US2994328A

US2994328A - Rod patenting

Info

Publication number: US2994328A
Application number: US599187A
Authority: US
Inventors: Lewis Dartrey
Original assignee: Morgan Construction Co
Current assignee: Siemens Industry Inc
Priority date: 1956-07-20
Filing date: 1956-07-20
Publication date: 1961-08-01
Anticipated expiration: 1978-08-01
Also published as: BE559389A; FR1179609A; GB843619A

Description

D. LEWIS ROD PATENTING Aug. 1, n1961 4 Sheets-Sheet 1 Filed July 20, 1956 ZDF-bepm 02:00u

MOFO

4 Sheets-Sheet 2 Ag- 15 1951 A D. LEWIS Ron PATENTING Filed July 2o, 195e Aug. 1, 1961 D. LEWIS Ron PATENTING Filed July 20, 1956 FIGB.

4 Sheets-Sheet 5 RADIATION RADIATION OMETER RADIATION PYRoME-rea TACHOMETER PYROMETER TACH PYRcMI-:TER

Aug. l, 1961 :n. LEWls ROD PATENTING Filed July 2o, 195e 4 Sheets-Sheet 4 M 7/ 2 4./ HRL no l G 8l 4| DL I EA F. mw WR WTV 6 .l MA 5m TAR l L L R ORE 8 D. :VLE EM MNT .M ER W OM A R R D O nO 2 AO w Il* V ,3 e C O 8 n 5 6 5 9]! 9,1 L 4l W. rR G L DL E E .R l lv.. IO O 4- w MMR 9 L EE F .O MEE D. VR VM PT M E E OA A R R W laan NW nited States Patent 2,994,328 ROD PATENTING Darn-ey Lewis, Trenton, NJ., assignor, by mesne assignments, to Morgan Construction Company, Worcester, Mass., a corporation of Massachusetts Filed July 20, 1956, Ser. No. 599,187 22 Claims. (Cl. 134-57) The present invention relates to the hot rolling and heat treating of carbon steel rods to facilitate their being drawn into wire.

In the .production of steel wire it is customary to reduce the steel ingots by hot rolling rst to billets and then to rods of the desired size, such as SAG" or 378" in diameter. The rolled rods are then heat treated as a separate operation generally known as patenting This is a heat treatment which produces a metallurgical structure in the rod that makes it especially suitable for wire drawing. Such patenting has frequently involved passing the rod very slowly through a furnace in which it is reheated to a temperature of about 1550 to l850 F. The rod as it emerges from the furnace is allowed either to cool naturally in the air, which is known as air patenting, or to be quenched in a bath of molten lead, usually within the temperature range 900 to l300 F. Most of the steel rods subjected to this treatment are of a plain carbon steel composition in which the carbon content ranges usually from about 0.20 to 0.95%. Rods of such composition as hot rolled contain a Very coarse sructure of pearlite, which is of irregular formation and makes the rods unsuitable for cold wire drawing except to a very limited extent. The patenting operation irnproves this structure by first getting the carbon back into solid solution in the iron and then allowing the carbon to come back out of solution in the form of very line plates of iron carbide (cementite) closely spaced. In fact, the pearlitic structure thus obtained is frequently so fine that it cannot readily be resolved under the microscope even at 1000 magniiications. Such a structure has much higher strength and is suitable for cold drawing through six or more successive dies until the total reduction of area is 90% or more of the original cross-sectional area.

In the co-pending United States patent application of lohn H. Corson et al., Serial No. 190,954, filed October 19, 1950, now Patent No. 2,756,169, there is set forth a method of heat treating hot rolled steel rods in which the hot rolling and patenting processes are combined to avoid the necessity for reheating the rods and the necessity for `all the separate handling operations necessarily involved in the foregoing procedure. The present invention is concerned with a process of the type set forth in said Corson et al. application. Finishing temperatures in a hot rolling mill are frequently of the order of l800 F., and in order to develop a metallurgical structure in this rod similar to that produced lby customary patent ing operations it is necessary to cool the rod rapidly and uniformly from the finishing temperature to a temperature within the range of about 900 to 1300 F. and then hold the rod within that range -for a period of 10 seconds or more while the carbon comes out of solution. If the rod is not cooled suiiiciently, the pearlitic structure will be too coarse, especially in the center of the rod. If the rod is cooled too much, the center of the rod may be of the proper ne pearlitic structure but the surface will be acicular or Bainitic in structure. In fact, if the cooling is too great, definite hardening may be produced with the formation of sorbite, martensite, or similar structures, which greatly impair the ability of the rods to be drawn.

In order to maximize the benets to be secured from a patenting operation of the type indicated, it is desirable Patented Aug. 1, 1961 rice that the cooling of the rod be carefully controlled with regard to the temperature of the rod from point to point, and also with regard to differences in temperature between one rod and the next. For example, it frequently occurs that the iinal portion of a rod has a higher term perature than those portions preceding the final portion. Usually the billets which are to be rolled into rod are heated in a furnace having a sloping hearth down which the rods are pushed in a direction at right angles to their length. The `furnace is heated by multiple burners located in the wall of the furnace towards which the billets are moving. The temperature of the billets will vary along their length depending upon burner adjustment. lt is common practice to heat the ends of the billets which will be rolled last to a higher temperature as this helps in controlling overiills in the last end of the rod.

lt is thus a principal object of the invention to provide, in a patenting operation, means for maintaining substantially constant the rod tempertaure at a particular early point in the patentin-g operation, despite the variations in temperature from point to point in the rod passing such early point of the patenting operation.

Another object of the invention has been to provide means for controlling the cooling water or other liquid pressure in the cooling system in accordance with variations in temperature frorn rod to rod and in accordance with variations in temperature along the length of any particlular rod.

Another object of the invention has been to provide means for delaying control action on the water pressure control until the temperature indicating means exposed to a new rod has arrived at an indication corresponding to the temperature of the rod.

Still another object of the invention has been the provision of means for presetting the cooling water pressure prior to passage of a rod through the cooling system.

A further object of the invention has been to provide means for varying the cooling water pressure in a patenting operation in response to changes in rod speed.

A feature of the invention has been the provision of rod guide means larranged to guide the moving rod within the field of vision of an optical pyrometer and adapted to permit fins and other variations in rod diameter to pass without causing the rod to cobb-le.

Other and further objects, features and advantages of the invention will appear more fully from the following description.

In accordance with the invention, in -a patenting operation in which a rod to be cooled is passed through successive spaced liquid cooling stations, a uniform desired temperature is maintained throughout the length of a hot rolled rod by providing means for varying the cooling liquid pressure at a iirst cooling station in response to fluctuations of temperature along the rod as measured before the rod reaches the irst cooling station, and in ressponse to deviations from the desired temperature as measured after the rod passes the iirst cooling station.

The invention will now be described in greater detail with reference to the appended drawings, in which:

FIG. l is a schematic diagram of apparatus in accordance with the invention for heat treating steel rods `as they come from a conventional mill for the continuous hot rolling of such rods;

FIG. 2 is a sectional plan View of a rod guide in accordance with the invention;

FIG. 3 is a circuit diagram illustrating a portion of the control circuit -in accordance with the invention;

FIG. 4 is a circuit diagram illustrating another portion of the Icontrol circuit in accordance with the invention; and

FIG. 5 is a. circuit diagram illustrating another portion of the control circuit in accordance with the invention.

Referring now to the drawings, and more particularly to FIG. ll, steel Abillets may be heated to hot rolling temperature in a furnace (not shown) and rolled through a suitable hot rolling mill, which might be, for example, a conventional tandem-type hot rolling mill consisting of 20 roll stands. Roll stands 13-20 of such a mill are shown diagrammatically in FIG. l. The rod being rolled is designated by the reference numeral 12. After passing roll stand 14, the rod 12 is guided past a radiation pyrometer or other suitable temperature indicating device 21 and through a switch mechanism 22 onto a Alooping table 23. From the looping table 23 the rod 12 passes through finishing stand 25, which consists of roll stands 15-20. The switch 22 may be moved to direct the rod across a looping table-24 and through another finishing stand 26. The stand 26 consists of roll stands 1520. The path of the rod in this case is shown by the dashed line designated 12'. In general, the finishing stands 25 and 26 will be used alternately for rods being rolled from successive billets.

After leaving the finishing stand 25, the rod 12 is guided through a first cooling station 27, then through a second cooling station 28, then through a third cooling station 29, and then through a fourth cooling station 30. When the finishing stand 26 is used instead of the stand 25, the rod therefrom passes through a first cooling station 27', then through a second cooling station 28', then through a third cooling station 29', and then through a fourth cooling station 30'. The

cooling stations

27 and 27 may conveniently be provided with four cooling or quenching units each, the

stations

28 and 28 with two each, and the

stations

29, 29', 30 and 30 with one each. The cooling medium may -be water or other suitable quenching liquid. Rod from the fourth cooling station 30 is coiled on a takeup reel 34, while rod from the fourth cooling station 30' is coiled on a takeup reel 35. The

cooling stations

27 and 28 are separated by a length of guide pipe 36, the cooling stations 27 and 28' are separated by a length of guide pipe 37, the

cooling stations

28 and 29 are separated by a length of guide pipe 38, the cooling stations 28' and 29' are separated by a length of guide pipe 39, the

cooling stations

29 and 30 are separated by a length of guide pipe 40, and the

cooling stations

29 and 30 are separated by a length of guide pipe 41. The guide pipes 36-41 provide time for the temperature at the center of the rod and 4at the outside of the rod to equalize after each water cooling. This equalization is necessary because each Water cooling stand cools the surface of the rod more than it does the center. Although omitted from the drawings for simplicity, a suitable Water separating or draining unit should be provided between each Water cooling station and its succeeding guide pipe. The cooling stations land the water separating units may, if desired, be constructed in accordance with the teachings of the aforementioned Corson et al. application. Between the end of the equalizing section or guide pipe 40 and the fourth cooling station 30, the rod 12 passes a radiation pyrometer or other suitable temperature indicating device 42. Similarly, between the end of the equalizing section or guide pipe 41 and the cooling station 30', the rod 12' passes a radiation pyrometer or other suitable temperature indicating device 43. The radiation pyrometers 42 and 43 should be spaced from the preceding respective cooling stations by a distance sufiicient to allow the interior and surface of the rod to equalize substantially in temperature, a time of travel preferably not less than 0.3 second.

Water flow to the first cooling station 27 is controlled by a motor operated water valve 44. Water flow to the rst cooling station 27 is controlled by a motor operated Water valve 45. Water ow to the second, third and fourth cooling stations may be controlled by manually adjustable valves designated 45.

The finishing stands 25 and 26 may be driven by

gear boxes

46 and 47, respectively. The gear boxes 46 47 are in turn operated by

Ithe motors

48 and 49, respectively. The motor 48 is furnished with an electric tachometer 50, while the motor 49 is provided with an electric tachometer 5&1.

The rod passing

radiation pyrometers

21, 42 and 43 should not `be permitted to move out of the field of focus of the pyrometer. For example, a pyrometer having a field of focus 1A in diameter may be used with a rod 3&6" in diameter, which will require the rod to be guided within i/g". In order to achieve this close tolerance in rod path a guide may advantageously be used. Hot rolled rod may have overfills, fins or other dimensional defects, and the guide must -allow such defects to pass through without causing a cobble. In accordance with one aspect of the invention, the rod path past the radiation pyrometers may be controlled within a close tolerance by means of the offset guide arrangement illustrated in FIG. 2. It will be understood that -a rod guide ofthe type illustrated in FIG. 2, while not shown in FIG. l, may be used for each of the

radiation pyrometers

21, 42 and 43.

Referring now to FIG. 2, the rod guide illustrated comprises four offset

guide elements

71, 72, 73 and 74. As few as two guide elements can be used if desired. Each guide element comprises a short, hollow, rectangular block 70 within which is carried a rectangular guide block 70A having an internal diameter decreasing (wall thickness increasing) toward the left in FIG. 2, which is the direction of travel of the rod through the rod guide. The guide blocks are held in desired offset posi-V tions within the blocks 70 by means of screws 75 acting against their peripheral surfaces. The guide blocks are xed vertically but may be moved horizontally by adjustment of screws 75. The screws 75 are threaded through suitable holes provided in the walls of the blocks 70. Preferably, three or four screws 75 Will be used for each guide element. The center of each guide block 70A constitutes a h'ole v'76 through which the rod 12 may pass. The guide blocks are offset from the center line of the guide elements by suitable adjustment of the screws 75. Thus in FIG. 2 the upper portion of the element 74 is in contact with the rod 12. For the element 73, the lower portion of the block 70A contacts the nod 12. For the element 72, the upper portion of the block 70A contacts the rod 12. For the element 71, the lower portion of the block 70A contacts the rod 12. The minimum diameter of holes 76 is considerably larger than the rod 12 (preferably at least three times the rod diameter) and is large enough to pass any variations in rod dimensions. The guide elements 71-74 are spaced from each other sufficiently to permit dimensional defects to snake through. 'I'his spacing is preferably at least five rod diameters. The rod 12 may enter the rod guide through a pipe 77 and may leave the rod guide through a pipe 78. The field of view of the optical pyrometer associated with the rod guide is designated 79. It will be lobserved that the guide blocks of the various guide elements are offset so as to maintain the rod 12 Within the field of focus of the optical pyrometer.4 Although not shown in FIG. 1, a rod guide of the type shown in FIG. 2 may be provided for each of the radiation pyrometers.

Referring now to FIG. 3, there are shown

radiation pyromcters

21, 42 and 43 and tachometers S0 and S1 of FIG. 1. Each radiation pyrometer produces a D.C. volt-4 age which increases with rod temperature. The radiation pyrometers 21, l42 and 43 are connected to recording controllers 52, S3 and 54, respectively. These record ing controllers each produce a D.C. output voltage pro?I portional to the deviation of the indicated temperature from the control temperature. For this purpose each` controller is provided with a temperature or speed indieating pointer and with a manually operated controlA pointer which may be set at the desired control temperature. The magnitude of the controller output-voltages is manually adjustable by means of

potentiometers

61 and 62. These output voltages also change in polarity according to whether the indicated temperature is above or below the control temperature. Ihe recording controllers 52-54 may be electronically operating machines of the type described in `Callender et al. Patent 2,175,985, issued October 10, 1939, and in Davis Patent 2,666,170, issued January l2, 1954.

As shown in FIG. 3, tachometer 50 is connected to a recorder 55 and to a potentiometer 61, the 'output voltage of which is designated V1. Tachometer 51 is similarly connected to a recorder 56 and to a potentiometer 62, whose output voltage is designated V2. Radiation pyrometer 21 is connected to recording controller 52, which produces two output voltages designated V3 and V4. Radiation pyrometer 42 is connected to recording controller 53, which produces an output voltage V7. Radiation pyrometer 43 is connected to recording controller 54, which produces an output voltage V8. The voltage V1, which is a portion of the output voltage of tachometer 50, as determined by the setting of potentiometer 61, is a D.C. voltage which increases with the speed fof motor 48. Similarly, the voltage V2 is a portion of the output Voltage of tachometer 51, as determined by the setting of potentiometer 62, and increases with the speed of motor 49. The voltages V3 and V4 are D.C. voltages whose magnitude and polarity vary with the deviation in the temperature indicated by radiation pyrometer 21 from a desired control temperature set into recording controller 52. Similarly, the voltages V7 and V8 vary in magnitude and polarity with deviations in the temperature indications of

radiation pyrometers

42 and 43, respectively, from the desired control temperatures as set into the recording controllers 53 and 54, respectively.

The voltages V1 and V3 are connected in series with each other and the combined voltage is applied to series connected capacitor 63 and resistor 65. Similarly, voltages V2 and V4 are connected in series with each other and the combined voltage is applied to series connected capacitor 64 and resistor 66. The direction of connection of voltage V1 with voltage V3 and of voltage V2 with voltage V4 is chosen so that increase in rod temperature or increase in rolling speed changes the voltages in the same direction. For example, an increase in nod temperature above the preset control temperature may cause the voltage V3 to increase from zero to some positive value. An increase in rolling speed of the rod will cause the voltage V1 to increase in a positive sense so that increase in speed, increase in temperature, or increase in both speed and temperature, will result in a higher net positive voltage applied to series connected capacito-r 63 and resistor 65. Capacitor 63 and resistor 65 preferably have a fairly large time constant, for example, one minute. Capacitor 64 and resistor 66 should have a similar time constant. The time constant of the RC circuits is related to the time required for a billet to be rolled into rod. For example, when the time for rolling one billet is one minute, the time constant should be at least one-half minute, and preferably one minute or more. When a local variation in temperature of rod is sensed by radiation pyrometer 21, the voltage V3 or the Voltage V4 will change. Similarly, a change in speed will cause a variation in voltage V1 or V2. Such a change will cause current to ow through

resistor

65 or 66, as the case may be, in order to change the charge on

capacitor

63 or 64. lf the time constant selected is one minute, at the end of this time, assuming the change persists so long, capacitor 63 or capacitor '64, as the case may be, will have received approximately 64% of its new charge. However, once the capacitor is fully charged, no current will ow in

resistor

65 or 66, even if the change still persists. Thus, the voltages appearing across

resistors

65 and 66, designated V10 and V11, respectively, will not be maintained and will gradually drop off toward zero. Voltages V10 and V11 only refleet changes in temperature or speed, but, because of the presence'

lof capacitors

63 and 64, do not reect the absolute level of either. Normally open relay contacts F-l and normally closed relay contacts A-2 are connected in parallel with resistor 65 and are used to switch voltage V10 on and off in a manner to be described hereinafter. Normally open relay contacts F-2 and normally closed relay contacts B-2 are each connected in parallel with resistor 66 for switching voltage V11 on and ot. The output voltage of recording controller 53, i.e., voltage V7, may be switched on or off by normally open relay contacts G-l and normally closed relay contacts A-3. The resulting output voltage is designated V9. Similarly, voltage V8 may be switched on or oi by normally open contacts G-Z or normally closed contacts B-3, the resulting output voltage being designated V12.

Output voltages V9 and V10 are used as input voltages in the circuit of FIG. 4 and their end eect in this circuit is to control the movement of Water valve 44. Similarly, voltages V11 and V12 are used as input voltages in FIG. 4 and their end result is to control the operation of Water valve 45.

In the upper part of FIG. 4 there is shown a bridge network comprising resistors A, 80B, 80C and 80D.

Resistors

80A and 80B are interconnected through a potentiometer `80, the slider 81 of which constitutes one terminal of the bridge. The opposite terminal of the bridge is formed by the junction of

resistors

80C and 80D. The other two terminals of the bridge are formed by the junction of

resistors

80A and 80C and by the junction of

resistors

80B and 80D, respectively. IA source of constant D.C. voltage V15 is connected to these latter two bridge terminals. The slider 81 is arranged to be driven by a reversible D.C. electric motor 82M, which motor also operates water valve 44. One terminal of voltage V10 is connected to the slider 81. The other terminal of voltage V10 and one terminal of voltage V9 are connected to one end of a potentiometer 82 and also to slider l85 of potentiometer 82 through normally open relay contacts A-4 and H-l. Voltages V9 and V10 are connected in additive relationship. The other end of potentiometer 82 is connected to the junction of

resistors

80C and 80D through a series connection of a resistor 83 and a capacitor 84. The voltage across series connected potentiometer 82 and resistor S3 is designated V17. The free terminal of voltage V9 is connected to one input terminal of a D.C. amplifier S6. The junction of resistor 83 and capacitor 84 is connected to the other input terminal of amplifier `86. The input voltage to amplifier 8'6 is designated V13. The output of ampliiier 86 Vis applied to a pair of reversing relays 87 which control reversible electric motor 82M. Thus, an output of amplifier 86 having a positive polarity will cause motor `82M to rotate in one direction, while an output having the opposite polarity will cause motor 82M to rotate in the other direction.

The amplier input voltage V13 may be considered the bridge network output voltage. The connections are such that presence of a Voltage V13 will cause electric motor 82M to rotate slider 81 in a direction or sense to reduce voltage V13 substantially to zero by balancing the bridge. The bridge is thus a self-balancing one, Water valve 44, which controls the water supplied to the rst cooling station 27, is also operated by the motor 82M. The water supplied to the first cooling station 27 is thus increased or decreased as the motor 82M is rotated in one direction or the other.

If the temperature of the rod 12 at the position of radiation pyrometer 42 diifers from the desired control temperature, a vloltage will exist at V9. The magnitude of this voltage will be dependent upon the difference between the rod temperature and the control temperature, and its polarity will depend upon whether the actual temperature is above or below the control temperature. 'Ihe existence of a voltage V9 Will produce a voltage at V13 which will cause the bridge to rebalance by moving slider 81 and causing a change in voltage V17 which will exactly balance V9 and thus reduce voltage V13 to zero. However, voltage V17 will gradually decrease toward zero as lcapacitor 84 becomes charged. If the rod temperature is still incorrect and voltage V9 persists, the bridge lwill rebalance again with another movement of slider 81. Movement of slider 81 will continue until a position thereof is found at which the water ow controlled by the valve 44 causes the rod temperature at pyrometer 42 to coincide with the desired control temperature at that point. At this time the voltages V9 and V17 will both approach zero. The rate of response of the reset action which causes the successive changes in the position of slider 81 will depend upon the time constant of the circuit including potentiometer 82, resistor 83 and Vcapacitor 8'4. This time constant may be changed manually by moving the slider 85 to vary the eiective resistance of potentiometer 82.

If the temperature of rod 12 varies at the position of radiation pyrometer 21 or if the rod speed varies as determined by tachometer 50, a voltage will be produced at V10 which will produce a voltage at V13, thereby causing a rebalancing of the bridge by a change in voltage at the slider 81, which will exactly balance V10. In the case of voltage V10, reset action is not involved since voltage V17 will not change except momentarily, and thus no change will occur in the voltage across capacitor 84. The eiect of change in position of slider 81 tobalance V10 is to increase or decrease the water ow to the iirst cooling stations 27 and 27' according to changes in temperature along the length of the rod at .pyrometer location 21 and according to changes in speed.

The magnitude of the increase or decrease in water ow for any given change in temperature may be altered by manual adjustment of potentiometers 61 or 62', and for any given change in speed by

potentiometers

61 and 62. In operation these potentiometers are adjusted so that variations in temperature and speed are compensated for by variation in water ilow at the rst cooling stations 27 and 27' so that the rod leaving these cooling stations is substantially unchanging in temperature along its length.

The eect of change in position of slider 81 to balance V9 is to increase or decrease water flow in the tirst cooling stations-27 or 27 according to the deviation of temperature of, the rod at pyrometer location 42 from the control temperature at which the controller has been set. Thus it is the function of

controllers

52, 55 and 56 to reduce Variations of temperature along the length of the rod and it is the function of controllers 53 and 54 to maintain the rod temperature at the right magnitude.

In the lower part of FIG. 4, there is shown another bridge circuit identical with the one just described. This bridge circuit, which includes a potentiometer 88 and

resistors

88A, 88B, 88C and 88D, is intended to control Water valve 45 and thus the cooling water supplied to cooling station 27' which acts on the rod 12'. Potentiometer 88 is provided with a slider 89 corresponding to the slider 81. A potentiometer 90, a resistor 91 and a capacitor 92 rcorrespond to the potentiometer 82, resistor 83 and capacitor 84, respectively. Slider 93 and normally open relay contacts H-Z and B-4 correspond to slider 85, con- 'tacts H-l and contacts A-4, respectively. The voltage V11 and voltage V12 are applied to this circuit and operate in the same way as the voltage V9 and the voltage V10, respectively, applied to the upper bridge circuit. A D C. amplifier 94, a set of reversing relays 95, and a reversible D.C. electric motor 96 correspond to the

elements

86, 87 and 82M, respectively, previously described. The bridge output or amplifier input voltage is designated V14, while the voltage lacross potentiometer 90 and resistor 91 is designated V18. Variations in temperature or speed of the rod 12 will cause changes in voltages V11 and V12, which in turn will cause seliJbalancing of the bridge circuit in the lower half of FIG. 4 with a result- -8 ing change in the setting of water valve 45, in a sense to cause the rod temperature to approach the desired control temperature at radiation pyrometer 43.

The control circuit which has been described in connection with FIGS. 3 and 4 would be capable of maintaining a uniform temperature in a continuously running rod. However, the rod in this case is rolled from individual billets so that at the location of radiation pyrometer 21 there will lbe intervals between successive rods during which the pyrometer will indicate a much lower temperature. The same thing is true at the locations of

radiation pyrometers

42 and 43, except that in this case the intervals of low temperature indication will be extended because the rods are switched alternately to the left-hand and right-hand sides of the mill. The control as so far described would act to close the motor operated water valves during the time interval between rods. Consequently, the water pressure would be too low for the start` ing end of each subsequent rod and therefore each rod would be too hot at the start. In accordance with one aspect of the invention, the proper amount of water pressure at the start of each rod is provided.

Referring now to FIG. 5, there are shown two conductors 97 and 98, to which are applied a suitable supply voltage V. A number of series circuits are connected across conductors 97 and 98. One of these circuits includes the coil of a relay A and normally open contacts 53-1. Normally open contacts 53-1 are located in recording controller 53 and are arranged to be closed at a predetermined temperature below the control temperature set into the controller 53. The temperature at which the contacts 53-1 close is usually set at about 100 F. below the control temperature. Thus, when a rod enters the location of radiation pyrometer 42, contacts 534 close when the indicated temperature reaches a temperature of about 100 F. below the control temperature. Closing of contacts 53-1 will result in energization of relay A.

Another circuit comprises the coil of a relay B and normally open contacts 54-1. The contacts 54-1 are located in recording controller 54 and are set to operate in the same way as contacts 53-1 when a rod approaches pyrometer 43.

Another circuit is formed by a timer clutch coil C in series with normally open contacts 52-1. Contacts 52-1 are located in recording controller 52 and are set to operate in the presence of a rod in the same way as contacts 53-1 and 54-1. A series circuit formed by timer motor MC and a normally closed switch MC-l is connected across the clutch `coil C. When contacts 52-1 close, which will occur when a rod reaches the zone of radiation pyrometer 21, so that the temperature indicated by this pyrometer will be about 100 F. below the control temperature, clutch roll C and motor coil MC of the timer will lboth be energized. At the end of a pre-set time, switch MC41 will be opened, stopping the motor MC. When contacts 52-1 open after the trailing end of a rod has passed radiation pyrometer 21, clutch coil C will be de-energized and the clutch will be released, thereby resetting the timer for another timing cycle.

Anothr circuit is formed by relay coil D and normally open contacts A-1. Still another circuit is formed by relay coil E and normally open contacts B-1. The junction of contacts A-1 and coil D and the junction of contacts B-l and coil E are connected by a conductor 97. A series circuit formed by a timer motor MD and a normally closed switch MD-1 is bridged between conductors 97' and 98. A similar circuit formed by timer motor ME and a normally closed switch ME-l is likewise connected 'between conductor 97' and conductor 98.

Three other series circuits are connected between conductors 97 and 98. A rst of these is formed by a relay coil F and a normally closed switch MC-Z. A secondis formed by relay coil G and a normally closed switch MD-2. A third is formed by a relay coil H and a normally closed switch ME-Z.

gestage When relay A or relay B is energized by the closing of contacts 53-1 or 54-1, contacts A-1 or B-1 will be closed, thereby connecting conductor 97' to conductor 97. This will result in the starting of timer motors MD and ME and the energization of their clutch coils D and E, respectively. At the end of a preset timing interval, switches MD-l and ME-ll will be opened, stopping timer motors MD and ME. Timer motors MC, MD and ME act to open normally closed switches IVIC-2, MD-Z and ME-2, respectively, at the same times that switches MC-l, MD-l and ME-l, respectively, are opened. Relay coils F, G and H are normally energized. When contacts 52-1 close, timer MC will be energized so that at a predetermined time later switch MC-Z Will open, deenergizing relay F. Similarly, when contacts 54-1 close, relay B will be energized, closing contacts B-l and energizing timer motors MD and ME, so that at predetermined times later switches MD-Z and ME-Z will open, de-energizing relays G and H. Relays G and H will be similarly de-energized upon the closing of contacts 53-1. Opening of contacts 52-1 and A-1 or B-1 will result in prompt re-energization of the coils F, G and H.

Referring again to FIGS. 3 and 4, as well as to FIG. 5, when relay coil A is energized, normally closed contacts A-2 and A-3 will be opened and normally open contacts A-4 will be closed. When relay B is energized, normally closed contacts B-2 and B-3 will be opened and normally open contacts B-4 will be closed. When relay F is energized, normally open contacts F41 and F-2 will be closed. When relay G is energized, normally open contacts G-1 and G-2 will be closed. When relay H is energized, normally open contacts H-l and H-Z will be closed. When the starting end of a rod enters the locations of

optical pyrometers

21, 42 or 43, control action by the recording controllers is delayed by appropriate setting of the timers until a steady temperature indication has been reached. For example, when the starting end of a rod approaches radiation pyrometer 21, so that the temperature thereof reaches about 100 F. below the control temperature, contacts 52-1 will be closed, energizing clutch coil C and timer motor MC. Until the time interval at which contacts MC-2 are to be opened has passed, relay F will remain energized, so that contacts F-l will be closed, eifectively shorting control voltage V10. Since contacts F-2 are likewise closed, control voltage V11 will also be shorted out. When the time interval for the timer MC has expired, contacts MC-2 will open, de-energizing relay F and opening contacts F-1 and PL2. However, control action is still prevented since voltages V and V11 will still be shorted out by normally closed contacts A2 and B2. Contacts A2 cannot open until relay A is energized by closing of contacts S3-1, which will occur when the starting end of a rod causes the indication produced by radiation pyrometer 42 to reach about 100 F. below the established control temperature for the recording controller 54. Voltage V9 is similarly shorted out by normally closed contacts A-3, which will not be opened until relay A is energized. Voltage V12 likewise is shorted out by normally closed contacts B-B, which will not be opened until relay B is energized. In other words, control action on motor operated water valve 44 can only take place a selected time interval after a rod has arrived at the location of radiation pyrometer 42. Similarly, control action on motor operated water valve 45 can only take place a selected time interval after a rod has arrived at the location of radiation pyrometer 43. This selected time interval is determined by the response time of the recording controllers. The control action which then occurs is such as to maintain the rod temperatures at the location of

radiation pyrometer

42 or 43 equal to the desired control temperatures at these points and to adjust the water ilow to the incoming rod temperature level.

When the trailing end of a rod leaves the location of radiation pyrometer 42, motor operated water valve 44 should be moved to the proper opening to cool the starting end of the next rod to the control temperature. Similarly, when the trailing end of a rod leaves the locatio of radiation pyrometer 43, motor operated water valve 45 should be moved to the proper opening to cool the starting end of the next rod to the control temperature. These desired results are also achieved by the control circuit of the invention. When the starting end of a rod enters the location of optical pyrometer 21, recording controller 52 shows the temperature increase, and when the temperature corresponding to the setting of contacts S12-1 is reached, contacts 52-1 are closed. Closing of contacts 5'2-1 energizes clutch coil C and timer motor MC. The timer MC is adjusted so that before it times out the recording controller reaches the temperature indication corresponding to the temperature of the rod. When the timer MC times out, switch MC-2 opens and de-energizes relay coil F. This in turn opens switch F-l, which has been short circuiting output voltage V10 from recording controller `52. Assuming that the rod switch 22 is set for the rod to go down the side containing radiation pyrometer 42 and motor operated water valve 44, when the rod reaches pyrometer 42 the temperature indication of recording controller 53 will rise until, at the temperature setting for contacts 53-1, these contacts will close, thereby energizing relay coil A. Energization of relay A will open contacts A-2, which were also shorting the output voltage V10 from recording controller 52. In this way, voltage V10 is applied to the upper bridge circuit in FIG. 4 and starts controlling water valve 44. Had the switch 22 put the rod on the other side, where radiation pyrometer 43 is located, by a similar action contacts F-Z and B-2 would be opened and output Voltage V11 would start controlling water valve 45. The shorting of

resistors

65 and 66, which will occur from the shorting of voltages V10 and V11, respectively, will maintain full charge on

capacitors

63 and 64. Thus, control action from

tachometers

50 and 51 and radiation pyrometer 21 will only be due to changes occurring after the control becomes effective, and are not affected by the initial level of speed or temperature.

When the starting end of the rod enters the location of pyrometer 42, the associated recording controller 53 shows an increase in temperature which, when it arrives at a predetermined level, e.g., about 100 F. below the control temperature, closes contacts 53-1, thereby energizing relay A. This in turn closes contacts A-1 and operates clutch D and timer motor MD. The timer MD is adjusted to allow time for the recording controller `53 to reach a reading corresponding to the rod temperature before the timer times out. When the timer MD times out, switch MD-2 opens, de-energizing relay G, which in turn opens contacts G-1, which had been short circuiting output voltage V9. Contacts A-3, which had also been short circuiting voltage V9, have already been opened by the prior energization of relay coil Thus, output voltage V9 joins voltage V10 in controlling motor operated water valve 44. Had the rod been switched to the other side containing radiation pyrometer 43, contacts A-3 would not have opened, but, by a similar sequence, contacts G-2 and B-3 would have opened, enabling output voltage V12 to join voltage V11 in controlling motor valve 45.

As previously explained, reset action is involved in the valve control effected by voltages V9 and V12. The amount of reset action depends upon the value of resistance of

potentiometers

82 or 90. Reset is rapid when these resistances are low, giving a low time constant, and slow when they are high, giving a large time constant. Contacts A-4, H-1, B-4 and H-2 operate to change the reset action. Assuming that the rod is to go down the side containing radiation pyrometer 42, when contacts 53-1 are closed in recording controller 53 and relay coil A is energized, contacts A-4 will be closed. Normally open contacts H-1 will also be closed at this time, because normally closed switch ME-2 is closed, so that relay coil H will be energized. Thus, at the start of the rod slider V short circuits a part of potentiometer 82. By adjusting the position of slider 85, the increased speed f the reset action may bemade-as great as desired. Faster reset action will be maintained until relay H drops out, at which time contacts H-1 open. Relay H will drop out when switch ME-Z opens upon the timing out of timer ME. The time interval provided by timer ME was initiated by the energization of relay A and the closing of contacts A-1. The resulting increased resistance of potentiometer 82 will act to slow the reset action, By adjusting the timer ME, a higher reset rate may be obtained for the starting end of the rod and a slow reset rate for the balance of the rod. This arrangement will result in the proper pressure of cooling water for the start of each rod providing the rod temperatures do not change substantially between successive rods, which is generally true.

The setting of the motor operated water valve 44 at the start of the rod is determined by the voltage across capacitors 84, because before the start of the rod voltages V9, V and V17 are zero. Consequently, the voltage across capacitor S4 equals the voltage difference between the junction of resistors 80-C and 80-D and slider 81. The position of the slider 81 is determined by the position of motor operated water valve 44. Thus, when the rod runs out and voltages V9 and V10y are shorted out, the Water valve 44 will return to a position determined by the charge of capacitor 84. This charge Will determine the water pressure for the starting end of the next rod. When the next rod enters, if the temperature is incorrect, contacts A-4 and H-l, being closed, will cause reset action to bring the charge on capacitor 84 to a value determined by the average temperature of the rod during the period the timer ME leaves contacts H-l closed. After contacts H-1 open, the larger value of the entire potentiometer 82 prevents a significant change in the charge on capacitor 84 for the balance of the rod. Consequently, the water pressure at the start of each rod is determined by the water pressure required to hold previous rods at the control temperature for a period at the starting end determined by the setting of the timer ME. In this way, any tendency for the trailing end of a rod to have a higher temperature than the starting end of the rod will not cause increased water pressure for the starting end of the next rodl. However, action of voltage V10 will cause the trailing end of a rod to receive more cooling water than the starting end, if this is necessary. If conditions are such that the rod temperature is substantially uniformtrom end to end, it may be satisfactory to have reset action taking place over the full length of the rod. In this case contacts A-4, H-l, B-4 and H-2 and timer ME would not be required.

Sliders

85 and 93 would be connected directly to V10 and V11, respectively, in order to provide adjustable reset action which would be constant over the full length of the rod.

While the invention has been described in connection with a specic embodiment thereof and in a specic use, various modifications thereof will occur to those skilled in the art without departing from the spirit and scope of the invention, as set forth in the appended claims.

What is claimed is:

1. In apparatus for heat treating rapidly moving hot rolled rod including a plurality of liquid quenching means for cooling said rod, said liquid quenching means being arranged at spaced intervals along the path of travel of said rod and each developing a sufficiently high rate of heat abstraction from said rod that a substantial temperature difference exists at the exit from each quenching means between the center and outside of said rod, the combination comprising means for determining the temperature of said rod at a selected point in said path located at a substantial distance from the preceding quenching means suicient for the interior yand surface of the rod substantially to equalize in temperature, and means responsive to the dilerence between said determined temperature and a predetermined control tempera- 12 ture for increasing or decreasing the supply of said quenching liquid to at least one of said quenching means depending upon whether said determined temperature is higher or lower than said predetermined control ternperature to cause said determined temperature to coincide with said predetermined control temperature.

2. In apparatus for heat treating rapidly moving hot rolled rod including a plurality of liquid cooling stations arranged at spaced intervals along the path of travel of said rod and each developing `a suiliciently high rate of heat abstraction from said rod that a substantial temperature dilierence exists at the exit from each cooling station between the center and outside of said rod, the combination comprising a radiation pyrometer for determining the temperature of said rod at a selected point in said path located at a substantial distance from the preceding cooling station suicient for the interior and surface of the rod substantially to equalize in temperature, and means responsive to the dijerence between said determined temperature and a predetermined control temperature for increasing or decreasing the supply of said cooling liquid to one of said cooling stations preceding said selected point depending upon whether said determined temperature is higher or lower than said predetermined control temperature to cause said determined temperature to coincide with said predetermined control temperature.

3. In apparatus for heat treating rapidly moving hot rolled rod including a plurality of liquid cooling stations arranged at spaced intervals along the path of travel of said rod and each developing a sufliciently high rate of heat abstraction from said rod that a substantial temperature difference exists at the exit from each cooling station between the center and outside of said rod, the combination comprising la radiation pyrometer for determining the temperature of said rod at a selected point in said path located at a substantial distance from the preceding cooling station corresponding to the rod travel time of not less than about 0.3 second, and means responsive to the difference between said determined temperature and a predetermined control temperature for increasing or decreasing the supply of said cooling liquid to the rst one of said cooling stations depending upon whether said determined temperature is higher or lower than said predetermined control temperature to cause said determined temperature to coincide With said predetermined control temperature.

4. In apparatus for heat treating rapidly moving hot rolled steel rod including a plurality of liquid cooling stations arranged at spaced intervals along the path of travel of said rod and each developing a sufficiently high rate of heat abstraction 4from said rod that a substantial temperature diierence exists at the exit from each cooling station between the center and outside of said rod, the combination comprising means for determining the temperature of said rod at a selected point in said path located at a substantial distance from the preceding cooling station sufficient for the interior and surface of the rod substantially to equalize in temperature, means to produce a voltage whose magnitude is proportional to the diierence between said determined temperature and a predetermined control temperature and whose polarity is dependent on whether said determined temperature is higher or lower than said predetermined control temperature, and means responsive tothe magnitude and polarity of said voltage to increase or decrease the supply of cooling liquid to a selected cooling station preceding said selected point depending upon whether said determined temperature is higher or lower than said predetermined control temperature to cause said determined temperature to coincide with said predetermined control temperature.

5. In apparatus for heat treating rapidly moving hot rolled steel rod including a plurality of liquid cooling stations arranged at spaced intervals along the path of travel of said rod, the combination comprising means for determining the temperature of said rod at a selected point in said path located at a distance from the preceding cooling station sufficient for the interior and surface of the rod substantially to equalize in temperature, means to produce a voltage whose magnitude is proportional to the difference between said determined temperature and a predetermined control temperature and whose polarity is dependent on whether said determined temperature is higher or lower than said predetermined control temperature, means responsive to the magnitude and polarity of said voltage to increase or decrease the supply of cooling liquid to a selected cooling station preceding said selected point depending upon whether said determined temperature is higher or lower than said predetermined control temperature to cause said determined temperature to coincide with said predetermined control temperature, and means responsive to the magnitude and polarity of said Voltage for adjusting the supply of cooling liquid to said selected cooling station after a particular rod has been treated and prior to arrival of the succeeding rod to be treated.

6. In `apparatus for heat treating rapidly moving hot rolled steel rod including a plurality of liquid cooling stations arranged at spaced intervals along the path of travel of said rod, the combination comprising means for determining the temperature of said rod at a selected point in said path located at a distance from the preceding cooling station suicient for the interior and surface of the rod substantially to equalize in temperature, means to produce a voltage whose magnitude is proportional to the diierence between said determined temperature and a predetermined control temperature and whose polarity is dependent on whether said determined temperature is higher or lower than said predetermined control temperature, means responsive to the magnitude and polarity of said voltage to increase or decrease the supply of cooling liquid to a selected cooling station preceding said selected point depending upon whether said determined temperature is higher or lower than said predetermined control temperature to cause said determined temperature to coincide with said predetermined control temperature, and means responsive to the magnitude and polarity of said voltage during a predetermined interval corresponding to travel of a first portion of a rod past said selected point for adjusting the supply of cooling liquid to said selected cooling station after a particular rod has been treated and prior to arrival of the succeeding rod to be treated.

7. In apparatus for heat treating rapidly moving hot rolled steel rod including a plurality of liquid cooling stations arranged at spaced intervals along the path of travel of said rod, the combination comprising means for determining the temperature of said rod at a selected point in said path located at a distance from the preceding cooling station suflicient for the interior and surface of the rod substantially to equalize in temperature, means to produce a voltage whose magnitude is proportional to the difference between said determined temperature and a predetermined control temperature and whose polarity is dependent on whether said determined temperature is higher or lower than said predetermined control temperature, means responsive to the magnitude and polarity of said voltage to increase or decrease the supply of cooling liquid to a selected cooling station preceding said selected point depending upon whether said determined temperature is higher or lower than said predetermined control temperature to cause said determined temperature to coincide with said predetermined control temperature, and means responsive to the magnitude and polarity of said voltage during a predetermined interval for adjusting the supply of cooling liquid to said selected cooling station after a particular rod has been treated and prior to arrival of the succeeding rod to be treated, said last mentioned means including a resistor and a capacitor forming a series circuit, Said circuit being arranged so that said capacitor is charged by said voltage.

8. In 'apparatus for heat treating rapidly moving hot rolled steel rod including a plurality of liquid cooling stations arranged `at spaced 4intervals along the path of travel of said rod, the combination comprising means -for determining the temperature of said rod -at a selected point in said path located `at a distance lfrom the preceding cooling station sufficient for the interior and sur-face of the rod substantially to equalize in temperature, means to produce a voltage whose magnitude is proportional to the diierence between said determined temperature and a predetermined control temperature and whose polarity is dependent on whether said determined temperature is higher or lower than said predetermined control tempenature, means responsive to the magnitude and polarity of said voltage to increase or decrease the supply of cooling liquid to a selected cooling station preceding said selected point depending upon whether said determined temperature is higher or lower than said predetermined control temperature to cause said determined temperature to coincide with said predetermined control temperature, means responsive to the magnitude Iand polarity of said voltage during a predetermined interval lfor adjusting the supply of cooling liquid to said selected cooling station after `a particular rod has been treated `and prior to `arrival of the succeeding rod to be treated, said last mentioned means including a resistor and a capacitor forming a series circuit arranged so that said capacitor is charged by said voltage, and switching means `for suppressing said voltage when a rod -is not passing said selected point.

9. Apparatus as set forth in claim 8 in which said predetermined interval corresponds to passage of a irst portion of said rod past said selected point `and in which `additional switching means is provided to` reduce the resistance value of said series circuit during passage of said first portion :of said rod past said selected point, said additional switching means being operatively connected to said resistor.

10. Apparatus as set forth in claim 9 in which said 'additional switching means includes `a timer arranged to time said predetermined interval starting in response to approach of a rod to said selected point, said timer causing said additional switching means to increase the resistance value of said series circuit at the end of said predetermined interval.

ll. Apparatus as set `forth in claim l0 in which the time constant of said series circuit during said predetermined interval is suiiciently small -to cause the charge `across said capacitor to stabilize at a value determined by said volt-age and in which the time constant of said series circuit except during said predetermined interval is sufficiently large so that changes in said voltage will not materially affect the charge on said capacitor.

l2. In apparatus -for heat treating rapidly moving hot rolled rod including a plurality of liquid quenching means arranged at spaced intervals lalong the path of travel of said rod, the combination comprising means for determining the temperature of said rod at la selected point in said path, controller means for producing a voltage having a magnitude proportional to the difference between said determined temperature and a predetermined control temperature and whose polarity is dependent on whether said determined temperature is higher or lower than said predetermined control temperature, valve means for increasing or decreasing the supply of said quenching liquid to at least `one of said quenching means, means responsive to the magnitude and polarity of said voltage for changing the setting of said valve means to increase or decrease the supply of said quenching liquid dependent on whether said determined temperature is greater or less than said predetermined control temperature, and switching means operatively connected to said controller means to suppress said voltage when said determined temperature is a predetermined value lower than said control temperature.

13. In apparatus for heat treating rapidly moving hot rolled rod including ya plurality of liquid quenching means arranged at spaced intervals along the path of travel of said rod, the combination comprising means for determining the .temperature of Said rod at a selected point in said path, controller means for producing -a voltage having a magnitude proportional to the difference between said determined temperature and a predetermined control temperature and whose polarity is dependent on whether said determined Itemperature is higher or lower than Said predetermined control temperature, valve means for increasing or decreasing the supply of said quenching liquid to at least one of said quenching means, means responsive to the magnitude and polarity of said voltage for changing the setting of said valve means to increase or decrease the supply of said quenching liquid dependent on whether said determined .temperature is greater or less than said predetermined control temperature, yand switching means operatively connected to said controller means to suppress said voltage when said determined temperature is a predetermined value lower than said control temperature, suppression of said voltage being maintained for a predetermined time interval after said detenmined temperature exceeds said predetermined value.

14. In apparatus for heat treating rapidly moving hot rolled rod including a plurality of liquid quenching means arranged at spaced intervals along the path of travel of said rod, the combination comprising means for detecting changes in temperature of said rod at a first selected point in said path prior to the first of said quenching means, means for increasing or decreasing the supply of said quenching liquid depending upon whether the temperature at said first point is increasing or decreasing, means for determining the ltemperature of said rod at a second selected point in said path located lat a distance from the preceding quenching means sufiicient for the 1interior and surface of the rod substantially to equalize in temperature, and means for increasing or decreasing the supply of said quenching liquid depending upon whether said determined temperature is higher or lower lthan a predetermined control temperature lto cause the determined temperature of said second point to coincide with said predetermined control temperature.

15. Apparatus as set forth in claim 14 comprising first and second controller means producing first and second voltages, said first voltage being independent in magnitude and polarity upon changes in temperature at said first selected point and said second voltage being dependent in magnitude and polarity upon the differences and direction of differences between said determined temperature and said control temperature, said first and second voltages being used for producing said increases or decreases in the supply of quenching liquid.

16. Apparatus as set forth in claim 15 comprising a valve mechanism for actually effecting the increases or decreases in supply of quenching liquid, motor means for operating said Valve mechanism, a normally balanced bridge circuit having a variable element, said motor means being electrically coupled to said bridge circuit for operation in response to unbalance of said bridge and being mechanically coupled to said variable element whereby operation of said motor means restores said bridge circuit toa balanced condition, and means to apply said rst and second voltages to said bridge circuit to unbalance said bridge circuit, resulting operation of said motor means tending to restore the balanced condition of said bridge and to reduce said second voltage toward zero.

17. Apparatus as set forth in claim 16 in which a capacitor is connected to said bridge circuit and is arranged to be charged by said second voltage.

18. Apparatus as set forth in claim 17 in which means is provided to suppress said first and second voltages in the absence of a rod at said first and second selected points, respectively, and in which the charge on said capacitor determines the setting of said valve mechanism While said second voltage is suppressed.

19. In vapparatus for heat treating rapidly moving hot rolled steel rod including a first plurality of liquid cooling stations arranged at spaced intervals along a first possible path of travel of said rod and a second plurality of liquid cooling stations arranged at spaced intervals along a second possible path of travel of said rod, the combination comprising a first radiation pyrometer located at a common point of said paths ahead of said cooling stations, second and third radiation pyrometers each located in a respective one of said paths at first and second selected points, respectively, said selected points each being located at a distance from the preceding cooling station suffcient for the interior and surface of the rod substantially to equalize in temperature, first, second and third controller means each associated with a respective one of said pyrometers for producing first, second and third voltages, respectively, said first, second and third voltages being proportional in magnitude to the differences between the temperatures determined by said respective first, second and third pyrometers and respective first, second and third predetermined control temperatures, the polarity of each of said voltages being dependent on whether the corresponding determined temperature is higher or lower than the corresponding predetermined control temperature, means for converting said first voltage into a fourth voltage proportional to changes in said first voltage, first and second normally balanced bridge circuits each having a variable element, means to apply said fourth and second voltages and said fourth and third voltages to said rst and second bridge circuits, respectively, to creat unbalance of said bridge circuits, first and second motor means operative in response to unbalance of said first and second bridge circuits, respectively, and first and second valve means for adjusting the flow of cooling liquid to at least one cooling station in each of said paths, respectively, said first motor means being mechanically coupled to the variable element of said first bridge circuit and to the first valve means, said second motor means being mechanically coupled to the variable element of said second bridge circuit and to said second valve means, said motor means each being arranged to operate in a direction to restore the corresponding bridge circuit to a balanced condition and, by varying the cooling liquid supply, `to reduce the corresponding one of the second and third voltages to zero.

20. In apparatus for heat treating rapidly moving hot rolled steel rod including a first plurality of liquid cooling stations arranged at spaced intervals along a first possible path of travel of said rod and ya second plurality of liquid cooling stations arranged at spaced intervals along a second possible path of travel of said rod, the combination comprising a first radiation pyrometer located at a common point of said paths ahead of said cooling stations, second and third radiation pyrometers each located in a respective one of said paths at first and second selected points, respectively, said selected points each being located at a distance from the preceding cooling station suicient for the interior and surface of the rod substanftially to equalize in temperature, first, second and third controller means each associated with a respective one of said pyrometers for producing first, second and third voltages, respectively, said first, second Iand third voltages being proportional in magnitude to the differencesbetween the temperatures determined by said respective first, second and third pyrometers and respective first, second and third predetermined control temperatures, the polarity of each of said voltages being dependent o n whether the corresponding determined temperature is higher or lower than the corresponding predetermined control temperature, means for converting said first voltage into a fourth voltage proportional to changes in said first voltage, ,first and second normally balanced bridge circuits each having a variable element, means to apply said fourth and second voltages and said fourth and third voltages to said rst and second bridge circuits, respectively, to creat unbalance of said bridge circuits, rst and second motor means operative in response to unbalance of said rst and second bridge circuits, respectively, first and second valve means for adjusting the ow of cooling liquid to at least one cooling station in each of said paths, respectively, said rst motor means being mechanically coupled to the variable element of said first bridge circuit and to the rst valve means, said second motor means being mechanically coupled to the variable element of said second bridge circuit and to said second valve means, said motor means each being arranged to operate in a direction to restore the corresponding bridge circuit to a balanced condition and to reduce the corresponding one of the second and third voltages to zero, flrst, second and third circuit means for suppressing said second, 'third and fourth voltages, respectively, while the temperatures determined by the corresponding pyrometers are below predetermined values, and means operatively connected with each of said bridge circuits for causing said motor means to set said valve means toa liquid ow setting corresponding to the setting provided for the starting end of the preceding rod passed along the corresponding path, said last mentioned means being operative to eti-ect said setting in the absence of the corresponding one of said second and third voltages.

21. In apparatus for heat treating rapidly moving hot rolled steel rod including a plurality of liquid cooling stations arranged at spaced intervals along the path of travel of said rod, the combination comprising means yfor determining the temperature of said rod at a selected point in said path located at a distance from the preceding cooling station suicient for the interior and surface of the rod substantially to equalize in temperature, means to determine the speed of said rod, means to produce a rst voltage whose magnitude is proportional to the difference between said determined temperature and a predetermined control temperature and whose polarity is dependent on whether said determined temperature is higher or lower than said predetermined control temperature, means to produce a second voltage whose magnitude is proportional to the speed of said rod, control means responsive lto the magnitude and polarity of said first voltage and to the magnitude of said second voltage to increase or decrease the supply of cooling liquid to a selected cooling station preceding said selected point depending upon whether said determined temperature is higher or lower than said predetermined control temperature to cause said determined temperature to coincide with said predetermined control temperature and, means responsive to the magnitude and polarity of said 'first voltage during a predetermined interval for adjusting the supply of cooling liquid to said selected cooling station after a particular rod has been treated and prior to arrival of the succeeding rod to be treated.

22. Apparatus as set forth in claim 21, comprising second means for determining the temperature of said rod at a point in said path located in advance of said cooling stations, means to produce a third voltage whose magnitude is proportional to the difference between said -last mentioned determined temperature and a second predetermined control temperature and whose polarity is dependent on whether said last mentioned determined temperature is higher or lower than said second predetermined control temperature, and means to combine said third voltage with said second voltage to produce a fourth voltage which, with said iirst voltage, operates said control means to control said increases or decreases in supply of cooling liquid.

References Cited in the le of this patent UNITED STATES PATENTS 1,350,618 Napier Aug. 24, 1920 2,111,919 Urschel Mar. 22, 1938 2,163,699 Paul June 27, 1939 2,205,182 Whitten June 18, 1940 2,309,745 Bergin Feb. 2, 1943 2,436,894 Magee Mar. 2, 1948 2,470,540 Young May 17, 1949 2,492,434 Mueller Dec. 27, 1949 2,661,009 Dunnegan et al Dec. 1, 1953 2,668,701 Dietrich Feb. 9, 1954 2,681,793 Miller June 22, 1954 2,681,874 Linney June 22, 1954 2,725,265 Daniels et al Nov. 29, 1955 2,747,587 Strachan May 29, 1956 UNITED STATES PATENT OEEICE CERTIFICATE 0F CORRECTlLONl Patent No. 2,994,328 August l., 1961 Dartrey Lewis I It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 8, line 53, for "roll" read Coil column 11, line 33, for "larger" read large column 15, line 44, for "independent," read dependent --5 column 18, line 24, for -"or" read and Signed and Sealed this 12th day of December 1961.

(SEAL) Attest:

ERNEST W. SWIDEE DAVID L. LADD Attesting Officer Commissioner of Patem USCOMMJ