| Titanium alloy has excellent comprehensive performance and is widely used in aerospace,aviation,weapons and other military fields.However,titanium alloy is difficult to process because of its low thermal conductivity and serious work hardening.With the development of laser processing technology,laser cutting technology has been introduced into titanium alloy processing,laser cutting has the advantages of fast cutting speed,small slit width and so on.During laser cutting,due to the area near the incision is heated,it is easy to cause a large range of heat affected zone,which has a certain impact on the material properties.The introduction of high heat flow cooling technology can effectively reduce the range of heat affected zone and improve the processing quality.Spray cooling technology has the advantages of strong heat dissipation,good temperature uniformity and long stability time,which is widely used in electronic components,aerospace and other fields.There are few researches in laser cutting field.Therefore,in order to explore the influence of spray cooling on laser cutting processing,TC4 high temperature titanium alloy was selected to study the laser cutting processing under atomization conditions.The main research content is as follows:(1)Based on the literature at home and abroad,the research status of high heat flow cooling technology and solution assisted laser processing is reviewed.The principle of laser generation is briefly introduced,the energy transmission characteristics of traditional laser cutting and water-assisted laser processing are analyzed,and the mechanism of spray cooling process is summarized.(2)Based on the discrete phase model,the Gaussian heat source was loaded by the udf function,and the spray cooling model was established.The finite element method was used to analyze the cooling effect and spray characteristics of the Gaussian heat source under different atomizing pressure,spray outlet velocity and nozzle height.The simulation results show that the cooling effect of heat source surface can be improved with the increase of atomizing pressure,the increase of spray speed and the decrease of nozzle height.(3)The laser cutting test of 2.5mm thick TC4 high temperature titanium alloy was carried out under atomization condition.The influence of single parameter change on cutting quality under atomization condition was analyzed by single factor test.Through orthogonal test and response surface analysis,the laser parameters under atomization conditions are optimized.The results show that when the laser power is1600 W,the cutting speed is 2000mm/min,and the air pressure is 0.9Mpa,the cutting surface roughness is 4.373μm,the cutting width is 0.2mm,and the hanging slag length is 0.101 mm,which is close to the lowest.(4)The optimal parameters were used for laser cutting of TC4 high temperature titanium alloy with or without atomization conditions.The cutting quality,heat-affected zone range,hardness and metallography of two cutting specimens were compared,and the influence of atomization conditions on laser cutting of titanium alloy was summarized.Through comparison,it is found that atomization conditions can reduce the cutting surface roughness and hanging slag length,and the range of heat affected zone is obviously reduced,and the highest hardness of heat affected zone can reach 450 HV,slightly higher than the hardness of heat affected zone without atomization.From the perspective of the microstructure of the heat affected zone,the martensite in the heat affected zone is finer under the condition of atomization,which promotes the dislocation hindering effect during the deformation of the material.Figure [49] table [19] reference [103]... |
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