Common defects and solutions for heat treatment of metal stamping dies

The stability of the heat treatment process directly determines the durability and precision of the metal stamping die. In our daily production, we have summarized some common defects and solutions in the heat treatment process of the metal stamping die, and shared with you. 1. The causes of overheating and overburning of parts during quenching: 1. Material confusion. 2. The heating temperature is too high. 3. The heat preservation time is too long at a higher temperature. Solution: 1. Spark identification must be performed on parts before quenching to prevent incorrect materials. 2. Strictly control the heating temperature and follow the process regulations. 3. Control a reasonable holding time. If the part has overheated or overburned, the workpiece should be normalized and annealed, and then heat treated according to the process regulations again in order to save it. Second, there are spots and corrosion on the surface of the quenched parts: 1. The surface protection is poor when heated in a box furnace. 2. Poor deoxidation in salt bath. 3. When the workpiece is air-cooled, the pre-cooling time is too long. 4. The temperature of the salt bath is too high or there are chloride ions mixed in it. 5. The workpiece was not cleaned in time after quenching. Solution: 1. The workpiece should be put into the box reasonably and protected, and the protective agent should be dried before use. 2. The salt bath should be fully deoxidized in time. 3. For high alloy steel, try not to use air quenching. 4. Control the salt bath temperature not to exceed 500℃ and keep it clean. 5. Clean the parts in time after quenching. Third, the causes of soft spots on the surface of quenched parts: 1. The raw material fiber structure is uneven, such as carbide segregation, aggregation, and uneven distribution. 2. When heating, the surface of the workpiece has oxide scale, rust spots, etc., which will cause partial surface decarburization. 3. The quenching medium is aging or contains too many impurities, which makes the cooling rate uneven. 4. After quenching the cooling medium for larger parts, they did not move smoothly up and down and left and right. Solution: 1. The raw materials need to be forged and annealed reasonably. 2. Check carefully before quenching to remove oxide scale and rust spots. 3. Regularly clean and replace the cooling medium, and always keep the cooling medium clean. 4. After the workpiece enters the quenching medium, it must be operated correctly according to the regulations. Fourth, the causes of quenching cracks: 1. Improper selection of materials or cracks in the material itself. 2. Cracks occur during forging. 3. There is machining stress. 4. Without preheating, heating is too fast. 5. The heating temperature is too high or the holding time is too long. 6. Improper selection of cold quenching medium or excessive cooling speed. 7. When quenching with water and oil, the workpiece stays in the water for too long. 8. When staged quenching, after the workpiece is taken out of the staged cooling liquid, it is cleaned too quickly in water. 9. The stress is too concentrated. 10. Quenching for many times without sufficient annealing in the middle. 11. Temper in time after quenching. 12. Surface carburization or decarburization. Solution: 1. Choose steel reasonably, strengthen management, and carefully inspect. 2. Reasonably control the forging temperature and forging process, and perform annealing treatment after forging. 3. Before the final processing and forming of the metal stamping die, the stress should be removed first, and then the size of the metal stamping die should be corrected, and finally quenched. 4. Use preheating and pre-cooling as much as possible. High-alloy steel is best preheated twice. 5. Strictly control the quenching temperature and holding time. 6. Correctly select the quenching medium to slow down the cooling rate, and it is best to use the hierarchical cooling process. 7. Strictly implement the correct cooling process. 8. When staged quenching, after the workpiece is taken out from the staged cooling liquid, it should be cooled to room temperature before being washed in water. 9. Before quenching, take protective measures such as iron wrapping, iron wire binding, and soil blockage on the stress concentration. 10. The re-quenched parts should adopt the intermediate annealing process. 11. Temper in time after quenching. 12. When quenching and heating, care should be taken to take reasonable protective measures. Such as the use of salt bath deoxidation, box furnace with protective gas, etc. Fifth, the reasons for insufficient quenching hardness: 1. The workpiece has low hardenability and large cross-sectional area. 2. The surface is decarburized during quenching and heating. 3. The quenching temperature is too high or too low, and the holding time is too short. 4. When staged quenching, the stay in the staged cooling medium is too long or too short. 5. When quenching with water and oil, the staying time of the workpiece in the water is too short. 6. Too much water in the alkaline bath. Solution: 1. Use steel correctly. 2. Pay attention to heating protection, and fully deoxidize the salt bath. 3. Strictly implement the quenching process specification. 4. Strictly implement the correct cooling process. 5. Operate according to the correct cooling process. 6. Strictly control the salt bath moisture in the range of 2%-4%. Sixth, there is corrosion on the surface after tempering: it is not cleaned in time after tempering. Solution: The metal stamping die parts after the same fire should be cleaned in time. Seven, the reasons for the excessive hardness after annealing: 1. The heating temperature is insufficient. 2. Insufficient heat preservation time. 3. The cooling rate is too fast. Solution: Operate strictly according to the correct process. For the phenomenon that the hardness is too high after annealing, it should be re-annealed according to the correct process. Eight, the reason for the greater temper brittleness: low tempering temperature or insufficient time for the same fire. Solution: Choose a suitable tempering temperature, and have sufficient tempering time, try to avoid tempering brittleness temperature range. 9. The cause of cracks found during grinding after tempering: insufficient tempering. Solution: After quenching, it should be fully tempered, and the secondary tempering should be used as far as possible for high-profile steel. Ten. Reasons for the existence of network carbides in the annealing structure: 1. The forging process is unreasonable. 2. The spheroidizing annealing process is not limited. Solution: 1. Reasonable forging. 2. Re-anneal according to the correct spheroidizing annealing process. 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