Ferromanganese

An alternative alloy is silicomanganese with, for example, 70% Mn, 15% Si and 2% C. Increased silicon content lowers the carbon content. Special grades for addition in stainless-steel production contain up to 30% Si and a very low C content. 

The world production of ferromanganese in the year 2000 was 3780 thousand tonnes of which 75% was made in electric furnaces and 25% in blast furnaces. The worldwide production of silicomanganese is almost as large as the ferromanganese production, so in 2000 a total of 7000 thousand tonnes were produced of the two manganese alloy types. China made 27% of the total, Ukraine 14, South Africa 11, France 7, Norway 7 and Japan 6%. [27.4]. 

---

Siemens s process A method of steel manufacture by addition of scrap metal, iron oxides and ferromanganese to molten pig (cast) iron. 

Ferroin complexes Ferromagnetic materials Ferromagnetism Ferromagnets Ferromanganese... 

Fig. 2. Schematic diagram of manganese metallurgy where HCFeMn = high carbon ferromanganese MCFeMn = medium carbon ferromanganese ...

SiMn = silicomanganese LCFeMn = low carbon ferromanganese LCSiMn = low carbon siUcomanganese FeMnN = nitrided ferromanganese and... 

Table 10. World Production of Ferromanganese and Silicomanganese, 10 t gross weight...

Data for blast fiimace ferromanganese iucludes spiegeleisen, if any. 

Ferromanganese is produced iu blast fiimaces and electric smelting fiimaces. Economics usually determine which smelting process is chosen for ferromanganese. Both methods require about the same amount of coke for reduction to metal, but iu the case of the blast fiimace, the thermal energy required for the smelting process is suppHed by the combustion of additional coke, which iu most countries is a more expensive form of energy than electricity. 

Table 11. Operating Data for a Ferromanganese Electric Furnace ...

This product is mainly used within the ferroalloy plant as the reducing agent in a silicothermic process to produce the low carbon grade of refined ferromanganese. 

Refined Ferromanganese. Refined ferromanganese refers to alloys that are not carbon saturated and range from less than 0.10 to 1.50% maximum carbon. Medium carbon grades are used in special grades of steels where in final additions carbon control is important. The low carbon grades are used mainly in the production of certain grades of stainless steels. 

In the past, all grades of refined ferromanganese were made by various modifications of multistep silicon reduction processes. Depending on the carbon content desired in the product, a manganese ore and lime mixture was allowed to react with the silicon in silicomanganese or low carbon silicomanganese in an open, electric-arc furnace. The equilibrium reaction is... 

Plant Safety. Of the many ferroalloy products produced in electric furnaces, ferromanganese has the greatest potential for furnace emptions or the more serious furnace explosions. The severity of the explosions increases with the size of the furnace. Such incidents are infrequent, but can occur, and when they do are often disastrous. Explosions usually result in extensive damage to the furnace and surrounding area, and often severe injuries or death to personnel in the immediate area. An emption is the sudden ejection of soHds, Hquids, or gases from the furnace interior. A more violent and instantaneous ejection of material, accompanied by rapid expansion of burning gas, is considered an explosion (38). 

Safe operation of ferromanganese furnaces requires careful control of raw material particle size, oxygen content of the ore blend, and charge stoichiometry (38). 

---