US1613726A - Art of annealing metal - Google Patents

Description

- Jan. 11, 1927.

H. w. SANFORD ART OF ANNEALING I ETAL Filed "Feb. 11v. 1922 IIIIIIIIIIII/IIIIII/IIIII/ III I I f m m E r 1 1 1 1 1 n u I 1 1 1 1 1 1 1 1 1 1 1 .1 1 1 1 n 1 1 1 1 1 I 1 H I I 1 1 1 I l 1 1 n 1 1 1 n I. u 1 1 1 1 1 1 n 1 1 1 1 n 1 I 1 1 U 1 n I U U 1 1 1 1 1 1 1v 1 H 1 1 n H U H 1 1 u 1 1 1 .1 I I 1 1 I I 1 I 1 n 1 1 1 1 1 1 1 1 1 1 1 n 1 1 1 n H H .H H H 1 1 1 1 1 1 H 1 1 1 1 n 1 1 1 H 1 I I 1 1 1 1 n. 1

1 m w 1 w m L1 L1 L L L L Patented Jan. 11, 19g7.

UNITED STATES v 1,613,7ze PATENT OFFICE."

HUGH w. slmronn, or xNoxvILL'n, 'rnmmssnn.

new or ANNnALInG METAL.

Application filed Februaryll, 1922. Serial No. 535,835...

My improvement relates especially to apparatus and methods; for annealing metal castings and forgings.

The. object of my improvement 1s to pro- 'vide means and a method for carrying on such an annealing operation under control,

. in order'that the castings may be brought to the desired high temperature and then cooled in such manner and under such control as the chamber.

will cause the cooling to beuniform.

According to the method heretofore practicedand now in general use,'t-he hot cast" ings are put into a closed chamber until such time as it is assumed that the castings have been sufficiently soaked and sufliciently cooled to efi'ect the intended treatment, the

. due to uneven shrinkage, are found to exist in the castings,

Generically speaking, my improved method involves the surrounding of the castings with a fluid medium and relatively moving the fluid medium and the castings, whereby the fluid medium is adapted to deliver heat to or take heat from the castings by contact with the castings. That isvto say, if at the begin- I ning' of the operation the temperature ofthe castings isnot sufliciently high to efiect the annealing, theirelative stream of the fluid medium 'may behotter than the castings, whereby the castings will receive heat from 'the fluid medium and-gradually attainthe desired high temperature.. And when the castings are atthe desired high temperature,

* either at the time they are put into the pit or subsequently made so by contact with the high temperature fluid medium, the tempera ture of the relative-stream of the fluid ,me-

7 of heat from all parts of the castings, in ordium is gradually reduced until the castingshave been sufi'iciently cooled for removal. This period is to bemade of such duration as will allow the annealing change and also allow the substantially uniform elimination der that inernal shrinkage strains may be substantially avoided.

' The fluid medium may be ordinary atmospheric air, or it may be the waste air and other gases from a cupola or other metal: lurgical furnace, or it may be a gas or combination-of gases other than those mentioned. For example, if, in the treatment of some castings, it is desirable to avoid the oxygenof the atmosphere, then nitrogen or carbon dioxide, or someother gas having no free oxygen may be used. In some cases it may be desirable to artificially prepare the fluid medium. For example, if atmospheric air is used,-it maybe desirable to mingle therewith some other gas or gases or vapor or va pors adapted to exert some physical or chemical effect upon the castings or adapted to prevent some other constituentfrom exerting an undesirable physical or chemical eflect upon the castings. And, at low heat,

the fluid medium maybe water or oil or other liquid. If the fluid medium is a liquid,

it may be desirable to introduce into the liquid a constituent or constituents intended to act favorably upon the castings or to prevent another constituent or constituents from acting 'unfavorably upon the castings.

In every form of the operation, there is relative movement between the'fluid medium and the castings, and such movement is positive and directed and controlled in such manner as to compel the change of tempera-' tureeither increasing or diminishing-to to be substantially uniform relative to all-- partsof the castings and relative to they rate of such change. I l

-- In the accompanying drawings,

Fig. 1 is a diagrammatic plan illustrating an apparatus adapted to be used for treating metal castings by my improved method;

Fig. 2 is a diagrammatic plan-oi a similar apparatus;

Fig. 3 is a diagrammatic plan of another similar apparatus;

Figs. 4, 5 and 6 are diagrammatic plans illustrating apparatus containing a plural: ity of annealing chambers;

Figs. 7, 8 and 9 illustrate modifications, Fig. '9 being a vertical section on the line, 9-9, of Fig. 7.

Referr ng first to Fig. 1

of said drawings,

A is a pit or chamber into which castings are to be placed for annealing.' G is a pipe or duct leading from said chamber and opening into the'atmosphere. G is a valve or gate for controlling the movement of the fluid medium from the chamber, A, through the v duct, G. D is a cupola or other furnace from which waste heated air or other gases may be taken. C is a pipe or duct leading from the cupola 0r furnace to the fan, F. B is a pipe or duct leading from the fan into the an nealing chamber, A, opposite the discharge pipe or duct, G. On the pipe or duet, C, is a branch duct, E, communicating with the atmosphere. In said branch duct is a valve or gate, E by means of which admission of air into said branch may be controlled.

The chamber and the ducts should be so constructed as to reduce seeping or leakage and thermal conduction, in order that the temperatures of the fluid medium in the chamber or ducts may be maintained with the least interference from temperature of the outside atmosphere.

The operation of this apparatus is as follows:

The castings to be annealed are placed into the annealing chamber, A, at any convenient temperature. Then said chamber is closed from the atmosphere. Then the gate, G is opened and'the tan. F. is set into motion for drawing hot gases from the cupola or furnace, D, through the duct, C, and drivingsaid gases through the duct, B, into and through the annealing chamber and the duct, G.

The adjustment of rapidity of such movement should depend upon the temperature of the castings in the annealing chamber and upon the temperature of the fluid medium passing from the duct, B, into the annealing chamber. If the castings need be brought to a higher temperature" than they have when put into the chamber, and the gases issuing from the furnace or cupola are at a sufliciently high temperature for the purpose, the fan, F, and the gate, G are controlled to allow the absorption of heat by the cast-- ings from the fluid medium. It the temperature of the castings is already sufliciently high, air is to be admitted through the branch duet, E, to mingle with the gases from the cupola, whereby the temperature of the fluid medium is reduced, to adapt. it to take heat from the castings. Hence the gates, G and E, and the fan are so controlled as to deliver the fluid medium through the annealing chamber at approxb mately the temperature of the castings, and thereafter the adjustment of saidgates and the, velocity of the fan are varied to reduce the temperature of the fluid medium in the annealing chamber gradually and at such rate as will cause uniform passing of heat from the castings into the fluid medium and as will subject the castings to the action of heat during a period of such duration as will be sulficient to anneal the castings. It is to be observed that the requn'ed temperature of the fluid medium in the duct, C,

will depend upon the efi'ectiveness of the thermal insulation of said duct and the duct, B, and the chamber, A. That is to say, if I or leakage of 001C er atmospheric air through the Walls of the duct, B, and through the I walls of the annealing chamber, A. For this purpose, the gate, G is 'to be open far enough to permit the passage of the fluid medium when the latter is under such pressure in the annealing chamber and the duct, B,as will balance or exceed the inward pressure of air from the outer atmosphere. such outward pressure exceeds the inward pressure, there will be outward seeping or leakage, and the entrance of colder-air will be prevented. Bythe method heretofore in use, the leakage of atmospheric air into the pit is not avoided. On the contrary, cold air may seep into the pit and drive out warm air. Furthermore, the gradual cooling of the contents of the pit causes the condensation of the air in the pit, whereby a partial vacuum is created and inward movement of air from the atmosphere is induced.

In Fig. 2, the apparatus is the same as in Fig. 1, excepting that a gate, C, is put into the duct, C, adjacent the cupola and a duct,

H, is placed with one end opening into the; duct, G, while its other end opens into the duct, C. In each end of this duct, H, is a be expected that the gases issuing from the annealing chamber into the duct, G, will be so highly heated that they may be made to circulate thence through the ducts, H, C and B. and again into theannealing chamber with only the reduction of temperature suit-.

able for the reduction of temperature in the castings. In such a case, the fluid medium may be circulated continuously, heat being gradually taken from the castings in the annealingehamber until the elapse of the desired anne'ahng perlod'and the desired. re-' duction of temperature in the castings. For

such operation the gates, G and E. are

closed and the gates, H, are opened. If the cooling in the annealing chamber is to be hastened, the gates, G and E, may be partially opened, the partial opening of the gate, G being for the purpose. of allowing; the escape through the duct, G, of gases to compensate for the air taken in. through the flow through the duct, G, be retarded sufficiently to cause-the gas pressure in the annealing chamber to equal or exceed outside atmospheric pressure, in order that, as above stated, inward leakage of air will be avoided.

But if it is deemed that the temperature in the annealing chamber is being reduced too rapidly while the gates,E and G ,'are yet closed, the gate, C may be part way opened, so that some heated gases will be drawn from the cupolato mingle with the gases coming througlnthe duct, H. i

In the form shown by Fig. 3, the fluid medium receives heat only in a stove, D. and from the hot castings 1n the annealing chamber, the stove being of checker-work or other form heretofore used for heating air before its admission into a metallurgical cupola or blast furnace. Or the stove may chamber, A. A by-pass-duct, J, leads from the duct, I, to the-duct, B. I Betweenthe bypass duct and the stove. the duct, I, has a gate or valve, 1; and the by-pass duct, J,

has a gate or valve, J -The duct,.B, has a the annealing chamber.

gate, 13 between'the stove and the by-pa ss duct, J. The duct, H, has a gate, Hfinear Un'the duct. H, is a branch'duct, K, which opens into the atmosphere. In said branch is a gate or Valve, K And on the duct-,l-I, near the annealing chamber, is a branch duct, K in which is a gate, K

Theoperation @of'this form of apparatus is as follows Y The castings are placed intg the annealing chamber. Then the chamber is closed. Then the fan is set into actionmvhereby the air is driven through the duct, I, and the stove and the duct, 13, into the annealing chamber the gates,-I and B being open and the gate J being closed; or the air is driven from the duct, I, through the by-pass duct, J, into the duct, B, and thence into the annealing chamber, the adjustment of said gates being reversed; or,.if.less heatis desired, a part of ,the air may be driven through the stove "and a part through the by-pass duct, the gates, B, I and J being partially opened.

The gate, H in the duct; may be closed 7 to any extent desired for the purpose of retarding flow of fluid medium out ofthe annealing chamber, in order that there may be outward fluid 'mediui'n' pressure in the an- "nealing chamber'for avoiding inward seeping or leaking'ot cool or cold atmospheric air. The function of the branch duct, K,

on the duct, H, is to admit atmospheric air the branch, K. When no air-is to be thus added to the circulation, the gate, K is to remain closed.

In Fig. 4, a groupof annealing chambers, A A A A and A, similar to the annealing chamber, A, are arranged to receive fluicL medium circulation from a common, circulation stream. These chambers are arranged parallel to each other in a straight row, their ends leading-to common lines.

,From the fan,'F, a duct, L, extends parallel to the left hand ends of the five-chain lters. Branch ducts L connect the duct, L,

with the respective chambers. From a stove, D, a duct, 0. leads to the fan. From the stove a duct, M, extends parallel to the right hand ends of the annealing chambers.

Branch ducts, M connect the duct, M, and the respective, annealing "chambers. Between the stove, D, and the chamber, A, a bv-pass duct, N, extends from the duct, M, to the duct, 0. In the branch ducts, L ,v I connecting the main duct, L, and the annealing chambers are gates, L Between the branch ducts, L gates, L, are placed in the main duct, L. In the branch ducts, M, are placed gates, M, In the main duct, M, between the branch ducts, M, are placed gates, M Between the stove, D,and the by-pass a gate, M is also placed in the main duct, M. In the bv-pass duct, N, is a gate, N. In the duct, 0, is a gate, 0 U, is a branch, P, communicating with the atmosphere. In said branch is a gate, P

.In' operation, if-the fluid medium is to pass through 'all the annealing chambers,

On the duct,

the gates, L and the gates, L are to be each annealing chamber the desired flow of.

fluid medium. For example, if'the phamber, A is filled with castings hafing the maximum temperature, the adjacent gate, M mav be nearly closed and the adjacent gate, L opened only far. enough to admit enough fluid medium to cause sutlicient pressure within that chamber to resist and avoid inward seeping or leaking of external air. sired to 'begin the cooling of the castings in that chamber. Then the gates, M and This may be continued until it is de L are to be adjusted to establish the dc sired flow otfluid medium through that chamber. And if the castings in another chamber are so nearly cooled as to make desirable a larger flow of fluid medium through that chamber, the gates at that chamber are to be adjusted to allow the largest flow through that chamber. When a chamber is to be emptied or charged, the gates at that chamber are to closed.

The fluid medium issuing from the annealing chambers through the branch ducts, M into the main duct, M, follow that duct toward the stove, D, and pass through that stove'g and the duct, 0, to the fan, if the gate,N in the .by-pass, N, is closed, and the gate, M", adjacent the stove is open. If the position of those gates isreversed, the flow willbe through the by-pass duct and not through the stove. In that case,

the gate, 0 in the duct, O, should also.

be closed, in order to avoid the eductionlot air or other gases from the stove. If it be entirely is desired to heat or re-heatonly a portion of the fluid medium coming along the main duct, M, the gates, M N and 0 may be partially opened in such relation to each other as to cause a part of the fluid medium to pass through the stove while the other part moves through the by-pass duct.

From the foregoing it will be seen that this multiple annealing chamber apparatus is adapted to large and economical capacity;

and that any one of the several chambers may be given the desired flow of the fluid medium and that any of the chambers may at any time be completely out ofli' from the circulation of the fluid medium. And it will be observed that by the alternating charging and discharging of the annealing chambers there should always be one or more highly heated chambers adapted to heat the circulating fluid medium, so that ordinarily it will not be necessary to ass the fluid medium through the stove, D. d it will be observed thatprovision is made by means of the branch, P, for reducin the temperature of the circulating ,flui medium, if that medium receives excessive heat by passing through the hot annealing chambers.

In Figs. 5 and 6, the structure is the same as in Fig. 4 with the addition of an outer main duct, Q, extending parallel to the main duct, L, and an outer main duct,

, S, extending parallel to the main duct, M.

Zach end of the main duct, Q, connects with the, duct-,L, and each end of the main duct L', connects with the main duct, M.-

At each junction of the duct, Q, is a gate, Q and at eachjunction of the duct, S, with the duct, M, is a gate,S

Whenthe gates, Q vand S are closed, this apparatus may be dperated in the manner described concerning the apparatus of Fig, 4. But by an appropriate setting of opened, and the alternate gates, L opened,

beginning with the gate, L between the fan and the adjacentbranch duct, L and closing the alternate gates, M beginning with the gate between theby-pass duct, N, and the adjacent branch duct, M When the gates have been so arranged, the fluid medium may take the course indicated by the arrows in Fig. 5; namely from the fan through the chamber, A into the main duct, M, and thence through the chamber, A, and thence into the main duct, L, and along said duct into and through. the chamber, A and again into the main duct, M, and along said duct and into and through the cham- L her, A, and then into. the main duct, L, and through the chamber, A and the branch duct, .M into the outer main duct, S, and through the length of that. duct into the duct, .M, adjacent the stove, and thence through the stove or through the by-pass duct, N, or through both of these members (according to the setting of the gate,

N, and the adjacent gate, M into the duct, 0, and again into the fan.

In Fig. 6, the gates are setto reverse the circulation above described. The fluid me dium then passes from the fan through the adjacent part of the main duct, L, and thence into and through the length of the outer main duct, Q, and through the adjacent branch duct, L ,,and then through the chamber, A5, the main duct, M, the chamber, A, the main duct, L, the chamber, A, the-main duct, M, the chamber, A the main duct, L, and the chamber, A into the main duct, M, and through the stove or the bypass duct, or through both. said members (according to the setting of the gate, N and the adjacent gate, M into the duct, 0, andiagain into the fan.

By thus reversing the circulation, the flow can be adapted to the heat in the chambers.

The circulation may be further varied by closing the gates leading into any two of five chambers; for example, by closing the.

gates leading into the chambers, A and A WVhcn that has been done, the flow will be through the remaining chambers. For such variation it is only necessary that an odd" number of chambcrs'be leftopcn.

This variation in circulation permits the charging and discharging of any chamber without suspending circulation through other chambers.

In Fig. 7 provision is made for passing the'fluidmedium into the annealing chamher, A, at different points. The duct, T, has branches, T one of which extends along each side wall of the Chamber, POrts. T

between the branch ductsand the interior of her will receive the fluid medium at the same the chamber. In said ports are gates, T temperature, alnd that temperature is under These gates are to be opened to admit the the control of the operator. -I -Ie canobserve fluid medium to diflerent parts of the inthe temperature of the fluid medium in the 'terior of the'chamber, as may be found'de duct which discharges into the chamber. If

sirable for successful operation. Not only he finds thattemperature too high, he can may the fluid medium be thus admitted into admit atmospheric air into the duct. If he the chamber at different places, but the finds the temperature too low, he can at-- quantities admitted at the. different ports tend to the heatingof the fluid medium bemay be varied by partiall closing the ates. fore it is discharged into the cham'berQ 4 In Fig. 8, a duet, U, lea s into one en wall of the annealing chamber, and a duct, U}, dium outside of the annealing chamber, it leads'outward from the opposite end wallot' is tobe Observed tha he up a r furnace said chamber. Near the admission end wall and the stove above described perform the in the chamber walls afiord communication parts of the interior of the annealing cham- Regarding the heating of the fluid m'ea of the chamber is an n ri ht cross wall U same function and are heaters orheatin in which are ports, U in which are gates, means external, to the annealing chamber. U. ,Near the opposite end wall is a simi- It has already been indicated that the means lar upright cross wall, U in which are for producing heat, in the heaters maybe ports, U, in whichare gates, U. When varied. If the heater is a metallurgical all these gates are opened, the fluid medium cupola) or furnace, then the heat is derived 3 entering through the duct, U, will pass -f1om, the operation carried on in the cupola medium to all parts of the interior of said through. all. the ports, U and, through the or furnace. If the heater is such a stovev chamber, A, and-then through all the ports, as has been described,- the interior of that U, andv out through'the duct,iU But any stove is( ordinarily heated by means of gas, of the gates may be closed or partially closed or devices for developing heat by electricity to vary the flow of fluid medium as may be may be. used, preferably by placing them found desirable to' reach all the castings in into the'stove.- V Y i the chamber. g g It is to be nnderstood that pieces of metal Furthermore, deflecting plates, T, may other thancastings may be-placed into the be placedion the inner face of the Walls of annealing chambers for the treatment herein the annealing chamber, as shown in Figs. 7, described, -the operation thenbeing varied as 8 and 9, in such positions and at such. in-. may be required for the particular kind of clinations'as will cause the desired movemetal. Hence whathas been said herein mentof the'fluid medium to all parts of the regarding castings is applicable also to other mass of castings in the chamber. metals which are to be annealed,

It is also to be observed that, in addition to the mechanical means described for efunderstand that the annealing of thick pieces fecting a distribution of the fluid medium of metal will require longer time than is in the annealing chamber, delivering the. required for smaller pieces, and that the fluid medium into the annealing chamber operation will have to'be regulated accordunder pressure will aid in driving the fluid ingly. v

It is thought well to also specifically direct chamber, and hence to allzparts of the stack attention to the fact that variation in the of castings in the chamber. For such an Operation may be effected by merely varyoperation it is specially desirable that there ing the velocityof the stream of fluid mebe in the chamber'no space in which the dium. ,If theflow is rapid, the contact befiu'id medium is stagnant. Thus delivering tween the fluid m'edium'and any metal surthe fluid medium into the chamber serves facein the chamber will be of short durathe double purpose of (1) moving said;me- .tion and hence only a relatively small quandium through all parts of the chamber tity of heat can be imparted to that part of and (2) preventing inward leakage of atthe fluid medium from that surface. But mospheric air into the chamber. immediately thereafter another portion of the Regarding the last above-mentioned fea fluid medium, ready to receive heat, is tak-' ture, it is to be noted that complete control ing heat from the same surface. Thus there of the operation can be .hadonly by provi' is a rapid elimination oi. heat from that sursion for preventing such inward leakage face with only a limited addition of heat to For the outside atmosphere varies in" tem-- every part of the stream of fluid medium.

perature at different times, and if there is If, in such a case, the rateof elimination of leakage into the annealing chamber, the heat from the metal is to be reduced, that quantity of air thus entering the chamber can be accomplished by reducing the velocity may be unequal in different parts of the of the stream of fluid medium.

chamber. By substantially avoiding such It will now be seen that for the treatment inward leakage and taking atmospheric air of-the metal, reliance is placed 11 nthe cirinto the. ducts, when cooling is desired,,all culatingor, traveling fluid medium which,

Those who are familiar with this art will i I in the form of a stream, surrounds the metal and receives heat from or imparts heat to the metal, depending upon whether the temperature of the fluid medium is lower or higher than the temperature of the metal, the fluid medium'being heated by means extraneous to the metal, if the temperature of the fluid medium is not as high as desired, or the fluid medium being at times, by means extraneous to the metal, kept at auniform temperature, when it is desired to keep the metal at a uniform temperature during a prolonged interval, and the heat received by the fluid medium from highly heated metal being at times utilized in the treatment of other metal surrounded by said streamafter said stream has left the highly heated metals I claim as my invention, 1. The herein-described method of annealing metal, which method consists in excluding the metal from the atmosphere, then relatively moving the metal and a fluid medium of higher temperature than the temperature of the metal, whereby the metal is surrounded by said fluid medium of high temperature and the metal is raised to a temperature high enough for annealing,

tion of heat from the metal by increasing the velocity of the relative movement of the metal and the fluid medium, substantially as described.

The herein-described method of annealing metal, which method consists in excluding said metal, when at annealing heat, from the atmosphere and establishing an endless stream of fluid medium, a portion of which stream surrounds said metal, the

temperature of the fluid medium of said ing metal, which method consists in isolate ing a plurality of masses of metal when at annealing'heat from the atmosphere and from each other, and then moving a stream of fluid medium to and around one of said masses and then moving the same stream to and around another of said masses for the controlled reduction of ten'iperature of the metal, substantially as described.

5. The herein-described method of anneal ing metal, which method consists in forming a plurality of groups of metal, when at annealing heat, the metal of one group being of a higher temperature than the metal of another group and the latter requiring higher temperature, thenpassing a fluid medium stream to and around the metal group of higher temperature and then moving the same fluid medium to and around another group, wherebysaid fluid medium will acquire a higher temperature while surrounding the first group and thereby be adapted to impart heat to the second group and then slowly cooling said metals, substantially as described.

6. The herein-described method of annealing metal, which method consists in contacting metal,whe n at annealingheat, with a cooler fluid medium and then contacting said fluid medium with metal of lower temperature whereby the latter metal is heated, and then slowly cooling said metals, substantially as described.

7. The herein-described method of annealing metal, which method consists in contacting metal, when at annealing heat, with an endless stream of cooler fluid medium and then contacting said fluid medium with metal of lower temperature whereby the latter metal is heated, and then slowly cooling said metals, substantially as described.

In testimony whereof I have signed my name, this first day of February, in the year one thousand nine hundred and twentyrtwo.

HUGH w. SANFORD.

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