| 摘要 |
PURPOSE:To decrease the frequency for renewal as compared to conventional casting and to obtain a lead alloy casting with the improved productivity by using a casting mold having a surface layer contg. tetra fluoro ethylene.perfluoroalkoxy resin polymer (PFA). CONSTITUTION:PFA powder having a prescribed average grain size is sprayed plural times by an electrostatic painting method onto the casting mold made of a cast iron for a grid body to obtain a surface layer 2 consisting of PFA. Air venting passages are provided at required points of the surface layer 2 by a scriber or knife. Window parts 3 of the grid are roughened to suitable roughness by blasting. The casting mold obtd. in the above-mentioned manner is used and the melt of the lead alloy contg. 5% Sb is poured into such mold under the conditions of, for example, 430 deg.C molten metal temp. and 170 deg.C casting mold temp. The grid body, i.e., casting, consisting of the lead alloy and having no seams is thus obtd.
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