Effect Of Ignited Supporting Surface On The Patterns Of Hot Particles From Welding

Electric welding irregularities often cause fire accidents,almost every year will cause more than a large number of fire accidents of the dead,the main investigation method through investigation and inquiry to collect witness testimony,simulation experiment as an auxiliary means of investigation,so as to identify the cause of fire.However,this kind of investigation method lacks the support of physical evidence,and the evidence chain is incomplete and easy to be questioned.Therefore,this subject takes the welding bead as the research object,adopts the method of simulation experiment and statistical analysis to observe and analyze the change of the bead s trace characteristics when it falls on different bearing surfaces,and finds out the typical trace characteristics of the bead that ignites,so as to provide physical evidence support for identifying the fire cause of this kind of fire.According to investigation and practice,choose glaze ceramic tile,polystyrene board,sawdust and absorbent cotton four bearing surfaces,respectively,represents the hard non-combustible surface,combustible in surface melting,combustible loose face and combustible loose face four typical load conditions,the bead shape and maximum diameter of statistical analysis,rough statistics each bead ignition conditions,then using field emission scanning electron microscope,the difficult to differentiate macroscopic characteristics of combustible melt in plane and ignition of the combustible loose with the ignition bead surface morphology observation analysis,try to distinguish from the details,the following conclusions:(1)at the experimental height,the welding bead directly fell on the hard ground,and since it was not completely solidified,secondary bolting occurred,resulting in its maximum diameter is less than 2.36mm,most of which are below 2mm,and its surface is(3)For the combustible collapse surface,the minimum ignition diameter is 2.05mm;for the combustible loose surface,the minimum ignition diameter is 2.75mm.Most of the welding beads show irregular shape.With the increase of the welding bead diameter,the ignition ability becomes stronger and stronger.(4)Microscopically,the weld bead holes on the hard and non-combustible surface are small and closely distributed,indicating that the solidification rate is fast;Compared with the hard non-combustible surface,the two types of electric welding bead on the combustible bearing surface,whether the ignition or not,will appear in the hole aggregation,irregular shape,wood chips dispersive hole more.According to the results of experiments and statistical analysis,it has been verified by inspection of fire cases,the ignition carries on in the face of the influence of the welding bead mark features related to research,to provide the welding work of fire science has a certain value,can be helpful for fire investigators found at the scene and extract the corresponding welding bead,analyze its ability.