DIE NOTWENDIGKEIT EINER IMPFBEHANDLUNG VON PERLITI-SCHEM GUSSEISEN MIT KUGELGRAPHIT IM GUSSZUSTAND ZUR STEIGERUNG DER MECHANI-SCHEN EIGENSCHAFTEN

摘要

It is essential to perform an inoculation treatment on the charge shortly before pouring or during pouring, if the combination of properties, in particular elongation in the cast condition, it to be achieved. It can be demonstrated in tests with sam-pels of 50 mm wall thickness, that with mould inoculation the average nodule count doubels, while at the same time nodular-ity improves and the mean nodule diameter decreases. Below a limiting nodule diameter (LND) of 40μm, elongation increases rapidly as particle size decreases and tensile strength rises dramatically to a new level. The 0,2% proof stress is unaffected by the particle diameter. As found already in the test piece, actual parts display the detrimental effect of poor nodularity and lower nodule count. The thicker the walls, the stronger this effect becomes. Although the 0,2% proff stress was less affected; the tensile strength, and particularly elongation (after fraction) degreased significantly. The only effective countermeasure is to ensure that a late inoculation is carried out properly. Moreover inoculation of the pouring stream is more effectiv than mould inoculation (limits to inoculants, partiel late dispersion). Optimum component quality stems from improving nodularity, increasing the nodule count, reducing nodule diameter an preventing silicon microsegregation through effectiv late inoculation.