Fusibility

The fusibility of a material refers to the ease at which the material can be fused together, or to the temperature or amount of heat required to melt a material.^[1] Materials such as solder require a relatively low melting point so that when heat is applied to a joint, the solder will melt before the materials being soldered together melt, i.e. high fusibility. On the other hand, firebricks used for furnace linings only melt at very high temperatures (and then they retract, or decompose, or become fracture-prone) and so have low fusibility. Perhaps refractory materials often have low fusibility.

Scientific methods

To find the fusibility of certain compounds/materials, there are 2 methods:

Heat test

The most common test used to determine fusibility is to join two pieces with a variable heat source, increasing the temperature or power used in steps, and testing bond strength for each step. If there is no step with good bond strength after joining, then fusibility is said to be low.

Ash fusibility test

In the context of coal analysis, ash fusibility values of the residual coal ash of a coal are often specified. The values are determined using an empirical method based on the geometrical changes upon heating to a relevant temperature, of a conical ash sample. The fusibility of the ash is of interest because it roughly indicates the properties of the clinker that will be produced during burning.^[2]

References

1. Atkins, Tony; Escudier, Marcel (2013). A dictionary of mechanical engineering (1st ed.). Oxford: Oxford University Press. ISBN 9780199587438.
2. Riley, John T. (2007). Routine coal and coke analysis : collection, interpretation, and use of analytical data (Online-Ausg. ed.). West Conshohocken, PA: ASTM International. pp. 61-64. ISBN 978-0-8031-4515-3.