To better understand forging, let's discuss some common forging defects. Forging defects are mainly divided into three categories, with the following causes and manifestations:

1. Raw Material Defects

1) Surface cracks: Cracks or subcutaneous bubbles on the surface of the raw material expand during forging.

2) Shrinkage cavity remnants: Incomplete removal of the ingot riser leaves residual shrinkage cavities after forging, leading to porosity and segregation.

3) Non-metallic inclusions: Impurities such as oxides and sulfides are mixed into the raw material, forming inclusions after forging.

4) White spots: Hydrogen precipitates during cooling, forming microcracks, commonly found in alloy steels.

2. Improper Process Defects

1) Folding: Uneven metal flow causes overlapping of surface metal.

2) Cracks:

* Heating cracks: Uneven temperature or overheating.

* Forging cracks: Excessive deformation speed or stress concentration.

* Cooling cracks: Excessive phase transformation stress.

3) Overheating and burning:

* Overheating: Coarse grains, reduced strength.

* Burning: Grain boundary oxidation or melting, rendering the material unusable.

4) Residual casting structure: Insufficient forging ratio, the cast structure is not eliminated.

5) Carbide segregation: Uneven distribution of carbides affects performance.

6) Banded structure: Alternating distribution of two phases reduces transverse plasticity.

7) Local underfilling: Mold or process problems lead to unclear contours.

3. Other Defects

1) Oxide scale pits: Unremoved oxide scale is pressed into the surface.

2) Coarse grains: Final forging temperature is too high or deformation is insufficient.

3) Irregular forging flow lines: Disordered flow lines, reduced performance.

4) Dimensional inaccuracies: Operation or mold problems lead to out-of-tolerance dimensions.