EP0028569B1 - Procédé de brassage d'un métal en fusion par injection de gaz - Google Patents

Procédé de brassage d'un métal en fusion par injection de gaz Download PDF

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Publication number
EP0028569B1
EP0028569B1 EP80401549A EP80401549A EP0028569B1 EP 0028569 B1 EP0028569 B1 EP 0028569B1 EP 80401549 A EP80401549 A EP 80401549A EP 80401549 A EP80401549 A EP 80401549A EP 0028569 B1 EP0028569 B1 EP 0028569B1
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.)
Expired
Application number
EP80401549A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0028569A1 (fr
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
Original Assignee
Air Liquide Canada Inc
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 filed Critical Air Liquide Canada Inc
Priority to AT80401549T priority Critical patent/ATE11795T1/de
Publication of EP0028569A1 publication Critical patent/EP0028569A1/fr
Application granted granted Critical
Publication of EP0028569B1 publication Critical patent/EP0028569B1/fr
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 displacement of the ingot and 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 stopper system and it is raised so that the stopper 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 steel tube is used, which is embedded in the refractory lining of a ladle, for example at the bottom or near the bottom.
  • This tube passes through the outer steel jacket and the inner lining of refractory material and it ends at the right of the inner surface 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.
  • a molten metal bath is treated by injecting high pressure oxygen, from 28.10 5 to 70.10 5 Pa, in at least one metal tube which passes through the outer casing and the internal refractory lining of the tank containing the metal bath and which ends in line with the internal surface of the refractory lining.
  • high pressure oxygen from 28.10 5 to 70.10 5 Pa
  • Various charges of molten metal are introduced and treated successively in the tank.
  • 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 steel 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 of stirring by introducing gas under pressure into a molten metal, which does not require any maintenance intervention between successive heaters.
  • the process according to the invention can be used for stirring molten metal, in the purpose of homogenizing the latter, but it 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 method in that it has a long service life and can be used in successive heating cycles without requiring maintenance. This distinguishes it from 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 injection tube has a small diameter to prevent the penetration of 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. In the case of ferrous metals such as iron and steel, 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 diameter can 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 through which it passes, of the order of 100 mm. at 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 processing conditions 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 uncorking 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 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 normal introduction of stirring gas into 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 10 5 Pa and 12-105 Pa, it is desirable to have an installation for applying a pressure of 10 6 to 10 7 Pa, at start of injection, to expel the solidified metal, and when the gas supply is stopped by closing the supply pipe, the pressure in this pipe is balanced with that of the bath and the plug hardly forms only 2 to 3 mm at the end of the tube.
  • 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 cover 21 protects the agitated surface of the molten metal bath C against humidity and oxygen from the 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 ,, 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 higher 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 L.D. 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 D s 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 oxygen.
  • 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 6 Pa and approximately 5.10 6 Pa, 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 passage 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 ⁇ 10 5 Pa, the plug on the tube is expelled completely 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 life of the tube depends on the repair campaign of the pocket refractory.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Continuous Casting (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
EP80401549A 1979-10-31 1980-10-31 Procédé de brassage d'un métal en fusion par injection de gaz Expired EP0028569B1 (fr)

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
CA338904 1979-10-31
CA000338904A CA1141174A (en) 1979-10-31 1979-10-31 Homogenization of metal using gas

Publications (2)

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

Family

ID=4115497

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80401549A Expired EP0028569B1 (fr) 1979-10-31 1980-10-31 Procédé de brassage d'un métal en fusion par injection de gaz

Country Status (7)

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

Families Citing this family (5)

* 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
AU541441B2 (en) * 1981-07-15 1985-01-10 Nippon Steel Corporation Bottom blowing nozzle embedded in a refractory block
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
US8510303B2 (en) 2009-01-07 2013-08-13 Divx, Llc Singular, collective and automated creation of a media guide for online content

Family Cites Families (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
US3395910A (en) * 1965-12-01 1968-08-06 Union Carbide Corp Metallurgical tuyere
US3495815A (en) * 1967-07-17 1970-02-17 Union Carbide Corp Outside change tuyere
DE1901563A1 (de) * 1968-08-13 1970-09-24 Maximilianshuette Eisenwerk Verfahren zum Frischen von Roheisen zu Stahl
CH478613A (de) * 1968-07-12 1969-09-30 Interstop Ag Schiebeverschluss für mit einer Bodenausgussöffnung versehene Behälter zum Giessen von flüssigen Metallen, insbesondere Stahl
US3633898A (en) * 1969-06-06 1972-01-11 Stora Kopparbergs Bergslags Ab Means for gas-flushing metal melts
US3684267A (en) * 1970-01-12 1972-08-15 United States Steel Corp Apparatus for introducing gas to hot metal in a bottom-pour vessel
US3809146A (en) * 1972-02-18 1974-05-07 Steel Corp Method of opening an intermediate vessel nozzle for continuous casting
US4135920A (en) * 1976-07-06 1979-01-23 Barbakadze Dzhondo F Method of introducing powdered material into molten metal

Also Published As

Publication number Publication date
ATE11795T1 (de) 1985-02-15
DE3070177D1 (en) 1985-03-28
AU6402680A (en) 1981-05-07
EP0028569A1 (fr) 1981-05-13
JPS5681641A (en) 1981-07-03
CA1141174A (en) 1983-02-15
US4311518A (en) 1982-01-19
AU540327B2 (en) 1984-11-15
JPH032934B2 (enrdf_load_stackoverflow) 1991-01-17

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