US2041313A - Apparatus for heat treating steel - Google Patents

Description

May 19, 1936. F. J. WINDER I 2,041,313

APPARATUS EoR HEAT TREATTNG STEEL original Filed oct. 15, 1934 s sheets-sheet 2 @@@QQQGO l l' l il im# Eg Eg A rroR/VEY May 19, 1936. F, J, WWDER 2,041,313

APPARATUS FOR HEAT TREATING STEEL Original Filed Oct. 13,1954 3 Sheets-She'et 3 ATTORNEY 4 20 Fig. 1;

Patented May 19, 1793-6 PATENT OFFICE APPARATUS FOR HEAT TREATING STEEL Frank J. Winder, Ottawa Hills, Ohio, assignor to Surface Combustion Corporation, Toledo, Ohio, a corporation of New York l Application October 13, 1934, Serial No. 748,250 Renewed January 20, 1936 i Claims.

This invention relates to improvement in annealing furnaces of the type comprising a base on which the material is supported during annealing, and a heating hood removably supported on the base to form the annealing chamber.

The object of the invention is to provide a furnace of the type indicated having a heating chamber which is rectangular in plan with an improved arrangement of combustion radiator tubes for effecting heating of a charge or pack of rectangular material.

Referring to the drawings wherein the preferred form of the invention is shown,-

Fig. 1 is a perspective view showing how the combustion radiator tubes are arranged within the heating hood;

Fig. 2 is a sectional plan taken on line 2-2 of Fig. 1;

Fig. 3 is a vertical section taken on line 3-3 of Fig. 4 is a perspective diagram of the piping arrangement for controlling the air and fuel supplies to the combustion tubes Fig. l5 is a view of one of the individual heating tubes;

Fig. 6 is an enlarged sectional view of a burner associated with the intake end of the several radiator tubes, the view being taken on line 8 6 of Fig. 5;

Fig. lis an enlarged sectional view of an exhauster associated with the outlet end of the several radiator tubes, and

Fig. 8 is a diagram showing the heat effect produced by the arrangement of heating tubes. 35 The base of the furnace is generally indicated at I. Resting on the base are a pluralityof stools 2 on which the material to be -annealed is supported, the material being indicated' in dotted lines at M. Removably mounted on the base is a heating hood generally indicated at 3. ,Surrounding the base is a trough 4 for receiving a depending ange 5 extending around the lower side of the hood. The trough will ordinarily be filled with sand or liquid to prevent iiiltration of air into the hood. During the annealing operation a non-oxidizing gas will be maintained in the hood. Y

Referring now more particularly to Figs. 1 and 2, 8 indicates one of a series of vertically spaced 5o heating tubes 'SI disposed horizontallyfalong one side wall 1 of the hood, the tube having a lateral portion 8 which extends along one end wall 3 of the hood, the ends of the tube being outside of the hood. AI indicates a burner for delivering 55 fuel to the tube and Bl an exhauster for inducing I2 indicates said side wall 1, the tube having a lateral portion I3 disposed along the other end wall I4, the ends of the tube being outside of the hood. A2 indicates a burner for delivering fuel to the tube and B2 an exhauster for inducing the gases to flow through the tube.

Il indicates one of another series of vertically spaced heating tubes S3, dispose-d horizontally along the side wall I8 of the hood, the tube having a lateral portion I9 extending along the end wall 9, the ends of the tube 'being outside of the hood. A3 indicates a burner for delivering fuel to the tube and B3 an exhauster for inducing the gases to ilow through the tube. 22 indicates one of another series of vertically spaced heating tubes S4 also disposed horizontally along the side Wall I8, the tube having a lateral portion 23 disposed along the end Wall I4. A4 indicates a burner for delivering the fuel to the tube and B4 an exhauster for inducing the gases to ow through the tube.

As already indicated, each heating tube has its own exhauster. comprises a Venturi tube 25 and a jet orice nozzle 26 set to discharge -into the inlet end of the tubethe Venturi tube and nozzle being supported by a fitting 21 coupled to the discharge Each exhauster preferablyI end of the heating tube. A supply pipe 28 having an ordinary shut-off valve 29 delivers iiuid, such as air, under pressure to the nozzle.

The main air supply pipe is indicated at 30 and leading from this line to the several exhausters is a branch'supply line 3|. A common waste gas ue or stack 32 is provided for each series of exhaustersf Leading from the main air supply line 30 is a branch line 35 which delivers to aninspirator 36 for mixing fuel gas and air. One large capacity inspirator might be used but it is preferred to use two or more of lesser capacity, two being shown. The main fuel 4supply line is indicated at 31, there being a branch 38 leading therefrom tothel respective inspirators. A pressure regulator 39, preferably one for each inspirator.

reduces the gas pressure to atmospheric pressure before the gas enters the inspirator. Each inspirator discharges into its own pipe line 40 and extending from this line are two series of branch pipes IS and 3S, respectively, each pipe line being provided with an ordinary shut-off valve 4I. The mixture from the inspirator contains the full complement of air required by the fuel for com plete combustion.

The IS series of pipes delivers to the respective burners AI of the SI series of heating tubes and the 3S series of pipes to the respective burners A3 of the S3 series of heating tubes, it being noted that these burners are at one end of the hood. A similar arrangement is provided at the other end of the hood. Leading from the main fuel supply line 31 is another branch line 42. This line has two branches 43 running to opposite ends of the hood. Extendingfrom each branch 43 are two series of branch pipes ISI and 3S3, respectively, each pipe being provided with an ordinary shutoil valve 44.

The ISI series of gas pipes deliver to the respective burners AI ot the SI series of heating tubes and the 3S3 series deliver to the respective burners A3 of the S3 series of heating tubes. A similar arrangement of gas pipes is provided at the other end of the hood.

' In the. branch air line 3I leading to the exhausters is a valve 45 adapted for mechanical operation and in the branch fuel line 42 leading to the burners is a similar valve 46. y 'Ihese two valves are simultaneously opened and closed by any preferred means 48 responsive to the temperature inside of the heating hood, the valves being opened when there is a call for heat and closed or partly closed when there is no call for heat in the heating hood.

The various burners are of identical construction. In its preferred form, the burner comprises a tubular head 50 which at one end is coupled to the heating tube and forms in effect anv extension thereof and which at its other end ares out- Wardly and is open to the atmosphere. Positioned centrally in the head is a chambered body 5I, the same being centrally supported in the head by any suitable means as by two series of radially spaced screws 52 and 53 extending through the head. Adjustably mounted on the body 5| is an air shutter 54 for controlling the admission of air into the heating tube. At one end of thebody 5| is a gas chamber 55 to which undiluted fuel gas ls supplied under relatively low pressure. Extending from this chamber centrally of the body 5I is a fuel discharge pipe 56, the tube passing through a wall 51 adjacent one end of said body. In the said wall is a circular series of Jet orifice discharge ports 58 through which the preformed mixture of air and fuel gas is discharged from an annular chamber 59 around the fuel tube 56, the mixture being supplied to said chamber by the Supply tube IS. The mixture discharged from the ports 58 serves when ignited as a constantly burning pilot flame for the fuel flowing from the fuel tube 56. By locating the wall 51 some distance inwardly from the adjacent end of the body 5I, the pilot flame will not be blown out by the air flowing into the heating tube and by extending the body 5I a substantial distance into the heating tube, any initial turbulence in the air is materially reduced by the time it reaches the gas flowing from the fuel tube 56.

The fuel gas flowing from the fuel tube 56 and the air for supporting combustion thereof are caused to flow toward the exhaust end of the heating tube by the suction effect produced by the exhauster at said end. It will be readily apparent that the exhauster tends to cause the air and fuel gas to travel in parallel streams toward thev exhauster and consequently the combustion 0f the fuel proceeds relatively slowly as compared, for example, with the combustion of an explosive mixture. Due to the relatively slow combustion,

the point of highest temperature in the tubeis considerably remote from the burner end of the tube. Moreover, since combustion is not instantaneous but is delayed; the fuel which is not immediately yburned becomes highly heated with consequent liberation of carbon, thus causing the ame in the tube to'be luminous with consequent radiation of heat to the interior walls of the heating tube.

The distribution of heat within the tube is dependent on two factors, namely, the rate at which combustion takes place and the velocity of the gases in the tube. The rate of combustion depends upon the rapidity with which the air and gasmix and since the air and gas flow lengthwise of the tube in more or less parallel streams, the rate of combustion is necessarily slow. The velocity of the gases through the tubes is controlled by the exhauster. By adjusting the'valve 29 in the line I6 which delivers fluid under pressure to the exhauster nozzle, the heat distribution in each tube may be readily controlled.-

The amount of fuel permitted to flow from the various burner tubes 56 is regulated in accordance with the temperature requirements inside of the heating hood, the amount of fuel being controlled by the main regulating valve 46. It is also important that the air which enters the burner end of the heating tube be varied in the same degree that the fuel delivered to the burner tubes 56 is varied, otherwise there would be an excessive amount of air entering the heating tube as compared with the amount of fuel discharged from the burner tube with resultant cooling of the heating tube and general upset in the combustion process. By opening and closing both of the main regulating valves 45 and 46 simultaneously, there will be no undue cooling of the heating tubes due to excess air. f

The point of highest temperature in the various tubes will be intermediate the ends of those portions thereof that are disposed along the side walls 1 and I8 of the hood. Since two series of heating tubes are disposed along each of the said side walls and the flow of heating gases in the two series is countercurrent, the point of maximum heat intensity is midway the ends of the respective side walls, or in other words, more heat is applied to the middle portion of the ad- `jacent vertical side of the material M than is applied near the vertical corners thereof. As a consequence of such heating, Vthe corners of the material do not tend to become overheated. Moreover, since the ilow of heating gases is countercurrent to the two series of tubes along' each of the end walls 9 and I4 of the hood, the point of maximum heat intensity at such end is also midway the end of said walls. The intensity of the heat at the ends of the material is, of course, much less than at the long side thereof but nevertheless such heat as is available is applied to the middle portion thereof. y

The chart comprising Fig. 8 illustrates diagrammatically the overlapping which occurs in the heat effect of the heating tubes, and the lo'- cation of such heat effects with respect to the heated material M. In the diagram, the dot and dash line (LI-q2 represents a heating tube of the SI series. The dash line bI-b2 represents a heating tube of the S3 series. The dotted line cI--c2 represents a heating tube of the S2 series and the two-dot and dash line dI-dZ represents a heating tube of the S4 series. The progressive increase and decrease in heat in the various heating tubes is indicated graphically by curved lines similar to the lines representing the heating tubes. Thus the curved dot and dash line, beginning at the point am on the line tl-a2, and extending to the point ay on the line aI--a2 indicates graphically by its distance from the line aI--aZ the intensity of the heat in the tube.

Similarly, the curved lines bm-by, csc-cy, and dazdy indicate respectively the intensity of heat in tubes lll-b2, c I-c2 and ti-d2. In order to show the overlapping of the heat effects, the area between the tube lines cil-a2, bI--b2, fri-c2, 1I-d2, and the respective heat curve lines ctx-ay, bnr-by, cs2-cy, and das-dy, are vertically and horizontally cross sectioned, there being only one set of section lines for a single area. Obviously where these sectional areas overlap the composite heating effect is clearly shown by the one overlapped section. It will be noted that the heat curve line aatay belonging to the tube LI-a2, crosses at the point m the heat curve line csccy belonging to the tube cl-c2. This point m occurs at the transfer center line of the pile of material M and indicates that a maximum heat effect will take place at this point, for the side of the pile in question. On the other side of the pile, the heat curve line bat-4311, and das-dy crosses the point m', which is aiso on the transverse center line of the pile of material M. Similarly, the points nv and 1t represent the points of maximum heat effect on the ends of the material and are located on the longitudinal forming a heating chamber which is rectangular in plan, two sets of heating tubes, one of said sets being disposed along one side wall and the other along the opposite side wall of the chamber, the tubes of both sets each having a lateral portion disposed along one and the same end wall of the heating chamber, two other sets of heating tubes, one of these sets being disposed along the said one side wall and the other along said opposite side wall, the tubes of both of the last mentioned sets each having a lateral portion disposed along the other end wall of the chamber.

2. A furnace comprising, in combination, walls forming a heating chamber which is rectangular in plan, two sets of heating tubes, one of said sets being disposed along one side wall and the other along the opposite side wall of the chamber, the tubes of both sets each having a lateral portion disposed along one and the same end wall of the chamber, two other s'ets of heating tubes, vone of these sets being disposed along the said one side wall and the other along the said opposite side wall, the tubes of both of the last mentioned sets each having a lateral portion disposed along the other end wall of the chamber, and means for supplying heating gases to one end of each of said tubes.

3. KA furnace comprising, in combination, Walls forming a chamber which is rectangular in plan, two sets of heating tubes, one of said sets being disposed along one side wall and the other along the opposite side wall of the chamber, the tubes .of both sets each having a lateral portion dising heating gases to one end of each of said tubes,

and means independent'of said means for controlling the rate of ow of the gases through the respective tubes.

4. A furnace comprising, in combination, walls forming a heating chamber which is rectangular in plan, two sets of heating tubes, one of said sets being disposed along one side wall and the other along the opposite side wall of the chamber, the tubes of both sets each having a lateral portion disposed along one and the same end wall of the chamber, two other sets of heating tubes, one of these sets being disposed along the said one side wall and the other along the said opposite side wall, the tubes of both of the last mentioned sets each having a lateral portion disposed along the other end wall of the chamber, means for supplying heating gases to one end of each of said tubes, said ends being open to the atmosphere, and regulable means for producing a partial vacuum at the other end of the respective tubes for controlling the admission of air into the fuel receiving end thereof.

5. A furnace comprising, in combination, walls forming a heating chamber which is rectangular in plan, a plurality of heating tubes inside of said chamber, each tube extending along two successive walls of the chamber and projecting from the chamber through the next succeeding wall.

6. A furnace comprising, in combination, walls forming a heating chamber which is rectangular in plan, two setsl of heat radiating tubes inside of said chamber and each tube having a bend intermediate its ends, the bend of the tubes of one set being adjacent one corner and the bend of the tubes of the other set being at the diagonally opposite corner of the chamber.

7. A furnace comprising, in combination, walls forming a heating chamber, heating tubes penetrating the walls and extending within the chamber, means arranged at the exit ends of the heating tubes for controlling gaseous flow through the tubes, such' means including piping for fluid under pressure, means arranged at the intake ends of the heating tubes for supplying fuel gas, such means including a piping for fuel gas, two valves arranged, one in the piping for said fluid, the other in said fuel gas piping, and common means for shifting said valves in response to variations of temperature in the heating chamber.

FRANK J. WINDER..

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