Abstract: For the production of stainless steel of the ferritic AISI 4xx group of steels, particularly the AISI 430 group of steels, based on liquid pig iron and FeCr solids, the invention proposes the use of the AOD (Argon Oxygen Decarburization) process in which oxygen and inert gas (inactive gas) together are blown into the bath through nozzles and top-blown onto the surface of the bath by a blowing lance. The aim of the treatment is to conclude a smelting charge within an optimal time period, to achieve the intended tapping temperature and composition, and to minimize chromium losses. This is achieved by a correspondingly applied technology and by means of a metallurgic process model which observes, prognosticates and controls the treatment of the smelting charge.
Abstract: A method and an apparatus for advantageously introducing a flame and a high velocity oxidizing gas into a furnace for metal melting, refining and processing, particularly steel making in an electric arc furnace. The steel making process of an electric arc furnace is made more efficient by shortening the time of the scrap melting phase and introducing an effective high velocity oxidizing gas stream into the process sooner to decarburize the melted metal. In one implementation of an apparatus, improved efficiency is obtained by mounting a fixed burner/lance closer to the hot face of the furnace refractory at an effective injection angle. This mounting technique shortens the distance that the flame of the burner has to melt through the scrap to clear a path to the molten metal and shortens the distance the high velocity oxygen from the lance travels to the slag-metal interface thereby increasing its penetrating power.
Abstract: The invention is directed to a method for operating a steelmaking furnace including the steps of charging steelmaking materials into the steelmaking furnace, blowing oxygen into the steelmaking furnace, discontinuing the oxygen blow when the charged steelmaking materials are reduced to a liquid steel product, determining the temperature of the finished liquid steel product, blowing a nitrogen gas coolant into the steelmaking furnace to reduce the temperature of the finished liquid steel product to an aim tapping temperature, discontinuing the nitrogen gas coolant blow when the finished liquid steel product temperature is lowered to the aim tapping temperature, and tapping the finished liquid steel product at the aim tapping temperature for downstream processing.
Abstract: A metal refining method particularly useful with a basic oxygen steelmaking process, wherein during an initial period, refining oxygen is provided into the furnace headspace surrounded by a shroud comprising oxygen and inert gas, and during a subsequent period refining oxygen is provided into the furnace headspace surrounded by a flame shroud.
Type:
Grant
Filed:
June 22, 2001
Date of Patent:
August 13, 2002
Assignee:
Praxair Technology, Inc.
Inventors:
Balu Sarma, Ronald Joseph Selines, John Erling Anderson, William John Mahoney
Abstract: Device and relative method to inject technological gases and solid material in powder form, in a furnace used in steel and metallurgical melting processes, comprising an emission element including an outlet mouth arranged at a certain distance from the liquid bath, said emission element being innerly shaped as a double nozzle, respectively first and second, the first nozzle having a convergent/divergent conformation defined by a neck and being predisposed for the emission of a jet of gas at supersonic speed, said second nozzle having at the end a conformation convergent towards the axis of the emission element and being pre-disposed, according to the step of the melting process in progress, for the emission of a jet at subsonic speed either of technological gases alone, such as for example oxygen, or of solid material in powder form on a gassy vehicle, or of liquid in atomized form.
Abstract: The invention relates to a method of manufacturing stainless steel, by treating a raw high-carbon steel in a first stage with a gaseous mixture that contains oxygen and inert gas, therewith lowering the carbon content of the raw steel to a value of 0.2-0.1%. The steel bath is then treated in a second stage with solely an inert gas, until the carbon content has fallen to the desired value. The invention is characterized in that the steel bath is treated in the first stage alternately with an oxygen-rich gas and with an inert gas, until the carbon content of the steel has fallen to the desired value.
Abstract: A refining method of decarburizing a molten steel containing a large quantity of chromium, which can be completed in a shorter period, and therefore, with reduced consumption of Ar gas, and with safety of operation. A mixed gas of O.sub.2 and Ar is blown into a molten steel in a refining vessel through a tuyere at the bottom of the vessel under atmospheric pressure, and when the C-concentration becomes to such a low level as 0.15% (by weight) or less, vacuum suction is applied to reduce the pressure to 150-200 Torr, and only Ar gas is blown. At the change of the refining conditions from atmospheric to vacuum or during the vacuum refining a reducing agent such as ferrosilicon is added to the molten steel to reduce Cr-oxides for recovery. Even if the amount of the reducing agent is less than that necessary for reducing all the Cr oxides, majority of Cr can be recovered. If an excess amount is used, a steel of low nitrogen in addition to low carbon is obtained.Whole or a portion of Ar can be replaced with N.sub.