水帘结构同步水冷装置对光-粉同路激光熔覆温度场的影响研究OA北大核心CSTPCD

Considering that the local temperature rise in laser additive repair of large equipment is likely to ablate the edge of the part, melt the internal wire and rubber ring, and damage the original structure, a water curtain surface synchronous water cooling technology is proposed in this paper, and its temperature field is numerically simulated and experimentally researched. Fluent software and VOF model were used to study the stable gas-liquid two-phase flow model in the dry zone under the curtain. Numerical models of temperature field and bending deformation were established by Abaqus software, three laws of heat conduction, thermos-elastoplastic theory and thermal deformation theory. The influence mechanism of synchronous water cooling on the temperature field of 316L stainless steel was verified by comparing the melt pool morphology, grain size, heat accumulation and bending deformation of the two methods of laser-powder co-path and synchronous water cooling. The water curtain inside the synchronous water cooling device scattered to all sides, forming a stable dry zone environment, and there were no obvious pores, cracks and other defects on the deposited metallographic surface. For single channel deposition with the same parameters, temperature pattern and molten pool morphology showed that water cooling effectively reduces the size of the molten pool, but it had little effect on the solidification rate of the molten pool, and there was only a slight difference in average grain size between them, which was 28.81 μm and 27.55 μm, respectively. During multi-channel deposition, the cooling effect of the water curtain elevated the temperature difference at the edge of the molten pool, reduced the heat accumulation in the epitaxial area, and increased the temperature gradient at the edge of the molten pool while reducing the overall temperature of the substrate. However, the increase in temperature difference brought greater thermal stress, resulting in different deformation degrees of the substrate under different deposition methods. It was found that the temperature on the back of the substrate could be kept below 50 ℃ by synchronous water cooling using thermocouple in the cantilever beam lap cladding experiment, and the maximum temperature of the laser-powder co-path could reach 500 ℃ . At the same time, when the cantilever beam was thin, the thermal stress caused by the temperature difference between the top and bottom of the substrate was greater than the binding force of the substrate itself, and the deformation of the sample with synchronous water cooling was more obvious. With the increase of thickness, the binding force of the specimen increased and the difference of deformation decreased gradually. The coupling of synchronous water cooling waterways limits the depth and diffusion of heat in the molten pool, which can effectively control the temperature of the processing area during the cladding process, and also lead to increased bending deformation degree when the workpiece is thin, but when the thickness of the plate is greater than 3 mm, the deformation difference tends to be the same and becomes smaller and smaller.