US847588A - Case-hardening. - Google Patents

Description

No. 847,588. PATENTED MAR. 19, 1907. A. w. MAGHLET. CASE HARDENING. APPLICATION FILED APR. 13. 1905.

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0000 e 0 M8 oooonrvoo OOOOOOOO QZZZZ Q W No. 847,588. PATENTED MAR. 19, 1907.

A. W. MAGHLET.

CASE HARDBNING. APPLICATION FILED APB.13.1905.

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N9. 847,588. PATENTED MAR. 19 1907. A. W.MAOHLET. CASE HARDENING.

APPLIOATION FILED APE. 13.1905.

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- Adogo/zwflaczzez W Afro/av ADOLPH w. MACHLET, OF ELIZABETH, NEW- JERSEY. f

.GASE-HARDENING.

I'atentedMarch 19, 1907.

No. 847,588. Specification .of Letters Patent.

Application filed April 13, 1905- Serial No, 255,355.

To all whom it may concern:

Be it known that I,.ADOL1 H W. MAGHLET, a-citize'n of the United States, residing in Elizabeth, in the county of Union and State of New Jersey, have invented certain new and useful Improvements in CaseHardening, of which thefollowing is a specification.

This invention relates to the case-hardening of steel and iron articles, and particularly of small articles in bulk.

Small articles or parts in' large qiiantities are commonly machined or shaped from wrought-iron or low-carbon steel in sheet, wire, or bar form, these metals owing to their lack of carbon being relatively soft and hence easily cut and workedby machinetools; but owingto thissoftness such articles are unsuited for wear, and accordingly it is the practice to case-harden them, usually by carburizing them to a depth of a few thousandths or possibly a few hundredths of an inch, so that they retain their shapes and are given sufliciently hard exteriors for the puroses for which they are intended. Caseardening is a rapid process of cementation, in which the surface of the wrought-iron or lowcarbon-steel article is converted into steel or into a higher-carbon steef by heating the article in contact with carbonous mate- According to common practice the articles.

1 are packed in carbonaceous substance and heated above red, heat; but the operation is slow and ex ensive and the carburization extends irregu arly to different depths at different points upon each article, some points often not becoming carburized at all. Anexcessive degree of heat must be applied for 'a long time in order to act through the non-conducting carbonaceous material upon the articles packed therein, and this excessive heat soon destroys the, iron boxes in whichthe articles are usually case-hardened. In many cases, also, it is necessary to cool, repack, and reheat the articles in order to produce a suf ficient depth of cementation. Moreover, it is found in. practice very"diflicul t and-some: times altogether impossible to carburize the articles just as deeply as required and no 5C deeper; In the case of thin or plate-like articles, where it is desired that the .cementation shall be very shallow or thin, but still complete all over the articles, it is found t0v be practically impossible to attain' the desired result, since the carburization is almost sure to proceed too far at some'portions of the article, which consequently is rendered toobrittle for. use, it being desired to preserve the relativelfy soft and tough character of the interior o case-hardened articles. No practicable Way has heretofore been found for not only insuring that the carbonization shall be ofv even thinness all .over smallthin articles,

but also causing such cementation to proceed to the exact depth required, so that it would be practicable to case-harden such articles.

The principal objects of my invention are to materially reduce the cost of case-hardening articles, to insure that the case-hardening operation shall produce a shell of uniform thickness allover the article regardless of its shape, to regulate or gage exactly the thicknessof the cementation or shell, to make it practicable to case-harden small articles cheaply and rapidly and uniformly in bulk, and to provide for inexpensively and effectue ally tempering the case-hardened articles by suddencooling thereof. I 1 5 I heat the articles to a point above redness, but below the melting-point, in an atmosphere of carbonous gas preferably under high pressuresay' from twenty-five up to one hundred pounds, or even more, to the square inch-and preferably efiect gentle agitation of the articlesduring the heating, thus exposing all portions thereof to the gas, so as to insure the uniform penetration of the carbon from the as at all points on the sur- .face of the article oth outside and inside and .without regard to the shape of the same.

Thus Iavoid the necessity and expense of first packing the articles in carbonaceous substances in the usual manner. I use a retort made, preferably, of metal, with which the articles directlycontact, so that they are quickly heated wlthout unduly heating'the retort, thus saving cost of. fuel and avolding destruction of the retort. The heat may be {110111 about 1,509' to about1,800 Fahreneit.

By: means presently to be described the progress of Tthe cementation may be ,known or predetermined, and the cementation may be arrested at any point, thethickness of the shellbeing determined in advance even to a thousandth partof an inch by an operator having fair skill in' using' the apparatus. I arrestthe process of cementation as soon as the predetermined thickness or depth is ac;

. quired, and since case-hardened arti-clesare' IIO usually tempered or made glass-hard I provide means for suddenly cooling them while still hot-that is, before they. lose the heat acquired in the carburizing-retort. This sudden cooling may be efl'ectedin any approved manner, as by plunging the articles into a cold liquid bath. If this is done while 1 the articles are still at carburizing heat. that is, above red heattheir tempering is 10.

effected, and this sort of tempering will answer-for numerous kinds of articles. where it is unimportant whether the shell has a coarse or fine grain When the articles are chilled at this high heat, the shell acquires a coarsev grain, as appears upon fracture. I

therefore provide for gradually. permitting the articles to cool from carburizing heat to cherry-red and then plunging them intothe cooling bath, whereby when desired a better quality of steel may be produced. When tempered in this manner, the shell appears to have a very fine grain when fractured, and the expense and delay of permitting the articles to cool gradually to ordinary atmos-' .even practicable tomanufacture large quantities of tools and articles and harden and temper them according. to my invention which heretofore it'has been necessary to produce .slowlyand expensively from fine igh-ca rbon or "tool steel.

Other objects and advantages will hereinafter appear.

In the accompanying drawings, Figure 1 represents a sectional elevation, taken from end to end, of one form of an apparatus constructedfor case-hardening and tem ering articles according to my mventlon.

' 3 an elevation ofthe right-hand end, of the carburizing a paratus seen -at Fig.1. Fig. 4 is a verti'ca cross-section taken at about the line X X of Fig. 1 Fig. 5 is a plan, and Fig. 6 a longitudinal section, of one form of tool used in charging the apparatus with articles to be carburized: Fig. 7 is a side view, and Fig. 8 an end viemof another form of charging-tool. Fig. 9 isfa sectional view of an exmple of a case-hardened articl i iillustrating a thin shellfiformed evenly allover the same.

The steel'or irori articles to be case-hardened are represented by a dotted line 1, de-

posited in bulk within a retort 2', formed of east-iron or other suitable metal, the retort being referably about half or two-thirds a barrelorelongate cylinder and is mounted ig. 2 is an elevation of the lefthar.d end, and Fig.

he retort is referably the form of' wholly within a flamechamber 3 of a furnace 4, the latter comprising a cylindrical or other body 5, having heads 6 and 7. The furnace is provided throughout with a refractory lining, the cylindrical portion thereof, which lines the body, being indicated at S, and that portion which lines the heads of the furnace being indicated at 9, all of said lining being usually set in laster-of-paris. (Seen at 10.) The space inc osed by said refractory lining forms said flame-chamber. Any suitable fuel may be consumed in the. furnace, and it may beotherwise constructed. Preferably a mixture of hydrocarbon fuel with air is used, the air being admitted through a pipe 11, and. the fuel, such as ordinary illuminating or heating gas, being admitted through a ipe 12, the supply of air and fuel being regu ated by valves 13 14. The air and fuel become mixed within the pipes 15 16, and the mixture is admitted to burners 1.7 18, inserted in horizontal openings 19 20, formed in the opposite walls of the furnace near the top of the flame-chamber. The burners point alternately in op osite directions, as seen at Fig. 4, so as to irect the flames across the top.and down around both sides of the retort and form two sets, extending along the top of the flame chamber above said retort. Two feed-pipes 21 22, extending along the furnace, connect the burners in the sets, said pipes bemgsupplied by the pipe l6, which extends across the top of the furnace. The gas-flames are directed upon and over the retort and play down around the same and escape throughan outlet 23, formed in the bottom of the furnace at the end of the retort, whereby even heating of the latter is assured. The supports for said retort are mounted upon the exterior of the furnaceheads and consist of a pair of rolls24, car.- ried upon brackets 25, fixed upon the righthand head 7, and a pair of rolls 26, mounted upon brackets 27, fixed upon the left-hand head '6. The retort is formed with cylindrical extensions at it. end, one extension 28 resting between and supported upon the rolls 24 and the other extensionv 29 being similarly supported upon rolls 26. It will be seen that said extensions project through openings 30, formed in the refractory lining 9, and through similar openings in the heads of the furnace. The purpose of sup or'ting the retort uplon the rolls is to enab e it to turn during t e heating thereof. Apartition 31, forming the top or right-hand end of the retort, is cast between the same and the tight end extension 28, the latter being prei erably of the same diameter as the retort itself.

The extension 29' is preferably of lar er diameter than the retort, so as to permitt e insertion and withdrawal of a cover 32, that is fitted to the left-hand end or bottom of the retort. This cover is intended to be clamped tightly upon the retort during the process of tension 29 by means of bolts and nuts By. turning the screw the cover may be clamped ti htly upon the retort or drawn off therefrom ar enough to permit the articles 1 to drop or discharge through. one of several apertures 36,'formed in said extension 29, ad oining the retort and overlying the outlet 23.

In order to diseharge the retort, the cover,

screw, and yoke are withdrawn, the latter being formed at its ends with hooksor open slots37, which engage said bolts 35 loosely, so that by simply turning said yoke to. the left at Fig. 2 it is disengaged from thebolts and may be removed, together with the screw and cover. The extension 29 is"also provided with a metal closure or head 38, having a lining of asbestos-said head 3Sbeing fixed to-the yoke 35. This head avoids Waste of heat and also revents the handles 34 from becoming undu y hot.

During the life of the apparatus the retort is alternately heated and cooled agreat many times and 'in consequence gradually ac uires a permanentexpansion-that is, it s owly grows larger? Hence the apertures 30 in-the furnace are made a little over size, as il1us-.

4 for illuminating. and heating in t trated, to" accommodate the gradual increase in circumference of the extensions,-and theperiphery of the extension 29'is smooth, so that it may slip in axial direction along the rolls 26- to accommodatethe permanent expansion or lengthening of the retort structure, the other extension 28 having flanges 39 :-to inclose the rollers 24 and prevent endwise movement of this end of. the retort. The aperture23 in thebottom of thefurnace. is made of sufficient dimension from left to right at Fig. 1 to accommodate'the permanent lengthening ofthe retort, so that the aperture 36may still overlie said openin 23, even when such lenf hening has reaciie da The carburizingas may beapfire hydros carbon, although ordinary city-gas, such asggenerally' e city of Elizabeth, New Jersey. Q'T'Good results ,can also be-obtained from coal gas andfrom oilgas' and also from carburetedhydrogen gas (or'water-gas) resulting from the"'passing of steam through a mass of incandescent car-.

bonand subsequent admixture of hydrocarbons or other enriching substances.

The gas which is used for cementation may be supplied under pressure in any suitable way; but for the sake of illustration I have I shown a gas receiver or tank 4Q, which con-- 'ust a little hi her than atmospheric pressure.

11 other wor s, the pressure may vary from (just sufficient to charge the retort to the highest that may be found practicable. This receiver is connected tofthe retort by means have .foundgin practice that good'results are obtained by, the use of supplied tains gas preferably at a pressure of one hun-j dred pounds to the-square inch, although a much lower or even hlgher pressure may be used, or-in-some cases .the pressure may be of flexible pipe '41,- rovided withvalve 42, and a pipe 43, the atter being in line with theaxis of retort 2. A gland is shown at 44 to accommodate therotation of the retort, since the pipe 43 remains stationary. A yoke or bracket 45 is fixed upon the head 7 of the furnace to support the. gland 46, into which pipe 43 is-threaded. The latter is provided with a cap. 47, which may be removed to give. access to the interior of'the pipe and gland for cleaning. I Threaded into the end or top 31 of the retort is a jet or sprayer 48, having numerous apertures 49 for directing the gas in small jets into theretort, said sprayer 48 being connected by a pipe 49 to the gland 144.- If Ioil-gas'is used, any suitable provision may be used for con-'- verting the .oil into gas and forcing it through the jet or spray 48 into the retort. The heat of the retort maybe used -'for converting the oil into gas.

'In operation the yoke 35 and cover 32--are removed and the-articles 1 deposited within the retort 2. i The yoke 35 is replaced I and the nuts and bolts 35? tightened and the screw 33 revolved. to clamp the cover-32 tight] against the lower or left-hand openend 0 the retort. The gas and air valves 13 f 14 are-opened and the fuelmixture ignited at the burners 17 18 the flames circulating in opposite directions over the to" and down a ong the sides of the retort an then to the left along the bottom 'of the retort at;F1g. 1-,-

finally'escapin downwardl through the orifice 23in the ottom of't e furnace.' The valve 42 is opened, and the carbur zmg-gas passes from t orced out from the I latter through a vent 50, .formed in the'cover 32' and having an' ad ustable valve or screw 51, said vent remaining. 115

slightly open throughout the-operation an the gasescaping therefrom igniting a-nd ;con stantly burning. The flames'in the the cemen'tation of. theart'ic es, which ess may-also be favoredjand hastenedyby'. reason of the hi hpressureat-whichfthefigas great-economy is e ccted in fuel, since the" time is materially shortened during which it is'necessary to consume fuelin maintaining r39 l 10 e tank 40 through the suPR y", pipe4'1 43 49nd into the retort, the ir g heat the retort until" thea'rticles'therein are ins may be supplie to the interior of'the retort. Owing tothe rapidity of-the cementation',

turn, since the gas actsbetter on t I of the gas and a the heat of the retort and other parts, while of course the daily capacity of the aplparatus es shall 7 is increased. In order thatthe artic be exposed uniformly to the action of the gas, I provide means for effecting gentle agitation thereof, suchvmeans in this instance consist-- in, which frequently are of delicate construc tion and particularly liable to become bent, owing to their heated condition. Said ear comprises a worm 53, fixed upon the pul eyshaft 54'- a nd turning within a drip-pan 55 and in mesh with a worm-wheel 56, secured bybolts 57 to the right-hand extension 28 of the retort. The rotation of the latter may be very slow indeed, as its object is merel to insure that each article shall be expose all over to the action of the gas, and that all sides of each article shall come uppermost in e top side than on' the bottom side .of any article in the retort. During the carbonizing operation fresh gas constantly enters through the supply41 to replace the gas which hasbecome vitiated bythe absorption of the carbon elements into the metal articles, such vitiated gas escaping through the vent and there producing a constant flame, which can be seen by the operator through the sight-hole 58, whereby he can ascertain by the color of such flame whether the gas retained in the retort is unduly yi tiated. If so, the valve 51 .may be opened a little more to permit freer escape morerapid infidw of fresh gas.

One advantage of the invention consists in the circumstance that the operator may ar rest the case-hardening process as soon as the cementation .has proceeded to any "predetermined depthupon the articles, it, being practicable to gage such a depth to within even a few thousandths ofan inch, or even.

less, according to the skill of the operator. In doing thisthe operator takes note of the time at which the articles reach the proper heat, which he can ascertainl by'obser through the sight-hole 58 the color of thebody of the retort and Which" can also be ascertained by reading a pyrometer 59, which may be inserted through an aperture'60 in the bottom of the furnace and projects slightly into the flame-chamber. By com arison of the readin of the pyrometer wit the appearance o the-incandescent retort the operator can determine precisely when the ax-ti cles have .reachedthe requlred heat for cementation and may then admit the gas through the supply 41,and so .cause the cementation to proceed for a predetermined length of timesay one hour or even less, ae-

, cording to the quality of the gas in the retort,

to which itis desired to have the case-hardening proceed upon the articles. The operator may make and preserve memoranda'of different results obtained by the use of different qualities of gas or different pressures of gas upon different qualities of iron or steel, noting the depth to which the case-hardenin iglroceeds under the different conditions, and 3 om such account he may readily predetermine at any time how deep the case-hardening shall proceed u on the particular articles being treated. This exactness, which is highly desirable in many instances, is rendered possible largely because of the fact that the heat of the retort is maintained absolutely uniform throughout the rocess of cementation, owing to the use 0 burners for burning mixed air and fuel, whereby the heat of the retort may be not only regulated, but rendered absolutely uniform, and thus it becomes practicable and inexpensive to produce upon the articles shells of even predetermined thickness all over the articles,-

which result it has not heretofore been found practicable to obtainwith certainty and in an inexpensive manner suitable for the purposes of ordinary manufacturing. As soon as the cementation has proceededtothe desired depth valve 42 may be closed, the handles 34 may be turned to open the cover 32, and the articles may drop through the opening or chute 43 into a tempering-bath of cold water or other liquid 61.

To facilitate the discharge of the retort, I arrange. to tilt the same up at its right-hand end, so that during the continued rotation thereof the articles will feed gradually down to the left-hand or bottom end and finally drop through the chute 23 into the bath 61. For this purpose I pivot or hinge the furnace at 62 upon a pair of standards 63 at the lefthand end of the apparatus and provide at the'right-hand end a vertical screw 64, so that by means of said screw the right-hand end ofthe furnace maybe elevated or tilted together with the retort therein. The screw 64 does not turn, but is pivoted at its upper end 66 to an ear 67,depe'nding from the furnace, and handles 65 are rovided upon a nut 68, threadedupon said screw and resting upon a washer 69, carried'by a block 70, pivoted at 71 to standards'72. The pivoting of the block at 7l accommodates the different angular positions assumed by the screw 64 as it rises with the furnace. As soon as the articles are ICO IIO

discharged from the retort the latter may be .rechanged without becoming cold, thus avoiding the delay and; expense of reheating the same. For the purpose of recharging the tool seen at Figs. 5, 6 maybe employed, consisting of a cylindrical scoop 73, having therein a piston 74, the latter provided with a rod gently turned so as to dump the articles. 4 into the retort. Then thecover 32 may be replaced, Y the gas admitted to the retort.

. and handle 6. The' piston may be drawn to the bottom of the scoop, and the latter filled with small articles. and inserted Within the hot retort. The operator then holds the.

handle 76 stationary While he pulls out the scoop by means of a handle 77, thus gently.

depositing the articles in the retort. Another form of scoop 78 is seen at Figs. 7, 8, having a handle 79. This tool may be filled with articles and inserted within the retort and then through the supply '41, and the. operation proceeds as before. Very little time is occupied in charging and recharging, so that Waste of fuel is minimized. Thus the furnace may be kept in constant operation, and many charges of .articles' may be case-hardened every daywith but little expense for labor and fuel as compared with the methods of case-hardening accepted at the present time.

\ While for some purposes the incandescent articles may without any cooling be dumped directly into the tempering-bath 61, still for other urposes it is desirable that the articles shall fii" cherry-red, and-in order 'to effect such gradual cooling I partly close the valves 1314, so that only a little gas passes through the burners 17 18, just sufficient to revent the ingress of air up through the or' ce 23, thus preventing oxidation of the exterior walls of the retort. Only a slight pressure of gas in the furnace is necessary for the purpose, and

this does not materially retard the cooling of the retort and the articles therein to the desired cherry-red heat. Thus while the articles are still heated'from the carburizing.

process the may discharge into thecoolingath and't e shells thereon may receive a fine temper. During such gradual cooling of the articles in. the retort the valve 42 may be closed, so that nofurther carburization may take place, or, on the other hand, the valves 13 14 may be prematurely partly closed to reduce the flow of gas into the fla'inechamher and ermitthe gradual coolingof the retort, and the valve 42.may be left open, so that cementation will corltinue'as far asv it may duringsuch gradual cooling.

The cooling apparatus seenfat Fig. 1 com- I prises a tank 80, which is provided with rollers 81 to run 'upon the floor, the top of the tank being just beneath the mouth of the chute 23. Within the, tank rests a sieve 82, through whose perforations 83 the li uid-circulates. The articles drop into tlnssieve,

which rests u on a sap ort' 84, provided in the bottom 0 the ta articlesare chilled by the bath the sieve is lifted out, the liquid escaping therefrom through said perforations 83. The articles are then dumped "from the sieve and the latst gradually cool until they are about and 'assoon as the ter replaced in the tank. Any other suitable apparatus or device may be .used for chilling or cooling the articles.

It will be seen that an im ortant economy is effected,because the artic es are directly in contact with-the metal retort, which is subj set to the heat of the flames from the burn.- e'rs, whereby owing to the convection of the heat through the metallic body of the retort necessity of forcing t e heat through the stance. Thus not only is fuel saved, but the necessity is avoided of damaging the retort itself, the life'of which is hence greatly prolonged. When it is desired to renew the retort, however, it'is only necessary to take out the screws 57, by which the worm-wheel to, and also, to disconnect the gland 44, whereupon the retort ma be pulled directly out of the furnace to the eft at Fig.1, a new one may be put in place, and the parts 39, 56, and 44 restored.

At Fig. 9 is seen an article comprising a hollow shaft 85 and flanges 86 87, formed a thin shell 88, which, it will be understood, is of uniform thickness, since both interior and exterior parts of the article are accessible to the gas. I

Variations may be resorted to Within the scorpeof my invention.

aving "claim hon-steel articles-to form thereon shells of uniform and exact predetermined thickness consisting in placing'the articles in a metal "carburizin -gas, uniformly heating the articlesthrou out by applying heat evenly tothe exterior o the retort so asto heat-the same ingthe heat of the articles umforr nwhile causing fresh carburizing-gas to circulate constantly through the retort, turning the retort to cause different sides of the articles body of non-conducting carbonaceous subthereon, the entire article being covered with.

thus describpd my invention, I"

1. The process of'-case-harderiing low-car-' -retort, closing the retort, filling the retortwith uniformly throughout until its temperature the articles are quick]. heated without the 56 and the flanged roll 39 are attached there- The process of case-hardening low-car uniforml tothe exterior of the retortuntil v .the artic es reach carburizing heat, mamtain- I2 5- to come uppermost during ther cementation, and arresting the cementation at the expiration of a predetermined interval of such lengththat the articles are cemented to the predetermined depth,

v 3. The process of case-hardening with uniformity low-carbonsteel articles to form upon each thereof a shell of uniform and excarburizingof the articles, maintaining. a

supply of fresh carburizing-gas during the cementing of the articles, turning the retort during the cementing operation to cause different sides-of the articles to come uppermost, and arresting. the cementation atthe expiration of,a redetermined interval of such len th that t e articles are cemented to the predhtermined depth.

' 4. The process of case-hardening in bulk with uniformity low-carbon steel articles to form upon each thereof a thin shell of a uniform and exact predetermined thickness,"

consisting in placing the articles ina metallic retort, closing the retort, filling the retort by carburizi-ng-gas, applying heat evenly around the retort until the articles are uniforml'y heated to a predetermined carburizing heat, maintaining such temperature approximately uniform throughout the retortfor apredetermined time, constantly displacing the vitiated gas by fresh supplies of carburizing-gas during the heating of the retort, agitating the articles during the carburizing operatlon, while the retort remains closed, and arresting the cementation at the expiration of a" redetermined interval of such length that t e articles are cemented to thepredeternfixgedlength.

.5. The process of case-hardening in bulk with uniformity low-carbon-steel articles to form upon each thereof a thin shell of a uniformand exact predetermined thickness, consisting in placing the articles in a metal retort, closing the retort, filling the retort with carburizmg-gas, in a state of high compression, uniformly heating the articles throughout by applying heat evenly to the exterior of the retort so as to heat the same uniformly throughout until its temperature \reaches from about 1',5Q0' to, about 1,800 Fahrenheit, maintaining the heat substani tially uniformduring the cementation of the artiel'es, and withdrawing the articles in an incandescent condition at the expiration of a predetermined interval of such length that the articlesare cemented to the predeterl mined depth.

6. The process Of3C8JS6 h3|TCl6DiI1g in bulk with uniformity lowcarbonsteel articles to i form upon each thereof a thin shell of a uniform and exact predetermined thickness, consistingin placing the articles in a metallic retort, closing the retort, filling the retort with 7 o carburizing-gas under a pressure high above atmospheric pressure, applying heat uni- I formly around the exterior of the retort until the articles are uniformly heated above red 5' heat but below the melting-point, maintaining the heat uniform throughout the carburi'zing operation, causing the vitiated gusto escape, maintaining a supply of fresh carbul rizing-gas under similar pressure during the heating of the'retort, and arresting the cementation at the expiration of a predetermined interval of such length that the articles are cemented to the predetermined length. g

7 The process of case-hardening steel or iron articles, consisting in confining the articles in an atmosphere of carburizing-gas within aclosedretort, heating them while so confined to a temperature above red heat but below the melting-poiut, effecting agitation of the articles whilebeing so confined and heated, andwhile the retort remains closed, to an-exten't to expose all surfaces of the articles to the gas, replacing thevitiated gas by fresh carburizing-gas during such heating and agitation, and arresting thecementation as soon as shells are formed upon the articles.

8. The process of case-hardening small steel or iron articles, consisting in confining them in bulk in an atmosphere of-carburizingwhile so confined to a temperature above red heat, but below the-meltingpoint, tumbling while the retort remains closed, and arrestin the cementation as soon as shells are forme upon the articles. The process of case-hardening small steel or iron articles, consisting in placing them in bulk in a metallic retort, fillm the retort with carburizing-gas, within a c osed retort, applying heat around the exterior of the retort until the articles are heated above red heat, maintainingv the heat substantially uniform throughout the retort, effecting repeated movements of the retort so as to agitate the articles therein, permitting the vitiated gas to escape, maintaining a supply of fresh carburizing-gas, and arresting t1e ce mentation as soon as shells are formed upon the articles.

10. The process of case-hardenin steel or iron articles, consisting in placing t 1cm in a metallic retort, closing the retort, substantially surrounding the retort by a series of controllable flames sufficient to heat the articles above'red heat but belowthe meltingpoint, maintaining the flames substantially the articles while soconfinedand heated, and

IOO

gas within a closed retort, heating them uniform, effectingrotationof the retort,'passretortwith substantial uniformity throughing a current of iron-oarbflrizing gasthrough U the retort while it remains closed, during such eating, and arresting the cementation as (ion as shells are formed upon the art cles. '-"*'11; 'The process of case-hardening steel or iron articles, consisting in confining themin an atmosphere of carburizinggas, heating them while so confined to a temperature of plunging the articles about 1,800 Fahrenheit, arresting the cementation as soon as shells are formed uponthe articles, causing the articles to cool grad-' ually to a suitable degree for hardening and immediately subjecting them to a hardening cool bath, 12. The process of case-hardening'steel or ironarticles, consisting in confining them in i bulk in a'metallic retort, applying controllable flames-t0 the exterior of the retort sufficiently to heat the articles uniformly to a carburizingtemperature, passing a current i of carburiaing-gas through the retort during such heating, until the c'em'entation has formed a shell on the articles, reducing said 2 flames to an extent to ermit the articles to cool gradually to a suitable degree for harde and immediately" pl ing the articles into a cooling-bath to har en them.

13. The process of case-hardening steel or iron articles, consisting in confining them in a metallic retort, applying controllable flames to the exterior ofthe retort suffii-' ciently to heat the articles uniformly to a such heating, until shells are formed on the articles, turning the retort during the cementation,'to cause different sides of the articles to come uppermost in the retort, reducing the flames to an extent to permit the articles to cool gradually to a suitable de ree for hardening, while the retort remains fi led with the carburizing-gas, and immediately into a cooling-bath to arden them.

14. The herein-describedprocess of casehardening low carbon-stee'l articles, consisting in confining'themv in bulk while heated uniformly throughout to apredeterminedcarburizing-point, in a current of compressed carburizing-gas, venting vitiated gas before it becomes incapable of burning brightly in air, maintaining the heat of the articles at a predetermined degree throughout substantially the entire period of cementation,

' and arresting the cementation after such predetermined duration as-causes the shell" of the exact thickness desired tobe produced. a

'15; Thel process of case-hardening lowcarbon steelrartioles, consisting in confining them inbul-k ina metallic retort, causing the current of compressed carbonized gas to flow through the retort during substantially l the-m uniformly throughout to a predetermined degree high above red heat, confining l them ma current of'compressed carburizmg;

gas and maintaining the temperature um- 5 form at saiddegree while-so confined, ar-

resting the cementation at the completion Eof the predetermined length of exposure such" that thin shells of a predetermined i depth are formed upon the articles, causing l the articles to cool gradually to 'asuitable degree for hardening, and immediately 5 plunging them into a hardening-bath.

417. The process of case-hardening lowcarbon steel or iron articles, consisting in below the melting-point, confining them burizing-gas, until thin shells are formed upon the articles, causing the articles to cool and immediately plunging them into a hardening-bath.

18. The process ciently hot for cementation, confining them in a currentof compressed carburizmg-gas while so heated, until thin shells are formed upon the articles, causing the articlesto cool gradually to a suitable degree for hardening, and immediately plunging them into a'hardening-bath. I

19 The process of case-hardening steel or the melting-point, confining them while so heated in a current of compressed carburizarticles, agitating the articles during the process of .cementation, gradually cooling heat, and immediately subjecting them to a hardening-bath. i 20. The processof case-hardening steel or iron articles, consisting in confining them in bulk in a metallic retort and in contact with articles reach a uniform carburizing heat, passmg a current of'compressed carburizinggas through the retort while so heated, agiand arresting the cementation as soon as l thm shells are formed upon the articles;

heating them to a degree above redness but while so'heatedin an atmosphere of car-- iron articles consisting in heating them inbulk to a degree above redness but below ing-gas, until thin shells are formed upon the.

the articles until they reach a hardening the walls thereof, heating the retort with substantial uniformity throughout until the V 95 gradually to a suitable degree for hardening,

of caseha rdening steel or 11'011 articles, consisting 1n making them suflitating the articles during their cementation,

5 the entire cementing operation, heating the '2l T-he process of case-hardening steel or 13 iron articles; consisting in confining them i-n tion as soon as shells are formed upon the bulk in a current of highly-com inessed; articles. carburizing-gas, :heating' them uniformly throughout While- S0 confined toa degree of 5 ADOLPH MACHLET' 5 heat sufficient to? carburize them, efi'ecting I Witnesses:

agitationof the articles While being so 0011-" SAMUEL R. OGDEN,

.fined and heated, and arrestingthe cementa- 1 PHILIP C. OSTERMAN.

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