SEM Analysis on Primary Short Circuited Melted Beads of Copper Wire

The Primary short circuited melted beads were prepared by using copper wires with different cross sections, and then heat-treated under different annealing conditions in a muffle furnace by simulating the fire scene. The influence of interference factors, such as the temperature and time in fire environment, the cooling rate, and the cross section of the wires, on the microstructures of the preformed primary short circuited melted beads were investigated systematically by using scanning electron microscope (SEM). The results show that the microstructures of the primary short circuited melted beads are influenced remarkably by the annealing conditions: the holes were reduced by increasing the annealing temperature, and the amount of the pieces form crystals increased by prolonging the heating time, and more nubby crystals were formed in the beads cooled by air. Meanwhile, the size of the grains in the beads could be changed with the cross section of the copper wires.