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2023-11-02
Electrical steel is not only an indispensable metal functional material in the power, electronics, military, and automobile industries, but also a key material for power equipment to improve efficiency and reduce energy consumption. This is due to its several desirable properties, such as low core loss, high magnetic permeability, good processing performance, smooth surface, and so on. Then, according to its actual usage, electrical steel is subdivided into many different kinds to better suit some specific applications. Today, let’s have a better understanding of electrical steel and its types.
Electrical steel, also known as silicon steel or transformer steel, is a soft magnetic alloy that is mainly composed of iron, silicon, and small amounts of other elements like aluminum, carbon, and manganese. Generally, the silicon content is between 0.5% and 4.5%. It is specifically designed to reduce power loss and improve magnetic properties. Therefore, this type of steel is very often used to build the cores of electromagnetic devices such as motors, generators, transformers, and other power supply and conversion systems.
As the most widely used soft magnetic alloy in the world, electrical steel is widely used in the real economy. Improving its overall performance and manufacturing level plays a very important role and significance in the development of the national economy.
Electrical steel can be divided into different classifications based on its silicon content, manufacturing process, magnetic properties, usage, and supply forms. Each type of electrical steel has its own unique set of properties that make it better suited for specific applications. Let’s have a closer look at them now.
Electrical steel mainly adds silicon instead of carbon to improve its performance. According to the silicon content, it can be divided into low silicon steel and high silicon steel.
| Product Name | Silicon Content |
| Low silicon steel | Less than 2.8% |
| High silicon steel | 2.8%-4.8% |
Low electrical steel has a silicon content of less than 2.8%. It has some certain mechanical strength and is widely used in the manufacturing of small civilian electrical appliances with low electromagnetic performance requirements. At the same time, due to its low silicon, its production process is simple and the cost is low, similar to that of ordinary carbon steel.
High electrical steel has a silicon content of 2.8%-4.8%. More silicon might be favorable due to increased resistivity and lower magnetostriction, but it will lead to complications in cold rolling. This type has good magnetism but a bit of brittlement, which is widely used in fabricating iron cores of large-scale transformers, generators, and motors. High electrical steel has extremely complex types and grades.
Electrical steel is often manufactured by rolling process, Which includes hot rolling and cold rolling. Therefore, it can be divided into hot rolled electrical and cold rolled electrical steel.
Hot rolled electrical steel: Hot rolled electrical steel is made by melting Fe-Si alloy in an open furnace or electric furnace, repeatedly hot-rolling it into the required thickness, and finally annealing it at 800-850°C. It is mainly used to manufacture the generator. However, its utilization is low and the energy loss is large. In recent years, it has been gradually eliminated by the market.
Cold rolled electrical steel: this type is made by cold rolling several times at room temperature. It has a silicon content of 0.5%-3.0%, and the finished product thickness is mostly supplied as 0.35mm and 0.5mm. Cold rolled electrical steel is mainly used for manufacturing generators, motors, and generators.
In addition, by comparing the two processing processes, we could find that cold rolled electrical steel has a smoother surface, thinner and uniform thickness, more precise dimension, and better magnetism than hot rolled electrical steel, which improves the filling factor and the magnetic properties of the material. Therefore, with the development of industry, cold-rolled electrical steel tends to replace hot-rolled electrical steel products in the market gradually.
The grain structure inside electrical steel is usually divided into oriented and non-oriented directions. Hot-rolled electrical steel products all have no grain orientation. The magnetic anisotropy of electrical steel is developed through the secondary recrystallization process after cold rolling. Therefore, only cold-rolled electrical steel can be divided into grain-oriented and non-grain-oriented.
Cold Rolled Non-oriented Electrical Steel (CRNGO Electrical Steel)
Cold rolled non-oriented electrical steel has low silicon content, scattered grain texture, and relatively uniform magnetic properties in all directions. This is because it doesn’t require a secondary recrystallization process for their property development, nor is a high-temperature anneal necessary. Hence, the lower limit on silicon is not essential. It usually contains between 0.5% and 3.25% Si plus up to 0.5% Al. This addition increases resistivity and lowers the temperature of primary recrystallization. Non-grain-oriented electrical steel can find usage in large rotating equipment, including motors, power generators, and AC alternators.
Besides, non-oriented electrical steel can come in two conditions: fully-processed or semi-processed.
1. Non-oriented fully processed electrical steel: it has varying silicon levels that range from 0.5% to 3.25% Si and uniform magnetic properties in all directions. This type is excellent for magnetic circuits in motors, transformers, and electrical system housing.
2. Non-oriented semi-processed electrical steel: it is made of largely non-silicon alloyed steel and is annealed at low temperatures after the final cold rolling. The punch ability of this electrical steel type is better than the non-oriented fully processed type, so organic coatings are not required. The non-oriented semi-processed grade is a good core material for small rotors, stators, and small power transformers.
Cold Rolled Oriented Electrical Steel (CRGO Electrical Steel)
Cold rolled oriented electrical steel is characterized by high silicon content (3%) and strong grain orientation in rolling direction. This type undergoes a recrystallization process resulting in an enhanced grain structure that exhibits better magnetic properties in the rolling direction of the sheet. Grain-oriented steels are mostly used for non-rotating applications, such as transformers.
Compared with cold-rolled non-oriented electrical steel, cold rolled oriented electrical steel has a stronger magnetic orientation. It also has superior permeability and lower loss characteristics in the direction of easy magnetization. The iron loss of the orientation steel in the direction of rolling is only one-third of the horizontal one, the ratio of the magnetic conductivity is 6:1, the iron loss is about 1/2 of the hot-rolled electrical steel, and the magnetic conductivity is 2.5 times that of the latter. However, the Bs of cold-rolled oriented electrical steel are lower than the non-oriented electrical steel.
Besides, cold rolled oriented electrical steel also comes in two conditions: common grain-oriented electrical steel (CGO) and high magnetic induction electrical steel (Hi-B).
According to the final uses of electrical steel, it can be divided into three categories: electrical steel for transformers, electrical steel for motors, and electrical steel for generators.
Electrical steel for transformers: mainly used in the manufacturing of various transformers. It can effectively reduce energy consumption and improve the energy efficiency of transformers.
Electrical steel for motors: mainly used in the manufacturing of various motors. It can improve the efficiency and performance of the motor and reduce energy consumption.
Electrical steel for generators: mainly used in the manufacturing of various generators. It can improve the efficiency of the generator and reduce energy consumption.
According to its final supply forms, electrical steel is mainly divided into four main types:
Special electrical steel structure
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