Study On The Solid Pulse YAG Laser Equipment And Cutting Techniques

Based on the numerous advantages of the laser, the exploitation of laser equipment and the progress of laser processing techniques is changing the traditionary processing techniques. So the manufacture of the high-power YAG laser and the laser process of the nonferrous metal is an important task. In this paper an industrial solid pulse YAG laser and the processing instrument were manufactured, the cutting tests of the AZ31 magnesium alloy and the 5A06 aluminum alloy were carried out, and micro-photographs were taken, the cutting processing and the formation mechanism of the surface appearance of the kerf were analyesd and discussed.During the manufacture of the laser processing equipment, the four key techniques of the high-power solid YAG laser design were established. A finished product of the high-power solid pulse YAG laser was obtained. The structure was adopted in the part of the machine tool, which was composed of the plane worktable, the crossbeam, the rolling setup and the distance follow-up assembly. It was controlled by the numerical control system, the combination of the laser power supply, the cooling system and the four axes servo system of the machine tool was come true. The fuction of the whole laser process system was perfected, and the every index of the using requires was met.After testing the power of the laser, the average power, the energy of the pulse and the peak power were greatly affected by the voltage; they were increasing with the increase of the voltage and the width of the pulse. The average power of the laser was affected by the frequency, but little of the energy of the pulse and the peak power. The maximum of the average power of this laser was reached 486 W, the energy of single pulse was 83.8 J, the peak power was 9200 W. The maximum of the energy transforming efficiency of this laser reached to 4.1 %. The beam parameter product K_f was calculated to 16.5 mm·mrad. The minimum of the diameter of the focused facula was 17μm through the perforating test.The laser cutting tests were carried out on the thickness of 4mm of AZ31 magnesium alloy. The width of the kerf was affected by the voltage, the width of the pulse, the power and the focus position. The back leavings of the kerf were affected by the voltage and the width of the pulse. A remelting layer was formed in the 1/4 place of the kerf surface to the upper surface of material in the laser cutted the magnesium alloy used Ar, which maximal thickness was 120μm. Many minute cracks were distributed on the remelting layer, which expanding depth was 140μm. There was no clear heat affected zone on the boundary of the remelting layer and based material. The same kind of matters and phases - Mg matrix and Al₁₂Mg₁₇ precipitate was achieved in the remelting layer and the base metal. The micro-hardness of the remelting layer was increased from inside to outside, the hardness of the HAZ closed to boundary of the remelting layer in the side of the base metal was higher than the base metal.The cutting quality of the laser to the magnesium alloy was greatly affected by the kind of the assistant gas. As a whole, Ar, N₂ and O₂ were in turn chose as the assistant gas, the cutting quality became worse. Thereinto, the width of the kerf used O₂ was wider, and the oxidation of the surface and the back side was badly.The thickness of 4 mm of the AZ31 magnesium alloy was cutted by air plasma-arc cutting, compared with the laser cutting, its width of the kerf was four times than that of the laser. And the oxiadation of the cutting surface was easier; the thickness of the remelting layer was thinner. There were lots of the pores in the remelting layer, but no cracks. The heat affected zone was clearly found, which thickness reached 50μm.The laser cutting tests were carried out on the thickness of 4mm of 5A06 aluminum alloy. The width of the kerf was greatly affected by the power, the efficiency and the focus position. The back leavings of the kerf were more, and there was no oxidation. Compared with laser cutted magnesium alloy, the remelting layer was formed on the fracture surface; there were lots of the minute cracks and little of the pores. The heat affected zone was not clear. The width of the kerf of the air plasma-arc cutting was four times than laser cutting; its perpendicularity was more the decuple. The thinner remelting layer was formed on the aluminum alloy cutted by the air plasma-arc, the maximum was 30μm, there was also no clear heat affected zone.