Why is cleaning required after slitting silicon steel sheets?

Why is cleaning required after slitting silicon steel sheets?

1.  Removing processing oil residues to prevent magnetic property degradation 

During slitting, the high-speed friction between the slitting machine's blades and the silicon steel sheets generates heat. Rolling oil or cutting oil is sprayed to cool and lubricate, preventing surface scratches on the sheets and blade wear. However, residual oil residues cause two critical issues:

Damage to core insulation layers: The silicon steel sheet surface carries an inherent insulating coating (e.g., magnesium oxide coating, organic insulation layer) designed to reduce eddy current losses between laminations (a primary source of transformer core losses). Oil residues can cover or corrode this insulation coating, causing interlaminar insulation failure and a significant increase in eddy current losses (measured to increase iron losses by 5%-15%), thereby undermining the transformer's energy-saving design objectives.

High-temperature carbonisation affects magnetic permeability: Following core lamination, the core undergoes annealing at 700–850°C (to relieve stress and restore silicon steel's magnetic properties). Residual oil carbonises at high temperatures, forming black residues that infiltrate the silicon steel sheet surface. This disrupts the grain structure, reducing magnetic permeability and increasing coercivity, directly impacting the transformer's no-load current and load losses.