US2186966A - Process for producing rails - Google Patents

Description

Jan.l6, 1940. H. s. EORGE 6 2,186,966

PROCESS FOR PRODUCING RAILS Filed Nov. 10, 1936 1 VENTOR: 44 7 3 ir pa Patented Jan. 16, 1 940 I V UNITED STATES PATENT OFFICE PROCESS FOR- PRODUCING RAILS Harry S. George, Massapequa, N. Y. Application November 10, 1936, Serial No. 110,045 11 Claims. (Cl. 29-169) This invention relates to railroad rails that have from h m ll in h -r l condition possess their treads reenforced or built up with a layer a hardness far short of that necessary to resist of wear resisting alloy, and comprises improvep c flow, usually amounting to about 75- 8 ments, in the disposition of the added metal Brinell. Furthermore, the hardness of rail ends thereon and in its final character, and also imbuilt up by former methods likewise is neither 'provements in the process of applying the same. u o adequate, usually ranging from 250- It is especially useful in building up the battered 0 tread surfaces at rail joints. Before describing I ave al found t t y depositing a strip the invention in detail certain facts will be set f w ld met l, restric in w h to about A to 10 forth pertaining to the deforming action of the /2 c s, t s to y to a Width less than 10 wheels on the rails, together with a brief discusthree-quarters of the width of the head of the sion of the prior art relating to the repair and rail, I am enabled, as hereinafter explained, to reenforcement of the rails, occasioned by such build up worn treads of any length and to attain action. a substantially uniform hardness of the deposited 15 The tread of a new rail is crowned, but the metal sufficient to greatly reduce and even to pre- 15 transverse contour of a car or locomotive wheel vent plastic flow, without the necessity of subin goodcondition forms a straight line having sequent heat treatment, the depositing operation an upward slope from the flange. The rail is itself being inherently of ahardening nature. usually canted. As a consequence of these 'con- Formerly, in the Case Of bui t up t ds longer ditions the line of contact between the wheel and than approximately three inches, the requisite the rail tread when the latter is new lies between hardness has not been attained throughout the the center and the outside edge of the rail. This deposited metal because the methods hitherto line or rather strip of contact gradually widens in use have been inherently softening.

because of abrasion and plastic flow until, after By making the built up strip of metal of less several years of service, it occupies practically width than three-quarters of the width of the 25 the full width of the rail head. rail throughout at least the major portion of its When and where the wheels contact the rail length, and such major portion being of a width tread at an edge (as along a side under some cirwhich can be conveniently deposited by an operacumstances, and always at the rail ends) the tor of ordinary skill at a single pass, it is possirate of plastic flow of the rail metal is more ble to cause the deposited strip to be built up so 7 rapid, and projecting fins of metal are formed in continuously from end to end without objectiona manner similar to the familiar mushrooming ably reheating any portion of the deposited metal of a hammer or chisel head. This lateral dewhich has cooled below the critical temperature formation is accompanied by a depression of the and without undue retardation of the cooling rate.

tread below the general level and, where it oc- By depositing the metal progressively from one 35 curs at rail joints, results in rough riding. The end to the other of the battered surface under battering, which originates at the rail extremityrepair and by restricting the heat input, the and which ismost severe n that e ion. is gradudeposited metal may be caused to cool naturally, ally extended along the rail from the end so that and at a rate sutlicient to induce a suitable hardit is likely to extend after a time for a distance ening, and without objectionable reheating and -of many inches. may, therefore, be caused to have a Brinell hard- 40 It is a customaryoperation in track mainteness of any desired value, including any value h n t u d up the att d a as at the joints in the range 330-350, within very close limits, by applying a coating of metal over the battered say five points, by controlling such variables as 5 surface either by the electric or the oily-acetylene the width of the strip and the rate of application,

process, so as to cover the entire battered area. as hereinafter described. The present invention will be discussed in con- The above discussion on hardening presupposes nection with the oily-acetylene process, but it is that the added metal as well as the rail is of suitnot restricted to that process. able composition, as hereinafter explained.

I have found that a. Brinell hardness of 350 on In accordance with one aspect of the present 50 the rail tread is suflicient to prevent batter under invention, a repaired rail section is provided havthe heaviest wheel loads, and that a somewhat ing a raised strip of hardenable metal (that is, lower hardness, say in the range 330-340, is sufraised with respect to the laterally adjacent batiicient to practically eliminate plastic flow under tered area, but at the same general level as that the average trafllc conditions. Rails as supplied of the tread) whiclr'is of not more than threequarters the width of the rail head throughout the major portion of its length and which stands above the laterally adjacent battered tread area to carry the load across the battered joint. Such a strip is hereinafter referred to as a causeway strip.

Such a repaired joint has the advantage of economizing repair metal since not more than three-quarters of the battered area is built up as a rule, and generallysubstantially less than half the battered area is built up.

Besides economizing metal, the application of a repair strip in accordance with the present invention also makes possible a corresponding economy of welding gases and a similar economy of the welders time. Extensive operations have shown that the cost of Joint repair per inch has been cut approximately in half.

Besides the advantages of economy heretofore pointed out, it may be definitely stated as a fact, based on extensive observations, that rail Joints repaired by the applicationbf causeway strips as above indicated will provide smooth riding for .longer periods than any rail repaired by prior methods, unless the latter are augmented by a separate heat treatment of the repaired rail.

Qther objects and advantages will hereinafter appear.

In the drawing forming part of this specification and illustrating structures embodying the present invention in a manner distinguishing I them from the practices of the prior art,

built up in accordance with various practices comprehended within the present invention; and

Fig. 4 illustrates diagrammatically the characteristic temperature changes occurring at a given point on a rail tread built up by (1) former processes, and (2) the present invention.

As a basis for understanding the present in-, v'ention, the conditions imposed by the rail construction and by the trailic which the rail bears, as well as the prior art practice,,will first be discussed briefly.

In Figure 1, a indicates the rail tread, w the wheel tread, C the transverse length of the contact between the rail and the wheel. (The vertical distances between the'successive positions.

of the wheel treads are shown about twicetheir actual amount at the time of repair in average" practice.) The parenthetical suflix (1) signifies before-or soon after service, (2) after several years'service, (J) at the joint after several years service. I

In all processes of building up rail treads, metal from a welding rod is meltediand deposited in a fluid puddle which is-progressivelyextended on the tread surface suitably prepared to receive it, all by well known procedures. Usually, a layer of metal about inch thick or less is applied. The width of the puddle is usually about-V to 1% inches depending upon the apparatus and skill employed. The worn tread surfaceon' the end of a rail, at the time of building up, is usually about 8 to 14 square inches in area and, because it has heretofore been considered necessary. to

cover completely the worn areas and build them up to the general level of the rest of the tread, previous methods have necessitated the applica tion-of several beads, as the deposits are termed, adjacent to each other (See Figure 2.)

The beads have been deposited'either in contin-' uous succession, or with an intermission to permit a certain amount of cooling of the metal first applied, as in the method of my co-pending application Serial Number 688,333, now Patent No. 2,075,810.

The chief object of my previous invention was to produce a satisfactory hardness'at' the extreme trated in Figure 2, causes the reheating of much of the previously deposited metal, because of the disposition of the successive beads adjacent to one another. Some parts are reheated above the critical range and, if the subsequent rate of cooling is sufficiently rapid, are given a certain amount of hardness; the major portion, however, is usually reheated tp ahigh temperature, but somewhat below the critical range. (See Figure 4, curve 1.) Such reheating, below the critical range, is known in heat treating as drawing or tempering and has a softening effect, thereby reducing the resistance of metal so treated to abrasion and plastic deformation;

I have found that it is possible and feasible to deposit a single bead of any desired length longitudinally on a depressed rail-tread area, as at a rail joint, without reheating any part of the bead .that may have cooled,below the critical range; and that the width of a the bead and its rate of I application may be utilized to control the amount of heat put into the rail and thereby the subsequent rate of cooling and'the hardness of the deposited metal. Other factors that control the hardness are the apparatus, the size of the rail..

the composition of the rod and they technique of its application. In the present invention, by the proper adjustment of all these factors relative to one another, it becomes possible and feasible to impart suihcient hardness to the deposited metal to prevent plastic deformation. Compare the slopes (rate of cooling) of curves l and 2, Figure 4, through the critical temperature.

Among the variations in the technique of gas welding are the ways in which the coating may be hammered while. hot and malleable. Such hammering is customary and universal and hastwo purposes, (1) to shape the coating to the contour of the rail and bring it to the general tread level, and (2) to improve the physical properties by compacting the metal, and by refining its metallographic or crystalline structure. Two

methods of hammering are in common use. The

first and oldest method, comprises a preliminary hammering witha hand hammer. followed by an operation known as flattering.

Flattering" consists in placing on the coating a properly shaped .metal shoe and hammering the latter. The second, more recent practice, comprises a preliminary hand hammering, as in the first method, followed by surface grinding, using a power driven grinding wheel.

Where "flattering" is employed, it is preferable .in connection with the present invention,- whenthe highest desirable degree, of hardness is the objective, to dispense with the preliminary hand hammering and to apply the flatter to successive short increments of the strip (1. e., 2 to 3 inches in length) immediately after they have been deposited. The flattering should be performed expeditiously to complete the hammering operation on each increment of coating, and.

permit the application of the next increment to be begun before the coating has cooled below the critical temperature. H

Variations in the technique of hand hammering have been practiced formerly, but the pre-. ferred methed in connection with the present invention is essentially the same as that described above for fiattering", namely, the hammering of short increments, and maintaining above the critical temperature that part of the deposits adjacent to the succeeding increment, until the deposition of the latter has been started. The purpose of the preferredtechniques,

whether of flattering or hand hammering is to prevent the reheating to a high temperature below the critical temperature, of any part of requiredythen departures from the preferred practices of depositing and hammering are permissible.

I have found that, satisfactorily to resist flow under the heaviest American wheel loads, the hardened strip whether heat. treated or built up, should have a Brinell hardness number of at least 350, before service, the corresponding scleroscope hardness being about 50. After service, the scleroscope hardnessof the surface is increased, by cold work, to about 55-58. The hardness of the cold worked layer, while not correctly indicated by the Brinell test, corresponds to a Brinell number of about 375-400. I have also found that in the alloys available and feasible for coating, and in fact in rail steel itself, a hardness greater than about 425 before service may be accom-. panied by an undesirable brittleness; therefore I consider the range of hardness most suitable for the purpose. to be from 350 to 42.5 Brinell, before service, corresponding to a scleroscope hardness of 50-60. After service the most desirable scleroscope range is 55455. An object of my invention is to provide a reenforced rail tread having a hardness throughout in the preferred range, but it is to be understood that the above discussion on hardness is for guidance and not for limiting purposes, and that the most desirable hardness may vary with circumstances as, for example, the composition of the coating.

An example of an alloy capable of possessing a hardness in the preferred range contains: C,

0.50; Cr, 0.90 to 1.10; Mn, 0.90 to 1.10; Si, 0.40 to 0.60; all in percent by weight); and the remainder principally iron. Such an alloy is now commonly used for repairing worn rail ends, but because prior processes are inherently softening in their nature and effect, as already explained, rail ends repaired in the usual manner with this and similar alloys do not possess a uniform or suflicient hardness, but are as soft as the rail itself and often even softer (that is, in substantialportions of the built up areas).

One operator may put as much heat into the Consequently it is advantageous and practicable to utilize the width of the strip as well as the composition of the coatthe usual gas pressures.

For unusually short deposits, less than about three inches long, and where maximum speed is desired, it is advisable to employ a welding rod having a somewhat lower alloy content than that indicated above, especiallyin respect to the chromium and carbon, in order to guard against the possibility of an excessive cooling rate causing heat cracks in the deposit.

An advantage of limiting the width of the bead is that it reduces the heat input, thereby increasing the subsequent cooling rate and, consequently, the hardness. If the rail head were coated its full width, even though only a single bead were applied (if such were practically possible without reheating), the heat input would be so great as to materially retard the cooling rate and the resulting hardness.

As an example'of the .method, using a welding rod of the composition specified above, a uniform hardness of the coating amounting to 58-64 scleroscope, after service, is attained by applying a central strip 1 inches wide at a rate of one linear inch per minute on the tread of a rail weighing in the range, 100-130 pounds per yard.

A welder of ordinary skill can apply the aforesaid coating at the stated rate, with a single burner, hand operated torch consuming oxygen and acetylene at a rate of about 80 cubic feet per hour, each.

By testing specimens of an operators work from time to time, for any given welding rod the necessary adjustment as to strip width or, alternatively the rate of application can be readily determined and hence by a proper control of these factors the production of repaired joints coming reasonably near to the most desirable hardness can be uniformly obtained.

The technique of the coating process is important chiefly because of its effect on the composition of the deposited metal. A flame adjusted to an excess of acetylene is preferable, and the metal is preferably applied according to the techniqu described in my previously patented selffluxing process of welding, (U. S. Patent No. 1,973,341) wherein the base metal preferably is maintained at a temperature several hundred degrees below its melting point while joining metal the one hand of loss of the essential elements in the rod by oxidation, and on the other hand of adding too much carbon from admixed rail metal.

An important precaution in any case is to refrain from operating too continuously with the inner cone of the flame (oxidizing in effect) buried in the molten deposit. .Excessive working over the molten deposit with the flame depletes the essential hardening elements. The flame is preferably pointed almost vertically downward, but if inclined, it should be directed ahead and not backward over the already deposited metal that has started tocool.

In case the application of metal is temporarily stopped, to hammer the bead, for example, after completing one rail end, care should be taken not to point the fiame toward the finished deposit when the operation is'resumed.

Although the essentials of the correct procedure for building up rail treads in accordance with the present invention haveben specified above, it is neither practicable nor necessary to restrict the individual technique or minor manipulations.

The requirement that the hardness of the product-shall fall within a specified rangeaifords a ready means, not hitherto available because not applicable to former processes, of establishing a criterion of the quality of the product and con- ,trolling it, as will be understood from metallurgical considerations.

The built-up tread may be finished smooth and r to the proper level by hammering or grinding or both, and the ends of the rails finished by slotting, as is customary.

The surface of the hardened strip is preferably shaped to produce a central strip thereon at a higher level than the sides, to cause the wheel to,

bear on the higher central strip and thereby protect' the edges of the strip from concentrated loading and possible deformation. In Figure 1, 8 represents the central contact strip and the width thereof on the hardened strip whose sides slope to the lines on the rail at the extremities of the depression, D. The elevation of the contact strip,

S, is the same as that of the rail tread intermediate of the rail ends.

When the present invention is practiced in the preferred form, that is, when the causeway strip,

composed of the cited rod composition or its equivalent, is applied progressively and without the reheating of any part thereof, the resulting metallographlc structure, of both the. coating and the contiguous rail metal, as well as their hardness, serves to distinguish them from the products of other processes. The coating is characterized by a crystalline structure typical of metal that has been'heated to its melting point and then cooled at asufiiciently .rapld rate to induce a substantial hardening, whil the structure throughout consists of sorbite or troostite, or a mixture thereof, without any pearlite or martensite. Even though pearlite, sorbite and troostite be considered a's variations of the same structure, yet these variations are readily identified, microscopically and otherwise.

One practical advantage in the production of,

say, troostite, by direct. p imary cooling; rather contiguous rail steel.

Although I have described a particular method of producing a pair of rail ends at a rail joint, having a hardened strip of metal on and longitudlnal to the tread, other methods may be employed; for example, by a suitable heat treatv ment as described below.

As a preliminary step in my invention I prefer to grind a depression about $4; to V4 inch deep to receive a strip of weld metal of more substantial thickness than has heretofore been provided on greases rail tread at joints, and this operation is necessary when utilizing the invention to reenforce new or slightly worn rails. For such rails the invention is valuable as a preventive measure,

and may be conducted much more economically inches, or more, on each rail end. I have found it to be unnecessary to reenforce the ends of new rails longer than about one inch on the leaving" rail end and about 3 inches on the receiving" end' and by so limiting the operation, whether heat treating or building up, I effect economies over previous practices, wherein the lengths of the hardened zones on each rail end are equal and unnecessarily extended.

For hardening a longitudinal strip of rail steel, as on the tread of a rail at an end thereof, I may apply heat from a row of oxy-acetylene torches, suitably supported lengthwise over the rail, spaced a suitable distance apart so that the several heated areas adjoin each other to form a continuous heated strip; after heating quickly to a bright red temperature, natural cooling is sufilcient to harden the metal. As an example: to harden a rail end I may space four oxy-acetylene torches, longitudinally over the center of a rail head, with the tips 1 inch apart, that nearest the rail end being inch therefrom; the flames, adjusted to a neutral condition, should point vertically downward, the-tips of the-inner cones being inch, approximately, above the tread surface of the rail. The rate of combustion of each fiame should be about cubic feet per'hour, each, of oxygen and acetylene. The flames shculd'be oscillated about once a second transversely of'the rail, the ends of the tips moving .a distance of about inch' on each stroke. The

flames should burn about 12 to 15 seconds.

For hardening a longitudinal strip of hardenable steel or alloy on the rail, a similar arrangement of torches may be used, but generally the rate of heat supply should be somewhat less and the time longer than that specified in the above example, but readily determined by trial.

Some types of electrical connections across the rail joints are brazed to the head of the rail in proximity to the rail ends. This is usually done prior to the building up process; otherwise, the brazing operation would tend to draw the temper of, or soften, the hardened strip. If for any reason the signal bonds are applied after the rail ends have been built up, the hardness can be restoredby a simple treatment, applying heat in approximately the same amount and manner as when applying the coating, but preferably heating to a bright red temperature.

It should be noted that the repairing of rail joints by the strip method as herein described provides a method which does notdamage signal bonds already applied whereas previous methods of repair which involve coating the entire width of the tread surface with the consequent heating of the rail metal throughoutlts width, frequently detaches the bonds.

The strip of deposited metal is preferably located about midway of the sides of the rail, see

Fig. 3a. but it may be near or alongone edge.

the metal deposited is of such character that it- The strip may be applied in either direction; for example, on a rail end it may start at the runoff, or point on the worn rail end most remote from the end edge or joint, and proceed across the joint to the other run-ofi; or, especially in the case of an open joint, it may be started at the end edge of one rail, proceed to the corresponding run-off, and this operation repeated in the opposite direction on the adjacent rail end. In the case of joints in which one or both ends are chipped extensively, it is preferable to build up the chipped ends first and then to proceed as above.

vThe side boundaries of the built-up strip may be straight or curved, and the width of the strip may be uniform or variable, as for example, wider at the ends than in the middle. See Figure 3d. As a desirable modification I may widen the strip where it joins the unbattered tread, whereby a merging or transitional hardness is obtained between that of the strip and the rail at this zone.

There are advantages in having the strip extend obliquely with relation to the rail though generally in the direction of the length thereof. For example, such disposition of the strip increases the width of the contact between the wheel and the strip with relation to the actual width of the strip as measured at right angles to the side boundaries of the strip. For illustrations of this kind of construction attention is called to Figures 3band 30. Generally, however.-where the strip is one inch wide'or more, there is little advantage in the above respect. I

There is also an advantage in locating the strip with respect to its position transversely of the rail to meet the special conditions imposed by various degrees of track curvature as they affect abrasion and plastic flow. For example, on curved track it is advisable in some cases to place the strip near or along the outside edge of the low rail.

The central position of the causeway strip has a decided advantage over a side position in most cases, because, among other reasons, where the wheel bears on the edge of a rail there is a much greater flow or tendency to "mushroom for a given hardness, than where the wheel bears in the center of the rail.

While I have illustrated and described in detail certain advantageous ways of practicing the invention, it is to be understood that such illustration and description is not to be construed ,in a limiting sense but that it is my purpose to claim the invention broadly in whatever form its principle may be utilized. a

No claim is made herein to the article produced by the present method. Claims to the repaired rail are included in my application Serial No. 189,484, filed February 9, 1938, for Repaired railroad rails, which application is a division of the present application.

I claim: 7

1. Th process of repairing the ends of worn rail treads which comprises depositing'a single continuous head of hardenable molten metal progressively from end to end or the area under repair over an area restricted in width to not more than three-quarters of the width of the rail head and with corresponding restriction of heat input, and allowing the deposited metal which acquires a Brinell hardness of 330-425 when cooled in the stated manner.

3. The process as set forth in claim 1 in which the metal deposited is of such character that it acquires a resistance to plastic deformation when deposited and cooled in the stated manner substantially greater than that of the rail metal.

4.,The process of repairing the ends of worn rail treads which comprises depositing hardenable .metalprogressively from end to end of the area under repair in the form of a single continuous longitudinal bead restricted to a width that is not greater than three quarters of the width of the rail head and that can be deposited conveniently by a torch welder at a single pass and with corresponding restriction of heat input, and causing the deposited metal which-has been cooled below the critical temperature to be further cooled to atmospheric temperature without reheating, sufflcient to draw the temper of the metal.

5; The process as set forth in claim 1 which further includes as a preliminary step the forming of a longitudinal depressed area in the worn surface for receiving a portion of the deposited metal.

6. The process as set forth in claim 1 in which the metal is deposited by the self-fiuxing, oxyacetylene torch method while maintaining the base metal at a temperature substantially below 'its melting point.

4 1y from end to end of a longitudinally extending area restricted in width to' a width not greater than three-quarters of the'width oi the rail head, said area being spaced inwardly from both side edges of the rail, and causing the heated metal at every point along the heated area to cool naturally to a state more resistant to plastic deformation than the original rail metal in its original state, and without subsequent reheating at any point suflicient to draw the temper of the conditioned metal.

8. A method of building up the tread surfaces of abutting rails at a rail joint, in track, the said abutting treads meeting at a depressed angle, either because of rail batter or because of angle bar wear, in which a hardenable steel welding rod is melted and deposited as a coating joined integrally with the rail, said coating being brought to the general longitudinal level of the treads of the abutting rails by a surfacing operation, to produce a smooth riding joint, said method comprising starting the building up operation at a point on one rail tread a suitable distance from the joint, depending on the extent of the depression, and depositing the rod metal as a single head of substantially less width than the width of the rail head, and progressively extending the molten puddle in a direction sub stantially longitudinally of the rail, toward the junction of the rails, and continuing on the abutting rail, in the same manner and in the same direction, away from the junction, to a point a suitable distance from the junction, to make a smooth riding joint, while applying the heat employed in the operation in a manner which avoids raising the temperature of any portion of the deposited metal that has cooled below the critical or hardening temperature, thereby retaining the hardness imparted to the deposited 7 metal by the natural cooling effect of the underlying and adjacent rail metal.

9. The method of producing a single, longitudinally extending, hard zone of restricted width on the tread of a railroad rail, which comprises progressively heating from end to end, to a temperature above the critical range, a zone on the, tread surface restricted in width to a dimension less than three-quarters of the width of the head of the rail throughout at least the major portion ofthe length 01 the zone, said zone being spaced inwardly from both side edges of the rail, the rate of progress, the rate of heat input. and the amount of heat input being so adjusted in relatlon to one another and to the width of the zone that a sharp temperature gradient is created between the zone metal and the adjacent metal of the rail head alongside of and beneath the zone metal, and the temperature gradient being so adjusted'in relation to the composition of the zone metal that a zone hardness of 350-425 Brinell results upon cooling.

l0 The process of repairing the ends or worn railway treads which comprises depositing a single continuous bead of hardenable molten metal progressively from end to end of the area under repair over an area restricted in width to not more than three-quarters of the width of the rail head throughout at least a major portion of its length and with corresponding restriction of heat input, and allowing at least the major greases 'hardenable molten metal on a centrally located zone on the tread surface restricted in width to a dimension less than three-quarters oi" the width of the tread surface throughout at least a major portion of the length of the zone, the rate of progress, the rate of heat input, and the amount ofheat input being so adjusted in relation to one another and to the width of the zone that a sharp temperature gradient is created between the zone metal and the adjacent metal of the rail head alongside of and beneath the zone metal, and the temperature gradient being so adjusted-in relation to the composition of the zone metal that throughout at'least the major portion of the length-of said zone, in-

cluding metal deposited at the end edge of the rail, a zone hardness of 330-425 Brinellresults upon cooling.

HARRY B GEORGE.

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