US3146288A - Apparatus for vacuum treatment of molten metal - Google Patents

Description

Aug. 25, 1964 J. B. GERO APPARATUS FOR VACUUM TREATMENT OF MOLTEN METAL Filed Jan. 5, 1961 4 Sheets-Sheet 2 J. B. GERO Aug. 25, 1964 APPARATUS FOR VACUUM TREATMENT OF MOLTEN METAL 4 Sheets-Sheet 3 Filed Jan. 5, 1961 Aug. 25, 1964 J. B. GERO 3,146,288

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United States Patent 3,146,288 APPARATUS FOR VACUUM TREATMENT OF MGLTEN METAL John B. Gero, lVlauchester-hy-the-Sea, Mass, assignor to Gero Metallurgical (Iorporation, Boston, Mass, a corporation of Delaware Filed Jan. 5, 1961, Ser. No. 80,901 2 Claims. (Cl. 266-34) This invention relates in general to vacuum processing of molten metal and more particularly to improved techniques and apparatus for degassing molten metal as it flows from a pouring ladle into a desired mold, ladle, or other receptacle. The invention is especially concerned with treatment of relatively large tonnages of carbon steel and other alloy steels in connection with which a suitable degassing vacuum may lie in a range of gauge readings of from 1,000 microns up to 2,000 microns. The term degassing as herein employed throughout the specification, is intended to refer to removal of gases such as oxygen, hydrogen, and nitrogen.

Molten steel, as produced by an electric furnace, open hearth, and other well-known processes, is characterized by the presence of gases such as oxygen, hydrogen and nitrogen. These gases tend to cause oxidized impurities and defects, as well as hydrogen embrittlement in the solidified metal produced. Various attempts have been made to cope with this problem and a number of vacuum treating devices have been developed. All of the devices, so far as I am aware, are lacking in satisfactory performance characteristics since they are expensive to build and difficult to operate. Such limitations tend to restrict the quantity of steel produced, and add to the cost of manufacture.

Having in mind, as one chief objective, the need in the steel industry for an economical, as well as a more efficient method and apparatus for degassing molten steel by vacuum treatment, I have conceived of a unique principle of continuous vacuumizing in which the vacuum treatment is carried out with respect to molten steel as it is transferred from a pouring ladle into another receptacle of a desired type. The pouring ladle may be conveniently comprised by conventional ladle structures commonly employed in steel mills.

My novel concept may be embodied in any one 'of a number of arrangements of scaled enclosure bodies which are combined with a pouring ladle. These several arrangements all operate on a new degassing principle based on the use of a vacuum chamber which is closed at one side by a liquid sealing body. This liquid sealing body is produced and maintained by the continuous introduction of molten metal into a vacuum chamber while simultaneously removing degassed metal.

An important feature of the invention is a relatively large capacity vacuum treatment technique for carbon and other alloy steel wherein conventional pouring ladle equipment is combined with vacuum chamber and vacuum pouring equipment in a unique manner. By means of the principles of the invention expensive vacuum casting equipment may be largely eliminated and replaced by a simplified system in which conventional pouring ladles may be advantageously utilized, with savings in labor and time being realized.

The nature of the invention and its other objects and novel features will be more fully understood and appreciated from the following description of preferred embodiments of the invention selected for purposes of illustration and shown in the accompanying drawings, in which:

FIG. 1 is an elevational view of one form of apparatus of the invention illustrating a pouring ladle and a degassing 3,145,288 Patented Aug. 25, 1964 apparatus which includes a stationary vacuum pump and vacuum chamber;

FIG. 2 is a side elevational view of another form of degassing apparatus somewhat similar to the apparatus of FIG. 1, but illustrating an arrangement in which a lowering ladle is used to collect degassed metal;

FIG. 3 is a side elevational view of still another arrangement of degassing apparatus wherein a travelling vacuum chamber and vacuum pump is combined with a travelling pouring ladle;

FIG. 4 is a perspective view illustrating in further de tail the mobility feature of the structure shown in FIG. 3; and

FIG. 5 is a detail cross sectional view of part of FIG. 3.

In carrying out the vacuum treatment of the invention, I have found that I may desire to employ several different forms of apparatus depending upon the particular conditions and requirements which are present in the steel mill where the degassing operation is to occur. Thus FIG. 1 illustrates one simplified form of degassing apparatus whereby degassed metal may be discharged into a pouring ladle. FIG. 2 illustrates another arrangement in which degassed metal is collected in a ladle suspended from the carrying hooks of an overhead crane and conveyor. FIG. 3 illustrates a somewhat different arrangement by means of which degassed metal may be poured into moulds which are movable along a railway.

Considering first the apparatus illustrated in FIG. 1, I provide a pouring ladle L1 which is of conventional nature being formed with a bottom outlet nozzle which is adapted to be closed by a stopper rod 4 controlled through an operating lever l and a linkage 2 of well-known character.

In accordance with the invention, I construct the bottom of the ladle L1 with a special sealing flange 8 securely welded to provide an airtight circumferential joint. To the flange 8 I attach a cylindrical enclosure body 10 which constitutes a vacuum chamber and which is designed with a matching flange 14 and a sealing ring 16. If desired, 1 may also employ a watercooling element 15 to maintain the flange 14 in a cooled state when molten metal is in the ladle L1 during "the degassing cycle.

The vacuum chamber 10 is supported in some conventional manner as by means of a horizontal arm 54 secured to a frame 55, and furnished with an airtight sight port 12. Immediately below the sight port 12 and communicating with the vacuum chamber 10 is a vacuum manifold 18, a flexible connection 13, a valve 11, and a vacuum pump 11a.

Vacuum chamber 10 is fitted with a rigid bottom or partition 10a completely sealed around its outer circumferential edge. Vertically disposed through the partition 10a is a conical conduit 20 which is welded, or otherwise secured, in sealed relation to the partition in a position to receive molten metal from nozzle 6. The conduit 20 is lined with a refractory material 22 and I may also desire to employ induction or resistant heating elements as 26. The lower end of conduit 20 is preferably formed with an open restricted cylindrical section 24 which projects downwardly for a short distance below the partition 10a.

Immediately below the cylinder section 24 is provided a receptacle 30 supported on suspension rods 56 attached to structural member 54, for example. The receptacle 30 surrounds the lower end of the part 24 and is lined with refractory 32 and fitted with a bottom pour nozzle 38.

I also provide a stopper rod 34 and an operating lever and linkage 36. Directly below the receptacle 30 I fur-' ther locate some suitable means of containing degassed metal such as, for example, a ladle member L2 supported on a car 50, movable along a railway 52. 1

In operation,*metal of a suitable type is tapped from an Q electric arc melting furnace or open hearth melting furnace into the ladle L1, while the latter member is supported on hooks carried by a pit crane of conventional nature.

The filled ladle L1 is then transferred by the pit crane into a position such as that illustrated in FIG. 1 wherein the flanged portion 8 of the ladle L1 is registered with the flange portion 14 of the enclosure body 10. These matching flanges are then tightly secured together in sealed relationship.

The stopper head 4 is then raised by an operator standing on a platform in close proximity to the casting apparatus. As soon as the stopper head is raised by means of handle 1, and linkage 2, molten metal starts to flow through the nozzle 6 into the chamber 10 and also in conduit 20 which conducts metal into the receptacle 36. The receptacle 30 is closed by means of the stopper head 37 at this time. In a short period of a few seconds the molten metal rises to a level in the receptacle 30 which is above the lower end of the conduit member 24 and thus there is formed a liquid sealing body around this conduit member. The seal completely excludes the vacuum chamber 10 and the conduit 20 from atmospheric pressure. At this point the valve 11 is opened with the vacuum pump 11a operating, and within a few seconds all air is evacuated from the members 10 and 20.

As the pressure in members 10 and 20 is decreased, atmospheric pressure, acting on the exposed surface of molten metal in the receptacle 30, forces this molten metal back up into the conical conduit until a ferrostatic head of metal is produced as illustrated by the levels H1 and H2. The theoretical height of molten steel, which an atmosphere of pressure will support, is known to be approximately 6 inches when compared with 29.9 inches of mercury.

As soon as the liquid sealing body B is formed in the receptacle 30, the operator raises the stopper 37 by linkage 36, and degassed metal is removed from the sealing body B. It will be apparent that by controlling the rate of flow of metal from the member 30, through the nozzle 38, in accordance with the rate of flow of metal into the vacuum chamber 10, there may be continuously maintained a suitable level H1 for holding the sealing body B in a fully effective sealing state. Thus that side of the vacuum chamber through which degassed metal is re moved is, at all times, maintained in a tightly sealed condition, as long as the two movements of molten metal are continued.

It will be observed that by means of the arrangement described, an exceedingly inexpensive vacuum apparatus is provided in comparison with standard types of vacuum equipment and moreover, there may be utilized conventional ladle equipment usually available in the steel foundary.

It is pointed out that the conical conduit 20 is formed with an enlarged opening at the top thereof which facilitates the operation of collecting disbursed metal as such metal falls from the ladle L1. Also, the exposed surface area of collected molten metal is maintained relatively large for the vacuum to act thereon after the metal has dropped through the vacuum chamber space. I find that a stream of metal leaving the nozzle 6 and entering the high vacuum chamber disintegrates violently in a manner corresponding to an explosion with particles being thrown outwardly to an angle of 90120 of arc.

It will also be observed that the lower end 24, of the conduit 20, tends to induce a more rapid movement of molten metal through this part of the conduit and minimizes heat loss and the chance of freezing and also reduces the volume of metal which is present in the conduit 20, so that a lesser volume of metal is required to start the vacuum operation and, therefore, a smaller quantity of molten metal which has not been degassed, enters into the well 30.

In FIG. 2, I illustrate another form of apparatus for carrying out the principle of employing a liquid sealing body to seal one side of a vacuum chamber, while molten metal is being continuously removed therefrom. Referring in detail to FIG. 2, 56 denotes a structural member horizontally supported in a foundry wall section at some convenient point and adapted to support thereon a ladle L3. The ladle L3 is positioned on the structural member by means of a ladle crane. The ladle L3 is fitted with a nozzle 6', and an operating handle 1, and linkage 2' for raising and lowering a stopper rod 4.

At the bottom of the ladle L3 is provided a large diameter flange 8' and a vacuum tight sight port 12 is fitted into the ladle flange 8'. Immediately below ladle L3, in sealed relation therewith, is a vacuum chamber 10', the upper portion of which is fitted with a large diameter steel flange 14. A sealing ring 16 is tightly secured between the flanges to provide an airtight joint. The gasket flange may be water-cooled by a member 15'. Communicating with the vacuum chamber 10' is a vacuum conduit 18' leading to a vacuum pump 11a and controlled by a valve 11.

The bottom of the vacuum chamber 10' is closed by means of a horizontal partition 10d which is sealed at its outer circumferential edge and which has vertically supported therein a conical conduit 20, the upper end of which is arranged to receive metal from the nozzle 6'. The lower portion of the conical conduit 20' projects downwardly and terminates in a restricted lower extremity 24. A refractory lining 22' is employed and may include heating units as 26'.

Supported immediately below the restricted lower extremity 24 of the conduit 20, is another ladle member L4 which is closed by a stopper member and operating linkage of the class already described and which may, for example, be adjustably supported on crane hooks H. The ladle L4 surrounds the conduit 20 in a position such that it may support a sealing body of molten metal B extending upwardly around the restricted end 24'.

In operation molten metal M is tapped from a suitable source of supply into the ladle L3. The ladle L3 is then transported by a conventional crane to the position shown in FIG. 2 where the ladle L3 is supported on the structural member 56 already described. The vacuum chamber 10 and conical conduit 20, are then secured through the matching flange portions and thereafter the ladle L4 is positioned by means of a ladle crane immediately below the conical conduit 20'.

When ladle L4 has been located in the position shown in FIG. 2, the stopper head 4, of ladle L3, is raised through the linkage 2' and metal M flows through the nozzle 6' into chamber 10' and conical conduit 20, finally reaching the ladle L4. In a very short interval the metal body B in ladle L4 will rise above the lower extremity 24' of the conical member. When the metal level reaches a point H1, the flow of metal from ladle L3 is stopped by lower stopper rod 4, valve 11 is opened with the vacuum pump operating and vacuum chamber 10 and conduit 20' are evacuated in a few seconds. As chamber 10' and conduit 20' are evacuated, atmospheric pressure on the metal in ladle L4 forces this metal back up into the conical conduit and the metal level H1 drops into the position shown in FIG. 2, and the level in the conduit is represented by the level line H2. These levels represent the manner in which a liquid seal is established to hold the vacuum in the system described above.

Once the vacuum has been established in chamber 10 the stopper head 4 is raised and metal M flows through nozzle 6 and into vacuum chamber 10'. On entering the evacuated chamber, the stream of molten metal now disintegrates into a rain of metal droplets due to the release of gases. A refractory sleeve 60 may, if desired, be used to minimize the scatter of droplets from nozzle 6. This in turn prevents the particles of falling metal from eroding the refractory 22 and also prevents the solidification of metal droplets at the upper end of the refractory 22.

The disintegrated and degassed metal is collected by the conical conduit 20' and flows slowly downward filling ladle L4. The position of the metal levels H1 and H2 in the ladle L4 and conical chamber 20', will change slowly as ladle L4 receives metal from ladle L3. To compensate for this ladle L4 is lowered slowly by the ladle crane while supported on the hooks 58. Alloy additions may be made to the degassed metal in ladles L3 and L4. When ladle L4 has become filled it may be transferred to a pouring platform and the molten metal discharged into ingot moulds.

It will be observed that in this arrangement both of the ladle members are open to atmospheric pressure and yet a flow of metal is vacuumized or degassed with one side of the vacuum chamber being sealed by a liquid sealing body from which metal is drawn for moulding purposes. This form of moulding apparatus differs essentially from the apparatus of FIG. 1 in that an intermediate receptacle is not employed.

In FIGS. 3 and 4, I have illustrated still another form of apparatus in which a receptacle is employed, but unlike the arrangement of FIG. 1, the receptacle is formed as an integral part of the vacuum chamber structure. Referring more in detail to FIG. 3, I provide a bottom pour ladle L5 which is adapted to be suspended on crane hooks 80. The ladle L5 is provided with a stopper member 4" operated through a linkage 2" which closes the opening through a discharge nozzle 6".

Welded to the bottom of the ladle L5 around the nozzle 6", is a flange 16". Attached to the flanged portion of the ladle through a matching flange section 14" is a vacuum chamber 10" which may be provided with a sight port 12" and heating member 15". Communicating with the vacuum chamber is a vacuum connection 18" having a flexible coupling 13" joined to a valve section V in turn connected to a vacuum pump 60". The valve 11" regulates the opening through which gas is removed by the vacuum pump 60".

The vacuum chamber 10 is formed with a receptacle or bottom section 90 separated from the upper section by means of a horizontal partition 82 through which is vertically supported a conical conduit 20' having a re stricted bottom end 24". The bottom section and upper section of the vacuum chamber are joined together by mating flanges 28, 28 and a sealing member 28". The conical conduit 20" and its bottom 24" may, if desired, be provided with a heating means 26. The lower portion extends into the bottom section of the vacuum chamber, as shown in FIG. 3. The receptacle or bottom section 90 is fitted with a removable stopper rod linkage 93, removable vacuum cover 85, bleeder valve 99, sight port 91, and sealing sleeve 95. Nozzle 96 is sealed with fusible disc 97. When metal is to be released the vacuum pump evacuates the chamber 10 and metal released from the ladle 5 is degassed in this chamber and then passes through the conduit 20" and collects as a liquid sealing body B" around the bottom of the restricted tubular section 24" in the receptacle 90. After the degassed liquid seal is formed, air is bled into evacuated receptacle 90 through valve 99. Vacuum cover 85 is removed and stopper rod linkage 93 is connected. Metal is released through nozzle 96 by raising stopper rod 94. Fusible disc 97 is melted through the fully degassed metal and enters mold 98.

An important feature of this arrangement is means for moving the vacuum pump and tubular connecting means together with the ladle L5 and its attached vacuum chamber as a unit along a pouring platform so that molten metal may be released into moulds supported on a railway extending beside the pouring platform.

In accordance with this form of the invention, I provide for successive pourings into moulds 98, 100, 102 and 104 as suggested in FIG. 4. This is accomplished by suspending the hooks 80 from a travelling crane 106 which is arranged to move along rails 108 and 110. Also 6 mounted for travel along rails and 112 is a vacuum pump holder 114. By means of this arrangement the crane operator moves the pouring ladle into position over a mould 98 which is mounted on a car 116. At a desired point a workman stands on the platform 118 and operates the linkage 92.

With respect to this arrangement of FIGS. 3 and 4 wherein the pouring ladle is combined with the vacuum chamber and vacuum pump as a unit, it is pointed out that the initial metal released for the ladle is thoroughly degassed since the reservoir is an integral part of the vacuum chamber. Thus I am able to pour uniformly treated metal from beginning to end of the cycle and the uniformly treated metal may be discharged into any desired mould.

From the foregoing description it will be observed that I have devised an improved method and apparatus for degassing molten metals whereby susbtantial improvements in efficiency and quality are realized with savings in labor costs.

The various forms of the invention disclosed are representative of varying forms of the invention included within the scope of the appended claims.

I claim:

1. An apparatus for vacuum treatment of molten metal comprising a ladle, a valve in the bottom portion of said ladle for regulating the rate of discharge of molten metal from said ladle, a housing including a side wall and a bottom wall, said side wall being in sealed association at its top portion with the discharge portion of said ladle and positioned to receive the flow of molten metal there from, means connected to the housing above its bottom wall for applying a vacuum to said housing, a conduit having a conical upper portion extending upwardly into said housing and in sealed association with the bottom wall thereof, the upper conical portion of said conduit positioned in alignment with the path of travel of the molten metal discharged from said ladle for conducting the molten metal from the vacuum housing whereby the metal discharged from said ladle is subjected to vacuum prior to entrance into said conduit, a receptacle open to atmospheric pressure enclosing the lower end of said conduit, said lower end of said conduit terminating at a point sufliciently below the top of said receptacle whereby the metal discharged through said conduit will accumulate in said receptacle and form a liquid seal for said conduit, a valve in the bottom portion of said receptacle for regulating the discharge of molten metal from the bottom portion of said receptacle at a rate substantially the same as the regulated rate of discharge of metal from said ladle to maintain the accumulation of molten metal therein to prevent release of the vacuum in said housing through said conduit, said valves permitting continuous flow of metal from said ladle through said housing and into and out of said receptacle.

2. An apparatus for vacuum treatment of molten metal comprising a ladle, a valve in the bottom portion of said ladle for regulating the rate of discharge of molten metal from said ladle, a housing including a side wall having its upper marginal portion fixed to and in sealed association with the discharge portion of said ladle and positioned to receive the flow of metal therefrom, said housing having a bottom wall and an intermediate partition defining upper and lower sealed chambers, said lower chamber defining a receptacle, means connected to said upper chamber for applying a vacuum thereto, a conduit having a conical upper portion extending upwardly through said 'p artition into said upper chamber and in sealed association with said partition, the upper conical portion of said conduit being positioned in alignment with the path of molten metal discharged from said ladle for conducting the molten metal from the upper chamber, the lower end of said conduit terminating at a point spaced sufliciently below the top of the receptacle whereby the metal discharged through the conduit will accumulate in said receptacle and form a liquid seal for said conduit, a valve in the bottom portion of said receptacle for regulating the discharge of metal from the bottom portion of said receptacle at a rate substantially the same as the regulated rate of discharge of metal from said ladle to maintain the accumulation of molten metal therein to prevent release of the vacuum in said upper chamber through said conduit, said valves permitting continuous flow of metal from said ladle through said upper chamber and into and out of said receptacle, and a valve in the top of the receptacle for admitting atmospheric air therein.

References Cited in the file of this patent UNITED STATES PATENTS Seidel Aug. 22, 1933 Summey Nov. 10, 1936 Southern Feb. 14, 1956 Ulrech et a1. Mar. 11, 1958 Rice Feb. 7, 1961 Hornak et al Dec. 19, 1961 Bigge Feb. 6, 1962 FOREIGN PATENTS Great Britain Sept. 17, 1958

Claims (1)

1. AN APPARATUS FOR VACUUM TREATMENT OF MOLTEN METAL COMPRISING A LADLE, A VALVE IN THE BOTTOM PORTION OF SAID LADLE FOR REGULATING THE RATE OF DISCHARGE OF MOLTEN METAL FROM SAID LADLE, A HOUSING INCLUDING A SIDE WALL AND A BOTTOM WALL, SAID SIDE WALL BEING IN SEALED ASSOCIATION AT ITS TOP PORTION WITH THE DISCHARGE PORTION OF SAID LADLE AND POSITIONED TO RECEIVE THE FLOW OF MOLTEN METAL THEREFROM, MEANS CONNECTED TO THE HOUSING ABOVE ITS BOTTOM WALL FOR APPLYING A VACUUM TO SAID HOUSING, A CONDUIT HAVING A CONICAL UPPER PORTION EXTENDING UPWARDLY INTO SAID HOUSING AND IN SEALED ASSOCIATION WITH THE BOTTOM WALL THEREOF, THE UPPER CONICAL PORTION OF SAID CONDUIT POSITIONED IN ALIGNMENT WITH THE PATH OF TRAVEL OF THE MOLTEN METAL DISCHARGED FROM SAID LADLE FOR CONDUCTING THE MOLTEN METAL FROM THE VACUUM HOUSING WHEREBY THE METAL DISCHARGED FROM SAID LADLE IS SUBJECTED TO VACUUM PRIOR TO ENTRANCE INTO SAID CONDUIT, A RECEPTACLE OPEN TO ATMOSPHERIC PRESSURE ENCLOSING THE LOWER END OF SAID CONDUIT, SAID LOWER END OF SAID CONDUIT TERMINATING AT A POINT SUFFICIENTLY BELOW THE TOP OF SAID RECEPTACLE WHEREBY THE METAL DISCHARGED THROUGH SAID CONDUIT WILL ACCUMULATE IN SAID RECEPTACLE AND FORM A LIQUID SEAL FOR SAID CONDUIT, A VALVE IN THE BOTTOM PORTION OF SAID RECEPTACLE FOR REGULATING THE DISCHARGE OF MOLTEN METAL FROM THE BOTTOM PORTION OF SAID RECEPTACLE AT A RATE SUBSTANTIALLY THE SAME AS THE REGULATED RATE OF DISCHARGE OF METAL FROM SAID LADLE TO MAINTAIN THE ACCUMULATION OF MOLTEN METAL THEREIN TO PREVENT RELEASE OF THE VACUUM IN SAID HOUSING THROUGH SAID CONDUIT, SAI VALVES PERMITTING CONTINUOUS

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