Influence of welding parameters on temperature field characteristics during laser welding of TA15 by infrared thermography

Using an infrared thermographic technique, the temperature field during laser welding of TA15 is quantitatively measured and investigated. The influence of two welding parameters on the weld temperature distribution is analyzed and the mechanism is discussed. New conclusions are drawn that are different from conventional weld temperature distributions. For the face of the weld, changes in welding speed induce changes in the temperature distribution because of different heat inputs and the cooling effect. Similar temperature features in the welds are observed for all speeds, which exhibit a relatively low temperature area below 1 500 ℃ between the high temperature area in the position of laser incidence and the sub-high temperature area at the end of the molten pool. For the influence of laser power on the face of the weld, the temperature on the weld is higher for P = 2.8 kW compared to P = 2.0 kW, especially the temperature in the sub-high temperature area. However, for the temperature field of the back of the weld, the influence of welding speeds is quite different compared to the results for the face of the weld. The highest temperature does not locate in the keyhole area, but instead in the middle of the molten pool. And there are different temperature features at different speeds. When v = 6 m/min, the temperature field is like a uniform color belt and the temperature along the center of the weld fluctuates between 300 and 450 ℃. When v = 4 m/min, the transient temperature distribution is not uniform and is unstable at different times. However, for v = 2.4 m/min and lower speeds, the temperature field becomes stable. The influence of laser power on the back of the weld temperature field is more complex. The measured temperature does not increase with increasing laser power, which seems to conflict with the conventional thermal conduction theory. This may be related with the characteristics of the keyhole area.