GB1594631A - Injectors for injecting gas into molten metal - Google Patents

Injectors for injecting gas into molten metal Download PDF

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Publication number
GB1594631A
GB1594631A GB1764077A GB1764077A GB1594631A GB 1594631 A GB1594631 A GB 1594631A GB 1764077 A GB1764077 A GB 1764077A GB 1764077 A GB1764077 A GB 1764077A GB 1594631 A GB1594631 A GB 1594631A
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United Kingdom
Prior art keywords
injector
slot
gas
sleeve
width
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
GB1764077A
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Electricity Council
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Electricity Council
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 Electricity Council filed Critical Electricity Council
Priority to GB1764077A priority Critical patent/GB1594631A/en
Publication of GB1594631A publication Critical patent/GB1594631A/en
Expired legal-status Critical Current

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    • 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

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Furnace Charging Or Discharging (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Description

(54) IMPROVEMENTS IN OR RELATING TO INJECTORS FOR INJECTING GAS INTO MOLTEN METAL (71) We, THE ELECTRICITY COUNCIL, a British Body Corporate, of 30 Millbank, London, SW1P 4RD, do hereby declare the invention, for which we pray that a patent may be granted to us, and the manner by which it is to be performed, to be particularly described in and by the following statement: This invention relates to injectors for the injection of a gas into molten metal.
It is known to inject gas into a molten metal through a porous plug or through a nozzle.
Such gas injection finds particular application in channel induction furnaces. It may be used for a number of purposes; for example, anon- reactive gas such as nitrogen or argon may be injected into the inductor loop of a channel induction furnace to promote metal circulation and to de-gas the metal and to remove inclusions in the metal. As another example, a chemically reactive gas may be injected into metal for chemical or metallurgical purposes, e.g. in a furnace acting as a holding vessel for molten metal. The rate of injection of gas depends on the particular requirements but there are circumstances in which a very low rate of gas flow is required. As an example, in a channel induction furnace used for melting aluminium and having a large power input to the inductor, it is found that alumina is deposited on the walls of the channel at quite a fast rate. This accumulation of alumina can be prevented by a small flow of inert gas into the channel. Typically nitrogen or argon might be injected into the channel at a flow rate of less than 0.5 litres per minute. It is undesirable to inject an inert gas into aluminium in the channel of channel induction furnaces at a high rate because of the disturbances to the inductor electrical characteristics which occur with gas injection at high flow rates. These disturbances arise from the gas forming large bubbles which can extend across the channel and thus interrupt the electrical circuit. The disturbances in the electrical characteristics due to gas injection at a high flow rate are undesirable because they cause waveform distortion in the supply, thereby affecting other electrical consumers.
There are however problems in injecting gas at a very low rate such as 0.5 litres per minute or less. It is found that, if the gas injection is effected through a nozzle, at such a low flow rate metal can flow back into the nozzle against the gas stream, eventually blocking the nozzle. If, on the other hand, a porous plug is used an oxide film gradually forms across the face of the plug and eventually the plug is blocked preventing any further gas flow.
It is one of the objects of the present invention to provide an improved form of injector for injecting gas into a molten metal at a low flow rate.
According to this invention an injector for injecting gas into a moletn metal comprises a refractory structure with a gas inlet duct leading from one face of the injector to one or more slots formed in the opposite face, the or each slot having a width of between 0.05 and 0.1 mm and having alength substantially longer than its width. In practice the length of the slot or of each slot might typically be from 10 to 500 times the width. Preferably the or each slot is at least 15 mm long.
With this construction of injector, the width of the slots is sufficiently narrow to prevent, or substantially to prevent, any metal penetration into the injector so as to avoid any metal or oxide build-up in the injector. These slots however are significantly wider than the pores in a porous body type of the injector and thereby reduces or eliminates the possibility of a film of oxide material building up across the face of the injector to block the gas outlet. The slot or each slot is elongate to provide a gas passage over a sufficient region to enable gas bubbles to form in the molten metal. In molten metal, a gas bubble has to reach a minimum size before it will detach itself from the injector and float up through the metal. In molten aluminium typically the gas bubbles will have a diameter at least about 15 mm. The length of the slot assists in the formation of gas bubbles for passing up through the metal.
Conveniently the or each slot is of arcuate form, for example of circular form; such a slot however may be sub-divided into two or more arcuate portions. With a circular slot, preferably the diameter of the slot is at least 15 mm in order to optimise the required bubble formation.
The invention furthermore includes within its scope an injector for injecting gas into a molten metal comprising a sleeve of gas impermeable refractory material having an internal bore at least partly in the shape of a frustum of a cone and inner element also of gas impermeable material fitting in said bore to leave a slot or slots between the inner surface of the sleeve and the surface of the inner member, with the narrower end of the frustum of the cone on one external surface of the injector, the or each slot having a width of between 0.05 and 0.1 mm and a length substantially longer than its width, e.g. 10 to 500 times its width, said injector furthermore having a gas entry duct leading from a surface opposite said one external surface to said slot or slots. Such an injector may have its sleeve cast into a refractory block for installation in the wall of a furnace, and, in particular, for installation in the wall of the loop of a channel induction furnace.
The invention furthermore includes within its scope a channel induction furnace having an injector as described above installed in the wall of the channel loop and having means for feeding gas at a controlled rate through said injector.
The following is a description of two embodiments of the invention, reference being made to the accompanying drawing, in which: Figure 1 is a longitudinal cross-section through an injector for injecting an inert gas into aluminium in the channel of a channel induction furnace; Figure 2 is a front elevation of the injector of Figure 1; and Figure 3 is an end view of part of a modified form of injector.
Referring to Figures 1 and 2 the injector shown comprises an outer sleeve 1 having internal and external faces each in the form of a frustum of a cone and made of a dense cast alumina refractory material which is impermeable to gas. Within the outer sleeve 1 is a plug 2 made of a similar gas impermeable material and externally of the same taper as the bore in the sleeve 1. At the wider end of the bore, the plug 2 fits closely within the sleeve 1. For a substantial part of its length towards the narrower end, the plug 2, although having the same taper as the sleeve, is of slightly smaller diameter so as to leave an annular slot 3 in the region between the plug 2 and the sleeve 1. In this particular embodiment, the slot 3 extends completely around the plug. The sleeve 1 and plug 2 together are cast into a refractory block 7 which may be clamped into a refractory wall of an inductor box of the channel induction furnace. The conical tapers are such that the narrower end of the conical slot is exposed to the molten metal in the furnace. A gas supply duct constituted by a stainless steel tube 5 extends from the opposite face of the block 7 into a bore extending a short distance axially into the plug 2; this duct leads to four radial passages 6 which extend outwardly to the inner end of the annular slot 3.
As shown in Figure 3, the plug 2 and outer sleeve 1 may be shaped to have a number of arcuate slots 4 instead of a circular slot 3 as in Figures 1 and 2.
In each of these embodiments described, the slots 3 or 4 have width between 0.05 mm and 0.1 mm. At the outer end where the slot or slots are exposed to the molten metal, the diameter of the plug is preferably at least 15 mm and typically might be 30 mm. The length of the slot or slots is thus may times greater than its width. A slot of this size permits of gas escape at a low flow rate, for example, 0.5 litres per minute but, because of the narrow width, molten aluminium would not enter the slot. The arrangement is such that it facilitates the formation of gas bubbles in the aluminium, the region of gas exit from the injector being sufficiently large to enable a bubble to form and then rise into the liquid metal.
WHAT WE CLAIM IS: 1. An injector for injecting gas into a molten metal comprising a refractory structure with a gas inlet duct leading from one face of the injector to one or more slots formed in the opposite face, the or each slot having a width of between 0.05 and 0.1 mm and having a length substantially longer than its width.
2. An injector as claimed in claim 1 wherein the length of the slot or of each slot is from 10 to 500 times the width.
3. An injector as claimed in either claim 1 or claim 2 wherein the or each slot is at least 15 mm long.
4. An injector as claimed in any of the preceding claims wherein the or each slot is of arcuate form.
5. An injector as claimed in claim 4 wherein a single slot is provided of circular form.
6. An injector as claimed in claim 5 wherein the slot is sub-divided into two or more arcuate portions.
7. An injector as claimed in either claim 5 wherein the diameter of the slot is at least 15 mm.
8. An injector for injecting gas into a molten metal comprising a sleeve of gas impermeable refractory material having an internal bore of at least partly in the shape of a frustum of a cone and inner element also of gas impermeable material fitting in said bore to leave a slot or slots between the inner surface of the sleeve and the surface of the inner member, with the narrower end of the frustum of the cone on one external surface of the injector, the or each slot having a width between 0.05 and 0.1 mm and having a length substantially longer than its width, said injector furthermore having a gas entry duct leading from a surface opposite said one external surface to said slot or slots.
9. An injector as claimed in claim 8 wherein said sleeve is cast into a refractory block for installation in the wall of a furnace.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

  1. **WARNING** start of CLMS field may overlap end of DESC **.
    molten metal comprising a sleeve of gas impermeable refractory material having an internal bore at least partly in the shape of a frustum of a cone and inner element also of gas impermeable material fitting in said bore to leave a slot or slots between the inner surface of the sleeve and the surface of the inner member, with the narrower end of the frustum of the cone on one external surface of the injector, the or each slot having a width of between 0.05 and 0.1 mm and a length substantially longer than its width, e.g. 10 to 500 times its width, said injector furthermore having a gas entry duct leading from a surface opposite said one external surface to said slot or slots. Such an injector may have its sleeve cast into a refractory block for installation in the wall of a furnace, and, in particular, for installation in the wall of the loop of a channel induction furnace.
    The invention furthermore includes within its scope a channel induction furnace having an injector as described above installed in the wall of the channel loop and having means for feeding gas at a controlled rate through said injector.
    The following is a description of two embodiments of the invention, reference being made to the accompanying drawing, in which: Figure 1 is a longitudinal cross-section through an injector for injecting an inert gas into aluminium in the channel of a channel induction furnace; Figure 2 is a front elevation of the injector of Figure 1; and Figure 3 is an end view of part of a modified form of injector.
    Referring to Figures 1 and 2 the injector shown comprises an outer sleeve 1 having internal and external faces each in the form of a frustum of a cone and made of a dense cast alumina refractory material which is impermeable to gas. Within the outer sleeve 1 is a plug
    2 made of a similar gas impermeable material and externally of the same taper as the bore in the sleeve 1. At the wider end of the bore, the plug 2 fits closely within the sleeve 1. For a substantial part of its length towards the narrower end, the plug 2, although having the same taper as the sleeve, is of slightly smaller diameter so as to leave an annular slot 3 in the region between the plug 2 and the sleeve 1. In this particular embodiment, the slot 3 extends completely around the plug. The sleeve 1 and plug 2 together are cast into a refractory block
    7 which may be clamped into a refractory wall of an inductor box of the channel induction furnace. The conical tapers are such that the narrower end of the conical slot is exposed to the molten metal in the furnace. A gas supply duct constituted by a stainless steel tube 5 extends from the opposite face of the block 7 into a bore extending a short distance axially into the plug 2; this duct leads to four radial passages 6 which extend outwardly to the inner end of the annular slot 3.
    As shown in Figure 3, the plug 2 and outer sleeve 1 may be shaped to have a number of arcuate slots 4 instead of a circular slot 3 as in Figures 1 and 2.
    In each of these embodiments described, the slots 3 or 4 have width between 0.05 mm and 0.1 mm. At the outer end where the slot or slots are exposed to the molten metal, the diameter of the plug is preferably at least 15 mm and typically might be 30 mm. The length of the slot or slots is thus may times greater than its width. A slot of this size permits of gas escape at a low flow rate, for example, 0.5 litres per minute but, because of the narrow width, molten aluminium would not enter the slot. The arrangement is such that it facilitates the formation of gas bubbles in the aluminium, the region of gas exit from the injector being sufficiently large to enable a bubble to form and then rise into the liquid metal.
    WHAT WE CLAIM IS: 1. An injector for injecting gas into a molten metal comprising a refractory structure with a gas inlet duct leading from one face of the injector to one or more slots formed in the opposite face, the or each slot having a width of between 0.05 and 0.1 mm and having a length substantially longer than its width.
  2. 2. An injector as claimed in claim 1 wherein the length of the slot or of each slot is from 10 to 500 times the width.
  3. 3. An injector as claimed in either claim 1 or claim 2 wherein the or each slot is at least
    15 mm long.
  4. 4. An injector as claimed in any of the preceding claims wherein the or each slot is of arcuate form.
  5. 5. An injector as claimed in claim 4 wherein a single slot is provided of circular form.
  6. 6. An injector as claimed in claim 5 wherein the slot is sub-divided into two or more arcuate portions.
  7. 7. An injector as claimed in either claim 5 wherein the diameter of the slot is at least
    15 mm.
  8. 8. An injector for injecting gas into a molten metal comprising a sleeve of gas impermeable refractory material having an internal bore of at least partly in the shape of a frustum of a cone and inner element also of gas impermeable material fitting in said bore to leave a slot or slots between the inner surface of the sleeve and the surface of the inner member, with the narrower end of the frustum of the cone on one external surface of the injector, the or each slot having a width between 0.05 and 0.1 mm and having a length substantially longer than its width, said injector furthermore having a gas entry duct leading from a surface opposite said one external surface to said slot or slots.
  9. 9. An injector as claimed in claim 8 wherein said sleeve is cast into a refractory block for installation in the wall of a furnace.
  10. 10. A channel induction furnace having an
    injector as claimed in any of the preceding claims installed in the wall of the channel loop and having means for feeding gas at a controlled rate through said injector.
  11. 11. An injector for injecting gas into a molten metal substantially as hereinbefore described with reference to Figures 1 and 2 or to Figure 3 of the accompanying drawings.
GB1764077A 1978-04-06 1978-04-06 Injectors for injecting gas into molten metal Expired GB1594631A (en)

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Application Number Priority Date Filing Date Title
GB1764077A GB1594631A (en) 1978-04-06 1978-04-06 Injectors for injecting gas into molten metal

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Application Number Priority Date Filing Date Title
GB1764077A GB1594631A (en) 1978-04-06 1978-04-06 Injectors for injecting gas into molten metal

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0087261A1 (en) * 1982-02-15 1983-08-31 Zirconal Processes Limited Improvements in the introduction of substances into molten metal
GB2120369A (en) * 1982-05-20 1983-11-30 Ksr Int Ltd An improved metallurgical lance
EP0148336A1 (en) * 1983-11-17 1985-07-17 Radex Deutschland Aktiengesellschaft für feuerfeste Erzeugnisse Gas flushing plug for metallurgical vessels
GB2179724A (en) * 1985-08-26 1987-03-11 Labate Michael D Device for introducing gas into molten metal
EP0221250A1 (en) * 1985-10-30 1987-05-13 Didier-Werke Ag Injector installation for metallurgical vessels
EP0230217A2 (en) * 1985-12-23 1987-07-29 Albert Dipl.-Ing. Tosin Gas-flushing brick for a metallurgical vessel
US4900357A (en) * 1986-02-20 1990-02-13 Injectall Limited Injection of substances into high temperature liquids
US4944496A (en) * 1987-04-10 1990-07-31 Injectall Limited Apparatus for injecting gas into high temperature liquids, e.g. molten metals
US5198179A (en) * 1989-04-24 1993-03-30 Injectall Limited Gas injector
USRE34418E (en) * 1982-11-23 1993-10-26 Injectall Limited Apparatus and method for introducing substances into liquid metal

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0087261A1 (en) * 1982-02-15 1983-08-31 Zirconal Processes Limited Improvements in the introduction of substances into molten metal
GB2120369A (en) * 1982-05-20 1983-11-30 Ksr Int Ltd An improved metallurgical lance
USRE34418E (en) * 1982-11-23 1993-10-26 Injectall Limited Apparatus and method for introducing substances into liquid metal
EP0148336A1 (en) * 1983-11-17 1985-07-17 Radex Deutschland Aktiengesellschaft für feuerfeste Erzeugnisse Gas flushing plug for metallurgical vessels
GB2179724A (en) * 1985-08-26 1987-03-11 Labate Michael D Device for introducing gas into molten metal
GB2179724B (en) * 1985-08-26 1990-02-28 Labate Michael D Apparatus for introducing gas into molten metal
EP0221250A1 (en) * 1985-10-30 1987-05-13 Didier-Werke Ag Injector installation for metallurgical vessels
EP0230217A2 (en) * 1985-12-23 1987-07-29 Albert Dipl.-Ing. Tosin Gas-flushing brick for a metallurgical vessel
EP0230217A3 (en) * 1985-12-23 1988-03-30 Albert Dipl.-Ing. Tosin Gas-flushing brick for a metallurgical vessel
US4900357A (en) * 1986-02-20 1990-02-13 Injectall Limited Injection of substances into high temperature liquids
US4944496A (en) * 1987-04-10 1990-07-31 Injectall Limited Apparatus for injecting gas into high temperature liquids, e.g. molten metals
US5198179A (en) * 1989-04-24 1993-03-30 Injectall Limited Gas injector

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PCNP Patent ceased through non-payment of renewal fee