Development of thick plate cutting technology with fiber-delivered high power Nd:YAG laser beam

Cutting of thick plate with laser beams has been put in practical use with a CO2 laser beam in plants. On the other hand, YAG laser beams are used in electronic industry until now because the output power of YAG laser beam was low. However, the output power of YAG laser beam increases up to 10kW in recent years, and applications in the heavy industry are also expected. Moreover, since the beam can be delivered easily with an optical fiber, the flexibility of cutting is extremely high. Therefore, since dismantlement work in detrimental spots for human being, such as a large-sized plant and a nuclear facility, is possible, the expectation for development of the cutting technology is increasing. In this research work, using a 6kW YAG laser system, the cutting mechanism of steel materials was investigated to develop the cutting technology. The obtained results were summarized as follows. (1) Mild steel plate could be cut up to 100mm thick using mixed gas of oxygen and nitrogen. (2) Stainless steel plate could be cut up to 70mm thick using gas of pure oxygen. (3) In the case of mild steel, usage of the mixed gas raised the cutting capability, but reduced the cutting capability in the case of stainless steel.