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Research on the composition, structure and properties of cold-rolled non-oriented electrical steel

07 Mar 2024
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Electrical steel is also called silicon steel sheet. Its development has a history of more than 100 years. Cold-rolled electrical steel includes oriented electrical steel and non-oriented electrical steel. Non-oriented electrical steel is used for large and medium-sized motors, generators, household motors and micromotors. Iron cores for ballasts and small transformers, etc. The main magnetic performance requirements are low total losses and high magnetic polarization. Low total losses can save a lot of power and extend the motor running time. High magnetic polarization intensity means strong magnetizing ability, and the current of the iron core is reduced, which is lower than the total loss and copper loss. Total losses and magnetic polarization are related not only to the chemical composition, but also to the internal organization. In order to better understand the characteristics of non-oriented electrical steel, better guide production and improve product quality.
Cold rolled non oriented steel 
Cold rolled Grain Non oriented electrical steel
Composition of cold-rolled non-oriented electrical steel

Non-oriented electrical steel grades are related to W600, W800, and W1300, and the steel plate thickness is 0.5 mm. The statistical averages of the three chemical components are shown in Table 1. The electricians are all ultra-low carbon non-oriented electricians. The main difference between the three components is the silicon and aluminum content.

In non-oriented electrical steel, silicon has the effect of increasing resistivity and reducing total loss, but non-magnetic elements reduce saturation magnetization, which is not beneficial to itself. At the same time, too high a content will make the steel brittle and make cold working difficult. Therefore, the upper limit of silicon content for cold-rolled electrical equipment is generally around 3.0%. Aluminum acts similarly to silicon. The effects on the large gamma phase area, rough grains, increased resistivity, reduced magnetic anisotropy, reduced total loss, reduced magnetic polarization intensity, and the strength and hardness of steel are not as obvious as those of silicon. Both silicon and aluminum control the mechanical and magnetic properties of non-oriented electrical steel by controlling the grain size or structure.

With the development of high-speed and miniaturized motors, higher performance requirements have been put forward for non-oriented electrical steel (such as low iron loss at high frequency and high magnetic induction strength, etc.). Non-oriented electrical steel is a silicon soft magnetic alloy with extremely low carbon and is an indispensable and important material in the power, electronics and military industries. According to statistics, the total output of electricians in the world in 2000 was 6.714 million tons, and by 2005 it exceeded 8 million tons. Domestic market consumption has far exceeded 3 million tons. Among them, non-oriented electrical steel is the core material of the rotors of motors and generators that work in rotating magnetic fields and require good magnetic and process properties.

The change trend of hardness of non-oriented electrical steel is consistent with the change trend of tensile strength, and the hardness reflects the punching performance of the steel. The higher the silicon content, the greater the hardness of the steel and the reduced punching properties. However, if the hardness of the steel is too low, the burrs of the punched sheets will increase and the punched sheet dimensions will be inaccurate. The suitable hardness of steel with good punching performance is 130HV~180HV.
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