Ductile cast iron is a high-strength cast iron material developed in the 1950s. Its comprehensive performance is close to that of steel. It is based on its excellent performance that it has been successfully used to cast some complex stress, strength, toughness, and wear resistance. Parts with high performance requirements. Ductile iron has rapidly developed into a cast iron material that is second only to gray cast iron and is widely used. The so-called “substituting iron for steel” mainly refers to ductile iron.
In order to obtain high-quality ductile iron castings, the spheroidization level of ordinary ductile iron castings in China is required to reach level 4 or above, that is, the spheroidization rate is 70%, and the ordinary casting reaches about 85%. In recent years, with the development of nodular cast iron production, especially in industries with high requirements for wind power casting production and casting quality, the nodularization grade is required to reach level two or above, that is, the nodularization rate of steel is over 90%. Through the analysis and improvement of nodular inoculation process, nodulizer and inoculant, the nodularization rate of nodular cast iron has reached over 90%.
So what are the functions of nodularizers and inoculants for ductile iron?
The nodularizer acts on the nodular cast iron, which can promote the crystallization of graphite into a spheroid, which is beneficial to obtain nodular graphite. The strength of the spheroidized nodular cast iron is much higher than that of gray cast iron, and its toughness is better than that of malleable cast iron, which effectively improves the mechanical properties of nodular cast iron. In particular, the plasticity and toughness of ductile iron are improved, so that cast iron has a higher strength than carbon steel.
China is rich in rare earth resources, and the commonly used nodulizers are ferrosilicon rare earth magnesium nodulizers. Most foreign countries use magnesium nodulizers, such as pure magnesium or magnesium alloys, and a few countries use calcium nodulizers.
Ferrosilicon Rare Earth Magnesium Nodulizer
Additives added to molten iron to make graphite crystals in cast iron spherical are called nodularizers. Magnesium is the element with the strongest spheroidizing ability, and the spheroidizing effect of rare earth is relatively stable, which can not be affected by other anti-spheroidizing elements. The effect of calcium is stable, but the spheroidizing ability is weak, and the addition amount is large. Metal calcium is easy to oxidize and cannot be used alone.
The inoculant acts on the ductile iron, mainly has the following functions:
1. Promote the formation of graphitization and reduce the tendency of whitening;
2. Refining grains, reducing segregation, uniform structure, and avoiding supercooled structure;
3. Improve the mechanical strength, the wall thickness sensitivity of light cast iron parts, so that the difference in microstructure between thin and thick sections of castings is small, and the difference in hardness is also small;
4. is conducive to the nucleation of eutectic clusters and increases the number of eutectic clusters;
5. The graphite in the cast iron is mainly in the form of fine and evenly distributed A-type graphite, thereby improving the mechanical properties of the cast iron.
Inoculants can not only act on ductile iron, but also improve the physical properties of gray iron and improve the performance. Commonly used inoculants for casting include ferrosilicon inoculant FeSi75/FeSi72, and silicon barium inoculant, 2-4 barium, particle size range is 0.2-0.8mm, 1-3mm, 3-8mm, Anyang Lishi Industrial can supply Inoculant and Nodulizer according to customers’ different needs, if any questions, feel free to contact us for more details.