There are many factors that affect the spheroidization rate and roundness of ductile iron. The following factors are analyzed from three aspects: chemical composition, technological process, and solidification control:
1. Chemical composition
1. Carbon equivalent and silicon
Carbon and silicon are the basic components that affect the roundness of ductile iron graphite balls. Under the relative cooling rate and inoculation conditions, increasing the carbon equivalent can improve the roundness of the graphite ball, increase the self-feeding ability, and reduce the carbide. Under the relative carbon equivalent conditions, with the increase of silicon content, especially large-section ductile iron, fragmented graphite will be produced. Therefore, in the case of no graphite floating, the carbon equivalent should be increased as much as possible; at the same time, the silicon content should be reduced as much as possible under the guarantee of inoculation conditions.
2. Magnesium
The control of effective residual magnesium content is very important to improve the roundness of graphite balls. When the effective residual magnesium is less than 0.045%, increasing the effective residual magnesium content can improve the roundness of graphite balls; when the effective residual magnesium is greater than 0.045%, metamorphic graphite will be produced, which will reduce the roundness of graphite balls.
3. Rare earth
Rare earth has two beneficial effects in molten iron: one is desulfurization and degassing, which plays the role of spheroidization and indirect spheroidization; the other is to interact with trace elements to eliminate the harmful side and play a favorable side. Both of these aspects can improve the roundness of graphite balls. However, excessive residual rare earth, especially large-section ductile iron, will deteriorate the shape of graphite, especially prone to fragmentation. The ideal range is 0.010% to 0.019%.
4. Trace elements
The relative amount of antimony and bismuth and supplemented by an appropriate amount of rare earth can improve the roundness of graphite balls and improve the mechanical properties. Appropriate addition range: 0.0025 to 0.005%.
2. Process
1. Spheroidization
(1) The heavy rare earth magnesium nodularizer can improve the roundness of graphite balls more than the light rare earth magnesium nodularizer. Mainly because of its strong desulfurization ability and strong anti-recession ability.
(2) If the process of light rare earth magnesium spheroidizer is well controlled and supplemented with trace elements, the roundness of graphite balls can also be improved.
(3) The quality of the molten iron is better than that of the subcontracting method, so it can also improve the roundness of the graphite ball.
2. Pregnancy treatment
(1) Strengthened inoculation can improve the roundness of graphite balls.
(2) The use of anti-recession inoculants can improve the roundness of graphite balls.
3. Using ductile iron filings as a covering agent for spheroidization can form a passivation graphite core similar to that of insoluble graphite dispersion, resulting in long-term concentration fluctuations, greatly increasing the effective nucleation rate, and improving the roundness of graphite balls. Spend.
4. Minimizing the pouring temperature can improve the roundness of the graphite ball.
3. Solidification control
1. The use of cold iron can improve the roundness of graphite balls.
2. The use of chromite sand can improve the roundness of graphite balls.
3. Other measures that can speed up the cooling and shorten the time during the eutectic transformation of the ductile iron can improve the roundness of the graphite ball.
Henan Aoudi Casting Co., Ltd.
Add：No. 90, Industrial Road, Tiexi District,
Qi County, Hebi, Henan
Tel：+86-0392-7275525
Email：ryan_shi@aoudi.cn
Copyright：© 2021 Henan Aoudi Casting Co., Ltd. 豫ICP备15009732号 Power by： 300.cn SEO
+86-0392-7275525
Email 