Magnesium alloy coiled springs (mechanical properties, spring workabilities of AZ31 wire and spring characteristics)

摘要

Recently the downsizing and the weight saving of mechanical structures asked for springs lighter, and the light metal alloys we paid attention to as spring materials. Magnesium is the lightest in the practical metals, and it is excellent in the damping capacity. But the tensile strength and the proof stress of the pure magnesium is much lower than the ones for other spring materials. Hence, it is necessary to improve its strength by alloying, hardning, heat treatment, and by other processes. The workabilities of magnesium alloy springs had not been studied, too. Therefore the authors studied the mechanical properties of magnesium alloy AZ31 and made coil springs from wires of a magnesium alloy AZ31 by a lathe type coiling machines. The workabilities of coils were studied. The effects of annealing on the dimensions of the coils and on the spring property were also studied. The main results we as follows; (1) Magnesium alloy wire AZ31 is much inferior to other spring wires, but not much inferior in specific strength because of small specific gravity. (2) It was possible to form coil of about 5.0 in spring index from wires of a magnesium alloy AZ31 by a lathe type coiling machines, so wires of a magnesium alloy AZ31 fill the workabilities as spring wires. (3) In magnesium alloy wire AZ31 the spring back of coil diameter is large compared with other spring steel wires. (4) By annealing the outside diameter increases but the free length hardly changes. (5) When the annealing temperature is over 180(℃), the elastic limit of coiled springs deteriorates.