before sintering.
  3. Pre-Sintering and Sintering: The green powder is transferred to a sintering furnace, where it is heated to temperatures below the melting point of solid metal. Pre-sintering occurs in the lower temperature zones of the furnace, allowing the powder particles to liquify and diffuse into each other. The main sintering process then bonds the particles together, with iron-based materials often sintered at temperatures exceeding 2050 degrees Fahrenheit, forming a solid part.
  4. Pressing (Casting) and Sizing: After sintering, some applications might require the parts to be pressed or cast to achieve higher densities or tighter dimensional tolerances. Sizing is a similar process that determines the final dimensions of parts, ensuring consistency across batches.
  5. Oil Impregnation: Sintered parts are oil-impregnated under vacuum to fill the material’s internal pores. This step is crucial for self-lubricating bushings as it provides the anti-friction properties needed for smooth operation. The oil also helps in rust prevention and meets the lubrication requirements of the finished product.
  6. Quality Control and Final Inspection: The final quality inspection of sintered bushings is conducted according to relevant standards, such as IS 3980, applicable to porous metal powder oil-impregnated bearings. Once quality control is passed, the products are packaged and shipped.

What Are the Different Materials of Sintered Bushings?

The materials for sintered bushings include:

  1. Sintered Steel Bushings: These bushings have a high load capacity and excellent fatigue resistance under high-temperature conditions, making them ideal for swing and low-frequency movement under high specific loads. They are used in agricultural machinery, heavy-duty trucks (such as engines and brakes), automotive exhaust after-treatment, heavy work engines, load-bearing trucks, hydraulic cylinders, industrial lifting equipment, industrial and household ovens, lifting applications, material handling, medical equipment, natural gas, and petrochemical product valves.
  2. Sintered Bronze Bushings: These bushings are used in fans, household appliances, electric tools, textile machinery, chemical machinery, automobiles, and official machinery.
  3. Sintered Sliding Bearings: Made from bronze or steel powder materials, suitable for vehicles, trucks, motors, engines, automobiles, electric fans, juicers, mixers.
  4. Sintered Porous Metal Bearings: These bearings are made from metal powder and belong to powder metallurgy parts.

What Are the Advantages of Sintered Bushings?

Sintered bushings offer several key advantages:

  1. Self-lubricating: The porous structure of sintered bushings retains lubricants, reducing friction and wear between mating surfaces. This makes them especially suitable for applications where maintenance is difficult or additional lubrication cannot be applied.
  2. Cost-effective: They are relatively inexpensive to manufacture, making them an economical choice for many applications.
  3. High load capacity: Sintered bushings can withstand heavy loads, providing robust support for rotating or oscillating shafts.
  4. Corrosion resistance: Many sintered bushing materials have good resistance to corrosion, making them suitable for use in harsh environments.
  5. High-temperature resistance: Some sintered bushing materials can withstand high temperatures, making them suitable for high-temperature applications.
  6. Compact space functionality: Sintered bronze bearings, similar in shape to sliding bushings and may include flanges, require few moving parts and can be installed in tight spaces, which is particularly beneficial for miniature drive systems and positioning instruments.
  7. Durability: Sintered bronze bushings are strong, dissipate heat quickly, and thus are durable, capable of handling high speeds.
  8. High sliding speed: Sintered bronze bushings can tolerate higher permissible sliding speeds, making them well-suited for rotational applications.
  9. Low friction coefficient: The low friction coefficient of sintered bronze bearings contributes to efficient operation.
  10. Low noise operation: Their self-lubricating properties help suppress noise and vibration, making sintered bushings suitable for applications where noise reduction is required.
  11. Maintenance-free: Due to their self-lubricating properties, sintered bushings almost require no maintenance, which helps reduce downtime and the overall costs associated with replacing worn parts.

What Are the Disadvantages of Sintered Bushings?

Despite their many benefits, sintered bushings have some drawbacks:

  1. Limited mechanical strength: Compared to other manufacturing methods, the powder metallurgy (P/M) process used to make sintered bushings can result in limited mechanical strength, making them less suitable for high-load applications.
  2. Limited lubrication: Although sintered bushings are impregnated with lubricating oil, their self-lubricating capability is not unlimited. In applications with slow or sporadic movement, lubrication may not be sufficient, possibly leading to increased wear or the need for additional lubrication.
  3. Sensitivity to edge loads and impacts: Sintered bushings are sensitive to edge loads and impacts, which can affect their structural integrity and performance.
  4. Risk of oil impregnation contamination: The oil impregnated in the bushings can contaminate other components or substances it comes into contact with, making them unsuitable for applications where contamination is a concern.
  5. Temperature and media resistance limitations: The oil in sintered bushings limits their tolerance to certain media and temperature stability. If the operating environment involves extreme temperatures or corrosive substances, the lubrication effect may be compromised.
  6. Sensitivity to dust: The porosity of sintered bushings can be clogged by dust and debris, affecting their lubrication and overall performance.
  7. Unsuitability for very hard shafts: Sintered bronze bearings perform best on very hard, expensive, precision-ground shafts, but not all applications are suitable or cost-effective.

What Are the Applications of Sintered Bushing?

Sintered Bushings Application

Due to their self-lubricating nature, durability, and cost-effectiveness, sintered bushings are used across various industries:

  1. Food Processing Industry: Used in food processing equipment due to their high temperature resistance, corrosion resistance, and self-lubricating structure.
  2. Automotive Industry: Employed in automotive applications where they function under high-speed and low-speed conditions, as well as high temperatures, including engine components.
  3. Pump Manufacturing: Utilized in pumps, benefiting from their corrosion resistance and self-lubricating capability.
  4. Steel Manufacturing: These industries leverage the strength, wear resistance, and ability to withstand harsh conditions of sintered bushings.
  5. Electrical Equipment: Applied in electrical equipment, their self-lubricating properties reduce maintenance requirements.
  6. Household Appliances: Used in various household appliances to enhance their reliability and lifespan.
  7. Printing Machinery: Employed in printing machinery due to their high load capacity and self-lubricating properties.
  8. Machine Tools: Beneficial for machine tools because of their durability and low maintenance needs.
  9. Engines and Bicycles: Used in engines and bicycles for their wear resistance and self-lubricating properties.
  10. Fishing Reels and Hydraulic Cylinders: Demonstrates their versatility and reliability in different mechanical environments in applications like fishing reels and hydraulic cylinders.
  11. Stage Lighting, Medical, and Dental Tools: Favored in sensitive applications like stage lighting and medical tools for their precision and reliability.
  12. Printer Rollers and Fitness Equipment: Benefits from the bushings’ low maintenance rate and durability.
  13. Monitoring Systems, Kitchen Appliances, Escalators, Automated Teller Machines: Widely used in these areas due to their long service life and low friction coefficient, regardless of the type of motion.

Is Sintered Metal Stronger?

Yes, sintered metal is stronger in several aspects. The sintering process, which involves heating compacted metal powder below its melting temperature, produces parts with higher tensile strength, bending fatigue strength, and impact energy. The controlled atmosphere during the sintering process ensures that the performance of the workpiece is not compromised, with all loose particles being bonded together, sealing the porous spaces. This makes sintered parts have superior electrical and magnetic properties, density, toughness, damping, and hardness.

Conclusion

Understanding the correct knowledge of sintered bushings can help you better choose the suitable bushing from the myriad of products available.
As a professional supplier of sintered bushings, our company is capable of providing expertly crafted sintered bushings to our customers. If you need our products or services, please contact us.

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