Kobe Steel : KOBELCO TECHNOLOGY REVIEW (No.39)

In recent years, attention has been being paid to global environmental problems, and even higher fatigue strength is required for crankshafts used in medium-speed diesel engines for onshore power generation. Surface treatment technology is drawing attention as one of the means to achieve this. In any of the surface treatment technologies, however, a tensile residual stress, which causes a decrease in fatigue strength, occurs at the boundary between the surface treated part and the untreated part, and it is necessary to understand the residual stress distribution around the surface treated part. This paper describes the evaluation of the influence of the macro-segregation peculiar to large, forged steel, and the X-ray incident angle and incident angle setting error, generated during fillet measurement, on the accuracy of X-ray stress measurement by the cos α method. Improvement measures are also described. In addition, the effectiveness of a system that can automatically and high-speed measure the residual stress in the cold rolled fillet has been demonstrated.