Intensification of pinhole formation in mold-inoculated cast iron with lamellar graphite due to decreasing casting temperature.
There are hydrogen pinholes and hydrogen-nitrogen pinholes, which cannot be distinguished from each other, and CO-slag reaction pinholes. Known possible root causes of this defect include specific properties of the iron on the one hand and specific properties of the mold material system on the other hand. In a concrete case, the formation of pinholes will often not result from only one cause but rather from the combined effect of several overlapping causes. Pinholes lead to impairments in coatings such as enameling, hot-dip galvanizing, powder coating, etc. The ability to withstand static stress is hardly affected by this defect, in particular in the case of ductile cast iron types and a low stress level. In the case of processed functional surfaces that also have to be leakproof, the defect leads to rejections. In addition, an unfavorable position of the defect can impair the dynamic strength, so that pinholes cannot be tolerated in safety components that are under vibratory stress.