硬质合金增塑粉末螺杆挤压成形

Worm Powder Extrusion Molding of Plasticizing Hardmetal Powder

摘要:

探讨了用于硬质合金粉末螺杆挤压成形技术的新粘结剂制备及挤压棒的组织形貌。新粘结剂由几种低分子量组元与1种热塑性弹性体高分子组元构成。采用溶剂溶解与加热熔融相结合的办法制备粘结剂。室温下，用合适的剪切力搅拌，能很快将粘结剂与YG8粉末混合均匀，制得组成均一的料浆式挤压用喂料。用扫描电子显微镜观察了挤压毛坯的微观组织及脱脂试样的组织结构与缺陷。用热重(TG)与微分热重(DTG)方法研究了热脱脂机理与动力学，发现了三维扩散控制热脱脂的速率。在脱脂的第1阶段，低分子量组元被脱除掉，挤压毛坯内形成了连通毛细孔。在脱脂的第2阶段，剩下的高分子量组元被完全脱除；第2阶段的热脱脂能以较快的升温速率进行。制备出了φ20mm的硬质合金挤压棒。

Abstract:

Worm powder extrusion molding(PEM) technology of hardmetal powder using novel binder system has been probed into. A newly developed binder system comprises a major fraction of low molecular weight components(LMWC) and a minor fraction of polymer.The binder was fabricated by heating melting method combined with solvent solving. The feedstock was mixed as a thick slurry at room temperature and was rapidly homogenised by stirring at a adequate shear force. The microstructure of the moulded specimes was observed by scanning electronics microscopy(SEM). The binder was debinded step by step. At the first stage of debinding, the LMWC were removed, and the interconnected capillaries were formed in the moluded green bodies. At the second stage of debinding, the remaining high molecular weight components were completely removed out. The second stage debinding heating rate can be faster than the first stage. The thermal debinding mechanism was studied by thermogravimetry (TG) and differential thermogravimetry(DTG). This research shows that the thermal debinding rate is controlled by three dimensional diffusion mechanism. The PEM hardmetal products with good properties and diameters of up to 20mm have been manufactured.