Mild forging folds can be repaired using mechanical methods such as grinding and scraping, but it is essential to ensure that the base material is not damaged and stress concentration is not caused. Furthermore, the repaired fold must be confirmed as acceptable by non-destructive testing.

For mild forging folds that are shallow, short, and located in non-critical stress areas, limited repair is possible if they do not lead to material microstructure deterioration (e.g., overheating, severe decarburization). The following are specific operating methods and precautions:

1. Applicable Repair Methods

1) Grinding with an abrasive wheel (preferred method)

* Applicable conditions: Fold depth ≤ 0.5mm, clear surface opening, no forging crack propagation around the fold.

* Key operating points:

. Use a handheld angle grinder or pneumatic abrasive wheel, grinding in the direction of the metal flow line, avoiding transverse cutting;

. The edges of the ground area should have a smooth transition, with an R-angle ≥ 3mm, to prevent the formation of new stress concentration points;

. Control the grinding depth, ensuring it does not exceed 2/3 of the machining allowance.

* Post-processing: After grinding, magnetic particle testing (MT) or penetrant testing (PT) must be performed to confirm complete removal of forging defects.

2) Pneumatic chisel cutting

* Applicable conditions: Forging folds are slightly deep (0.5~1mm), but not penetrating, and the workpiece has sufficient wall thickness.

* Key points of operation:

. Use a pneumatic chisel to remove metal from the forging fold area, forming a U-shaped groove and avoiding sharp corners;

. The surface roughness after chiseling should be ≤Ra12.5 for easy inspection and subsequent processing.

* Note: After chiseling, it is necessary to assess whether the remaining cross-section meets the strength requirements, and stress checking should be performed if necessary.

3) Rotary file finishing

* Applicable scenarios: Localized small-area folds, such as rounded corners, rib roots, hole edges, and other narrow areas.

* Advantages: Flexible operation, can accurately remove forging defects without damaging surrounding metal.

2. Repair Prerequisites and Limitations

1) Conditions for Permitted Repair:

* The forging fold is a single, isolated defect;

* It is not accompanied by internal structural damage such as overheating or white spots;

* The dimensions after repair are still within tolerance;

* Non-critical load-bearing parts (such as non-shoulder, tooth root, mounting surface).

2) Situations Where Repair is Prohibited:

* The fold has cracked or expanded into a forging crack;

* It is located in a high stress concentration area;

* The forging fold was discovered after quenching (it may have expanded);

* Repair will lead to dimensional deviations or affect assembly performance.

3. Post-Repair Processing Requirements

1) 100% Non-Destructive Testing: The repaired area must be re-tested using MT or PT to ensure no residual forging defects.

2) Record Tracking: Establish a repair log, recording the location, depth, treatment method, and test results for quality tracking.

3) Performance Verification: For important parts, it is recommended to conduct local hardness testing or simulated working conditions to ensure safety.