Simple Solutions That Work! Issue 7

Granular iron pyrites additions were at a rate of 1.0 pound (0.49 pounds of contained sulfur or 0.032% S) per 1,550 pounds of treated metal, with a target of 0.03% Mg residual after Mg treatment. Iron sulfide briquettes were added at a rate of 0.75 pounds (0.225 pounds of contained sulfur or 0.015% S) per 1,500 pounds of metal. The influence of initial sulfur level in the base iron was examined for several magnesium addition levels (Mg(add) additions of 0.04 to 0.05%) and a late sulfur addition (S(add) additions were 0.031%) in the form of one pound of finely granulated FeS2. The use of the finely granulated iron pyrites produced poor and inconsistent recoveries. Resulf 30 FeS2 briquettes containing 30% sulfur allowed for consistent sulfur recoveries and control over the final sulfur content. The results summarized in Table 1 show the various rations of magnesium added, magnesium recovered, initial sulfur and final sulfur levels and the level of CG iron produced using Resulf 30 FeS2 briquettes. The amount of compacted graphite produced was 83.75% with a standard deviation of 5.7 based on 17 heats. The use of iron sulfide briquettes provided significantly improved control of sulfur. Final magnesium levels and sulfur levels were 0.030% and 0.021% respectively. The ratio of Mg (fin) to S (fin) was 1.463 with a standard deviation of 0.30. TABLE 1: Magnesium and Sulfur Relationships in CG Iron - Resulf 30 Iron Sulfide Briquettes Initial S (in) % % Mag add % S add Mg(add)/ Final Final % Mg(fin)/S(fin) Mg(fin)/S(in) % CG Mg(add) S(add)briquettes S(in)ratio %Mg(fin) S(fin) ratio ratio 0.0136% 0.0333% 0.0186% 2.480 0.0296% 0.0209% 1.43 2.24 83.75% Std Dev. 0.0026% 0.0024% 0.0025 0.0072% 0.0064% 0.30 0.656 Sulfur additions rates for briquettes were reduced to an average of 0.019% compared to 0.031% for granular powder additions of iron pyrites. The briquetted iron pyrites appeared to provide the consistency for producing compacted graphite with 80% minimum compacted structures. The standard deviation for compacted graphite production decreased to 5.7 compared to 10.82 for granular additions tested under the same conditions. Because of the favorable results obtained with the Resulf 30 iron sulfide briquettes, a series of heats were made from a gray base iron having an initial sulfur content of 0.057 percent. The averages of 6 heats of resulfurizing a gray base iron after magnesium treatment is shown in Table 2. TABLE 2: Magnesium and Sulfur Relationships in CG Iron from Gray Base irons - Resulf 30 Iron Sulfide Briquettes Initial S (in) % % Mag add % S add Mg(add)/ Final Final % Mg(fin)/S(fin) Mg(fin)/S(in) % CG Mg(add) S(add)briquettes S(in)ratio %Mg(fin) S(fin) ratio ratio 0.057% 0.037% 0.016% 0.64 0.024% 0.014% 1.70 0.410 81% Std Dev. 0.0011% 0 0.025% 0.0039% 0.0021% 0.42 0.07 6.5 Table 2 shows that it was possible to produce compacted graphite iron from a gray iron furnace chemistry. The compacted graphite irons so produced exhibited microstructures containing an average of 81% compacted graphite. The ratios of Mg (fin) to S (fin) to the percentage of compacted graphite formed increased somewhat to 1.7. This ratio is still well within the standard deviation calculated in Table 1, where the most consistent compacted graphite structures were obtained. Precise control of sulfur recovery is an essential feature of this technology and it has been demonstrated to be easily achievable in foundry conditions, for both ductile iron and compacted graphite iron. The addition of controlled amounts of sulfur widen the magnesium “window” from which CGI can form. This technique has been found to be a low cost and reliable method to consistently manufacture CGI without costly thermal analysis equipment, licensing fees and without the use of harmful trace elements. Additional details and findings can be found from the paper entitled “Magnesium-Sulfur Relationships in Ductile and Compacted Graphite as Influenced by Late Sulfur additions”, paper No. 03-093 that was published in 2003 at the AFS, authored by I. Riposan and R. L. Naro. 30 Contact: ROD NARO [email protected]