Magnetic materials always has been important part with their application in electrical engineering, energy, computer engineering, electronics, radio engineering and other fields. Not only that they are nowdays a major contributor for physico-chemical and electrophysical properties in the field of research and advanced technological developement.
Here are the following magnetic materials are used for the manufacture of magnetic cores in electrical engineering are 3 prime magnetic materials used for the manufacturing of Electrical Componenets: pure iron, Electrical Silicon Steel, Nickel-Iron Alloys.
Let us briefly consider some of their important magnetic material properties and application possibilities.
1. Pure Iron
Pure iron is commonly used for relay magnetic loops, electromagnetic meters, electromagnetic couplings, magnetic barriers, etc. This material has a very low carbon content (less than 0.1%) and a minimum amount of manganese, silicon and other impurities.
These products typically include: Armco-iron, pure Swedish iron, carbonyl and Electrolyte iron, etc. The consistency of pure iron is based on negligible amounts of impurity.
Carbon and oxygen exert the most harmful effect on the magnetic properties of iron. The acquisition of chemically pure iron is fraught with great technological challenges and is a complex and costly process. Technology developed particularly in laboratory conditions with double high-temperature annealing in hydrogen allowed a single crystal of pure iron with extremely high magnetic properties to be obtained.
Which is the most popular type steel iron?
The most popular is Armco-type steel iron, obtained through the open-hearth process. The material has a relatively high magnetic permeability, substantial induction of saturation, relatively low cost and good mechanical and technical properties at the same time.
Gray Cast Iron
As a rule, grey cast iron is not used due to poor magnetic properties for magnetic systems. Economic considerations can justify the use of it for powerful electromagnets. It also applies to bases, boards, racks, and other parts.
It is cast well and is easy to process. Specially annealed malleable cast iron, as well as some grades of gray alloyed cast iron, have satisfying magnetic properties.
Thin-sheet electrical steel has been widely used in electrical engineering and system manufacturing and is used for all types of electrical measurement instruments, mechanisms, relays, chokes, ferroresonant stabilizers and other devices working with a normal and high frequency alternating current. 28 grades of sheet steel with a thickness of 0.1 to 1 mm are manufactured depending on the technical requirements for steel losses, magnetic properties, and the frequency of alternating current applied.
How Silicon Steel are playing an important role?
With the advent of silicon steel losses diminish, magnetic permeability increases in weak and medium fields, and coercive force decreases. In this case impurities (especially carbon) have a weaker effect, steel ageing decreases (losses in steel change only slightly over time).
To increase electrical resistance to eddy currents, a different quantity of silicon is applied to and depending on the quality of the steel composition.
The use of silicon steel enhances the reliability of the electromagnetic structures, increases the reaction and release speed and decreases the anchor’s “sticking” probability. At the same time the mechanical properties of steel deteriorate with the addition of silicone.
Steel becomes brittle, hard to process with a significant silicon content (more than 4.5 per cent). Small stampings give the stamp considerable scraping and quick wear. An increase in silicone also decreases the induction of saturation. There are two types of silicon steels: hot rolled and cold rolled.
Importance of Cold Rolled Steel as Magnetic Material
Cold rolled steels exhibit various magnetic properties depending on the orientation of the crystallography. They are broken down into textured and low-texture. Textured steel shows much stronger magnetic properties. Cold-rolled steel has a higher magnetic permeability and lower losses compared to hot-rolled steel when given the magnetic flux correlates with the steel’s rolling path. They are classified into two CRGO(Cold Rolled Grain Oriented Steel) and CRNGO(Cold Rolled Non Grain Oriented Steel) based on grain size and orientation.
The use of cold rolled steel for electromagnets for traction and other electromagnetic devices that work at relatively high inductions provides significant savings in from which reduce the magnetic circuit’s overall dimensions and weight.
How to Know Grade of Magnetic Materials?
According to Euro-Asian Council for Standardization, the letters and numbers of individual steel grades indicate: first digit 1, 2, 3 and 4 after the letter indicates the degree of silicon alloy, namely: (1- low alloy, 2 – medium alloy, 3 – high alloy and 4 – heavy alloys).
The second digit after letter 1, 2, and 3 denotes the amount of steel losses per 1 kg of weight at a frequency of 50 Hz and magnetic induction B in strong fields, with a figure of 1 characterizing common individual losses, a figure of 2-reduced and 3-low. The second digit 4, 5, 6, 7 and 8 behind the letter E indicates: 4 -steel with specific losses at 400 Hz frequency and magnetic induction in middle fields, 5 and 6 – steel with magnetic permeability in low fields from 0.002 to 0.008 a / cm (permeability, 6 -increased), 7 and 8 – steel with medium magnetic permeability.
The third in order after the letter E, the number 0 means that the steel is textured cold-rolled, the third and fourth number suggest that the steel is low-textured cold-rolled.
E3100 steel, for example, is a strongly alloyed cold-rolled low-textured steel with typical clear losses at 50 Hz.
Placed after all of these numbers, letter A indicates an especially low specific steel loss.
For current transformers and some types of communication devices which operate at very small inductions on magnetic circuits.
3. Nickel-Iron alloys
These alloys, also known as permalloys , are mainly used for the manufacture of communication and automation devices. The characteristic properties of permalloys are: high magnetic permeability, low coercive force, low losses in steel, and for a number of grades with the presence, in addition, of a rectangular shape of a hysteresis loop .
The iron-nickel alloys are available in several grades and have different characteristics depending on the ratio of iron and nickel, as well as the contents of other parts.
Nickel-iron alloys are made in the form of cold-rolled thermally untreated strips of different widths and lengths with a thickness of 0.02-2.5 mm. Also available are hot rolled strips, rods, and wires but not standardized.
How Nickel and other Alloys are important for manufacturing of electrical component?
Alloys with a nickel content of 45-50 per cent have the highest induction of saturation and relatively high electrical resistivity of all grades of permalloy. Thus these alloys enable the necessary traction force of an electromagnet or relay with small losses to be obtained with small air gaps.
The residual force of friction gained because of the coercive force of the magnetic material is very important for electromagnetic mechanisms. Using permalloy lowers the energy.
For more efficient electromagnets, relays, and other relatively large electromagnetic devices. Permalloy does not have any specific benefits over carbon and silicon steels, as the induction of saturation is much lower and the quality of the material is greater.
Iron-cobalt alloys An alloy consisting of 50 percent cobalt, 48.2 percent iron, and 1.8 percent vanadium used for industrial use. It provides the greater induction of all known magnetic materials.
For example, its use with small air gaps for electromagnet traction and electromagnetic relays has a certain effect. With momentum, the magnetic circuit can be achieved with smaller dimensions.
This material is produced in the form of 0.2-2 mm thick cold-rolled sheets and 8-30 mm diameter rods. A major drawback of iron-cobalt alloys is their high cost, due to process difficulties and higher cobalt costs. For example, iron-nickel-cobalt alloys, which have constant magnetic permeability and very small losses of hysteresis in weak fields, are also used in electrical devices in addition to the listed materials.