Electrical steel varnishes for non-oriented grades are designed to enhance the behaviour of fully processed electrical steels. Their main purpose is to provide inter-laminar insulation and to improve the punchability of these steels. Each type has its own specific properties, such as insulation level, punchability effect, corrosion protection, temperature resistance and weldability; hence it is material use that determines the optimum choice of varnish. All varnishes have been selected and developed to be environmentally friendly: they are hydro-soluble and chromium-free.
The C5-type varnish is is the preferred varnish for automotive applications: it is a pigmented varnish, made with thermo-stable resins, mineral products and pigments. For the EC-5-N varnish, the type of mineral products and the amount used have been selected to obtain a coating with excellent temperature resistance during prolonged thermal treatments. This is of particular interest where stress-relief annealing is required after punching. Additionally, the mineral part of the coating provides high thermal conductivity. The combination of resins and mineral products achieves a good compromise between corrosion protection and weldability.
The EC-5-P has an increased amount of organic components compared to the EC-5-N, in order to achieve a better punchability, whilst maintaining a good weldability. The standard gauge range is from 0.5 to 1.5 µm per side.
These coatings are used for fully processed grades for hybrid and electric traction machines and compressors. For alternators, uncoated solutions can be used.
|ArcelorMittal name||ArcelorMittal Code||EN 10342:2005||ASTM A976:2003||IEC/CEI 60404-1-1:2004|
|Chemical composition||Inorganic (minerals, pigments)
Organic (synthetic resin)
|Gauge (µm/side)||0.5 to 1.5|
|Typical insulation resistance (Ω.cm2/side)||10|
|Temperature resistance (°C)
|Main properties||Punchability||Heat resistance|
Insulation resistance measurement: Franklin test according to the standard EN 60404-11:2013.
Continuous temperature resistance according to the standard IEC/CEI 60404-12:1992.
The raw materials used in these coatings have a chemical composition – both in the liquid and cured varnish state – which does not require specific protective measures during the processing of the coated steels or during use in a given application.