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 created in cold-rolled strips under 2 mm thick. These strips are cut to shape to make laminations which can be stacked together to form the laminated cores of transformers, as well as the stator and rotor of electric motors. Laminations could be cut for their finished shape by way of a punch and die or, in smaller quantities, may be cut by way of a laser, or by wire EDM.
Electrical steel is an iron alloy which can have from zero to 6.5% silicon (Si:5Fe). Commercial alloys normally have silicon content as much as 3.2% (higher concentrations usually provoke brittleness during cold rolling). Manganese and aluminum could be added approximately .5%.
Silicon significantly boosts the electrical resistivity of the steel, which decreases the induced eddy currents and narrows the hysteresis loop from the material, thus decreasing the core loss. However, the grain structure hardens and embrittles the metal, which adversely affects the workability of the material, specially when rolling it. When alloying, the concentration levels of carbon, sulfur, oxygen and nitrogen has to be kept low, since these elements indicate the existence of carbides, sulfides, oxides and nitrides. These compounds, even just in particles as small as one micrometer in diameter, increase hysteresis losses as well as decreasing magnetic permeability. The actual existence of carbon has a more detrimental effect than sulfur or oxygen. Carbon also causes magnetic aging in the event it slowly leaves the solid solution and precipitates as carbides, thus resulting in a rise in power loss with time. Therefore, the carbon level is kept to .005% or lower. The carbon level may be reduced by annealing the steel in a decarburizing atmosphere, including hydrogen.
Non-oriented Gi Wire (image made out of magneto-optical sensor and polarizer microscope)
Electrical steel made without special processing to regulate crystal orientation, non-oriented steel, usually features a silicon degree of 2 to 3.5% and contains similar magnetic properties in all directions, i.e., it is isotropic. Cold-rolled non-grain-oriented steel is usually abbreviated to CRNGO.
Grain-oriented electrical steel usually includes a silicon level of 3% (Si:11Fe). It really is processed in such a way the optimal properties are created in the rolling direction, due to a tight control (proposed by Norman P. Goss) from the crystal orientation relative to the sheet. The magnetic flux density is increased by 30% inside the coil wnhsva direction, although its magnetic saturation is decreased by 5%. It is utilized for the cores of power and distribution transformers, cold-rolled grain-oriented steel is often abbreviated to CRGO.
CRGO is usually supplied by the producing mills in coil form and has to be cut into “laminations”, that are then used to create a transformer core, which can be an integral part of any transformer. Grain-oriented steel is 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 price is more essential than efficiency and for applications in which the direction of magnetic flux will not be constant, as in electric motors and generators with moving parts. You can use it should there be insufficient space to orient components to make use of the directional properties of Electrogalvanized Steel Sheet.