US968602A - Manufacture of manganese steel. - Google Patents

Description

facture of Manganese Steel;

'ing ladle, or like WINFIELD S. POTTER,

orrioE j on NEW Yo'aK,

MANUFACTURE OF MANGANESE STEEL.

N 0 Drawing.

Specification of Letters Patent. Application filed June 18, 1910.

Serial No. 567,696.

To all whom it may concern:

Be it known that I, Winrlnno S. Porran, I a citizen of the United States, residing in the city and State of New York, and whose post-olfice address is 30 Church street, New York city, New York, have invented certain new and useful Improvements in the Menuand I do herebydeclare the followin 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.

In an application forLetters Patent of the United btates, filed by me under date of May 20, 1910, Serial 0. 562,374, I have described and claimed the production of a manganese steel ingot, devoid of dendrites and other objectionable freezing structures and of a strong uniform fine grained structure throughout by a series of steps beginning with the treatment of the molten metal itself before the ingots are cast, and continuing with the subsequent reconstruction of theingot desirable for adapting it toasuccessful commercial rolling, forging or shap- H10. is broadly set forth in my application" referred to, the fundamental discovery emf bodied therein was, that by suitably deoxi-' dizing and cleansing the molten metal as described, while still in the furnace, castsource of supply, it is possible to standardize the subsequent heat treatment of the cast ingot, and, particula'rly, for steel of any given composition, to practically eliminate variations. in tliatrpart of the heat treatment of the termines the reconstruction of thedendritic portion and its conversion into the strong uniform fine grained structure desired. .The invention, as described in mysaid'application, involved the furtherdiscovery, that the preliminary deoxidation and cleansing of the metal has the functionof establish ing a practically definite and short period of time for the. complete conversion ofthe dendrites and the removal ofthe other -objectionable freezing structures, therebyx V-enabling the operator to promptly terminate that stage of the heat treatment,- which would otherwise tend to the formation and building upiof large and coarse-crystals, or

grains. n The present application, which is based upon the same fundamental features of discovery above noted, is directed specifically I f to a particular method ingot which desecured -theladle itself and With for carrying out the general operation and for realizing its char: acteristic advantages.

-More particularly stated, this specific en1'-- invention involves, the

bodiment of the general operation, the feature-of preventing the formation and building up of large and coarse crystals of grains, .by lowering the Patented Aug. 30, 1919,

temperature of the outer portions of the in 5 got, after the objectionable freezing structures have been removed and the desiredreconstruction into metal of uniform fine grain has been accomplished.

It also includes the-further.feature of supplementing this lowering of the temperature of the outer portions of the ingot for additional condition in which it then finds itself, to

receive, by light rolling, the tough thick skin contemplated. v p

The preliminary treatment of the metal, includingthe compounding thereof, is fully set forth in its application for Letters Patent of the United States hereinbefore referredto, wherein it is assumed that, in the particular instance given, the manganese. steel is to, be 1 compounded from suitably dephosphorized and desulfurized open hearth steel from aniopen hearth furnace, and molten ferro-manganese, mixed in the desired. ladleof large capacity or other suitable container appropriate for the purpose. v The operations of compoundingthe metal, deo xizdizmg' and cleansing, 1t,

, ay, oweve be effected in theopen hearth-or like furnace itself, although, in thecase of thishveryread- 11y oxidized inetal,the most complete deoxi dizing, cleansing and washing can only be by continuing those operations in the employment of a protective cover of acid slag, as lierein- .aft'er'described' I I that. the compounding of the Assuming metal is to be effected inthecastmg ladle of large capacit (say sixty tens .or more) the ladle will bellined with the usual silicious or acid lining, preheated in the customary proportions in "a casting preferred embodiment, in my" to obtain such acid slag formed 'dients such as sodium silicate,lime,

manner The charge of dephosphorizcd 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. I As the charge of molten metal rises in the ladle, it is essential for the purpose of the invention to maintain upon its upper surface a protecting layer of acid slag. F or 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 readily fusible acid slag, before the steel is running from the furnace; or in lieu thereof, or in addition thereto, the acid slag making material may be added from time to time to the charge, as thelevel of the metal rises in the ladle. The acid slag making materials may conveniently consist of silica or other silicious material associated with a sufficient amount of tiuxing ingreor lead oxid, to make it readily fusible at a sufficiently low temperature, and the proportion of silica should be sufiicientto balance the oxids present in the steel, (as, for instance, the oxid of iron and oxid of manganese) which it is the purpose of my invention-to eliminate, as far as possible, by the treatment proposed. The purpose of charging the acid ,slag making materials into the ladleeither before or during the charging of the molten steel is, furthermore, an intimate contact of the and the metal as to insure, tothe 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 sufficient 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 of any 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 furnace slag. This may be effected in any suitable manner, as, for instain: by diverting the slag over; the side of the furnace spout into a slag receptacle.

Tilting furnaces may be used to advanfilled, the metal wlth tionof the slag andtage for the production of the steel, and the opening through which the metal is ischarged 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 slag may be afterward poured separately into another rece tacle. After the ladle is its rotecting top layer of acid slag is permitte to remain at rest for a period sufficient to insure the separametal, and is permitte to cool to the temperature desirable for casting or teeming into the ingot molds.

In order to effect an entirely satisfactory cleansing of the metal in the ladle, it should be at a relatively high temperature during the cleansing operation, as compared with the temperature of final pouring into the ingot molds. For instance, the cleansing operation may be carried on with the metal at a temperature of say M00 C. to 14:50 O. The metal in the ladle will preferably contain about 12% (if manganese an 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, or permitted to cool, before the pouring operation begins, to a temperature of say 1875 C. The pouring from the ladle is effected through a bottom pouring aperture, and the temperature 0 the metal and the attendant conditions'are tobe 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.

While 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 of 1000 0., (say from 950 C. to 1050 C.) except at the edges where it will be unavoidably considerably lower. This enables it to be transferred, without suffering any rupture, into a soaking pit or other furnace, wherein it 18 to be subjected to the heat treatment designed for reconstructing and it also permits its exterior portions;

take place without this heat treatment to cracking the ingot. trance into the soaking pit or like furnace, the ingot has set and developed its freezing structures to a depth of say siX inches ormore 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 down these dendrites and to substitute therefor a strong uniform structure of fine grain, then slowly raise the temperature of the soaking 1 average temperature in the neighborhood fit like heating 11 At the time of its en- 12 pit to 1l75 perature (for example 1225 C.) slowly or evenly, this rise in temperature being efected in a smoky or reducing atmosphere, so that the periphery of the ingot will not be oxidized. I have found that with the pre liminary deoxidation and cleansing of the result that the periphery metal, as hereinbefore described, the breaking down of the dendrites and the substitution therefor of a strong uniform fine grained structure or about the temperature of 117 5 C. fied, within a comparatively 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 temperature and the period of half an hour referred to. I have also found that, for steel of any given composition or analysis, the preliminary deoxidizing and cleansing step permits the operator to predetermine the temperature and the time necessary for the desired breaking down of the dendrites and the reconstruction of the steel. So that,

specishort period C. or a somewhat higher tem not only is the period referred to shortened,

but the operation as a 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 desired, 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 coarser grains.

To this end, the temperature prevailing within the soaking pit or other heating furnace may be lowered by the injection'of water vapor, in the form of a steamfjet, carrying with it water" in suspension, with the of the ingot is reduced in temperature to say 1100 C.; 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 ofthe outer portions of the ingot has occurred, and the steam jet has been out off, the outer portions ofthe ingot are preferably permittedfto rise again in temperature to say l125 (3., in order to equalize the surface temperaturesand to obtain the desirable maximum ductility, whereupon the ingot maybe removed from the soaking pit and is in condition tobe 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 nese steel of what may can be accomplished at addition to this,

of the rolls at a temperature which will permit it to be toughened by quenching without being firstsubjected to a reheating operation.

I t will be understood that the cooling temperature of 1l 00 C. and the reheating temperature of 1125 C. referred to are not to be regarded as absolute. They are the temperatures which are appropriate to mangabe termed a soft analysis, that is, having, say, 1.10% of carbon, or less, whereas, when the percentage of car bon is higher, say, 1.20%, tei'nperatnre of cooling will b'eisomewhat lower, and the temperature to which the steel may be reheated will also be lower. In other 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 deoxidizing 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 andconverted into a uniform fine grained structure, but by clearing the metal of its oxids throughout, makes it correspondingly strong as a final roduct and less tender during the inanipu ation to which it is subjected from the time the ingot is cast until the rolling operation is completed. In the preliminary deoxidation and cleansing of the metal and the f0rma-tion thereon of a tough thick skin by the cooling to which the ingot has been subjected after its period of reconstruction, brings it into a larly appropriate to a still further consolidation'and toughening of the skin by subjecting it to light its periphery. This light mechanical working has the effect of imparting to the thick skin the characteristics of wrought metal, so that, when thereafter subjected to heavy reductions incident to its passage through the 'rolls of the mill, it ,will have greater ductility and the danger of rupture will be correspondingly lessened. The light mechanical working referred to will take place as a subsequent step to the coolingoperation hereinbefore described, that is, immediately before the ingot (after such cooling operation) would otherwise be rolled in the ordinary mill.

The welding or consolidating of the outer portions of the ingot by the light mechanical working described is of particular importance, where the mill work immediately following is heavy and where it involvessudden reductions or rapid eiongations.

In order to the practice of the invention, I will assume that the manganese steel ingot is a 20" x 20 square section. The light preliminary rolland iv award, the

state or condition particumechanical Working over give a concretei'nstance of the li ht )reluninar workin a ro riate to" s l y a: PP P ing would be ettected by actin first simultaneously upon two horizontal sides, and then turning the ingot and acting simultaneously upon the two remaining sides. Where the analysis of the manganese steel of the ingot shows it to be low in warbon (say containing 1.10% of 'arbon, or somewhat less than that amount), the reduction in the first on I or two passes of the preliminary light roiling may be about one inch in each pass. 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, a somewhat greater reduction can take place, say one and one-half or one an l. threepiarter inches. These two preliminary reducing passes will in general sullice for the light preliminary rolling intended, although, 1n some instances, they may be supplemented by a third or even a fourth pass, if the mill conditions are such that 'the light preliminary rolling can be effected quickly. When the manganese steel has a harder analysis, i. 0., when the percentage of carbon is as high as 1.20%, or higher, it will usually be advisable to limit the first reductions of the series of light preliminary passes to from one-half to three-quarters of an inch, it being permissible, however, to somewhat increase the reduction. in the sub sequent pass or passes, for the reason hereinbefore explained, e., because 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.

\Yhen an electric furnace is used for the making or compounding of the manganese steel, and when there is present in that furnace a considerable proportion of manganese, it is tillllClllt to avoid the productionof a large amount of manganese oxid. To

meet this difiiculty, 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-titaniuni, or the like) in sutlicient quantity to properly reduce the orids contained in the metal. The metal would then be charged into the ladle, as free as possible from the furnace slag. in view of the highly oxidizable character of the metal, further oxidation will take place dur ing the transfer of the metal from the furnace into the ladle, and therefore the final deoxidation, cleansing and washing of the steel will proceed in the ladle as hereinbefore described. i

As has been hereinbc't'ore indicated, the twnperature of the ingot may be raised in the soaking pit, in some instances, to a degree higher than 1175- C. in its exterior portions; in fact, to somewhat exceed this limit (say, by bringing the temperature of the exterior nations to 1225 C.) will be found useful in most instances in order to insure greater reliability in case the casting conditions should be more or less unfavorable to the operation, and in order to obtain a corresprunlingly greater ductility of the metal during its passage through the roll,

hat I. claim is:

1. in the production of manganese steel ingots and theirsubsequent heat treatment, in order to remove their objectionable freezing structures, the preliminary step of cleansing and deoxidizing the metal. 1' which the ingot is cast to an extent suilicici to sul'istantially eliminate variations in the temperature necessary for the reconstruction desired, subjecting the ingot to a reoonstrncting temperature until the objectionable freezing structures have been removed, and, after such reconstrnctimi, lowering the temperature of the outer portions of the ingot so as to avoid the production of large and coarse grains; substantially asdescrihed,

2. 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 sutlicicin to substantially eliminate variations in the temperature necessary for the reconstruction desired, casting the metal at a temperature but slightly above its freezing or setting point, subjecting the ingot to the recon structing temperatureuntil the objectimiable "reezing structures have been removed, and, after such reconstruction, lowering the temperature of the outer portions of the ingot so as to avoid the production of large and coarse grains; substantially "as described.

3. In the production of manganese steel. ingots and their subsequent heat treatment in order to convert their dendrites into structures of uniform finegrain, the preliminary step of cleansing and deoxidizing the metal fronf which the ingot is cast to an extent sufficient to substantially eliminate variations in the temperature necessary for the reconstruction desired, subjecting the ingot to the reconstructing temperature until the desired uniform tine crystalline structure has been produced, and, after such recon-- struction, lowering the temperature of the outer portions so as to avoid the production of large and coarse grains; substantially as described.

4:. In the production of manganese steel ingots and their subsequent heat treatment in order to convert; their dendrites into struc tures of uniform line grain, the preliminary step of cleansing and deoxidizing the metal from which the ingot is *ast to an extent sufficient to substantially eliminate variations in the temperature necessary for the I desired, subjecting the ingot to the reconstructing "temperature until the desired uniform fine crystalline structure has been produced, and, after such reconstruction, lowering the temperature of the outer portions so as to avoid the production of large and coarse grains, and finally lightly Working the outer portions of the ingot so as to produce a wrought tough thick skin; substantially as described" 5. In the production of manganese steel ingots and their subsequent heat treatment, in order to remove their objectionable freezing s'tructures,. the preliminary step of cleansing and deoxidizing manganese steel containing about 12% Mn and about 1% C. from which the ingot is cast, the cleansreconstruction ing and deoxidati tent sufficient to on being carried to an exsubstantially eliminate variations in the temperature necessary for the bjecting theingot g temperature until the objectionable freezing structures have been after such reconstruction, mperature of the outer por tions' of the ing otso as to avoid the production of large and coarse grains; substantially as described.

In testimony whereof I afiix my signature, in presence of two Witnesses.

Witnesses ELSA M. VVILLIAM 'WIN FIELD S. POTTER.

H. DAVIS.