纹影法激光焊保护气流态

Outflow Forms of Shielding Gas in Laser Welding by Schlieren

为了对喷嘴结构设计及气流工艺参数的调整提供理论依据,采用双反射式纹影仪对激光焊接用喷嘴冷态时的气流流态进行了系统观测,并结合气体动力学原理对气流的流态进行了分析.结果表明,单层保护气喷嘴自由射流时,气流的Re控制在400～700可获得较好的层流长度及挺度;双层保护气喷嘴自由射流时,内、外层气流的Re相近可使综合性能达到最佳,最后给出了几种常用保护气喷嘴和保护气帘的气流形态.

The nozzle, in laser welding, plays avery important role in ensuring the protection of melting pool and the qualities of laser welding. In order to get the theoretic gists for designing the structure of nozzle and adjusting the technological parameter, the jet＇s form of double-layer nozzle used in laser welding was systemically researched in the experiment by a two-reflector schlieren instrument and analysed with the principle of aerodynamics. The results showed that, in the case without laser kindling, to obtain the satisfying length in laminar flow of shielding gas and velocity of flow, the Reynolds-number of single-layer nozzle＇s free-jet should range from 400 to 700. Nevertheless, for the double-layer nozzle, the Reynolds-numbers of the inner and the outer layer should be kept close to each other in order to get the best laminar flow form. Several gas outflow forms about nozzles and a protect-curtain are also shown in this paper.