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3716863 
Book/Book Chapter 
Influence of Mn and S on Mechanical Properties of Gray Cast Iron: Part I - Historical Perspective 
Gundlach, RB; Amer Foundry Soc 
2014 
Transactions of the American Foundry Society 
122 
287-303 
WOS:000381165800029 
A literature review has been conducted to investigate the roles of Mn and S in gray cast iron and their influence on mechanical properties. Sulfur is generally considered a tramp element, and its level must be controlled. At low manganese concentrations, sulfur reacts with iron to produce a low-melting phase (FeS) that may produce carbides and hot-shortness. Consequently, industry routinely adds Mn to control S.



Many investigators studied the influence of Mn and S on the strength of gray cast iron. Most studies showed a pronounced effect. Several correlated Mn and S with strength based on stoichiometric balancing. Some correlated strength with Mn and found dramatic increases in strength at lower Mn concentrations, particularly at concentrations insufficient to balance S. Others correlated strength with S and saw strength both increase and, at times, decrease with increasing sulfur content.



For many years, it has been recommended that Mn should be added in excess of the stoichiometric ratio (Mn:S = 1.7:1). The concept of 'excess Mn' suggests that Mn can completely tie up S prior to solidification. However, thermodynamic calculations show that, at any Mn concentration, there is always some free S in solution in the molten iron during eutectic solidification. Based on thermodynamic calculations, the equilibrium constant, K-eq, for the reaction Mn + S -> MnS is around 0.03 at the eutectic temperature.



A few investigators revealed that strength peaks at certain Mn and S levels. The peak strength was as much as 37% higher than strengths above and below the optimum, and was found to coincide with the limit of MnS solubility. Hence, there are two regions in cast iron chemistries: (1) the region above the solubility limit of MnS, when MnS precipitates from the melt prior to reaching the eutectic temperature and (2) the region where Mn and S are fully soluble at the onset of eutectic solidification.



The results of this literature review were used as the basis for a research project (Parts II and III) to further understand how to balance Mn and S for maximum strength. 
cast iron; cell count; chill; hardness; manganese; Mn:S ratio; nucleation; strength; sulfur