fusible

Fusible refers to materials or devices that are designed to melt or fuse when exposed to heat or excessive current, in order to interrupt a circuit, seal a gap, or otherwise prevent damage. The term is used in both electrical and metallurgical contexts.

In electrical engineering, a fusible element is the core of a fuse, a protective device that conducts current until a rated threshold is exceeded, at which point the element melts and opens the circuit. Fuses are specified by current rating, voltage rating, and time-current characteristics, which distinguish fast-acting from time-delay types. They are widely used to protect wiring, appliances, and equipment from overloads and short circuits. Fusible links are longer, more rugged conductors used in automotive and other high-energy circuits; they burn through under fault conditions to isolate a circuit.

In metallurgy, fusible describes alloys that melt at relatively low temperatures, enabling applications such as safety devices, temperature sensing, and rapid casting aids. Common fusible alloys include Wood's metal, Rose's metal, and Field's metal, which liquify in the approximate range of 60–100°C. These alloys are chosen for predictable melting behavior and, depending on composition, varying degrees of toxicity and mechanical properties. Fusible alloys are used to create temperature fuses, thermal links, and safety mechanisms, or to fuse materials together in a controlled manner.

Fusible devices such as plugs and links are used to respond to overheating, for example in radiator safety plugs or boiler safety plugs. In standards and practice, fusible components are specified by melting point, composition, and reliability requirements, and are covered by relevant electrical, material, and safety standards that govern their design and testing.