Fusible alloy
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.
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 bismuth, lead, tin, cadmium, zinc, indium and sometimes thallium-containing alloys
- Other alloys (rarely used)
Some reasonably well known fusible alloys are Wood's metal, Field's metal, Rose metal, Galinstan, and NaK.
Applications
Melted fusible alloys can be used as coolants 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 reactors.
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 sprinklers 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.[1]
Low melting alloys and metallic elements
| Composition in weight-percent | °C | eutectic? | Name or remark |
|---|---|---|---|
| Cs 73.71, K 22.14, Na 4.14[2] | −78.2 | yes | |
| Hg 91.5, Tl 8.5 | −58 | yes | used in low readings thermometers |
| Hg 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 |
| 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 | −19 | no | Galinstan |
| Ga 75.5, In 24.5 | 15.7 | yes | |
| Cs 100 | 28.6 | (yes) | |
| Ga 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 |
| 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 |
| In 66.3, Bi 33.7 | 72 | yes | |
| Bi 50, Pb 30, Sn 20, Impurities | 92 | no | Onions' Fusible Alloy[3] |
| 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 |
| Bi 50.0, Pb 28.0, Sn 22.0 | 109 | no | Rose's metal |
| Bi 56.5, Pb 43.5 | 125 | yes | |
| Bi 58, Sn 42 | 139 | yes | |
| In 100 | 157 | (yes) | |
| Sn 62.3, Pb 37.7 | 183 | yes | |
| Sn 63.0, Pb 37.0 | 183 | no | Eutectic solder |
| Sn 91.0, Zn 9.0 | 198 | yes | |
| Sn 92.0, Zn 8.0 | 199 | no | Tin foil |
| Bi 100 | 271.5 | (yes) | |
| Zn 100 | 419.5 | (yes) |
See also
- List of elements by melting point
References
- ↑
Chisholm, Hugh, ed. (1911). "Fusible Metal". Encyclopædia Britannica (11th ed.). Cambridge University Press - ↑ Oshe, Ed. R.W., "Handbook of Thermodynamic and Transport Properties of Alkali Metals", Oxford. UK, Blackwell Scientific Publications Ltd, 1985, p. 987
- ↑ Jenson, W.B. "Ask the Historian - Onion's fusible alloy", J. Chem. Ed., 2010, 87, 1050-1051.
Further reading
- ASTM B774—Standard Specification for Low Melting Point Alloys. ASTM International. 1900. doi:10.1520/B0774.
- Weast, R.C., "CRC Handbook of Chemistry and Physics", 55th ed, CRC Press, Cleveland, 1974, p. F-22