316L stainless steel samples were manufactured by selective laser melting (SLM). The microstructure of SLM-made 316L stainless steel and the room temperature tensile properties both perpendicular and along the building direction were studied and characterized. The static temperature field during the molten pool formation was simulated by finite element simulation. It indicates that the nonlinear asymmetrical inclined temperature gradient in SLM process produces a large surface tension gradient. The melt forms a Marangoni flow with different convection modes under the action of surface tension as well as a micro-molten pool morphology with subgrain structures such as strip, hexagonal and elongated cellular structures. In addition, there are also epitaxially grown columnar grains. The growth of columnar crystals is not affected by the boundary of the molten pool. Subgrain structures and low-angle grain boundaries make the tensile strength and the elongation of SLM-made 316L sample higher as compared to those of the cast and wrought samples. The room temperature tensile strength of the sample perpendicular to the building direction is higher than that of the sample along the building direction, while the elongation is lower than that of the sample along the building direction.

316L不锈钢样品是通过选择性激光熔化（SLM）制造的。研究并表征了SLM制成的316L不锈钢的显微组织以及垂直和沿建筑方向的室温拉伸性能。通过有限元模拟对熔池形成过程中的静态温度场进行了模拟。这表明SLM过程中的非线性非对称倾斜温度梯度会产生较大的表面张力梯度。熔体在表面张力的作用下形成具有不同对流模式的Marangoni流，以及具有亚晶粒结构（如条状，六角形和细长的蜂窝状结构）的微熔池形态。另外，还存在外延生长的柱状晶粒。柱状晶体的生长不受熔池边界的影响。与铸造和锻造样品相比，亚晶粒结构和低角度晶界使得SLM制316L样品的拉伸强度和伸长率更高。垂直于构造方向的样品的室温拉伸强度高于沿着构造方向的样品的室温拉伸强度，而伸长率低于沿着构造方向的样品的室温拉伸强度。