CLU process for Stainless Steel Production Dec28

CLU process for Stainless Steel Production...

CLU process for Stainless Steel Production Stainless steel production process has some basic features such as carbon (C) removal, deoxidation and desulphurization. In the production process, these operations are generally combined with some alloying with solid material as well as nitrogen (N2) control.  These requirements are met in different ways in various processes being deployed for the production of stainless steel. The CLU process is similar to the AOD (argon oxygen decarburization) process for making stainless steels. CLU refers to the Creusot-Loire Uddeholm process for stainless steel production. It also uses liquid steel from an electric arc furnace (EAF) or any other similar primary steel making furnace.  The major impetus for the development of the CLU process was the idea to use superheated steam as the diluting gas instead of argon (Ar) gas which is used in the AOD process. Superheated steam has been used as a process gas in stainless steel production since the early 1970s when this technology was developed at Uddeholms Degerfors steel plant in Sweden. In France a similar development took place within the Creusot-Loire group. The developed process was named Creusot Loire Uddeholm (CLU) process. The converter originally used in CLU process was a bottom blown converter thus differentiating it from the side blown AOD converter. However, presently CLU process with the use of a side blown converter is also available. The first commercial plant using the CLU process was built in 1973 by Uddeholm. Between 1973 and 2003 stainless steel was produced in Uddeholms Degerfors steel plant in an 80 ton converter where superheated steam, Ar, N2, oxygen (O2) and compressed air were used as process gases. The converter in the Degerfors steel plant was operated for 30 years as a CLU process for stainless steel production before...

Argon Oxygen Decarburization Process Apr28

Argon Oxygen Decarburization Process...

Argon Oxygen Decarburization Process Argon oxygen decarburization (AOD) is a process primarily used in production of stainless steel and other high grade alloys such as silicon steels, tool steels, nickel-base alloys and cobalt-base alloys with oxidizable elements such as chromium and aluminum. AOD was invented in 1954 by the Lindé division of The Union Carbide Corporation, which became Praxair in 1992. An AOD converter is shown in Fig 1. Fig 1 AOD converter Today, over 75 % of the world’s stainless steel is made using the AOD process. The process is very popular because it combines higher metallic yields with lower material costs. It provides an economical way to produce stainless steel with a minimum loss of precious elements. It is part of a duplex process in which scrap or virgin raw materials are first melted in an electric arc furnace (EAF) or induction furnace (IF). The molten metal is then decarburized and refined in an AOD converter to less than 0.05 % carbon. The key feature in the AOD converter is that oxygen for decarburization is mixed with inert gas such as argon or nitrogen and injected through submerged tuyeres. This argon dilution of oxygen minimizes unwanted oxidation of precious elements contained in specialty steels, such as chromium. Other benefits of AOD process include pinpoint accuracy in chemistry control down to 0.01 % carbon and lower, rapid desulfurization to less than 0.001 %, and lead removal to less than 0.001 %. The end result is a cleaner metal coupled with increased productivity. AOD process uses dilution technique for the decarburization of steel bath. The injection of inert gas (argon or nitrogen) lowers the partial pressure of CO in the bath, thus allowing  higher chromium content to be in equilibrium with lower carbon contents. The amount...

Use of Hot Metal in Electrical Arc Furnace Jun04

Use of Hot Metal in Electrical Arc Furnace...

Use of Hot Metal in Electrical Arc Furnace Steel making by the electric arc furnace (EAF) has very good flexibility with respect to the selection of charge materials. The traditional charge material for the EAF process has been 100 percent cold scrap but as the issues regarding scrap such as its availability and quality, market price fluctuations and restrictions imposed by scrap in making some steel grades due to residual elements and nitrogen level etc. have increased, EAF operators intensified the search for alternative iron materials. Direct reduced iron (DRI), hot briquetted iron (HBI), pig iron (PI) and hot metal (HM) are the alternative iron materials which have been used in varying percentage successfully by EAF operators. The use of hot metal is more popular in those areas where there is shortage of scrap and/or electric power. The source of hot metal is blast furnace hence hot metal can be used in those EAFs which are in close proximity of the blast furnace, otherwise the EAF operator has to use pig iron. Pig iron will need extra energy for its melting. Presently EAF can be designed for using up to 80 percent of hot metal in the charge. Influence of HM on key parameters of EAF process In recent times the main emphasis in EAF steel making has been related to achieving maximum energy efficiency. Further the feed charge materials are influencing the design of the EAFs and their operation practices. The influence of HM as a charge material on various key parameters of an EAF process of steel making is detailed below. Residual elements – Residual elements also known as tramp elements cannot be removed from the steel during processing. Therefore, the amount of these elements in the product is a direct function...