Electrotechnical steel: production and use

The Production of this type of steel holds a leading position among other magnetic materials. Electrotechnical steel is an alloy of iron with silicon, the proportion of which is from 0.5% to 5%. The wide popularity of products of this type may explain the high electromagnetic and mechanical properties. This steel is made from common components, deficiency of which is not. This explains its low value.

Impact of silicon

This component is in interaction with iron forms solid solution with high resistivity, the value of which depends on the percentage of silicon in the alloy. When exposed it to pure iron, it loses its magnetic properties. But when exposed to the technical, on the contrary, has a positive effect. The permeability of iron increases, and an improvement of stability of metal. The beneficial effect of silicon (Si) can be explained as follows. Under the influence of this element is the transfer of carbon to graphite from the state of cementite, which has less magnetic. The element Si has an unwanted effect on the reduction of induction. His influence extends to the thermal conductivity and the density of iron.

Impurities in the composition

In its composition of electrical steel may contain other components, sulfur, carbon, manganese, phosphorus, and others. The most harmful of them is the carbon (C). It may be in the form as cementite, and graphite. It impacts differently on the alloy, as well as the percentage of carbon content. To avoid unwanted inclusions of the element, not the steel rapidly to cool for the next aging and stabilization.

A Negative impact on the material properties have the following components: oxygen, sulfur, manganese. They reduce its magnetic quality. Technical iron in its composition has impurities. Here they have to be considered together, not as for pure iron.

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It is Possible to improve the properties of steel by purification from impurities. But this method is not always advantageous in the large-scale production. But with the help of cold rolling electrical steel sheet forms in its structure magnetic properties. This allows you to achieve the best results. But it is necessary further firing.

Cold rolling

For a long time believed that silicon increases the brittleness of steel. Production took place mainly with hot rolling. The profitability of cold rolling was low.

Only after it was discovered that cold treatment along the direction improves the magnetic properties of the material, it is widely used. Other areas showed itself only with the worst hand. Cold rolling had a beneficial effect on the mechanical properties and to improve the quality of the leaf surface, increasing its sinuosity and has given the opportunity stamping.

The Distinctive properties that received electrical steel through the use of cold treatment, can be explained by the formation in it of crystallographic texture. It differs several degrees. They, in turn, depend on the temperature at which rolling is also the thickness required of the sheet and from that, to what extent it is compressed.

The Cost of a single sheet thickness of hot rolled steel in 2 times below, than cold rolled. But this negative quality is fully kompensiruet low heat losses (they are less than about two times), high quality and good ability of forming cold-rolled alloy. The difference in these steels the silicon content. The amount ranges from 3.3% to 4.5%, respectively.

GOST

Manufacturers produce only two types of steel meet the standards. The First 802—58 "Electric sheet". The second electrotechnical steel of GOST 9925—61 "Tape cold rolled electrical steel".

Marking

Is Marked with the letter “e”, followed by the room numbers which have a special meaning:

• The First digit in the value of the marking indicates the degree of alloying of steel with silicon. From low-alloyed to high-alloyed, respectively, in figures 1 to 4. Dinamia – steel from the groups E1 and E2. Transformer – E3 and Э4.
• The Second figure marking has a range from 1 to 8. It shows electromagnetic properties of a material at its application in certain operating conditions. This marking is possible to know in what areas you can take steel.

The Number zero followed by the second digit means that the steel is textured. If there are two zeros, then it is a little textured.

At the end of the marking you can find the following letters:

• “And” - specific material loss is very low.
• “P” - material with high strength rolled and high surface finish.

Area of operation

Alloy is Divided by application into three types:

• Suitable for medium and strong magnetic fields (purity of magnetization reversal 50 Hz);
• Suitable for work in secondary fields at frequencies up to 400 Hz;
• Steel that is used in medium and small magneticfields.

The electrical steel Sheets produced in the following sizes: width from 240 to 1000 mm, the length can be from 720 mm up to 2000 mm, the thickness is in the range from 0.1 to 1 mm. the most used are textured steel, as they have a high value of electromagnetic properties. Sheets of such material often used in electrical engineering.

Electrical steel properties

The properties of the alloy:

• Resistivity. From this indicator depends directly on the quality of the material. Steel is used where it is necessary to keep the electricity inside the conductor and to deliver it to its destination.
• Coercive force. Responsible for the ability of the internal magnetic field for demagnetization. For certain applications this property is required in varying degrees. In transformers and electric motors use parts with high ability demagnetization. Steel the indicator has a low value. But in the electromagnets necessary, on the contrary, a high coercive force. To adjust the magnetic properties, the alloy steel is added the desired percentage of silicon.

• Width of the hysteresis loop. This figure should be as small as possible.
• Magnetic permeability. The higher the figure, the better the material "cope" with their problems.
• The thickness of the sheet. For the manufacture of many devices and parts using materials whose thickness does not exceed one millimeter. If necessary, however, this figure reduces to 0.1 mm.

Usage

From sheet materials of the first class can produce different types of magnetic cores for relays and regulators.

Electrical steel grade of the second class can be used for starters of electric machines of direct and alternating currents, the cores of the rotors. The Third class will be suitable for the manufacture of magnetic cores for power transformers and starter motors large synchronous machines.

To make a skeleton for electric machine, you need to use steel casting, in which the carbon content is equal to no more than 1%. Products from such material are subjected to a gradual annealing. Carbon steel used in the manufacture of machine parts subjected to welding. Of these types of materials make the main poles for DC machines.

For those machine parts that carry the maximum load (springs, rotors, shafts, anchors), used alloys with high mechanical properties. This material may contain Nickel, chromium, molybdenum and tungsten. It is possible to produce magnetic cores from electrical steel. They are used for power transformers low frequency – 50Hz.

Magnetic Core

The magnetic Cores they are divided into armor and core. Each species has its own characteristics.

Rod: such a magnetic rod vertical and has a stepped cross-section inscribed in a circle. On their particular cylindrical form of the winding of the magnetic circuit.

Armor

The Product of this design have a rectangular shape, and the rods have a cross section, they are located horizontally. This type of yoke is used only in complex devices and structures. Therefore, such structures have not received wide acceptance.

So, we found the electrotechnical steel and where it is used.