Due to large size, multiple processes, long cycle, unbalanced process, and many unstable factors, large forgings often have serious uneven structure and performance, and cannot pass mechanical property tests, metallographic structure inspections, non-destructive testing, etc.

The following factors may cause serious uneven structure and performance of large forgings and unqualified quality.

1. Segregation of chemical composition of ingots,

2. Aggregation of inclusions,

3. Influence of various pore defects,

4. Slow temperature change,

5. Uneven distribution,

6. Large internal stress,

7. Many defects,

8. High temperature and long time forging,

9. Local deformation,

10. Plastic flow conditions,

11. Degree of compaction,

12. Uneven deformation distribution,

13. Slow cooling and diffusion process,

14. Complex structure transformation,

15. Large additional stress.