Abstract
In studying the influence of casting conditions on pinholing, it seems to be necessary to first find out in what parts of castings pinhole defects are formed and develop test pieces best suited to study this, and then establish the evaluation method of pinholes formed in the test castings. This report presents the results of the investigation of this relation among the casting thickness, the gating system and the pinholing tendency, and describes the evalution method of pinhole defects in test castings. The results obtained were summarized as follows. 1) No definite tendency to pinhole formation was observed between casting thicknesses of 5 and 20mm. 2) A gating system decreasing the casting speed was more prone to give rise to pinhole defects. 3) There was a correlation between the location of pinhole defects formed and the gating system employed. The pinhole defects were apt to be concentrated on the part of castings where the first cold metal entering the mold or the slag formed by the metal-mold reaction finally stayed and solidified. 4) It was found that the number of pinholes which appeared on the internal surface of the test castings machined by 0.5mm and 1.0mm, respectively, can be regarded as a representative number and volume of pinholes in the castings.
