| 摘要 |
PROBLEM TO BE SOLVED: To provide a density measuring device accurately measuring the density of a part of a sintered cold molded body especially requiring mechanical strength. SOLUTION: This density measuring method comprises: a wall thickness measuring process of measuring the wall thickness (d) of a tip 4a requiring the mechanical strength of a gear 4 obtained by cold-forging a preliminarily molded preform after sintering a compression molded article; a propagation time measuring process of radiating ultrasonic wave from an ultrasonic irradiator to the tip 4a of the gear 4 submerged in water in a water tank 10 and measuring the propagation time (t) of the ultrasonic wave by measuring the reflected wave; a density calculation process of calculating the density of the tip, using the wall thickness value and propagation time; and a determining process of comparing a density reference value of the whole forged molded body with the density value of the tip and determining goodness/badness of the molded body. COPYRIGHT: (C)2007,JPO&INPIT
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