Application of Nd:YAG laser to aluminum alloy sorting

It is important to develop an effective sorting system of aluminum to reduce the cascade recycling of aluminum scraps by instead returning the scraps to wrought aluminum. A feasibility study has been conducted to develop a new sorting process of aluminum scraps. In this study, irradiation of an aluminum surface by pulsed Nd:YAG laser and an automatic sorting method by a pattern-matching method were tested to identify the alloy number of a aluminum scraps. For sorting test samples, seven aluminum alloys (1050, 2024, 3003, 4343, 5052. 6063, 7075) were selected from seven wrought aluminum alloy series. The surface of the aluminum irradiated and melted by a YAG laser beam. The surface morphology, including the molten area, brightness profile and change in color, was observed after irradiation. There was a difference in the surface morphology among the aluminum alloys after irradiation. The effect of laser irradiation conditions such as the defocus distance. input energy and laser irradiation angle on the surface morphology after irradiation was investigated to establish the appropriate conditions of laser irradiation for sorting aluminum alloys. It was clear that the surface morphology of aluminum seems to depend on physical properties such as thermal conductivity and liquidus temperature. Therefore, it seems possible to establish an automated aluminum sorting method by using the pattern matching method on irradiated aluminum samples.