保險絲(Fuse)是由什麼金屬/合金組成的?

FUSIBLE ALLOYS

Fusible alloys are those with melting points
below the boiling point of water (100°C). They
are used as binding plugs in automatic sprinkler
systems, for low-temperature boiler plugs, for
soldering pewter and other soft metals, for tube
bending, and for casting pattern and many ornamental
articles and toys. They are also used for
holding optical lenses and other parts for grinding
and polishing. They consist generally of
mixtures of lead, tin, cadmium, and bismuth.
The general rule is that an alloy of two metals
has a melting point lower than that of either
metal alone. By adding still other low-fusing
metals to the alloy a metal can be obtained with
almost any desired low melting point.
Newton’s metal, used as a solder for pewter,
contains 50% bismuth, 25% cadmium, and
25% tin. It melts at 95°C, and will dissolve in
boiling water. Lipowitz alloy, another early
metal, contains 3 parts cadmium, 4 tin, 15 bismuth,
and 8 lead. It melts at 70°C, is very
ductile, and takes a fine polish. It was employed
for casting fine ornaments, but now has many
industrial uses. A small amount of indium
increases the brilliance and lowers the melting
point 1.45°C for each 1% of indium up to a
maximum of 18%. Wood’s alloy, or Wood’s
fusible metal, was the first metal used for automatic
sprinkler plugs. It contained 7 to 8 parts
bismuth, 4 lead, 2 tin, and 1 to 2 cadmium. It
melts at 71°C, and this point was adopted as
the operating temperature of sprinkler plugs in
the United States; in England it is 68°C. The
alloy designated as Wood’s metal contains 50%
bismuth, 25% lead, 2.5% tin, and 12.5% cadmium.
It melts at 70°C.
Cerrobend, or Bendalloy, is a fusible alloy
for tube bending that melts at 71°C. Cerrocast
is a bismuth–tin alloy with pouring range of
138 to 170°C, and shrinkage of only 0.0025
cm/cm, used for making pattern molds. Cerrosafe,
or Safalloy, is a fusible metal used for toycasting
sets, as the molten metal will not burn
wood or cause fires. Alloys with very low melting
points are sometimes used for this reason
for pattern and toy casting. A fusible alloy with
a melting point at 60°C contains 26.5% lead,
13.5% tin, 50% bismuth, and 10% cadmium.
These alloys expand on cooling and make accurate
impressions of the molds.
The Tempil pellets are alloy pellets made
with melting points in steps of –10.8, 10, and
37.7°C for measuring temperatures from 45 to
1371°C. The Semalloy metals cover a wide
range of fusible alloys with various melting
points. Semalloy 1010 with a melting point at
47°C can be used where the melting point must
be below that of thermoplastics. It contains 45%
bismuth, 23% lead, 19% indium, 8% tin, and
5% cadmium. Semalloy 1280, for uses where
the desired melting is near the boiling point of
water, melts at 96°C. It contains 52% bismuth,
32% lead, and 16% tin.