US3275432A

US3275432A - Oxygen steel making

Info

Publication number: US3275432A
Application number: US439497A
Authority: US
Inventors: Alexandrovsky George
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-02-23
Filing date: 1965-02-23
Publication date: 1966-09-27
Anticipated expiration: 1983-09-27

Description

Sept- 27, 1965 G. Al ExA1\|DRovsKY` 3,275,432

OXYGEN STEEL MAKING 2 Sheets-Sheet 1 Filed Feb. 23, 1965 OXYGEN STEEL MAKING Filed Feb. 23, 1965 2 Sheets-Sheet 2 INVENTOR. @C0/@af 4mm/@wmf 'jl .rl A IJ- BY WPW United States Patent O 3,275,432 OXYGEN STEEL MAKING George Alexandrovsky, Bradley St., Yonkers, N Y. Filed Feb. 23, 1965, Ser. No. 439,497 10 Claims. (Cl. 75--60) This invention relates to oxygen steel making processes and equipment, and is a continuation-in-part of Ser. No. 123,215, filed July 11, 1961, now abandoned.

The use of pure oxygen in pneumatic steel making processes has two purposes. The first is to exclude nonoxidizing gases, such as the nitrogen in air, because such gases absorb a large amount of the heat developed by the oxidizing reaction and carries this heat away from the reaction zone so that it is wasted. The second is to avoid the nitrogen pick-up by the metal which occurs in the older processes relying on air for oxidation of the impurities which must be removed. Therefore, the aim of oxygen steel making is to produce steel of high quality in a more economical manner.

However, prior art oxygen steel making processes all involve various disadvantages. One`is, of course, the high cost of oxygen as compared to air. In the case of the so-called L-D process a converter, as a container, does notv permit full use of the heat from the reaction, only pig iron of limited phosphorous content can be processed as a practica1 matter, and only a narrow range of steel grades can be produced. Although the L-D process widely replaces the less economical open hearth steel making process, it has natural limits for its application. These limits are caused by (1) limited dispersion of oxygen impact on the bath of metal, and (2) limited interaction between the metal and slag. In order to increase the dispersion of oxygen, lances with multiple nozzles are now utilized; however, the increase of interaction between the metal and slag is possible only by means of rotation of the bath as it is done in the so-called Kaldo and Rotor processes. Both the so-called Kaldo and Rotor processes have a higher heat eiciency and can handle pi-g iron having a wider range of phosphorous content, but the processing times are longer and there is a higher consumption of furnace lining refractories. In the latter two processes, dephosphorizing requires the formation of two or more diierent slags which each must be ushed for replacement by the next, and both processes involve the disadvantage that they require a rotating furnace, which requires expensive maintenance of its highly delicate rotating mechanisms. Furthermore, being necessarily rotary furnaces, only a single type of refractory can be used regardless of the well-known fact that it is preferable to use one type of refractory for confining the metal bath and another type in the chamber confining the -ga-ses above the bath. vOrdinarily it is desirable to use still another refractory type to confine the slag on top of the metal bath.

The objects of the present invention include the pro- Vision of a new oxygen steel making process which substantially overcomes the objectionable features of the prior art processes, which, in many instances, permit continuous operation, as a whole greatly reduces the oxygen cost, provides high heat eiiiciency and, further, the provision of simple, practical equipment without moving furnace parts for practicing this new process. Additionally in order to increase the interaction between metal and slag without the need of a rotary furnace, the objects include the vprocess of blowing on the surface of the metallic bath in a state of ow at an angle less than ninety degrees or of moving blowing lances in relation to a stationary bath at an angle less than ninety degrees. Other objects will become apparent when the invention and-its advantages are understood.

For the purpose of briefly summarizing the general ice nature of the present invention, attention is called to this inventors Patent No. 2,862,810, issued Dec. 2, 1958. There, this inventor discloses and claims a process and apparatus for reducing the silicon content and increasing the temperature of molten pig iron. This earlier invention provides a means for continuously treating a continuous flow of molten pig iron by the pneumatic process using air, as contrasted to pure oxygen, in such a manner as to greatly reduce the silicon content without substantially reducing the carbon content and without adding undesirable amounts of nitrogen to the metal. A partial reduction in the manganese and partial removal of sulphur is also eiected. In addition, the temperature of the metal is increased substantially by the oxidation of the silicon. The resulting metal, low in lsilicon and havin-g a high temperature, of course requires further processing to make it into steel.

Basically the present invention involves an improvement of the above-cited patent by adding a second passage of the high-temperature desilconized pig iron through a second apparatus substantially duplicating the patented apparatus, but in this instance blowing the metal with pure oxygen instead of air.

As explained in the mentioned patent, additional air is blown into the space above the metal and therefore the carbon monoxide produced by the reaction with the carbon of the oxygen in the lair injected into the bath, is burned substantially completely in this space before it leaves the apparatus. This also occurs when the carbon monoxide is formed by the reaction of the pure oxygen with the carbon in the bath. This space has the height and length required for the purpose of reducing the carbon monoxide content of the exhaust gases to about 10%, the balance being carbon dioxide. The result is enough heat to handle any ordinary steel makin-g situation, such as the addition of substantial amounts of scrap, ore, mill scale, lime and the like.

It can be objected that the replacement of oxygen by air in the first stage of the steel making would cause a loss of heat from the reaction zone comparatively to certain prior art processes using oxygen for the Whole steel making. However, the heat of reaction developed by burning one pound of carbon into carbon monoxide amounts only to 4230 B.t.u., and-to 5240 B.t.u. in the L-D process where 10% of carbon is burned into carbon dioxide.

On the contrary, one pound of carbon burned'fully into carbon dioxide develops 14,100 B.t.u. In the process according to the present invention the burning of carbon can achieve a content of carbon dioxide in the exhaust gases of nearly and the developed heat from burning one pound of carbon amounts to 12,700 B.t.u. Thus, by 12,700-524.0:7460 B.t.u. larger than in the L-D process for example. Y

However, using air instead of pure oxygen in the rst stage lof the present process a part of the developed heat in the rate of 3960 B.t.u. is carried out by nitrogen which accompanies oxygen in air. The resulting net gain of heat is 7460-3960:'3500 B.t.u. per pound of carbon, in comparison with the L-D process.

In the second stageofthe present process when oxygen is blown the net gain is still higher and amounts to 5230 B.t.u., therefore the total available heat is twice the heat available in the L-D process.

It is obvious that this excess of heat permits melting of more scrap, iron `ore or the like, to perform a formation of heat and time-requiring dephosphorizing slags and other heat absorbing operations.

The invention is disclosed in detail hereinafter but this summary serves to facilitates an understanding of ysome of the inventions many advantages described below.

3 j Even this brief summary shows that a great advantage of the present invention is the large reduction in oxygen cost. One-third to one-half of the pure oxygen consumption that would be required by the prior art oxygen steel making processes, is replaced by the oxygen content of the air which is free from expense other. than for its handling. The oxygen cost is almost cut in half.

The advantages of continuous operation are soV apparent that no comment is needed.

Each piece of apparatus can be made Iand operated individually 4as best suits its function. Because of its high production rate, the kfirst stage apparatus may be made small. By using two for the second stage, alternating receiving and discharging metal rhythmically to keep up with `the rst stage, all units may be kept small and therefore .economical in every way. The molten metal Vin each apparatus may be confined by a refractory of for deoxidizing, degasication, alloying or the like,-and

to hold'the metal for any time required in such instances.

Oner advantagevof this is that when handling high phosphorous pig iron, thefslag from the final treatment of a precedingA heat having lbeen brought to a high state of oxidation, may be retained, instead of being continuously withdrawn, and used as a kdephosphorizing slag for the next oncomingheat. Because the amount of slag formed in the second stage is reduced due tothe absence of silicon, which is` removed in the first stage, a reduction of the loss of iron in the slag is obtained.

The partial removal of sulphur in the' rst or pretreatment step, permits greater than usual desulphurization, and thus the initially charged metal may be of higher than usual sulphur content while'p'ermitting the production of steel of adequately low sulphur content.

The first or pretreating apparatus unit is always operated continuously.` A single second, pure oxygen supplied yunit therefor might be unable to operate fast enough for some processing if made no substantially larger than the irst unit: known, dephosphorizing requires time. involve limits on speed of reactions. stances the pretreating .or rst unit may feed as many of the second` units asfare needed to split orl dividethe delivery by the rst unit.

Other; treatments holding the heat,to processy that amount properly, the balance Ygoing to another or possibly several other units each accepting its share as determined by the time requirements in' each instance.

The above is not to `be construed as meaning that the i use of pure oxygen with the patented apparatus involves great time requirements. To the contrary, in many instances` the 4entire process may be continuous with the metal remaining in each unit a very short time as com- .pared to prior art processing times. A consequent saving 0n theconsumption of refractories resulted per ton of processed metal. Being capable of such high lproduction per unit, the initial investment requiredvfor the steel mak-V l ing facilities is substantially less than usual.

Being continuous, this new process does not suffer from the great disadvantage of the prior art oxygen steelr making processes in connection with controlling the reactions and lthe composition of the metal produced,

It has already been indicated that, as is well- In such circum- In other words, the lirst unit may deliverI just enough tonnage to one second unit to vpermit the latter, `whether operating continuously or by Vreduces the production of this annoying` smoke."

tions change rapidly only a small part'of thel total production is affected, and `because prompt correction is possible, departures from analysis or temperature as to thel whole heat can he kept very small.

In addition, temperature control is an easy matter, a change in formationof heat beingpossible either by controlling the volume of oxygen injected and the amount of oxidizablel material, or by a change `in the rate` of cooling effected by .the addition of nonoxidizable material such as steell scrap and the like or by combination of both.

In yany oxygen steel making process the -use'rof pure:

oxygen produces whatis called red smoke.l This smoke is caused becausethe very high temperatures resulting from the useof pure oxygen causes the iron to sublime and pass off as a kind of vapor which then oxidizes and forms extremely fine particles of iron oxide which pass from the equipment as the psmoke. This lpresents a nuisance to the surrounding neighborhood andrepresents 4-a direct iron loss.

q To the same extentthatthe present invention reduces the consumption of ,pure oxygenfit nuisanceV is abated and iron is saved. The dust collection system for the exhaust gas maybe of correspondingly lesser capacity l'andthus is made less expensive.

Referring now Vto the accompanying drawings, in which:

FIG. l is a vertical longitudinalV section showing schematically one form of the present invention; i

FIG. 2 .is a vertical transverse section takenron the'.

line 2--2 `in FIG. 1; and

FIG. 3 is a horizontal section takenon the` lineY3-3 l in FIG. l.

Referring `to FIGS. 1 4and 42, the apparatus` of Patent` 2,862,810 is s hown on the higher level, 'two being shown because ,afstand-by unit is` desirable. As describedby -the patent, each `includes a bottom wall 1, upstanding,

side walls 2,.upstanding front and rear `walls 3 and :4,

respectively, andY an archedV roof 5., The insideof the enclosure is constructed to form an elongated container 6 which extends from the front wall3 to the rear wall 4 and has a bottom which declines Afrom'the front to the` rear Walls. The container 6 functions `as a horizontally elongated hearth for containing an elongated pool of molten pig iron.

.In the patent permanent tuyereswere disclosed for mJectmg oxidizing gas into the molten bath. kSince .that

time, the development of the oxygen steel making process has resulted in the development and commercialization of lances capable of continuous use for the injection of gas into the enclosed space 7 at a point above thepool of molten pig iron and in a discharge stream at an angle less than `-ninety degrees onto the surface of the bath i of the molten metal. Therefore, the wall 3 is shown as lhaving a port3a closed by a door 3b and through which such a .lance 8 `is located, the lance` being `carried by a carriage v8c so that it` may ibe `positioned as desired, the

door 3b being provided with fa slot sothatit maybe i A plurality of` lances closed While the lance is in use.l may be used.

Further, in the present instance, the molten pig iron is fed'nto the hearth 6 by arranging the inletpassage; 9 t in one ofthe side walls instead of through theend wall i' 3, the passage portion 10,y described bythe patent, lbeing' j on this side of the apparatus.y The outlet passage` 11 and lts upstanding portion 12 are substantially as shown by the patent.

because in this continuous process continuousV sampling is;

possible, land when this shows that more orless heat is needed,`immediate correction is possible.. When condi- The gas outlet 13, for the space 7, is shown as connect- 4 mg with a gas collector system 14; Ithe entire enclosure is:

substantially gas tight.

The lance 8 projects vinto the enclosedspace 17 at a point above the pool `of molten pig `iron1so as to discharge a stream of gas at an angle less than ninety degrees onto the surface of the bath and it has an yair pipe 17 mounted on its'top and having van inner end which pro- The The upstanding walls generally `and.y the roofS form an enclosed space 7 above the container .for the collection of gas.

jects upwardly so as to inject air directly into the space 7. This air is injected so that it can burn the carbon monoxide collected in the space 7 and in this way add heat to the molten metal. This space is high enough and long enough to permit substantially all of the carbon monoxide to burn to carbon dioxide ybefore the gases leave the apparatus.

A transverse wall 18 functions as a dam 'for the container 6, and over which flows a thin stream of the molten pig iron, along with the slag which forms on the metal. A slag collection chamber 21 is defined by this wall 1S and a second transverse wall 22 which completely closes the upper part of the container 6, and the space above it excepting for the gas `outlet 13.` The chamber 21 gives the Slag an opportunity to separate from the molten .pig iron, the slag exiting through a port 24 positioned just above the level of the molten pig iron. This port 24 may be more or less plugged as required for the operation of the apparatus. A roof passage 25 is provided with Ia hopper 26 so that slag forming additions may be made as desired. The Wall 22 is provided with a passage 23 for the molten iron, and this w-all 22 and the wall 4 define a quieting or tranquillizing chamber 27 for the metal. Above the wall 22 the gas outlet 13 is constructed as an elongated passage pointing diagonally upwardly and rearwardly. This passage is formed by a correspondingly extending shelf 28 which extends from the top of the walll 22 almost to the inside of the wall 4 and defines Van opening 29 above the chamber 27.

As explained by the patent, molten pig iron, in this case delivered to the trough -T from a suitable source, is continuously poured into the passage portion 10 of the operating one of the units, so that it fills the container 6 where it forms an elongated pool, the treated metal leaving by way of the port 11. The container may have a basic or neutral hearth. A continuous flow is established, the pig iron therefore continuously traveling past the location at which the stream of air at high pressure comes from the lance 8. This causes a violent agitation and occasional splashing of the slag up in the air, the patented construction preventing loss of either slag or metal. The throttling effect of the gas outlet system maintains the atmosphere in the apparatus at a pressure slightly above atmospheric. Slag is constantly removed through the port 24, if necessary, and the metal quiets in the chamber 27. The rates with which the iron is fed and the air is supplied are controlled to maintain the temperature of the pig iron feeding from the pool in the container 6, in the neighborhood of 14U0 C. as measured by an optical pyrometer. The use of a modern thermocouple pyrometer would probably show a temperature about 100 Vto 150 C. higher.

In the above fashion, the apparatus continuously delivers a supply of molten iron, very substantially desiliconized through the combustion of silicon with the oxygen of the air, without a pick-up of nitrogen, due to operation in the neighborhood of the temperature described, and free from slicious slag and relatively free from gases.

It is to be noted that air or oxygen can be used during this desiliconizing phase. It is done in a continuous fashion. The necessary equipment is non-rotary and therefore its lining may comprise the three types of refractories most suitable for the hearth, slag line and roof or upper portions. The necessary agitation of the metal is obtained by relative movement between the metal and the location where the air 0r oxygen is injected, the resulting gases inducing a boiling zone through which all of the metal and slag musttravel.

Now in the present invention the desiliconized and very hot, incompletely refined molten pig iron, containing most of its original carbon, is fed from the port 11 to a delivery trough 30 which carries the metal to a transverse trough 31 which may be rocked to deliver to either of two

troughs

32 and 33 which feed to the inlet passage portion 10a or 10b of either of two or more second units made substantially the same as the one just described. These two second stage units are alike and lall parts which correspond to the first two units are indicated by similar numerals individually identified by the small letters a and 5b.5,

The main differences are that the wall 18a holds back the slag so that it may be continuously available, the port 19a being located at the bottom. The wall 22a has two laterally interspaced ports 23a at its vtop (see FIG. 3), either of which may be closed in the usual manner with a refractory material by working through access ports P formed in the side walls of the apparatus. The respective ports 23a feed separate spaces-27a defined by a wall W extending between the wall 22a and the end wall 4a. Metal may be removed from each of the chambers 27a through ports 11a controlled -by the insertion or removal of refractory material.

When it is necessary to remove the slag, the ports 24a may be used, all units being mounted on a-rocker system R so that it may be tilted for this and general use purposes. When not in use, this port 24a is closed. A rotating exhaust collection hood 14a is provided for each unit. This may be separate from the system 14,- or a part of the latter.

When the present invention is operatedv in a continuous manner throughout, the desiliconized, highly heated pig iron ows into container 6a, of the unit in use, and forms an elongated pool. At the start of operations this-container 6a would `be charged with a predetermined amount of scrap, lime, iron ore, scale, all charged through the door 3a, and slag from previous processing, or other additions. During the processing, such additions may be made from time to time through the passage 25a.

In this case, the lance 8a is supplied with substantially pure or commercially pure oxygen. More than one lance may be used in this manner. The flow of metal'from end to endl through the pool causes relative movement between the pool and the location Where this oxygen is injected. In addition, the carriage Sca may be constantly reciprocated. Rotation of the equipment is unnecessary and, of course, impossible. The necessary agitation `is effected by the evolvement ofthe carbon monoxide with its consequent boiling action ofthe metal and slag. Violent agitation results. The carbon monoxide is burned to carbon dioxideby the introduction of air or oxygen through the pipe 17a fixed to the lance, with all of the heat saving advantages described previously.

Additional heat is obtained because air orV oxygen introduced to the space 7a by the pipe'17a, burns the carbon monoxide escaping from the bath, the resultingheat being largely returned to the bath. The slag S is retained on top of the elongated pool in the container 6a.

In the above fashion the carbon inthe metall is rapidly burned out until it reaches the content desired, the steel then flowing into the chamber 21a relatively free from slag. The steel then flows into one or another of the chambers 27a, these being provided in multiplicity so that although continuously operating, a quiet pool may be formed and held in one or the other to give time to deoxidize with additions of ferromanganese and to degas the steel by making ferrosilicon or aluminum additions, for example. Basic or neutral refractories may be used to hold the metal bath and the slag, so basic steel making is possible and would normally :be practiced.

When operating continuously, the refined steel continu- Because the steel continuously leaves this second stage or secondary apparatus, it may be sampled at closely spaced time intervals or, in etect, continuously. Therefore, continuous correction is possible. Such correction may consist of raising or lowering the temperature by v-arying the ratio between the constantly added hot pretreated metaland the oxygen blown through themetal,

and the necessarily constantly charged scrap, iron ore or ,other cooling additions.

Compositional adjustment `is possible for varying alloying constituents which may be finement;

Although the use .of-an inclined lance is. shown, top

Iblowing is a possibility. In such an instance, the velocity of the oxygen jet, fed by a straight lance or an inclined lance having a depending nozzle with one or more openings, must be great enough to blow through the slag and -reach the metal bath. However, by utilizing the variable inclined lauceof this invention, proper control ofl they .amount of oxygen, or air, as may be alternatively usedk in the desiliconizing chamber,.delivered to the slag and .metal bath is achieved. This is accomplished by inclint ing the` lance 8a at an angle relative to the. surface of the molten bath within a range from 30 degrees to 85 degrees; the greater the angle Aof inclination, the greater the amount of oxygen delivered to the metal bath. With continuousoperation the metal ows so that constant .relative movement between the oxygen blast and the metal is achieved, and if desired the oxygen blasting element may be reciprocated by reciprocating the carriage 8ca. In either instance, because of the patented Yconstruction of the equipment, large displacements of slag and metal throughout the blasting area, are possible without causing operating troubles, and relatively little heat is lost through the exiting gases because of the air or oxygen constantly introduced through theV pipe 17a burns the carbon monoxide within the enclosure instead of permitting it to escape-without burning.

The treatment of the hot, desiliconized iron of low `or negligible nitrogencontent, inthis second stage apparatus may follow prior art oxygen steel making practices. At the same time, the disadvantages of'these practices are overcome..

In particular, the oxygen cost is very greatly reduced when practicing the. present invention.. The lining of the equipmentlasts much longer because it need not be of the same type throughout as required when rotary equipment is involved. Large scale .rhythmical production vfrom two small units is possible such as can be achieved `by prior art top blowing oxygen steel makingequipment continuously fed to the 'metal during its continuous rey only by using very large units with their attendant problems. The constant heat loss represented by the constantv withdrawal of the highly heated gases containing unburnedcarbon monoxide, is avoided because the `carbon monoxide is burned within the enclosure. The invention m-akes possible a very high production ratefor the initial and operating cost of the .equipment required.

In order to accomplish a further saving especially. of refractories, the recent progress in the prior art oxygen steel making processes is inthe direction of the use of I larger units with the batch of metal being up to 300 tons to date. Y

This increase of capacity of the vessel poses a difcult problem in the supply and in the charging of large f amounts of scrap that must be performed in a very short Agreatly on slag-metal reactions.

steel is evenly distributedduring4 the operation time and therefore is performed in small portions more frequently. This permits the use of equipment of relatively small i capacity yin lightly constructed and less` expensive buildings.y A rush of workis avoided.

The production rate of the primary or dirst stage apt paratus using air alone for desiliconizing and heating the 1 pig iron delivered .asa starting material, is very high.

Furthermore, some ofithe sulphur is removed from the starting pig iron, during this rst stage treatment.; In

the second stage apparatus the carbon is burned out by the oxygen very quickly. Howeventhe effective removal of phosphorous and the remaining sulphur depends` Although the. violent turbulence eifected by the introduction of the Yoxygen with constantrelative movement between its location of introduction and the metal produces violent turbulence both of the metal and slag, time is required for the slagt metal reaction to proceed to the desired degree.

For the above reasons the second stage of the present process cannot-sometimes. keep up withthe tirst stage unless there is a great diiference in the sizeof the two pieces of apparatus desired. One of. `the `advantages of the patented apparatus is its com-pactness and ease-of maintenance and repair, and it is ordinarily not desirable to 4attempt to make it with abnormall proportions. Furthermore, there is an'economical advantage in `having all of the pieces of equipmentof` almost the `same size and general construction, permittingY easy replacement of any part. f

Units of. similar size; may

more of lthe second stage units. This is illustrated by FIG. 2 wherein the delivery trough 31y is shown in a posit tion ,to deliver the continuously produced desiliconized4 iron to either. of the two lower units. This trough may `be rocked to control its delivery.

The delivery trough 30 of the rst lor upper. unit in use, may feed both of the two lower or second stage units,

this permitting the latter to retain the metal for the longer periods of time required for slag-metal reactions to proceed to the desired degree of completion during the second stage. Both units may be operated continuously as described and both deliver :the iinished `metal through` their outlets lila and 11b.

Now the continuous addition of scrap, as required for; continuous operation, necessitates scrap `of a uniform,

compact` and small-sized nature. The .practice `of` the present invention results in large production trates and. this type of scrap is expensive and frequently unavailable? In such instances alternate. or rhythmic operationof the. two second stage unitsis preferable; YWhile oneV is opert ating, there is time to charge the other unit with'lthe required amount of scrap, ironfore, lime .and the like,

in Ythe large quantities required .'by this'invention.

prior to its receiving the hot desiliconized iron.

In such operations,` the delivery `trough .31 maybe A .rocked to deliver the continuous .flow of hot, desiliconized, or .partly refined, iron to the inlets 10b of they lowerY unit which has been tapped, 'the lother lower unit 1 being in operation.

Assuming that the primary or first apparatus, Vusing air, where desiliconizing occurs, has a capacity of 200 tons of desiliconized iron per hour, for each 20 minutes it delivers some 66 tons of the pretreated metal." This l metal goes to, for example, the right hand side of the lower units using pure. oxygen. Each of the two lower units can hold about 66 tons of molten metal and appropriate .amounts of scrap. With the right hand unit charged, this referring to the lower units as shown in lFIG. 2, and in thisfashion each of the lower units opert ating continuouslywith pure oxygen and with the lance or-lances reciprocating, has a holding time of some 20 minutes. Ordinarily this vis suicient time, but obviously` more umts couldbe provided if necessary to provide more time in each.

be used byY providing two or If it was necessary to provide a longer retention time for slag-metal reactions in the second stage units and in the same time to have a free time interval for prior charging of scrap, four or more units (not shown) are required in this case alternative feeding is providedfor two simultaneously and continuously operating units. The additional second stage units can be installed between. the lower or peripheral units shown in FIG. 2. All units m-ay be fed from the same transfer trough 31.

To provide a longerk time period for dephosphorizing, a form of batch operation may be resorted to. If two available batch operating peripheral units do not provide a sutiicient margin of time .for complete dephosphorizing, more unitscould be installed.

With two batch operated units fed alternatively, the available time for prior charging of scrap and for holding time to accomplish the normal slag-metal reactions to proceed to a satisfactory degree, is 20 minutes. With three second stage units, having the capacity of 66 tons of molten metal and of appropriate amounts of scrap, a feeding time .is 20 minutes and an available time for charging and holding the heat is 40 minutes. With four second stage units of the same capacity the feeding time is the same andan availabletime for charging and holding is 1 hour. If four units had a capacity of only 33 tons of molten metal and of appropriate amounts of scrap, a feeding time is minutes ,and an available time for charging and holding is 30 minutes.

It is obvious that a frequent delivery of finished steel .in small portions is very suitable for` continuous casting of steel.

The 200 ton per hour production rate from the-rst stage desiliconiziug unit 1 is practically proved, by actual operation. AObviously this rate can be kept also at a slower rate and the steel making capacity of the whole installation could be decreased.

It now becomes apparent that units using the patented construction may operate in series with air supplied to the metal bath in the first unit and pure oxygen to the metal bath in the second, air or oxygen being supplied in both instances in the high and long space above the metal, to burn the carbon monoxide to provide enough heat to permit large additions of the temperature-reducing agents in the second stage unit or units, as requi-red for control or analysis specifications. Alternately the primary unit may deliver its pre-treated iron alternately to a plurality of second stage units, with the constant production of the first unit split and continuously fed slowly through a plurality of the second stage units, or fed alternately to one ora plurality of the latter.

With pig iron having a low phosphorous content, the present invention may be operated in the fully continuous manner described. When the steel specification requires almost negligible phosphorous, it may be necessary to remove the slag and replace it with a new slag which is then retained for one subsequent reuse. It is in such instance that the batch type of operation is indicated.

When the pig iron is high in phosphorous it may again be necessary to Withdraw slag after it has acquired a high phosphorous content and replace it with a new slag which may then be subsequently reused once again. It is apparent that all of the recognized dephosphorizing techniques'may be used in the case of the present invention.

It is to be understood that in the batch type operation the metal outlet of the apparatus in use is plugged by a refractory material until it must be opened for delivery. In all cases, recognized oxygen steel making ltechniques are available for use.

It is important to note that with the present invention the first stage using cheap air eliminates the silicon and reduces sulphur, and raises the temperature of the metal without introducing nitrogen. In the second stage the metal is formed into an elongated pool with the necessary refining slag on top and without necessarily moving the vessel containing the metal, substantially pure oxygen is injected on the surface of the metal bath. This is done with the metal constantly fiowing or by means of oxygen lances which are reciprocated lengthwise of the pool, or by using both techniques. The resulting escape of carbon monoxide keeps the pool in a state of violent boiling substantially throughout its length, whereby there is a good inner contact between the slag and metal. The carbon monoxide is confined and burned to carbon dioxide by the introduction of the necessary air, above the reaction zone, thus providing enough heat to permit the larger addition of temperature reducing additions such as scrap or iron ore. For the production of very high grade steels oxygen can be used for this purpose also.

The present invention accommodates the desired continuous operation of the patented desiliconiziug apparatus. However, the second stage of this process could be supplied with molten iron from other sources. With fully continuous operation continuous sampling and therefore continuous compositional control is possible. The use of basic hearth linings is, of course, fully possible so that basic steel can be produced. Obviously the production of acid steel is also possible by using acid hearth linings when this is acquired.

Suitable charging and discharging ports may be located Where desired and each piece of equipment may be mounted for universal rocking action as indicated by the two-way rockers generally indicated by the letter R. Such arrangements permit the ready removal of used slag, fast tapping, complete emptying for cleaning and purging, repairs and the like.

Although capable of variation, in all cases the units should include the structural essentials described by the previously mentioned Patent 2,862,810. Provision should be made for the elongated hearth for containing the elongated pool of metal. Very high gas injection velocities are required for the violent agitation desired. The hearth lining may be of the type dequired by the slag formed. The reaction space must be enclosed to prevent the escape of splashed material. The enclosed space above the bath must be large enough so that the velocity of the gases therein will be low enough to permit all displaced material to fall back into the bath and to burn the carbon monoxide escaping from the bath into carbon dioxide. The use of an aspirating jet above the chambers formed at the outlet end of the apparatus is not essential in the case of the use of pure oxygen, but throttling of the exhausting gases may be desirable to further decrease the loss of molten material.

I claim:

1. An oxygen steel making two-step process including forming molten pig iron into a first elongated pool, feed- 1ng additional molten pig iron to and from the opposite ends of said first pool While blowing air into said first pool under conditions burning mainly only the silicon from said iron Without adding substantial amounts of nitrogen to the iron feeding from said first pool, forming the molten pig iron from said first pool into a second elongated pool 1n at least one non-rotary container, forming a refining slag on the top of said second pool, and introducing substantially pure oxygen at an angle smaller than into the space above said second pool while causing relative motion between the pool and the location where the oxygen is introduced, to cause carbon monoxide to form at varying locations in the pool and rise through said slag.

2. The process of claim 1 in which said relative motion is caused by feeding said incompletely refined molten pig iron into one end of said second pool and withdrawing the heated metal from the other end of this second pool to cause fiow relative to the location where the oxygen is introduced.

3. The process of claim 1 in which said relative motion is caused by introducing said oxygen with at least one lance reciprocated lengthwise with respect to said second pool.

' second pool therein. Y

5. `The process of claim 1 and including forming at 4. `The process of claim 1 inV which scrap metal. is charged in the non-rotary container prior to forming said least a third elongated pool from said iron from said iirst pool and forming a reiining slag on Vsaid third pool and introducing oxygen thereto ina manner corresponding to that described in the case of said second pool, and maintaining said iiow through said iirst pool and alternately" feeding said incompletely refined iron from said iirst pool to said second and third pools while withdrawing therefrom steel when refined to the desired degree.

6. An oxygen lsteel making process including forming molten pig iron into a pool, continuously feeding molten pig iron to and from said pool respectively at interspaced locations While blowing air through the pool between said i locations to burn the silicon and raise theV temperature of f the iron feeding from the pool, while controlling the rates of said feeding and blowing to maintain the temperature of the iron feeding from the pool in the neighborhood of 1400 C., measured by optical'pyrometer, the iron 'con-V tinuously feeding from the pool being thereby substantially desiliconized, partly desulphurized, and substantially` free from nitrogen, delivering this continuously feeding iron from said pool to a non-rotary container and forming 1 a second pool therein with a relining slag on its top, in-KV carbon monoxide and produce heat which adds to thetemperature of the second pool, thus permitting the addition of temperature reducingadditions to the second pool, and

ultimately feeding the at least partly refined .steel from said second poolwhen finished to the desired degree and to permit replacement by the continuously feeding iron i v,from the` first-named pool. 7. The process of claim ,6 4in to cause ow relative to oxygenintroduction location. 8. The process of claim 6 in which said relative motion is caused by introducing Ysaid oxygen 4with at least one lance reciprocated length wise with respect to said second vlpool.

lv9. `The process ,of claim 6 in which the scrap metal is charged in the non-rotary container priorv to forming said second pool therein.

10. The process of claim` 6 in which the `molten iron I' from said rst-named pool is fed alternately to a plurality of said second pools. f

References Cited by the Examiner t n UNITED STATES lPATENTS i 3/1937V Clair 75f-60 2,649,366 -8/1953 Jordan 754-60 2,862,810 12/ 1958 Alexandrovsky 75'-60 2,965,370 12/ 1960 Kesterton et al 75;60

3,010,820 11/ 1961 Graef et; al 75--52 3,057,616r 10/1962 n Wohlfahrt et a1.` 75-60 FOREIGN PATENTS Y 744,935 2/ 1956 Great Britain.

BENJAMIN HENKIN, Primary Examiner.

p which'said riron is coni ytinously fed to and theisteel is fed from said ysecond pool

Claims

1. AN OXYGEN STEEL MAKING TWO-STEP PROCESS INCLUDING FORMING MOLTEN PIG IRON INTO A FIRST ELONGATED POOL, FEEDING ADDITIONAL MOLTEN PIG IRON TO AND FROM THE OPPOSITE ENDS OF SAID FIRST POOL WHILE BLOWING AIR INTO SAID FIRST POOL UNDER CONDITIONS BURNING MAINLY ONLY THE SILICON FROM SAID IRON WITHOUT ADDING SUBSTANTIAL AMOUNTS OF NITROGEN TO THE IRON FEEDING FROM SAID FIRST POOL, FORMING THE MOLTEN PIG IRON FROM SAID FIRST POOL INTO A SECOND ELONGATED POOL IN AT LEAST ONE NON-ROTARY CONTAINER, FORMING A REFINING SLAG ON THE TOP OF SAID SECOND POOL, AND INTRODUCING SUBSTANTIALLY PURE OXYGEN AT AN ANGLE SMALLER THAN 90* INTO THE SPACE ABOVE SAID SECOND POOL WHILE CAUSING RELATIVE MOTION BETWEEN THE POOL AND THE LOCATION WHERE THE OXYGEN IS INTRODUCED, TO CAUSE CARBON MONOXIDE TO FORM AT VARYING LOCATIONS IN THE POOL AND RISE THROUGH SAID SLAG.