Study and redesign of high temperature batch annealing furnace for production of grain oriented electrical steel

Grain oriented electrical steel coils are batch annealed at 1200°C to develop the magnetic properties of the strip. Temperature gradients are known to exist within the coils, which can affect the three important reactions occurring in the steel during annealing. These gradients result from the anisotropic conduction properties of the coil and the application of furnace heat. Heat is applied from the furnace to the coil in the radial direction. Studies of the conduction properties of an electrical steel coil have shown that the radial coefficient is ∼20% of the axial coefficient. Computational fluid dynamics was employed to simulate a furnace redesign, comprising increased axial heating and a larger coil size. The results show that the annealing cycle time may be shortened and annealing conditions simultaneously improved. The difference between process requirements and process performance can be significantly narrowed by use of the redesigned furnace.