AZ91Dマグネシウム合金製ダイカスト薄肉塗装材のリサイクル Recycling of thin walled AZ91D magnesium alloy die-castings with paint finishing
A new recycling process for the thin wall AZ91D magnesium die-castings with paint-finishing was developed in order to avoid contamination by impurities and the generation of harmful gases. Slow heating up of the scrap from room temperature results in generation of a large quantity of harmful gases. However, when a virgin ingot with the same weight as the scraps is firstly melted and then scraps are directly charged into the melt, the generation of the harmful gases are extremely reduced. But some of the involatile ingredients of the paint contaminate the melt. Therefore, a sound ingot is successfully produced by increasing the killing time after the flux treatment and removing the slug from the top and bottom of the crucible before casting. Tensile properties of the recycled ingots satisfy the JIS values. The ingot recycled from scraps of the components of video for non-professional use indicates the same level of corrosion behavior with the virgin material. Whereas the ingot recycled from scraps of those for professional use shows a poor corrosion behavior. The paint film of the professional use video components is thick and, therefore, impurities such as Fe, Ni and Cr from undercoating and paint remarkably contaminate the melt. This increases the amount of crystallized Al–Mn compound containing these impurities. As a result the recycled ingot from scraps of the professional use video components exhibits the poor corrosion behavior.
軽金属 48(1), 19-24, 1998-01-30
The Japan Institute of Light Metals