US1590739A - Purification of iron - Google Patents

Description

June 29 1926.

G. S. EVANS PURIFICATION OF IRON 1 Filed April 10, 1925 INVENTOR emye Eva/7s 1 I I ATTO R N EYS Patented June 29,

UNITED STATES PATENTL OFFICE.

GEORGE S. EVANS, 0F OAK PARK, ILLINOIS, ASSIGNOB TO THE MATHIESON ALKAIMI WORKS, OF NEW YORK, N. Y.;' A CORPORATION 01 VIRGINIA..

PURIFICATION or men.

Application filed April 10, 1925. Serial No. 22,047.

This invention relates to improvements in the refining of cast iron. The mvention relates more particularly to the refinin of molten iron for the production of-chllled iron castings such as car wheels, but the invention is of value and application in con nection with the refininggof cast iron genere ally where high grade castings are required. In my prior application filed April 23, 1924, Serial No. 708,410, I have described an improved method of refining molten cast iron with alkaline reagents, such as soda ash or inixtiires of soda ash with materials such as calcium carbonate, and, in one aspect, the

present invention relates to further improve,

ments upon the method described in this prior application. Various proposals have been made for refining molten cast iron as it comes from the cupolaor other melting furnace and before itis cast, but the methods hitherto proposed have involved the refiningof individual batches or ladles of molten iron as a whole,

the entire batch or ladle thenbeing cast, suc

cessive batchesor ladles being treated with freshrefining material. In the processes of i such prior proposals, the removal from each batchor ladle of the slag formed is usually.

important, and it is common in the case of such processes to provide for the addition of other materials such as limestone or sand together with the refining material to thicken up the resultant slag, so that it can more v such processes. For example, it has usually involved delays in holding up the batch or. ladle; of'iron being treated for therefining been necessary in the practice of such processes to employ an, excessive amount of refining material to remove a, iven quantity of sulfur or otherwise to re ne the metal,

and the excess of refinin material has frequently had an adverse e ect upon otherelements which are contained in the iron and whichit is undesirable to: remove, such" as silicon and manganese. Variations incident .to such batch refining i operations, have also tended to reduce erratic casting results due to variations in the compositlon of the treated product. -Such operations also have operation to completed, interfering wit foundry routine and also unnecessarily cooling the molten metal, sometimes below the desirable cast-mg temperature, particularly for pouring light castings. The complete removal of the slag formed in such processes is-also difficult, and in the case of highly alkaline slags is dangerous due to spattering of the slag which is very corrosive to the. skin of workers, Incomplete removal of the-slag, moreover, results in thepossibility of pourmg some slag with the molten iron which destroys the molds resulting in bad castin s. Where materials are used to thicken u i t e slag whichis formed, they have an o l) tionable cooling effect and frequently. reduce the efficiency of the refining material. In the production of cast iron of high quality, and particularly in the case of specifica tion work where rigid standards must be met,ichemical composition" of the iron and v7. ,portant both from the standpoint of abso- :lute analysis and physical properties and physical structure ofthe castings are. im-

from the standpoint of unlformity. The sulfur content and the degree ofdeoxidation,

- for example, vary considerably in ordinary cupola or melting furnace practice, and the batch by batch or ladle-by ladle refining processes of previous This invention provides an improved I pro osals are not adapted to-correct these con itions with the production of a uniformly high grade product.

method of refining molten cast .ironas it 'comesfrom'. the cupola. or other melting furnace without application ofextraneousheat which overcomes. or reduces theldisa dv'am tages incident to methods. heretofore avail -f able and which haspa-rtic'ularly the important advantage of enabling the production of a more uniform cast iron throu hout prolonged periods of operation provi form metal forpouring. This invention provides an .improved method of desulfur izing molten cast iron, and the refining i method 0 the present inventionfis-also useful in deox'dizmg the molten iron as. well as; in removi g, impurities suchv as oxides-and occluded or entrained slag gaseswhih tend 9. p ucedisfcctive I ings. Themetliod of this inventomimore over is readily .e'm'loyed' in 00 auctionitlii'oldilifll y found m o rations without-7. iflte'nsives modification o equipment'-jand" without interfering with the normal 1ofi'ioundryoperat1ons. Other features"'and advantages of the invention will appear as the description proceeds.

According to the present invention, the molten iron is subjected to the action of an alkaline refining agent during its passage from the cupolaor melting furnace to the mold. A pool of molten cast iron is maintained in a suitable mixing reservoir or bull ladle and molten iron is supplied to this pool from the cupola or melting furnace and refined iron is withdrawn from this pool fol pouring as required in the foundry operation, and the refining operation is carried out upon this pool of molten cast iron. This pool of molten iron, upon which the refining operation is carried out, is relatively large with reference to the amounts of iron added to and withdrawn therefrom, and the additions and withdrawals of molten iron from the pool are correlated to maintain the pool during the entire period of operation or heat. The refining operation is carried out by an alkaline slag bath which is maintained in contact with the molten iron in the pool. The refining slag is maintained active by the addition, as required, of fresh quantities of alkaline refining material. The impurities removed from the iron accumulate in the slag and excess slag may be removed during the operation. The addition of fresh alkaline refining material to the slag may be periodic, as may be the withdrawal of molten iron from the pool and the removal of excess slag. The withdrawal of molten iron from the pool for pouring, for example, may be in batches amounting to somewhat less than 20 or 30% of the then contents of the pool. The additions of fresh material to the slag and the removals of excess slag, for example, may be in the neigh- L borhood of 10% of the slag body or somewhat more. Molten iron from the cupola or melting furnace may be supplied to the pool either in a more or less continuous manner or, in periodic batches. Molten iron for pouring is withdrawn from the pool below the slag level to separate the iron and slag and to avoid contamination of the withdrawn metal with slag.

The alkaline refining material employed, according to the present invention, is fused soda ash (commercial sodium carbonate) or an equivalent soda ash reagent. The soda ash refining material may be employed in admixture with limestone, dolomite or the like. Other alkaline chemicals or earths, such as potash, calcium oxide, barium or magnesium carbonates and various mixtures and proportions of these reagents are also useful in carrying out the invention. The refining material, if a mixture, is advantageously prepared by thoroughly mixing the dry ingredients in the powdered form, after which the mixture is fused together and cast into briquettes, or.sintered into lump form,

-or briquetted under pressure, to prevent the loss of material as dust and to prevent any injurious effects upon the health and comfort of workers during the carrying out of the rocess. Single refining reagents may simi arly, withadvantage, be fused and cast or pressed into briquettes or sintered into lump form. The refining material is employed in such proportions as are required to efiect the maximum reduction of sulfur andentrained slag particles per unit of reagent with a minimum injurious effect upon the other elements usually found in the cast iron and upon the lining of the ladle or reservoir in which the process is carried out.

In carrying out the present invention, accordingly, amolten pool of cast iron is main tained, to whichmolten iron is supplied and from which refined iron is withdrawn as required, and an alkaline refining slag is maintained on the pool of molten iron, fresh alkaline refining material being added to the slag and excess slag being removed from time to time as necessary. Close control over the content of sulfur, silicon, manganese, carbon and other elements contained in the cast iron, which is essential tothe proper regulation of the physical properties of the finished castings, is provided by the improved refining operation, and uniformity is promoted by carrying out the refining operation upon a pool which is maintained throughout the period of operation. Varia tions in constitution of the molten iron supplied to the pool are, to a large extent, overcome in the pool by admixture-of the unrefined molten iron with the relatively large amount of molten iron in the pool as it is supplied tothe pool. The pool thus acts to equalize variations in the constitution of molten iron supplied to the pool. The maintenance of the slag body on the pool of molten iron with progressive replacement by increments also promotes a more uniform refining operation by assisting in maintaining a more uniform slag composition. The maintenance of the pool of molten iron also assists in maintaining correct temperature conditions, the uniform temperature conditions obtainedin carrying out the invention being of special value in insuring correct pouring temperature. The maintenance of the pool .of molten iron also provides a supply of molten iron for pouring which is" not cut off or interrupted'by the'refining operation but which is always available for pouring in the regular routine of foundry operation. The equalizing effect of the .pool of molten iron as employed in the refining operation of this invention, moreover, makes-it possible to correct changes in the composition of the molten iron supplied from the in production the metal already melted or melted in the interim. Theicorrect balance between the different elements in the treated or processed metal to give the desired physical properties in the finished castings may thus be controlled and maintained. The slag body maintained on the pool of molten iron' also assists in distributing fresh refin-- ing material'as it is added'in contact with the molten iron and makes for more efiective use of. the refining material. The maintenance of the pool of molten iron and the slag body incontact with each other also provides for prolonged contact between the molten iron and the refining slag, further PI'OIYlOli' 'ing the effectiveness of the refining material. The invention will be further described in connection with the accompanying drawings, which illustrate in a diagrammatic and conventional manner apparatus adapted for carrying the process of the invention into practical efiect. It will be understood that the apparatus illustrated in the drawings 18 chosen for thepurposes of illustration as 2 representing types of apparatus in which the invention may be carried out but that the invention is not limited to operations carried out in the specific types of apparatus shown.

In the drawings-- I Fig. 1 is a vertical sectional view through the lower portion of a cupola shown together with ,a mixing reservoir or bull ladle. Fi 2 is a view similar to Fig. 1 showing t e lower portion of a modified type of cupola shown together with a different type of mixing reservoir or bull ladle and with' a pouring'ladle, and

Fig. 3 is a section on line 3-3 of Fig? 2 showing a detail of the cupola spout."

The cupolas illustrated in both figures of the drawings are in general of the usual constru'ction and operation, and comprise a refractor lined shell '1 supported on legs 2,

.. the furnace bottom '3, also refractory lined,

being supported on doors 4 held closed by I support 5. A number of-tuyeres 6 are arranged opening into the. furnace at some distance above. the bottom and are connected to a. common blast pipe 7. A slag spout '8, is also rovided o ening into the furnace 'a short istance be 0w the tuyeres. Two general methods of carrying out the process of the invention will be' described in connection with the apparatus illustrated, that is either with eontinuous'tappin'g of themoL ten iron-froriithe cupola or with removal ofthe molten'iron from the cupola 'periodical 1y with separation of the cupola slag in the I cupola proper. For convenience the first of these two methods willbe described as car- I ried out in ap aratus as illustrated in Fig. 2

and the secon as carried out in the appara-' Y tusas illustrated in Fig.1. .Difierentt'ypes of mixing or refining ladles are also shown ing out the invention, the tappin hole 17 is 19. The molten iron is thus withdrawn from in the two figures, but it'will be apparent that the use of ajmrticular type of refinmg ladle is not essential-to either way of carrying out the process, It is, however, advantageous to emplo certain types of ladles as will be pointe out in the followingFdescription. The bull ladle illustrated n 1g 1 1s of the bottom pouring type, and l comprises a refractory lined shell 9 provided with a pouring nozzle 10 arranged in the bottom, a stopper of refractory material 11 operated by means of lever 12 and seating on the pouring nozzle being arran ed to control the discharge of molten meta from the ladle. The bull ladle illustrated in Fig. 2is

of the teapot type and is provided with a pouring spout adapted to separate molten metal from'the refinin slag in the ladle, the spout being arrange to pour metal from the lower part of the pool in the ladle. This q5 ladle comprises a refractory lined shell 13 1 mounted on trunnions and provided. with tilting means. A pouring spout 14 divided from the interior of the ladle by a refractory slag bridge 15 is arranged opening into the bottom of the ladle, and a draining spout 16 for the discharge of'slag is arranged in the opposite 'side of the ladle. Referring to Fig. 1, in oneway otcarrystopped up with plastic clay in t e ordinary way andthe molten iron together with the slag resulting from the coke ash and other impurities in the iron gradually rise in the cupola, the slag being lighter remaining on the top surface so that when itreaches the level of the cupola slag hole 18 it drains ofi; The tapping hole 17 is then opened and the 1 a metal is allowed to flow into the bull ladle the cupola in periodic batches. As soon as the molten iron-begins to flow into the bull ladle, the refining agent is dumped into the cupola spout and washed down into the mixing ladle, or it may be dumped directly into the refinin ladle. Initially, a suflioient quantity 0 refining material is added to form a covering-bath over the'surfa'ce of the metal, for example of a depth of about 1 inch,\and this initial quantity is usually from 2 to' 5 times more per ton than is used throughout the-remainder of the heat there,

after. ;This large amount of refining material supplied at the start assists in pro- .moting the desired reaction at the beginr30 ning of the operation and assists in maintaining a uniform com 'osition of; refined metal throughout. the eat. The initial 'amount of refining material supplied may,

for example, be about 10 to 15 l s. based on 2 the soda ash reagent content of the refining material, per ton capacity of the .bull ladle;

With-a cupola '01 melting furnace melting 3 about 15 tons per hour, the refining ladle may have a capacity in the neighborhood of f") the impurities are again drained off through the slag spout 18, when the operation is repeated; After the initial operation, how ever, about or a less quantity of the amount of refining agent initially employed is added per ton of metal, for example, sub- 10 as required for pouring castings. Afterthe slag bath on the surface of the pool of.

sequent additions of the refining agent may approximate 3 lbs. per ton of metal orsomewhat more. The fresh refining material mixes with .the slag containing partially 0 spent material emaining on the pool of iron in the ladle and the fresh batches of hot molten iron mix with the refined iron which is held in the ladle. Refined iron is withdrawn from the ladle through the pouring nozzle molten iron in the refining ladle increases from 2 to 4 fold, a portion of the slag is drawn off, but leaving a sufiicient amount of slag to provide a sufficient bath to properly tire heat and the entire slag mass may be re- 0 into the refining reservoir or ladle.

carry out the operation on subsequent additions of metal. In short heats, using small quantities of refining materials, the slag may be allowed to accumulate throughout the en moved at the conclusion of the heat.

Another,rand more advantageous way to carry out the invention, is with continuous tapping of the molten metal-from the cupola l/Vith continuous tapping, hotter metal available because the cupola is kept clear of slag so that the coke bed below the tuyere level is kept alive. by the blast and is available for heating the drop of molten iron as it flows over the coke in its passage to the hearth. A fuel saving mayalso be effected by lowering the tuyere level. The continuous addition of molten iron' as melted to the. pool in the mixing reservoir also results a more uniform temperature and composition of the iron as poured and avoids rapid changes that sometimes develop between cupola taps in the case of intermittent tapping. -Referring to Fig. 2, in this way of carrying out the invention, the molten metal is-withdrawn more or less continuously from .the cupola through the tapping hole 20 as it is melted, and the slag and impurities resulting from the melting process *lIl thecupola are removed by skimming them off as'the metal flows from the cupola into the mixing ladle 21. For this purpose, a slag spout is provided, the metal flowing I through the trap 22 under the slag bridge 23 and slag being removed through spout 24. In carrying out the process in this way, the tapping hole 20 is initially stopped up and -the molten iron is allowed'to accumulate in the cupolauntil it approaches the slag hole 25, after which the tapping hole is opened and the. metal is allowed to flow continuously thereafter throughout the length of the heat, passing through the slag trap under the bridge. The refining. material is either dumped into the. spout beyond the bridge and allowed to flow into the refining ladle with the molten iron or the refining material may be dumped into the ladle directly. As previously described, a greater quantity. of refining material per ton of .metal is employedon the start than is used thereafter. After all of the initially collected molten iron has run from the cupola, slag-begins to come off with the stream of iron and -is skimmed off while the molten iron continues to pass through the slag trap and 'nto the refining ladle at a more or less 11 iform rate. per hour. The refining material may be added either to the molten ironflowing through the spout and allowed to be washed down into the ladle or dumped into the ladle every 5 to 20 minutes throughout the remainder of the heat oras may be found to give the most uniform results. Initially, suflicient molten metal is run into'the bull ladle before the addition of refiningmaterial to seal up the opening to the ladle spout in order to prevent the refining material from passing into the spout, and afterwards sufficient molten metal is heldin the ladle to keep the full ladle spout sealed. Slag is withdrawn from the bull ladle illustrated by tipping the ladle backwards and pouring the excess slag off through the spout 16. The

refined iron is drawn off through the ladle spout into the pouring ladle 26 as required for pouring and without particular regard to the refining operation, the slag bath being held back by the refractory bridge 15. The hot molten -iron fresh from the cupola, together action causcs agitation, and the movement of the highly fiuid alkaline slag bath and of the molten metal rapidly brings practically the entire pool of molten iron into contact with the active reagents in the refining. slag bath. The alkaline slag employed accordr ing to the present invention, has a very low specific gravity, even lower than ordinary cupola slag, so that the slag does not penetrate the bathof molten iron to any substantial extent. The slag is also very fluid. The low specific gravity and the high fluidity of the refining slagassists in reventing any possibility of the slag or re ing material being absorbed or entrained in the iron and carried into the molds. NVhile the reaction goes on only'at the surface of the pool, the movement of the'massis so rapid that repeated tests of samples taken at the same time from the surface and the bottom of a 10 ton refining ladle show no appreciable difference in chemical composition. The slag bath covering the surface of the pool of molten metal in the refining reservoir is also highly refractive and assists in preventln losses of heat from the pool of molten metal by radiation.

One of the important advantages of the present invention is the uniformity as to constitution, temperature and supply of molten cast iron which it makes available. One of the principal difiiculties previously encountered in the refining of cast iron has been the non-uniformity of the metal as supplied from the cupola or melting furnace or from batch refining operations, and this invention is well adapted to' overcome difficulties of this nature. Another important advantage of the present invention is that it makes it possible to use a larger percentage of scrap ll'OIl in the cupola or melting furnace charge with a saving in mixture cost and at the same time obtaining a more uniform metal with lower foundry losses. This invention also makes possible the use of lower grade scrap, e. g. scrap of excessively high sulfur content. which is now lost' to the industry.

The entire chilled iron wheel industry, is based u on what is known as the chilling quality ofmolten cast iron of certain com- .positions when cast against a chiller. This propert varies with the composition and physica condition of the iron and it is necessary-to hold the metal within very close 1 limits to insure satisfactory results. In producing chilled iron wheels in ordinary foundry practice this characteristic of chillin quality is followed, or controlled, by chil test ingots\which are cast about every to wheelspoured. Mixture changes in the cupola or melting-furnace charge, or additions ofcorrective alloys to the ladle, are then made as required to hold the chillwi'th- I in the proper rangethroughoutthe heat. It

has been found in the commercial application of thisinvention overa period of a year that the chill test ingots, or control tests, run

'more uniform, that is they stay within a hatrower range of chill where thecontinuous refining and mixing process of this invention is ;-emp1oyed --than is the case where molten iron=-fromgsimilar charge mixtures are cast without refinement. As an illustration, the

following log of a typical heat covering approximately 300 standard railway chilled I iron wheels is given. Each test was taken every 30 wheels. The first table shows the actual-chill test'of the control ingots from a heat cast under the ordinary practice, and the second table shows the same from a heat wherein the refining process of the present invention was used."

Log of unrefined heat.

It will be noted that the extreme variation inthe tests of the untreated heat is 0.25

inches in depth of chill as compared to an extreme variation of .15 inch for the refined heat. The chill on test ingots is a comparative indication of the chill on the finished wheel. The wearing quality, or life, as well as the strength, of the finished wheel also yaries with the chill and it is therefore important to keep this factor reasonably con .stant'. Specifications covering wheels for use on the American Railway Association Lines cover rather close chill limits in the tread of the wheels and where the test ingots vary much from the regular standards it is often necessary to rejectwheels either for too low or for too high chill. ,This forms a considerable burden upon the chilled wheel industry, particularly when foundries are operating under stress of output and when'it is impossible to securesthe usual high grade of coke necessary for the manufacture of specification castings.

In the usual foundry wheels are poured between t e time of actual taking of the control test and its examination, the lapsed time beingrequired fon the test ingot to properly cool, and it often happens that wheels are lost, due to change in composition of the metal before it can be corrected by ladle additions of ferro alloys after seeing the test ingot, thus resulting in an expense both for wheels lost and for the high priced alloys added. T The use of the present process in oneinstance' showed a reduction in losses on account of defects ractice, several chargeable to such metal conditions of 39%" for 9 months practical operation as compared to the operations before the process was employed. v

In addition to the removaL of sulfur,-

present' metalloids, occluded slag particles, and gases which tend'to produce segregation and otherwise produce defective castings, the processed metal will generally show more uniform composition, as illustrated in the followlng table, wlnch 1s a log of a regular chilled iron Wheel heat, showing analyses of samples taken of the molten iron before and after the refining treatment.

'7 Silicon Com lhned 7 Sulfur 'ganese. carbon 0 Be- Be- Be- Be- Sample No.1.-. .70 .70 .72 as .86 .so 187 137 2- 77 71 82 70 76 78 178 134 3. .75 .70 .80 .70 .75 .83 .180 .130 4... .72- .70 .64 .66 .77 .77 .202 .138 5... .71 .70 .63 .69 .82 .78 .200 .135 6... .75 .67 .73 .60 .80 .80 .199 .139 7 .80 .70 .80 .60 .84 .82 .200 .141 8 .75 72 .89 .68 .81 .81 .195 .142 Average sam- 85 74 70 75 6B 80 80 193 137 1-8 points vari- Uniformity of composition is the prime essential to uniform castings and particularly so as to uniform chilled cast wheels where the elements silicon, manganese, and carbon are required to be held, in'very close limits in order properly to control the chill, shrinkage and strength of the finished wheel; and it is borne out by a practical use of the process, covering the production of over 1,000,000 wheels, that greater uniformity and generally better castings are obtained from the refined metal. .Therefined metal shows a more uniform physical structure with less tendency to segregation of impurities due both to the removal of the loosel held impurities and probably to thoroug deoxidation of the metal.

The refining process also appears to break up the larger graphite flakes and results in f a generally denser structure in the castings. For example, 36 test bars each of untreated and treated iron were broken on a testing machine and the fracture of each bar was closely inspected for any min rte defects showing up on microscopic examination, and it was found that 48% of bars from the untreated iron showed some minor defects as against only 16.7% of bars fromt'he treat "the finished wheel and its ability to withstand the stralns of railway service.

The final effects of the treatment upon the wearing quality of .-chilled iron, which of course isthe fact governing the life of chilled iron wheels in service, can only be determined through observation of a large number of Wheels over a period of years, since the life of the average chilled iron wheel varies from 3 to 5 years. However, it is believed that the lower sulfur, and particularly the removal of occluded slag particles which with the sulfur tend to segre gate in the casting, will have a tendency to prevent what is commonly termed shellouts in the wheel industry or breaking down of the chill in spots in the tread of the wheelvas sometimes occurs in service. It is also impracticable to determine whether the chill from a thoroughly refined iron has .a greater density, however, it has been found other advantageof thepresent invention as actually obtained in wheel foundry practice. In the refining of cast iron' having a sulfur content of 20%, the sulfur content was reduced to 137% with the use of approximately 5 lbs. of refining material per ton of metal applied in accordance with the present invention. To obtain a similar reduction in sulfur content of thesame metal and using the same refining material, under similar temperature conditions, in the ordinary batch method of treatment, 8% lbs. of re-' fining material per ton of metal were rcquired. The process of the invention is also of special advantage for treating cast irons having a sulfur content of .12% or less The following instance will illustrate anwhere it is desired to'reduce the sulfur to 05% or less, and in the treatment of such low sulfur irons the process of the invention has been found peculiarly effective.

In carrying out the process of the Invention, the quantity of sulfur, occluded slag particles,gases, etc. which are refined out of the molten metal will depend upon the composition of the metal as it comes from the cupola or melting furnace. its temperature, and the quantity of refining material added er ton of metal, and is under control of the operator-at all times, The process of ,the invention has seen worked out in the drawals of molten iron being correlated to alkaline refining slag on the said pool of molten iron and periodically supplymaintain the said pool, maimtain'iing an 001 of molten iron and supplying fresh alkaline refining material to said slag as the operation proceeds.

2. An improved process for desulphurizing and refining iron which comprises maintaining a molten pool of the iron exteriorly of the melting furnace, supplying molten iron to the said pool and periodically withdrawing refined iron therefrom, the additions and withdrawals of molten iron being correlated tomaintain the said pool, maintaining an alkaline refining slag on the said ing fresh alkalirie refining material thereto as the operation proceeds. 3. An improved process for desulphurizing and refining iron which comprises maintaming a molten pool of the ironexteriorly of the melting furnace, continuously supplying molten iron to the said pool, wit draw ng refined iron therefrom, the withdrawals of molten iron being correlated with the supply to maintain the said pool, maintain ing an alkaline refining slag on the said pool of molten iron and-supplying fresh alkaline refining material thereto as the operation proceeds.

4. An improved process for desulphurizing and refining iron which comprises maintaining a molten pool of the ironexteriorly of the melting furnace, continuously su plying molten iron to the said pool, perio ically withdrawing refined iron therefrom, the

periodic withdrawals of molten iron being correlated with the supply to maintainthe said pool, maintain sla on the'said poo of molten iron and per odically supplying fresh alkaline refinan alkaline refining" ing material thereto as the operation proceeds.

5. An improved process for desulphurizing and refining iron which com rises dis-- charging molten iron from a me ting furnace into a non-heated receptacle, maintaining an alkaline refining slag on the molten iron in the said receptacle, supplying fresh alkaline refining material to the said slag as the operation progresses, and periodically withdrawing art of the refined molten iron from thesai receptacle, a pool of molten iron being maintained incontact with the refining slag in the said receptacle during the operation. I

6. An ini roved' process for desulphurizing and re ning iron which comprises discharging molten iron from a melting fur: nace into anon heated receptacle, maintaining an alkaline refining slag on the molten iron in the said receptacle, supplying fresh alkaline refining material to the stream of 'molten iron flowing from the melting furnace to the receptacle as the operation progreases, and periodically withdrawing a part of the refined molten iron from the receptacle, a pool of molten iron being maintained in contact with the refining slag in the said receptacle during the operation.

--7. An improved process for desulphuriz ing and refining iron which comprises maintaming a, molten pool of the iron exteriorly of the melting furnace, supplying molten iron tothe said pool and withdrawing refined iron therefrom, the additions and withdrawals of molten iron being correlated to maintain the said pool, maintaining it refining slag containing a soda ash reagent on the said pool of molten iron, and su plying fresh soda ash reagent to the sai slag as the operation roceeds. v

8. An improve process for desulphurizing and refining iron which comprises main:

'taining a molten pool of theiron exteriorly of the melting furnace, continuously supplying molten iron to the said pool, withdrawing refined iron therefrom, the withdrawals of molten. iron from the pool being correlated-with thesupply to maintain the pool, maintainiing a refining slag containing a soda ash reagent on the said 01 of molten iron, and supplyingfresh so a ash reagent to the slag as the operation rooeeds.

'9. An improved process or desulphurizingand refining iron which comprises maintaming a molten pool of the iron exteriorly of the melting furnace, continuously supplying molten iron to the said pool and eriodically withdrawing refined/iron t erefrom, the withdrawals" of m, lten iron from the pool bein correlated ithjthe supply to maintain t esaid p0 maintaininga refining slag containing a soda ash reagent on the said pool of molten iron; and peri odically-supplying fresh soda ash reagent to the said slag during the operation.

10. An improved process for desulphurizing and refining iron which comprises discharging molten iron from a melting furnace into a non-heated receptacle, maintaining 'a refining slag containing a soda a'sh reagent on the molten iron in the receptacle, supplying fresh soda ash reagent to the said slag during the operation, and periodically withdrawing a part of the refined molten iron from the receptacle, a pool of molten iron being maintained in contact with the refining slag in the receptacle during the refining operation.

11. An improved process for desulphurizing and refining iron which comprises discharging molten iron from a melting furnace into a non-heated receptacle, maintaining a refining slag containin a soda ash reagent on the molten iron in t e receptacle, supplying fresh soda ash reagent to the stream of molten iron flowing from the melting furnace to the receptacle as the operation progresses, and periodically withdrawing a part of the refined molten 1I0I1 from the receptacle, a pool of molten iron being maintained therein in contact with the refining slag during the operation. In testimony whereof I alfix my signa ture. I

GEORGES. EVANS.

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