In order to minimize the content of harmful elements, the selected raw materials should be relatively pure, so high-quality pig iron, scrap steel and some reheated iron are used for melting. Melt in the furnace according to a certain feeding sequence; Control appropriate melting temperature, sampling temperature and overheating temperature; Ensure that the process is compact and free from tarpaulin, overburning and other phenomena.
1. Burden ratio
In order to achieve the pre selected chemical composition, the burden ratio is determined according to the proportion in Table based on the experience of producing nodular cast iron all the year round.
| Pig iron /% | Scrap /% | Return material /% |
| 30-50 | 10-30 | 30-50 |
2. Spheroidizing treatment
The addition amount of nodularizing agent for nodular cast iron is mainly related to the content of s in the original molten iron and the temperature of molten iron. The addition amount is 0.9% ～ 1.2%. FeSiMg alloy is selected, and its main chemical components are 4% ～ 6%mg and 40% ～ 45%si. The spheroidizing agent of nodular cast iron is embedded in the ladle, and the spheroidizing treatment is carried out by the impact method to ensure that the spheroidizing reaction begins when the iron tapping is more than 70%. The appropriate tapping temperature should be controlled to avoid the oxidation and burning loss of the nodulizer during the nodulizing process.
3. Inoculation treatment
Basi inoculant is selected for inoculation. Its main components are 70% – 75% Si and 4% – 6% ba. The particle size of nodular cast iron inoculant is moderate, and the addition amount is 0.8% – 1.0%, so as to ensure that the inoculated molten iron is uniform and sufficient.