1. The white spot of the internal defect, that is, the longitudinal section of the steel after hot processing has a smooth surface of silver and white spots, the shape is a circle or oval. It seriously affects the elongation, section shrinkage and impact toughness of the workpiece.

2. Due to improper forging, there are internal cracks in the shape of chicken feet or herringbone, and subtle cracks will appear, destroying the continuity of the metal. Early failure occurs when the workpiece is subjected to high loads, especially repeated loads.

3. Surface defects have surface scarring, which makes the workpiece easy to produce stress concentration and cause fatigue fracture. The resulting burrs or scratches will affect the correct clamping and efficiency of the machining, and serious scratches will reduce the strength of the steel and lead to cracks.

4. The end concave caused by rolling increases the amount of turning or causes the forgings to be scrapped.