EP0281796B1 - Method of producing affined ferromanganese - Google Patents

Description

The invention relates to a process for the production of low-carbon and low-silicon ferromanganese (ferromangan affine) by freshening a ferromanganese with high carbon content (ferromangan carbure) produced in the blast furnace in a converter by blowing pure oxygen onto the high-carbon manganese melt by means of an inflation lance and by simultaneous blowing of pure oxygen and inert gas below the melt pool level through bottom nozzles into the melt during an oxidation phase and by adding solid reducing agents with continued blowing of inert gas in a subsequent reduction phase to recover the slagged manganese.

In such a method known from JP-A 6 067 608, medium or low carbon ferromanganese is produced by freshening a high carbon ferromanganese in a converter by blowing pure oxygen onto the high carbon manganese melt by means of an inflation lance and simultaneously blowing pure Oxygen and inert gas below the molten bath level through bottom nozzles into the melt during an oxidation phase and by adding solid reducing agents with continued blowing of inert gas in a subsequent reduction phase to recover the slagged manganese. Such a method, in which oxygen is blown from above and below at the same time, is disadvantageous because both the refractory converter lining and the blowing nozzles are quickly destroyed by the oxygen blown into the melt from below and because a complicated and complex system technology for controlling the Blowing is required.

It is known that low-carbon ferromanganese (ferromangan affine) in the converter can be freshened by blowing in oxygen with the help of jacket gas nozzles without any significant formation of a slag rich in manganese oxide, the alloy melt being heated to a temperature of over 100 _° C. over the melting range and before blowing in the oxygen about 15 Nm3 of oxygen are blown into the ferroalloy to be blown for each 1% of carbon to be removed and per ton of alloy. The heating over the melting range is carried out by adding or adding oxygen-affine metals or their alloys, for example silicon metal, ferrosilicon, aluminum, at the beginning of the blowing period and oxidizing them with oxygen. The working temperature of the alloy melt is kept constant by adding solid cooling material, for example, its own return metal, its own slag-containing metal, fine ore, pre-reduced ore or the like (DE-PS 22 01 388).

In a further development of this process, the temperature of the alloy melt is raised to a temperature of over 1650 to 1900 _° C. by blowing in the oxygen without the addition of coolants, a high-melting manganese oxide phase being formed. This phase is then reduced on the one hand by introducing lime and on the other hand by adding solid reducing agents, such as silicon and aluminum and / or their alloys (DE-OS 25 31 034).

According to a further proposal, up to about 20% solid alloy metal is added to the alloy melt, and the quantity and the oxygen feed rates are selected so that the decarburization reaction takes place in focal spots over the jacket gas nozzles (DE-PS 25 40 290).

From DE-OS 20 01 707 a method for the production of ferromanganese is also known by blowing in an oxidizing gas, water vapor and / or an inert gas below the molten metal level by means of immersed nozzles which are protected by introducing a circumferential cooling fluid that opens into the bath to be freshly cleaned . In this process, pure oxygen is blown through the nozzles up to an intermediate carbon content of 2 to 3.5% until the temperature of the bath to be refreshed is between 1650 and 1750 _° C. Up to a carbon content of at most 1.6% is then passed through the nozzles are blown separately or in a mixture of pure oxygen and water vapor with or without inert gas, the volume fractions of the pure oxygen being at most 50%, the water vapor being at least 30% and the inert gas being at most 70% of the total gas volume blown and the regulation of these fractions constant maintenance of the temperature of the ferromanganese bath between 1670 and 1700 _° C.

Furthermore, from DE-OS 30 01 941 a process for the production of ferromanganese is known, with a carbon content of 0.5 to 2% by decarburization of a ferromangan melt with a carbon content of 3 to 8% and up to 7% silicon with an oxidizing agent in a reactor. In this process the oxidizing agent, e.g. Oxygen, introduced into the lower region of the melt, which is kept under an atmospheric pressure, preferably from 1.5 to 15 bar. A temperature-regulating gas in the form of carbon dioxide, air, nitrogen, argon and / or water vapor can be added to the oxidizing agent.

All of the methods described above work with jacket gas nozzles through which the oxygen required for the decarburization reaction is blown in. These nozzles are below the surface of the bath and, as a result, additional cooling media, such as hydrocarbons, must be applied to prevent them from burning back. These protective media are expensive and metallurgically insignificant and therefore represent a considerable cost factor.

In addition, complex evaporator and heating devices and additional control stations are necessary for such gases. Carbon-containing cooling gases also lead to increased oxygen consumption or can also limit the achievable carbon content due to their carburizing effect. Because the nozzle cross section te are necessarily dimensioned according to the amount of oxygen required for the fresh speed, they must be flowed through in converter empty or idle times of similarly high amounts of inert gas (Ar, N ₂ ), which leads to an additional cost burden on the process.

Experience has shown that blowing oxygen through the converter floor or below the bath surface leads to strong local bath turbulence, which, due to the erosion effect, leads to severe premature refractory wear on the floor and the adjacent areas. This results in additional repair times and refractory costs.

Finally, US Pat. No. 3,305,352 describes a process for producing ferromanganese with a carbon content of not more than 1.5% by oxygen inflation. This process is based on a ferromanganese which has been produced, for example, in a blast furnace, with a carbon content of at least 3% and a silicon content of up to 5%. This high-carbon ferromanganese is brought to a decarburization temperature of at least 1550 _° C. Oxygen is then blown up in an amount sufficient to bring the melt to a temperature of about 1700 _° C. before the carbon has been reduced to 1.5%. The blowing operation is continued until the temperature of the melt reaches 1750 _° C, and is stopped when this temperature is reached, whereby a ferromanganese is obtained with a carbon content of not more than 1.5%. A quarter of the total oxygen required can be blown to reach the decarburization temperature of at least 1550 _° C. However, the melt can also be brought to this temperature by induction heating in an induction furnace.

This method has the advantage that it is possible to work in comparatively simple units which are known in principle from steelmaking. The significant disadvantage of this process, on the other hand, is that at the end of the process there is a high proportion of manganese oxide-rich, high-melting slag, which makes high tapping and casting temperatures necessary to ensure adequate metal-slag separation. In addition, this slag represents a significant manganese loss, which is reflected in a comparatively low metal or manganese yield.

The invention has for its object to provide a process for the production of low-carbon and low-silicon ferromanganese (ferromanganese affine) by refining a ferromanganese with a high carbon content (ferromanganese carbure) produced in the blast furnace by means of pure oxygen in a converter, in which the essential advantages of known bottom blowing method used, the significant disadvantages are avoided, ie low-energy, loss-free production without major feed wear is made possible.

To achieve this object, the measures of claim 1 are proposed according to the invention.

After the addition of solid reducing agents has ended, the melt is preferably cooled to the casting temperature in a cooling phase, while the stirring gas is continued to be blown in, to the casting temperature.

The tapping temperature can be adapted to the requirements of the casting technology within wide limits. The amount of floor gas can be reduced by the choice of the nozzle cross-section, the number and arrangement of the nozzles, and by the regulation of the gas quantity, which is predetermined by process parameters, as necessary to maintain the bath movement necessary for the individual process stages.

In an embodiment of the invention, in the oxidation phase the amount of oxygen blown is 1.50 to 4.0 Nm ³ / min ç t FeMn carbure, preferably 2.5 to 3.5 Nm ³ / min ₉ t FeMn carbure and the amount of stirring gas is 0.02 up to 0.50 Nm ³ / min ₉ t FeMn carbure, preferably 0.02 to 0.15 Nm ³ / min ₉ t FeMn carbure. In the reduction and cooling phase, it is advantageous to work with a stirring gas amount of 0.05 to 0.50 Nm ³ / min 51 t FeMn carbure.

According to the invention, nitrogen, argon, carbon dioxide or exhaust gases are used as stirring gas in the oxidation phase and argon or nitrogen in the reduction phase.

Silicomanganese, ferrosilicon, silicon, aluminum or their alloys are preferably used as solid reducing agents in the reduction phase in amounts of 5 to 15 kg silicon or aluminum / t ferromanganese carbure; the quantity of lime depending on the silicon content is 10 to 40 kg / t ferromanganese carbure.

According to a further feature of the invention, manganese ore or filter dusts separated in the process are used for cooling both during and after the fresh phase, and the subsequent reduction phase is modified so that manganese is obtained both from the fresh slag and from the manganese ore in which the others mentioned above are obtained solid reducing agents are added.

In the cooling phase following the reduction, ferromanganese affine is preferably added in amounts of 40 to 350 kg / t ferromanganese carbure, preferably 60 to 180 kg / t ferromanganese carbure. However, the ferromanganese affine as a coolant can be replaced in whole or in part by Manganez or filter dusts separated during the process.

Dolomite and / or magnesite can be used as additional slag formers in quantities of up to 40 kg / t ferromangan carbure, which, in addition to the desired cooling effect, provide special protection for the refractory lining of the vessel.

In the method according to the invention for the production of ferromanganese affine, there is a significant advantage in the use of blowing nozzles arranged under the bath surface, which by blowing in small amounts of stirring gas during the fresh process and after the end result in a sufficiently strong bath movement.

As a result, a sufficient bath-slag conversion is maintained in the oxidation phase when the decarburization decreases and in a subsequent reduction phase the reduction of the manganese oxide-rich slag is made possible, so that a necessary metal-slag separation with a sufficient degree of liquid is present during tapping.

A converter which is conventional for steel production can be used as the production vessel, in which 2 to 20, preferably 6 to 10, nozzles for blowing in stirring gas are arranged in the converter base according to the invention.

A water-cooled inflation lance, which is characterized by 3 to 10, preferably 4 to 6, nozzle openings at the tip of the lance is used to inflate the oxygen.

The blowing speed and the lance height are set according to the decarburization process and are also dependent on the analysis of the ferromanganese carbure to be blown and the ferromanganese affine to be produced.

The individual process stages are assigned the type and amount of the stirring gas to be blown in below the bath.

The blowing nozzles are arranged and dimensioned in such a way that they can be operated with comparatively small amounts of gas, so that the known disadvantages do not occur with jacket nozzles charged with large amounts of gas. The floor nozzles are preferably arranged in the middle of the floor in a row parallel to the axis of rotation of the converter or completely in the part of the floor of the converter which is free of melt and slag when the converter is turned over. As a result, an effective orbital movement of the melt can be set, so that metal and slag are constantly in intensive contact without increased wear of the refractory lining of the converter. The proposed arrangement of the nozzles in the converter base has the further advantage that the nozzles are exposed when the converter is turned over and the amount of stirring gas can be reduced accordingly in this process section. In addition, evaporation of the metal by sputtering can be avoided. The inside diameter of the floor nozzles is 3 to 12 mm, preferably 7 to 9 mm.

• - durch das Einblasen von Rührgas in die Schmelze die Inertgasmenge nach der für die einzelnen Phasen erforderlichen Mengen bemessen werden kann, was zu einer erheblichen Verminderung des Inertgasverbrauches führt,
• - die gegenüber bekannten mantelgasgekühlten Düsen veränderten Düsen und die Schlackenführung zu einer starken Reduzierung des Feuerfestverschleißes insbesondere im Bodenbereich führen,
• - auf die Anwendung von teuren Kühlgasen, die überdies komplizierte Regel- und aufwendige Verdampfereinrichtungen erfordern, verzichtet werden kann,
• - die Konverterbodenkonstruktion durch Einsetzen einfacher rohrförmiger Düsen erheblich vereinfacht wird,
• - durch die Reduktions- und Kühlphase im Anschluß an die Oxidationsphase eine gezielte Einstellung der Abstichtemperatur in weiten Grenzen möglich wird,
• - hohe Ausbringensverluste in der Schlacke vermieden werden.

The advantages achieved with the invention can be seen in particular in that

• by blowing stirring gas into the melt, the amount of inert gas can be measured according to the amounts required for the individual phases, which leads to a considerable reduction in the consumption of inert gas,
• the nozzles modified compared to known jacket gas-cooled nozzles and the slag guidance lead to a strong reduction in refractory wear, particularly in the floor area,
• the use of expensive cooling gases, which moreover require complicated control and complex evaporator devices, can be dispensed with,
• the converter base construction is considerably simplified by using simple tubular nozzles,
• - The reduction and cooling phase following the oxidation phase enables the tapping temperature to be set within wide limits,
• - high output losses in the slag can be avoided.

The invention is explained in more detail below on the basis of exemplary embodiments.

example 1

eingefüllt.120,700 kg of high-carbon ferromanganese (FeMn carbure) with a temperature of 1335 _° C. and the following composition were placed in a converter with a capacity of 140 t

filled.

Subsequently, oxygen was blown onto the melt at a rate of 300 Nm ³ / min using an inflation lance with four nozzle openings. At the same time, argon was introduced into the melt through six bottom nozzles at a speed of 6.3 Nm ³ / min.

The oxygen supply through the lance was switched off when the amount of oxygen was 8150 Nm ³ 0 ₂ and the lance was pulled out of the converter. Following the oxidation phase, 5838 kg of SiMn were added to the converter from above within 2 minutes. With a delay of one minute, 2144 kg of lime were drawn into the converter. During this reduction phase, 12.6 Nm ³ argon / min were blown into the melt through the bottom nozzles. The melt was then cooled in the converter to the tapping temperature of approx. 1580 _° C using its own coolant. The coolant consumption was 6902 kg ferromanganese affine. At the same time, 4032 kg of dolomite lime were added as slag formers.

112000 kg of ferromanganese-affine were tapped from the converter with the following analysis:

The amount of slag was approx. 10500 kg, the slag had the following composition:

The metal output was 83.9%. The Mn output was 88%.

Example 2

eingefüllt.In a converter such as Example 1, 127400 kg of ferromanganese carburized at a temperature of 1345 _° C and the following analysis

filled.

Subsequently, oxygen was blown onto the melt at a speed of 300 Nm ³ / min using an inflation lance with four nozzle openings. At the same time, argon was introduced into the melt through six bottom nozzles at a speed of 6.3 Nm ³ / min.

The oxygen supply through the inflation lance was interrupted after a blown quantity of 9000 Nm ³ 0 ₂ and the inflation lance was moved out of the converter.

Then - similar to example 1 - the manganese oxide from the slag was reduced back into the melt. For this purpose, 788 kg of AI and 2280 kg of lime were drawn into the converter and at the same time 10.5 Nm3 argon / min were blown into the bath through the floor nozzles. After the reduction had taken place, the melt was brought to a temperature of 1611 _° C. in the converter using its own coolant. This required 11,820 kg of cooling affinity. At the same time, 4284 kg of dolomite lime were added as slag formers.

117000 kg of FeMn-affine were tapped from the converter with the following analysis:

The amount of slag was about 11100 kg; the slag had the following composition:

The metal output was 83.6%. The manganese yield was 87.4% Mn.

• Fig. 1 zeigt in schematischer Darstellung die Draufsicht eines Konverters in einer Ausführung mit Bodendüsen und
• Fig. 2 die Draufsicht eines Konverters mit einer anderen Anordnung der Bodendüsen.

Two preferred arrangements of the floor nozzles in the converter floor are shown in the drawing.

• Fig. 1 shows a schematic representation of the top view of a converter in an embodiment with floor nozzles and
• Fig. 2 is a plan view of a converter with a different arrangement of the floor nozzles.

1, the floor nozzles 5 are arranged in the middle of the converter floor 2 in a row parallel to the axis of rotation 3 and in the center plane of the converter 1. The pivots are designated by 4.

In the exemplary embodiment according to FIG. 2, the floor nozzles 5 are arranged in the part of the converter floor 2 which is free of melt and slag when the converter 1 is folded over, that is the upper part of the converter floor 2 when the converter 1 is folded over. These arrangements of the floor nozzles 5 in the converter floor 2 ensures that the floor nozzles 5 are exposed after the converter 1 has been flipped. The amount of stirring gas can be reduced accordingly in this process section. There is no atomization of slag and metal and thus no evaporation of metal.

Claims (19)

1. A process for the production of low-carbon, low-silicon ferromanganese solely by the top-blowing in an oxidation phase with pure oxygen in a converter, using a top-blowing lance, of a blast-furnace-produced high-carbon ferromanganese melt, inert gas being injected at the same time through bottom nozzles into the molten metal below its level, and by the addition in a following reduction phase of solid reducing agents, with the continued injection of inert gas, to recover the slagged manganese, characterized in that during the reduction phase lime is added in lumps to the melt in addition to the solid reducing agents and, in a cooling phase following the completion of such addition, the melt is cooled with homogeneous material to casting temperature, with the continued injection of .inert gas as an agitating gas.

2. A process according to claim 1, characterized in that the high-carbon ferromanganese is blown with a blowing speed of 1.5 to 4.0 Nm³0₂/min per tonne of high-carbon ferromanganese.

3. A process according to claims 1 and 2, characterized in that in the oxidation phase the quantity of agitating gas is between 0.02 and 0.50 Nm³/min per tonne of high-carbon ferromanganese.

4. A process according to claims 1 to 3, characterized in that in the reduction and cooling phase the quantity of agitating gas is 0.05 to 0.50 Nm³/min per tonne of high-carbon ferromanganese.

5. A process according to claims 1 to 4, characterized in that nitrogen, argon, carbon dioxide or waste gases are injected in the oxidation phase, argon or nitrogen being introduced as an agitating gas into the melt in the reduction phase.

6. A process according to claims 1 to 5, characterized in that in the reduction phase 10 to 15 kg of silicon are added per tonne of high-carbon ferromanganese in the form of silicomanganese, ferrosilicon, silicon, aluminium or their alloys, and also between 20 and 40 kg of lime per tonne of high-carbon ferromanganese, in dependence on the silicon content of the high-carbon ferromanganese.

7. A process according to claims 1 to 6, characterized in that manganese ore or filter dusts separated during the process are added for cooling purposes both during and following the oxidation phase.

8. A process according to claim 7, characterized in that during the reduction phase the reducing agents set forth in claim 7 are added to reduce the slagged manganese and manganese ore.

9. A process according to claims 1 to 8, characterized in that in the cooling phase 40 to 350 kg of low-carbon ferromanganese are added per tonne of high-carbon ferromanganese.

10. A process according to claim 9, characterized in that manganese ore or filter dusts separated during the process are substituted wholly or partially for the low-carbon ferromanganese added in the cooling phase.

11. A process according to claims 1 to 10, characterized in that in the cooling phase dolomite and/or magnesite are added in quantities of up to 40 kg per tonne of high-carbon ferromanganese as additional slag formers.

12. A water-cooled oxygen top-blowing lance for the performance of the process according to claims 1 to 12, characterized by 3 to 10 nozzle openings at the lance tip.

13. A water-cooled oxygen top-blowing lance according to claim 12, characterized by 4 to 6 nozzle openings at the lance tip:

14. A converter for the molted metallurgical treatment of metal melts, more particularly for the production of low-carbon, low-silicon ferromanganese according to one of claims 1 to 10, characterized in that the converter bottom is formed with 2 to 20 nozzles for the injection of agitating gas.

15. A converter according to claim 14, characterized in that the converter bottom is formed with 6 to 10 bottom nozzles.

16. A converter according to claims 14 or 15, characterized in that the bottom nozzles are disposed in the centre of the converter bottom in a row parallel with the axis of rotation of the converter.

17. A converter according to claims 14 or 15, characterized in that all the bottom nozzles are disposed in that part of the converter which is free from melt and slag when the converter is turned down.

18. A converter according to claims 16 or 17, characterized in that the internal diameters of the bottom nozzles are 3 to 12 mm.

19. A converter according to claim 18, characterized in that the internal diameters of the bottom nozzles are 7 to 9 mm.

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