Many people know that steel is a product obtained by smelting other elements. But which ones? What is included in steel? Today, this substance is a deformable alloy of iron with carbon (its amount is 2.14%), as well as a small fraction of other elements.
General information
It is worth noting that steel is an alloy that has exactly up to 2.14% carbon in its composition. The alloy, in which there is more than 2.14% carbon, is already called cast iron.
It is known that the composition of carbon steel and ordinary varies. If carbon and other alloying (improving) components are included in the usual substrate, then there are no alloying elements in the carbon product. If we talk about alloy steel, then its composition is much richer. In order to improve the operational characteristics of this material, elements such as Cr, Ni, Mo, Wo, V, Al, B, Ti, etc. are added to its composition. It is important to note that the best properties of this substance are provided precisely by the addition of doped complexes rather than one or two substances.
Classification
We can classify the material under consideration by several indicators:
- The first indicator is the chemical composition of steel.
- The second is the microstructure, which is also very important.
- Of course, steel differ in its quality and method of production.
- Also, each type of steel has its own application.
In more detail, the composition can be considered by the example of chemical composition. On this basis, two more types are distinguished - these are alloyed and carbon steels.
Among carbon steels, there are three varieties, the main difference of which is the quantitative content of carbon. If the substance contains less than 0.3% carbon, then it is classified as low carbon. The content of this substance in the region from 0.3% to 0.7% transfers the final product to the category of medium-carbon steels. If the alloy contains more than 0.7% carbon, then the steel belongs to the category of high carbon.
Alloy steels are similar. If the material contains less than 2.5% of the alloying elements, then it is considered low alloyed, from 2.5% to 10% - medium alloyed, and from 10% and above - highly alloyed.
Microstructure
The microstructure of steel differs depending on its condition. If the alloy is annealed, then its structure will be divided into carbide, ferritic, austenitic and so on. With a normalized microstructure of the substance, the product can be pearlitic, martensitic or austenitic.
The composition and properties of steel determine whether a product belongs to one of these three classes. The least alloyed and carbon steels are the pearlite class, the middle ones are martensitic, and the high content of alloying elements or carbon transfers them to the category of austenitic steels.
Production and quality
It is important to note that an alloy such as steel may include some negative elements, the high content of which worsens the performance of the product. These substances include sulfur and phosphorus. Depending on the content of these two elements, the composition and types of steel are divided into the following four categories:
- Ordinary steel. This is an alloy of ordinary quality, it contains up to 0.06% sulfur and up to 0.07% phosphorus.
- Qualitative. The content of the above substances in these steels is reduced to 0.04% sulfur and 0.035% phosphorus.
- High quality. They contain only up to 0.025% of both sulfur and phosphorus.
- The highest quality is assigned to the alloy if the percentage of sulfur content is not more than 0.015 and phosphorus is not more than 0.025%.
If we talk about the production process of an ordinary alloy, then most often it is obtained in open-hearth furnaces or in Bessmerovsky, Thomasovsk converters. This product is bottled in large bullion. It is important to understand that the composition of steel, its structure, as well as qualitative characteristics and properties are determined precisely by the method of its manufacture.
Open-hearth furnaces are also used to produce high-quality steel, however, more stringent requirements are imposed on the smelting process in order to obtain a high-quality product.
Melting of high-quality steels is carried out only in electric furnaces. This is due to the fact that the use of this type of industrial equipment guarantees a practically minimal content of non-metallic additives, that is, it reduces the percentage ratio of sulfur and phosphorus.
In order to obtain an alloy of particularly high quality, they resort to the method of electroslag remelting. The production of this product is possible only in electric furnaces. After the end of the manufacturing process, these steels are always obtained only alloyed.
Types of alloys by application
Naturally, a change in the composition of steel greatly affects the operational characteristics of this material, and hence the scope of its use is changing. There are structural steels that can be used in construction, cold stamping, and can also be cemented, improved, high-strength and so on.
If we talk about building steels, then they most often include medium-carbon, as well as low alloy alloys. Since they are used mainly for the construction of buildings, the most important characteristic for them is good weldability. Various parts are most often made from cemented steel, the main purpose of which is to work under conditions of surface wear and dynamic loading.
Other steel
Other types of steel include improved. This type of alloy is used only after heat treatment. The alloy is exposed to high temperatures for hardening, and then subjected to tempering in any environment.
High-strength steels are classified as those in which, after selecting the chemical composition, as well as after passing the heat treatment, the strength reaches almost maximum, that is, approximately twice as much as that of the usual type of this product.
You can also distinguish spring steel. This is an alloy which, as a result of its production, has received the best qualities in terms of elasticity, resistance to stress, and fatigue.
Stainless steel composition
Stainless steel is a type of alloy. Its main property is high corrosion resistance, which is achieved by adding an element such as chromium to the alloy. In some situations, nickel, vanadium or manganese may be used instead of chromium. It is worth noting that when melting the material and adding the necessary elements to it, it can get the properties of one of the three grades of stainless steel.
The composition of these types of alloy, of course, is different. The simplest are conventional alloys with increased corrosion resistance 08 X 13 and 12 X 13. The next two types of this corrosion-resistant alloy must have high resistance not only at normal, but also at elevated temperatures.