| 2.25Cr-1Mo-0.25V low alloy bainite steel with characteristic of high strength, heat resistance, high plasticity and resistance of hydrogen corrosion is the key manufactured materials of hydrogenation reactor in petrochemical industry. With the development of petrochemical industry, the size of hydrogenation reactor is becoming bigger and the properties of material is becoming increasingly demanding, which makes high efficient machining of 2.25Cr-1Mo-0.25V steel becoming more difficult.In order to improve production efficiency and to prolong the tool life in the processing of hydrogenation reactor cylindrical shell, material and geometric parameters of tools and cutting parameters were optimized by intermittent turning experiment and finite element simulation. The cutting principle and failure mechanism of different tools in different machining conditions were studied. Experimental data and theoretical guidance were provided for efficient machining of 2.25Cr-1Mo-0.25V steel.The cutting parameter was optimized by orthogonal experiments of intermittent cutting of 2.25Cr-1Mo-0.25V steel with uncoated cemented carbide YT5, the influence of cutting parameter on material removal amount and cutting force and the failure mechanism of tools with different cutting parameter were analyzed. The optimized cutting parameter was v=50m/min,f=0.5mm/r, ap=1.2mm. The empirical equations of material removal amount and cutting force were set up.The tools life and cutting force of cemented carbide YT5 tool and coated fine grain cemented carbide GC4235 tool in same cutting parameter were compared, the failure mechanism of tools were analyzed. The results showed that the cutting performance of GC4235 coated tool was much better than that of YT5 tool. According to this result, the tools life, cutting force and failure mechanism of coated cemented carbide GC4235 with different geometrical shape (quadrate one, rhombic one, circular one) were mainly compared. The results showed the cutting performance of quadrate GC4235 tool was better than that of rhombic and circular tools in intermittent cutting of 2.25Cr-1Mo-0.25V steel.It was finally focused on the cutting parameter optimization of quadrate GC4235 through the orthogonal experiments in intermittent cutting of 2.25Cr-lMo-0.25V steel, the failure mechanism in different cutting condition was also investigated. The result showed that with the optimal cutting parameter of v=50m/min,f=0.4mm/r,ap=3mm, the amount of material removal reached to the maximum in this study. The cutting performance of quadrate GC4235 tool was also good with the cutting parameter of v=100m/min,/=0.3mm/r, ap=3mm, which can get high cutting efficiency and a long tool life. Thus it can be concluded that the quadrate coated cemented carbide GC4235 tool was fit for efficient intermittent cutting of 2.25Cr-1Mo-0.25V steel with the cutting speed ranged from 50m/min to 100m/min. The empirical equations of material removal amount and cutting force were set up.The mechanism of negative shear and deflection of shear angle was simulated by AdvantEdge FEM software, the influence of cut-out angle and rake angle on the stress condition of tools in intermittent cutting was studied. The result showed that deflection of shear angle always appeared with different cut-out angle and rake angle; however negative shear appeared while cut-out angle was in a certain range. While negative shear and deflection of shear angle appeared, the stress condition of nose of tool changed severely which result in the breakage failure of tool in intermittent cutting.*This thesis is supported by National High Technology Research and Development Program of China (863 Program) (2009AA044302) and Natural Science Foundation of Shandong Province (2009ZRB01385). |
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