US2900479A - Furnace construction - Google Patents

Description

J. A. REDMOND ETAL FURNACE CONSTRUCTION Filed April 24, 1958 Aug. 18, 1959 WITNESSES INVENTOR James W.v Peach, Richard K. Wurfel,

John A. Redmpnd a Ernest L Weight ATTORNEY United States Patent FURNACE CONSTRUCTION John A. Redmond, James W. Peach, Richard K. Wuerfel, and Earnest L. Weight, Baltimore, Md., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 24, 1958, Serial No. 730,627

14 Claims. (Cl. 21910.67)

This invention relates to furnace construction with particular reference to structure for support and guidance of a workpiece into and through an induction heating fur nace chamber for heating such workpiece to forging or extruding temperatures.

In the heating of a workpiece for forging or extrusion by automatized apparatus, the advantages of using electrical induction apparatus capable of heating the workpiece rapidly, successively, and accurately to a predetermined temperature is well recognized. In inductance coil billet heating apparatus it is usual to position the billet centrally of the induction coil and to shift the billet longitudinally through a tunnel formed within the convolutions of the coil. In order to keep a power factor of the induction coil reasonably near unity, it is desirableto keep the air gap between the workpiece and the convolutions of the induction coil as small as possible.

In conflict with the foregoing desirabilities, is the necessity of providing thermal and electrical insulation between the workpiece pathway and the convolutions of the induction coil. An accepted practice in the art has been to provide metal or ceramic liners of heat resistant material surrounding the workpiece pathway to protect the induction coils from heat radiated by the workpieces and from physical injury which might be caused by insertion or withdrawal of heavy workpieces from the coil. In addition to providing thermal and physical protection for the induction coil, the liner structure should be sufficiently strong, rigid and rugged to support the workpieces during the heating cycle.

Since it is desirable that the insulating liner be kept as thin as possible and be capable of withstanding forging temperatures of about 2000 F. and above, the lining is usually made of a highly efiicient heat insulating refractory material such as fire brick. Since such refractory material is frangible, it becomes necessary to provide wear rails extending longitudinally inside the fire brick lining to guide and support the workpieces through the furnace. At-the working temperatures of about 2000 F., workpiece supporting and guiding rails of known metal alloys have very little strength, in bending, so that it has been the practice to provide relatively. heavy, thick, watercooled rails for this purpose. The allowance of addi tional space for heavy rails necessitates a relatively great air gap between the induction coil and the metal to be heated, while the internalcooling of these rails tends to introduce a temperature differential between diiferent portions of the heated workpiece, which is undesirable where substantially uniform temperature throughout the workpieceis desired. This requirement becomes increasingly important'in automatized apparatus wherein the heated workpiece is delivered to the forging presses almost immediatelyafter being ejected-from the induction heating furnace and the dwell time between furnace and forging press is so short that temperature equalization of the different portions of the billet is not obtained.

7 Accordingly, it is an objectof this invention to provide a furnace having improved workpiece supporting means. i

2,900,179 Patented Aug. 18, 1959 It is another object of the invention to provide an in duction heating furnace having improved workpiece supporting means which will not cause cooling of the workpiece surface engaging same for support.

It is a further object of the invention to provide an induction heating furnace having improved workpiece support and guide means which may be readily removed for inspection or replacement.

It is an additional object of the invention to provide improved means for support and guidance of the workpiece in a furnace, comprising a plurality of wear elements which may be replaced separately.

It is still a further object of the invention to provide a novel wear rail assemblage which may readily be removed and inserted in a heating furnace and which includes a plurality of separate wear elements which may be selectively removed and inserted in such assembly.

A further object of the invention resides in the provision of a wear rail structure adapted to be readily removed and installed in a heating furnace, which includes a plurality of removable metal wear elements for slidable supporting contact with a workpiece in a furnace or region of a furnace in which the furnace chamber temperature is less than that at which the physical properties of such metal wear elements are materially degraded.

Another object of the invention is to provide a novel wear rail assemblage adapted to be readily removed and installed in a furnace and including a plurality of removable refractory wear elements for employment in a furnace or a region of a furnace in which the furnace chamber temperature exceeds that at which the physical properties of metal wear elements would be materially affected.

Another object of the invention resides in the provision of an induction heatingfurnace having a relatively long hollow horizontal support member, carrying workpiecesupportable wear rail members interiorly and heating coil means exteriorly, directly supported intermediate its ends without creation of excessive gaps along such heating coil means.

It is still a further object of the invention to provide a novel wear rail assemblage including a plurality of workpiece-supporting elements any one of which may be replaced without necessitating cooling the furnace employing such assemblage.

Other objects will become apparent from the following description of the invention taken in accordance with the accompanying drawing throughout which like reference characters indicate like parts, which drawing forms a part of this application and in which:

Figure 1 is a longitudinal side view of an electrical induction heating furnace embodying the invention;

Fig. 2 is a sectional view taken along the line II-II in Fig. 1 and illustrating structural details of the exemplified induction heating furnace embodying the invention;

Fig. 3 is a longitudinal section view taken along the line III-III in Fig. 2 and showing additional details of (the exemplified induction heating furnace embodying the invention;

Fig. 4 is a View taken in the direction of the arrow 4 in Fig. 3 showing in outline, certain sections being cut away, additional details with respect to novel wear rail and support structures as embodied in the exemplified heating furnace constructed in accordance with the invention; and V Fig. 5 is a view taken along the line VV of Fig. 1 showing, partly in outline and partly in section a novel arrangement for support of the induction coil assemblage intermediate ends thereof whereby the applicantsnovel removable wear rail assemblage is rendered practicable heating furnace.

Referring to the several figures in the drawing, the induction heating furnace embodying the invention constructed in accordance with certain features of the invention comprises a hollow horizontal support member" ofrectangular cross section which is supported adjacent -to its opposite ends by vertical support members 12 in the form of end plates each having a suitable opening 14 therein to accommodate member 14 and each'being connected to common base member 15. Preferably, one end of the support member 10 will be secured to a respective one of the vertical support members 12 by means of Welds or the like (not'shown) while'the opposite end of said member 10 will be in slidable support by the wall ofthe opening 14 in the respective vertical support member 12, to provide for expansion of such member 10 in the presence of heat.

Referring particularly to Fig. l and to Fig. 5, the support member 10 is supported intermediate its ends through the medium of a plurality of longitudinally the medium of yieldable means in the form of respective compression springs Ztla. Pedestals 19 in turn are suitably attached by means (not shown) to the base member 15.

The furnace further comprises a plurality of coil sec tions 20 formed of a single layer of respective sections .of electrical conductor 21 and arranged in end-to-end "relationship surrounding the support member 10 for .support thereby.

For protection of coil sections 20 from excessive heat radiated from the workpieces being handled by the furnace, cooling means in the form of fluid conduits 24 are provided in interposition between the outer surface of the hollow support member 10 and the inner surface of [the coil sections 20. Conduits 24 are suitably spaced around the periphery of member 10 and are preferably welded thereto or otherwise suitably intimately associated therewith for adequate thermal ex change through the medium of member 10 for proper cooling of sections 20 in their entirety. Feeder conduits 25 provide for circulation of cooling fluid through fiuid conduits 24.

The hollow support member 10 is preferably made of a relatively rigid, strong, non-magnetizable material such as stainless steel and, as can be seen in Figs. 2 and 5, is provided with a separation 26 extending longitudinally thereof to prohibit the induction coil from inducing a circulating current in such member 10 which would reduce the efficiency of the furnace and tend to overheat such member.

In accord with the prime feature of the invention, the hollow support member 10 is provided with laterallyspaced-apart track guide elements 30 (Figs. 2 and 4) extending longitudinally as can be seen in Figs. 2 and 4, to define a guideway in interposition between portions of a refractory lining 31 for slidable insertion and removal of a novel wear rail assemblage 32, as well as to cooperate with such assemblage to maintain proper location thereof when disposed within the hollow member 10. Preferably there are two such sets of track guide elements 30 associated with adjacent downwardly extending flat walls of the hollow support member 10 to provide for accommodation of two such wear rail assemblages 32 for dis tribution of the workpiece supporting load between the two assemblages, while at the same time affording a a trough-like structure which affords a guideway for the workpieces 33 while enroute through the furnace.

Each wear rail assemblage 32 comprises a sub-rail element 34 in the form of a flat plate substantially equal in length to that of the hollow support member 10 and substantially equal in width to the lateral distance be tween track guide elements 30, thus being adapted for slidable movement longitudinally of member 10 between such guide elements. Carried by the sub-rail element 34 and arranged consecutively therealong are a plurality of wear elements 36 locked into abutment with such subrail element through the medium of T-shaped retaining members 38 spaced apart longitudinally of sub-rail element 34 and between which wear elements 36 extend. Retaining members 38 are preferably T-shaped in cross section to provide an upright portion, which is anchored at its base by means such as welds to sub-rail element 34, and a transverse portion for extension or projection into accommodating transverse slots 40 formed in adjacent ends of wear elements 36.

Referring particularly ltO Fig. 3, it will be apparent that by virtue of such means for retaining wear elements 36 onto the sub-rail element 34, thrusts forces created by movement of workpieces 33 along a wear rail assemblage 32, in passing over a given wear element 36 will be transmitted by such element to a respective one of retaining members 38 at one end thereof, and the total friction force resulting from movement of the workpieces over the several wear elements will be received by the sub-rail element 34 through the medium of the respective retaining members 38. Sub-rail element 34 is properly secured to the member 10 by removable means such as bolts 42 to remain stationary with respect to such members which thereby absorbs such friction load.

It is preferable that a cushioning layer 45 of heatresistant yieldable material, with insulating qualities such as aluminum silicate felt, for example (Fig. 3), be interposed between each of the wear elements 36 and the sub-rail element 34 to more evenly transmit the vertical load therebetween during sliding movement of workpieces 33 over the wear elements. During sliding movement of the wear rail assemblage 32 into and out of the furnace chamber, in absence of any supporting load imposed by the presence of workpieces, the inherent resiliency afforded by the layer of resilient material 45 tends to urge the respective wear element 36 into frictional engagement with the cross member portion of the respective retaining members 38, as well as provide frictional interengagement between such wear elements and the sub-rail element 34, whereby such wear elements will be retained on said sub-rail element when portions of such wear rail assemblage 32 are removed from the containing influence of the track guide elements 30 within the furnace.

As indicated by the showing in Fig. 2, the sub-rail element 34 may be disposed in direct abutment with the inner wall of the hollow support member 10 so that such sub-rail element 34 will he slid along such wall during removal and insertion of the wear rail assemblage 32 for inspection and/ or replacement of wear elements 36 when desired. However, according to additional refinements of the invention as shown in Fig. 3, it is preferable that a smooth-surfaced thin-walled metal linear member 48 be interposed between the sub-rail element 34 and the wall of the support member 10 to define a replaceable, smooth-surfaced member along which the subrail element 34 may be slid with relative ease, thus avoiding the necessity for providing a smooth surface on said hollow support member 10 and avoiding introduction of undue wear to this member. To prevent sliding movement of the metal liner 48 relativeto the support member 10 during sliding movement of the wear rail assemblage 32 into and out of the furnace, the metal liner member 48 is provided with a plurality of longitudinally-spaced-apart tongues 50 (Fig. 4) at its outermost edges which project between the track guide elements 30 to interlock said liner member 48 therewith while permitting such member, when necessary, to be lifted upwardly between such guide elements for removal.- It is also preferable that a layer 52 (Fig. 3) of heat-resistant yieldable material be interposed between the metal liner member 48 and the wall of the hollow support member in behalf of more evenly distributing transmission of vertical forces therebetween.

'In accord with one aspect of the invention, where furnace operating temperatures are relatively low, it will be appreciated that all of the several wear elements 36 may be made of a suitable metal such, for example as Hastelloy Alloy X capable 'of withstanding sliding movement of workpieces such as steel billets thereover -without undue wear.

It is preferable that such wear elements 36 when made of metal be provided with a cavity therein intermediate its uppermost and lowermost surfaces to provide for accommodation of heat insulating material 54, asshown in Fig. 3, to reduce tranmsission of heat between the supported workpiece surface and the cooled surface of the hollow support member 10, thereby acting in behalf of preventing creation of cold spots on the supported surface of the workpieces 33 passing. through the furnace. In this behalf, layers 45 and 52' of yieldable heat resistant material may also serve in the same behalf.

Where the operating temperatures throughout the furnace are in the neighborhood of 2000 F., for example all of the wear elements 36 will be made of refractory material such as aluminum oxide or silicon carbide, for example. Such refractory material in addition to being capable of withstanding relatively high temperatures, also possesses desirable wear properties and affords a relatively high degree of resistance to transmission of heat therethrough, thereby assuring that these elements will not absorb any material amount of heat from the workpieces which they support and thus they act to prevent creation of cold spots on the supported surface of such workpieces. At the same time, by virtue of affording a relatively high degree of resistance to transmission of heat therethrough, the refractory wear elements36 enable the sub-rail elements 34 to be maintained at relatively cool temperatures without withdrawal of an excessive amount of heat therefrom by circulation of cooling water through the conduits 24. As a further refinement, the refractory wear elements 36 are constructed to extend over the cross member portions of v retaining members 37 to shield same from radiation exposure to the heated workpieces supported by such elements, as may be observed in Fig. 3. In similar fashion the side portions of refractory wear elements 36 are preferably made to extend over the track guide elements 30 at their sides for such shielding purposes, as may be observed in Fig. 2.

Where a furnace, such as the furnace shown in Fig. l, is intended to be employed in an automatic operation in which the workpieces 33 are in continuous movement therethrough, workpieces entering such furnace at its right-hand end, for example, as viewed in Figs. 1 and 3 in the drawing, will be relatively cool compared to workpieces disposed at the opposite end of such furnace, since the heating of such workpieces is progressive during such transit. Under such circumstances and in accord with a further feature of the invention, it is preferable that the removable wear elements 36 which are disposed in the cold end of the furnace be made of metal in order to take advantage of the superior wear qualities of this material, while those elements 36 disposed in the hotter portions of the furnace will be made of refractory material, both the elements 36 of metal and of refractory material, being removably mounted on the sub-rail element 34 common to each.

While the present invention has been shown in one form only, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various other changes and modifications without departing from the spirit and scope thereof.

We claim as our invention:

1. Heating apparatus comprising furnace-chamberdefining means for accommodating a workpiece to be heated therein, guide means extending into said furnacechamber-defining means, metal sub-rail means slidably disposed in said guide means, cooling means for said subrail means, and a plurality of workpiece-supportable wear rail elements of refractory material removably attached to said metal sub-rail means, said wear rail elements being of greater width than said sub-rail means to prevent exposure of the latter to heated workpieces supported on said wear rail elements.

2. Heating apparatus comprising furnace-chamberdefining means substantially lined with frangible refractory material, guide means extending into said furnacechamber-defining means in interposition between portions of said frangible refractory material, metal sub-rail means slidably disposed in said guide means for facile removal and insertion into and out of said furnace-chamberdefining means, means for cooling said sub-rail means, a plurality of workpiece-supportable wear rail elements of refractory material removably attached to said metal subrail means, and heat resistant cushioning means interposed between said wear rail elements and said sub-rail means.

3. Heating apparatus comprising furnace-chamberdefining means for accommodating a workpiece to be heated therein, guide means extending into said furnacechamber-defining means, sub-rail means slidably disposed in said guide means, a plurality of workpiece-supportable wearrail elements disposed longitudinally along said subrail means, each of said workpiece-supportable Wear rail elements having a respective connection with said subrail means capable of transmitting thrust forces 1ongitudinally therebetween and of permitting lateral movement therebetween for selective replacement of such elements.

4. Heating apparatus comprising furnace-chamben defining means for accommodating a workpiece to be heated therein, guide means extending into said furnacechamber-defining means, sub-rail means slidably disposed in said guide means, a plurality of workpiece-supportable wear rail elements disposed longitudinally along said subrail means, each of said workpiece-supportable wear rail elements having a respective connection with said subrail means capable of transmitting thrust forces longitudinally therebetween and of permitting lateral movement therebetween for selective replacement of such elements, and means for locking and unlocking said sub-rail means against longitudinal movement relative to said guide means.

5. Heating apparatus comprising furnace-chamberdefining means for accommodating a workpiece to be heated therein, guide means extending into said furnacechamberdefining means, sub-rail means slidably disposed in said guide means, a plurality of workpiece-supportable wear rail elements disposed longitudinally along said subrail means, each of said workpiece-supportable wear rail elements having a respective connection with said subrail means capable of (transmitting thrust forces longitudinally therebetween and of permitting lateral movement therebetween for selective replacement of such elements, said guide means serving to prevent such transverse movement of said Wear rail elements when said sub-rail means carrying same is disposed in said guide means.

6. Heating apparatus comprising furnace-chamberdefining means having dilferentatemperature heat zones through which a workpiece is to be passed consecutively from colder to hotter zones thereof, guide means extending into said furnace-chamber-defining means through said heat zones, sub-rail means slidably disposed in said guide means, and a plurality of workpiece-supportable wear rail elements disposed longitudinally along said sub-rail means and removably attached thereto, said wear rail elements respective to the hotter of said heat zones being wear-resistant refractory material and said wear "rail elements respective to the colder of said zones being of metallic material.

material interposed between said liner and said guide means.

8. Heating apparatus comprising furnace-chamberdefining means for accommodating a workpiece to be heated therein; guide means extending into said furnacechamber-defining means, said guide means including a flat bottom member and parallel rows of longitudinallyspaced-apart guide elements cooperable with said bottom member to form a guide channel; a workpiece-supportable wear rail assemblage disposed in said guide channel; and a replaceable thin-sheet metallic guide surface liner interposed between said bottom member and said wear rail assemblage and interlocked with said guide elements to prevent relative longitudinal movement between such liner and bottom member during longitudinal movement of said wear rail assemblage.

9'. An induction heating apparatus comprising an induction coil having a workpiece pathway extending longitudinally therethrough, a hollow thin-walled support member disposed within said coil, metal sub-rail means extending longitudinally within said hollow thin-walled support member in slidable contact with the inner surface thereof, workpiece-contactable rail means of wearresistant refractory material removably attached to said sub-rail means, and means for cooling said coil, said thin-walled support member, and said metal sub-rail means.

10. An induction heating apparatus comprising an induction coil having a workpiece pathway extending longitudinally therethrough, a hollow thin-walled support member disposed within said coil, metal sub-rail means extending longitudinally within said hollow thin-walled support member in slidable contact with the inner surface thereof, workpiece-supportable wear rail means of wearresistant refractory material removably attached to said sub-rail means, and means for cooling said coil, said thin walled support member, and said metal sub-rail means, said wear rail means being of greater width than said sub-rail means.

11. In an induction heating furnace comprising a hollow thin-walled support member disposed withinan electrical coil, the combination therewith of guide elements attached to said support member to define parallel side walls of a longitudinally-extending guide channel within said support member, smooth-surfaced thin-sheet metallic liner means disposed between said guide elements to define the bottom surface of said guide channel, and a removable workpiece supportable wear rail assemblage disposed in said guide channel.

12. In an induction heating furnace comprising a hollow thin-walled support member disposed within an electrical heating coil, the combination therewith of glide elements attached to said support member to define parallel side walls of a longitudinally extending guide channel within said support member, smooth-surfaced thin-sheet metallic liner means disposed between said guide elements to define the bottom surface of said guide channel, heat resistant yieldable cushioning material interposed between said liner and said support member, and a removable workpiece supportable wear rail assemblage disposed in said guide channel.

13. In an induction heating furnace comprising a hollow support member disposed within an electrical heating coil, the combination therewith of parallel rows of longitudinally-spaced-apart guide elements cooperable/with an interior wall of said support member to define a guide channel extending longitudinally therein, a thin smoothsurfaced metallic liner member defining the bottom surface of said guide channel and interlocked with said guide elements to prevent longitudinal movement therebetween, a wear rail assemblage slidably mounted in said guide channel, and means for locking and unlocking said wear rail assemblage against longitudinal movement in said channel.

14. An induction heating apparatus comprising a horizontally extending hollow thin-walled support member supported at opposite ends, a plurality of electrical coil sections arranged in end-to-end relationship around said support member, thin plate like means interposed between coil sections in vertically supporting cooperation with said support member intermediate its ends, a thin plate like wear rail member extending longitudinally within said support member in continuous support thereby, and a plurality of workpiece supporting wear rail elements removably attached to said plate like wear rail member.

References Cited in the file of this patent UNITED STATES PATENTS 2,809,263 Segworth Oct. 8, 1957 FOREIGN PATENTS 787,874 Great Britain Dec. 18, 1957

Images