Common Defect Analysis in Shaft Forging

Surface cracks and folds are high-frequency defects in shaft forging. Surface cracks are often caused by subcutaneous bubbles or rolling scratches in steel ingots, extending linearly along the direction of deformation. Folds are caused by the wear or burrs of the roll groove being rolled in, forming a folded seam with iron oxide inclusions, which easily leads to cracking.

Internal defects such as layered fractures and non-metallic inclusions pose significant hazards. Layered fractures are caused by inclusions being elongated along the rolling direction, leading to material delamination and a sharp drop in transverse performance. Non-metallic inclusions (such as sulfides and oxides) directly reduce material strength and cause forging cracking.

Process defects such as forging overheating and quenching cracks need to be strictly controlled. Overheating is caused by excessively high heating temperatures, leading to grain boundary oxidation or even melting, with a surface resembling orange peel. Quenching cracks are caused by excessively rapid cooling, where internal stress exceeds the material strength, resulting in a diagonal or network-like distribution. Optimizing process parameters and material selection is key to improving quality.