Identification on the Fuse Fracture Properties of Electro thermal Apparatus

In the fire scene, the fracture trails of fuse were often found. There are various reasons of fracture, such as outside mechanical force, melting fracture due to overheating, short-circuit and high temperature of fire. By the fuse fracture experiments of daily electrothermal apparatus and corresponding trace analysis; this paper summarizes an identification method of fuse fracture properties, which can provide technical support for the investigators to identify the cause of the fire. Trace traits can be applied to the macro method and metallographic method. By macro method it is seen that the cut edge of mechanical force and tensile fracture is right or sharp-angled form. Traces ends formed under the condition of short-circuit are most spherical. The shape of trace formed by high temperature of fire is between the traces shapes of the above, a smooth, but less spherical shape. Using metallographic method, untouched region by the temperature of ruptured fuse by mechanical force is observed with the ferrite microspheres small equiaxial crystal. Deformation organization is noticed of tensile fracture and cut of fuse fracture place. While the microstructure in the high temperature effect is the equiaxial crystal, and the microstructures of short-circuit fusing in molten mark end (or local) show big grain boundaries, inner of which still has not neat columnar crystal, in addition, there is an obvious transition region between the melting parts and matrix.