US2218958A - Apparatus for the hardening of tubular steel articles - Google Patents

Description

Oct. 22, 1940. H, NELSON I 2,218,958

APPARATUS FOR THE HARDENING 0F TUBULAR STEEL ARTICLES Original Filed March 5, 1939 8 Sheets-Sheet 1 INVENTOR Tu m Hnl'land Nels m1 ATTORNEYS .Oct. 22, 1940. -r. H. NELSON APPARATUS FOR THE HARDENING 0F TUBULAR STEEL ARTICLES Origi al Filed March 3, 1939 8 Sheets-Sheet 2 l NVENTOR Tum Holland Nelson.

BY flaw W TTORN EYS Oct. 22, 1940. T. H. NELSON APPARATUS FOR THE HARDENING 0F TUBULAR STEEL ARTICLES Original Filed March 5, 1939 8 SheetsI-Sheet 3 /////////V/ V//////////// w GE Oct. 22,1940.

, T. H. NELSON 2,218,958

APPARATUS FOR THE HARDENING 0F TUBULAR STEEL ARTICLES Original Filed March 3, 1959 8 Sheets-Sheet 4 FIG. 10.

INVENTOR Tum Holland Nelson I d fllw ATTORNEYS Oct. 22, 1940.

T. H. NELSON APPARATUS FOR THE HARDENING 0F TUBULAR STEEL ARTICLES FIG. 11.

Ori i l Filed March 5, 1939 8 Sheets-Sheet 5 n INVENTOR Turn. Hull-and N215 on.

flwq ATTORNEY? Oct, 22, 1940. T. H. NELSON 2,218,958 I APPARATUS FOR THE HARDENING OF TUBULAR STEEL ART ICLES I Original Filed March 3, 1959 8 Sheets-Sheet 6 INVENTOR Tcrrn. Holland N 215 an.

BY 6 2 ZTTORNEYS Oct. 22, 1940. ."r. H. .NELSQN 2,218,958

APPARATUS FOR THE HARDENING OF TUBULAR swam, ARTICLES Original Filed March s, 1939 8 Sheets-Sheet 7 5mm G 1 33 5; FIG. 1 7.

Hardness EU BUD 5D SOD ODD 3!] EDD 21] ZDO IUD inEl" .l

Bria-L211 EDD Thicknesi Hardne s S SUD FIG. 18. 4GB

sun

ZDU

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Liner L '1' hickness Eminz'll Hardness SUD FIG. 1 9. 4GB

ZDU

IUD

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INVENTOR Tum Holland N215 cm.

ATTORNEYS Oct. 22, 1940. T. H. NELSON 2,218,958

APPARATUS FOR HARDENINGH OF TUBULAR STEEL ARTICLES Original Filed March 3, 1939 8 Sheets-Sheet 8 Hardness Pogyveu brine" FIG. 20.

-v 5 1. A i INVENTOR.

Tum Holland N215 cm ATTORNEYS.

Patented Oct. 22,1940

UNITED STATES. PATENT OFFICE APPARATUS FOR THE HABDENING 01' TU- BULAR STEEL ARTICLES Tom Holland Nelson, Villanova, Pa. assignor to Harrisburg Steel-Corporation, Harrisburg, 2a.,

a corporation Original application March 3, 1939, Serial No. 259,680, Divided and this application October 25, 1939, Serial No. 301,288

, 6..Claims.

i The present application relates to a hardened article made of steel or alloy, and is a division out of my co-pending application, Serial No. 259,680, filed March 3, 1939.

Many wrought steel cylinders or tubular articles, such as pump liners, are subjected to wear and abrasion on the internal surface thereof, due to the action of pistons or moving parts, and the abrasive effect of grit. For that reason it is the present invention relates to the development of a, pump liner or other tubular article the inner surface of which is hardened to the maximum degree for which the steel or alloy is capable of developing, with a normal or soft conditionto adesired depth on the outer wall of the liner, and with a rather uniform pr gradient hardness onthe intermediate portion of the wall, The

- liner on its inner surface preferably develops a maximum hardness, for example approaching 650 Brinell, is attained; the Brinell hardness rather uniformly decreasing in the direction of the outer surface of the liner or cylinder, where it is desired to have a Brinell hardness of approximately 250. s

I am well aware that heretofore'varlous methods for producing surface hardness have been used, such, for instance, as case hardening,

nitriding, alloy metal spraying, and inserted liners, but these methods are limited in their application. For instance, case hardening to be commercial has a limited depth and involves considerable length of time at higher temperatures than is desirable for certain steels. Nitridlng is very restricted so far as depth is concerned, and the time factor is longer by far than case hardening.

In both case hardening by cementation," or nitriding by the nitriding process, considerable length of time is required and they are restricted by depth of penetration andother commercial factors, and are prone to cracking and spauling under severe load.

I have found the art known as flame harden ing to be unsuitable for the internal hardening of tubular articles such'as pump liners. Extensive experiments have been conducted to thatv end, and have resulted in very marked differences when compared to the process which is set forth in my parent application above identified, so far as surface hardening is concerned. In flame hardening heat is applied to merely a portion of the surface of the article from a source so much higher in temperature than the desired ultimate temperature that very definite strains and stresses are set up, remembering of course that other portions of thetubular article are at normal temperatures. Further, with flame hardening additional stresses more severe than with my process are developed during the quenching action in bringing the heated portion down through the critical stage. Thus there are dual risks of setting up stresses and strains by the art of flame hardening, each of which in turn is capable ofzcausing distortion and cracking of the article. The dimensional accuracy, uniformity of surface hardness, and abrasive resistance demanded of a pump liner arewell known. These three features I have found unattainable by flame hardening. By my process the entire mass of material is heated to a uniform temperature and'the article can be considered almost in a state of rest, free from strain. As an incident of the insulation jacket and the uniform. spraying desirable characteristics of my liner as hereinoutlined are obtained, and they cannot be obtained with any of the other processes of the prior art above mentioned.

With the present method the wrought steel is of the same chemical composition throughout, and no other element is added in the process such as carbon in the case of case-hardening, or nitrogen for the formation of ironnitrlde'in the case of nltrlding. I

the production of a hardened cylinder, liner, or the like, by means of internally spraying the liner which has been heated to a point above its critical temperature. The inner or outer surface of thecylinder or liner which is not to be hardenedis encased, during such spraying, in some refractory material; the volume of quenching.

A further object of the present invention is 5 Other objects and advantages of the invention will be apparent during the course of the following detailed description.

In the accompanying drawings, forming a part this specification, and wherein similar reference characters designate corresponding parts throughout the several views,

Figure 1 is a side. elevation of an improved machine used for the hardening of such tubular and cylindrical articles as pump liners.

Figure 2 is a longitudinal sectional view taken through the improved machine showing a cylinder or pump liner in position on the machine, for hardening.

Figure 3 is a plan view of the machine shown in Figure -1.

- Figure 4 is an end view of the machine.

Figures 5 and 6 are cross sectional views taken substantially on their respective lines shown in Figure 3 of the drawings.

Figure 7 is an enlarged fragmentary sectional view. taken through the spray nozzle of the improved machine; showing its mounting means.

Figure 8 is a fragmentary longitudinal sectional view taken through a control piston of the machine.

Figure 9 is a side elevation of the quenchingmedium control handle or lever.

Figure 10 is a longitudinal sectional view taken substantially on the line l0|0 of Figure 9.

Figure 11 is an enlarged fragmentary longitudinal sectional view taken through one of the roller shafts adapted to support the article to be hardened.

Figure 12 is a fragmentary end view of a refractory jacket adapted to receive the article to be hardened.

Figure 13 is an end view of the jacket shown in Figure 12.

Figure 14 is a side elevationof a modified form of the invention.

Figure 15 is an end view of the machine shown in Figure 14.

Figures 16 to 19 inclusive are charts showing curves which designate the degree of hardness through varying thicknesses of liners or cylinders, under different conditions of quenching control.

Figure 20 designates a fragment or wall section of a liner which has been Rockwell tested for hardness; the accompanying figure at the hardened portion of the' liner designating the- Rockwell C hardness and the corresponding Brinell hardness.

Figure 21 designates micro-photographic views of various micro-structures taken at four points in the wall thickness of the liner shown in Figme 20, from the martensitic 60 Rockwell inner hardened surface to the normal, soft or unhardened pearlitic .outer surface of the liner having a Rockwell hardness of 24.

In the accompanying drawings, forming a part of this specification, and wherein are shown preferred and modified formsof the invention, the letter A may generally designate thepreferred form of cylinder hardening machine, which includes a foundation frame 13 having means C thereon to rotatably receivea pump liner or cylinder D to be hardened. This liner or cylinder is ordinarily encased in a refractory jacket E of suitable insulating material; the supporting means C being driven by means F. Spray means G is provided for supplying quenching medium; means G being movably located by means H for movement towards or away from the liner or cylinder D. 1

The supporting frame Bis designed primarily toreceive a'cylinder or liner with its axis in hori-' zontal position. However, it is to be understood that this invention .is not to be limited to a method or mechanism for hardening treatment of cylinders or liners while in horizontal position, since it is entirely feasible to have the cylinders or liners vertically positioned orinclined at an angle to the vertical or horizontal. The frame 13 includes a supporting bed 25 supported by legs 26. The frame B may be of metal or other construction and is preferably anchored at 21 to a H concrete foundation 28. The bed 25 includes a piston cylinder I53 adapted to receive the piston of means H which regulates movement of the spray apparatus G.

As is more particularly shown in Figures 2, 3

and 5 of the drawings the means C for supporting the linerand" its refractory jacket consists of roller shafts having keyed therewith serrated supporting rollers 31, in any approved number,

upon which the liner E and its encased jacket is adapted to rest. 'The means F is used to drive the rollers 44 in the same direction, that is, either clockwise or counter-clockwise. The manner in which these shafts 44 are supported is detailed in Figure 11 of the drawings where it is shown that the shafts 44 are rotatably supported upon suitable anti-friction bearings 40 located in the end walls of the bed 25; suitable means 4| being procups or casings wherein the anti-friction bearings are received. Both shafts 44 extendoutwardly at their rear ends through the end wall of the supporting bed 25, where they are provided with suitablesprocket wheels 45 to receive a drive chain 46 constituting part of the drive means F.

Itis to be understood that other articles than cylinders and pump liners may be hardened according to the method herein described. For the most part the machine is adapted to internally harden pump liners, such as that shown at 'D inFigure 2 of the drawings. As will be subsequently described, a feature of the method is the encasement of the liner within a cylindrical refractory jacket E, preferably of asbestos. This jacket is shown in Figures 2, -12 and 13 of the drawings and consists of complementary jacket portions 50 and 5|, which are hinged at 52 and provided with suitable pin operated latch means 53, shown in Figure 12 of the drawings; These vided for feeding grease or other lubricant to the jacket portions and 5| may include a thin walled casing filled with asbestos or other insulating material, or they may be themselves made up of any refractory insulating material desired. The jacket E snugly fits around the external surface of the liner D to be hardened, but it does not obstruct in any degree the openings at the end walls of the liner. It is of course understood that various size refractory jackets will have to be employed; their use depending upon the size of cylinder or pump liner which it is desired to harden. 1

The lower shafts 44 may be suitably spaced so that the serrated rings or enlargements 31 thereon may take liners and jackets of different diam- .eters. However, liners vary in length; it very idles on its supporting'shaft; the forward end ment against the opposite end of the jacket .or'

liner; this roller IiI being positioned for rotation on a vertical axis but being mounted on a slidable base 62. The base 62 has a slot 63 disposed longitudinally therein along the longitudinal axis of the machine; a set screw 64 being mounted on the to accommodate a jacket of determined length.

Referring to the drive means F, .shown best in Figures 3 and 4 of the drawings, a motor I is provided for driving a change speed gearing II. The latter has a drive shaft I2 provided with a sprocket wheel I3.upon which the drive wchain 4B is trained. Means I4 is provided for changing the speed of rotation of the chain 46. The latter is trained about an idler sprocket 80, in order' to insure driving of the roller shafts 44 in the same direction, and a belt tightener 0| may be associated therewith. 6

Referring to the means G for spraying of the quenchingmedium in the liner or cylinder, the same includes a movable carriage 90 slidably supported upon parallel bars 9| the bars at one end being connected with the frame B of the machine and at the other end having a supporting standard 92. This carriage 00 is U-shaped, as shown in Figure 6 of the drawings. It is moved along the parallel bars 9 I by means to be subsequently described, in order to move it into and out of spraying and quenching relation with a liner supported upon the machine.

The spray means includes a horizontal spray nozzle supporting tube I00, adjustably supported upon the carriage 90 by means of a screw IN; the tube I00 having a yoke and nut I02 attached thereto, and depending normal thereto within which the screw IOI fits. The screw MI is provided with a handle I02 for rotating the same; the handle I02 being freely ro'tatably supported in the depression of the U-shaped carriage, as shown in Figures 2 and 6 of the drawings. It is readily apparent that upon turning the handle I02 the nozzle will be vertically adjustedto suit the size of the liner being quenched.

The spray nozzle mounting tube I00 is provided with a valve casing I at an end thereof; the valve beingoperated by means of a lever I06, shown best in Figures 9 and 10 of the drawings; the lever having a spring actuated detent II! which operates against a quadrant H3 in order that the lever may assume any of several welldefined positions; an adjustable stop H4 being provided in the quadrant to limit the open movement of the valve to any desired maximum. The tube I00 is of course provided with a flexible hose I I5, as shown in Figure 1, so that the spray may be connected with any suitable water supply source and still move to permit its entrance and exit with respect to the liner.

Suitable guide rods I20 are provided upon the carriage, as shown in Figure 6, to prevent turning of the spray nozzle; clamping levers I2I being associated with" the carriage and engageable against the rods I20 to clamp the yoke I02 at a desired level.

A spray nozzle I25, as shown in Figure '7 of the drawings, is closed at one end by-a screw plug I26 and it is provided with radial openings I21 therein arranged in spiral relation around the periphery of the spray nozzle. The latter is inserted into a counterbored tapered opening I20 in the end of the spray nozzle supporting tube I00, as shown in Figure 7 of the drawings; a split tapered clamping sleeve I30 being provided for seating against the tapered counterbore of the tube I00. A clamping nut I32 associated with follower rings I34 is adjustably positioned in threaded relation on the end of the tube I00;

and upon turning thereof the followers will urge the splitsleeve into the tube I00 and due to its seating relation on the tapered counterbore the spray nozzle will be clamped in position.

The means for advancing and retracting the spray nozzle and its supporting carriage is best illustrated in Figures 2 and 8 of the drawings. This means H includes a rod I50 supported by the carriage, having a piston I5I on the end thereof slidable within the piston chamber I53 of the frame B. Ports I52 are provided at opposite sides of the piston I5I for ingress and egress of fluid so that the piston may be moved back and forth in the chamber I53. The operating medium is preferably air, although steam or any fluid, may be used. Control is effected through a two-way valve I55, as shown in Figure 8; the valve I55 being positioned on the frame of the machine as shown in Figure 3.

In a modified form of the invention shown in Figures 14 ,and of the drawings a supporting frame K is provided, having suitable tracks II0 thereon. A pump liner supporting carriage L has suitable "wheels "I which travel along the tracks I10. The carriage L is provided with suitable rollers I12 actuated by means of a motor I13; the liner and its refractory casing being adapted to rest on the rollers in the same relation as above invention. The spray nozzle I15 is mounted in a stationary position upon the frame K; the

quenching medium being controlled by a valve I16. The carriage L may be manually or otherwise moved to advance and retract the pump liner or cylinder to be hardened with respect to the spray nozzle.

It is within the scope of the present invention to rotate the spray nozzle instead of the article to be hardened. In that case the liner or article to bevhardened will preferably be vertically positioned to insure an even distribution of water or quenching medium.

' It should be noted that the refractory jacket encases and is in contact with the outer surface of the article to be hardened. This not only excludes the quenching medium from contact with the outer surface of the pump liner or article to be hardened, but also excludes air. In order to obtain the best gradient hardness through the wall where special steels may be involved, a jacket could be so constructed that it may be heated to a temperature just below the critical point of the material. This jacket may, or may not be a refractory. It could, for instance,

be a double sleeve' with any type. of heating me- 1 the interior, yet at the same time obtain the maximum degree vof softness on the interior.

The speed'of rotation of the article is such as to centrifugally distribute the quenching medium accordance with the curves shown in Figures 16 to 19 inclusive areas follows:

Carbon Sulphur .027 Phosphorus .018 Manganese a .49 Silicon -1 .26 Chrome .16 Nickel .17 Molybdenum .426

' time for initial spray at full volume.

heat into the liner.

The preferred method of treatment is to adjust the valve lever I06 so that a full or approxi mately full flow of the quenching medium is initially forced into the pump liner, which has been heated to above the critical temperature. After a predetermined time the quantity of quenching medium fed through the nozzle is lessened by adjustment' of the valve and the quenching medium is permitted to spray into the pump liner at a reduced volume and over a predetermined periodoftime which is preferably longer than the This insures proper gradient hardening of the pump liner or cylinder; preventing run-back of the Thus, the factors of volume and time are co-related. The speed of rotation of the cylinder may also be a factor co-related to controlled volume and time treatment; it being necessary to produce a proper centrifuging of the quenching medium within the liner.

In the charts shown in Figures 16 to 19 inclusive, the horizontal lines designate Brinell hardness, and the vertical lines from left to right designate the liner" thickness.

The charts I6 and I1 designate the hardness curve for a liner with a wallof inch thickness; the two charts designating different time treatment of liners of inch thickness. The curves shown in Figures 18 and 19 designate the hardness curves for liners of 1 inch wall thickness. These curves were plotted from Rockwell hardness tests.

The inch wall thickness liner whose hardness curve is illustrated in Figure 16, was heated above the critical temperature to a hardening temperature of '1510 F. The spray medium, with the valve lever at full position (No. 5) shown in Figure 9 of the drawings, was permitted to flow into the pump liner for a period of twenty seconds, during which time 13.40 gallons of water or quenching medium was disposed of. The valve lever was then thrown to the No.1 position, reducing the volume of flow approximately to 1 th, and this treatment was carried out over a period of 140 seconds, during which time 13.30 -additional gallons of quenching medium was used. At this time the finishing temperature of the liner was F.

For the hardness curve shown in Figure 1'7,

1 the liner was heated above the critical temperature to a hardening temperature of 1510 F.,'and

' quired.

the liner over a period of thirty seconds, during which time 20.10 gallons of quenching medium was disposed of. .The valve lever was then thrown to the No. 1 position, reducing the volume of flow to 'th, and this treatment was extended over a period of seconds, during which 14.73 additional gallons of quenching .medium was disposed of. The liner registered Cold at the termination of the treatment.

The size of the inch wall thickness liner treated according to the hardness curve shown in Figures 16 and 17 was 81 5' inches outer diameter by 21% inches in length. It is a noticeable feature of the treatment above referred to that the liner will elongate during hardness. Therefore, to compensate for this characteristic, I may take a liner which is shorter than that re- Tlfe degree of elongation appears to be proportionate to the depth and degree of hardness obtained. For instance, the liner whose hardness curve is shown in Figure 17 was noted, for the composition of steel used, to have elongated th of an inch.

The size of the liner with 1 inch wall thickness, whose curves are plotted in Figures 18 and 19 was 86 th inches outer diameter by 22 inches in length. v

The liner whose curve is shown in Figure 18 was heated to a hardness temperature of 1510 F. With the valve in the No. 5 position, full flow of the quenching medium was permitted to enter the cylinder liner over 'a period of twenty seconds, during which time 13.30 gallons of water was disposed of. The valve lever was then thrown to the No. 1 position, reducing the volume of flow to one-fifth, and the treatment was carried out over a period of 260 seconds, during which 24.70 gallons of quenching medium was used. The finishing temperature of the liner was F. and the elongation of the liner was th of an inch.

Referring to the chart shown in Figure 19, the liner was heated-above the critical temperature to a hardening temperature of 1510 F. and with the valve open at the No. 5 position treatment is carried out over a period of thirty seconds, during which 20.10 gallons of quenching medium entered the liner. The valve lever was then thrown to the No. 1 position, reducing the volume of flow to 3th, and the treatment was carried out over a period of 220 seconds, during which additional quenching medium in amount of 20.90 gallons entered the pump liner. The finishing temperature of the article-was 140 F. and the'elongation of the cylinder was M ths of an inch.

Referring to the micro-phonograph reproduced in Figure 21 of the drawings, the magnification is x 500. The upper reproduction designated at 300 illustrates the martensitic structure of the hardened inner wall of the, liner, this section being taken somewhere in. the area of the wall thickness designated at 300 in Figure 20 of the drawings. The micro-photograph portions 30! and 3 02 designated in Figure 21 of the drawings designates the Troostitic-Sorbitic transition between the inner and outer wall thicknesses of the liner; the micro-photograph 30| being taken somewhere in, the area of the wall thickness designated at 30! in Figure 20 of the drawings, and the micro-photograph 302 being taken at a section somewhere in the area 302" shown in Figure 20 of the drawings. The

' micro-photograph 303 shown in Figure 20 of the drawings illustrates a typical normal pearlite a desired to obtain in the pump liner or other structure andjis taken somewhere f inthe area designated ati303 in Figure 20 of thedrawings. This wall section is comparatively soft and it is distinguished "as normalf from fully annealed".

From the micro-photographs it will be noted that the martensitic structure 300 is recognizable by reason of its accicular formation, and that the Troostitic-Sorbitic micro-photographs 3M and 302 are recognizable by reason of their finely divided structures which have little if any definite outline. The white areas of ferrite in the micro-photograph 303 and the darker areas which designate carbide of iron in this microphotograph 303 of course identify the structure as normal, or unhardened and machinable pearlitic. r

It is not believed necessary to designate a curve for the hardness of the section of liner shown in Figure 20. This liner is of one inch thickness. The liner was of course heated to a hardening temperature of 1510 F. With the valve in No. 5 position, full flow of the quenching medium was permitted to e ter the cylinder liner over a period of 45 seco ds, during which time 30.15 gallons of water was disposed of. The valve lever was then thrown to the No. 1 position, reducing the volume of flow to 1 th, and the treatment was carried out over a period of 105 seconds, during which 9.98 gallons of quenching medium was used. The finishing temperature of this liner was cold, and the elongation of the liner was knd of an inch. This liner of course was treated according to the above outlined process, and initially the liner was of a length so that the elongation would compensate and bring the total over-all length to that desired of the liner.

/ It is readily apparent from the foregoing that a homogeneous steel pump liner is provided, so far as chemical analysis is concerned, the hardness of which gradually tapers from the inner to the outer surface where maximum toughness and ductility is obtainable. In other words the line of demarcation between the hardened part I and the softer part" of the metal is eliminated, and this is the undesirable characteristic of hardening processes heretofore used. The initial full volume fiow of quenching medium, according to the tests above enumerated, cools the puinp liner to the desired depth, and the subsequent slowing up of the volume quenching medium is just sufficient to maintain the interior of the liner cold, or substantially below the critical at which desired hardness is to be maintained; the cooling of the outer shell of the cylinder being slowed up so that it will fall below the critical hardening point slowly and be free of the quenching hardening effect. It will be understood by those 'the liner; the fracture representing a complete skilled in the art that the outer shell having once dropped below the critical point will not harden.

While the above hardness curves are plotted according to Rockwell hardness tests, I have provided a destructive test, as follows: A piece of the liner after heat treatment is broken off cross-section of the wall thickness. It is then tempered for the purpose of coloring to any of the well known tempered colors. The result is somewhat surprising, since instead of the metal thru the thickness thereof having a uniform color; such, for instance, as straw, brown, purple, or blue, the wall thickness will develop very definitely in two colors; the one color definitely representing the depth of hardness which it is the cylinder is made article which has been hardened according to the above method, and the other color definitely representing the unhardened or softer portion. This method does not, as yet, establish the degree of hardness, but it very definitely establishes the depth of hardness. This is very important,since in combination with a hardness testing machine it is possible to obtain the maximum hardness obtained on the face of the liner and by the color tempered process above outlined it is possible to obtain the depth of hardness. It is within the scope of this invention to harden a tubular liner on the outer surface and provide inner machinable ductile surface, by practicing the above process in reverse.

An optimum condition is a liner hardened on its inner surface to between 500 and 650 Brinell, graded to the outer surface which has a hardness of 200 to 350 Brinell.

It is of course understood that various tubular articles, and indeed otherarticles may be treated according to the method herein outlined, and that the size of the liner is immaterial.

I claim:

l.- In a machine for the hardening of steel cylinders the combination of an insulating cylindrical shaped jacket, means forrotatably supporting the jacket with the cylinder fixed therein on a horizontal axis, means for rotating the jacket and its cylinder, means for spray quenching the interior of the is being rotated, and means for variably controlling speed of rotation of the cylinder and volume.feed of the quenching medium whereby they may be synchronized to. most effectively harden the cylinder to the maximum hardening at the quench location that the material of which is capable of developing.

2. In means for the hardening of tubular steel articles such as cylinders the combination of an insulating jacket for receiving the steel article to be hardened, means for rotating said insulating jacket and the steel article therein, and spray means for quenching portions of the cylinder not covered by said insulating jacket.

3. In a machine for the hardening of tubular articles the combination of means for circumferentially encasing the tubular article in an insulation jacket, means for rotating the article and its encasing jacket during the hardening operation, and means for spray quenching the interior of the article while it is being rotated. 1

4. In a machine for the hardening of tubular articles one circumferential surface of which is ,to be soft and the other circumferential surface an insulation jacket provided with means to lat- I erally open and close the same throughout the length thereof, said jacket adapted to receive the tubular article to be hardened, and said jacket being rotatably supported upon said roller bed, and spray quenching means operatively related to the roller bed and said jacket so that the spray may be disposed within the jacket and the tubular article therein for quenching the latter.

6. Apparatus for the hardening of tubular steel articles comprising an insulation jacket provided with means to open and close the same for attaching itself upon and enclosing a circumferential surface 01' a tubular steel article for protecting that circumferential surface against being hardened vduring a quenching operation, means for rotating said steel article and the insulating jacket therewith, and spray means for simultaneously enveloping the other circumferential surface of the tubular steel article, in a.

quenching bath for hardening of the latter circumferential surface. TOM HOLLAND NELSON.

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