アルミナセラミックスと鋳鉄との鋳ぐるみ材の強度評価

抄録

  The authors have developed a technique to envelope a ceramic bar insert with cast iron without preheating the bar by covering the bar with a cast iron cover, fixing it in a sand mold and then pouring molten metal. This technique allows the heat energy of the molten metal to be utilized to produce cast iron products which are added with functions of ceramic materials. The enveloping materials in the cast iron products produced in our laboratory were evaluated on the basis of presence/absence of cracks in the ceramic insert and presence/absence of voids in the cast iron-ceramic interface. However, to use an enveloping material in an actual mechanical part, it is first necessary to evaluate its strength quantitatively, because it is necessary to prevent such problems as the disjoining of the ceramic material from the cast iron. In this study, the strength of cast iron with ceramic insert was evaluated by conducting a punching test on specimens taken from products having a ceramic insert by slicing the products perpendicular to their long axes in parts of the products with the inserts. Moreover, computer simulations were performed to estimate the thermal stress and thermal shock generated during the process of enveloping the ceramic insert of each product, and the results were analyzed in relation to the measured results. The analysis showed that the shear strength (as measured through punching testing) increases as the amount of molten metal increases and that the development of cracks in the ceramic insert increases the strength of the enveloping material. The analysis also showed that enveloping the ceramic insert directly without using a cast iron cover after preheating the insert increases the shear strength.