94 • Marine Minerals: Exploring Our New Ocean Frontier 



Manganese 

 Properties and Uses 



Manganese plays a major role in the production 

 of steels and cast iron. Originally, manganese was 

 used to control oxygen and sulfur impurities in 

 steel. As an alloying element, it increases the 

 strength, toughness, and hardness of steel and in- 

 hibits the formation of carbides which could cause 

 brittleness. Manganese is also an important alloy- 

 ing element for nonferrous materials, including alu- 

 minum and copper. 



Hadfield steels containing between 10 and 14 

 percent manganese, are wear-resistant alloys used 

 for certain railroad trackage and for mining and 

 crushing equipment. An intermediate form of man- 

 ganese alloy — ferromanganese — is usually used in 

 the manufacture of steels, alloys, and castings. Be- 

 cause manganese can exist in several chemical ox- 

 idation states, it is used in batteries and for chemi- 

 cals. Several forms of manganese are used in the 

 manufacture of welding- rod coatings and fluxes and 

 for coloring bricks and ceramics. 



National Importance 



Demand for manganese is closely related to steel 

 production. Two major trends have combined to 

 lessen domestic consumption of manganese. First, 

 domestic steel production has declined; in 1986, it 

 was at about half of its peak year in 1973, when 

 the U.S. produced 151 million tons of raw steel. 

 Second, developments in steel manufacturing tech- 

 nology have reduced the per-unit quantities of man- 

 ganese needed. As a result, manganese consump- 

 tion decreased from 1.5 million tons (contained 

 manganese) in 1973 to 700,000 tons in 1986. 



In the early 1970s, the United States was import- 

 ing about 70 percent of its manganese in the form 

 of ores, a large share of which was processed into 

 ferromanganese by U.S. producers. By 1979, the 

 picture had reversed, with imports of foreign- 

 produced ferromanganese running at about 70 per- 

 cent and manganese ores at about 30 percent. Since 

 1 983 , imports have been about one-third as ore and 

 two-thirds as ferromanganese and metal (figure 3- 

 5). There currently is no remaining domestic ca- 

 pacity for ferromanganese production. 



Figure 3-5.— Percentage of Manganese Imported 

 Into the United States as Ferromanganese, 1973-86 



79 80 81 82 83 84 85 86 

 Year 

 Like chromium and ferrochromium, tlie proportion of man- 

 ganese imported by tlie United States as ferromanganese and 

 manganese metal has increased compared to imported man- 

 ganese ore. Manganese producing countries find it advan- 

 tageous to ship processed ferromanganese or metal rather 

 than unprocessed ore to gain the value added for export. 



SOURCE: Office of Tecfinology Assessment, 1987. 



Today, the United States is highly dependent on 

 foreign sources for manganese concentrates, ores, 

 ferromanganese, and manganese metal. About 30 

 percent of the imports (based on contained man- 

 ganese) are from the Republic of South Africa, 16 

 percent from France (produced largely from ore im- 

 ported from Gabon), 12 percent from Brazil, 10 

 percent from Gabon, and 32 percent from diverse 

 other sources. ^^ 



Manganese is a strategic material which is criti- 

 cal to national security and is potentially vulner- 

 able to supply interruptions (table 3-1). Several 

 forms of manganese are stockpiled in the National 

 Defense Stockpile (table 3-5). However, the diver- 

 sification of imports among many producing coun- 

 tries tends to somewhat reduce U.S. vulnerability 

 to supply interruptions, although some supplier na- 

 tions obtain raw material from less-secure African 

 sources. 



Domestic Resources and Reserves 



Manganese pavements and nodules (approxi- 

 mately 15 percent manganese) on the Blake Pla- 

 teau in the U.S. EEZ off the southeast coast are 



'°T. Jones, "Manganese," Mineral Commodity Summaries — 1987 

 (Washingtons DC: U.S. Bureau of Mines, 1987), p. 98. 



