US2190125A

US2190125A - Wear-resistant plating

Info

Publication number: US2190125A
Application number: US192178A
Authority: US
Inventors: Sembdner Gustav
Original assignee: Individual
Current assignee: Individual
Priority date: 1935-11-23
Filing date: 1938-02-23
Publication date: 1940-02-13
Anticipated expiration: 1957-02-13

Description

- Feb. 13, 1940. G, SEMBDNER A 2,190,125

WEAR-RESISTANT PLATING Filed Feb. 23, 1958 s Sheets-Sheet a 'III(IIIII4/" Feb. 13, 1940. a. S EMBDNER 2,190,125

WEAR-RESISTANT PLATING V Filed Feb. 2a, 1938 s sheets-sheet 2 Feb. 13, 1940. s. SEMBDNER 0,

WEAR-RESISTANT PLATING Filed Feb. 23, 1938 s Sheets-sheaf s 78 7 Infevfor:

i 9 J6 if 95 92 I Y Ahorvay ausrAv sumo/v5 Patented Feb. 13, 1940 UNITED STATES' WEAR-RESISTANT PLATING Gustav Bembdner. Berlin-Tempelhol, Gas-many Application February as, me, Serial No. loans In Germany November 28, I085 8 Claims.

This invention relates to metallic parts having improved wear-resistant surfaces and to methods and devices for producing wear-resistant surface layers on metallic parts, more particularly on wheels for rail-vehicles.

It is the object of the invention to incorporate wear-resistant material in such a manner into the metallic parts that its structure and strength is not changed, at least not deteriorated.

or .secure the wear-resistant layer to the metallic part. or support in such a manner that while an undesired or inadvertentdetachment or loosening is absolutely prevented, it is possible to relii place or detach the wear-resistant layer with simple means, if desired.

Another object of the invention is to provid simple devices and apparatus for applying the wear-resistant layers to and for removing same from, their support.

A special object of the invention is to increase the duration of wheels and wheel sets for railway cars.

Still another object of the invention is to apply the wear-resistant layer by means of existing machines which require slight modification only to meettheir novel purpose.

with these and further objects in view, I incorporate into the surface of metallic parts which are subjected to heavy stresses and wear and tear separate layers of a material having substantially higher resistance against wear and tear than the metallic part to be improved. In the practice of my invention, I force a wear-resistant plating in the form of a plate or strip into recesses of the surface to be improved, by a cold or preferably hot hammering, rolling or pressing operation. The recess in the metallic part to be improved is preferably undercut or "backed off".

0 for instance. in the form of a dovetail groove or recess which is engaged by the wear-resistant plating when it is forced into the recess and deformed.

According to a special feature of the invention,

' the wear-resistant plates or hands are formed with a curved or embed convex cross section so that there remains clearance in the middle between the metallic part and. the wear-resistant plate which clearance renders it possible to depress and flatten the wear-resistant plates, whereby. their lateral-edges are deformed and project and engage or intermesh with the under I cut faces.

According to a modified form of the invention.

M one flank of the groove or recess is detachable Another object of my inverition is to'attach so that by detaching this flank part the wearresistant plate can be removed and replaced by a new one, without deformation.

I may incorporate the wear-resistant plates into the metallic parts or supports by cold work- 5 ing. but generally, I prefer to heat the wearresistant material to facilitate its deformation without changing its inner structure. I have found that red hot temperature of the wearresistant material is very favourable for the i0 pressing and deforming operation. Also, it is thus possible to harden the wear-resistant material by quenching it immediately following the. rolling. forging, hammering or pressing operation.

According to a further feature of my invention, I remove or interchange the wear-resistant plating by cutting out a portion of the wear-resistant material, for example, in the form of one or more wedges or the like: To this end I may use cutting torches, grinding wheels or the like. It will be understood that the wear-resistant material on both sides of the out can thus be moved towards the cut and disengaged from the undercut faces for replacement by a new wear-resistant plating.

The metallic part or support may be iron or any other metal which is capable'of forming a support for tightly securing the wear-resistant plating. The wear-resistant plating may be steel which is improved or alloyed in any known manner, for instance, manganese steel containing 12-14% manganese, steel containing chromium and nickel or vanadium. Other than steel alloys may also be used, for instance, metals of the hard metal group, such as tungsten. carbide or the like. Furthermore, where the wear is due to chemical attacks, platings of anti-corrosive or non-rusting material may be employed. The coefiicient of thermal expansion or heat elongation of the wear-resistant material should be at least approximately'similar to the corresponding coefficient of the metallic support.

My invention offers special advantages in connection with wheels for rail-vehicles. As is well known, the bearingor running surface and the flange of such wheels are heavily stressed and worn out very soon. My invention renders it possible to use'such wheels for a much longer period of time, by incorporating wear-resistant material in the flanges or tires or all over the running surface of new wheels or wheels which are to be repaired, without changing the wheel diameter.

.A special advantage of my novel fastening sys- 2 aisles tem lies in the fact that the wear-resist ma terial can be easily applied or incorporated =1: when it is worn out, can be easily removed and interchanged, by means of simple or devices.

The invention will be better understood by reference to the following detailed description in connection with the accompaiwin drawings showing by way of example and schematically some embodiments of the invention, viz;

Fig. 1 is a view of a cross head bar having the invention applied thereto.

Fig. 2 is a fragmentary longi section of the cross head bar shown in Fig. 1, on an enlarged scale.

Fig. 3 is a cross section on line m-m in Fig. 1, on an enlarged scale.

Fig. 4 is a cross section through a plate or strip of a material which is rt against gear and tear, for use according to the inven- Fig. 5 is a cross section of another form of a plate.

Fig. 6 is a perspective schematical view of a curved surface improved according to the invention.

Fig. 7 is a cross section of a wear-resistant plate which'may be used for the purpose hereinafter set forth: v

Fig. 8 is an elevation, partly in section, of a capstan or winch drum improved according to the invention.

Figs. 9 and 10 are fragmentary longitudinal and cross sections of the rim of a rope pulley brake drum or the'like, having the invention applied thereto.

Fig. 11 is a fragmentary cross section of the rim or tire of a wheel for rail vehicles, provided with a wear-resistant plating according to the invention.

Fig. 12 is a fragmentary cross section showing a method of inserting the wear-resistant Plating. I

13 to 18 are further fragmentary cross sections of the rim of a wheel for rail vehicles, having the invention applied thereto.

Fig. 19 is a cross section of a machine part on the surface of which the wear-resistant plating is fastened in a modifier manner.

Fig. 20 is a fragmentary cross section of a wheel rim of a rail vehicle in which the wearresistant surfaceis inserted in a similarmanner as in Fig. 19. v v

Fig. 21 is a cross section similar to Fig. 20, showing swear-resistant surface composed of a plurality of parts.

Fig. 22 is a fragmentary plan view of a wheel as shown in Fig. 21, showing a staggered arrangement of the abutting faces or ends of the wear-resistant strips.

Fig. 23 is a fragmentary cross section of a wheel rim illustrating a manner in which the wear-resistant plating can be fastened and-removed.

Figs. 24 and 25, are a fra mentary cross section and longitudinal section, respectively, showing a faulty manner of rolling a wear-resistant plating'into the surface to be improved.

Figs. 26'and 2'7 are fragmentary cross, section and a longitudinal section of a device for removing or avoiding the defects occurring according to Figs. 24 and 25.

Fig. 28 is aschematic view of an-arrangement for heating, rolling in and quenching wearresistant bands in wheels for rail vehicles.

Fig. 29 is a side view, partly in section, of

. Fig. 28.

'Fig. 39 is a schematic plan view, partly in section, of a rolling device.

Figs. 31 to 35 are plan and sectional views, respectively, of joints similar to Fig. 22.

. 36 is a section on line E-F in Fi 35.

Figs. 37 and 38 are schematical sectional views, illustrating the removal of wear-resistant platings from their base or support.

39 is a perspective view of an arrangement for rolling-in wear-resistant strips in railway wheels, adapted for use with an ordinary wheel set lathe.

Fig. so is a side elevation of the arrangement shown in Fig. 39.

Fig. 41 is a front elevation of the same arrangement.

Fig. 42 is an elevation of a detail of the machine shown in Figs. 39 to t1.

Fig. 43 is a plan view of the parts shown in It will be understood that the principle according to this invention can be applied wherever it is possible to provide on parts or members subject to wear and tear due to friction, shocks or the like, interchangeable surface'layers, irrespective of whether the parts or memhere to be protected have prismatic surfaces, as for instance, grinding surfaces or sliding surfaces, or curved or profiled surfaces, as for instance wheels for rail vehicles, brake drums, pulleys, rollers etc. The wear-resistant platings may be of any material which is entirely different from thehasic or support material provided only that the wear-resistant material is capable of being deformed by pressing, rolling, hammering, forging or the like.

Referring now to the drawing in greate detail, and first to Figs. 1 and 2, it will be seen that a cross head slide plate of a locomotive has been illustrated. Inserted into the slide plate body I of soft steel are two slide surfaces 2 and 8 of a material oflering a higher resistance against wear. To this end grooves or recesses of the type shown at Q or 5 in Fig. 3, having undercut flanks or dove-tailed cross sections, are milled or out into the slide body i. Embodied in these grooves are wear-resistant strips or plates 6 or 3, respectively, of a. suitable cross section so as to form the desired surface in connection with the grooved surface. These strips are held in the grooves merely by engagement in the undercut faces of the grooves, without welding, soldering or otherwise heating the slide body I. Die strips or plates 6, 'I are so shaped tho-t the dovetail flanks are formed only by forcing the wear-resistant material into the grooves or recesses 8 or 5, under action of pressure. The required shape of the strips 6 and I will be seen from Figs. 3, 4 and 5. The platings 6 or I may he secured against longitudinal displacement by thickened portions at the groove ends, as indicatedat 8 in Fig. 2. Advantag'eously, a strip having" an arched, convex section is urged into the groove in red hot condition, and flattened.

after the strips'B, I have been inserted into the grooves l and 5, the wear-resistant material may he hardened, for instance, by quenching it by means of water, air or any other suitable hardening or quenching agent. The undercut grooves will prevent warping or other deformation of the wear-resistant strip. Where the wear-resistant material is applied in the form of the strip 8, a shrinking action will additionally occur which aids in obtaining a reliable joint. The surface layers thus tightly connectedwiththebodyimaybegroundor otherwise machined in the usual manner. when the wear-resistant material is completely worn out, after ithas been ground repeatedly. the wear-resistant material may be removed by cutting it into two parts lengthwise in suitable manner, for example by a cutting torch, without impairing the grooves of the slide body I, and replaced by new wear-resistant platings, in the manner hereinbefore described.

The cross section of the strips t or I may be produced in a rolling operation, but it will be understood that small quantitiesof the wearresistant strips may be produced in any other suitable manner, for instance, by forging the material in a swage or by shaving. A plurality of wear-resistant plates of a similar cross section may be arranged side by side, as shown at 9 in Fig. 6. The cross section of the platings according to Fig. 6 before the pressing operation is shown in Fig. '7, indicating an arched convex form of the cross section. As will be seen from Fig. 6, concave and convex surfaces may be provided with platings having the same initial cross section. i i

. Circular surfaces of any form may also be plated with wear-resistant material. For instance, Fig. 8 shows a capstan drum having wearresistant working surfaces incorporated in ordinary material. As shown in the right hand half of Fig. 8, a strip in of convex cross section is put on the surface to be plated which is recessed as shown and the strip is now depressed or pressed on, preferably by means of rollers, in red hot condition, so as to assume the shape shown in the left hand half of Fig. 8 and to lie flush with the surface of the capstan drum.

Referring now to Figs. 9 and 10, it will be seen that the rim or running surface'of a wheel, brake drum or pulley is. plated with two strips ii parallelly arranged insaid rim. The right hand strip in Fig. 10 indicates the initial cross section of the strip beforeit is deformed while on the left hand side of Fig. 10 the strip Ii is shown pressed or rolled into the dovetail recesses of the groove in the rim.

Various embodiments of wheels for rail vehicles, as used in railway cars or tramway cars, are shown in Figs. 11 to 18 and 20 to 23. As is well known, the running surfaces of such wheels are subjected to many different stresses and have to be corrected as to their cross section at regular intervals. Now, I provide those portions of the cross section of the rim which are mostly stressed and worn out with a plating or insert of a material offering extremely high resistance against these stresses and wear and tear, whereby the wheels may be usedfor a much longer time until correction and machining is again required. Moreover, when the cross section of the rim is worn down to the admissible limit, my novel system of fastening the wear-resistant plating to thewheel surface renders it possible to interchange or replace the wear-resistant plating'in a simple manner, as will be hereinafter described. 7

Figs. 11 and 12 show the cross section of a tire of a railway wheel having its mostly stressed portion at l2. In order to protect the wheel against wear, I cut a groove or recess into said portion l2 having undercut flanks l3 and It.

Now a strip l5 of a material offering a very high resistance against wear is hammered. forged,

pressed or rolled into said groove, whereby it is securely and intimately connected-with the rim. The wheel may'nowbeuseduntiltheadmissible lowerlimitofthecrosssectionoftherimls reached. In this 'case'the wear-resistant striplllsusuallyalsowornouttosuchanextentthat anewwear-resistantstriporinserthastobe applied. To this end,the wheel rim is turned down to the smaller standard cross section II. It is not necessary in this turning operation to turn the whole rim down to the lowest point of the worn flank II of the wheel flange, since a groove l'l having undercut flanks II, it, is turned. into this flank. into which a strip similar to the" strip II in Fig. 11 is forced. Asshownin Fig. 12. the strip is at first S-shaped so that it can be inserted into the groove .11. After the strip It has been inserted. it isstretched in the groove, by means of a press punch or roller II, in the manner hereinbeforedescribed. It will be understood that instead of a narrow groove and strip as shown in 88- 11 and 1 a wider groove and .strip may be used, as indicated by the dotted line 20 in Fig. 12, so as to cover practically the whole running surface of the wheel.

Further manners of fastening the wear-resistant plating on the wheel rim are shown in Figs. 13 and 14, illustrating two dovetail grooves 2|, 2| and 22, 22' into which a suitably curved andarched strip' 43 is inserted, the initial shape of which is shown in Fig. 13. This strip 43 is rolled wear-resistant plating is preferably. additionally secured to the wheel rim at the back of the flange at 23, by means of a dovetail or undercut groove. Figs; 15 and 17 show the wear-resistant strip in its initial cross sectional shape, while Figs. 6 and 18 show the same strip finished and deformed to be smooth and fast in the groove of the wheel rim.

According to a further feature of the invention I may provide one of the flanks of the dovetail groove-to be detachable from the metallic support. This renders it possible to insert the wearresistant plating without deformation thereof and to remove the wear-resistant plating without cutting it into pieces. Embodiments of this modification are shown in Figs. 19 to 21. Fig. 1 is a cross section of a machine part 24, for instance, a slide plate provided with wear-resistant surfaces 25 and 25'. The body 24 consists of a and deformed as shown in Fig. 14 to form a.

soft material offering a small resistance only against wear andtear and is provided with platlugs 21, 28, the undersides of which have undersponding projections 30'.- and attached to' the body 24 by means of screws Si or like means. It will be understood that the platings 21, 28 may be hardened and/or ground after or prior to being secured to the body 24.

';A slrnilar'fastening is shown in Figs 20 and 21,

showing in Fig. 20 a wheel rim 36 provided with a ring as of wear-resistant material interlocked inthedirectionofthearrowinarecessliofu a reliable and durable metallic contact between the wheel rim and secured in position by means of a closure ring 32 fastened to the wheel rim 36 by means of screws 3| and engaging the ring 35 by a projection 33. By way of alternative, the closure ring 32 may be fastened on the rim 55 by putting it on in a heated condition and allowing it to shrink so as to be held on the rim 36 by adhesion. According to Fig. 21 the ringof wear-resistant material 35 is-composed of three component rings 35', 35", 35', the arrangement being for the rest the same as in Fig. 20. It will be understood that this construction renders it possible to interchange or replace worn out strips 35 or single portions 35', 35", 35" by merely detaching the closure member 32. The wear-resistant rings or ring portions may then be readily'stripped off from the wheel rim and replaced by new wear-resistant rings.

Another modification is shown in Fig. 23, showing a wheel rim 36 which is provided with an annular strip 31 engaging the open groove 39 and secured in its position by a further annular strip 38 which is rolled in and engages a dovetail projection 36' of the rim 36, thus locking the strip 31 in its position. It will be understood that the two parts of the wear-resistant strip thus applied can be removed by a single annular cut of a cutting torch applied at 40 which cut does not require to go through to the bottom of the groove and therefore cannot injure the same. The two parts of the strip 38 thus obtained can now be readily removed to permit removal of the strip 31.

Where a plurality of parts of wear-resistant material, for example several parallelly arranged strips are used for plating the surface of a wheel, as indicated in Fig. 21, the difierent joints 4|, 4|", 4l' of the strips are staggered as shown in Fig. 22 so that the joints are protected against excessive wear and tear. Further possibilities of arranging a joint will be hereinafter described.

Generally, there is a very small clearance only between the groove or recess and the wear-resistant material inserted in the recess; therefore, water or other aggressive substances will not usually be permitted to enter into the groove. Where it is intendedto protect the groove additionally against corrosion, the surface of the groove and/or the inwardly directed surface of the wearresistant material may be provided with an anticorrosive or non-rusting coating which may be very thin, since it is protected against mechanical injuries by the wear-resistant strip. In Fig. l3 a coating 42 of anti-corrosive material has been indicated on the surface of the recess which coating may be applied by a galvanic process, by a spreading process Y or by a metal spraying process. A similar coating 43 is shown on the inner face of the wear-resistant strip in Fig. 13. Where the strip is not heated in the attaching operation, this coating may be applied in the same manner as the coating 42; where the strip is attached in hot condition, a coating of a refractory or fire-proof material has to be applied.

The provision of a protective coating between the wear-resistant material and its support is an important feature of my invention. More particularly this coating renders it possible to ensure the wear-resistant material and its support which contact is important, for instance, in case of wheels for rail-vehicles or slide contacts intended'to transmit electric current from the rail to the wheel or slide contact. Moreover, I have found that the said protective coating forms a bar for the flame of a cutting torch so that the surface of the groove is not impaired or injured by the cutting flame.

In some instances when the wear-resistant strip is rolled into the recess of its support with a corresponding increase inwidth, the portion of the strip shortly prior to the rolling station tends also to become wider, whereby difficulties arise in inserting the strip into the recess. This is shown schematically in Fig. 25 and in Fig. 24 which is a section on line A--B in Fig. .25. 44 is the band or strip to be inserted which is ar'ched as at 45. The support is provided with a dovetail groove 46 into which the wear-resistant strip is forced by means of a roller 41. Now, I have found that the strip 44 tends to flatten already prior to the point where it is depressed by the roller 41, whereby its exterior edges 48, 48 over- 'lie the groove, leaving a clearance 43 between strip and groove. In order to avoid this defect, I guide the strip 44 through a guiding device, as shown in Figs. 26 and 27 which is adapted to the width of the strip and prevents flattening of the strip outside the groove, and ensures at the same time a smooth rolling operation. As will be seen in Figs. 26 and 27, guiding members 50, 50', 50", 50" are provided in front of the roller 41 for guiding the strip. It will be understood that the guiding members 50, 50', 50", 50' may be constructed in the form of a single unitary device.

Figs. 28 and 29 illustrate by .way of exampleand schematically the rolling operation applied to a rail wheel of the kind shown in Figs. 11 and 12. The wear-resistant strip of convex shape is guided through a heating device 52, for instance, a muflie furnace and pressed intothe groove 54 of the wheel rim by means of the roller 53, the cross section of which corresponds to the flank of the flange of the wheel. The finished strip 5| can be hardened by means of a quenching device 55 in the form of a water spraying nozzle or the like. A modified form of the roller is shown in Fig. 30, illustrating a roller 56 which is provided to roll a. wear-resistant strip 51 into the groove 53 of a rail wheel 59, so as to improve the running surface and the flank thereof. It will be understood that a roller of the shape shown in Fig. 30 may also be used in'the device shown in Fig. 28 and 29, instead of the roller 53. Various forms of joints of wear-resistant strips are shown in Figs. 31-36. According to Figs. 31-32, the two abutting strip ends overlap each other at ill, 6|, leaving

gaps

62, 63. The joint shown in Figs. 33 and 34 is connected by a welded seam 64. Figs. 35 and 36 show a staggered oblique joint. It will be understood that the construction and form of the joint depends on the stress to which the respective metallic part is subjected in operation.

In order to remove platings of material from their metallic supports, the plating may be cut into pieces, as shown in Fig. 37, by means of a cutting torch 55, so as to form a wedge-shaped middle portion 61 separated from the lateral portions by cuts 56. According to Fig. 38, the middle portion 61 is then taken oflf or raised and the side 58 and 53' are moved to the center so that they can be easily lifted out of the groove. Where the cut is made very wide, a single cut will be sufllcient in many instances, to permit removal of the wear-resistant portions. With some of the fastening constructions, as for instance, that shown in Fig. 23, only a separating out 40 is required. The cut may be made by any suitable cutting tool other than a cutting torch, for instance, by means of grinding wheels, cutting chi'sels. saws or the like.

It will be' understood that my novel principle can be applied not only to existing wheels for 'rail vehicles having separate tires, as for instance, illustrated in Fig. 29, but the invention especially permits of the manufacture of wheels having no tire at all, but having simply a grooved rim into which the wear-resistant stripis rolled, as indicated in Fig. 23. In this case the wear-resistant strip can be removed groin the wheel and replaced by a new one when t is worn'out.

Generally, any'suitable rolling machine or apparatus may be used to apply the wear-resistant material to its support, but in case of round me tallic parts, more particularly wheels, I prefer to employ ordinary wheel set laths reconstructed or modified to meet the purpose in question. By way of example, Figs. 39 to 43 show a device of this kind, comprising a face plate or disc 1| of a wheelset lathe and a base plate 12 for the slides. The wheel set 13, one wheel of which 18 has been shown only, for the sake of clarity, is inserted on chucked in the usual manner. preferably in such a way that the axle stub 15 of the wheel set rotates on the center 18 of the face plate 1| while the wheel set is rotated in usual manner, for instance. by drivers from .the opposite face plate which is not shown in the drawings. The two slides are removed from the plate 12 and replaced by a device 11 (Fig. 40) by which the strip 18 can be rolled into the groove 18 of the wheel. The strip 18 passes through a guiding device 88 heating device for the strip at the same time..

The device 11 comprises a roller 8| which hasthe anchor plate 85 by means of a screwing de vice 88. so that the roller "is supported by this which, as already mentioned, may receive the a rod 88 (Figs. 42 and 48) which is adjustable in anchor plate 85. 'The plate 88 in turn is relieved from the forces thus acting upon it by brackets 81,81 (Fig. 41) surroundingthe axle 18 of the wheel set andthe. emergency nmning surface 88 or the axle stub 15 of thewheel 18, and connected by tension rods 88, 88' to the anchor plate. The plate 85 isthus quasi suspended from the axle of the wheel. bracket 81 and rollers or slide bodies are pro- Rollers 88 are provided in thevided in the bracket 81'. In this manner the roller II can be adjusted to exert the desired pressure by means of the screwing device 88 which advantageously is connected with the rod 88 by a ball and socket joint.

The roller 8| due to thehdiiferentathicknesses of the flanges or tires 88 will sometimes have-a lateral clearance with respect to the said tire or flange 88 which should be advantageously limited or entirely eliminated. To-this end I provide a circular disc 8|, the shaft '88 of which is inclined with respect to the shaft of the roller 8| and the surface 88 of which is wedge-shaped so as to engage the space between the tire 88 and the roller flange 8|. It will .be understood that the play or clearance between the tire 88 and theroller 8| can be easily changed or eliminated-by moving or pressing the disc 8| more or less into this inter-- space, by means of the screwing device 88. The disc 8| is supported on the bracket 85 which may be secured to the fork 82 by means of screws. According to another modification of the invention the clearance between the tire and the '1. the roller may be eliminated by providins the.

moimted insaid groove, a first of said elements circumferential groove with undercut side walls.

5 roller u with interchangeable or adjustable lateral flanges 8|, as shown in Fig. 43. Also the clearance between the roller 8| and'the' tire may be eliminated by means of lateral pressure rollers (not shown) or the I Provided at 88 between the guide plate 88 and the flange 80 in Figs. 39 and 42 is the guiding device for the strip 18 which has been hereinbefore described with reference to Figs. 26 and 2'1: the shape of this device isadapted to the profile or cross section of the groove and strip.

It will he understood that the machine operates in such a manner that the wheel set 18 rotates in a counter-clockwise direction, whereby the strip 18 is pressed into a grooveof the wheel 18 under action of the pressure exert by the roller 8|. The groove portion of the wheel and a salt solution. Alternatively, a squirting device may be provided as in Fig. 28. While I have herein shown and described certain preferred. embodiments of my invention, 1- wish it to be understood that I do not confine myself to all the precise details herein set forth by way of illustration, as modification and variation may be made without departing from the spirit of the invention or exceeding the scope of e the appended claims. 80

I claim:

1. In a method of removing from-a metallic support a wear-resistant 'layer engaged in undei'cut recesses'of said support, the steps which comprise cutting out a portion ofthe wear-resistantmaterial coextensive with the undercut v recesses so thatthewear-resistant. layer is split 1 up in two parts, and withdrawing the two wearresistant parts from the undercuts so that they can be taken oil from the support.

circumferential groove with undercut retaining means in triplicate in and coextensive with said groove. and a pair of wear resistant elements having preformed portions thereof. engaged with a pair of said retaining means and having one edge thereof comprising an undercut retaining means for the other of said elements, said other element having preformed portions thereof en-' gaged with the third of the first said retaininfl means and the last said retaining means. said elements of strip members having in combination substantially the same cross-sec-- tlonal shape as said groove. the ends of the respective strip members, arranged to adjoin each other in circumferentially displaced 3.'A wheel including a'rim portion having a one ofsaldsidewallsbeingintegral with saidrim portion, a retaining element removably secured to said rim portion and shaped to provide the other of the undercut side walls ofsaid groove, a wear resistant element mounted in said groove with preformed portions of said element engaged with complementary portions of said groove, said element consisting of a strip of substantially the same cross-sectional shape as said groove with the ends of said striparranged to adioin eacli 10 other in said groove to provide a smoothrlmning surface for said wheel, said strip element being removable and replaceable upon removal of said retaining element.

' GUSTAV SDIBDNER. ll