Philippe Baudouin

Effect of laser cutting on microstructure and on magnetic properties of grain non-oriented electrical steels

Non-oriented electrical steels have been cut with two different techniques, the laser cutting and the mechanical cutting. In order to investigate the effect of the first technique on magnetic properties, different cutting parameters have been tested. Despite this, the best magnetic properties have been obtained after mechanical cutting. The laser cutting causes a coercive field increase and a permeability drop. Due to thermal effect, internal stress seems to be the main process drawback. No correlation between the heat affected zone and the magnetic properties has been found.

The effect of the guillotine clearance on the magnetic properties of electrical steels

Measurements of the bulk magnetic properties of four non-oriented electrical steels after guillotine cutting with varying clearances are reported. A heterogeneous state of deformation is observed at the sheared edge. The deformation-affected zone extends to several millimeters away from the cut edge and possibly occupies the entire sample volume. An obvious correlation was established between the clearance of the guillotine cut and the general deterioration of the magnetic properties such as the total core losses (at 50 Hz), the coercive field, the relative permeability and the remanent induction. The existence of a transition zone was demonstrated in the range of applied clearances for which the magnetic properties were severely deteriorated. This clearance transition zone corresponds with the drastic change of one shearing parameter: the knife displacement at fracture. The observed effects are discussed in terms of the strain heterogeneities that are introduced in the sample by the guillotine cutting process.

Induced stresses due to the mechanical cutting of non-oriented electrical steels

In this paper numerical and experimental results are presented regarding the definition of the deformation-affected zone due to punching. Measures to reduce this zone are considered.

Magnetic local investigations of non-oriented electrical steels after tensile deformation

Abstract The experimental results of investigations of non-oriented steels after tensile deformation are reported. The steel samples were tested using the magnetovision method and the single strip tester. The applied deformation was up to 15% but the most significant changes were detected in the first step—at 0.5%. In several cases it was observed that after stress the homogeneity of the structure of the samples was destructed.

Simulation of the HAZ and magnetic properties of laser cut non-oriented electrical steels

Abstract An attempt has been made to simulate the heat-affected zone observed in laser cut samples in order to investigate the influence of laser cutting on the magnetic properties of electrical steels. The thermal cycles, after experimental calibration, are calculated from the Rosenthal modeling. The cycles have been reproduced in massive samples in order to characterize both the microstructure and the magnetic properties of high- and low-alloyed silicon steels. Results show the harmful effect of the bainite and the thermal stresses on the magnetic properties.

Effects of laser and mechanical cutting modes on the magnetic properties of low and medium Si content nonoriented electrical steels

Nonoriented electrical steels have been cut using pulsed or continuous-laser techniques and mechanical cutting has been used as a reference. The corresponding states of internal stresses at the cut edges have been systematically investigated by X-ray diffraction, for both laser and mechanical cut samples. The characteristic magnetic properties measured at 50 Hz and 1.5 tesla, total weight losses P, coercive field Hc, remanent induction Br, and maximum differential permeability /spl mu/, have been determined. Results tend to prove the superiority of mechanical cutting for the larger samples. Whereas higher thermal stresses were induced when using the laser-pulsed mode, magnetic properties were less deteriorated compared with the continuous-laser cutting technique.

Effect of the rapid heating on the magnetic properties of non-oriented electrical steels

Abstract Measurements of the bulk magnetic properties for two non-oriented electrical steels after a rapid heating are reported. A deterioration of the magnetic properties was observed for the fully processed non-oriented grade and an improvement for the semi-processed non-oriented grade. This publication emphasizes the effects due to the competition between the increase of the grain size and the appearance of thermal stresses during the rapid heating on the magnetic properties of the steels.

The study of two different strain paths on the deterioration of the magnetic properties of non-oriented electrical steels

Measurements of the bulk magnetic properties at 50 Hz are reported for non-oriented electrical steels after a uniaxial or a cold rolling deformation. The importance of the used strain paths on the deterioration of the magnetic properties has been emphasized, showing that the cold rolling deformation is generally less harmful for the magnetic properties than the tensile deformation.

Effects of two laser cutting modes on the magnetic properties of low and medium Si grain non-oriented electrical steels

Summary form only given. Laser cutting is a non-contact cutting technique, which also provides flexibility for the design of electrical components. Therefore it can appear as the ideal technical solution for electrical steels manufacturers. Nevertheless the laser cutting deteriorates more of the magnetic properties of the electrical steels than mechanical cutting. The magnetic properties have been measured on one mini-SST especially built for non conventional magnetic measurements. 3 grades have been selected, 2 fully-processed (FP): SC and EB with respectively 0.31 and 2.98% Si and one semiprocessed (SP): EC with 2.32% Si. The magnetic properties for EC after laser and mechanical cuttings are equivalent for all the samples. On the contrary, the 2 FP grades EB and SC are sensitive to the different modes of laser cutting. The obtained results emphasize the superiority of the SP grade EC and the difficulty to keep the magnetic quality of FP grades. Nevertheless the different magnetic behavior after laser cutting of coercive field (Hc), remanent induction (Br) and the maximum relative permeability (/spl mu/) for EB and SC points out the importance of the modes (pulsed or continuous) on the induced thermal stresses. An optimization of the laser parameters is thus possible.