Taisei Nakayama

Effects of manganese and sulfur contents and slab reheating temperatures on the magnetic properties of non-oriented semi-processed electrical steel sheet

The effects of manganese and sulfur contents and slab reheating temperatures (SRTs) on the magnetic properties of non-oriented semi-processed electrical steel sheets were investigated. The core loss W15/50 of the steels increases with an increase of sulfur content in each steel with different manganese contents, while, the magnetic induction B50 hardly changed with an increase of the sulfur content at any manganese level. The SRTs affect the core loss in steels without hot band annealing, and in steels processed at an SRT of 1273 K showed the lowest core loss. Steels with higher sulfur content processed at an SRT of 1523 K showed deterioration of the core loss caused by the retardation of the grain growth at the recrystallization annealing by the fine MnS (ca.0.1 μm in diameter).

Effects of vanadium on magnetic properties of semi-processed non-oriented electrical steel sheets

The effects of vanadium inclusions on the magnetic properties of non-oriented electrical steel sheets were investigated. The magnetic induction and core loss of test specimens deteriorated at a vanadium content of 0.016 wt%. Electron microscope study revealed that the deterioration was caused by the “pinning effects” of vanadium carbonitrides on the recrystallization of cold-rolled sheets.

Interlocking Performances on Non-Oriented Electrical Steels

Interlocking performance as fastened strength and magnetic deterioration by interlocking were investigated. The thickness of a surface insulation coating affected the interlocking fastened strength. Sheets with a thin coating resulted in a better interlocking performance than those with a thick coating due to the lubricating effect by resin as coating materials. Sheet gauge affected the interlocking fastened strength. The fastened strength of thin gauge sheet was less than that of a thick one, because of the reduction of the sticking area of interlocking protuberances. The protuberance shapes affected the fastening strength. The rectangular types are stronger than the circular ones, due to the ‘hooked by corners’ effect. Magnetic deteriorations by interlocking was caused by the core loss increased by the obstruction of magnetic flux flows and eddy current loss through the laminations. The core loss increased by the eddy current loss through the laminations was 78% of all deterioration by interlocking.

Effect of zirconium on the magnetic properties of nonoriented semiprocessed electrical steel sheet

The effects of zirconium precipitates on the magnetic properties of nonoriented semiprocessed electrical steel sheets were investigated. Core loss of the test specimens declined for zirconium contents of 0.01 wt.%, whereas the magnetic induction did not change due to the addition of zirconium less than 0.133 wt.%. Precipitates and texture studies revealed that the zirconium precipitates had no effect on the grain coarsening at hot rolling and after final annealing after being cold rolled.

Effect of antimony surface treatment on nitrogen absorption during batch annealing of an electrical steel sheet

Nitrogen absorption is usually observed during batch-type hot-band annealing of electrical steel sheets containing aluminium. This nitrogenizing causes the deterioration of magnetic properties, such as core loss and induction. In order to prevent nitrogenizing, we investigate an antimony treatment on the hot strip surface of electrical steel sheets containing aluminium. Potassium antimonyl tartrate and colloidal antimony oxides (Sb2O5) are effective against nitrogenizing. It seems that active sites on the surface of the hot strip after pickling are covered with antimony oxides to block the adsorption of nitrogen. Magnetic properties, after cold-rolling and continuous annealing of the nitrogenizing hot band, deteriorate due to small grains near the surface whose boundaries are pinned by aluminium nitrides.