matters for production of ductile iron

After inoculation, the cast iron with spherical graphite replaces the usual flake graphite cast iron, which is called ductile iron.

(1)The sulfur content and other trace elements of the original molten iron should not be too high. If the sulfur content and other trace elements in the original molten iron are too high, more spheroidizing agent or the spheroidizing agent with a higher RE content is required, so the cost of the spheroidizing agent will increase, and excessive spheroidizing  agent will cause more slag, which is not conducive to the stability of casting quality. Too much RE content will easily produce fragmented graphite on large-section castings.

(2)The stability of spheroidization. The spheroidizing process is a key process in the production of nodular cast iron. Only when the spheroidizing process is stable can the quality of the casting be stable. For different products, different sulfur content of the original molten iron, how much nodulizer and inoculant should be added, must be written into the work instruction and strictly implemented.

(3)Avoid long waiting times. After the spheroidization inoculation, pouring should be carried out immediately. Because over time, the residual magnesium will burn and the inoculation effect will decline.

(4) Avoid excessively high residual magnesium content. Higher residual magnesium content will increase the shrinkage tendency of castings. For general ductile iron, the residual magnesium content should be controlled within 0.035%~0.045%, and for high nickel ductile iron, the residual magnesium content should be controlled within 0.06% ~0.07%.

(5)Use better inoculant for castings with higher requirements. For wind power parts and high-speed rail parts with higher requirements, the inoculant with strong inoculation effect  should be selected. Its characteristic is that it can significantly increase the number of graphite spheres, and the graphite spheres are rounded.

Spheroidizing agent and inoculant are the most important materials in the process of spheroidization. In addition to stable quality, the following factors need to be considered when choosing a suitable spheroidizing agent.

(1)Spheroidizing temperature: If the spheroidizing temperature is >1480℃, the spheroidizing reaction will be more intense, resulting in a lower magnesium absorption rate. In order to make the spheroidizing reaction stable, a spheroidizing agent with relatively high calcium content can be selected. If the spheroidizing temperature is less than 1480°C, a spheroidizing agent with a relatively low calcium content can be used.

(2)Treatment bag size: If the height-to-diameter ratio of the treatment bag is 1:1, the loss of magnesium vapor will reduce the magnesium absorption rate. It is recommended to use a spheroidizing agent with a higher calcium content. If the height-to-diameter ratio of the treatment package is 2:1, the spheroidization reaction will be relatively stable, the magnesium vapor will diffuse into the molten iron, and the magnesium absorption rate will be improved.

There are various types of spheroidizing agent and inoculant for choice, the inoculant general types such as ferro silicon granule 3-8mm, ferro barium silicon, ferro barium silicon calcium etc, the spheroidizing agent such as RE ferro silicon magneisum 5-35mm or 5-30mm etc, Anyang Huatuo Metallurgy Co.,Ltd in materails for production of ductile iron more than 10 years, if you 

do not know how to chooce proper types can contact us.