Title of Invention

A PROCESS AND AN APPARATUS FOR THE DECARBURIZATION OF STEEL MELTS

Abstract (57) Abstract: The presant invention relates to a process for decarburizing steel melt in a closed metallurgical vessel and an apparatus thereof comprising the steps of filling the closed metallurgical vessel with a steel malt containing carbon; adjusting the pressure in the closed metallurgical vessel to below 100 mbar; introducing a replenishment supply of oxygen to the closed metallurgical vessel to implement decarburization of the steel melt to remove the carbon; introducing a metallic combustible, substance at an even introduction rate to the closed metallurgical vessel after said step of introducing a replemishiment supply of oxygen ; and introducing amount of oxygen during said step of introducing ametallic combustible substance needed to combust the metallic combustible susbstance during the decarburization of the steel melt, wherein said steps of introducing a metallic combustible substance and introducing an additional amount of oxygen are preformed during the first 10 minutes follwing completion of said step of adjusting the pressure. PRICE: THIRTY RUPEES
Full Text



A process for decarburizing steel melt in a closed metallurgical vessel that is connected to a vacuum unit.
In the so-called forced decarburization, it is known for oxygen to be added during the decarburization phase. This addition of oxygen is always necessary in cases when the oxygen present in the steel is not sufficient for decarburization purposes, or is so low that the removal of carbon is not completed in the time available. In a process of this kind, for example, immersion pipes of an RH-vessel are dipped into the melt. The decarburization process starts at the same time as the commencement of the reduction in pressure, as a factor depending on the lowering in pressure. When a negative pressure of p In the course of decarburization, up to 70 % of CO is formed. Part of this gas
automatically reacts with parts of the oxygen added to form CO2. The degree of
afterburning with this type

of operation is less than 30 %.
It is also common practice in the field of metallurgy to use aluminium for chemically heating steel melts in atmospheric plants. In this chemical heating procedure, the energy yield resulting from the combustion of the aluminium with the added oxygen is used to heat the melt.
In addition to the purely thermal heating using aluminium, it is possible for the latter to be used together with other matter for treating the melt. Thus, a process for treating steel in the ladle with reactive slags is known from EP 0 110 809, a metallothermic reaction being provided in said process, in which a lance is used to inject oxygen into a bubble cap which is dipped into the melt, combustible metallic materials react, forming reactive slags, and a neutral or reducing circulation gas is injected below the pipe in which the steel treatment is taking place.
The drawback of this process involving desulphurization, deoxidation and cleaning reactions in respect of steel melts is the formation of the reactive slags which takes place in the bubble cap which is dipped into the liquid metal.
In addition, a process for degassing and decarburization of molten steel is known from EP 0 347 884 Bl, in which steel is directed from a container into a vacuum chamber, an oxygen lance being arranged at a predetermined spacing, in said vacuum

chamber, from which lance oxygen or an oxygen-containing gas is injected for the combustion of the CO in the vicinity of the surface of the molten steel disposed in the vacuum chamber. Taking into consideration a predetermined ratio of (CO + CO2) / quantity of waste gas or CO / (CO + CO2)., oxygen or an oxygen-containing gas is injected by a lance for the combustion of CO in the vicinity of the surface of the molten steel disposed in the vacuum chamber.
In connection with this process, no mention is made of a chemical heating of the melt under specific pressure conditions and injecting a defined excess quantity of oxygen.
It is the object of the invention to provide a process and a suitable apparatus for the decarburization of a steel melt, in which, while ensuring a high degree of oxidic purity, the decarburization time is reduced and/or the final carbon content is reduced.
According to the invention, there is provided a process for the decarburization of steel melts in a closed metallurgical vessel which is connected to a vacuum plant and into which oxygen is designed to be injected via a lance and combustible material is designed to be introduced via a feeding device, which process includes the following steps:
a) once the vessel is filled with melt and after continuous lowering of the pressure to below 100 mbar, a predeterminable quantity of excess oxygen is

injection in addition to supplementary oxygen which is used during the decarburization phase for carrying out the combustion of carbon, and b) when there is a partial oxygen surplus, metallic combustible material is added in a uniformly distributed manner.
The metallic combustible material may be aluminium powder or aluminium grit or a mixture of combustible material, e.g. Al, Fe, Si, Mn. The metallic combustible material may be added discontinuously in portions. The excess oxygen may be injected during the first 10 minutes injection time, once the pressure is below p = 100 mbar.
The' invention further provides an apparatus for the decarburization of steel melts, comprising a sealable vessel which is connected to a vacuum plant and into an interior of which gases and granular solid material are designed to be fed via supply means, for carrying out the process according to claim 1, in which measuring elements are provided in the sealable vessel for detecting the melt temperature or pressure, which elements are connected, via a measuring and controlling instrument, to control means for supplying oxygen and metallic combustible material.
In the above apparatus, the sealable vessel may be a vacuum vessel which is provided with a cover and in which a metallurgical vessel is designed to be placed in position, in

which a lance, which is provided with a measuring element and projects into the melt disposed in the metallurgical vessel, is designed to be directed through the cover, and in which supply pipes for oxygen and metallic combustible material project through the cover, the control means being arranged on said supply pipes.
In the above apparatus, the sealable vessel may be designed to be an RH-vessel, the supply and discharge pipes of which dip into the melt disposed in a metallurgical vessel, and in which the control means are connected to shut-off means which are arranged in supply pipes for oxygen and/or combustible material.
In the above apparatus, a bubble cap may be provided and is directed through a cover which seals off the vessel opening of the metallurgical vessel, projecting into the melt, and in which apparatus supply pipes for oxygen and metallic combustible material are provided, which pipes project into an interior of the bubble cap and on which are arranged control means which control shut-off means.
A combination lance may be provided and in it are arranged the supply pipes for oxygen and/or metallic combustible material.
In addition to the supply pipe for metallic combustible material in the combination lance, a pipe may be provided to project into the vessel for supplying, in particular, coarse

solid material from a container.
According to the invention, in addition to the supplementary-oxygen used during the decarburization phase for carrying out the removal of the carbon, additional oxygen is injected and, simultaneously, metallic combustible material is added and distributed.
In known vacuum plants, only killed cast (Al, Si or Al-Si deoxidation) melts or rimmed cast melts (decarburization melts) were previously chemically heated after completed decarburization and subsequent deoxidation. The reason was the reduction of the oxygen required for decarburization when adding the heating aluminium. The energy yield, which results from the reaction from the combustion of the aluminium with the added oxygen, is used. In this process, however, the decarburization reaction was slowed down considerably, and the anticipated decarburization oxygen was not obtained.
According to the invention, this drawback is circumvented and the drop in temperature occurring during decarburization is compensated for by the heating operation using aluminium or similar products. With the suggested addition of oxygen, a time-limited partial oxygen surplus arises in the melt. Partial oxygen surplus is the additional oxygen which is additionally required during the decarburization of rimmed cast melts in vacuum plants for the combustion of metallic combustible material or mixtures of combustible materials.

without thereby adversely affecting the decarburization process. This surplus manifests positive thermodynamic and kinetic effects and, in a surprising manner, assists the decarburization process. The decarburization reaction [C] + [0] = (CO) , which is not only highly pressure-dependent but especially also temperature-dependent, is accelerated in that the superheating of part of the melt, in particular in the RH--vessel, briefly occurring during the chemical heating procedure, has a catalytic effect on the decarburization reaction.
In addition, it is possible, in particular, for the chemical heating agent, for example in the form of aluminium grit, to be used to accelerate the decarburization process. This, because, in addition to the thermodynamic effect, the kinetics of the reaction are influenced by the AI2O3 particles formed during heating. These deoxidation products serve as foreign nuclei and are thus capable of forcing the rate of decarburization, in particular by forming CO bubbles.
In an advantageous further development, a combination lance is used for conveying the oxygen and the metallic combustible material. In the event of particularly granular material, it is suggested that this be fed into the vessel through a separate pipe.
Applying this process, it is possible to provide any partial temperature increase during a decarburization procedure under



Accordingly, the present invention also provides an apparatus for decarburization of steel as described above, comprising a scalable vessel provided with a cover member connected to a vacuum plant, said cover having a supply means for the supply of oxygen and metallic combustible material, said supply means being provided with control means, a metallurgical vessel positioned within said isealable vessel, a lance with measuring elements projecting into the melt disposed within said vessel, said measuring elements are provided with temperature and pressure detecting means and said control means are provided with means to control the supply of oxygen and metallic combustible material into said metallurgical vessel.
It is possible to apply the proposed process for the widest range of vessel shapes, as illustrated in the following example shown in the attached drawing, in which:
Figure 1 shows the treatment in a vacuum vessel. Figure 2 shows the treatment in a RH-vessel. Figures shows the treatment in a closed ladle.

Figure 1 shows a vacuum vessel 43 which is provided with a cover 44 and is connected to a vacuum plant 41 via a suction pipe 42. Disposed within the vacuum vessel is a metallurgical vessel 10 which comprises a shell 12 which is inwardly provided with a refractory lining 13. The vessel is filled with melt S.
A measuring lance 2 8 and a combination lance 31 project through the cover 44.
The combination lance 31 comprises a supply pipe 3 2 for oxygen and a supply pipe 33 for metallic material. A shut-off means 34 is provided on the supply pipe 32 and a shut-off means 35 on the supply pipe 33. The shut-off means 34 and 35 have control means 23, 25 which are connected to a measuring and controlling instrument 22 via the control lines 24, 26. Said measuring and controlling instrument 22 is connected, via a measuring line 27, to a measuring element 21, which is provided on the measuring lance 2 8 for measuring the temperature T, and to a measuring element 2 9 for measuring the pressure P prevailing within the vessel.
In the case of Figure 2, an open metallurgical melt-filled vessel 10 is used, a supply pipe 46 and a discharge pipe 47 of an RH-vessel 45 dipping into the melt. The RH-vessel is connected to a vacuum plant 41 via a suction pipe 42. In addition to the combination lance 31, a pipe 38, for the supply, in particular, of coarse solid material,, projects into

•the RH-vessel, and this pipe is in communication with a container 36 via a shut-off means 37. The measuring and controlling device and the control device are the same as illustrated in Figure 1.
Figure 3 shows a vessel 10 which is sealed by a cover 15 which comprises a bubble cap 14 which, on its open side, dips into the melt S disposed in the vessel 10.
The suction pipe 42 connected to the vacuum plant 41 is designed such that a branch, which is adapted to be shut off, is provided, firstly in the direction of the bubble cap 14 via the shut-off means 48 and, secondly, in the direction of the cover 15 via the shut-off means 49.
The measuring and controlling device and the control device are designed such as those of Figure 1 or Figure 2. The elements 29 in the interior 17 of the bubble cap 14 and in the interior ■11 of the vessel, in the present instance the ladle 10, are provided for measuring the pressure.
The temperature measuring element 21 is directed deeply into the refractory lining 13 through the metal shell 12 of the vessel 10.

List of Reference Numbers
10 metallurgical vessel
11 interior of vessel
12 shell
13 refractory lining
14 bubble cap
15 cover
17 interior of bubble cap
Measuring and controlling device
21 measuring element
22 measuring and controlling instrument
23 control means - O2
24 control line - O2
25 control means - combustible material
26 control line - combustible material
27 measuring line
28 measuring lance - temperature
29 measuring element - pressure
Media
31 combination lance
32 supply pipe - oxygen
33 supply pipe - metallic combustible material
34 shut-off means O2
35 first shut-off - combustible material

f
36 container for combustible material
37 second shut-off - solid material
38 pipe - solid material
Vacuum installation
41 vacuum plant
42 suction pipe
43 vacuum vessel
44 cover
45 RH-vessel
46 pipe - supply
47 pipe - discharge
48 shut-off - bubble cap
49 shut-off - ladle
A combustible material
O2 oxygen
T temperature
P pressure


WE CLAIM:
1. A process for decarburizing steel melt in a closed metallurgical vessel that is connected to a vacuum unit, comprising the steps of filling the closed metallurgical vessel with a steel melt containing carbon; adjusting the pressure in the closed metallurgical vessel to below 100 mbar; introducing a replenishment supply of oxygen to the closed metallurgical vessel to implement decarburization of the steel melt to remove the carbon; introducing a metallic combustible, substance at an even introduction rate to the closed metallurgical vessel after said step of introducing a replenistenent supply of oxygen; and introducing amount of oxygen during said step of introducing a metallic combustible substance needed to ccwnbust the metallic combustible substance during the decarburization of the steel melt, wherein said steps of introducing a metallic combustible substance and introducing an additional amoimt of oxygen are performed during the first 10 minutes following completion of said step of adjusting the pressure.
2. The process according to claim 1, wherein said step of introducing a metallic combustible substance comprises the step of introducing one of an aluminium powder, granular aluminium, or a combustible mixture such as Al, Fe, Si and Mn.
3. The process according to claim 2, wherein said step of introducing a metallic combustible substance comprises introducing the metallic combustible substance in discontinuous portions.

4. An apparatus for decarburization of steel as claimed in claims 1-3 comprising a scalable vessel provided with a cover member connected to a vacuum plant, said cover having a supply means for the supply of oxygen and metallic combustible material, said supply means being provided with control means, a metallurgical vessel positioned within said scalable vessel, a lance with measuring elements projecting into the melt disposed within said vessel, said measuring elements are provided with temperature and pressure detecting means and said control means are provided with means to control the supply of oxygen and metallic combustible material into said metallurgical vessel.
5. The apparatus according to claini 4, wherein the scalable vessel is designed to be an RH-vessel, the supply and discharge pipes (46, 47) of which dip into the melt (S) disposed in a metallurgical vessel, and in which the control means (23, 25) are connected to shut-off means (34, 35) which are arranged in supply pipes (32,33) for oxygen (O2) and/or combustible material (A).
6. The apparatus according to claim 5, wherein a bubble cap (14) is provided and is directed through a cover (15) which seals off the vessel opening (16) of the metallurgical vessel (10), projecting into the melt (S), and in which supply pipes (32, 33) for oxygen (O2) and metallic combustible material (A) are provided, which pipes project into an interior (17) of the bubble cap and which are arranged control means (23,25) which control shut-off means (34,35).
7. The apparatus according to any one of preceding claims 4 to 6, wherein a combination lance (31) is provided and in it are arranged the supply pipes (32, 33) for oxygen (O2) and/or metallic combustible material (A).

8. The apparatus according to claim 7, wherein in addition to the supply pipe (33)
for metallic combustible material in the combination lance (31), a pipe (38) is
provided to project into the vessel for supplying, in particular, coarse solid
material from a container (36).
9. A process for decarburizing a steel melt in a closed metallurgical vessel,
substantially as herein described with reference to the accompanying drawings.
10. An apparatus for decarburization of steel, substantially as herein described with
reference to the accompanying drawings.


Documents:

2020-mas-1996 abstract.pdf

2020-mas-1996 claims.pdf

2020-mas-1996 correspondence -others.pdf

2020-mas-1996 correspondence -po.pdf

2020-mas-1996 description (complete).pdf

2020-mas-1996 drawings.pdf

2020-mas-1996 form-2.pdf

2020-mas-1996 form-26.pdf

2020-mas-1996 form-4.pdf

2020-mas-1996 form-6.pdf

2020-mas-1996 others.pdf

2020-mas-1996 petition.pdf


Patent Number 194256
Indian Patent Application Number 2020/MAS/1996
PG Journal Number 08/2007
Publication Date 23-Feb-2007
Grant Date 05-Jan-2006
Date of Filing 13-Nov-1996
Name of Patentee M/S. MANNESMANN AKTIENGESELLSCHAFT
Applicant Address MANNESMANNUFER 2, D-40213 DUSSELDORF,
Inventors:
# Inventor's Name Inventor's Address
1 DR. HORST-DIETER SCHOLER, SCHWEIZER STRASSE 563, D-47058 DUISBURG,
2 VOLKER WIEGMANN, DR. ING., IM WALDFRIEDEN17, D-47055 DUISBURG,
3 RAINER DITTRICH, DIPL, ING.ZU DEN REHWIESEN 6, D-47055 DUISBURG,
4 FRANK HAERS, DR. ING,SMISEST 6, B-9970 KAPRIJKE, BELGIUM, LEO PEETERS,
5 LEO PEETERS, DR. BOEKHOUTESTRAAT 8, B-9968 BASSEVELDE
PCT International Classification Number C21C7/10
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 19544166.4 1995-11-17 Germany
2 195 48641.2 1995-12-13 Germany