US2251303A - Treating molten metal - Google Patents

Description

Aug 5, 1941 E. B STORY ET AL TREATING MOLTEN METAL Filed Jah. 24, 1940 INVENTOR 5 Edward B. Story @flfrederick W VWzite l atented Aug. 5, 1941 UNITED STATES PATENT OFFICE TREATING MOLTEN METAL Edward B. Story, Bethel Township, Allegheny County, and Frederick W. White, New Brighton, Pa., assignors to A. M. Byers Company, Pittsburgh, Pa., a corporation of Pennsylvania Application January 24, 1940, Serial No. 315,298

11 Claims. (Cl. 7560) done by tilting the converter and pouring the refined metal out into a receiving ladle.

Ever since the commercialization of the Bessemer process of refining molten ferrous metal the-formation of so-called kidneys in the converter has provided a vexing problem. These are accretions which build up on the converter lining at the sides of the converter. They are composed primarily of slag and during repeated sible to tilt the converter rapidly during the first part of the discharging operation as, if this were done, the stream of molten metal would overshoot the receiving ladle. The receiving ladle must of course be positioned so that at the end of the discharging operation the dregs will flow into the receiving ladle when the converter is turned almost upside down. This imposes a limitation on the position of the receiving ladle necessitating the relatively slow pouring in the early portion of the discharging operation.

We provide for greatly speeding up the rate of discharge of the refined molten metal from a Bessemer converter by making provision for receiving the metal as'discharged from the con verter so that the metal can be discharged faster than if the same were discharged in the ordinary way into the. ordinary stationary receiving operations of the converter such accretions not only grow larger andlarger but also become very hard and difilcult to remove. Various attempts to obviate kidney formation have heretofore been made but without much success. r

We have discovered that kidney formation may be controlled to a large extent by the speed of discharging the refined molten metal from the converter. We have found that when a converter is discharged relatively 'rapidly the tendency toward kidney formation is greatly reduced and ladle. Such provision may be made in various difierent ways. We prefer to use a standard receiving ladle and to move the same toward the converter during discharging of the metal therefrom and relatively to the stream of discharged metal. We prefer at the beginning of the discharging operation to position the receiving receptacle at a point remote from the converter relatively to the point at which the receiving ladle is normally positioned when the metal is to be discharged from the converter'into a'stationary ladle. Thus the stream of molten metal issuing from the converter at the beginning of l the discharging "operation strikes the receiving it the speed of discharge of the contentsof the converter is sufliciently increased, kidneys will form not at all or only to a negligible extent.

Thestandard practice in discharging the re- I fined metal from a Bessemer converter is to tilt the converter and pour the refined molten metal into a stationary ladle. Such ladle naturally is of such size and design as conveniently to receive the discharged contents. of theconverter. It is necessary, in discharging a converter into such a stationary receiving ladle, to

tilt the converter very slowly during the first part of the discharging operation to avoid overshooting the ladle. As the ladle is ordinarily positioned the'stream of molten metal being discharged by the converter initially strikes the wall of the ladle most remote from the converter and near the rim of the ladle. As the converter is tilted further the stream of metal issuing therefrom continues to strike against such wall of the receiving ladle and the result is rapid deterioration of the receiving ladle and also undesirable spattering of the metal. It isimposreceptacle at a point nearer the converter than the point at which such stream strikes the re-' ceiving ladle when the converter is discharged into a stationary ladle positioned'in the usual manner. As a result the converter can be tilted much more rapidly than when its contents are being discharged into a stationary'receiving ladle. Preferably the receivingreceptacle is positioned so that upon quite rapid tilting of the converter to begin the discharging operation the stream of molten refined metal strikes the receiving receptac'le substantially at its bottom. Rapid tilting of the converter is continued and simultaneously therewith as the discharging operation progresses the. receiving receptacle is ,moved" toward the converter, such movement preferably being controlled so that during at least the greater portion of the discharging operation the stream of molten metal issuing from the converter strikes the receiving receptacle on its bottom I rather than on its sides. The movement of the receiving receptacle may be so controlled that substantially throughout the discharging operathe center of the bottom of such receptacle.

Thus the speed of discharging of the contents of the converter may be greatly increased. Moreover, the life of the receiving receptacle is likewise increased as the wall of such receptacle remote from the converter is not subjected to the impingement of the stream of molten metal during the early part of the discharging operation as when the converter is discharged into a stationary receiving ladle. Still further, undesirable spattering of the metal is reduced to a minimum as a cushioning pool of metal is almost immediately formed in the bottom of the receiving receptacle at the beginning of the discharging operation nto which the stream passes tion the stream is directed approximately toward and which serves t prevent the following molten metal from striking against the solid metal of the receiving receptacle and spattering as a result.

.By the provision above described the size and fixed positioning of the receiving receptacle cease to be the factors limiting the speed at which converters can be discharged. With a ladle of standard size for a converter of given capacity the converter can be tilted as rapidly as is mechanically possible so far as the question of receiving the stream of molten metal therefrom in the ladle is concerned, and the factor which limits the speed of tilting of the converter and, consequently, the speed of discharging of its contents is the ebullience of the molten metal in'the receiving receptacle. There is a certain churning of the metal due to the physical action of the entering stream and there is also a tendency of the metal to boil and emit gases. When the provision above described is employed the converter may be tilted asrapidly as desired, the speed of tilting being limited only by the tendency of the metal to overflow the receiving receptacle during the discharging operation.

By the provision above described we can discharge the contents of a converter in less than half the time required to discharge the same quantity of molten metal from the same converter into an ordinary stationary receiving ladle. While the time required to discharge the con tents of a converter varies somewhat depending upon the character of the metal and physical factors relating to the discharging thereof from the converter and receiving thereof in the receiving ladle, we. have enabled the discharging of approximately twelve tcns of refined metal from a converter whose actual capacity is but little greater than twelve tons in a period ranging between one and twominutes whereas this same operation previously required three minutes or more. A pouring time of one minute represents very rapid pouring indeed, while a pouring time of two minutes represents considerably more rapid pouring than was previously possible and sumciently rapid for our purposes. aware it was not previously possible under conditions comparable to those which we have met to completely discharge the contents of a Bessemer converter in a period as short as two minutes. This applies not only to converters of'about the size above mentioned but to converters of-all sizes when considered in relation to the problems involved in their discharge. Of .course a-relatively large converter has a relatively large ladle to receive its contents and a relatively small converter has arelatively small ladle to receive its contents and the pouring time with converters of different sizes does not vary greatly. l

So far as we are The temperature of the metal being discharged from the converter is also a factor to be taken into consideration. Molten ferrous metal as discharged from a Bessemer converter may range in temperature from about 2950 F. to about 3400 F. We have found that when the temperature of the metal being discharged from the converter is above about 3200 F. the tendency to form kidneys is so slight as to be negligible for all practical purposes, even when the metal is discharged from the converter at ordinary speed and into an ordinary stationary receiving ladle. When, however, the temperature of the metal being discharged from the converter is below about 3200 F. the tendency to form kidneys is substantial when the converter is discharged in the ordinary manner. Consequently it is with metal at temperatures not substantially greater than 3200 F. that we are primarily concerned.

It is diificult to determine the .theory of action underlying our invention and we shall not attempt to state any exact theory. We at present believe that the tendency toward kidney formation arises by reason of the fact that when the refined molten metal is being discharged from the converter slag formed during the refining.

process, being lighter than the metal, lies on top of the metal and as the converter is tilted to discharge the metal the layer of slag atop the metal seems to cling at its edges to the converter lining. As the converter continues to tilt the slag continues to cling to the sides of the converter lining and the metal flows out therebeneath. Of course some slag also flows out with the metal, but a substantial portion of the slag clings to the lining and this is what builds up kidneys. Apparently when the refined molten metal in the converter is at relatively high temperatureas we have determined, above about 3200 F.the slag thereon is relatively fluid and in any event it does not seem to have the same tendency to cling to the converter lining as when the metal is cooler. With the cooler metal, however, we find that increase in the rate of discharging the contents of the converter eliminates or at least greatly reduces kidney formation. We believe that this is because the more rapid discharging of the contents of the converter results in carrying of the slag with the metal so that the slag passes out along with the metal instead of clinging to the converter lining and forming large kidneys; apparently the clinging tendency of the slag is overcome.

Various types of apparatus may be employed for carrying out the invention. As above mentioned, we prefer to employ a standard ladle and wepreferably mount the ladle so that during the discharging operation it can be moved relatively to the converter and generally toward the converter in the plane described by the stream of molten metal being discharged. The accompanying drawing shows one form of apparatus,

I which may be employed.

- Other details, objects and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof and'a present-preferred method of practicing the same proceeds.

' tional'view of a converter and a ladle for receiving the refined contents of the converter, the conmencement of the discharge of the refined molten 4 metal from the converter; and

Figure 2 is a view similar to Figure 1 in which the converter and the receiving ladle are shown in the positions they respectively occupy at about the end of the discharge of the refined molten metal from the converter.

Referring now more particularly to the drawing, there is shown a Bessemer converter 2 which may be of standard construction. The converter is mounted for the usual pivotal movement in a vertical plane about trunnions 3 which are rotatably mounted in bearings 4 carried by pedestals 5. It is provided with the usual tuyeres and other accessories (no shown). The particular converter shown is one Whose nominal capacity is twelve tons of molten ferrous metal and whose actual capacity is somewhat greater.

A ladle 6 is provided for receiving the refined molten metal from the converter 2 at the end of the bessemerizing operation. The ladle 6 maybe of standard size and shape for use with a twelve-ton converter. The capacity of the ladle is great enough that it will receive an entire heat of refined molten metal from the converter. The ladle 6 has at each side projecting supporting member 11 whereby, the ladle is adapted to be supported in a cradle 8 having recesses Qshaped and positioned to receive the supporting members l of the ladle. The ladle also has lifting trunnions l and handling eyes H. I

The cradle Bis mounted upon a car l2. Carried atop the car l2 and mounted for rotation are rollers l3. The cradle 8 carries inclined slides l4, one adapted to cooperate with each of the rollers I3. Each of the slides I 4 is adapted to ride upon the corresponding roller l3 In Figure-1 the converter 2 and ladle 6- are in the positions which they respectively occupy at the beginning of the discharge of the refined molten metal from the converter. The angle of tilt of the converter is such that the refined metal is just about to begin to flow over the converter lip l5. At such time, as shown in Figure 1, the ladle 6 is disposed at its position'most remote from the converter in the horizontal direction. The ladle is moved toward the left viewing the drawing in any suitable manner, as, for example, by a cable connected with the left-hand end of the cradle 8 and with any suitable source of power (not shown) which draws the cradle toward the left. This causes the. slides M to ride up On the respective rollers l3 as is clearly apparent from the drawing. As the converter is tilted in the counterclockwise direction during the discharging operation the cradle is allowed to return gradually to the right viewing the drawing until at the end of the discharging operation it is at its extreme right-hand position verter, there refining the metal and bringing it asshown in Figure 2. Movement of the cradle 3 and ladle 6 toward the right is accomplished by gravity due to the inclination of the slides M. Thus unless the cradle is positively moved or held toward the left it will assume the right-hand position shown in Figure 2.

The converter is shown in Figure 2 in its extreme discharging position and it assumes this position when the last of the heat'of refined molten metal is being discharged into the ladle. The converter positions shown in the drawing are only approximate and depend upon various factors, including primarily the size of the charge on the particular heat being discharged. By properly manipulating the ladle B in the manner above explained the converter can be discharged very rapidly,- the speed of tilting of the converter being limited only by the tendency of the metal to boil up and overflow theladle during the discharging operation.

While we have shown and described a present preferred embodiment of the invention and a present preferred method of practicing the same, it is to be distinctly understood that th invention is not limited thereto but maybe otherwise variously embodied and practiced within the scope of the following claims.

We claim: 7

1. A method of treating molten ferrous metal comprising introducing the same into a converter, there refining the metal and bringing it to a final temperature not substantially greater than about 3200 F., moving a receiving receptacle toward the converter during discharging of the metal therefrom and relatively to the stream of discharged metal so that the metal can'be discharged faster than would otherwise be possible and discharging the metal from the converter at such a speed as to eliminate or greatly reduce the building up of accretions commonly termed "kidneysf in the converter.

2. A method of discharging from a converter molten ferrous metal at a temperature not substantially greater than about 3200 F. comprising moving a receiving receptacle toward the con-- verter during discharging of the metal therefrom and relatively to the stream of discharged metal greatly reduce the building up of accretions comm'only termed kidneys in the converter.

'4. A method of treating molten ferrous metal comprising introducing the same into a conto a final temperature not substantially greater than about 3200 F., moving a receiving recep tacle toward the converter during discharging of the metal therefrom and'relatively to the stream of discharged metal so that the metal can be discharged faster than would otherwise be possible and discharging the metal from the converter in a period of time not substantially greater than about two minutes, whereby to eliminate or greatly reduce the building up of accretions commonly termed kidneys in the converter.

5. A method of discharging from a converter molten ferrous metal at a temperature not substantially reater than about 3200 F. comprising moving a receiving receptacle toward the converter during discharging of the metal therefrom and relatively tdthe stream of discharged metal so that the metal can be discharged faster than would otherwise be possible and discharging the receptacle toward the converter during discharging of the metal therefrom and relatively to the stream of discharged metal so that the metal can be discharged faster than would otherwise be possible and discharging the metal from the converter at such a speed as to eliminate or greatly reduce kidney formation.

7. A method of treating molten ferrous metal comprising introducing the same into a converter,

there refining the metal and bringing it to a final temperature such that if such refined molten metal were discharged, by tilting the converter,

into a receiving ladle of conventional shape and.

having a capacity of the order of the capacity of the converter accretions commonly termed kidneys" would be built up in the converter,

tilting the converter to discharge the metal therefrom, moving a receiving receptacle toward the converter during discharging of the metal therefrom and relatively to the stream of discharged metal so that the metal can be discharged faster than would otherwise be possible and discharging the metal from the converter at such a speed as to eliminate or greatly reduce kidney formation.

8. A method of discharging from a converte molten ferrous metal at such a temperature that if such metal were discharged, by tilting the converter, into a receiving ladle of conventional shape comprising tilting the converter to discharge the metal therefrom and discharging the metal from the converter in a period of time not substantially greater than about two minutes, whereby to eliminate or greatly reduce kidney formation.

9. A method of discharging from a converter molten ferrous metal at such a temperature that a substantial tendency exists to form in the converter accretions commonly termed kidneys" upon discharging the metal therefrom, comprising tilting the converter so rapidly as to discharge themetal therefrom at such a speed that kidney formation is eliminated or' greatly reduced.

10. A method of discharging from a converter molten ferrous metal at such a temperature that a substantial tendency exists to form in the converter accretions commonly termed kidneys upon discharging the metal therefrom, comprising moving a receiving receptacle toward the converter during discharging of the metal therefrom and relatively to the stream of discharged metal so that the metal can be discharged faster than would otherwise be possible and discharging the metal from the converter at such a speed as to eliminate or greatly reduce kidney formation.

11. A method of dischargingrfrom a converter molten ferrous metal at a temperature not substantially greater than about 3200 F. comprising discharging the metal from the converter at such a speed as to eliminate or greatly reduce the building up of accretions commonly termed kidneys in the converter.

EDWARD B. STORY, FREDERICK W. WHITE.

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