| 摘要 |
<p>PURPOSE:To obtain the title investment material by blending a mixture of cristobalite of refractory and/or quartz and hemihydrate of binder with natural starch and a specific transition metal compound as an expanding agent and aluminum phosphate as a cast cavity inhibitor. CONSTITUTION:100 pts.wt. mixture of cristobalite of refractory and/or quartz and hemihydrate as binder is blended with 0.1-5 pts.wt. natural starch and 0.1-10wt.% one or more of carbide, nitride, boride, silicide and sulfide of transition metal of groups IV, V and VI of the periodic table as an expanding agent and aluminum phosphate as cast cavity inhibitor to give a gypsum-based investment material having large thermal expansion and improved heat resistance of gypsum. The investment material is preferably blended with 0.1-1 pt.wt. soluble starch. The investment material is safe because of no evolution of toxic gas.</p> |
