US1959344A

US1959344A - Process of heat treating steel

Info

Publication number: US1959344A
Application number: US377182A
Authority: US
Inventors: Clarence J Coberly
Original assignee: Kobe Inc
Current assignee: Kobe Inc
Priority date: 1929-07-10
Filing date: 1929-07-10
Publication date: 1934-05-22
Anticipated expiration: 1951-05-22

Description

May 22, 1934- c. J. COBERLY PROCESS OF HEAT TREATING STEEL Filed July 10, 1929 5 Sheets-Sheet l Patented May 22, 1934 UNITED STATES 1,959,344 PROCESS OF HEAT TREATING STEEL Clarence J. Coberly, Los Angeles, Calif., assignor to Kobe, Inc., Los Angcles, Calif., a corporation of California Application July 10, 1929, Serial No. 377,182

18 Claims.

My invention relates to the heat-treating of metals to improve their properties, and more particularly to a novel method of and apparatus for heat-treating relatively long bodies of metal such as metal bars, rails, pipes, etc.

The physical properties of all steels are improved by proper heat-treatment, but great difficulty has been heretofore encountered in heating, quenching, and tempering relatively long and narrow bodies such as long lengths of shafting, pipe, etc, Some success has been achieved by performing these operations with the longitudinal axis of the pipe or shafting into a vertical position, and lowering this pipe or shafting into a deep quenching bath in the usual manner. It is also true that more or less successful attempts have been made to slide the pipe or shafting into the quenching medium at anangle of about 45 from the horizontal. However, in either event the equipment necessary is both bulky and expensive, inasmuch as the lengths of pipe and shafting are frequently very long, often exceeding forty feet in length.

Such long lengths of pipe find a particular utility in the oil-well drilling and pumping industries where seamless tubing is being more and morewidely used. Seamless tubing is used not only in the capacity of well-casing, but is also used in drilling operations, and I have found that the yield-point and ultimate strength of such seamless tubing may. be increased respectively from s'xty thousand pounds per square inch and ninety thousand pounds per square inch, to one hundred and twenty thousand pounds per square inch and one hundred and sixty thousand pounds per square inch by proper heat-treatment. Furthermore, by proper heat-treatment the treated steel will have a ductility equal to that of the untreated steel. Even greater increases in strength, and even greater maximum yield-point and ultimate strength may be obtained by properly heat-treating alloy steels. The adoption of such alloy steels in the oil-well drilling and pumping industry has been retarded by the high cost d thereof.

It is primarily an object of this invention to provide an improved method of and apparatus for heat-treating bodies of metal.

A further object of this invention is to provide an apparatus for successfully heating and quenching relatively long bodies when these bodies are in a horizontal position.

My apparatus is furthermore not limited to any length of pipe or other body to be heat-treat In the oil-well pumping industry perforated pipe finds numerous utilities, and it is desirable that this pipe be heat-treated.

Another object of this invention lies in the provision of a novel method of and apparatus for quenching such a perforated pipe while in a horizontal position without danger of the quenching medium backing up into the furnace in a manner to prematurely quench the pipe being heated therein.

It is known that steel experiences a change in magnetic properties when passing through the critical temperature. In other words, iron in the alpha allotropic form is highly magnetic below the A1 transformation point, and at least partially changes into the very feebly magnetic beta allotropic form when heated between the A2 and the A3 transformation points. At this last transformation point the gamma allotropic form of iron suddenly appears which is substantially non-magnetic. Temperatures corresponding to the A2 and A3 transformation points form a basis for determining the correct temperature for quenching a given steel.

Thus, when raising the temperature of a piece of steel, the magnetic properties thereof suddenly change asthe steel passes throughv the critical temperature or critical range. Becoming suddenly non-magnetic, the permeability of this steel correspondingly increases at a very fast rate, and it is this change in permeability which I utilize for controlling the quenching temperature of the steel. Inasmuch as the critical temperature or range is dependent upon the analysis of the steel, and inasmuch as the magnetic properties of the steel vary correspondingly, it follows that my method compensates for any irregularities in composition of the steel body, and insures that all portions of the body will be raised to the critical temperature or range corresponding to the analysis of the body at any particular section.

It is an object of this invention to provide a method of heat-treating a body which includes the step of controlling the quenching temperature as a function of the magnetic properties of this body.

A further object of this invention isto provide a method of heat-treating a bodyby firstheating the body to a primary temperature. slightly below the critical temperature or range, and further heating the body to a secondary temperature at or slightly above the critical temperature, this secondary heating being controlled as a function of the magnetic properties of the heated body.

A further object of this invention is to provide 'a process for heat-treating a body wherein the body is utilized as the core of a transformer in a manner to magnetically connect a primary and secondary winding, the primary winding being utilized for setting up a magneto-motive force which passes a magnetic flux through the body, this flux linking the secondary winding in a manner, to generate an electromotive force in the secondary winding, this induced electromotive force in the secondary winding being utilized for controlling the amount of heat transmitted to the body.

Several methods of heating a body are possible and fall within the scope of this invention. In

' the first place, the body may be subjected to a large magnetomotive force which causesa heating of the body due to hysteresis losses and to circulating currents set up in the body itself by the magnetomotive force. I have found this method to be impractical in most commercial installations, due to the fact that excessive currents are necessary, and also to the fact that the body can never be raised above the critical temperature or range due to the fact that the steel becomes non-magnetic at this temperature-and therefore will not carry the magnetic flux necessaryfor the production of the heat therein. However, this critical temperature can be closely approached by guarding against radiation losses, and in certain installations this method can be successfully used this arrangement can be used to operate a circuit controlling the amount of heat reaching the body from the heating flame so as to maintain a temperature corresponding to a'certain state of magnetizatiomor having a definite relation to this temperature. The time lag of such a system can be made relatively low. f

It is an object of this invention to provide a method and apparatus for heat-treating a body by directing a heating flame against or adjacent the body, the amount of heat transmitted to this body from the flame being a function of the magnetic properties of the heated body.

Afurther object of this invention is to provide a novel electrically operated regulating mechanism for controlling the heating of such a body.

Still a further object of this invention is to provide a novel water-cooled winding which surrounds, or is adjacent to, the body in such a manner that the winding is influenced by the flux passing through the body, or so that the body is in the magnetic pathof the flux generated by the V winding.

Further objects of this invention lie in the particular apparatus utilized,,and especially in the novel magnetically operated control valve, and

the control valve. I

the motor-operatedtiming switch for regulating Referring particularly to the drawings, in

which I have illustrated one form of my invention,-'-

Fig. 1 is a diagrammatic utility view illustrating the respective positions of the pieces of apparatus utilized inmy process.

Fig. 2 is a cross-sectional view of the quench ing device of my invention taken on the line 22.

Fig. 7 is a detailed view of the toggle mechanism of the control valve, and is taken in the direction of the arrow 7 of Fig. 6. r

Fig. 8 is a diagrammatic sectional view of one of the furnaces utilized in my invention, this view being taken along the line 8-8 of Fig. 1.

Fig. 9 is a partial wiring diagram of the apparatus of my invention.

Fig. 10 is a graphical representation of the relationship between permeability and temperature.

The successive steps of my process may be best understood by reference to Fig. 1 wherein I have diagrammatically shown a combination of elements for performing my process. It should be understood that this combination of elements is not the only one by which the novel steps of my process may be performed, but is herein shown and described only for the purpose of illustration and definiteness.

The apparatus shown in Fig.1 is adapted to heat-treat a relatively long and narrow body such as a pipe 10. For the purpose of illustration we will assume that the pipe 10 is perforated inas- 'much as sucha pipe presents the most difficult problems in the heat-treating thereof by a continuous process.

A given section of the pipe 10 is successively passed through a surface combustion furnace 11, a furnace 12, primary and secondary sets of

gas burners

13 and 14, a quenching device 15, a vacuum hood 16, and a pair of standard annealing furnaces 1'7 and 18, the horizontal axes of all of these pieces of apparatus being in alignment'so that the pipe 10 may pass successively and continuously therethrough. The surface combustion furnace 11 is of novel construction, and the details thereof are best shown in Fig.8. This furnace has a shell 19 through which a tube of refractory material 20 extends, this tube surrounding the pipe 10 and being preferablyformed of coarse-grained carborundum, or other material which will stand very high temperatures.

The space around the tube 20 is suitably heated by any means such as gas jets 21 which extend through an outer porous tube 22 concentric with the tube 20, the gas discharging into an annular space 23 therebetween. The space 23 is preferably fllled with loose carborundum particles. Combustion takes place near and in the tube of refractory material 20. A suitablebrickwork 25 supports the porous tube 22 inside the shell 19. The heat is transmitted to the pipe 10 mostly by radiation from the heated tube 20. This furnace operates at a temperature of 3000 F., and is utilized for preliminarily heating the pipe to a point somewhat below the criticaltemperature or range thereof. The temperature of the pipe will depend, of course, upon numerous factors including the initial temperature thereof, the speed at which it passes through the furnace, the size of the pipe, etc. The furnace 11 may be provided with a temperature-regulating pyrometer, but I have found it preferable to operate this furnace at a temperature close to the maximum obtainable therein, this temperature being manually controlled. A pyrometer is preferably. utilized for measuring the furnace temperature, and an optical pyrometer for measuring the temperature of the pipe as it passes from this furnace.

The pipe then moves to the furnace 12 which is automatically controlled by a pyrometer, not shown, the temperature thereof being only slightly less than the critical temperature or range of the steel in the pipe 10. This temperature is ordinarily around 1450 F., but will, of course, vary with different steels.

Hence the pipe passes successively into the path of the sets of

gas burners

13 and 14, each of which is composed of two burners spaced 180 apart and directed against the external surface of the pipe, the burners of set 13 being designated by numerals 28 and 29. The heat transmitted to the pipe by each of these gas burners is regulated as a function of the magnetic properties of the heated pipe in a manner to be described, so that the temperature of the pipe after it leaves the vicinity of the set of gas burners 14 is at, or slightly above, the critical temperature or range of the steel.

The temperature of the pipe drops only a few degrees before the pipe enters the quenching device 15. Here the pipe is suddenly cooled by means of a cooling medium tangentially supplied to the interior of acircular shell 30, medium being supplied through tangential nozzles 31. The nozzles 31 are designed to convert substantially all of the potential energy of the quenching medium, supplied thereto under pressure from a suitable source, into kinetic energy so that this cooling medium is circulated in the housing at a high velocity in a direction indicated by arrows 32 of Fig. 2, this medium forming a cylinder of rotating quenching medium which contacts the periphery of the pipe. The centrifugal force on this medium continuously throws it outward and does not exert an undue radial pressure on the walls of the pipe.

Eventually, however, the medium flows through the perforations of the pipe, in the event that the pipe 10 is perforated, and into the vacuum hood 16. This vacuum hood provides a vacuum chamber 34 which communicates with the interior of the circular shell 30 through the opening of an apron 35, best shown in Fig. 3. This opening is only slightly larger than the periphery of the pipe. The intake of a blower 36 communicates with the chamber 34 and decreases the pressure therein so that any of the quenching medium passing through the perforations of the pipe will be drawn to the right and into the vacuum hood 16 rather than flowing leftward along the pipe, thus prematurely quenching this pipe.

The quenching medium drawn into the vacuum hood by the blower 36 drops to the lower end thereof and is withdrawn therefrom by a circulating pump 3'7 driven by a motor 38, this pump forcing the quenching medium through a pipe 39 to a cooling tower, not shown, where the quenching medium is cooled and again supplied to the nozzles 31 under pressure.

After leaving the vacuum hood 16, the pipe and 12 or the furnaces 1'7 and 1.8.

passes through the standard annealing furnace 1'1 where it is brought up to a tempering temperature. Subsequently, the pipe passes through the furnace 18 which holds the pipe at the correct tempering temperature for such a length of time that a correct amount of tempering takes place. The pipe is then cooled in the air after leaving the furnace 18.

The pipe 10 is continuously fed through the furnaces 11, 12, 17, and 18 and the remainder of the apparatus, by three driving devices, one being situated before the furnace l1 and indicated by the numeral 40, another being situated after the furnace 18 and indicated by the numeral 41, and the third being in the vacuum hood 16 and indicated by dotted lines 42. Each of these driving devices comprises a pair of skewed rolls, individually designated as a drive roller 43 and an idler roller 44. The drive roller 43 of. each of the driving devices 40, 41, and 42 may be simultaneously driven by a shaft 45 gemed to a shaft 46 by gears 47. The shaft 46 is in turn driven by a motor 48 through a suitable gear reduction box 49. The pipe 10 rests on the drive roller 43, and the idler roller 44 rests on top of the pipe 10 and due to its weight holds the pipe firmly against the drive roller.

The driving devices 40 and 41 have

frames

50 and 51 in which journalling structures 52 and 58 may vertically slide, these structures journalling the idler rollers 44. Due to the fact that the rollers 43 and 44 of each driving device are skewed, a rotation of the drive rollers will cause the pipe 10 .to be turned about its longitudinal axis, and also pushed forward through the furnaces and quenching device. The center of each of the rollers 43 and 44 is of smaller diameter than the ends, as clearly shown in Fig. 1, to increase this turning and driving action. It is entirely possible to drive the rollers 44 as well as the rollers 43, but I have found that such a procedure is unnecessary.

In certain instances it is desirable to drive the rollers 43 of the three driving devices 40, 41, and 42 separately. By thus doing, it is entirely possible by having these rollers run at slightly different speeds to place a tension on that portion of the pipe passing through the furnaces 11 Similarly, it becomes possible to place compressive stresses on the pipe when passing through these furnaces. I am thus not limited to a unitary drive for all of the rollers 43.

An important part of this invention lies in the provision of the regulating means for regulating the amount of heat'transmitted to the pipe 10 by the sets of gas burners l3 and 14 as a function of the magnetic properties of the pipe being treated.

There are numerous methods whereby the magnetic properties of the pipe may be utilized for controlling the quenching temperature of the pipe 10, but the preferred method comprehends im pressing on the heated pipe at magnetomotive force which tends to pass magnetic flux through the heated pipe, the amount of this flux being suitably measured. If the magnetomotive force is substantially constant the flux passing through the pipe will vary inversely as the permeability thereof. If a curve of permeability of plotted against temperature, it is possible to obtain several curves of different shapes depending upon the flux density in the pipe.

In Fig. 10 I have illustratedthree typical curves, curve A being for low flux density, curve B for medium flux density, and curve C for high fiux density. From these curves. it will be apparent that as the material in the pipe approaches and passes through the critical temperature or range, the permeability thereof dropi very rapidly. I utilize this sudden change in permeability for regulating the amount of heat transmitted to the pipe 10 by the sets of -burners 13 and 1.4. The

means for accomplishing this end is best illustrated in Figs. 1 and 9, and inasmuch as the sets of

gas burners

13 and 14 are identical, onlyone set is shown in Fig. 9 and will be particularly described.

Referring particularly to Figs. 1 and 9, I have illustrated primary and secondary windings and 61 surrounding the pipe 10 and being spaced a small distance therefrom. Each of these windings comprises a. single turn of copper tubing bent around the pipe, as shown in Fig. 9, and

spaced from each other a distance of one inch or more. I prefer to direct the heating flame issuing I from the burners 28 and 29 between the primary and

secondary windings

60 and 61, although this arrangement is not essential to the operativeness of the device. The primary winding 60 is connected to the secondary of a step-down transformer 62 which delivers a low voltage and high amperage to the primary 60 through a circuit 63, the wires of this circuit being connected to the winding 60 by clamp members 64 which clamp around the tube forming the primary winding 60 leaving the ends of the pipe free so that a cooling medium in the form of water or other fluid may be passed therethrough, as indicated by the arrows of Fig. 9.

This cooling medium is supplied thereto through a pipe 65 and a manifold 66, this manifold also supplying cooling medium to the secondary windv ing in a similar manner, the flow of cooling medium being suitably controlled by valves positioned both in the pipe. 65 and in the individual pipes communicating with the tubing forming .the primary and secondary windings ,60 and 61.

The transformer 62 supplies a low voltage current of several hundred amperes through the primary winding 60, this current setting up a magnet-emotive force which acts upon the pipe 10 to force magnetic flux therethrough. The secondary wind ng 61 is linked with the primary winding 60 by means of the flux passing through the pipe 10, and the amount of voltage generated in the secondary winding 61 will be, of course, a function of the amount of flux passing through the pipe 10. If, now, the permeability of the pipe 10 suddenly decreases, the voltage generated in the secondary winding 61 will correspondingly decrease. Thus, by connecting a contact voltmeter or other voltage-responsive means to the secondary winding 61, it becomes possible to utilize this voltmeter for controlling the amount of heat reaching the pipe 10 from any suitable electrically controlled heating means.

, I have developed a particular type of contacting voltmeter which finds a particular utility in con- However, other types of grammatically illustrated such a meter as having a coil '73 connected to the secondary 61 by conductors forming a circuit-'74. The vane. of the voltmeter is shown at '75, this vane being mounted on a shaft '76 to which a pointer or hand 7'7 is secured.

The coil '73 exerts a torque on the vane '75, thus tending to turn the shaft 76 against the action of a spiral spring '78 connected thereto, the free end of this spring being connected to a zero-adjustment means in the form of 'a lever 79 pivoted at 80 so that a movement of this lever about the pivot 80 changes the zero reading of the hand '77, and consequently changes by a proportionate amount the readings throughoutthe scale over which this hand normally moves.

Mounted in one end of the box structure '70 is a motor 82 driving a worm 83 meshed with a pinion 84 secured to a eountershaft 85, this countershaft journalling in bearings 86. Also secured to the countershaft 85 is a worm 8'7 which is meshed with a pinion 88 secured to a countershaft 89 the cam immediately thereabove, and is held in contact with this cam by the arm 94. The extreme forward end of the spring arm is bent downward to form a blade 97 which is moved downward at fixed time intervals due to the action of the cam 92 on the roller 96. The motor 82 is so geared to the countershaft 89 that the

cams

92 and 93 make one complete revolution approximately every ten seconds so that'the blade 9'7 is lowered at intervals of approximately ten seconds.

Mounted on the box structure 70 are primary and secondary switch arms and 102, shaped as best shown in Fig. 4, and pivoting on

pivot pins

103 and 104. These switch arms are in the form of hell cranks, and the upper arm'of each extends toward each other and is bifurcated,.as best illustrated in Fig. 4. The blade 97 is disposed directly above the space between the bifurcations of these upper arms, so that were it not for the hand '77 of the voltmeter, the blade 97 would move downward between the bifurcations of the primary and'secondary switch arms at fixed intervals of time. However, the voltmeter is so mounted that the plane of movement of the hand '77 is between the lower edge of the blade 97 and the upper edges of the primary and secondary switeharms 100 and 102. In other words, when the blade is injits uppermost position the hand '77 of the voltmeter may swing unobstructed in the space between the lower edge of the blade 9'7 and the upper edge of the primary and

secondary switch arms

100 and 102. i

The amount of movement of the hand '77 is, however, mechanically limited by stops 105 formed on each of the primary and

secondary switch arms

100 and 102. These switch arms are always held in such'aposition that the upper edges thereof lie just below the hand '77, this being made possible by a spring 108 connecting the two switch arms and holding thelower ends of these arms respectively in engagement with armadjusting screws 109 and 110 which are threaded through bosses 111 and 112 and engage the lower endof their respective switcharms, as best shown in Fig; 5. I I

The current through the primary-winding 60 is so regulated, and the position of the zero-adjustment lever 79 is so regulated, that the hand 77 is positioned above or adjacent the ends of both switch

arms

100 and 102 when the pipe 10 is at a correct quenching temperature. In this capacity it should be clear that the position of the hand 77 is determined by the permeability of the pipe 10 which is in turn controlled by the temperature of this pipe. Thus, if the temperature of the pipe 10 is too high, the hand 77 will move to the right, as viewed in Figure 5, and when the blade 9'7 momentarily moves downward this blade will come into contact with the hand 77 and will force the hand downward into contact with the secondary switch arm 102, thus momentarily moving this arm into a position shown in the left half of Fig. 5. If, onthe other hand, the temperature of the pipe 10 is not high enough, the permeability thereof will be high and the'voltage induced in the secondary winding 61 will be high, thus causing the hand 77 to move leftward as viewed in Fig. 5 above the primary switch arm during the time that the blade 97 is raised. When this blade is again momentarily lowered, the hand will be forced into contact with the primary switch arm 100 and will momentarily depress this arm.

The

switch arms

100 and 102 thus become a very convenient means for operating electric circuits which control the amount of heat transmitted to the pipe by the sets of

gas burners

13 and 14.

In accomplishing this end, I, provide contact springs and 116 mounted in a block 117 and extending leftward beyond the secondary switch arm 102. These contact springs have

contacts

118 and 119 thereon, which are normally separated, but which are closed whenever the upper arm of the secondary switch arm 102 is depressed.

Both these contact springs 115 and 116 normally tend to move leftward, the spring 115 remaining in contact with the lower end of the arm 102, and the spring 116 moving leftward until it engages a contact-adjusting screw 120, after which the

contacts

118 and 119 separate until the secondary switch arm is again momentarily depressed. A similar set of

spring contacts

121 and 122 are similarly mounted and extend forward beyond the primary switch arm 106, these contact springs having a normal rightward tension which keeps the spring contact 122 in engagement with the lower end of the primary switch arm 160 and maintains the spring contact 121 in engagement with a contact-adjusting screw 124.

I utilize the apparatus illustrated in Figs. 4 and 5 for controlling the amount of heat supplied to the pipe by the sets of

gas burners

13 and 14. In this capacity, the windings of the voltmeter 71 are connected to the secondary winding 61 associated with the set of gas burners 13, while the winding of the voltmeter 72 is connected to the secondary winding associated with the set of gas burners 14.

The burners 28 and 29 of the set of gas burners 13 are supplied with a combustbile mixture through pipes and 131 respectively, these pipes also connecting to a suitable magnetically operated globe valve 132, best illustrated in Fig. 6.

Referring to Fig. 6, the valve 132 has an inlet pipe 133 communicating with an inlet passage 134, this passage being separated from the

pipes

130 and 131 by a wall 135 having a valve seat 136 therein. Adapted to engage this seat is a valve member 137 mounted on a stem 138. The vertical position of the stem 138, of course, determines the amount of gas supplied to the

pipes

130 and 131. The position of this stem is controlled by a pair of

windings

139 and 140 which are mounted respectively in a head member 141 and a base member 142 and act upon an armature 143. The winding 140 is connected to the contact springs 115 and 116 by

conductors

145 and 146, while the Winding 139 is connected to the contact springs 121 and 122 through the conductor 146 and a conductor 147. A source of potential 149 is inserted in the conductor 146. Thus, when the

contacts

125 and 126 momentarily come into engagement a circuit is com-- pleted through the winding 139, thus tending to attract the armature 143 and move this armature upward in a manner to allow a greater quantity of gas to reach the burners 28 and 29. The uppermost position of this armature is determined by contact with the head member 141, and I prefer to make this head member adjustable by means of a bolt 151 passing through a supporting frame 152 and threaded into the head member 141.

Similarly, the lowermost position of the armature 143 is determined by contact between the base member 142 and this armature, and I provide a pair of adjusting bolts 153 for controlling the position of the base member 142 in a manner to control the lowermost position of the valve member 137. The bolts 153 are threaded into the base member 142 and pass through openings in the supporting frame 152.

I prefer to provide a toggle mechanism for holding the armature either in its extreme upper position or in its extreme lower position. This toggle mechanism may be of any desired type, the one illustrated in Fig. 7 comprising an arm pivoted to the'supporting frame 152 by a pin 161. A slot 162 formed in the arm 160 is adapted to receive a pin 163 which is mounted in a ledge 164 of the armature 143. A toggle spring 165 connects a pin 166 on the free end of the

arm

1,60 and a pin 167 fastened in the supporting frame 152. These pins are so arranged that when the armature is in its lower position, the axis of the spring 165 lies below the axis of the pin 161 and when the armature is moved into its upper posi tion, the axis of the spring moves to the upper side of the axis of the pin 161, thus insuring that the armature will remain in either extreme upper or extreme lower positions until moved therefrom by the energization of the correct winding. Thus, when the armature is moved into its lower position due to the momentary energization of the winding 140, the globe valve 132 will be opened to admit a minimum amount of combustible mixture to the gas burners 28 and 29.

Any successive energizations of the winding 140 due to a successive closing of the

contacts

118 and 119 will not move the armature 143. The amount of heat transmitted to the pipe will decrease, due to the limited amount of combustible mixture passing through the valve 132 and when the temperature has been sufficiently lowered the permeability will rise and increase the voltage generated in the secondary winding 61 which will in turn move the hand 77 above the primary switch arm 100.

Upon the next movement of the blade 97 by the cam 92, the

contacts

125 and 126 will be momentarily closed, thus completing a circuit through the upper winding 139 which moves the armature 143 into an upper position wherein a maximum amount of gas is allowed to pass through the valve 132. The amount of gas passing through the valve when the armature is in T an upper position and in a lower position may be readily determined by adjusting the bolts 151 and 153. By making the difierence in flow when the valve is in these two positions relatively small,

a very uniform temperature may be maintained I due to the action of the gas burners 28 and 29.

This arrangement is very sensitive, especially if the flux density in the pipe is adjusted to such a value that the change in permeability near the critical temperature is rapid.

, It should be understood that Fig. 9 shows the control for only the set of gas burners 13, and

that a similar control is utilized for a valve 170 which controls the amount of heat transmitted to the pipe from the set of gas burners 14, this valve being magnetically controlled in amanner similar to the valve shown in Fig. 6, and being controlled by the voltmeter '72 in the same manner that the voltmeter 71 controls the valve 132. The setting of the voltmeters 71 and 72 is slightly different due to the fact that the set of burners 13 raise the temperature somewhat above the temperature developed in the furnace 12, and the set ofburners 14 raise this pipe to the proper quenching temperature or slightly above to compensate ,for the slight cooling which takes place before quenching. In certain installations it is possible to dispense with one of the sets of

burners

13 and 14 and to utilize a single burner for raising the temperature of the pipe from that of the furnace 12 to the proper quenching temperaturer It should be understood that it is not necessary to control the flow of combustible gas to the gas amount of heat transmitted to this pipe. Such systems fall within the scope of the appended claims. I

Furthermore, it should be understood. that I I am not limited to any particular type of voltmeter '71 and 72, the one illustrated in Fig. 9 being of the iron vane type only for the purpose of illustration. Furthermore, the relative position of the vane 75 and the hand '77, as shown in Fig. 9, has been shown only for the purpose of clearness. It is ordinarily desirable that the hand 77 be in the upper portion of its path of travel over the ordinary meter scale at the time that it lies between the stops 105 on the primary and

secondary switch arms

100 and 102. This is due to the relationship which ordinarily exists on an alternating current meter, whereby the hand 77 is much more sensitive to small changes in voltage over this portion of the scale than over the lower portion of the scale.

The temperature to which the pipe is raised by the burners may, of course, be regulated in nu-= merous ways. With the apparatus illustrated, this regulation may be effected (1) by changing the current through the primary winding, (2) by changing the distance between the primary and secondary winding, (3) by changing the position of the voltmeter relative to the boxstructure 70,

' or (4) by changing the position of the lever '19 which controls thezero reading of the hand 77;

I interior of said pipe through said perforations.

I claim as my invention:

1. A process of continuously heat-treating a relatively long and narrow body, which includes the steps of moving said body through a heating zone in a manner to raise to a quenching temperature that portion of said body leaving said heating zone; immediately moving said body through a quenching zone and rotating a quenching medium around said body in said quenching zone to quench said body as it moves into said quenching zone.

2. A process of continuously heat-treating a relatively long and narrow body, which includes the steps of: moving said body when in a substantially horizontal position through a heating zone in a manner to raise to a quenching temperature that portion of said body leaving said heating zone; and subjecting said body to the action of a quenching medium rotating therearound in a substantially vertical plane.

3. A process of heat-treating a perforated pipe while in a substantially horizontal position, which comprises: moving said pipe through a heating zone in a manner to raise to a quenching temperature that portion of said pipe leaving said 1 heating zone; subjecting said pipe to a stream of quenching medium rotating around said pipe in a quenching zone; and reducing the pressure in said quenching zone to draw said quenching medium through the perforations and to prevent any of said quenching medium passing through the perforations of said pipe from flowingalong said pipe toward said heating zone.

4. A process of heat-treating a perforated pipe, which includes the steps of: heating said pipe; quenching said pipe by passing a quenching medium therearound and in contact with the periphery thereof in such a manner that a portion of said quenching medium passes through the perforations of said pipe; and subsequentlyremoving from the interior of said pipe and in a direction away from the zone where said heating takes'place any quenching medium entering the 5. A process of heat-treating a perforated pipe, which includes the steps of: heating said pipe; quenching said pipe by passing a quenching medium therearound and in contact with the periphery thereof in such a manner that a portion of saidquenching medium passes through the perforations of said pipe; and withdrawing from the interior of said pipe in a direction away from the zone where said heating takes place any of said quenching medium passing through said perforations.

3 6. A process of heat-treating a relatively long body, which includes the steps of: moving said body slowly along its longest dimension; applying heat to a relatively short section of said slowly moving body; controlling the amount of heat applied to said relatively short section as a function of the magnetic properties of this particular short section so that successive sections of said body will be heated in amount determined by their own characteristics; immediately moving the heated section of said moving body into a quenching body, which-includes the steps of: continuously moving said body through a heating zone and a quenching zone; passing a magnetic flux through a portion of said continuously moving body which lies in said heating zone; heating said continuously movingbody in said heating zone; controlling the amount of heat supplied to said body in said heating zone in response to the amount of flux flowingthrough said portion of said body; and quenching said body in said quenching zone.

8. A method as defined in claim '7 including the step of rotating said body as it moves through said heating and quenching zones whereby a point on said body moves through a helical path.

9. A method of heat-treating a body, which includes the steps of: successively applying heat to adjacent portions of said body by relatively moving said body with respect to a heating source; setting up a magnetic field adjacent said portions to which heat is successively applied, thereby passing a magnetic flux through only that portion of said body which is being heated; controlling the application of heat to said body in response to variations in the amount of said flux flowing through the section beingheated; and immediately quenching the section oi-said body which has been heated.

10. A method of heat-treating a relatively long body, which includes the steps .oizcontinuously moving said body through a heating zone; applying heat to said body in said heating zone; setting up a magnetomotive force at a given section adjacent said heating zone and tending to force flux longitudinally through said body; utilizing the variations in said flux passingthrough said body for generating an electromotive force at another section adjacent said heating zone and spaced longitudinally along said body from said given section at which said magnetomotive force is generated; and controlling the amount of heat applied to said body in response to the electromotive force generated at the other section,

11. A method of heat-treating a relatively long body, which includes the steps of: applying heat to said body at a section; generating a magnctomotive force on one side oi said section and acting to send flux longitudinally through said body; and controlling the amount of heat applied to said body in response to the amount of said flux passing through and beyond sa d section at which the heat is applied.

12. A process 01' heat-treating a body, which includes the steps of: preliminarily heating said body to a temperature just below the desired quenching temperature; further heating said body; passing a magnetic flux through said body; controlling the degree of heat applied during said further heating in response to the amount of said magnetic flux flowing through said heated body to bring said body to the quenching temperature; and quenching said body.

13. A process of heat-treating a body, which includes the steps oi preliminarily heating said body to a temperature just below the desired quenching temperature; body by directing a heating flame against the surface of said body; passing a magnetic flux through that portion of said body which is under the influence of said heating flame; controlling the amount of heat supplied to said body by said heating flame in response to the amount oi. said magnetic flux flowing through said heated body to further heating said bring said body to the quenching temperature; and quenching said body.

14. A process oi continuously heat-treating a relatively long and narrow body, which method includes the steps 0!; moving said body longitudinally through a heating zone in a manner to raise to a quenching temperature that portion of said body leaving said heating zone; immediately thereafter moving said body into a quenching zone; introducing a quenching liquid into said quenching zone and into contact with said body whereby said body is quenched; and creating a vaouumin said quenching zone to remove from said quenching zone and in a direction away from said heating zone the quenching liquid and any vapors formed when said quenching liquid comes density in said portion of said body in said heating zone.

16'. A method of heat-treating a relatively long and narrow body, which includes the steps of: extending said body through a heating zone, end portionsoi said body extending outside said heating zone; applying a longitudinal force to each of said end portions whereby the section of said body lying in said heating zone is subjected to a stress, one of said i'orces being greater than the other to produce a resulting movement of said body through said heating zone; heating the section of said body in said heating zone during the application of said stress; and cooling the heated portion 0! said body after it moves from said heating. zone.

17. A method of heat-treating a body, which method includes the steps of: passing a magnetic flux through said body; applying heat to said body; increasing and decreasing the amount of heat applied to said body during the heating operation in response to the change in flux density in said body; and quenching said body when it becomes substantially non-magnetic.

18. A method of heat-treating a relatively long body, which method includes the steps 0!: applying heat to said body at a relatively short section,

said heat being applied in a heating zone; passing a magnetic flux through said relatively short section of said body; continuously moving said body relative to said heating zone whereby successive sections thereoi' come within the influence of the heat and magnetic flux; and controlling the amount of heat applied to that relatively short section of said body in said heating zone in response to changes in the amount of said magnetic flux so that each 01' said successive sections of a said body will be heated in amount determined by its own magnetic properties.

CLARENCE J. COBERLY.