Product Code: ICA13_801

The Full Spectrum Absorptance of Engineering Grade Metals with Diverse Surface Appearances
Authors:
Heng Zhao, Institute of Laser Engineering, Beijing University of Technology; Beijing Peoples Republic of China
Dongyun Zhang, Institute of Laser Engineering, Beijing University of Technology; Beijing
Rui Wu, Institute of Laser Engineering, Beijing University of Technology; Beijing Peoples Republic of China
Congyang Li, Institute of Laser Engineering, Beijing University of Technology; Beijing Peoples Republic of China
Presented at ICALEO 2013

Acquisition of the as-received industrial material absorptance of light is important for guiding the laser machining processing. However, most of the published absorptance data presently used take only polished pure metals into account rather than the engineering grade alloys which are actually being processed with diverse surface appearances in manufacturing. Moreover, the previous studies usually aimed at measuring a single wavelength laser absorptance, though there are various kinds of lasers in practical application.

In our study, we achieve the full spectrum(200-1050nm) absorptance of various types of engineering grade metals. The samples used include machining stainless steels and titanium alloys by turning and grinding, and vertical milling and plane abrasion steel reference blocks, whose surfaces present distinct microstructures and have different roughness. The measurements were made using an integrating sphere plus spectrometer with halogen and deuterium light source so that they could provide a wide incident spectrum(200-1050nm). Surface 3D microstructure figure and associated 2D roughness curve were obtained using a LSCM(laser scanning confocal microscope).

Some clear trends were found in our measurement results. For all ferrous alloy samples, respectively, the absorptance increased when the wavelength value decreased. As to the titanium alloy, it appeared a more complicated trend through the results, that was, the absorptance firstly decreased and then began to go up along with the decreasing wavelength.Meanwhile, for reference block samples, an explicit trend correlating absorptance with roughness was discovered that the absorptance of samples which were under the same processing method increased for roughness rising. However, for turning titanium alloys and stainless steels, the trend proved to be opposite. It presented a significant decrease of absorptance for an increasing roughness. Further study indicates that this result was due to the influence of different surface periodic microstructure. In addition, at the similar roughness value, the absorptance of a same material using grinding or plane abrasion was considerably higher than that of using turning or milling. This may help improve the materials' practical machining parameters for laser processing.