Metallurgy does not stand still, but is constantly evolving. One of the best achievements so far is anti-friction alloys. What are they? Where are they used? What are the requirements for anti-friction alloys?
General information
So, for starters, let's decide why antifriction alloys are needed. They are used to increase the durability of the rubbing surfaces of mechanisms and machines. An example is the anti-friction bearing alloy. Thanks to the use of this material, this component works for a longer time and wears out more slowly. Also, due to the chemical and physical properties, we can say that optimal conditions are created for applying the lubricant. As a result, it will be better kept in the applied places.
Features
We continue to consider anti-friction alloys. The properties of these developments largely depend on the source materials. Tin, lead, copper, aluminum and many others can be used to obtain the desired purposes. Due to the soft base, the resulting product will be well run in whenfriction. The presence of hard metals (such as copper, zinc, antimony) contributes to an increase in the level of stress that the part can withstand. Due to the combination, it is possible to obtain an element with a low coefficient of friction, high thermal conductivity and good run-in. It should be noted that there are quite a lot of developments in this area. Depending on the goals pursued, they form the requirements for anti-friction alloys.
Babbits
This is the name of antifriction materials based on lead or tin. Their greatest distribution is the casting of plain bearing shells. Parts made using babbits have shown good results at high circumferential speeds. They also cope well with variable and shock loads. The requirements for antifriction alloys differ depending on whether they belong to one of the three groups. So, they can be almost completely made of tin, lead and with different percentages of these materials. It should be noted that here you have to choose between efficiency and durability. Thus, tin babbits have the best anti-friction properties. The addition of lead has a positive effect on the service life of the part itself, but negatively on the quality of work and the erasure of other elements of the mechanisms. It is also worth noting that babbits based on this material are cheaper. To find a balance, lead parts are used in light working conditions.
Bronzes
There are quite a few of them:
- Tin Phosphorous Bronzesare used in cases where high antifriction properties are required. They can offer low friction, low wear and high thermal conductivity. Thus, these parts can be successfully used when working with heavy load and high peripheral speed.
- Aluminum bronzes are highly wear resistant. However, their use may reduce the life of the shaft.
- Lead bonzes are designed to withstand shock loading.
If it is planned to use the mechanism at moderate loads and low speeds, then brass can be used.
Using aluminum
It is necessary to note a certain scarcity of lead and tin. Therefore, anti-friction alloys based on aluminum have become common practice. They have good corrosion resistance, as well as mechanical, technological and anti-friction properties. Anti-friction aluminum alloys are applied in a thin layer on a steel base. Thus, technologists get a useful bimetallic material. It should be noted that the resulting result may differ in its chemical properties. There are two groups of alloys:
- This includes aluminum with antimony, copper and other elements that can form a solid phase in a soft base. There is a clear leader among this group. So, the most widely used alloy, which, in addition to aluminum, also contains antimony and magnesium. Received material is well behavedproven in fluid friction conditions even at high speeds and high loads. They named it ASM. Crankshaft bearing shells made from it can be found in car and tractor engines.
- This group includes alloys of aluminum with copper and tin. They are used in conditions of semi-fluid and dry friction. In terms of their antifriction properties, they are very close to babbits. Parts created using these alloys can be found in cars, various vehicles and machines.
Individual achievements
Anti-friction cast iron is used to keep bearings running. Three types of these parts are currently produced:
- gray;
- high-strength nodular graphite;
- malleable.
Anti-friction cast iron is used to make worm gears, slider guides and other machine parts that operate under friction.
It should be noted that the use of the globoidal form of graphite has a positive effect on the wear resistance of the metal. It is also necessary to check that there is as little free ferrite in the cast iron as possible. It is recommended that the anti-friction material have no more than 15 percent of the total weight. An indicator of good cast iron is the fact that it does not contain free cementites. True, poor run-in, sensitivity to lack of lubrication and reduced resistance to shock load prevent it from gaining popularity. Besides,attention should also be paid to cermet alloys, which can be obtained by pressing and sintering bronze powder with graphite. Alternatively, iron can be used instead of this metal. The proportion of graphite does not change.
The use of iron as a basis for anti-friction alloys
The most important is the use of steel. Its use is justified in very light working conditions, when there is little pressure and low sliding speed. It must be recalled (or reported) that steels are hard and have a high melting point. Because of this, they are quite poorly run in. Also, steels can relatively easily seize the mating surface and form scratches. There are some of the most popular applications. So, the first involves the use of copper steel, which contains a small amount of carbon. Material with the inclusion of free graphite can also be used.
Conclusion
The quality of the materials from which various products are made determines their service life.
Therefore, the end consumer is interested in getting the very best products. It should be noted that there is such a negative phenomenon here as the creation of parts with a limited service life. Manufacturers deliberately when creating do everything so that the mechanism fails after a certain period of time. So, it can be calculated that the part served only two or three years. And thenyou have to go and buy a new gasket or other element. Alas, such a negative phenomenon exists and it is necessary to fight against it. Moreover, this must be done not just within the framework of one state, but in general of the entire planet. There are especially many claims here against the factory of the world - China, which is the world leader in the supply of counterfeit parts, elements, products and equipment all over the world.
