Hirotsugu Kawanaka

Laser narrow gap welding of thick carbon steels using high brightness laser with beam oscillation

Laser narrow gap welding with beam oscillation was developed to prevent lack of fusion and hot cracking in the welding of thick steel plates. The weld qualities of carbon steel joints with a thickness of 60 and 150mm were examined in this work. The results show that beam oscillation condition, especially oscillation amplitude affects soundness of the weld, and must be adjusted by considering the change in groove width to avoid lack of fusion on the side wall of the groove. In addition, geometry control of each weld bead in build-up welding is required to avoid solidification cracking of weld metal. Mechanical properties of the joints such as tensile strength, ductility, hardness distribution and toughness were also evaluated, and confirmed to meet product requirements. Beam oscillation in narrow gap welding with high power laser has a great potential to improve weld qualities of large scale weld structure.Laser narrow gap welding with beam oscillation was developed to prevent lack of fusion and hot cracking in the welding of thick steel plates. The weld qualities of carbon steel joints with a thickness of 60 and 150mm were examined in this work. The results show that beam oscillation condition, especially oscillation amplitude affects soundness of the weld, and must be adjusted by considering the change in groove width to avoid lack of fusion on the side wall of the groove. In addition, geometry control of each weld bead in build-up welding is required to avoid solidification cracking of weld metal. Mechanical properties of the joints such as tensile strength, ductility, hardness distribution and toughness were also evaluated, and confirmed to meet product requirements. Beam oscillation in narrow gap welding with high power laser has a great potential to improve weld qualities of large scale weld structure.

Adaptive shape control of laser-deposited metal structures by adjusting weld pool size

LMD (Laser Metal Deposition) is a technique used to repair damaged components and directly form three dimensional structures. From the aspect of productivity, improvement of the shape accuracy of the deposit is required to reduce machining process after LMD. Objective of this work is to control the build-up shape by adjusting the weld pool size. Configurations of deposits made with various LMD process conditions were measured in cross section. In addition, the signal intensity of heat radiation, plume emissions and laser reflections from the weld pool was monitored by photodiodes intergrated in laser processing head during LMD process. The results showed a strong correlation between weld pool size and signal intensity of heat radiation. Adaptive shape control system, which consists of in process monitoring system and PID (Proportional-Integral-Derivative) controller using that correlation, was developed to control build-up shape. Due to the liner relationship with weld pool size, laser power was selected ...

Adaptive shape control of laser metal deposition by adjusting weld pool size

Laser Metal Deposition (LMD) has been developed for repair of damaged components and for the direct forming of three-dimensional structures. From the aspect of productivity, shape accuracy of the deposit must be improved to shorten the machining process after LMD. The objective of this work is to control build-up shape by adjusting weld pool size. Configurations of deposits made with various LMD process conditions were measured by cross sectional observation. In addition, signal intensity of heat radiation, plume emission and laser reflection from weld pool were monitored by photodiodes integrated in a laser processing head during the LMD process. The results showed strong correlation between weld pool size and signal intensity of heat radiation. An adaptive shape control system, which consists of an in-process monitoring system and Proportional-Integral-Derivative (PID) controller using that correlation, was developed for controlling build-up shape. Due to the linear relationship with weld pool size, laser power was selected as a PID output parameter adjusted by heat radiation signal. Since the target value of heat radiation signal can be changed flexibly during LMD process in our PID control system, deposit shape is successfully controlled as required with sufficient profile accuracy of build-up layers.Laser Metal Deposition (LMD) has been developed for repair of damaged components and for the direct forming of three-dimensional structures. From the aspect of productivity, shape accuracy of the deposit must be improved to shorten the machining process after LMD. The objective of this work is to control build-up shape by adjusting weld pool size. Configurations of deposits made with various LMD process conditions were measured by cross sectional observation. In addition, signal intensity of heat radiation, plume emission and laser reflection from weld pool were monitored by photodiodes integrated in a laser processing head during the LMD process. The results showed strong correlation between weld pool size and signal intensity of heat radiation. An adaptive shape control system, which consists of an in-process monitoring system and Proportional-Integral-Derivative (PID) controller using that correlation, was developed for controlling build-up shape. Due to the linear relationship with weld pool size, las...