To provide a plumb bob made of a lead-free copper alloy made of a material which is free from lead having a possibility of causing accumulation of toxicity and environmental pollution and has excellent corrosion resistance particularly in environments continuously exposed to water, such as seawater, freshwater and brackish water, and also has relatively high specific gravity.
The plumb bob is: a plumb bob made of a lead-free copper alloy having a composition consisting of, by weight, 3 to 12% Al and the balance Cu with incidental inevitable impurities; a plumb bob made of a lead-free copper alloy having a composition consisting of, by weight, 3 to 12% Al, 1 to 5% each of one or more elements from the group of Fe and Ni, and the balance Cu with incidental inevitable impurities; and a plumb bob made of a lead-free copper alloy having a composition prepared by further incorporating 0.1 to 2% each of one or more elements from the group of Mn, Sn, Ti, Si, Cr, V and Zn into the composition of either of the above plumb bobs made of lead-free copper alloy.
YAGO WATARU
YAMAMOTO KENZO
TABATA HIRONOBU
