GB2123535A - Injection lances for molten metal - Google Patents
Injection lances for molten metal Download PDFInfo
- Publication number
- GB2123535A GB2123535A GB08215724A GB8215724A GB2123535A GB 2123535 A GB2123535 A GB 2123535A GB 08215724 A GB08215724 A GB 08215724A GB 8215724 A GB8215724 A GB 8215724A GB 2123535 A GB2123535 A GB 2123535A
- Authority
- GB
- United Kingdom
- Prior art keywords
- lance
- refractory concrete
- tubular member
- molten metal
- reinforcing members
- 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.)
- Withdrawn
Links
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
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/42—Constructional features of converters
- C21C5/46—Details or accessories
- C21C5/4606—Lances or injectors
- C21C5/4613—Refractory coated lances; Immersion lances
Abstract
An injection lance for injecting gas and/or powders into molten metals comprises a refractory concrete tube containing reinforcing members 12 extending between annular collars 13 embedded in the end faces of the refractory tube. The reinforcing members 12 are under tensile stress and serve to place the refractory concrete in compressive stress, thereby reducing the tendency of the refractory concrete to form cracks by the action of tensile stress in use. <IMAGE>
Description
SPECIFICATION
Injection lances for molten metal
This invention relates to injection lances for injecting materials for instance gases and/or powders into molten metal.
It has long been the practice to stir a ladle of molten metal by means of injecting a gas into it, often to try to ensure that the whole ladle is of uniform temperature and to improve the homogeneity of the molten metal in the ladle. A practice which is becoming increasingly common is the injection of various powders in a gaseous carrier into the molten metal in order to affect some metalluryical change in the molten metal.
An example of this is the desulphurising of molten iron in a ladle by means of an injection of lime mixtures or mixtures containing calcium carbide.
This practice has grown up with the increasing demand for low sulphur steels.
Gas is primarily injected by one of two means.
The first is a porous plug which is most commonly placed in the bottom of the ladle as illustrated in
Figure 1 of the accompanying drawings. The second method is by means of a lance as is illustrated schematically in Figure 2 of the accompanying drawings.
The porous plug aliows gas under sufficient pressure to overcome the head of molten metal to enter the ladle but at the same time is so constructed that no molten metal is allowed to flow out of the ladle through the plug.
In the case of the lance injection system, gas is again injected at a sufficiently high pressure to overcome the pressure of the head of molten metal at the end of the lance. The gas is injected continuously whilst the lance is submerged. Unlike the porous plug which essentially acts as a oneway valve, many lances are open ended so that a cessation of gas injection or a drop in gas pressure below that exerted by the head of molten metal results in metal entering the lance head and blocking it. The gas on entering the body of molten metal forms bubbles and these expand as they naturally move towards the surface of the bath or ladle. In so doing they both stir up the colder metal from the region of the ladle bottom and help mix it with the remainder of the molten metal in the ladle.This helps to obtain a more uniform temperature throughout the molten metal and helps make it a more metallurgically homogeneous metal.
When the injection lance is used to inject a powder in a gaseous carrier the gas acts in a similar way to that just described. The powder is intimately mixed with the molten metal, the mixing being aided both by the action of the gas described above and any reactivity which may occur between the powder and the metal. The powder is invariably in practice of a lower melting point than the molten metal and dissolves into it in some manner, most usually to change the metallurgical characteristics of the molten metal.
The injection lances are frequently fabricated in the plants in which they are used to inject materials into molten metal. Such lances often comprise a steel tube protected from the effects of the molten metal by the use of a series of relatively short refractory sleeves arranged along the length of the steel tube and joined by refractory cement. Such a lance is illustrated in
Figure 3. The refractory sleeves of the same kind as are used in the casting ladle as part of the stopper rod assembly controlling metal outflow from the ladle. These have been used mainly because they are readily available on the piant.
Often, these made up sleeve lances, whilst relatively inexpensive, only last for one application of the injectant (gas or gas/powder) and a new lance must be made ready for the next ladle. With this type of lance, failure often occurs caused by the molten metal or slag penetrating one of the joints between the sleeves. Sometimes, failure accurs during the actual process of injecting the gas which causes expensive delays in the steelmaking (where that is the metal concerned) and casting processes.
Both to increase the number of times a lance can be used and to increase its reliability during use, lances have been made and used consisting of a central steel tube protected by a layer of suitable refractory concrete. Such a lance is illustrated in Figure 4 of the accompanying drawings. Whilst the lance is immersed in the molten metal, it is heated up by the molten metal reaching the temperature of the molten metal at its outer surface with a decreasing temperature towards the centre. The temperatures present cause both refractory concrete and the steel to expand and due to the fact that they usually have differing coefficients of linear expansion, and due to the temperature differential mentioned above, some relative movement between the steel and the concrete may result, breaking down any bond between the two at the outside circumference of the steel tube.The process of gas or gas powder injection into molten metal almost invariably causes vibration along the lance and movement of it ill the molten metal. The movement is often most pronounced at the extreme tip of the lance immersed in the metal. This tends to shake the refractory concrete away from the tube. As the lance flexes under the process of gas or gas/powder injection parts of the lance are placed in tension. This is shown diagrammatically in
Figure 5. Refractory concrete is comparatively weak in tension, and as a smali tensile strain develops in the concrete a crack may appear which is often entered by the molten metal or slag and the development of this crack over a period of use eventually leads to metal or slag penetration to the central tube then the failure of the lance.
To inhibit the breaking down of the bond between the steel tube and the refractory concrete due to the differences in thermal expansion between the-steel tube and the concrete and the physical forces tending to break up the concrete as the lance flexes in use, steel reinforcing of various types have been used in the concrete in an effort to hold the tube and the concrete together.
Sometimes the reinforcing is anchored to the steel tube. The type of reinforcing which has been extensively used is of a "barbed-wire" type wound in helical fashion around the steel tube and anchored to cleats welded to the tube in the manner shown in Figure 4 of the accompanying drawings.
Such reinforcement does help to hold the concrete together under tensile strain but of itself cannot prevent the stresses and strains occurring due to the differences in thermal expansion or contraction the steel tube and the refractory concrete. Lance failure is generally brought about by refractory concrete spalling off the lance at some point brought about by metal or slag penetration which is in turn allowed by cracks forming in the refractory concrete where it is put under tensile stress and strain.
Slag is particularly penetrative and many lances fail at the slag line (see Figure 5 of the accompanying drawings). To attempt to prolong lance life some lances are increased in diameter by increasing the refractory concrete thickness.
The present invention now provides a lance for injecting material into molten metal, comprising a tubular member of refractory concrete placed under longitudinal compressive stress to inhibit the formation of tensile cracks during use.
Preferably, the lance further comprises a metal tubular member extending within the refractory concrete tubular member so that the refractory concrete tubular member acts as a protective sheath for the metal tubular member. In order to partially or wholly avoid the difficulties described above arising from differential thermal expansion, it is preferred that the metal tubular member and the refractory concrete tubular member are able to expand and contract substantially independently in response to temperature change.
Preferably the tubular member and protective sheath are fixedly connected at one location along their length. This has the effect of holding the two components firmly together whilst still allowing longitudinal expansion and contraction to take place in each member independently. Fixedly connecting the two components at two points longitudinally spaced along their length would, of course, prevent independent expansion and contraction between the two points of fixing.
Preferably, the connection between the protective sheath and the tubular member is provided by one or more radially extending members attached to the tubular member. Such radially extending members may for instance be welded to the tubular member and may be of the same material as the tubular member, for instance steel. There may be a number of radially extending members arranged around the circumference of the tubular member or there may be a continuous flanged provided on the tubular member.
The reinforcement is preferably fixed to the radially extending member or members, e.g. by welding.
Preferably, the lance comprises longitudinally extending reinforcing members in the refractory concrete placed under tensile stress and exerting compressive stress on the refractory concrete.
The reinforcement may take the form of a generally cylindrical cage of reinforcing rods of metal, preferably steel, each rod having a retaining means at each end thereof which retaining means is wholly or partially embedded in the refractory concrete so that the retaining means form fixed points between which the rod may be tensioned.
Preferably, the retaining means for the rods comprise a pair of annular end collars wholly or partially embedded in the refractory concrete between which collars all of the reinforcing rods extend.
The invention includes a method for forming a lance for injecting material into molten metal, which method comprises tensioning elongate reinforcing members and casting refractory concrete thereover to form a reinforced refractory concrete tubular member wherein the tension reinforcing members exert a compressive stress on the refractory concrete.
The invention also includes a method for producing a lance for injecting material into molten metal which method comprises casting refractory concrete over elongate reinforcing members to form a reinforced refractory concrete tubular member having the elongate reinforcing members extending longitudinally therein and appiying tension to the reinforcing members relative to the refractory concrete whereby the refractory concrete is placed under compressive stress.
In such a method, it is preferred that means be provided to inhibit the formation of a bond between the refractory concrete and the surface of the reinforcing members during casting so that relative movement of the members and the concrete will be facilitated during tensioning.
Suitable means for avoiding a bond between the refractory concrete and the reinforcing material is a sheath of suitable material such as plastics over the surface of each part of the reinforcing material.
The invention will be further illustrated and contrasted with the prior art arrangements by the following specific description with reference to the accompanying drawings in which: Figure 1 illustrates a ladle for molten metal equipped with a porous plug for gas injection.
Figure 2 illustrates a ladle for molten metal provided with an injection lance for injecting gas or gas/powder mixtures.
Figure 3 shows a prior art injection lance.
Figure 4 shows a second type of known injection lance.
Figure 5 is a cross-section through a lance and a ladle showing the bending of the lance in use.
Figure 6 shows a section through a lance according to the present invention.
Figure 7 shows the lance of Figure 6 in cutaway perspective view together with a detaii of the reinforcing members used, and
Figure 8 illustrates a lance in accordance with an alternative embodiment of the invention.
Figure 1 illustrates the practice of injecting gas through a porous plug 1 into a ladle 2 containing molten metal 3.
Figure 2 illustrates schematically the practice of injecting gas into a ladle 2 of molten metal 3 through an injection lance 4 supported by means schematically shown at 5. The introduction of gas into the lance is illustrated by the arrow.
Figure 3 shows a lance of the kind conventionally made at the site of injection. The lance 4 comprises a central steel tube 6 along which are raised a series of close-fitting refractory concrete sleeves 7 joined together by refractory cement 8.
Figure 4 illustrates a further type of known injection lance in which a central steel tube 6 is provided with radially extending welded on cleats 9 over which is wound steel reinforcing 10 to form a cage of reinforcement over which refractory concrete 11 is cast.
Figure 5 illustrates the effect of the stresses which occur when a lance is used for injecting gas into molten metal. The turbulence induced in the molten metal by the gas injection exerts sideways thrusts on the lance causing it to flex. This flexing places one side of the lance in tension and the other in compression. The refractory concrete in tension is particularly liable to crack. Because slag is particularly penetrative, failure is particularly likely to occur where the lance is in contact with slag at the surface of the molten metal.
Figure 6 shows a section through a lance according to the present invention. The lance comprises a refractory concrete tubular member 11 having reinforcing rods 12 extending from end to end therethrough between annular collars 13 embedded in the end faces of the refractory concrete tubular member. The rods 12 are under tension and therefore place compressive stress on the refractory concrete. A steel tube 14 is provided connected to the annular collar at the upstream end of the refractory concrete tubular member to allow for coupling through a gas supply.
The construction described above is illustrated in greater detail in Figure 7. As shown in Figure 7, the reinforcing members 12 form a cylindrical cage between end collars 13 in which they are retained and end collar 13 is coupled to the gas entry tube 14.
To help hold the refractory concrete in place and to add structural strength to the lance, the concrete can be further reinforced with steel mesh wire or other suitable material.
The refractory concrete of the lance may be cast to form the lance in the normal way. The tension applied to the rods shown in Figures 6 and 7 can be applied either before or after the lance is cast. If the latter way is chosen, then a sheath of suitable material may be used to cover the length of each rod in the concrete to allow relative movement between the two when the rods are tensioned. The tension applied to the rods may be calculated to give a compressive stress and strain in the refractory concrete under lance operating conditions so as to greatly inhibit the formation of any tensile cracks that might otherwise form in the refractory concrete.
The lance may be made up of a number of precast refractory segments in each of which there is reinforcement under tensile stress.
In place of the steel rods specifically illustrated above, the reinforcement may be wire or other means of imparting a compressive stress and strain to the refractory concrete of the injection lance.
The lance may be either entirely of reinforced refractory concrete in which case a suitable holding collar to join the lance to the injectant supply equipment may be provided as shown in
Figure 7, or a metal tube, e.g. a steel tube, may extend along the centre of the lance so that the refractory concrete tubular member acts as a protective sheath for the metal tube. The steel tube may be used to join the lance to the injectant equipment employed.
If a steel tube is used in this way, then it is preferred that means be employed to allow the steel tube and the refractory concrete sheath to expand and contract independently or substantially independently in response to temperature changes to avoid setting up stresses in the refractory concrete sheath. This means may take the form of means for preventing the formation of a bond between the surface of the metal member and the refractory concrete. Means for preventing the formation of a bond between the surface of the tubular member and the refractory concrete may for instance be a refractory concrete -- impermeable sheathing.
This may be a sheathing of plastics material, e.g. a helical winding of plastics tape. Additionally, means may be provided to further prevent the refractory concrete forming a bond to the sheathing. For instance, the sheathing may be greased.
To further reduce the likelihood of the lance being damaged by tensile fracture of the refractory concrete, a porous plug or nozzle may be provided at the outlet to provide a gas or gas/powder distribution away from the lance end into the molten metal with reduced turbulence in the metal.
Further, to help alleviate slag attack on the refractory at the vulnerabie slag line, a preformed precast high quality dense refractory sleeve can be set in that part of the lance close to the slag line.
This is illustrated in Figure 5 where the sleeve is indicated at 1 5. This can be in the form of the sleeve, the thickness of which can be varied to suit the particular operating conditions. Whilst a preformed sleeve is likely to give the best results in casting a lance, a similar effect may be achieved by casting a special high quality refractory in the slag line area of the lance.
Figure 8 shows an alternative embodiment of the invention, in which the compressive stress on the refractory concrete is applied by means of a knot. In Figure 8, a tubular member 20 shown partially in section has a threaded end portion 21, carrying a nut 22. A metal flange 22 is welded to the lower end of the tubular member 20 to provide a stop against which compressive force may be applied. A refractory concrete sheath 23 is then cast around the tubular member, after first providing the tubular member with an impermeable sheath to prevent the concrete from adhering to the tubular member on the whole of its length, for example a helical winding of plastics tape, as described above. Thus, the refractory concrete sheath 23 is anchored to the tubular member 20 only in the region of the said flange 22. A steel disc 24 is embedded in the refractory concrete during the casting operation.
Reinforcement may also be incorporated in the refractory concrete in any desired form.
When the refractory concrete is set, compressive stress is applied by tightening the nut 22 onto steel disc 24, to obtain a lance having a coating of refractory concrete with compressive stress.
It is an advantage of the lance specifically described above that by placing an initial compressive stress and strain in the refractory concrete its tendency to crack when in use is severely reduced and hence the number of uses of this design of lance can be expected to be higher than are obtained with the type of prior art lance described above.
Furthermore, the steel bars or wires used as reinforcement in the lance according to Figures 6 and 7 can be further away from the centre line of the lance than is the case where the lance relies from its strength on a centrally extending steel tube. Because of this, the lance can be made stiffer than the type of lance shown in Figure 3 and Figure 4. The greater the stiffness of the lance, the less it will flex under operating conditions, which helps further inhibit the development of tensile cracks in the lance.
Claims (9)
1. A lance for injecting into molten metal, comprising a tubular member of refractory concrete placed under longitudinal compressive stress to inhibit the formation of tensile cracks during use.
2. A lance as claimed in claim 1 further comprising a metal tubular member extending within the refractory concrete tubular member so that the refractory concrete tubular member acts as a protective sheath for the metal tubular member.
3. A lance as claimed in claim 2 wherein the metal tubular member and the refractory concrete tubular member are able to expand and contract substantially independently in response to temperature change.
4. A lance as claimed in any preceding claim comprising longitudinally extending reinforcing members in the refractory concrete placed under tensile stress and exerting compressive stress on the refractory concrete.
5. A lance substantially as hereinbefore described with reference to and as illustrated in
Figures 6 and 7, or Figure 8 of the accompanying drawings.
6. A method for producing a lance for injecting material into molten metal, which method comprises tensioning elongate reinforcing members and casting refractory concrete thereover to form a reinforced refractory concrete tubular member wherein the tensioned reinforcing members exert a compressive stress on the refractory concrete.
7. A method for producing a lance for injecting material into molten metal which method comprises casting refractory concrete over elongate reinforcing members to form a reinforced refractory concrete tubular member having the elongate reinforcing members extending longitudinally therein, and applying tension to the reinforcing members relative to the refractory concrete whereby the refractory concrete is placed under compressive stress.
8. A method for producing a lance substantially as hereinbefore described with reference to
Figures 6 and 7, or Figure 8 of the accompanying drawings.
9. A lance produced by a method as claimed in any one of claims 6 to 8.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08215724A GB2123535A (en) | 1982-05-28 | 1982-05-28 | Injection lances for molten metal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08215724A GB2123535A (en) | 1982-05-28 | 1982-05-28 | Injection lances for molten metal |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2123535A true GB2123535A (en) | 1984-02-01 |
Family
ID=10530719
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08215724A Withdrawn GB2123535A (en) | 1982-05-28 | 1982-05-28 | Injection lances for molten metal |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2123535A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4792125A (en) * | 1987-08-24 | 1988-12-20 | Bethlehem Steel Corporation | Consumable lance |
| US4852860A (en) * | 1987-08-24 | 1989-08-01 | Bethlehem Steel Corporation | Consumable injection lance |
| EP1659188A1 (en) * | 2004-11-05 | 2006-05-24 | Jankowski GmbH & Co. KG | Lance for introduction of particularly gaseous media into a liquid metal and its manufacturing method |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB741953A (en) * | 1953-03-23 | 1955-12-14 | Preload Co Inc | An improved method of prestressing concrete articles |
| GB1079279A (en) * | 1965-05-27 | 1967-08-16 | Nippon Concrete Ind Co Ltd | Improvements in or relating to prestressed concrete pile sections |
| GB1251111A (en) * | 1968-02-26 | 1971-10-27 | ||
| GB1483675A (en) * | 1974-04-29 | 1977-08-24 | Interpace Corp | Prestressed concrete pipes |
| GB1548461A (en) * | 1964-03-17 | 1979-07-18 | Desaar R | Lance for desulphurising cast iron or steel |
| GB2021242A (en) * | 1977-12-10 | 1979-11-28 | Duport Steels Ltd | Blowing Lance for Solid Materials |
-
1982
- 1982-05-28 GB GB08215724A patent/GB2123535A/en not_active Withdrawn
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB741953A (en) * | 1953-03-23 | 1955-12-14 | Preload Co Inc | An improved method of prestressing concrete articles |
| GB1548461A (en) * | 1964-03-17 | 1979-07-18 | Desaar R | Lance for desulphurising cast iron or steel |
| GB1079279A (en) * | 1965-05-27 | 1967-08-16 | Nippon Concrete Ind Co Ltd | Improvements in or relating to prestressed concrete pile sections |
| GB1251111A (en) * | 1968-02-26 | 1971-10-27 | ||
| GB1483675A (en) * | 1974-04-29 | 1977-08-24 | Interpace Corp | Prestressed concrete pipes |
| GB2021242A (en) * | 1977-12-10 | 1979-11-28 | Duport Steels Ltd | Blowing Lance for Solid Materials |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4792125A (en) * | 1987-08-24 | 1988-12-20 | Bethlehem Steel Corporation | Consumable lance |
| WO1989001983A1 (en) * | 1987-08-24 | 1989-03-09 | Bethlehem Steel Corporation | Consumable lance |
| US4852860A (en) * | 1987-08-24 | 1989-08-01 | Bethlehem Steel Corporation | Consumable injection lance |
| WO1990007011A1 (en) * | 1988-12-19 | 1990-06-28 | Bethlehem Steel Corporation | Improved consumable injection lance |
| EP1659188A1 (en) * | 2004-11-05 | 2006-05-24 | Jankowski GmbH & Co. KG | Lance for introduction of particularly gaseous media into a liquid metal and its manufacturing method |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |