Selected insulating varnishes specially designed for each area of application
We offer excellent quality in our insulating varnish systems. In close cooperation with leading European producers, we supply insulating varnishes that meet your requirements. The varnishes do not contain any toxic, carcinogenic or mutagenic substances. The insulating varnish systems are classified in compliance with ASTM 976.
Organic insulation system
This insulation system improves punchability.
Inorganic/organic insulation system
C5 insulation systems have good weldability and resistance to annealing (under inert gas up to 850 °C).
Inorganic/organic insulation system
C6 coatings are pressure-resistant, thermally resistant up to 420 °C and thus suitable for burn-off repair.
Backlack
Self-bonding technology is an innovative joining process for the production of electrical steel stacks. By means of a controlled chemical process, the coated sheet laminations are joined cleanly and firmly into packages.
Backlack: The process that connects
The stator and rotor cores of electrical machinery are manufactured using thin sheets stacked together in order to minimize eddy current losses. The laminations must be joined in order to create a stable core. A general distinction is made between techniques integrated into the punching process (interlocking, dot bonding or face bonding) and those downstream from the punching process (welding, clamping, conventional bonding).
Using self-bonding varnish as a bonding medium minimizes processing effects, especially the effects on magnetic properties.
Face bonding is a technique used in the production of stator and rotor cores.
Fully processed and self-bonding varnish coated electrical steel is used as the basis for adhesive-bonded electrical steel cores. After the laminations have been punched, they are subjected to temperature and pressure to initiate the bonding reaction of the self-bonding varnish. Homogeneous pressure distribution within the stack is crucial to ensure uniform contact between the laminations and to minimize the risk of varnish leakage caused local pressure increase. The bonding reaction of the self-bonding varnish is achieved by heating to bonding temperature. Homogeneous temperature distribution is essential because the entire stack must achieve bonding temperature.
The processing windows for processing the self-bonding varnish in the voestalpine portfolio can be found in the Backlack Processing Guidelines.
In as-delivered condition, varnish supplied by voestalpine is in the so-called B state: In this condition, the varnish is applied to the steel strip in the desired layer thickness and is physically dried but remains chemically reactive. This reactivity is important for bondability at the customer.
Additional requirements are mandatory to ensure bondability during storage and transport. More detailed information can be found in the Backlack Processing Guidelines.
Key factors in the transport and storage of self-bonding varnish coated electrical steel are as follows:
- A limit temperature of +40 °C must not be exceeded. This limit temperature may be reached for a maximum of one month. The recommended storage temperature is +23 °C.
- The period of maximum storage is six months, beginning at the time the material is supplied by voestalpine.
- Dry storage must be ensured, and condensation must be avoided.
