An Improved Process for the Production of Low-Carbon Ferromanganese in the Electric Arc Furnace
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ORIGINAL ARTICLE
An Improved Process for the Production of Low-Carbon Ferromanganese in the Electric Arc Furnace Navneet Singh Randhawa1
•
Rajesh Kanyut Minj1
Received: 5 November 2019 / Accepted: 18 May 2020 Ó The Indian Institute of Metals - IIM 2020
Abstract Low-carbon ferromanganese (LC-FeMn) is an essential ingredient for making high-strength low-alloy steel and stainless steel. The conventional industrial-scale silicothermic method for the production of LC-FeMn comprises several energy intensive complex steps consuming about 2000 kWh/ton. We have attempted an improved silicothermic process, which is based on a single step smelting of optimized charge mix in the electric arc furnace. Thermochemical simulation of the smelting process by FactSage 6.4 showed significant effect of the charge mix basicity (B = CaO/SiO2) on manganese, iron, silicon and phosphorous distribution between the metal and slag. The optimum basicity was found to be 1.5 at the charge mix ratio i.e., Mn ore/lime/SiMn of 1:1:0.6 in the smelting tests. Under optimum conditions, the energy consumption was about 690 kWh/ton. This approach has potential benefits for the ferromanganese industry in terms of simpler and energy efficient process. Keywords Electric arc furnace Manganese ore Low-carbon ferromanganese Silicomanganese Silicothermic reduction
1 Introduction Manganese is an essential alloying element in the steel making process [1]. Many of the properties of the steel are achieved by appropriate addition of manganese ferroalloys. & Navneet Singh Randhawa [email protected]; [email protected] 1
CSIR-National Metallurgical Laboratory, Jamshedpur 831007, India
Basic manganese ferroalloys, viz. Ferromanganese (FeMn) and silicomanganese (SiMn), represent about 42% of the total ferroalloy production in India [2]. Ferromanganese is classified as low-carbon (LC-FeMn/0.2%Cmax), mediumcarbon (MC-FeMn/1-3%C) and high-carbon (HC-FeMn/68%C) alloys by carbon content. The manganese ferroalloys have high utilization in the steel making process. Some of the special steels such as high strength low alloy steel and stainless steel need LC-FeMn for alloying to maintain the carbon content. Indian Bureau of Mines [2] has archived a couple of low-capacity (* 25 T/year) LC-FeMn production units in Mineral Year Book 2014. However, specific plant information on the generation of low-carbon (LC) and medium-carbon ferromanganese (MC-FeMn) is not available. The supply of LC-FeMn ferroalloy has been largely met through imports. There are three methods to produce the LC-FeMn. They are (1) decarburization of HC-FeMn, (2) aluminothermic reduction of manganese ore, and (3) silicothermic reduction of manganese ore [3]. All these methods involve exothermic reactions. The decarburization of HC-FeMn entails top or bottom blowing of oxygen into the molten HC-FeMn in a converter. This process generally operates at tonnage scale giving high throughput. Low manganese yield is the major drawback of this process. The low yield is attributed to the loss of manganese b
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