Babbitt metal is a tin based and lead based bearing alloy with anti friction properties, named after the American Babbitt. Due to its white color, it is also known as white alloy. The main alloy components of Babbitt alloy are tin, lead, antimony, and copper. Antimony and copper are used to improve the strength and hardness of alloys.

Babbitt alloy is used to manufacture sliding bearings. There is strong friction between sliding bearings and high-speed heavy-duty shafts during operation, so the microstructure of sliding bearing alloys is required to have two types: soft matrix hard points and hard matrix soft particles. The soft substrate can withstand impact and vibration, and has good break in properties; Hard points can reduce the contact surface with the shaft, decrease the friction coefficient, reduce wear, and have good wear resistance. The concave convex gap between the soft matrix and the hard point is also conducive to the storage of lubricating oil.

Babbitt alloy belongs to the soft matrix hard point structure. The commonly used sliding bearing alloys for hard matrix soft particle structures are copper based and aluminum based bearing alloys.

Babbitt alloy is divided into two types: tin based and lead based.

Babbitt metal

Tin based Babbitt alloy is an alloy composed of tin as the base and a small amount of antimony and copper added. The soft matrix of tin based bearing alloy is a solid solution of antimony dissolved in tin, and the hard points are metal compounds such as SnSb and Cu3Sn. The code for tin based bearing alloys consists of ZCh (the first two characters of "cast bearing" in Chinese Pinyin), basic element chemical symbols, main additive element chemical symbols, and the average percentage value of main additive element content. ZChSnSb11-6 represents a tin based cast bearing alloy with a main antimony content wSb=11% and an auxiliary copper content wCu=6%.

Tin based Babbitt alloy has good plasticity and thermal conductivity, low friction coefficient and expansion coefficient, but low fatigue strength and allows for lower working temperatures. It is mainly used for casting bearings for large machines, such as high-power high-speed steam engines, steam turbines, and spindle bearings for high-speed large machine tools.

Lead based Babbitt alloy

Lead based Babbitt alloy is a bearing alloy based on lead, with added alloying elements such as tin, antimony, and copper. The soft matrix of lead based bearing alloy is a solid solution of antimony dissolved in lead, and the hard points are metal compounds such as SnSb and Cu3Sn. The code for lead based bearing alloys is similar to that of tin based bearing alloys, consisting of ZCh, basic element symbols, main additive element symbols, and element content numbers. ZChPbSb16-16-2 represents a lead based bearing alloy with a main antimony content of wSb=16%, an auxiliary tin content of wSn=16%, and a copper content of wCu=2%.

Lead based Babbitt alloy has inferior performance compared to tin based Babbitt alloy, with a higher coefficient of friction and lower impact resistance, but it is inexpensive. Therefore, it is generally used for bearings with working temperatures not exceeding 120 ℃ and medium speed loads without significant impact loads, such as bearings for electric motors, crushers, compressors, and vacuum pumps. There are five commonly used lead based bearing alloys, numbered 1-5.

Both tin based and lead based Babbitt alloys have relatively low strength and cannot withstand high pressure. Therefore, centrifugal casting is commonly used to embed them on steel bearings (08 steel) to form a thin and uniform inner lining (<0.1mm).

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Pillow Block:

A pillow block bearing (or plummer block) is a mounting used to support a rotating shaft with the use of bearings and various accessories. The assembly consists of a mounting block which houses a bearing. The block is mounted to a foundation, and a shaft is inserted, allowing the inner part of the bearing/shaft to rotate. The inside of the bearing is typically 0.025 millimetres (0.001 in) larger diameter than the shaft to ensure a tight fit. Set screws, locking collars, or set collars are commonly used to secure the shaft. Housing material for a pillow block is typically made of cast iron or cast steel.

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