| Because of the low costs and large thickness processing,numerical control flame cutting machine is widely used in shipbuilding,construction of mining machinery,construction of ocean drilling platform,bridge construction and steel construction,etc.But in the actual cutting,it is common to see that steel plate cutting surface appears to collapse of edge,large roughness,poor flatness,formation of cracks and other defects.To solve the above problems,this paper completed the following research work.1.Various quality defects of steel plate cutting surface in gas flame cutting were classified and analyzed,then the related influence factors of the cutting quality defects and their mechanism were explored.2.Based on the principle of electromagnetic field on the ions generates the electric field force and Lorentz force,through the method of test in laboratory,the effect of electric field and magnetic field on the flame straight degree were be studied.The results showed that suitable electric field and magnetic field can improve the flame straight degree,thus the cutting quality can be improved effectively.When parallel plate electrode as 46 mm apart,the voltage was 2000 v,the deflection angle of electric field and parallel direction was close to 90°,the flame was the longest,and the combustion temperature was high;When magnetic field intensity was 0.6 T,the angle of N pole and horizontal was 45 °,the height of flame had no obvious change,but the combustion temperature increased.3.Based on the one-dimensional continuity equation,the problem that speed of oxygen which exited from conventional cutting nozzle was low was analyzed.According to the principle of Laval nozzle,the supersonic nozzle was designed.Research data showed that the structure can effectively improve oxygen cutting straight degree,improve the speed of cutting oxygen,improve the momentum of cutting oxygen,and improve the keeping ability of oxygen purity,it can help to improve the cutting quality.4.The flow field of isobaric internal mixing nozzle of 301-4 was simulated and analyzed by the method of numerical simulation which was used the flow field simulation software FLUENT,then the variation of cutting oxygen mass fraction,velocity and turbulence kinetic energy which were in the change of cutter axis and so on was got.Results showed that cutting oxygen' mass fraction and velocity distribution which along the axis reduced sharply in the position that apart 75 mm from the cutting nozzle,it showed cutting oxygen' purity and speed reduced sharply in the position that apart 75 mm from the cutting nozzle,the cutting oxygen' purity reduced to 95%here,the temperature and turbulence kinetic energy of the nozzle flow field in 75-150 mm range from cutting nozzle increased significantly,they were all showed that the cutting thickness limit of isobaric internal mixing nozzle of 301-4 was 75mm,when thickness of steel plate was more than 75mm,the cutting quality would be especially bad,even the steel plate can't be cut.the uniformity of simulating flow field and the actual flow field's parameters was good.5.Gantry CNC flame cutting machine of CFS-E10M was adopted to cut the steel plates that their thickness were 60 mm,through the productive test,the cutting quality of ordinary pressure type nozzle and supersonic nozzle were been compared.Experimental results showed that the flatness and roughness of cutting surface which was cut by supersonic nozzle was superior to the ordinary pressure type nozzle. |
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