PURPOSE: To attain high wear resistance and electric conductivity, by dispersing alumina in copper or aluminum to provide a reinforced alloy contg. dispersed grains for coating a steel core.

CONSTITUTION: Semi-molten aluminum is cooled while being stirred, so that aluminum powder is produced. The aluminum powder is mixed with about 10W 40% of alumina. The mixture is sintered and extruded so that an aluminum alloy billet containing the alumina is produced. The aluminum alloy 3 is extruded on a steel core 1 to coat it. A combined trolley wire is thus manufactured. The wear resistance of the wire is heightened by the hardness of the alumina in accordance with its content. However, if the content is too high, the electric conductivity falls. For that reason, the alumina content of the alloy 3 is normally set at 30W40%.