US3843105A - Apparatus and method for contacting molten metal with gas - Google Patents

Abstract

Apparatus and method for introducing oxygen into a molten metal bath for refining steel comprising an injector lance having a submerged tip section provided with upright elongated thermal ridges and in the alternative with thermal ridges and gas emitting slots below the ridges to prevent the formation of a ring of frozen metal from developing around the copper tip section which would endanger the life of the injector tip. Alternately, the tip may have its thermal ridges of copper, at least at their crests covered by a layer of consumable but replaceable refractory material of low thermal conductivity such as ceramic, cermet or alloy steel which may be applied to the copper ridge by welding, spraying or mechanical securing. The injector lance has its immersible tip cooled by a coolant such as water, liquid ammonia, molten salts, molten metal, and liquid organic material. The coolant is circulated through a pipe system and the lance by a positive pressure above the atmosphere or alternately by creating a vacuum on the down stream side of the coolant system where the pressure existing in the coolant will be less than atmospheric pressure so that if a leak occurs in the submerged tip in the steel bath the molten steel will tend to flow into the coolant and plug the hole. A control system automatically withdraws the lance from the furnace when the flow rate and temperature rise of the coolant exceeds desirable limits.

Description

United States Patent [191 Chang Oct. 22, 1974 APPARATUS AND METHOD FOR CONTACTING MOLTEN METAL WITH GAS Yi-Chung Chang, Murrysville, Pa.

[73] Assignee: Berry Metal Company, Harmony,

[22] Filed: Apr. 5, 1973 [2]] Appl. No.: 348,350

[75] Inventor:

[52] US. Cl. 266/34 L, 239/1323 [51] Int. Cl. F27d 23/00 [58] Field of Search 75/52, 60; 239/1323; 266/34 L, 34 LM, 34 T [56] References Cited UNITED STATES PATENTS 2,836,411 5/1958 Auer 266/34 L 3,201,104 8/1965 Berry 266/34 L 3,385,586 5/1968 Kemmetmueller... 266/34 L 3,436,068 4/1969 Beals et a1. 266/34 LM 3,525,508 8/1970 Berry et al. 266/34 L 3,647,198 3/1972 Munson 266/34 LM 3,744,780 7/1973 Pelczarski et a1. 266/34 L FOREIGN PATENTS OR APPLICATIONS 902,122 7/1962 Great Britain 266/34 LM Primary Examiner-Gerald A. Dost Attorney, Agent, or Firm-Richai'd J. Myers [57] ABSTRACT Apparatus and method for introducing oxygen into a molten metal bath for refining steel comprising an injector lance having a submerged tip section provided with upright elongated thermal ridges and in the alternative with thermal ridges and gas emitting slots below the ridges to prevent the formation of a ring of frozen metal from developing around the copper tip section which would endanger the life of the injector tip. Alternately, the tip may have its thermal ridges of copper, at least at their crests covered by a layer of consumable but replaceable refractory material of low thermal conductivity such as ceramic, cermet or alloy steel which may be applied to the copper ridge by welding, spraying or mechanical securing. The injector lance has its immersible tip cooled by a coolant such as water, liquid ammonia, molten salts, molten metal, and liquid organic material. The coolant is circulated through a pipe system and the lance by a positive pressure above the atmosphere or alternately by creating a vacuum on the down stream side of the coolant system where the pressure existing in the coolant will be less than atmospheric pressure so that if a leak occurs in the submerged tip in the steel bath the molten steel will tend to flow into the coolant and plug the hole. A control system automatically withdraws the lance from the furnace when the flow rate and temperature rise of the coolant exceeds desirable limits.

24 Claims, 9 Drawing Figures I, II/IIIIIIIIII ///////I/// I I PATENTED 11m 2 2 19m 3.843105 SHEET 20$ 4 PATEHTEI] URI 22 I974 SHEET 3!]? 4 VENT TO ATMOSPHERE APPARATUS AND METHOD FOR CONTACTING MOLTEN METAL WITH GAS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention pertains to the field of art of contacting molten metal with a gaseous substance and, in particular, relates to apparatus and method for contacting oxygen gas with hot metal i.e. molten pig iron, to refine this impure metal to steel in an open-hearth type of furnace. The invention involves the injecting of high purity oxygen gas into a bath of molten iron under its surface at selected location and depth.

2. Description of the Prior Art It is known to submerge an oxygen lance below the bath of molten iron with the injected gas breaking up into bubbles which rise to the free surface of the bath from the depth of the molten metal, thus providing very intimate contact between the oxygen gas and the iron metal with relatively little splashing. The tip of the lance that is submerged in the bath is made of high conductivity copper. The cooling of the submerged tip is so intense that some of the superimposed molten metal of the bath is chilled and is caused to solidify on the cooler lance surface to form a frozen layer. Throughout the operation, the rate of removing heat from the submerged lance tip wall must be controlled to maintain this protective layer of frozen metal. Failure to do so will endanger the life of the injector tip. This protective layer of frozen metal essentially forms a complete encircling band around the cylindrical lance tip. Upon cooling, due to thermal contraction, the steel shell or band develops a hoop compressive force. If this force becomes greater than the yield strength of the submerged copper tip at the operating temperature, plastic deformation in the wall of the copper lance tip will occur resulting in damaging the lance tip. Hence, for successful operation of the lance tip submerged in the metal bath, means must be provided to-prevent or to compensate for the hoop compression force due to the contraction of the frozen layer of steel on the tip. It is this difficulty that this invention overcomes. Further, the tip must be cooled by a coolant and also a coolant circulation system must be provided. For safety measures, a lance withdrawal system which is responsive to the flow rate and temperature rise of the coolant is also provided.

- SUMMARY OF THE INVENTION This invention has for its general object to provide for an apparatus and method for submersing an oxygen injector lance below the surface of the molten iron bath whereby the oxygen gas that is injected breaks up into bubbles which rise to the surface of the bath from the depth of the molten metal, thus providing very intimate contact between the gas and the metal with relatively little splashing. The advantages of this mode of contacting oxygen gas and liquid iron are 1) less brown fume being formed, 2) a greater charge capacity for a given rating of furnace, and 3) a faster refining action.

It is a further object of this invention to provide for the copper tip of the oxygen injector lance to be submerged, the lance itself entering the open hearth furnace from a hole located either in its roof or in its side wall. The lance, and especially the tip that is exposed to the molten environment, is cooled intensely by circulating a liquid coolant in a jacket underneath the exposed wall of the lance tip. To prevent the formation of a complete band of frozen steel around the circumference of the submerged lance tip and thereby introduce undesirable hoop compressive forces, the tip is provided with a plurality of vertically extended elongated ridges about the periphery thereof. A further modified form of this invention provides for gas injection openings under these ridges which also breaks up the formation of the undesirable steel band. A further object is to provide a covering layer of consumable but replaceable refractory material of low thermoconductivity such as ceramic, cermet, or alloy steel for the ridges.

A further object of this invention is to provide for a coolant system which may be under a positive pressure or a vacuum and provides for circulation of the coolant in the lance tip and elminates the chance of coolant entering the molten bath.

Another object of this invention is to provide an automatic withdrawal system for the lance from the furnace when the flow rate and the temperature rise of the coolant exceeds certain limits. A further object of this invention is to provide for various liquid coolants for this system and for a method of submerged injection of oxygen by a lance in a molten bath.

These and other objects and advantages of the invention will become apparent from reference to the following description, the appended claims, and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational sectional viewof an open hearth furnace using the submerged lance tip of my invention;

FIG. 2 is a sectional view taken along line 22 of FIG. 1;

FIG. 3 illustrates insertion of the lance into the side of the open hearth furnace;

FIG. 4 shows an-injection lance with an immersible lance tip provided with the thermal ridges of the invention;

FIG. 5 is an enlarged view of the injection lance tip shown in FIG. 4, I

FIG. 6 shows a modified form of oxygen injector lance tip;

FIG. 7 is a diagrammatic view of the recycling system for the injection lance coolant; v

FIG. 8 is a diagrammatic view of an alternate form of coolant recycling system like that shown in FIG. 7 but operating under a vacuum, and

FIG. 9 is a diagrammatic view of an automatic withdrawal system for the submerged lance.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference now to the drawings, and in particular with reference to FIGS. 1-3, there is shown in FIGS. 1 and 2 an open hearth furnace l which has a roof 2 with openings 3 through which extnd oxygen gas injection lances 4 having their lower ends or tip sections 5 extending below the slag 6 and just below the surface of the molten bath of pig iron and steel 7 being refined by the oxygen gas being emitted from the bottom of the tip sections 5 into the molten bath. FIG. 3 shows the introduction of the oxygen gas injection lance through a side opening 8 in the side 9 of the furnace I.

The details of the oxygen gas injection lance 4 is more readily seen in FIG. 4 and includes an adaptor or upper section 10, an intermediate or barrel section 11 and the lower tip section 5. The upper section is provided with a bail 12 to be held by the hoist when introducing the lance into the furnace. The upper section is also provided with an oxygen inlet line 13, a liquid coolant inlet line 14 and a liquid coolant exit line 15. The barrel section 11 communicates with the coolant inlet and outlet lines and the oxygen lines by central oxygen gas-containing tube 16 and by coolant inlet annular passage 17 and coolant outlet annular passage 18 defined by concentric intermediate tube 19 and concentric outer tube 20. The lower or tip section 5 is also provided with the oxygen or central passage or tube 21 surrounded by the inlet coolant passage 22 and the outlet coolant passage 23 as defined by the intermediate and outer concentric tubes 24 and 25 respectively. As so far described, the injection lance 4 is known and is shown as, for instance, in US. Pat. No. 3,525,508 to W. W. Berry, et al issued on Aug. 25, I970. The lance tip section 5 is made of copper. A single orifice (i.e. hole) 26 is provided by a single converging/diverging nozzle 27. However, the orientation of the tip section can be either straight, as shown, or at some angle with respect to the barrel section. Also, a multiple orifice (i.e. hole) lance could be used and the multiple nozzles could have straight bores or converging bores as distinguished from the converging/diverging type shown. Numerous liquids may be used as the cooling medium besides water such as liquid ammonia, molten salts, molten metal, and liquid organic material such as a mixture of diphenyl oxide and diphenyl such as Dowtherm A, ortho dichlorobenzene such as Dowtherm E, glycerine, ethylene glycol, chlorinated biphenyls such as Aroclor, aromatic mineral oils such as Mobiltherm and Humbletherm," aromatic ether such as Therminol, or a mixture of fused salts of sodium nitrate, and potassium nitrate.

However, my inventive lance tip section is new and different from the prior art in that I provide on the exterior of said tip section a plurality of circumferentially spaced vertically elongated ridges 30. Each of the ridges is made of the same material as the lance tip section, namely, copper. These thermal ridges 30 are best seen in FIG. 5 and provide crests 31 on the tops of the ridges and troughs 32 on the surface of the tip section between the ridges. These ridges 30 on the submerged portion or tip section 5 have a length, at least, equal to the depth of submersion, and a height from its trough or root 32 to its crest 31, at least, equal to the expected thickness of the frozen metal or steel layer that develops on the copper tip section 5 when the submerged tip section is withdrawn from the molten bath of pig iron and steel. Each ridge 30 is an integral part of the outer wall of the lance tip and is made of the same material (copper) as the tip except that the ridge, at its crest 31, is covered by a layer of consumable but replaceable refractory material of low thermoconductivity which is greater than a sixteenth of an ince thick and is usually an eighth of an inch thick and may be an inch or more thick. The layer 33 of consumable replaceable refractory material is indicated in cross-section at 34 on the right side of FIG. 5. Each ridge 30 can be either machined, welded, or cast onto the tip 5. The refractory covering layer 33 can be made of either a ceramic, cermet, or alloy steel and can be applied to the copper 2,800 F. (Fahrenheit) whereas the temperature at the troughs of the ridge runs around l,000 F. (Fahrenheit) and, therefore, when the tip 5 is withdrawn the liquid metal at the ridge does not cling so that no skull or solid ring of metal or steel can form in a continuous band around the tip and produce undesirable compressive stresses on the tip. The further introduction of the refractory layer 33 on the crest or even along the sides of the ridge towards the trough of the ridge provides for thermal insulation of the outer portions of the ridge so that the water coolant in the coolant passages 22 and 23 cannot cool down the tip at the crest of the ridges to sufficiently solidify'the steel in a continuous band around the tip. Thus, the ridges and the refractory layers on the ridges prevent the coolant from sufficiently chilling out solidified metal in a continuous band around the tip and, therefore, prevent development of any compressive forces caused by a continuous band of solidified steel. The layers 33 like the effect of the crests of the ridges maintain the surface at about 2,800 F. as distinguised from the temperature of the valleys or troughs 32 which can be as low as 500 to l,000 F. to cause the molten steel to freeze. The layers 33 are applied only on the thermal ridges and particularly at their crests.

FIG. 6 shows a modified form of lance tip section 5 where it is seen that half of the upper vertical extent is provided with the vertically elongated thermal ridges 30' that are like the ridges 30 of FIG. 5 but that the lower half of the lance tip section 5' is provided with long and narrow vertically extending oxygen exit openings or passages 36 that communicate with the oxygen central passage 21 and the orifice 26 is sealed at its exit and as shown partially in section in FIG. 6. These oxygen openings or gas slots 36 let the oxygen gas out of the oxygen passages in the tip and blow away the molten metal therefrom so that no continuous ring can form around the lower half portion of the tip 5' below the thermal ridges 30' of the lance 4'. Therefore, the openings 36 cooperate with the ridges 30 to prevent the formation of high stress developing solid bands of steel about the periphery of the lance tip section.

When a coolant other than water is used, a closed circulation system is needed. As seen in FIG. 7, the coolant 37 is circulated through the piping system 38 from a coolant storage tank 39 by a pump 40 through the injector lance 4, through a coolant filter 41 and a second pump 42 and a heat exchanger 43 which cools the coolant from its own outside cooling medium through its lines 44 and pump 45. The coolant for the lance can be an organic coolant and the coolant for the heat exchanger can be a water coolant. The coolant system for the lance operates under a positive pressure above atmospheric pressure. However, as seen in FIG. 8, the coolant for the lance is circulated by creating a vacuum on the downstream side by suction pump 45', the coolant 37 in the tank 39 in this instance being vented to atmosphere in order to cool the lance 4. With the arrangement shown in FIG. 8 with the pressure existing in the coolant tubing being less than atmospheric pressure, when a leakage occurs in the lance tip section of the lance when it is in the steel bath, the molten steel tends to flow into the coolant chambers of the tip and plug the hole on the lance tip so that there is provided a self-sealing feature for the lance tip.

For safety measures, as seen in FIG. 9, a control system 46 is shown which automatically withdraws the lance 4 from the furnace 1 when the flow rate (F) and the temperature (T) of the coolant exceed certain limits. The lance 4 is automatically withdrawn by the lance drive mechanism 47 with its pulley arrangement 48, as the lance drive mechanism is acted upon and controlled by the controller or computer arrangement 49. The inlet coolant line 50 which takes coolant 51 from tank 52 sends the coolant through flow rate measuring device 53 which measures the volumetric flow rate F, of the ingoing coolant in gallons-per-minute and also sends the coolant through the temperature device 54 which measures the temperature T, of the ingoing coolant in degrees Fahrenheit. The coolant exiting from the lance 4 is measured by the temperature measuring device 55 to give the outgoing coolant temperature T, and the outgoing coolant has its volumetric flow rate F measured by the flow rate measuring device 56. The symbols a, b, c, d, are indicators of predetermined set values for the variables T,, T F and F As seen in FIG. 9 the temperatures T, and T must be smaller than their preset values a and b, and the flow rates F, and F must be greater than their preset values 0 and d or otherwise the computer will tell the lance drive mechanism to raise the lance out of the molten bath of the furnace as a safety precaution. For an example, a -inch diameter lance using water as a cooling'medium F, should be 1,000 gpm and F should be 1,000 gpm, T, should be 70'80 F, and T should be ll40 F. Conditions that would call for withdrawal of the lance are when F is less than F, or when F, is less than 800 gpm (80 percent of normal) or when the ingoing coolant is appreciably hotter than normal by l0l50, for a normal ingoing temperature of 70-80 F, the withdrawal temperature is 90 F or higher, or when the outgoing coolant temperature is higher than the usual value, for normal T or l20l40 F, the withdrawal temperature is 150 or higher.

The foregoing description and drawings merely explain and illustrate the invention and the invention is not limited thereto, except insofar as the appended claims are so limted, as those skilled in the art who have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

1 claim:

I. An oxygen injection lance having a substantially upper elongated section and an immersible nozzle tip section for submersion in the molten bath in a high temperature furnace, said nozzle tip section being at the lower end of the lance and comprising:

a longitudinally extending oxygen passage extending in each section,

oxygen orifice means in the nozzle tip section communicating with the oxygen passage.

coolant passageway means in the nozzle tip section,

said nozzle tip section having a generally outer annular side surface portion for submersion in the molten bath for injecting oxygen from said orifice means within said bath while cooling said nozzle surface portion by coolant in said coolant passageway means, skull-forming prevention means carried on the nozzle tip section that is submerged in the molten bath whereby the formation of a frozen band of steel about the coolant-cooled nozzle tip section is prevented, said skull-forming prevention means comprising a plurality of raised generally vertically elongated circumferentially spaced thermal ridge means mounted on the outer surface of the nozzle tip section to define vertically extending crest and trough areas, whereby molten metal runs off the crest areas which are at higher temperatures than the trough areas where the metal solidifies preventing the formation of a continuous band of metal or skull around the submerged nozzle tip section,

each ridge means having on its crest area a substantially thick layer of refractory material to insulate the crest area of the ridge means from the interior cooling effect of the coolant within the submerged nozzle tip section thereby allowing the ridge crest area to remain warmer in the bath to prevent solidification of metal on the crest area.

2. The invention according to claim 1, and

said layer of refractory material having a thickness that is substantially one-sixteenth of an inch or more.

3. The invention according to claim 1, and

said layer of refractory material having a thickness of substantially one-eighth of an inch or more.

4. The invention according to claim 1, and

said layer of refractory material being approximately between one-quarter inch and two inches.

5. An oxygen injection lance having a substantially upper elongated section and an immersible nozzle tip section for submersion in the molten bath of a high temperature furnace, said nozzle tip section being at the lower end of the lance and comprising:

a longitudinally extending oxygen passage in each section, oxygen orifice means in the nozzle tip section communicating with the oxygen passage,

coolant passageway means in the nozzle tip section,

said nozzle tip section having a generally outer annular side surface portion for submersion in the molten bath and for injecting oxygen from said orifice means into said bath while cooling said nozzle surface portion by coolant in said coolant passageway means when said nozzle section is immersed into said bath,

skull-forming prevention means carried on the nozzle tip section that is submerged in the molten bath whereby the formation of a frozen band of steel about the coolant-cooled nozzle tip section is prevented, said skull-forming prevention means comprising a plurality of raised generally vertically elongated circumferentially spaced thermal ridge means mounted on the outer surface of the nozzle tip section to define vertically extending crest and trough areas, whereby molten metal runs off the crest areas which are heated to a higher temperature level than the trough areas where the metal solidifies such crest areas preventing the formation of acontinuous band of metal or skull around the submerged nozzle tip section,

said orifice means including a plurality of generally elongated slotted gas ports disposed circumferentially about the periphery of the tip section and communicating with the oxygen passage to prevent formation of a continuous encircling frozen layer of molten material on the nozzle tip section, and each ridge means having on its crest area a substantially thick layer of refractory material to insulate the crest area of the ridge means from the interior cooling effect of the coolant within the submerged nozzle tip section, thereby allowing the ridge crest area to remain warmer in the bath so as to prevent solidification of metal on the crest area.

6. The invention according to claim 5, and

the length of each gas port being generally parallel with the longitudinal axis of the nozzle tip section.

7. The invention according to claim 5, and the gas ports being below the ridge means. 8. The invention according to claim 5, and each gas port being located directly below a respective ridge means. 9. The invention according to claim 1, and said ridge means extending substantially the full vertical extent of the submerged nozzle tip section. 10. An oxygen injection lance having a substantially upper elongated section and an immersible nozzle tip section for submersion in the molten bath in a high temperature furnace, said nozzle tip section being at the lower end of the lance and comprising:

a longitudinally extending oxygen passage extending in each section, oxygen orifice means in the nozzle tip section communicating with the oxygen passage, coolant passageway means in the nozzle tip section,

said nozzle tip section having a generally outer annular side surface portion for submersion in the molten bath for injecting oxygen from said orifice means within said bath while cooling said nozzle surface portion by coolant in said coolant passageway means,

skull-forming prevention means carried on the nozzle tip section that is submerged in the molten bath whereby the formation of a frozen band of steel about the coolant-cooled nozzle tip section is prevented, said skull-forming prevention means comprising a plurality of raised generally vertically elongated circumferentially spaced thermal ridge means mounted on the outer surface of the nozzle tip section to define vertically extending crest and trough areas, whereby molten metal runs off the crest areas which are at higher temperatures than the trough areas where the metal solidifies preventing the formation of a continuous band of metal or skull around the submerged nozzle tip section, and

each coolant passageway means including a coolant recycling system having a suction pump for circulating the coolant under a vacuum.

11. The invention according to claim 1, and

each coolant passageway means including a recycling system having a circulation pump and a cooling heat exchanger.

12. The invention according to claim 1, and

having an automatic withdrawal system for raising the lance from the molten bath when the coolant temperature and coolant flow rate exceeds certain predetermined values. 13. The invention according to claim 1, and each ridge means having a length equal to the depth of submersion of the nozzle tip section in the molten bath.

14-. The invention according to claim 1, and

each ridge means having a height from the crest area to the trough area at least as thick as thickness of the frozen band of steel formed in the valleys between the plurality of ridge means.

15. The invention according to claim 1, and

each of said ridge means reaching to the very bottom of the lance.

16. The invention according to claim 1, and

each ridge means having a length equal to the depth of submersion of the nozzle tip section in the molten bath,

each ridge means having a height from the crest area to the trough area at least as thick as the thickness of the frozen band of steel formed in the valleys between the plurality of ridge means.

17. An oxygen injection lance having a substantially upper elongated section and an immersible nozzle tip section for submersion in the molten bath in a high temperature furnace, said nozzle tip section being at the lower end of the lance and comprising:

a longitudinally extending oxygen passage extending in each section,

oxygen orifice means in the nozzle tip section communicating with the oxygen passage,

coolant passageway means in the nozzle tip section,

said nozzle tip section having a generally outer annular side surface portion for submersion in the molten bath for injecting oxygen from said orifice means within said bath while cooling said nozzle surface portion by coolant in said coolant passageway means, skull-forming prevention means carried on the nozzle tip section that is submerged in the molten bath whereby the formation of a frozen band of steel about the coolant-cooled nozzle tip section is prevented, said skull-forming prevention means comprising a plurality of raised generally vertically elongated circumferentially spaced thermal ridge means mounted on the outer surface of the nozzle tip section to define vertically extending crest and trough areas, whereby molten metal runs off the ,crest areas which are at higher temperatures than the trough areas where the metal solidifies preventing the formation of a continuous band of metal or skull around the submerged nozzle tip section, each ridge means having on its crest area a substantially thick layer of refractory material to insulate the crest area of the ridge means from the interior cooling effect of the coolant within the submerged nozzle tip section thereby allowing the ridge crest area to remain warmer in the bath to prevent solidification of metal on the crest area, said layer of refractory material having a thickness that is substantially one-sixteenth of an inch or more. 18. An oxygen injection lance having a substantially upper elongated section and an immersible nozzle tip section for submersion in the molten bath in a high temperature furnace, said nozzle tip section being at the lower end of the lance and comprising:

a longitudinally extending oxygen passage extending in each section, oxygen orifice means in the nozzle tip section communicating with the oxygen passage, coolant passageway means in the nozzle tip section, annular said nozzle tip section having a generally outer side surface portion for submersion in the molten bath and for injecting oxygen from said orifice means within said bath while cooling said nozzle surface portion by coolant in said coolant passageway means, skull-forming prevention means carried on the nozzle tip section that is submerged in the molten bath whereby the formation of a frozen band of steel about the coolant-cooled nozzle tip section is prevented, said skull-forming prevention means comprising a plurality of raised generally vertically elongated circumferentially spaced thermal ridge means mounted on the outer surface of the nozzle tip section to define vertically extending crest and trough areas, whereby molten metal runs off the crest areas which are heated to a higher temperature level than the trough areas where the metal solidifies such crest areas preventing the formation of a continuous band of metal or skull around the submerged nozzle tip section, said orifice means including a plurality of generally elongated slotted gas ports circumferentially disposed about the periphery of the tip section and communicating with the oxygen passage to prevent formation of a continuous encircling frozen layer of molten material on the nozzle tip section, the length of the ridge means and the gas port thereunder being substantially equal to the depth of submersion of the nozzle tip section, and each ridge means having on its crest area a substantially thick layer of refractory material to insulate the crest area of the ridge means from the interior cooling effect of the coolant within the submerged nozzle tip section thereby allowing the ridge crest area to remain warmer in the bath so as to prevent solidification of metal on the crest area.

19. The invention according to claim 1, and

said coolant passageway means containing a coolant selected from the group consisting of oils, glycerine, ethylene, tetra aryl silicates, water.

20. The invention according to claim 1, and

said nozzle tip section and said ridge means being copper metal.

21. The invention according to claim 1, and

said coolant passageway means containing a coolant selected from the group consisting of water, liquid ammonia, molten salts, molten metal, diphenyl oxide and diphenyl, ortho dichlorobenzene, glycerine, ethylene glycol, chlorinated biphenyls, aromatic mineral oils, and a mixture of fused salts of sodium nitrate, and potassium nitrate.

22. The method of forming an internally cooled and submergible nozzle tip section of an oxygen type lance having alternate crest and trough areas disposed thereabout that are adapted to be disposed just below the surface of a molten bath of metal comprising the step of selecting different materials for the trough and crest areas so as to have different thermal conductivity characteristics whereby a given crest area has a thermal conductivity lower than the trough area upon immersion of the tip section into a molten bath as the tip section is internally cooled such that the crest area of lower thermally conductive material in being heated to a higher temperature level than the trough area effectively prevents the formation of a fused metal ring about said tip section.

23. The method as set forth in claim 22, including the step of applying a refractory coating of highly insulative refractory material to said crest.

24. The method as set forth in claim 22, including the step of directing a gaseous stream through an opening in said tip section in a direction outwardly of said tip section at a point below said crest and ridge means thereon upon immersion of said tip section into a molten bath of metal whereby said crest and ridge means cooperate with the directed gaseous stream to effectively prevent the formation of a fused metal ring about said tip section.

Claims (24)

1. An oxygen injection lance having a substantially upper elongated section and an immersible nozzle tip section for submersion in the molten bath in a high temperature furnace, said nozzle tip section being at the lower end of the lance and comprising: a longitudinally extending oxygen passage extending in each section, oxygen orifice means in the nozzle tip section communicating with the oxygen passage, coolant passageway means in the nozzle tip section, said nozzle tip section having a generally outer annular side surface portion for submersion in the molten bath for injecting oxygen from said orifice means within said bath while cooling said nozzle surface portion by coolant in said coolant passageway means, skull-forming prevention means carried on the nozzle tip section that is submerged in the molten bath whereby the formation of a frozen band of steel about the coolant-cooled nozzle tip section is prevented, said skull-forming prevention means compriSing a plurality of raised generally vertically elongated circumferentially spaced thermal ridge means mounted on the outer surface of the nozzle tip section to define vertically extending crest and trough areas, whereby molten metal runs off the crest areas which are at higher temperatures than the trough areas where the metal solidifies preventing the formation of a continuous band of metal or skull around the submerged nozzle tip section, each ridge means having on its crest area a substantially thick layer of refractory material to insulate the crest area of the ridge means from the interior cooling effect of the coolant within the submerged nozzle tip section thereby allowing the ridge crest area to remain warmer in the bath to prevent solidification of metal on the crest area.

2. The invention according to claim 1, and said layer of refractory material having a thickness that is substantially one-sixteenth of an inch or more.

3. The invention according to claim 1, and said layer of refractory material having a thickness of substantially one-eighth of an inch or more.

4. The invention according to claim 1, and said layer of refractory material being approximately between one-quarter inch and two inches.

5. An oxygen injection lance having a substantially upper elongated section and an immersible nozzle tip section for submersion in the molten bath of a high temperature furnace, said nozzle tip section being at the lower end of the lance and comprising: a longitudinally extending oxygen passage in each section, oxygen orifice means in the nozzle tip section communicating with the oxygen passage, coolant passageway means in the nozzle tip section, said nozzle tip section having a generally outer annular side surface portion for submersion in the molten bath and for injecting oxygen from said orifice means into said bath while cooling said nozzle surface portion by coolant in said coolant passageway means when said nozzle section is immersed into said bath, skull-forming prevention means carried on the nozzle tip section that is submerged in the molten bath whereby the formation of a frozen band of steel about the coolant-cooled nozzle tip section is prevented, said skull-forming prevention means comprising a plurality of raised generally vertically elongated circumferentially spaced thermal ridge means mounted on the outer surface of the nozzle tip section to define vertically extending crest and trough areas, whereby molten metal runs off the crest areas which are heated to a higher temperature level than the trough areas where the metal solidifies such crest areas preventing the formation of a continuous band of metal or skull around the submerged nozzle tip section, said orifice means including a plurality of generally elongated slotted gas ports disposed circumferentially about the periphery of the tip section and communicating with the oxygen passage to prevent formation of a continuous encircling frozen layer of molten material on the nozzle tip section, and each ridge means having on its crest area a substantially thick layer of refractory material to insulate the crest area of the ridge means from the interior cooling effect of the coolant within the submerged nozzle tip section, thereby allowing the ridge crest area to remain warmer in the bath so as to prevent solidification of metal on the crest area.

6. The invention according to claim 5, and the length of each gas port being generally parallel with the longitudinal axis of the nozzle tip section.

7. The invention according to claim 5, and the gas ports being below the ridge means.

8. The invention according to claim 5, and each gas port being located directly below a respective ridge means.

9. The invention according to claim 1, and said ridge means extending substantially the full vertical extent of the submerged nozzle tip section.

10. An oxygen injection lance having a substantially upper elongateD section and an immersible nozzle tip section for submersion in the molten bath in a high temperature furnace, said nozzle tip section being at the lower end of the lance and comprising: a longitudinally extending oxygen passage extending in each section, oxygen orifice means in the nozzle tip section communicating with the oxygen passage, coolant passageway means in the nozzle tip section, said nozzle tip section having a generally outer annular side surface portion for submersion in the molten bath for injecting oxygen from said orifice means within said bath while cooling said nozzle surface portion by coolant in said coolant passageway means, skull-forming prevention means carried on the nozzle tip section that is submerged in the molten bath whereby the formation of a frozen band of steel about the coolant-cooled nozzle tip section is prevented, said skull-forming prevention means comprising a plurality of raised generally vertically elongated circumferentially spaced thermal ridge means mounted on the outer surface of the nozzle tip section to define vertically extending crest and trough areas, whereby molten metal runs off the crest areas which are at higher temperatures than the trough areas where the metal solidifies preventing the formation of a continuous band of metal or skull around the submerged nozzle tip section, and each coolant passageway means including a coolant recycling system having a suction pump for circulating the coolant under a vacuum.

11. The invention according to claim 1, and each coolant passageway means including a recycling system having a circulation pump and a cooling heat exchanger.

12. The invention according to claim 1, and having an automatic withdrawal system for raising the lance from the molten bath when the coolant temperature and coolant flow rate exceeds certain predetermined values.

13. The invention according to claim 1, and each ridge means having a length equal to the depth of submersion of the nozzle tip section in the molten bath.

14. The invention according to claim 1, and each ridge means having a height from the crest area to the trough area at least as thick as thickness of the frozen band of steel formed in the valleys between the plurality of ridge means.

15. The invention according to claim 1, and each of said ridge means reaching to the very bottom of the lance.

16. The invention according to claim 1, and each ridge means having a length equal to the depth of submersion of the nozzle tip section in the molten bath, each ridge means having a height from the crest area to the trough area at least as thick as the thickness of the frozen band of steel formed in the valleys between the plurality of ridge means.

17. An oxygen injection lance having a substantially upper elongated section and an immersible nozzle tip section for submersion in the molten bath in a high temperature furnace, said nozzle tip section being at the lower end of the lance and comprising: a longitudinally extending oxygen passage extending in each section, oxygen orifice means in the nozzle tip section communicating with the oxygen passage, coolant passageway means in the nozzle tip section, said nozzle tip section having a generally outer annular side surface portion for submersion in the molten bath for injecting oxygen from said orifice means within said bath while cooling said nozzle surface portion by coolant in said coolant passageway means, skull-forming prevention means carried on the nozzle tip section that is submerged in the molten bath whereby the formation of a frozen band of steel about the coolant-cooled nozzle tip section is prevented, said skull-forming prevention means comprising a plurality of raised generally vertically elongated circumferentially spaced thermal ridge means mounted on the outer surface of the nozzle tip section to define vertically extending crest and trough areas, whereby molten metal runs off The crest areas which are at higher temperatures than the trough areas where the metal solidifies preventing the formation of a continuous band of metal or skull around the submerged nozzle tip section, each ridge means having on its crest area a substantially thick layer of refractory material to insulate the crest area of the ridge means from the interior cooling effect of the coolant within the submerged nozzle tip section thereby allowing the ridge crest area to remain warmer in the bath to prevent solidification of metal on the crest area, said layer of refractory material having a thickness that is substantially one-sixteenth of an inch or more.

18. An oxygen injection lance having a substantially upper elongated section and an immersible nozzle tip section for submersion in the molten bath in a high temperature furnace, said nozzle tip section being at the lower end of the lance and comprising: a longitudinally extending oxygen passage extending in each section, oxygen orifice means in the nozzle tip section communicating with the oxygen passage, coolant passageway means in the nozzle tip section, annular said nozzle tip section having a generally outer side surface portion for submersion in the molten bath and for injecting oxygen from said orifice means within said bath while cooling said nozzle surface portion by coolant in said coolant passageway means, skull-forming prevention means carried on the nozzle tip section that is submerged in the molten bath whereby the formation of a frozen band of steel about the coolant-cooled nozzle tip section is prevented, said skull-forming prevention means comprising a plurality of raised generally vertically elongated circumferentially spaced thermal ridge means mounted on the outer surface of the nozzle tip section to define vertically extending crest and trough areas, whereby molten metal runs off the crest areas which are heated to a higher temperature level than the trough areas where the metal solidifies such crest areas preventing the formation of a continuous band of metal or skull around the submerged nozzle tip section, said orifice means including a plurality of generally elongated slotted gas ports circumferentially disposed about the periphery of the tip section and communicating with the oxygen passage to prevent formation of a continuous encircling frozen layer of molten material on the nozzle tip section, the length of the ridge means and the gas port thereunder being substantially equal to the depth of submersion of the nozzle tip section, and each ridge means having on its crest area a substantially thick layer of refractory material to insulate the crest area of the ridge means from the interior cooling effect of the coolant within the submerged nozzle tip section thereby allowing the ridge crest area to remain warmer in the bath so as to prevent solidification of metal on the crest area.

19. The invention according to claim 1, and said coolant passageway means containing a coolant selected from the group consisting of oils, glycerine, ethylene, tetra aryl silicates, water.

20. The invention according to claim 1, and said nozzle tip section and said ridge means being copper metal.

21. The invention according to claim 1, and said coolant passageway means containing a coolant selected from the group consisting of water, liquid ammonia, molten salts, molten metal, diphenyl oxide and diphenyl, ortho dichlorobenzene, glycerine, ethylene glycol, chlorinated biphenyls, aromatic mineral oils, and a mixture of fused salts of sodium nitrate, and potassium nitrate.

22. The method of forming an internally cooled and submergible nozzle tip section of an oxygen type lance having alternate crest and trough areas disposed thereabout that are adapted to be disposed just below the surface of a molten bath of metal comprising the step of selecting different materials for the trough and crest areas so as to have different thermal conductivitY characteristics whereby a given crest area has a thermal conductivity lower than the trough area upon immersion of the tip section into a molten bath as the tip section is internally cooled such that the crest area of lower thermally conductive material in being heated to a higher temperature level than the trough area effectively prevents the formation of a fused metal ring about said tip section.

23. The method as set forth in claim 22, including the step of applying a refractory coating of highly insulative refractory material to said crest.

24. The method as set forth in claim 22, including the step of directing a gaseous stream through an opening in said tip section in a direction outwardly of said tip section at a point below said crest and ridge means thereon upon immersion of said tip section into a molten bath of metal whereby said crest and ridge means cooperate with the directed gaseous stream to effectively prevent the formation of a fused metal ring about said tip section.

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