选区激光熔化直接成型零件工艺研究

为了提高选区激光熔化成型金属零件致密性与精度，首先对激光扫描单道熔池形成特性进行研究，讨论扫描速度、激光功率对熔池宽度影响，观察到熔池附近无粉区宽度 与熔池宽度 的关系为： = ×（1.5~2）。根据单道熔池成型特性，采用层间错开扫描策略提高零件致密性到近乎100%，显微观察层间与层内熔池搭接紧密。接着成型包括圆柱圆孔等几何单元讨论热影响、原始尺寸对尺寸精度的影响，当光斑补偿 与聚焦光斑直径 满足 时，尺寸精度达到（0.04~0.06）mm。对SLM成型件拉伸强度、延伸率、显微硬度测试分别为636Mpa、15%~20%与HV0. 3 250~285。结果表明，层间错开扫描策略与优化的光斑补偿值对SLM直接成型金属零件的致密性与精度具有较好效果。

Technical study on direct fabrication of metal part by selective laser melting

In order to improve metal part density and dimensional accuracy in selective laser melting process, single laser scanned molten pool character was investigated first, and the impacts of scan speed and laser power on melt width were discussed later. And relationship between no powder distance around molten pool and molten pool width could be expressed as = ×（1.5~2）. Considering the single molten pool character, layer stagger scan strategy was adopted to improve part density to as high as nearly 100%，and the compact joint effect among molten pools between inner layers and inter-layers were micro-observed. Then, geometrical unit, including cylinders and holes was fabricated to discuss the heat effect and original unit size on dimensional accuracy, when beam compensation and focused beam diameter meet the equation , dimensional accuracy 0.04mm~0.06mm can be achieved. The tensile strength, elongation and micro-hardness of SLM part achieves respectively at 636Mpa, 15%~20% and HV0. 3 250~285. Results show that layer stagger scan strategy and optimized beam compensation have good effect for improving the parts’ relative density and dimensional accuracy in SLM process.