Comparison between laser thermal effects and ablation effects with ultrashort pulses Laser on GO SiFe electrical steel

摘要

We investigate the influence of different laser parameters on Grain-Oriented electrical silicon steels (GO SiFe). Theadvanced use of ultra-short laser pulses for scribing steel sheets with magnetic domains refinement and loss reductionpurpose is proposed. The GO steel samples are commercial ones, commonly used in transformer cores. We comparelaser impact on domains refinement obtained by thermal effects (with CW and long laser pulses), with thermal-freeablation produced by an ultrashort source. The laser scribing conditions (power or pulse energy, speed and patterngeometry, size and orientation) are optimized to have minimal deformation on material surface, while maximizing theinfluence and benefits on the magnetic properties. The steels used for these experiments have got one fixed composition(Silicon Iron alloy with 3% Silicon), the sheets used have got one thickness of 0.23 mm, very big grains size around 3mm in average and one preferred lamination direction. The effects of the laser on steel samples are studied with differenttechniques, in order to show the impact on the surface topography, the metal microstructure and on the scalar magneticproperties. The confocal microscopy is used to probe the surface topography. The MFM (Magnetic Force Microscopy)is used to analyze in detail the formation of magnetic domains in the vicinity of laser patterns at the nanoscopic scale.The MOKE microscopy (Magneto-Optic Kerr Effect) is used to get images of magnetic domains at the microscopicscale. The SST (Single Sheet Tester) and the Epstein frame are used to measure the static and dynamic behavior and thepower losses with two or one directional flux at the macroscopic scale. The motivation is to find the best laser treatmentand patterns to improve the scalar magnetic properties and to reduce the energy consumption of electrical devices madewith this steel.