US3224051A

US3224051A - Method of introducing addition agent into a melt

Info

Publication number: US3224051A
Application number: US170204A
Authority: US
Inventors: Jr John W Brown; Arthur C Buesing; Francis T Kaiser
Original assignee: Brown Fintube Co
Current assignee: Brown Fintube Co
Priority date: 1962-01-31
Filing date: 1962-01-31
Publication date: 1965-12-21
Anticipated expiration: 1982-12-21
Also published as: DE1433425A1

Description

Dec. 21, 1965 J. w. BROWN, JR., ETAL 3,224,051

METHOD OF INTRODUCING ADDITION AGENT INTO A MELT Filed Jan. 31, 1962 5 Sheets-Sheet 1 INVENTORS Jae/M M EFOh M J42,

Bow/ wi 5W W14 knew-Z04 Dec. 1965 J. w. BROWN, JR.. ETAL 3,224,051

METHOD OF INTRODUCING ADDITION AGENT INTO A MELT Filed Jan. 31, 1962 5 Sheets-Sheet 2 Dec. 21, 1965 J. w. BROWN, JR, ETAL 3,224,051

METHOD OF INTRODUCING ADDITION AGENT INTO A MELT D 1965 J. w. BROWN, JR.. ETAL 3,224,051

METHOD OF INTRODUCING ADDITION AGENT INTO A MELT Filed Jan. 31, 1962 5 Sheets-Sheet 4- BmwoM,S14m M i/(MA 1965 J. w. BROWN, JR.. ETAL 3,224,051

METHOD OF INTRODUCING ADDITION AGENT INTO A MELT Filed Jan. 31, 1962 5 Sheets-Sheet 5 500M, 3% MM 4 Km United States Patent 3,224,051 METHOD OF INTRODUCING ADDITION AGENT INTO A MELT John W. Brown, Jr., Lakewood, Arthur C. Buesing, North Olmsted, and Francis T. Kaiser, Fairview Park, Ohio, assignors to Brown Fintube Company, Elyria, Ohio, a corporation of Ohio Filed Jan. 31, 1962, Ser. No. 170,204 6 Claims. (Cl. 22-215) This invention relates to method and apparatus for introducing any desired quantity up to a relatively large quantity of particles of one or more addition agents into a melt such as molten metal to obtain thorough distribution of the particles in the melt; more particularly the invention relates to method and apparatus for introducing into a melt addition agents which are lighter than the material of the melt.

While the invention may be employed to introduce a wide variety of addition agents into various kinds of molten metals or other materials, it is described below primarily in the introduction of particles of metallic aluminum into molten steel for deoxidizing the steel or providing residual aluminum for control of grain structure or alloying of the solidified steel, and for capping of steel in ingot molds.

In the manufacture of steel by the open hearth process, for example, it is common practice to add metallic aluminum into the ladle containing the molten steel which has been poured from the furnace, or to add metallic aluminum into both the ladle and the ingot mold into which the steel has been poured from the ladle, in order to deoxidize the steel and/ or control its structure or other properties. The aluminum metal is usually added to the ladle in the form of bars, large pieces of scrap or shot, by manually throwing or shoveling pieces of aluminum into the molten metal in the ladle. Aluminum is usually added to the ingot mold in the form of shot manually thrown into the mold. The shot particles in either case usually are substantially oircular, fiat pieces about A to /2 inch in diameter and A; to inch thick. Although in many cases it has been desired to make the entire addition of aluminum in the ladle because of the economies in operation and the possibilities of obtaining more thorough dispersion of the aluminum, it usually has been found necessary to make a partial addition of aluminum in the mold for finishing purposes. However, the temperature of the molten metal in the mold often is too low to insure adequate melting and dispersion of such large pieces of aluminum, so that undesirable concentrations or inclusions of aluminum or aluminum oxide often occur.

In the production of rimmed steel, metallic aluminum in the form of shot has been thrown into the top of an ingot mold filled with molten steel to cap the steel to cut off the flow of escaping gases and allow the metal to solidify with the gases trapped in the steel.

The above described rather crude prior methods of introducing aluminum have involved substantial difiiculties. For example, it has been impossible to distribute the relatively small amount of aluminum sufficiently uniformly throughout the large volume of molten steel in the ladle to cause the aluminum to react or otherwise combine with the oxygen contained in the steel, or to control grain size, or to alloy with the steel, to produce a desired uniformity of composition or structure of the steel. Furthermore, a large part of the thrown aluminum has been wasted by dropping it onto the floor rather than into the ladle or mold. Even more seriously, as much as 75% of the metallic aluminum added to the molten steel in the ladle heretofore has been wasted by being oxidized by ambient air or by oxygen combined in the slag, rather than by being usefully employed in carrying out an intended function such as deoxidizing of the steel. This occurs primarily because pieces of aluminum which are thrown into the ladle melt and tend to form a thin layer of molten metallic aluminum which floats on top of the molten steel with only its lower surface in contact with the uppermost portions of the molten steel, which portions are very small as compared to the total mass of steel in the ladle, so that the aluminum in the film cannot permeate and deoxidize the large body of molten steel as intended. The layer of molten aluminum floating on the steel contacts the air which rapidly oxidizes it, and also may contact and be oxidized by slag floating on the steel in the ladle, some of which slag is unavoidable even though precautions are taken to prevent discharge of slag into the ladle until the end of the pouring cycle.

Prior attempts to cap steel in the ingots by use of aluminum have not been uniformly satisfactory because the shot thrown into the top of the ingot mold often has not been sufiiciently uniformly distributed in the upper layer of steel to cap the metal satisfactorily.

In order to compensate for these losses and in an attempt to overcome these problems, it has been the practice to add considerably more aluminum than theoretically required. The excess necessarily has been added by estimation, since there has been no definite method of determining how much aluminum would be lost by dropping on the floor, how much would be oxidized by the air, and how much would be usefully used as by reacting with the oxides in the steel. Yet it is extremely important that the proper amount of aluminum be introduced into and properly distributed relatively to the steel. If too much aluminum is added not only are costs increased of waste of expensive metal, but the steel may be overly deoxidized when it is desired to produce rimmed or even semikilled steel. Residual aluminum or aluminum oxide in the steel may also exceed specifications, causing difiiculties in further processing of the steel and in the physical characteristics of the finished products. If, on the other hand, insufiicient aluminum is added, the steel will not deoxidize to the desired degree and may have undesirable metallurgical or physical characteristics. Moreover, if it is attempted to avoid the formation of the previously mentioned easily oxidizable film of molten aluminum on the top of the molten steel in the ladle by holding one or more large pieces or bodies of aluminum below the surface of the molten steel, as has been heretofore proposed, the steel in the vicinity of the large aluminum body may be chilled, the aluminum may be incompletely melted, and aluminum or aluminum oxide may be harmfully localized in the solidified steel. Because of improper distribution of aluminum in the steel for such reasons, blow holes, streaks, inclusions, concentrations of aluminum) or aluminum oxide, and other defects may develop which can be sufficiently harmful to require the steel to be downgraded or even scrapped.

Various proposals have been made for injecting addition agents into baths of molten metal in the ladle or the like. In general, the injecting means has not been satisfactory for injection of aluminum or other material lighter than the molten metal, either because it has not had sufiicient capacity, or has been so complicated in structure as to lack the dependability necessary in steel making operations, or has been incapable of injecting such light material into the heavier steel.

It is an object of this invention to provide methods and apparatus by which there may be added to melts such as molten steel particles of one or more addition agents such as aluminum having a lower density than the material of the melt, in such manner that accurately controlled amounts of addition agents will be very uniformly distributed throughout the body of the melt or in only a top layer thereof to overcome or avoid the above and other difficulties.

A further object is the provision of a method whereby a predetermined quantity of particles of one or more addition agents such as aluminum are introduced into a stream of molten metal pouring from a furnace into a receptacle such as a ladle under conditions which cause thorough distribution of the particles in the metal and adequate time for them to react or alloy with the metal before the addition agent can come into contact with the ambient air.

Another object is the provision of a fluid-actuated gun for discharging into or onto molten metal particles of addition agents under conditions and in accurately controllable quantities which will promote uniformity of distribution, and action. A further object is the provision of such a fluid-actuated gun by which an accurately measured amount of an addition agent, either alone or in a mixture with other addition agents, can be introduced into a stream of molten material such as steel as it passes from a furnace to a receptacle such as a ladle, during an accurately predetermined time and with a particle velocity sufficient to cause substantial penetration of the particles into the molten material, even though the addition agent is a material substantially lighter than the molten material. Another object is the provision of such a gun which makes possible the introduction of a large amount of addition agent within a short time. A further object is to provide such a gun in which the particles of aluminum or the like can be supplied from an easily filled hopper or the like at atmospheric pressure.

Another object is the provision of apparatus which can be easily manually directed, and which is of simple and rugged construction permitting its use over extended periods of time without damage, under the severe conditions obtaining in steel mills or similar services.

Other objects and advantages of the invention will be apparent from the following description of several embodiments of the invention, in connection with the accompanying drawings in which:

FIGURE 1 is a plan view showing apparatus embodying a preferred form of the invention as used to introduce metallic aluminum particles into a stream of molten steel pouring from an open hearth furnace into a ladle according to a method embodying the invention;

FIGURE 2 is a perspective view from line 2-2 of FIGURE 1 showing in more detail the end of the apparatus and the stream of particles discharged from it into the stream of molten steel pouring from the furnace spout into the ladle;

FIGURE 3 is a perspective view, to an enlarged scale, showing the apparatus used in the arrangement of FIG- URES l and 2;

FIGURE 4 is a cross section on line 4-4 of FIG- URE 1, but to an enlarged scale;

FIGURE 5 is a vertical sectional elevation, to a considerably enlarged scale, of the impelling portion of the apparatus of FIGURE 3;

FIGURE 6 is a sectional elevation along line 6-6 of FIGURE 5, and to the same. scale;

FIGURE 7 is a perspective elevation showing another form of apparatus embodying the invention as used to discharge metallic aluminum particles onto the top surface of molten steel in each of several ingot molds after it has been filled with molten steel from a ladle, to cap the steel, according to another method embodying the invention;

FIGURE 8 is a side view of the apparatus of FIGURE 7, but to a larger scale;

FIGURE 9 is a vertical sectional elevation of the impelling portion of the apparatus of FIGURE 8, generally corresponding to the same section as FIGURE 5 is 4 of the apparatus of FIGURE 3, and to the same scale as FIGURE 5; and

FIGURE 10 is a perspective of the discharge end of the barrel of the apparatus of FIGURE 8, showing in particular the deflector for directing the particles downwardly.

In FIGURES 1, 2 and 3, a preferred form of apparatus embodying the invention is indicated in general by reference numeral 1 and is shown in FIGURES 1 and 2 as standing on the pouring platform 2 along the pouring side of an open hearth furnace 3. The furnace has a conventional pouring spout 4 which is shown as discharging a stream 5 of molten steel in the conventional manner into a ladle 6 to form a body 7 of molten steel in the ladle. The apparatus 1 (sometimes referred to herein as a gun) is shown as discharging particles 8 of metallic aluminum into the stream 5 of molten steel pouring into the ladle 6. This process and its advantages will be described in more detail later.

As shown in FIGURE 3, gun 1 comprises a supply hopper 11 the upper end of which is open to the atmos-- phere and hence readily available for filling or inspection of the quantity or type of contents. The hopper containsa preferably accurately weighed amount of finely divided aluminum particles 8. The aluminum particles may take the form of the usual shot particles described above. The hopper 11 is fixed to a frame 12 the lower portion of which is supported by a pair of wheels 13. The frame 12 also has handles 14 for guiding and positioning the apparatus, front and rear bracing

members

15 and 16 to aid in supporting the apparatus when it is stationary. A propelling portion 17 is fixed to the frame below the hopper 11 to receive particles of aluminum from the lower portion of the hopper, which is preferably tapered downwardly and inwardly as shown to facilitate movement by gravity of aluminum particles into the propelling portion. The propelling portion, which is described in detail below, is connected by a hose or other suitable conduit 18 to a control valve 19 mounted on one of the handles 14 of the apparatus and adapted to be actuated by a valve handle 20. The control valve is a conventional high volume flow type adapted to operate between a full on and a full off position, to control the flow of fluid to the propelling portion 17, and requires no further description. This valve is connected by hose 2]. to a suitable source of propellant fluid under pressure, such as air at about pounds per square inch commonly available in steel plants.

The other end of the propelling portion 17 of the apparatus makes a fluid-tight connection to one end of a short length of flexible conduit 22, the other end of which is connected to the feed end of an elongated barrel 23. This barrel preferably is a tube of heat resistant material such as stainless steel of a length such that when the discharge end 24 of the barrel is in operative position about three feet from the stream 5 of molten metal, the hopper 11 and persons working around it are not exposed to excessive heat. Preferably, the barrel length should not be greater than about 16 feet, to avoid excessive weight and resistance of flow of particles through the barrel.

Preferably, as shown in FIGURE 4, the discharge portion of the barrel 23 has heat insulating means to prevent its distortion or damage from excessive heat when the barrel is in operative position. The illustrated heat insulating means is a cylindrical jacket sleeve 25, preferably formed of heat resistant metal such as stainless steel, which surrounds and is spaced from the discharge portion. of the barrel 23 for a substantial length; this jacket has" a radial wall 26 at the discharge end of the barrel 23 and another radial wall 27 at the opposite end of the jacket 25. Several openings 28 through the wall of the barrel portion 23 connect the interior of the barrel with the annular space 29 between sleeve 25 and the barrel; these openings are near the end wall 27 and are small enough to permit the air or other propellant fluid to pass from the barrel into the annular space while preventing escape of the particles of aluminum or other addition agent from the barrel. Several outlet openings 31 also extend through the jacket sleeve 25 at a location spaced longitudinally from openings 28 and preferably adjacent the end wall 26. Thus, some of the propellant fluid in the barrel 23 passes through openings 28 in the space 29 within the jacket 25, travels lengthwise of the space to cool the portion of the barrel in the space, and passes to the atmosphere through the outlet openings 31 at the discharge end of the barrel. The discharge portion of the barrel is thus protected from heat.

The propelling portion 17 of the gun I is shown in cross section in FIGURES 5 and 6. This portion comprises a downwardly extending tubular feed conduit 32 with an internal passage 33 communicating at its upper end with the bottom of hopper 11 and at its lower end with a transversely extending tubular body member 34 having a substantially cylindrical internal passage 35. The body member 34 supports a nozzle 36 having a bore 37 communicating with the air supply hose 18. The bore 37 is substantially smaller in cross section than the passage 35. Preferably, nozzle 36 is adjustable axially of body member 34 so that discharge end 38 of the nozzle can be moved across the lower end port of the feed passage 33 partially or completely to close the port or passage against the fiow of particles from hopper 11 into passage 35 of body 34. To accomplish this, nozzle 36 is slidably mounted and closely fits in passage 35. The rear portion of the nozzle has an externally projecting circumferential flange 39 and removable collar 41 held in place by set screws 42. An inwardly projecting flange 43 fixed to the rear portion of a rotatable adjusting member 44 is disposed between flange 39 and collar 41. Member 44 has a longitudinally extending bore 45 terminating in a front portion 46 having internal threads 47. The diameter of bore 45 is larger than the external diameter of flange 39, and front portion 46 is removably rigidly fixed to member 44 to make possible assembly and disassembly. The internal threads 47 engage external threads 48 on body portion 34. Preferably, hand wheel 49 is provided on the exterior of member 44.

When member 44 is rotated by hand wheel 49, engagement of threads 47 with threads 48 causes member 44 to move axially of member 34, and nozzle 36 is correspondingly moved within the member 34. By rotation of member 44, the discharge end 38 of nozzle 36 can be moved from the position shown in full lines in FIGURE 5 in which the passage 33 of the feed conduit 32 is completely open, to a position in which the passage is completely closed as shown in broken lines in FIGURE 5, or to any position in between, the length of threads 48 being suitable for this purpose. If desired, means may be provided to indicate the position of discharge portion 38 of nozzle member 36 relatively to the passage 33, such as an indicating pointer 50 fixed to the feed portion 32 and cooperating with suitable indicating marks 51 on the exterior of member 44.

In order to obtain a high discharge velocity of air from the nozzle 36, the walls of bore 37 at the discharge end 38 of the nozzle taper inwardly as shown at 52 to define a throat or orifice 53 of a cross sectional area substantially smaller than that of the bore 37, and much smaller than the cross sectional area of passage 35 into which it discharges. The configuration is such that in the immediate vicinity of the discharge portion 38 of the nozzle member 36, the propellant air or other fluid under pressure traveling through passage 37 substantially increases in velocity as it passes through orifice 53' into the substantially larger passage 35 of body member 34. The air discharging from the orifice 53 travels in an expanding stream, indicated diagrammatically by broken lines A, which in the immediate vicinity of the orifice 53, has a relatively small cross sectional area comparable to that of the orifice and travels at its highest velocity. As the distance from the orifice increases, the velocity of the stream decreases and its cross sectional area increases until finally the area approaches that of the passage 35 and the stream velocity is substantially reduced.

As a result of these varying areas and velocities, the pressure in the zone B surrounding the stream A is substantially lower than elsewhere in the passage 35; preferably, the configuration of the parts is such that the pressure at the zone B is less than atmospheric pressure. This low pressure promotes flow of particles 8 of aluminum or other addition agent from the passage 33 into the passage 35 of body portion 34 and the entrainment of these particles into the air stream discharged from the nozzle member 36 and traveling through body member 34 into and through the barrel 23. The configuration of parts, including the restricted orifice 53, greatly increases the weight of particles which can be entrained into the air stream and discharged from the barrel per unit of time with the same air pressure; increases in the rate of discharge of more than 200% have been obtained by the use of the restricted orifice, without other changes in the design of the gun.

Another important feature which greatly increases the quantity of particles which can be drawn into and discharged from the gun is the return conduit generally indicated by reference numeral 55 through which some of the air passing through the body portion 34 flows into the passage 33 of the particle supply conduit 32 and preferably int-o the portion of the hopper discharging into such conduit 32. The illustrated conduit 55, which preferably is formed with large radius curves to facilitate streamline flow, communicates with the interior passage 35 of body member 34 at a location downstream from the opening of particle passage 33 into the passage 35 and from the low pressure zone described above; it has a branch 55a communicating with the particle passage 33 at a substantial distance from its opening into the passage 35 and another branch 55b having a downwardly directed discharge end 56 located in hopper 11 directly above and in close proximity to the entrance from hopper 11 into discharge conduit 33.

Surprisingly, the use of the return conduit greatly increases the rate at which material can be discharged by the apparatus. Tests have shown that the conduit increases the flow of particles by as much as by weight over that possible without the conduit. While the reasons for this result are not entirely understood by us, we believe that the capacity of the gun of the type contemplated by the present invention is, in the absence of this feature, limited by the gross volume of the mixture of air and particles which can pass through the gun barrel. The conduit 55 removes a portion of the air from passage 35 after it has acted to entrain particles into the air stream and to impart substantial kinetic energy to the particles. The removal of air through conduit 55 thus provides space for an additional volume of particles to pass through the gun barrel, and also reduces air resistance in the barrel. Furthermore, since the air removed from passage 35 and discharged by branch conduits 55a and 55b into passage 33 is at superatmospheric pressure, it exerts on the particles in and about to enter the passage 33 an air pressure tending to urge the particles through passage 33 and into the passage 35 of the gun; and it also agitates the particles in the supply passage 33 sufificiently to prevent clogging of passage 33. All of these factors cooperate to increase greatly the capacity of the gun.

The location C at which the conduit 55 communicates with the gun passage 35 should preferably be at a zone downstream from the orifice 53 of the nozzle member 36 where there is greater than atmospheric pressure on the Walls of passage 35, and where a substantial portion of the kinetic energy of the air has been transferred to the particles. For a given installation and size of parts, the

optimum location of the opening conduit 55 into passage 35 can be readily determined by experiment. Generally speaking, a satisfactory arrangement is as shown in FIG- URE 5, wherein the distance D that conduit 55 is downstream from the passages 33 is a little greater than the maximum diameter of passage 33.

The location E at which the conduit branch 55a discharges into the particle supply passage 33 should be sufficiently remote from the outlet of passage 33 into passage 35 to prevent air under pressure emanating from conduit 55a from short circuiting into passage 35 without acting on the particles in passage 33. In other words, there should be a substantial thickness of particles between the outlet of conduit 55a into passage 33 and the outlet of passage 33 into passage 35. A distance F that is equal to or a little greater than the maxium diameter of passage 33 gives satisfactory results, and again the optimum can be determined by testing. The depth of the column of particles above the point of connection of conduit 55a with passage 33 ordinarily will be equal to several maximum diameters of the passage, except when the gun is being emptied. The internal diameter of each conduit branch 55a and 55b can be varied considerably, but preferably is about one third the maximum diameter of the passage 35. Branch conduit 55a includes a valve 56a, and branch conduit 55b includes a valve 56b to enable the flow of air through each of the branch con duits to be adjusted for best results.

. While only one conduit 55 has been shown since this has been found sufficient in most cases, it is obvious that more than one can be used. Moreover, while the conduit 55 shown has two branches 55a and 55b, it may have more branches, or only a single branch; in the latter case best results are obtained in facilitating flow of particles through passage 33 if the single branch corresponds to branch 55a.

While, as indicated above, the restricted orifice portion and the return conduit 55 each individually greatly increases the output of the gun over that possible without such feature, it has been found, surprisingly, that both these features in combination increase the output of partiles discharged from the gun much more than the mere additive effect of these feaures, so that very large amounts of particles can be discharged within relatively short times without clogging of the gun.

By measuring the amount of particles put in the hopper 11, and by predetermining the rate of flow by adjustment of the air pressure or by adjustment of the position of the nozzle member 36 or both, it is possible accurately to control the rate of discharge of particles from the gun, which is extremely beneficial in adding agents to molten metal.

For some installations it has been found desirable to employ a clamping means 57 (FIGURES 1 and 3) for accurately and firmly holding the barrel 23 of the gun in a predetermined position so the gun will discharge particles from a desired point and in a desired direction. The clamping means 57 shown in FIGURE 3 comprises a stationary, upright stanchion 58 fixed to the floor of the pouring platform, as by welding. Stanchion 58 has an upwardly open socket 59 into the side of which a clamping screw 61 is threaded; the socket receives the lower end of an upright member 62, the upper end of which pivotally supports a member 63 which can be clamped by screw 64 in any one of a wide variety of angular positions deviating from the vertical. Thus, the member 63 is capable of essentially universal adjustment within the range of movement provided. To the upper end of member 63 is fixed a lower plate 65 which is channeled to accept the gun barrel 23. An upper plate 66 is connected at one side by hinge 67 to the lower plate 65 and at the other side has clamping screws 68 or other suitable quick clamping means; upper plate 66 is channeled to accept the upper half of barrel 23.

As an example of advantageous practice in a steelmaking operation, before the molten steel of the heat is poured from the furnace into the ladle, the apparatus 1 is moved into position and its barrel 23 is quickly and accurately located by clamping means 57 so that the stream of particles 8 discharged from the barrel 23 will intersect the stream 5 of molten steel pouring from the spout. Usually, the discharge end of the barrel 23 is preferably located from about six inches to about three feet from the localized area of the stream 5 into which the addition agent is to be injected. The hose line 21 is connected through a source of air under pressure which in a steel plant ordinarily is a line supplying air at approximately psi. The hopper 11 is filled initially or during operation with the predetermined amount of the desired addition agent, such as aluminum. Preferably this amount is determined by calculating the amount theoretically required to produce the desired effect in the heat, and increasing the calculated amount by a few percent to allow for small losses that may take place. From past experience with the furnace the pouring time is known and the number of minutes and seconds during which the gun can be operated to add the aluminum or other addition agent to the stream of molten metal is determined. On the basis of previous calibration, the nozzle member 36 is adjusted to provide the rate of flow of the addition agent so that the desired quantity will be added when the gun is operated for the predetermined period of time.

The furnace is then tapped and the stream of molten metal 5 starts falling freely in a generally vertical path into ladle 6. A predetermined time after flow starts, usually determined by the time required to accumulate a desired volume of steel in the ladle, the valve 19 is opened and a stream of particles 8 of addition agent is projected from the end of gun barrel 23 at a velocity sufficient to travel through the air and to impinge upon and penetrate the stream of molten metal. The apparatus is so directed that, for practical purposes, all particles enter the essentially solid stream 5 at a velocity high enough to cause them to penetrate the stream 5 to a distance great enough to prevent oxidation of the material of the particles by the air surrounding the stream of molten steel. The gun is operated steadily, or intermittently if desired, for the predetermined period of time required to discharge the proper amount of addition agent, and then the valve 19 is closed and the discharge stopped. Preferably, the particle discharge is halted before the large quantity of slag drains from the furnace at the end of the pour. A small amount of slag unavoidably is in the stream 5 of molten metal, either from the steel in the furnace or resulting from reaction of the steel with the linings of the furnace, pouring spout, or ladle; this slag, which is not concentrated in the stream 5, tends to collect in a thin layer at the top of the molten metal in the ladle. Since, however, the particles 8 are propelled into the stream 5 as it pours and the stream essentially consists of molten metal, the particles cannot contact a concentrated mass of slag and hence are not wasted by reaction with slag. Furthermore, few if any of the particles are lost by dropping or falling to the floor. For all practical purposes, therefore, all particles are captured by the flowing stream 5 and are distributed and utilized effectively in the molten steel.

As a more specific example of the above operation, assume the furnace to be a 400 ton open hearth furnace, the molten contents of which can be discharged in about 5 minutes into a suitable ladle. From the analysis of the metal it is determined that four lbs. per ton, or 1600 lbs. of aluminum shot of the previously described type is required to produce the desired results. This amount (or more) of shot is placed in the hopper of the apparatus 1. It is desirable to run some steel into the bottom of the ladle before starting the discharge of the aluminum. Therefore, it is determined that the aluminum should be added in about 4 minutes, or at the rate of 400 lbs. per minute and the apparatus adjusted to discharge the aluminum at this rate. The apparatus is arranged so its discharge end is about 2 feet from the path of the molten metal flowing from the pouring spout of the furnace; and the apparatus also is connected to a plant air line supplying air at about 100 psi. The furnace is tapped; about one minute after tapping the apparatus is operated to initiate discharge of aluminum shot into the stream of molten steel freely falling from the furnace spout into the ladle. The apparatus is operated for four minutes and discharges aluminum shot at the rate of 400 lbs. per minute into the stream of molten metal freely falling from the furnace spout into the ladle. The injection of aluminum is then stopped before the slag is drained from the furnace onto the metal in the ladle.

In such process the particles of aluminum, lower in density than the steel, are projected into and well below the unconfined surface of the freely falling stream 5 of molten metal at a location where the metal is considerably hotter than it subsequently is in the ladle, and where the particles 8 cannot be defl cted or otherwise impeded in their access to and penetration into the metal. The complete penetration of the particles for a substantial distance into this exceptionally hot metal causes them to melt more rapidly than would otherwise be the case, while they are protected by this surrounding molten metal from the ambient air. Depending on the size of material of the particles, melting may be largely or even cornpletely achieved before the metal in the stream enters the mass of molten metal in the ladle.

The aluminum is thoroughly and uniformly distributed in the molten metal, both while in particle form and after melting. In the preferred form described above the particles are added throughout substantially the entire duration of the flowing stream at a rate that supplies to each increment of metal in the stream substantially the amount of aluminum that is required for that increment. Thus, the particles are distributed throughout the metal flowing in the stream, and also these relatively small increments of molten metal containing submerged particles or droplets of addition material are dropped into and thoroughly mixed with the large body of molten material in the ladle. While it is preferred to add aluminum to the stream at a rate commensurate with the flow of molten metal in the stream, in many instances satisfactory results can be obtained if the aluminum is added at a higher rate for a shorter time, in which case, the apparatus is operated for less than substantially the entire duration of flow of the stream of metal. Under these circumstances, thorough dispersion and distribution of the addition agent material are promoted by the turbulence of the liquid molten metal, which arises from several causes, such as turbulance of the liquid metal in stream 5 itself caused by a discharge of the metal from the furnace and pouring spouts; turbulence imparted by impingement of the particles on the metal in stream 5; and the great turbulence arising when the metal in stream 5 plunges into and agitates the metal in the ladle.

For the above and other reasons, aluminum or other addition agents thus added to the molten steel according to the present invention can be thoroughly distributed throughout the body of molten steel in the ladle in an extremely finely divided condition and with a high degree of uniformity, so that molecular dispersion is approached. The finely dispersed aluminum reacts with the iron oxides and with dissolved or combined oxygen in the steel to deoxidize the steel effectively and uniformly; if added in sufiicient quantity it also performs alloying or grain size control functions effectively and with a high degree of uniformity. Furthermore, the extremely finely dispersed aluminum performs the deoxidizing, alloying or other functions before it can collect in a film on the surface of the steel, where it could be wasted by reaction with air or slag; and in its finely dis- W persed state it cannot chill the steel or form harmful concentrations or inclusions of metallic aluminum or aluminum oxide. Degradation or scrap loss due to improper deoxidation arising from improper amounts and poor dispersion of addition agents are greatly reduced if not entirely eliminated for these reason.

Furthermore, since the invention makes possible the reproducible, accurate introduction of a precisely controllable predetermined amount of addition agent into a small volume stream of molten steel at an accurately controllable period in the pouring cycle, it is possible to obtain reproducible results from heat to heat. Consequent- 1y a great deal of guess work which has heretofore been necessary in steelmaking can be completely eliminated and the quality of steel from heat to heat can be improved aud rendered more uniform.

For these reasons, required amounts of addition agents can be reduced by as much as 75%, which is particularly important in cases where large amounts of relatively expensive addition agents are ordinarily required.

FIGURES 7 to 10 inclusive illustrate a different apparatus embodying the invention as employed to cap steel by another method embodying the invention. The apparatus of the invention generally indicated by reference numeral 7]. stands on a pouring platform 72. Several ingot molds 73 are arranged in a row along the platform in the conventional manner. A ladle 74 successively pours a stream 75 of molten steel to fill the molds according to common practice. The apparatus 71 (sometimes referred to as a gun hereafter) is shown as discharging particles 8 of metallic aluminum onto the upper portion of the molten steel 76 in the third filled ingot mold 73 after that being filled by the ladle, to cap the steel.

The gun 71, as shown in FIGURE 8, comprises a supply hopper 77 open to the atmosphere at its upper end, and adapted to contain a desired quantity of aluminum particles 8. The hopper is supported by a frame 78 mounted on wheels 7? and having handles 81 for guiding and positioning the apparatus. The frame also supports a propelling portion generally indicated by reference numeral 82 and communicating with the lower end of the hopper; the rear end of the propelling portion 82 is connected to a hose 83 supplying air at a suitable pressure such as about 100 psi. and controlled by valve 84, and the other end is rigidly connected to a barrel portion 85. At its discharge end, the barrel portion 85 carries a direction changing member 86 which causes the aluminum particles to be discharged downwardly from the gun in a fan shaped stream into the top of the ingot molds.

The propelling portion 82 of the gun 71 is shown in longitudinal section in FIGURE 9. In certain respects it is identical to the propelling portion 17 of the gun I of the previous embodiment, and identical parts therefore bear the same reference characters in both embodiments. The propelling portion 82 comprises a tubular body member 34 with .a substantially cylindrical internal passage 35, in which is slidably mounted a nozzle 36 having a bore 37 substantially smaller than passage 35 and communicating with air supply hose 83. As is preferable, nozzle 36 is adjustable axially of body member 34 so that the discharge end 38 of the nozzle can be moved across the lower end or part of the feed passage 87 extending upwardly through the tubular feed conduit 88 into the bottom of the hopper 77, so that the passage 87 can be partially or completely closed against the flow of particles from hopper 77 into passage 35 of body 34. As in the previous embodiment, the rear portion of nozzle 36 has an externally projecting circumferential flange 39 and removable collar 41 held in place by set screws 42. There is a surrounding rotatable adjusting member 44 having at its rear end an inwardly projecting flange 43 disposed between flange 39 and collar 41 of the nozzle member, an intermediate longitudinally extending bore 45, and a rigidly mounted front portion 46 having internal threads 47 which engage external threads 48 on the body portion 34. A hand wheel 49 makes possible manual rotation of member 44 to move it and nozzle member 36 axially of member 34 by engagement of the threads 47 with threads 4-8. Thus, the discharge end 38 of nozzle 36 can be moved from the completely open position shown in full lines in FIGURE 9 to the completely closed position shown in broken lines in such figure, or to any intermediate position, to control the flow of particles from hopper 77. As in the previous embodiment, an indicating pointer 50 on the feed conduit 87 cooper-ates with marks 51 on the exterior member 44- to indicate the position of the nozzle member.

The walls of the bore 37 at the discharge end 38 of the nozzle 36 taper inwardly as shown at 52 to define an outlet orifice 53 of a cross section substantially smaller than that of bore 37 and much smaller than that of passage 35 into which it discharges. Therefore, in the immediate vicinity of the discharge portion 38, the propellant air or other fluid under pressure traveling through passage 37 substantially increases in velocity as it passes through the small orifice 53 and through the larger passage 35 of body member 34, and travels in an expanding stream which has a relatively small cross section area in the vicinity of the orifice 53 and increases in cross section as the distance of the orifice increases and the velocity of the stream decreases. The pressure in the zone surrounding the stream is substantially lower than elsewhere, so that the flow of particles 8 of aluminum from the passage 87 into the passage 35 is promoted. As in the previous embodiment, this arrangement of parts greatly increases the weight of particles which can be entrained into the air stream and discharged from the barrel 85; increases in the rate of discharge of more than 200% have been obtained by the use of such restricted orifice without other changes.

The quantity of particles which can be drawn into and discharged from the gun is also greatly increased by the means identified by reference numeral 90 for removing a portion of the propellant fluid at a location between the feed conduit 87 and the discharge end of the barrel portion 85. The illustrated means 90 is a tubular member formed of two frustoconical portions joined together at their larger ends, that at one end of the member 90 being connected to the barrel portion 85 and that .at the other end forming part of the propelling portion 82. In the conical portion nearest the feed passage 87 there are several elongated air passages 91 extending transversely of the longitudinal direction of the gun barrel. The passages .a-re narrow enough to prevent the escape of the aluminum shot through them; however, the total area of the passages is great enough to permit removal of a substantial proportion of the air passing through the impelling portion of the gun. Surprisingly by use of such means, the rate at which the material can be discharged by the apparatus is very greatly increased. Tests have shown that the air removal means 90 increases the flow of particles by as much as 100% by weight over that possible without such means.

Although the reasons for this result are not entirely understood, we believe that the capacity of a gun of the type contemplated by the invention, in the absence of this feature or the bypass conduit 55 of the previous embodiment, is limited by the gross volume of the m1xture of air and particles which can pass through the gun barrel. The means 90 permits the withdrawal or discharge of a substantial portion of the air from passage 35 after it has acted to entrain particles into the air stream and to impart substantial kinetic energy to the particles. The removal of such air thus provides space for an additional volume of particles to pass through the gun barrel and also reduces air resistance in the barrel. The location at which the air passages 91 communicate with the passage 35 preferably should be at a zone downstream from the orifice 53 in nozzle member 36 and from passage 87 where there is a superatmospheric pressure on the walls of passage 35 and where a substantial portion of the kinetic energy of the air has been trans fer-red to the particles. For a given installation and size of parts, the optimum location of the member and the air passages 91 can be readily determined by experiment. While, as indicated above, the restricted orifice portion and the air removal means 90 each individually greatly increases the output of the gun over that possible without such feature, it has been found, surprisingly, that both these features in combination increase the output of the particles discharged from the gun much more than the mere aggregative effects of these features, so that very large amounts of particles can discharge within a relatively short time. Moreover, the particles can be discharged at both high and low rates without clogging of the gun.

The particular conformation of the air removal means 90 shown in FIGURE 9 is advantageous since it provides a space of an enlarged cross section into which the air can expand and reduce in velocity before discharging through openings 91, and since it makes possible the location of openings 91 in the portion of the frustoconical Wall which expands in the direction of flow so that they are not directly exposed to the particles 8 traveling through the means 90. Consequently, the openings 91 will not be clogged by the particles, or provide passages for the escape of particles. The expansion of the air and the reduction in velocity in member 90 promotes the removal of a substantial portion of the air, with consequent increase in the space available for particles.

Other types of and configurations of air removal means are possible. For example, beneficial results can be obtained even if there is no enlarged cross section, but the cross section throughout the air removal zone is uniform. The openings corresponding to air pasages 91 can be differently arranged, or even of different shapes than shown, if desired.

FIGURE 10 shows a type of direction-changing member 86 which may be advantageously employed on the end of the gun barrel to discharge aluminum particles downwardly for ingot capping purposes. The member comprises a rear portion 92 adapted to be mounted on the discharge end of the gun and having a passage communicating with the slotted discharge opening 93 at the lower forward edge of the member 86. Opening 93 is shaped to discharge a fan-shaped stream of particles of aluminum from the gun.

By gun 71 it is possible rapidly and accurately to introduce aluminum particles into the top layer of a body of molten metal in an ingot mold, with only one or two passes of the discharge end of the gun. The particles are uniformly distributed and penetrate completely into the steel so that they effectively cap the entire surface of the molten metal and promote the formation of the desired solidified ingot structure. Moreover, the method is much less wasteful of aluminum than those heretofore employed, since the aluminum is accurately deposited where needed with no dropping on the pouring floor or into the space around the ingot mold. The apparatus and the process also make possible increased safety since it is not necessary that a workman closely approach the molten metal in the ingot mold.

In a typical operation embodying the invention, the apparatus is used to cap each ingot of a row of ingot molds being filled from a ladle, as shown in FIGURE 7. Most advantageously, in each case the third ingot mold after that being filled by the ladle is capped, since this provides sufficient time for the turbulent rimming action to commence and progress to the desired degree before the steel is capped and the action is modified by addition of aluminum. It is possible to cap the molten metal in a typical 15 ton ingot mold with 15 pounds of aluminum distributed across the unconfined surface of the molten metal at the top of the mold by one pass of the discharge end of the gun 71 during 6 or 7 seconds. The capping is effective and reproducible to provide desired ingot structures with considerable savings in time, labor and aluminum.

It is apparent from the above that the present invention provides method and apparatus which overcomes the grave problems inherent in prior methods and apparatus for introducing addition agents into or onto a molten melt such as molten metal. Required amounts of agents are reduced by as much as 75%, and addition agents may be introduced in a manner and by means causing a high degree of dispersion and uniformity of reaction or combination with the metal, even though the addition agent such as aluminum has a lower density than the material of the melt, with consequent improvement in the structure, in uniformity of composition, and in the quality of the solidified metal.

The methods of the invention and the forms of apparatus which may be employed in carrying out the methods make possible reproducible results in the introduction of addition agents in the manufacture of steel or other similar materials requiring the use of addition agents, since they provide for the introduction of accurately controlled or metered amounts of addition agents over an accurately determined period of time under conditions which provide highly uniform dispersion of the addition agents into or onto the molten metal. Guess work is eliminated, waste of addition agents is eliminated, quality and uniformity of composition are increased, and degradation of metal and scrap losses are greatly reduced.

The apparatus is simple and substantially foolproof in construction and can be made to withstand the hard usage to which it will be subjected in steel mills and other plants handling molten metals.

While the invention has been discussed in connection with the addition of aluminum to steel, it is apparent that it may be employed in the introduction of other addition agents, either alone or in a mixture, into steel or other molten materials. Examples of such other addition agents are lime, calcium carbide, various types of finely divided alloying metals, etc.

The term finely divided as used in the claims is intended to include particles ranging in size from a small fraction of an inch to approximately an inch or more, to include the sizes of addition agent particles commonly used in metallurgical industries.

Although the invention has been described in connection with the introduction of addition agents into steel poured from an open hearth furnace, it may be employed to introduce addition agents into steel emanating from other types of heating equipment for producing molten steel, such as oxygen convertor equipment or electric furnaces; and the term furnace in the claims is intended to cover such equipment.

A propelling proportion like that of FIGURE 9 may be employed in the gun 1, while the propelling portion similar to that shown in FIGURE may be employed in gun 71. Although each gun illustrated as embodying the invention has been disclosed as carried by groundsupported wheels, it may be supported in other matters, as from an overhead hoist. Guns embodying the invention may be used for other purposes than those disclosed, and methods embodying the invention may be carried out by means other than the disclosed guns.

It is to be noted that modifications other than those indicated above may be made to both the methods and apparatus described above as illustrative of the invention. The essential characteristics of the invention are set forth in the appended claims.

We claim:

1. A process of supplying to molten metal an additive of a density less than that of the metal, comprising causing the molten metal to flow in a freely falling, essentially solid stream into a receptacle and to impinge therein with substantial turbulence, propelling by air under pressure a substantially continuous stream of solid particles of additive having a minimum dimension of essentially inch into said freely falling stream of molten metal at a velocity sufficient to cause the particles to penetrate below the surface of the molten metal in said stream and so that substantially all propelled particles are captured by the metal in said freely falling stream, and controlling the rate and duration of said propelling of said particles to cause substantially the amount of additive required to produce the desired reaction in the total amount of molten metal discharged during the duration of flow of said stream of molten metal to penetrate said stream of molten metal and be carried along therewith.

2. The process of claim 1 in which said propelling of said particles of additive is continued substantially throughout the entire duration of flow of said freely falling essentially solid stream of molten metal, and the rate at which said additive particles are propelled with respect to the rate of flow of molten metal in said freely falling stream is controlled to cause substantially the amount of additive required to produce the desired reaction in each increment of molten metal in said freely falling stream to penetrate each such increment and be carried along therewith.

3. The process of claim 2 in which said molten metal is steel and said additive is aluminum.

4. The process of claim 1 in which said molten metal is steel and said additive is aluminum.

5. The process of introducing into the top layer of an amorphous body of molten metal in a mold an additive of a density less than that of the metal, comprising filling the mold with molten metal and thereafter propelling by air under pressure a stream of solid particles of additive having a minimum dimension of essentially /8 inch in a downward path from a location above said molten metal at a velocity sufficient to cause said particles to penetrate below the surface of and completely into said molten metal, while moving said downwardly directed stream of particles laterally across the top layer of molten metal in said mold to introduce said particles of additive over substantially the entire area of the top layer of molten metal in said mold.

6. The process of introducing particles of finely divided aluminum into molten steel in an ingot mold for capping purposes, comprising filling the mold with an amorphous body of molten steel, permitting rimming action to occur in the steel for a predetermined period of time, and propelling by air under pressure a fan-shaped stream of finely divided particles of aluminum having a minimum dimension of essentially A; inch in a downward path from a location above said molten steel at a velocity sufiicient to cause particles to penetrate below the surface of and completely into molten steel, while moving said downwardly directed stream of particles across the top layer of the molten steel in said ingot mold to introduce said particles of aluminum over substantially the entire area of said top layer of molten steel in said ingot mold.

References Cited by the Examiner UNITED STATES PATENTS 1,590,730 6/1926 Evans 22-215 1,814,584 7/1931 Bost et al. 22-215 2,108,254 2/1938 Devaney 22-215 2,803,533 8/1957 Bieniosek et al. -53 2,805,147 9/1957 Schreiber 75-53 2,819,503 1/1958 Boucek 22-215 2,869,857 1/1959 Kopke et al. 266-34 2,872,180 2/1959 Tietig et al. 266-34 3,089,767 5/ 1963 Rhinesch 22-215 3,141,767 7/1964 Funk 22-215 FOREIGN PATENTS 622,419 5/1949 Great Britain.

796,369 6/ 1958 Great Britain.

799,943 8/ 8 Great Britain.

MARCUS U. LYONS, Primary Examiner.

DAVID L. RECK, MICHAEL V. BRINDISI. WILLIAM J. STEPHENSON, Examiners.

Claims

1. A PROCESS OF SUPPLYING TO MOLTEN METAL AN ADDITIVE OF A DENSITY LESS THAN THAT OF THE METAL, COMPRISING CAUSING THE MOLTEN METAL TO FLOW IN A FREELY FALLING, ESSENTIALLY SOLID STREAM INTO A RECEPTACLE AND TO IMPINGE THEREIN WITH SUBSTANTIAL TURBULENCE, PROPELLING BY AIR UNDER PRESSURE A SUBSTANTIALLY CONTINUOUS STREAM OF SOLID PARTICLES OF ADDITIVE HAVING A MINIMUM DEMENSION OF ESSENTIALLY 1/8 INCH INTO SAID FREELY FALLING STREAM OF MOLTEN METAL AT A VELOCITY SUFFICIENT TO CAUSE THE PARTICLES TO PENETRATE BELOW THE SURFACE OF THE MOLTEN METAL IN SAID STREAM AND SO THAT SUBSTANTIALLY ALL PROPELLED PARTICLES ARE CAPTURED BY THE METAL IN SAID FREELY FALLING STREAM, AND CONTROLLING THE RATE AND DURATION OF SAID PROPELLING OF SAID PARTICLES TO CAUSE SUBSTANTIALLY THE AMOUNT OF ADDITIVE REQUIRED TO PRODUCE THE DESIRED REACTION IN THE TOTAL AMOUNT OF MOLTEN METAL DISCHARGED DURING THE DURATION OF FLOW OF SAID STREAM OF MOLTEN METAL TO PENETRATE SAID STREAM OF MOLTEN METAL AND BE CARRIED ALONG THEREWITH.