局部干法水下Nd:YAG激光焊接技术

本文采用填丝热导焊的方法研究了水下激光焊接的基本物理现象,结果表明,利用气体喷嘴可形成局部干燥空间,其保护效果取决于喷嘴结构和气体流量等参数。喷嘴的外径大小对保护效果影响显著。当保护条件差时,局部干燥空间将有水浸入,导致焊缝由良好保护条件下的浅而表面光滑平整的形状变为深而表面起伏的形状。良好保护条件下的水下焊缝的力学性能和大气中一致。

Underwater Nd:YAG Laser Beam Welding with local dry cavity

In this paper, heat-conduction underwater welding of Type-304 stainless steel with filler wire by using a 4kW Nd: YAG laser was investigated. In underwater welding, the shielding conditions of the local dry cavity have strong influence on the weld bead shape and weld properties. The structure of the nozzle and the gas flow speed are the main factors affecting the stability of the local dry cavity. In specific, appropriate enlarging the outside diameter of the nozzle can obtain perfect shielding condition. If the shielding condition is incomplete, the oxygen content of the weld metal may increase from the normal value of about 80ppm under good shielding condition to800ppm. The increase in oxygen content leads to the severe decrease in the elongation rate and the reduction of area in tensile test, although no variation in tensile strength. Under appropriate shielding condition, the chemical composition and mechanical properties of the underwater laser welds can be as same as that in air.