The oriented silicon steel is thermally annealed and coated with insulation

The oriented silicon steel is thermally annealed and coated with insulation

After annealing at high temperature, oriented silicon steel must also be thermally flat and coated with insulation layer.

The steel strip of oriented silicon steel coil is not flat due to the action of thermal stress during high temperature annealing, so it must be stretched and annealed to make the steel strip flat. In addition, the excess excess coating caused by the previous process is removed, and then the insulation film is applied.

The hot leveling annealing process steps are as follows:
◆ The special coating MgO and other dirt remaining on the surface of the steel strip must first be cleaned with water and light pickling of dilute sulfuric acid.

It is then cleaned and dried. The mass fraction of sulfuric acid is 4% to 8%, and the pickling temperature is 70 to 90℃.

◆ Apply insulation layer and dry below 500℃.

◆ The coating is sintered in the nitrogen atmosphere continuous furnace, and the steel strip is stretched and levelled with appropriate tension. The annealing temperature is controlled at 830-900 ℃, which varies with the type of coating, the thickness of the steel plate and the speed of the unit. In the tensile heat leveling, the minimum tension that does not reduce magnetism and can make the steel strip flat should be selected, generally controlled at 3 ~ 6N/mm