H13模具钢电子束选区熔化热行为的模拟研究

Simulation study on the thermal behavior of electron beam selective melting of H13 die steel

为了提高H13模具钢在电子束选区熔化技术过程中成型件的表面质量,并探明其成型过程缺陷问题的原因,文章基于离散元法建立了随机分布的金属粉末床模型,对熔体的热流体动力学行为进行数值模拟。单道结果表明,当电子束功率从600 W提高到1 080 W,扫描速度为1.5 m/s时,单道熔池平均深度从15.2μm增加到49.2μm,单道熔池宽度从79.2μm增加到140.1μm,同时发现电子束功率为960 W,单熔道形貌表面质量最好。双道结果表明,Z型扫描路径会导致熔道的一端形貌粗糙,S型扫描路径熔道内易形成热量累积现象。当电子束能量较低时,会出现球化效应和单道不平直现象。当电子束能量较高时,熔道易出现热量累积现象,影响后续的熔道形貌和尺寸。

In order to improve the surface quality of the formed parts of H13 die steel in the process of electron beam selective melting technology and to explore the causes of the defective problems in the forming process,numerical simulations of the thermohydrodynamic behaviors of the melt were carried out based on a randomly distributed metal powder bed model established by the discrete element method.The single-pass results show that the average depth of the single-pass melt pool increases from 15.2μm to 49.2μm and the width of the single-pass melt pool increases from 79.2μm to 140.1μm when the electron beam power is increased from 600 W to 1080 W and the scanning speed is 1.5 m/s.It is also found that the single-pass shape surface quality is best with an electron beam power of 960 W.The results of the single-pass results are summarized as follows.The two-pass results show that the Z-shaped scanning path leads to roughness at one end of the melt path,and the S-shaped scanning path is prone to heat accumulation in the melt path.When the energy of the electron beam is low,the spheroidization effect and single-path unevenness will occur.When the electron beam energy is high,the heat accumulation in the melt channel is easy to occur,which affects the subsequent shape and size of the melt channel.