US2799604A

US2799604A - Method of protecting surfaces of hot metallic bodies against oxidation

Info

Publication number: US2799604A
Application number: US197939A
Authority: US
Inventors: Harold J Ness
Original assignee: Metallurgical Processes Co
Current assignee: Metallurgical Processes Co
Priority date: 1950-11-28
Filing date: 1950-11-28
Publication date: 1957-07-16
Anticipated expiration: 1974-07-16

Description

NESS

-6 Sheets-Sheet 1 July 16, 1957 H. J.

' METHOD OF PROTECTING SURFACES 0F HOT METALLIC BODIES AGAINST OXIDATION Flled Nov 28, 1950 N INVENTOR H.J.NE$S

ATTORNEY Jul 16, 1957 H. J. NESS 2,799,604 METHOD OF PROTECTING SURFACES OF HOT METALLIC BODIES AGAINST OXIDATION Filed Nov. 28, 1950 6 Sheets-Sheet 2 INVENTOR H J. N E SS July 16, 1957 f H. .1. NESS 2,799, 4

METHOD OF PROTECTING SURFACES os- HOT METALLIC BODIES AGAINST OXIDATION Filed Nov. 28, 1950 e Sheefs-Sheet s INVENTOR H.J.NESS

ATTORNEY July 16, 1957 H. J. NESS 2,7 METHOD OF PROTECTING SURFACES OF HOT METALLIC BODIES AGAINST OXIDATION Filed Nov. 28. 1950 s Sheets-Sheet 5 1 .53 V II f /{9.3 45 51 I i: j!

i 1 J4 1 m? 44 42 1a; A fig 1 INVENTOR July 16, 1957 H. J. NESS 2,7 4

METHOD OF PROTECTING SURFACES OF HOT METALLIC BODIES AGAINST OXIDATION Filed Nov. 28, 1950 6 Sheets-Sheet 6 95 xx 91' xx 101 T T T i M M .A.' L B .97 /k INVENTOR H.J.NESS

' A TORNEY United States Patent METHOD OF PROTECTING SURFACES OF HOT METALLIC BODIES AGAINST OXIDATION Harold? J. Ness, Montcl'air, N. J., assignor to Metallurgical Processes Co., Newark, N. J., a corporation of New Jersey Application November 28, 1950, Serial No. 197,939

Claims. (Cl. 148-13-.1)

This: invention relates. to a. process for the protection of metallic bodies against oxidation, and more particularly tm the prevention or retardation of scale formation. on predetermined surfaces of such bodies during heating and, if desired, during mechanical working thereof.

It is described herein with particular reference to the protection of the interior surfaces of tubular or recessed bodies but it is not limited thereto.

In the fabrication of steel tubing, such as pipe of large diameter, it is the practice to heat a billet of suitable size and shape to a temperature of about 2300 F. and toform a tubular blank therefrom by passing a piercing tool through the billet. The passage thus formed and the diameter of the blank are then increased by expanding, ballooning or repiercing of the tube in successive steps, with intermediate reheating of the tube. For this operation a number of piercing and expanding stations are provided with intermediate reheating furnaces connected by suitable conveyor mechanism. The invention is herein described as applied to one of such reheating furnaces.

In heating the tubular blanks a serious problem arises due tothe fact that each tube as it is placed into the reheating furnace at a temperature of from 1100 F. to 1400 F. contains a large volume of air, more or less entrapped within its interior, whichis replaced or consumed by the furnace gases only at a slow rate. As a consequence the interior surfaces of the tubes become strongly oxidized or scaled .as the tubes are brought up to heat.

Scaling of the tubes is also increased by the nature of the general furnace atmosphere. In order to obtain rapid heating or maximum production from such furnaces it is necessary to operate the burners with an excess ofoxygen, as a result of which the products of combustion are strongly oxidizing to the metal and severe scale formation is inherent in the normal operation of such furnaces.

The scale formation on the interior of the tubes causes severe pitting of the surface due in part to being rolled or pressed into the surface of the metal in the mechanical working of the tube so that its removal by the subsequent pickling operation leaves holes or pits therein. The interior scale also impedes the piercing and expand- .ing operations, the scale gathering before or accumulating on the piercing and expanding tools so as to gouge the metal and slow down the working speed. It also causes excessive wear of the tools and necessitates their appreciable proportion of rejections becomes a serious "ice matter, not only in time and labor consumed in form ing: the tubes but in. that required to cut the: tubes by torch into usable scrap. sizes for remelting- One of the objects. of the present invention is to elimi nate or reduce to an acceptable amount, the interior scale ing occurring in the heating of tubular or other hollow or recessed metal bodies.

Another object is to eliminate rapidly. the oxidizing condition existent in the interior of hollow metal bodies when they are placed in a. heating furnace.

A further object is to provide a neutral or. scale retard; ing atmosphere condition in contact with predetermined surfaces of metal bodies during, heating thereof, such condition being produced, at least in. part, independently of the general furnace atmosphere.

Still another object is to provide a method of locally producing an atmosphere in contact with a surface: of a metal body during heating thereof in a furnace which is less. oxidizing. to the metal than the general furnace atmosphere of said furnace.

A still further object is to provide: an atmosphere in contact with a predetermined surface or surfaces of a metal body being heated which will produce an oxidizing resistant and lubricating coating thereon.

Still another object is to protect metal partsfrom-oxidation after removal from a. furnace and during hot work,- ing thereof.

A further object is to increase the speed and uniformity of heating of hollow bodies.

Other objects and advantages will hereinafter appear.

in accordance with the present invention a hydrocarbon fuel or a mixture of fuel and air or other gas is sprayed or otherwise injected, in an atomized or finely divided and highly dispersed condition, into contact with the surface of the metal to be protected from oxidation in such manner as to produce a gaseous atmosphere by rapid reaction of the hydrocarbon fuel adjacent toor in contact with the surface of the metal, which atmosphere will be less oxidizing to the metal than the general atmosphere surrounding the metal.

The fuel should be supplied at a rate not materially greater and in some cases somewhat less than the reaction. rate thereof adjacent the metal surface to be protected' so as to avoid any substantial accumulation of the fuel. Furthermore, the reaction rate, as determined by the flash point and degree of atomization or dispersion of the fuel, should be sufliciently rapid and the rate of supply such as to generate gaseous reaction products at. a rate greater than the rate of dissipation of such products, so as to maintain a positive pressure of such reaction products adjacent to the surface of the metal to be protected. In the case of hollow bodies, such as tubes, the. generation of the gaseous reaction products should be rapid enough to completely fill the tube under a pressuresomewhat greater than the external atmosphere of the tube so as to preclude any influx of such external atmosphere into the interior of the tube. In such cases the fuel or fuel-gas mixture serves the double purpose of eliminating the oxygen trapped therein and, by proper control, to produce an atmosphere which is non-oxidizing to. the metal or is sufiiciently low in CO2 content to reducethe oxidation of the inner surface of the tube to an acceptable amount.

If desired, a small amount of a lithium compound, such as lithium carbonate, may be included inthe mixture to facilitate obtaining of the desired neutral atmosphere condition and for producing a protective coating on the treated surface which will serve, both during heating and upon the subsequent removal of the work from the furnace, to reduce scaling of thesurface and to act as a hot lubricant during any desired mechanical Working of the metal.

The following description will be directed primarily to the preferred embodiment of the invention, namely, to the applying of a lithium compound containing air-fuel mixture, but it is to be understood that for certain purposes suflicient protection is afforded by the fuel or airfuel mixture alone.

The neutralizing material may comprise any suitable liquid, solid or gaseous fuel, and may contain in solution or admixed therewith a suitable amount of a lithium compound, such as the chloride or carbonate of lithium, and may be applied to the surface to be protected just prior to or shortly after such parts are introduced into the furnace.

The hydrocarbon constituent of the neutralizing medium may comprise a light oil, such as kerosene or a mixture of hydrocarbon liquids having different flash points. An example of a medium comprising essentially a simple oil may consist of a mixture of kerosene or light fuel oil and lithium naphthalate, and may in addition contain a proportion of lithium carbonate in suspension. In formulating this medium the lithium carbonate is added to naphthenic acid in the proportion of 3 /2 pounds of lithium carbonate to 5 gallons of naphthenic acid of 200 acidity. Approximately 1.9 pounds of the carbonate will be in solution and about 1.6 pounds will be in suspension. The lithium carbonate laden naphthenic acid is then added to the liquid fuel in the ratio of l to 10. The use of naphthenic acid is only a convenient Way of introducing the lithium compounds into the oil whereby a portion thereof will remain in solution and, if desired, the compounds may be added directly to the fuel and retained in suspension during use by agitation. Other hydrocarbons, such as light alcohols, may also be used either alone or in various mixtures.

Examples of solid fuels which may be used are any of the heavy hydrocarbon soaps or greases, such as s'tearate or petroleum jelly, and pulverized fuels such as coal, either alone or mixed with a lithium compound. Gaseous fuels, such as propane, methane, natural gas or an endothermically cracked gas of suitable composition may also be employed suitably lithiated, if desired.

The amount of fuel employed will depend primarily on the volume of oxygen to be consumed within the tube or other hollow part and the COz/CO ratio desired in the gas in contact with the surface to be protected. It should preferably be a volume of fuel which will produce a rich exothermic or an endothermic reaction with the oxygen or oxides within the tube and with any oxygen containing gas supplied with the fuel, so as to produce a neutral or substantially neutral gas atmosphere within the tube. This condition is obtained when the COz/CO ratio, by volume, is of the order of magnitude of 1.0 or less, depending upon the temperature. The amount of fuel required in a tube having a given internal capacity is not critical or difl'icult to determine. It will depend, of course, upon the composition of the fuel and the amount of supplemental air or other oxygen containing gas supplied with the fuel. The amount of lithium compound employed also is not critical, its principal purpose being to lower the HzQ/Hz ratio in the atmosphere and to provide a protective coating on the surface of the metal, both of which enhance the non-scaling properties of the atmosphere produced. In general, when lithium compounds are added to the fuel, a somewhat less rich fuel mixture is required, the presence of the lithium permitting a neutral or substantially neutral condition to be obtained with a somewhat higher CO content in the gaseous atmosphere. With the lithium carbonate-naphthenic acid fuel oil mixture specified above, highly satisfactory results have been obtained in protecting the interior of steel tubes having a diameter of 20 inches and a length of 45 feet, by applying approximately one pint of the mixture, atomized with air, into the interior of the tube. In place of lithium carbonate alone I have found that other carbonates, such as barium carbonate and strontium carbonate, may be mixed therewith; the lithium carbonate upon melting on the surface of the work either dissolves the other salts or reduces their melting point so that the mixture becomes entirely fluid above about 1200 F. to 1500 F. depending upon the proportion of lithium carbonate in the mixture, 10% to 20% lithium carbonate being sufficient for this purpose.

The temperature of the metal body at the time of application of the hydrocarbon liquid to the surface thereof should be above the reaction temperature of the fuel, or fuel and oxidizing gas used therewith. If lithium carbonate or a mixture thereof with alkaline earth carbonates is added to or supplied with the fuel, the metal to be treated should be above the fusion point of the compound to insure the deposit of a fused layer of the compound on the surface being, treated. When lithium carbonate is used alone, this temperature is about 1150 F.

The hydrocarbon is most conveniently supplied to the surface to be protected by spraying it onto the part under suitably controlled conditions, although other methods of application may be employed, the principal considerations being to have the tube in a properly heated condition at the time of application of the fuel; to employ a fuel having a rapid reaction rate, either by nature or by virtue of a high degree of atomization or dispersion, so that the reaction products are formed substantially upon contact with the surface or prior thereto; to control the rate of injection of the fuel so as to produce a positive pressure of the gaseous reaction products at the surface of the metal; and to supply a quantity of fuel and, if necessary, air or other oxygen producing medium to obtain reaction products which are substantially neutral to the metal.

In treating tubular bodies it is desirable to apply the medium in such manner that it will enter the tube at a velocity greater than the propagation rate of the reactions so that they occur only Within the tube, preferably at the entering end, and continue the hydrocarbon fuel supply for a period and at a rate which will create a sufficient volume of gas to billow rapidly through the length of the tube by expansion thereof and by the maintenance of a pressure behind the traveling column, so as to completely vfill 'the tube and displace or react with the gas therein. This is most conveniently effected by spraying a liquid, solid or gaseous hydrocarbon, preferably with air and maintaining a fine spray cone thatengages the inner walls of the tube near the end thereof adjacent to the spray nozzle.

The lithium compound or mixture thereof with alkaline earth carbonates, when employed with the hydrocarbon fuel, deposits onto the surface to be protected and forms a molten layer thereon principally of the carbonate which serves to isolate the surface, in part, from the gaseous atmosphere. While this coating gradually evaporates from the surface, it will ordinarily remain throughout the short heating cycle required to bring the metal up to working temperature. Likewise, while the protective atmosphere is gradually displaced or reacted with the general furnace gases, it persists in a sufficient degree throughout the time required under rapid heating to bring the metal to heat, to prevent any harmful oxidation of the surface. However, if heating cycles beyond the effective life of the coating or of the protective atmosphere are to be employed, it may be desirable to retreat the surfaces to be protected. In the case of tubular bodies, a single injection will provide protection for an average five to ten minute heating cycle. With surfaces where less entrapment of the reaction products is provided, more frequent or even continuous treatment may be employed. It is also advantageous to renew the carbonate coating just prior or just after removal of the tube from the furnace, since this coating serves both to-protect the surface from oxidation during working of the part outside of the furnace and, as heretofore stated, serves as a hot lubricant. for the piercing heads. or other tools employed. in the. hot working of the: part.

The. process. of the. presentinveution will. best be. understood. by reference to. the accompanying drawings. which by way of example disclose one form. of mechanism for carrying out, the process. In. the drawings:

Fig. 1; is a. horizontal. sectional view of a tube. heating furnace having the present invention applied thereto;

Fig. 2 is: a. vertical sectional viewof the furnace taken on the line 22 of Fig. 1;

Fig. 3 is a fragmentary el'evationalv view of the furnace as seen. from. the left in Fig. 1., showing the hydrocarbon liquid injecting mechanism. associated. therewith;

Fig. 4: is a front elevational. view of one of the. injecting mechanisms shown. in Fig. 3;

Fig. 5 is a side elevation of the mechanism of Fig. 4;

Fig. 6 is a sectional viewof the injection nozzle;

Fig. 7 is a wiring diagram. of the electrical mechanism for controlling the operation of the. injecting mechanism;

Fig. 8 isa vertical. sectional view of. a pump and nozzle mechanism for injecting liquid fuel into a tube, without the use of an atomizing' gas; and

Fig. 9v shows mechanism for employing a solid hydrocarbon. fuel.

Referring first to Figs. 1 and 2, a. typical tube heating furnace. isshown as comprising the two

side walls

11, 12, end. walls. 13, 14, a roof and an inclined floor 16. Burners. 17 extend through. theupper side walls 11. and 12, alternating with. vent stacks 18 extending from floor level vent ports 19; Doors 21, 22. normally close the tube charging and discharging ports. 23 and 24, respectively, and. similar doors 25 and. 26 normally close ports 27 and 28 disposed opposite to the charging anddischarging ports. The doors 21, 22, 25. and 26 are vertically movable to. openposition by means not shown.

The tubes 29 to be heated are fed. into the furnace through the port 23 by means of aroller conveyor 31 and. associated. pusher mechanism notshown but indicated by. the arrow 31'. They move from the loading position opposite

ports

23, 27, tothe discharge position, opposite ports. 24,. 28, by gravity, the furnace normally being filledas shown. Removal of. the tubes from. the furnace at the lower, or discharge, position is. effected by pusher mechanism not shown but indicated. by the arrow 32, insertable throughv the port 28, the tubesbeing pushed onto. a. discharge conveyor 32.

The furnace. structure shown. and the. pusher and conveyor mechanism are well known. in theart and. form no part of the present. invention.

The tubes charged into the furnace, following a piercing or expanding operation, will normallybe. at a temperature of from 1100- F. to 1400 F. They contain within their interior a largevolume of air which is to a considerable degree trapped therein and in the absence of. the present invention is only slowly replaced by or combined with, the combustion gases of the furnace. As a consequence severe scaling of the interior of the tubes occurs. This scale, as previously stated, interferes with internal working, of the-tubes in subsequent expanding or straightening, operations andv often causesrejection of the tubes inwhole. or in part.

In. order to prevent or reduce to acceptable. amounts the internal scaling of the tubes, I have provided mechanism for injecting a hydrocarbon fuel. into the interior of the tubes while they are within the. furnace chamber. This. injection serves the. purpose of eliminating the free oxygen, from the tube and. of creating a neutral or substantially neutral atmosphere condition therein. In addition, as stated, it may serve tov produce a lithium compound containing coating on the interior Wall of each tube, which serves as a continuing supply of lithium, during the heating period, to neutralize any oxidizing effects caused by. displacement of the interior atmosphere of the tube by the combustion. gases. surrounding the tubes. Injecting mechanism for this purpose. is indicated at 33,

6 in. Fig, 1,. disposed opposite the port 27 and at33 adjacent. to the port 28,. the. detailed structure and operation of which Will subsequently be described.

The general sequence of operation of the furnace loading, unloading, and injecting mechanism is as follows. The

doors

22 and 26. are opened and the pusher mechanism, operating through the port 28, moves the lowermost tube 29" onto the conveyor 32, from which is passes directly to the hotworking machine 9, allowing the entire charge of tubes to move by gravity to bring. the next tube into discharge position.

Doors

22 and 26 are closed and door 21 opened. for the admission of another tube at the upper end of the run. Thereafter, the door 21' is closed and door 25 is. opened to. permit the injecting apparatus 33 to introduce the hydrocarbon fuel, suitably lithiated, if desired, into the interior of the tube, in a pressurized spray. The amount of fuel supplied to the tube should be such. as to react with the oxygen within the tube to consume the same, preferably but not necessarily, by av rich exothermic reaction so as to. produce a COz/CO ratio of approximately 1.0 or less. The amount of fuel required can best. be determined by trial. It is not critical but should be maintained within reasonable limits. The lithium content. of the oil serves to facilitate the production of the desired: neutral atmosphere at somewhat higher COz/CO ratiosv than would otherwise be possible. This phenomenon is more fully disclosed in my copending application Serial No. l39,906, filed January 21, 1950. In. addition the. lithium compound with or without other additions heretofore referred to is deposited in a thin adherent layer on the interiorwall of the tube, as stated, to provide continuing protection from oxidation as the tube is passed through the fur nace.

The carbonate coating produced on the work serves the additional function of lubricating the interior. surface in the subsequent expanding, operation. Since a part of the coating will be consumed as thetube passes through. the furnace, it. is desirable to replace-or augment it just prior to or just after discharge. of thetube from the furnace. I prefer to do this in the furnace. by means of the injecting. machanism. 33. However, in the discharge position of thetube, the gaseous filling will'consist of the usual products of combustion, slightly'modified by the lithium reactions therein, rather than atmospheric air. Consequently, a somewhat less" rich hydrocarbon spray may be employed, the chief function of the injection being to. coat the interior Wall rather than to modify the gaseous atmosphere. If desired, a compoundof'lithium', such as the carbonate admixed, if desired, with barium or strontium carbonate, may be sprayed into the tube at the discharge position, unmixed with. a hydrocarbon fuel, but I prefer to employ a suitable mixture of the chemically treated fuel-and air and to release the coating'compounds by either an endothermic or" rich exothermic. reaction of the fuel within the tube;

The injecting mechanisms 33 and 33' associated with the ports 27 and 28, respectively, are. each shown some what diagrammatically in'Fig. 3. Since they are identical in structure only that one 33shown in the'charging position of the furnace will be described, thecorresponding parts of the other injector 33' being designatedby corresponding reference numerals primed. The injector 3'3 compnses the injecting 'head36 mounted onia'carriage 37 adapted to slide on a table'38 fromaposition to one side of the-port 27" to a. position in alignment therewith, under actuation of a hydraulic cylinder 39. The injecting head 36 of injector 33' is shown in Fig. 3 in its normal offfiring position whereas the head 36 of injector 33 is shown in its off-normal, or. firing position. Referringnow to. Figs. 4 and 5 for a more detailedjdescription ofthe injector 33, it will be seen that the injector head 36.com-: prises a cylindricalshield having a solid peripheral flange 4'1 and a rear wall 42,- suitably reinforced'by radial flanges- 432 Apipe coupling 44, adaptedto receive an injector nozzle 45, extends through a central opening in the wall 42 and is welded or otherwise secured thereto. A pair of channel members 48 welded to the peripheral wall 41 serve to support the injector head on the carriage 37, as will presently appear.

In Fig. 6 I have shown a detail of the injector nozzle. It comprises a casting 51 threaded into the pipe coupling 44 and apertured to receive an atomizing gas conduit 52 and a hydrocarbon liquid conduit 53, the latter communicating with a central bore 54 having a liquid outlet port 55 adapted to be closed by a needle stem 56, adjustably threaded in a gland member 57. A passageway 58 extends from the gas conduit 52 into a conical passageway 59 surrounding the liquid outlet port 55 in such manner as to inspirate the hydrocarbon liquid in a narrow angle stream. The gas and liquid are supplied under sufiicient pressure to produce a spray of sufiicient velocity to penetrate into the adjacent end of the tubes contained within the furnace and having an angle such as to engage the inner wall of the tube near the end thereof. The manner of supplying the nozzle 51 with air and hydrocarbon liquid under pressure and the proportioning and control thereof will be described with reference to Figs. 4 and 7.

Referring again to Figs. 4 and 5, the carriage 37 by which the injector head is supported comprises a pair of spaced channels 61 bridged by a plate 62 upon which two stanchions 63, 64 are carried The stanchions each comprise spaced truncated

triangular web plates

65, 66 welded to the injector head supporting plates 67 and secured to the base plate 62, as by welding. The injector head is bolted to the plate 67, between the

plates

65 and 66, by means of the channel members 48. A guide foot 68 is welded to the base of each of the channels 61 and extends outwardly therefrom for sliding engagement between spaced

longitudinal guides

71 and 72, carried by I-

members

73, 74 supported on a structural iron framework 75 forming the table 38.

The hydraulic cylinder 39 is also supported on the framework by means of brackets 76 and is provided with compressed

air inlet conduits

77 and 78, at either end, whereby, by means of suitable operation of a reversing valve mechanism 79 through a solenoid 80, the piston contained therein may be operated in either direction in a predetermined stroke. The piston shaft 81 is connected through a head 82 to a bracket 83 depending from the carriage 37 and serves to move the carriage and the injector head from one end of the guide rails 73, 74 to the other so as to position the injector head in alignment with the furnace inlet port or to one side thereof.

A pair of

limit switches

84 and 85 are carried by the table 75 in position to be engaged by the head 82 in each of its extreme positions of movement. These switches, as will subsequently appear, control both the movement of the carriage and the operation of the injector nozzle. Since the limit switches for the injectors located at the charging and discharging end of the furnace are electrically interconnected, I have, for clarity, designated those at the discharge position as 84 and 85.

Air or other atomizing gas, such as carbon monoxide, carbon dioxide, or a gaseous hydrocarbon fuel, or the reaction products of a hydrocarbon fuel, is supplied under suitable pressure to the gas inlet conduit 52 of the injector nozzle, from the gas line 86, through the flexible connection 87 and solenoid valve 88. A lithiated hydrocarbon is also supplied to the nozzle 45 from a tank 89, by the pump 90, connected by a flexible conduit 91 and solenoid valve 92 to the liquid inlet conduit 53 of the nozzle. A pressure operated relief valve 93 permits the fuel to be circulated through the tank 89 continuously, thereby insuring constant agitation of the contents of the tank so as to maintain the lithium compound in suspension in the liquid fuel.

Reference will now be had to Fig. 7, wherein the electrical apparatus and control circuits are shown. These comprise the limit switches 84 and 85, air and

oil supply solenoids

88 and 93, respectively, cylinder reversing switch solenoid 80, control relay 94, a timing switch 95, and a manual switch 96 associated with injector mechanism 33; and similar elements bearing primed numbers associated with the injector mechanism 33. A power or line switch 97 is also included. Limit switches 84, 84, 85 and 85 are normally open and are adapted to be closed by the carriage head 82 or 82'.

The intercontrol of the two injectors is such that only one can be moved into firing position at a time. Normally, both are retained in their non-firing or extreme outer positions. In such position, head 82 of injector 33 serves to hold normally open switch 84 closed and head 82' of injector 33' holds normally open switch 85 closed. Assuming the injector heads to be in these positions and power switch 97 closed, if the operator desires to inject the hydrocarbon fuel into a tube newly charged into the furnace, the door 25 is first opened, and switch 96 momentarily closed. A circuit is then completed from the power line A, conductor 98, winding of control relay 94 and cylinder solenoid 8!), in parallel, thence by switch 96 normally closed contacts of timer 95 and by conductor 99 through the closed contact of limit switch 85' (with carriage 33 in non-firing position), and thence by conductor g 101 to the power line B. Relay 94 picks up and at its upper contacts short-circuits the switch 96 so that the circuit will remain energized independently thereof. 0peration of solenoid 88 operates the reversing valve 79 to supply air to the right end of the cylinder 39 and to vent the opposite end thereof whereby the carriage 37 of in jector 33 moves to the left. At its lower contacts relay 94 prepares parallel circuits to the winding of the timer 95 and to the

nozzle solenoids

93 and 88, through open contacts of limit switch 85, which circuit is completed by closing of contacts of switch 85 at the end of the travel of carriage 37. When this occurs the gas and fluid valves to the nozzle 45 are operated to inject the desired fuel and gas mixture into the tube being heated. Energy through the timer 95 starts its operation and upon completion of the timed interval its contacts open, breaking the circuit to the relay 94 whereby its contacts open, and releasing the cylinder reversing valve solenoid whereupon it reverses the air connections to the cylinder 39. Opening of the contacts of relay 94 interrupts the circuit to the

nozzle solenoids

93 and 88, to discontinue the spray, and the circuit to the timing switch 95 to permit the timer mechanism to return to normal with the consequent opening of its contacts. The carriage 37 is thus restored to its right hand position. In this position of the carriage, limit switch will again be open and switch 84 closed, and the entire electrical system restored to normal.

In a similar manner, operation of manual switch 96' will start the cycle of operation of the injector head 36' causing it to move to the right to firing position, fire for the period determined by the timer and then return to its normal left hand position. In actual practice the manual switches 96 and 96' are replaced by relays which are momentarily energized in coordination with the opening of the doors 25 and 26 and the operation of the rams which effect loading and unloading of the tubes so that injector head 36 automatically operates immediately following a tube loading operation, and head 36' operates just prior to the removal of the tube from the furnace.

It will be noted that operation of control switch 96 is effective to energize the relay 94 only when the limit switch 85' is closed, that is, when the injector head 36 is in its normal or non-firing position, and likewise relay 94' is operative only when limit switch 84 of head 36 is closed, that is, when the head 36 is in its non-firing position. This prevents the operation of either of the injector heads except when the other is in its non-firing position.

In Fig. 8 I have shown a suitable form of apparatus for introducing a liquid fuel without air atomization. This apparatus comprises a positive displacement pump 100 having a plunger 101 operated in any suitable manner, as

by a revolving crank (not shown) a fuelinlet. port 102, and an outlet port 103, each provided with-check valves 104 and 105, respectively. The inlet port 102. is connected by a conduit 106 to a liquid fuel supply tank, and the outlet port 103 is joined by a conduit 107 to a. spray nozzle 10.8 disposed opposite a tube 109- to be internally treated. The nozzle 108 hasv a fuel duct 11.0. and a spray tip. 111 controlled by a needle-valve 11-2 in the usual manner. Control of the spray interval may be obtained by substituting a relay in the circuit of Fig. 7 inplace of the valve magnets 88 and. 93., for energizing the pump motor.

In Fig. 9 I have shown a method ofsupplying a. gaseous fuel to the. interior of atube 113,. admixed. with lithium carbonate or a suitable coating. and protective material containing lithium carbonate. In. this modification the powdered compounds are contained within a hopper 114 having an electric vibrator 1150f conventional design secured thereto. The hopper discharges into a horizontal tubular chamber 116 having a plunger 117 operative therein by anexternal solenoid 118'. Spaced from. the plunger 117 by the shaft 119 is a disc 120 which, in cooperation with the end of 'the plunger, formsa powder receiving recess for conveying a measured amount of powder from its load receiving position shown, to its discharge position to the left of'the chamber 116. The chamber 16 is in alignment with. a discharge passageway 121 containing an orifice 122, and associated with thepassageway 121 is .a venturi injector 123 suppliedv with a source of fuel gas under pressure, by a conduit 124' provided with an electrical control valve 125'. The powder discharged into the passageway 121, on energization of the: solenoid 118', flows through the orifice 122 under the combined action of gravity and thesuction effect of theventuri nozzle 126. The rate of feeding of the powder through the orifice 122 may becontrolled, to some extent by regulating the pressure above the powder in. the chamber 121 by a vent or a source of pressurized air or gas 127, under control of a valve 128. The instant of injection is determined by energization of the solenoid 1'18 and the operating magnet of the valve 125 which, as will beunderstood, may be substituted for the

magnets

88 and 93 of Fig; 7. The electric vibrator is-controlled overa circuit including a switch 129, which is closed in the retracted position ofthe solenoid plunger, anda timing switch 130, which opens a predetermined interval after'the energizing of the circuit. Hence, upon the return movement, to the. right of the solenoid plunger, after delivering-a charge to the chamber 121, switch 129 closes, energizing the vibrator. 115 for a short interval to assist. in feeding -of;a new charge to the piston recess. The. subsequent. opening of the vibrator circuit, on the delivering of this charge to the chamber 121, causes the timer. 130 to restore to normal so as to reclose its contacts. in. readinessfor'the next timing operation.

The injector 123 directs the steram of powder laden fuel gas into the interior of the hot tube 113, for the protective and coating purpose described.

It is to be understood, of course, that the process herein disclosed may be carried on with still further types of apparatus or by means of manually operated spray equipment, and therefore I do not desire to be restricted to the particular means disclosed.

What is claimed is:

l. The method of protecting the surface of heated metal from scale while it is enclosed in a furnace comprising combusting a hydrocarbon fuel and air mixture in said furnace containing suflicient air to effect substantially complete combustion of said fuel, whereby to produce a gaseous heating atmosphere in said furnace which is oxidizing to the surface of said metal at elevated temperatures, subjecting said metal to the heating effect of said combustion to heat the same in said atmosphere to a temperature above 1200 F., while said metal is above said temperature applying locally to the surface thereof to be protected,

unassociated. with oxygen. in: combustion. supporting amounts, a hydrocarbon fuel. in a highly dispersed con; dition, and continuing said application of hydrocarbon fuel tosaid surface until saidfuelreacts with the. portion of said atmosphere which is in contact with such surface to reduce the. oxidizing nature thereof and. to produce a body of gas in.-contact with-said surface. having a compo.- s-itionv which is substantially less oxidizing in nature than said atmosphere.

2.. The method. of protecting the. surface. of. heated metal from scale while it. is enclosed in a. furnace com? prising combusting a hydrocarbon fuel and air mixture. in. said. furnace containing sufficient air to effect substantially complete combustion. of. said fuel, whereby to produce. a gaseous heating atmosphere in. said. furnace which is oxidizing to the surface: ofsaid. metal at elevated temperatures, subjecting said metalto the heating. effect of. said. combustion to heat the samev in. said atmosphere to a temperature above. 1200 F., while said. metal. is above. said. temperature applying locally to the surface thereof to be protected,.unassociated withv oxygenin com? bustion supporting. amounts a hydrocarbon fuel and a compound-of lithium, and continuing said applicationof fuel and compound of. lithium until the same. reacts with the said atmosphere in-contact with. such surface to reduce the oxidizing nature thereof and to. produce a .body. of gas in contact with said surface. having a composition which is. substantially non-oxidizing, said lithium. com.- pound. being. provided in a quantity which will produce a lithium compound coatingv on-said surface to be. protected.

3. The method of protecting the. surface of heated metal from scale. while it is enclosed in. a furnacecomprising combusting a. hydrocarbon fuel and air mixture in said furnace containing sufiicient air to effect sub: stantially complete combustion of said fuel, whereby to produce a gaseous heating atmosphere in said furnace which is oxidizingv to-the. surface of said metal at elevated temperatures, subjecting said metal to the heatingv effect. of said combustion to heat the same in said. atmos; phere to a. temperature above 12.00 E, while. said metal is above said temperature applying locally to the surface thereof to be protected, unassociated with oxygen in combustion supporting amounts hydrocarbon fuel containinglithium carbonate, and continuing said application of lithium carbonate containing hydrocarbon fuel to said surface until the same reacts with the said atmosphere at said surface to reduce the oxidizing nature thereof 'and produces a body of gas in contactwith said surface having a composition which is substantially. non oxidizing in nature, saidv lithium carbonate being provided in said hydrocarbon fuelin a quantity which will form a continuous fused coatingwof lithium carbonateon said surface to be protected.

4. The method of'protecting the surface of heated metal from scale while it is enclosed in a furnace comprising cornbusting a hydrocarbon fuel and air mixture in said furnace containing sufficient air to effect substantially complete combustion of said fuel, whereby to produce a gaseous heating atmosphere in said furnace which is oxidizing to the surface of said metal at elevated temperatures, subjecting said metal to the heating effect of said combustion to heat the same in said atmosphere, while said metal is above said temperature applying locally to the surface thereof to be protected unassociated with oxygen in combustion supporting amounts a hydrocarbon fuel and a mixture of lithium carbonate and an alkaline earth carbonate, containing at least 10% lithium carbonate, while the metal is at a temperature above the melting point of said mixture, and continuing said application of said hydrocarbon fuel and carbonate mixture to said surface until the same reacts with the said atmos phere in contact with said surface to render the atm0sphere substantially non-oxidizing in nature, said carbonate mixturebeing provided in a quantity which will form a fused coating thereof on said. surface.

5. The method of protecting the surface of heated metal from scale while it is enclosed in a furnace comprising combusting a hydrocarbon fuel and air mixture in said furnace containing suflicient air to effect substantially complete combustion of said fuel, whereby to produce a gaseous heating atmosphere in said furnace which is oxidizing to the surface of said metal at elevated temperatures, subjecting said metal to the heating effect of said combustion to heat the same in said atmosphere, while said metal is above said temperature applying locally to the surface thereof to be protected, unassociated with oxygen in combustion supporting amounts; a hydrocarbon fuel and a mixture of barium carbonate and lithium carbonate, containing at least 10% lithium carbonate, while the metal is at a temperature above the melting point of said mixture, and continuing said application of hydrocarbon fuel and carbonate mixture to said surface until the same reacts with the said atmosphere to substantially reduce the oxidizing nature of said atmosphere in contact with said surface, said carbonate mixture being provided in a quantity which will form a fused coating thereof on said surface.

6. The method of protecting'the surface of heated metal while it is enclosed in a furnace comprising combusting a hydrocarbon fuel and air mixture in said furna ce containing sufficient air to effect substantially complete combustion of said fuel, whereby to produce a gaseous heating atmosphere in said furnace which is oxidizing to the surface of said metal at elevated temperatures, subjecting said metal to the heating eifect of said combustion to heat the same in said atmosphere, while said metal is above said temperature applying locally to the surface thereof to be protected, unassociated with oxygen in combustion supporting amounts a liquid hydrocarbon fuel while the surface is at a temperature sufficiently high to effect a reaction between said fuel and said atmosphere in contact with such surface, and continuing said spraying until a substantial layer of reaction products is formed in contact with said surface, having an oxidizing potency substantially less than that of said atmosphere.

7. The method of protecting the interior surface of hot tubular metal bodies containing an oxidizing gas from scale which comprises injecting a hydrocarbon fuel free of oxygen in combustion supporting amounts and lithium carbonate into said tubular body, while the body is at a temperature above 1200 F, said lithium carbonate being present in sufficient quantity to produce a fused coating on the interior surface of said tubular body and said fuel being provided in sufficient quantity to reduce substantially the oxidizing nature of said gas.

8. The method of protecting the interior surface of a metal body having a hollow portion during heating thereof in a normally oxidizing combustion furnace atmosphere which comprises momentarily introducing a hydrocarbon fuel free of oxygen in combustion supporting amounts into said hollow portion of said body while the latter is at a temperature between 1200 F. and 1500 R, such hydrocarbon fuel being provided in a quantity which will reduce the oxidizing nature of the gaseous atmosphere within said hollow portion of said body and produce a positive pressure of a gaseous medium thercinhaving a COz/CO ratio by volume of the order of magnitude of 1.0 or less and thereafter rapidly heating said body to above 2000 F.

9. The method of protecting the interior surface of a metal body having a hollow portion during heating thereof in a normally oxidizing combustion furnace atmosphere which comprises injecting regulated amounts of a hydrocarbon fuel free of oxygen in combustion supporting amounts in a highly dispersed condition into said hollow portion of said body while the latter is at a temperature above the reaction temperature of said fuel and below the temperature at which appreciable sealing occurs, said regulated amount being sufficient to reduce the oxidizing nature of the gaseous atmosphere within said hollow portion and to produce a positive pressure of a gaseous atmosphere therein which is substantially non-oxidizing in nature, thereafter discontinuing said injection of hydrocarbon fuel and rapidly heating said body to above 2000 F.

10. The method of protecting the interior surface of a metal body having a hollow portion during heating and subsequent hot working thereof comprising momentarily introducing a hydrocarbon fuel free of oxygen in combusition supporting amounts and iithium carbonate into said hollow portion while the said body is at a temperature above 1150 F. and below the temperature at which substantial sealing occurs in sufficient amount to produce a substantially non-oxidizing gaseous atmosphere in said hollow portion and a fused coating of lithium carbonate on the interior surface thereof, thereafter rapidly heating said body to its hot working temperature, then injecting an additional amount of lithium carbonate into said hollow portion to augment the fused coating thereon.

References Cited in the file of this patent UNITED STATES PATENTS 1,674,431 Giesecke June 19, 1928 1,812,837 Winter June 30, 1931 1,873,999 Coriolis et al. Aug. 30, 1932 1,960,808 Cope May 29, 1934 2,078,348 Simpson Apr. 27, 1937 2,181,093 Ness Nov. 21, 1939 2,229,642 Davidson Jan. 28, 1941 2,230,484 Comstock Feb. 4, 1941

Claims

1. THE METHOD OF PROTECTING THE SURFACE OF HEATED METAL FROM SCALE WHILE IT IS ENCLOSED IN A FURNACE COMPRISING COMBUSTING A HYDROCARBON FUEL AND AIR MIXTURE IN SAID FURNACE CONTAINING SUFFICIENT AIR TO EFFECT SUBSTANTIALLY COMPLETE COMBUSTION OF SAID FUEL, WHEREBY TO PRODUCE A GASEOUS HEATING ATMOSPHERE IN SAID FURNACE WHICH IS OXIDIZING TO THE SURFACE OF SAID METAL AT ELEVATED TEMPERATURES, SUBJECTING SAID METAL TO THE HEATING EFFECT OF SAID COMBUSTION TO HEAT THE SAME IN SAID ATMOSPHERE TO A TEMPERATURE ABOVE 1200*F., WHILE SAID METAL IS ABOVE SAID TEMPERATURE APPLYING LOCALLY TO THE SURFACE THEREOF TO BE PROTECTED, UNASSOCIATED WITH OXYGEN IN COMBUSTION SUPPORTING AMOUNTS, A HYDROCARBON FUEL IN A SLIGHTLY DISPERSED CONDITION, AND CONTINUING SAID APPLICATION OF HYDROCARBON FUEL TO SAID SURFACE UNTIL SAID FUEL REACTS WITH THE PORTION OF SAID ATMOSPHERE WHICH IS IN CONTACT WITH SUCH SURFACE TO REDUCE THE OXIDIZING NATURE THEREOF AND TO PRODUCE A BODY OF GAS IN CONTACT WITH SAID SURFACE HAVING A COMPOSITION WHICH IS SUBSTANTIALLY LESS OXIDIZING IN NATURE THAN SAID ATMOSPHERE.