As cast crankshaft castings with nodular cast iron trademark of QT800-2 are selected as the samples. After testing, the nodularity grade is grade 2, the graphite size is grade 5~6, and the chemical composition is shown in Table.
| Element | C | Si | Mn | P | S |
| Content | 3.78-3.99 | 1.83-2.26 | 0.46-0.50 | 0.05-0.06 | 0.022 |
Considering the test sample requirements, processing difficulties, heat treatment oxidation decarburization and other factors, it is first processed into quasi tensile samples and quasi notchless impact samples with a machining allowance of not more than 1 mm under the as cast condition, and then processed into standard tensile samples and standard impact samples after isothermal quenching of ductile iron.