US2462202A - Heat treating - Google Patents

Description

Fejb. 22, 1949. v J. KNIVETON 2,462,202

HEAT TREATING vv/T/vass SY W I V @Jarrow/ver Feb 22, 1.949 x.KNlvE-roN 452,202

' HEAT TREATING" Filed Jams, 1944 v j 2 shears-Sheet 2 50d /NVENTUR Patented Feb. 22, 1949 HEAT TREATING James Kniveton, Wyncote, Pa., assigner to Selas Corporation of America, a corporation of Pennsylvania Application January 29, 1944, Serial No. 520,271

7 Claims.

My invention relates to the art of heat treating strips, sheets, wires and the like which are passed continuously through a furnace.

The rate at which work of the above-described type can be heat treated in the usual type of furnace is dependent upon the rate at which heat is transferred to the work and the size of the Work passed through a particular length of heating chamber of a furnace. Thus, in a heat treating furnace in which annealing is effected, the work passes into the charging end of the furnace at room temperature and during its travel through the furnace it must be heated to the annealing temperature. When this annealing temperature is reached, only a portion of the length of the heating chamber is utilized to maintain and hold the work at this annealing temperature.

In accordance with my invention, in order to increase the rate at which strips, sheets, wiresv and the like can be heat treated, it is proposed to provide a high temperature heating chamber immediately ahead of the charging end of the heat treating furnace. This high temperature heating chamber, which may be referred to as a preheating chamber, is of relatively high heat capacity and effective to heat saturate the work rapidly substantially to the desired elevated temperature. By heat saturating the work it is meant that either complete heat saturation of successive portions of the work may be effected in the high temperature heating chamben or such surface heat saturation may be effected that the inner core of the work will be brought up to the desired high temperature for the heat treating operation to be effected in the heat treating furnace.

' In annealing, for example, theadvantage of rapidly heating the work to a denite elevated temperature in the preheating chamber, before the work enters the chamber of the annealing furnace, is that the furnace substantially in its entirety may serve as a holding and stabilizing chamber. In other words, the work can be held and maintained at the desired annealing temperature substantially during its entire travel through the annealing furnace, so that a tremendous increase in the rate at which work is annealed can be effected. In this way the production rate of existing annealing furnaces can be stepped up to a substantial degree. Further, such faster speeds at which work can be annealed may be effected without operating the annealing furnace at excessive furnace temperatures which would burn the work when the work stops moving in the annealing furnace.

An object of my invention is, therefore, to pro-V vide an improvement for increasing the rate at which work passing continuously through a furnace can be heat treated in which the surface of the work or the work in its entirety is rapidly heat saturated to a desired elevated temperature immediately before the work enters the charging end of the heat treating furnace.

Another object'of my invention is to heat work rapidly to a high temperature for a heat treating operation just before entering the charging end of the heat treating furnace by a high heat capacity heating chamber capable of producing a relatively high thermal head.

' A further object of my invention is to provide such a high heat capacity heating'chamber immediately ahead of the charging end of a heat treating furnace, such as an annealing furnace, for example, which may be readily rendered ineffective to heat the work sufficiently to burn it, in the event of work stoppage in the heating chamber.

1 The novel features which I believe to be characteristic of my invention are set forth with particularity in the claims. however, both as to organization and method, together with further objects and advantages thereof, will be better understood by reference to the following description taken in connection with the accompanying drawings ofwhich Fig. 1 more or less diagrammatically illustrates a sectional view of annealing apparatus embodying the invention; Fig. 2 is an enlarged fragmentary view of the preheating chamber shown in Fig. l, to illustrate the invention more clearly; Fig. 3 is a top plan view of the preheating chamber shown in Fig. 2; and Fig. 4 is a sectional view more or less diagrammatically illustrating a modification of the invention.

In the drawings my invention has been shown in connection with the annealing of Wires, although it is to be understood that the invention is equally applicable to the annealing of strips, sheets and the like and to Iother heat treating operations. Referring more particularly to Fig. 1, a wire i0 to be annealed is unwound from a coil Il and passed over a guide pulley I2. From the guide pulley l2 the wire l0 passes downwardly through a preheater I4 and an annealing furnace l5 into a quench tank I6 containing a body of quenching liquid I '1, such as water, for example. The wire I 0 then passes over a guide pulley I8 in quench tank i6 and upwardly through a drying unit I9. From the drying unit i9 the wire l0 passes over a guide pulley -20 and The invention itself,

- 3 thence rewound at coil 2 I. Although only a single strand of wire I'U is shown in Figs. l and 2, it should be understood that a plurality of strands of wire III may be passed simultaneously through heating chamber I4, furnace I5, quench tank Iii, and drying unit l. In Fig. 3 a plurality of such strands of wire` il) are shown passing through heating chamber I4.

The annealing furnace I5 illustrated is of a gas fired type having vertical walls 22 and a roof 23- formed of suitable refractory material. The vertical walls 22 and roof 23 are disposed within a framework or outer shell 24 supported by a foundation 24a on a supportingsurface. Theroof 23 constitutes the charging end of the furnace I5 and is formed with an openingI 25 into which the Wire I9 passes for the annealingi operation. A plurality of hinged flaps 26 may be provided at the top of the shell 24, in the immediate vicinity of opening 25, to form a narrow space through which the wires il) niaypass into the' furnace I5. A downwardly depending' hollow skirt'. 2'7 is. se`' cured to the lower end of furnace I5V and extends into the quench` tank I6 below the liquid leveI therein to seal the lower end" of the furnace.

A. plurality' of 'burners 2'8 are mounted and incorporated in the side walls 22 of furnace I5. The burners 28 are: arranged at diiferentelevations and disposed alongside of each other inY a plurality of rows, the number of burners and' distribution being suchth'at the' desired heating is effected of the' wire IG' passing; through the furnace' chamber 29.

The burners 28 are mounted in and form a part o'f the side walls 22. Each burner 28' comprises a molded block of ceramic material having a central passage within' which is disposed a burner tubeor sleeve 30. The outer ends ofV sleeves 3Ill are connected to manifolds 3l4 to which a gas mixture is deliveredthrough conduits3la from a.

suitable source of supply. Suitable valves32` may. be provided to controly the. pressure and'rate at whichthe gasmixturei's supplied tothe manifolds 3I.,.aI-1d. the. supply of the. gas. mixture for each burner 25. may be individually controlled by a valve, (not shown)V operable by a control member 33 disposed. at the exterior of. the manifold 3|.

The gas. mixture, which. may be a mixtureof air. and ordinary city gas, supplied to each of the'A burners 28'4 and subdivided into a. plurality of` gasA streams by a distributor or tip 3'4 fixed to the inner. endY of the tube or sleeve 29 which terminates. at acup-shaped space 35. A plurality' of burner flames are produced andmaintained about the peripheral surface of. each distributor. 3`4` and project outwardly therefrom into the cupshapedV spaces 35 inwhich combustion of the gas mixture is effected. The combustion spaces 35Y are of such shape and the flames project outwardly at such an angle from the axes of the burners that the ames. are closely adjacent to and. follow the cup-shaped refractory walls. to: heat the latter-to high temperatures approaching. incandescence.

The burners 28 are of the kind described and illustrated ingHessPatent. No. 2,215,079, granted on June 23, 1942, and' assigned to the same assignee as this application. The burners. 28 are fully disclosed in the aforementioned Hess patent which may be considered as being incorporated in this application, and,.ifA desired, reference may be had thereto for a detailed description of the burner structure.

By providing thel control valves 32 and33,Y the gas mixture suppliedD to the burners 28 may be accurately controlled so that the desired heating effect may be produced in chamber 22 throughout the height of the chamber. The burners 2: are so constructed that combustion of the gas mixture is substantially completed in the cup-shaped spaces 35, whereby flame impingernent on the work isreadily avoided. The refractory wall surfaces of the cup-shaped spaces are heated to incandescence and constitute high temperature zones or regions from which heat is radiated to the work. This radiated heat, together with convection heating resulting from the heated products of combustion passing toward the work and downwardly in chamber 29, provides a heating effect which is'readily controlled to maintain the wire I8 at the desired annealing temperature during itstravel through the furnace I5.

The hinged flaps '26 provide a seal at the top part of furnace I5 so that a positive pressure of the heated products of combustion will be maintained' in chamber 29' and prevent iiow of air into the furnace chamber. The heated products of combustion pass from the bottom of the furnace chamber 29 through a fiue 21a which is connected at' its lower end to skirt ZIand may extend upwardto a height above the preheater I4;

Since combustion of the gas mixture is substantially completed' in the cup-shaped spaces 35, the need for passing the wire I0 through a tube containing a protective atmosphere to protect the wire from burning gases, is avoided. Moreover, the burners 28 may be supplied with a slight excess ofgas so that a reducing atmosphere will be maintained in chamber. 29. rom the furnace I5' the wire. Ipasses into the quench tank I6 for the requisite quenching operation when this is necessary.

After being cooled the wire I0 passes through the drying unit I3 comprising an outer shell or framework 36 supported at 3i at one side of the quench. tank IS. Within the outer shell 38 are formed. walls 38 of refractory material in which areincorporatedburners 39 similar to the burners 23'. embodied in furnace I5 and described above. The burners 39 are. connected to intermediate manifoldsIl-which in turn are connected to main manifolds 40a to which. are secured iiexible ccnduits 4I through which a gas mixture is delivered from a source of. supply. Valves 42 may be providedto control the supply of the gas mixture to the manifolds 40 and individual valves (not shown) may be provided in the conduits leading to the several burners 39 for individually controlling the supply of the gas mixture to each burner 39. The burners 39 are adjusted to producethe desired heating effectin drying chamber lili, and, after the annealed wire has passed through this chamber, the wire I0 passes over the guidepulley 20 and is rewound at coil 2|.

Inorder to provide a controlled temperature in vannealing chamber 29, the burners 2B are preferably controlled responsive. to the rtemperature within the chamber. Thus, in the event the rate of movement of the wire decreases, or of complete stoppage of the work, the supply of the gas mixture to the burners 28 may be reduced automatically so that the temperature in chamber 29 will always remain substantially at the desired annealing temperature and not become excessively high to. cause burning of the work at slow speedsV andwhencomplete stoppage of the work occurs.

In accordance'y with my invention, in order to increase the rate'at which the wirev IB can .be annealed in furnace I5, a high temperature heating chamber I4 is provided immediately ahead of of the wire lil passing therebetween. The vertical banks of yburners are movable to an operating position near the wire IG, and are movable rearwardly from the operating position in the event cf work stoppage.

As shown in Figs. 2, 3 and 4, the burners 45 are in thev form of molded blocks of ceramic material similar to the burners 28 in furnace I5 and are incorporated in and form a part of refractory walls 45. The burners 45 are positioned in the shallow or recessed central parts o-f the refractory walls 45 disposed within frameworks or outer shells 4l which are U-shaped both in horizontal and vertical sections.

In the illustrated embodiment each bank of burners 45 consists of two horizontal rows of three burners. Each horizontal row of three burners 45 is connected to a horizontally disposed manifold 48, and the horizontal manifolds are in turn connected at intermediate regions to vertically disposed manifolds 49' to which the gas mixture is delivered through flexible conduits 50 from a suitable source of supply. The supply of the gas mixture to each horizontal manifold 48 is controlled by a valve 5I, and the supply of the gas mixture to each burner 49 is individually controlled by a Valve (not shown) having an adjustable member 52 associated therewith and adjustable at the exterior of the horizontal manithe' banks of burners 45 toward the work passing therebetween. The rear of each carriage 53 is connected by cables 5l to a wire 58 which passes over a guide pulley 58a and extends downwardly therefrom. When it is desired to move the banks of burners 45 rearwardly from the operating position shown in Fig. 1, the lower ends of the wires 58 are pulled downwardly, thereby causing the carriages 53 to ride upwardly on the incline-d guideways 55.

The preheater or heating chamber I4 is so con structed and arranged that it is capable of heating successive portions of wire l0 rapidly while passing through this chamber. By heating the wire if! substantially to the desired annealing temperature before the wire enters the charging end of furnace l5, the' furnace chamber 29 serves as a holding and stabilizing chamber substantially throughout its entire length and the wire will be substantially at the annealing temperature at the instant it enters the upper end of chamber or within a short interval of time after it enters chamber 29, and then maintained at the annealing temperature throughout substantially its entire travel through the chamber.

The burners 45 are similar to the burners 28 described above and are operated to provide a plurality of zones of radiant heat at temperatures as high as 2600 to 2800 F. These high temperatures are obtained by subdividing the fuel mixture, such as air and ordinary city gas, to produce a incandescence the refractory i wall surfaces ci' the cup-shaped spaces of burners 45. The workVv passing through the heating chamber I4 is rapidly heated to a high temperature by heat derived from the heated productsof combustion passing to the work from the cup-shapedspaces in which combustion of the fuel mixture is substantially completed, and by heat radiated from the incan descent wall surfaces.

In this Way an efficient high temperature heating chamber ill is provided which is capable of operating at a high heat capacity and can rapidly heat wires, strips and sheets and the like to the desired annealing temperature before entering the charging end of the annealing furnace l5. By heating the wire i0 to or substantially to the desired annealing temperature immediately before entering the upper end of furnacev l5, the wire i 3' can be passed through the annealing furnace at a considerably fester rate than when such preheating is not effected, thereby stepping up the production rate to a substantial dgree.

The embodiment just described and illustrated is especially suitable for the bright or clean anhealing of work formed of copper, brass, bronze nickel or stainless steel. Although the work may be oxidized when passing through the high temperature heating chamber I4, such work will be deoxidized and cleaned while passing through the furnace chamber 29 by operating the furnace I5 vwith excess gas to produce a reducing atmosphere in the furnace chamber 29.

The following example of the practice of my invention is given for purposes of illustration only. vIn a particular installation thirteen (13) gage copper wire has been annealed in an annealing furnace l5 feet long at the rate of 60 feet per minute, the wire being initially heated when first entering the annealing furnace and held and maintained at an annealing temperature of about 1180" F. after being heated to this elevated temperature. When the'copper wire is heat saturated to the annealing temperature of about 1180 F. before entering the charging end of the annealing furnace, it is possible to accelerate and step up the rate at which such copper wire is annealed by as much as 30 to 50 per cent. This represents' a substantial increase in the rate at which the wire can travel through the annealing furnace and the same bright annealing can be effected at much higher wire speeds.

One of the features contributing to the increased rate of annealing Work is due to the provision of relatively high temperature sources of heat provided in heating chamber I4. By providing sources of radiant heat at temperatures varying from 2400 to 2800 F. when an annealing temperature of about 1180" F. is desired in the work itself, as in the example just given, for example, a high thermal head is obtained which results in quick heat penetration in successive portions of the work passing rapidly through the heating chamber I4.

In the event of work stoppage, the supply of gas mixture to all of the burners 39 and 45 may be shut off. This may be effected either manually or automatically responsive to a reduction in the rate of movement of the work. Since the burners 45 in heating chamber I4 operate at relatively high heat capacity and are positioned close to the work passing therethrough, there may be suiiicient residual heat to cause burning of the work-even after the supply of thegas mixture to the burners 45 is shut off. V"Fo'r' this plurality of relatively small flames which heat to 15 reason provision is made for moving the banks of burners 45l rearwardly and away from the work when work ,stoppage does occur or the rate of movement of the wire should decrease.

In Fig. 4 is illustrated a modification of the invention in which the annealing furnace 15a is of a horizontal type having a hearth 9, roof 23a and side walls 22a formed of refractory material and disposed within a framework or outer shell 24a. In the roof 23a are incorporated a plurality of burners 28a similar to the burners 28 shown in Fig. 1 and described above.

The burners 28a are connected to an intermediate manifold 30a which in turn is connected to a main manifold 30h to which the gas mixture is delivered from a source of supply through a flexible conduit 3la. Although a single row of burners 28a is shown in Fig. 4, it should be understood that a plurality of rows of burners 28a may be provided, and that the number of burners and distribution thereof in the roof 23a, is such that the desired heating effect may be produced in furnace chamber 29a.

The supply of gas mixture to each intermediate manifold 30a is controlled by a valve 32a, and the delivery of gas mixture to each burner is controlled by a member 33a which is associated with a valve (not shown) in the connection between the manifold 30a and the conduit leading to each individual burner.

In Fig. 4 the wire Illa to be annealed passes into a tube 60 at the charging end 25a of the furnace I5a. The tube 60 extends from the charging end 25a to the discharge end 21a of the furnace from which the annealed wire may pass into a quench tank and thence to a drying Aunit like those shown in Fig. l, before being rewound. Although a single strand of Wire is shown in Fig. 4, it is to be understood that in practice a plurality of strands of wire may be passed simultaneously through the furnace I5a alongside of each other and through tubes similar to the tube 60.

Immediately ahead of the charging end 25a of furnace i5a is provided a preheater or heating chamber Ida. The heating chamber Ida is similar to that in the embodiment first described and includes two banks of burners 45a similar to the burners 45. The burners 45a are mounted in and form a part of refractory walls 46a disposed within a framework or outer shell 41a. The burners 45a are connected to intermediate manifolds 48a which in turn are connected to a main manifold 49a to which Aa gas mixture is delivered through a flexible conduit 50a from a source of supply.

Although a single row of burners 45a is shown for each bank of burners in Fig. 4, it is to be understood that several rows of burners may be provided, as in the embodiment rst described, and that each group of burners may be connected to an intermediate manifold 48a which in turn is connected to the main manifold 49. The supply of gas mixture to each intermediate manifold 48a is controlled by a valve Ela, and the delivery of gas to the individual burners is controlled by a member 52a which is associated with a valve (not shown) adjustable to control the supply of gas mixture to each individual burner.

In order to protect the wire lila from burning in heating chamber V |4a in the event of work stoppage, a housing 6I is secured to the shell 47a at the inlet side of the heating chamber. The housing 6I is formed to provide a plurality of spaced bearing surfaces B2 for supporting and guiding a movable annular sleeve 63. Under normal. operating conditions the sleeve .63 is in 8 the position shown in Fig. 4. However, in, the, event of work stoppage, the sleeve 63 is moved into the interior of heating chamber Ila between the topand bottom burners 45a, thereby protecting the Wire Illa from excessive heating.

In the embodiment of Fig. 4, the burners 45a, are of a type capable of producing sources of radiant heat at temperatures varying from 2400 to 2800 F., thereby providing a preheater which will rapidly heat wires, strips and sheets and the like to an elevated annealing temperature, thereby permitting the furnace chamber 29a to serve as a holding and stabilizing chamber for its entire length. With this arrangement the work can be passed through furnace lia at higher speeds than when introduced into the charging end of the annealing furnace without first being heated to the annealing temperature.

In View of the foregoing, it will be understood that I have provided an arrangement for heat treating work, such as sheets, strips, wires and thelike, in which such work is held and maintained at a desired elevated temperature substantially during its entire travel through the heat treating furnace, thereby permitting the heat treating operation to be effected at relatively high speeds. While the supply of combustible fuel to the preheater may be immediately shut off in the event of work stoppage. it is nevertheless desirable to reduce the rate of heat input to the work when the rate of movement of the work decreases by either moving the burners 45 away from the work or by moving the sleeve 63 into the preheating chamber, as described above, because of the residual heat present at the refractory cupped burners embodied in the preheating chambers.

It may be desirable in some instances to effect annealing in the embodiment of Fig. 4 without the use of tubes through which the wires may pass, and in such case the burners 28a may be operated with a slight excess of gas to produce a reducing atmosphere. Although the annealing furnace I5a in Fig. 4 is provided with tubes, and such tubes are not shown in the embodiment illustrated in Fig. 1, it should be understood that tubes like tube 6D may also be provided in the furnace I5 of Fig. 1, if so desired. Further, when tubes like the tube 69 are employed, a suitable gas may be introduced into one end of the tubes to provide a protective atmosphere for the work passing through the tubes.

It has been previously .pointed out that the work may be heat saturated in its entirety to a desired high temperature in the high heat capacity heating chamber, or that surface heat satura tion may be eiected with the inner core of the work heated to a desired high temperature requisite for the heat treating operation. In the claims, therefore, the words heat saturated should be interpreted to include either surface heat saturation of work or heat saturation of work in its entirety.

Although I have shown and described several embodiments of my invention, therefore, such variations and modifications are contemplated as fall within the true spirit and scope of my invention, as pointed out in the following claims.

What is claimed is:

1. A method of heat treating which includes the steps of rapidly heating continuously metallic work of relatively long extent substantially to a desired elevated temperature by one or more relatively high temperature sources of heat in a place out of communication with a holding and stabilizing chamber so that the Work will be at the desired elevated temperature before it reaches the holding and stabilizing chamber, then passing said work through said holding and stabilizing chamber, and stabilizing said work substantially at said elevated temperature practically during its entire travel through said holding and stabilizing chamber, and reducing the heating effected by said high temperature source or sources of heat when the rate of movement of said work decreases to prevent overheating of the latter.

2. A method of annealing which includes the steps of rapidly heating continuously metallic work of relatively long extent substantially to an annealing temperature in a place out of coinmunication with an annealing furnace by subjecting the strip to a temperature well above the annealing temperature so that the work will beat annealing temperature before it reaches said anneling furnace, immediately thereafter passing such work through said annealing furnace, holding said work substantially at the annealing temperature practically during its entire travel through said annealing furnace, and reducing the rate at which said work is heated prior to entering said furnace when the rate of movement of said work decreases.

3. A method of annealing which includes the steps of rapidly heating successive portions of metallic work of relatively long extent substantially to an annealing temperature in a place out of communication with a holding and stabilizing chamber by one or more relatively high temperature sources of heat, then passing said work through said holding and stabilizing chamber, maintaining said work substantially at the annealing temperature practically during its entire travel through said holdingand stabilizing chamber, and moving said source or sources of heat in a direction from said work when the rate of movement of said work decreases.

4. Apparatus for heat treating continuous lengths of metallic work moving through a path at a high rate of speed including a heat treating furnace through which the work passes, an auxiliary heater through which said work passes before it reaches said furnace, said heater being formed of a plurality of parts located on opposite sides of the work as it moves through the path, means to heat said heater and furnace to impart heat to said Work, said last-mentioned means bein-g operative to supply a higher degree of heat to said heater than to said furnace, and means to move the parts of which said heater is formed away from the work to thereby prevent burning of the Work, should its speed of movement be reduced.

5. Apparatus for heat treating continuous lengths of work moving through a path at a high rate of speed, an auxiliary heater located along said path, said heater comprising parts located on different sides of said work and movable relative to each other toward and from said work, a furnace surrounding said work and located in said path at a point beyond said heater, means located in the parts of said heater to produce a temperature suicient to burn said work if it stopped moving to thereby rapidly raise the temperature of the work, means located in said furnace to maintain a given temperature in said work substantially the same as that attained in said heater, and means to move the parts of said heater away from said work to thereby prevent burning of the same if said work should stop or slow down.

6. Apparatus for heat treating a continuous length of metallic work moving through a vertical path including a furnace having a chamber surrounding said work as it moves through said path, heating means located in said furnace to heat said work, tracks located on top of said furnace on opposite sides of said work at a point adjacent that `at which said work enters said chamber, an auxiliary heater including parts mounted for movement on said tracks to- Wardand away from said work, said parts c0- operating to form a second chamber through which said work passes before it passes through said hist-mentioned chamber, and means td move said parts along said tracks toward and from said work.

7. Apparatus for heat treating a continuous length of metallic work moving through a vertical path comprising a furnace having a 'chamber surrounding said work as it moves through said path, heating means located in said furnace to heat said work, an auxiliary heater mounted upon said furnace and having a chamber surrounding said work prior to the time it reaches said furnace chamber, said heater being formed of a plurality of separable .parts located on opposite sides of said work, the chambers of said heater and said furnace being entirely separated, heating means located in the chamber of said heater operable to produce a higher thermal head than the heating means located in said furnace chamber, and means to move said parts of said heater toward and from said work to thereby vary the heating eifect of said heater.

JAMES KNIVETON.

REFERENCES CITED The following references are of recordin the le of this patent:

UNITED STATES PATENTS OTHER REFERENCES Industrial Furnaces, vol. '1, 3rd edition, pp.. 136, 137, 138, 189, and edited by Trinks; published in 1934 by John Wiley and Sons, New York.

Making, Shaping, land Treating of Steel, 5th edition, pp. 1201 to 1204; published in 1940 by the Carnegie Illinois Steel Corporation, Pittsburgh, Pennsylvania.

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