US968601A - Manufacture of manganese steel. - Google Patents

Description

UNITED STATES PATENT OFFICE. I

WINFIELD S POTTER,

OF NEW YQRK, N. Y.

MANUFACTURE OF MANGANESE STEEL.

No Drawing.

To, alt whom it may concern:

Be it known that I, WINFIELD S. POTTER, a citizen of the United States, andwhose post-office address is'30 Church street, borouglrof Manhattan, city of New York,

county of New York, and State of New York, have invented certain new and useful Improvements .in the Manufacture of ManganeseSteel; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

which are closely-related to each other and which co-act to bring about with certainty the desired result. This series of ste'psbeginswith the treatment of the molten metal.

itself before the ingots are cast, and continues with the subsequent reconstruction of 'the ingot desirable for adapting it to successful commercial rolling, forging or shaping. a

My invention is based upon 'the discovery that, by suitably deoxidizing and cleansing the molten metal, as. hereinafter described, while still in the4furnace, loasting ladle or like source of supply, it is possible -to standardize the subsequent 'heat treatment-of the cast ingot, and, particularly, for steel of *any given composition, to practically. eliminate variations in; that part of the heat=treatinent of the ingot which determines the-reconstruction-ofth'e dendritic portion-and its conversion into the strong uni-formfine grained structura desired. a

The invention is further based upon" the discovery*that thfe preliminary deoX-ijdation and cleansing of the metal'ha's-the function ofestablishn'ig a practically' definite and short period of time for the" complete conversion of the d'el'rdrites, thereby enabling the operator" to "promptly terminate that stage of the "heat treat'n'ient, which would otherwise tend to the formationand building up"of"la1"ge and coarse -crystals, or

grains.

Specification. of Letters Patent. Patented Aug, 30, 1910. Application filed May 20, 1910. Serial No. 562,374.

In order to further illustrate and make clear the generic character of the invention and the principles of operation upon which it is based, I will now describe a suitable specific method or series of operations for putting it into practice so as to realize its characteristic advantages, and, for this purpose will assume that in the particular instance given, the manganese steel is to be compounded from suitably dephosphorized and desulfurized molten open hearth steel from an open hearth furnace, and molten ferro-manganese, mixed in the desired pro? portions in a casting ladle of large capacity or other suitable container appropriate for the purpose. However, as hereinbefore in dicated, the operations of compounding the metal, deoxidizing and cleansing it, may be effected in the open hearth or other like furnace itself, although, in the case of this very readily oxidized metal, the most complete deoxidizing, cleansing and washing can only be secured by continuing those operations in the ladle itself-and with the employment of the protective cover of acid slag as hereinafter described.

Assuming that the compounding of the metalis to be efi'ected in the casting ladle of large capacity, (say sixty tons or more) the ladle will be lined with the usual siliciou s or acid lining, preheated in the customary manner. The charge of dephosphorized molten steel from the open hearth or like furnace will then be-run into the ladle and simultaneously therewith the molten ferromanganese will likewise'be' charged therein.

As the chargej f molten metal rises in the ladle, itis essential for the purpose of my present'inventiori 'to' 'maintain upon its up per. surface a protecting layer of acid slag. For this purpose, the ladle may, if desired,

be charged with a small quantity of readily fusible acid slag making materials, or a mixture which will form a readil fusible acid slag, before the steel is running from the fu'rnacetorin lieu thereof, or in, addi-.

tion thereto, the tacid slag making material may be added from time to time to the charge, as the level of the metal rises in the ladleh-The acid slag making materialsmay conveniently consist of silica or other sili-.

cious materia'rassociated with a suflicient amount of fiuxing ingredients such as sodium silicate" lime, or lead oxid, to make it readily fusiblesat a suiiiciently low temperature, and the proportion of silica should be terials into the ladle either before or during the charging of the molten steel is, furthermore, to obtain such an'intimate contact of the acid slag formed and the metal as to insure, to the greatest extent possible, the washing out of the oxids from the steel throughout the entire mass thereof. Usually, it will not be found feasible to charge the steel from the open hearth or other furnace into the ladle Without likewise encumbering it with a practically unavoidable'proportion. of the furnace slag containing basic oxids; and, it will be understood that the amount of acid slag making materials to be charged into the ladle should be suflicient to likewise balance and neutralize these basic oxids from the furnace. In fact, the quantity of acid slag making materials charged into the ladle should be somewhat in excess of that required both for cleansing the steel from its contained oxids and also for balancing the oxide admitted from the furnace with the furnace slag, in order that the body of slag finally floating upon the charged metal in the ladle shall be devoid ofany oxidizing effect upon the charge. In charging the molten steel into the ladle it will, of course, be understood that it is preferable to avoid as far as possible the entrance of any large portion of the furnaceslag. This may be eflected in any suitable manner, as, for instance, by diverting the slag over the side of the furnace spout into'a slag receptacle.

Tilting furnaces may be used to advantage for the production .of the steel, and the opening through which the metal is discharged from the furnace will be made of such size and the furnace so tilted during the pouring operation that the steel enters the ladle with but little slag, whereupon the slagmay be afterward .poured separately into another receptacle. After the ladle is filled, the metal with its protecting top layer 3f acid slag is permitted to remain at rest for a period sufficient to insure the separa- ;ion'of the slag and metal, and is permitted cool to the temperature desirable for cast- .ng or teeming into the ingot molds.

In order to effect an entirely satisfactory :leansing of themetal in the ladle, it should a )e at a relatively high temperature during 1110. cleansing operation, as compared with .he temperature of final pouring into the ngot molds. For instance. the cleansing op-q rration may be carrier on with the metal at I. temperature of say H00" C. to 1450" (J. lhe metal in the ladle will preferably conain about 12% of'nmnganesc and from 80% to 1.10% of carbon; and, in order to have as little piping as possible in the ingots and to permit the metal to set without undue delay in the molds, the metal in the ladle should be cooled, orpermit-ted to cool, before the pouring operation begins, to a temperature of say 1375 C. The pouring from the ladle is effected through a bottompourin aperture, and the temperature of the meta and the attendant conditions are to be so established that the metal will set in the ingot molds promptly, with the exception, perhaps, of a small proportion in the innermost longitudinal center or core of the ingot. \Vhile the ingot is still in the mold, I preferably cool it in such manner that, when stripped from the mold, the outer portions (to a-depth fully including. the thickness of, the zone of the dendrites) will have an average temperature in the neighborhood of 1000 C., (say from 950 C. to 1050 C.)

except at the edges where it will be unavoidably considerably lower. This enables itto be transferred, without suffering any rupture, into a soaking pit or other like heating furnace, wherein it 1s to be subjected to the heat treatment designed for reconstructing its exterior portions; and it also permits this heat treatment to take place Without crack- "ing the ingot. At the time of its entrance into the soaking pit or like furnace, the ingothas set and developed its freezing struc tures to a depth of say six inches or more inwardly from its outer skin or periphery and a zone of dendrites has formed which usually occupies say about one-half of this depth. In order to break downthese dendrites and to substitute therefor a strong uniform structure of fine grain, I thenslowly raise the temperature of the'soaking pit to 117 5 C. or a somewhat higher temperature slowly or evenly, this rise in temperature being eifected in a smoky -or reducing atmosphere, so that the periphery of the' ingot will not be oxidized. I have found that with the preliminary deoxidation and cleansing of the' metal, as hereinbefore described, the breaking down of the dendrites and the substitution therefor of a strong uniform fine grained structure can be accomplished at or about the temperature of 1175 C. specified, with- .in a comparatively short period of time, say half an hour, the temperature and the time of reconstruction varying somewhat with the particular composition of the metal, but within relatively narrow limits, one. way or the other, from the tem erature and the period of half'an hour is erred to I have also found that, for steel of any given com- "position or analysis, the preliminary dcoxidizing and cleansing step permits the operator to predeternnn'e the temperature and the time necessary for the desired bro-a king down of the dendrites and the IGL'OllStl'llCtiOll of the steel. So that, not only is the period rcfcrrcd to shortened, but the operation as a eesscu whole is so standardized that the desired result can be anticipated with confidence. After the ingot has remained at the temperature of 1175 C. or thereabout for'the period necessary for the reconstruction de sired, this stage of the heat treatment is arrested by lowering the temperature so as to prevent the building up within the mass of larger and coarsergrains. To this end, the ten'iperature prevailing within the soaking pit-or other heating. furnace may be lowered by the injection of water vapor, in the form of a steam jet, carrying with it water in suspension, with the result that the periphery of the ingot is reduced in temperature to say 1100 (1.; or for the same purpose, the ingot may be cooled by transferring it into a cooler soaking pit, for example. The lowering of the temperature of the exterior portions of the ingot is accompanied with the formation of a tough thick skin, which shrinks upon and works the still plastic interior. Finally, after the cooling of the outer portions of the ingot has occurred, and the steam jet has been cut oil", the outer portions of the ingot are preferably permitted to rise again in temperature to'say l125 (1.,

in order to equalize the surface temperatures and to obtain the desirable maximum ductility, whereupon the ingot may be removed from the soaking pit and is in condition to be immediately rolled into rails or other products, in mills of ordinary construction. Moreover, the temperature conditions are such that a track rail, for instance, of standard length and section, rolled from such an ingot, will be delivered from the final pass of the rolls at a temperature which will permit it to be toughened by quenching without being first subjected toareheating operation.

It will be understood that the cooling temperature of1100' C. and the reheating temperature of 1125 (lreferred to are not to be regarded as absolute. They are the temperatures which are appropriateto manganese steel of' what may be termed a soft analysis, that-is, having, say, 1.10% of carbon, or less, whereas, when the percentage of carbon is higher, say, 1.20%, andupward,

the temperature of cooling will be somewhat lower, and the tern erature to which the steel, may bereheate will also be lower. In

ether words, these temperatures will depend upon the analysis of the steel, especially with regard to its content of carbon.

As hereinbefore stated, the preliminary step of deoxldizing and cleansing the manganese steel has for its effect not only to permit the shortening and'standardizing of the period in which the dendrites are broken down and converted into a. uniform fine grained structure, but by clearing the metal .of its oXids throughout, makes it correspondingly stronger as a final product and less tender during the manipulation to which it is subjected from the time the ingot is cast until the rolling operation is com pleted. Furthermore, the preliminary deoxidation and cleansing of the metal will permit, to great advantage, the practice of an alternative way of toughening the outer portions of the ingot instead of subjecting it to cooling in the soaking pit. That is, the ingot may be taken from the soaking pit, in which it has been slowly and evenl heated to a temperatureof from 1175 C. to 1225 (1, depending upon the analysis of the metal, and is then subjected to light. mechanical working over its periphery for the purpose ofproducing a wrought thick skin thereon. The lower temperature (117 (1., or thereabout) is preferred when the amount of carbon present in the ingot is above 1.20% and the higher temperature (1225 (1., or thereabout) is preferred when the amount of carbon present is 1.10%, or less, it being assumed in both of these instances that any phosphorus present is low in amount. The preliminary deoxidizing. and cleansing operation greatly facilitates the welding of this outer skin and also makes it possible to execute this step, of thev operation at a higher temperature. This welding or consolidating of the outer por tions of the ingot to produce a wrought skin or shell is of particular importance where the reduction contemplated in the rolling millis considerable for the initial passes thereof. It is carried out quickly, so that there may be no material drop in temperature, and the ingot is then delivered to the rolling mill and rapidly reduced in the usual manner. I Y

In order to give a concrete instance of the light preliminary working appropriate to the practiceof the invention, I will assume that themanganese steel ingot is a -X20 square section. The light preliminary roll-; ing would be effected by acting first simultaneously upon two horizontal sides,.andfthen.- turning the ingot and. actingsimultaneously upon the two remaining sides. Where'the analysis of the manganese steel of. thef ingot shows itto be low in carbon (say containing; 1.10% 'of carbon, or somewhat less than that amount), the reduction in the first one or two passes of the perliminary light rolling maybe about: one inch in each pass.v This first reduction along the two horizontal sides of the ingot renders the metal of those sides capable of greater elongation, and consequently, when the ingot is turned over and rolled along its opposite sides, asomewhat ke, place, say. one

greater reduction can ta and one-half or one andthree-quarter nches.

.These two preliminary reducing passes will ingeneral suflice for the light preliminary rolling intended, although, in some instances, they may be supplemented by a third or even a fourth pass, if the mill conditions limit the first reductions of the series passes to-from one-half to nese steel has a aresuch that" the light preliminary rolling can be effected quickly. When the manga' harder analysis, 2'. 6., when as high as 1.20%, be advisable tcf the percentage of carbon is or higher, it Wlll usually light preliminary three-quarters of aninch, it beingpermis sible, however, to somewhat increase the reduction in the subsequent pass or passes,'for

" thereason hereinbefore explained, i. 6., be

cause the metal of those sides which have been subjected to the action of the reducing rolls is capable of greater elongation for the next succeeding pass. I

When an electric furnace is used for the making or compounding of the manganese steel, and when there is present in that fur pace at considerable proportion of manga nese, it 'isdiflicult to avoid the production of a large amount of manganese oxid. To meet thisdifiiculty,

it will be desirable, just before the metal is tapped from the electric furnace into the ladle, to add-to the furnace charge a reducing agent (such as silico-calcium, aluminum, ferro-titanium, or the like) in sufficient quantity to properly reduce the, oxids contained in the metal. The metal wouldthen as possible from the furnace slag. In view of'the highly oxidizable character of the metal, further oxidation will take place dur- 7 nace into the ladle, deoxidation, cleansing and washlng of the steel will proceed in the ladle as hereinbe-- gree higher p the metal from the furing the transfer of l and therefore the final insurergreater reliability in" case the casting conditionsishould be more or less unfa and in order to ob;

vorable to theoperation,

j tain' a correspondingly greater ductility] of the inetal passage 9 5 "lVliatllclaim 1S2,

through the i L lu the production of manganese "steel ns by converting the ends contained therein into morereadily separable compounds" anti} permitting compounds to separate out by flotat on," and preserving the molten 1.

face oxidation thereafterby" ma ntaining thereon: a protective layervof ingbts, the step "of preliminarily cleansing the body of molten be charged into theladle, as free bringing the temperature" of' oiwwil p. e found juseful" in most instances in order to from which H sufficient 'tofsubstantlally chnnuate variaf s, the step of preliminarily clez'tnjsing the mai anesesteehflwhile 1n the molten cond tion and before casting into the ingot I'nfoltl',

manganese steel, While in the molten condition and before casting into the ingot mold,

by converting a portion of theoxids contained therein into more readily separable compounds and permitting said compounds to separate out by flotation, and reducing other portions of said oxids by the introducltion into the molten metal of a reducing agent substantially as described.

3. Inthe production of manganese steel ingots, the step of preliminarily cleansing the manganese steel, while in the molten condition and before casting into the ingot mold, by intimately mixing and washing the steel with silica, thereby separating out con tained oxids as silicates, and separating the silicates by flotation, and thereafter maintaining aprotecting layer ofthe acidslag upon the top of the metal; substantially as described.

suitable condition for making the desired lng ot, by muting 1n an acid-lined ladle a steel from a furnace and a body of molten ferro-inanganese, diverting the ma] or portion of the furnace slag so izing or balancing such portion of the fur nace slag as thatit'will not enter the ladle, and neutralacid material for that purpose;substantially as described.

. 5. In the production of m anganese steel ingots and their subsequent heat treatment inorder to remove their objectionable freez= in g structures, the preliminary step of cleansing and deoxidizing the metal from which the ingot is cast, to an extent sear cient to substantially eliminate the variations in the temperature necessary for the reconstruction desired, and subjecting the :ingot to thereconstructing temperature until the" objectionable freezing structures have i been removed; substantially as .describedJf In the production of manganese steel ingots andtlieir"subsequent heat treatment,

in order tofconve'rt. their dendrites'into structures of uniform fine grain, the p'relimlnary step of cleans ng and ClGOXILlIZHlg the metal the lingot is cast "to an extent tions in the temperature necessary for the reconsthiction desired, and siibjecting the ingot to the reconstructing temperature un til the desired uniform fine crystalline strucstructuresof' uniform fine grain, the preliminary step of cleansingand deoxi'di'zing' the" metal from which the ingot isca'st to an eX-' tent sufficient to substantiallyeliminate vatureihasbeen produced; substantially as de- 85 4. In the productlon of manganese steel ingots, the step ofobtainlng the metal in 'riations in the temperature necessary for the reconstruction desired, cooling the ingot un til the exterior portions have temperatures in the neighborhood of 1000 (1., and sub jecting the ingot to the reconstructing temperature until the desired uniform fine crystalline structure has been produced; substantially as described.

8.-In the production of manganese steel ingots and their subsequent heat treatment in order to convert their dendrites into structures of uniform fine grain, the preliminary step of cleansing and deoxidizing the metal;v

from which the ingot is cast to an extent sufficient to substantially eliminate variations in the temperature necessary for the reconstruction desired, and subjecting the ingot to the reconstructing temperature until the desired uniform fine crystalline structure has been produced, and lightly working the ingot so as to produce a tough wrought skin; substantially as described. I

9. In the production of manganese steel ingots and their subsequent heat treatment in order to convert their dendrites into structures of uniform fine grain, the preliminary step of cleansing and deoxidizing the -manganese steel containing about 12% Mn. and about 1.10% C. from which the ingot is cast to an extent sufiicient to substantially eliminate variations in the temperature necessary for the reconstruction desired subjecting the ingot to the reconstructing temperature until the desired uniform fine crystalline structure has been produced, and lightly working the ingot so as to produce a tough wrought skin; substantially as described. I

10. In the production of manganesesteel ingots and their subsequent heat treatment in order to remove their objectionable freezing structures, the preliminary step of cleansing and deoxidizing the metal from which the ingot is cast to an extent suflicient to substantially eliminate variations in the temperature necessary for the reconstruction desired, castin the metal at a temperature but slightly a ove its freezing or setting point, cooling the'outer portions of the ingot .to about 1000 (1, and subjecting the ingot to the reconstructing temperature until the desired fine crystalline structure has been produced; substantially as described.

11. In the production of manganese steel ingots and their subsequent heat treatment in order to remove their objectionable freezing structures, the preliminary step of cleansing and deoxidizing the metal from which the ingot is cast to an extent sufiicient to substantially eliminate variations in the temperature necessary for the reconstruction desired, casting the metal at a temperature approximating 1375 (l, and "heating the ingot slowly and evenly to from 117 5 C. to 1225 (1; substantially as described.

12. In the production of manganese steel ingots and their subsequent heat treatment in order to remove their objectionable freezing structures, the preliminary step of cleansing and deoxidizing metal from which the ingot is cast to an extent sufiicient to substantially eliminate variations in the temperature necessary for the reconstruction desired, casting the ingot at a temperature approxim-ating 137 5 C., coolingit to a term perature of about 1000 (l, and slowly and evenly heating it to from 1175 C. to 1225 (l; substantially as described.

In testimony whereof I affiX my signature,

in presence of two witnesses.

WIN FIELD S. POTTER.

Witnesses JOHN C... PENNIE, WILLIAM H. DAVIS.