Common defects and solutions of metal stamping die heat treatment

The stability of the die and the stability of the metal stamping process are determined. We summarized some common defects and solutions of metal stamping die in the process of heat treatment in daily production, and shared with you. First of all, the causes of overheating and excessive combustion of parts during quenching: 1. Material confusion. 2. The heating temperature is too high. 3. The holding time at high temperature is too long. Solution: 1. Spark identification must be carried out on the parts before quenching to prevent the use of wrong materials. 2. Strictly control the heating temperature and observe the process regulations. 3. Control reasonable holding time. If the part is overheated or burned excessively, normalizing and annealing shall be carried out on the workpiece, and then heat treatment shall be carried out according to the technical procedures to save parts. Secondly, the spots and corrosion on the surface of quenched parts are caused by the following reasons: 1. When heated in a box furnace, the surface protection is very poor. 2. Poor deoxidation in salt bath. 3. When air cooling the workpiece, the precooling time is too long. The temperature of chlorine ion is too high. 5. The workpiece cannot be cleaned in time after quenching. Solutions: 1. The workpiece should be correctly packed in the packaging box and protected, and the protective agent should be dried before use. 2. The salt bath should be deoxidized completely in time. 3. For high alloy steel, try not to use air cooling quenching. 4. Control the temperature of the salt bath not to exceed 500 ° C and keep it clean. 5. Clean the parts in time after quenching. Thirdly, the soft spots on the surface of quenched parts are caused by the following reasons: 1. The structure of raw fiber is not uniform, such as carbide segregation, aggregation and distribution. 2. During the heating process, there are oxide scales and rust spots on the surface of the workpiece, resulting in partial surface decarburization. 3. Aging of quenching medium or excessive impurities, uneven cooling rate. 4. After cooling the cooling medium of large parts, the movement is not smooth. Solutions: 1. The raw materials need reasonable forging and annealing. 2. Before quenching, please check carefully to remove scale and rust spots. 3. Clean and replace the cooling medium regularly, and keep the cooling medium clean all the time. 4. After the workpiece enters the quenching medium, it should be operated correctly according to the regulations. 4、 The causes of quenching cracks are: 1. Improper material selection or cracks in the material itself. 2. Cracks occurred during forging. 3. There is machining stress. 4. There is no need to preheat and the heating speed is too fast. 5. Heating temperature is too high or holding time is too long. 6. Improper selection of cold quenching medium or too fast cooling speed. 7. After quenching with water and oil, the workpiece stays in water for a long time. 8. In the stage quenching, the workpiece is washed too fast with water after taking out the stage cooling liquid. 9. The pressure is too concentrated. 10. Quenching many times, there is not enough annealing in the middle. 11. Tempering in time after quenching. 12. Surface carbonization or decarburization. Solutions: 1. Reasonable selection of steel, and strengthen management and careful inspection. After forging and annealing, the temperature should be controlled reasonably. 3. Before the final processing of the metal die, the size of the metal die should be corrected after stress relief, and then the final quenching should be carried out. 4. Use preheating and cooling as much as possible. It is better to preheat high alloy steel twice. 5. Strictly control quenching temperature and holding time. 6. Choose the quenching medium correctly to slow down the cooling rate, and it is better to use the stage cooling process. 7. Strictly implement the correct cooling process. When the cooling liquid is quenched to room temperature, the cooling liquid should be taken out first and then graded. 9. Before quenching, take protective measures, such as binding with iron, binding iron wire and scaling. 10. Intermediate annealing process shall be adopted for re quenched parts. 11. Tempering in time after quenching. 12. During quenching and heating, take reasonable protection measures. If salt bath deoxidization is adopted, the box furnace is used to pass the protective gas. The fifth is the reason of insufficient quenching hardness: 1. Low hardenability and large cross-sectional area. 2. Surface decarburization during quenching and heating. 3. The quenching temperature is too high or too low, and the holding time is short. 4. When grading and quenching, the time left in the cooling medium is too long or too short. 5. After water and oil quenching, the time of workpiece staying in water is too short. 6. Too much water in alkaline bath. Solutions: 1. 2. Pay attention to heating protection and make the salt bath completely deoxidized. 3. Strictly implement quenching process specification. 4. Strictly implement the correct cooling process. 5. Operate according to the correct cooling process. 6. Strictly control the water content of salt bath in the range of 2% - 4%. 6. The surface is corroded after tempering. Cause: no timely cleaning after tempering. Solution: metal stamping die parts burned in the same fire should be cleaned in time. 7、 The reason of high hardness after annealing: 1. 2. Insufficient insulation time. 3. The cooling speed is too fast. Solution: strictly follow the correct process. If the hardness is too high after annealing, it should be annealed again according to the correct method. Eighth, tempering brittleness is caused by low tempering temperature or insufficient tempering time. Solution: choose suitable tempering temperature and enough tempering time to avoid tempering brittleness temperature. 9、 After tempering, cracks were found in the grinding process. The reason was insufficient tempering. Solution: complete tempering should be carried out after quenching, and secondary tempering should be used for high grade steel as much as possible. The reasons for the existence of network carbide in annealed microstructure are as follows: 1. The forging process is unreasonable. 2. Unlimited spheroidizing annealing process. Solutions: 1. Reasonable forging. 2. Re annealing according to the correct spheroidizing annealing process.