US1905272A - Heat treating process - Google Patents

Description

2 Sheets-Sheet 1 Original Filed Nov. 28, 1930 /f/ f /N/ /7/ SB QNNJ Y April 25, 1933. H. A. DREFFEIN HEAT TREATING PROCESS Original Filed Nov. 28, 1930 2 Sheets-Sheet 2 -/1 u oooio oooooo ooo one o oo NNM) Patented Apr. 25, 1933 UNITED STATES PATENT f orrlcE may la. nanrrnm, o1- emcaeo, rumors maar ranma rnocnss Original application iledlovember 28, 1930, Serial lo. 498,689. Divided and this application illed Jalyf 1a, fasi. Iserial nu. 550.5%. t

This invention relates to processes for heat treating metals and 'monevparticularly to a process for annealing or normalizing sheet metals, and is a division of my pending application, Serial N o. 498,669,

led Nov. 28, 1930. l

An object of this invention is to provide a process for heat treating metal sheets or the like, as, for example, to a temperature which will etlect normalizing and thereafter quickly and satisfactoril cooling the same in a minimum of time in a reducing-'or nonoxidizing atmosphere.

Another objectof the invention is to rovide a process of heat treating which e ec'ts decided economies Ain plant structure and apparatus usually employed for the purpose.

A further object of the invention is to provide means in a heat treating process for rapidly cooling the treated material in a reducing atmosphere. before it leaves the treating furnace or unit.

Still another object of the invention is to provide in a heat treatingprocess for utilizing the products of combustion of the heatmg means in preventing the transfer by Yradiation or conduction of heat from the chamber in which the heating is accomplished to a cooling chamber contiguous thereto 1in such a manner that the treated materia in assmg' cooling chambe gradient which will assure satisfactory annealing or normalizing of such material in a relatively short time.

Other objects andoadvantages inherent in this invention will be more fully pointed out in the following description and accom.- panying drawings, in which:v

Fig. 1a is a sectional plan view of a portion of a heat treating furnace adapted to the practice of the present processes looking from the charging end thereof; p

Fig. 1b shows the same view looking toward the discharge end of the furnace;

Fig. 2a is a sectional elevation of the porh tion of the furnace shown in Fig. 1a; and

Fig. 2b is a sectional elevation of that portion of the furnace shown in Fig. 1b.

from the heating to the 'th rs encounters a temperature which 1s another y Throughout the drawings like .numerals refer to similar elements.

In Figs. la and 1b are illustrated in horizontal section the major portion of the heating chamber 10 of practice of my process. This chamber extends to the restricting baie 11, part shown in Fig. 1b, at which intbegms the cooling chamber, gener y designated by numeral 12. M60

The walls and door of the` heating and cooling chambers are formed of' suitable reracto material, there being slots 14 in the floor o the chambers to permit the passage of conveyor members for the continuous 65 conveyance of metal sheets, or the like, through the furnace structure. At the entrance or charging end 8 of the furnace 5 is provided a vertically adjustable door 16 (better shown in Flg. and similarly 70 there is provided at the-'disc arge end of the furnace an adjustable door 17 (Fig. 2b).

I have found it expedient and desirable to use for heat generation and su ply the invention disclosed in my Patent o. 1,779, 75 964 issued October 28, 1930, although I do not wishtoberestrictedtothesecilc combustion units except -as limited to etails thereof b the claims. A t one side of the heat' chamber adjacent the charging end 80 ereo the wallis offset at 18 to accommodate a burner 19 into and through' whichI introduce at substantialvelocity an admixture of fuel and air, such as producer gas and air. spaced therefrom is a restricted chamber 20, formedby the wall 21, there being a ga 22 between .one end of said wall and the cgi set furnace wall 18. .At the to of the wall 21 are ports or passages 23 see 2a) 90 formed by the partitions 23-12 extending upward from the top of the wall 21. These partitions 23-a are inclinedY in such 'wisev as to direct the gases ilo out of the chamber 20 into the heating c amber prop- 95 er partially toward the entrance end ofthe eating furnace. The restricted chamber 20 is terminated at the end opposed to the burner 19 by the wall 25, at the opposite side Yof a furnace suitable for the j Opposed to the burner 19 and as' restricted chamber 10,

Aformed by a partition wall 28 having partitions 28-a extending upward from the wall 28. These partitions are substantially at right angles to the major axis of the furnace structure. In alignment with the restricted chamber 27 is the burner 30 similar to burner 19, there also being asimilar gap 31 between the burner and the wall 28.

These combustion units function similarly. Burning fuel mixture is introduced, as

stated,"at substantial velocity through or- `.of the same, over, around and in contact with the metal sheets, for example. The

flow of gases into the restricted chamber 2() is such as to set up an inductive action whereby a portion of the products of com- 'bustion is induced into recirculation with the gases flowing intothe restricted chamber. Due to the inclination of the partitions 23a, the flow of gases from the restricted chamber 20 is such as to enhance or aid the general flow of gases in the fur-h nace toward the charging end thereof. As stated, a similar action obtains in the opposed adjacent burner unit except that the gases flow from the vrestricted chamber 27 at right angles to the general flow of the gases are repeatedly reheated and recircul' gases through the heating chamber.

At the opposite sides of the furnace is provided a similar pair of burner units generally indicated by numerals 33 and 34, being staggered with respect to the first described units.. The function and operation is identical with those previously described.

The side walls of the furnace are offset or inset to accommodate the burners affording easy access to the air supply ducts 35 an gas supply ducts 36 for adjustment or regu` lation.

The supply of fuel and air is preferably such that pressure is set up in the heating chamber in excess of atmosphericv to prevent infiltration of air. The arrangement of the ports from theirespective restricted chambersis such as to assist or enhance the general flow ofY gases toward and out the charging endof the heatin chamber. With the burner units of the c aracter described and .arranged as described, products of combustion will be successively picked up and recirculated in part as they pass each heating unit, so that some of the lated in their travel through the heating chamber, which contributes markedly to the efliciency of operation. Also with the i an increasing temperature as they flow toward the discharge end of the furnace since, as their temperatureincreases, they exercise a lesser cooling action upon the products of combustion. Another advantage resides in the fact that the gases during combustion thereof need not be contacted with the product, but only plroducts of combustion which eliminates t e hazardous stratiiication of air and fuel -which might cause oxidization of the sheets. It also reduces the deposit of soot, tarry substances or the like upon the sheets. Forming a continuation with the heating chamber is the cooling chamber 12, there being a restricting transverse wall or baille 11, previously described, with an opening ll-a therethrough to permit the passage of the sheets and the conveying means. Leading from the heating chamber, preferably at the -charging end thereof, is the outlet 40 communicatingwith the extended exterior duct 41 having the in. itial portion 41--a thereof insulated in the embodiment illustrated. This duct 41 is j located above the furnace structure and leads to an exhauster or fan 43, shown as driven by an electric motor 44 throu h the medium of a belt 45. From the an 43 leads the elbow or delivery pipe 47 through the top of the cooling chamber into communication with a transversely extending box 48 having outlet .orifices 48 arranged to deliver jets of gas downwardly upon and along the surfaces of the sheets-justl rior to their discharge from the cooling c amber 12. Extending upwardly from the roof of the cooling chamber adjacent its juncture with the heating chamber is a plurality of vent pipes or stacks 49, each of which is provided with an adjustable damper'50.

Extending transversely through the cooling chamber intermediate its extremities` is. a plurality of air pipes 52,' terminating at each end in a manifold or header 53-54, these headers-being located on the outside of the cooling chamber for convenience. Communicating with they header 53 is the duct 55 also in communication-with a motor driven fan 56, whichsupplies atmos heric air to the header 53, pipes 52 andjhea er 54. From the last, leads a duct 57l and a branch duct 58, the former communicating vwith the adjacent burner to supply air thereto,.` and the latter to the opposed burner as` .illustrated in Fig. 1b. Similarly a branch 59 is provided to supply air to the burners on the oppositeside of the heating chamber.

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'of combustion, as stated Pipes 52 are located above the plane of travel of the sheets in the cooling chamber and in the embodiment shown begin a substantial distance from the restricting wall A motor 60, speed reducing mechanism 61 and chain 62 together with suitable sprocketls1 .furnish driving power for the shaft63. w the conveyer mechanism which may be of any suitable construction. y

In the practice of my process with apparatus of the type described above, vmetal sheets, for example, are continuously fed into the heating chamber through the charging end thereof where theyl encounter the outflowing heated gases. They are subjected to an increasing temperature as they travel toward the discharge ing chamber until the desired maximum is reached. as, for example, from 1750o F. to 1950 F. for normalizing. The heated gases above, flow. rearwardly from the discharge end of the heating-chamber toward the charging end thereof, a portion of said gases being picked up in their flow past each of the restricted chambers and induced into recirculation with the incoming burning or burned gases for subsequent delivery mto the heating chamber proper. From the4 heating chamber the sheets travel into and through the cooling chamber maximum temperature.

Duringthis travel through the cooling chamberthey are submitted to the cooling action of the products of combustion which have been extracted from the heating chamber by the exhauster 43 through duct 41. These cooling gases are delivered downwardly and upon and around these sheets as they are about to pass out of the cooling chamber. so that the flow of cooling gases is toward the heating chamber. During this tlow of the cooling gases they encounter sheets which present a generally rising temperature asthese cooling gases progress against the direction of movement of the sheets and are raised in temperature to a maximum where they encounter the sheets at their maximum vtemperature when they are passed from the heating chamber into the cooling chamber. This insures against subjecting the sheets to a marked drop in temperature as they pass froln one chamber to the other, while at the same time their temperature is rapidly but more or less uniformly reduced to the desired point when they leave the cooling chamber.

The heated cooling-gases, as they approach the barrier 11, in part at least, -will then flow upwardly and back along the roof of the cooling chamber, and in part those beneath the sheets will be forced yrearwardly along the Hoor of the coolino' chamber for outward flow through the discharge open-- ich carries sprockets 64 for actuation of jfrom the extracted end of the heat- 12, arriving therein at a."

ing of the furnace. The spacing of the orifices 48' permits this discharge of the upper rearwardly flowing hot gases.

The pipes 52 conveying air at`atmospherie temperature serve materially to cool or contribute to the maintenance of the cooling gases in relatively cooled condition in their How in the cooling chamber, thus contributing to the rapid cooling `of the sheets. At the same time the heat which is extracted from the cooling gases by the air in the pipes to preheat such air prior. to its 1 52 serves delivery to the burners, which also adds to the eiciency of operation as will be readily recognized by those skilled in the art." 'Ihe long travel through the duct 41 permits the substantial radiation of heat gases and products of combustion, so that they are very substantially reduced in temperature before they are' discharged into the cooling chamber. The operation of the exhauster 43 may be controlled to set up any desirable pressure in the cooling chamber, so that the pressure of the gases in the heating chamber may -be balanced or, if desired, overbalanced by the pressure of the cooling gases, so that the latter serve to batile or obstruct the flow of heating gases and prevent their substantial entry into the cooling chamber. A damper 4.1-b is provided in duct 41 on suction side of exhauster 43 for control of gas flow through ductl etl'and consequent cooling effect. In this wise, cooling gases are or may be utilized to initiate and contribute to the rearward How of the heating gases toward the charging end of the furnace, as describedabove. i

An increase in the quantity of the product being" handled by the furnace may require an increase in the cooling action in thecooling chamber, in which event anincreased delivery of cooling gases may be required. In such event, in addition-` to use of the l. damper 41b,.the dampers 50 in the vent pipes or stacks 49 maybe adjusted to permit the necessarv discharge of cooling gases.

into the atmosphere, thereby permitting an increased delivery of such cooling gases without increasing the amount thereof which are recirculated in the cooling chamber.

By the construction and process described above, I am enabled to use a relatively very short length of cooling chamber with respect to the associated heating chamber. In fact, in a furnace of approximately overall length of onehundred feet I have been able I to devote seventy feet thereof to the heating chamber and thirty feet thereof 4to the cooling chamber, while obtaining temperatures of 17 50 F. to 19500. F. in the heating chamber with'a reduction of the temperature of the sheets in the cooling chamber before discharge thereof to from 800 F. to 1200o F., i. e. to a dull red heat or therebelow.

I find it desirable in the practiceof my process to thus heat the sheets to the desired temperature in the heating chamber and thereafter cool them to or below a dull red heat While maintaining a reducing or non-oxidizing atmosphere, after which' they. may be discharged into the open air Without danger of scaling, oxidization or other impairment. l

The advantage of being able to devote as much as possible of the length of aiurnace of. this character to the annealing,I normalizing or other heating operation will bereadily appreciated by those skilled kin the art, particularly as the cost of such structures is more or less proportional to the length thereof. Therefore, -the less such structures are utilized for cooling the greater capacity and efliciency which will be obtained.

It will be obvious that my process and apparatus are susceptible of modification and I do not Wish toV be restriced to the forms illustrated and described, except as I may be so restricted by the appended claims properly interpreted with respect to the prior art.

What I claim is:

1. A process of treating metal sheets consisting of passing said sheets through a heating chamber, supplying heating gases to said chamber in such Wise as to maintain a non-oxidizing atmosphere, and heating said sheets to the desired temperature, there-- after continuing the,y travel of said sheets through av cooling chamber, and {ioWing products of combustion therein against the line of travel of said sheets and maintaining a non-oxidizing atmosphere in said cooling chamber.

2. A process of treating metal sheets consisting of passing said sheets through a heating chamber, supplying heating gases to said chamber in such Wise as to maintain a non-oxidizing atmosphere and heating saidl sheets to the desired temperature, thereafter continuing the travel of said sheets through a cooling chamber, and supplying products of combustion thereto for cooling said sheets, and forcing said products of combustion back againstO the advancing sheets,

.maintaining a non-oxidizing atmosphere in said coolin chamber and reducing the temperature o said sheets to a point approximating that of a dull red heat or less.

3. A (process of treating metal sheets consisting of advancing said sheets through a heating chamber, supplying heating gases to said chamber in such wise asto maintain a non-oxidizing atmosphere and heating said sheets to the desired temperature, thereafter continuing the travel of said sheets through a.cooling chamber, and supplying productsv of combustion thereto Vfor cooling said sheets, -said products of combustion being flowedv back over the n advancing sheets pmore, thereafter continuing the travel of said sheets through a cooling chamber, supplying products of combustion. thereto for cooling said sheets, and causing said products of combustion to flow against the movement of said sheets, and maintaining a `nonchamber, supplying heatinggases oxidizing atmosphere in said cooling chamber.

5. A process of treating metal sheets consisting, of passing said sheets through a heating chamber, supplying heating gases to said'chamber in such Wise as to maintain a non-oxidizing atmosphere, and heating said sheets to the desired temperature, thereafter continuing the travel of said sheets through a cooling chamber, extracting products of combustion from said heating chamber, cooling and discharging the same into said cooling chamber to cool said sheets passing therethrough.

6, A process of treating metal sheets consisting of passing said sheets through a heating chamber, supplying heating gases to such chamber, flowing said. gases in said heating chamber in adirection opposite to the direction of travel of said sheets, thereafter passing said sheets into and through a cooling chamber while supplying cooled products of combustion thereto. J l

7. A process of treating metal sheets c onsisting of passing said sheets through a heating chamber, supplying heating gases to such chamber, flowing said gases in said heating chamber in a direction opposite to the direction of. travel of said sheets, thereafter passing said sheets into and through a cooling' chamber whilesupplying products of combustion thereto'2 said products of combustion bein flowed in a direction opposite to the direction of travel of said sheets.

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8. A process of treating metal sheets consisting of passing said sheets through a heating chamber,4 supplying'-vheating gases to said chamber, thereafter passing said' sheets through an extensionof said heating chamber comprising a coolingchamber, and rsupplying cooled products .of combustion to against the iiow of cooled products of combustion.

Y 10. In metal treating processes which include the steps of heating the metal by combustion in a heating chamber, and passing it through a cooling chamber, the method of. maintaining a desired temperature in said cooling chamber, which comprises removing gases of combustion from said heating chamber, cooling them and flowing them uniformly over the h t metal in-said cooling chamber.

11. The method of normalizing metals which comprises heating such metals in a heating and combustion chamber free from oxidizing gases, passing said heated metal through a contiguous cooling chamber, extracting products of combustion from said heating and combustion chamber, cooling the same, and flowing them back over the heated metals passing through said cooling chamber.

12. In normalizing furnaces having heating chambers provided With combustion means and a contiguous cooling chamber and means for conveying materials to be normalized continuously from said heating chamber through said cooling chamber, the method of maintaining desired temperatures in said cooling chamber, which comprises extracting quantities of products of combustion from said heating chamber, cooling the same, and flowing them uniformly and continuously through said cooling chamber in a direction opposite to the movement of materials carried by said conveying means.

13. In a normalizing process including the steps of heating a metal in a combustion chamber and passing' it through a length of cooling chamber, the method of cooling Which comprises extracting products of combustion from said combustion chamber, cooling the same, and forcing them in a counter flow from the remote extremity of said cooling chamber back toward said combustion chamber, and bailling the iniiltration of heat from said combustion chamber to said cooling chamber by said counter flow.

In witness whereof, I hereunto subscribe, my name this 6 day of July, 1931.

. HENRY A. DREFFEIN.

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