Development of the Technology of Electric Arc Furnace Steelmaking May05

Development of the Technology of Electric Arc Furnace Steelmaking...

Development of the Technology of Electric Arc Furnace Steelmaking  Development of the steelmaking technology takes place for meeting of a number of requirements. These requirements can be classified into four groups as given below. The technology has to meet the process requirements needed for producing different steel grades of required qualities. The technology is to meet the economic requirements needed for controlling the cost of production so that produced steel products are competitive. The technology is to meet the emission levels set by the regulatory agencies. The technology is to meet the health and safety requirements so that operators work in the area without any dangers, stress and stains. To understand electric arc furnace (EAF), it is necessary to understand what an electric arc is. An electric arc is a form of electrical discharge between two electrodes, separated by a small gap (typically, normal air). The best known example of this is lightning. Anyone who has performed arc welding is also familiar with electric arcs. If one connects the work piece to the negative side of a DC power source and an electrode to the positive side, touch the electrode momentarily and draw it a small distant apart from the work piece, then a stable electric arc forms between the electrodes and the work piece  and the heat from this arc is sufficient to melt the electrode and weld the work pieces together. The same idea is used in a larger scale in an electric arc furnace. The history of electric arc furnace (EAF) steelmaking is not very old. It is only slightly more than a century when the first furnace was commissioned to melt steel by utilizing electric power. The initial development of the technology took place, since these units made it possible...

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...

Submerged Arc Furnaces Jul15

Submerged Arc Furnaces...

Submerged Arc Furnaces  industrial utilization of electrical energy started with the development of the dynamo machine by Werner von Siemens. Electric arc furnaces have been used for many years both for the melting of scrap iron (open arc furnaces) and for reduction processes (submerged arc furnaces). In case of the submerged arc furnace (SAF), ore and reducing agent are fed to the furnace continuously from the top so that the electrodes are buried in the mix and the arc is submerged. The furnace is named submerged-arc furnace since the arc is submerged. The most common physical arrangement consists of a circular bath with three vertical electrodes arranged in a triangle. Six electrode furnaces with circular or rectangular baths are also used but they are less common. Submerged arc furnaces have found their application in more than 20 different main industrial areas such as ferro alloy, chemical industry, lead, zinc, copper, refractory, titanium oxide, recycling, phosphorus etc. A typical schematic diagram of a submerged arc furnace for ferro chrome production along with material balance is given at Fig.1 Fig 1 Typical schematic diagram of a submerged arc furnace for ferro chrome production along with material balance.  History  The increasing demand for ferro alloys and deoxidation agents in steel making in the beginning of the twentieth century led to the development of the first submerged arc furnace. The construction of the first SAF was started in 1905. This 1.5 MVA unit was installed in Horst Ruhr, Essen, Germany for the production of calcium carbide. It was successfully commissioned in 1906 and was based on DC (direct current) technology. Since then a large number of SAFs (both with DC and AC based furnaces) have been commissioned with diverse applications. Today, the majority of submerged arc furnaces are...

Iron Nuggets

Iron Nuggets  The process of production of iron nuggets is capable of directly producing solid, high density, highly metalized iron nuggets from dry green balls. These green balls are made out of iron ore fines, pulverized coal, fluxes and binders. The pulverized coal is reductant which is added to the system to supply the carbon required for the reduction and carburization. Binder (bentonite) in conjunction with the finely ground iron ore particles serves to improve the properties of green balls in wet and dried conditions. The flux is limestone, which fluidizes the slag and also prevents excessive iron losses in the slag. The iron nuggets are produced using a direct reduction process. The reduction process is carried out in a rotary hearth furnace, using coal as the reductant and energy source. The direct reduction of iron by this process is more energy efficient and more environmentally friendly than traditional iron making processes. The process for producing iron nuggets by ITmk3 is described in the article having link http://ispatguru.com/itmk-3-process-of-making-iron-nuggets/ Iron nuggets are an ideal feed material for steelmaking and iron casting. This material consists of essentially all iron and carbon, with practically no gangue (slag) and low levels of metal residuals. Fig 1 shows sample of iron nuggets. Fig 1 Iron nuggets  Iron nuggets are a premium grade iron product with superior shipping and handling characteristics. They can be shipped in bulk either inland in railway wagons or trucks or in the ocean going vessels. Iron nuggets can be stored outside with no special precautions. They can be handled as a bulk commodity using conventional magnets, conveyors, bucket loaders, clams, and shovels. The physical properties of iron nuggets are as follows. Colour – Gray Shape and appearance – Pebble shaped elliptical structure Size – 5...

Stainless Steel Manufacturing Processes May04

Stainless Steel Manufacturing Processes...

Stainless Steel Manufacturing Processes Stainless steels contain from 10 % to 30 % chromium. These steels also contain varying amounts of nickel, molybdenum, copper, sulphur, titanium, and niobium etc. The majority of production of stainless steel was through the electric arc furnace (EAF) till around 1970. With the use of tonnage oxygen in steel production, the EAF stainless steel making practice changed. Oxygen gas could be used for improving the decarburization rate. This could be achieved by injecting high oxygen potential but it was accompanied by the adverse reaction of extensive oxidation of chromium to the slag. This necessitated a well defined reduction period in which ferro silicon was used to reduce the oxidized chromium from the slag. Production of stainless steel started by duplex process with the successful development of argon oxygen decarburization (AOD) converter process. Though duplex process with AOD converter is the prominent one, there are several duplex processes are being used today for making stainless steels. In these processes there is an EAF or similar furnace that melts down scrap, ferroalloys and other raw materials to produce the liquid steel. This liquid steel, which contains most of chromium and nickel as well as some other alloying elements, is the charge of the converters. The converters are used to achieve low carbon stainless steels. The versatility of the EAF-AOD duplex process led steelmakers to re-examine the use of different converters for melting of stainless steels. This led to the development of several other converters for duplex processes. The development work to make stainless steels using conventional BOF (basic oxygen furnace) had begun in the late 1950s and early 1960s. By the mid 1960s, some steelmakers were using existing BOF converters for a partial decarburization followed by decarburization in a ladle under...