Effect of laser radiation absorption on efficiency of laser welding of copper and its alloys

Abstract

Due to a high reflection power of copper it is usually assumed that the laser welding of products of this material is not rational. However, in the modern industry the problems of joining the parts of copper and its alloys periodically arise, applying narrow welds with a deep vapor-gas channel. Moreover, for technical reasons the use of electron beam welding is not always possible and a sufficiently wide availability of fiber (wavelength of 1.07 mm) and disc (wavelength of 1.03 mm) industrial lasers of the latest generation makes the problem of laser welding of these materials challenging. Therefore, the aim of the work was to study the conditions of absorbing the laser radiation with the wavelength of 1.03-1.07 mm by copper and its alloys in laser welding with a deep penetration, as well as to determine the basic parameters of the welding mode and to evaluate the process effectiveness. It was shown in the work that for certain combinations of thickness of copper alloy and density of radiation power with the wavelength of 1.03-1.07 mm, the optimal speed of welding process exists, at which its technical and economic efficiency is maximum. This speed should be such that the absorbing capacity (integrated over the spot of laser heating) can be at the level of about 13-15 %. The exceeding of welding speed leads to a sharp decrease in absorbing capacity, and, consequently, to the need in increasing the radiation power and growing the cost of the process. The decrease in welding speed relatively to the optimal one leads to decrease in efficiency, overheating of metal in the weld pool and to such defects of weld shaping, as sagging and metal splashes. 11 Ref., 8 Figures.

High-Speed Laser Melt Injection of Tungsten Carbide in Highly Conductive Copper Alloys

“…When investigating the absorptivity of copper as a function of temperature, an abrupt rise occurs at the melting point [9]. In consequence, the substrate absorbs energy of the laser significantly better once the material is melted.…”