Electrical steel, also known as silicon steel sheet, has a history of more than 100 years. Cold-rolled electrical steel includes oriented and non oriented electrical steel, which is used as the iron core for large and medium-sized motors, generators, household motors, micro motors, ballasts, and small transformers. The main magnetic property requirements are low total loss and high magnetic polarization strength. Low total loss can save a lot of power and prolong the running time of the motor. High magnetic polarization means strong magnetization and a decrease in the current of the iron core, which is lower than the total loss and copper loss. The total loss and magnetic polarization intensity are not only related to the chemical composition, but also to the internal structure. In order to better understand the characteristics of non oriented electrical steel, better guide production, and improve product quality.

Composition of cold rolled non oriented electrical steel

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

In non oriented electrical steels, silicon has the effect of increasing resistivity and reducing total loss, but nonmagnetic elements reduce saturation magnetization, which is detrimental to itself. At the same time, excessive content can make steel brittle, causing difficulties in cold working. Therefore, the upper limit for silicon content in cold rolled electrical equipment is generally around 3.0%. Aluminum acts similarly to silicon. The effect on large gamma phase area, coarse grains, increased resistivity, decreased magnetic anisotropy, reduced total loss, decreased magnetic polarization strength, and the strength and hardness of steel is not as obvious as that of silicon. Both silicon and aluminum control the mechanics and magnetism of non oriented electrical steels by controlling their grain size or structure.

With the development of high-speed and miniaturization of electrical machines, higher requirements are put forward for the performance of non oriented electrical steel (such as low iron loss and high magnetic induction strength at high frequencies). Non oriented electrical steel is a silicon soft magnetic alloy with extremely low carbon content, and is an indispensable and important material in power, electronics, and military industries. According to statistics, the total output of electricians worldwide in 2000 was 6.714 million tons, and by 2005, it had exceeded 8 million tons. The consumption in the domestic market has far exceeded 3 million tons. Non oriented electrical steel is the core material for motors and generator rotors operating in rotating magnetic fields, requiring good magnetic and technological properties.

The variation trend of hardness of non oriented electrical steel is consistent with that 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 lower the formability of the sheet. However, the lower the hardness of the steel, the larger the burrs on the sheet, and the inaccurate size of the sheet. The suitable hardness of steel with good punching performance is 130HV~180HV.