Investigations On Fiber Laser Polishing Die Steel

Wearing- and corrosion-resistance as well as the precision of the workpiece made by the mould could be improved by polishing. Also, a well-polished mould have a longer service age and maintenance intervals. Therefore, polishing is an important procedure in the manufacture of the mould. The finish machining of mould surface, however, remains a problem. Currently, the majority of automated mould polishing technology, such as electro-polishing, electro-chemical polishing, grinding and so on, have many drawbacks. For example, the corner is rounded, and the deeper zone is not polished. Thus, the aforementioned technology is unfeasible to polish moulds which are uneven or have corners. Primarily, mould surface finish machining is achieved by handcraft, which is a tedious and labor-consuming job. Laser-polishing is deemed as a potential finish method owing to many advantages that it possesses. Fiber laser device have a lot of characteristics that is suit for industrial-use, and so the laser-polishing techniques that was performed by fiber laser on continuous mode is explored.For the consideration of controlling the energy density, two cases were proposed, that is lower focal-offset distance lower power and higher focal-offset distance higher power; single-track experiments were carried out on 2316 tool steels with the varying focal-offset distance, while power and scanning velocity were fixed. In these two cases, along with the increment of the focal-offset distance, the roughness of the as received surface firstly decrease and then increase, which is coincident with the SSM and SOM mechanism. By the means of analyzing the laser polishing flow fields and thermal fields, the causes of the surface profile’s transformation with the energy density was explained. And it turns out that the larger the spot size is, the bigger induced melt zone. So, in the parameter selection, larger focal-offset distance is preferred.With the method of orthogonal experimental design, several parameters, namely power scanning velocity, scanning interval and focal-offset distance, that may influence two-dimensional plane laser polishing were optimized. Power and scanning interval had the greatest impact on the final polishing results, and scanning velocity took the second place, while focal-offset distance had the least influence. About the velocity, whether the Level 2 or Level 3 made a little difference, so with the consideration of efficiency, higher scanning velocity is preferred. The polishing results would be better with a larger focal-offset distance and proper power, scanning velocity and scanning interval. Under the best parameters, the sample’s roughness made from 2316 tool steel is reduced from about Ra= 1.000 μm to 0.231 μm.