The Simulation And Experimental Analysis Of Oxygen-assisted Laser Drilling On Thick Plate

Laser drilling technology has fast processing speed, high efficiency,large ratio of depth and width，small deformation, low cost, and wideapplicability, etc. Laser Drilling have been widely used in the field ofpower electronics, aerospace and medical devices. The main object to beprocessed is the metal sheet. With the development of machiningtechnology, materials are more diverse, plate thickness of processingmaterial is increasing，its processing are also increasingly difficult.Laser drilling is a very complex process, including severe action ofheat transfer and fluid dynamics. With the hole depth increases, theliquefaction process, the molten layer of the metal material and thetemperature distribution of the sheet are difficult to be observed directly.Inorder to the liquefaction in laser drilling on thick plate and formation of thedrilling hole, a complete simulation model was established.Experimentalverification was carried out. Details are as follows:First, the area structure of the laser drilling process on the sheetmaterial was described. The drilling include a solid plate zone, the molten metal region, and the auxiliary gas-filled holes. A complete model has beenestablished considering a10mm thick mild steel plate as the researchobject. This model was including laser divergence angle, auxiliary gaspressure on the molten metal and the oxidation reaction. FEM was used forthis model to describe the formation of the hole and the thermaldistribution of the plate.Analysis of the laser drilling process, the metal sheet heated in thelaser irradiation zone and melt, the chemical reaction of liquid metal withthe oxygen in auxiliary gas, the molten metal evaporation or removal bytheauxiliary gas. The depth and width of the hole and temperaturedistribution throughout the drilling process over time. Plates melt at thebottom of the hole during a single pulse, and the liquid metal have beenremoved.Analysis of the different trends of formation of the hole shapeand drilling speed with different laser power, laser focal spot diameter anddefocusing distance during the laser drilling process. Pointed out that in thelaser drilling process, the divergence angle of the laser and thedefocusingdistancehas an important influenceon the formation process ofthe drilling hole.Experiment was designed for the verification of the simulation, forthe description ofthe holeshapeof different momentsduring the drilling process. Noted thatthe metal vapor barrier effect increased as the holedepth increases, causeddrilling speed slower.The study finds that, the laser divergence angle in simulation must beconsidered for its influence on drilling speed in thick plate; in laser drillingprocess, the drilling hole is filled with metal vapor, and these metal vaporis located in the path of laser, so the laser energy can not fully reach thebottom of the hole. With the increase of hole depth, laser energy reachesthe bottom of the hole decreases, the drilling speed reduced.Finally, a summary of the work was done, and further study in thefuture was prospected.