US2472416A - Blowing tube for molten metal - Google Patents

Description

June 7, 1949. R. M. GIBSON 2,472,416

BLOWING TUBE FOR MOLTEN METAL Filed ,Aug. 28, 1944 4 Sheets-She et 1 1 I. 1 i i jabertM Gibson M MMJM June 1949. R. M. GIBSON 2,472,416 BLOWING TUBE FOR MOLTEN METAL 4 Sheets-Sheet 2 Filed Aug. 28', 1944 INVENTOR .ZZ-gbertM Gibsan 4 Sheets-Sheet 3 INVENTOR Rob'ertM Gibson R. M. GIBSON BLOWING TUBE FOR MOLTEN METAL June 7, 1949.

Filed Aug. 28, 1944 June 7, 1949. R. M. GIBSON BLOWING TUBE FOR MOLTEN METAL 4 Sheets-Sheet 4 Filed Aug. 28, 1944 ii I INVENTOR Ji'abcrtM Gibson MMM Patented June 7, 1949 UNIT ED STAT ES OFFICE BLOWING TUBE FOR MOLTEN META!) Robert M. Gibson, Pittsburgh. Pa. Application August 28, 1944; swarm; 551392 8 Claims.

My invention relates to metallurgical appa:

ratus, particularlyto apparatus folrefining metal in molten state, such as apparatus for practicing the Bessemer process.

In Letters Patent oi the United States Nos. 2,291,221 and 2,291,222,- granted to me on July 28, 194-2, I illustrate and describe certain improvementsih apparatus :for producing steel by the Bessemer process. Intheproduction oisteel by such processa bathotmolten iron (typically pig-iron) is blown through with air. By the-inblovm air thesil'icomthezmanganese, and the carcon present in the: iron are burned out, with a generation of heat sufiicient to maintain the metal in molten state. Afterward manganese and carbon in measured quantities and'to the required degree are restored to the metal, and other and various desired components of the ultimate steel consists in improvements in method, whereby thebasic Bessemer procedure may be practicedwithaccuracy and expedition, and the slag expeditiously dealt with, in the courseof operation, according to its changing character; The'apparatus for practicing such method consists essentially of a vertical tube which is soarranged that its lower end can be gradually submerged and retracted ina vessel containing molten iron. Means are provided for delivering air through the tube; whereby the molten iron is blown through with air. The apparatus is adapted for the introduction of.various substances into the iron, .and for disposing of the slagor retainingit, as desired. Also provision is made in the. apparatus. forthe observation of the iron under treatment,

My present inventionconsists in certain new and useful improvement'ssin apparatus, to the end that the practice: of the-Bessemer process shall be facilitated and: more readily adapted topresent day' large. scale production, all with substantial continuity o-f'operatiom and'withredu'ction in labor, time: and-operational expenditures.

The invention willbe understood upon reference to the accompanyingdrawingsim which:

Figure 1 isa-view partly in elevation and'partly'r 2'; in vertical sectiom or an: apparatus embodying the invention;

Figure-2: is a fragmentary view to larger scale, showing: partly inside" elevation and partly in vertical section the-blowing; tube; and its adjusting support;

Figure liaamafialis'eiititahal view'of'the blowmg tubetothesames soaleasrFlgure 2;

Figure 4 is a topplan view of the blowing tube;

Figure 5 is a crose'sectionarview-otthe blowing tuhe as section: the broken plane V -V of Figure 3 Figure this a View iniperspective of: a certain clamping element oi the blowing tube structure; and- Figure -7 is aview in perspective of a; certain refractory block used' in the construction of the blowing tube ofithezapparatus.

Reierring to'shi'gure ofithefirawings, the container'for the b8thaB* of metal to-be' treated is shown to consist; in; as conventionallofi-ton opentop Iadle-Zmounted on:asuitahle chassis for travel on: a railway: Ga leading:- to. the blowing station 5 adjustment: in.- a cylindrical-, housing formed in two sections 8 and e; thezlower section 8" being rigidly borne: by steeli frame; of; the buildin and tneupper'sectiom e being, mounted on a carriage l'llsadaptedi toiti'avell' on1rails H5 laid on. the floor izxoiztheilmildiusi. ASRWfllEpYESGHtIY appear, meanstareprovlded withinatheupper. housing sectionMa-lowet thezblowing: 'lzprogressively iii-.- to: the bath of moltenmetal. imthe'lame placed in". station: 5;, and,v alternately, to raise the tube from the; metal andflinto position. entirely: within the upper section: 850i theicylindricalhousing.

at itsup-per end" the housingime'mber; 915 detachabl'y I andphemeticallmconnected to: aheader I it. rigidly united: with a; tubular bonnet; M; into which apipe: i5; including, a valve. it; is adapted to deliverairrunders pressurerfromsa pressure; tank or-othensupplyv W; Upon theivtop of; the; bonnet. I4 is" aahousing: II? whichbe; understood to. haveia windowin it's :top': walhthrough; which an:

attendant standing on floor 18 may look down through: the? bonnet.- H; headert3l. housing: 8,. 9 and: tube. k intm the: molten. metal; undergoing treatment. The: housing. 19} may: contain pyrometricandcontrol' instruments (with which the: art isiamfliar); inncletectingzor revealing-the conditiono!themoltenpmetaliwithin the,ladleorcon: vertex-i. 21.4 Extendihgdaterally oithezheader l 3 are two: axially aligned; conveyor: pipes; la and: 2a,

leading respectively from the discharge openings of a bin 2! for dolomite or lime and a hopper 22 into which reagent materials are introduced. Each conveyor pipe includes a conveyor screw, and the two screws may be mounted upon a common shaft 23. The shaft may be driven in obvious fashion by an electric motor (not shown), and a controlled rotation of the shaft 23 may be established as need be. One conveyor screw, 24, may be a left-hand screw, and the other, 25, may be a right-hand screw, whereby the rotation of the screw shaft 23 will eiTect delivery of materials from bin 2| and hopper 22 to the vertical bore 38, Figure 2, of the header, whence the materials descend under gravity and/or under the propulsion of the blast of air streaming downward through the housin 8, 9 and blowing tube 1 into the molten metal. The header l3 and the associated equipment described are all mounted upon the steel framework and floor [8 of the building 6.

Above the floor 18 a, plurality of bins 42 is provided for such reagent or rectifying materials as may be required to make desired additions to the molten metal. A scale car 26, movable manually or under motor power over the floor It, receives in accurately weighed quantities the materials as required from the bins, and transports and delivers the materials to the hopper, 22, whence introduction thereof to the molten metal is effected in the manner already described.

In operation, the ladle 2 carrying a proper charge of molten metal still in unrefined state (pig-iron, for example) is brought to position in blowing room 5. It is conveniently tipped on its trunnions to position such as that shown. Theblowing tube 1 is caused to descend from above and its lower end to be plunged beneath the surface of and to be immersed in the bath of molten metal within ladle 2. Air blast is applied, excluding molten metal from the pipe, so that the tube 1 is open from end to end; and through the tube air is admitted and caused to penetrate the molten metal. The air so admitted attacks primarily the silicon and secondarily the manganese and the carbon of the bath, and progressively burns these elements out. -As this operation progresses a siliceous slag forms, floating upon the bath of molten metal.

As this initial burning-out operation progresses the tube '1 is caused to advance downwardly in the bath of molten metal. Such; downward advance is serviceable, both to give progressive effect in the burning-outof the silicon (beginning near the surface and advancing more and more deeply) but also, by displacement, to effect a spilling of the slag as its accumulates, from the rim or spout 2a of the ladle into a trough 2b leading to a suitable receptacle that stands ready to receive it. Such downward advance of the tube with progressive burning out of impurities is valuable in that the emergent air comes into immediate contact, not with refined but with unrefined metal; the reaction that progresses downwardly with the descent of the tube is maintained at maximum intensity; and the overlying refined metal is protected from immediate access to it of the injected stream of air. I

Meanwhile, through the open and unobstructed tube 1 the condition of the molten metal is subject to detection, optically or otherwise, through windowed housing 10. And thus in the progress of the refining operation the instant may be determined when the burning-out of the silicon is substantially accomplished and the point reached when the sequent burning-out of the phosphorus 4 is to be accomplished. By such procedure it is possible to arrest the blowing while the desired small quantities of manganese and of carbon are retained.

When the desired point has been reached, and by the means described made known to the operator, the downward progress of the blowing tube is arrested and its upward retraction begun. By the retraction, th spilling of slag from the rim of the receptacle is arrested. As the retraction of the tube continues, basic material may be added to the bath, either through the tube or otherwise. But in any case, whether the basic material for the phosphorus reaction is derived from the converter lining alone or is introduced, the burning-out of the phosphorus goes forward; and,

' as it goes forward, in consequence of the retraction of the tube 7, there is no spilling of the slag. The phosphorus-containing slag of this later portion of the refining operation is retained, floating upon the bath of refined metal; and may in appropriate manner be eventually removed and turned to economic use.

While I have dwelt upon the introduction of basic material to the bath, it is manifest that other desired additions, such as ferro-manganese and other alloying additions may be introduced, either with basic material or alone; and; at the proper point in the progress of the refining operation carbon also may by such means be introduced.

Such is the general organization and mode of operation of the improved apparatus of my present invention. It will be understood the blowing tube is in service subjected to the extreme deleterious effects of the molten metal as agitated by the air blast, and in order to insure practical continuity of service of the apparatus my invention also consists in certain valuable features of tube structure, with provision for ready tube repair and reconstruction, as well as in particularly effective means for raising and lowering the tube.

Referring to Figures 3 to 6, the tube 1 is formed of a vertical column of refractory rings 21, each formed of a plurality of segmental blocks 28 of refractory material. The individual blocks are so formed that the hollow rings are cylindrical internally and externally, with the exception of the blocks 28a that form the lowermost ring 21a of the column, and these lowermost blocks areformed with downwardly sloped faces 2%, whereby the assembly of superposed rings forms of refractory tube having a cylindrical bore whose lower end is outwardly flared as shown in Figure 3. The refractory assembly of blocks is integrated by means of a plurality of vertical rods 29 of steel, or other suitable metal, anchored at their upper ends to a head 30 of cast iron or steel.

More particularly, there are eight rods 29 in this case, and they are arranged in spaced rela tion circumferentially of the tube, and at their upper ends, threaded as shown, extend through orifices in a horizontal web 3| of the head, where they receive nuts 32. The rings 21 of blocks 28 are assembled successively upon the rods 29 to form the completed blowing tube, the top ring of blocks being assembled upon the rods first and secured by means of a metal ring 33, with pins 34 projected through holes in the such ring and anchored in holes provided therefor in the rods 29. It will be noted, Figure 7, that each block 28 is formed as a quarter segment of a hollow cylinder; two bores 35 are formed in the block for the passage through of the two rods 29,

Then, the tube is, by rotation of the hollow spindle 44, lowered to the point where the webs 54 of the tube-carrying head 30 are presented below the lower edge of housing 9, and hangers 64, attached to the steel frame of the building 6, are engaged in eyes 65 in the webs 54 of such head; Thereafter the tube is further lowered until the hangers are placed under tension, and then the bolts Bil are removed, disengaging the tube assembly l, 30 from the sleeve-nut 43 and leaving such assembly suspended upon the hangers, where it can be repaired or rebuilt as need be.

A spare blowing tube assembly 1', 3!! is maintained on hand, in position where the carriage 9 may be spotted over it, and connection made with the sleeve-nut 43. Thereupon, the hangers 64 which normally support the spare tube assembly '7, 38 are disengaged; the tube assembly is drawn upward into the housing portion 9; the carriage I is returned to itsoriginal position; and all connections are re-established for normal operation of the apparatus.

Advantageously, an oven 55, fired by a fuel burner:6'l, is provided at the station where the spare blowing tube assembly is stored. Before placing a spare tube in service, it is thoroughly dried and/or preheated in the oven.

Features of operation It will be seen that a suitable optical system arranged in housing can be sighted down through the blowing tube assembly, and focused upon an exposed, and constantly renewed, surface of the metal, presenting a field large enough for spectroscope, radiation pyrometer, or other such instruments. Also the visual aspect, such as bubbles and other surface phenomena, can be observed accurately and easily.

It is not necessary nor desirable that the blowing tube 1 be submerged in the molten metal to full depth at once, but it ordinarily is caused to descend slowly into as the reaction progresses, so that the inblown air is constantly presented to new metal rather than to the metal already treated. In this manner less air is used and is more eifectively, and the finished metal is not oxidized. This is in contrast to the old Bessemer method.

'The air volume can be varied to control the speed of reaction, and the generation of heat, and the air can be shut off entirely, if desirable, and turned on again at will.

The moderate velocity of the ascending gases assists the slag in rising through the metal, and is not great enough to mix the slag with the metal. Also a greater time will be allowed to complete the reaction. This again is in contrast with the old Bessemer process in which, due to the enormous velocity, a mixture of slag and metal is treated rather than metal alone. In my process the slag separates by gravity and is allowed to flow away.

'Suitable reagents can be introduced directly into the metal in proper proportion, and at such time as they are most effective. Roll scale may be introduced to furnish additional oxygen, and additions of sodium carbonate and calcium carbonate serve to oxidize the carbon more rapidly, in such a manner that desirable quantities of silicon and manganese may be retained in the iron, and. sulphur and phosphorous removed. The sodium carbonate resolves into sodium (vaporized) which combines with oxygen and hydrogen elsewhere in the iron. Its combination with nitrogen or the nitrides is not known to me,-

but .issuspected; In case .the ladleis provided with anacid' lining, an optimum may be found only when sufiicient of these reagents is used to benefit the process, but not enough to produce a basic slag. With a basic lining, such as monolithic dolomite, a basic slag is made and as it contains a high percentage of double phosphates of. calcium and sodium, the sale of this slag for fertilizer provides a valuable by-product.

Alloys. and light scrap may be introduced directly 'into the ,metal, Without loss in the slag, and yet may be uniformly distributed. Also deoxidizers and the action of such additions can be instantly observed through the optical system. Calcium-silicon-aluminum alloys may be used efficiently and eflectively.

It will be seen that steel can be made in the ladle cars with no transfers such as into and out of the usual Bessemer converter.. This is equally true, whether duplexing, or with or without a mixer, and, while the ladle car is stationary during the blowing'period, this small delay is no longer than the time consumed in pouring into and out of the usual Bessemer converter.

Since the air and resulting gases will rise in the area around the blowing tube, the lining in the ladle is not subjected to undue destruction. Indeed,its destruction is far less than that of a converter lining. The refractory portion of the tube is subjected to erosion, but fortunately most of this is at the bottom course of refractory blocksywhich is easy to replace, and is of such small size that superior refractory material can be used to advantage. In any event the cost of renewing the 50 ton tube shown is less than the cost of renewing the bottoms of two 25 ton converters, assuming that the tube lasts only as longas the Bessemer converter bottoms.

It will be seen that there will be no difficulties such as arise from blocked, dirty or broken tuyeres of the usual Bessemer converter or from one-tuyere burning away more rapidly than the others. Mechanical efiiciency will be increased as the friction loss through the tuyeres is eliminated. This friction loss is equivalent to about 50% of the static pressure required for the old Bessemer converter.

My process permits the use of metal of widely difiering analyses (or off metal) from the blast furnace; conversely, the blast furnace may be operated to its best economy with the wider specification permitted.

The idea of blowing air into the metal from the top isnot new. The nearest attempt at reducing it to practice appears to be a hollow tube having at its lower end a few conventional tuyere blocks mounted in a suitable refractory container, which tube is submerged in the metal contained in a ladle car. Such a tube appears to have been tried in theindustry, but was not found suitable because: (a) silicon and manganese were removed, and apparently no carbon removed; (1)) operations had to be suspended early as the metal became too cool; (0) an immense amount of vibration took place, to the extent that there was danger of the refractories fracturing. Each of these effects can be traced to each of the following causes: (a) the area of the tuyeres was such that the reaction was extremely local with respect to the large amount of metal in the ladle, so that heat was dissipated into the surrounding metal faster than produced, and a temperature was not reachedsuch as is required to oxidize the carbon-norinally one-halfway through the blow;

(DI: the loc'al'sili'con becoming exhausted, and no.

upon which the block is assembled; and the botblock is undercut or recessed from the outer cylindrical face inward, as'shown at 36, to receive the metal ring. 33. Specifically, when the four blocks 28tthat form-the uppermost ring 2! have been placed, each on two of the eight rods 29 and slid upward top. position against the web 3| of the head 39, a metal ring 33, snugly encompassing theeightrods 29- (cf. Figure 5), is moved into position in theannular recess formed by the undercuts 3B in the four blocks that form the said refractoryring 21, and is secured by means of pins 34. With the top ring 21 thus assembled and secured,- thenext lower ring of blocks 28 is assembled upon the rodsand secured by means of a ring 33 and pins; and so each of the rings of blocksis successively assembled and secured upon the rods 29. Then, the lowermost ring 21a is assembled to complete the refractory blowing tube 1;

Before describing the assembly of the lowermost ring 21a, it is to be noted that preferably, if not essentially, the. blocks 28 in the upper rings 21 are so arranged that the points or meeting faces of the blocksin one ring are staggered with respect to the blocks in the next-adjacent ring. This may be seen in Figure 3; Between the rings 21 the recesses 36- in the individual blocks 21a. form annular grooves that open outwardly from the metal rings 33; These grooves are closed by means of refractory filler blocks 31, as shown in Figures 3 and 5. When this has been done the nuts 32 on the-upper ends of the rods 29 are turned, drawing the rods, and the metal rings 33 secured thereto, upward to lock the assembled blocks tightly in place. Then the blocks 280. are applied to the lower-ends of the rods 29 to complete the tube assembly, it being noted that the rod receiving passages 38 in the blocks 28a extend only partway through the block bodies. A lateral bore 39- extends outward from each passage or pocket 38, and in such bore a pin 40 is introduced and-inserted in the rod 29 in the pocket. The pin 49 is provided with an eccentric portion 40s. that engages the wall of the bore 39 in theblock, and a head portion 49b that is adapted to receive a socket wrench or the like. By means of such a wrench the several pins 49 that secure the lower ring of blocks to the rods 29 are rotated and the eccentric portions 400. of the pins are caused to cam the blocks upward into tight contact with the lower face of the ring of blocks 2Bimmediately above. Closure plugs 4| of refractory material then are inserted to close the bores 39. The

tom portion of the structure thus constructed formsin effect an integral tube of refractory material, but with additional advantages over an integral refractory tube: The rods 29 areenclosed and protected so that the metal structure-that supports the weight of the tube, which may be as much as fifty tons, does not contact the hot metal or gases, while the rings 33 provide-lateral reinforcement of the tube against the internal pressure of the air injected through the-tube into the bath of molten metal undergoing treatment, and against the ferrostatic pressure of molten metal on the outside of the'tube when immersed in the metal.

In service the blowing tube '1 is secured as by bolts 89, Figure 2, to a sleeve-nut 43 that engagesv an externally threaded; hollow. spindle 44 which is rotatably borne by the: upper housing portion 9 mounted on the carriage ll]; More particularly,

a collar. portion 45 is united rigidly:

to over either one of repair to a knee-ring 46 sweated or otherwise locked upon the hollow spindle 44, and this collar portion rides two races 41 and 48 of anti-friction bearings provided in a head 49 that forms the upper end of the housing 9. A worm-gear 59 is carried by the collar portion 45, and a wormthe gear 59. provided for rotating either direction of rotation,

rotated in either direction within the sleevenut. Means are provided for preventing the sleeve-nut from rotating, and such means come prise rollers 53 which are trunnioned between paired webs 54 on the cast metal head 30 of the blowing tube, and at their edges extend between vertical metal strips in parallel pairs upon the inner surface of the. housing 9, the strips in each pair being spaced;

apart a sufficient interval to provide a vertical way for the rollers 53. Accordingly, when the hollow threaded spindle 44 is rotated, with the sleeve-nut held from rotating, the result is that the sleeve-nut, and with it the supported tube assembly 1, depending upon the direction of spindle rotation. Thus, the blowing tube may be moved downward from telescoped position within the upper housing portion 9, and projected through the lower housing 8 into the charge of molten metal to be processed.

The upper end of the rotary hollow spindle 44 is hermetically united to the header I3 whence the blast of air and the reagent materials are delivered, and the bore of this spindle 44 forms with the bore of the refractory tube 1 a continuous passageway to the surface of the molten metal into which the tube is injected. The sea-led union between the header [3 and the upper end of the hollow spindle comprises a rotary joint formed of ring members 55 and 51 shaped to telescope and compress between them, under stress applied by bolts 58, a ring 59 of lubricated packing material. The spindle is free to rotate relatively to the stationary header l3 with which it has a sealed union, and the blowing tube may be raised and lowered, as desired, without interfering .with the delivery of air or reagent materials to the charge of molten metal in the ladle 2.

In the course of prolonged service the refractory body of the tube erodes away to the extent that repair or renewal is required, and a feature of my invention resides in the organization of means whereby the operation of the plant may be conducted without loss of time on that account. To this end the housing portion 9 is detachable from the housing portion 8, and the rotary joint that unites the hollow spindle 44 to the stationary header 13 is separable. Comparing Figures 1 and 2, it will be perceived that the upper housing portion 9 extends downward from its supporting carriage l9 and is united to the lower housing portion 8 in a bolted flange joint 69', and that by removing the bolts 61 the two housing portions may be separated. Similarly, by removin the bolts 59, the rotary joint members 56 and 5.1 may be disengaged from the stationary header i3. Thereupon, by drawing the blowing tube assembly i, 30 upward into position entirely within the upper housing 9, the carriage 19 maybe shifted to the right on the rails H, Figure 1,"

to. bring the, housing portion 9 and the. worn refractory tube 1 contained therein into position. stations; 6-2- 01"63'.

55 that are welded.

39, is moved upward or downward,

means of circulation were provided, and an increase in the volume of air only cooled the metal faster; the flat bottom of the tube acted as a cover over an area in which there was a violent commotion, and the inertia of the surrounding iron with respect to the inertia of the tube was such that the flat bottom of the tube received most of the forcevariations in this force reacting with impacts on the flat bottom of the tube. Even without the violent chemical reactions, the pulsation of these air streams produced this vibration-as if for instance the tube had been submerged in a similar heavy liquid, such as mercury. Contrast this with my blowing tube; the air approaches the metal at relatively low velocity through a tube 14" in diameter (not through 48 orifices /g" diameter as hitherto). The air then enters the metal from around the lower edge of the plunger, in a circle 38" in diameter. Around this circle (and not underneath the plunger), the reaction begins and continues as the air bubbles ascend. The forces evolved are dissipated in causing the metal to flow upward around the outside of the tube. The 14" diameter column of air, even if pulsation occurred, acts as a cushion and dampens it. The volume of air, not being limited by the capacity of the small orifices, is such that proper temperature may be reached faster than heat is dissipated; in fact the tendency is toward overheating.

The invention is defined in the appended claims, and it will be understood that within the terms of such claims many variations and modifications of the structure described are permissible without departing from the spirit of the invention.

Notice is given of my divisional application Serial No. 7,777, filed February 12, 1948.

I claim:

1. A blowing tube for metallurgical use comprising a plurality of rods, a tubular body formed of perforate refractory blocks threaded and locked upon said rods, a block at the end of said tube including a pocket that receives the end of one of said rods, a bore extending laterally from said pocket, and means in said bore engaging the end of said rod and reacting on the block to lock it in tight assembly with the adjacent blocks.

2. A refractory tube for metallurgical use comprising a plurality of rods, a plurality of perforate refractory blocks threaded on said rods in the form of a tube, and means for tightening and locking the assembly of blocks upon said rods, a block at the end of said tube including a pocket that receives the end of one of said rods, a bore extending laterally from said pocket, and means in said bore engaging the end of said rod and reacting on the block to lock it in tight assembly with the adjacent blocks.

3. A refractory tube for metallurgical use comprising a plurality of spaced parallel rods, a succession of rings formed each of a plurality of perforate blocks of refractory material mounted upon said rods, a metal ring encompassing each ring of blocks and engaged to said rods, and means cooperating with said rods to tighten and secure such assembly.

4. The structure of claim 3, said rods and metal rings being enclosed with the assembly of refractory blocks.

5. A tube for metallurgical use comprising a metal supporting head, a plurality of spaced metal rods extending in parallelism from said head, a

succession of rings formed each of a plurality of perforate refractory blocks threaded upon said rods, metal rings severally encompassing said rings of blocks, means engaging the metal rings to said rods, and means cooperating with said rods to tighten and secure such block and ring assembly.

6. A tube for metallurgical use comprising a metal supporting head, a plurality of spaced metal rods extending in parallelism from said head, a succession of rings formed each of a plurality of perforate refractory blocks threaded upon said rods, metal rings severally encompassingsaid rings of blocks, means engaging the metal rings to said rods, and means cooperating with said rods to tighten and secure such block and ring assembly, the ring of blocks at the end of the tube opposite to said head including pockets that receive the distal ends of said rods, bores opening laterally from said pockets, and means in said bores engaging said ends of the rods and reacting upon the block bodies to lock them tightly against the adjacent ring of blocks.

7. A blowing tube for metallurgical use comprising a series of refractory rings assembled upon a plurality of spaced parallel rods, each of said rings comprising a plurality of refractory blocks, and means arranged adjacentto the joints between successive rings in the series and cooperating with said rods for securing rings of assembled blocks severally upon the rods and for reinforcing the tube against internal pressure developed in the bore of the tube in service, said rods and said means being enclosed within the bodies of said blocks between the inner and outer surfaces of the wall of the tube.

8. A metallic blowing tube comprising a tube body constructed of refractory blocks assembled upon longitudinal extending elongate members, in combination with circumferentially extendingmembers arranged in spaced relation with respect to said longitudinal members for reinforcing the wall of the tube against pneumatic pressure developed in the bore of the tube in service, said longitudinal and circumferentially extending members being enclosed within the assembled blocks between the inner and outer surfaces of the wall of the tube constructed thereof.

ROBERT M. GIBSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 605,464 Reese et al. June 7, 1898 660,477 Wellman et a1 Oct. 23, 1900 689,372 Taylor Dec. 17, 1901 905,948 Stromborg Dec. 8, 1908 1,073,587 Billings Sept. 23, 1913 1,312,474 Fisk Aug. 5, 1919 1,729,196 Welch Sept. 24, 1929 1,876,732 Neuhauss Sept. 13, 1932 1,933,577 Wille Nov. 7, 1933 2,218,458 Wright Oct. 15, 1940 2,291,221 Gibson July 28, 1942 2,291,222 Gibson July 28, 1942 FOREIGN PATENTS Number Country Date 82,103 Sweden Nov. 27, 1934

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