Masakazu Hayashi

The mechanism of high speed leading path laser-arc combination welding

In order to fully understand the causes of high speed welding defects in Leading Path Laser-Arc Combination (LPLAC) welding, the authors observed the welding process with a high speed video camera and a long distance microscope under a variety of conditions using various arc voltage and arc current settings, and also varied the distance between the laser and arc. These experiments revealed how the arc parameters affect the interaction between the laser plasma and the arc, the effects of various arc setting combinations on both the quantity and behavior of the molten metal produced by the arc, and the ways in which the interaction between the laser and molten metal can be affected. In LPLAC welding, the behavior of the molten metal produced by the arc, and the interaction between the laser and arc are both critical factors. As the distance between the laser and arc directly affects their interaction, it must be carefully considered for each welding speed.In order to fully understand the causes of high speed welding defects in Leading Path Laser-Arc Combination (LPLAC) welding, the authors observed the welding process with a high speed video camera and a long distance microscope under a variety of conditions using various arc voltage and arc current settings, and also varied the distance between the laser and arc. These experiments revealed how the arc parameters affect the interaction between the laser plasma and the arc, the effects of various arc setting combinations on both the quantity and behavior of the molten metal produced by the arc, and the ways in which the interaction between the laser and molten metal can be affected. In LPLAC welding, the behavior of the molten metal produced by the arc, and the interaction between the laser and arc are both critical factors. As the distance between the laser and arc directly affects their interaction, it must be carefully considered for each welding speed.

Welding and forming of thick steel plates with a high power density diode laser

Diode lasers offer the advantage of higher conversion efficiency than conventional CO2 and YAG lasers, but their beam properties are very poor. Nevertheless, they can be focused into a spot 0.96mm in diameter at a laser power of 2kW. The feasibility was thus examined of welding and forming thick steel plates using a diode laser with a high power of 2kW and a high power density of 236kW/cm2. Steel plates ranging from 0.5mm to 10mm in thickness were successfully welded without porosities or cracks. The diode laser beam’s top hat shape was found to be suitable for welding. Laser forming of thick steel plates with a high power density diode laser was also investigated. A 5mm thick steel plate was bent at an angle of about 9.23° by scanning it 50 times with a 4mm diameter beam at a power of 1kW and a scanning speed of 1.5m/min. Even though the diode laser has a short focusing length, it was found to be suitable for laser forming because it does not require the melting of specimen’s surface.Diode lasers offer the advantage of higher conversion efficiency than conventional CO2 and YAG lasers, but their beam properties are very poor. Nevertheless, they can be focused into a spot 0.96mm in diameter at a laser power of 2kW. The feasibility was thus examined of welding and forming thick steel plates using a diode laser with a high power of 2kW and a high power density of 236kW/cm2. Steel plates ranging from 0.5mm to 10mm in thickness were successfully welded without porosities or cracks. The diode laser beam’s top hat shape was found to be suitable for welding. Laser forming of thick steel plates with a high power density diode laser was also investigated. A 5mm thick steel plate was bent at an angle of about 9.23° by scanning it 50 times with a 4mm diameter beam at a power of 1kW and a scanning speed of 1.5m/min. Even though the diode laser has a short focusing length, it was found to be suitable for laser forming because it does not require the melting of specimen’s surface.