Insulating varnishes for the electrical steel can be broken down into classes ranging from C0 to C6. Diveng is mainly involved in supplying four classes of varnishes, namely C3 - C6, which are the most widely used types of varnishes, but we supply lower classes of varnishes as well.
C3 varnishes improve punchability of the steel, which makes it suitable for stamped laminations. This varnish can be applied on the steel that would be used in the devices and equipment that would be working at normal temperatures, not exceeding 180C, but it will not pass the stress relief annealing test.
Insulating varnishes belonging to C4 usually give a moderate insulation resistance and the coating of the steel should withstand the stress relief annealing test, but with some reduction of the surface insulation resistance. C5 varnishes usually have inorganic fillers that help to increase the electrical resistance. Sometimes C5 varnishes are applied as a topcoat, over C2 varnishes, if additional insulation is required. Steel with such a coating can be used for the cores of the power transformers, while single application of C5 insulating varnish can be applied on cold rolled motor lamination steel. Varnishes of this class will withstand stress relief annealing, assuming the temperatures will not exceed 810 – 820 C.
C6 varnishes are organic based and usually have inorganic fillers to increase the insulating properties of the varnishes. After the varnish is applied, the surface is then cured by heating. The coating will not withstand stress relief annealing, however in addition to the insulation, it enhances the punchability of the steel, which makes it suitable for stamped lamination.
Insulating varnishes for the electrical steel can be single or multi component. Majority of the steel producers prefer single component varnishes, mainly because two component varnishes have some disadvantages including additional labor costs for mixing the components, increased energy consumption, decrease in the accuracy of the right formulation, during the preparation of the varnish. Diveng mainly supplies single component varnishes, however, if requested by the customer, we can also provide two component varnishes. In addition, insulating varnishes differ in terms of viscosity, mass fractions of dry matter and PH values, among other characteristics. It is also important to mention that some varnishes might contain chromium, however due to the increased regulation and the concern for the environment, many companies prefer using chromium free varnishes.
Diveng works closely with the leading producers of the varnishes, as well as with its customers, which allows it to offer cost efficient and technologically advanced solutions. Our varnishes for the electrical steel comply with the European and North American regulations, however our varnishes are produced outside of North America and Europe, which allows us to offer competitively priced products that match the quality of the leading chemical producers. Below is an overview of some of the insulating varnishes that Diveng currently supplies (we also offer lower grade varnishes and every varnish can be adapted to the specific needs of the customer):
