Abstract
With the object to obtain sound AC8A aluminium alloy piston, the rate of solidification of this alloy was computed with method of electrical analogy and cleared up the relationship between solidification rate and casting conditions. The summarized results are as follows:
1) For analog calculation, an electrical model circuit were set up with oil condensers and carbon resisters. The computed results were nearly in coincidence with the experimental values in practical range of accuracy.
2) As to the casting condition, varying the thickness of the mold and casting, also temperature of the mould and pouring temperature, the effects of those aboves to solidifying velosity were measured.
3) Owing to the pouring disturbance of molten metal, it was found that the mold near the runner was overheated, and the solidification rate was exceedingly retarded. To prevent this retardation, the most simple and effective means is to be considered water cooling around the runner.
4) On the calculation of solidification rate of the piston pin boss, it was found that the core of piston pin, with the same reason described in item (3), reaches to high temperature owing to less heat capasity of that place at the end of pouring. This reduces the solidification rate and causes the development of typical micro-shrinkage-porosity on a inner surface of the piston-pin boss. The solidification rate and soundness of piston-pin boss shall be improved by applying water cooling in the core of piston-pin boss.
