US2677609A - Method and apparatus for metallurgical alloy additions - Google Patents

Description

l Mayil, 1954 w. H. MOORE E-r AL 2,677,609

METHOD AND APPARATUS FOR METLLURGICAL. ALLOY ADDITIONS Filed Aug. 15, 195o 2 sheets-sheet 1 I N VEN TORS WILL/AM H MOORE WALTER IM SMITH May 4, 1954 w. H. MOORE l-:TAL

METHOD AND APPARATUS F'OR METALLURGICAL ALLOY ADDITIONS Filed Aug. 15, 195o 2 Sheets-Sheet 2 INVENTORS WILL/AM H. MOORE 8 WALTER W SMITH Patented May 4, 1954 METHOD AND APPARATUS FOR METAL- LURGICAL ALLOY ADDITIONS William H. Moore, Larchmont, N. Y., and Walter W. Smith, New Philadelphia, Ghio, assignors to Meehanite Metal Corporation, a corporation of Tennessee Application August 15, 1950, Serial No. 179,488

4 Claims. i

This invention relates generally to the production of nodular cast iron, but relates specically to improved methods and apparatus for the introduction of highly volatile and explosive additives to molten metal of all types and for all purposes.

At the outset, is is to be understood that there are various mechanical means known which are used to stir pots or ladles of molten metal for various purposes, including the mixing of alloying agents, and that apparatus is available for mixing additives into molten metal by taking advantage of natural laws. The latter devices include production of a vortex over an escape opening and dropping powdered alloying metal at the vortex, and another method comprises pouring molten metal and the alloying metal into a reduced-area passageway leading to the bottom of a ladle. By the last method the alloying metal is carried to the bottom of a pool or" molten metal and is distributed as it tends to rise.

In the production of nodular cast iron, and in other metallurgical processes, highly volatile and explosive additives are useful to produce improved properties in castings. However, the commercial production of metals alloyed with such explosive and volatile agents has been seriously hampered, because the amounts of the volatile and explosive additives must be quite large in commercial operations. When such large additions are attempted by the methods, and with the equipment, known and used heretofore, serious loss of alloy, incomplete incorporation, and explosions are encountered. On a laboratory scale, of course, experiments can be readily carried on to learn what additives would be desirable, and no real problems arise because of the very small amount of volatile and explosive additive used. When full-scale production is at tempted, however, quite serious problems are encountered.

Specifically, it is common practice to add volatile materials directly to a ladle of iron for the purpose of purification of the cast iron, with subsequent improvement of graphite structure in physical properties. The addition of volatile materials such as magnesium or alloys of magnesium, is accompanied by intense burning and the evolution of gaseous products under pressure. Because these materials ignite at the temperature of molten cast iron, the instantaneous addition of a quantity of magnesium or similar volatile and inflammable material to the ladle of metal is extremely dangerous. It is not uncommon for the addition to be accompanied by an 2 explosion and by the evolution of a tremendous quantity of heat.

Furthermore, since the materials are volatile their addition to the surface of a ladle of metal does not allow intimate Contact with the whole body of metal, and therefore it is practically impossible to completely control the eifect of the addition. For example, a laboratory experiment may determine that a particular given percentage of magnesium or magnesium alloy is beneficial for improving the properties of a cast iron. The amount necessary for addition to a ladle iilled with such cast iron can be calculated and an additional amount added to make up the usual losses to be expected, and that calculated amount oi the additive is then thrown into a ladle. If the operator is fortunate enough to get the additive below the surface of the iron before it completely volatilizes and burns, nevertheless, he may not be able to distribute the additives evenly throughout the metal by simply stirring the entire ladle. Further, although alloying additive practice may frequently be theoretically discussed, a practical point often overlooked is that molten iron will rapidly cool as long as it is in a ladle, and therefore the time available for adding the alloying additive to a ladle of molten metal is extremely limited if the casting to be made is poured before the cast iron becomes too cold for maximum desirable properties.

Therefore, an object of this invention is to provide an improved method of incorporating volatile and explosive agents into molten metal.

Another object of this invention is to provide a commercial method and apparatus for mechanically controlling the feeding of meta-carbide stabilizing agents to a stream of molten iron coordinated with the now rate of the iron, without loss of temperature, in order that the iron will be hot and castings may be poured from the molten metal after the metal has been treated.

Anotherobject of this invention is to provide a coordinated alloying system including a controlled stream of molten metal to be treated, addition oi alloy in relation to the rate of molten metal flow, and mechanical stirring in timed relationship to both metal flow and alloy addition.

Still another object of this invention is to provide apparatus for producing a stream of molten metal flowing at a regulated rate, with means to add alloying agents at a selected point in the stream, and mechanical stirring means immediately downstream therefrom, to secure complete control over the incorporation oi the alloy into the molten metal.

Another object of this invention is to provide a trough for forming a stream of molten metal iiowing at a regulated rate, and providing for continual movement of dross and slag through said trough.

Another object of this invention is to produce a stream of molten cast iron and add volatile and explosive alloying agents at a rate relative to the rate of flow of the cast iron, thereby reducing the mass of alloying additive entering the molten iron at a given time to a minimum, and yet fully incorporating the alloy into the iron before the iron can cool below good casting temperature.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

Figure l is a front-elevational view of a cupola, with an incorporator, made according to the teaching of this invention, placed to receive a flow of molten metal from the cupola tap hole;

Figure 2 is a perspective view of a portion of the incorporator illustrating the trough and overflow construction, together with the revolving paddle, and the bottom drain control rod, which are further features of this embodiment of the invention; and

Figure 3 is an enlarged longitudinal sectional View through the incorporator, with a `corner of the cupola illustrated in section to show the position of the tap hole withrespect to the trough of the incorporator.

The mechanical apparatus illustrated in the drawings has been developed to carry out the principles of this invention. The apparatus may be called an incorporator, and is either mobile for use with a plurality of separate cupola furnaces, or may be statonarily mounted with respect to one particular cupola.

The illustrated incorporator comprises generally a trough I I extending to the tap hole 21 of a cupola i. The trough II provides a gentle slope from the tap hole 2 to a sump I2. Referring to the Figure l of the drawings, it will be seen that the incorporator is narrow with respect to its length, and therefore the sump I2 provides a long and narrow confinement for the flow of the molten metal. sump provides a confinement in order to produce a stream of the molten metal of appreciable depth. A discharge port 28 opens through the bottom of the sump I2 at the end thereof opposite from the trough II.

A suitable shield I3 extends upwardly above the sump E2 and is covered by a hood I5 suitably exhausted by a stack or fan. Thus, flames and fumes emitted from the molten metal within the sump I3 will be led upward into the hood I5 and will thus be discharged without contaminating the air of the room. Also, the shield I2 provides an expansion area to allow any dangerously large explosion and extremely high heat emission to be exerted upwardly away from the 1 workman within the room.

A funnel 25 of any suitable form is provided at the upstream side of the shield I3, and is fed by a feed pipe 26. Alloying agents and other additives may be supplied through the feed pipe 26 by any suitable mechanical devices now available, and the alloying agents will be directed to the surface of metal within the sump I2 by the funnel 25.

Downstream from the funnel 25, a ,paddle l1,

In other words, the

preferably having openings I8 therethrough, is provided to extend into sump I2 and stir the owing metal within the sump I2, and a plug rod I9 is provided to extend into the discharge port 28 and control the rate of flow of metal from the sump I2 into a suitable ladle.

In order to make the incorporator as practical and efficient as possible, the upper portion of the shield I3 is indented as illustrated best in the Figure 3, and thereby forms a support for a motor carriage I4. The motor carriage I4 may be made of metal in such a manner as to provide a framework to support an electric motor 23 with a gearbox 24 thereon. A stir rod I3 extends from the gearbox 24 downwardly to the sump I2, and the paddle Il is secured on the end thereof by any suitable means, but is preferably secured by a removable means, such, for example, as the set screw 34, in order that the paddle I'I may be removable and allow the rod I6 to be pulled up through the shield I3.

The motor carriage I4 is also fitted to support a pneumatic cylinder 20, sometimes referred to as a servomotor, to operate the plug rod I9. The plug rod I9 extends through the shield I3 and into the discharge port 28. The rod I9 is tapered and is smaller than opening 23 at the end, but fully as large rearwardly of the end, and therefore will close the outlet 28 to any selected degree. The pneumatic cylinder 20 is serviced by air lines 2i and 22 which extend around the outside of the shield I3, to a valve located on the outside of the shield I3 just above the trough II. Also, a switch is provided at the same location to control the electric motor 23. Thus, the operator of this improved device may stand in such a position that he can View the flow of metal from the tap hole 21, and the height of the molten metal stream within the sump I2, and then operate the pneumatic cylinder 20 to open or restrict the discharge port 28, or order the tap hole 2'1 opened or closed, in order to maintain the stream within the sump I2 at the desired level. Further, if desired, a system of electrical controls, operated by contact with the molten metal, could be used to maintain a desired level.

The incorporator is entirely lined with a heavy coating of refractory, as illustrated, and like all metallurgical equipment requires constant observation to determine the state of repair of the refractory lining. Therefore, an inspection door 32 is provided on the side of the incorporator, and a clean-out door 33 is also provided in order to provide a large opening when repairs and cleaning are necessary. Only the inspection door 32 need be opened for most minor repairs and inspections, but the entire opening can be provided by the door 32 and the door 33 whenever major repairs and clean-out are necessary.

Figure 2 of the drawings illustrates the overflow discharge feature of the invention which eliminates the accumulation of dross or slag.

Dress and slag accumulation difficulties have heretofore made the operation of a continuous flow additive process impractical. Glass, for example, has been treated in a continuously flowing stream to incorporate coloring matter and other types of additives to the glass. An attempt to employ this glass process to molten iron was unsatisfactory because the dross and slag accumulates in the trough and eventually the trough becomes plugged with a solid mass of the high melting point foreign matter. v

This invention features an overflow dam 29 in the side wall of the trough II. The dam 2l has a height at the proper level to which the. molten metal is desired to be maintained within the trough. An overow box 3@ is attached to the side of the trough il to catch molten material ilowing over the 29. An outlet 3l in the bottom of the box 3@ directs the molten material into a ladle placed below the box til. The box 323 in effect is a funnel;

With this apparatus the plug rod I9 is inserted into the discharge port 2t until the port 28 is completely closed. The molten material will then fill the trough il to the height of the dam 29. The molten material, as it flows through the trough I l and over the dam 29, will lloat the dross and slag over the top of the dam and out of the trough l I, with substantially no accumulation within the trough. The plug I? may be withdrawn slightly during the flow of metal in the trough to allow simultaneous discharge of clean metal from the bottom of the trough through the port 28 along with the discharge of the metal through the outlet 3l. However, whether or not the port 28 is used for withdrawing metal during the flow of metal, it is used at the end of the now of metal to drain the remaining metal from the trough li below the level of the dam 29.

The illustrated preferred embodiment of the apparatus may be used to carry out the new process developed for incorporating volatile and explosive additives to molten metal with the minimum of loss and danger, coupled with the maximum incorporation of the alloy into the molten metal. By regulating the rate of flow of a metal stream under a point where the additive alloy material is added at a predetermined rate, the intensity of the addition may always be kept below the danger point. By incorporating a mechanical stirring device in the metal stream at a point immediately following the addition point, it is possible to secure complete control of the incorporation of the alloy into the molten metal.

In the operation of the apparatus to carry out the new process, the molten metal is allowed to flow from the cupola furnace in the conventional manner, and a pool of metal is allowed to form in the sump l2 by having the rod i9 in its lower position to substantially close the port 28. In this closed position, the port 2t will deliver the molten metal at a rate from one to ten times slower than the cupola tap hole 2lI will supply it, and therefore the level of metal in the sump l2 will gradually rise. Preferably, the molten metal should be restricted until the level within the sump l2 is substantiallyv as high as illustrated in Figure 3 of the drawings.

The alloy material is introduced through the funnel 25 at the additive point to the surface of the ilowing stream and it moves into the path. of the revolving paddle il. The paddle Il is preferably adapted to revolve at a speed substantially between 5 and 500 R. P. M., and is provided with openings which tend to cut through the metal and cause a turbulence for thorough mixing. When using a paddle, the best speed of revolution may be determined by considering the volume between the paddle blades. Then volume multiplied by speed of revolution equals pounds per minute of stream flow.

From the foregoing description, it will be seen that the rate of metal flow, rate of addition of agents, and rate of stirring, are all closely interrelated and are not independent. The flow of metal from the furnace may be the controlling factor, or with many Volatile and explosive additions the safe and useful additive rate will control.

By the processes of this invention volatile and explosive additives may be successfully added to molten metal because the amount of additive supplied to the molten metal in a given period of time is reduced to an extremely low value, and therefore the explosive and volatile nature of the additive is reduced to a useful minimum. In other words, the molten metal is conducted in a stream which is deep enough to permit thorough agitation for mixing the additive into the molten metal, but the amount of molten metal and volatile additive coming into contact at one instantaneous period of time is considerably less than by the method of adding the entire amount of alloy to a ladle containing a full body of the molten metal.

By adjusting the rate of flow of the metal from the cupola furnace and through the sump l2, and by simultaneously adjusting the rate of addition of the alloying agents, and also simultaneously controlling the rate of stirring by the paddle Il, it has been found that the addition can be made conveniently with complete success and very little loss of the additive material.

As an example, it has been found that the rate of flow of the molten metal from the cupola furnace may be between 300 pounds per minute and 4000 pounds per minute, but it is preferable to keep the flow rate between 500 and 1500 pounds per minute. Also, the rate of flow 0f the alloying additive may be varied between l pound and pounds per minute, but it is preferably kept between 5 and 45 pounds per minute, depending upon the severity of action of the additive material when applied to the molten metal.

Many metallurgical compositions have been developed for the production of nodular and other types of iron, as well as producing various types of alloys, and cleansing various types of alloys. These processes and products are well known and need no extensive elaboration to explain the value of the invention disclosed herein, but probably the most outstanding example of explosive alloying material is the addition of magnesium to molten cast iron for the purpose of producing nodular cast iron. Magnesium, of course, will ignite at the temperature of molten iron, and will tend to lloat on the top of the molten iron and thus prevent incorporation of the magnesium. Furthermore, even if a quantity of magnesium were plunged below the surface of a ladle of molten iron, the` high volatile nature of the material at the temperature of the molten iron will prevent thorough mixing and distribution of the alloy without considerable stirring to circulate the molten iron throughout the ladle. Of course, it is entirely possible to stir the ladle of molten iron for a suitable period of time to incorporate the magnesium thoroughly, but attempts to carry out such a procedure on a commercial scale have been extremely disappointing, because after the ladle of metal has been stirred to assure the thorough distribution of the magnesium, it has always been found that the ladle of metal has cooled to such an extent that successful castings cannot be poured from the ladle. Therefore, it is of no value to assure complete alloy distribution only to und that the resulting product is useless. The process and apparatus of this invention provide a complete incorporation of the volatile and explosive alloy, and at the same time assure the delivery of the properly alloyed molten metal at a temperature which will permit successful casting.

On the other hand, many alloy materials, a1-

though not highly volatile and explosive; areof extremelgr high melting point. Others `resistfeven distribution throughout lthe body of 'the molten metal without thorough mixing. Ferromolybdenum vand ferrochromium -aretwo examples fof high meltingpoint alloys, and 'sodium carbonate, sodium silicate and graphite are examples of additives which must he thoroughly stirred intothe molten loody to effect proper contact. "Theaddition -of small amounts of these materials 'to 'the moving stream, followed immediately'by thorough agitation, will-assure complete incorporation fof thea-dditive into the molten body.

Although my invention `has been described in its preferred form Witha certain degree o'f particularity, it is understood that the present disclosure of the preferred form has-been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts maylbe resorted to without departing from the spirit and the -scope of the invention as hereinafter claimed.

What is claimed is:

1. Apparatus for the introduction of additives to molten metal as the metal'is removed'from a furnace comprising, a longitudinal trough having an'entrance end and an exit end, saidtrough having a small cross sectionalar'ea with respect to the length thereof, means for introducing molten metal into said entrance end '0f said trough, a spillway outlet from said exit end of said trough, saidtrough having a continual slope to said spillway outlet, said spillway outletbeing at a selected height above the bottom'of said trough to `provide escape of metal and slag from the top of the stream, bottom escape port means in said exit vend of said trough, variable valve means to provide 'a regulated escape of uid from the said port as slag lspills over the spillway outlet, said spilway outlet and bottom escape port providing substantially continual escape of metal and slag separately from said trough and a constant predetermined depth Within the trough, means for adding material at a given station to a stream of molten metal passing through said trough, and means for agitating said stream at a downstream point from said station.

2. Apparatus for the introduction of additives to molten metal as the metal is removed from a furnace comprising, a longitudinal trough having an entrance end and an exit end, said trough having a small cross sectional area with respect to the length thereof, means for introducing molten metal into said entrance end of said trough, spill- Way outlet means providing controlled continual escape of metal and slag from the surface of the metal stream, bottom escape port means below said outlet means, variable valve means to provide a regulated escape of fluid from said `port means as metal and slag spills over the spillway outlet,

8, said spillway-outlet and bottom escape port means providing substantially continual escape of metal and'slag' over-the spillway maintaining a constant predetermined depth oi molten metal therein and preventing'the accumulation of slag, means for adding material at a'given station to the stream of molten metal passing through said trough, and means for agitating said stream at a downstream point'from said-station.

3. 'Apparatus for the introduction of additives to molten metal as the metal is removed from a furnace 'comprisinga longitudinal trough having an entrance end and an exit end, said trough having 1a small cross sectional area with respect to the length' thereof, means for providing a constant discharge of varying iloivfrom the surface of the molten metal invsaid trough, bottom escape port meansin saidtrough, `variable valve means to provide aregulated escape of uid from the saidport as metal and slag are discharged from the surface'o'ithe-molten metal in the trough, the depth and rate of the molten metal through the trough thereby y.loeing Aconstant, and accurately controllable, lwhereby additives may be introduced at a rate based upon the rate of flow of the molten metal past a point and avoid over-concentration and improper distribution of additive material.

4. The processor incorporating additive material to a 'molten metal comprising, providing a channel mixing trough having a small cross sectional area with respect to the length thereof, introducing untreated molten metal into a rst end of said trough at a first rate to form a stream, introducing slag forming additive material to the surface of the stream at an additive point downstream from the said rst end of the trough and at a rate related to the rate of molten metal flowing past the said additive point, allowing the iiow of molten metal to carry the additive material down-stream away from said additive point, permitting the slag and some molten metal to escape said trough from the surface of said stream at a second end of the trough and at a second rate, regulating said first and second rates to maintain a pre-determined depth of molten metal stream and rate of ilow through said channel, and skimming the slag from the surface of the stream.

VReferences Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,169,270 Langguth Jan. 25, 1916 1,635,414 Hirst July 12, 1927 1,863,686 Corsalli June 21, 1932 1,942,202 Cohn Jan. 2, 1934 2,060,177 Clamer Nov. 1), 1936 2,115,408 Brosse Apr. 26, 1938 l2,355,885 Merle Aug. 15, '1944 l2,519,593 Oienhauer Aug. 22, 1950

Claims (1)

1. 4. THE PROCESS OF INCORPORATING ADDITIVE MATERIAL TO A MOLTEN METAL COMPRISING, PROVIDING A CHANNEL MIXING TROUGH HAVING A SMALL CROSS SECTIONAL AREA WITH RESPECT TO THE LENGTH THEREOF, INTRODUCING UNTREATED MOLTEN METAL INTO A FIRST END OF SAID TROUGH AT A FIRST RATE TO FORM A STREAM, INTRODUCING SLAG FORMING ADDITIVE MATERIAL TO THE SURFACE OF THE STREAM AT AN ADDITIVE POINT DOWNSTREAM FROM THE SAID FIRST END OF THE TROUGH AND AT A RATE RELATED TO THE RATE OF MOLTEN METAL FLOWING PAST OF SAID ADDITIVE POINT, ALLOWING THE FLOW OF MOLTEN METAL TO CARRY THE ADDITIVE MATERIAL DOWN-STREAM AWAY FROM SAID ADDITIVE POINT, PERMITTING THE SLAG AND SOME MOLTEN METAL TO ESCAPE SAID TROUGH FROM THE SURFACE OF SAID STREAM AT A SECOND END OF THE TROUGH AND AT A SECOND RATE, REGULATING SAID FIRST AND SECOND RATES TO MAINTAIN A PRE-DETERMINED DEPTH OF MOLTEN METAL STREAM AND RATE OF FLOW THROGH SAID CHANNEL, AND SKIMMING THE SLAG FROM THE SURFACE OF THE STREAM.

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