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The material in issue is a case-hardening steel, type 20MnCr5 (UNI 8550), that has been previously undergone to a softening annealing process conferring therefore to the material one equal Hardness Brinnel 200 to 220 HB. This steel is very difficult to weld as by laser technology as by other welding technologies by fusion. It has been experienced a power at first laser of 1500 W (for requirements begins them of understanding of the process and the relative to you parameters to set up then) and of 3000 W, like previewed. They have been used a covering gas and a laser beam focusing mirror. All the welded tests have been at first subordinates to taken care of a visual examination to eye and then to an Image Acquisition System, computerized and connected to both metallographic and stereo microscope. Then cut to you with metallographic apparatus, workings to the abrasive papers and metallographic cloths, in order to end with a chemical etching of type NITAL. The best ones turn out to you have been then always visualize in shape of macro and micro-graphs, acquired with the same Image Acquisition System of type NIKON - LUCIA 4.82 vers. by LIM, to storage and automatically measure the cross-section area (melted zone) and then to calculate the efficiency level, on each joint and bead on plate, expressed in Dau unit, to verify the laser welding efficiency, correlated to the laser working parameters. To a better characterization of the produced joints many micro-hardness tests and relate family hardness trends and profiles have been carried out. At the end from the comparison of the values of ETE % and MR % (Model of Swift- Hook & Gick) and of the values of WE in Dau (Model DA.LU.), lead on some beads of the 20MnCr5, has turned out an ulterior and substantial validity and goodness (as well as easiness of employment and calculation of WE) of this last Model and Unit of Measure. In fact the values of ETE % and WE (in Dau) are appeared substantially similar, respecting both all the substantial correlations between the job parameters, to laser.
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