Sms Siemag Aktiengesellschaft

Sms Demag Ag

Sms Group Gmbh

Johann Reichel

Lutz Rose

Bernt Rollinger

Stefan Lemke

Miroslav Karbowniczek

Karl Reiner Götzinger

Jan Bader

Thomas Germershausen

An installation for producing 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. 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 is separated and introduced into two classic 'twin' AOD-L converters, where the required chemical process steps (of the DDD treatment and of the heating, decarburization 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 and the decarburization being carried out first in the second twin AOD-L converter.

Method and device for producing pig-iron based stainless steel without using a supply of electrical energy

During the production of non-stainless steel, slag containing a high proportion of metal oxides, primarily iron oxide, is formed during the smelting of the solid material in the electric arc furnace. The concentration of the iron oxide often reaches values of more than 20%. This slag has a poor foaming capability and does not permit the typical characteristics of a carbon steel slag to be achieved. In order to cause such a slag to foam, according to the invention it is proposed to load the electric arc furnace with pellets or briquettes () which consist of a defined mixture of an iron oxide carrier and an iron carrier as ballast material, of carbon as reducing agent and also of a binder material, which react in the electric arc furnace in a reducing manner, floating under the slag () in the steel melt (). The reaction gases () produced in this way consist primarily of carbon monoxide and advantageously support the foaming of the slag.

Process for slag foaming a non-stainless steel melt in an electric arc furnace

In order to carry out foaming of a slag having a high ratio of chromium oxide having values of often above 20% of a non-corrosive melt in an AOD (Argon Oxygen Decarburization) or MRP (Metallurgical Refining Process) converter or CONARC SSt for stainless steel by adding a foam material, according to the invention a previously defined mixture () of a metal oxide, iron carrier, carbon and binding material in the form of pellets or briquettes () is introduced into the converter, which reacts in a chemically reducing manner under the slag layer () due to the high ambient temperature, wherein gaseous carbon monoxide formed in particular by means of the reduction process of the metal oxide with the carbon within the pellets or briquettes () induces the slag foaming with the gas bubbles () thereof and wherein the specific density of the pellets or briquettes () and the resolve time of the reduction process are selected so that optimal bubble formation in respect of size and duration is achieved.

Method for foamed slag generation of a non-corrosive melt in a converter

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.

Method for controlling foamed slag in a stainless melt in an electronic arc furnace

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.

Process for producing foamed slag

Modern steel production processes require precise knowledge of the current composition and temperature of the liquid metal being processed. In particular during steel production in a converter, high match rates for final carbon content and bath temperature are required. Quantitatively precise blowing of oxygen corresponding to the final target carbon content, and the metal temperature, are decisive factors affecting the economic efficiency of the process and the quality of the steel produced. In order to allow relatively precise process monitoring, various processes and procedures are known, the application thereof being based on measuring exhaust gas composition and on mass flow balances. All models work at an exactness that depends on the precision of the input data, particularly with respect to the weight data of the raw materials and the chemical properties of the metal used. In order to allow control of the converter process for producing steel independently of the predefined process model, in particular when blowing oxygen, the invention proposes that detected values for the critical decoking point (t') and for the end of O-blowing (t&#x2032;) are obtained by means of a submodel operating as a process monitor based on the exhaust gas analysis and independent of the process model, by sensibly combining the constituent signals obtained, by means of which values the oxygen content predicted by the process model is corrected at the start of the process and matched to the actual conditions near the end of the decoking period.

Control of the converter process by means of exhaust gas signals

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 (dephosphorization, desiliconization and desulfuration), is heated, finished or alloyed and deoxidated. The quantity of slag-free liquid pig-iron that has been pre-treated in the blast furnace () is separated and introduced into two classic 'twin' AOD-L converters (), where the required chemical process steps (of the DDD treatment and of the heating, decarburization 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 () and the decarburization being carried out first in the second twin AOD-L converter ().

An installation for producing 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. The liquid pig-iron, after being pre-treated in a blast furnace, is subjected to a DDD treatment (dephosphorization, desiliconization and desulphurization), 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, decarburization and alloying stages) take place in parallel contrary processes using autogenous chemical energy. The heating stage is carried out first in the first twin AOD-L converter and the decarburization is carried out first in the second twin AOD-L converter.

Method and device for producing stainless steel without using a supply of electrical energy, based on pig-iron that has been pre-treated in a DDD installation

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.

Process for producing a foamed slag on austenitic stainless melts in an electric arc furnace

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.

Indirect determination of the waste gas rate for metallurgical process

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

Process for producing stainless steel using direct reduction furnaces for ferrochrome and ferronickel on the primary side of a converter

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 (dephosphorization, desiliconization 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, decarburization 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 decarburization being carried out first in the second twin AOD-L converter ().

A method for producing a foamed slag () on a metal bath () in a metallurgical furnace (), in which a mixture () containing at least one metal oxide and carbon is introduced into the furnace (), the metal oxide is reduced by the carbon below the slag () 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 () is delivered into the furnace () in such a way that a desired height (h) or a desired section of the height (h) of the layer of foamed slag () is generated or maintained.

Method for the production of a foamed slag in a metal bath

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 (), 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 () in the steel melt () with the metal oxides of the slag (), particularly with the chromium oxide present, in a floating, chemical, and reducing manner. The reaction gases () produced in the process, which are mainly made of carbon monoxide, advantageously support a foaming of the slag ().

Method for the reduction of a slag having a high degree of chromium in an electric arc furnace

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.

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Düsseldorf, Germany

Johann Reichel