Steel is considered an alloy of iron with other chemical compounds. Among the components included in the composition, there is carbon in an amount of 2.14%. Due to its presence, iron alloys acquire their strength. The specific gravity of steel is 75500-77500 N / m³. The alloy may sometimes contain alloying elements. The specific heat of steel at 20 ° C is measured at 460 J / (kg * ° C), or 110 cal / (kg * ° C).
Classification
There are various parameters according to which the material in question is characterized. So, for example, steel is instrumental and structural. High-speed alloy is considered one of the types of instrumental. There are also differences in accordance with the chemical composition. Depending on which elements are present in the alloy, alloyed and carbon are separated. A classification by carbon concentration level is also accepted. So, there are three types of alloys:
1. Low carbon. It has a carbon content of up to 0.25%.
2. Steel is medium carbon. In this carbon alloy, about 0.25-0.6%.
3. High carbon steel. About 0.6–2% carbon is present in this alloy.
Alloy steel is similarly classified according to the percentage of alloying elements:
1. Low alloy steel contains up to 4%.
2. In the medium alloyed alloy, up to 11% is present.
3. High alloy steel. It contains more than 11%.
Steel is produced by various methods and using special technologies. Depending on a particular method, the composition of the alloy contains various metal inclusions. This indicator affects the specific gravity of steel. Classifying alloys by the number of impurities, distinguish:
1. Mixtures of ordinary quality.
2. Qualitative.
3. High quality.
4. Particularly high quality.
There is also a classification according to the structural composition of the material. For example, ferritic, bainitic, austenitic, pearlitic and martensitic alloys are produced. Undoubtedly, the structural composition also affects the specific gravity of steel. Alloys are also divided into two-phase and multiphase. It depends on the presence of phases in the structure. Also, alloys are classified by the nature of solidification and the degree of deoxidation. So, there is a calm, semi-calm and boiling steel.
Steel Production Methods
Cast iron is used as raw material for the manufacture of steel. The presence of a large amount of carbon, phosphorus and sulfur in its composition makes it brittle and brittle. To process one material into another, it is necessary to reduce the content of these substances to the desired concentration. At the same time, the specific gravity of steel and its properties will change. One or another method of producing alloys involves different methods of oxidizing carbon in cast iron. Most commonly used:
1. Open-hearth steelmaking method . It should be noted that this option has recently competed poorly with other methods.
2. Converter method. Today, most steel products are manufactured using this technology.
3. Electrothermal - one of the advanced technological methods for producing steel. As a result, the material produced is of very high quality.
Converter method
Using this technological method, excess iron, phosphorus and sulfur are oxidized with oxygen. A purge is carried out under pressure through the molten material in a special furnace. It is called a converter. This oven has the shape of a pear. In its internal part there is a lining with refractory bricks. This furnace is highly mobile: it can rotate 360 degrees. The capacity of the converter is about 60 tons. For lining, as a rule, two types of raw materials are used:
1. Dinas - it contains SiO2, which has acidic properties.
2. Dolomite mass - MgO and CaO. It is obtained from the dolomite material MgCO3 * CaCO3 having base properties.
Due to the different materials for lining, converter furnaces are divided into Thomas and Bessemer. Pressure purged air covers the entire metal area. It should be noted that the processes occurring in the furnace have a duration of not more than 20 minutes. The length of time the material stays in the converter affects the heat capacity of the steel. The alloy that is obtained in converter furnaces often contains a large amount of iron monoxide. That is why the material is often obtained in poor quality.
Open hearth furnace
This cast iron processing method is outdated. Undoubtedly, when using somewhat backward technologies during processing, the quality of the material significantly decreases, its technical characteristics change (heat capacity of steel and others). The open-hearth furnace is a large melting bath. It is covered with a vault of refractory bricks and recuperator chambers. These compartments are designed to heat combustible gas and air. They are filled with a nozzle made of brick (refractory). A stream of hot gas and air is blown into the furnace through the third and fourth recuperators. And the first and second, meanwhile, are heated by furnace gases. After a sufficient temperature increase, the whole process goes in the opposite direction.
Electrothermal method
This method has several advantages over the open-hearth and converter. The electromechanical method allows you to change the chemical composition of the resulting steel. Moreover, the mixture after the processing process is very high quality. Due to the limited air access in the electric furnace, the amount of iron monoxide is reduced. It is known that it contaminates steel with its impurities. And this, in turn, has a significant impact on its quality. In an electric furnace, the temperature does not drop below 2000 ° C. Thus, such harmful impurities as sulfur and phosphorus are completely removed from the composition of cast iron.
Furnace Method
Due to their high temperature, electrothermal furnaces make it possible to alloy steel with the help of refractory metals. These include, in particular, tungsten and molybdenum. The electric steelmaking method allows to obtain a high-quality mixture: the specific heat of steel, as well as its qualitative characteristics, are at the highest level. But, unfortunately, these furnaces consume a large amount of electric energy (up to 800 kW per hour per ton of raw material). The capacity of electric furnaces can range from 500 kg to 360 tons. The units use conventional lining. The charge structure can be 90% of scrap iron and 10% of cast iron. Sometimes the proportions of the raw materials may be different. Lime, which is added to the mixture, plays the role of flux. The main chemical processes in electric arc furnaces are not very different from open-hearth furnaces.
Specific gravity
Currents of industrial frequency carry out induction heating of the metal. Due to the large mass of the core, such an effect is quite enough. For melting steel weighing up to 100 tons, a current of 50 Hz is sufficient. It must be said that some parameters of different types of one raw material may coincide. So, for example, corrosion, heat resistant and stainless steel have a specific gravity 7.9 g / cm 3 .
This indicator is directly related to the weight of the finished product at the output. That is, the larger it is, the product is, accordingly, heavier. And the specific gravity of galvanized steel is also about 7.9 g / cm
3 . A slight difference may be noted depending on the type. But the specific gravity of sheet steel is 7.85 g / cm
3 . As you can see, the indicator is slightly lower, which means that the material is lighter. It must be assumed that the specific gravity of cast iron and steel is different. The alloy output is higher, as a rule. This is largely due to the fact that during the processing, despite the fact that some components are removed from the raw material, additional elements are added to the mixture. They influence the parameters of the output product. Different
types of cast iron have their own specific gravity (in g / cm
3 ):
- white - 7.5 ± 0.2;
- gray - 7.1 ± 0.2;
- malleable - 7.5 ± 0.2.
Payment
The ratio between the volume of the alloy and its mass is characteristic only for a particular substance. In addition, this parameter is constant. Using a special formula, you can find out the density of a substance. It is directly related to the calculation of the specific gravity of the alloy. Here is how it looks.
The specific gravity of the metal is assigned in the formula as γ. It is equal to the ratio of P - the weight of a homogeneous body - to the volume of the connection. And it is calculated by the following formula: γ = P / V.
It works only when the metal has an absolutely dense state, non-porous.
Conclusion
New technologies that are used in heavy industry are very different from those used at the initial stage of development of this industry. Thanks to scientific progress, the modern metal industry produces a huge number of alloy variations. The specific gravity of the compounds affects the choice of a particular type of raw material that will be used in production. If you take three different metals: iron, brass and aluminum with the same volume, then everyone will have a different mass. Therefore, when choosing one or another metal, its specific gravity should be taken into account, among other parameters.