US1990707A - Heat treating method and apparatus - Google Patents

Description

Feb. 12, 1935. w MOORE 1,990,707

HEAT TREATING METHOD AND APPARATUS Filed June 14, 1952 3 Sheets-Sheet 1 Feb. 12, 1935. W E, MOQRE 1,990,707

HEAT TREATING METHOD AND APPARATUS Filed June 14, 1932 5 Sheets-Sheet 2 if i} Mow/"e m llrm Mow M Feb. 12, 1935. v w E, MOORE 990,797

HEAT TREATING METHOD AND APPARATUS Filed June 14, 1932 3 Sheets-Sheet 3 Patented Feb. 12, 1935 UNITED A STATES PATENT OFFICE HEAT TREATING METHOD AND APPARATUS Application June 14, 1932, Serial No. 617,230

32 Claims.

My invention relates to improvements in methods of heat treating metals and to an apparatus for carrying out the method.

In the annealing of, metal plates, sheets and 5 the like it has heretofore been the practice to stack the material on a base, cover it with an annealing cover, or shield, heat the metal and hood in a suitable furnace, and then withdraw the cover and metal from the furnace and allow it to cool while protected from oxidation by the presence of the annealing cover. With such a practice, a considerable bulk of metal, usually from live to twenty tons, is contained under each of the annealing covers. In order to heat such a mass of metal within a reasonable time, the temperature in the outer parts of the pack must rise considerably above the desired maximum temperature, and this high temperature must be maintained for a period of time suflicient to.

allow the interior of the pack to come up to the minimum annealing temperature. In cooling the metal arranged in stacks, a sufiiciently rapid and even cooling is impossible, and even more so when the shield is kept in place over the metal to prevent oxidation. With this method of heating and cooling, therefore, even treatment and the production of a uniform metallographic structure is not obtained.

Attempts have been made to accelerate the rate of cooling by circulating a cooled gas through the annealing hood but this treatment has only proved feasible when a. relatively small bulk of metal has been treated, which necessitates the use of many small annealing furnaces to handle a fair sized tonnage of metal at a large increase in the cost of the operation.

An important object of my invention is to provide a method of heat treating metals which will avoid the difficulties heretofore encountered and which will produce an even and uniform annealing of the metal in a rapid, emcient and inexpensive manner.

A further object of my invention is to provide a novel apparatus for heat treating metals.

Another object of my invention is to provide a method and apparatus for handling metal sheets or other articles without scratching or otherwise marring the metal.

Still another object of my invention is the provision of a means and a method of controlling the cooling of the metal after the heat treatment.

A still further object of my invention is to provide a continuous and progressive method of treating metal and to provide an apparatus for carrying out such a method.

Yet another object of my invention is to control automatically the various steps of my heat treating method.

Other objects and advantages of my invention will be apparent during the course of the following description.

In the accompanying drawings which form a part of this specification and wherein like charl0 acters of reference denote like parts throughout the same,

Figure 1 is a longitudinal section through a heat treating apparatus embodying my invention,

Figure 2 is a transverse sectional view through the heating chamber thereof,

Figure 3 is a sectional view of a slightly modified form of cooling plates,

Figure 4 is a transverse sectional view showing a slightly modified form of furnace hearth with a metal sheet in position thereon,

Figure 5 is an'elevation of a modified means for cooling, parts being shown in section,

Figure 6 is a detail section showing my furnace used with a quench tank,

Figure '7 is a diagram of the automatic control of the various parts of the heat treating apparatus,

Figure 8 is an elevation of one of the control disks thereof, and,

Figure 9 is a more or less diagrammatic illustration of a further modified form of my invention.

In the accompanying drawings, wherein for the purpose of illustration is shown a preferred embodiment of my invention, the numeral 10 designates a heat treating furnace inclined from its inlet to its outlet end and provided with a suitable electrical heating element represented at 11, althoughother forms of heating may be employed, my invention not being limited to an electrically heated furnace. A suitable gas trap 12 is arranged at the inlet of the furnace and suitable grip rollers 13 or similar devices are arranged within the inlet to pass the metal sheet or sheets into the furnace.

The furnace hearth 14 is inclined from both side edges down to its center to form a substantially V-shape or slightly dished cross-section as seen in Figure 2. When the sheet, represented at 15, enters the furnace through gas trap 12 and rollers 13 it rests upon the V-shaped hearth and contacts therewith only at its extreme longitudinal edges, there being a space between the hearth and the portion of the sheet between its edges. A wind box 16 is secured to the under side of the furnace centrally thereof and communicates with the interior thereof by a relatively large opening 17 which extends upwardly from the wind box through the hearth. A fan or pump 18 is connected to the wind box by conduit 19 and to an opening 20 in the top of the furnace by conduit 21.

A valve 22 is slidably arranged in said wind box to cover and uncover the port 17 and is provided with an operating rod 23 extending through the side of the wind box and adapted to be reciprocated by any suitable means. It will be seen that when the valve 22 is opened, gas may be circulated through opening 17 to opening 20 and back through fan 18 to the wind box.

In order to cool or chill the heated plates I provide a pair of spaced chill plates 24 arranged at the outlet end of the furnace. The upper plate 24 is shown as stationary while the lower plate is attached to a piston rod 25 which extends into a hydraulic cylinder 26 and has a piston 27 operating in said cylinder. A suitable control valve 28 connects the cylinder with a source of fluid supply by means of suitable conduits 29 and may be operated in any suitable manner to pass fluid to and from the cylinder. Pipes 30 extend through the chill plates 24 adjacent the chilling surface thereof, and cold water or other chilling fluid is circulated through said pipes.

A detent 31 is slidably arranged between the furnace and the chill plates and is attached at one end to a pivoted spring pressed lever 32 which normally holds the detent in extended position to prevent passage of the sheets of metal from the furnace to the chill plates. Any suitable means may be employed to withdraw the detent 31, to allow passage of the sheets from the furnace to the chill plates.

A similar detent 33 is slidably arranged between the other end of the chill plates 24 and a sheet receiving platform 35, and is attached to a pivoted spring pressed lever 34 normally holding the detent in extended positon to prevent passage of the sheets. The detent 33 may be withdrawn by any suitable means.

In operation the sheets 15 either singly, or several at a time, are passed through trap 12 and rollers 13 to the furnace hearth 14 where they are subjected to the heat of the element 11. When the sheet has reached the desired temperature, the valve 22 is opened and a blast of suitable non-oxidizing gas enters through opening 17 into the space between the sheet and the hearth and raises the sheet from the hearth. The detent 31 is withdrawn and the heated sheet passes on a cushion of gas under the force of gravity, to the space between the chill plates, while a new sheet or sheets is passed into the furnace. The valve 28 is then operated to raise the lower chill plate and clamp the sheet or sheets between the chill plates to chill the sheet and press it to flatness. When the sheet has been chilled to the desired temperature, detent 33 is withdrawn and the sheet passes to platform 35 under the force of gravity while another sheet is taking its place.

The clamping effect of the chill plates insures a close and even contact with the sheet to be cooled and as the sheets are cooled from their entire surfaces they will be evenly cooled throughout and will have a uniform metallographic structure. The valve 22 may be so adjusted that the sheets 15 are at all times partly or wholly supported by a cushion of gas the gas circulating through the furnace chamber and escaping through port 20 to be recirculated. Where the valve 22 is only operated to discharge the sheet 15 from the furnace, however, a suitable gas may be circulated through valved pipes 36 to maintain a non-oxidizing, reducing, or other desired atmosphere in the furnace at all times.

In Figures 1 and 7, I have shown diagrammatically one method of operating the valves and detents, although obviously any other suitable means may be employed. A solenoid or electromagnet 37 is connected to valve rod 23 and is adapted when energized to move the valve 22 into open position. Any means, such as a spring, may be used to return the valve to closed posi-- tion. A similar solenoid 38 is connected to detent 31 or lever 32 to withdraw the detent when energized. A solenoid 39 is attached to valve 28 to operate the same, and solenoid 40 is connected with detent 33.

An opening 41 is arranged in the furnace bottom and hearth and a radiation or light sensitive vacuum tube or similar temperature responsive device 42 is arranged in line with this opening and "looks on" the under side of the sheet on the hearth. An amplifier tube 43 is connected to the tube 42, and the tubes 42 and 43 are arranged in a circuit 44 connecting an electric motor 45 with a suitable source of current. The circuit 44 is normally open at a relay or switch 46. When the sheet 15 reaches the desired temperature, tube 42 acting through amplifier tube 43 energizes relay 46 to close the circuit to motor 45.

The motor shaft 47 is provided with a series of spaced contact disks 48 and is connected to a wire 49 leading to a source of current 50 and to each of the solenoids 37, 38, 39 and 40. The disks 48 are of fiber or other insulating material mounted on a metal hub attached to the shaft and are provided with segmental contact plates 51 connected to the disk hubs. Suitable stationary spring contacts 52 are in constant engagement with the peripheries of the disks 48, and are each connected by wires 53 to one of the solenoids 37, 38, 39 and 40. The disks 48 are so arranged on the shaft 47 that the contacts 52 engage the segmental contacts 51 in properly timed succession to energize the solenoids.

When the sheet 15 has reached the desired temperature tube 42 starts motor 45 and solenoid 37 is actuated to open valve 22 and direct a blast of gas under sheet 15. Solenoid 38 is actuated to withdraw detent 31 and allow sheet 15 to pass to the chilling plates 24. Solenoid 39 is then actuated to clamp the sheet between plates 24, for a, suitable period and solenoid 40 is then actuated to release detent 33 to allow sheet 15 to pass onto platform 35. The cycle is continuous, and as one sheet leaves the furnace, another enters to take its place and follows it into the chilling portion of the apparatus.

The diagram of Figure 7 is a simple illustration of one method of operating the valves and detents and is illustrative only as I contemplate employing other electrical, pneumatic or mechanical control devices.

When very uniform annealing is desired, the sheets are fed through the furnace one at a time but for some classes of work several sheets arranged in a thin pack may be passed through the furnace and chilling chamber together.

In Figure 3, I have shown a slightly modified arrangement of the chilling plates in which the upper plate is provided centrally with a socket 54 adapted to receive a ball 55 depending from the supporting member 56. Suitable filling of fibrous or other compressible or resilient material may be arranged between the upper plate 24 and the member 56 if desired. With this arrangement the upper plate 24 is free to pivot in any direction about the ball and socket joint, and will therefore adjust itself to any inequalities in the sheet clamped between the plates.

The hearth 14, instead of being V-shaped, may be slightly arcuate as shown in exaggerated form in Figure 4 for the purpose of illustration. With this arrangement the sheet 15 will be supported at its edges only and will adjust itself to the center of the hearth.

In Figure 5, I have shown a modification in which a cooling chamber is provided in which the sheets may rest for a suitable period of time. The cooling chamber 57 is shown to be arranged at the end of the chill plates 24 but if preferred the chill plates may be omitted and the. cooling chamber connected directly to the furnace. A conveyor 58 carries spaced vanes 59 which divide the conveyor into compartments 60. The plates 15 drop from the chill plates into one of the compartments 60 in the cooling chamber. The plates continue to drop into the compartment until it is filled, and the conveyor is then moved forward to bring an empty compartment into position to receive the plates, the filled compartment remaining within the cooling chamber in a non-oxidizing atmosphere maintained by suitable gas traps such as indicated at 61. The conveyor 58 may be operated intermittently to fill the compartments successively without requiring an exceptionally long cooling chamber.

In Figure 6, I have shown a modification in which a quench tank 62 takes the place of the chill plates 24 for work which permits this form of chilling. If desired, however, the quench tank 62 may be used in conjunction with the chill plates as seen in Figure 9, or the cooling chamber 57 may be used in place of thechill plates and a quench tank used in conjunction therewith.

The arrangement of an inclined furnace structure for feeding the sheets by gravity may be dispensed with and a. horizontal arrangement of the furnace and chill plates or other cooling means employed, as shown in Figure 9. With such an arrangement a conveying mechanism must be used to move the sheets and the conveyor 63 is therefore provided, and has spaced fingers 64 adapted to pass through suitable slots in the furnace and chill plates to engage the sheets and move them through the furnace and chill zone. The conveyor 63 may be operated intermittently by any suitable mechanism controlled by additional contact diskson motor shaft 4'7 or by other suitable means. With this arrangement the sheets may be supported or partially supported on a film of gas and moved by the fingers 64 contacting with the trailing edge of the sheets. The gas film prevents scratching of the sheets, and as the fingers 64 only engage the trailing edge of the sheet, no damage will be done to the sheet.

Preferably the entire process is carried out in a controlled atmosphere to avoid oxidation of the metal. The heat to which the metal is subjected may be easily controlled by adjustment of the control tube and associated mechanism which determines the period of time during which the sheet is exposed to the heat of the furnace. With this arrangement therefore I am enabled to utilize the intense heat of highly incandescent resistor elements, or electric arcs, and by Shortening the period of exposure to this heat, prevent overheating of the metal. The temperature of the sheets may also be controlled in the usual manner by controlling the temperature of the heating element.

A very important advantage of my invention is the easy control of the cooling step and the uniform cooling of the entire sheet. Practically any desired cooling rate may be obtained by adjusting the time the sheets remain between the chill plates and by adjusting the temperature of the cooling medium circulated through pipes 30. The sheets are cooled from their surfaces, and not from their edges as usually occurs. In certain classes of work several sheets may be heated and cooled together, the cooling still proceeding from the surfaces of the sheets. Accuracy in controlling the cooling rate is further insured by the close and even contact of the chill plates with the surfaces of the sheet. -Where extremely rapid cooling is required the quench tank 62 may be employed and where extremely slow rates of cooling are desired, the cooling chamber 5'? is used. The important feature of the cooling chamber 57 is the piling or stacking of the sheets, and moving the stack of sheets further along the cooling zone while forming another stack. This feature permits the use of a relatively short cooling chamber and also allows an independent adjustment of the rates of heating and cooling over a wide range. The sheets may be piled in separate containers and moved manually or by other suitable means, if desired, in place of the conveyor arrangement shown.

The cooling chamber 57 may also be used for subjecting the sheets to'a draw-back tempera ture. This may be accomplished by leaving sufficient unchilled heat in the sheets to supply the necessary draw-back temperature effect, or an electric or other form of heating element 65 may be arranged in the chamber 57 adjacent the forward end thereof for this purpose.

While metal sheets are not easily scratched or marred when cold, they are subject to scratching by rollers, skids or the like when heated, and my form of hearth and gas film prevents such scratching of the sheets. When the sheets are completely supported by the gas film, there is no contact of the sheet with the hearth, and any accidental contact Will be at the edges of the sheet. Where the sheets are moved by a conveyor as in Figure 9, or only partially supported by the gas film, the only contact will be at the edges of the sheets.

The tube 42 looks on the under side of the sheet and therefore assures the heating of the sheet throughout to the desired temperature before it is ejected from the furnace. My method of heat treatment may be applied to the annealing of steel sheets or tin plates, or to the treatment of other metals such as copper, aluminum or the like. Other forms than sheets or plates may be treated, as the sheets shown throughout the drawings are used as illustrative examples only.

For some classes of work it may not be desirable to clamp the sheets between the chilling plates, and the plates may therefore be spaced apart and the metal cooled by the adjacent cooling surfaces without actual clamping.

While I have shown and described the preferred embodiment of my invention it is to be understood that various changes in the size, shape and arrangement of parts may be resorted to without departing from the spirit of my invention or the scope of the subjoined claims.

Having thus described my invention what I claim and desire to protect by Letters Patent is:

1. In a heat treating apparatus, a heating zone, a cooling zone in communication therewith, means to feed material to said heating zone, and means to introduce fluid under pressure into said heating zone in such manner as to provide a film of fluid on which the material may pass from the heating zone to the cooling zone.

2. In a heat treating furnace, a hearth therein adapted to receive a plate to be heated, said hearth being higher adjacent its edges than at its center, whereby the central portion of the hearth is spaced from the plate to be heated, and means adjacent the center of the hearth to supply a fluid to the space between the hearth and plate.

3. In a heat treating furnace, a substantially dished hearth adapted to receive a relatively flat plate to be heated, and means adjacent the center of the hearth to supply fluid to the dished portion of said hearth.

4. In a heat treating furnace a substantially dished hearth inclined to the horizontal and adapted to receive a relatively flat plate to be heated, a cooling zone located adjacent the lower end of said hearth, and means to introduce a fluid under pressure to the dished portion of the hearth to raise the plate therefrom and to permit it to pass gravitationally to the cooling zone.

5. In a heat treating furnace, a substantially dished hearth inclined to the horizontal and adapted to receive a relatively flat plate to be heated, a cooling zone located adjacent the lower end of said hearth, a detent arranged between the furnace hearth and the cooling zone and adapted to be engaged by the edge of said plate, means to withdraw the detent, and means to introduce a fluid under pressure between the dished hearth and the plate to cause the plate to pass from said hearth to said cooling zone while substantially out of contact with said hearth.

6. In a heat treating furnace, a generally rectangular hearth to receive a flat plate adapted to be moved longitudinally thereover, said hearth being slightly V-shaped in transverse cross section whereby the edges of the plate will engage the hearth and support the remainder of the plate out of contact therewith.

7. In a heat treating furnace, a hearth adapted to receive a flat plate, said hearth being slightly V-shaped in transverse cross section whereby the edges of the plate will engage the hearth and support the remainder of the plate out of contact therewith, and means to introduce a fluid under pressure to said hearth beneath said plate.

8. In a heat treating furnace, a generally rectangular hearth to receive a flat plate adapted to be moved longitudinally thereover, said hearth being slightly concave in transverse cross section whereby the edges of the plate will engage the hearth and support the remainder of the plate out of contact therewith.

9. In a heat treating furnace, a hearth adapted to receive a flat plate, said hearth being slightly concave in cross section whereby the edges of the plate will engage the hearth and support the remainder of the plate out of contact therewith, and means to introduce a fluid under pressure to said hearth intermediate the edges thereof and beneath said plate.

10. In a heat treating furnace, a cooling zone associated with said furnace comprising a pair-of substantially parallel chill plates, one of said plates being pivotally supported and free to move about a horizontal axis, and means to move the other plate toward and away from the pivotally supported plate.

11. In a heat treating furnace, a cooling zone associated therewith and comprising a support, a pair of chill plates, one of said plates having a ball and socket connection with the support, and means to move the other chill plate toward and away from the flrst named chill plate.

12. In a heat treating furnace, a cooling zone associated therewith and comprising a support, a pair of chill plates, one of said plates having a ball and socket connection with the support, means to move the other chill plate toward and away from the first named chill plate, said first named chill plate being spaced from the support, and a compressible filling material arranged in the space between the support and chill plate.

13 In a heat treating furnace, an inclined hearth adapted to receive the material to be treated, an inclined chilling apparatus arranged in communication with said furnace, a sliding detent located between the hearth and chilling apparatus and adapted to normally prevent passage of the material from the hearth to the chilling apparatus, and means to automatically withdraw said detent to allow the material to slide under the force of gravity from the hearth to the chilling apparatus, said means being set into operation when the material on the hearth rises to a predetermined temperature.

14. In a heat treating furnace, a substantially dished hearth inclined to the horizontal and adapted to receive a relatively flat plate to be heated, a cooling zone adjacent the lower end of said hearth, a detent located between the furnace hearth and the cooling zone and adapted to be engaged by the edge of said plate, means to withdraw the detent, and means to supply a fluid under pressure between the dished hearth and the plate to cause the plate to pass from said hearth to said cooling zone while substantially out of contact with said hearth, said cooling zone consisting of a pair of spaced substantially parallel chilling plates, and means to move one of said chilling plates toward and away from the other chilling plate while maintaining their substantially parallel relation.

15. In a heat treating apparatus, a furnace having an inclined hearth, an inclined chilling apparatus adjacent the lower end of said hearth, a source of fluid supply, means connecting the source of fluid supply with said hearth, a valve to control the supply of fluid, sliding detents located at each end of the chilling apparatus, and thermally controlled means to operate said valve and withdraw said detents in accordance with a predetermined cycle.

16. In a heat treating furnace, a heating zone, a chilling zone adjacent to and in communication therewith, a draw back zone adjacent to and in communication with said chilling zone, a conveyor arranged in said draw back zone, means to continuously pass material through said heating and chilling zones to said conveyor, and means to intermittently operate said conveyor, whereby material will be stacked thereon and moved through said draw back zone.

17. In a heat treating furnace, a heating zone, a chilling zone adjacent to and in communication therewith, a transversely dished hearth in said heating zone to receive the material to be heated, and means to move the heated material longitudinally over said dished hearth to the chilling zone.

18. In a heat treating furnace, a heating zone, a chilling zone adjacent to and in communication therewith, a transversely dished hearth in said heating zone to receive the material to be heated, and a conveyor adapted to. engage said material and slide it from thehearth to the chilling zone, and through the chilling zone.

19. In a heat treating furnace, a hearth adapted to receive thematerial to be heated, a chilling apparatus comprising a pair of chill plates one of which is hydraulically operated toward and away from the other chill plate, said chilling apparatus being adjacent to and in communication with the hearth, a sliding detent located between said hearth and chilling apparatus, a source of fluid supply connected to said hearth, a valve controlling the source of fluid supply, a valve controlling the hydraulically operated chill plate of the chilling apparatus, and thermally operated means to operate said detent and valves in accordance with a predetermined cycle.

20. In the operation of a heat treating rurnace, the method of heat treating an article which comprises heating the article in the furnace, and moving the heated article through said furnace on a fluid film.

21. In the operation of a heat treating furnace, the method of treating an article to be annealed comprising heating said article in the furnace, introducing a fllm of fluid beneath said article, and moving the article from said furnace while partially supported on said film of fluid.

22. In the operation of a heat treating furnace, the method of treating an article to be annealed comprising heating said article in the furnace, introducing a film of gas beneath said article, moving said article from said furnace while substantially supported on said film of gas, and then cooling said article.

23.'In the operation of a heat treating furnace, the method of treating an article to be annealed comprising heating said article in the furnace, introducing a film of non-oxidizing gas beneath the article, moving the article from said furnace while partially supported on said film of non-oxidizing gas,- and then cooling said article.

24. The method of heat treating an article which comprises placing said article in a heating zone, introducing a. film of gas beneath said article, moving the article from the heating zone to a cooling zone while substantially supported on said film of gas, and then cooling said article while subjecting it to mechanical pressure.

25. The method of treating an article on an inclined substantially dished hearth which cornprises placing the article on the hearth, heating the article to the desired temperature and then introducing a film of gas between said hearth and article to facilitate movement of said article from the hearth by the force of gravity.

26. The method of annealing a series of articles which comprises placing the articles successively in a heating zone, moving the articles successively to a cooling zone, placing the heated articles in stacks in the cooling zone, and moving the stacks of articles through the cooling zone.

27. In the operation of a heat treating furnace, the method of heat treating an article which comprises heating the article in the furnace while partially supporting the article on a film of fluid introduced therebelow.

28. In the operation of a heat treating furnace, the method of heat treating an article which comprises heating the article in the furnace while partially supporting the article on' a fiuid film, and moving the article through the furnace while partially supported on the fluid film.

29. In a heat treating furnace, a hearth therein adapted to receive a plate to be heated, said hearth being higher adjacent its edges than at its center, whereby the central portion of the hearth is spaced from the plate to be heated, and means to introduce a fluid under pressure to the space between the hearth and plate to raise the plate from the hearth.

30. In the operation of a heat treating furnace, the method of heat treating an article which comprises heating the article in the furnace, and moving the heated article through said furnace under the influence of gravity and on a film of fluid.

31. In the operation of a heat treating furnace, the method of treating an article to be annealed comprising heating said article in the.

, which comprises placing the article on the hearth of the furnace, introducing a film of fluid beneath the article to support it substantially out of'contact with the furnace hearth, and heating the article while it is supported substantially out of contact with the hearth.

WILLIAM E. MOORE.

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