Summary of Nodulizing Agent in the Production of Nodular Graphite Cast Iron
Release time:
2024-07-25
Ductile iron with ferrite and pearlite as the matrix still accounts for the vast majority of the output of ductile iron, so pay attention to improve the performance and quality of regular ductile iron.
regular ductile iron
At present, regular ductile iron, which is based on ferrite and pearlite, still accounts for the vast majority of the output of ductile iron, so pay attention to improving the performance and quality of regular ductile iron, which plays an important role in maintaining the competitive position of ductile iron.
1.1 Strengthen the Control of Factors Affecting the Quality of Ductile Iron
The organization and properties of ductile iron depend on the composition and crystallization conditions of cast iron and the quality of the spheroidizing agent used, and it is believed that in order to ensure the mechanical properties of ductile iron, it is necessary to strictly control the specific wall thickness of the casting, pouring temperature, spheroidizing agent used, spheroidizing treatment process, optimization of cooling parameters and effective slag removal measures, and appropriate reduction of carbon equivalent, alloying and heat treatment are effective measures to improve ductile iron.
1.2 effective control of the production of ferritic ductile iron and spheroidal ductile iron
The main factors controlling the ductile iron matrix are the composition of cast iron, the type of spheroidizer and inoculant used, the method of addition and the cooling conditions.
Composition Control of As-cast Ferrite Ductile Iron
Micro-hypereutectic composition, in which carbon is slightly higher, but graphite floating does not occur, silicon content is slightly lower, silicon content of inoculant should be less than 3%, manganese is as low as possible, Mn<0.4, sulfur and phosphorus should be low, S ≤ 0.02%, P ≤ 0.02%, this is because silicon can improve ductile iron structure and corresponding plasticity, Si = 3.0~3.5% can obtain all ferrite structure. Some studies have pointed out that when Si = 2.6~2.8%, cast iron has the highest elongation and impact toughness, but with the increase of phosphorus content, the microsegregation of silicon in iron is more serious and has adverse effects on mechanical properties, especially when the temperature is lower than zero, and low sulfur content can be used to spheroidize low magnesium and low rare earth spheroidizing agent, and reduce the generation of "black spot" defects, the "black spots" are mainly aggregates of magnesium, cerium sulfides and oxides. In addition, low-silicon spheroidizing agents are also used to ensure multiple inoculation.
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