Electrical steel is a ferromagnetic material made up of iron that contains varying amounts of silicon (Si) that range from 1% to 6.5%. The development of electrical steels was brought on by electrical devices requiring steels that can decrease the dissipation of heat, an issue that results in energy wastage. Iron was found to be the most economically sound option but its impurities are not optimal. It was found that the addition of silicon increases resistivity, improves permeability, and decreases hysteresis loss. The most widely used commercially available electrical steel contains about 3.25% Si as higher silicon content tends to make the resulting material too brittle for cold rolling. Electrical steel with 6.5% Si has the most improved magnetic and electrical properties, but additional thermomechanical processes are required in order to overcome its brittleness and limited ductility.

Properties of electrical steel

The addition of silicon in iron greatly improves the physical properties of electrical steels. Electrical steels have the following desirable properties for supporting the generation, distribution and consumption of electricity:

• High permeability - increased capacity to support magnetic fields
• Low magnetostriction - low tendency to expand or contract in magnetic fields
• High electrical resistivity - lessens the core loss by reducing the eddy current component

• Decreased hysteresis loss - low hysteresis loss means less wasted energy in the form of heat from alternating magnetising force.

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Electrical steel production

Electrical steels are typically cast continuously or melted in oxygen furnaces. They are then hot rolled as they pass through the annealing and descaling process line, where dirt and scale are removed from the surface. Afterwards, they go through cold reduction, where the thickness of the steel is reduced and corrected according to the end-user specifications. Subsequently, carbon content within the steel is reduced by a decarburising anneal, in which the steel roll is heated in a mixture of hydrogen, nitrogen, and water vapour. Other contaminants, like sulphur, are removed in this process, as well, resulting in a less brittle material. For grain-oriented type steel, the coil undergoes a high-temperature coil anneal (HTCA) at about 1100°C in order to achieve the required magnetic properties and grain growth.

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