Bell hammer improves the composition of the metal by friction and sliding friction of the metal to a surface with less friction.
Even after the oil and fat have diminished, the metal itself will be lubricated as long as the flat metal surface is not worn out and the basic composition does not come out.
(The state of amorphous metal has a very low friction coefficient and the life of the metal prolongs)
Therefore, it is durable even in hot places and in water.