EP0028569A1 - Verfahren zum Spülen einer Metallschmelze durch Einblasen von Gas - Google Patents

Verfahren zum Spülen einer Metallschmelze durch Einblasen von Gas Download PDF

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Publication number
EP0028569A1
EP0028569A1 EP80401549A EP80401549A EP0028569A1 EP 0028569 A1 EP0028569 A1 EP 0028569A1 EP 80401549 A EP80401549 A EP 80401549A EP 80401549 A EP80401549 A EP 80401549A EP 0028569 A1 EP0028569 A1 EP 0028569A1
Authority
EP
European Patent Office
Prior art keywords
molten metal
gas
tube
injection
metal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP80401549A
Other languages
English (en)
French (fr)
Other versions
EP0028569B1 (de
Inventor
Guy Savard
Robert Gum Hong Lee
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Air Liquide Canada Inc
Canadian Liquid Air Ltd
Original Assignee
Air Liquide Canada Inc
Canadian Liquid Air Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Air Liquide Canada Inc, Canadian Liquid Air Ltd filed Critical Air Liquide Canada Inc
Priority to AT80401549T priority Critical patent/ATE11795T1/de
Publication of EP0028569A1 publication Critical patent/EP0028569A1/de
Application granted granted Critical
Publication of EP0028569B1 publication Critical patent/EP0028569B1/de
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
    • B22D1/002—Treatment with gases
    • B22D1/005—Injection assemblies therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F33/00—Other mixers; Mixing plants; Combinations of mixers
    • B01F33/40—Mixers using gas or liquid agitation, e.g. with air supply tubes
    • B01F33/403—Mixers using gas or liquid agitation, e.g. with air supply tubes for mixing liquids
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D3/16—Introducing a fluid jet or current into the charge

Definitions

  • the present invention relates to the treatment of molten metals by methods which involve the intervention of a gas. It relates more particularly to a method and a device for stirring a molten metal, which can be used in particular for the homogenization or degassing of steel or other metals.
  • inert gas to ensure the agitation of molten steel is increasing.
  • the inert gas is used to homogenize the molten steel, in its chemical composition and in temperature, after its extraction from the refining furnace and before its casting in ingots or in continuous casting devices. Mixing with a gas in the ladle makes it possible to obtain a steel whose characteristics are more uniform in all respects.
  • molten steel is stirred, by means of a steel ingot which is lowered using a traveling crane, into the molten steel contained in the ladle.
  • the movement of the bridge causes a displacement of the ingot and the agitation of the metal. This process is impractical, it takes time and it is not effective enough.
  • a stopper which consists of a rod which is hollow, so that it can convey gas.
  • the stopper rod has at its end small orifices arranged radially, allowing the outlet of the gas. It is protected by a refractory sleeve.
  • the stopper system instead of being attached to the pocket, is attached to a fixed raised horizontal beam; the rod is placed upside down and the gas is introduced into it by a gas inlet at the top and it exits at the bottom, through the head orifices.
  • a pocket containing molten metal is brought, by a crane, into position under the sys stopper rod and it is lifted so that the stopper rod is immersed in the molten metal.
  • the gas exiting the head of the stopper spears through the molten metal, thereby producing the desired agitation.
  • a porous refractory is used to introduce the gases into the molten metal.
  • This process is implemented industrially. It uses a refractory brick or a porous plug having the property of being permeable to gas under pressure but substantially impermeable to molten metal.
  • the porous plug constitutes part of the internal lining of the bag, in a place where it is submerged when the bag is filled with molten metal.
  • the gas is introduced into the molten metal through the porous plug and the desired degree of agitation is obtained by action on the gas flow rate.
  • such porous plugs can have a life expectancy of 10 to 25 cycles, and in the case of the composition of molten iron, the life can be from 50 to 200 heating cycles.
  • a metal tube is used, made of steel, which is embedded in the refractory lining of a ladle, for example at the bottom or near the bottom.
  • This tube passes through the steel outer casing and the internal lining of refractory material and ends at the surface interior of the latter.
  • the introduction of gas begins before the metal is poured into the pocket and after obtaining the desired agitation, the introduction of gas is stopped.
  • the metal then flows back into the tube and solidifies.
  • the tube should be replaced after each cycle.
  • the tube can be cleaned after use, by broaching using a steel bar or by drilling and removing the solidified metal, and it can be reused until it becomes too short.
  • porous refractory and metal tube processes are also applied for the introduction of a relatively non-reactive gas at the bottom of a bath of molten metal in the steelworks field, in certain oxygen converters of the LD type.
  • these gas distribution stirring devices can also be used to stir the molten metal.
  • the subject of the present invention is a method and a device for stirring by introducing pressurized gas into a molten metal, which does not require any maintenance intervention between successive heaters.
  • the method and the device according to the invention can be used for stirring molten metal, in order to homogenize the latter, but they can also be used to partially or completely expel a particular gas dissolved in the molten metal.
  • the gas can be an inert gas, playing only a stirring role, it can also be a reactive gas in the presence of the molten metal, for example a reducing gas or an oxidizing gas, or any other gas to be introduced into the molten metal or to be mixed with it.
  • the dimensions of the metal tube through which the gas is injected are chosen so that the molten metal solidifies at the end of the tube and completely closes the mouth, the inlet of molten metal in the inner conduit of the metal tube thus being prevented.
  • the closed end is easy to unclog by gas pressure when the metal tube is put into service.
  • the metal tube according to the invention therefore makes it possible to avoid the drawbacks of the metal tubes used in the prior process in that it has a long service life and can be used in successive heating cycles without requiring maintenance. This distinguishes it from the metal tubes according to the prior art, of larger diameter, which must be replaced after each use. In addition, there is no need for a special device to prevent the entry of molten metal into the gas supply circuit, since the metal tube itself prevents this entry.
  • the invention thus relates to a device for stirring a molten metal by gas injection, characterized in that it comprises a tank for containing the molten metal, comprising an outer casing provided with a refractory lining and at minus a metal injection tube which passes through this envelope and ends at the right of the interior surface of the refractory lining, means for admitting a gas under pressure into the tank through the injection tube, from a source of supply of gas under pressure external to the tank and means for interrupting the injection by closing a connection pipe between the injection tube and said source, and means for creating at least temporarily an inlet pressure for the gas sufficient to expel a solidified metal plug possibly formed at the end of the tube during an interruption of the injection.
  • the invention also relates to a method of stirring molten metal by means of the preceding device, which essentially consists in using a tank for containing the molten metal, comprising an outer casing provided with a refractory lining and at least one tube.
  • the injection tube advantageously has a small diameter to prevent the penetration of the molten metal into the tube, the maximum value of which is determined by the condition that the molten metal must not enter the tube.
  • the maximum diameter can be determined experimentally, for particular molten metals.
  • the maximum admissible diameter of the interior passage of the tube is of the order of 2.5 mm.
  • the minimum admissible diameter is determined by the condition that the injection tube is capable of distributing an inert gas at a suitable rate and under pressure to ensure mixing of the molten metal.
  • the internal diameter may generally be between 0.25 and 2.5 mm, over a length of at least 2 mm, and in particular over the entire thickness of the lining, which it passes through, of the order of 100 mm to 1 meter.
  • the thickness of the wall of the injector tube is determined to ensure sufficient mechanical strength of the tube for normal handling.
  • the injection tube can be made of any metal which does not deform or soften under the operating conditions.
  • the injection tube can be made of stainless steel, low carbon steel or copper.
  • the conditions of treatment can be modified according to the nature of the metal used to manufacture the tubes.
  • the injection tube passes through the refractory lining, so that the end or gas outlet mouth of the tube stops at the right of the interior surface of the lining.
  • the injection tube must not extend beyond the refractory lining, taking into account the high temperatures to which it would be subjected.
  • Molten metal for example molten steel, is poured into the pocket and the injection tube then becomes closed by the metal which solidifies on the free end. When the temperature of the injection tube increases, the tube becomes very weak mechanically.
  • gas pressure is applied to the tube to unclog it.
  • the unblocking can take place by expulsion of the only solidified metal on the end, or by bursting of the hot part, therefore weak, of the tube, near the end where it approaches the temperature of the molten metal.
  • the gas can flow through the tube.
  • the introduction of gas is stopped and the molten metal again closes the end of the tube, by solidification on the mouth.
  • the hot molten metal which is poured into the pocket heats the injection tube and the solidified metal plug, so that this plug is expelled or the tube bursts as described above, which allows the introduction normal brewing gas in the pocket.
  • Copper and low carbon steel tubes have the advantage that a lower gas pressure is required to unclog them compared to stainless steel tubes.
  • the supply pressure suitable for stirring is normally between 1 and 12 bars, it is desirable to have an installation making it possible to apply a pressure of 10 to 100 bars, at the start of the injection, to expel the solidified metal, and when the gas supply is stopped by closing the supply duct, the pressure in this duct is balanced with that of the bath and the plug hardly forms for 2 to 3 mm at the end of the tube.
  • the same device according to the invention can also be used with profit in converter installations for refining cast iron, although in this case it is not necessary to interrupt the gas injections. between two charges and that we can therefore avoid the formation of the solidified metal plug.
  • Figure 1 is a vertical section through a ladle containing a metal bath and equipped with an injection tube according to the present invention, this tank can be an LD type converter, an electric oven or a street lamp.
  • Figure 2 is a horizontal section along line 2-2 of Figure 1, a bag equipped with several injection tubes.
  • Figures 3a and 3b are respectively a side view and an end view of an injection tube usable in the invention.
  • Figure 4 is a partial vertical section through a pocket, showing a group of injection tubes.
  • Figure 5 is a partial section, on a larger scale, illustrating an injection zone in a tank bottom for the reception of molten metal.
  • Figure 6 is a longitudinal section through another embodiment of the injection tube according to the invention, the tube being housed in a thin metal sleeve.
  • Figure 7 is a cross-section along line 7-7 of the tube of Figure 6.
  • the ladle is generally designated by the reference B.
  • the ladle B has a steel casing 15 and a refractory lining 17 and it contains a bath C of molten metal.
  • the bottom of the bag B is equipped with a refractory piece 19, through which an injection tube D enters for the introduction of inert gas into the bath C.
  • the bag B is provided with a cover 21, coated on the inside of a refractory lining 23.
  • the lid 21 protects the surface of the stirred metal C melt, against moisture and oxygen - 'ambient atmosphere. To increase the effectiveness of this protection, it may be desirable to introduce an additional inert gas through the cover 21. An inlet pipe, not shown, can be provided for this purpose.
  • the cover 21 also reduces heat loss by radiation. For example, in an installation treating 60 tonnes of steel heated under argon, the temperature drop rate is reduced from around 7 ° C / min without cover 21, to around 3.8 ° C / min with cover 21.
  • FIG. 2 represents a bag B equipped with four injection tubes D, D 1 , D 2 , D 3 , and a pouring nozzle 31.
  • the diameter of the interior passage of the injection tube D should not be greater than about 2.5 mm when the bath C is a molten ferrous metal. A diameter greater than this value can allow drips of molten metal penetrating further into the tube and causing internal blockages which cannot be removed by the pressure of gas alone. Such blockages would require cleaning the tube D mechanically or replacing it between successive uses.
  • the admissible internal diameter, up to a maximum of 2.5 mm, is determined by the gas flow rate and the pressure for expulsion. In practice, the minimum internal diameter is of the order of 0.25 and preferably 0.8 mm.
  • the wall thickness of tube D must be between 0.25 mm and 4 mm.
  • the minimum wall thickness is determined by the mechanical strength required for the tube.
  • the maximum wall thickness is determined by the combination of the temperature of the molten metal with which the tube comes into contact, the gas pressure and the type of refractory that surrounds the tube.
  • the heat transmission, under the conditions prevailing in the area surrounding the injection tube D, the refractory and the contact with the molten metal, is extremely complex. Consequently, the optimal dimensions must be specified experimentally.
  • the injection tube D can be a single tube, as shown in FIG. 3. If a greater flow rate is necessary to obtain the desired agitation in the molten metal, several tubes can be used.
  • FIG. 4 illustrates this device. It can be seen in this figure that a common inlet tube 1 leads to a bundle of tubes D, D 1 , through a steel casing 15 and a refractory lining 17. This makes it possible to multiply the gas flow, in any conditions, while remaining for the individual tubes within suitable dimensional tolerances.
  • multiple bundles of injection tubes can be provided, arranged for efficient operation.
  • the number of tubes D can be chosen as a function of several factors, and makes it possible to overcome certain difficulties inherent in the use of a single source of gas for expulsion.
  • the ladle has a dimension to receive a full load of steel from the refining furnace.
  • the distribution of the gas in a bundle of injection tubes makes it possible to ensure the mixing of such a complete charge, while the use of a single source could lead to projections which, to be avoided, would require reducing the quantity of metal in the pocket so as to increase the upper free space for projections.
  • the projection conditions in an LD converter, an electric oven and a reverberatory oven are less strict than in a ladle.
  • FIG. 5 is a view, on a larger scale, of an injection tube D through the steel casing 15 and the refractory lining 17.
  • the tube D is surrounded by refractory elements 33 and 35 which may be prefabricated bricks from compressed or suspended refractory material.
  • the refractory elements 33 and 35 constitute a part of the refractory lining 17.
  • the end E of the tube D does not extend beyond the free interior surface of the refractory element 35.
  • their ends can be modified so as to receive a material of lower resistance than that of the adjacent refractory, for example graphite, which can burst or break during the withdrawal of the worn tube.
  • a material of lower resistance than that of the adjacent refractory for example graphite
  • FIGS. 6 and 7 show such a tube D5 provided with a thin sleeve 8.
  • inert or relatively inert gases it is understood that it is not limited to the use of such gases. It can be used with reducing gases, for example natural gas, propane, etc. Liquid hydrocarbons can also be used. Active oxidizing gases, for example oxygen, can be sent through the injection tube not in commercially pure form, but diluted with an inert gas, for example argon, helium, nitrogen, etc. Oxygen can be present up to a content of 75% by volume. In a particular embodiment, the gas contains by volume 70% of molecular oxrygene.
  • the molten metal treated by the process according to the invention can be subjected to a lower or higher pressure than atmospheric pressure, depending on the desired results.
  • the gas pressure necessary to open the closed end of the injection tube can advantageously be between approximately 10 bars and approximately 50 bars, although higher pressures can be used. Once the tube is opened, which is almost immediate, the gas pressure can be reduced to the desired value, which essentially depends on the agitation useful for homogenizing the molten metal.
  • a mild steel injection tube is used, having an outside diameter of 3.2 mm, a wall thickness of 0.8 mm, and an inside pass diameter of 1.55 mm.
  • the tube is embedded in the refractory lining at the base of a pocket B, as shown in Figure 1.
  • 112 kg of molten iron are poured into pocket B and the metal solidifies on the exposed end of the tube, sealing the latter.
  • Argon is sent under a pressure of 15.7 bars, the plug on the tube is completely expelled and the metal is stirred with argon.
  • the gas supply is stopped by closing the supply duct and the end of the tube is again closed by the molten metal.
  • the latter is then emptied.
  • 112 kg of molten metal are poured into pocket B.
  • Argon pressure is applied and the normal gas flow is established.
  • the cycle can be renewed continuously.
  • the effective service life of the tube depends on the repair campaign of the pocket refractory.
EP80401549A 1979-10-31 1980-10-31 Verfahren zum Spülen einer Metallschmelze durch Einblasen von Gas Expired EP0028569B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT80401549T ATE11795T1 (de) 1979-10-31 1980-10-31 Verfahren zum spuelen einer metallschmelze durch einblasen von gas.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA000338904A CA1141174A (en) 1979-10-31 1979-10-31 Homogenization of metal using gas
CA338904 1979-10-31

Publications (2)

Publication Number Publication Date
EP0028569A1 true EP0028569A1 (de) 1981-05-13
EP0028569B1 EP0028569B1 (de) 1985-02-13

Family

ID=4115497

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80401549A Expired EP0028569B1 (de) 1979-10-31 1980-10-31 Verfahren zum Spülen einer Metallschmelze durch Einblasen von Gas

Country Status (7)

Country Link
US (1) US4311518A (de)
EP (1) EP0028569B1 (de)
JP (1) JPS5681641A (de)
AT (1) ATE11795T1 (de)
AU (1) AU540327B2 (de)
CA (1) CA1141174A (de)
DE (1) DE3070177D1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0070197A1 (de) * 1981-07-15 1983-01-19 Nippon Steel Corporation Düsenanordnung für Durchblasstahlwerkskonverter

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5871343A (ja) * 1981-10-22 1983-04-28 Kobe Steel Ltd 溶融金属容器に設けるガス吹込み用ノズル
US4462824A (en) * 1983-06-14 1984-07-31 Allegheny Ludlum Steel Corporation Annular tuyere
US4699654A (en) * 1986-04-08 1987-10-13 Union Carbide Corporation Melting furnace and method for melting metal
CN105072454B (zh) 2009-01-07 2019-04-19 索尼克Ip股份有限公司 针对在线内容的媒体指南的特定化、集中式、自动化创建

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2855293A (en) * 1955-03-21 1958-10-07 Air Liquide Method and apparatus for treating molten metal with oxygen
FR1503078A (fr) * 1965-12-01 1967-11-24 Union Carbide Corp Lance métallurgique
US3495815A (en) * 1967-07-17 1970-02-17 Union Carbide Corp Outside change tuyere
FR2012888A1 (de) * 1968-07-12 1970-03-27 Interstop Ag
DE1901563A1 (de) * 1968-08-13 1970-09-24 Maximilianshuette Eisenwerk Verfahren zum Frischen von Roheisen zu Stahl
FR2076057A1 (de) * 1970-01-12 1971-10-15 Uss Eng & Consult
US3633898A (en) * 1969-06-06 1972-01-11 Stora Kopparbergs Bergslags Ab Means for gas-flushing metal melts
FR2172057A1 (de) * 1972-02-18 1973-09-28 Uss Eng & Consult
US4135920A (en) * 1976-07-06 1979-01-23 Barbakadze Dzhondo F Method of introducing powdered material into molten metal

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2855293A (en) * 1955-03-21 1958-10-07 Air Liquide Method and apparatus for treating molten metal with oxygen
FR1503078A (fr) * 1965-12-01 1967-11-24 Union Carbide Corp Lance métallurgique
US3495815A (en) * 1967-07-17 1970-02-17 Union Carbide Corp Outside change tuyere
FR2012888A1 (de) * 1968-07-12 1970-03-27 Interstop Ag
DE1901563A1 (de) * 1968-08-13 1970-09-24 Maximilianshuette Eisenwerk Verfahren zum Frischen von Roheisen zu Stahl
US3633898A (en) * 1969-06-06 1972-01-11 Stora Kopparbergs Bergslags Ab Means for gas-flushing metal melts
FR2076057A1 (de) * 1970-01-12 1971-10-15 Uss Eng & Consult
FR2172057A1 (de) * 1972-02-18 1973-09-28 Uss Eng & Consult
US4135920A (en) * 1976-07-06 1979-01-23 Barbakadze Dzhondo F Method of introducing powdered material into molten metal

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0070197A1 (de) * 1981-07-15 1983-01-19 Nippon Steel Corporation Düsenanordnung für Durchblasstahlwerkskonverter

Also Published As

Publication number Publication date
AU6402680A (en) 1981-05-07
AU540327B2 (en) 1984-11-15
JPH032934B2 (de) 1991-01-17
CA1141174A (en) 1983-02-15
JPS5681641A (en) 1981-07-03
DE3070177D1 (en) 1985-03-28
US4311518A (en) 1982-01-19
ATE11795T1 (de) 1985-02-15
EP0028569B1 (de) 1985-02-13

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