Babbitt is a special alloy made on the basis of lead, tin and other metals. Its main advantage is a low coefficient of friction. This alloy was named after the American businessman and jeweler I. Babbit, his inventor.
History of creation
This alloy was obtained by I. Babbitt in 1839. The main purpose of its creation was to increase the life of bearings of steam engines. Manufacturers of such units immediately appreciated the excellent performance properties of the new alloy and began to widely use it. In 1841, I. Babbitt, who previously worked as a jeweler, received a prize of $ 20,000 from the US Congress for his invention. This was a turning point in his career. Since then, Babbitt began to deal with alloys.
In 1844, the metal he discovered was patented in England. And already in 1847, babbitt was also registered in Russia as a new alloy.
What is a
In the manufacture of babbitt, copper or antimony are most often used as additional metal to lead and tin . This alloy has high antifriction properties primarily because it consists of both hard and soft elements. The advantages of babbitt, in addition to a low coefficient of friction, include wear resistance. Even under heavy load, such an alloy can last a very long time.
Primary Use
As in the century before last, in our time babbitt is most often used to improve the operational characteristics of bearings and increase their service life. The melt of this metal is poured into their internal surfaces, subject to friction. Bearings made using babbitt, due to the high antifriction properties of the latter, among other things, are also more tightly attached to the shafts. Indeed, to overcome friction in this case, you need to make less effort. Babbitt can be used to improve the performance of bearings of various types.
The service life of bearings with babbitt directly depends on the thickness of its layer. The lower this indicator, the longer the part can be used.
Advantages and disadvantages
The advantages of this alloy, in addition to low coefficient of friction and wear resistance, include fusibility. The melting point of babbitt is only 240 about C. Also the advantages of this metal are:
ability to withstand not only rotational, but also reciprocating movements;
resistance to corrosion;
high degree of thermal conductivity;
increased softness at temperatures above 100 ° C;
high degree of toughness.
Has a babbit filling of internal parts of bearings and one more advantage. In this metal, among other things, microchannels are formed, through which lubricant enters the rubbing elements.
The disadvantages of this alloy are practically nonexistent. However, he still has one rather serious minus. Unfortunately, babbitt is a metal that is not very strong. That is why bearings are not made entirely from it. The body of these elements is made of more durable metals - most often steel.
Main types
Babbitt is, therefore, a metal characterized by very good performance characteristics. In addition, such alloys are also quite simple to manufacture. Currently, there are only three main varieties of babbitt . This alloy is classified primarily by the type of metals used in the manufacture. On this basis, babbits are distinguished:
Calcium Babbits
The basis of the alloy of this brand is lead. The babbits of this group got their name because they include calcium and sodium. The main advantage of the alloys of this group is low cost. Babbitt made using calcium and sodium has a high degree of thermal conductivity and is a very dense material. The disadvantage of this group of alloys is the ability to oxidize very quickly.
Most often, such babbits are used in the manufacture of bearings for frames of railway cars. This is explained by the fact that railway structures of this type are carefully monitored. And therefore, bearings that fail due to oxidation of babbitt are replaced in a timely manner.
Tin alloys
The main advantage of babbits of this group is a high degree of strength. These alloys are made, as can already be judged by their name, from tin. The advantages of this metal, in addition to wear resistance and ductility, include excellent corrosion resistance. Tin babbits are also about twice as strong as the alloys of the other two groups. Therefore, with their use, bearings of the most important components of various mechanisms and assemblies are manufactured. Most often, such elements are used in the construction of low-speed engines.
In addition to tin, the composition of babbitts in this group also includes metals such as nickel (can be replaced by cadmium) or copper or antimony. The only drawback of tin alloys is their high cost. The price of bearings manufactured using them is higher than any other.
Lead Babbits
The main advantage of alloys of this variety is their resistance to elevated temperatures. Such babbits are made from lead and antimony. They do not differ in special elasticity. And therefore, for the manufacture of bearings that are subjected to heavy loads during operation, they are not used. Also, babbits of this group, unfortunately, do not differ in resistance to rust. Bearings manufactured with their use are used in the assembly of mainly agricultural heavy equipment and vehicles.
Bearing Application
The scope of use of babbitt, therefore, is quite wide. This alloy can be used for the manufacture of bearings:
Stamps of babbits
When choosing such an alloy for the manufacture of bearings, manufacturers, among other things, should pay attention to its brand. There are only six of them - B88, 83, 83C (for tin alloys), B16, H, C6 (for lead). Babbits are metals that are labeled depending on the proportions of their constituent components - copper, cadmium, nickel.
In any case, in the manufacture of alloys of this variety must comply with the requirements of GOST. Lead and tin babbits are made according to GOST 1320-74, calcium - according to GOST 1209-90.
Zinc and aluminum alloys
There are three main varieties of babbits, as already mentioned. However, in the manufacture of bearings, alloys of this group can also be used, such as:
Babbits of these two varieties are rarely used in the industry. But still, sometimes bearings with their use are made. The main advantage of aluminum babbits is considered low cost. In zinc alloys , the eutectic is the soft element, and Al or CuZn 3 is the hard element . The main component of such babbits is zinc.
GOST requirements
According to standards, babbitt of any group should:
be made of primary or secondary metals cast in ingots weighing no more than 22 kg;
smelted in pigs with a clean surface, without any kind of slag pollution.
In kink of ingots, babbit, according to GOST, must be absolutely homogeneous. To produce this alloy should be in workshops equipped with ventilation systems. According to the standards, the proportion of lead in the air of the working area at the enterprise should not exceed 0.01 / 0.005 mg / m 3 , antimony - 0.5 / 0.2 mg / m 3.
Who produces
They supply this alloy to the market, but it is over, mainly metallurgical enterprises. For example, companies such as:
There are other large manufacturers of babbitt on the market . This metal is worth, depending on the variety and brand, in the range of 200-800 rubles per kilogram.