US2034045A - Method of making rail joint bars - Google Patents

Description

Filed Aug. 30, 1934 Patented Mar. '17, 1936 UNITED" STATES METHOD OF MAKING RAIL JOINT BARS George Langford, Joliet, 111., assignor to McKenna Process Company of Illinois, Joliet, 11]., a corporation of Illinois Application August 30, 1934, Serial No. 742,191

1 Claim.

This invention relates to the making of splice bars or joint bars commonly used in railway tracks, and is applicable to what are known in the art as high carbon bars whose steel contains about 0.40 per cent or more of carbon. Bars of high carbon steel are generally heat treated to give them hardness and tensile strength by oilquenching with certain mollifications to also insure toughness. My invention comprises in part, a method of heat treatment used in combination with a method of forging or shaping the bar cross-sectionally so as to cause a re-distribution of its metal, with the particular object besides other objects, of re-distributing the metal in the top member of the bar.

One of the main objects of my invention is to produce a high carbon bar of suflicient hardness, tensile strength and toughness to pass the present rigid inspection.

Another equally important object is to make the metal flow at a relatively low temperature so as to produce the desired changes in the bars cross-sectional shape.

Still another object is to produce changes in the bars cross-sectional shape without harmful distortion which is liable to occur at a low temperature generally considered too low for the beginning of a forging operation.

A feature of my forging method is that I not only remove dead resistance to the forging pressure but utilize the removal of resistance in various ways to convert bars of one fishing surface type into bars of another fishing type. This is a preferred practice to attain a particular object but it will become apparent from the following description that the invention has a wide range of practice, and that many useful results may be obtained by variations of its practice.

In the drawing:

Figure 1 is an end view of a bar and die ele ments in operating relation thereto, illustrating my improved forging method of re-shaping a top fishing surface of a rail joint bar.

, Figures 2 and 3 are similar views illustrating modifications of such method of re-shaping the top fishing surface of the bar.

Before the advent of open hearth steel, bars were made by the Bessemer process. Low carbon bars were specified to contain not over 0.10 per cent carbon. They were punched cold for bolt-holes and spike-slots and were required to.

have a 55,000 to 65,000 per square inch tensile strength. Some of the first open hearth steel bars were made to these specifications.

To secure greater tensile strength, bars were then made of medium carbon open hearth steel with carbon not under 0.80 per cent, and a tensile strength requirement of not less than 68,000 pounds per square inch.

Bessemer steel was finally abandoned in favor 5 of open hearth steel high carbon bars of carbon not under 0.45 per cent and manufactured so as to give a tensile strength of not less than 85,000 pounds per square inch. Extra high carbon bars were also made to some extent, the purpose being to attain a tensile strength of 100,000 pounds per square inch. However such practice has in general yielded to the existing practice of using open hearth steel of ordinary high carbon, reheating the bars after rolling and hot quenching them in oil.

High carbon bars in future referred to will be understood to mean ones permitting a range of 0.35 to 0.40 per cent carbon or over, and which will give a tensile strength when cold after quenching of not less than 100,000 pounds per square inch. They must also pass a cold bend test to an angle of 45 degrees without rupture. In the matter of specifications and tests, the general tendency among railroad purchasers is to throw the burden of securing results more upon the manufacturer with a few restrictions. They specify that high carbon quenched bars shall be punched, slotted and shaped, in the case of special designs, at a temperature not less than 800 degrees centigrade, equivalent to about 1470 degrees Fahrenheit, and subsequently quenched from a temperature of 810 degrees centigrade or 1490 degrees Fahrenheit. These are American Railway Engineering Association (A. R. E. A.) specifications. Shaping bars in the case of special designs, has thus far been confined to bending the flanges or foot portion of the bar to make various special types of joints known commercially as "Bonzana, Duquesne, Continuous, Wolhaupter and possibly a. few others. The special shaping consisted of shearing or bending the foot portion, and like the punching for bolt-holes and spike-slots, was considered too severe punishment for cold, high carbon steel, and which therefore was required to be done while the steel was at a relatively high temperature so as to avoid any sharp distortions whichmight eventually cause rupture in the bar. These operations of punching, shearing and bending were quite distinct from what I define as forging which will hereafter be understood to mean an operation wherein the steel is made to flow under pressure and change its cross-sectional shape. Rolling, hammering, die-pressing and drop-forging are herein considered as forging operations.

The present manufacture of high carbon quenched bars proceeds as follows:

To insure good test results, the manufacturer aims to secure a .45 to .50 carbon steel, avoiding as a rule the higher tolerance of .60. An open hearth high carbon steel ingot is rolled down to a bloom in the ordinary manner, the bloom while still hot being further reduced to its final joint bar cross-section, and being allowed to cool in a length of over 30 feet. This completes the forging operation which begins in the shaping of the bar, at a temperature of over 1,000 degrees centigrade or over 1832 degrees Fahrenheit, usually higher.

After it has become cold enough to touch, the long-bar length is sheared to a multiple of short lengths, and heated in a furnace to a temperature whereat the carbon in the steel acquires its hardening element, and proceeding above this to the required hot-working temperature but not high enough to damage the steel by overheating. This temperature is not below 800 degrees and not over 900 degrees centigrade. The bars are then drawn from the furnace; punched for bolt-holes; punched for spike-slots; hot-straightened by passing under a constantly reciprocating hammer head; and finally dumped hot in heated oil, from which they are drawn out after a short time and allowed to cool, after which they are examined and tested for shipment.

The above described method now practiced consists of two distinct operations; the first wherein the bar is forged by rolling into its final crosssectional shape; and the second, wherein the final steps of punching, bending and heat-treating are accomplished.

Inasmuch as the temperature of the steel falls from its initial furnace heat to its quenching heat because of the intermediate delays caused by punching, etc., the steel does not receive all of the hardness of which its carbon content is capable. I find that high carbon bars can be hardened so as to give tensile strengths above 140,000 pounds per square inch. These are generally thought to be too high, particularly in view of the cold bend test to follow, and manufacturers generally aim to secure well above 100,000 and not above 125,000 tensile strength, which appears to satisfactorily meet all test requirements. This gives time for the punching, etc. steps without cooling the bar too much before oil-quenching. This heat-treatment of bars combines tempering with hardening, the bar not being given all the hardness of which its carbon content is capable.

The practice of reforming worn bars in dies under a press is now well known in the art. The worn bars are heated in a furnace; forged to final shape in dies; often punched or drifted to insure the correct size and spacing of holes; and finally quenched in heated oil. Until recent years, most of the bars reformed were of low or medium carbon Bessemer, sometimes open hearth, steel. These could be initially heated and forged at 900 degrees centigrade or higher and apparently to advantage, for they could be bent cold when finished. Because of their relatively low carbon content they could not as a rule be hardened to attain a tensile strength as high as 100,000, nevertheless they gained considerably in tensile strength by quenching and were accepted although not fully meeting the requirements imposed upon high carbon open hearth bars.

However, high carbon bars have begun to come out of track in appreciable quantities, and barreformers are faced with a serious problem. Inspection heretofore perfunctory, often lacking. has now become rigid as in new bars, and the reformed bars must meet the requirements for strength and toughness as determined by the hardness and cold bend tests. For convenience. the tensile strength is determined by the related Brinell test, and the low limit of toughness is determined by bending the bar cold to 45 degrees without rupture.

Reformed high carbon bars are generally too brittle; often too soft. Given an initial temperature previously considered suitable for forging, the bars break under the cold bend test. Drenching the bars with cold water before forging does not remedy this, nor does delaying them before quenching. These practices merely reduce hardness without a corresponding decrease in brittleness. Attempts to reduce the initial forging temperature have resulted in unsatisfactory finish. The wom fishing surfaces are not fully restored because of the reluctance of the metal to fiow to the right places. In the past it has been thought by many to be sufficient to restore merely the top central part of the bar where most wear occurs, but the inspection for accuracy and general finish has proceeded as in the physical test requirements. A better product is demanded. Bars wear at the bottom and other places, as well as at the top. The shift of metal is greatest at the top central portion, and yet the bar must be sufficiently finished at both top and bottom throughout its length to be accurate and to give a good appearance. A bar is not a thick mass but three rather thin elements combined to present a large surface. A great many bars are 36 inches long and over. The total of surface areas subject to pressure is extremely large. The final distribution of metal must be made correctly with a single stroke of the press. If the bar temperature be below that considered suitable for forging, the heat-treatment may show improvement and yet the bar may not be properly shaped.

In the drawing and description I will not go into detail in the matter of ordinary manufacture. Those skilled in this art are familiar with the machinery and methods of rolling the bars in one operation and then fabricating and heattreating them in a second operation. My invention contemplates no particular changes in general equipment, and its procedure involves only slight although important departures from ordinary practice.

I find from my own experience in bar-reforming and that of others that worn, high-carbon rail joint bars require special treatment to get satisfactory results. At present, due to the relatively high initial heat employed, wholesale rejections are the rule, the finished bars being too brittle to stand the cold bend test. Bars delayed before quenching in the endeavor to secure toughness by making them softer, have also been rejected. The practice has been to re-treat these rejected bars by re-heating them and then requenching them, and if the initial heat be kept below a forging heat, and the bars quenched at not too low a heat, the bars should meet the required tests. This means a second operation, and the extra cost is prohibitive.

From numerous experiments I have found that toughness in the finished bar is dependent upon the initial heating. If the initial temperature be above '7 50 degrees centigrade when the forging or die-reforming begins, the finished bar is liable to fail in the cold bend test. Lowering the quenching temperature does not cure this defect. The, bar may be softer and still be brittle. However if the temperature be not above 750 degrees centigrade for initial forging, the bar will be tough regardless of the quenching temperature.

Hardness and tensile strength are dependent upon the quenching temperature as I have found from numerous trials. If the delivery of the bar from the forging press to the oil quenching tank be intentionally or otherwise delayed, the resultant tensile strength may be made under 100,000. However if the same bar at the same initial heat be hastened in its journey from the forging press to the quenching tank, it may be given a tensile strength of 140,000 or even more, and will be tough enough to stand the cold bend test.

From this can be seen that low Brlnell hardness and low tensile strength do not insure toughness; nor do great hardness and high tensile strength mean that the bar is brittle. A relatively low initial forging temperature insures toughness; and the hardness and tensile strength are controlled independently and wholly by the quenching temperature. Faulty initial heating may not be remedied by quenching; nor will faulty quenching be remedied by initial heating. These two steps "function independently and have little relation to each other.

However the great difiiculty is to reform or forge the bar at a temperature of 750 degrees centigrade or less. The metal is reluctant to flow, and there is the tradition to overcome that any shaping of metal should not begin at such a low temperature. But reforming bars in dies under a press with a single blow is an unusual operation. The metal is compressed, and is not stretched or greatly distorted as in rolling, hammering, multiple drop-forging, etc. These latter operations require high initial forging temperatures, otherwise injurious strains in the steel will result. This is true to some extent in worn bar reforming. Although the movement of metal need be slight and is spread over a large area, nevertheless strains may be induced in the steel by too abrupt indentations aimed to accelerate movement of the resistant metal. The low initial forging temperature necessary to secure proper heat treatment, requires a very careful forging operation to properly finish the bar and not subject it to abrupt or injurious deformations. It is not enough to concentrate pressure upon the portions of the bar where the greatest flow of metal is desired. There must be distinct reliefs from pressure, and a graduation of pressures and reliefs to properly finish the bar without harniful distortion.

The forging of a worn high carbon bar at a low initial temperature, is as can be seen, a greatly restricted operation. An ordinary bar must be made into a crowned, head free or entirely different type, with a single blow of the press. A new article of new type must be produced from an old and discarded one, by one and not by successive forging steps as in the case of other steel articles.

The forging method whereby I accomplish this surface of the bar, and this is clearly exemplifled and illustrated in Figures 1, 2 and 3 of th drawing.

Referring first to the forging method illustrated in Figure 1 of the drawing which shows an end view of a bar I positioned in a fixed die 2 with a moving die 3 closed down upon the bar surface a. A guide 4 is shown to indicate that the bar head is kept from tilting out of position. The bottom of die 3 presses the surface a of the bar to position a." and the whole inner portion of the bar head bends downward, surface b bending to surface b. If these depressions are placed between the center and ends of the bar and the bar head reformed, the intermediate depressions created in Fig. 1 will remain as they were, after reforming, because of the reliefs b" which insure the retention of the depressions, after they are once pressed in. Innumerable other variations may be created, and these may be applied to the bottom member as well as to the top one. In the operations thus far described, it is important to note that the die wall for the surface a" is a smooth surface from end to end free from indentations and projections which would be diificult to machine and could not be made as accurately as a smoothly planed die wall. In my selections of surfaces for reliefs, I avoid disturbing the die walls corresponding to the top and bottom fishing surfaces of the bar. These reliefs from pressure may 'be used very conveniently to change the type of a fishing surface. They need be only slight, for only a slight shift of metal is needed to alter a fishing surface, and even though the initial forging temperature be low, the small amount of required shift of metal is possible and it is insufficient to cause injurious distortion. In the case of newly made high carbon bars, various applications of my method may be used. In Fig. 2 which is a fragmentary end view similar to Fig. 1, the upper die 3 indents the bar so that the indented surface is parallel to the fishing surface a or it may be at a lesser angle in a plane on the line 6. This is a forging operation, the top member 5 of the bar being crushed down upon the web-member, whereas in Fig. 1, the top member is merely bent down at its inner portion. If as in Fig. 3, the top member be supported at b ande, the top member would be bulged laterally, surface 0 bulging to c, and surfaces at and f to d and 1" respectively. In these two cases of Figs. 2 and 3, these operations constitute a complete forging operation.

The method of my invention permits of many variations in the forging operation, which as has. been described, may make a preliminary operation desirable and this may or may not be a forging operation. New or worn bars may be reformed into ordinary or special types, and my invention is intended to include their manufacture within the limits I claim.

At present new high carbon bars are hard enough. It is better that they wear than to wear out the rail ends as might happen if the bars were made much harder. But rail manufacturers are trying by heat-treating and other methods to make the rail ends harder, and when this is done successfully, joint bars may contain more carbon and also be made harder. They cannot be made brittle however and my method will prevent this by forging at a temperature not over 750 degrees centigrade and by providing pressure reliefs so that the forging may not merely end but begin at this low temperature and give the bar a satisfactorily finished form. Where there is any irregularity of heating which often occurs unavoidably in practice, the important central portion of the bar is where the limitation of low temperature is to be determined Forging of the bar is herein considered as distinct from punching, shearing and bending, and as synonymous with reforming whereby the metal is made to flow and change its cross-sectional shape in portions of at least the top member.

What I claim is:

The method of reshaping a top fishing surface of a rail joint bar, consisting in heating the bar and subjecting a portion at least of its top inner extension to pressure, said pressure being directed so as to depress said inner portion out oi. the plane of normal rail fishing contact, with means provided to prevent either vertical or lateral deformation of the web, the bottom member, or the top outer face of the bar.

GEORGE LANGFORD.

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