电火场铜导线熔痕形态特征的识别

Identification of morphological features of copper wire melting trace caused by an electric fire

通过扫描电镜对电火场中铜导线熔痕宏观及微观形态特征进行识别,为火灾的鉴定工作提供科学依据。火烧熔痕与短路熔痕特征主要区别是:火烧熔痕线径是短路熔痕线径的2倍;火烧熔痕与导线连接处有明显的温度过渡区而短路熔痕没有;多股导线火烧熔痕铜丝呈粘连态,多股导线短路熔痕铜丝呈分散态;火烧熔痕表面和内部均没有孔洞,短路熔痕表面和内部分布着大量的气孔和缩孔。一次短路熔痕断面上的孔洞直径较小,数密度较大,分布较均匀,二次短路熔痕断面上的孔洞直径较大,数密度较小,分布不太均匀。

Micro-characteristics and macro-characteristics of copper wire melting trace are observed by scanning electron microscopy（SEM） in order to provide a scientific evidence for the identification of elec- tric fire. The main differences between melting traces due to fire burning and short-circuit arethat the diameter of fire burned melting trace is about twice as that of the melting trace formed by short-circuit. Secondly there is a remarkable temperature transition region at the place where the fire burned melting trace connects with the wire, but there is no such a temperaturetransition region at the place where the short-circuit melting trace connect with the wire. The cores of copper wire burned by fire are adhered to each other, while the cores of copper wiremehing trace caused by short-circuit are separated from each other. There are no holes on the surfaceor underneath of fire burned melting trace, but there are plenty ofgas and shrinkage porosity on the surface or underneath of short-circuit melting trace. The holes on cross-section of first short-circuit melting trace are of a shorter diameter, higher numerical density, more evenly distributed, while the holes on the cross-sections of second short-circuit melting trace larger, with a smaller numerical density, and less evenly distributed the and are