US1334379A - Treating steel - Google Patents

Description

E.F!KENNEY.'

TREATING STEEL.

APPLICATION FILED NOV-20.1919.

1,334,379. Patented Mar. 23, 1920.

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EDWARD F. KENNEY, OF PHILADELPHIA, PENNSYLVANIA.

TREATING s'rnnn Specification of Letters Patent.

Patented Mar. 23, 1920.

Application filed November 20, 1919. Serial 1T0. $39,343.

To all whom it may concern:

Be it known that I, EDWARD F. KENNET, a citizen of the United States, and a resident of the city of Philadelphia, county of Ph11adelphia, and State of Pennsylvania, (whose post-ofiice address is Philadelphia, Pennsylvania,) have invented certain new and useful Improvements in Treating Steel; and I do hereby declarethe following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to the treatmentof steel with particular reference to steel rails, which, after having been rolled in a rolling mill, are ordinarily placed upon cooling beds and are cooled to atmospheric temperature. This practice results in first cooling the exterior portions of the steel while the interior is hot, and as the hot interior further cools the contraction thereof is resisted by the cooler and stifi'er exterior with the'result of setting up internal stresses which may afterward, in' use, add to the stresses of service and shorten the life or usefulness of the rail.

Although my method of treatment may apply to any kind of rolled steel bars, forgings, etc., I will, for the sake of simplicity of description, confine the same to the treatment of rails, thereby making the phraseology herein more simple.

In conducting my process I roll the ra ls in the usual Way at a temperature permitting the plastic flow and deformation of the material, and, generally speaking, the rolling of the rails is finished when they come out of the finishing passes at a good red heat, that is at an approximate temperature of from N00 to 1900 degrees Fahrenheit. The rails heretofore have been then ordmar 1ly run through a cambering machine to give them a certain amount of camber so that when they are cool they are approximately straight, the reason for the camberlng bein g that the thicker head portions cool last and unless the camber or curve is given the rails would be crooked when cool.

On accountof contact with the metal rolls in the operation of rolling and also because of the cooling eifect of the atmosphere, the exterior portions. of the rail 0001 more rapidly than the interior. I This is particularly true of the head which is the thickest portion of. the rail, and results in the interior of the head being red hot when the exterior is black hot. This difi'erence in temperature is continued as the rail cools. As long as all the metal of the rail is plastic, no harm results, but as soon as the exterior is cool enough to become rigid, it resists the shrinkage of the hotter interior. This resistance to shrinkage results in tensile stresses in the interior of the rail which tend to shorten the life of the rail as previously mentioned.

In order to obviate this diiiiculty, after the rails have issued from the finishing passes of the rolls, I camber them, to a certain extent, and place them on a cooling bed and when the exterior of a rail has reached a temperature of approximately 800 to 1000,degrees Fahrenheit, I introduce it into a furnace at a temperature of about 800 degrees Fahrenheit, more or less, so that the outside is kept hot While the inside is cooling, thereby equalizing the temperature of the inner and outer portions and preventing the undue stresses above mentioned.

At a temperature of about 800 degrees Fahrenheit the material of the rail is quite plastic or comparatively Weak and the interior and exterior portions can readily become harmonized with respect to their cooling, obviating difi'erences in stresses between the two portions.

The tensile strength of steel increases from ordinary atmospheric temperature up to about 500 degrees Fahrenheit, then sharply declines to about 900 degrees Fahrenheit where it rises slightly and then as ,it becomes hotter there is a very marked reduction in tensile strength.

Similarly the elastic limit of steel -from atmospheric temperature declines gradually to about 800 degrees Fahrenheit, then increases very slightly to about 900 degrees and then decreases very quickly as the temperature is increased beyond 900 degrees. Therefore, the most advantageous temperature for equalizing the heat is between 500 and 1200 degrees Fahrenheit, the exact temperature selected varying, however, with the carbon content of the steel, the contour of the rail and other conditions. The elastic limit of rail steel at ditferent temperatures is plainly shown on diagram herewith which, with thelegends thereon, will be readily read and understood and from which it can be seen that the elastic limit of zero Fahrenheit is about 60,000 pounds per square inch and at about 800 degrees Fahrenheit it is only 38,000 pounds per square inch, and other figures for other temperatures.

In order to make sure that the rail may vbe straight without again setting up un due stresses due to cold straightening, I also straighten the rails between the temperatures of 500 and 1200 degrees Fahrenheit. The straightening of the rails in this manner may be done with either a roller or gag straightening press, but I prefer a roller straightener as this will effect the results with less local stresses.

Although I have described and illustrated my invention in considerable detail, I do not wish to be limited to the exact and specific details thereof as shown and described, but may use such' modifications in, substitutions for, or equivalents thereof, as are embraced within the scope of my invention,-or as pointed out in the claims.

Having thus described my invention,

what I claim and desire to secure by Let ters Patent is 2- 1. The process of treating steel shapes which consists in finishing them in a rolling mill at a red heat, then allowing the temperature to fall to between 500 degrees and 1200 degrees Fahrenheit, then substantially equalizing the heat of the different portions tween these temperatures, allowing them to remain in said furnace until all portions are substantially of the same temperature, then withdrawing them from said furnace and promptly straightening the same.

In witnesswhereof I hereunto affix my signature.

.EDWARD F. KENNEY.

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