Kobe Steel Ltd., Japan, reports that it has recently developed a new die-forging method that increases the fatigue strength of crankshaft material by 20% compared with conventional forging. As a result, long-stroke crank throws of higher reliability and lighter weight can now be commercially mass produced for diesel engines in ships.
In engine development, ships are using larger propellers that rotate at slower speeds, driving the need for low-rpm propellers with high output. To meet this trend, long-stroke engines are growing in popularity. When long-stroke engines are used, the crank throws are longer and heavier than conventional, leading to higher load stress on the crankshaft and higher bearing loads.
Along with the development of the new die-forging method, Kobe Steel developed automatic ultrasonic inspection technology and numerical inspection technology that digitally evaluates the part where the crankshaft touches the bearing. These technologies provide substantial improvement on the reliability of the crankshafts, which face higher load stress and bearing loads when used with long-stroke engines.
In addition to the new die-forging method, Kobe Steel conducts research and development of advanced materials for marine parts. Responding to customer needs, Kobe Steel is contributing to the advancement of the shipping and shipbuilding industries.
