Defects and Countermeasures of Large Forgings
With the deepening of industrialization, rising labor costs and environmental pollution, large forgings have become an indispensable technology in the machinery manufacturing industry. Big forgings are often used in the manufacture of precision machine parts, automobile and motorcycle parts, pecified tools, etc. They have the advantages of high strength, good wear resistance, and a variety of complex shapes. Due to the relative complexity of the forging process, some forging defects are inevitable and require special attention. Generally speaking, the common defects of large forgings are shrinkage holes and looseness.
Shrinkage holes refer to the internal or external surface of the forging with small or large round or polygonal pits or bubbles, which are located at the same spot or scattered in different parts of the forging surface. The appearance of shrinkage holes on forgings is generally caused by the too large amount of plastic strain contained in the metal at the time of forging, and the shrinkage hole size is affected by different factors such as the strain, the residual stress, the structure of the material, and the deformation conditions.
The loosening of large forgings generally refers to the fragmentation of forgings due to excessive stress or long-term use of forgings, which is often caused by improper heat treatment or changes in external forces such as tension or vibration. Under normal circumstances, the larger the friction force and the agitation force, the more likely it is to cause loosening of the forgings.
Defects of shrinkage holes and looseness of large forgings are likely to cause serious economic losses, and it is necessary to take corresponding countermeasures. The following 6 points can serve as prevention measures:
1. Choose the right material: Generally speaking, the lower the density, the lower the forgings shrinkage, and the better the close-fitting forging process.
2. Reasonable planning of forging process: Ensure the forging temperature and forging pressure is appropriate.
3. More attention should be paid to the heat treatment process: Choose the appropriate heat treatment time, temperature and cooling method to ensure the correctness of the heat treatment process.
4. Strengthen the surface finishing of the forgings: Use enough pickling intensity, polishing intensity and grinding intensity to clear the shrinkage holes and other defects on the forgings surface.
5. Properly strengthen the assembly structure: Use appropriate assembly method to ensure firm connection between the forgings and increase the firmness of the forgings.
6. Take measures to ensure that the use environment of the forgings is safe: Pay attention to the temperature, humidity, vibration and other factors that affect the use of the forgings.
In the forging process of large forgings, there will always be shrinkage holes and looseness in the forgings, and if the relevant countermeasures are not taken or taken late, serious economic losses will result. Therefore, it is necessary to take corresponding preventive measures in production to ensure the quality of the forgings.
