Research On Simulating Device For Fire Environment Atmosphere And Q235 Steel?Cu And Pure Iron Corrosion Mechanism

In the case of arson,high temperature,burning,destruction of fire extinguishers,blisters,etc.,will increase the difficulty of extracting suspected accelerants fragments,especially for volatile accelerants.At the same time,samples with low purity are not conducive to detection and identification.However,the complex fire environment can cause characteristic oxidation of metallic materials.The oxidizing atmosphere,high temperature,carbon produced by incomplete combustion,plasma in flames,and air convection caused by turbulence in the fire scene will affect the formation of oxide layers on the surface of metal materials.In this paper,a simulating device for oxidizing atmosphere in a fire site environment is built to simulate three oxidation scenarios in a fire site caused by accelerators.In addition,the oxidation behavior of common indoor materials: Q235 carbon structural steel,copper,and pure iron when ethanol and kerosene are used as combustion aids was studied.Macroscopic photographs,scanning electron microscope(SEM)and atomic force microscope(AFM)were used to analyze the surface and cross-sectional morphology of the oxide layer;energy spectrometer(EDS),X-ray diffractometer(XRD)and X-ray photoelectron spectroscopy were used XPS)and transmission electron microscopy(TEM)analysis of the phase composition of the oxide layer;using a precision analytical balance to study the oxidation kinetics of the sample.And the interface behavior of different combustion agents on different metal surfaces.The main results obtained are as follows:(1)The Fe O phase in the oxide layer is not found,when the carbon steel is oxidized in the combustion atmosphere of the accelerants,which is very different from the composition of the oxide layer when the carbon steel is oxidized in hot air.Which is related to a variety of strong oxidizing atmospheres generated by the combustion of the accelerants,that accelerates the oxidation of the metal.(2)The flame combustion causes the air convection around the sample to tear the oxide layer,which causes abnormal weight loss of the metal.At the same time,this is also the reason for the preferential growth of the(111)face grains in the Cu oxide layer,which is very different from the oxidation of Cu in ordinary hot air.(3)Incomplete combustion of hydrocarbon-based liquid accelerants will deposit carbon on the metal surface,which is mostly in the form of organic carbon,and the deposited carbon does not enter the crystal lattice of the metal substrate,which is more likely to be carbon and metal oxides form a symbiotic phenomenon.At the same time,the content of deposited carbon is related to the length of the carbon chain of the accelerants.(4)A variety of oxidizing atmospheres produced by the combustion of accelerants will form a synergistic oxidizing system,forming an effect of 1+1>2,which accelerates the oxidation of metals.At the same time,a variety of carbon-containing components in the atmosphere will also form a certain carburizing tendency on the metal oxide layer.The functional group elements(N,S,P,etc.)in the accelerates will also leave characteristic components on the metal surface during the oxidation process,which will help the identification of the accelerates in the fire.