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Silicomanganese (Si-Mn):

Silicomanganese (Si-Mn):

Silicomanganese is used as a more effective deoxidizing agent than high carbon ferromanganese in the production of various types of steels. It is also used as feed stock to produce refined alloys like medium and low carbon ferromanganese. There is an increase in usage of silicomanganese in the steel making. Silicomanganese is preferred in many of the mini steel mills because it contains the right proportion of manganese and silicon and low carbon. As per the BIS specifications (IS: 1470-1990) the silicomanganese contains 14-28% Si, 50-74% Mn and 1to 2.5% C.

The presence of silicon has the added advantage of producing cleaner steel and also has the property of reducing the time required from the stage of alloy addition to the pouring of ingot. Besides, it gives better mechanical properties due to change in morphology of deoxidation products in regular round shape, and consequently the non-metallic inclusions are brought down in finished products.

Manufacture of silicomanganese

  • For the manufacture of silicomanganese, the grade of manganese ore should be much of the same as for the manufacture of ferromanganese, but lower percentage of manganese as low as 35% are permissible with higher silica content. There are no BIS specifications for use of manganese ore in the production of silicomanganese. However, specifications prescribed by BIS for the manufacture of silicomanganese are available.
  • The BIS has specified six grades of silico manganese. The requirements for various grades of silicomanganese commonly used in iron & steel industry as per IS: 1470-1990 of BIS are given in Table: 2.6.
  • It is lumpy material with a silvery metallic surface.
  • Both silicon and manganese have an important influence on the properties of steel
  • Silicon and manganese have a strong affinity for oxygen, and will act as deoxidisers
  • Deoxidation with SiMn results in cleaner steel, as the liquid manganese silicate formed coagulates and separates easier from the melt.
  • It finds extensive applications as deoxidizer and an alloying element in steel.