Project

Study on Annealing Effect of Ultrathin Electrical Steel with Control of Strip Tension

Tension annealing of thin electrical steels allows for greater tailoring of grain size and crystal texture, improving magnetic properties

Completed

Technical description

Ultrathin Fe–Si alloy sheets have some benefits in high frequency application such as high magnetic flux density and low-cost fabrication. This project studies the effect of applied tensile stress during annealing on grain growth and primary recrystallization texture formation in FeSi ultrathin alloy with thickness below 0.2mm. A custom tension annealing system was designed and built at Pitt to anneal samples at tensions over 15MPa and over 1000°C. Through tension and temperature optimization grain size and orientation can be tailored. XRD and EBSD was used for phase identification and grain size. Lake Shore VSM 8604 was used for rotational tests, observing the magnetization change at different angles.

Strain annealing system designed and manufactured at Pitt for electrical steels and ribbon samples.
Example of magnetization and angle dependance for a strain annealed electrical steel sample

Why it matters

  • Better-controlled texture in thin Fe-Si sheet can mean lower core loss, supporting smaller, lighter, more efficient motors and transformers.
  • A tension-annealing route could give manufacturers a new way for tailoring grain structure without changing alloy chemistry.