US975371A - Production, treating, and rolling of ingots of manganese steel. - Google Patents

Description

WINFIELD S. POTTER, OF NEW YORK, N. Y.

PRODUCTION, TREATING, AND ROLLING OF INGOTS OF MANGANESE STEEL.

No Drawing.

. To all whom it may concern:

Be it known that I, IVINFIELD S. Forum, a citizen of the United States, residing in the borough of Manhattan, city, county, and State of New York, have invented certain new and useful Improvements in Production, Treating, and Rolling of Ingots of Man anese Steel; and I do hereby declare the ollowing 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.

My invention relates to methods of producing, heating and rolling ingots of manganese steel, that .is to say, steel usually containing from 10} to 15% or more of man-' ganese, and from 80% to 1.25% or more of carbon. Steels for treatment in accordance with my invention may also have lower percentages of manganese, in which event the percentage of carbon may be diminished to advantage as the percentage of manganese is decreased. So also, for certain purposes, the steel may be provided additionally with a suitable proportion of someother metal or alloy, as for instance, chromium.

In the practice of my invention it is desirable to vary the details of the operation to some extent, as hereinafter indicated, to accord with the composition of the metal and the character and dimensions of the article to be produced or the shape to be rolled. In all cases, however, I have found that there are certain underlying principles and laws which must be duly taken into consideration in the treatment of the metal in accordance with the invention if the best products and the greatest degree of economyare to be secured. These principles and laws and their utilization in the practice ofthe invention will now proceed to set forth, at first dealing with the steel, for the sake of simplicity, as a ternary compound of iron, manganese and carbon; although the steel will usually contain small quantities of such elements as phosphorus, sulfur and silicon and may also, as above indicated, contain other metals in addition to the iron and manganese.

When the liquid metal is cast and is permitted to freeze, certain substances or mix tures separate out of the mass and freeze first, with the formation of crystals of a composition nearly or quite the same as the average analysis of the metal poured, de pending principally upon the composition Specification of Letters Patent.

while other Patented Nov. 8, 191.0.

Application filed October 7, 1910. Serial No.585,796.

of the steel whichhas been made. These first formed crystals are composed of iron with manganese alloyed with or in solution in the iron and will be hereinafter termed mix crystals. The mix crystals forming in a steel containing carbon have in solution a proportion of carbids of iron and man'- ganese.

When the carbon content of the metal is considerable, a secondary structure is produced-at a lower temperature than the freezmg point of the mix crystals, by a separation, from the balance of the metal, of alloys richer in manganese and carbon than the average of the whole mass. This richer metal crystallizes in the open spaces of the network of mix crystals previously formed. The portions last freezing, (the eutectic), consist of one or more carbids of iron and manganese, and for convenience'will be hereinafter referred to as carbids. The carbids themselves may also be separated by selective freezing, so that certain microscopic layers may be formed containing manganese approximately 40% and carbon 6% or more, layers may form containing manganese about 20% and carbon 4% or more, in a mass of which the average analysis is for example manganese 13% and carbon 1.40%. The carbids containing the higher manganese percentage freeze first, that is, at the higher temperature. These separations are most pronounced in steel of high manganese content which has frozen slowly and when, the steel is hyper-eutectoid, that is, when it contains carbon in excess of the eutectoid ratio for the percentage of manganese present. The eutectoid ratio will for the purposes of this specification, be defined as that percentage of carbon for a given manganese percentage which produces a quantity of carbids equal to the amount which the mix crystals are capable of taking into solid solution when the mass is heated to a temperature above the melting point of the eutectic, but belowthe melting temperature of the mass. Steel containing more carbon than this ratio will be classed as hypereutectoid, and steels containing less as hypoeutectoid.

The proportion of carbids in the whole mass when it is frozen depends upon the total average percentage of manganese in the metal before freezing, and .more particularly upon the total average percentage of carbon. Thus, steel containing 12 7; of manin grain and consists of small ganese with a proportion of carbon as high as .857 or a higher proportion of carbon, will, when frozen in agiven manner and at a certain rate, have less free carbids than steel-containing the same percentage or content ofcarbon and containing but 10%, for exam 1e, of manganese. The amount of the carbid s selectively frozen out in the whole mass is also a function of the rate of freezing, and the distribution of the carbids throughout the mass is likewise dependent principally thereon, the rate of freezing being determined by additional considerations such as the temperature at which the metal is poured, the chilling capacity of the walls of the mold, the dimensions of the ingot to be cast, and the like.

The outer layer of the ingot is usually fine 7 mix crystals surrounded by very thin layers, if any, of carbids. Within this fine-grained skin, a structure, normal to the surface of freezing, forms, in which the mix crystals arebuilt one upon the other in nearly straight lines, and the resulting columns or dendrites are separated by layers of crystals of the carbids. The remaining interior portion of the mass is made up of a very uniform network of the mix crystals filled in with the carbids.

lVhen the period of freezing is long, the layers of carbids forming between the dendrites are heavy. of the mass may even be hyper-eutectoid when the remaining portions of the ingotare hypo-eutectoid. Very high carbon-steel cooled slowly in the mold will produce ingots highest in manganese inthe dendritic portion, and highest in carbon in the central portion. while hypo eutectoid steel cooled slowly in the mold results in ingots having both manganese and carbon highest in the zone of dendrites.

When the ingot is frozen throughout rapilly, the local carbid enrichments are less and are more nearly equal between the different parts of the ingot, than when the period of freezing is ong; so that the average metal in the dendrite portion of the ingot may show. by analysis, the same manganese and carbon as the central portion. and both may contain the same percentage of these elements as the skin or first layer frozen. This equality in average composition between the different localities in the mass cannot be secured in a large ingot when the carbon of the steel is at or above the eutectoid ratio. On this account, when manganese stcel of a specified carbon content is desired. the manganese per cent. should be raised to equal or exceed the eutectoid ratio, and the steel should be cast in the smallest or thinnest ingot sections which will produce the required shape with the proper amount of mechanical work, that is, the amount of mechanical work which and this dendritic portion willweld and unite theparticles and properly break down any coarse structures or crystals which maybe present. 4

v hen the steel is heated to temperatures above the change point'lying usually in the neighborhood of"10:25 C. the ca'rbids become weak in consequence of the close approach to their several melting temperatures and at about the same temperature, that. is, at about 1025 C., the carbon of the carbids As the temperature is raised above the change point the outlines of the carbid areas are gradually lost and the carbids finally disappear altogether by absorption into the balance of, the mass if the heating is sufliciently prolonged, and providing the specimen is. not hyper-eutectoid. The freezing grains are also broken up during the absorption of the cal-bids in such a manner that the mass is strol'iger, the contact of the mix crystals being no longer broken by the weak cleavage planes of the carbi ds.-

If the mix crystals in any part of the ingot form such a proportion to the local carbids that the mix crystalscan be made to take into solid solution the excess carbon of these local carbids, the metal which thereafter remains in the position of the original -carbi(ls will have a carbon content more nearly equal to the average of the whole mass, but will have a higher percentage of rendered ductile in consequence of its loss of excess carbon, although its ductility will be less at a given temperature than that of the adjoining mixcrystals of lower manganese content; but if the time and temperature have been sufficientthe cal-bid residuals will recrystallize homogeneously with the other mix crystals. The ductility of the whole mass will still depend upon the quantity and original character of the carbids and will be greater as manganese and carbon were originally lower in the poured metal and as the freezing was more rapid.

If the heating to temperatures vabove 1025 C. or thereabout, 'is'sufiiciently prolonged, themix crystals will first absorb a bids and by still longer heating theexcess manganese of the cal-bids will also to some extent be distributed. By prolonged heating, at temperatures below the. melting in this way be rendered suflicient-ly ductile for rolling at temperatures ranging from 1025 C. to 1150 C. If, however. the whole mass is raised to a temperature above the melting for example, a temperature of 1175 C.. a portion or all of the carbids in any locality in the ingot will be taken into solid solution by the adjoining local mix crystals. If. in any locality, the steel hyper-eutccl'oid the manganese. This cal-bid residual will be,

portion or all of the excess carbon of the carpoint of the carbids, the whole mass mav begins to distribute into the mix crystals.

point of the carbids, or carbid residuals. as

the mold, and examined.

excess carbids may, by long heating, be in part distributed throughout the mass and away from their original location, providing the poured steel has the eutectoid ratio or a lesser amount of carbon. \Vhen the melted composition is, for example 12% manganese an 1.40% carbon, the excess carbids render the metal very weak at all temperatures above 1050 C. or thereabout. It is, therefore, important that the steel should not be hyper-eutectoid, if the metal must be rolled into shapes requiring considerable ductility of the ingot, and requiring a high rolling temperature. In the case of a typical steel containing about 12% of manganese, a percentage greater than about 1.25% of carbon would make the steel hyper-eutectoid. This eutectoid carbon percentage depends also on the content of silicon and of chromium and the like. \Vhen the percentage of carbon in a given locality is much greater than this amount, but when the total proportion is not hyper-eutectoid, the-uniform distribution of carbon is to be brought about only by a very long period of heating, which for most purposes is not commercial. Generally, the metal is satisfactory if it contains 1.15%, or even a less proportion of carbon, and when the percentages of carbon range from 1% to 1.15% and the freezing has been rapid, the re-distribution of carbon may usually be effected in from one to four hours heating at temperatures ranging from 117 5 C. to 1100 C.

The melting point of the carbids first frozen out ranges from about 1120 C.;to 1250 (3., rising with tent; while, for a given manganese per cent, the carbon having already been in part diffused into the balance of the mass during a reheating operation, the melting point of the remaining metal in the locus of the original carbid will now be higher. This rise in meltin point temperature by loss of carbon usua ly stops at about 1160 0., when the whole mass has been quickly frozen and when it is hypo-eutectoid steel. Steel which is above or near the eutectoid ratio and which has been slowly frozen, and particularly such steel when it has afterward been slowly heated to even as high as 1200 C., may still contain unmelted carbid residuals which may require a temperature as high as 1250 C. for their melting, solution and diffusion. a i

.To determine whether steel of a given composition is-hyper-eutectoid or hypoeutectoid within the significance of these terms as used in this specification, the following procedure will sutiice: -A casting of the steel in question is made, removedfrom a test piece is broken off and Another test piece is reheated to the proposed rolling temperature, held at this temperature for atime which would-be their manganese concommercial in the heating of ingots or blooms, and is then rapidly cooled. The reheated steel is now examined. Fractures are obtained which run in various directions, such that the freezing structures, if any still remain, are exhibited. Sections of the metal are also examined under the microscope. If carbids or their residuals are still in evidence, separating the freezing grains or structures or their original outlines, or if considerable carbid areas appear within the grains of the mix crystals, the steel is hypereutectoid for the temperature and time used. A further test at a, higher that any suitable rolling temperature or suitable time in heating will effect the solution and disappearance of the carbids, it can be decided that the steel can only be rolled by first cooling the exterior portions of an ingot or by using moderate drafts and avoidin considerable elongations of the ingot be ore its exterior portions are rendered ductile. 1

In order to illustrate the method to be employed in practicing my invention, I will now describe a specific instance of the procedure. Thus, in order to reduce the cost of manufacture and produce the best prodfailmg to show not when a rail containing 12% manganese is required, the steel, which should be as free as possible of dissolved oxide, is made to contain a percentage of carbon well below the eutectoid, as, for instance, 1.15% or less of carbon, and is poured into m'olds comprising chills of sufficient mass to cause the steel to set rapidly, the steel being poured at a temperature preferably not more than 50 C. above its freezing or setting point, i. 6., at a temperature of 14:00 O. or less. The ingots are allowed to cool in the molds until they have frozen to or nearly to their central portions. They are then still further permitted to cool, if necessary, until the freezing structures which may still be present have so cooled and solidified, and until their interior portions have so cooled, that, when placed in the heating fur-. nace, the'ingots will not be heated in their outer portions too rapidly by transmission y to said outer portions of the interior heat. The dendrites of the ingc are, however,

preferably broken down and reconstructed.

by permitting the dendritic zone to be slowly or evenly reheated to the necessary temperature for that purpose by heat from the interior portions, before the removal of the ingots from the molds. The ingots are then placed in the soaking pit orheating furnace. with an average temperature of 1000 C. to 1100 (3., and are heated, during a period of from half an hour to an hour, to an average temperature lying between 1150 C. and 1200 C., until the carbids are distributed intothe mix crystals. This-will usnally;be

temperature or a longer commercial period of heating still portions.

'tions thereafter as to the transfer.

tions, theheating from 1025' accom lished in between one and two hours, depen ing upon the original composition, and the rate of freezing, the lesser time being required for the lower carbon and manganese contents and the most rapid freezing. The steel is now in a state of chemical equilibrium, and will have a uniform fine gamma-iron structure, and the ingots may be taken to the'mill and rolled with heavy reduction in the first passes and with reduc- (lesired, Without any other preliminary cooling of the exterior portions than that which is usually incident This usually results in dropping the exterior temperature about 20 to 50 0.

The rail, as it leaves the rolls, should be cooled rapidly to avoid separation of carbids in the steel, and to avoid the structural rearran ement caused by slow cooling to about 600 whether'the rolling of the ingot to the finished shape has taken place in a single heat, or in two heats (by the preliminary production of a bloom). The cooling of the finished product should proceed at a moderately rapid rate to below 600 (3., (preferably below 400 C.) as by means of a water shower on some portion of the mill table or hot bed. The cooling will usually be sufi'iciently rapid with such steel if it is done in or six minutes or less in the mill, and one minute or less under the water shower, the essential feature being to get the ingot or bloom in a condition of chemical equilibrium and to then roll and cool either with mechanical work or with rapid cooling going on continuously until the rail has temperatures preferably below 400 C.

If it is found necessary to pour the steel at a higher temperature, or in the large ordinary iron molds and to get the ingotsto the soaking pits with a dendritic structure still remaining in their exterior por- C. upward, until the eutectic in the outer ortions of the ingot has entered into solid solution, should be longer than as above stated to avoid any dislntegrationof the dendritic For the reason that ingots poured at high temperatures have, as previously stated, considerable local enrichments in their exterior portions, it will usually be found safestto lower the temperature of the outer portions of the ingot to 1120 C. or a lower temperature depending, upon the original composition, before the ingot enters the rolls. Also when a high maximum temperature has been maintained for a long time, the cooling step will sufiiciently strengthen the mass by shrinking and weldin the grains of steel.-

Manganese steels containing considerably less carbon than the eutectoid ratio, and especially those steels which are without considerable free carbid areas when slowly arrangement from for which manganese steel is employed. In-

deed, for many uses, the steel should be made hyper-eutectoid.

When it is desirable to produce rolled shapes from hyper-eutetoid steel, the prelimlnary heating above 1025 C. and up to the maximum temperature employed should be very slow. The maximum tem perature in the case, particularly of large ingots, which have cooled slowly, should be upward of 1200 (3., and the outer portions of the ingot and to a considerable depth as, for exam le, two or more inches-measured inward rom the surface of t ein ct, should be cooled to a temperature consi erably lower than the freezin temperature of the .remaining v undissolved carbids. When the ingots of hyper-eutectoid ste el are of a moderate thickness, ductility for a preliminary rolling may be obtained by heating to a temperature which willin part distribute the excess carbon of the high manganese carbids as, for example, a temperature of 1100 C. or slight-1y less, until the redistribution of carbon has gone as far as possible, about four hours at the maximum temperature. The preliminary breaking down of the grain by a light blooming operation is then executed, and the slab or other bloomed shape is then reheated to a temperature usually ranging from 1100 C. to 1150 C. and de ending upon the amount remaining of undissolved carbids, the highest permissible tem erature beinglower as the proportion of carbids not capable of re-solution 1s greater. Steel of this character should be finally quenched in preferably between 1025 C. and 1075 C. and, if necessary, should be reheated to the necessary water at a temperature which will usually require within this range of temperature for quench- If the steel is found to be eutectoid or hypo-eutectoid, in making examination of a trial casting as previously described, it may be rolled by heating to the predetermined temperature and for the predetermined time, and without preliminary cooling or preliminary compression or otherwise welding the exterior portions of the ingot. If the steel consists of large loosely cohering grains of gannna-iron, but of different size and the freezing structures found in the casting before reheating, the temperature, or the duration of the heating at the maximum temperature has been excessive for rolling without first welding or cooling. If, by further testing at lower vtemperatures the reconstruction of the metal cannot be effected without obtaining evidcnces of overheating, then the steel of given composition can only be rolled by cooling its outer portions to below the freezing point of the undissolved eutectic, or by first lightly rolling and compressing, or both. \Vhen steel of eutectoid or of softer composition is investigated. as above indicated, it is frequently converted into a fine uniform gamma-iron structure by a temperature and time considerably less than that which produces the overheated condition. Ingots of such steel may be rolled to advantage with a higher temperature in their exterior than in their interior portions. Furthermore, I

have found that when steel containing about 12% of manganese and 1.10% of carbon 18 past at temperatures ranging from 1350 C. to-1550 (3., depending upon the size of the ingot, the interior portions of the ingot may be suitably reconstructed by heating to temperatures above 1120 C., and the exterior portions may be reconstructed by heating to the same or a higher temperature, as for example 1175 C., the higher temperature for the higher casting heat and the slower freezing. So that, when large ingots of eutectoid or softer steel have been cast at more than about 50 C. above the freezing point of the metal, the outer portions of the ingot usually require a higher temperature for their reconstruction in a iven time. As the evidences of overheating seldom appear until the steel is heated to about 1200 C. it is usually a safe rocedure to heat the outer portions of the ingot to any temperature below this point, or even to heat the outer portions for a short time to tem eratures somewhat above 1200" 0.. while iolding the in- -terior temperature maintain a strong supporting central core; as, for example, heating the ingot a; 1190 (I. at its surface, and 1140 C. at its center, or, for example, heating the ingot until the interior portions are strong and ductile with a temperature of 1150 C. and bringing the outer portions to 1200 C. for a few-minutes, and then taking the ingot from the heating furnace to the rolls. This method has the further advantage of avoiding an excessive central temperature, caused by the combined effects of the initial heating at the center and the heat of internal friction generated during rapid rolling.

Having thus described my invention, what I claim is:

1. The method of preliminarily treating and subsequently rolling manganese steel ingots containing carbids, consisting in heating the ingot to temperatures above the change point at which the carbon begins to somewhat lower so as to be rapidly absorbed from thecarhids by the mix crystals and until as .mix crystals have absorbed substantially the maximum amount of carbon that they are capable of abstracting at the tem erature employed, and continuing the heating until the carbid residuals are recrystallized, forming with the mix crystals a gamma-iron structure, and then rolling the ingot; substantially as described.

2. The method of preliminarily treating and subsequently rolling manganese stee ingots containing carbids, consisting in heating the ingot to temperatures above the change point at which the carbon begins to be rapidly absorbed from the carbids by the mix crystals and until the mix crystals have absorbed substantially the maxlmum amount of carbon that they are capable of abstracting at the temperatures employed, and continuing the heating until the carbid residuals together with .any undecomposed carbids are recrystallized,tforming with the mix crystals a gamma-iron structure, and then rolling the mgot; substantially as described. 1

3. The method of reliminarily treati and subsequently ro ling manganese stee ingots containing carbids, consisting in heating the ingot to temperatures above the change oint at which the carbon begins to be rapi ly absorbed from the carbids by the mix crystals and until the mix crystals have absorbed substantially the maximum amount of carbon that they are capable of abstracting at the temperatures em continuing the heating until the car 1d residuals are recrystallized, forming with the mix crystals a gamma-iron structure, welding the gamma-iron crystals into a more cohesive ductile mass before subjecting the ingot to heavy reductions,.and then rolling the in ct; substantially as described.

4. he method of casting, treating, and subsequently rolling manganese steel ingots containing carbids, consisting in pouring the metal at a temperature not more than 50 C. above its freezing poi t, freezing the metal at such a rate as to avoid considerable variations in composition between different localities of the ingot and so as to avoid considerable separation of carbids, heating the ingot to temperatures above the change point at which the carbon begins to be rapidly absorbed from the carbide by the mix crystals and until. the mix crystals have absorbed substantially the maximum amountof carbon that, they are capable of abstracting at the temperatures employed, and continuing the heating until the oarbid residuals are recrystallized, forming with the mix crystals a gamma-iron structure, and then rolling the ingot; substantially as described.

' The method of casting, treating, and

- crystals and until the mix crystals have ab- 1120 C. and 1200 sorbed substantially the maximum amount of carbon that they are capable of abstracting at the temperatures employed, and continuing the heating until the cal-bid residuals are recrystallized, forming with the mix crystals a gamma-iron structure, and then rolling the ingot; substantially as described.

6. The method of preliminarily treating and subsequently rolling manganese steel ingots containing carbids, consisting in heating the ingot to temperatures above the change point at which the carbon begins to be rapidly absorbed from the carbids by the mlx crystals and until the outer portions of the ingot have a uniform strong gamma-iron structure, and then rolling the ingot; substantially as described.

7. The method of preliminarily.treating and subsequently rolling manganese steel ingots containing carbids, consisting in heating the ingot until the carbids have been partly decomposed and heating further to temperatures above the melting point of the resulting carbid residuals until said resid-.

uals have been taken intosolution by the mix crystals, substantially as described.

8. The method of preliminarily treatingand subsequently rolling manganese steel ingots containing carbids, consisting in heating the ingot to temperatures lying between C. until the excess carbon of the carbids is redistributed throughout the mass and until the carbid residuals have been taken into solid solution to sub stantially the limit of the capacity of the mix crystals for such solution at the tem perature employed and thereby rendering the ingot ductile and coherent, and then rolling the ingot; substantially as described.

9. The method of preliminarily treating and subsequently rolling manganese steel in gots containing'carbids, consisting in heating the ingot until the carbids have been partly decomposed and heating further to melted portion of the residuals to dissolve in the melted portions, and maintainin the temperature until the carbid-residuals ave been distributed throughout the remainder and then rolling the ingot;

gamma-iron structure throu resulting from (18-.

of th mass; tosub'stantiall the limit of the capacitof such remain er for effecting such SOlItI Oh Ht the temperature ein loye and then rolling the ingot; substantially as described.

10. The method of preliminarily treating and subsequently rolling manganese steel ingots containing carbids, consisting in heat ing the ingot to a predetermined tem erature above 1120 (J. and continuing the eating operation for a predetermined time such that any free carbids will be taken into so lution in the mix crystals, and then-rolling the in 0t; substantially as described.

11. he method ofv and subsequently rolling ingots of manganese steel of hypo-eutectoid composition,

consisting in heating the ingot'until the carbids have been partly decomposed and heating melting point of the resulting carbid residuals until said residuals have entered into solid solution in the mix crystals, and then rolling the ingot; substantially ,as described.

12. The method of preliminarily treating and subsequently rolling manganese steel ingots of hypo-eutectoid composition, consisting in heating the ingot until the carbids have been partly decomposed and heating further for a-predetermined time Within a predetermined range of temperature until the carbidmesiduals have been absorbed by th'e mix crystals, with the production of a uniform gamma-iron structure, and rolling the steel with the distribution of temperature then obtaining; substantially as described. i

13. The method of preliminarily treating and subsequently rolling manganese steel ingots, consisting in heating the ingot to temperatures above the change point at which the carbon begins to be rapidly absorbed from the carbids by the mix crystals, heating the outer portions of the ingot to higher temperatures until said outer portions have a uniform strong gamma-iron structure, and

then rolling the ingot; substantially as described.

14. The method of preliminarily treatin and subsequently rolling manganese" steel ingots containing carbids, consisting in heating the ingot to temperatures above 1120 C. until the lngot has a substantially uniform hout, which temperatures if above 1200 in the outer portions shall be maintained for a short time only, and then rolling the ingot; substantially as described.

15. The method of preliminarily treating and subsequently rolling manganese steel ingots, consisting in heatingthe ingot to tem peratures above l120 the outer portions of the ingot a strong gamma-iron structure, heating the said outer portions to higher temperatures, Which latpreliminarily treat-ing further to temperatures above the C., thereby forming in I t'er temperatures it above 1200 C. shall be ture, then rolling, and cooling the resulting maintained for a short time only, and then shape at a rate sufficiently rapid to avoi removing the ingot to the mill and rolling said ingot; substantially as described.

16. The method of preliminarily treatin and subsequently rolling hypo-eutectoid manganese steel ingots, consisting in heating .the ingot of hypo-eutectoid steel to temperatures above those atwhich the carbids and carbid residuals are distributed throughout the mass, and until said distribution has been effected, then rolling the ingot, and cooling the finished shape at a rate sufliciently'rapid to avoid separation of carbids; substantially as described.

17. The method of preliminarily treating and subsequently rolling hypo-eutectoid manganese steel ingots, consisting in heating the ingot to temperatures above those at which the cal-bids and carbid residuals are distributed throughout the mass, and until said distribution has been effected, preserving said distribution until the rolling operation begins, then rolling and cooling the finished shape at a rate sufiiciently rapid to and avoid structural rearrangement during the coolin substantially as described.

18. he method of preliminarily treating subsequently rollmg manganese steel,

consisting in heating a mass of manganese steel having carbids in solution in the-mix crystals to temperatures above 1120 C. until the mass has a uniform gamma-iron strucstructural rearrangement during the cooling; substantially as described.

19. The method of casting, treating and subsequently rolling manganese steel in ots, which consists in pouring the ingot rom metal substantially free from oxids, freezing the metal at a rate to avoid considerable variations in composition between difierent localities of the ingot and to avoid considerable separation of'carbids, reconstructing the outer portions of the ingot by raising their temperature slowly and evenly while stlll in the mold, then transferring the in 0t to a soaking pit and heating until byre tion of their carbon and carbid residuals the outer portions of the ingot have dropped below the hyper-eutectoid ratio' heating until the mix crystals of the entire mass have absorbed substantially the maximum amount of carbon that they are capable of abstracting at the temperature employed and until the carbid residuals throughout are recrystallized forming with the mix crystals a gamma-iron structure, and then rolling the ingot; substantially as described.

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

WINFIELD S. POTTER. Witnesses:

JOHN C. PENNIE, WILLIAM H. DAVIS.

istribu-