The Study On Characteristics Of Infrared Radiation During Laser Welding Of TA15

Compared with traditional methods, laser welding has advantages, such as high energy density, high depth-to-width ratio, a narrow heat affected zone, narrow heat affected zone, low welding deformations, high production efficiency and automation. Due to the rapid development of high-power laser, laser welding technology has developed rapidly in the field of aerospace, energy, ship, electronics and other industries, and becomes one of the most promising manufacturing technologies in the 21st century. Because of the extensive application of laser welding in these important areas, the requirements of welding quality are more strictly; the online monitoring techniques of the welding quality are becoming increasingly significant.In this paper, a CCD camera and infrared radiation monitoring system are used to systematically record the images of the molten pool, the surface and back molten pool, as well as the relative intensities of the infrared radiation during laser welding of high strength structural TA15 Ti-alloy aerial materials. Respectively, the size of molten pool will be calculated through professional software. The results show that in the quasi-stable state welding process, Ti-alloy laser welding process of light radiation signal is mainly from three regions, namely the vapor/plasmas, keyhole and molten pool area. Their respective peak wavelength of the radiation and the frequency varies.Analyzed the original signal of infrared radiation the surface and back, the signal along the whole weld seam is divided into three phases:the starting state of welding, the quasi-stable state, and the arc suppressing of welding. This article adopts the method of digital filtering to reduce the influence of radiation signals of the vapor/ plasma keyholes by analyzing the signal, and mainly focuses the infrared radiation from the molten pool.In this paper, a set of experiments were completed by using diverse weld heat input, while other parameters keep constant. By quantitatively analyzing the rule, it can be found that the area of molten pool regularly varies along with the heat input, meanwhile the relative intensity of infrared radiation signal linear changes along with the heat input. the results showed that:power pool with the welding line present law of change, while infrared light is also linearly with the change of heat input. Results indicate that there are the same regularity existing between molten pool and relative intensities of infrared radiation, so the infrared radiation could instead of pool area for further study.Based on these, the results after analyzing the test about different thickness on the plates showed when the material thickness changes, the final pool and infrared radiation also have a distinction even if the heat input keeps the same, the results of full penetration laser welding is mainly determined by the heat input and metal thickness. Compared the gas shielding between Ar and He, it can be found that the gas shielding makes little impact on the area of molten pool, The experimental results show that the temperature of molten pool and keyhole has a close relation with the gas shielding, but they have the same varying rules, correspondingly the range of infrared radiation varies. At the same time during the monitoring the back of the welding,the signal changes little when the heat input is low, but it changes obviously when the welding is between a penetrating keyhole and un-penetrating keyhole process. We can monitor the unstable penetrating keyhole and welding process by using infrared radiation signal.In a word, during full penetration laser welding process, the relative intensity of infrared radiation and the molten pool have a fairly consistent regular pattern, Therefore, we can monitor changes about the area of molten pool and stability of welding process quite exactly. More research can offer a theoretic foundation and practical method for high quality control of the welding process in the future.