Part integrity during forging refers to avoiding internal cracks, voids, inclusions, surface defects, abnormal grain structure, and dimensional deviations. Integrity assurance encompasses raw materials, heating, forging process, cooling, and post-processing.

1. Raw Material Control

1) Select qualified steel ingots/bars with low content of non-metallic inclusions, shrinkage cavities, and porosity. Conduct incoming material inspection, such as ultrasonic testing.

2) Before forging, remove surface defects such as oxide scale, cracks, scratches, and decarburized layers by grinding or turning.

3) Optimize cutting positions: Remove ingot risers and bottoms where defects are concentrated.

2. Reasonable Heating Process

1) For large workpieces, use slow heating to avoid excessive thermal stress leading to internal cracks. Prevent localized overheating and scorching.

2) Strictly control the forging temperature range: the initial forging temperature and the final forging temperature must match the alloy material. Low temperatures can cause forging cracks; excessive ablation can damage grain boundaries and is irreparable.

3) Ensure uniform overall workpiece temperature to reduce the temperature gradient between the surface and core.

3. Forging Deformation Control

1) Select a suitable forging method: upsetting, drawing, stamping, etc. Control the deformation amount in each forging. Excessive deformation in a single forging will cause cracks; insufficient deformation will fail to close internal voids.

2) Control the deformation rate: For difficult-to-deform alloys, reduce the hammering speed or pressure speed to ensure sufficient metal flow and avoid brittle fracture.

3) Optimize die design: Smooth rounded corners, reasonable draft angles, and avoid creating stress-concentrated sharp corners. Good lubrication can improve metal flow and reduce surface tearing.

4. Proper Cooling After Forging

1) Avoid rapid and uneven cooling. For high-strength alloy steels, use slow cooling (in an insulated box, embedded in an insulating medium) to prevent cooling cracks caused by residual stress. 2) Control the cooling rate to balance residual stress, prevent deformation and cracking, and avoid harmful microstructures.

5. Post-Forging Heat Treatment

1) Perform normalizing, annealing, or quenching and tempering as needed. Eliminate forging residual stress, homogenize the grain structure, and remove banded structures.

2) Prevent cracking and deformation during heat treatment by controlling heating and cooling rates.

6. Inspection and Quality Assurance

1) In-process inspection: Visually inspect for surface cracks, folds, and laminations.

2) Non-destructive testing: Ultrasonic testing for internal voids and cracks; magnetic particle or penetrant testing for surface defects.

3) Metallographic inspection: Verify grain size, microstructure, and detect forging-related defects.

7. Equipment and Die Maintenance

1) Maintain the forging hammer/press in good condition to ensure stable load output.

2) Die maintenance: Regularly repair die wear, cracks, and sharp edges.

Final Summary

The integrity of forgings depends on end-to-end management: defect-free raw materials, precise temperature control, appropriate deformation amplitude and rate, controlled cooling, proper post-forging heat treatment, and effective non-destructive testing.