46 high alloy content is not optimal for achieving the maximum flux density. Another essential property of electrical steel is strength. This can also be adjusted by increasing the alloy content and by modifying the final annealing parameters. However, it should be noted that a high alloy content complicates the manufacturability of the electrical steel, particularly its cold-rollability. For this reason, the electrical steel grades used typically contain a maximum silicon content of 3.5 wt%. In addition to magnetic and mechanical properties, there are other technical factors involved in selecting the electrical steel to be used: a crucial factor is the processability of the electrical steel into stamped parts and subsequently into stacks. Contributing factors include the uniformity in the material and geometric properties, as well as optimal surface finish. The desired final thickness is achieved during cold rolling through several consecutive rolling passes. The goal is a very uniform thickness of the finished electrical steel strip over the entire strip length, which typically lies well within the specified standard limits. The uniform thickness allows the customer to efficiently produce the stacks because the required stack height can always be achieved with a nearly constant number of laminations. The tight geometric tolerances required for motor components mean the thickness across the width of the strip is of critical importance in addition to consistency along the strip length. Only uniform thickness across the strip width enables the production of rotors and stators that are as geometrically perfect as possible from the individual, stacked laminations. To minimise eddy currents in the stack, an insulating layer must be applied to the electrical steel. This electrically isolates the individual laminations from one another within the stack. This insulating coating must also be suitable for subsequent joining processes or play a crucial role in the joining process. Deep insight | E-motor production technology July/August 2026 | E-Mobility Engineering A selection of steel grades in the triangle of core loss, polarisation and yield strength (Image: voestalpine)
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