Now briefly summarize the precautions for the production of ductile iron.
(1) The sulfur content of the original molten iron and other trace elements should not be too high. If the original molten iron content and other trace elements are too high, more spheroidizing agent or spheroidizing agent with higher rare earth content is needed, so that the cost of the spheroidizing agent increases, and too much spheroidization The agent will cause more slag, which is not conducive to the stability of the casting quality. If the content of rare earth is too large, it will easily produce broken graphite on the casting of large section.
(2) Stability of spheroidization treatment. The spheroidizing process is a key process in the production process of ductile iron. Only the spheroidizing process is stable, and the quality of the casting can be stabilized. For different products, different raw iron liquid sulfur content, how many spheroidizing agents, inoculants, etc., should be written into the operation instructions and strictly enforced.
(3) Avoid long waiting times. After the spheroidizing treatment, the pouring should be carried out immediately. Because over time, residual magnesium will burn out and the inoculation effect will decline.
(4) Avoid excessive magnesium content. Higher residual magnesium content will increase the tendency of the casting to shrink. For general ductile iron, the residual magnesium content (mass fraction) should be controlled at 0.035%~0.045%. For high nickel ductile iron, the residual magnesium content should be controlled at 0.06%. ~0.07%.
(5) Use a better inoculant for castings with higher requirements. For high-demand wind power components, high-iron parts, etc., you should choose a flow-inducing agent (such as the patented Ultraseed/Ce) that has a strong effect. It is characterized by a significant increase in the number of graphite balls and a rounded shape of the graphite.