Electrical steel (lamination steel, Non Grain Oriented Steel, silicon steel, relay steel, transformer steel) is a special steel tailored to produce specific magnetic properties: small hysteresis area resulting in low power loss per cycle, low core loss, and high permeability.
Electrical steel is normally produced in cold-rolled strips lower than 2 mm thick. These strips are cut to contour around make laminations which can be stacked together to create the laminated cores of transformers, as well as the stator and rotor of electric motors. Laminations could be cut for their finished shape by a punch and die or, in smaller quantities, may be cut by way of a laser, or by wire EDM.
Electrical steel is definitely an iron alloy which can have from zero to 6.5% silicon (Si:5Fe). Commercial alloys usually have silicon content up to 3.2% (higher concentrations usually provoke brittleness during cold rolling). Manganese and aluminum can be added as much as .5%.
Silicon significantly raises the electrical resistivity in the steel, which decreases the induced eddy currents and narrows the hysteresis loop in the material, thus decreasing the core loss. However, the grain structure hardens and embrittles the metal, which adversely affects the workability of the material, especially when rolling it. When alloying, the concentration amounts of carbon, sulfur, oxygen and nitrogen has to be kept low, as these elements indicate the presence of carbides, sulfides, oxides and nitrides. These compounds, even just in particles as small as one micrometer in diameter, increase hysteresis losses while also decreasing magnetic permeability. The existence of carbon includes a more detrimental effect than sulfur or oxygen. Carbon also causes magnetic aging if it slowly leaves the solid solution and precipitates as carbides, thus causing a rise in power loss with time. Therefore, the carbon level is kept to .005% or lower. The carbon level could be reduced by annealing the steel in a decarburizing atmosphere, including hydrogen.
Non-oriented Hot Dip Galvanized Steel Wire (image made out of magneto-optical sensor and polarizer microscope)
Electrical steel made without special processing to manage crystal orientation, non-oriented steel, usually includes a silicon level of 2 to 3.5% and it has similar magnetic properties in most directions, i.e., it is isotropic. Cold-rolled non-grain-oriented steel is frequently abbreviated to CRNGO.
Grain-oriented electrical steel usually has a silicon amount of 3% (Si:11Fe). It really is processed in such a way the optimal properties are created in the rolling direction, because of a tight control (proposed by Norman P. Goss) from the crystal orientation in accordance with the sheet. The magnetic flux density is increased by 30% within the coil wnhsva direction, although its magnetic saturation is decreased by 5%. It is actually used for the cores of power and distribution transformers, cold-rolled grain-oriented steel is usually abbreviated to CRGO.
CRGO is normally provided by the producing mills in coil form and needs to be cut into “laminations”, which can be then used to create a transformer core, which is an integral part of any transformer. Grain-oriented steel can be used in large power and distribution transformers as well as in certain audio output transformers.
CRNGO is cheaper than CRGO. It really is used when expense is more essential than efficiency as well as for applications where the direction of magnetic flux will not be constant, like electric motors and generators with moving parts. You can use it should there be insufficient space to orient components to benefit from the directional properties of Electrogalvanized Steel Sheet.