微热压成形石墨件的快速碳化工艺

Rapid carbonization process of graphite parts formed by micro-thermocompression moulding

针对石墨件在碳化过程中易开裂的问题,基于多材料组装技术原理,提出在石墨粉末微热压成形过程中构造烧蚀性二维有机物网络以形成排气通道、避免开裂的方法。研究了碳化速率、石墨件径向尺寸及网络结构、分布方式对石墨件成形质量和力学性能的影响。结果表明:较快的碳化速率会加剧有机物热解,开裂的现象越明显,较大径向尺寸的石墨件气体逸出阻力越大;提高有机物网络密集度有助于改善排气效果,但对石墨件力学性能产生不利影响;在有机物网络沿成形高度方向的布置中,当间距为10 mm时,石墨件不出现裂纹。采用优化的工艺制备的石墨件结构完整,经过浸渍增强后其抗压强度达到15.8 MPa,Z轴导热系数仅为1.894 W/(m·K),综合性能与水玻璃型砂相当,在铸造行业有广泛应用前景。

In order to address the problem of cracking in graphite parts during carbonization,based on the principle of multi material assembly technology,a method was proposed to construct an ablative two-dimensional organic network during the micro-thermocompression moulding process of graphite powder to form an exhaust channel and avoid cracking.The influence of carbonization rate,radial size of graphite parts,as well as the structure and distribution mode of the network on the forming quality and mechanical properties of the graphite parts was studied.The results show that a faster carbonization rate will intensify the pyrolysis of organic matter,resulting in more obvious cracking phenomenon,and the graphite parts with larger radial sizes present the greater gas escape resistance.Increasing the density of organic matter networks can help improve exhaust efficiency,but it has a negative effect on the mechanical properties of the graphite parts.In the arrangement of the organic network along the forming height direction,there are no cracks in the graphite parts when the spacing is 10 mm.The graphite parts prepared by the optimized process have a complete structure,and after impregnation reinforcement,its compressive strength reaches 15.8 MPa,and the Z-axis thermal conductivity is only 1.894 W/(m·K).Its comprehensive performance is comparable to that of water-glass sands,showing a wide range of application prospects in the casting industry.