US2061264A - Process of reconditioning metal articles - Google Patents

Description

Patented Nov. 17, 1936 UNITED STATES PATENT OFFICE PROCESS OF RECONDITIONING MIETAL ARTICLES Lawrence S. Wilbur, Evanston, 111.

'5 Claims.

This invention relates to the reconditioning of worn metal articles to render them suitable for reuse.

More specifically, this invention relates to a process for restoring worn splice bars that have been used for joining railroad rails.

While the process of this invention is applicable to the reconditioning of any worn shaped metal article, it is particularly adapted to the reconditioning of ferrous metal articles and has particular utility in the reshaping, reclaiming and restoring of railroad splice bars. For the sake of convenience, the invention will hereafter be described as embodied in the preferred form applied to railroad splice bars.

It is readily appreciated that splice bars in use at the junction of railroad rails are subjected to various conditions that'induce "wear to such an extent as to render themunfit for service sitter a period of time. These worn splice bars must be replaced by new'bars or subjected to :a irreconditioning treatment to make them again serviceable.

Most of the splice bars now in use are made of heat-treated, highcarbon steel, and iztiis with such material that the process of this invention is particularly applicable. Generally, the splice bars havea carbon range or from ..'3% to 37 and a tensile strength before heating approximating '85,000 pounds per square inch. After heat-treatment, the tensile strength is increased to around 125,000 :pound'sper square inch.

in the manufacture of new :splice bars, the steel mills have an accurate analysis of each batch made so that the proper heat-treatment may be given to "the batch to bring the bars to the desired tensile strength. Although the different batches may vary considerably :in carbon content within the range indicated above, the heat-treatment is controlled for each batch to produce the same final tensile strength .ior all batches. Thus the finished bars from various batches will vary-widely in carbon content lbllt will all have a tensile strength of approximately 110,000-130,000 pounds per square inch.

When the bars have been placed into service and are removed because of wear or for other reasons, they are ihopelessly mixed as to carbon content, solthat the carbon content of any single bar or any group of bars is unknown. It would be necessary to analyze eachindividu'a'l bar in any group for its carbon content 'so that the proper heat treatmentcould be given to the bars to bring them to the uniform tensile strength which they possessed when newly made. it is obvious that the cost and'time involved in analyz ing each individual bar would defeat any recondition'ing process, from a commercial standpoint.

The purpose of my invention is to provide a process whereby the bars are considerably equal- 5 ized so that they may all undergo the identical reconditioning steps and possess satisfactory tensile strength and ductility to pass the specification tests.

It is therefore "an object of this invention to provide an economical process for reconditioning worn metal objects.

Another object of this invention is to provide a reconditioning process for worn metal objects that .is applicable toierrous metals of unlike carbon contents to yield reconditioned articles of similar physical characteristics.

Another object of this invention is to provide a heat .treati-ng'prooess forworn splice bars that will change the steel structure of the bars so that the treated bars "will :be superior to the new bars.

Another object of this invention is to relieve the strains set up in splice bars during their use in railroad tracks.

A specific object of this invention is to provide an economical reconditioning process that is appli'cable tobatches of splice bars having unknown carbon contents to produce reconditioned bars having :similartensile strength and bending properties. I

Other and further objects of this invention will be apparent to those skilled in the art from the following specification;

The "process of my invention will now be described as applied to :a batch of worn-out splice bars formed of steel having a carbon content of .3'% and 37%, which steel has been heat-treated to have a tensile strength of approximately 125,000 pounds per square inch. These worn-out bars most probably have been subjected to years 40 of service and are cracked, bent, warped, rusted and strained. It will be appreciated that the carbon content of each individual bar is unknown, except that it is within the range above indicated because railroad specifications call for the use of steel having this carbon range.

The worn bars are first placed in an annealing furnace and heated to temperatures above the point of decalescence or upper critical A01 point. These temperatures, for steels of the grades indicated, are between 1600 to 1800 F.

The heated bars are then removed from the furnace and stacked together in piles so that they may (:00! slowly in the air. 'Ihisstep of the ,proc- 55 ess is called a normalizing step and is practiced to relieve strains set up in the bars during usage.

The cooled, normalized bars are next placed in a furnace and heated to a forging temperature, preferably between 1450 to 1800 degrees F. The heated bars, at the temperature indicated, are removed from the furnace one at a time, and placed between re-forming dies where they are re-shaped under pressure applied to the bars. The pressure causes the metal of the bars to flow into the recesses of the dies so that the bars are covers a preferred working operation, it is obvious thatjsome of these steps may be omitted in some instances, and that other auxiliary steps I can be included. For example, the normalizing step may be used alone in some instances or may be dispensed with in other instances. )may be ground with an abrasive wheel at the cenre-formed to the desired dimensions.

The pressed bars are next subjected to a The).

quenching operation to harden the steel. quenching material may be any ,type of wellknown quenching oil, water or any suitable quenching medium. The quench, howevenmust; be severe enough to cause the bars having a lower carbon content (bars of .3% carbon) to attain a tensile strength above 100,000 pounds per square" inch, preferably approximately 110,000 pounds per square inch. This severe quench will increase the tensile strength of the higher carbon content bars to approximately 160,000 pounds per square inch.

The re-formed carbon bars having .the;lo,wer carbon content are satisfactory for use, because they possess a suitable tensile strength and, also, are ductile enough to pass the required bend test. Railroad specifications require thatsplice bars must not fail when bended, cold, to a 45 degree angle. However, the splice bars formed of higher carbon steel are too brittle to pass the bend test and it is therefore necessary to reduce the brittleness of the higher carbon bars. This must be accomplished without materially lowering the tensile strength of the lower carbon bars. Since the carbon analysis of the bars being treated is not known, it is impossible to segregate the batch so that the brittle bars may be treated alone.

I have found that the malleability and tensile strength of the bars may be considerably equalized by treating the splice bars in a drawingfurnace at suitable temperatures for a length of time that will reduce the strain setup in the higher carbon bars during the. violent quench treatment, but will not seriously impair the tensile strength of the lower carbon bars. 4 v

It is known that high'carbon steels that have been quenched to higher tensile strengths .are affected much more by a drawing operation'than are lower carbon steels with lower tensile strengths. Because of this 'phenomenonyI am able to bring the extremes ofbrittleness and tensile strengths of the bars closer itogether,.or, in other words, to equalize the physical characteristics of the batch. For example, a low carbon content bar having a tensile strength of 110,000 pounds per square inch'and a high carbon content bar having a tensile strength'of'1'60,000 pounds per square inch, when treated in accordance with my invention, in a drawing furnace, can be equalized sothat the first bar is only reduced in tensile strength toapproximately 100,000 pounds per square inch, while the second bar.is reduced to about 125,000 pounds per square inch. In this manner, the low tensile strength bar can still pass the railroad specifications for a minimum of 100,000 pounds per square inch tensile strength, while the higher tensil strength bars will have sufficient malleability or ductility to pass the required bend test.

Ihave found that a given batch of rail bars may thus be equalized by heating in a drawing liurnace to temperatures of about/500 to 800 "R,

for about 30 minutes to two hours. Obviously, this treatment can be varied considerably to fit specific conditions without departing from the principle of this invention.

The normalizing, forging, quenching and drawing operations of this process each cooperates to produce bars having a better grain structure than the new bars. It is well known to metallurgists that the working of a metal benefits its grain structure.

While the above description of my process The bars ter part of the upper bearing surface to search for cracks, or they may be subjected to a cleaning or pickling process to remove rust and dirt. The cleaning operation may be inserted just before the bars are placed in the forming dies. The formingdies may be provided with pins to preserve the holes, or the bars may be repunched, or the holes may be ignored during the re-forming operation.

From the above description it is evident that I have provided a process, including several steps, which may be performed in proper sequence to recondition worn-out splice bars of unknown and mixed carbon contents so that the treated bars will pass therequirements of new bars. As pointed out above, the process is applicable to the reconditioning of other shaped metallic articles.

I am aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this invention, and I, therefore, do not purpose limiting the ,patent granted hereon otherwise than necessitated by the prior art.

I claim as my invention: 1. The process of reconditioning a batch of worn railroad splice bars having unknown carbon contents within'the range of 0.3 to 0.7% and having unknown tensile strengths within the range of 110,000 to 160,000 pounds per square inch to produce reformed bars which are sufiiciently ductile to pass railroad bend test requirements and having tensile strengths not lower than 100,000 pounds per square inch which comprises heating said bars to temperatures between 1600 to 1800 F., allowing the heated bars to cool slowly, reheating said cooled bars to forging temperatures between 1450 to 1800 F., reforming said bars under pressure at the forging temperatures, quenching the re-formed bars and again reheating the bars to temperatures around 600 F.

2. The process of reconditioning a batch of worn out splice bars of unknown carbon contents within the range of 0.3% to 0.7% and unknown tensile strengths within the range of 110,000 to 160,000 lbs/sq. in. to produce re-formed splice 'bars sufficiently ductile to pass railroad bend test requirements and strong enough to pass railroad tensile strength requirements which comprises heating said worn out splice bars to temperatures between 1600 to 1800 F., stacking the heated splice bars in piles in contact with the air, allowing the stacked bars to cool, reheating the bars to temperatures between 1450 and 1800 F., reshaping the reheated bars under die pressure, quenching the reshaped bars in a quenching liquid and reheating the quenched bars to temperatures around 600 F. in a drawing iurnace.

3. The process of reconditioning a batch of worn railroad splice bars having unknown carbon contents within the range of 0.3 to 0.7% and having unknown tensile strengths within the range of 110,000 to 160,000 pounds per square inch to produce re-formed bars which are sufficiently ductile to pass railroad bend test requirements and having tensile strengths not lower than 100,000 pounds per square inch which comprises heating said splice bars to temperatures between 1450 to 1800 F. in an annealing furnace, stacking the bars in piles in the air, allowing said stacked bars to cool, reheating the cooled bars to temperatures between 1450 to 1800 F., reshaping said heated bars under pressure, quenching the reshaped bars in a quenching medium to increase their tensile strength and subjecting the quenched bars to a drawing operation to temperatures around 600 F. for about 40 minutes to increase their ductility.

4. The process of reconditioning worn splice bars of unknown carbon contents within the range of 0.3% to 0.7% and having unknown tensile strengths Within the range of 110,000 to 160,000 lbs/sq. in. to produce re-formed bars the cooled bars to forging temperatures, re-forming the bars under pressure at the forging temperatures, quenching the re-formed bars, and heating the quenched bars to increase their ductility.

5. The process of reconditioning worn splice bars of unknown carbon contents within the range of 0.3% to 0.7% and having unknown tensile strengths within the range of 110,000 to 160,000 lbs/sq. in. to produce re-formed bars which are sufficiently ductile to pass railroad bend test requirements and having tensile strengths not lower than 100,000 lbs/sq. in. which comprises heating said bars to temperatures between 1600 degrees and 1800 degrees F., allowing the heated bars to cool slowly, reheating the cooled bars to temperatures between 1450 degrees and 1800 degrees F., reshaping the heated bars under die pressure, quenching the reshaped bars in a quenching liquid, and reheating the quenched bars in a drawing furnace to increase their ductility.

LAWRENCE S. WILBUR.