Lamination Coatings

Lamination Coatings

Electrical steel is usually coated to increase electrical resistance between laminations, reducing eddy currents, to provide resistance to corrosion or rust, and to act as a lubricant during cutting. There are various coatings, organic and inorganic, and the coating used depends on the application of the steel the type of coating selected depends on the heat treatment of the laminations, whether the finished lamination will be immersed in oil, and the working temperature of the finished apparatus.

 

Very early practice was to insulate each lamination with a layer of paper or a varnish coating, but this reduced the stacking factor of the core and limited the maximum temperature of the core. 

 

ASTM A976-03 classifies different types of coating for electrical steel. 

Classification Description For Rotors/Stators Anti-stick treatment
C0 Natural oxide formed during mill processing No No
C2 No No No
C3 Organic enamel or varnish coating No No
C3A As C3 but thinner Yes No
C4 Coating generated by chemical and thermal processing No No
C4A As C4 but thinner and more weldable Yes No
C4AS Anti-stick variant of C4 Yes Yes
C5 High-resistance similar to C4 plus inorganic filler No No
C5A As C5, but more weldable Yes No
C5AS Anti-stick variant of C5 Yes Yes
C6 Inorganic filled organic coating for insulation properties Yes Yes
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