A forgingThe process of working metal to a desired shape by impact or pressure in hammers, forging machines (upsetters), presses, rolls, and related forming equipment. defect caused by metal flow past the base of a ribA relatively flat (but generally with draft) thin portion of a forging, generally perpendicular to the forging plane. with consequent rupture of the grainAn individual crystal in a polycrystalline metal or alloy. structure.