Understanding Electric Arc Furnace Steel Making Operations Feb18

Understanding Electric Arc Furnace Steel Making Operations...

Understanding Electric Arc Furnace Steel Making Operations  Electric arc furnace (EAF) steel making technology is more than hundred years old. Though De Laval had patented an electric furnace for the melting and refining of iron in 1892 and Heroult had demonstrated electric arc melting of ferro alloys between 1888 and 1892, the first industrial EAF  for steel making only came into operation in 1900. Development was rapid and there was a tenfold increase in production from 1910 to 1920, with over 500,000 tons being produced in 1920, though this represented still only a very small percentage of the global production of steel  of that time. Initially, EAF steelmaking was developed for producing special grades of steels using solid forms of feed such as scrap and ferro alloys. Solid material were firstly melted through direct arc melting, refined through the addition of the appropriate fluxes and tapped for further processing. Fig 1 shows a typical plan and section view of an EAF Fig 1 Typical plan and section view of an EAF  Electric arc furnaces range in capacity from a few tons to as many as 400 tons, and a steel melting shop can have a single furnace or up to three or four. In brief, these furnaces melt steel by applying an AC current to a steel scrap charge by mean of graphite electrodes. It requires a tremendous quantity of electricity. The melting process involves the use of large quantities of energy in a short time and in some instances the process has caused disturbances in power grids. These disturbances have usually been characterized as ‘flicker’ (brief irregularities in voltage a fraction of the 50 -60 Hz cycle in length), and ‘harmonics’ (irregularities that tend to occur in a pattern repetitive to the 50-60 Hz...

Ladle Metallurgy Apr23

Ladle Metallurgy

Ladle Metallurgy After tapping of steel from a primary steelmaking furnace such as BOF, EAF or EOF, molten steel for high quality or specialty applications is subjected to further refining in a number of alternative processes collectively known as ladle metallurgy. Ladle metallurgy is sometimes also called ladle refining or secondary steelmaking. Ladle metallurgy processes are commonly performed in ladles. Tight control of ladle metallurgy is associated with producing high grades of steel in which the tolerances in chemistry and consistency are narrow. The objectives of ladle metallurgy are the following. Homogenization – Homogenization of chemical composition and temperature of liquid steel in the ladle Deoxidization or killing – Removal of oxygen Superheat adjustment – Heating of the liquid steel to a temperature suitable for continuous casting Ferro alloys and carbon additions – Making adjustments in the chemistry of liquid steel. Vacuum degassing – Removal of hydrogen and nitrogen Decarburization – Removal of carbon for meeting the requirement of certain grades of steel. Desulfurization – Reduction of sulfur concentrations as low as 0.002% Micro cleanliness – Removal of undesirable nonmetallic elements Inclusion morphology – Changing the composition of remaining impurities to improve the microstructure of the steel Mechanical properties – Improvement in toughness, ductility, and transverse properties Depending on the types of steel required, one or more of the following ladle metallurgy processes are used. These are (i) rinsing or stirring, (ii) ladle furnace, (iii) ladle injection (iv) ladle refining, (v) degassing processes, (vi) AOD process, and (vii) CAS-OB (Composition adjustment by sealed argon bubbling with oxygen blowing) process. Some of the ladle metallurgy processes are shown in Fig 1. Fig 1 Some of the ladle metallurgy processes  Historical background  The treatment of steel in the ladle started around 45 years ago when the first ladle-to-ladle and ladle-to-ingot mold vacuum...