US2101312A - Process for cooling rails - Google Patents

Description

2 'Sheets-Sheet 1 R. B. GERHARDT PROCESS EOR COOLING RAILS Filed Dec. 5, 193] Dec. 7, 1937.

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Fmmqf Dec. 7, 1937. R. B. GERHARD-r 4 `PROCESS FOR COOLING RAILS 2` sheets-sheet 2 Filed Dec. 5, 193] Cltrmwaf/ Patent PRGCESS 1F63 @GGG Reald llt. Gerhardt, Steelton, a., gnor to Beth-Mary Steel Coration, a corporation of Maryland Application December 5, 1931, Serial No. 579,316

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My invention relates to a process for cooling rails in such manner that dangerous stresses and strains are prevented in the rail metal.

An important problem in the manufacture of 5 rails at the present time is the avoidance of stresses and strains in the metal which may develop into dangerous rail defects such as, for example, transverse or similar ssures. Among the causes which may introduce dangerous stresses in the rail metal, it has been suggested that a primary factor may be the conditions under which the rail is cooled. If, in cooling, substantial diierences in temperature occur between the various parts of the rail, as say between the web and anges and the head, or between the interior and exterior portions, particularly of the head, these temperature dierences may give n'se to stresses which in turn may produce strains which ultimately may lead to the production of dangerous defects in the rail structure.

It has vbeen proposed that the rails be slowly cooled through a range of temperature extending from about 500 C. to 350 C., the thought being that this range is a danger zone and that if substantial differences of temperature occur between the djierent portions o the rail while passing through such range, permanent defects of structure may ensue. In such a process the rail, while 'fl to conditions to provide a slow cooling through the alleged danger zone. Obviously in such processes to prevent the occurrences of substantial temperature dierences between the various parts of the rail in the temperature range 500 to 350 C. it is usually important to begin the slow cooling at a temperature appreciably in excess of 500 C. It will be readily apparent that in doing this there is some likelihood of producing more or less soitening of the rail because of the more or less elevated temperatures at which the rail is held.

I have discovered that while it is important to effect a slow cooling of the rail at a certain stage the retardation of cooling should take place at a lower temperature. I have found that the important thing is to eiect a protracted cooling between 300 and 200 C. The cooling of the rail prior to 300 C. may be of the ordinary character such as commonly takes place on the hot bed' or it may be greatly accelerated as in the case where it is desired to eiect a hardening of the rail to produce 'a heat treated rail. But whether cooled rapidly or at the normal rate I nd it important to subject the rail to a protracted cooling through the range 300 C. to 200 C., preferably irom 300 C. down to a temperature not still at a temperature above 500 C., is' subjectedA (ci. 14a-2i) greatly in oxces of ordinary atmospheric temperatures.

My invention comprises the cooling of a rail from above the critical range to a temperature less than 500 C. in the normal way on the hot 5 bed, or by an accelerated cooling, and then placing the rail in closed containers before the temperature has dropped as low as 300 C. and cool ing lslowly either to approximately atmospheric temperatures or to a somewhat higher tempera- 10 ture, but not higher than 200 C.

I shall rst describe an example of my process applied to the preparation of ordinary or unheat treated rails. The rails from the mill are run on to the hot bed in the usual way, the temperature of course then being well above the critical range. lI`hey are allowed to cool on the hot bed in the usual way until the temperature of a consequential portion of the metal of the rail head has dropped below 500 C. Without allowing the 20 temperature of the major mass of the head of the rail to drop below 300 C. the rails are then placed in more or less close proximity to each other in containers which are closed and the rails allowed to cool to approximately atmospheric 2g, temperature. The important range of temperature ior this slow cooling is between 300 and 200 C. In practice I ordnarily'allow the rails to remain in the chamber until the temperature of the head of the rail has dropped to 50 to 75 C. 3@ when they are then removed. Preferably the temperature of the exterior of the head of the rail ranges between 325 and 400 C. when placed in the closed chamber.

A suitable chamber for this purpose is shown 35 in the accompanying drawings. Referring to these drawings:

Fig. 1 is a 'plan view of this structure; and

Fig. 2 is `a cross section therethrough taken on the line 2-2 of Fig. 2.

The chamber is comprised of the masonry walls lli covered by roof i2, the front and back walls being of unequal height to give the structure an inclination downwardly from the rail receiving end to the rail delivery end. Inclined skids i3 5 mounted on pedestals i4 within the chamber project at their ends from the front and rear. At the rear of `the structure are inwardly swinging doors l5 and at the forward end are plvotally mounted outwardly swinging doors I6. At the 50 ,rear of the furnace chamber are relatively short skids l1 plvotally connected to the pistons of hydraulic cylinders I8. 'Ihe forward ends oi these skids are plvotally connected by means of rods 2n to skids I3.

The rails are received from the hot bed on skids I 1 while such skids are in the horizontal position. To charge the rails into the slow cooling chamber, the cylinders I8 are actuated to elevate skids Il, and rails I0 are discharged onto the projecting ends of skids I3. The rails are then pushed into the chamber through swinging doors l5. After the chamber has been lled with rails the addition of further rails causes the discharge of rails from the forward side of the chamber through swinging doors I6 into receiving cradles 2|.

`I shall now briefly outline a process, involving the principles of my invention, for the production of a heat treated rail. While the major mass ot the rail is still above the critical point it is immersed in water, oil or other suitable quenching medium and cooled rapidly through the critical range. This quench is of such duration that the temperature of the major mass of the metal does not cool to the blue heat zone, but is preferably 0i' such a degree as to cool at least substantial proportions of the rail head metal to a temperature less than 500 C. vIf for any reason it is important that the quench be insufliciently drastic to lower the temperature of a substantial proportion of the head metal below 500 C., the rail is allowed to cool to a temperature below this point on the hot bed or in any other suitable location. When the temperature of the exterior is appreciably below 500 C. but with the major mass of the interior metal still above 300 C. the rails are placed in a suitable closed container to cool slowly through such temperature range as to include the range 300 to 200 C. A suitable device for this purpose may be the oven or hood shown in the drawings and already mentioned in connection with a normally treated rail.

In carrying out the process for the heat treatment of rails, following the quenching operation, the temperature of the rail may be equalized before being subjected to the slow cooling in the closed chamber. For example, the rails following the quench may be placed in a furnace which is artificially heated andthe temperature of the rail equalized. The rail may remain in such a furnace for a substantial period of time to effect a drawing action, to eliminate strains due to the quenching operation. From this furnace the rails may then pass to the closed chamber for effecting the slow cooling operation through the range 300 to 200 C. It will be noted in vboth of the examples of my process given above the'rails are subjected to a relatively rapid cooling until a temperature of the rail has been obtained. less than 500 C. and then before the temperature of the rail. or the major portion thereof, has dropped to 300 C. placing in a closed chamber for eilecting a slow cooling to a temperature at least as low as 200 C.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a process for cooling a rail, the steps of cooling the rail at the normal rate on the hot bed through the critical range, placing the rails in a closed chamber after a substantial part of the metal of the head of the rail has been lowered to less than 500 C. but before the temperature of the major mass of the metal of the head has cooled as low as 300 C. and cooling slowly therein to approximately atmospheric temperature.

2. In a process for cooling a rail from above the critical range, the steps of cooling therail in the normal way on the hot bed until a substantial part of the metal of the head of the rail has been dropped below 500 C., placing the rail in a chamber before the temperature of the major mass of the head of the rail has dropped as low as 300 C., and cooling the rail slowly therein to a temperature less than 200 C.

3. In a process for treating a rail, the steps of quenching the rail through the critical range and then after the temperature of the rail has been lowered to less than 500 C., but before it has been cooled below 300? C., placing in a closed chamber and cooling slowly to a temperature below 200 C.

4. A process for cooling rails from the original mill heat comprising the steps of cooling the rails from a temperature above the critical range at a. rate at least as rapid as that which normally occurs on the hot bed until the temperature of the rails is substantially below 500 C., and after such cooling but before the major mass of the head metal has cooled below 300 C. from the original mill Aheat enclosing the rails and cooling slowly Y through a temperature range which includes an extended range below 300 C. to prevent the development of those stresses and strains which tend to produce nssures in the heads of the rails.

5. A process for cooling rails from the original mill heat comprising the steps of cooling the rails from a temperature above the critical range at a s rate at least as rapid as that which normally occurs on the hot bed until the temperature of the rails is substantially below 500 C., and preventing the `deveiopment of stresses and strains which tend to produce fissures in the heads of the rails by 'cooling slowly through a range of temperatures whichA includes the range 300 to 200 C., such slow cooling being begun before the major mass of head metal of the rails has cooled to 300 C. from the original mill heat, and being at a rate considerably slower than the normal hot bed rate of cooling.

6. A process for cooling rails from the original mill heat, comprising the steps of cooling the rails from a temperature above the critical range at the rate which normally occurs on the hot bed until the temperature of the rails is substantially below 500 C., and after such cooling but before the major mass of the head metal has cooled below 300 C. from the original mill heat enclosing the rails and cooling slowly through a temperature range which includes an extended range below 300 C. to prevent the development of those stresses and strains which tend to produce fissures in the heads of the rails.

REGINALD B. GERHARDT.

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