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Silicon steel, often called electrical steel, is steel with silicon added to it. The addition of silicon to steel increases its electrical resistance, improves the ability of magnetic fields to penetrate it, and reduces the steel’s hysteresis loss. This type of steel is used in many electrical applications where electromagnetic fields are important, such as in transformers, magnetic coils and electrical motors.
While the silicon in silicon steel can reduce the rate of corrosion of the iron within it, the primary purpose of adding silicon is to improve the steel’s hysteresis loss. Hysteresis is the lag between the time when a magnetic field is first generated or applied to the steel and when the field fully develops. The addition of silicon to steel makes the steel more efficient and faster in terms of building and maintaining magnetic fields. Thus, silicon steel improves the efficiency and effectiveness of any device using steel as a magnetic core material.
The percentage of silicon added to silicon steel varies with its intended use up to 6.5 percent. For some items, such as high-efficiency motors and transformers, silicon comprises approximately 3 percent of the steel’s makeup. In other items requiring less efficiency, such as certain types of motor applications, the amount of silicon can be as low as 2 percent. Though expensive when compared to regular carbon steel, silicon steel can be produced with whatever percentage of silicon is needed for a specific application.
This product is produced in strips or rolls, cut into the needed shapes and then heat-treated to control the size of the grain of the steel. Through control of the grain size, the hysteresis loss of the steel can be accurately controlled. The direction of the grain in the steel can also affect its efficiency. The grain can be oriented in one direction through rolling to improve its density or the grain can be non-oriented and run in all directions, making the silicon steel less expensive.
Once the heat-treating process is completed, silicon steel is often coated or varnished, to further retard corrosion, then stacked to the needed thicknesses. These thicknesses are called laminations, and they may, or may not, be physically attached or bonded to one another. These stacked laminations serve as the cores of almost all electromagnetic devices in modern use, from power adapters for home electronics to substation transformers supplying electrical power to homes and businesses.
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