Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : October 07, 2017 - October 09, 2017
Although it is generally recognized that forgings has anisotropy in the fatigue strength, there are few reports on the relationship between the forging ratio and fatigue strength. In production, forging ratio becomes sometimes higher when the different sizes of products are taken from one ingot. It is also often in the case that the grain flow of the surface is out by machining to from the product. In this study, rotating bending fatigue tests were conducted using the specimens of four forging ratio cut out in the orthogonal direction to the grain flow. The fracture surfaces were observed with scanning electron microscope. In addition, the distributions of the size of inclusions were investigated using high-frequency ultrasonic testing. From the result of fatigue tests, it was shown that fatigue strength of the specimens of the highest forging ratio is lower than others. From the result of observation of fracture surface, the inclusions of the higher aspect ratio were included in those with higher forging ratio. From the result of high-frequency ultrasonic testing, the size of inclusions are larger as the forging ratio is higher. From the above investigation, it is concluded that lower fatigue strength of the higher forging ratio is caused by the larger size of inclusions related with the higher aspect ratio by forging.
