Study On The Fiber Laser Cutting Aluminium-lithium Alloy

Al-Li alloy is the most ideal of lightweight, high strength structural materials in the aerospace field, which enables component density decreased by 10% to 15%, the stiffness increased by 15% to 20% instead of the conventional aluminum alloys, good high temperature and low temperature performance and other features. For the high processing efficiency, narrow kerf width, perfect cutting quality, little heat-affected zone, laser cutting is suitable for the fields of high accuracy and efficiency requirements. Especially the fiber laser, which as a representative of the third generation lasers developed in recent years, has many advantages such as short wavelength and high processing flexibility over the traditional lasers. But research on Al-Li alloy which cut by fiber laser is rarely reported.In this paper, a cutting experiment of 2.0mm thick 2198 Al-Li alloy with 4kW fiber laser had been carried out, followed by measuring the slag height, kerf width and surface roughness. Then the auxiliary nitrogen pressure, focal point, the effects of laser light power and cutting speed on cutting quality were studied by single factor experiment, obtaining the optimal process parameters of continuous laser cutting mode: focal point-1.5 mm, auxiliary nitrogen gas pressure 1.6 MPa, laser light power 1000 W, cutting speed 3 m/min.On the basis of this, the cutting orthogonal test with pulsed laser type had been conducted, it showed that the material cutting quality was much more better in pulsed laser type. Meanwhile, the excellent cutting quality was obtained by the further optimized and designed process parameters resulted from the visual analysis, analysis of variance, signal to noise ratio analysis and other mathematic statistics of the orthogonal test: slag height 0.087 mm, surface roughness 4.81μm, At this point the corresponding process parameters is laser power 1000 W, cutting speed 1.8m/min, frequency 150 Hz, duty ratio 80%, auxiliary gas pressure 1.6MPa.Considering that the cutting objects are usually three-dimensional curved surface pieces, a three-dimensional laser cutting test was conducted on the basis of the above mentioned studies, and the effects of laser beam attitude and laser beam incident angle on cutting quality were studied. Then the images of molten metal to the incision frontier were collected and analyzed by means of high-speed camera technology, establishing a relational model between the cutting striation interval and process parameters, and the accuracy of the model had been verified by experiments:with the increase of laser power and auxiliary gas pressure, the cutting striation interval decreased.