Fusible alloy
Encyclopedia
A fusible alloy is a metal
alloy
capable of being easily fused, i.e. easily meltable, at relatively low temperatures. Fusible alloys are commonly, but not necessarily, eutectic alloys.
Sometimes the term "fusible alloy" is used to describe alloys with a melting point
below 150 °C (302 °F). Fusible alloys in this sense are used for solder
.
Some reasonably well known fusible alloys are Wood's metal
, Field's metal
, Rose metal, Galinstan
, and NaK
.
s as they are stable under heating and can give much higher thermal conductivity than most other coolants; particularly with alloys made with a high thermal conductivity
metal such as indium
or sodium
. Metals with low neutron cross-section
are used for cooling nuclear reactor
s.
Such alloys are used for making the fusible plugs inserted in the furnace crowns of steam boilers, as a safeguard in the event of the water level being allowed to fall too low. When this happens the plug being no longer covered with water is heated to such a temperature that it melts and allows the contents of the boiler to escape into the furnace. In automatic fire sprinkler
s the orifices of each sprinkler is closed with a plug that is held in place by fusible metal, which melts and liberates the water when, owing to an outbreak of fire in the room, the temperature rises above a predetermined limit.
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
capable of being easily fused, i.e. easily meltable, at relatively low temperatures. Fusible alloys are commonly, but not necessarily, eutectic alloys.
Sometimes the term "fusible alloy" is used to describe alloys with a melting point
Melting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...
below 150 °C (302 °F). Fusible alloys in this sense are used for solder
Solder
Solder is a fusible metal alloy used to join together metal workpieces and having a melting point below that of the workpiece.Soft solder is what is most often thought of when solder or soldering are mentioned and it typically has a melting range of . It is commonly used in electronics and...
.
Introduction
From practical view, low melting alloys can be divided up into:- Mercury-containing alloys
- Only alkali metal-containing alloys
- Gallium-containing alloys (but neither alkali metal nor mercury)
- Only bismuthBismuthBismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...
, leadLeadLead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
, tinTinTin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
, cadmiumCadmiumCadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
, zincZincZinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
, indiumIndiumIndium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...
and sometimes thalliumThalliumThallium is a chemical element with the symbol Tl and atomic number 81. This soft gray poor metal resembles tin but discolors when exposed to air. The two chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861 by the newly developed method of flame spectroscopy...
-containing alloys - Other alloys (rarely used)
Some reasonably well known fusible alloys are Wood's metal
Wood's metal
Wood's metal, also known as Lipowitz's alloy or by the commercial names cerrobend, bendalloy, pewtalloy or MCP 158, is a eutectic, fusible alloy with a melting point of approximately . It is a eutectic alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by weight. It...
, Field's metal
Field's metal
Field's metal, or Field's alloy is a fusible alloy that becomes liquid at approximately . It is a eutectic alloy of bismuth, indium, and tin, with the following percentages by weight: 32.5% Bi, 51% In, 16.5% Sn....
, Rose metal, Galinstan
Galinstan
Galinstan is a family of eutectic alloys mainly consisting of gallium, indium, and tin, which are liquids at room temperature, typically freezing at . Due to the low toxicity and low reactivity of its component metals, it finds use as a replacement for many applications that previously employed...
, and NaK
NaK
NaK, or sodium-potassium alloy, an alloy, of potassium , and sodium , is usually liquid at room temperature. Various commercial grades are available. NaK is highly reactive with water and may catch fire when exposed to air, so must be handled with special precautions...
.
Applications
Melted fusible alloys can be used as coolantCoolant
A coolant is a fluid which flows through a device to prevent its overheating, transferring the heat produced by the device to other devices that use or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor...
s as they are stable under heating and can give much higher thermal conductivity than most other coolants; particularly with alloys made with a high thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
metal such as indium
Indium
Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...
or sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
. Metals with low neutron cross-section
Neutron cross-section
In nuclear and particle physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. In conjunction with the neutron flux, it enables the calculation of the reaction rate, for example to derive the thermal power...
are used for cooling nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
s.
Such alloys are used for making the fusible plugs inserted in the furnace crowns of steam boilers, as a safeguard in the event of the water level being allowed to fall too low. When this happens the plug being no longer covered with water is heated to such a temperature that it melts and allows the contents of the boiler to escape into the furnace. In automatic fire sprinkler
Fire sprinkler
A fire sprinkler system is an active fire protection measure, consisting of a water supply system, providing adequate pressure and flowrate to a water distribution piping system, onto which fire sprinklers are connected...
s the orifices of each sprinkler is closed with a plug that is held in place by fusible metal, which melts and liberates the water when, owing to an outbreak of fire in the room, the temperature rises above a predetermined limit.
Low melting alloys and metallic elements
| Composition in weight-percent | °C | eutectic? | Name or remark |
|---|---|---|---|
| Cs 73.71, K 22.14, Na 4.14 | −78.2 | yes | |
| Hg 91.5, Tl 8.5 | −58 | yes | used in low readings thermometers |
| Hg Mercury (element) Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum... 100 |
−38.8 | (yes) | |
| Cs 77.0, K 23.0 | −37.5 | ||
| K 76.7, Na 23.3 | −12.7 | yes | |
| K 78.0, Na 22.0 | −11 | no | NaK NaK NaK, or sodium-potassium alloy, an alloy, of potassium , and sodium , is usually liquid at room temperature. Various commercial grades are available. NaK is highly reactive with water and may catch fire when exposed to air, so must be handled with special precautions... |
| Ga 61 , In 25, Sn 13, Zn 1 | 8.5 | yes | |
| Ga 62.5, In 21.5, Sn 16.0 | 10.7 | yes | |
| Ga 69.8, In 17.6, Sn 12.5 | 10.8 | no | |
| Ga 68.5, In 21.5, Sn 10 | 11 | no | Galinstan Galinstan Galinstan is a family of eutectic alloys mainly consisting of gallium, indium, and tin, which are liquids at room temperature, typically freezing at . Due to the low toxicity and low reactivity of its component metals, it finds use as a replacement for many applications that previously employed... |
| Ga 75.5, In 24.5 | 15.7 | yes | |
| Cs Caesium Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature... 100 |
28.6 | (yes) | |
| Ga Gallium Gallium is a chemical element that has the symbol Ga and atomic number 31. Elemental gallium does not occur in nature, but as the gallium salt in trace amounts in bauxite and zinc ores. A soft silvery metallic poor metal, elemental gallium is a brittle solid at low temperatures. As it liquefies... 100 |
29.8 | (yes) | |
| Bi 40.3, Pb 22.2, In 17.2, Sn 10.7, Cd 8.1, Tl 1.1 | 41.5 | yes | |
| Bi 40.63, Pb 22.1, In 18.1, Sn 10.65, Cd 8.2 | 46.5 | ||
| Bi 32.5, In 51.0, Sn 16.5 | 60.5 | yes | Field's metal Field's metal Field's metal, or Field's alloy is a fusible alloy that becomes liquid at approximately . It is a eutectic alloy of bismuth, indium, and tin, with the following percentages by weight: 32.5% Bi, 51% In, 16.5% Sn.... |
| Bi 49.5, Pb 27.3, Sn 13.1, Cd 10.1 | 70.9 | yes | Lipowitz's alloy |
| Bi 50.0, Pb 25.0, Sn 12.5, Cd 12.5 | 71 | no | Wood's metal Wood's metal Wood's metal, also known as Lipowitz's alloy or by the commercial names cerrobend, bendalloy, pewtalloy or MCP 158, is a eutectic, fusible alloy with a melting point of approximately . It is a eutectic alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by weight. It... |
| In 66.3, Bi 33.7 | 72 | yes | |
| Bi 50, Lead 30, Sn 20, Impurities | 92 | no | Onions' Fusible Alloy |
| Bi 52.5, Pb 32.0, Sn 15.5 | 95 | yes | |
| Bi 50.0, Pb 31.2, Sn 18.8 | 97 | no | Newton's metal Newton's metal Newton's metal is a fusible alloy with a low melting point. Its composition by weight is 8 parts bismuth, 5 parts lead and 3 parts tin; its melting point is 97 °C.... |
| Bi 50.0, Pb 28.0, Sn 22.0 | 109 | no | Rose's metal Rose's metal Rose's metal, Rose metal or Rose's alloy is a fusible alloy with a low melting point.-Properties:Rose's metal consists of 50% bismuth, 25–28% lead and 22–25% tin; its melting point is . The alloy does not contract on cooling.-Uses:... |
| Bi 56.5, Pb 43.5 | 125 | yes | |
| Bi 58 , Sn 42 | 139 | yes | |
| In Indium Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two... 100 |
157 | (yes) | |
| Sn 62.3, Pb 37.7 | 183 | yes | |
| Sn 63.0, Pb 37.0 | 183 | no | Eutectic solder Solder Solder is a fusible metal alloy used to join together metal workpieces and having a melting point below that of the workpiece.Soft solder is what is most often thought of when solder or soldering are mentioned and it typically has a melting range of . It is commonly used in electronics and... |
| Sn 91.0, Zn 9.0 | 198 | yes | |
| Sn 92.0, Zn 8.0 | 199 | no | Tin foil Tin foil Tin foil, also spelled tinfoil, is a thin foil made of tin. Actual tin foil was superseded by cheaper and more durable aluminium foil after World War II, and aluminium foil is sometimes confused with "tin foil" because of its similarity to the former material.-History:Foil made from a thin leaf of... |
| Bi Bismuth Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead... 100 |
271.5 | (yes) | |
| Zn Zinc Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2... 100 |
419.5 | (yes) |
Further reading
}}.- Weast, R.C., "CRC Handbook of Chemistry and Physics", 55th ed, CRC Press, Cleveland, 1974, p. F-22