US2075810A - Built-up rail and method of building up the same - Google Patents

Description

P 6, 1937. H. s. GEORGE v 2,075,810

BUILT-UP RAIL AND.METHOD OF BUILDING UP THE SAME Filed Sept. 6, 1933 2 Sheets-Sheet 1 ATTORNEY Patented Apr. 6, 1937 UNITED, STATES PATENT OFFICE BUILT-UP RAIL AND METHOD ORBUILDING UP THE SAME Harry S. George, Massapequa, N. Y., asslgnor, by

mesne assignments, to Union Carbide and Carbon Corporation, a corporation of New York Application September c, 1933, Serial No. 688,333

24 Claims. (Cl. 29-169) the rest of the tread surfaces of rails, because i at the ends of rails there is no support against end flow of rail metal at the tread surfaces thereof hence, the rate at which tread surfaces of.

rails become battered is greatest at rail ends. This lowering of the running or tread surfaces of rails at rail joints increases the effect of the pressure of rolling traffic by converting it into a downward blow as the wheels pass over rail joints. This action still further increases the rate at which the tread surfaces at the ends of rails become battered over that of the rest of the rails. After a few years of service the amount of batter at rail joints becomes so great that,

in order to increase the life of rails, the battered tread surfaces at the ends of rails are built-up to the general level of\the rails by depositing metal on the depressed" areas.

In order to facilitate an understanding of this invention, it seems expedient at the outset to consider the manner in which metal deposited on the battered or worn tread surface areas of rails cools and hardens. The metal generally deposited is a steel, and, generally speaking, n the more rapidly steel cools the greater its hardness becomes. After a depressed worn tread surface area of a rail is built-up by depositing the metal thereon at an elevated temperature, as by welding, the cooling from such elevated temper- :s ature of the metal deposited and the rail metal adjacent thereto is chiefly brought about naturally by the conduction of heat into the rail itself. It is to be understood that the expression natural cooling signifies the combined cooling effect of 40 convection and radiation of heat from the rail to the surrounding air plus the cooling effect of the underlying and adjacent mass of the rail which is relatively cool. I have found that the latter effect is much greater than. the cooling 13 effect of air where a relatively small tread surface in an ordinary rail is heated as in the case of building up the tread surfaces at the ends of rails.

From an observation of the performance of m built-up rails under modern tramc conditions, I

have discovered that built-up tread surface areas at the extreme endsof rails at joints should possess a hardness of at least Scleroscope after being subjected to service if they are to withstand 55 the tendency to flow. In order to attain this tinuous operation, as by progressively depositing 15 suitable weld metal, such as weld metal of the 1 hardness is not attained when it is deposited metal depositedat the end zone" or the portion hardness, the metal must have a Scleroscope hardness of about 50 to 52 after it is deposited and before the metal is subjected to service, the Scleroscope hardness increasing with serviceor cold work, as it is commonly called. The Sclero- 5 scope hardness of about 50 to 52 corresponds to a Brinell hardness of about 350. It has been found that the increase in hardness due to cold work is generally not indicated, by the Brinell test, and hence the Brinell value of hardness 10 remains substantially the same before and after service.

It has generally been the practice heretofore to build up worn areas on rail heads in one conthe metal thereon. with rails of Y the size nowgenerally used, such as rails weighing to pounds per yard, it is possible to attain the desired hardness mentioned above at rail ends and tread surface areas intermediate the ends of rails when worn areas approximately up to three inches in length and of average depth of wear are built up in one continuous operation with composition hereinafter described. In such cases natural cooling is sufficiently rapid to produce built-up rail tread surface areas having a hardness of at least 50 to 52 Scleroscope before service and a hardness of at least 60 Scleroscope after service.

The tread surfaces of modem rails now supplied to railroad companies possess a hardness of about 250 to 275 Brinell. This hardness is less than that required to prevent the flow of tread surface metal at the ends of rails. Although weld metal of the character hereinafter described is capable of possessing a hardness sufllcient to prevent flow of rail tread surface metal, such by prior methods, as just described. 4 The desired hardness is not uniformly attained, however, where longer worn areas, such as areas of more than three inches in length having an average depth of wear, are built up in one continuous operation; or where short areas of about three inches in length having an excessive depth of wear are built up in a similar manner in the 1 tread surfaces of tracks. This is particularly true at the tread surfaces at rail ends where it has been found that the metal deposited at the run ofl" zone orthe portion adjacent to the unworn tread I surface of the rail is considerably harder than the adjacent to the extrem'e end of the rail head. With prior methods not only is the endlonef' the softest part of the built-up rail head, but it does not possess sunlcient hardness to withstand the pounding and hammering of rolling tramc. Tests of built-up rails of the type lust described 5 indicate that only the portion of the deposit adjacent to the unworn tread surface attains the desired hardness mentioned above. This is due to the fact that the metal at the run of!" zone of the deposit is adjacent to the unheated part of the rail and will cool more rapidly than the metal at the end zone, which is away from the un-. heated part of the rail. Stated another way, the heat input is greater with a larger deposit and the rate of cooling of the portion near the extreme end of the rail head is dependent upon the relatively cool mass at the end of the rail where the heat applied tends to be concentrated. The mass of the rail back from the end thereof is considerably cooler, because there is no tendency of the heat to be concentrated. Hence, the conduction of heat from the metal deposited on the rail head is faster at the portion adjacent to the unworn tread surface of the rail.

in addition to the manner in which the metal 5 deposited cools and hardens, other factors that afiect the rate of cooling are the size of the rail, the size of the worn area, and the temperature of the rail, which, in turn, is dependent upon the heat input required for depositing the metal on a 9 worn area of a rail head. Laboratory tests indicate that none of the above factors can be controlled enough to sufficiently increase the hardnose when a worn area on a rail head is built-up in one continuous operation. In other words,-

" long deposits of metal of the character above do scribed cannot be made fast enough on worn tread surface areas to insure a minimum hardness at the extreme end of the rail head of about Scieroscope before service, even when the particular operator, such as a welder, is highly skilled. Building up worn areas of rail tread surfaces in this manner is objectionable, because it is desired that the metal deposited be of sumcient and adeuuate hardness at the extreme end of the rail head where the tendency of the metal deposited to wear and how is severest. Further, such builtup rails are lacking in uniformity as to thickness, composition and hardness of the metal deposited, primarily because of the differences of skill of the 50 individualoperators in depositing the metal on the worn areas of rails.

far as is known, no successful method of building up worn tread surface areas of rails has been dev sed to overcome the objections mentioned to above. For example, in Railway Engineering and Maintenance, February, 1933, it is stated on page '26 that the greater hardness of metal deposited on worn tread surface areas at the run-oil zone, as compared with the lower hardness thereof at (iii the "end zone, cannot be overcome.

F. have found that the difficulties previously en--' countered in building up worn tread surface areas of rails can be overcome by what I term the "interrupted method; In this method metal isdci5 posited only on a portion of a worn area and cooled. Subsequently, after the metal first deposited has cooled, metal is deposited on another portion of the worn tread surface, area and cooled. In carrying out my interrupted" method of buildin 76 up worn tread surface areas of rails in practice, the metal deposited on each portion of a worn tread surface area is preferably hardened entirely by natural cooling, without employing any external quenching medium to assist in the cooling and hardening of the metal deposited on the rail head. In this preferred method of building up worn tread surface areas of rail, the metal deposited on each portion of a worn area is allowed to cool sufficiently before metal is deposited on another portion, so as not to render ineffective the natural cooling and hardening of the metal that is deposited on each succeeding portion. In this'manner metal deposits of adequate hardness can be produced on worn areas of rail heads by an operator of average skill, irrespective of the length or depth of the deposit. Further, by the interrupted method, the required hardness can be imparted to the deposited metal,

such as metal of the character hereinafter described, which is potentially capable of being so hardened.

I have also found that the relatively large worn areas at ends of rails now generally encountered in practice can be avoided by forming a much smaller built up tread surface area at the ends of rails when they are new and before they are subjected to service.

An object of this invention, therefore, is to provide rails having steel or alloy steel deposited on worn tread surface areas thereof which hardens sufficiently so that it will not wear and flow away when subjected-to service.

Another object of my invention is to provide such rails having built-up tread surface areas at the ends thereof in which the metal deposited possesses a hardness of at least 350 Brinell before service at the portions where the tendency of the metal to wear and flow is greatest.

A. further object of my invention is to provide such rails having built-up tread surface areas in which at least portions of the metal deposited possess adequate hardness to withstand wearing and flowing and are of such shape that they are utilized most effectively when subjected to traffic.

- A further object of my invention is to provide an interrupted method of building up worn tread surface areas of rails uniformly whereby the differences of skill of the individual operators, such as welders, in depositing the metal on the worn areas, is substantially eliminated.

A further object of my invention'is to provide an improved method of building up worn tread surface areas of rails in which the rate of natural cooling of the metal deposited can be controlled.

. A further object of myinvention is to provide an improved method of building up worn tread surface areas of rails whereby a portion of the metal deposited on a worn area is reheated and hardened to a higher degree than before with the subsequent depositing of metal on another portion of the worn area adjacent to the metal previously deposited.

A further object is to provide a method of building up tread surface areas of new rails or rails not subjected to service whereby the life of rails is prolonged and track maintenance is reduced considerably.

Further objects and advantages of my inven-. tlon will become apparent as the following description proceeds, and the various features of novelty which characterize my invention are pointed out with particularity in the claims annexted to and forming a part of this specification. In the drawings:

Fig. l is a plan view of a typical rail joint showing the battered areas before the rails are built up;

Fig. 2 is a side view of the rail joint shown in Fig. l;

Figs. 3, 4 and 5 are plan views of rail joints,

hardness at different points of the rail joint illu'strated in Fig. 1 when built up by my improved method. e

In Fig. l is illustrated diagrammatically the approximate shape of the battered areas It and ll of a typical worn rail joint formed by aligned rails l2 and. i3 .having an opening l4 therebetween. This 'figure represents an open joint of a straight and level track on which the trafllc is unidirectional or one-way inthe direction indicated by the arrow. The average depth of batter or wear normally encountered in practice varies from approximately .02 to .06 inches at the extreme ends of the heads of therails, and this distance, which is purposely exaggerated, is indicated at l5 between the arrowed lines in Fig. 2. In order to illustrate one particular application of building up rails by my improved interrupted" method, it will be assumed that the worn tread surface area ill on leaving rail I2 extends back approximately three inches from the extreme end of the rail l2; that the worn tread surface area II on receiving rail l3 extends back approxi-'' mately five inches from the extreme end of the rail i3; and that the weight of the rails is about 130 pounds per linear yard. The above assumptions closely approximate actual track conditions.

Since the worn tread surface area ill is assumed to be. approximately three inches in hardness when metal is deposited thereon in one continuous operation, because natural cooling will be sufliciently rapid to effect the proper rate of cooling of the metal deposited. The desired ,-hardness is not attained, however, when the metal is deposited in one continuous operation on worn tread surface area ll, because the rate of cooling will not be sufliciently rapid, especially at theextreme end of the head of the rail i3.

The desired degree of hardness can be attained,

however, when the worn tread surface area II is built up by my interrupted" method. In

accordance with this improved method, metal is deposited on the entire worn area ll except a portion at the extreme end of the rail head; and, subsequently, after an interruption to allow the rail to'cool, metal isdeposited on the remaining 65 solid lines, is built up first by-depositing metal directly on the head of the rail. The depositing of metalon the worn area I I is then interrupted to allowthe metal deposited'to harden with natural cooling. In order to utilize effectively the 70 timeduring this interruption in building up worn tread surface area H, the entire worn tread surface area III, which is shaded by dotted lines. may be built up by depositing metal on the head of the rail. When natural cooling is m-;

- opening in a joint is relatively small, the oper- 75 ployed' the operator generally can start to i I portion of the .wom tread surface area II at the posit metal directly on the rail head at the partion ll of the worn-area .H, which isshown by solid cross hatching, immediately after the worn area II) has been built up. The metal should be deposited on the portion ll of the worn tread surface area Ii so that it will form a sound and firm deposit at the extreme end of the rail head, and so that, it will unite thoroughly with the metal-previously deposited on the rail head at the portion It. To insure hardening of the metal deposited on the portion II with natural cooling, the metal first deposited on the portion It should be allowed to cool to at least a black heat. A

. considerable increase in hardness is obtained when the metal first deposited only on the portion It is allowed ,to cool to atmospheric temperature before any-metal whatsoever is deposited on portion II.

When a considerable number of successive joints in an entire section of track are to be built up, the following procedure, whicheflec-" tively economizes time, has been carried out in practice in building up depressed tread surfaces at rail ends by the interrupted method: Each operator, such as a welder, is assigned ten successive rail joints along a section of track. The f portions ii of the worn tread surface areas H and the worn tread surface areas it are first built up successively on all ten"joints. Afterwards the operator builds up the portions I! of the worn areas H successively on all ten Joints in the same order as the building up previously done. In this manner the interruption in building upthe worn areas II is suniciently long to allow the metal first deposited on the rail head only at the portion It to cool nearly to atmospheric temperature before metal is deposited on the rail heads at the portions H.

. In building up rails bi the interrupted methl, od, two factors that influence the hardnessci .themet'al deposited on the tread surface atjth; extreme end of the rail I! are the sine offthe,

rail and the area of the portion II. Generally.i'

the larger the size of'the rail the greater is the rate of natural cooling. As shown in Fig. 4,;1, the size of the portion II' of the worn area ll' 1 is considerably smaller than the portion l1 shown l1 may be that the rails i2 and I3 are of smaller weight than the rails i2 and I3; and another reasonmay be that it is desired to obtain an increased hardness of the metal deposited on the tread surface at the extreme end of the rail head by effecting a more rapid rate of natural cooling.

When open rail joints of the type illustrated in Figs. 3 and 4 are built up by my interrupted" method, some consideration should be given to themanner in which the welding heat is applied when metal is deposited on the rail heads at the portions l1 and I1, so that there will be no tendency for the hardnes to be drawn from the previously built-up areas I0 and Hi. In building up the last portions l1 and H, the welding heat for depositing metal on the rail heads may be applied in sucha manner that a minimum amount of heat is applied to the adjacent areas l0. and It, so that the hardness of the 'metal previously deposited on the rail heads at the areas i0 and I0 'willremain substantially' unchanged. This particular manner of building up worn tread surface areas of rails has been successfully carried out in practice.-

' in Fig. 3. One reason for such a smaller portion V In certain instances, particularly where the ator or welder in building up the portions l1 and 11' may apply the welding heat for depositing metal on the rail heads in such a manner that the extreme end portions of the metal deposited on the areas II and iii are reheated to at least a hardening heat. These end portions of deposited metal which are reheated are preferablyof the same size and shape as the portions I1 and II which are built up last, so as 'not to attain too great a hardness of the portions of metal which are'reheated. With this procedure a high degree of hardness of the metal deposited on the rail heads at the portions I1 and I1 is attained, and

at the same time the end portions of the metal deposited on the worn tread surface areas 10 and it will harden with natural cooling. 7 In order to assist in preventing the drawing of the hardness of the metal deposited on the worn tread surface area at the extreme end Gil of one rail at a rail joint when metal is to be deposited on a worn tread surface area at the extreme end of theabutting rail, it may be desirable in certain instances to arrange a metal- 110 block over the worn areaflrst built up to shield the metal deposited thereon from the welding; heat which is applied on the rail head of the shutting rail when the worn tread surface area at the end thereof is built up. For.

The mass of the copper block should be sum cientiy large so that it will stand. up during the application of heat when the last portions oi the depressed surfaces oi rail heads are huilt up, and preferably of U-ehape so that the side walls thereof extend downward over the sides of the rail head and rest on the angle cars so as to "t the elect: in position. An end wall or he. he provided ior further protection at one end oi the ll-ehaped hlocls, which and wall is to extend downward into the opening between the ends of the abutting rails of a joint. The hloclz. is preferably made oi copper because of its high heat capacity and conductivity so as to prevent any melting thereof on the r sln'iace while exposed to the heat which is onplierl on the rail.

in cert. instances, where the rail joints are so eloze together that the metal deposited on ahuttt worn areashridges over the ends of the o ed rails, the interrupted" method of building up tread surface areas of rails at rail joints is slightly mowed. In Fig. ii is illu..= treted 3 roll joint comprising aligned rails ill" and i3 shutting each other. in this modified method is first deposited on the heads of rails l2" and iii only at the portion it" of the worn area ii" and the portion it" oi the worn area id". The depositing of metal is then intempted, and, after the metal deposited has cooled, metal m deposited in one continuous operation on the rail heads at the remaining porill" and is" of the worn areas i0" and ii".

end of the receiving rail in a section of track' in which the traffic is one way or unidirectional.

In such cases the end of the "receiving rail generally has the largest worn area. when the worn tread surface areas at both rail ends at a rail Joint are of such length that the desired hardness is not attained by building them up continuously in one operation, as in a section-0f track where the trafhc moves in both directions,,each worn area of a rail joint may be built up by the interrupted method. Also, the end of the fleaving" rail may have a worn tread surface area more than three inches in length in certain instances, and in such cases the worn area at the end of the leaving rail is built up by the interrupted method.

As will be noticed in Fig. 1, the shapes of the worn tread surface areas are such that the inside edges 20 and 2| of the rail heads are worn a greater distance back from the extreme ends of the rails l2 and it than the outside edges 22 and 23 of the rail heads. This is due to the fact that, as the wheels of rolling stock move over a straight track in which the rails are usually only slightly canted, the tires of the wheels bear on the middle portion of the tread surfaces and inside edges of the rail heads. The wearing and flowing of rail metal starts at the ends and inside edges of the heads of the rails i 2 and i3, and gradually works back. from the ends of the rail heads. After considerable wearing and flowing, the depressed worn areas it and H are produced which slope downward and toward the inside edges 20 and iii of the rail heads. The greatest flowing and wearing of the metal at rail ends, therefore, occurs at the extreme ends of the rail heads, the inside edges of the rail heads, and the inside and middle portions of the tread surfaces of the rails.

, Taking into consideration the manner in which traffic tends to cause deformation or wear at the ends of rail heads in straight track, I preferably build up worn tread surface areas of rails by the interrupted method so that the last portions built up, such as the portion i1, extend a longer distance back from the ends of the rails on the inside edges than on the outside edges of the rail heads. In cases where rails are canted a considerable amount and where track maintenance is such that the greatest wear occurs from the middle to the outside edges of rail heads, the last portions can be preferably built up so that they extend a longer. distance back from the ends of the rolls on the outside edges than on the inside edges of the rail heads. In this manner the portions of tread surfaces of rail heads having the greatest tendency to wear when subjected to trellis are included in the last portion on which metal is deposited.

In order to attain an adequate degree of hardness of the metal deposited on rail heads at the extreme ends of rails, it is desirable that the last portions built up be not unduly large, so that a rapid rate of natural cooling is effected. For this reason I prefer to make the last portions ouilt up of approximately trapezoidal shape, as shown in Fig. 3, or of approximately triangular shape, as

shown in Figs. 4 and 5, because for a sufilciently head is not worn away at its outside edge, the last portion built up need not extend across the entire width of the rail head, as illustrated by the portion ll' in Fig. 4, for example. The metal having a greater alloy content than that of the rail metal may be deposited on the rail heads at the worn tread surface areas either by gas, by electric welding, or by any other suitable source of high temperature heat. I preflo erably build up rails by gas welding with a suitable combustible gas, such as a mixture of oxygen and acetylene. A hardenable steel I prefer to deposit on worn areas of rail heads contains approximately .50% carbon, 0.90 to 1.10% manganese, 0.90 to 1.10% chromium, 0.40 to 0.60% silicon and the remainder iron. However, any suitable steel or alloy steel having characteristics similar to the composition of steel just mentioned can be used that is capable of hardening when cooled from an elevated temperatures Before the metal is welded on the worn areas of rail heads by the interrupted method, any chips or cracks requiring an abnormal amount of welding are preferably built up flrst to the general level of the battered area. Also, if the depth of a battered or worn area is less than .04 to .06 of an inch, additional rail metal may be removed if desired, as'by grinding or with a welding torch, so that all built-up rails will have a deposit of appreciable depth after leveling and smoothening by grinding. s

I prefer to use a gas flame or flames as the source of high temperature heat for depositing a hardenable metal on worn tread surface areas, and for this purpose a suitable burner, such as a blowpipe, may be employed. The burner may be supplied with a suitable combustible gas, such as a mixture of oxygen and acetylene. When building up rail tread surfaces by depositing a 40 hardenable metal thereon with an oxy-acetylene v flame, a strictly neutral flame can be used. Since frequent adjustments may be necessary to maintain a neutral flame, an excess acetylene flame having a feather of excess acetyleneof about 5 two to three times the length of the inner cone ispreferred because of the protection of the rail metal and metal deposited from oxidation. Fur.- ther, an excess acetylene flame tends to carburize the surface of the rail metal and superficially melt it by the formation of a high-carbon-iron alloy having a melting point below that of the rail steel. This superficial melting, or wetting" or sweatlng" as it is sometimes termed, is an aid in insuring a perfect union between the metal deposited'and the rail metal. Since there is a continuous tendency for rail metal at the tread surface to be chilled by the withdrawal of heat therefrom by the relatively cool mass of the rail, it is desirable for the less skillful welder, when 60 using an excess acetylene flame, to melt into the rail tread surface slightly below the "wet film while depositing metal, so as to insure good fusion of the metal deposited and rail metal.

In welding metal to the first portion of a bat-- tered area of a rail head, such as the portion I5,

it is preferable in the present instance to deposit the metal last at the ins de edge of the tread surface to insure a maximum hardness at the flange or inside edge of a rail head, which is back from the extreme end of the rail. The welding of metal on the portion of the tread surface at the extreme ends of rail heads should be continuous, so that the entire portion last built upthe metal last deposited on the rail head is thoroughly welded both to the adjacent underlying rail metal and to the metal flrst deposited and cools as a unit from an elevated hardening tem- 'rehardened to a higher degree than before, be-

cause ,of the heat applied on the metal flrst deposited when metal is deposited on rail heads.

at the extreme ends of the rails. In other words, when the metal l'ast deposited on the rail head is welded to the edge of the metal first deposited on the rail head, a portion of the metal first deposited is reheated to an elevated hardenin temperature. rally with the metal last deposited at the extreme end of rail heads, and its degree of hardness is increased considerably. This is an important advantage of the interrupted method of building up rails, because the relatively harder portions of built-up tread surface areas at the extreme ends of rail heads are increased in. size.

By making the portions of worn areas last built up of substantially triangular or trapezoidal longitudinal direction of the rail head, a diagonal This reheated metal cools naturun-off is provided whereby the wheels of rolling the length of the worn tread surface area at the end of the "receiving rail is approximately five inches long, and the length of the worntread surface area at the end of the leaving rail is approximately three inches long. The irregular 'lines 24 and 25 indicate the hardness produced of the metal deposits at different points of such a Joint by an operator or welder above average skill. At the end of the leaving rail, where the metal is deposited continuously on the rail head, it will be noticed that the maximum hardness at the end of the rail head at A is about 66 Solemscope after service or cold work, and remains at a hardness above 60 Scleroscope for approximately the full length of the deposit. At the end of the receiving" rail, where the metal is deposited by the interrupted" method, it will .be noticed that the hardness of themetal deposit is adequate to withstand wearing and flowing for at least a distance of 2 inches from the extreme end of the rail head, varying between 68 and. 71 Scleroscope at the points B and C. This distance 5 not only represents the portion of the metal de posited last, but also a part of the portion of the metal deposited first which is rehardened to a higher degree than before, when the last portion of the worn area is built up at the extreme end of the rail head. The hardness of the metal first deposited is lower than that at the extreme end of the rail, increasing from 58 wleroscope at D to about so Scleroscope at E, which is adjacent to the imworn' tread surface of the receiving" of the worn tread surface area adjacent to theextreme end of the rail, the portion E-D of the irregular line has been extended as a dotted line to the point G, to indicate the relative hardness of a metal deposit built up by the continuous method. It will be noticed that, with such a method of building up worn tread surface areas 1 of rails, the deposit is softest at the extreme end of the rail head and of a hardness below that which will withstand deformation and wear. Irregular lines 2% and 25', similar to lines 24 and 25, indicate the hardness attained of the metal deposits at diiierent points of a joint by an operator or welder of average skill. In suchcases,

the hardness at A is about 61 Scleroscope, the

hardness between B'- and C varies from 62 to 65 Scleroscope, and the hardness between D and E varies from about 55 to 58 Scleroscope. The

lower relative hardness of a. metal deposit built up by the continuous method is indicated by the dotted line between D and G.

It will thus be seen that, when worn tread surface areas or" rails are built up by the inter- 5 rupted method, built-up rails are produced having a hardness of at least 60 Scleroscope after cold work or service at the extreme ends of the rail heads, and that this hardness is produced by an operator or welder of average skill as well as an operator above average skill. In order to produce built-up rail tread surface areas along a section of track which are of substantially uni-. form hardness, the size of the portion of the worn tread surface area last built up can be determined to suit the natural speed and habit of each operator or welder. Thus, if an operator of average skill can produce built-up worn tread surface areas of the desired hardness with the last portion of the worn area of a given size, the 69 size of the last portion built up can be increased for an operator above average skill. In this manner the rate of natural cooling,,- and hence .the hardness produced of the metal deposited, can be controlled and made substantially uniform for alloperators. v

In the explanatory diagram just described, the different values of hardness given are those attained when the metal deposited is of the com- 70 position mentioned above. It is to be understood that the composition of the metal deposit is somewhat diflerent from that of the metal supplied, as there is some loss-of metal in slagging and some of the metal deposited mixes with 7 the rail metal, which, together with the effect of the flame, will slightly increase the carbon' face areas can be built up by the interrupted method so that themetal last deposited on a portion of a worn area will be of adequate and suflicient hardness to withstand wearing and flowing.

The relatively large worn areas now generally encountered in practice can be avoided by building up portions of tread surfaces when rails are new and before they are subjected to service. Thus wearing and flowing of rail tread surface metal which normally occurs is anticipated,

' thereby prolonging the life of rails from the very beginning and reducing track maintenance considerably. This is particularly true at the ends of rail tread surfaces, although in many instances it is applicable to tread surface areas intermediate to the ends of the rails.

In building up tread surface areas at the ends of unworn rails, the original rail metal on the top of the rail head is remdved in any suitable manner, as by machining, grinding, or with a welding torch. The original rail metal is removed to a sufllcient depth, such as .04 to .16 of an inch, for example, so. that the metal deposited will be of appreciable depth after leveling and smoothening by grinding. A suitable metal, such as the hardenable metal of the composition mentioned above-having adequate hardness to withstand wearing and flowing when subjected to service is then deposited on the tread surface area to build the same up to the general level of the rail. Since such a tread surface-area is generally relatively small. it may be possible and is preferable to deposit the metal in one continuous operation, and to limit the size'of the area in accordance with the principles employed in the interrupted method, so as to control the hardness of the deposited metal between maximum and minimum limits. The built up tread surface area may then be leveled and smoothened by grinding. At rail ends the build-up areas are preferably triangular or trapezoidal in shape because, as stated before, it is the smallest area which will give sufficient length longitudinally of the rail in such a manner that the area is effectively utilized to prevent wearing and flowing of rail metal. By building up small tread surface areas on the top surfaces of rail heads in the manner Just described, considerably larger worn areas are avoided. For example, if the end of the rail l3 lll'Flg. 3 had been built up before being subjected to service so that the builtup area only constituted the portion ll, the much larger worn area H would have been avoided.

Throughout the specification a distinction has been made in Scleroscope hardnessbefore and after service. While a definite relation exists between Brinell and Scleroscope hardness for the some metal, this relation is not the same for a thin alloy deposit, or for a rail that has been in service and has a cold worked surface. It has been found that hardening due to cold work further tends to prevent flow of the metal deposited, and therefore constitutes a beneficial or protective action.

As a result of considerable experience, it has been found that the Brinell test is not suitable for testing the hardness of rails having a thin surface layer whose hardness is different from that of the underlying metal. It has been found that the increase in hardness due to cold work is not fully indicated by the Brincll test, whereas such increase in hardness is indicated by the Scleroscope test. For the above reasons, the Brinell hardness is compared with the Scleroscope hardness before the metal tested is subjected to cold work, and a different Scleroscope' hardness is indicated for metal after cold work.

From an observation of the performance of rail ends, it has been stated above that a Brinell hardnessof about 350 and a Scleroscope hardness of about 50 to 52 before service and 60 after service is adequate to prevent flow of the metal deposited. There is no objection to an even greater hardness, such as a hardness of 70 Scleroscope after service, if the deposit is sound and tough and not accompanied by brittleness and heat cracks. In view' of the foregoing, it will be apparent that by the interrupted method of building up rail tread surfaces the hardness at the deposited metal acquired can be controlled, especially at the extreme ends of the rails; and this control of hardness is such as to insure the attainment of not only the minimum hardness required to prevent flow of tread surface metal, but also to insure that the hardness does not exceed any desired maximum value, thereby obviating the occurence of cracks in the deposited metal.

While I have shown and described built-up rails and a method of building them up by the interrupted method with a single interruption, it will be obvious that battered or worn tread surface areas of rails can be built up by depositing metal on rail heads and interrupting the depositing of such metal on several successive portions of a worn area, and that the interrupted method can be employed in building up worn tread surface areas at points intermediate the ends of rails as well as at the ends of rails. It is to be understood that new or unworn and worn rails can-be built up by the methods described either with gas flames or the electric arc, and that modified methods of producing built-up rails having a hardness of at least 60 Scleroscope will occur to those skilled in the art Without departing from the spirit and scope of my invention.

I claim:

1. A rail having at an end thereof a builtup tread surface portion comprising metal having an alloy content greater than that of the rail metal, such portion being more than three inches in length longitudinally of the rail and having adjacent the extreme end of the rail a hardness of at least 60 Scleroscope after cold rolling, said portion being of such shape that at least a part of the boundary between said builtup portion and the portion of the rail tread surface adjacent thereto extends approximately diagonally across the rail tread surface.

2. A rail having at an end thereof a builtup tread surface portion comprising metal having an alloy content greater than that of the tread surface metal adjacent thereto, such portion being more than three inches in length longi tudinaliy of the rail and having adjacent the extreme end of the rail a hardncss'of at least 60 Scleroscope after cold rolling, said built-up tread surface portion at the extreme end of the rail being of such shape that it extends back from the end of the rail a greater distance at one edge than the other edge'of the rail head.

3. A method of improving substantially unworn rails having a tread surface portion at an end thereof tending to wear and flow when subjected to service, which comprises removing a surface layer of original rail metal at such a tread surface portion, the length of such layer longitudinally of the rail being less than about three inches, and subsequently depositing thereon before the rail is subjected to service a metal capable of acquiring a hardness of at least 60 Scleroscope' after cold rolling.

4. A method of improving substantially unworn rails having a tread surface portion of an end thereof tending to wear and flow when subjected to service, which comprises removing a surface layer of original rail metal at such a tread surface portion, the length of such portion longitudinally of the rail being less than about three inches; and subsequently depositing there on, before the rail is subjected to service, a metal capable of acquiring a hardness of at least 60 Scleroscope after cold rolling, the layer of deposited metal being of such shape that the boundary between said deposited metal and the portions of the rail tread surface adjacent thereto extends diagonally across the rail tread surface.

5. A method of increasing the wearing characteristics of the tread surface areas at the ends of substantially unworn rails, which comprises removing a surface layer of original rail metal at such a tread surface area, the length of such layer longitudinally of the rail being less than about three inches, and subsequently depositing thereon before the rail is subjected to service a metal capable of acquiring a hardness of at least 60 Scleroscope after cold rolling, the shape of the area formed by the metal deposited being such that it extends back from the end of the rail a greater distance at one edge than the other edge of the rail head.

6. A rail having at an end thereof a built-up tread surface portion comprising metal having an alloy content greater than that of the rail metal, such portion being more than about three inches in length longitudinally of the rail a d having the greatest hardness at the portion adjacent to the end of the rail head.

7. A rail having at an end thereof a built-up tread surface area portion comprising metal having an alloy content greater than that of the rail metal; such portion being more than three inches in length longitudinally of the rail and having the greatest hardness at the portion adjacent to the extreme end of the rail head, such portion adjacent to the extreme end of the rail head having a hardness of at least 60 Scleroscope after cold rolling,

8. A method of building up a depressed tread surface at the end of a rail which comprises first welding a layer of metal to the major portion of said surface but not to a portion of the surface adiacent to the end of the rail, and welding additional metal to the portion of the surface adjacent to the end of the rail-after the first-welded layer has cooled.

9. A method of building upa depressed tread surface of a rail in which a steel capable of hardening upon cooling irom an elevated temperature is deposited on such surface by welding; such method comprising depositing the steel by welding on one portion of the surface and subsequently depositing the steel successively to other portions of the surface so that the steel deposited on each portion joins the steel previously deposited to form an integral deposit; the steel deposited and rail metal adjacent thereto always being sufficiently cool so as not to render ineffective the quenching effect produced by the mass of the rail on the steel deposited on each succeeding portion and the rail metal adjacent thereto, whereby welding heat is withdrawn from the steel welded to each succeeding portion to cool and harden the same naturally.

1.0. A method of building up a depressed tread surface of a rail in which a steel capable of hardening upon cooling from an elevated temperature is deposited on such surface by welding; said method comprising welding the steel on one portion of the surface and subsequently welding the steel to the remaining portion of the surface; the steel welded to the first portion of the surface and the rail metal adjacent thereto being sufficiently cool before the steel is welded to the remaining portion of the surface so as to render effective the quenching effect produced by the mass of the rail on the steel welded to the remaining portion of the surface and rail metal adjacent thereto, whereby welding heat is withdrawn from the steel welded to the remaining portion of the surface to cool and harden the same naturally.

11. A method of building up a depressed tread surface of a rail in which a steel capable of hard ening upon cooling from an elevated temperature is deposited on such surface by welding; said method comprising depositing the steel by welding on a portion of the surface; and thereafter, after such deposited steel and rail metal adjacent thereto have cooled to at least a black heat, depositing the steel by welding to another portion of the surface so that the steel subsequently deposited joins the steel previously deposited to form an integral deposit. 7

12. A method of building up a depressed tread surface of a rail in which a steel capable of hardening upon cooling from an elevated temperature is deposited on such surface by welding; said method comprising depositing the steel by welding to one portion of the surface; and thereafter, after such deposited steel and rail metal adjacent thereto have cooled to at least a black heat, depositing the steel by welding to the remaining portion of the surface.

13. A method of building up a worn tread surface at the end of a rail in which a steel capable of hardening upon cooling from an elevated temperature is deposited on such surface by welding; said method comprising depositing the steel by welding to the entire worn surface except a portion at the extreme end of the rail head; interrupting the depositing of the steel; and subsequently depositing the steel by welding to the portion of the surface at the extreme end of the rail head; said interruption being of such duration that the steel deposited first and rail metal actjacent thereto are sufficiently cool to render effecfive the quenching effect produced by the mass of the rail on the steel deposited on the portion at the extreme end of the rail head and the rail metal adjacent thereto, whereby welding heat is withdrawn from the steel deposited on the portion at the extreme end of the rail head to cool and harden the same.

14. A method of building up a depressed tread surface at the end of a rail in which a steel capable of hardening upon cooling from an elevated temperature is deposited on such surface by welding; said method comprising depositing the steel by welding to the entire surface except a portion at the extreme end of the rail head; interrupting the depositing of the steel; and subsequently depositing the steel by welding to the portion of the surface at the extreme end of the rail head; the steel being so deposited on the first portion that at least a portion-of the boundary between the steel deposited first and the steel subsequently deposited at the extreme end of the rail head extends approximately diagonally across the rail tread surface; said interruption being of such duration that the steel deposited first and rail metal adjacent thereto are sufficiently cool to render effective the quenching effect produced by the mass of the rail on the steel deposited at the extreme end of the rail head and the rail metal adjacent thereto, whereby welding heat is withdrawn from the steel deposited on the portion at the extreme end of the rail to cool and harden the same.

15. A method of building up a depressed tread surface at the end of a rail in which a steel capable of hardening upon cooling from an elevated temperature is deposited on such surface by welding; said method comprising depositing the steel by welding on the entire surface except a portion at the extreme end of the rail head; interrupting the depositing of steel until the steel deposited and rail metal adjacent thereto have cooled to at least a black heat; and subsequently depositing the steel by welding to the portion of the surface at the extreme end of the rail head.

16. A method of building up a worn tread surface area at the end of a rail in which a steel capable of hardening upon cooling from an elevated temperature is deposited on such surface by welding; said method comprising depositing the steel by welding on the entire worn surface except a portion at the extreme end of the rail head; interrupting the depositing of steel until the steel deposited and rail metal adjacent thereto have cooled to at least a black heat; and subsequently depositing the steel by welding to the portion of the surface at the extreme end of the rail head; the steel being so deposited on the first portion that at least a portion of the boundary between the steel deposited first and the steel subsequently deposited at the extreme end of the rail head extends approximateiy diagonally across the rail tread surface.

17. A self-hardening method of building upia depressed tread surface of a rail in which a metal capable of hardening upon cooling from an elevated temperature is deposited on such surface by welding; said method comprising depositing the metal successively on several portions of the surface and allowing the metal deposited on each portion to cool naturally before the metal is deposited on a succeeding portion.

18. A self-hardening method of building up a depressed tread surface of a rail in which a metal capable of hardening upon cooling from an ele vated temperature is deposited on such area by welding; such method comprising depositing the metal on one portion of the surface and allowing the same to cool naturally; and subsequently dedepositing the metal on the remaining portion of the surface and allowing the same to cool naturally.

19. A method of building up a worn rail joint comprising abutting rails having depressed tread surfaces at the ends thereof, one of mendepressed surfaces being larger than the other; said method comprising first welding metal on 6 such surfaces but not the portion at the end of the rail head having the largest depressed surface; and subsequently welding the metal on the portion of the surface at the end of the railhaving the largest depressedarea after the first- 1 welded metal has cooled.

20. A method of building up a worn rail join comprising abutting rails having depressed tread surfaces at the ends thereof; said method comprising first welding metal on such surfaces but 15 not the portions at the endo! the rails; and subsequently welding metal on the portions of the depressed surfaces at the ends of the rails after the first-welded metal has cooled.

21. A rail having at an end thereof a builtup tread surface area comprising metal having an alloy content greater than that of the rail metal, the portion of such area adjacent to the extreme end of the rail head having a greater hardness than the portion back from the extreme end of therailhead, theshape of the pertiom being such that at least a part of the boundary therebetween extends approximately diagonally across the rail tread surface.

up tread surface area comprising metal having an alloy content greater than that of the rail metal, the portion of such area adjacent to the extreme and of the rail headhaving a greater hardness than the portion back from the extreme end of the rail head, the shape of the portion adjacent to the extreme end of the rail head being such that it extends a greater distance Back from the extreme end of the rail head at one "edge of the rail' than, at the other edge thereof.

23. A rail having adjacent an end thereof a built-up top tread surface portion comprisins fusion-deposited metal having a greater hardness than the rail metal, said built-up portion being of such shape that at least a sumcient portion of its boundary distant from the end of the rail extends diagonally across the rail tread surface to provide a diagonal run-oi! which will prevent rolling stock from passing abruptly from the harder built-up portion to the adjoining tread surface.

24. A rail as claimed in claim 23, in which the distance of said boundary from the end of the rail is greatest adjacent the inner edge of said tread surface.

HARRY B. GEORGE.

22. A rail having at an end'thereof a built-

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