Metallurgy does not stand still, but is constantly evolving. One of the best achievements at the moment is antifriction alloys. What are they? Where are used? What are the requirements for anti-friction alloys?
general information
So, for starters, let's decide why anti-friction alloys are needed. They are used to increase the durability of the friction surfaces of mechanisms and machines. An example is the anti-friction bearing alloy. Thanks to the use of this material, this component part works for a longer time and wears out more slowly. Also, due to the chemical-physical properties, we can say that optimal conditions are created for applying lubricant. As a result, it will be better kept on 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 goals. Thanks to the soft base, the resulting product will be well earned during friction. The presence of solid metals (such as copper, zinc, antimony) contributes to an increase in the level of stresses that the part can withstand. Thanks 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 in this area there are quite a few developments. Depending on the objectives pursued, they form the requirements for antifriction alloys.
Babbits
So called anti-friction materials based on lead or tin. Their greatest distribution is the filling of plain bearing shells . Parts used in the manufacture of babbits showed good results at high peripheral speeds. They also cope well with variable and shock loads. Requirements for antifriction alloys vary depending on belonging to one of the three groups. So, they can be almost entirely from tin, from lead and with a different percentage of the content of these materials. It should be noted that here you have to choose between efficiency and durability. So, the best anti-friction properties of tin babbits. Adding lead positively affects the life of the part itself, but negatively affects 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 balance, lead parts are used in light working conditions.
Bronze
There are quite a lot of them:
- Tin-phosphorous bronzes are used in cases where the manifestation of high antifriction properties is necessary. They can offer low friction, low wear and high thermal conductivity. Thus, these parts can be successfully used when it is expected to work with significant load and high peripheral speed.
- Aluminum bronzes are characterized by high wear resistance. But their use can lead to a reduction in shaft service life.
- Lead bonzes are adapted for work in conditions of shock loading.
If you plan to use the mechanism at moderate loads and low speeds, you can use brass.
Use of aluminum
It should be noted a certain deficiency of lead and tin. Therefore, antifriction alloys based on aluminum have become common practice. They have good corrosion resistance, as well as mechanical, technological and antifriction properties. Anti - friction aluminum alloys are applied in a thin layer on a steel base. Thus, technologists obtain useful bimetallic material. It should be noted that the resulting result may differ in its chemical properties. Two groups of alloys are distinguished:
- This includes aluminum with antimony, copper and other elements that can form a solid phase in a soft base. Among this group there is a clear leader. So, the most widespread alloy, in which, in addition to aluminum, contains more antimony and magnesium. The resulting material has proven itself in liquid friction even at high speeds and high loads. They called him AFM. The bearing shells for the crankshaft made from it can be found in automobile engines and tractors.
- This group includes aluminum alloys with copper and tin. They are used in semi-fluid and dry friction. By their antifriction properties, they are very close to babbits. Parts created using these alloys can be found in cars, various vehicles and cars.
Individual achievements
Anti-friction cast iron is used to maintain the operation of bearing assemblies. Three types of these parts are currently being produced:
- gray
- high strength with spherical graphite;
- malleable.
Anti-friction cast iron is used to make worm gears, guides for sliders and other machine parts that function under friction conditions.
It should be noted that the use of the globoidal form of graphite positively affects the wear resistance of the metal. It is also necessary to check that there is as little free ferrite in cast iron as possible. It is recommended that the antifriction material possess no more than 15 percent of the total mass. An indicator of good cast iron is the fact that there are no free cementites in it. True, poor run-in, sensitivity to lack of lubrication and reduced resistance to shock load prevent it from spreading. In addition, attention should be paid to cermet alloys, which can be obtained by pressing and sintering bronze powder with graphite. Alternatively, iron may be used instead of this metal. The proportion of graphite does not change.
The use of iron as the basis for anti-friction alloys
Of utmost importance 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 the steels are solid and have a high melting point. Due to this, they are pretty poorly earned. Also, steel can relatively easily grasp onto the mating surface and form scores. There are some of the most popular uses. So, the first involves the use of copper steel, which contains a small amount of carbon. Can be used with the inclusion of free graphite.
Conclusion
The quality of the materials from which various products are made depends on their service life.
Therefore, the end user is interested in getting the best products. It should be noted that there is such a negative phenomenon as the creation of parts with a limited service life. When creating, manufacturers deliberately do everything so that the mechanism fails after a certain period of time. So, it can be calculated that the part lasts only two or three years. And then you have to go and buy a new gasket or other element. Alas, such a negative phenomenon exists and it is necessary to fight it. Moreover, this must be done not just within the framework of one state, but in general the entire planet. There are especially many complaints here to the factory of the world - China, which is a world leader in the supply of counterfeit parts, components, products and equipment worldwide.