The key to avoiding overheated workpieces being misjudged is to establish a dual inspection mechanism of "macroscopic initial screening + metallographic confirmation," and strictly implement standardized judgment procedures to eliminate the risk of releasing workpieces based solely on appearance or a single method.
1. Strictly Control the Inspection Process to Prevent Missed Detections and Misjudgments
Prohibit reliance solely on macroscopic inspection: The absence of surface abnormalities does not guarantee the absence of internal overheating. High-risk workpieces (such as hot runners and molds) must be sampled for mandatory metallographic analysis.
Implement a "dual-person, dual-position" review system: One technician conducts the initial inspection, and another senior engineer reviews it to reduce the probability of human error.
Retain Inspection Image Archives: Archive metallographic photographs, SEM images, etc., for easy traceability and dispute arbitration.
Practical Recommendation: Make metallographic analysis a necessary condition for release; workpieces without a metallographic report must not be used.
2. Clarify Judgment Criteria and Unify Identification Basis
Features | Key Points for Correct Identification | Common Reasons for Misjudgment
Intergranular Cracks: Cracks extend strictly along grain boundaries, appearing "candy-like". Mistakenly identified as cooling cracks or processing cracks.
Grain Boundary Oxide Network: Black continuous oxides distributed along grain boundaries; EDS shows oxygen enrichment. Mistakenly identified as ordinary oxide scale or contamination.
Remelted Balls: Rounded, droplet-shaped solidified structures located at grain boundary junctions. Ignored or mistakenly identified as inclusions.
Judgment Basis: Must be judged comprehensively by combining GB/T 6394 grain size rating and microstructure morphology. The presence of any one of these characteristics indicates overheating.
3. Strengthen Personnel Capabilities and Equipment Management
Regular Training for Testing Personnel: Organize specialized metallographic identification training to improve the ability to identify overheating characteristics;
Equipment Calibration: Ensure that the errors of instruments such as microscopes, thermocouples, and hardness testers are within the allowable range (e.g., thermocouples ≤ ±5°C);
Use Standard Samples for Comparison: Provide control samples with known overheating conditions to assist new employees in accurate identification.
Preventive Value: Through systematic management, the misjudgment rate can be reduced by more than 90%.
4. Establish a Misjudgment Prevention Mechanism and Closed-Loop Responsibility System
Mandatory Pre-Welding Review: Any workpiece requiring welding must first provide a metallographic inspection report; otherwise, operation is prohibited;
Full Inspection of High-Load Workpieces: Implement 100% metallographic sampling inspection for workpieces that have been in continuous service for more than 6 months or have undergone multiple high-temperature cycles;
Establish Traceability Records: Record the number of heating cycles, maximum temperature, and test results for each workpiece to achieve full life-cycle management.
