With the progressively higher outputs of marine diesel engines due to their increasing size and supercharging size and supercharging equipment, their mean effective pressure is also increasing, subjecting white metal bearings, which receive major fluctuating loads from cranks, cross head pin shafts, and other important components, to extremely severe usage conditions. Under these conditions conventional white metals are prone to damage such as cracking and peeling, demanding the development of more crack and peel-proof white metals as well as higher adhesive strength with the back metal. Answering to such social and technological demands, Osaka Asahi Metal conducted research on alloy additional elements to strengthen the matrix (base) of white metals. By adding inoculate seed to increase the fineness of the deposited crystal grain, we succeeded in developing WL-2 and SC-371, that are far tougher, harder, and malleable than required by the Japan Industrial Standards.

Photo 1 is a microphotograph of WL-2, which in contrast to the standard JIS material WJ-2 shown in Photo 2, shows the well-formed balance of the needle Cu-Sn compound deposits, as well as the striking fineness of the structure. This increased fineness remarkably improves hardness, tensile strength, elongation, and resistance to abrasion.

Photo 3 shows a bending test of WL-2. After applying vertical downward pressure using a hydraulic universal testing machine on a sample bar finished to 20φ by 150L, we measured the angle θ at the breaking point. As can be seen in Photo 4, WJ-2 completely broke at a bending angle of 20゜, while WL-2 (Photo 5) sustained hairline cracks at 36°and broke at 40°. From such tests we can see that WL-2 (Photo 5) is tough against tension and compression, and that WL-2 stands apart from other white metals in its resistance against the occurrence and growth of cracks.