Sampling and testing from the fracture of failed steel castings showed that their chemical composition was qualified, and their mechanical properties had low impact energy. Their strength and elongation were both lower than the standard values, and their mechanical properties did not meet the requirements.
| Project | Tensile strength/MPa | Yield strength/MPa | Elongation rate/% | Impact absorption energy/J | Hardness/HB |
| Standard requirements | ≥ 550 | ≥ 355 | ≥ 22 | ≥ 27 | 146~196 |
| Detection result | 535 | 335 | 17 | 18 | 162 |
Analysis suggests that the main reason is unreasonable heat treatment. The mechanical performance testing of steel castings is shown in the table.