Metals are a large group of simple elements with characteristic features, such as high thermal and electrical conductivity, positive temperature coefficient and more. In order to correctly classify and understand what's what, you need to deal with all the nuances. Let's try to consider with you such basic types of metals as ferrous, non-ferrous, precious, and also alloys. This is a rather extensive and complex topic, but we will try to sort things out.
What should everyone know?
Before classifying metals into groups, it is necessary to understand the main features. Negative conductivity coefficient of electricity is considered paramount. This suggests that with decreasing temperature, the conductivity increases, and some conductors become superconductors. At the same time, an increase in temperature leads to a partial or complete loss of throughput. Secondary signs include metallic luster, as well as a high melting point. In addition, some metals in the form of compounds play the role of a reducing agent in redox reactions. Pay attention to the fact that pure metals are almost never found in nature, so you do not need to forget about ore and nuggets either.
About ferrous metals
This group includes iron, as well as its alloys (cast iron, ferroalloys). In fact, ferrous metals are an alloy of iron with carbon, but in addition to this, there are other chemical elements in the composition, such as sulfur, phosphorus, silicon, etc. If you need to give the alloy specific properties necessary to fulfill certain goals, alloying substances are added to which are most often copper, chrome or nickel. All types of ferrous metals are classified by carbon content. So, the following alloys exist:
- Cast iron - the amount of carbon varies from 2 to 4.3%, in some cases reaches a critical level of 5%. Various chemical elements directly affect the properties of the product. So, sulfur with phosphorus increases brittleness, and chrome and nickel additives make cast iron more heat-resistant and resistant to corrosion.
- Steel - carbon content up to 2%. It differs from cast iron in high ductility, as well as in high technological parameters (it is easier to process).
Features of cast iron and steel in detail
Currently, there are several types of cast iron that are used in everyday life, as well as industry: foundry (gray) and pig iron (white). The latter differs from the first type in that carbon is in a bound state in the form of cement, in the first case, in a free state in the form of graphite. The decrease in strength of this material is due to the fact that graphite plates violate the metal structure, thereby weakening it. There is a modified gray cast iron. Its features are that graphite is in spherical shape, which increases the mechanical properties of the product.
You probably already managed to understand that they have become more versatile, which is due to not so much carbon in the composition. So, structural steels contain from 0.02 to 0.85% carbon and are used for construction. Their main advantage is good ductility. The degree of fragility is low. There are also instrumental ones in which the carbon content is slightly higher - from 0.65 to 1.4%, therefore, it is a more durable alloy, but brittle. It is used, as the name implies, as a blank for creating tools (cutting, sawing working bodies of machines and assemblies). Here we have examined the types of ferrous metals, so let's go further.
Noble metals
This group includes chemically stable alloys that are not oxidized in water and air. It is worth noting that the amount of such metals on the entire planet is relatively small, and the process of mining and processing is extremely complex and time-consuming. If for a long time humanity knew only about 7 groups, today there are several more of them. So, the most famous types of precious metals: gold, silver, platinum, osmium, rhodium, palladium, iridium, etc. All of them are found in nature. There are also so-called isotopes. They are obtained in laboratories through complex chemical reactions. The most expensive such metal is California-252 worth 500 thousand dollars per gram. Osmium-187 obtained in modern laboratories belongs to the most popular ones.
About silver and gold
Since the Stone Age, people have known metal such as gold. We can say with confidence that this is the most important precious metal in the whole world. In nature, it most often occurs as nuggets with a small amount of impurities or in an alloy with silver. Exceptional features include thermal conductivity and a very low resistance. Of course, one cannot fail to note the malleability of gold, which is why it is an extremely popular material for making jewelry. Interesting fact: the largest gold nugget found in Australia. He weighed about 90 kilograms.
If we consider the main types of precious metals, then we can not say about silver. In nature, this material is found in a native form (silver ore). But it is worth noting that the main mining is carried out from complex ores, where there is relatively little silver, but deposits of such minerals are more common. This is a very soft and ductile metal that has exceptional electrical and thermal conductivity.
Rhodium and Platinum
Rhodium is a metal that does not have its own minerals; therefore, it is one of the most expensive. Per gram will have to pay more than 220 dollars. This noble metal has a silver color with a bluish tint. It is distinguished by its resistance to chemical and thermal influences, but is extremely vulnerable to mechanical damage due to its fragility. Since it is quite expensive, it is used only where it is impossible to choose an analogue.
If we consider the types and types of metals, then we can not say about platinum, discovered in 1952 by a Swedish chemist. This is a rather rare material and is found in nature only in combination of alloys with other metals. The mining process is extremely time-consuming and requires large investments, but it is worth it, because no acid known to date acts on platinum. When heated, does not change its color and does not oxidize.
Types of non-ferrous metals
This group is the most popular, since most materials are raw materials for metal rolling. If we talk about the scope, it is quite extensive, these are: engineering, metallurgy, electronics, high technology, etc. According to the physical properties, there are the following types of non-ferrous metals:
- heavy (lead, zinc, tin, nickel, etc.);
- light (aluminum, titanium, magnesium, etc.).
According to this classification, there is metallurgy of light and heavy metals. It is no secret that from this group you can make absolutely any technique. Please note that non-ferrous metals include all types of metal alloys, except iron. Now let's move on.
The main types of heavy metals
To date, there are approximately 40 definitions of the concept of this group of materials. Among the distinguishing features - an impressive atomic weight, as a rule, more than 50. From this we can conclude that the list should include everything that comes after vanadium (regardless of density). But if you use a different definition, the determining parameter may be the density, which should be more than that of iron (8 g / cm 3 ). In this case, the list will include: lead, mercury, copper, but tin will be behind the list. Today, the issue of environmental pollution by this group is extremely acute. This is due to the fact that many metals are used in heavy industry and end up in the ocean along with wastewater. The main problem is the high toxicity of mercury, lead, cadmium. In addition, some types of heavy metals tend to accumulate in living organisms. So, due to mercury poisoning in 1977, there were more than 2,300 victims.
Mercury, Lead and Cadmium
These are the most dangerous non-ferrous metals related to heavy. They are the main environmental pollutants. Mercury is a highly toxic metal for humans; it enters the ocean through the atmosphere and with wastewater. When coal is burned at power plants, mercury compounds enter the atmosphere and then fall into the ocean as precipitation. In addition, many freshwater and marine inhabitants accumulate a significant amount of mercury in their body, which more than once led to human poisoning, and even death.
Cadmium is a scattered and rather rare element that enters the ocean along with the wastewater of metallurgical and ore-dressing plants. It should be noted that cadmium is present in the human body, but it is very small. In chronic poisoning, bones are destroyed and anemia begins. As for lead, this metal in a scattered state is almost everywhere. These types of metals, the photos of which we presented above, are excreted from the body, but rather slowly, so their excessive amount causes serious health problems. Along with continental dust, about 25 thousand tons of lead gets into the ocean along with precipitation.
On a note
As you can see, there are a wide variety of types and properties of metals. Something is not at all dangerous, and every day we wear a silver cross and a gold ring on our hands. Radioactive substances can kill people, so environmentalists around the world are trying to partially solve the issue of the release of hazardous metals into the ocean and atmosphere. Of course, solving such problems is very difficult, especially considering the fact that most entrepreneurs do not make contact at all. Nevertheless, do not forget that without conductors, which also consist of metal, electrical circuits are impossible, and without iron there will be no cars and other things familiar to us.
We did not affect the group of so-called radioactive metals of the periodic table. These include: technetium, polonium, promethium, etc. The main purpose is the use in nuclear reactors and weapons, which makes them very dangerous.
Conclusion
You probably noticed that there are a variety of types of metals. In nature, most of them are present in the form of ores and form various sulfides, carbonates and other chemical compounds. To obtain pure metals and their further application, modern technological treatment and concentration lines are used. Surely you will be interested to know that the human body also contains a small amount of metal compounds - about 3%. So, we have calcium in the bones, iron in the blood, magnesium is constantly accumulating in the muscles, and there is copper in the liver.
Well, here, in principle, and all that can be said about what types of metal alloys exist. Despite the fact that this is a rather complicated topic, it may be of interest to those who are fond of metallurgy.