钨基高比重钨合金注射坯溶剂脱脂工艺研究

Investigation of solvent debinding process on tungsten heavy alloy injection parts

迄今为止,粉末注射成形技术只限于制备厚度较小的零部件,而脱脂是整个工艺过程中限制零部件向大厚度发展的最关键步骤.为了实现厚度达20mm的高比重钨合金大棒的无缺陷脱脂,作者研究了溶剂脱脂中脱脂率与溶剂组成、脱脂时间、样品厚度和溶剂温度等参数的关系.研究结果表明,采用多组元低分子有机溶剂的混合物在45℃下溶剂脱脂效果最好.样品厚度对溶剂脱脂时间、脱脂率等的影响非常显著,厚度为1mm的样品在脱脂4h时,其脱脂率可达70％以上,厚度为10mm的样品在溶剂脱脂6～8h时,脱脂率只有43％.对于直径为20mm的大棒,溶剂脱脂时间为24～30h时,脱脂量为50％～60％,其余粘结剂采用热脱脂工艺脱脂.采用溶剂脱脂不仅可以大大缩短热脱脂时间,关键是可以成功地实现较大厚件的脱脂,对部分溶剂脱脂后的样品,用扫描电镜观察了断面粘结剂的分布,溶剂脱脂过程中粘结剂的溶解、扩散与脱除均由表向里进行.

Up to now, powder injection molding(PIM) technology can only be used to manufacture small Parts.The debinding step is the key technology to limit the thickness of PIM parts. In order to succeed indebinding thick parts (the thickness is about 20 mm), the solvent debinding process was studied, includ-ing the relationship of binder loss with solvent composition, debinding time, sample thickness, and sol-vent debinding temperature and so on. The experimet shows that the multi-component low molecule sol-vent mixture has best results at 45 ℃. The effects of sample thickness on solvent debinding time andbinder loos are dominant. With the thickness of 1 mm, the binder removal is above 70% after debindingfor 4 h, while with the thickness of 10 mm, the binder removal is ouly 43% after debinding for 4～8 h.For the diameter of 20 mm bar, the binder loss is 50%～60%. After debinding for 24～30 h, the resi-dual binder is removed completely by thermal debinding. All experiments show that solvent debindinggreatly shortens the subsequent thermal debinding time, and the large thick injected parts can be success-fully debound. After solvent debinding, the parts were observed by using scanning electronic microscopy(SEM).