When nodular cast iron is cast, the amount of nodularizing agent will directly affect the graphite morphology in cast iron, the comprehensive properties of nodular cast iron and the production cost. Therefore, since the appearance of nodular cast iron, the amount of nodulizing agent has been one of the most important factors to be considered in the production of nodular cast iron. There are many factors that affect the addition amount of nodulizer, mainly including the composition, specific gravity, particle size and metallurgical quality of nodulizer; The content of sulfur in molten iron, the temperature of molten iron and its metallurgical quality; Geometric dimensions of castings; The spheroidizing treatment process adopted during pouring, including the shape and size of the ladle, as well as the coverage of the spheroidizing agent during the spheroidizing treatment.
Therefore, the spheroidizing treatment of nodular cast iron is a complex metallurgical process, which is affected by many factors. In order to determine the influence of the addition amount of spheroidizing agent on the graphite morphology of cast iron, the Y-shaped pattern is selected as the research object in this part of the test. When its structure and size are shown in the figure, different contents of spheroidizing agent are added to the metal solution. The spheroidizing agent added during the test is fesimg8re3 alloy, and the addition amount is 1.4%, 1.1%, 0.8% and 0.5% of the burden weight respectively. In order to make the silicon content in cast iron similar and reduce the difference of cast iron matrix structure caused by different silicon content, the addition amount of inoculant is 0.4%, 0.6%, 0.7% and 0.9% of the weight of furnace charge respectively, and the treatment temperature of molten iron is 1510 ° C. The chemical composition of castings obtained is shown in the table.
| Addition amount of spheroidizing agent | C | Si | Mn | S | P | Mg residue | Re residue |
| 1.4% | 3.67 | 2.185 | 0.561 | 0.015 | 0.029 | 0.049 | 0.021 |
| 1.1% | 3.74 | 2.164 | 0.523 | 0.018 | 0.024 | 0.033 | 0.016 |
| 0.8% | 3.62 | 2.201 | 0.507 | 0.020 | 0.019 | 0.021 | 0.013 |
| 0.5% | 3.70 | 2.177 | 0.414 | 0.015 | 0.023 | 0.009 | 0.011 |
After casting, metallographic observation was carried out at the bottom of Y-shaped sample to study the effect of nodulizing agent on graphite morphology and matrix structure of cast iron alloy.