US2589495A - Apparatus for hardening rolls - Google Patents

Description

March 18, 1952 F. o. HESS ET AL APPARATUS FOR HARDENING ROLLS 2 SHEETSSHEET 1 Filed Jan. 10, 1948 INVEN'II'ORS -FREDERIE EH25: JAMES Kmvsrcm X41.

ATTORNEY March 18, 1952 5, H S ET AL 2,589,495

APPARATUS FOR HARDENING ROLLS Filed Jan. 10, 1948 SHEETSSHEET 2 lNVENfORS FBEDERIE El. Hess 8, JAMES KNIVETUN.

Patented Mar. 18, 1952 UNITED STATES PATENT OFFICE APPARATUS FOR HARDENING ROLLS tion of Pennsylvania Application January 10, 1948, Serial No. 1,564

3 Claims.

The present invention relates to the heat treating of rolls, and more particularly to the method of and apparatus for hardening rolls of the type used in steel mills for rolling strip, and for other purposes.

Rolls of the type to which the present invention relates are of various sizes but often reach twenty-five inches in diameter and have a length of eighty-four inches, not including journal portions that project from each end thereof. The finished rolls which may weigh several tons should have a hard, smooth surface, with the center portion and the journals thereof tough enough to withstand the shocks and stresses to which they are subjected.

At the present time it is customary to place a number of rolls in a large furnace and heat them slowly until the entire roll has been raised to a hardening temperature. Often the journals are wrapped with asbestos in an attempt to prevent the heating of the journals to the extent to which the roll surface is heated. The rolls are then removed one at a time to be quenched. The quenching process is a highly exacting operation since care must be exercised to apply the quenching medium onlyto the surface of the roll. If th'quenching medium should get on the journal portions they would in all probability also be hardened and consequently lose their desired toughness. throughout their entire area, the stresses that are created when the surface is chilled by quenching are tremendous, and not infrequently the rolls split as a result of the treatment. In any event the further treatment of drawing the rolls is required. It is also noted that the long heating time produces a large amount of scale on the roll surface that must subsequently b removed.

In practicing the present invention a roll to be heat treated is mounted on a support So that it may be rotated. While in this position a furnace of special construction is placed around it so that heat of a high temperature gradient will be applied only to the roll surface and for a time sufficient to heat the roll to the desired depth. The fast heating reduces to a negligible quantity the scale produced on the roll surface. The journals of the roll are shielded from the heat so that they will not be raised to the hardening temperature. desired amount the parts of the furnace are withdrawn from the roll and a quenching device is placed over it. While the roll is still being rotated the roll is subjected to the action of the quench- Since the rolls have been heated After the roll has been heated the ing mechanism. Since the roll has not been heated to a hardening temperature throughout its entire area the quench will not produce internal strains of the type produced by conventional heating methods. Also the quenching operation is not as critical as with conventional practice as the journals have not been heated, and therefore will not be hardened. Provision can also be made to cool the interior of the roll while the exterior is being heated.

It is an object of the invention to provide a method of and apparatus for hardening the surface areas of rolls without affecting the center portion and the journals thereof.

It is a further object of the invention to provide a method of and apparatus for rapidly heating and quenching rolls so that a roll with the desired hard surface and tough core is produced. The entire heat treating operation is carried out without moving the roll from a single working position.

It is therefore a further object of the invention to provide apparatus by means of which a roll may be heated and quenched without being moved from a support upon which it is mounted. The operation may take place rapidly and with a minimum of handling of the roll.

The description herein will be directed specifically to the heat treating of steel mill rolls used in strip mills, by way of example only. It will be obvious that the same method may be followed and the same apparatus used for other types of rolls such as those used in the rubber and paper industries. While only one form of apparatus is disclosed other forms which are capable of operating in the manner described and are within the scope of the invention may be devised, so that the description is intended to be illustrative rather than restrictive.

The various features of novelty which characterize our invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages, and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described a preferred embodiment of the invention.

In the drawings:

Figure l is a sectional view through the furnace with a roll mounted therein, taken on line l-l "of Figure 2;

Figure 2 is a View taken on line 2-2 of Figure l and including the rotatable supporting means for the rolls;

Figure 3 is a view taken on line 3--3 of Figure *2; and

Figure 4 is a diagrammatic end view of the furnace showing the control system and the quench operating mechanism.

Referring to the drawings there is shown a roll R. which is to be hardened. This roll has a central surface portion I, the. surface of which is to be hardened while the interior thereof andthe journals 2 projecting from the ends of the central portion are to remain tough. Prior to the beginning of the heat treatment the roll is moved into position by an overhead crane or other suitable mechanism of a type which is capable of handling material as heavy as the roll. The roll is lowered until it is centered with respect to a pair of supports 3 and 4 which are then moved toward each other to support the roll. The left support 3 comprises a carriage 5 which is mounted on rollers B-that move along a pair of tracks which are belowthe surface of the floor and are not shown. This carriage has on it a rotatable shaft! that is mounted in bearings 8. When loading a rollthe carriage is moved to the right until the end of shaft 7 is received by a central opening in the roll to support the same. The carriage is properly positioned axially relative to the roll when a disc or plate 9 that is attached to the shaft engages the end of a journal 2. As seen in Figure 3, a chuck consisting of a pair of blocks II and I2 are attached to the face of the plate 9. -Each of these blocks is provided with a pair of guide slots l3 through which extend bolts l4. The blocks forming a chuck are separated when the carriage is to be moved into engagement with the end of the roll. Thereafter bolts [5, which extend through block [2 and are threaded into block I I, are rotated to bring the blocks together so that they will grip tightly the end of the journal. Carriage 4 which supports the right end of the roll consists 'of a carriage l6, that is mounted on rollers I! which move along tracks (not shown) that are sunk into the floor. This carriage also has on it a shaft [8 the end of which is received by the journal of the roll. This shaft is mounted in bearings l9 and is provided with a disc or plate 23 that serves to locate the carriage with respect to the end of the roll. Plate 23 has on it a chuck similar to that on plate 9.

During the heating and quenching process the roll is rotated, and to this end there is provided a gear reduction unit 2| and a motor 22 so arranged that the motor can rotate the shaft H! at the proper speed.

When the roll is lowered into position carriages 3 and 4 are moved to the right and left respectively, until the roll is engaged thereby. The

'chuck members are then tightened so that the roll will be held in position on the shafts 1 and 1 l8 respectively. Thereafter the carriages and the roll can be moved axially as a unit until the roll is properly lined up with respect to the furnace .in which it is to be heated, the furnace being described below. When the carriages and the roll .are properly positioned they are maintained in .place by means of a clamping device including ;ing provided in the carriage l6 and is threaded on its upper end, which threads are received by a hand wheel 21. Therefore when the carriages and roll are properly positioned, rotation of the hand wheel will cause the clamping member 25 to engage rail 26 to thereby lock the entire mechanism axially in the proper position.

When the roll has been located the furnace will be moved into a position surrounding the roll. The furnace is made of two substantially semicylindrical parts 28 and 29 that can be moved together to form a cylindrical furnace chamber or can be moved away from each other to permit access to the roll. The furnace sections are substantially identical, and a description of one applies equally as well to the other. Like parts on each furnace section are given similar reference characters. Each furnace section includes a rigid frame 3| made of structural steel members. Attached to these frame members is a metal backing sheet 32 which serves to back up and position a plurality of ceramic burner blocks 33 and such intermediate ceramic blocks as are necessary in order properly to locate the burner blocks with respect to each other. Each ceramic burner block forms part of a radiant type burner, such as is shown in Hess Patent No. 2,215,079, granted September 17, 1940, wherein the details of the burner and its manner of operation are described. It is sufficient for purposes of this description to say that the blocks are provided with cups 34 to-which a fuel mixture consisting of gas and air is supplied by a pipe 35 and a distributing tip 36 and in which this mixture is burned. It will be seen from Figure 1 of the drawing that each of the furnace sections has five rows of these burner blocks located around the upper part of its circumference and it will be seen from Figure 2 that the burner blocks of the various rows are staggered with respect to each other so that, in effect, the inner wall of the furnace chamber is a radiant panel, and because of the staggered relation of the burners there will be an even distribution of heat. The lower part of the furnace is formed of ceramic 31'which may be made of blocks or may be molded as a monolithic member. Around the edge of the furnace section and helping to hold the burners and the ceramic 31 in position is a metallic water cooled jacket or chamber 38. Each of the chambers 38 of the furnace sections is provided with an inlet 39 at its lower end and an outlet 4| at its upper end.

The lower portion of the framework of each furnace section consists of a horizontal platform section 42 which is mounted upon rollers or Wheels 43 that move along tracks 44 which are set in the floor of the place in which the furnace is located. Each of the furnace sections is provided underneath the platform portion 42 with a rack 45 that is engaged by a gear 46. The gear is rotated by a worm 4'! that is connected to the shaft of a motor 48. Therefore by suitably connecting the two motors 48 in the same circuit the furnace sections can be moved toward and away from each other in unison to either enclose the roll for heating purposes or to be opened so that the roll may be placed in position or quneched, as the case may be. As indicated above the motors 48 are preferably operated in unison, but if it is so desired they can be connected so that each furnace section is moved independently. This is purely a matter of preference on the part of the operator.

As noted above, heat is supplied to the furnace by burning an air-gas mixture in the cups 34 of the burner members 33. Gas is supplied to each distributor 36 by a pipe 35 extending through and beyond the burner block, each pipe having in it an individual valve 49. The pipes and supply valves of each horizontal row of burners are connected to manifolds 5| which also extend horizontally along the furnace sections. Because of the manner in which the burners areconnected through manifolds for each horizontal row of. burners and the individual valves for each burner, the burnersmay be so" adjusted that any desired heat pattern can be obtained. If, for example,

a long roll is being heated in the furnace all of the burners of any horizontal row' will be supplying heat to the furnace chamber. If, however,v a shorter roll is being heated it may well be that one or more of the end burners of each horizontal row will be cut off by closing the valves 49 leading to those burners. Thus, with the arrangement of valves and manifolds any desired number of burners may be used for heating rolls of any length.

As shown in Figure 4, each of the horizontal manifolds 5! is connected to a master manifold 52, which is in turn connected by a flexible connection 53 with supply pipe 54. This pipe is supplied through a control valve 55 that is in turn supplied by a mixing machine 56. Mixing machines of this type are well known in the art and may be of the type shown, for example, in Hess Patent No. 2243,704, granted May 27, 1941. These machines are supplied with air through a pipe 5'! and gas, such as ordinary city gas or natural gas, through a pipe 58. The machine mixes the gas and air in suitable proportions and supplies the mixture through the various pipes and manifolds to the burners in the furnace sections.

The temperature of the furnace is controlled in response to the surface temperature of the roll. The temperature is shown herein as being measured by a radiation pyrometer 5| that is attached to the outer end of an open-ended sighting tube 62 which projects through the lower portion of one of the furnace sections. The sighting tube is placed in this position so that the pyrometer will be responsive to the temperQture of the roll surface rather than to the temperature of one of the furnace walls where the heated cups 34 are located. Since rolls of. different diameters will be heated the sighting tube is preferably slidable in the furnace wall so that its open end may be adjusted to the proper distance from the surface of the roll being heated. Pyrometer Si is connected with a conventional potentiometric type of control instrument 63. As shown diagrammatically in Figure 4 of the drawing, this instrument is of the air control type in which air under a regulated pressure is supplied through a pipe 64 to the instrument which acts in a well known manner to adjust the output of the air and apply the adjusted pressure through a tube 65 to the diaphragm of control valve 55. The manner in which control systems of this type operate is well known and forms no part of the present invention. It is sufficient to point out herein that the pyrometer responds to the temperature of the roll surface and in response to the temperature thereof is used to adjust the air pressure applied to control valve 55 so that the air-gas mixture supplied to the burners will vary in accordance with the surface temperature 'of the roll. It is noted that the pyrometer may well be of the time temperature control type in which the temperature of the roll Will-be raised a predetermined number of de- 6 grees per hour'- if. it is desired. With this type of control the temperature of the roll will be raised in accordance witha predeterined schedule. so that the heating can take place ina predetermined manner that is best suited for the type of roll'bei-ng heat treated. Othercontrol systems accomplishing the same result could be used.

As noted above, it is highlyv desirable" to heat only the surface of the roll and a desired depth beneath the surface to the hardening temperature, and it is highly desirable to keep the journ'al portions of the roll at a temperature well below the hardening temperature. To this end the journals are protected by water cooled shields 56, one of which is: attached to each end of each furnace section. Each of the water cooled shields takes the form of a hollow semi-cylindrical member that is provided with a water inlet 61 on its lower portion and an outlet 68' on its upper portion. Bafiles may be provided in the interior of the shields in order to insure proper circulation of the water if it is so desired. The shields can be fastened to the ends of the furnace sections in any desired manner, but they are shown herein as being provided with keys 59 that are received by suitable hey ways formed in the end portions of the furnace. In any event provisions must be made to adjust the shields inwardly and outwardly with respect to the furnace so that they can be positioned in such a manner that the journal portions of the rolls of different lengths are protected from the direct heat of the radiant walls of the furnace. According to the present disclosure, the shields, with their keys may be moved to the right or to'the left in Figure 2 of the drawing depending upon the length of the roll and the amount of the journal that is located within the furnace proper.

The shields will protect the journal portions of the roll from the direct radiation produced by the furnace walls and cool them to prevent raising the temperature of the journals above the hardening temperature. As noted above, if a short roll is being heated, the end burners of the furnace will not be operating, and this taken in connection with the shields insures that the journal portions will not be overheated.

After the roll has been heated to hardening temperature it 'must be quenched. With the apparatus herein, upon completion of the heating cycle the-furnace sections are moved outwardly and a quench device is lowered over the roll. Referring to Figures 1 and 4 it will be seen that the quench device comprises a hollow U-shaped body H that is of a length equal to the longest roll which will be heated and of a width sufficient for it to be placed over the largest diameter roll to be heated. This body is provided on its inner surface with a plurality of nozzles 12 through which the quenching medium, which is usually water, may be sprayed against the surface of the roll. Water is supplied to the body 1' I through a supply pipe 13.

The U-shaped body 'H' is suspended in position above the roll by means of supports 15 that are attached to the body through rings 14 projecting from its outer surface. As shown diagrammatically in Figure 4 of the drawing, a rope 16' is attached to the supports and passes over a pair of pulleys l! to' a drum l8. Thisdrum is mounted in any suitable stand or support 19 and may be rotated by a handle 8!. A ratchet 82 is fastened to the drum shaft and is engaged by a pawl 83 to prevent rotation of the drum and therefore lowering of the body H until after the heating has taken place. It will be understood, of course that the means of raising and lowering the body H is purely diagrammatic. Power operated'means may be used to raise and lower the quenching body 1| if it is so desired.

, The operation of the system should be apparent from the above description. A short r-' sum, however, will be made at this point. A roll to be heat treated is moved into position between the roll supports 3 and 4 and lowered until'it is in axial alignment with the shafts 1 and I8 respectively of the supports. The supports are then moved into engagement with the ends of the journals of the roll and the entire unit is located in position in axial alignment with the furnace. Thereafter the furnace sections are moved together to form a cylindrical furnace around the surface I of the roll with the journals projecting through the openings in the ends thereof. Shields 66 are adjusted axially with respect to the roll so that they protect the journals from the heat. Motor 22 is then started to rotate the rolls at a speed of 3 or 4 revolutions per minute during the time that the heating operation is taking place. The furnace is then started and heat is supplied to the surface of the roll in accordance with the temperature setting of the pyrometer. This heating continues until the surface of the roll has been brought up to temperature and the heat has penetrated to a desired depth. Normally rolls of this type will be brought up to a surface temperature of 1760 F., and the temperature may be raised at the rate of 10 F. per minute. After the proper roll surface temperature has been reached, the furnace temperature will be lowered so heat penetration of the roll will take place without overheating the surface. During the heating process the shielding of the journals will prevent them from rising above 1100" E, which is well below the critical hardening temperature. After the roll has been heated and the heat has penetrated to the desired depth, the furnace is opened, and, while the roll is still rotating, the quenching device is lowered to a position surrounding the roll. Water or other quenching medium, as the case may be, is supplied through pipe 13 and will be sprayed through nozzles 12 to the surface of the roll. During the time that the quenching is taking place, it is preferable that the speed of the rotation of the roll be increased to 10 or 11 revolution per minute. This insures an even quenching around the surface of the roll. Since the journal portions of the roll have not been heated above the critical hardening temperature no care must be exercised in preventing the water from being sprayed upon the journal portions as is necessary with conventional heating methods. After the roll has been thoroughly quenched, which will take approximately 15 minutes, the quenching device can be raised to its idling position and the supply of water turned off. It is noted that a sump and drain 84 is provided beneath the furnace so that the water which is used for quenching purposes can be drained away. The entire operation of heatin and quenching can take place within a time of 3 or 3 hours at a maximum, as compared with to hours with conventional methods and with less scale and less danger of damaging the roll. Immediately after a single roll has been heated and quenched to harden its surface this roll can be taken to .a place in which a succeeding operation on its surface is to be performed, and the new. roll "may be moved into position for the 8 heating and quenching operations to be per formed upon it.

When the roll is quenched the outer surface first contracts while the center is still warm. Contraction of the outer surface produces tremendous stresses in the roll. One of the advantages of heating rolls by the present method is that heat is applied from the surface only until the desired heat penetration is obtained so that the center of the roll does not become highly heated and therefore the stresses induced in the roll by quenching are considerably less than those produced in the rolls heated by conventional methods. In some cases it may be desirable to supply a cooling medium to the center of the roll while the heating is taking place in order to lower even further the temperature of the interior of the roll so-that these stresses producedduring quenching will be further reduced. Such cooling of the center of the roll may be easily accomplished by the present apparatus by forcing a liquid cooling medium or air through the center of the roll during the heatingcycle. It is for this reason that shafts l and it upon which the roll journals are mounted are shown as having openings through the center thereof. If the cooling medium, either liquid or air, is to be forced through the roll it may be supplied through shaft 7 to the center of the roll, and out through the opening provided in shaft l8. It is noted that the opening in the latter shaft terminates above the support 16 upon which this shaft is mounted. Therefore, the cooling medium can be exhausted to the atmosphere or to a suitable reservoir that is formed in this support. Whether liquid or air is used, the cooling of the center ofthe roll while the surface is being heated tends to reduce the temperature of the interior of the roll and therefore reduce the stresses that are induced in the I roll during a quenching process. Whether or not such cooling is used will depend upon the composition of the roll, its size and the depth to which the roll is to be heated for hardening purposes.

While in accordance with the provisions of the statutes, We have illustrated and descflbed the best form of embodiment of our invention now known to us, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit and scope of our inven,- tion, as set forth in the appended claims, and that in some cases certain features of our invention may be used to advantage without a corresponding use of other features.

What is claimed is:

1. Apparatus for hardening a roll having a cylindrical portion and a journal portion projecting from each end of said cylindrical portion including a furnace comprising a pair of complementary semi-cylindrical portions forming a cylindrical chamber having a restricted opening in each end thereof, the cylindrical portion of the roll being received in said chamber with the journal portions projecting through the openings, a burner mounted in each of said portions, means through which fuel is supplied to said burners to heat the said chamber, separate means to mount each of said complementary portions for linear movement toward and from each other at right angles to the axis of the chamber whereby the portions of said furnace may be separated to receive said roll and closed while the same is being heated, horizontally disposed means located outside of said furnace upon which the journal portions of the roll are individually supported, means to rotate said supporting means, and means to mount said supporting means for movement toward and from said journal portions whereby a roll can be placed between them and adjusted thereby.

2. Apparatus for hardening the surface of a roll having a cylindrical portion the surface of which is to be hardened, anda journal portion projecting from each end of said cylindrical portion comprising in combination means forming a substantially cylindrical furnace chamber with openings in each end, said cylindrical portion being received in said chamber with the journal portions projecting through said openings, heat shielding members carried by said means and surrounding said journal portions and extending through said openings into said chamber to protect said journal portions from the heat in said chamber, and means for mounting said shielding members for sliding movement in said openings whereby a larger or smaller length of said journal portions may be protected.

3. In apparatus for heating a cylindrical roll having journals extending from each end thereof, means to support said roll for rotation by said journals, a substantially cylindrical furnace to surround the cylindrical portion of said roll with the journals projecting through openings formed in the ends thereof, said furnace being formed of a pair of sections separated on a plane extending diametrically through said roll, a carriage upon which each of said sections is mounted, means to guide said carriages for movement toward and from said r011, means to move said carriages from a position in which said sections surround said roll to a position away from said roll, and means to move said supporting means in a direction axially of said roll whereby said roll may be centered in said furnace.

FREDERIC O. HESS.

JAMES KNIVETON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,711,835 Davis May 7, 1929 1,783,764 Adams Dec. 2, 1930 1,987,752 Salzman Jan. 15, 1935 2,015,699 Trainer et a1. Oct. 1, 1935 2,044,334 Ferree June 6, 1936 2,089,829 Ferree Aug. 10, 1937 2,275,402 Crowe Mar. 3, 1942 2,290,031 Brooke July 14, 1942 2,354,267 Lytle et al July 25, 1944 2,365,183 Forsberg Dec. 19, 1944

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