Abstract: During the production of stainless steel, a slag is formed during the melting of the solid material in the electric arc furnace, the slag having a high degree of metal oxides, particularly chromium oxide. The chromium concentration often reaches values of more than 30%. Currently, such slags cannot be reduced to a desired degree due to their composition. In order to minimize the resulting high loss of recyclable material, the invention provides to charge the electric arc furnace with pellets, or briquettes (8), which are made of a defined mixture of an iron carrier as the ballast material, carbon, or carbon and silicon, as the reducing agent, and a binder, wherein they react beneath the slag layer (7) in the steel melt (6) with the metal oxides of the slag (7), particularly with the chromium oxide present, in a floating, chemical, and reducing manner. The reaction gases (12) produced in the process, which are mainly made of carbon monoxide, advantageously support a foaming of the slag (7).

Abstract: The aim of the invention is to produce stainless steel for all stainless steel products both in the austenitic and the ferritic range, based on liquid pig-iron and FeCr solids, without using a supply of electrical energy. According to the invention, the liquid pig-iron, after being pre-treated in a blast furnace, is subjected to a DDD treatment (dephosphorisation, desiliconisation and desulphuration), is heated, finished or alloyed and deoxidated. The quantity of slag-free liquid pig-iron that has been pre-treated in the blast furnace and a DDD device is separated and introduced into two classic “twin” AOD-L converters, where the required chemical process steps (of the heating, decarburisation and alloying stages) take place in parallel contrary processes using autogenous chemical energy, the heating stage being carried out first in the first twin AOD-L converter and the decarburisation being carried out first in the second twin AOD-L converter.

Abstract: A process and material for producing foamed slag by which the foaming of a slag with a high chromium oxide content can be achieved. An electric arc furnace is charged with a mixture of metal oxides and carbon and, below the slag at the metal-slag interface, the metal oxide is reduced by carbon and limestone and becomes thermally discordant. The occurring gases cause the slag to foam due to the formation of bubbles.

Abstract: A method for controlling foamed slag in a stainless melt in an electric arc furnace. Slag level in the electric arc furnace is continuously detected thermographically as a function of time and slag level, and an addition of foaming material is controlled depending on the temperature and temperature gradient.

Abstract: A process for producing a foamed slag on austenitic stainless melts in an electric arc furnace. A mixture of metal oxides and carbon is introduced into the furnace, the metal oxide is reduced by the carbon below the slag at the metal/slag interface, and the resulting gases bring about the foaming of the slag by bubble formation. The mixture to be charged, which is added in the form of preforms such as briquets or pellets, contains iron oxide, iron carriers, carbon and the required binders in addition to nickel oxide.

Abstract: In order to allow a significant reduction of the steel production costs when producing stainless steel with the alloying elements chromium and nickel, according to the invention, it is proposed to perform the intermediate production of ferrochromium and ferronickel in two separate direct reduction processes based on low-cost chromium ore and nickel ore in two SAF (3, 4) arranged in parallel on the primary side of a processing converter (6).

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 for the indirect determination of the waste gas rate in metallurgical processes. A reference gas such as helium is first added to the waste gas, specifically at a time which, with respect to flow, sufficiently precedes the taking of a sample such that a thorough mixing of the reference gas and waste gas is carried out, i.e., a virtually homogeneous distribution is achieved, and a quantitative helium analysis and nitrogen analysis of the waste gas, measured by a mass spectrometer, is carried out while taking into account the added amount of helium.

Abstract: During the production of stainless steel, a slag is formed during the melting of the solid material in the electric arc furnace, the slag having a high degree of metal oxides, particularly chromium oxide. The chromium concentration often reaches values of more than 30%. Currently, such slags cannot be reduced to a desired degree due to their composition. In order to minimize the resulting high loss of recyclable material, the invention provides to charge the electric arc furnace with pellets, or briquettes (8), which are made of a defined mixture of an iron carrier as the ballast material, carbon, or carbon and silicon, as the reducing agent, and a binder, wherein they react beneath the slag layer (7) in the steel melt (6) with the metal oxides of the slag (7), particularly with the chromium oxide present, in a floating, chemical, and reducing manner. The reaction gases (12) produced in the process, which are mainly made of carbon monoxide, advantageously support a foaming of the slag (7).

Abstract: The aim of the invention is to produce stainless steel for all stainless steel products both in the austenitic and the ferritic range, based on liquid pig-iron and FeCr solids, without using a supply of electrical energy. According to the invention, the liquid pig-iron, after being pre-treated in a blast furnace (1), is subjected to a DDD treatment (dephosphorisation, desiliconisation and desulphuration), is heated, finished or alloyed and deoxidated. The quantity of slag-free liquid pig-iron that has been pre-treated in the blast furnace (1) and a DDD device (2) is separated and introduced into two classic “twin” AOD-L converters (3, 4), where the required chemical process steps (of the heating, decarburisation and alloying stages) take place in parallel contrary processes using autogenous chemical energy, the heating stage being carried out first in the first twin AOD-L converter (3) and the decarburisation being carried out first in the second twin AOD-L converter (4).

Abstract: The aim of the invention is to produce stainless steel for all stainless steel products both in the austenitic and the ferritic range, based on liquid pig-iron and FeCr solids, without using a supply of electrical energy. According to the invention, the liquid pig-iron, after being pre-treated in a blast furnace (1), is subjected to a DDD treatment (dephosphorisation, desiliconisation and desulphuration), is heated, finished or alloyed and deoxidated. The quantity of slag-free liquid pig-iron that has been pre-treated in the blast furnace (1) is separated and introduced into two classic “twin” AOD-L converters (2, 3), where the required chemical process steps (of the DDD treatment and of the heating, decarburisation and alloying stages) take place in parallel contrary processes using autogenous chemical energy, the DDD treatment being carried out first in the first twin AOD-L converter (2) and the decarburisation being carried out first in the second twin AOD-L converter (3).

Abstract: The invention relates to a method for producing a foamed slag (1) on a metal bath (2) in a metallurgical furnace (3). According to said method, a mixture (4) containing at least one metal oxide and carbon is introduced into the furnace (3), the metal oxide is reduced by means of the carbon below the slag (1) that is located there, and the gases produced during the reduction process form bubbles such that the slag is foamed. In order to optimize the formation of foamed slag, the mixture (4) is delivered into the furnace (3) in such a way that a desired height (h) or a desired section of the height (h) of the layer of foamed slag (1) is generated or maintained.

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: The invention relates to a method for producing foamed slag on high-chromium steel melts in an electric furnace, whereby a mixture consisting of a metal oxide and carbon is introduced into the furnace, the metal oxide in the slag is reduced by the carbon, and the gases created in the slag form bubbles which thus foam up the slag. In order to be able to control the gas formation and thus the foaming process, the mixture consisting of a metal oxide and carbon and optionally an iron carrier is introduced as preforms, such as pellets, which are compressed and/or provided with a binding agent. The gas formation can be controlled in terms of location, type and time, by adjusting the characteristics of the pellets, especially the density and/or compression characteristics thereof.

Abstract: The invention relates to a method for recovering metallic elements, especially metallic chromium, from slag containing oxides, especially chromium oxides, in an electric-arc furnace. According to said method, the slag is not reduced in a separate step after melting, but the following steps are carried out: a charge is introduced into tile electric-arc furnace, and melted, forming a molten metal and slag; said molten metal is tapped off, leaving the unreduced slag in the furnace vessel; a further charge of scrap metal including reducing agents for tile slag is added; the slag is reduced during the melting of said charge; and the slag and the molten metal are then lapped off. The inventive method can also be used in ladle metallurgy or converter metallurgy.

Abstract: The invention relates to a method for producing stainless steels, in particular steels containing chromium and chromium-nickel. The method is carried out in a melting device containing a metallurgical vessel, or in a melting device (1) containing at least two vessels (2, 3) for supplying a steel-casting installation, an electric arc furnace process (1) and an air-refining process taking place alternately in the two vessels (2, 3). To improve the efficiency of a method of this type, the aim of the invention is to carry out a reversible treatment of unreduced converter slag in the electric-arc furnace mode. To achieve this, in the first treatment stage, the slag (19) with a high chromium content is melted together with the added charge, the slag is then reduced during the melting process with the silicon and carbon under favorable thermodynamic conditions of the arc, once the slag has reached a minimum temperature of 1,490° C. and the slag is subsequently removed.

Abstract: The invention relates to a method for producing stainless steels, in particular steels containing chromium and chromium-nickel. The method is carried out in a melting device containing a metallurgical vessel, or in a melting device (1) containing at least two vessels (2, 3) for supplying a steel-casting installation, an electric arc furnace process (1) and an air-refining process taking place alternately in the two vessels (2, 3). To improve the efficiency of a method of this type, the aim of the invention is to carry out a reversible treatment of unreduced converter slag in the electric-arc furnace mode. To achieve this, in the first treatment stage, the slag (19) with a high chromium content is melted together with the added charge, the slag is then reduced during the melting process with the silicon and carbon under favourable thermodynamic conditions of the arc, once the slag has reached a minimum temperature of 1,490° C. and the slag is subsequently removed.

Abstract: A process for decarburizing a steel melt for the production of high-chromium steels by blowing in oxygen in which the decarburization rate is continuously measured and the amount of oxygen to be injected is adjusted depending on the measured values. The following controlled quantities are calculated:a) the duration of the Al--Si oxidation phase at the start of the decarburization process,b) the duration of a principle decarburization phase immediately following the Al--Si oxidation phase until the transition point from the decarburization reaction to the metal oxidation is reached, andc) the decarburization rate in the principal decarburization phase. The injected oxygen quantity is increased at an accelerated rate immediately following the Al--Si oxidation phase to the oxygen quantity of the principal decarburization phase until the decarburization rate calculated in c) is reached.